1 /* 2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #if !defined(__clang_major__) && defined(__GNUC__) 26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess. 27 #endif 28 29 #include "precompiled.hpp" 30 #include "code/codeCache.hpp" 31 #include "code/icBuffer.hpp" 32 #include "gc_implementation/g1/bufferingOopClosure.hpp" 33 #include "gc_implementation/g1/concurrentG1Refine.hpp" 34 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 35 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 36 #include "gc_implementation/g1/g1AllocRegion.inline.hpp" 37 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 38 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 39 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 40 #include "gc_implementation/g1/g1EvacFailure.hpp" 41 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 42 #include "gc_implementation/g1/g1Log.hpp" 43 #include "gc_implementation/g1/g1MarkSweep.hpp" 44 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 45 #include "gc_implementation/g1/g1RemSet.inline.hpp" 46 #include "gc_implementation/g1/g1StringDedup.hpp" 47 #include "gc_implementation/g1/g1YCTypes.hpp" 48 #include "gc_implementation/g1/heapRegion.inline.hpp" 49 #include "gc_implementation/g1/heapRegionRemSet.hpp" 50 #include "gc_implementation/g1/heapRegionSeq.inline.hpp" 51 #include "gc_implementation/g1/vm_operations_g1.hpp" 52 #include "gc_implementation/shared/gcHeapSummary.hpp" 53 #include "gc_implementation/shared/gcTimer.hpp" 54 #include "gc_implementation/shared/gcTrace.hpp" 55 #include "gc_implementation/shared/gcTraceTime.hpp" 56 #include "gc_implementation/shared/isGCActiveMark.hpp" 57 #include "memory/gcLocker.inline.hpp" 58 #include "memory/generationSpec.hpp" 59 #include "memory/iterator.hpp" 60 #include "memory/referenceProcessor.hpp" 61 #include "oops/oop.inline.hpp" 62 #include "oops/oop.pcgc.inline.hpp" 63 #include "runtime/prefetch.inline.hpp" 64 #include "runtime/orderAccess.inline.hpp" 65 #include "runtime/vmThread.hpp" 66 #include "utilities/ticks.hpp" 67 68 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 69 70 // turn it on so that the contents of the young list (scan-only / 71 // to-be-collected) are printed at "strategic" points before / during 72 // / after the collection --- this is useful for debugging 73 #define YOUNG_LIST_VERBOSE 0 74 // CURRENT STATUS 75 // This file is under construction. Search for "FIXME". 76 77 // INVARIANTS/NOTES 78 // 79 // All allocation activity covered by the G1CollectedHeap interface is 80 // serialized by acquiring the HeapLock. This happens in mem_allocate 81 // and allocate_new_tlab, which are the "entry" points to the 82 // allocation code from the rest of the JVM. (Note that this does not 83 // apply to TLAB allocation, which is not part of this interface: it 84 // is done by clients of this interface.) 85 86 // Notes on implementation of parallelism in different tasks. 87 // 88 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism. 89 // The number of GC workers is passed to heap_region_par_iterate_chunked(). 90 // It does use run_task() which sets _n_workers in the task. 91 // G1ParTask executes g1_process_strong_roots() -> 92 // SharedHeap::process_strong_roots() which calls eventually to 93 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses 94 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also 95 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). 96 // 97 98 // Local to this file. 99 100 class RefineCardTableEntryClosure: public CardTableEntryClosure { 101 G1RemSet* _g1rs; 102 ConcurrentG1Refine* _cg1r; 103 bool _concurrent; 104 public: 105 RefineCardTableEntryClosure(G1RemSet* g1rs, 106 ConcurrentG1Refine* cg1r) : 107 _g1rs(g1rs), _cg1r(cg1r), _concurrent(true) 108 {} 109 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 110 bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false); 111 // This path is executed by the concurrent refine or mutator threads, 112 // concurrently, and so we do not care if card_ptr contains references 113 // that point into the collection set. 114 assert(!oops_into_cset, "should be"); 115 116 if (_concurrent && SuspendibleThreadSet::should_yield()) { 117 // Caller will actually yield. 118 return false; 119 } 120 // Otherwise, we finished successfully; return true. 121 return true; 122 } 123 void set_concurrent(bool b) { _concurrent = b; } 124 }; 125 126 127 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 128 int _calls; 129 G1CollectedHeap* _g1h; 130 CardTableModRefBS* _ctbs; 131 int _histo[256]; 132 public: 133 ClearLoggedCardTableEntryClosure() : 134 _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set()) 135 { 136 for (int i = 0; i < 256; i++) _histo[i] = 0; 137 } 138 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 139 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 140 _calls++; 141 unsigned char* ujb = (unsigned char*)card_ptr; 142 int ind = (int)(*ujb); 143 _histo[ind]++; 144 *card_ptr = -1; 145 } 146 return true; 147 } 148 int calls() { return _calls; } 149 void print_histo() { 150 gclog_or_tty->print_cr("Card table value histogram:"); 151 for (int i = 0; i < 256; i++) { 152 if (_histo[i] != 0) { 153 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 154 } 155 } 156 } 157 }; 158 159 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure { 160 int _calls; 161 G1CollectedHeap* _g1h; 162 CardTableModRefBS* _ctbs; 163 public: 164 RedirtyLoggedCardTableEntryClosure() : 165 _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set()) {} 166 167 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 168 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 169 _calls++; 170 *card_ptr = 0; 171 } 172 return true; 173 } 174 int calls() { return _calls; } 175 }; 176 177 YoungList::YoungList(G1CollectedHeap* g1h) : 178 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 179 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 180 guarantee(check_list_empty(false), "just making sure..."); 181 } 182 183 void YoungList::push_region(HeapRegion *hr) { 184 assert(!hr->is_young(), "should not already be young"); 185 assert(hr->get_next_young_region() == NULL, "cause it should!"); 186 187 hr->set_next_young_region(_head); 188 _head = hr; 189 190 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 191 ++_length; 192 } 193 194 void YoungList::add_survivor_region(HeapRegion* hr) { 195 assert(hr->is_survivor(), "should be flagged as survivor region"); 196 assert(hr->get_next_young_region() == NULL, "cause it should!"); 197 198 hr->set_next_young_region(_survivor_head); 199 if (_survivor_head == NULL) { 200 _survivor_tail = hr; 201 } 202 _survivor_head = hr; 203 ++_survivor_length; 204 } 205 206 void YoungList::empty_list(HeapRegion* list) { 207 while (list != NULL) { 208 HeapRegion* next = list->get_next_young_region(); 209 list->set_next_young_region(NULL); 210 list->uninstall_surv_rate_group(); 211 list->set_not_young(); 212 list = next; 213 } 214 } 215 216 void YoungList::empty_list() { 217 assert(check_list_well_formed(), "young list should be well formed"); 218 219 empty_list(_head); 220 _head = NULL; 221 _length = 0; 222 223 empty_list(_survivor_head); 224 _survivor_head = NULL; 225 _survivor_tail = NULL; 226 _survivor_length = 0; 227 228 _last_sampled_rs_lengths = 0; 229 230 assert(check_list_empty(false), "just making sure..."); 231 } 232 233 bool YoungList::check_list_well_formed() { 234 bool ret = true; 235 236 uint length = 0; 237 HeapRegion* curr = _head; 238 HeapRegion* last = NULL; 239 while (curr != NULL) { 240 if (!curr->is_young()) { 241 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 242 "incorrectly tagged (y: %d, surv: %d)", 243 curr->bottom(), curr->end(), 244 curr->is_young(), curr->is_survivor()); 245 ret = false; 246 } 247 ++length; 248 last = curr; 249 curr = curr->get_next_young_region(); 250 } 251 ret = ret && (length == _length); 252 253 if (!ret) { 254 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 255 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 256 length, _length); 257 } 258 259 return ret; 260 } 261 262 bool YoungList::check_list_empty(bool check_sample) { 263 bool ret = true; 264 265 if (_length != 0) { 266 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 267 _length); 268 ret = false; 269 } 270 if (check_sample && _last_sampled_rs_lengths != 0) { 271 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 272 ret = false; 273 } 274 if (_head != NULL) { 275 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 276 ret = false; 277 } 278 if (!ret) { 279 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 280 } 281 282 return ret; 283 } 284 285 void 286 YoungList::rs_length_sampling_init() { 287 _sampled_rs_lengths = 0; 288 _curr = _head; 289 } 290 291 bool 292 YoungList::rs_length_sampling_more() { 293 return _curr != NULL; 294 } 295 296 void 297 YoungList::rs_length_sampling_next() { 298 assert( _curr != NULL, "invariant" ); 299 size_t rs_length = _curr->rem_set()->occupied(); 300 301 _sampled_rs_lengths += rs_length; 302 303 // The current region may not yet have been added to the 304 // incremental collection set (it gets added when it is 305 // retired as the current allocation region). 306 if (_curr->in_collection_set()) { 307 // Update the collection set policy information for this region 308 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 309 } 310 311 _curr = _curr->get_next_young_region(); 312 if (_curr == NULL) { 313 _last_sampled_rs_lengths = _sampled_rs_lengths; 314 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 315 } 316 } 317 318 void 319 YoungList::reset_auxilary_lists() { 320 guarantee( is_empty(), "young list should be empty" ); 321 assert(check_list_well_formed(), "young list should be well formed"); 322 323 // Add survivor regions to SurvRateGroup. 324 _g1h->g1_policy()->note_start_adding_survivor_regions(); 325 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 326 327 int young_index_in_cset = 0; 328 for (HeapRegion* curr = _survivor_head; 329 curr != NULL; 330 curr = curr->get_next_young_region()) { 331 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 332 333 // The region is a non-empty survivor so let's add it to 334 // the incremental collection set for the next evacuation 335 // pause. 336 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 337 young_index_in_cset += 1; 338 } 339 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 340 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 341 342 _head = _survivor_head; 343 _length = _survivor_length; 344 if (_survivor_head != NULL) { 345 assert(_survivor_tail != NULL, "cause it shouldn't be"); 346 assert(_survivor_length > 0, "invariant"); 347 _survivor_tail->set_next_young_region(NULL); 348 } 349 350 // Don't clear the survivor list handles until the start of 351 // the next evacuation pause - we need it in order to re-tag 352 // the survivor regions from this evacuation pause as 'young' 353 // at the start of the next. 354 355 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 356 357 assert(check_list_well_formed(), "young list should be well formed"); 358 } 359 360 void YoungList::print() { 361 HeapRegion* lists[] = {_head, _survivor_head}; 362 const char* names[] = {"YOUNG", "SURVIVOR"}; 363 364 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 365 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 366 HeapRegion *curr = lists[list]; 367 if (curr == NULL) 368 gclog_or_tty->print_cr(" empty"); 369 while (curr != NULL) { 370 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d", 371 HR_FORMAT_PARAMS(curr), 372 curr->prev_top_at_mark_start(), 373 curr->next_top_at_mark_start(), 374 curr->age_in_surv_rate_group_cond()); 375 curr = curr->get_next_young_region(); 376 } 377 } 378 379 gclog_or_tty->cr(); 380 } 381 382 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 383 { 384 // Claim the right to put the region on the dirty cards region list 385 // by installing a self pointer. 386 HeapRegion* next = hr->get_next_dirty_cards_region(); 387 if (next == NULL) { 388 HeapRegion* res = (HeapRegion*) 389 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 390 NULL); 391 if (res == NULL) { 392 HeapRegion* head; 393 do { 394 // Put the region to the dirty cards region list. 395 head = _dirty_cards_region_list; 396 next = (HeapRegion*) 397 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 398 if (next == head) { 399 assert(hr->get_next_dirty_cards_region() == hr, 400 "hr->get_next_dirty_cards_region() != hr"); 401 if (next == NULL) { 402 // The last region in the list points to itself. 403 hr->set_next_dirty_cards_region(hr); 404 } else { 405 hr->set_next_dirty_cards_region(next); 406 } 407 } 408 } while (next != head); 409 } 410 } 411 } 412 413 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 414 { 415 HeapRegion* head; 416 HeapRegion* hr; 417 do { 418 head = _dirty_cards_region_list; 419 if (head == NULL) { 420 return NULL; 421 } 422 HeapRegion* new_head = head->get_next_dirty_cards_region(); 423 if (head == new_head) { 424 // The last region. 425 new_head = NULL; 426 } 427 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 428 head); 429 } while (hr != head); 430 assert(hr != NULL, "invariant"); 431 hr->set_next_dirty_cards_region(NULL); 432 return hr; 433 } 434 435 #ifdef ASSERT 436 // A region is added to the collection set as it is retired 437 // so an address p can point to a region which will be in the 438 // collection set but has not yet been retired. This method 439 // therefore is only accurate during a GC pause after all 440 // regions have been retired. It is used for debugging 441 // to check if an nmethod has references to objects that can 442 // be move during a partial collection. Though it can be 443 // inaccurate, it is sufficient for G1 because the conservative 444 // implementation of is_scavengable() for G1 will indicate that 445 // all nmethods must be scanned during a partial collection. 446 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 447 HeapRegion* hr = heap_region_containing(p); 448 return hr != NULL && hr->in_collection_set(); 449 } 450 #endif 451 452 // Returns true if the reference points to an object that 453 // can move in an incremental collection. 454 bool G1CollectedHeap::is_scavengable(const void* p) { 455 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 456 G1CollectorPolicy* g1p = g1h->g1_policy(); 457 HeapRegion* hr = heap_region_containing(p); 458 if (hr == NULL) { 459 // null 460 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p)); 461 return false; 462 } else { 463 return !hr->isHumongous(); 464 } 465 } 466 467 void G1CollectedHeap::check_ct_logs_at_safepoint() { 468 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 469 CardTableModRefBS* ct_bs = g1_barrier_set(); 470 471 // Count the dirty cards at the start. 472 CountNonCleanMemRegionClosure count1(this); 473 ct_bs->mod_card_iterate(&count1); 474 int orig_count = count1.n(); 475 476 // First clear the logged cards. 477 ClearLoggedCardTableEntryClosure clear; 478 dcqs.set_closure(&clear); 479 dcqs.apply_closure_to_all_completed_buffers(); 480 dcqs.iterate_closure_all_threads(false); 481 clear.print_histo(); 482 483 // Now ensure that there's no dirty cards. 484 CountNonCleanMemRegionClosure count2(this); 485 ct_bs->mod_card_iterate(&count2); 486 if (count2.n() != 0) { 487 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 488 count2.n(), orig_count); 489 } 490 guarantee(count2.n() == 0, "Card table should be clean."); 491 492 RedirtyLoggedCardTableEntryClosure redirty; 493 JavaThread::dirty_card_queue_set().set_closure(&redirty); 494 dcqs.apply_closure_to_all_completed_buffers(); 495 dcqs.iterate_closure_all_threads(false); 496 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 497 clear.calls(), orig_count); 498 guarantee(redirty.calls() == clear.calls(), 499 "Or else mechanism is broken."); 500 501 CountNonCleanMemRegionClosure count3(this); 502 ct_bs->mod_card_iterate(&count3); 503 if (count3.n() != orig_count) { 504 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 505 orig_count, count3.n()); 506 guarantee(count3.n() >= orig_count, "Should have restored them all."); 507 } 508 509 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 510 } 511 512 // Private class members. 513 514 G1CollectedHeap* G1CollectedHeap::_g1h; 515 516 // Private methods. 517 518 HeapRegion* 519 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 520 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 521 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 522 if (!_secondary_free_list.is_empty()) { 523 if (G1ConcRegionFreeingVerbose) { 524 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 525 "secondary_free_list has %u entries", 526 _secondary_free_list.length()); 527 } 528 // It looks as if there are free regions available on the 529 // secondary_free_list. Let's move them to the free_list and try 530 // again to allocate from it. 531 append_secondary_free_list(); 532 533 assert(!_free_list.is_empty(), "if the secondary_free_list was not " 534 "empty we should have moved at least one entry to the free_list"); 535 HeapRegion* res = _free_list.remove_region(is_old); 536 if (G1ConcRegionFreeingVerbose) { 537 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 538 "allocated "HR_FORMAT" from secondary_free_list", 539 HR_FORMAT_PARAMS(res)); 540 } 541 return res; 542 } 543 544 // Wait here until we get notified either when (a) there are no 545 // more free regions coming or (b) some regions have been moved on 546 // the secondary_free_list. 547 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 548 } 549 550 if (G1ConcRegionFreeingVerbose) { 551 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 552 "could not allocate from secondary_free_list"); 553 } 554 return NULL; 555 } 556 557 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 558 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, 559 "the only time we use this to allocate a humongous region is " 560 "when we are allocating a single humongous region"); 561 562 HeapRegion* res; 563 if (G1StressConcRegionFreeing) { 564 if (!_secondary_free_list.is_empty()) { 565 if (G1ConcRegionFreeingVerbose) { 566 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 567 "forced to look at the secondary_free_list"); 568 } 569 res = new_region_try_secondary_free_list(is_old); 570 if (res != NULL) { 571 return res; 572 } 573 } 574 } 575 576 res = _free_list.remove_region(is_old); 577 578 if (res == NULL) { 579 if (G1ConcRegionFreeingVerbose) { 580 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 581 "res == NULL, trying the secondary_free_list"); 582 } 583 res = new_region_try_secondary_free_list(is_old); 584 } 585 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 586 // Currently, only attempts to allocate GC alloc regions set 587 // do_expand to true. So, we should only reach here during a 588 // safepoint. If this assumption changes we might have to 589 // reconsider the use of _expand_heap_after_alloc_failure. 590 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 591 592 ergo_verbose1(ErgoHeapSizing, 593 "attempt heap expansion", 594 ergo_format_reason("region allocation request failed") 595 ergo_format_byte("allocation request"), 596 word_size * HeapWordSize); 597 if (expand(word_size * HeapWordSize)) { 598 // Given that expand() succeeded in expanding the heap, and we 599 // always expand the heap by an amount aligned to the heap 600 // region size, the free list should in theory not be empty. 601 // In either case remove_region() will check for NULL. 602 res = _free_list.remove_region(is_old); 603 } else { 604 _expand_heap_after_alloc_failure = false; 605 } 606 } 607 return res; 608 } 609 610 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions, 611 size_t word_size) { 612 assert(isHumongous(word_size), "word_size should be humongous"); 613 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 614 615 uint first = G1_NULL_HRS_INDEX; 616 if (num_regions == 1) { 617 // Only one region to allocate, no need to go through the slower 618 // path. The caller will attempt the expansion if this fails, so 619 // let's not try to expand here too. 620 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 621 if (hr != NULL) { 622 first = hr->hrs_index(); 623 } else { 624 first = G1_NULL_HRS_INDEX; 625 } 626 } else { 627 // We can't allocate humongous regions while cleanupComplete() is 628 // running, since some of the regions we find to be empty might not 629 // yet be added to the free list and it is not straightforward to 630 // know which list they are on so that we can remove them. Note 631 // that we only need to do this if we need to allocate more than 632 // one region to satisfy the current humongous allocation 633 // request. If we are only allocating one region we use the common 634 // region allocation code (see above). 635 wait_while_free_regions_coming(); 636 append_secondary_free_list_if_not_empty_with_lock(); 637 638 if (free_regions() >= num_regions) { 639 first = _hrs.find_contiguous(num_regions); 640 if (first != G1_NULL_HRS_INDEX) { 641 for (uint i = first; i < first + num_regions; ++i) { 642 HeapRegion* hr = region_at(i); 643 assert(hr->is_empty(), "sanity"); 644 assert(is_on_master_free_list(hr), "sanity"); 645 hr->set_pending_removal(true); 646 } 647 _free_list.remove_all_pending(num_regions); 648 } 649 } 650 } 651 return first; 652 } 653 654 HeapWord* 655 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 656 uint num_regions, 657 size_t word_size) { 658 assert(first != G1_NULL_HRS_INDEX, "pre-condition"); 659 assert(isHumongous(word_size), "word_size should be humongous"); 660 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 661 662 // Index of last region in the series + 1. 663 uint last = first + num_regions; 664 665 // We need to initialize the region(s) we just discovered. This is 666 // a bit tricky given that it can happen concurrently with 667 // refinement threads refining cards on these regions and 668 // potentially wanting to refine the BOT as they are scanning 669 // those cards (this can happen shortly after a cleanup; see CR 670 // 6991377). So we have to set up the region(s) carefully and in 671 // a specific order. 672 673 // The word size sum of all the regions we will allocate. 674 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 675 assert(word_size <= word_size_sum, "sanity"); 676 677 // This will be the "starts humongous" region. 678 HeapRegion* first_hr = region_at(first); 679 // The header of the new object will be placed at the bottom of 680 // the first region. 681 HeapWord* new_obj = first_hr->bottom(); 682 // This will be the new end of the first region in the series that 683 // should also match the end of the last region in the series. 684 HeapWord* new_end = new_obj + word_size_sum; 685 // This will be the new top of the first region that will reflect 686 // this allocation. 687 HeapWord* new_top = new_obj + word_size; 688 689 // First, we need to zero the header of the space that we will be 690 // allocating. When we update top further down, some refinement 691 // threads might try to scan the region. By zeroing the header we 692 // ensure that any thread that will try to scan the region will 693 // come across the zero klass word and bail out. 694 // 695 // NOTE: It would not have been correct to have used 696 // CollectedHeap::fill_with_object() and make the space look like 697 // an int array. The thread that is doing the allocation will 698 // later update the object header to a potentially different array 699 // type and, for a very short period of time, the klass and length 700 // fields will be inconsistent. This could cause a refinement 701 // thread to calculate the object size incorrectly. 702 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 703 704 // We will set up the first region as "starts humongous". This 705 // will also update the BOT covering all the regions to reflect 706 // that there is a single object that starts at the bottom of the 707 // first region. 708 first_hr->set_startsHumongous(new_top, new_end); 709 710 // Then, if there are any, we will set up the "continues 711 // humongous" regions. 712 HeapRegion* hr = NULL; 713 for (uint i = first + 1; i < last; ++i) { 714 hr = region_at(i); 715 hr->set_continuesHumongous(first_hr); 716 } 717 // If we have "continues humongous" regions (hr != NULL), then the 718 // end of the last one should match new_end. 719 assert(hr == NULL || hr->end() == new_end, "sanity"); 720 721 // Up to this point no concurrent thread would have been able to 722 // do any scanning on any region in this series. All the top 723 // fields still point to bottom, so the intersection between 724 // [bottom,top] and [card_start,card_end] will be empty. Before we 725 // update the top fields, we'll do a storestore to make sure that 726 // no thread sees the update to top before the zeroing of the 727 // object header and the BOT initialization. 728 OrderAccess::storestore(); 729 730 // Now that the BOT and the object header have been initialized, 731 // we can update top of the "starts humongous" region. 732 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 733 "new_top should be in this region"); 734 first_hr->set_top(new_top); 735 if (_hr_printer.is_active()) { 736 HeapWord* bottom = first_hr->bottom(); 737 HeapWord* end = first_hr->orig_end(); 738 if ((first + 1) == last) { 739 // the series has a single humongous region 740 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 741 } else { 742 // the series has more than one humongous regions 743 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 744 } 745 } 746 747 // Now, we will update the top fields of the "continues humongous" 748 // regions. The reason we need to do this is that, otherwise, 749 // these regions would look empty and this will confuse parts of 750 // G1. For example, the code that looks for a consecutive number 751 // of empty regions will consider them empty and try to 752 // re-allocate them. We can extend is_empty() to also include 753 // !continuesHumongous(), but it is easier to just update the top 754 // fields here. The way we set top for all regions (i.e., top == 755 // end for all regions but the last one, top == new_top for the 756 // last one) is actually used when we will free up the humongous 757 // region in free_humongous_region(). 758 hr = NULL; 759 for (uint i = first + 1; i < last; ++i) { 760 hr = region_at(i); 761 if ((i + 1) == last) { 762 // last continues humongous region 763 assert(hr->bottom() < new_top && new_top <= hr->end(), 764 "new_top should fall on this region"); 765 hr->set_top(new_top); 766 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 767 } else { 768 // not last one 769 assert(new_top > hr->end(), "new_top should be above this region"); 770 hr->set_top(hr->end()); 771 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 772 } 773 } 774 // If we have continues humongous regions (hr != NULL), then the 775 // end of the last one should match new_end and its top should 776 // match new_top. 777 assert(hr == NULL || 778 (hr->end() == new_end && hr->top() == new_top), "sanity"); 779 780 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 781 _summary_bytes_used += first_hr->used(); 782 _humongous_set.add(first_hr); 783 784 return new_obj; 785 } 786 787 // If could fit into free regions w/o expansion, try. 788 // Otherwise, if can expand, do so. 789 // Otherwise, if using ex regions might help, try with ex given back. 790 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 791 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 792 793 verify_region_sets_optional(); 794 795 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords); 796 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords); 797 uint x_num = expansion_regions(); 798 uint fs = _hrs.free_suffix(); 799 uint first = humongous_obj_allocate_find_first(num_regions, word_size); 800 if (first == G1_NULL_HRS_INDEX) { 801 // The only thing we can do now is attempt expansion. 802 if (fs + x_num >= num_regions) { 803 // If the number of regions we're trying to allocate for this 804 // object is at most the number of regions in the free suffix, 805 // then the call to humongous_obj_allocate_find_first() above 806 // should have succeeded and we wouldn't be here. 807 // 808 // We should only be trying to expand when the free suffix is 809 // not sufficient for the object _and_ we have some expansion 810 // room available. 811 assert(num_regions > fs, "earlier allocation should have succeeded"); 812 813 ergo_verbose1(ErgoHeapSizing, 814 "attempt heap expansion", 815 ergo_format_reason("humongous allocation request failed") 816 ergo_format_byte("allocation request"), 817 word_size * HeapWordSize); 818 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) { 819 // Even though the heap was expanded, it might not have 820 // reached the desired size. So, we cannot assume that the 821 // allocation will succeed. 822 first = humongous_obj_allocate_find_first(num_regions, word_size); 823 } 824 } 825 } 826 827 HeapWord* result = NULL; 828 if (first != G1_NULL_HRS_INDEX) { 829 result = 830 humongous_obj_allocate_initialize_regions(first, num_regions, word_size); 831 assert(result != NULL, "it should always return a valid result"); 832 833 // A successful humongous object allocation changes the used space 834 // information of the old generation so we need to recalculate the 835 // sizes and update the jstat counters here. 836 g1mm()->update_sizes(); 837 } 838 839 verify_region_sets_optional(); 840 841 return result; 842 } 843 844 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 845 assert_heap_not_locked_and_not_at_safepoint(); 846 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 847 848 unsigned int dummy_gc_count_before; 849 int dummy_gclocker_retry_count = 0; 850 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 851 } 852 853 HeapWord* 854 G1CollectedHeap::mem_allocate(size_t word_size, 855 bool* gc_overhead_limit_was_exceeded) { 856 assert_heap_not_locked_and_not_at_safepoint(); 857 858 // Loop until the allocation is satisfied, or unsatisfied after GC. 859 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 860 unsigned int gc_count_before; 861 862 HeapWord* result = NULL; 863 if (!isHumongous(word_size)) { 864 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 865 } else { 866 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 867 } 868 if (result != NULL) { 869 return result; 870 } 871 872 // Create the garbage collection operation... 873 VM_G1CollectForAllocation op(gc_count_before, word_size); 874 // ...and get the VM thread to execute it. 875 VMThread::execute(&op); 876 877 if (op.prologue_succeeded() && op.pause_succeeded()) { 878 // If the operation was successful we'll return the result even 879 // if it is NULL. If the allocation attempt failed immediately 880 // after a Full GC, it's unlikely we'll be able to allocate now. 881 HeapWord* result = op.result(); 882 if (result != NULL && !isHumongous(word_size)) { 883 // Allocations that take place on VM operations do not do any 884 // card dirtying and we have to do it here. We only have to do 885 // this for non-humongous allocations, though. 886 dirty_young_block(result, word_size); 887 } 888 return result; 889 } else { 890 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 891 return NULL; 892 } 893 assert(op.result() == NULL, 894 "the result should be NULL if the VM op did not succeed"); 895 } 896 897 // Give a warning if we seem to be looping forever. 898 if ((QueuedAllocationWarningCount > 0) && 899 (try_count % QueuedAllocationWarningCount == 0)) { 900 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 901 } 902 } 903 904 ShouldNotReachHere(); 905 return NULL; 906 } 907 908 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 909 unsigned int *gc_count_before_ret, 910 int* gclocker_retry_count_ret) { 911 // Make sure you read the note in attempt_allocation_humongous(). 912 913 assert_heap_not_locked_and_not_at_safepoint(); 914 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 915 "be called for humongous allocation requests"); 916 917 // We should only get here after the first-level allocation attempt 918 // (attempt_allocation()) failed to allocate. 919 920 // We will loop until a) we manage to successfully perform the 921 // allocation or b) we successfully schedule a collection which 922 // fails to perform the allocation. b) is the only case when we'll 923 // return NULL. 924 HeapWord* result = NULL; 925 for (int try_count = 1; /* we'll return */; try_count += 1) { 926 bool should_try_gc; 927 unsigned int gc_count_before; 928 929 { 930 MutexLockerEx x(Heap_lock); 931 932 result = _mutator_alloc_region.attempt_allocation_locked(word_size, 933 false /* bot_updates */); 934 if (result != NULL) { 935 return result; 936 } 937 938 // If we reach here, attempt_allocation_locked() above failed to 939 // allocate a new region. So the mutator alloc region should be NULL. 940 assert(_mutator_alloc_region.get() == NULL, "only way to get here"); 941 942 if (GC_locker::is_active_and_needs_gc()) { 943 if (g1_policy()->can_expand_young_list()) { 944 // No need for an ergo verbose message here, 945 // can_expand_young_list() does this when it returns true. 946 result = _mutator_alloc_region.attempt_allocation_force(word_size, 947 false /* bot_updates */); 948 if (result != NULL) { 949 return result; 950 } 951 } 952 should_try_gc = false; 953 } else { 954 // The GCLocker may not be active but the GCLocker initiated 955 // GC may not yet have been performed (GCLocker::needs_gc() 956 // returns true). In this case we do not try this GC and 957 // wait until the GCLocker initiated GC is performed, and 958 // then retry the allocation. 959 if (GC_locker::needs_gc()) { 960 should_try_gc = false; 961 } else { 962 // Read the GC count while still holding the Heap_lock. 963 gc_count_before = total_collections(); 964 should_try_gc = true; 965 } 966 } 967 } 968 969 if (should_try_gc) { 970 bool succeeded; 971 result = do_collection_pause(word_size, gc_count_before, &succeeded, 972 GCCause::_g1_inc_collection_pause); 973 if (result != NULL) { 974 assert(succeeded, "only way to get back a non-NULL result"); 975 return result; 976 } 977 978 if (succeeded) { 979 // If we get here we successfully scheduled a collection which 980 // failed to allocate. No point in trying to allocate 981 // further. We'll just return NULL. 982 MutexLockerEx x(Heap_lock); 983 *gc_count_before_ret = total_collections(); 984 return NULL; 985 } 986 } else { 987 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 988 MutexLockerEx x(Heap_lock); 989 *gc_count_before_ret = total_collections(); 990 return NULL; 991 } 992 // The GCLocker is either active or the GCLocker initiated 993 // GC has not yet been performed. Stall until it is and 994 // then retry the allocation. 995 GC_locker::stall_until_clear(); 996 (*gclocker_retry_count_ret) += 1; 997 } 998 999 // We can reach here if we were unsuccessful in scheduling a 1000 // collection (because another thread beat us to it) or if we were 1001 // stalled due to the GC locker. In either can we should retry the 1002 // allocation attempt in case another thread successfully 1003 // performed a collection and reclaimed enough space. We do the 1004 // first attempt (without holding the Heap_lock) here and the 1005 // follow-on attempt will be at the start of the next loop 1006 // iteration (after taking the Heap_lock). 1007 result = _mutator_alloc_region.attempt_allocation(word_size, 1008 false /* bot_updates */); 1009 if (result != NULL) { 1010 return result; 1011 } 1012 1013 // Give a warning if we seem to be looping forever. 1014 if ((QueuedAllocationWarningCount > 0) && 1015 (try_count % QueuedAllocationWarningCount == 0)) { 1016 warning("G1CollectedHeap::attempt_allocation_slow() " 1017 "retries %d times", try_count); 1018 } 1019 } 1020 1021 ShouldNotReachHere(); 1022 return NULL; 1023 } 1024 1025 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1026 unsigned int * gc_count_before_ret, 1027 int* gclocker_retry_count_ret) { 1028 // The structure of this method has a lot of similarities to 1029 // attempt_allocation_slow(). The reason these two were not merged 1030 // into a single one is that such a method would require several "if 1031 // allocation is not humongous do this, otherwise do that" 1032 // conditional paths which would obscure its flow. In fact, an early 1033 // version of this code did use a unified method which was harder to 1034 // follow and, as a result, it had subtle bugs that were hard to 1035 // track down. So keeping these two methods separate allows each to 1036 // be more readable. It will be good to keep these two in sync as 1037 // much as possible. 1038 1039 assert_heap_not_locked_and_not_at_safepoint(); 1040 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1041 "should only be called for humongous allocations"); 1042 1043 // Humongous objects can exhaust the heap quickly, so we should check if we 1044 // need to start a marking cycle at each humongous object allocation. We do 1045 // the check before we do the actual allocation. The reason for doing it 1046 // before the allocation is that we avoid having to keep track of the newly 1047 // allocated memory while we do a GC. 1048 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1049 word_size)) { 1050 collect(GCCause::_g1_humongous_allocation); 1051 } 1052 1053 // We will loop until a) we manage to successfully perform the 1054 // allocation or b) we successfully schedule a collection which 1055 // fails to perform the allocation. b) is the only case when we'll 1056 // return NULL. 1057 HeapWord* result = NULL; 1058 for (int try_count = 1; /* we'll return */; try_count += 1) { 1059 bool should_try_gc; 1060 unsigned int gc_count_before; 1061 1062 { 1063 MutexLockerEx x(Heap_lock); 1064 1065 // Given that humongous objects are not allocated in young 1066 // regions, we'll first try to do the allocation without doing a 1067 // collection hoping that there's enough space in the heap. 1068 result = humongous_obj_allocate(word_size); 1069 if (result != NULL) { 1070 return result; 1071 } 1072 1073 if (GC_locker::is_active_and_needs_gc()) { 1074 should_try_gc = false; 1075 } else { 1076 // The GCLocker may not be active but the GCLocker initiated 1077 // GC may not yet have been performed (GCLocker::needs_gc() 1078 // returns true). In this case we do not try this GC and 1079 // wait until the GCLocker initiated GC is performed, and 1080 // then retry the allocation. 1081 if (GC_locker::needs_gc()) { 1082 should_try_gc = false; 1083 } else { 1084 // Read the GC count while still holding the Heap_lock. 1085 gc_count_before = total_collections(); 1086 should_try_gc = true; 1087 } 1088 } 1089 } 1090 1091 if (should_try_gc) { 1092 // If we failed to allocate the humongous object, we should try to 1093 // do a collection pause (if we're allowed) in case it reclaims 1094 // enough space for the allocation to succeed after the pause. 1095 1096 bool succeeded; 1097 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1098 GCCause::_g1_humongous_allocation); 1099 if (result != NULL) { 1100 assert(succeeded, "only way to get back a non-NULL result"); 1101 return result; 1102 } 1103 1104 if (succeeded) { 1105 // If we get here we successfully scheduled a collection which 1106 // failed to allocate. No point in trying to allocate 1107 // further. We'll just return NULL. 1108 MutexLockerEx x(Heap_lock); 1109 *gc_count_before_ret = total_collections(); 1110 return NULL; 1111 } 1112 } else { 1113 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1114 MutexLockerEx x(Heap_lock); 1115 *gc_count_before_ret = total_collections(); 1116 return NULL; 1117 } 1118 // The GCLocker is either active or the GCLocker initiated 1119 // GC has not yet been performed. Stall until it is and 1120 // then retry the allocation. 1121 GC_locker::stall_until_clear(); 1122 (*gclocker_retry_count_ret) += 1; 1123 } 1124 1125 // We can reach here if we were unsuccessful in scheduling a 1126 // collection (because another thread beat us to it) or if we were 1127 // stalled due to the GC locker. In either can we should retry the 1128 // allocation attempt in case another thread successfully 1129 // performed a collection and reclaimed enough space. Give a 1130 // warning if we seem to be looping forever. 1131 1132 if ((QueuedAllocationWarningCount > 0) && 1133 (try_count % QueuedAllocationWarningCount == 0)) { 1134 warning("G1CollectedHeap::attempt_allocation_humongous() " 1135 "retries %d times", try_count); 1136 } 1137 } 1138 1139 ShouldNotReachHere(); 1140 return NULL; 1141 } 1142 1143 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1144 bool expect_null_mutator_alloc_region) { 1145 assert_at_safepoint(true /* should_be_vm_thread */); 1146 assert(_mutator_alloc_region.get() == NULL || 1147 !expect_null_mutator_alloc_region, 1148 "the current alloc region was unexpectedly found to be non-NULL"); 1149 1150 if (!isHumongous(word_size)) { 1151 return _mutator_alloc_region.attempt_allocation_locked(word_size, 1152 false /* bot_updates */); 1153 } else { 1154 HeapWord* result = humongous_obj_allocate(word_size); 1155 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1156 g1_policy()->set_initiate_conc_mark_if_possible(); 1157 } 1158 return result; 1159 } 1160 1161 ShouldNotReachHere(); 1162 } 1163 1164 class PostMCRemSetClearClosure: public HeapRegionClosure { 1165 G1CollectedHeap* _g1h; 1166 ModRefBarrierSet* _mr_bs; 1167 public: 1168 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1169 _g1h(g1h), _mr_bs(mr_bs) {} 1170 1171 bool doHeapRegion(HeapRegion* r) { 1172 HeapRegionRemSet* hrrs = r->rem_set(); 1173 1174 if (r->continuesHumongous()) { 1175 // We'll assert that the strong code root list and RSet is empty 1176 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1177 assert(hrrs->occupied() == 0, "RSet should be empty"); 1178 return false; 1179 } 1180 1181 _g1h->reset_gc_time_stamps(r); 1182 hrrs->clear(); 1183 // You might think here that we could clear just the cards 1184 // corresponding to the used region. But no: if we leave a dirty card 1185 // in a region we might allocate into, then it would prevent that card 1186 // from being enqueued, and cause it to be missed. 1187 // Re: the performance cost: we shouldn't be doing full GC anyway! 1188 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1189 1190 return false; 1191 } 1192 }; 1193 1194 void G1CollectedHeap::clear_rsets_post_compaction() { 1195 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1196 heap_region_iterate(&rs_clear); 1197 } 1198 1199 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1200 G1CollectedHeap* _g1h; 1201 UpdateRSOopClosure _cl; 1202 int _worker_i; 1203 public: 1204 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1205 _cl(g1->g1_rem_set(), worker_i), 1206 _worker_i(worker_i), 1207 _g1h(g1) 1208 { } 1209 1210 bool doHeapRegion(HeapRegion* r) { 1211 if (!r->continuesHumongous()) { 1212 _cl.set_from(r); 1213 r->oop_iterate(&_cl); 1214 } 1215 return false; 1216 } 1217 }; 1218 1219 class ParRebuildRSTask: public AbstractGangTask { 1220 G1CollectedHeap* _g1; 1221 public: 1222 ParRebuildRSTask(G1CollectedHeap* g1) 1223 : AbstractGangTask("ParRebuildRSTask"), 1224 _g1(g1) 1225 { } 1226 1227 void work(uint worker_id) { 1228 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1229 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, 1230 _g1->workers()->active_workers(), 1231 HeapRegion::RebuildRSClaimValue); 1232 } 1233 }; 1234 1235 class PostCompactionPrinterClosure: public HeapRegionClosure { 1236 private: 1237 G1HRPrinter* _hr_printer; 1238 public: 1239 bool doHeapRegion(HeapRegion* hr) { 1240 assert(!hr->is_young(), "not expecting to find young regions"); 1241 // We only generate output for non-empty regions. 1242 if (!hr->is_empty()) { 1243 if (!hr->isHumongous()) { 1244 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1245 } else if (hr->startsHumongous()) { 1246 if (hr->region_num() == 1) { 1247 // single humongous region 1248 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1249 } else { 1250 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1251 } 1252 } else { 1253 assert(hr->continuesHumongous(), "only way to get here"); 1254 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1255 } 1256 } 1257 return false; 1258 } 1259 1260 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1261 : _hr_printer(hr_printer) { } 1262 }; 1263 1264 void G1CollectedHeap::print_hrs_post_compaction() { 1265 PostCompactionPrinterClosure cl(hr_printer()); 1266 heap_region_iterate(&cl); 1267 } 1268 1269 bool G1CollectedHeap::do_collection(bool explicit_gc, 1270 bool clear_all_soft_refs, 1271 size_t word_size) { 1272 assert_at_safepoint(true /* should_be_vm_thread */); 1273 1274 if (GC_locker::check_active_before_gc()) { 1275 return false; 1276 } 1277 1278 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1279 gc_timer->register_gc_start(); 1280 1281 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1282 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1283 1284 SvcGCMarker sgcm(SvcGCMarker::FULL); 1285 ResourceMark rm; 1286 1287 print_heap_before_gc(); 1288 trace_heap_before_gc(gc_tracer); 1289 1290 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1291 1292 verify_region_sets_optional(); 1293 1294 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1295 collector_policy()->should_clear_all_soft_refs(); 1296 1297 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1298 1299 { 1300 IsGCActiveMark x; 1301 1302 // Timing 1303 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1304 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); 1305 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1306 1307 { 1308 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id()); 1309 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1310 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1311 1312 double start = os::elapsedTime(); 1313 g1_policy()->record_full_collection_start(); 1314 1315 // Note: When we have a more flexible GC logging framework that 1316 // allows us to add optional attributes to a GC log record we 1317 // could consider timing and reporting how long we wait in the 1318 // following two methods. 1319 wait_while_free_regions_coming(); 1320 // If we start the compaction before the CM threads finish 1321 // scanning the root regions we might trip them over as we'll 1322 // be moving objects / updating references. So let's wait until 1323 // they are done. By telling them to abort, they should complete 1324 // early. 1325 _cm->root_regions()->abort(); 1326 _cm->root_regions()->wait_until_scan_finished(); 1327 append_secondary_free_list_if_not_empty_with_lock(); 1328 1329 gc_prologue(true); 1330 increment_total_collections(true /* full gc */); 1331 increment_old_marking_cycles_started(); 1332 1333 assert(used() == recalculate_used(), "Should be equal"); 1334 1335 verify_before_gc(); 1336 1337 pre_full_gc_dump(gc_timer); 1338 1339 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1340 1341 // Disable discovery and empty the discovered lists 1342 // for the CM ref processor. 1343 ref_processor_cm()->disable_discovery(); 1344 ref_processor_cm()->abandon_partial_discovery(); 1345 ref_processor_cm()->verify_no_references_recorded(); 1346 1347 // Abandon current iterations of concurrent marking and concurrent 1348 // refinement, if any are in progress. We have to do this before 1349 // wait_until_scan_finished() below. 1350 concurrent_mark()->abort(); 1351 1352 // Make sure we'll choose a new allocation region afterwards. 1353 release_mutator_alloc_region(); 1354 abandon_gc_alloc_regions(); 1355 g1_rem_set()->cleanupHRRS(); 1356 1357 // We should call this after we retire any currently active alloc 1358 // regions so that all the ALLOC / RETIRE events are generated 1359 // before the start GC event. 1360 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1361 1362 // We may have added regions to the current incremental collection 1363 // set between the last GC or pause and now. We need to clear the 1364 // incremental collection set and then start rebuilding it afresh 1365 // after this full GC. 1366 abandon_collection_set(g1_policy()->inc_cset_head()); 1367 g1_policy()->clear_incremental_cset(); 1368 g1_policy()->stop_incremental_cset_building(); 1369 1370 tear_down_region_sets(false /* free_list_only */); 1371 g1_policy()->set_gcs_are_young(true); 1372 1373 // See the comments in g1CollectedHeap.hpp and 1374 // G1CollectedHeap::ref_processing_init() about 1375 // how reference processing currently works in G1. 1376 1377 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1378 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1379 1380 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1381 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1382 1383 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1384 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1385 1386 // Do collection work 1387 { 1388 HandleMark hm; // Discard invalid handles created during gc 1389 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1390 } 1391 1392 assert(free_regions() == 0, "we should not have added any free regions"); 1393 rebuild_region_sets(false /* free_list_only */); 1394 1395 // Enqueue any discovered reference objects that have 1396 // not been removed from the discovered lists. 1397 ref_processor_stw()->enqueue_discovered_references(); 1398 1399 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1400 1401 MemoryService::track_memory_usage(); 1402 1403 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1404 ref_processor_stw()->verify_no_references_recorded(); 1405 1406 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1407 ClassLoaderDataGraph::purge(); 1408 MetaspaceAux::verify_metrics(); 1409 1410 // Note: since we've just done a full GC, concurrent 1411 // marking is no longer active. Therefore we need not 1412 // re-enable reference discovery for the CM ref processor. 1413 // That will be done at the start of the next marking cycle. 1414 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1415 ref_processor_cm()->verify_no_references_recorded(); 1416 1417 reset_gc_time_stamp(); 1418 // Since everything potentially moved, we will clear all remembered 1419 // sets, and clear all cards. Later we will rebuild remembered 1420 // sets. We will also reset the GC time stamps of the regions. 1421 clear_rsets_post_compaction(); 1422 check_gc_time_stamps(); 1423 1424 // Resize the heap if necessary. 1425 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1426 1427 if (_hr_printer.is_active()) { 1428 // We should do this after we potentially resize the heap so 1429 // that all the COMMIT / UNCOMMIT events are generated before 1430 // the end GC event. 1431 1432 print_hrs_post_compaction(); 1433 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1434 } 1435 1436 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1437 if (hot_card_cache->use_cache()) { 1438 hot_card_cache->reset_card_counts(); 1439 hot_card_cache->reset_hot_cache(); 1440 } 1441 1442 // Rebuild remembered sets of all regions. 1443 if (G1CollectedHeap::use_parallel_gc_threads()) { 1444 uint n_workers = 1445 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1446 workers()->active_workers(), 1447 Threads::number_of_non_daemon_threads()); 1448 assert(UseDynamicNumberOfGCThreads || 1449 n_workers == workers()->total_workers(), 1450 "If not dynamic should be using all the workers"); 1451 workers()->set_active_workers(n_workers); 1452 // Set parallel threads in the heap (_n_par_threads) only 1453 // before a parallel phase and always reset it to 0 after 1454 // the phase so that the number of parallel threads does 1455 // no get carried forward to a serial phase where there 1456 // may be code that is "possibly_parallel". 1457 set_par_threads(n_workers); 1458 1459 ParRebuildRSTask rebuild_rs_task(this); 1460 assert(check_heap_region_claim_values( 1461 HeapRegion::InitialClaimValue), "sanity check"); 1462 assert(UseDynamicNumberOfGCThreads || 1463 workers()->active_workers() == workers()->total_workers(), 1464 "Unless dynamic should use total workers"); 1465 // Use the most recent number of active workers 1466 assert(workers()->active_workers() > 0, 1467 "Active workers not properly set"); 1468 set_par_threads(workers()->active_workers()); 1469 workers()->run_task(&rebuild_rs_task); 1470 set_par_threads(0); 1471 assert(check_heap_region_claim_values( 1472 HeapRegion::RebuildRSClaimValue), "sanity check"); 1473 reset_heap_region_claim_values(); 1474 } else { 1475 RebuildRSOutOfRegionClosure rebuild_rs(this); 1476 heap_region_iterate(&rebuild_rs); 1477 } 1478 1479 // Rebuild the strong code root lists for each region 1480 rebuild_strong_code_roots(); 1481 1482 if (true) { // FIXME 1483 MetaspaceGC::compute_new_size(); 1484 } 1485 1486 #ifdef TRACESPINNING 1487 ParallelTaskTerminator::print_termination_counts(); 1488 #endif 1489 1490 // Discard all rset updates 1491 JavaThread::dirty_card_queue_set().abandon_logs(); 1492 assert(!G1DeferredRSUpdate 1493 || (G1DeferredRSUpdate && 1494 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1495 1496 _young_list->reset_sampled_info(); 1497 // At this point there should be no regions in the 1498 // entire heap tagged as young. 1499 assert(check_young_list_empty(true /* check_heap */), 1500 "young list should be empty at this point"); 1501 1502 // Update the number of full collections that have been completed. 1503 increment_old_marking_cycles_completed(false /* concurrent */); 1504 1505 _hrs.verify_optional(); 1506 verify_region_sets_optional(); 1507 1508 verify_after_gc(); 1509 1510 // Start a new incremental collection set for the next pause 1511 assert(g1_policy()->collection_set() == NULL, "must be"); 1512 g1_policy()->start_incremental_cset_building(); 1513 1514 // Clear the _cset_fast_test bitmap in anticipation of adding 1515 // regions to the incremental collection set for the next 1516 // evacuation pause. 1517 clear_cset_fast_test(); 1518 1519 init_mutator_alloc_region(); 1520 1521 double end = os::elapsedTime(); 1522 g1_policy()->record_full_collection_end(); 1523 1524 if (G1Log::fine()) { 1525 g1_policy()->print_heap_transition(); 1526 } 1527 1528 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1529 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1530 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1531 // before any GC notifications are raised. 1532 g1mm()->update_sizes(); 1533 1534 gc_epilogue(true); 1535 } 1536 1537 if (G1Log::finer()) { 1538 g1_policy()->print_detailed_heap_transition(true /* full */); 1539 } 1540 1541 print_heap_after_gc(); 1542 trace_heap_after_gc(gc_tracer); 1543 1544 post_full_gc_dump(gc_timer); 1545 1546 gc_timer->register_gc_end(); 1547 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1548 } 1549 1550 return true; 1551 } 1552 1553 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1554 // do_collection() will return whether it succeeded in performing 1555 // the GC. Currently, there is no facility on the 1556 // do_full_collection() API to notify the caller than the collection 1557 // did not succeed (e.g., because it was locked out by the GC 1558 // locker). So, right now, we'll ignore the return value. 1559 bool dummy = do_collection(true, /* explicit_gc */ 1560 clear_all_soft_refs, 1561 0 /* word_size */); 1562 } 1563 1564 // This code is mostly copied from TenuredGeneration. 1565 void 1566 G1CollectedHeap:: 1567 resize_if_necessary_after_full_collection(size_t word_size) { 1568 // Include the current allocation, if any, and bytes that will be 1569 // pre-allocated to support collections, as "used". 1570 const size_t used_after_gc = used(); 1571 const size_t capacity_after_gc = capacity(); 1572 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1573 1574 // This is enforced in arguments.cpp. 1575 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1576 "otherwise the code below doesn't make sense"); 1577 1578 // We don't have floating point command-line arguments 1579 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1580 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1581 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1582 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1583 1584 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1585 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1586 1587 // We have to be careful here as these two calculations can overflow 1588 // 32-bit size_t's. 1589 double used_after_gc_d = (double) used_after_gc; 1590 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1591 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1592 1593 // Let's make sure that they are both under the max heap size, which 1594 // by default will make them fit into a size_t. 1595 double desired_capacity_upper_bound = (double) max_heap_size; 1596 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1597 desired_capacity_upper_bound); 1598 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1599 desired_capacity_upper_bound); 1600 1601 // We can now safely turn them into size_t's. 1602 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1603 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1604 1605 // This assert only makes sense here, before we adjust them 1606 // with respect to the min and max heap size. 1607 assert(minimum_desired_capacity <= maximum_desired_capacity, 1608 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1609 "maximum_desired_capacity = "SIZE_FORMAT, 1610 minimum_desired_capacity, maximum_desired_capacity)); 1611 1612 // Should not be greater than the heap max size. No need to adjust 1613 // it with respect to the heap min size as it's a lower bound (i.e., 1614 // we'll try to make the capacity larger than it, not smaller). 1615 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1616 // Should not be less than the heap min size. No need to adjust it 1617 // with respect to the heap max size as it's an upper bound (i.e., 1618 // we'll try to make the capacity smaller than it, not greater). 1619 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1620 1621 if (capacity_after_gc < minimum_desired_capacity) { 1622 // Don't expand unless it's significant 1623 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1624 ergo_verbose4(ErgoHeapSizing, 1625 "attempt heap expansion", 1626 ergo_format_reason("capacity lower than " 1627 "min desired capacity after Full GC") 1628 ergo_format_byte("capacity") 1629 ergo_format_byte("occupancy") 1630 ergo_format_byte_perc("min desired capacity"), 1631 capacity_after_gc, used_after_gc, 1632 minimum_desired_capacity, (double) MinHeapFreeRatio); 1633 expand(expand_bytes); 1634 1635 // No expansion, now see if we want to shrink 1636 } else if (capacity_after_gc > maximum_desired_capacity) { 1637 // Capacity too large, compute shrinking size 1638 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1639 ergo_verbose4(ErgoHeapSizing, 1640 "attempt heap shrinking", 1641 ergo_format_reason("capacity higher than " 1642 "max desired capacity after Full GC") 1643 ergo_format_byte("capacity") 1644 ergo_format_byte("occupancy") 1645 ergo_format_byte_perc("max desired capacity"), 1646 capacity_after_gc, used_after_gc, 1647 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1648 shrink(shrink_bytes); 1649 } 1650 } 1651 1652 1653 HeapWord* 1654 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1655 bool* succeeded) { 1656 assert_at_safepoint(true /* should_be_vm_thread */); 1657 1658 *succeeded = true; 1659 // Let's attempt the allocation first. 1660 HeapWord* result = 1661 attempt_allocation_at_safepoint(word_size, 1662 false /* expect_null_mutator_alloc_region */); 1663 if (result != NULL) { 1664 assert(*succeeded, "sanity"); 1665 return result; 1666 } 1667 1668 // In a G1 heap, we're supposed to keep allocation from failing by 1669 // incremental pauses. Therefore, at least for now, we'll favor 1670 // expansion over collection. (This might change in the future if we can 1671 // do something smarter than full collection to satisfy a failed alloc.) 1672 result = expand_and_allocate(word_size); 1673 if (result != NULL) { 1674 assert(*succeeded, "sanity"); 1675 return result; 1676 } 1677 1678 // Expansion didn't work, we'll try to do a Full GC. 1679 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1680 false, /* clear_all_soft_refs */ 1681 word_size); 1682 if (!gc_succeeded) { 1683 *succeeded = false; 1684 return NULL; 1685 } 1686 1687 // Retry the allocation 1688 result = attempt_allocation_at_safepoint(word_size, 1689 true /* expect_null_mutator_alloc_region */); 1690 if (result != NULL) { 1691 assert(*succeeded, "sanity"); 1692 return result; 1693 } 1694 1695 // Then, try a Full GC that will collect all soft references. 1696 gc_succeeded = do_collection(false, /* explicit_gc */ 1697 true, /* clear_all_soft_refs */ 1698 word_size); 1699 if (!gc_succeeded) { 1700 *succeeded = false; 1701 return NULL; 1702 } 1703 1704 // Retry the allocation once more 1705 result = attempt_allocation_at_safepoint(word_size, 1706 true /* expect_null_mutator_alloc_region */); 1707 if (result != NULL) { 1708 assert(*succeeded, "sanity"); 1709 return result; 1710 } 1711 1712 assert(!collector_policy()->should_clear_all_soft_refs(), 1713 "Flag should have been handled and cleared prior to this point"); 1714 1715 // What else? We might try synchronous finalization later. If the total 1716 // space available is large enough for the allocation, then a more 1717 // complete compaction phase than we've tried so far might be 1718 // appropriate. 1719 assert(*succeeded, "sanity"); 1720 return NULL; 1721 } 1722 1723 // Attempting to expand the heap sufficiently 1724 // to support an allocation of the given "word_size". If 1725 // successful, perform the allocation and return the address of the 1726 // allocated block, or else "NULL". 1727 1728 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1729 assert_at_safepoint(true /* should_be_vm_thread */); 1730 1731 verify_region_sets_optional(); 1732 1733 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1734 ergo_verbose1(ErgoHeapSizing, 1735 "attempt heap expansion", 1736 ergo_format_reason("allocation request failed") 1737 ergo_format_byte("allocation request"), 1738 word_size * HeapWordSize); 1739 if (expand(expand_bytes)) { 1740 _hrs.verify_optional(); 1741 verify_region_sets_optional(); 1742 return attempt_allocation_at_safepoint(word_size, 1743 false /* expect_null_mutator_alloc_region */); 1744 } 1745 return NULL; 1746 } 1747 1748 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1749 HeapWord* new_end) { 1750 assert(old_end != new_end, "don't call this otherwise"); 1751 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1752 1753 // Update the committed mem region. 1754 _g1_committed.set_end(new_end); 1755 // Tell the card table about the update. 1756 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1757 // Tell the BOT about the update. 1758 _bot_shared->resize(_g1_committed.word_size()); 1759 // Tell the hot card cache about the update 1760 _cg1r->hot_card_cache()->resize_card_counts(capacity()); 1761 } 1762 1763 bool G1CollectedHeap::expand(size_t expand_bytes) { 1764 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1765 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1766 HeapRegion::GrainBytes); 1767 ergo_verbose2(ErgoHeapSizing, 1768 "expand the heap", 1769 ergo_format_byte("requested expansion amount") 1770 ergo_format_byte("attempted expansion amount"), 1771 expand_bytes, aligned_expand_bytes); 1772 1773 if (_g1_storage.uncommitted_size() == 0) { 1774 ergo_verbose0(ErgoHeapSizing, 1775 "did not expand the heap", 1776 ergo_format_reason("heap already fully expanded")); 1777 return false; 1778 } 1779 1780 // First commit the memory. 1781 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1782 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1783 if (successful) { 1784 // Then propagate this update to the necessary data structures. 1785 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1786 update_committed_space(old_end, new_end); 1787 1788 FreeRegionList expansion_list("Local Expansion List"); 1789 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1790 assert(mr.start() == old_end, "post-condition"); 1791 // mr might be a smaller region than what was requested if 1792 // expand_by() was unable to allocate the HeapRegion instances 1793 assert(mr.end() <= new_end, "post-condition"); 1794 1795 size_t actual_expand_bytes = mr.byte_size(); 1796 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1797 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1798 "post-condition"); 1799 if (actual_expand_bytes < aligned_expand_bytes) { 1800 // We could not expand _hrs to the desired size. In this case we 1801 // need to shrink the committed space accordingly. 1802 assert(mr.end() < new_end, "invariant"); 1803 1804 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1805 // First uncommit the memory. 1806 _g1_storage.shrink_by(diff_bytes); 1807 // Then propagate this update to the necessary data structures. 1808 update_committed_space(new_end, mr.end()); 1809 } 1810 _free_list.add_as_tail(&expansion_list); 1811 1812 if (_hr_printer.is_active()) { 1813 HeapWord* curr = mr.start(); 1814 while (curr < mr.end()) { 1815 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1816 _hr_printer.commit(curr, curr_end); 1817 curr = curr_end; 1818 } 1819 assert(curr == mr.end(), "post-condition"); 1820 } 1821 g1_policy()->record_new_heap_size(n_regions()); 1822 } else { 1823 ergo_verbose0(ErgoHeapSizing, 1824 "did not expand the heap", 1825 ergo_format_reason("heap expansion operation failed")); 1826 // The expansion of the virtual storage space was unsuccessful. 1827 // Let's see if it was because we ran out of swap. 1828 if (G1ExitOnExpansionFailure && 1829 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1830 // We had head room... 1831 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1832 } 1833 } 1834 return successful; 1835 } 1836 1837 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1838 size_t aligned_shrink_bytes = 1839 ReservedSpace::page_align_size_down(shrink_bytes); 1840 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1841 HeapRegion::GrainBytes); 1842 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1843 1844 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove); 1845 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1846 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1847 1848 ergo_verbose3(ErgoHeapSizing, 1849 "shrink the heap", 1850 ergo_format_byte("requested shrinking amount") 1851 ergo_format_byte("aligned shrinking amount") 1852 ergo_format_byte("attempted shrinking amount"), 1853 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1854 if (num_regions_removed > 0) { 1855 _g1_storage.shrink_by(shrunk_bytes); 1856 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1857 1858 if (_hr_printer.is_active()) { 1859 HeapWord* curr = old_end; 1860 while (curr > new_end) { 1861 HeapWord* curr_end = curr; 1862 curr -= HeapRegion::GrainWords; 1863 _hr_printer.uncommit(curr, curr_end); 1864 } 1865 } 1866 1867 _expansion_regions += num_regions_removed; 1868 update_committed_space(old_end, new_end); 1869 HeapRegionRemSet::shrink_heap(n_regions()); 1870 g1_policy()->record_new_heap_size(n_regions()); 1871 } else { 1872 ergo_verbose0(ErgoHeapSizing, 1873 "did not shrink the heap", 1874 ergo_format_reason("heap shrinking operation failed")); 1875 } 1876 } 1877 1878 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1879 verify_region_sets_optional(); 1880 1881 // We should only reach here at the end of a Full GC which means we 1882 // should not not be holding to any GC alloc regions. The method 1883 // below will make sure of that and do any remaining clean up. 1884 abandon_gc_alloc_regions(); 1885 1886 // Instead of tearing down / rebuilding the free lists here, we 1887 // could instead use the remove_all_pending() method on free_list to 1888 // remove only the ones that we need to remove. 1889 tear_down_region_sets(true /* free_list_only */); 1890 shrink_helper(shrink_bytes); 1891 rebuild_region_sets(true /* free_list_only */); 1892 1893 _hrs.verify_optional(); 1894 verify_region_sets_optional(); 1895 } 1896 1897 // Public methods. 1898 1899 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1900 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1901 #endif // _MSC_VER 1902 1903 1904 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1905 SharedHeap(policy_), 1906 _g1_policy(policy_), 1907 _dirty_card_queue_set(false), 1908 _into_cset_dirty_card_queue_set(false), 1909 _is_alive_closure_cm(this), 1910 _is_alive_closure_stw(this), 1911 _ref_processor_cm(NULL), 1912 _ref_processor_stw(NULL), 1913 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1914 _bot_shared(NULL), 1915 _evac_failure_scan_stack(NULL), 1916 _mark_in_progress(false), 1917 _cg1r(NULL), _summary_bytes_used(0), 1918 _g1mm(NULL), 1919 _refine_cte_cl(NULL), 1920 _full_collection(false), 1921 _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()), 1922 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1923 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1924 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1925 _free_regions_coming(false), 1926 _young_list(new YoungList(this)), 1927 _gc_time_stamp(0), 1928 _retained_old_gc_alloc_region(NULL), 1929 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1930 _old_plab_stats(OldPLABSize, PLABWeight), 1931 _expand_heap_after_alloc_failure(true), 1932 _surviving_young_words(NULL), 1933 _old_marking_cycles_started(0), 1934 _old_marking_cycles_completed(0), 1935 _concurrent_cycle_started(false), 1936 _in_cset_fast_test(NULL), 1937 _in_cset_fast_test_base(NULL), 1938 _dirty_cards_region_list(NULL), 1939 _worker_cset_start_region(NULL), 1940 _worker_cset_start_region_time_stamp(NULL), 1941 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1942 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1943 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1944 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1945 1946 _g1h = this; 1947 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1948 vm_exit_during_initialization("Failed necessary allocation."); 1949 } 1950 1951 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1952 1953 int n_queues = MAX2((int)ParallelGCThreads, 1); 1954 _task_queues = new RefToScanQueueSet(n_queues); 1955 1956 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1957 assert(n_rem_sets > 0, "Invariant."); 1958 1959 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1960 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1961 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1962 1963 for (int i = 0; i < n_queues; i++) { 1964 RefToScanQueue* q = new RefToScanQueue(); 1965 q->initialize(); 1966 _task_queues->register_queue(i, q); 1967 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1968 } 1969 clear_cset_start_regions(); 1970 1971 // Initialize the G1EvacuationFailureALot counters and flags. 1972 NOT_PRODUCT(reset_evacuation_should_fail();) 1973 1974 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1975 } 1976 1977 jint G1CollectedHeap::initialize() { 1978 CollectedHeap::pre_initialize(); 1979 os::enable_vtime(); 1980 1981 G1Log::init(); 1982 1983 // Necessary to satisfy locking discipline assertions. 1984 1985 MutexLocker x(Heap_lock); 1986 1987 // We have to initialize the printer before committing the heap, as 1988 // it will be used then. 1989 _hr_printer.set_active(G1PrintHeapRegions); 1990 1991 // While there are no constraints in the GC code that HeapWordSize 1992 // be any particular value, there are multiple other areas in the 1993 // system which believe this to be true (e.g. oop->object_size in some 1994 // cases incorrectly returns the size in wordSize units rather than 1995 // HeapWordSize). 1996 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1997 1998 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1999 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 2000 size_t heap_alignment = collector_policy()->heap_alignment(); 2001 2002 // Ensure that the sizes are properly aligned. 2003 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2004 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2005 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 2006 2007 _cg1r = new ConcurrentG1Refine(this); 2008 2009 // Reserve the maximum. 2010 2011 // When compressed oops are enabled, the preferred heap base 2012 // is calculated by subtracting the requested size from the 2013 // 32Gb boundary and using the result as the base address for 2014 // heap reservation. If the requested size is not aligned to 2015 // HeapRegion::GrainBytes (i.e. the alignment that is passed 2016 // into the ReservedHeapSpace constructor) then the actual 2017 // base of the reserved heap may end up differing from the 2018 // address that was requested (i.e. the preferred heap base). 2019 // If this happens then we could end up using a non-optimal 2020 // compressed oops mode. 2021 2022 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 2023 heap_alignment); 2024 2025 // It is important to do this in a way such that concurrent readers can't 2026 // temporarily think something is in the heap. (I've actually seen this 2027 // happen in asserts: DLD.) 2028 _reserved.set_word_size(0); 2029 _reserved.set_start((HeapWord*)heap_rs.base()); 2030 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 2031 2032 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes); 2033 2034 // Create the gen rem set (and barrier set) for the entire reserved region. 2035 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 2036 set_barrier_set(rem_set()->bs()); 2037 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) { 2038 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS"); 2039 return JNI_ENOMEM; 2040 } 2041 2042 // Also create a G1 rem set. 2043 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 2044 2045 // Carve out the G1 part of the heap. 2046 2047 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 2048 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 2049 g1_rs.size()/HeapWordSize); 2050 2051 _g1_storage.initialize(g1_rs, 0); 2052 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 2053 _hrs.initialize((HeapWord*) _g1_reserved.start(), 2054 (HeapWord*) _g1_reserved.end()); 2055 assert(_hrs.max_length() == _expansion_regions, 2056 err_msg("max length: %u expansion regions: %u", 2057 _hrs.max_length(), _expansion_regions)); 2058 2059 // Do later initialization work for concurrent refinement. 2060 _cg1r->init(); 2061 2062 // 6843694 - ensure that the maximum region index can fit 2063 // in the remembered set structures. 2064 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2065 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2066 2067 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2068 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2069 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2070 "too many cards per region"); 2071 2072 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 2073 2074 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 2075 heap_word_size(init_byte_size)); 2076 2077 _g1h = this; 2078 2079 _in_cset_fast_test_length = max_regions(); 2080 _in_cset_fast_test_base = 2081 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC); 2082 2083 // We're biasing _in_cset_fast_test to avoid subtracting the 2084 // beginning of the heap every time we want to index; basically 2085 // it's the same with what we do with the card table. 2086 _in_cset_fast_test = _in_cset_fast_test_base - 2087 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); 2088 2089 // Clear the _cset_fast_test bitmap in anticipation of adding 2090 // regions to the incremental collection set for the first 2091 // evacuation pause. 2092 clear_cset_fast_test(); 2093 2094 // Create the ConcurrentMark data structure and thread. 2095 // (Must do this late, so that "max_regions" is defined.) 2096 _cm = new ConcurrentMark(this, heap_rs); 2097 if (_cm == NULL || !_cm->completed_initialization()) { 2098 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2099 return JNI_ENOMEM; 2100 } 2101 _cmThread = _cm->cmThread(); 2102 2103 // Initialize the from_card cache structure of HeapRegionRemSet. 2104 HeapRegionRemSet::init_heap(max_regions()); 2105 2106 // Now expand into the initial heap size. 2107 if (!expand(init_byte_size)) { 2108 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2109 return JNI_ENOMEM; 2110 } 2111 2112 // Perform any initialization actions delegated to the policy. 2113 g1_policy()->init(); 2114 2115 _refine_cte_cl = 2116 new RefineCardTableEntryClosure(g1_rem_set(), 2117 concurrent_g1_refine()); 2118 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 2119 2120 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2121 SATB_Q_FL_lock, 2122 G1SATBProcessCompletedThreshold, 2123 Shared_SATB_Q_lock); 2124 2125 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2126 DirtyCardQ_FL_lock, 2127 concurrent_g1_refine()->yellow_zone(), 2128 concurrent_g1_refine()->red_zone(), 2129 Shared_DirtyCardQ_lock); 2130 2131 if (G1DeferredRSUpdate) { 2132 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2133 DirtyCardQ_FL_lock, 2134 -1, // never trigger processing 2135 -1, // no limit on length 2136 Shared_DirtyCardQ_lock, 2137 &JavaThread::dirty_card_queue_set()); 2138 } 2139 2140 // Initialize the card queue set used to hold cards containing 2141 // references into the collection set. 2142 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, 2143 DirtyCardQ_FL_lock, 2144 -1, // never trigger processing 2145 -1, // no limit on length 2146 Shared_DirtyCardQ_lock, 2147 &JavaThread::dirty_card_queue_set()); 2148 2149 // In case we're keeping closure specialization stats, initialize those 2150 // counts and that mechanism. 2151 SpecializationStats::clear(); 2152 2153 // Here we allocate the dummy full region that is required by the 2154 // G1AllocRegion class. If we don't pass an address in the reserved 2155 // space here, lots of asserts fire. 2156 2157 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2158 _g1_reserved.start()); 2159 // We'll re-use the same region whether the alloc region will 2160 // require BOT updates or not and, if it doesn't, then a non-young 2161 // region will complain that it cannot support allocations without 2162 // BOT updates. So we'll tag the dummy region as young to avoid that. 2163 dummy_region->set_young(); 2164 // Make sure it's full. 2165 dummy_region->set_top(dummy_region->end()); 2166 G1AllocRegion::setup(this, dummy_region); 2167 2168 init_mutator_alloc_region(); 2169 2170 // Do create of the monitoring and management support so that 2171 // values in the heap have been properly initialized. 2172 _g1mm = new G1MonitoringSupport(this); 2173 2174 G1StringDedup::initialize(); 2175 2176 return JNI_OK; 2177 } 2178 2179 void G1CollectedHeap::stop() { 2180 // Stop all concurrent threads. We do this to make sure these threads 2181 // do not continue to execute and access resources (e.g. gclog_or_tty) 2182 // that are destroyed during shutdown. 2183 _cg1r->stop(); 2184 _cmThread->stop(); 2185 if (G1StringDedup::is_enabled()) { 2186 G1StringDedup::stop(); 2187 } 2188 } 2189 2190 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2191 return HeapRegion::max_region_size(); 2192 } 2193 2194 void G1CollectedHeap::ref_processing_init() { 2195 // Reference processing in G1 currently works as follows: 2196 // 2197 // * There are two reference processor instances. One is 2198 // used to record and process discovered references 2199 // during concurrent marking; the other is used to 2200 // record and process references during STW pauses 2201 // (both full and incremental). 2202 // * Both ref processors need to 'span' the entire heap as 2203 // the regions in the collection set may be dotted around. 2204 // 2205 // * For the concurrent marking ref processor: 2206 // * Reference discovery is enabled at initial marking. 2207 // * Reference discovery is disabled and the discovered 2208 // references processed etc during remarking. 2209 // * Reference discovery is MT (see below). 2210 // * Reference discovery requires a barrier (see below). 2211 // * Reference processing may or may not be MT 2212 // (depending on the value of ParallelRefProcEnabled 2213 // and ParallelGCThreads). 2214 // * A full GC disables reference discovery by the CM 2215 // ref processor and abandons any entries on it's 2216 // discovered lists. 2217 // 2218 // * For the STW processor: 2219 // * Non MT discovery is enabled at the start of a full GC. 2220 // * Processing and enqueueing during a full GC is non-MT. 2221 // * During a full GC, references are processed after marking. 2222 // 2223 // * Discovery (may or may not be MT) is enabled at the start 2224 // of an incremental evacuation pause. 2225 // * References are processed near the end of a STW evacuation pause. 2226 // * For both types of GC: 2227 // * Discovery is atomic - i.e. not concurrent. 2228 // * Reference discovery will not need a barrier. 2229 2230 SharedHeap::ref_processing_init(); 2231 MemRegion mr = reserved_region(); 2232 2233 // Concurrent Mark ref processor 2234 _ref_processor_cm = 2235 new ReferenceProcessor(mr, // span 2236 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2237 // mt processing 2238 (int) ParallelGCThreads, 2239 // degree of mt processing 2240 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2241 // mt discovery 2242 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2243 // degree of mt discovery 2244 false, 2245 // Reference discovery is not atomic 2246 &_is_alive_closure_cm); 2247 // is alive closure 2248 // (for efficiency/performance) 2249 2250 // STW ref processor 2251 _ref_processor_stw = 2252 new ReferenceProcessor(mr, // span 2253 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2254 // mt processing 2255 MAX2((int)ParallelGCThreads, 1), 2256 // degree of mt processing 2257 (ParallelGCThreads > 1), 2258 // mt discovery 2259 MAX2((int)ParallelGCThreads, 1), 2260 // degree of mt discovery 2261 true, 2262 // Reference discovery is atomic 2263 &_is_alive_closure_stw); 2264 // is alive closure 2265 // (for efficiency/performance) 2266 } 2267 2268 size_t G1CollectedHeap::capacity() const { 2269 return _g1_committed.byte_size(); 2270 } 2271 2272 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2273 assert(!hr->continuesHumongous(), "pre-condition"); 2274 hr->reset_gc_time_stamp(); 2275 if (hr->startsHumongous()) { 2276 uint first_index = hr->hrs_index() + 1; 2277 uint last_index = hr->last_hc_index(); 2278 for (uint i = first_index; i < last_index; i += 1) { 2279 HeapRegion* chr = region_at(i); 2280 assert(chr->continuesHumongous(), "sanity"); 2281 chr->reset_gc_time_stamp(); 2282 } 2283 } 2284 } 2285 2286 #ifndef PRODUCT 2287 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2288 private: 2289 unsigned _gc_time_stamp; 2290 bool _failures; 2291 2292 public: 2293 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2294 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2295 2296 virtual bool doHeapRegion(HeapRegion* hr) { 2297 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2298 if (_gc_time_stamp != region_gc_time_stamp) { 2299 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2300 "expected %d", HR_FORMAT_PARAMS(hr), 2301 region_gc_time_stamp, _gc_time_stamp); 2302 _failures = true; 2303 } 2304 return false; 2305 } 2306 2307 bool failures() { return _failures; } 2308 }; 2309 2310 void G1CollectedHeap::check_gc_time_stamps() { 2311 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2312 heap_region_iterate(&cl); 2313 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2314 } 2315 #endif // PRODUCT 2316 2317 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2318 DirtyCardQueue* into_cset_dcq, 2319 bool concurrent, 2320 uint worker_i) { 2321 // Clean cards in the hot card cache 2322 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2323 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2324 2325 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2326 int n_completed_buffers = 0; 2327 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2328 n_completed_buffers++; 2329 } 2330 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2331 dcqs.clear_n_completed_buffers(); 2332 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2333 } 2334 2335 2336 // Computes the sum of the storage used by the various regions. 2337 2338 size_t G1CollectedHeap::used() const { 2339 assert(Heap_lock->owner() != NULL, 2340 "Should be owned on this thread's behalf."); 2341 size_t result = _summary_bytes_used; 2342 // Read only once in case it is set to NULL concurrently 2343 HeapRegion* hr = _mutator_alloc_region.get(); 2344 if (hr != NULL) 2345 result += hr->used(); 2346 return result; 2347 } 2348 2349 size_t G1CollectedHeap::used_unlocked() const { 2350 size_t result = _summary_bytes_used; 2351 return result; 2352 } 2353 2354 class SumUsedClosure: public HeapRegionClosure { 2355 size_t _used; 2356 public: 2357 SumUsedClosure() : _used(0) {} 2358 bool doHeapRegion(HeapRegion* r) { 2359 if (!r->continuesHumongous()) { 2360 _used += r->used(); 2361 } 2362 return false; 2363 } 2364 size_t result() { return _used; } 2365 }; 2366 2367 size_t G1CollectedHeap::recalculate_used() const { 2368 double recalculate_used_start = os::elapsedTime(); 2369 2370 SumUsedClosure blk; 2371 heap_region_iterate(&blk); 2372 2373 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2374 return blk.result(); 2375 } 2376 2377 size_t G1CollectedHeap::unsafe_max_alloc() { 2378 if (free_regions() > 0) return HeapRegion::GrainBytes; 2379 // otherwise, is there space in the current allocation region? 2380 2381 // We need to store the current allocation region in a local variable 2382 // here. The problem is that this method doesn't take any locks and 2383 // there may be other threads which overwrite the current allocation 2384 // region field. attempt_allocation(), for example, sets it to NULL 2385 // and this can happen *after* the NULL check here but before the call 2386 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2387 // to be a problem in the optimized build, since the two loads of the 2388 // current allocation region field are optimized away. 2389 HeapRegion* hr = _mutator_alloc_region.get(); 2390 if (hr == NULL) { 2391 return 0; 2392 } 2393 return hr->free(); 2394 } 2395 2396 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2397 switch (cause) { 2398 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2399 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2400 case GCCause::_g1_humongous_allocation: return true; 2401 default: return false; 2402 } 2403 } 2404 2405 #ifndef PRODUCT 2406 void G1CollectedHeap::allocate_dummy_regions() { 2407 // Let's fill up most of the region 2408 size_t word_size = HeapRegion::GrainWords - 1024; 2409 // And as a result the region we'll allocate will be humongous. 2410 guarantee(isHumongous(word_size), "sanity"); 2411 2412 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2413 // Let's use the existing mechanism for the allocation 2414 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2415 if (dummy_obj != NULL) { 2416 MemRegion mr(dummy_obj, word_size); 2417 CollectedHeap::fill_with_object(mr); 2418 } else { 2419 // If we can't allocate once, we probably cannot allocate 2420 // again. Let's get out of the loop. 2421 break; 2422 } 2423 } 2424 } 2425 #endif // !PRODUCT 2426 2427 void G1CollectedHeap::increment_old_marking_cycles_started() { 2428 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2429 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2430 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2431 _old_marking_cycles_started, _old_marking_cycles_completed)); 2432 2433 _old_marking_cycles_started++; 2434 } 2435 2436 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2437 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2438 2439 // We assume that if concurrent == true, then the caller is a 2440 // concurrent thread that was joined the Suspendible Thread 2441 // Set. If there's ever a cheap way to check this, we should add an 2442 // assert here. 2443 2444 // Given that this method is called at the end of a Full GC or of a 2445 // concurrent cycle, and those can be nested (i.e., a Full GC can 2446 // interrupt a concurrent cycle), the number of full collections 2447 // completed should be either one (in the case where there was no 2448 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2449 // behind the number of full collections started. 2450 2451 // This is the case for the inner caller, i.e. a Full GC. 2452 assert(concurrent || 2453 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2454 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2455 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2456 "is inconsistent with _old_marking_cycles_completed = %u", 2457 _old_marking_cycles_started, _old_marking_cycles_completed)); 2458 2459 // This is the case for the outer caller, i.e. the concurrent cycle. 2460 assert(!concurrent || 2461 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2462 err_msg("for outer caller (concurrent cycle): " 2463 "_old_marking_cycles_started = %u " 2464 "is inconsistent with _old_marking_cycles_completed = %u", 2465 _old_marking_cycles_started, _old_marking_cycles_completed)); 2466 2467 _old_marking_cycles_completed += 1; 2468 2469 // We need to clear the "in_progress" flag in the CM thread before 2470 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2471 // is set) so that if a waiter requests another System.gc() it doesn't 2472 // incorrectly see that a marking cycle is still in progress. 2473 if (concurrent) { 2474 _cmThread->clear_in_progress(); 2475 } 2476 2477 // This notify_all() will ensure that a thread that called 2478 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2479 // and it's waiting for a full GC to finish will be woken up. It is 2480 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2481 FullGCCount_lock->notify_all(); 2482 } 2483 2484 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2485 _concurrent_cycle_started = true; 2486 _gc_timer_cm->register_gc_start(start_time); 2487 2488 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2489 trace_heap_before_gc(_gc_tracer_cm); 2490 } 2491 2492 void G1CollectedHeap::register_concurrent_cycle_end() { 2493 if (_concurrent_cycle_started) { 2494 if (_cm->has_aborted()) { 2495 _gc_tracer_cm->report_concurrent_mode_failure(); 2496 } 2497 2498 _gc_timer_cm->register_gc_end(); 2499 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2500 2501 _concurrent_cycle_started = false; 2502 } 2503 } 2504 2505 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2506 if (_concurrent_cycle_started) { 2507 trace_heap_after_gc(_gc_tracer_cm); 2508 } 2509 } 2510 2511 G1YCType G1CollectedHeap::yc_type() { 2512 bool is_young = g1_policy()->gcs_are_young(); 2513 bool is_initial_mark = g1_policy()->during_initial_mark_pause(); 2514 bool is_during_mark = mark_in_progress(); 2515 2516 if (is_initial_mark) { 2517 return InitialMark; 2518 } else if (is_during_mark) { 2519 return DuringMark; 2520 } else if (is_young) { 2521 return Normal; 2522 } else { 2523 return Mixed; 2524 } 2525 } 2526 2527 void G1CollectedHeap::collect(GCCause::Cause cause) { 2528 assert_heap_not_locked(); 2529 2530 unsigned int gc_count_before; 2531 unsigned int old_marking_count_before; 2532 bool retry_gc; 2533 2534 do { 2535 retry_gc = false; 2536 2537 { 2538 MutexLocker ml(Heap_lock); 2539 2540 // Read the GC count while holding the Heap_lock 2541 gc_count_before = total_collections(); 2542 old_marking_count_before = _old_marking_cycles_started; 2543 } 2544 2545 if (should_do_concurrent_full_gc(cause)) { 2546 // Schedule an initial-mark evacuation pause that will start a 2547 // concurrent cycle. We're setting word_size to 0 which means that 2548 // we are not requesting a post-GC allocation. 2549 VM_G1IncCollectionPause op(gc_count_before, 2550 0, /* word_size */ 2551 true, /* should_initiate_conc_mark */ 2552 g1_policy()->max_pause_time_ms(), 2553 cause); 2554 2555 VMThread::execute(&op); 2556 if (!op.pause_succeeded()) { 2557 if (old_marking_count_before == _old_marking_cycles_started) { 2558 retry_gc = op.should_retry_gc(); 2559 } else { 2560 // A Full GC happened while we were trying to schedule the 2561 // initial-mark GC. No point in starting a new cycle given 2562 // that the whole heap was collected anyway. 2563 } 2564 2565 if (retry_gc) { 2566 if (GC_locker::is_active_and_needs_gc()) { 2567 GC_locker::stall_until_clear(); 2568 } 2569 } 2570 } 2571 } else { 2572 if (cause == GCCause::_gc_locker 2573 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2574 2575 // Schedule a standard evacuation pause. We're setting word_size 2576 // to 0 which means that we are not requesting a post-GC allocation. 2577 VM_G1IncCollectionPause op(gc_count_before, 2578 0, /* word_size */ 2579 false, /* should_initiate_conc_mark */ 2580 g1_policy()->max_pause_time_ms(), 2581 cause); 2582 VMThread::execute(&op); 2583 } else { 2584 // Schedule a Full GC. 2585 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); 2586 VMThread::execute(&op); 2587 } 2588 } 2589 } while (retry_gc); 2590 } 2591 2592 bool G1CollectedHeap::is_in(const void* p) const { 2593 if (_g1_committed.contains(p)) { 2594 // Given that we know that p is in the committed space, 2595 // heap_region_containing_raw() should successfully 2596 // return the containing region. 2597 HeapRegion* hr = heap_region_containing_raw(p); 2598 return hr->is_in(p); 2599 } else { 2600 return false; 2601 } 2602 } 2603 2604 // Iteration functions. 2605 2606 // Iterates an OopClosure over all ref-containing fields of objects 2607 // within a HeapRegion. 2608 2609 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2610 MemRegion _mr; 2611 ExtendedOopClosure* _cl; 2612 public: 2613 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl) 2614 : _mr(mr), _cl(cl) {} 2615 bool doHeapRegion(HeapRegion* r) { 2616 if (!r->continuesHumongous()) { 2617 r->oop_iterate(_cl); 2618 } 2619 return false; 2620 } 2621 }; 2622 2623 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2624 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2625 heap_region_iterate(&blk); 2626 } 2627 2628 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { 2629 IterateOopClosureRegionClosure blk(mr, cl); 2630 heap_region_iterate(&blk); 2631 } 2632 2633 // Iterates an ObjectClosure over all objects within a HeapRegion. 2634 2635 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2636 ObjectClosure* _cl; 2637 public: 2638 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2639 bool doHeapRegion(HeapRegion* r) { 2640 if (! r->continuesHumongous()) { 2641 r->object_iterate(_cl); 2642 } 2643 return false; 2644 } 2645 }; 2646 2647 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2648 IterateObjectClosureRegionClosure blk(cl); 2649 heap_region_iterate(&blk); 2650 } 2651 2652 // Calls a SpaceClosure on a HeapRegion. 2653 2654 class SpaceClosureRegionClosure: public HeapRegionClosure { 2655 SpaceClosure* _cl; 2656 public: 2657 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2658 bool doHeapRegion(HeapRegion* r) { 2659 _cl->do_space(r); 2660 return false; 2661 } 2662 }; 2663 2664 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2665 SpaceClosureRegionClosure blk(cl); 2666 heap_region_iterate(&blk); 2667 } 2668 2669 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2670 _hrs.iterate(cl); 2671 } 2672 2673 void 2674 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2675 uint worker_id, 2676 uint no_of_par_workers, 2677 jint claim_value) { 2678 const uint regions = n_regions(); 2679 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 2680 no_of_par_workers : 2681 1); 2682 assert(UseDynamicNumberOfGCThreads || 2683 no_of_par_workers == workers()->total_workers(), 2684 "Non dynamic should use fixed number of workers"); 2685 // try to spread out the starting points of the workers 2686 const HeapRegion* start_hr = 2687 start_region_for_worker(worker_id, no_of_par_workers); 2688 const uint start_index = start_hr->hrs_index(); 2689 2690 // each worker will actually look at all regions 2691 for (uint count = 0; count < regions; ++count) { 2692 const uint index = (start_index + count) % regions; 2693 assert(0 <= index && index < regions, "sanity"); 2694 HeapRegion* r = region_at(index); 2695 // we'll ignore "continues humongous" regions (we'll process them 2696 // when we come across their corresponding "start humongous" 2697 // region) and regions already claimed 2698 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2699 continue; 2700 } 2701 // OK, try to claim it 2702 if (r->claimHeapRegion(claim_value)) { 2703 // success! 2704 assert(!r->continuesHumongous(), "sanity"); 2705 if (r->startsHumongous()) { 2706 // If the region is "starts humongous" we'll iterate over its 2707 // "continues humongous" first; in fact we'll do them 2708 // first. The order is important. In on case, calling the 2709 // closure on the "starts humongous" region might de-allocate 2710 // and clear all its "continues humongous" regions and, as a 2711 // result, we might end up processing them twice. So, we'll do 2712 // them first (notice: most closures will ignore them anyway) and 2713 // then we'll do the "starts humongous" region. 2714 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) { 2715 HeapRegion* chr = region_at(ch_index); 2716 2717 // if the region has already been claimed or it's not 2718 // "continues humongous" we're done 2719 if (chr->claim_value() == claim_value || 2720 !chr->continuesHumongous()) { 2721 break; 2722 } 2723 2724 // No one should have claimed it directly. We can given 2725 // that we claimed its "starts humongous" region. 2726 assert(chr->claim_value() != claim_value, "sanity"); 2727 assert(chr->humongous_start_region() == r, "sanity"); 2728 2729 if (chr->claimHeapRegion(claim_value)) { 2730 // we should always be able to claim it; no one else should 2731 // be trying to claim this region 2732 2733 bool res2 = cl->doHeapRegion(chr); 2734 assert(!res2, "Should not abort"); 2735 2736 // Right now, this holds (i.e., no closure that actually 2737 // does something with "continues humongous" regions 2738 // clears them). We might have to weaken it in the future, 2739 // but let's leave these two asserts here for extra safety. 2740 assert(chr->continuesHumongous(), "should still be the case"); 2741 assert(chr->humongous_start_region() == r, "sanity"); 2742 } else { 2743 guarantee(false, "we should not reach here"); 2744 } 2745 } 2746 } 2747 2748 assert(!r->continuesHumongous(), "sanity"); 2749 bool res = cl->doHeapRegion(r); 2750 assert(!res, "Should not abort"); 2751 } 2752 } 2753 } 2754 2755 class ResetClaimValuesClosure: public HeapRegionClosure { 2756 public: 2757 bool doHeapRegion(HeapRegion* r) { 2758 r->set_claim_value(HeapRegion::InitialClaimValue); 2759 return false; 2760 } 2761 }; 2762 2763 void G1CollectedHeap::reset_heap_region_claim_values() { 2764 ResetClaimValuesClosure blk; 2765 heap_region_iterate(&blk); 2766 } 2767 2768 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2769 ResetClaimValuesClosure blk; 2770 collection_set_iterate(&blk); 2771 } 2772 2773 #ifdef ASSERT 2774 // This checks whether all regions in the heap have the correct claim 2775 // value. I also piggy-backed on this a check to ensure that the 2776 // humongous_start_region() information on "continues humongous" 2777 // regions is correct. 2778 2779 class CheckClaimValuesClosure : public HeapRegionClosure { 2780 private: 2781 jint _claim_value; 2782 uint _failures; 2783 HeapRegion* _sh_region; 2784 2785 public: 2786 CheckClaimValuesClosure(jint claim_value) : 2787 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2788 bool doHeapRegion(HeapRegion* r) { 2789 if (r->claim_value() != _claim_value) { 2790 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2791 "claim value = %d, should be %d", 2792 HR_FORMAT_PARAMS(r), 2793 r->claim_value(), _claim_value); 2794 ++_failures; 2795 } 2796 if (!r->isHumongous()) { 2797 _sh_region = NULL; 2798 } else if (r->startsHumongous()) { 2799 _sh_region = r; 2800 } else if (r->continuesHumongous()) { 2801 if (r->humongous_start_region() != _sh_region) { 2802 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2803 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2804 HR_FORMAT_PARAMS(r), 2805 r->humongous_start_region(), 2806 _sh_region); 2807 ++_failures; 2808 } 2809 } 2810 return false; 2811 } 2812 uint failures() { return _failures; } 2813 }; 2814 2815 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2816 CheckClaimValuesClosure cl(claim_value); 2817 heap_region_iterate(&cl); 2818 return cl.failures() == 0; 2819 } 2820 2821 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2822 private: 2823 jint _claim_value; 2824 uint _failures; 2825 2826 public: 2827 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2828 _claim_value(claim_value), _failures(0) { } 2829 2830 uint failures() { return _failures; } 2831 2832 bool doHeapRegion(HeapRegion* hr) { 2833 assert(hr->in_collection_set(), "how?"); 2834 assert(!hr->isHumongous(), "H-region in CSet"); 2835 if (hr->claim_value() != _claim_value) { 2836 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2837 "claim value = %d, should be %d", 2838 HR_FORMAT_PARAMS(hr), 2839 hr->claim_value(), _claim_value); 2840 _failures += 1; 2841 } 2842 return false; 2843 } 2844 }; 2845 2846 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2847 CheckClaimValuesInCSetHRClosure cl(claim_value); 2848 collection_set_iterate(&cl); 2849 return cl.failures() == 0; 2850 } 2851 #endif // ASSERT 2852 2853 // Clear the cached CSet starting regions and (more importantly) 2854 // the time stamps. Called when we reset the GC time stamp. 2855 void G1CollectedHeap::clear_cset_start_regions() { 2856 assert(_worker_cset_start_region != NULL, "sanity"); 2857 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2858 2859 int n_queues = MAX2((int)ParallelGCThreads, 1); 2860 for (int i = 0; i < n_queues; i++) { 2861 _worker_cset_start_region[i] = NULL; 2862 _worker_cset_start_region_time_stamp[i] = 0; 2863 } 2864 } 2865 2866 // Given the id of a worker, obtain or calculate a suitable 2867 // starting region for iterating over the current collection set. 2868 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2869 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2870 2871 HeapRegion* result = NULL; 2872 unsigned gc_time_stamp = get_gc_time_stamp(); 2873 2874 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2875 // Cached starting region for current worker was set 2876 // during the current pause - so it's valid. 2877 // Note: the cached starting heap region may be NULL 2878 // (when the collection set is empty). 2879 result = _worker_cset_start_region[worker_i]; 2880 assert(result == NULL || result->in_collection_set(), "sanity"); 2881 return result; 2882 } 2883 2884 // The cached entry was not valid so let's calculate 2885 // a suitable starting heap region for this worker. 2886 2887 // We want the parallel threads to start their collection 2888 // set iteration at different collection set regions to 2889 // avoid contention. 2890 // If we have: 2891 // n collection set regions 2892 // p threads 2893 // Then thread t will start at region floor ((t * n) / p) 2894 2895 result = g1_policy()->collection_set(); 2896 if (G1CollectedHeap::use_parallel_gc_threads()) { 2897 uint cs_size = g1_policy()->cset_region_length(); 2898 uint active_workers = workers()->active_workers(); 2899 assert(UseDynamicNumberOfGCThreads || 2900 active_workers == workers()->total_workers(), 2901 "Unless dynamic should use total workers"); 2902 2903 uint end_ind = (cs_size * worker_i) / active_workers; 2904 uint start_ind = 0; 2905 2906 if (worker_i > 0 && 2907 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2908 // Previous workers starting region is valid 2909 // so let's iterate from there 2910 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2911 result = _worker_cset_start_region[worker_i - 1]; 2912 } 2913 2914 for (uint i = start_ind; i < end_ind; i++) { 2915 result = result->next_in_collection_set(); 2916 } 2917 } 2918 2919 // Note: the calculated starting heap region may be NULL 2920 // (when the collection set is empty). 2921 assert(result == NULL || result->in_collection_set(), "sanity"); 2922 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2923 "should be updated only once per pause"); 2924 _worker_cset_start_region[worker_i] = result; 2925 OrderAccess::storestore(); 2926 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2927 return result; 2928 } 2929 2930 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i, 2931 uint no_of_par_workers) { 2932 uint worker_num = 2933 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U; 2934 assert(UseDynamicNumberOfGCThreads || 2935 no_of_par_workers == workers()->total_workers(), 2936 "Non dynamic should use fixed number of workers"); 2937 const uint start_index = n_regions() * worker_i / worker_num; 2938 return region_at(start_index); 2939 } 2940 2941 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2942 HeapRegion* r = g1_policy()->collection_set(); 2943 while (r != NULL) { 2944 HeapRegion* next = r->next_in_collection_set(); 2945 if (cl->doHeapRegion(r)) { 2946 cl->incomplete(); 2947 return; 2948 } 2949 r = next; 2950 } 2951 } 2952 2953 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2954 HeapRegionClosure *cl) { 2955 if (r == NULL) { 2956 // The CSet is empty so there's nothing to do. 2957 return; 2958 } 2959 2960 assert(r->in_collection_set(), 2961 "Start region must be a member of the collection set."); 2962 HeapRegion* cur = r; 2963 while (cur != NULL) { 2964 HeapRegion* next = cur->next_in_collection_set(); 2965 if (cl->doHeapRegion(cur) && false) { 2966 cl->incomplete(); 2967 return; 2968 } 2969 cur = next; 2970 } 2971 cur = g1_policy()->collection_set(); 2972 while (cur != r) { 2973 HeapRegion* next = cur->next_in_collection_set(); 2974 if (cl->doHeapRegion(cur) && false) { 2975 cl->incomplete(); 2976 return; 2977 } 2978 cur = next; 2979 } 2980 } 2981 2982 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2983 return n_regions() > 0 ? region_at(0) : NULL; 2984 } 2985 2986 2987 Space* G1CollectedHeap::space_containing(const void* addr) const { 2988 Space* res = heap_region_containing(addr); 2989 return res; 2990 } 2991 2992 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2993 Space* sp = space_containing(addr); 2994 if (sp != NULL) { 2995 return sp->block_start(addr); 2996 } 2997 return NULL; 2998 } 2999 3000 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 3001 Space* sp = space_containing(addr); 3002 assert(sp != NULL, "block_size of address outside of heap"); 3003 return sp->block_size(addr); 3004 } 3005 3006 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 3007 Space* sp = space_containing(addr); 3008 return sp->block_is_obj(addr); 3009 } 3010 3011 bool G1CollectedHeap::supports_tlab_allocation() const { 3012 return true; 3013 } 3014 3015 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 3016 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 3017 } 3018 3019 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 3020 return young_list()->eden_used_bytes(); 3021 } 3022 3023 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 3024 // must be smaller than the humongous object limit. 3025 size_t G1CollectedHeap::max_tlab_size() const { 3026 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment); 3027 } 3028 3029 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 3030 // Return the remaining space in the cur alloc region, but not less than 3031 // the min TLAB size. 3032 3033 // Also, this value can be at most the humongous object threshold, 3034 // since we can't allow tlabs to grow big enough to accommodate 3035 // humongous objects. 3036 3037 HeapRegion* hr = _mutator_alloc_region.get(); 3038 size_t max_tlab = max_tlab_size() * wordSize; 3039 if (hr == NULL) { 3040 return max_tlab; 3041 } else { 3042 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab); 3043 } 3044 } 3045 3046 size_t G1CollectedHeap::max_capacity() const { 3047 return _g1_reserved.byte_size(); 3048 } 3049 3050 jlong G1CollectedHeap::millis_since_last_gc() { 3051 // assert(false, "NYI"); 3052 return 0; 3053 } 3054 3055 void G1CollectedHeap::prepare_for_verify() { 3056 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 3057 ensure_parsability(false); 3058 } 3059 g1_rem_set()->prepare_for_verify(); 3060 } 3061 3062 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 3063 VerifyOption vo) { 3064 switch (vo) { 3065 case VerifyOption_G1UsePrevMarking: 3066 return hr->obj_allocated_since_prev_marking(obj); 3067 case VerifyOption_G1UseNextMarking: 3068 return hr->obj_allocated_since_next_marking(obj); 3069 case VerifyOption_G1UseMarkWord: 3070 return false; 3071 default: 3072 ShouldNotReachHere(); 3073 } 3074 return false; // keep some compilers happy 3075 } 3076 3077 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 3078 switch (vo) { 3079 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 3080 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 3081 case VerifyOption_G1UseMarkWord: return NULL; 3082 default: ShouldNotReachHere(); 3083 } 3084 return NULL; // keep some compilers happy 3085 } 3086 3087 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 3088 switch (vo) { 3089 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 3090 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 3091 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 3092 default: ShouldNotReachHere(); 3093 } 3094 return false; // keep some compilers happy 3095 } 3096 3097 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 3098 switch (vo) { 3099 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 3100 case VerifyOption_G1UseNextMarking: return "NTAMS"; 3101 case VerifyOption_G1UseMarkWord: return "NONE"; 3102 default: ShouldNotReachHere(); 3103 } 3104 return NULL; // keep some compilers happy 3105 } 3106 3107 class VerifyRootsClosure: public OopClosure { 3108 private: 3109 G1CollectedHeap* _g1h; 3110 VerifyOption _vo; 3111 bool _failures; 3112 public: 3113 // _vo == UsePrevMarking -> use "prev" marking information, 3114 // _vo == UseNextMarking -> use "next" marking information, 3115 // _vo == UseMarkWord -> use mark word from object header. 3116 VerifyRootsClosure(VerifyOption vo) : 3117 _g1h(G1CollectedHeap::heap()), 3118 _vo(vo), 3119 _failures(false) { } 3120 3121 bool failures() { return _failures; } 3122 3123 template <class T> void do_oop_nv(T* p) { 3124 T heap_oop = oopDesc::load_heap_oop(p); 3125 if (!oopDesc::is_null(heap_oop)) { 3126 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3127 if (_g1h->is_obj_dead_cond(obj, _vo)) { 3128 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 3129 "points to dead obj "PTR_FORMAT, p, (void*) obj); 3130 if (_vo == VerifyOption_G1UseMarkWord) { 3131 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3132 } 3133 obj->print_on(gclog_or_tty); 3134 _failures = true; 3135 } 3136 } 3137 } 3138 3139 void do_oop(oop* p) { do_oop_nv(p); } 3140 void do_oop(narrowOop* p) { do_oop_nv(p); } 3141 }; 3142 3143 class G1VerifyCodeRootOopClosure: public OopClosure { 3144 G1CollectedHeap* _g1h; 3145 OopClosure* _root_cl; 3146 nmethod* _nm; 3147 VerifyOption _vo; 3148 bool _failures; 3149 3150 template <class T> void do_oop_work(T* p) { 3151 // First verify that this root is live 3152 _root_cl->do_oop(p); 3153 3154 if (!G1VerifyHeapRegionCodeRoots) { 3155 // We're not verifying the code roots attached to heap region. 3156 return; 3157 } 3158 3159 // Don't check the code roots during marking verification in a full GC 3160 if (_vo == VerifyOption_G1UseMarkWord) { 3161 return; 3162 } 3163 3164 // Now verify that the current nmethod (which contains p) is 3165 // in the code root list of the heap region containing the 3166 // object referenced by p. 3167 3168 T heap_oop = oopDesc::load_heap_oop(p); 3169 if (!oopDesc::is_null(heap_oop)) { 3170 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3171 3172 // Now fetch the region containing the object 3173 HeapRegion* hr = _g1h->heap_region_containing(obj); 3174 HeapRegionRemSet* hrrs = hr->rem_set(); 3175 // Verify that the strong code root list for this region 3176 // contains the nmethod 3177 if (!hrrs->strong_code_roots_list_contains(_nm)) { 3178 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" " 3179 "from nmethod "PTR_FORMAT" not in strong " 3180 "code roots for region ["PTR_FORMAT","PTR_FORMAT")", 3181 p, _nm, hr->bottom(), hr->end()); 3182 _failures = true; 3183 } 3184 } 3185 } 3186 3187 public: 3188 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 3189 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 3190 3191 void do_oop(oop* p) { do_oop_work(p); } 3192 void do_oop(narrowOop* p) { do_oop_work(p); } 3193 3194 void set_nmethod(nmethod* nm) { _nm = nm; } 3195 bool failures() { return _failures; } 3196 }; 3197 3198 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 3199 G1VerifyCodeRootOopClosure* _oop_cl; 3200 3201 public: 3202 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 3203 _oop_cl(oop_cl) {} 3204 3205 void do_code_blob(CodeBlob* cb) { 3206 nmethod* nm = cb->as_nmethod_or_null(); 3207 if (nm != NULL) { 3208 _oop_cl->set_nmethod(nm); 3209 nm->oops_do(_oop_cl); 3210 } 3211 } 3212 }; 3213 3214 class YoungRefCounterClosure : public OopClosure { 3215 G1CollectedHeap* _g1h; 3216 int _count; 3217 public: 3218 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3219 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3220 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3221 3222 int count() { return _count; } 3223 void reset_count() { _count = 0; }; 3224 }; 3225 3226 class VerifyKlassClosure: public KlassClosure { 3227 YoungRefCounterClosure _young_ref_counter_closure; 3228 OopClosure *_oop_closure; 3229 public: 3230 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3231 void do_klass(Klass* k) { 3232 k->oops_do(_oop_closure); 3233 3234 _young_ref_counter_closure.reset_count(); 3235 k->oops_do(&_young_ref_counter_closure); 3236 if (_young_ref_counter_closure.count() > 0) { 3237 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3238 } 3239 } 3240 }; 3241 3242 class VerifyLivenessOopClosure: public OopClosure { 3243 G1CollectedHeap* _g1h; 3244 VerifyOption _vo; 3245 public: 3246 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3247 _g1h(g1h), _vo(vo) 3248 { } 3249 void do_oop(narrowOop *p) { do_oop_work(p); } 3250 void do_oop( oop *p) { do_oop_work(p); } 3251 3252 template <class T> void do_oop_work(T *p) { 3253 oop obj = oopDesc::load_decode_heap_oop(p); 3254 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3255 "Dead object referenced by a not dead object"); 3256 } 3257 }; 3258 3259 class VerifyObjsInRegionClosure: public ObjectClosure { 3260 private: 3261 G1CollectedHeap* _g1h; 3262 size_t _live_bytes; 3263 HeapRegion *_hr; 3264 VerifyOption _vo; 3265 public: 3266 // _vo == UsePrevMarking -> use "prev" marking information, 3267 // _vo == UseNextMarking -> use "next" marking information, 3268 // _vo == UseMarkWord -> use mark word from object header. 3269 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3270 : _live_bytes(0), _hr(hr), _vo(vo) { 3271 _g1h = G1CollectedHeap::heap(); 3272 } 3273 void do_object(oop o) { 3274 VerifyLivenessOopClosure isLive(_g1h, _vo); 3275 assert(o != NULL, "Huh?"); 3276 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3277 // If the object is alive according to the mark word, 3278 // then verify that the marking information agrees. 3279 // Note we can't verify the contra-positive of the 3280 // above: if the object is dead (according to the mark 3281 // word), it may not be marked, or may have been marked 3282 // but has since became dead, or may have been allocated 3283 // since the last marking. 3284 if (_vo == VerifyOption_G1UseMarkWord) { 3285 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3286 } 3287 3288 o->oop_iterate_no_header(&isLive); 3289 if (!_hr->obj_allocated_since_prev_marking(o)) { 3290 size_t obj_size = o->size(); // Make sure we don't overflow 3291 _live_bytes += (obj_size * HeapWordSize); 3292 } 3293 } 3294 } 3295 size_t live_bytes() { return _live_bytes; } 3296 }; 3297 3298 class PrintObjsInRegionClosure : public ObjectClosure { 3299 HeapRegion *_hr; 3300 G1CollectedHeap *_g1; 3301 public: 3302 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3303 _g1 = G1CollectedHeap::heap(); 3304 }; 3305 3306 void do_object(oop o) { 3307 if (o != NULL) { 3308 HeapWord *start = (HeapWord *) o; 3309 size_t word_sz = o->size(); 3310 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3311 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3312 (void*) o, word_sz, 3313 _g1->isMarkedPrev(o), 3314 _g1->isMarkedNext(o), 3315 _hr->obj_allocated_since_prev_marking(o)); 3316 HeapWord *end = start + word_sz; 3317 HeapWord *cur; 3318 int *val; 3319 for (cur = start; cur < end; cur++) { 3320 val = (int *) cur; 3321 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 3322 } 3323 } 3324 } 3325 }; 3326 3327 class VerifyRegionClosure: public HeapRegionClosure { 3328 private: 3329 bool _par; 3330 VerifyOption _vo; 3331 bool _failures; 3332 public: 3333 // _vo == UsePrevMarking -> use "prev" marking information, 3334 // _vo == UseNextMarking -> use "next" marking information, 3335 // _vo == UseMarkWord -> use mark word from object header. 3336 VerifyRegionClosure(bool par, VerifyOption vo) 3337 : _par(par), 3338 _vo(vo), 3339 _failures(false) {} 3340 3341 bool failures() { 3342 return _failures; 3343 } 3344 3345 bool doHeapRegion(HeapRegion* r) { 3346 if (!r->continuesHumongous()) { 3347 bool failures = false; 3348 r->verify(_vo, &failures); 3349 if (failures) { 3350 _failures = true; 3351 } else { 3352 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3353 r->object_iterate(¬_dead_yet_cl); 3354 if (_vo != VerifyOption_G1UseNextMarking) { 3355 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3356 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3357 "max_live_bytes "SIZE_FORMAT" " 3358 "< calculated "SIZE_FORMAT, 3359 r->bottom(), r->end(), 3360 r->max_live_bytes(), 3361 not_dead_yet_cl.live_bytes()); 3362 _failures = true; 3363 } 3364 } else { 3365 // When vo == UseNextMarking we cannot currently do a sanity 3366 // check on the live bytes as the calculation has not been 3367 // finalized yet. 3368 } 3369 } 3370 } 3371 return false; // stop the region iteration if we hit a failure 3372 } 3373 }; 3374 3375 // This is the task used for parallel verification of the heap regions 3376 3377 class G1ParVerifyTask: public AbstractGangTask { 3378 private: 3379 G1CollectedHeap* _g1h; 3380 VerifyOption _vo; 3381 bool _failures; 3382 3383 public: 3384 // _vo == UsePrevMarking -> use "prev" marking information, 3385 // _vo == UseNextMarking -> use "next" marking information, 3386 // _vo == UseMarkWord -> use mark word from object header. 3387 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3388 AbstractGangTask("Parallel verify task"), 3389 _g1h(g1h), 3390 _vo(vo), 3391 _failures(false) { } 3392 3393 bool failures() { 3394 return _failures; 3395 } 3396 3397 void work(uint worker_id) { 3398 HandleMark hm; 3399 VerifyRegionClosure blk(true, _vo); 3400 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3401 _g1h->workers()->active_workers(), 3402 HeapRegion::ParVerifyClaimValue); 3403 if (blk.failures()) { 3404 _failures = true; 3405 } 3406 } 3407 }; 3408 3409 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3410 if (SafepointSynchronize::is_at_safepoint()) { 3411 assert(Thread::current()->is_VM_thread(), 3412 "Expected to be executed serially by the VM thread at this point"); 3413 3414 if (!silent) { gclog_or_tty->print("Roots "); } 3415 VerifyRootsClosure rootsCl(vo); 3416 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3417 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3418 VerifyKlassClosure klassCl(this, &rootsCl); 3419 3420 // We apply the relevant closures to all the oops in the 3421 // system dictionary, the string table and the code cache. 3422 const int so = SO_AllClasses | SO_Strings | SO_CodeCache; 3423 3424 // Need cleared claim bits for the strong roots processing 3425 ClassLoaderDataGraph::clear_claimed_marks(); 3426 3427 process_strong_roots(true, // activate StrongRootsScope 3428 false, // we set "is scavenging" to false, 3429 // so we don't reset the dirty cards. 3430 ScanningOption(so), // roots scanning options 3431 &rootsCl, 3432 &blobsCl, 3433 &klassCl 3434 ); 3435 3436 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3437 3438 if (vo != VerifyOption_G1UseMarkWord) { 3439 // If we're verifying during a full GC then the region sets 3440 // will have been torn down at the start of the GC. Therefore 3441 // verifying the region sets will fail. So we only verify 3442 // the region sets when not in a full GC. 3443 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3444 verify_region_sets(); 3445 } 3446 3447 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3448 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3449 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3450 "sanity check"); 3451 3452 G1ParVerifyTask task(this, vo); 3453 assert(UseDynamicNumberOfGCThreads || 3454 workers()->active_workers() == workers()->total_workers(), 3455 "If not dynamic should be using all the workers"); 3456 int n_workers = workers()->active_workers(); 3457 set_par_threads(n_workers); 3458 workers()->run_task(&task); 3459 set_par_threads(0); 3460 if (task.failures()) { 3461 failures = true; 3462 } 3463 3464 // Checks that the expected amount of parallel work was done. 3465 // The implication is that n_workers is > 0. 3466 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3467 "sanity check"); 3468 3469 reset_heap_region_claim_values(); 3470 3471 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3472 "sanity check"); 3473 } else { 3474 VerifyRegionClosure blk(false, vo); 3475 heap_region_iterate(&blk); 3476 if (blk.failures()) { 3477 failures = true; 3478 } 3479 } 3480 if (!silent) gclog_or_tty->print("RemSet "); 3481 rem_set()->verify(); 3482 3483 if (G1StringDedup::is_enabled()) { 3484 if (!silent) gclog_or_tty->print("StrDedup "); 3485 G1StringDedup::verify(); 3486 } 3487 3488 if (failures) { 3489 gclog_or_tty->print_cr("Heap:"); 3490 // It helps to have the per-region information in the output to 3491 // help us track down what went wrong. This is why we call 3492 // print_extended_on() instead of print_on(). 3493 print_extended_on(gclog_or_tty); 3494 gclog_or_tty->cr(); 3495 #ifndef PRODUCT 3496 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3497 concurrent_mark()->print_reachable("at-verification-failure", 3498 vo, false /* all */); 3499 } 3500 #endif 3501 gclog_or_tty->flush(); 3502 } 3503 guarantee(!failures, "there should not have been any failures"); 3504 } else { 3505 if (!silent) { 3506 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3507 if (G1StringDedup::is_enabled()) { 3508 gclog_or_tty->print(", StrDedup"); 3509 } 3510 gclog_or_tty->print(") "); 3511 } 3512 } 3513 } 3514 3515 void G1CollectedHeap::verify(bool silent) { 3516 verify(silent, VerifyOption_G1UsePrevMarking); 3517 } 3518 3519 double G1CollectedHeap::verify(bool guard, const char* msg) { 3520 double verify_time_ms = 0.0; 3521 3522 if (guard && total_collections() >= VerifyGCStartAt) { 3523 double verify_start = os::elapsedTime(); 3524 HandleMark hm; // Discard invalid handles created during verification 3525 prepare_for_verify(); 3526 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3527 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3528 } 3529 3530 return verify_time_ms; 3531 } 3532 3533 void G1CollectedHeap::verify_before_gc() { 3534 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3535 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3536 } 3537 3538 void G1CollectedHeap::verify_after_gc() { 3539 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3540 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3541 } 3542 3543 class PrintRegionClosure: public HeapRegionClosure { 3544 outputStream* _st; 3545 public: 3546 PrintRegionClosure(outputStream* st) : _st(st) {} 3547 bool doHeapRegion(HeapRegion* r) { 3548 r->print_on(_st); 3549 return false; 3550 } 3551 }; 3552 3553 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3554 const HeapRegion* hr, 3555 const VerifyOption vo) const { 3556 switch (vo) { 3557 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3558 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3559 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3560 default: ShouldNotReachHere(); 3561 } 3562 return false; // keep some compilers happy 3563 } 3564 3565 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3566 const VerifyOption vo) const { 3567 switch (vo) { 3568 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3569 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3570 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3571 default: ShouldNotReachHere(); 3572 } 3573 return false; // keep some compilers happy 3574 } 3575 3576 void G1CollectedHeap::print_on(outputStream* st) const { 3577 st->print(" %-20s", "garbage-first heap"); 3578 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3579 capacity()/K, used_unlocked()/K); 3580 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3581 _g1_storage.low_boundary(), 3582 _g1_storage.high(), 3583 _g1_storage.high_boundary()); 3584 st->cr(); 3585 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3586 uint young_regions = _young_list->length(); 3587 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3588 (size_t) young_regions * HeapRegion::GrainBytes / K); 3589 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3590 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3591 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3592 st->cr(); 3593 MetaspaceAux::print_on(st); 3594 } 3595 3596 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3597 print_on(st); 3598 3599 // Print the per-region information. 3600 st->cr(); 3601 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3602 "HS=humongous(starts), HC=humongous(continues), " 3603 "CS=collection set, F=free, TS=gc time stamp, " 3604 "PTAMS=previous top-at-mark-start, " 3605 "NTAMS=next top-at-mark-start)"); 3606 PrintRegionClosure blk(st); 3607 heap_region_iterate(&blk); 3608 } 3609 3610 void G1CollectedHeap::print_on_error(outputStream* st) const { 3611 this->CollectedHeap::print_on_error(st); 3612 3613 if (_cm != NULL) { 3614 st->cr(); 3615 _cm->print_on_error(st); 3616 } 3617 } 3618 3619 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3620 if (G1CollectedHeap::use_parallel_gc_threads()) { 3621 workers()->print_worker_threads_on(st); 3622 } 3623 _cmThread->print_on(st); 3624 st->cr(); 3625 _cm->print_worker_threads_on(st); 3626 _cg1r->print_worker_threads_on(st); 3627 if (G1StringDedup::is_enabled()) { 3628 G1StringDedup::print_worker_threads_on(st); 3629 } 3630 } 3631 3632 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3633 if (G1CollectedHeap::use_parallel_gc_threads()) { 3634 workers()->threads_do(tc); 3635 } 3636 tc->do_thread(_cmThread); 3637 _cg1r->threads_do(tc); 3638 if (G1StringDedup::is_enabled()) { 3639 G1StringDedup::threads_do(tc); 3640 } 3641 } 3642 3643 void G1CollectedHeap::print_tracing_info() const { 3644 // We'll overload this to mean "trace GC pause statistics." 3645 if (TraceGen0Time || TraceGen1Time) { 3646 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3647 // to that. 3648 g1_policy()->print_tracing_info(); 3649 } 3650 if (G1SummarizeRSetStats) { 3651 g1_rem_set()->print_summary_info(); 3652 } 3653 if (G1SummarizeConcMark) { 3654 concurrent_mark()->print_summary_info(); 3655 } 3656 g1_policy()->print_yg_surv_rate_info(); 3657 SpecializationStats::print(); 3658 } 3659 3660 #ifndef PRODUCT 3661 // Helpful for debugging RSet issues. 3662 3663 class PrintRSetsClosure : public HeapRegionClosure { 3664 private: 3665 const char* _msg; 3666 size_t _occupied_sum; 3667 3668 public: 3669 bool doHeapRegion(HeapRegion* r) { 3670 HeapRegionRemSet* hrrs = r->rem_set(); 3671 size_t occupied = hrrs->occupied(); 3672 _occupied_sum += occupied; 3673 3674 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3675 HR_FORMAT_PARAMS(r)); 3676 if (occupied == 0) { 3677 gclog_or_tty->print_cr(" RSet is empty"); 3678 } else { 3679 hrrs->print(); 3680 } 3681 gclog_or_tty->print_cr("----------"); 3682 return false; 3683 } 3684 3685 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3686 gclog_or_tty->cr(); 3687 gclog_or_tty->print_cr("========================================"); 3688 gclog_or_tty->print_cr("%s", msg); 3689 gclog_or_tty->cr(); 3690 } 3691 3692 ~PrintRSetsClosure() { 3693 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3694 gclog_or_tty->print_cr("========================================"); 3695 gclog_or_tty->cr(); 3696 } 3697 }; 3698 3699 void G1CollectedHeap::print_cset_rsets() { 3700 PrintRSetsClosure cl("Printing CSet RSets"); 3701 collection_set_iterate(&cl); 3702 } 3703 3704 void G1CollectedHeap::print_all_rsets() { 3705 PrintRSetsClosure cl("Printing All RSets");; 3706 heap_region_iterate(&cl); 3707 } 3708 #endif // PRODUCT 3709 3710 G1CollectedHeap* G1CollectedHeap::heap() { 3711 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3712 "not a garbage-first heap"); 3713 return _g1h; 3714 } 3715 3716 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3717 // always_do_update_barrier = false; 3718 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3719 // Fill TLAB's and such 3720 accumulate_statistics_all_tlabs(); 3721 ensure_parsability(true); 3722 3723 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3724 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3725 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3726 } 3727 } 3728 3729 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3730 3731 if (G1SummarizeRSetStats && 3732 (G1SummarizeRSetStatsPeriod > 0) && 3733 // we are at the end of the GC. Total collections has already been increased. 3734 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3735 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3736 } 3737 3738 // FIXME: what is this about? 3739 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3740 // is set. 3741 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3742 "derived pointer present")); 3743 // always_do_update_barrier = true; 3744 3745 resize_all_tlabs(); 3746 3747 // We have just completed a GC. Update the soft reference 3748 // policy with the new heap occupancy 3749 Universe::update_heap_info_at_gc(); 3750 } 3751 3752 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3753 unsigned int gc_count_before, 3754 bool* succeeded, 3755 GCCause::Cause gc_cause) { 3756 assert_heap_not_locked_and_not_at_safepoint(); 3757 g1_policy()->record_stop_world_start(); 3758 VM_G1IncCollectionPause op(gc_count_before, 3759 word_size, 3760 false, /* should_initiate_conc_mark */ 3761 g1_policy()->max_pause_time_ms(), 3762 gc_cause); 3763 VMThread::execute(&op); 3764 3765 HeapWord* result = op.result(); 3766 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3767 assert(result == NULL || ret_succeeded, 3768 "the result should be NULL if the VM did not succeed"); 3769 *succeeded = ret_succeeded; 3770 3771 assert_heap_not_locked(); 3772 return result; 3773 } 3774 3775 void 3776 G1CollectedHeap::doConcurrentMark() { 3777 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3778 if (!_cmThread->in_progress()) { 3779 _cmThread->set_started(); 3780 CGC_lock->notify(); 3781 } 3782 } 3783 3784 size_t G1CollectedHeap::pending_card_num() { 3785 size_t extra_cards = 0; 3786 JavaThread *curr = Threads::first(); 3787 while (curr != NULL) { 3788 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3789 extra_cards += dcq.size(); 3790 curr = curr->next(); 3791 } 3792 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3793 size_t buffer_size = dcqs.buffer_size(); 3794 size_t buffer_num = dcqs.completed_buffers_num(); 3795 3796 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3797 // in bytes - not the number of 'entries'. We need to convert 3798 // into a number of cards. 3799 return (buffer_size * buffer_num + extra_cards) / oopSize; 3800 } 3801 3802 size_t G1CollectedHeap::cards_scanned() { 3803 return g1_rem_set()->cardsScanned(); 3804 } 3805 3806 void 3807 G1CollectedHeap::setup_surviving_young_words() { 3808 assert(_surviving_young_words == NULL, "pre-condition"); 3809 uint array_length = g1_policy()->young_cset_region_length(); 3810 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3811 if (_surviving_young_words == NULL) { 3812 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3813 "Not enough space for young surv words summary."); 3814 } 3815 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3816 #ifdef ASSERT 3817 for (uint i = 0; i < array_length; ++i) { 3818 assert( _surviving_young_words[i] == 0, "memset above" ); 3819 } 3820 #endif // !ASSERT 3821 } 3822 3823 void 3824 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3825 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3826 uint array_length = g1_policy()->young_cset_region_length(); 3827 for (uint i = 0; i < array_length; ++i) { 3828 _surviving_young_words[i] += surv_young_words[i]; 3829 } 3830 } 3831 3832 void 3833 G1CollectedHeap::cleanup_surviving_young_words() { 3834 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3835 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3836 _surviving_young_words = NULL; 3837 } 3838 3839 #ifdef ASSERT 3840 class VerifyCSetClosure: public HeapRegionClosure { 3841 public: 3842 bool doHeapRegion(HeapRegion* hr) { 3843 // Here we check that the CSet region's RSet is ready for parallel 3844 // iteration. The fields that we'll verify are only manipulated 3845 // when the region is part of a CSet and is collected. Afterwards, 3846 // we reset these fields when we clear the region's RSet (when the 3847 // region is freed) so they are ready when the region is 3848 // re-allocated. The only exception to this is if there's an 3849 // evacuation failure and instead of freeing the region we leave 3850 // it in the heap. In that case, we reset these fields during 3851 // evacuation failure handling. 3852 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3853 3854 // Here's a good place to add any other checks we'd like to 3855 // perform on CSet regions. 3856 return false; 3857 } 3858 }; 3859 #endif // ASSERT 3860 3861 #if TASKQUEUE_STATS 3862 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3863 st->print_raw_cr("GC Task Stats"); 3864 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3865 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3866 } 3867 3868 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3869 print_taskqueue_stats_hdr(st); 3870 3871 TaskQueueStats totals; 3872 const int n = workers() != NULL ? workers()->total_workers() : 1; 3873 for (int i = 0; i < n; ++i) { 3874 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3875 totals += task_queue(i)->stats; 3876 } 3877 st->print_raw("tot "); totals.print(st); st->cr(); 3878 3879 DEBUG_ONLY(totals.verify()); 3880 } 3881 3882 void G1CollectedHeap::reset_taskqueue_stats() { 3883 const int n = workers() != NULL ? workers()->total_workers() : 1; 3884 for (int i = 0; i < n; ++i) { 3885 task_queue(i)->stats.reset(); 3886 } 3887 } 3888 #endif // TASKQUEUE_STATS 3889 3890 void G1CollectedHeap::log_gc_header() { 3891 if (!G1Log::fine()) { 3892 return; 3893 } 3894 3895 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id()); 3896 3897 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3898 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3899 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3900 3901 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3902 } 3903 3904 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3905 if (!G1Log::fine()) { 3906 return; 3907 } 3908 3909 if (G1Log::finer()) { 3910 if (evacuation_failed()) { 3911 gclog_or_tty->print(" (to-space exhausted)"); 3912 } 3913 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3914 g1_policy()->phase_times()->note_gc_end(); 3915 g1_policy()->phase_times()->print(pause_time_sec); 3916 g1_policy()->print_detailed_heap_transition(); 3917 } else { 3918 if (evacuation_failed()) { 3919 gclog_or_tty->print("--"); 3920 } 3921 g1_policy()->print_heap_transition(); 3922 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3923 } 3924 gclog_or_tty->flush(); 3925 } 3926 3927 bool 3928 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3929 assert_at_safepoint(true /* should_be_vm_thread */); 3930 guarantee(!is_gc_active(), "collection is not reentrant"); 3931 3932 if (GC_locker::check_active_before_gc()) { 3933 return false; 3934 } 3935 3936 _gc_timer_stw->register_gc_start(); 3937 3938 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3939 3940 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3941 ResourceMark rm; 3942 3943 print_heap_before_gc(); 3944 trace_heap_before_gc(_gc_tracer_stw); 3945 3946 verify_region_sets_optional(); 3947 verify_dirty_young_regions(); 3948 3949 // This call will decide whether this pause is an initial-mark 3950 // pause. If it is, during_initial_mark_pause() will return true 3951 // for the duration of this pause. 3952 g1_policy()->decide_on_conc_mark_initiation(); 3953 3954 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3955 assert(!g1_policy()->during_initial_mark_pause() || 3956 g1_policy()->gcs_are_young(), "sanity"); 3957 3958 // We also do not allow mixed GCs during marking. 3959 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3960 3961 // Record whether this pause is an initial mark. When the current 3962 // thread has completed its logging output and it's safe to signal 3963 // the CM thread, the flag's value in the policy has been reset. 3964 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3965 3966 // Inner scope for scope based logging, timers, and stats collection 3967 { 3968 EvacuationInfo evacuation_info; 3969 3970 if (g1_policy()->during_initial_mark_pause()) { 3971 // We are about to start a marking cycle, so we increment the 3972 // full collection counter. 3973 increment_old_marking_cycles_started(); 3974 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3975 } 3976 3977 _gc_tracer_stw->report_yc_type(yc_type()); 3978 3979 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3980 3981 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3982 workers()->active_workers() : 1); 3983 double pause_start_sec = os::elapsedTime(); 3984 g1_policy()->phase_times()->note_gc_start(active_workers); 3985 log_gc_header(); 3986 3987 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3988 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3989 3990 // If the secondary_free_list is not empty, append it to the 3991 // free_list. No need to wait for the cleanup operation to finish; 3992 // the region allocation code will check the secondary_free_list 3993 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3994 // set, skip this step so that the region allocation code has to 3995 // get entries from the secondary_free_list. 3996 if (!G1StressConcRegionFreeing) { 3997 append_secondary_free_list_if_not_empty_with_lock(); 3998 } 3999 4000 assert(check_young_list_well_formed(), "young list should be well formed"); 4001 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 4002 "sanity check"); 4003 4004 // Don't dynamically change the number of GC threads this early. A value of 4005 // 0 is used to indicate serial work. When parallel work is done, 4006 // it will be set. 4007 4008 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 4009 IsGCActiveMark x; 4010 4011 gc_prologue(false); 4012 increment_total_collections(false /* full gc */); 4013 increment_gc_time_stamp(); 4014 4015 verify_before_gc(); 4016 4017 COMPILER2_PRESENT(DerivedPointerTable::clear()); 4018 4019 // Please see comment in g1CollectedHeap.hpp and 4020 // G1CollectedHeap::ref_processing_init() to see how 4021 // reference processing currently works in G1. 4022 4023 // Enable discovery in the STW reference processor 4024 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 4025 true /*verify_no_refs*/); 4026 4027 { 4028 // We want to temporarily turn off discovery by the 4029 // CM ref processor, if necessary, and turn it back on 4030 // on again later if we do. Using a scoped 4031 // NoRefDiscovery object will do this. 4032 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 4033 4034 // Forget the current alloc region (we might even choose it to be part 4035 // of the collection set!). 4036 release_mutator_alloc_region(); 4037 4038 // We should call this after we retire the mutator alloc 4039 // region(s) so that all the ALLOC / RETIRE events are generated 4040 // before the start GC event. 4041 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 4042 4043 // This timing is only used by the ergonomics to handle our pause target. 4044 // It is unclear why this should not include the full pause. We will 4045 // investigate this in CR 7178365. 4046 // 4047 // Preserving the old comment here if that helps the investigation: 4048 // 4049 // The elapsed time induced by the start time below deliberately elides 4050 // the possible verification above. 4051 double sample_start_time_sec = os::elapsedTime(); 4052 4053 #if YOUNG_LIST_VERBOSE 4054 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 4055 _young_list->print(); 4056 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4057 #endif // YOUNG_LIST_VERBOSE 4058 4059 g1_policy()->record_collection_pause_start(sample_start_time_sec); 4060 4061 double scan_wait_start = os::elapsedTime(); 4062 // We have to wait until the CM threads finish scanning the 4063 // root regions as it's the only way to ensure that all the 4064 // objects on them have been correctly scanned before we start 4065 // moving them during the GC. 4066 bool waited = _cm->root_regions()->wait_until_scan_finished(); 4067 double wait_time_ms = 0.0; 4068 if (waited) { 4069 double scan_wait_end = os::elapsedTime(); 4070 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 4071 } 4072 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 4073 4074 #if YOUNG_LIST_VERBOSE 4075 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 4076 _young_list->print(); 4077 #endif // YOUNG_LIST_VERBOSE 4078 4079 if (g1_policy()->during_initial_mark_pause()) { 4080 concurrent_mark()->checkpointRootsInitialPre(); 4081 } 4082 4083 #if YOUNG_LIST_VERBOSE 4084 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 4085 _young_list->print(); 4086 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4087 #endif // YOUNG_LIST_VERBOSE 4088 4089 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info); 4090 4091 _cm->note_start_of_gc(); 4092 // We should not verify the per-thread SATB buffers given that 4093 // we have not filtered them yet (we'll do so during the 4094 // GC). We also call this after finalize_cset() to 4095 // ensure that the CSet has been finalized. 4096 _cm->verify_no_cset_oops(true /* verify_stacks */, 4097 true /* verify_enqueued_buffers */, 4098 false /* verify_thread_buffers */, 4099 true /* verify_fingers */); 4100 4101 if (_hr_printer.is_active()) { 4102 HeapRegion* hr = g1_policy()->collection_set(); 4103 while (hr != NULL) { 4104 G1HRPrinter::RegionType type; 4105 if (!hr->is_young()) { 4106 type = G1HRPrinter::Old; 4107 } else if (hr->is_survivor()) { 4108 type = G1HRPrinter::Survivor; 4109 } else { 4110 type = G1HRPrinter::Eden; 4111 } 4112 _hr_printer.cset(hr); 4113 hr = hr->next_in_collection_set(); 4114 } 4115 } 4116 4117 #ifdef ASSERT 4118 VerifyCSetClosure cl; 4119 collection_set_iterate(&cl); 4120 #endif // ASSERT 4121 4122 setup_surviving_young_words(); 4123 4124 // Initialize the GC alloc regions. 4125 init_gc_alloc_regions(evacuation_info); 4126 4127 // Actually do the work... 4128 evacuate_collection_set(evacuation_info); 4129 4130 // We do this to mainly verify the per-thread SATB buffers 4131 // (which have been filtered by now) since we didn't verify 4132 // them earlier. No point in re-checking the stacks / enqueued 4133 // buffers given that the CSet has not changed since last time 4134 // we checked. 4135 _cm->verify_no_cset_oops(false /* verify_stacks */, 4136 false /* verify_enqueued_buffers */, 4137 true /* verify_thread_buffers */, 4138 true /* verify_fingers */); 4139 4140 free_collection_set(g1_policy()->collection_set(), evacuation_info); 4141 g1_policy()->clear_collection_set(); 4142 4143 cleanup_surviving_young_words(); 4144 4145 // Start a new incremental collection set for the next pause. 4146 g1_policy()->start_incremental_cset_building(); 4147 4148 // Clear the _cset_fast_test bitmap in anticipation of adding 4149 // regions to the incremental collection set for the next 4150 // evacuation pause. 4151 clear_cset_fast_test(); 4152 4153 _young_list->reset_sampled_info(); 4154 4155 // Don't check the whole heap at this point as the 4156 // GC alloc regions from this pause have been tagged 4157 // as survivors and moved on to the survivor list. 4158 // Survivor regions will fail the !is_young() check. 4159 assert(check_young_list_empty(false /* check_heap */), 4160 "young list should be empty"); 4161 4162 #if YOUNG_LIST_VERBOSE 4163 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 4164 _young_list->print(); 4165 #endif // YOUNG_LIST_VERBOSE 4166 4167 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 4168 _young_list->first_survivor_region(), 4169 _young_list->last_survivor_region()); 4170 4171 _young_list->reset_auxilary_lists(); 4172 4173 if (evacuation_failed()) { 4174 _summary_bytes_used = recalculate_used(); 4175 uint n_queues = MAX2((int)ParallelGCThreads, 1); 4176 for (uint i = 0; i < n_queues; i++) { 4177 if (_evacuation_failed_info_array[i].has_failed()) { 4178 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 4179 } 4180 } 4181 } else { 4182 // The "used" of the the collection set have already been subtracted 4183 // when they were freed. Add in the bytes evacuated. 4184 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 4185 } 4186 4187 if (g1_policy()->during_initial_mark_pause()) { 4188 // We have to do this before we notify the CM threads that 4189 // they can start working to make sure that all the 4190 // appropriate initialization is done on the CM object. 4191 concurrent_mark()->checkpointRootsInitialPost(); 4192 set_marking_started(); 4193 // Note that we don't actually trigger the CM thread at 4194 // this point. We do that later when we're sure that 4195 // the current thread has completed its logging output. 4196 } 4197 4198 allocate_dummy_regions(); 4199 4200 #if YOUNG_LIST_VERBOSE 4201 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 4202 _young_list->print(); 4203 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4204 #endif // YOUNG_LIST_VERBOSE 4205 4206 init_mutator_alloc_region(); 4207 4208 { 4209 size_t expand_bytes = g1_policy()->expansion_amount(); 4210 if (expand_bytes > 0) { 4211 size_t bytes_before = capacity(); 4212 // No need for an ergo verbose message here, 4213 // expansion_amount() does this when it returns a value > 0. 4214 if (!expand(expand_bytes)) { 4215 // We failed to expand the heap so let's verify that 4216 // committed/uncommitted amount match the backing store 4217 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 4218 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 4219 } 4220 } 4221 } 4222 4223 // We redo the verification but now wrt to the new CSet which 4224 // has just got initialized after the previous CSet was freed. 4225 _cm->verify_no_cset_oops(true /* verify_stacks */, 4226 true /* verify_enqueued_buffers */, 4227 true /* verify_thread_buffers */, 4228 true /* verify_fingers */); 4229 _cm->note_end_of_gc(); 4230 4231 // This timing is only used by the ergonomics to handle our pause target. 4232 // It is unclear why this should not include the full pause. We will 4233 // investigate this in CR 7178365. 4234 double sample_end_time_sec = os::elapsedTime(); 4235 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4236 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info); 4237 4238 MemoryService::track_memory_usage(); 4239 4240 // In prepare_for_verify() below we'll need to scan the deferred 4241 // update buffers to bring the RSets up-to-date if 4242 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4243 // the update buffers we'll probably need to scan cards on the 4244 // regions we just allocated to (i.e., the GC alloc 4245 // regions). However, during the last GC we called 4246 // set_saved_mark() on all the GC alloc regions, so card 4247 // scanning might skip the [saved_mark_word()...top()] area of 4248 // those regions (i.e., the area we allocated objects into 4249 // during the last GC). But it shouldn't. Given that 4250 // saved_mark_word() is conditional on whether the GC time stamp 4251 // on the region is current or not, by incrementing the GC time 4252 // stamp here we invalidate all the GC time stamps on all the 4253 // regions and saved_mark_word() will simply return top() for 4254 // all the regions. This is a nicer way of ensuring this rather 4255 // than iterating over the regions and fixing them. In fact, the 4256 // GC time stamp increment here also ensures that 4257 // saved_mark_word() will return top() between pauses, i.e., 4258 // during concurrent refinement. So we don't need the 4259 // is_gc_active() check to decided which top to use when 4260 // scanning cards (see CR 7039627). 4261 increment_gc_time_stamp(); 4262 4263 verify_after_gc(); 4264 4265 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4266 ref_processor_stw()->verify_no_references_recorded(); 4267 4268 // CM reference discovery will be re-enabled if necessary. 4269 } 4270 4271 // We should do this after we potentially expand the heap so 4272 // that all the COMMIT events are generated before the end GC 4273 // event, and after we retire the GC alloc regions so that all 4274 // RETIRE events are generated before the end GC event. 4275 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4276 4277 if (mark_in_progress()) { 4278 concurrent_mark()->update_g1_committed(); 4279 } 4280 4281 #ifdef TRACESPINNING 4282 ParallelTaskTerminator::print_termination_counts(); 4283 #endif 4284 4285 gc_epilogue(false); 4286 } 4287 4288 // Print the remainder of the GC log output. 4289 log_gc_footer(os::elapsedTime() - pause_start_sec); 4290 4291 // It is not yet to safe to tell the concurrent mark to 4292 // start as we have some optional output below. We don't want the 4293 // output from the concurrent mark thread interfering with this 4294 // logging output either. 4295 4296 _hrs.verify_optional(); 4297 verify_region_sets_optional(); 4298 4299 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4300 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4301 4302 print_heap_after_gc(); 4303 trace_heap_after_gc(_gc_tracer_stw); 4304 4305 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4306 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4307 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4308 // before any GC notifications are raised. 4309 g1mm()->update_sizes(); 4310 4311 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4312 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4313 _gc_timer_stw->register_gc_end(); 4314 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4315 } 4316 // It should now be safe to tell the concurrent mark thread to start 4317 // without its logging output interfering with the logging output 4318 // that came from the pause. 4319 4320 if (should_start_conc_mark) { 4321 // CAUTION: after the doConcurrentMark() call below, 4322 // the concurrent marking thread(s) could be running 4323 // concurrently with us. Make sure that anything after 4324 // this point does not assume that we are the only GC thread 4325 // running. Note: of course, the actual marking work will 4326 // not start until the safepoint itself is released in 4327 // SuspendibleThreadSet::desynchronize(). 4328 doConcurrentMark(); 4329 } 4330 4331 return true; 4332 } 4333 4334 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4335 { 4336 size_t gclab_word_size; 4337 switch (purpose) { 4338 case GCAllocForSurvived: 4339 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4340 break; 4341 case GCAllocForTenured: 4342 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4343 break; 4344 default: 4345 assert(false, "unknown GCAllocPurpose"); 4346 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4347 break; 4348 } 4349 4350 // Prevent humongous PLAB sizes for two reasons: 4351 // * PLABs are allocated using a similar paths as oops, but should 4352 // never be in a humongous region 4353 // * Allowing humongous PLABs needlessly churns the region free lists 4354 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4355 } 4356 4357 void G1CollectedHeap::init_mutator_alloc_region() { 4358 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 4359 _mutator_alloc_region.init(); 4360 } 4361 4362 void G1CollectedHeap::release_mutator_alloc_region() { 4363 _mutator_alloc_region.release(); 4364 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 4365 } 4366 4367 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) { 4368 assert_at_safepoint(true /* should_be_vm_thread */); 4369 4370 _survivor_gc_alloc_region.init(); 4371 _old_gc_alloc_region.init(); 4372 HeapRegion* retained_region = _retained_old_gc_alloc_region; 4373 _retained_old_gc_alloc_region = NULL; 4374 4375 // We will discard the current GC alloc region if: 4376 // a) it's in the collection set (it can happen!), 4377 // b) it's already full (no point in using it), 4378 // c) it's empty (this means that it was emptied during 4379 // a cleanup and it should be on the free list now), or 4380 // d) it's humongous (this means that it was emptied 4381 // during a cleanup and was added to the free list, but 4382 // has been subsequently used to allocate a humongous 4383 // object that may be less than the region size). 4384 if (retained_region != NULL && 4385 !retained_region->in_collection_set() && 4386 !(retained_region->top() == retained_region->end()) && 4387 !retained_region->is_empty() && 4388 !retained_region->isHumongous()) { 4389 retained_region->set_saved_mark(); 4390 // The retained region was added to the old region set when it was 4391 // retired. We have to remove it now, since we don't allow regions 4392 // we allocate to in the region sets. We'll re-add it later, when 4393 // it's retired again. 4394 _old_set.remove(retained_region); 4395 bool during_im = g1_policy()->during_initial_mark_pause(); 4396 retained_region->note_start_of_copying(during_im); 4397 _old_gc_alloc_region.set(retained_region); 4398 _hr_printer.reuse(retained_region); 4399 evacuation_info.set_alloc_regions_used_before(retained_region->used()); 4400 } 4401 } 4402 4403 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) { 4404 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() + 4405 _old_gc_alloc_region.count()); 4406 _survivor_gc_alloc_region.release(); 4407 // If we have an old GC alloc region to release, we'll save it in 4408 // _retained_old_gc_alloc_region. If we don't 4409 // _retained_old_gc_alloc_region will become NULL. This is what we 4410 // want either way so no reason to check explicitly for either 4411 // condition. 4412 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 4413 4414 if (ResizePLAB) { 4415 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4416 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4417 } 4418 } 4419 4420 void G1CollectedHeap::abandon_gc_alloc_regions() { 4421 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 4422 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 4423 _retained_old_gc_alloc_region = NULL; 4424 } 4425 4426 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4427 _drain_in_progress = false; 4428 set_evac_failure_closure(cl); 4429 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4430 } 4431 4432 void G1CollectedHeap::finalize_for_evac_failure() { 4433 assert(_evac_failure_scan_stack != NULL && 4434 _evac_failure_scan_stack->length() == 0, 4435 "Postcondition"); 4436 assert(!_drain_in_progress, "Postcondition"); 4437 delete _evac_failure_scan_stack; 4438 _evac_failure_scan_stack = NULL; 4439 } 4440 4441 void G1CollectedHeap::remove_self_forwarding_pointers() { 4442 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4443 4444 double remove_self_forwards_start = os::elapsedTime(); 4445 4446 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4447 4448 if (G1CollectedHeap::use_parallel_gc_threads()) { 4449 set_par_threads(); 4450 workers()->run_task(&rsfp_task); 4451 set_par_threads(0); 4452 } else { 4453 rsfp_task.work(0); 4454 } 4455 4456 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4457 4458 // Reset the claim values in the regions in the collection set. 4459 reset_cset_heap_region_claim_values(); 4460 4461 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4462 4463 // Now restore saved marks, if any. 4464 assert(_objs_with_preserved_marks.size() == 4465 _preserved_marks_of_objs.size(), "Both or none."); 4466 while (!_objs_with_preserved_marks.is_empty()) { 4467 oop obj = _objs_with_preserved_marks.pop(); 4468 markOop m = _preserved_marks_of_objs.pop(); 4469 obj->set_mark(m); 4470 } 4471 _objs_with_preserved_marks.clear(true); 4472 _preserved_marks_of_objs.clear(true); 4473 4474 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4475 } 4476 4477 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4478 _evac_failure_scan_stack->push(obj); 4479 } 4480 4481 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4482 assert(_evac_failure_scan_stack != NULL, "precondition"); 4483 4484 while (_evac_failure_scan_stack->length() > 0) { 4485 oop obj = _evac_failure_scan_stack->pop(); 4486 _evac_failure_closure->set_region(heap_region_containing(obj)); 4487 obj->oop_iterate_backwards(_evac_failure_closure); 4488 } 4489 } 4490 4491 oop 4492 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, 4493 oop old) { 4494 assert(obj_in_cs(old), 4495 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4496 (HeapWord*) old)); 4497 markOop m = old->mark(); 4498 oop forward_ptr = old->forward_to_atomic(old); 4499 if (forward_ptr == NULL) { 4500 // Forward-to-self succeeded. 4501 assert(_par_scan_state != NULL, "par scan state"); 4502 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4503 uint queue_num = _par_scan_state->queue_num(); 4504 4505 _evacuation_failed = true; 4506 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size()); 4507 if (_evac_failure_closure != cl) { 4508 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4509 assert(!_drain_in_progress, 4510 "Should only be true while someone holds the lock."); 4511 // Set the global evac-failure closure to the current thread's. 4512 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4513 set_evac_failure_closure(cl); 4514 // Now do the common part. 4515 handle_evacuation_failure_common(old, m); 4516 // Reset to NULL. 4517 set_evac_failure_closure(NULL); 4518 } else { 4519 // The lock is already held, and this is recursive. 4520 assert(_drain_in_progress, "This should only be the recursive case."); 4521 handle_evacuation_failure_common(old, m); 4522 } 4523 return old; 4524 } else { 4525 // Forward-to-self failed. Either someone else managed to allocate 4526 // space for this object (old != forward_ptr) or they beat us in 4527 // self-forwarding it (old == forward_ptr). 4528 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4529 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4530 "should not be in the CSet", 4531 (HeapWord*) old, (HeapWord*) forward_ptr)); 4532 return forward_ptr; 4533 } 4534 } 4535 4536 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4537 preserve_mark_if_necessary(old, m); 4538 4539 HeapRegion* r = heap_region_containing(old); 4540 if (!r->evacuation_failed()) { 4541 r->set_evacuation_failed(true); 4542 _hr_printer.evac_failure(r); 4543 } 4544 4545 push_on_evac_failure_scan_stack(old); 4546 4547 if (!_drain_in_progress) { 4548 // prevent recursion in copy_to_survivor_space() 4549 _drain_in_progress = true; 4550 drain_evac_failure_scan_stack(); 4551 _drain_in_progress = false; 4552 } 4553 } 4554 4555 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4556 assert(evacuation_failed(), "Oversaving!"); 4557 // We want to call the "for_promotion_failure" version only in the 4558 // case of a promotion failure. 4559 if (m->must_be_preserved_for_promotion_failure(obj)) { 4560 _objs_with_preserved_marks.push(obj); 4561 _preserved_marks_of_objs.push(m); 4562 } 4563 } 4564 4565 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4566 size_t word_size) { 4567 if (purpose == GCAllocForSurvived) { 4568 HeapWord* result = survivor_attempt_allocation(word_size); 4569 if (result != NULL) { 4570 return result; 4571 } else { 4572 // Let's try to allocate in the old gen in case we can fit the 4573 // object there. 4574 return old_attempt_allocation(word_size); 4575 } 4576 } else { 4577 assert(purpose == GCAllocForTenured, "sanity"); 4578 HeapWord* result = old_attempt_allocation(word_size); 4579 if (result != NULL) { 4580 return result; 4581 } else { 4582 // Let's try to allocate in the survivors in case we can fit the 4583 // object there. 4584 return survivor_attempt_allocation(word_size); 4585 } 4586 } 4587 4588 ShouldNotReachHere(); 4589 // Trying to keep some compilers happy. 4590 return NULL; 4591 } 4592 4593 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : 4594 ParGCAllocBuffer(gclab_word_size), _retired(false) { } 4595 4596 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp) 4597 : _g1h(g1h), 4598 _refs(g1h->task_queue(queue_num)), 4599 _dcq(&g1h->dirty_card_queue_set()), 4600 _ct_bs(g1h->g1_barrier_set()), 4601 _g1_rem(g1h->g1_rem_set()), 4602 _hash_seed(17), _queue_num(queue_num), 4603 _term_attempts(0), 4604 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4605 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4606 _age_table(false), _scanner(g1h, this, rp), 4607 _strong_roots_time(0), _term_time(0), 4608 _alloc_buffer_waste(0), _undo_waste(0) { 4609 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4610 // we "sacrifice" entry 0 to keep track of surviving bytes for 4611 // non-young regions (where the age is -1) 4612 // We also add a few elements at the beginning and at the end in 4613 // an attempt to eliminate cache contention 4614 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 4615 uint array_length = PADDING_ELEM_NUM + 4616 real_length + 4617 PADDING_ELEM_NUM; 4618 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); 4619 if (_surviving_young_words_base == NULL) 4620 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR, 4621 "Not enough space for young surv histo."); 4622 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4623 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); 4624 4625 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4626 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4627 4628 _start = os::elapsedTime(); 4629 } 4630 4631 void 4632 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4633 { 4634 st->print_raw_cr("GC Termination Stats"); 4635 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4636 " ------waste (KiB)------"); 4637 st->print_raw_cr("thr ms ms % ms % attempts" 4638 " total alloc undo"); 4639 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4640 " ------- ------- -------"); 4641 } 4642 4643 void 4644 G1ParScanThreadState::print_termination_stats(int i, 4645 outputStream* const st) const 4646 { 4647 const double elapsed_ms = elapsed_time() * 1000.0; 4648 const double s_roots_ms = strong_roots_time() * 1000.0; 4649 const double term_ms = term_time() * 1000.0; 4650 st->print_cr("%3d %9.2f %9.2f %6.2f " 4651 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4652 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4653 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4654 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4655 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4656 alloc_buffer_waste() * HeapWordSize / K, 4657 undo_waste() * HeapWordSize / K); 4658 } 4659 4660 #ifdef ASSERT 4661 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4662 assert(ref != NULL, "invariant"); 4663 assert(UseCompressedOops, "sanity"); 4664 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4665 oop p = oopDesc::load_decode_heap_oop(ref); 4666 assert(_g1h->is_in_g1_reserved(p), 4667 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p)); 4668 return true; 4669 } 4670 4671 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4672 assert(ref != NULL, "invariant"); 4673 if (has_partial_array_mask(ref)) { 4674 // Must be in the collection set--it's already been copied. 4675 oop p = clear_partial_array_mask(ref); 4676 assert(_g1h->obj_in_cs(p), 4677 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p)); 4678 } else { 4679 oop p = oopDesc::load_decode_heap_oop(ref); 4680 assert(_g1h->is_in_g1_reserved(p), 4681 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p)); 4682 } 4683 return true; 4684 } 4685 4686 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4687 if (ref.is_narrow()) { 4688 return verify_ref((narrowOop*) ref); 4689 } else { 4690 return verify_ref((oop*) ref); 4691 } 4692 } 4693 #endif // ASSERT 4694 4695 void G1ParScanThreadState::trim_queue() { 4696 assert(_evac_failure_cl != NULL, "not set"); 4697 4698 StarTask ref; 4699 do { 4700 // Drain the overflow stack first, so other threads can steal. 4701 while (refs()->pop_overflow(ref)) { 4702 deal_with_reference(ref); 4703 } 4704 4705 while (refs()->pop_local(ref)) { 4706 deal_with_reference(ref); 4707 } 4708 } while (!refs()->is_empty()); 4709 } 4710 4711 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, 4712 G1ParScanThreadState* par_scan_state) : 4713 _g1(g1), _par_scan_state(par_scan_state), 4714 _worker_id(par_scan_state->queue_num()) { } 4715 4716 void G1ParCopyHelper::mark_object(oop obj) { 4717 #ifdef ASSERT 4718 HeapRegion* hr = _g1->heap_region_containing(obj); 4719 assert(hr != NULL, "sanity"); 4720 assert(!hr->in_collection_set(), "should not mark objects in the CSet"); 4721 #endif // ASSERT 4722 4723 // We know that the object is not moving so it's safe to read its size. 4724 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4725 } 4726 4727 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) { 4728 #ifdef ASSERT 4729 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4730 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4731 assert(from_obj != to_obj, "should not be self-forwarded"); 4732 4733 HeapRegion* from_hr = _g1->heap_region_containing(from_obj); 4734 assert(from_hr != NULL, "sanity"); 4735 assert(from_hr->in_collection_set(), "from obj should be in the CSet"); 4736 4737 HeapRegion* to_hr = _g1->heap_region_containing(to_obj); 4738 assert(to_hr != NULL, "sanity"); 4739 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet"); 4740 #endif // ASSERT 4741 4742 // The object might be in the process of being copied by another 4743 // worker so we cannot trust that its to-space image is 4744 // well-formed. So we have to read its size from its from-space 4745 // image which we know should not be changing. 4746 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4747 } 4748 4749 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) { 4750 size_t word_sz = old->size(); 4751 HeapRegion* from_region = _g1h->heap_region_containing_raw(old); 4752 // +1 to make the -1 indexes valid... 4753 int young_index = from_region->young_index_in_cset()+1; 4754 assert( (from_region->is_young() && young_index > 0) || 4755 (!from_region->is_young() && young_index == 0), "invariant" ); 4756 G1CollectorPolicy* g1p = _g1h->g1_policy(); 4757 markOop m = old->mark(); 4758 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4759 : m->age(); 4760 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4761 word_sz); 4762 HeapWord* obj_ptr = allocate(alloc_purpose, word_sz); 4763 #ifndef PRODUCT 4764 // Should this evacuation fail? 4765 if (_g1h->evacuation_should_fail()) { 4766 if (obj_ptr != NULL) { 4767 undo_allocation(alloc_purpose, obj_ptr, word_sz); 4768 obj_ptr = NULL; 4769 } 4770 } 4771 #endif // !PRODUCT 4772 4773 if (obj_ptr == NULL) { 4774 // This will either forward-to-self, or detect that someone else has 4775 // installed a forwarding pointer. 4776 return _g1h->handle_evacuation_failure_par(this, old); 4777 } 4778 4779 oop obj = oop(obj_ptr); 4780 4781 // We're going to allocate linearly, so might as well prefetch ahead. 4782 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4783 4784 oop forward_ptr = old->forward_to_atomic(obj); 4785 if (forward_ptr == NULL) { 4786 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4787 4788 // alloc_purpose is just a hint to allocate() above, recheck the type of region 4789 // we actually allocated from and update alloc_purpose accordingly 4790 HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr); 4791 alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured; 4792 4793 if (g1p->track_object_age(alloc_purpose)) { 4794 // We could simply do obj->incr_age(). However, this causes a 4795 // performance issue. obj->incr_age() will first check whether 4796 // the object has a displaced mark by checking its mark word; 4797 // getting the mark word from the new location of the object 4798 // stalls. So, given that we already have the mark word and we 4799 // are about to install it anyway, it's better to increase the 4800 // age on the mark word, when the object does not have a 4801 // displaced mark word. We're not expecting many objects to have 4802 // a displaced marked word, so that case is not optimized 4803 // further (it could be...) and we simply call obj->incr_age(). 4804 4805 if (m->has_displaced_mark_helper()) { 4806 // in this case, we have to install the mark word first, 4807 // otherwise obj looks to be forwarded (the old mark word, 4808 // which contains the forward pointer, was copied) 4809 obj->set_mark(m); 4810 obj->incr_age(); 4811 } else { 4812 m = m->incr_age(); 4813 obj->set_mark(m); 4814 } 4815 age_table()->add(obj, word_sz); 4816 } else { 4817 obj->set_mark(m); 4818 } 4819 4820 if (G1StringDedup::is_enabled()) { 4821 G1StringDedup::enqueue_from_evacuation(from_region->is_young(), 4822 to_region->is_young(), 4823 queue_num(), 4824 obj); 4825 } 4826 4827 size_t* surv_young_words = surviving_young_words(); 4828 surv_young_words[young_index] += word_sz; 4829 4830 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4831 // We keep track of the next start index in the length field of 4832 // the to-space object. The actual length can be found in the 4833 // length field of the from-space object. 4834 arrayOop(obj)->set_length(0); 4835 oop* old_p = set_partial_array_mask(old); 4836 push_on_queue(old_p); 4837 } else { 4838 // No point in using the slower heap_region_containing() method, 4839 // given that we know obj is in the heap. 4840 _scanner.set_region(_g1h->heap_region_containing_raw(obj)); 4841 obj->oop_iterate_backwards(&_scanner); 4842 } 4843 } else { 4844 undo_allocation(alloc_purpose, obj_ptr, word_sz); 4845 obj = forward_ptr; 4846 } 4847 return obj; 4848 } 4849 4850 template <class T> 4851 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4852 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4853 _scanned_klass->record_modified_oops(); 4854 } 4855 } 4856 4857 template <G1Barrier barrier, bool do_mark_object> 4858 template <class T> 4859 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) { 4860 T heap_oop = oopDesc::load_heap_oop(p); 4861 4862 if (oopDesc::is_null(heap_oop)) { 4863 return; 4864 } 4865 4866 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 4867 4868 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4869 4870 if (_g1->in_cset_fast_test(obj)) { 4871 oop forwardee; 4872 if (obj->is_forwarded()) { 4873 forwardee = obj->forwardee(); 4874 } else { 4875 forwardee = _par_scan_state->copy_to_survivor_space(obj); 4876 } 4877 assert(forwardee != NULL, "forwardee should not be NULL"); 4878 oopDesc::encode_store_heap_oop(p, forwardee); 4879 if (do_mark_object && forwardee != obj) { 4880 // If the object is self-forwarded we don't need to explicitly 4881 // mark it, the evacuation failure protocol will do so. 4882 mark_forwarded_object(obj, forwardee); 4883 } 4884 4885 if (barrier == G1BarrierKlass) { 4886 do_klass_barrier(p, forwardee); 4887 } 4888 } else { 4889 // The object is not in collection set. If we're a root scanning 4890 // closure during an initial mark pause (i.e. do_mark_object will 4891 // be true) then attempt to mark the object. 4892 if (do_mark_object) { 4893 mark_object(obj); 4894 } 4895 } 4896 4897 if (barrier == G1BarrierEvac) { 4898 _par_scan_state->update_rs(_from, p, _worker_id); 4899 } 4900 } 4901 4902 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p); 4903 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4904 4905 class G1ParEvacuateFollowersClosure : public VoidClosure { 4906 protected: 4907 G1CollectedHeap* _g1h; 4908 G1ParScanThreadState* _par_scan_state; 4909 RefToScanQueueSet* _queues; 4910 ParallelTaskTerminator* _terminator; 4911 4912 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4913 RefToScanQueueSet* queues() { return _queues; } 4914 ParallelTaskTerminator* terminator() { return _terminator; } 4915 4916 public: 4917 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4918 G1ParScanThreadState* par_scan_state, 4919 RefToScanQueueSet* queues, 4920 ParallelTaskTerminator* terminator) 4921 : _g1h(g1h), _par_scan_state(par_scan_state), 4922 _queues(queues), _terminator(terminator) {} 4923 4924 void do_void(); 4925 4926 private: 4927 inline bool offer_termination(); 4928 }; 4929 4930 bool G1ParEvacuateFollowersClosure::offer_termination() { 4931 G1ParScanThreadState* const pss = par_scan_state(); 4932 pss->start_term_time(); 4933 const bool res = terminator()->offer_termination(); 4934 pss->end_term_time(); 4935 return res; 4936 } 4937 4938 void G1ParEvacuateFollowersClosure::do_void() { 4939 StarTask stolen_task; 4940 G1ParScanThreadState* const pss = par_scan_state(); 4941 pss->trim_queue(); 4942 4943 do { 4944 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4945 assert(pss->verify_task(stolen_task), "sanity"); 4946 if (stolen_task.is_narrow()) { 4947 pss->deal_with_reference((narrowOop*) stolen_task); 4948 } else { 4949 pss->deal_with_reference((oop*) stolen_task); 4950 } 4951 4952 // We've just processed a reference and we might have made 4953 // available new entries on the queues. So we have to make sure 4954 // we drain the queues as necessary. 4955 pss->trim_queue(); 4956 } 4957 } while (!offer_termination()); 4958 4959 pss->retire_alloc_buffers(); 4960 } 4961 4962 class G1KlassScanClosure : public KlassClosure { 4963 G1ParCopyHelper* _closure; 4964 bool _process_only_dirty; 4965 int _count; 4966 public: 4967 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4968 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4969 void do_klass(Klass* klass) { 4970 // If the klass has not been dirtied we know that there's 4971 // no references into the young gen and we can skip it. 4972 if (!_process_only_dirty || klass->has_modified_oops()) { 4973 // Clean the klass since we're going to scavenge all the metadata. 4974 klass->clear_modified_oops(); 4975 4976 // Tell the closure that this klass is the Klass to scavenge 4977 // and is the one to dirty if oops are left pointing into the young gen. 4978 _closure->set_scanned_klass(klass); 4979 4980 klass->oops_do(_closure); 4981 4982 _closure->set_scanned_klass(NULL); 4983 } 4984 _count++; 4985 } 4986 }; 4987 4988 class G1ParTask : public AbstractGangTask { 4989 protected: 4990 G1CollectedHeap* _g1h; 4991 RefToScanQueueSet *_queues; 4992 ParallelTaskTerminator _terminator; 4993 uint _n_workers; 4994 4995 Mutex _stats_lock; 4996 Mutex* stats_lock() { return &_stats_lock; } 4997 4998 size_t getNCards() { 4999 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 5000 / G1BlockOffsetSharedArray::N_bytes; 5001 } 5002 5003 public: 5004 G1ParTask(G1CollectedHeap* g1h, 5005 RefToScanQueueSet *task_queues) 5006 : AbstractGangTask("G1 collection"), 5007 _g1h(g1h), 5008 _queues(task_queues), 5009 _terminator(0, _queues), 5010 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 5011 {} 5012 5013 RefToScanQueueSet* queues() { return _queues; } 5014 5015 RefToScanQueue *work_queue(int i) { 5016 return queues()->queue(i); 5017 } 5018 5019 ParallelTaskTerminator* terminator() { return &_terminator; } 5020 5021 virtual void set_for_termination(int active_workers) { 5022 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 5023 // in the young space (_par_seq_tasks) in the G1 heap 5024 // for SequentialSubTasksDone. 5025 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 5026 // both of which need setting by set_n_termination(). 5027 _g1h->SharedHeap::set_n_termination(active_workers); 5028 _g1h->set_n_termination(active_workers); 5029 terminator()->reset_for_reuse(active_workers); 5030 _n_workers = active_workers; 5031 } 5032 5033 void work(uint worker_id) { 5034 if (worker_id >= _n_workers) return; // no work needed this round 5035 5036 double start_time_ms = os::elapsedTime() * 1000.0; 5037 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 5038 5039 { 5040 ResourceMark rm; 5041 HandleMark hm; 5042 5043 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 5044 5045 G1ParScanThreadState pss(_g1h, worker_id, rp); 5046 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 5047 5048 pss.set_evac_failure_closure(&evac_failure_cl); 5049 5050 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); 5051 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp); 5052 5053 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); 5054 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp); 5055 5056 bool only_young = _g1h->g1_policy()->gcs_are_young(); 5057 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false); 5058 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young); 5059 5060 OopClosure* scan_root_cl = &only_scan_root_cl; 5061 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s; 5062 5063 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5064 // We also need to mark copied objects. 5065 scan_root_cl = &scan_mark_root_cl; 5066 scan_klasses_cl = &scan_mark_klasses_cl_s; 5067 } 5068 5069 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 5070 5071 // Don't scan the scavengable methods in the code cache as part 5072 // of strong root scanning. The code roots that point into a 5073 // region in the collection set are scanned when we scan the 5074 // region's RSet. 5075 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings; 5076 5077 pss.start_strong_roots(); 5078 _g1h->g1_process_strong_roots(/* is scavenging */ true, 5079 SharedHeap::ScanningOption(so), 5080 scan_root_cl, 5081 &push_heap_rs_cl, 5082 scan_klasses_cl, 5083 worker_id); 5084 pss.end_strong_roots(); 5085 5086 { 5087 double start = os::elapsedTime(); 5088 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 5089 evac.do_void(); 5090 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 5091 double term_ms = pss.term_time()*1000.0; 5092 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 5093 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 5094 } 5095 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 5096 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 5097 5098 if (ParallelGCVerbose) { 5099 MutexLocker x(stats_lock()); 5100 pss.print_termination_stats(worker_id); 5101 } 5102 5103 assert(pss.refs()->is_empty(), "should be empty"); 5104 5105 // Close the inner scope so that the ResourceMark and HandleMark 5106 // destructors are executed here and are included as part of the 5107 // "GC Worker Time". 5108 } 5109 5110 double end_time_ms = os::elapsedTime() * 1000.0; 5111 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 5112 } 5113 }; 5114 5115 // *** Common G1 Evacuation Stuff 5116 5117 // This method is run in a GC worker. 5118 5119 void 5120 G1CollectedHeap:: 5121 g1_process_strong_roots(bool is_scavenging, 5122 ScanningOption so, 5123 OopClosure* scan_non_heap_roots, 5124 OopsInHeapRegionClosure* scan_rs, 5125 G1KlassScanClosure* scan_klasses, 5126 uint worker_i) { 5127 5128 // First scan the strong roots 5129 double ext_roots_start = os::elapsedTime(); 5130 double closure_app_time_sec = 0.0; 5131 5132 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 5133 5134 assert(so & SO_CodeCache || scan_rs != NULL, "must scan code roots somehow"); 5135 // Walk the code cache/strong code roots w/o buffering, because StarTask 5136 // cannot handle unaligned oop locations. 5137 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */); 5138 5139 process_strong_roots(false, // no scoping; this is parallel code 5140 is_scavenging, so, 5141 &buf_scan_non_heap_roots, 5142 &eager_scan_code_roots, 5143 scan_klasses 5144 ); 5145 5146 // Now the CM ref_processor roots. 5147 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 5148 // We need to treat the discovered reference lists of the 5149 // concurrent mark ref processor as roots and keep entries 5150 // (which are added by the marking threads) on them live 5151 // until they can be processed at the end of marking. 5152 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 5153 } 5154 5155 // Finish up any enqueued closure apps (attributed as object copy time). 5156 buf_scan_non_heap_roots.done(); 5157 5158 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds(); 5159 5160 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 5161 5162 double ext_root_time_ms = 5163 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 5164 5165 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 5166 5167 // During conc marking we have to filter the per-thread SATB buffers 5168 // to make sure we remove any oops into the CSet (which will show up 5169 // as implicitly live). 5170 double satb_filtering_ms = 0.0; 5171 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 5172 if (mark_in_progress()) { 5173 double satb_filter_start = os::elapsedTime(); 5174 5175 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 5176 5177 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 5178 } 5179 } 5180 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 5181 5182 // If this is an initial mark pause, and we're not scanning 5183 // the entire code cache, we need to mark the oops in the 5184 // strong code root lists for the regions that are not in 5185 // the collection set. 5186 // Note all threads participate in this set of root tasks. 5187 double mark_strong_code_roots_ms = 0.0; 5188 if (g1_policy()->during_initial_mark_pause() && !(so & SO_CodeCache)) { 5189 double mark_strong_roots_start = os::elapsedTime(); 5190 mark_strong_code_roots(worker_i); 5191 mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0; 5192 } 5193 g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms); 5194 5195 // Now scan the complement of the collection set. 5196 if (scan_rs != NULL) { 5197 g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i); 5198 } 5199 _process_strong_tasks->all_tasks_completed(); 5200 } 5201 5202 void 5203 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) { 5204 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 5205 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs); 5206 } 5207 5208 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 5209 private: 5210 BoolObjectClosure* _is_alive; 5211 int _initial_string_table_size; 5212 int _initial_symbol_table_size; 5213 5214 bool _process_strings; 5215 int _strings_processed; 5216 int _strings_removed; 5217 5218 bool _process_symbols; 5219 int _symbols_processed; 5220 int _symbols_removed; 5221 5222 bool _do_in_parallel; 5223 public: 5224 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 5225 AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive), 5226 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()), 5227 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 5228 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 5229 5230 _initial_string_table_size = StringTable::the_table()->table_size(); 5231 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 5232 if (process_strings) { 5233 StringTable::clear_parallel_claimed_index(); 5234 } 5235 if (process_symbols) { 5236 SymbolTable::clear_parallel_claimed_index(); 5237 } 5238 } 5239 5240 ~G1StringSymbolTableUnlinkTask() { 5241 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size, 5242 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT, 5243 StringTable::parallel_claimed_index(), _initial_string_table_size)); 5244 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 5245 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT, 5246 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size)); 5247 } 5248 5249 void work(uint worker_id) { 5250 if (_do_in_parallel) { 5251 int strings_processed = 0; 5252 int strings_removed = 0; 5253 int symbols_processed = 0; 5254 int symbols_removed = 0; 5255 if (_process_strings) { 5256 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 5257 Atomic::add(strings_processed, &_strings_processed); 5258 Atomic::add(strings_removed, &_strings_removed); 5259 } 5260 if (_process_symbols) { 5261 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 5262 Atomic::add(symbols_processed, &_symbols_processed); 5263 Atomic::add(symbols_removed, &_symbols_removed); 5264 } 5265 } else { 5266 if (_process_strings) { 5267 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed); 5268 } 5269 if (_process_symbols) { 5270 SymbolTable::unlink(&_symbols_processed, &_symbols_removed); 5271 } 5272 } 5273 } 5274 5275 size_t strings_processed() const { return (size_t)_strings_processed; } 5276 size_t strings_removed() const { return (size_t)_strings_removed; } 5277 5278 size_t symbols_processed() const { return (size_t)_symbols_processed; } 5279 size_t symbols_removed() const { return (size_t)_symbols_removed; } 5280 }; 5281 5282 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 5283 bool process_strings, bool process_symbols) { 5284 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5285 _g1h->workers()->active_workers() : 1); 5286 5287 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 5288 if (G1CollectedHeap::use_parallel_gc_threads()) { 5289 set_par_threads(n_workers); 5290 workers()->run_task(&g1_unlink_task); 5291 set_par_threads(0); 5292 } else { 5293 g1_unlink_task.work(0); 5294 } 5295 if (G1TraceStringSymbolTableScrubbing) { 5296 gclog_or_tty->print_cr("Cleaned string and symbol table, " 5297 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, " 5298 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed", 5299 g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(), 5300 g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed()); 5301 } 5302 5303 if (G1StringDedup::is_enabled()) { 5304 G1StringDedup::unlink(is_alive); 5305 } 5306 } 5307 5308 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure { 5309 public: 5310 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 5311 *card_ptr = CardTableModRefBS::dirty_card_val(); 5312 return true; 5313 } 5314 }; 5315 5316 void G1CollectedHeap::redirty_logged_cards() { 5317 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates."); 5318 double redirty_logged_cards_start = os::elapsedTime(); 5319 5320 RedirtyLoggedCardTableEntryFastClosure redirty; 5321 dirty_card_queue_set().set_closure(&redirty); 5322 dirty_card_queue_set().apply_closure_to_all_completed_buffers(); 5323 5324 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5325 dcq.merge_bufferlists(&dirty_card_queue_set()); 5326 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5327 5328 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 5329 } 5330 5331 // Weak Reference Processing support 5332 5333 // An always "is_alive" closure that is used to preserve referents. 5334 // If the object is non-null then it's alive. Used in the preservation 5335 // of referent objects that are pointed to by reference objects 5336 // discovered by the CM ref processor. 5337 class G1AlwaysAliveClosure: public BoolObjectClosure { 5338 G1CollectedHeap* _g1; 5339 public: 5340 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5341 bool do_object_b(oop p) { 5342 if (p != NULL) { 5343 return true; 5344 } 5345 return false; 5346 } 5347 }; 5348 5349 bool G1STWIsAliveClosure::do_object_b(oop p) { 5350 // An object is reachable if it is outside the collection set, 5351 // or is inside and copied. 5352 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5353 } 5354 5355 // Non Copying Keep Alive closure 5356 class G1KeepAliveClosure: public OopClosure { 5357 G1CollectedHeap* _g1; 5358 public: 5359 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5360 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5361 void do_oop( oop* p) { 5362 oop obj = *p; 5363 5364 if (_g1->obj_in_cs(obj)) { 5365 assert( obj->is_forwarded(), "invariant" ); 5366 *p = obj->forwardee(); 5367 } 5368 } 5369 }; 5370 5371 // Copying Keep Alive closure - can be called from both 5372 // serial and parallel code as long as different worker 5373 // threads utilize different G1ParScanThreadState instances 5374 // and different queues. 5375 5376 class G1CopyingKeepAliveClosure: public OopClosure { 5377 G1CollectedHeap* _g1h; 5378 OopClosure* _copy_non_heap_obj_cl; 5379 OopsInHeapRegionClosure* _copy_metadata_obj_cl; 5380 G1ParScanThreadState* _par_scan_state; 5381 5382 public: 5383 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5384 OopClosure* non_heap_obj_cl, 5385 OopsInHeapRegionClosure* metadata_obj_cl, 5386 G1ParScanThreadState* pss): 5387 _g1h(g1h), 5388 _copy_non_heap_obj_cl(non_heap_obj_cl), 5389 _copy_metadata_obj_cl(metadata_obj_cl), 5390 _par_scan_state(pss) 5391 {} 5392 5393 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5394 virtual void do_oop( oop* p) { do_oop_work(p); } 5395 5396 template <class T> void do_oop_work(T* p) { 5397 oop obj = oopDesc::load_decode_heap_oop(p); 5398 5399 if (_g1h->obj_in_cs(obj)) { 5400 // If the referent object has been forwarded (either copied 5401 // to a new location or to itself in the event of an 5402 // evacuation failure) then we need to update the reference 5403 // field and, if both reference and referent are in the G1 5404 // heap, update the RSet for the referent. 5405 // 5406 // If the referent has not been forwarded then we have to keep 5407 // it alive by policy. Therefore we have copy the referent. 5408 // 5409 // If the reference field is in the G1 heap then we can push 5410 // on the PSS queue. When the queue is drained (after each 5411 // phase of reference processing) the object and it's followers 5412 // will be copied, the reference field set to point to the 5413 // new location, and the RSet updated. Otherwise we need to 5414 // use the the non-heap or metadata closures directly to copy 5415 // the referent object and update the pointer, while avoiding 5416 // updating the RSet. 5417 5418 if (_g1h->is_in_g1_reserved(p)) { 5419 _par_scan_state->push_on_queue(p); 5420 } else { 5421 assert(!Metaspace::contains((const void*)p), 5422 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) " 5423 PTR_FORMAT, p)); 5424 _copy_non_heap_obj_cl->do_oop(p); 5425 } 5426 } 5427 } 5428 }; 5429 5430 // Serial drain queue closure. Called as the 'complete_gc' 5431 // closure for each discovered list in some of the 5432 // reference processing phases. 5433 5434 class G1STWDrainQueueClosure: public VoidClosure { 5435 protected: 5436 G1CollectedHeap* _g1h; 5437 G1ParScanThreadState* _par_scan_state; 5438 5439 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5440 5441 public: 5442 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5443 _g1h(g1h), 5444 _par_scan_state(pss) 5445 { } 5446 5447 void do_void() { 5448 G1ParScanThreadState* const pss = par_scan_state(); 5449 pss->trim_queue(); 5450 } 5451 }; 5452 5453 // Parallel Reference Processing closures 5454 5455 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5456 // processing during G1 evacuation pauses. 5457 5458 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5459 private: 5460 G1CollectedHeap* _g1h; 5461 RefToScanQueueSet* _queues; 5462 FlexibleWorkGang* _workers; 5463 int _active_workers; 5464 5465 public: 5466 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5467 FlexibleWorkGang* workers, 5468 RefToScanQueueSet *task_queues, 5469 int n_workers) : 5470 _g1h(g1h), 5471 _queues(task_queues), 5472 _workers(workers), 5473 _active_workers(n_workers) 5474 { 5475 assert(n_workers > 0, "shouldn't call this otherwise"); 5476 } 5477 5478 // Executes the given task using concurrent marking worker threads. 5479 virtual void execute(ProcessTask& task); 5480 virtual void execute(EnqueueTask& task); 5481 }; 5482 5483 // Gang task for possibly parallel reference processing 5484 5485 class G1STWRefProcTaskProxy: public AbstractGangTask { 5486 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5487 ProcessTask& _proc_task; 5488 G1CollectedHeap* _g1h; 5489 RefToScanQueueSet *_task_queues; 5490 ParallelTaskTerminator* _terminator; 5491 5492 public: 5493 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5494 G1CollectedHeap* g1h, 5495 RefToScanQueueSet *task_queues, 5496 ParallelTaskTerminator* terminator) : 5497 AbstractGangTask("Process reference objects in parallel"), 5498 _proc_task(proc_task), 5499 _g1h(g1h), 5500 _task_queues(task_queues), 5501 _terminator(terminator) 5502 {} 5503 5504 virtual void work(uint worker_id) { 5505 // The reference processing task executed by a single worker. 5506 ResourceMark rm; 5507 HandleMark hm; 5508 5509 G1STWIsAliveClosure is_alive(_g1h); 5510 5511 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5512 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5513 5514 pss.set_evac_failure_closure(&evac_failure_cl); 5515 5516 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5517 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5518 5519 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5520 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5521 5522 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5523 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5524 5525 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5526 // We also need to mark copied objects. 5527 copy_non_heap_cl = ©_mark_non_heap_cl; 5528 copy_metadata_cl = ©_mark_metadata_cl; 5529 } 5530 5531 // Keep alive closure. 5532 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5533 5534 // Complete GC closure 5535 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5536 5537 // Call the reference processing task's work routine. 5538 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5539 5540 // Note we cannot assert that the refs array is empty here as not all 5541 // of the processing tasks (specifically phase2 - pp2_work) execute 5542 // the complete_gc closure (which ordinarily would drain the queue) so 5543 // the queue may not be empty. 5544 } 5545 }; 5546 5547 // Driver routine for parallel reference processing. 5548 // Creates an instance of the ref processing gang 5549 // task and has the worker threads execute it. 5550 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5551 assert(_workers != NULL, "Need parallel worker threads."); 5552 5553 ParallelTaskTerminator terminator(_active_workers, _queues); 5554 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5555 5556 _g1h->set_par_threads(_active_workers); 5557 _workers->run_task(&proc_task_proxy); 5558 _g1h->set_par_threads(0); 5559 } 5560 5561 // Gang task for parallel reference enqueueing. 5562 5563 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5564 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5565 EnqueueTask& _enq_task; 5566 5567 public: 5568 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5569 AbstractGangTask("Enqueue reference objects in parallel"), 5570 _enq_task(enq_task) 5571 { } 5572 5573 virtual void work(uint worker_id) { 5574 _enq_task.work(worker_id); 5575 } 5576 }; 5577 5578 // Driver routine for parallel reference enqueueing. 5579 // Creates an instance of the ref enqueueing gang 5580 // task and has the worker threads execute it. 5581 5582 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5583 assert(_workers != NULL, "Need parallel worker threads."); 5584 5585 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5586 5587 _g1h->set_par_threads(_active_workers); 5588 _workers->run_task(&enq_task_proxy); 5589 _g1h->set_par_threads(0); 5590 } 5591 5592 // End of weak reference support closures 5593 5594 // Abstract task used to preserve (i.e. copy) any referent objects 5595 // that are in the collection set and are pointed to by reference 5596 // objects discovered by the CM ref processor. 5597 5598 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5599 protected: 5600 G1CollectedHeap* _g1h; 5601 RefToScanQueueSet *_queues; 5602 ParallelTaskTerminator _terminator; 5603 uint _n_workers; 5604 5605 public: 5606 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5607 AbstractGangTask("ParPreserveCMReferents"), 5608 _g1h(g1h), 5609 _queues(task_queues), 5610 _terminator(workers, _queues), 5611 _n_workers(workers) 5612 { } 5613 5614 void work(uint worker_id) { 5615 ResourceMark rm; 5616 HandleMark hm; 5617 5618 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5619 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5620 5621 pss.set_evac_failure_closure(&evac_failure_cl); 5622 5623 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5624 5625 5626 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5627 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5628 5629 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5630 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5631 5632 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5633 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5634 5635 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5636 // We also need to mark copied objects. 5637 copy_non_heap_cl = ©_mark_non_heap_cl; 5638 copy_metadata_cl = ©_mark_metadata_cl; 5639 } 5640 5641 // Is alive closure 5642 G1AlwaysAliveClosure always_alive(_g1h); 5643 5644 // Copying keep alive closure. Applied to referent objects that need 5645 // to be copied. 5646 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5647 5648 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5649 5650 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5651 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5652 5653 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5654 // So this must be true - but assert just in case someone decides to 5655 // change the worker ids. 5656 assert(0 <= worker_id && worker_id < limit, "sanity"); 5657 assert(!rp->discovery_is_atomic(), "check this code"); 5658 5659 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5660 for (uint idx = worker_id; idx < limit; idx += stride) { 5661 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5662 5663 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5664 while (iter.has_next()) { 5665 // Since discovery is not atomic for the CM ref processor, we 5666 // can see some null referent objects. 5667 iter.load_ptrs(DEBUG_ONLY(true)); 5668 oop ref = iter.obj(); 5669 5670 // This will filter nulls. 5671 if (iter.is_referent_alive()) { 5672 iter.make_referent_alive(); 5673 } 5674 iter.move_to_next(); 5675 } 5676 } 5677 5678 // Drain the queue - which may cause stealing 5679 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5680 drain_queue.do_void(); 5681 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5682 assert(pss.refs()->is_empty(), "should be"); 5683 } 5684 }; 5685 5686 // Weak Reference processing during an evacuation pause (part 1). 5687 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5688 double ref_proc_start = os::elapsedTime(); 5689 5690 ReferenceProcessor* rp = _ref_processor_stw; 5691 assert(rp->discovery_enabled(), "should have been enabled"); 5692 5693 // Any reference objects, in the collection set, that were 'discovered' 5694 // by the CM ref processor should have already been copied (either by 5695 // applying the external root copy closure to the discovered lists, or 5696 // by following an RSet entry). 5697 // 5698 // But some of the referents, that are in the collection set, that these 5699 // reference objects point to may not have been copied: the STW ref 5700 // processor would have seen that the reference object had already 5701 // been 'discovered' and would have skipped discovering the reference, 5702 // but would not have treated the reference object as a regular oop. 5703 // As a result the copy closure would not have been applied to the 5704 // referent object. 5705 // 5706 // We need to explicitly copy these referent objects - the references 5707 // will be processed at the end of remarking. 5708 // 5709 // We also need to do this copying before we process the reference 5710 // objects discovered by the STW ref processor in case one of these 5711 // referents points to another object which is also referenced by an 5712 // object discovered by the STW ref processor. 5713 5714 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5715 no_of_gc_workers == workers()->active_workers(), 5716 "Need to reset active GC workers"); 5717 5718 set_par_threads(no_of_gc_workers); 5719 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5720 no_of_gc_workers, 5721 _task_queues); 5722 5723 if (G1CollectedHeap::use_parallel_gc_threads()) { 5724 workers()->run_task(&keep_cm_referents); 5725 } else { 5726 keep_cm_referents.work(0); 5727 } 5728 5729 set_par_threads(0); 5730 5731 // Closure to test whether a referent is alive. 5732 G1STWIsAliveClosure is_alive(this); 5733 5734 // Even when parallel reference processing is enabled, the processing 5735 // of JNI refs is serial and performed serially by the current thread 5736 // rather than by a worker. The following PSS will be used for processing 5737 // JNI refs. 5738 5739 // Use only a single queue for this PSS. 5740 G1ParScanThreadState pss(this, 0, NULL); 5741 5742 // We do not embed a reference processor in the copying/scanning 5743 // closures while we're actually processing the discovered 5744 // reference objects. 5745 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5746 5747 pss.set_evac_failure_closure(&evac_failure_cl); 5748 5749 assert(pss.refs()->is_empty(), "pre-condition"); 5750 5751 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5752 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL); 5753 5754 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5755 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL); 5756 5757 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5758 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5759 5760 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5761 // We also need to mark copied objects. 5762 copy_non_heap_cl = ©_mark_non_heap_cl; 5763 copy_metadata_cl = ©_mark_metadata_cl; 5764 } 5765 5766 // Keep alive closure. 5767 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss); 5768 5769 // Serial Complete GC closure 5770 G1STWDrainQueueClosure drain_queue(this, &pss); 5771 5772 // Setup the soft refs policy... 5773 rp->setup_policy(false); 5774 5775 ReferenceProcessorStats stats; 5776 if (!rp->processing_is_mt()) { 5777 // Serial reference processing... 5778 stats = rp->process_discovered_references(&is_alive, 5779 &keep_alive, 5780 &drain_queue, 5781 NULL, 5782 _gc_timer_stw, 5783 _gc_tracer_stw->gc_id()); 5784 } else { 5785 // Parallel reference processing 5786 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5787 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5788 5789 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5790 stats = rp->process_discovered_references(&is_alive, 5791 &keep_alive, 5792 &drain_queue, 5793 &par_task_executor, 5794 _gc_timer_stw, 5795 _gc_tracer_stw->gc_id()); 5796 } 5797 5798 _gc_tracer_stw->report_gc_reference_stats(stats); 5799 // We have completed copying any necessary live referent objects 5800 // (that were not copied during the actual pause) so we can 5801 // retire any active alloc buffers 5802 pss.retire_alloc_buffers(); 5803 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5804 5805 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5806 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5807 } 5808 5809 // Weak Reference processing during an evacuation pause (part 2). 5810 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5811 double ref_enq_start = os::elapsedTime(); 5812 5813 ReferenceProcessor* rp = _ref_processor_stw; 5814 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5815 5816 // Now enqueue any remaining on the discovered lists on to 5817 // the pending list. 5818 if (!rp->processing_is_mt()) { 5819 // Serial reference processing... 5820 rp->enqueue_discovered_references(); 5821 } else { 5822 // Parallel reference enqueueing 5823 5824 assert(no_of_gc_workers == workers()->active_workers(), 5825 "Need to reset active workers"); 5826 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5827 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5828 5829 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5830 rp->enqueue_discovered_references(&par_task_executor); 5831 } 5832 5833 rp->verify_no_references_recorded(); 5834 assert(!rp->discovery_enabled(), "should have been disabled"); 5835 5836 // FIXME 5837 // CM's reference processing also cleans up the string and symbol tables. 5838 // Should we do that here also? We could, but it is a serial operation 5839 // and could significantly increase the pause time. 5840 5841 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5842 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5843 } 5844 5845 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) { 5846 _expand_heap_after_alloc_failure = true; 5847 _evacuation_failed = false; 5848 5849 // Should G1EvacuationFailureALot be in effect for this GC? 5850 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5851 5852 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5853 5854 // Disable the hot card cache. 5855 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5856 hot_card_cache->reset_hot_cache_claimed_index(); 5857 hot_card_cache->set_use_cache(false); 5858 5859 uint n_workers; 5860 if (G1CollectedHeap::use_parallel_gc_threads()) { 5861 n_workers = 5862 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5863 workers()->active_workers(), 5864 Threads::number_of_non_daemon_threads()); 5865 assert(UseDynamicNumberOfGCThreads || 5866 n_workers == workers()->total_workers(), 5867 "If not dynamic should be using all the workers"); 5868 workers()->set_active_workers(n_workers); 5869 set_par_threads(n_workers); 5870 } else { 5871 assert(n_par_threads() == 0, 5872 "Should be the original non-parallel value"); 5873 n_workers = 1; 5874 } 5875 5876 G1ParTask g1_par_task(this, _task_queues); 5877 5878 init_for_evac_failure(NULL); 5879 5880 rem_set()->prepare_for_younger_refs_iterate(true); 5881 5882 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5883 double start_par_time_sec = os::elapsedTime(); 5884 double end_par_time_sec; 5885 5886 { 5887 StrongRootsScope srs(this); 5888 5889 if (G1CollectedHeap::use_parallel_gc_threads()) { 5890 // The individual threads will set their evac-failure closures. 5891 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5892 // These tasks use ShareHeap::_process_strong_tasks 5893 assert(UseDynamicNumberOfGCThreads || 5894 workers()->active_workers() == workers()->total_workers(), 5895 "If not dynamic should be using all the workers"); 5896 workers()->run_task(&g1_par_task); 5897 } else { 5898 g1_par_task.set_for_termination(n_workers); 5899 g1_par_task.work(0); 5900 } 5901 end_par_time_sec = os::elapsedTime(); 5902 5903 // Closing the inner scope will execute the destructor 5904 // for the StrongRootsScope object. We record the current 5905 // elapsed time before closing the scope so that time 5906 // taken for the SRS destructor is NOT included in the 5907 // reported parallel time. 5908 } 5909 5910 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5911 g1_policy()->phase_times()->record_par_time(par_time_ms); 5912 5913 double code_root_fixup_time_ms = 5914 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5915 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5916 5917 set_par_threads(0); 5918 5919 // Process any discovered reference objects - we have 5920 // to do this _before_ we retire the GC alloc regions 5921 // as we may have to copy some 'reachable' referent 5922 // objects (and their reachable sub-graphs) that were 5923 // not copied during the pause. 5924 process_discovered_references(n_workers); 5925 5926 // Weak root processing. 5927 { 5928 G1STWIsAliveClosure is_alive(this); 5929 G1KeepAliveClosure keep_alive(this); 5930 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5931 if (G1StringDedup::is_enabled()) { 5932 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive); 5933 } 5934 } 5935 5936 release_gc_alloc_regions(n_workers, evacuation_info); 5937 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5938 5939 // Reset and re-enable the hot card cache. 5940 // Note the counts for the cards in the regions in the 5941 // collection set are reset when the collection set is freed. 5942 hot_card_cache->reset_hot_cache(); 5943 hot_card_cache->set_use_cache(true); 5944 5945 // Migrate the strong code roots attached to each region in 5946 // the collection set. Ideally we would like to do this 5947 // after we have finished the scanning/evacuation of the 5948 // strong code roots for a particular heap region. 5949 migrate_strong_code_roots(); 5950 5951 purge_code_root_memory(); 5952 5953 if (g1_policy()->during_initial_mark_pause()) { 5954 // Reset the claim values set during marking the strong code roots 5955 reset_heap_region_claim_values(); 5956 } 5957 5958 finalize_for_evac_failure(); 5959 5960 if (evacuation_failed()) { 5961 remove_self_forwarding_pointers(); 5962 5963 // Reset the G1EvacuationFailureALot counters and flags 5964 // Note: the values are reset only when an actual 5965 // evacuation failure occurs. 5966 NOT_PRODUCT(reset_evacuation_should_fail();) 5967 } 5968 5969 // Enqueue any remaining references remaining on the STW 5970 // reference processor's discovered lists. We need to do 5971 // this after the card table is cleaned (and verified) as 5972 // the act of enqueueing entries on to the pending list 5973 // will log these updates (and dirty their associated 5974 // cards). We need these updates logged to update any 5975 // RSets. 5976 enqueue_discovered_references(n_workers); 5977 5978 if (G1DeferredRSUpdate) { 5979 redirty_logged_cards(); 5980 } 5981 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5982 } 5983 5984 void G1CollectedHeap::free_region(HeapRegion* hr, 5985 FreeRegionList* free_list, 5986 bool par, 5987 bool locked) { 5988 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 5989 assert(!hr->is_empty(), "the region should not be empty"); 5990 assert(free_list != NULL, "pre-condition"); 5991 5992 // Clear the card counts for this region. 5993 // Note: we only need to do this if the region is not young 5994 // (since we don't refine cards in young regions). 5995 if (!hr->is_young()) { 5996 _cg1r->hot_card_cache()->reset_card_counts(hr); 5997 } 5998 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5999 free_list->add_ordered(hr); 6000 } 6001 6002 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 6003 FreeRegionList* free_list, 6004 bool par) { 6005 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 6006 assert(free_list != NULL, "pre-condition"); 6007 6008 size_t hr_capacity = hr->capacity(); 6009 // We need to read this before we make the region non-humongous, 6010 // otherwise the information will be gone. 6011 uint last_index = hr->last_hc_index(); 6012 hr->set_notHumongous(); 6013 free_region(hr, free_list, par); 6014 6015 uint i = hr->hrs_index() + 1; 6016 while (i < last_index) { 6017 HeapRegion* curr_hr = region_at(i); 6018 assert(curr_hr->continuesHumongous(), "invariant"); 6019 curr_hr->set_notHumongous(); 6020 free_region(curr_hr, free_list, par); 6021 i += 1; 6022 } 6023 } 6024 6025 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 6026 const HeapRegionSetCount& humongous_regions_removed) { 6027 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 6028 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 6029 _old_set.bulk_remove(old_regions_removed); 6030 _humongous_set.bulk_remove(humongous_regions_removed); 6031 } 6032 6033 } 6034 6035 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 6036 assert(list != NULL, "list can't be null"); 6037 if (!list->is_empty()) { 6038 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 6039 _free_list.add_ordered(list); 6040 } 6041 } 6042 6043 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 6044 assert(_summary_bytes_used >= bytes, 6045 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT, 6046 _summary_bytes_used, bytes)); 6047 _summary_bytes_used -= bytes; 6048 } 6049 6050 class G1ParCleanupCTTask : public AbstractGangTask { 6051 G1SATBCardTableModRefBS* _ct_bs; 6052 G1CollectedHeap* _g1h; 6053 HeapRegion* volatile _su_head; 6054 public: 6055 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 6056 G1CollectedHeap* g1h) : 6057 AbstractGangTask("G1 Par Cleanup CT Task"), 6058 _ct_bs(ct_bs), _g1h(g1h) { } 6059 6060 void work(uint worker_id) { 6061 HeapRegion* r; 6062 while (r = _g1h->pop_dirty_cards_region()) { 6063 clear_cards(r); 6064 } 6065 } 6066 6067 void clear_cards(HeapRegion* r) { 6068 // Cards of the survivors should have already been dirtied. 6069 if (!r->is_survivor()) { 6070 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 6071 } 6072 } 6073 }; 6074 6075 #ifndef PRODUCT 6076 class G1VerifyCardTableCleanup: public HeapRegionClosure { 6077 G1CollectedHeap* _g1h; 6078 G1SATBCardTableModRefBS* _ct_bs; 6079 public: 6080 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 6081 : _g1h(g1h), _ct_bs(ct_bs) { } 6082 virtual bool doHeapRegion(HeapRegion* r) { 6083 if (r->is_survivor()) { 6084 _g1h->verify_dirty_region(r); 6085 } else { 6086 _g1h->verify_not_dirty_region(r); 6087 } 6088 return false; 6089 } 6090 }; 6091 6092 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 6093 // All of the region should be clean. 6094 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6095 MemRegion mr(hr->bottom(), hr->end()); 6096 ct_bs->verify_not_dirty_region(mr); 6097 } 6098 6099 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 6100 // We cannot guarantee that [bottom(),end()] is dirty. Threads 6101 // dirty allocated blocks as they allocate them. The thread that 6102 // retires each region and replaces it with a new one will do a 6103 // maximal allocation to fill in [pre_dummy_top(),end()] but will 6104 // not dirty that area (one less thing to have to do while holding 6105 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 6106 // is dirty. 6107 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6108 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 6109 if (hr->is_young()) { 6110 ct_bs->verify_g1_young_region(mr); 6111 } else { 6112 ct_bs->verify_dirty_region(mr); 6113 } 6114 } 6115 6116 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 6117 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6118 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 6119 verify_dirty_region(hr); 6120 } 6121 } 6122 6123 void G1CollectedHeap::verify_dirty_young_regions() { 6124 verify_dirty_young_list(_young_list->first_region()); 6125 } 6126 #endif 6127 6128 void G1CollectedHeap::cleanUpCardTable() { 6129 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6130 double start = os::elapsedTime(); 6131 6132 { 6133 // Iterate over the dirty cards region list. 6134 G1ParCleanupCTTask cleanup_task(ct_bs, this); 6135 6136 if (G1CollectedHeap::use_parallel_gc_threads()) { 6137 set_par_threads(); 6138 workers()->run_task(&cleanup_task); 6139 set_par_threads(0); 6140 } else { 6141 while (_dirty_cards_region_list) { 6142 HeapRegion* r = _dirty_cards_region_list; 6143 cleanup_task.clear_cards(r); 6144 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 6145 if (_dirty_cards_region_list == r) { 6146 // The last region. 6147 _dirty_cards_region_list = NULL; 6148 } 6149 r->set_next_dirty_cards_region(NULL); 6150 } 6151 } 6152 #ifndef PRODUCT 6153 if (G1VerifyCTCleanup || VerifyAfterGC) { 6154 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 6155 heap_region_iterate(&cleanup_verifier); 6156 } 6157 #endif 6158 } 6159 6160 double elapsed = os::elapsedTime() - start; 6161 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 6162 } 6163 6164 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) { 6165 size_t pre_used = 0; 6166 FreeRegionList local_free_list("Local List for CSet Freeing"); 6167 6168 double young_time_ms = 0.0; 6169 double non_young_time_ms = 0.0; 6170 6171 // Since the collection set is a superset of the the young list, 6172 // all we need to do to clear the young list is clear its 6173 // head and length, and unlink any young regions in the code below 6174 _young_list->clear(); 6175 6176 G1CollectorPolicy* policy = g1_policy(); 6177 6178 double start_sec = os::elapsedTime(); 6179 bool non_young = true; 6180 6181 HeapRegion* cur = cs_head; 6182 int age_bound = -1; 6183 size_t rs_lengths = 0; 6184 6185 while (cur != NULL) { 6186 assert(!is_on_master_free_list(cur), "sanity"); 6187 if (non_young) { 6188 if (cur->is_young()) { 6189 double end_sec = os::elapsedTime(); 6190 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6191 non_young_time_ms += elapsed_ms; 6192 6193 start_sec = os::elapsedTime(); 6194 non_young = false; 6195 } 6196 } else { 6197 if (!cur->is_young()) { 6198 double end_sec = os::elapsedTime(); 6199 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6200 young_time_ms += elapsed_ms; 6201 6202 start_sec = os::elapsedTime(); 6203 non_young = true; 6204 } 6205 } 6206 6207 rs_lengths += cur->rem_set()->occupied_locked(); 6208 6209 HeapRegion* next = cur->next_in_collection_set(); 6210 assert(cur->in_collection_set(), "bad CS"); 6211 cur->set_next_in_collection_set(NULL); 6212 cur->set_in_collection_set(false); 6213 6214 if (cur->is_young()) { 6215 int index = cur->young_index_in_cset(); 6216 assert(index != -1, "invariant"); 6217 assert((uint) index < policy->young_cset_region_length(), "invariant"); 6218 size_t words_survived = _surviving_young_words[index]; 6219 cur->record_surv_words_in_group(words_survived); 6220 6221 // At this point the we have 'popped' cur from the collection set 6222 // (linked via next_in_collection_set()) but it is still in the 6223 // young list (linked via next_young_region()). Clear the 6224 // _next_young_region field. 6225 cur->set_next_young_region(NULL); 6226 } else { 6227 int index = cur->young_index_in_cset(); 6228 assert(index == -1, "invariant"); 6229 } 6230 6231 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6232 (!cur->is_young() && cur->young_index_in_cset() == -1), 6233 "invariant" ); 6234 6235 if (!cur->evacuation_failed()) { 6236 MemRegion used_mr = cur->used_region(); 6237 6238 // And the region is empty. 6239 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6240 pre_used += cur->used(); 6241 free_region(cur, &local_free_list, false /* par */, true /* locked */); 6242 } else { 6243 cur->uninstall_surv_rate_group(); 6244 if (cur->is_young()) { 6245 cur->set_young_index_in_cset(-1); 6246 } 6247 cur->set_not_young(); 6248 cur->set_evacuation_failed(false); 6249 // The region is now considered to be old. 6250 _old_set.add(cur); 6251 evacuation_info.increment_collectionset_used_after(cur->used()); 6252 } 6253 cur = next; 6254 } 6255 6256 evacuation_info.set_regions_freed(local_free_list.length()); 6257 policy->record_max_rs_lengths(rs_lengths); 6258 policy->cset_regions_freed(); 6259 6260 double end_sec = os::elapsedTime(); 6261 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6262 6263 if (non_young) { 6264 non_young_time_ms += elapsed_ms; 6265 } else { 6266 young_time_ms += elapsed_ms; 6267 } 6268 6269 prepend_to_freelist(&local_free_list); 6270 decrement_summary_bytes(pre_used); 6271 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6272 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6273 } 6274 6275 // This routine is similar to the above but does not record 6276 // any policy statistics or update free lists; we are abandoning 6277 // the current incremental collection set in preparation of a 6278 // full collection. After the full GC we will start to build up 6279 // the incremental collection set again. 6280 // This is only called when we're doing a full collection 6281 // and is immediately followed by the tearing down of the young list. 6282 6283 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6284 HeapRegion* cur = cs_head; 6285 6286 while (cur != NULL) { 6287 HeapRegion* next = cur->next_in_collection_set(); 6288 assert(cur->in_collection_set(), "bad CS"); 6289 cur->set_next_in_collection_set(NULL); 6290 cur->set_in_collection_set(false); 6291 cur->set_young_index_in_cset(-1); 6292 cur = next; 6293 } 6294 } 6295 6296 void G1CollectedHeap::set_free_regions_coming() { 6297 if (G1ConcRegionFreeingVerbose) { 6298 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6299 "setting free regions coming"); 6300 } 6301 6302 assert(!free_regions_coming(), "pre-condition"); 6303 _free_regions_coming = true; 6304 } 6305 6306 void G1CollectedHeap::reset_free_regions_coming() { 6307 assert(free_regions_coming(), "pre-condition"); 6308 6309 { 6310 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6311 _free_regions_coming = false; 6312 SecondaryFreeList_lock->notify_all(); 6313 } 6314 6315 if (G1ConcRegionFreeingVerbose) { 6316 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6317 "reset free regions coming"); 6318 } 6319 } 6320 6321 void G1CollectedHeap::wait_while_free_regions_coming() { 6322 // Most of the time we won't have to wait, so let's do a quick test 6323 // first before we take the lock. 6324 if (!free_regions_coming()) { 6325 return; 6326 } 6327 6328 if (G1ConcRegionFreeingVerbose) { 6329 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6330 "waiting for free regions"); 6331 } 6332 6333 { 6334 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6335 while (free_regions_coming()) { 6336 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6337 } 6338 } 6339 6340 if (G1ConcRegionFreeingVerbose) { 6341 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6342 "done waiting for free regions"); 6343 } 6344 } 6345 6346 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6347 assert(heap_lock_held_for_gc(), 6348 "the heap lock should already be held by or for this thread"); 6349 _young_list->push_region(hr); 6350 } 6351 6352 class NoYoungRegionsClosure: public HeapRegionClosure { 6353 private: 6354 bool _success; 6355 public: 6356 NoYoungRegionsClosure() : _success(true) { } 6357 bool doHeapRegion(HeapRegion* r) { 6358 if (r->is_young()) { 6359 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6360 r->bottom(), r->end()); 6361 _success = false; 6362 } 6363 return false; 6364 } 6365 bool success() { return _success; } 6366 }; 6367 6368 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6369 bool ret = _young_list->check_list_empty(check_sample); 6370 6371 if (check_heap) { 6372 NoYoungRegionsClosure closure; 6373 heap_region_iterate(&closure); 6374 ret = ret && closure.success(); 6375 } 6376 6377 return ret; 6378 } 6379 6380 class TearDownRegionSetsClosure : public HeapRegionClosure { 6381 private: 6382 HeapRegionSet *_old_set; 6383 6384 public: 6385 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 6386 6387 bool doHeapRegion(HeapRegion* r) { 6388 if (r->is_empty()) { 6389 // We ignore empty regions, we'll empty the free list afterwards 6390 } else if (r->is_young()) { 6391 // We ignore young regions, we'll empty the young list afterwards 6392 } else if (r->isHumongous()) { 6393 // We ignore humongous regions, we're not tearing down the 6394 // humongous region set 6395 } else { 6396 // The rest should be old 6397 _old_set->remove(r); 6398 } 6399 return false; 6400 } 6401 6402 ~TearDownRegionSetsClosure() { 6403 assert(_old_set->is_empty(), "post-condition"); 6404 } 6405 }; 6406 6407 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6408 assert_at_safepoint(true /* should_be_vm_thread */); 6409 6410 if (!free_list_only) { 6411 TearDownRegionSetsClosure cl(&_old_set); 6412 heap_region_iterate(&cl); 6413 6414 // Note that emptying the _young_list is postponed and instead done as 6415 // the first step when rebuilding the regions sets again. The reason for 6416 // this is that during a full GC string deduplication needs to know if 6417 // a collected region was young or old when the full GC was initiated. 6418 } 6419 _free_list.remove_all(); 6420 } 6421 6422 class RebuildRegionSetsClosure : public HeapRegionClosure { 6423 private: 6424 bool _free_list_only; 6425 HeapRegionSet* _old_set; 6426 FreeRegionList* _free_list; 6427 size_t _total_used; 6428 6429 public: 6430 RebuildRegionSetsClosure(bool free_list_only, 6431 HeapRegionSet* old_set, FreeRegionList* free_list) : 6432 _free_list_only(free_list_only), 6433 _old_set(old_set), _free_list(free_list), _total_used(0) { 6434 assert(_free_list->is_empty(), "pre-condition"); 6435 if (!free_list_only) { 6436 assert(_old_set->is_empty(), "pre-condition"); 6437 } 6438 } 6439 6440 bool doHeapRegion(HeapRegion* r) { 6441 if (r->continuesHumongous()) { 6442 return false; 6443 } 6444 6445 if (r->is_empty()) { 6446 // Add free regions to the free list 6447 _free_list->add_as_tail(r); 6448 } else if (!_free_list_only) { 6449 assert(!r->is_young(), "we should not come across young regions"); 6450 6451 if (r->isHumongous()) { 6452 // We ignore humongous regions, we left the humongous set unchanged 6453 } else { 6454 // The rest should be old, add them to the old set 6455 _old_set->add(r); 6456 } 6457 _total_used += r->used(); 6458 } 6459 6460 return false; 6461 } 6462 6463 size_t total_used() { 6464 return _total_used; 6465 } 6466 }; 6467 6468 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6469 assert_at_safepoint(true /* should_be_vm_thread */); 6470 6471 if (!free_list_only) { 6472 _young_list->empty_list(); 6473 } 6474 6475 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); 6476 heap_region_iterate(&cl); 6477 6478 if (!free_list_only) { 6479 _summary_bytes_used = cl.total_used(); 6480 } 6481 assert(_summary_bytes_used == recalculate_used(), 6482 err_msg("inconsistent _summary_bytes_used, " 6483 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6484 _summary_bytes_used, recalculate_used())); 6485 } 6486 6487 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6488 _refine_cte_cl->set_concurrent(concurrent); 6489 } 6490 6491 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6492 HeapRegion* hr = heap_region_containing(p); 6493 if (hr == NULL) { 6494 return false; 6495 } else { 6496 return hr->is_in(p); 6497 } 6498 } 6499 6500 // Methods for the mutator alloc region 6501 6502 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6503 bool force) { 6504 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6505 assert(!force || g1_policy()->can_expand_young_list(), 6506 "if force is true we should be able to expand the young list"); 6507 bool young_list_full = g1_policy()->is_young_list_full(); 6508 if (force || !young_list_full) { 6509 HeapRegion* new_alloc_region = new_region(word_size, 6510 false /* is_old */, 6511 false /* do_expand */); 6512 if (new_alloc_region != NULL) { 6513 set_region_short_lived_locked(new_alloc_region); 6514 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6515 return new_alloc_region; 6516 } 6517 } 6518 return NULL; 6519 } 6520 6521 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6522 size_t allocated_bytes) { 6523 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6524 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 6525 6526 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6527 _summary_bytes_used += allocated_bytes; 6528 _hr_printer.retire(alloc_region); 6529 // We update the eden sizes here, when the region is retired, 6530 // instead of when it's allocated, since this is the point that its 6531 // used space has been recored in _summary_bytes_used. 6532 g1mm()->update_eden_size(); 6533 } 6534 6535 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 6536 bool force) { 6537 return _g1h->new_mutator_alloc_region(word_size, force); 6538 } 6539 6540 void G1CollectedHeap::set_par_threads() { 6541 // Don't change the number of workers. Use the value previously set 6542 // in the workgroup. 6543 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6544 uint n_workers = workers()->active_workers(); 6545 assert(UseDynamicNumberOfGCThreads || 6546 n_workers == workers()->total_workers(), 6547 "Otherwise should be using the total number of workers"); 6548 if (n_workers == 0) { 6549 assert(false, "Should have been set in prior evacuation pause."); 6550 n_workers = ParallelGCThreads; 6551 workers()->set_active_workers(n_workers); 6552 } 6553 set_par_threads(n_workers); 6554 } 6555 6556 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 6557 size_t allocated_bytes) { 6558 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 6559 } 6560 6561 // Methods for the GC alloc regions 6562 6563 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6564 uint count, 6565 GCAllocPurpose ap) { 6566 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6567 6568 if (count < g1_policy()->max_regions(ap)) { 6569 bool survivor = (ap == GCAllocForSurvived); 6570 HeapRegion* new_alloc_region = new_region(word_size, 6571 !survivor, 6572 true /* do_expand */); 6573 if (new_alloc_region != NULL) { 6574 // We really only need to do this for old regions given that we 6575 // should never scan survivors. But it doesn't hurt to do it 6576 // for survivors too. 6577 new_alloc_region->set_saved_mark(); 6578 if (survivor) { 6579 new_alloc_region->set_survivor(); 6580 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6581 } else { 6582 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6583 } 6584 bool during_im = g1_policy()->during_initial_mark_pause(); 6585 new_alloc_region->note_start_of_copying(during_im); 6586 return new_alloc_region; 6587 } else { 6588 g1_policy()->note_alloc_region_limit_reached(ap); 6589 } 6590 } 6591 return NULL; 6592 } 6593 6594 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6595 size_t allocated_bytes, 6596 GCAllocPurpose ap) { 6597 bool during_im = g1_policy()->during_initial_mark_pause(); 6598 alloc_region->note_end_of_copying(during_im); 6599 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6600 if (ap == GCAllocForSurvived) { 6601 young_list()->add_survivor_region(alloc_region); 6602 } else { 6603 _old_set.add(alloc_region); 6604 } 6605 _hr_printer.retire(alloc_region); 6606 } 6607 6608 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 6609 bool force) { 6610 assert(!force, "not supported for GC alloc regions"); 6611 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 6612 } 6613 6614 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 6615 size_t allocated_bytes) { 6616 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6617 GCAllocForSurvived); 6618 } 6619 6620 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 6621 bool force) { 6622 assert(!force, "not supported for GC alloc regions"); 6623 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 6624 } 6625 6626 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 6627 size_t allocated_bytes) { 6628 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6629 GCAllocForTenured); 6630 } 6631 // Heap region set verification 6632 6633 class VerifyRegionListsClosure : public HeapRegionClosure { 6634 private: 6635 HeapRegionSet* _old_set; 6636 HeapRegionSet* _humongous_set; 6637 FreeRegionList* _free_list; 6638 6639 public: 6640 HeapRegionSetCount _old_count; 6641 HeapRegionSetCount _humongous_count; 6642 HeapRegionSetCount _free_count; 6643 6644 VerifyRegionListsClosure(HeapRegionSet* old_set, 6645 HeapRegionSet* humongous_set, 6646 FreeRegionList* free_list) : 6647 _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list), 6648 _old_count(), _humongous_count(), _free_count(){ } 6649 6650 bool doHeapRegion(HeapRegion* hr) { 6651 if (hr->continuesHumongous()) { 6652 return false; 6653 } 6654 6655 if (hr->is_young()) { 6656 // TODO 6657 } else if (hr->startsHumongous()) { 6658 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->region_num())); 6659 _humongous_count.increment(1u, hr->capacity()); 6660 } else if (hr->is_empty()) { 6661 assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->region_num())); 6662 _free_count.increment(1u, hr->capacity()); 6663 } else { 6664 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->region_num())); 6665 _old_count.increment(1u, hr->capacity()); 6666 } 6667 return false; 6668 } 6669 6670 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) { 6671 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length())); 6672 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6673 old_set->total_capacity_bytes(), _old_count.capacity())); 6674 6675 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length())); 6676 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6677 humongous_set->total_capacity_bytes(), _humongous_count.capacity())); 6678 6679 guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length())); 6680 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6681 free_list->total_capacity_bytes(), _free_count.capacity())); 6682 } 6683 }; 6684 6685 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 6686 HeapWord* bottom) { 6687 HeapWord* end = bottom + HeapRegion::GrainWords; 6688 MemRegion mr(bottom, end); 6689 assert(_g1_reserved.contains(mr), "invariant"); 6690 // This might return NULL if the allocation fails 6691 return new HeapRegion(hrs_index, _bot_shared, mr); 6692 } 6693 6694 void G1CollectedHeap::verify_region_sets() { 6695 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6696 6697 // First, check the explicit lists. 6698 _free_list.verify_list(); 6699 { 6700 // Given that a concurrent operation might be adding regions to 6701 // the secondary free list we have to take the lock before 6702 // verifying it. 6703 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6704 _secondary_free_list.verify_list(); 6705 } 6706 6707 // If a concurrent region freeing operation is in progress it will 6708 // be difficult to correctly attributed any free regions we come 6709 // across to the correct free list given that they might belong to 6710 // one of several (free_list, secondary_free_list, any local lists, 6711 // etc.). So, if that's the case we will skip the rest of the 6712 // verification operation. Alternatively, waiting for the concurrent 6713 // operation to complete will have a non-trivial effect on the GC's 6714 // operation (no concurrent operation will last longer than the 6715 // interval between two calls to verification) and it might hide 6716 // any issues that we would like to catch during testing. 6717 if (free_regions_coming()) { 6718 return; 6719 } 6720 6721 // Make sure we append the secondary_free_list on the free_list so 6722 // that all free regions we will come across can be safely 6723 // attributed to the free_list. 6724 append_secondary_free_list_if_not_empty_with_lock(); 6725 6726 // Finally, make sure that the region accounting in the lists is 6727 // consistent with what we see in the heap. 6728 6729 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); 6730 heap_region_iterate(&cl); 6731 cl.verify_counts(&_old_set, &_humongous_set, &_free_list); 6732 } 6733 6734 // Optimized nmethod scanning 6735 6736 class RegisterNMethodOopClosure: public OopClosure { 6737 G1CollectedHeap* _g1h; 6738 nmethod* _nm; 6739 6740 template <class T> void do_oop_work(T* p) { 6741 T heap_oop = oopDesc::load_heap_oop(p); 6742 if (!oopDesc::is_null(heap_oop)) { 6743 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6744 HeapRegion* hr = _g1h->heap_region_containing(obj); 6745 assert(!hr->continuesHumongous(), 6746 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6747 " starting at "HR_FORMAT, 6748 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6749 6750 // HeapRegion::add_strong_code_root() avoids adding duplicate 6751 // entries but having duplicates is OK since we "mark" nmethods 6752 // as visited when we scan the strong code root lists during the GC. 6753 hr->add_strong_code_root(_nm); 6754 assert(hr->rem_set()->strong_code_roots_list_contains(_nm), 6755 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT, 6756 _nm, HR_FORMAT_PARAMS(hr))); 6757 } 6758 } 6759 6760 public: 6761 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6762 _g1h(g1h), _nm(nm) {} 6763 6764 void do_oop(oop* p) { do_oop_work(p); } 6765 void do_oop(narrowOop* p) { do_oop_work(p); } 6766 }; 6767 6768 class UnregisterNMethodOopClosure: public OopClosure { 6769 G1CollectedHeap* _g1h; 6770 nmethod* _nm; 6771 6772 template <class T> void do_oop_work(T* p) { 6773 T heap_oop = oopDesc::load_heap_oop(p); 6774 if (!oopDesc::is_null(heap_oop)) { 6775 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6776 HeapRegion* hr = _g1h->heap_region_containing(obj); 6777 assert(!hr->continuesHumongous(), 6778 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6779 " starting at "HR_FORMAT, 6780 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6781 6782 hr->remove_strong_code_root(_nm); 6783 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm), 6784 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT, 6785 _nm, HR_FORMAT_PARAMS(hr))); 6786 } 6787 } 6788 6789 public: 6790 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6791 _g1h(g1h), _nm(nm) {} 6792 6793 void do_oop(oop* p) { do_oop_work(p); } 6794 void do_oop(narrowOop* p) { do_oop_work(p); } 6795 }; 6796 6797 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6798 CollectedHeap::register_nmethod(nm); 6799 6800 guarantee(nm != NULL, "sanity"); 6801 RegisterNMethodOopClosure reg_cl(this, nm); 6802 nm->oops_do(®_cl); 6803 } 6804 6805 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6806 CollectedHeap::unregister_nmethod(nm); 6807 6808 guarantee(nm != NULL, "sanity"); 6809 UnregisterNMethodOopClosure reg_cl(this, nm); 6810 nm->oops_do(®_cl, true); 6811 } 6812 6813 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure { 6814 public: 6815 bool doHeapRegion(HeapRegion *hr) { 6816 assert(!hr->isHumongous(), 6817 err_msg("humongous region "HR_FORMAT" should not have been added to collection set", 6818 HR_FORMAT_PARAMS(hr))); 6819 hr->migrate_strong_code_roots(); 6820 return false; 6821 } 6822 }; 6823 6824 void G1CollectedHeap::migrate_strong_code_roots() { 6825 MigrateCodeRootsHeapRegionClosure cl; 6826 double migrate_start = os::elapsedTime(); 6827 collection_set_iterate(&cl); 6828 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0; 6829 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms); 6830 } 6831 6832 void G1CollectedHeap::purge_code_root_memory() { 6833 double purge_start = os::elapsedTime(); 6834 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent); 6835 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6836 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6837 } 6838 6839 // Mark all the code roots that point into regions *not* in the 6840 // collection set. 6841 // 6842 // Note we do not want to use a "marking" CodeBlobToOopClosure while 6843 // walking the the code roots lists of regions not in the collection 6844 // set. Suppose we have an nmethod (M) that points to objects in two 6845 // separate regions - one in the collection set (R1) and one not (R2). 6846 // Using a "marking" CodeBlobToOopClosure here would result in "marking" 6847 // nmethod M when walking the code roots for R1. When we come to scan 6848 // the code roots for R2, we would see that M is already marked and it 6849 // would be skipped and the objects in R2 that are referenced from M 6850 // would not be evacuated. 6851 6852 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure { 6853 6854 class MarkStrongCodeRootOopClosure: public OopClosure { 6855 ConcurrentMark* _cm; 6856 HeapRegion* _hr; 6857 uint _worker_id; 6858 6859 template <class T> void do_oop_work(T* p) { 6860 T heap_oop = oopDesc::load_heap_oop(p); 6861 if (!oopDesc::is_null(heap_oop)) { 6862 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6863 // Only mark objects in the region (which is assumed 6864 // to be not in the collection set). 6865 if (_hr->is_in(obj)) { 6866 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 6867 } 6868 } 6869 } 6870 6871 public: 6872 MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) : 6873 _cm(cm), _hr(hr), _worker_id(worker_id) { 6874 assert(!_hr->in_collection_set(), "sanity"); 6875 } 6876 6877 void do_oop(narrowOop* p) { do_oop_work(p); } 6878 void do_oop(oop* p) { do_oop_work(p); } 6879 }; 6880 6881 MarkStrongCodeRootOopClosure _oop_cl; 6882 6883 public: 6884 MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id): 6885 _oop_cl(cm, hr, worker_id) {} 6886 6887 void do_code_blob(CodeBlob* cb) { 6888 nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null(); 6889 if (nm != NULL) { 6890 nm->oops_do(&_oop_cl); 6891 } 6892 } 6893 }; 6894 6895 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure { 6896 G1CollectedHeap* _g1h; 6897 uint _worker_id; 6898 6899 public: 6900 MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) : 6901 _g1h(g1h), _worker_id(worker_id) {} 6902 6903 bool doHeapRegion(HeapRegion *hr) { 6904 HeapRegionRemSet* hrrs = hr->rem_set(); 6905 if (hr->continuesHumongous()) { 6906 // Code roots should never be attached to a continuation of a humongous region 6907 assert(hrrs->strong_code_roots_list_length() == 0, 6908 err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT 6909 " starting at "HR_FORMAT", but has "SIZE_FORMAT, 6910 HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()), 6911 hrrs->strong_code_roots_list_length())); 6912 return false; 6913 } 6914 6915 if (hr->in_collection_set()) { 6916 // Don't mark code roots into regions in the collection set here. 6917 // They will be marked when we scan them. 6918 return false; 6919 } 6920 6921 MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id); 6922 hr->strong_code_roots_do(&cb_cl); 6923 return false; 6924 } 6925 }; 6926 6927 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) { 6928 MarkStrongCodeRootsHRClosure cl(this, worker_id); 6929 if (G1CollectedHeap::use_parallel_gc_threads()) { 6930 heap_region_par_iterate_chunked(&cl, 6931 worker_id, 6932 workers()->active_workers(), 6933 HeapRegion::ParMarkRootClaimValue); 6934 } else { 6935 heap_region_iterate(&cl); 6936 } 6937 } 6938 6939 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6940 G1CollectedHeap* _g1h; 6941 6942 public: 6943 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6944 _g1h(g1h) {} 6945 6946 void do_code_blob(CodeBlob* cb) { 6947 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6948 if (nm == NULL) { 6949 return; 6950 } 6951 6952 if (ScavengeRootsInCode) { 6953 _g1h->register_nmethod(nm); 6954 } 6955 } 6956 }; 6957 6958 void G1CollectedHeap::rebuild_strong_code_roots() { 6959 RebuildStrongCodeRootClosure blob_cl(this); 6960 CodeCache::blobs_do(&blob_cl); 6961 }