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 bool _concurrent; 102 public: 103 RefineCardTableEntryClosure() : _concurrent(true) { } 104 105 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 106 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 107 // This path is executed by the concurrent refine or mutator threads, 108 // concurrently, and so we do not care if card_ptr contains references 109 // that point into the collection set. 110 assert(!oops_into_cset, "should be"); 111 112 if (_concurrent && SuspendibleThreadSet::should_yield()) { 113 // Caller will actually yield. 114 return false; 115 } 116 // Otherwise, we finished successfully; return true. 117 return true; 118 } 119 120 void set_concurrent(bool b) { _concurrent = b; } 121 }; 122 123 124 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 125 size_t _num_processed; 126 CardTableModRefBS* _ctbs; 127 int _histo[256]; 128 129 public: 130 ClearLoggedCardTableEntryClosure() : 131 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set()) 132 { 133 for (int i = 0; i < 256; i++) _histo[i] = 0; 134 } 135 136 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 137 unsigned char* ujb = (unsigned char*)card_ptr; 138 int ind = (int)(*ujb); 139 _histo[ind]++; 140 141 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val(); 142 _num_processed++; 143 144 return true; 145 } 146 147 size_t num_processed() { return _num_processed; } 148 149 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 private: 161 size_t _num_processed; 162 163 public: 164 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 165 166 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 167 *card_ptr = CardTableModRefBS::dirty_card_val(); 168 _num_processed++; 169 return true; 170 } 171 172 size_t num_processed() const { return _num_processed; } 173 }; 174 175 YoungList::YoungList(G1CollectedHeap* g1h) : 176 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 177 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 178 guarantee(check_list_empty(false), "just making sure..."); 179 } 180 181 void YoungList::push_region(HeapRegion *hr) { 182 assert(!hr->is_young(), "should not already be young"); 183 assert(hr->get_next_young_region() == NULL, "cause it should!"); 184 185 hr->set_next_young_region(_head); 186 _head = hr; 187 188 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 189 ++_length; 190 } 191 192 void YoungList::add_survivor_region(HeapRegion* hr) { 193 assert(hr->is_survivor(), "should be flagged as survivor region"); 194 assert(hr->get_next_young_region() == NULL, "cause it should!"); 195 196 hr->set_next_young_region(_survivor_head); 197 if (_survivor_head == NULL) { 198 _survivor_tail = hr; 199 } 200 _survivor_head = hr; 201 ++_survivor_length; 202 } 203 204 void YoungList::empty_list(HeapRegion* list) { 205 while (list != NULL) { 206 HeapRegion* next = list->get_next_young_region(); 207 list->set_next_young_region(NULL); 208 list->uninstall_surv_rate_group(); 209 list->set_not_young(); 210 list = next; 211 } 212 } 213 214 void YoungList::empty_list() { 215 assert(check_list_well_formed(), "young list should be well formed"); 216 217 empty_list(_head); 218 _head = NULL; 219 _length = 0; 220 221 empty_list(_survivor_head); 222 _survivor_head = NULL; 223 _survivor_tail = NULL; 224 _survivor_length = 0; 225 226 _last_sampled_rs_lengths = 0; 227 228 assert(check_list_empty(false), "just making sure..."); 229 } 230 231 bool YoungList::check_list_well_formed() { 232 bool ret = true; 233 234 uint length = 0; 235 HeapRegion* curr = _head; 236 HeapRegion* last = NULL; 237 while (curr != NULL) { 238 if (!curr->is_young()) { 239 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 240 "incorrectly tagged (y: %d, surv: %d)", 241 curr->bottom(), curr->end(), 242 curr->is_young(), curr->is_survivor()); 243 ret = false; 244 } 245 ++length; 246 last = curr; 247 curr = curr->get_next_young_region(); 248 } 249 ret = ret && (length == _length); 250 251 if (!ret) { 252 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 253 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 254 length, _length); 255 } 256 257 return ret; 258 } 259 260 bool YoungList::check_list_empty(bool check_sample) { 261 bool ret = true; 262 263 if (_length != 0) { 264 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 265 _length); 266 ret = false; 267 } 268 if (check_sample && _last_sampled_rs_lengths != 0) { 269 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 270 ret = false; 271 } 272 if (_head != NULL) { 273 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 274 ret = false; 275 } 276 if (!ret) { 277 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 278 } 279 280 return ret; 281 } 282 283 void 284 YoungList::rs_length_sampling_init() { 285 _sampled_rs_lengths = 0; 286 _curr = _head; 287 } 288 289 bool 290 YoungList::rs_length_sampling_more() { 291 return _curr != NULL; 292 } 293 294 void 295 YoungList::rs_length_sampling_next() { 296 assert( _curr != NULL, "invariant" ); 297 size_t rs_length = _curr->rem_set()->occupied(); 298 299 _sampled_rs_lengths += rs_length; 300 301 // The current region may not yet have been added to the 302 // incremental collection set (it gets added when it is 303 // retired as the current allocation region). 304 if (_curr->in_collection_set()) { 305 // Update the collection set policy information for this region 306 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 307 } 308 309 _curr = _curr->get_next_young_region(); 310 if (_curr == NULL) { 311 _last_sampled_rs_lengths = _sampled_rs_lengths; 312 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 313 } 314 } 315 316 void 317 YoungList::reset_auxilary_lists() { 318 guarantee( is_empty(), "young list should be empty" ); 319 assert(check_list_well_formed(), "young list should be well formed"); 320 321 // Add survivor regions to SurvRateGroup. 322 _g1h->g1_policy()->note_start_adding_survivor_regions(); 323 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 324 325 int young_index_in_cset = 0; 326 for (HeapRegion* curr = _survivor_head; 327 curr != NULL; 328 curr = curr->get_next_young_region()) { 329 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 330 331 // The region is a non-empty survivor so let's add it to 332 // the incremental collection set for the next evacuation 333 // pause. 334 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 335 young_index_in_cset += 1; 336 } 337 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 338 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 339 340 _head = _survivor_head; 341 _length = _survivor_length; 342 if (_survivor_head != NULL) { 343 assert(_survivor_tail != NULL, "cause it shouldn't be"); 344 assert(_survivor_length > 0, "invariant"); 345 _survivor_tail->set_next_young_region(NULL); 346 } 347 348 // Don't clear the survivor list handles until the start of 349 // the next evacuation pause - we need it in order to re-tag 350 // the survivor regions from this evacuation pause as 'young' 351 // at the start of the next. 352 353 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 354 355 assert(check_list_well_formed(), "young list should be well formed"); 356 } 357 358 void YoungList::print() { 359 HeapRegion* lists[] = {_head, _survivor_head}; 360 const char* names[] = {"YOUNG", "SURVIVOR"}; 361 362 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 363 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 364 HeapRegion *curr = lists[list]; 365 if (curr == NULL) 366 gclog_or_tty->print_cr(" empty"); 367 while (curr != NULL) { 368 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d", 369 HR_FORMAT_PARAMS(curr), 370 curr->prev_top_at_mark_start(), 371 curr->next_top_at_mark_start(), 372 curr->age_in_surv_rate_group_cond()); 373 curr = curr->get_next_young_region(); 374 } 375 } 376 377 gclog_or_tty->cr(); 378 } 379 380 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 381 { 382 // Claim the right to put the region on the dirty cards region list 383 // by installing a self pointer. 384 HeapRegion* next = hr->get_next_dirty_cards_region(); 385 if (next == NULL) { 386 HeapRegion* res = (HeapRegion*) 387 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 388 NULL); 389 if (res == NULL) { 390 HeapRegion* head; 391 do { 392 // Put the region to the dirty cards region list. 393 head = _dirty_cards_region_list; 394 next = (HeapRegion*) 395 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 396 if (next == head) { 397 assert(hr->get_next_dirty_cards_region() == hr, 398 "hr->get_next_dirty_cards_region() != hr"); 399 if (next == NULL) { 400 // The last region in the list points to itself. 401 hr->set_next_dirty_cards_region(hr); 402 } else { 403 hr->set_next_dirty_cards_region(next); 404 } 405 } 406 } while (next != head); 407 } 408 } 409 } 410 411 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 412 { 413 HeapRegion* head; 414 HeapRegion* hr; 415 do { 416 head = _dirty_cards_region_list; 417 if (head == NULL) { 418 return NULL; 419 } 420 HeapRegion* new_head = head->get_next_dirty_cards_region(); 421 if (head == new_head) { 422 // The last region. 423 new_head = NULL; 424 } 425 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 426 head); 427 } while (hr != head); 428 assert(hr != NULL, "invariant"); 429 hr->set_next_dirty_cards_region(NULL); 430 return hr; 431 } 432 433 #ifdef ASSERT 434 // A region is added to the collection set as it is retired 435 // so an address p can point to a region which will be in the 436 // collection set but has not yet been retired. This method 437 // therefore is only accurate during a GC pause after all 438 // regions have been retired. It is used for debugging 439 // to check if an nmethod has references to objects that can 440 // be move during a partial collection. Though it can be 441 // inaccurate, it is sufficient for G1 because the conservative 442 // implementation of is_scavengable() for G1 will indicate that 443 // all nmethods must be scanned during a partial collection. 444 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 445 HeapRegion* hr = heap_region_containing(p); 446 return hr != NULL && hr->in_collection_set(); 447 } 448 #endif 449 450 // Returns true if the reference points to an object that 451 // can move in an incremental collection. 452 bool G1CollectedHeap::is_scavengable(const void* p) { 453 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 454 G1CollectorPolicy* g1p = g1h->g1_policy(); 455 HeapRegion* hr = heap_region_containing(p); 456 if (hr == NULL) { 457 // null 458 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p)); 459 return false; 460 } else { 461 return !hr->isHumongous(); 462 } 463 } 464 465 void G1CollectedHeap::check_ct_logs_at_safepoint() { 466 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 467 CardTableModRefBS* ct_bs = g1_barrier_set(); 468 469 // Count the dirty cards at the start. 470 CountNonCleanMemRegionClosure count1(this); 471 ct_bs->mod_card_iterate(&count1); 472 int orig_count = count1.n(); 473 474 // First clear the logged cards. 475 ClearLoggedCardTableEntryClosure clear; 476 dcqs.apply_closure_to_all_completed_buffers(&clear); 477 dcqs.iterate_closure_all_threads(&clear, false); 478 clear.print_histo(); 479 480 // Now ensure that there's no dirty cards. 481 CountNonCleanMemRegionClosure count2(this); 482 ct_bs->mod_card_iterate(&count2); 483 if (count2.n() != 0) { 484 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 485 count2.n(), orig_count); 486 } 487 guarantee(count2.n() == 0, "Card table should be clean."); 488 489 RedirtyLoggedCardTableEntryClosure redirty; 490 dcqs.apply_closure_to_all_completed_buffers(&redirty); 491 dcqs.iterate_closure_all_threads(&redirty, false); 492 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 493 clear.num_processed(), orig_count); 494 guarantee(redirty.num_processed() == clear.num_processed(), 495 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT, 496 redirty.num_processed(), clear.num_processed())); 497 498 CountNonCleanMemRegionClosure count3(this); 499 ct_bs->mod_card_iterate(&count3); 500 if (count3.n() != orig_count) { 501 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 502 orig_count, count3.n()); 503 guarantee(count3.n() >= orig_count, "Should have restored them all."); 504 } 505 } 506 507 // Private class members. 508 509 G1CollectedHeap* G1CollectedHeap::_g1h; 510 511 // Private methods. 512 513 HeapRegion* 514 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 515 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 516 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 517 if (!_secondary_free_list.is_empty()) { 518 if (G1ConcRegionFreeingVerbose) { 519 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 520 "secondary_free_list has %u entries", 521 _secondary_free_list.length()); 522 } 523 // It looks as if there are free regions available on the 524 // secondary_free_list. Let's move them to the free_list and try 525 // again to allocate from it. 526 append_secondary_free_list(); 527 528 assert(!_free_list.is_empty(), "if the secondary_free_list was not " 529 "empty we should have moved at least one entry to the free_list"); 530 HeapRegion* res = _free_list.remove_region(is_old); 531 if (G1ConcRegionFreeingVerbose) { 532 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 533 "allocated "HR_FORMAT" from secondary_free_list", 534 HR_FORMAT_PARAMS(res)); 535 } 536 return res; 537 } 538 539 // Wait here until we get notified either when (a) there are no 540 // more free regions coming or (b) some regions have been moved on 541 // the secondary_free_list. 542 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 543 } 544 545 if (G1ConcRegionFreeingVerbose) { 546 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 547 "could not allocate from secondary_free_list"); 548 } 549 return NULL; 550 } 551 552 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 553 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, 554 "the only time we use this to allocate a humongous region is " 555 "when we are allocating a single humongous region"); 556 557 HeapRegion* res; 558 if (G1StressConcRegionFreeing) { 559 if (!_secondary_free_list.is_empty()) { 560 if (G1ConcRegionFreeingVerbose) { 561 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 562 "forced to look at the secondary_free_list"); 563 } 564 res = new_region_try_secondary_free_list(is_old); 565 if (res != NULL) { 566 return res; 567 } 568 } 569 } 570 571 res = _free_list.remove_region(is_old); 572 573 if (res == NULL) { 574 if (G1ConcRegionFreeingVerbose) { 575 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 576 "res == NULL, trying the secondary_free_list"); 577 } 578 res = new_region_try_secondary_free_list(is_old); 579 } 580 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 581 // Currently, only attempts to allocate GC alloc regions set 582 // do_expand to true. So, we should only reach here during a 583 // safepoint. If this assumption changes we might have to 584 // reconsider the use of _expand_heap_after_alloc_failure. 585 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 586 587 ergo_verbose1(ErgoHeapSizing, 588 "attempt heap expansion", 589 ergo_format_reason("region allocation request failed") 590 ergo_format_byte("allocation request"), 591 word_size * HeapWordSize); 592 if (expand(word_size * HeapWordSize)) { 593 // Given that expand() succeeded in expanding the heap, and we 594 // always expand the heap by an amount aligned to the heap 595 // region size, the free list should in theory not be empty. 596 // In either case remove_region() will check for NULL. 597 res = _free_list.remove_region(is_old); 598 } else { 599 _expand_heap_after_alloc_failure = false; 600 } 601 } 602 return res; 603 } 604 605 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions, 606 size_t word_size) { 607 assert(isHumongous(word_size), "word_size should be humongous"); 608 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 609 610 uint first = G1_NULL_HRS_INDEX; 611 if (num_regions == 1) { 612 // Only one region to allocate, no need to go through the slower 613 // path. The caller will attempt the expansion if this fails, so 614 // let's not try to expand here too. 615 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 616 if (hr != NULL) { 617 first = hr->hrs_index(); 618 } else { 619 first = G1_NULL_HRS_INDEX; 620 } 621 } else { 622 // We can't allocate humongous regions while cleanupComplete() is 623 // running, since some of the regions we find to be empty might not 624 // yet be added to the free list and it is not straightforward to 625 // know which list they are on so that we can remove them. Note 626 // that we only need to do this if we need to allocate more than 627 // one region to satisfy the current humongous allocation 628 // request. If we are only allocating one region we use the common 629 // region allocation code (see above). 630 wait_while_free_regions_coming(); 631 append_secondary_free_list_if_not_empty_with_lock(); 632 633 if (free_regions() >= num_regions) { 634 first = _hrs.find_contiguous(num_regions); 635 if (first != G1_NULL_HRS_INDEX) { 636 for (uint i = first; i < first + num_regions; ++i) { 637 HeapRegion* hr = region_at(i); 638 assert(hr->is_empty(), "sanity"); 639 assert(is_on_master_free_list(hr), "sanity"); 640 hr->set_pending_removal(true); 641 } 642 _free_list.remove_all_pending(num_regions); 643 } 644 } 645 } 646 return first; 647 } 648 649 HeapWord* 650 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 651 uint num_regions, 652 size_t word_size) { 653 assert(first != G1_NULL_HRS_INDEX, "pre-condition"); 654 assert(isHumongous(word_size), "word_size should be humongous"); 655 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 656 657 // Index of last region in the series + 1. 658 uint last = first + num_regions; 659 660 // We need to initialize the region(s) we just discovered. This is 661 // a bit tricky given that it can happen concurrently with 662 // refinement threads refining cards on these regions and 663 // potentially wanting to refine the BOT as they are scanning 664 // those cards (this can happen shortly after a cleanup; see CR 665 // 6991377). So we have to set up the region(s) carefully and in 666 // a specific order. 667 668 // The word size sum of all the regions we will allocate. 669 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 670 assert(word_size <= word_size_sum, "sanity"); 671 672 // This will be the "starts humongous" region. 673 HeapRegion* first_hr = region_at(first); 674 // The header of the new object will be placed at the bottom of 675 // the first region. 676 HeapWord* new_obj = first_hr->bottom(); 677 // This will be the new end of the first region in the series that 678 // should also match the end of the last region in the series. 679 HeapWord* new_end = new_obj + word_size_sum; 680 // This will be the new top of the first region that will reflect 681 // this allocation. 682 HeapWord* new_top = new_obj + word_size; 683 684 // First, we need to zero the header of the space that we will be 685 // allocating. When we update top further down, some refinement 686 // threads might try to scan the region. By zeroing the header we 687 // ensure that any thread that will try to scan the region will 688 // come across the zero klass word and bail out. 689 // 690 // NOTE: It would not have been correct to have used 691 // CollectedHeap::fill_with_object() and make the space look like 692 // an int array. The thread that is doing the allocation will 693 // later update the object header to a potentially different array 694 // type and, for a very short period of time, the klass and length 695 // fields will be inconsistent. This could cause a refinement 696 // thread to calculate the object size incorrectly. 697 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 698 699 // We will set up the first region as "starts humongous". This 700 // will also update the BOT covering all the regions to reflect 701 // that there is a single object that starts at the bottom of the 702 // first region. 703 first_hr->set_startsHumongous(new_top, new_end); 704 705 // Then, if there are any, we will set up the "continues 706 // humongous" regions. 707 HeapRegion* hr = NULL; 708 for (uint i = first + 1; i < last; ++i) { 709 hr = region_at(i); 710 hr->set_continuesHumongous(first_hr); 711 } 712 // If we have "continues humongous" regions (hr != NULL), then the 713 // end of the last one should match new_end. 714 assert(hr == NULL || hr->end() == new_end, "sanity"); 715 716 // Up to this point no concurrent thread would have been able to 717 // do any scanning on any region in this series. All the top 718 // fields still point to bottom, so the intersection between 719 // [bottom,top] and [card_start,card_end] will be empty. Before we 720 // update the top fields, we'll do a storestore to make sure that 721 // no thread sees the update to top before the zeroing of the 722 // object header and the BOT initialization. 723 OrderAccess::storestore(); 724 725 // Now that the BOT and the object header have been initialized, 726 // we can update top of the "starts humongous" region. 727 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 728 "new_top should be in this region"); 729 first_hr->set_top(new_top); 730 if (_hr_printer.is_active()) { 731 HeapWord* bottom = first_hr->bottom(); 732 HeapWord* end = first_hr->orig_end(); 733 if ((first + 1) == last) { 734 // the series has a single humongous region 735 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 736 } else { 737 // the series has more than one humongous regions 738 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 739 } 740 } 741 742 // Now, we will update the top fields of the "continues humongous" 743 // regions. The reason we need to do this is that, otherwise, 744 // these regions would look empty and this will confuse parts of 745 // G1. For example, the code that looks for a consecutive number 746 // of empty regions will consider them empty and try to 747 // re-allocate them. We can extend is_empty() to also include 748 // !continuesHumongous(), but it is easier to just update the top 749 // fields here. The way we set top for all regions (i.e., top == 750 // end for all regions but the last one, top == new_top for the 751 // last one) is actually used when we will free up the humongous 752 // region in free_humongous_region(). 753 hr = NULL; 754 for (uint i = first + 1; i < last; ++i) { 755 hr = region_at(i); 756 if ((i + 1) == last) { 757 // last continues humongous region 758 assert(hr->bottom() < new_top && new_top <= hr->end(), 759 "new_top should fall on this region"); 760 hr->set_top(new_top); 761 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 762 } else { 763 // not last one 764 assert(new_top > hr->end(), "new_top should be above this region"); 765 hr->set_top(hr->end()); 766 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 767 } 768 } 769 // If we have continues humongous regions (hr != NULL), then the 770 // end of the last one should match new_end and its top should 771 // match new_top. 772 assert(hr == NULL || 773 (hr->end() == new_end && hr->top() == new_top), "sanity"); 774 775 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 776 _summary_bytes_used += first_hr->used(); 777 _humongous_set.add(first_hr); 778 779 return new_obj; 780 } 781 782 // If could fit into free regions w/o expansion, try. 783 // Otherwise, if can expand, do so. 784 // Otherwise, if using ex regions might help, try with ex given back. 785 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 786 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 787 788 verify_region_sets_optional(); 789 790 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords); 791 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords); 792 uint x_num = expansion_regions(); 793 uint fs = _hrs.free_suffix(); 794 uint first = humongous_obj_allocate_find_first(num_regions, word_size); 795 if (first == G1_NULL_HRS_INDEX) { 796 // The only thing we can do now is attempt expansion. 797 if (fs + x_num >= num_regions) { 798 // If the number of regions we're trying to allocate for this 799 // object is at most the number of regions in the free suffix, 800 // then the call to humongous_obj_allocate_find_first() above 801 // should have succeeded and we wouldn't be here. 802 // 803 // We should only be trying to expand when the free suffix is 804 // not sufficient for the object _and_ we have some expansion 805 // room available. 806 assert(num_regions > fs, "earlier allocation should have succeeded"); 807 808 ergo_verbose1(ErgoHeapSizing, 809 "attempt heap expansion", 810 ergo_format_reason("humongous allocation request failed") 811 ergo_format_byte("allocation request"), 812 word_size * HeapWordSize); 813 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) { 814 // Even though the heap was expanded, it might not have 815 // reached the desired size. So, we cannot assume that the 816 // allocation will succeed. 817 first = humongous_obj_allocate_find_first(num_regions, word_size); 818 } 819 } 820 } 821 822 HeapWord* result = NULL; 823 if (first != G1_NULL_HRS_INDEX) { 824 result = 825 humongous_obj_allocate_initialize_regions(first, num_regions, word_size); 826 assert(result != NULL, "it should always return a valid result"); 827 828 // A successful humongous object allocation changes the used space 829 // information of the old generation so we need to recalculate the 830 // sizes and update the jstat counters here. 831 g1mm()->update_sizes(); 832 } 833 834 verify_region_sets_optional(); 835 836 return result; 837 } 838 839 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 840 assert_heap_not_locked_and_not_at_safepoint(); 841 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 842 843 unsigned int dummy_gc_count_before; 844 int dummy_gclocker_retry_count = 0; 845 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 846 } 847 848 HeapWord* 849 G1CollectedHeap::mem_allocate(size_t word_size, 850 bool* gc_overhead_limit_was_exceeded) { 851 assert_heap_not_locked_and_not_at_safepoint(); 852 853 // Loop until the allocation is satisfied, or unsatisfied after GC. 854 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 855 unsigned int gc_count_before; 856 857 HeapWord* result = NULL; 858 if (!isHumongous(word_size)) { 859 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 860 } else { 861 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 862 } 863 if (result != NULL) { 864 return result; 865 } 866 867 // Create the garbage collection operation... 868 VM_G1CollectForAllocation op(gc_count_before, word_size); 869 // ...and get the VM thread to execute it. 870 VMThread::execute(&op); 871 872 if (op.prologue_succeeded() && op.pause_succeeded()) { 873 // If the operation was successful we'll return the result even 874 // if it is NULL. If the allocation attempt failed immediately 875 // after a Full GC, it's unlikely we'll be able to allocate now. 876 HeapWord* result = op.result(); 877 if (result != NULL && !isHumongous(word_size)) { 878 // Allocations that take place on VM operations do not do any 879 // card dirtying and we have to do it here. We only have to do 880 // this for non-humongous allocations, though. 881 dirty_young_block(result, word_size); 882 } 883 return result; 884 } else { 885 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 886 return NULL; 887 } 888 assert(op.result() == NULL, 889 "the result should be NULL if the VM op did not succeed"); 890 } 891 892 // Give a warning if we seem to be looping forever. 893 if ((QueuedAllocationWarningCount > 0) && 894 (try_count % QueuedAllocationWarningCount == 0)) { 895 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 896 } 897 } 898 899 ShouldNotReachHere(); 900 return NULL; 901 } 902 903 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 904 unsigned int *gc_count_before_ret, 905 int* gclocker_retry_count_ret) { 906 // Make sure you read the note in attempt_allocation_humongous(). 907 908 assert_heap_not_locked_and_not_at_safepoint(); 909 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 910 "be called for humongous allocation requests"); 911 912 // We should only get here after the first-level allocation attempt 913 // (attempt_allocation()) failed to allocate. 914 915 // We will loop until a) we manage to successfully perform the 916 // allocation or b) we successfully schedule a collection which 917 // fails to perform the allocation. b) is the only case when we'll 918 // return NULL. 919 HeapWord* result = NULL; 920 for (int try_count = 1; /* we'll return */; try_count += 1) { 921 bool should_try_gc; 922 unsigned int gc_count_before; 923 924 { 925 MutexLockerEx x(Heap_lock); 926 927 result = _mutator_alloc_region.attempt_allocation_locked(word_size, 928 false /* bot_updates */); 929 if (result != NULL) { 930 return result; 931 } 932 933 // If we reach here, attempt_allocation_locked() above failed to 934 // allocate a new region. So the mutator alloc region should be NULL. 935 assert(_mutator_alloc_region.get() == NULL, "only way to get here"); 936 937 if (GC_locker::is_active_and_needs_gc()) { 938 if (g1_policy()->can_expand_young_list()) { 939 // No need for an ergo verbose message here, 940 // can_expand_young_list() does this when it returns true. 941 result = _mutator_alloc_region.attempt_allocation_force(word_size, 942 false /* bot_updates */); 943 if (result != NULL) { 944 return result; 945 } 946 } 947 should_try_gc = false; 948 } else { 949 // The GCLocker may not be active but the GCLocker initiated 950 // GC may not yet have been performed (GCLocker::needs_gc() 951 // returns true). In this case we do not try this GC and 952 // wait until the GCLocker initiated GC is performed, and 953 // then retry the allocation. 954 if (GC_locker::needs_gc()) { 955 should_try_gc = false; 956 } else { 957 // Read the GC count while still holding the Heap_lock. 958 gc_count_before = total_collections(); 959 should_try_gc = true; 960 } 961 } 962 } 963 964 if (should_try_gc) { 965 bool succeeded; 966 result = do_collection_pause(word_size, gc_count_before, &succeeded, 967 GCCause::_g1_inc_collection_pause); 968 if (result != NULL) { 969 assert(succeeded, "only way to get back a non-NULL result"); 970 return result; 971 } 972 973 if (succeeded) { 974 // If we get here we successfully scheduled a collection which 975 // failed to allocate. No point in trying to allocate 976 // further. We'll just return NULL. 977 MutexLockerEx x(Heap_lock); 978 *gc_count_before_ret = total_collections(); 979 return NULL; 980 } 981 } else { 982 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 983 MutexLockerEx x(Heap_lock); 984 *gc_count_before_ret = total_collections(); 985 return NULL; 986 } 987 // The GCLocker is either active or the GCLocker initiated 988 // GC has not yet been performed. Stall until it is and 989 // then retry the allocation. 990 GC_locker::stall_until_clear(); 991 (*gclocker_retry_count_ret) += 1; 992 } 993 994 // We can reach here if we were unsuccessful in scheduling a 995 // collection (because another thread beat us to it) or if we were 996 // stalled due to the GC locker. In either can we should retry the 997 // allocation attempt in case another thread successfully 998 // performed a collection and reclaimed enough space. We do the 999 // first attempt (without holding the Heap_lock) here and the 1000 // follow-on attempt will be at the start of the next loop 1001 // iteration (after taking the Heap_lock). 1002 result = _mutator_alloc_region.attempt_allocation(word_size, 1003 false /* bot_updates */); 1004 if (result != NULL) { 1005 return result; 1006 } 1007 1008 // Give a warning if we seem to be looping forever. 1009 if ((QueuedAllocationWarningCount > 0) && 1010 (try_count % QueuedAllocationWarningCount == 0)) { 1011 warning("G1CollectedHeap::attempt_allocation_slow() " 1012 "retries %d times", try_count); 1013 } 1014 } 1015 1016 ShouldNotReachHere(); 1017 return NULL; 1018 } 1019 1020 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1021 unsigned int * gc_count_before_ret, 1022 int* gclocker_retry_count_ret) { 1023 // The structure of this method has a lot of similarities to 1024 // attempt_allocation_slow(). The reason these two were not merged 1025 // into a single one is that such a method would require several "if 1026 // allocation is not humongous do this, otherwise do that" 1027 // conditional paths which would obscure its flow. In fact, an early 1028 // version of this code did use a unified method which was harder to 1029 // follow and, as a result, it had subtle bugs that were hard to 1030 // track down. So keeping these two methods separate allows each to 1031 // be more readable. It will be good to keep these two in sync as 1032 // much as possible. 1033 1034 assert_heap_not_locked_and_not_at_safepoint(); 1035 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1036 "should only be called for humongous allocations"); 1037 1038 // Humongous objects can exhaust the heap quickly, so we should check if we 1039 // need to start a marking cycle at each humongous object allocation. We do 1040 // the check before we do the actual allocation. The reason for doing it 1041 // before the allocation is that we avoid having to keep track of the newly 1042 // allocated memory while we do a GC. 1043 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1044 word_size)) { 1045 collect(GCCause::_g1_humongous_allocation); 1046 } 1047 1048 // We will loop until a) we manage to successfully perform the 1049 // allocation or b) we successfully schedule a collection which 1050 // fails to perform the allocation. b) is the only case when we'll 1051 // return NULL. 1052 HeapWord* result = NULL; 1053 for (int try_count = 1; /* we'll return */; try_count += 1) { 1054 bool should_try_gc; 1055 unsigned int gc_count_before; 1056 1057 { 1058 MutexLockerEx x(Heap_lock); 1059 1060 // Given that humongous objects are not allocated in young 1061 // regions, we'll first try to do the allocation without doing a 1062 // collection hoping that there's enough space in the heap. 1063 result = humongous_obj_allocate(word_size); 1064 if (result != NULL) { 1065 return result; 1066 } 1067 1068 if (GC_locker::is_active_and_needs_gc()) { 1069 should_try_gc = false; 1070 } else { 1071 // The GCLocker may not be active but the GCLocker initiated 1072 // GC may not yet have been performed (GCLocker::needs_gc() 1073 // returns true). In this case we do not try this GC and 1074 // wait until the GCLocker initiated GC is performed, and 1075 // then retry the allocation. 1076 if (GC_locker::needs_gc()) { 1077 should_try_gc = false; 1078 } else { 1079 // Read the GC count while still holding the Heap_lock. 1080 gc_count_before = total_collections(); 1081 should_try_gc = true; 1082 } 1083 } 1084 } 1085 1086 if (should_try_gc) { 1087 // If we failed to allocate the humongous object, we should try to 1088 // do a collection pause (if we're allowed) in case it reclaims 1089 // enough space for the allocation to succeed after the pause. 1090 1091 bool succeeded; 1092 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1093 GCCause::_g1_humongous_allocation); 1094 if (result != NULL) { 1095 assert(succeeded, "only way to get back a non-NULL result"); 1096 return result; 1097 } 1098 1099 if (succeeded) { 1100 // If we get here we successfully scheduled a collection which 1101 // failed to allocate. No point in trying to allocate 1102 // further. We'll just return NULL. 1103 MutexLockerEx x(Heap_lock); 1104 *gc_count_before_ret = total_collections(); 1105 return NULL; 1106 } 1107 } else { 1108 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1109 MutexLockerEx x(Heap_lock); 1110 *gc_count_before_ret = total_collections(); 1111 return NULL; 1112 } 1113 // The GCLocker is either active or the GCLocker initiated 1114 // GC has not yet been performed. Stall until it is and 1115 // then retry the allocation. 1116 GC_locker::stall_until_clear(); 1117 (*gclocker_retry_count_ret) += 1; 1118 } 1119 1120 // We can reach here if we were unsuccessful in scheduling a 1121 // collection (because another thread beat us to it) or if we were 1122 // stalled due to the GC locker. In either can we should retry the 1123 // allocation attempt in case another thread successfully 1124 // performed a collection and reclaimed enough space. Give a 1125 // warning if we seem to be looping forever. 1126 1127 if ((QueuedAllocationWarningCount > 0) && 1128 (try_count % QueuedAllocationWarningCount == 0)) { 1129 warning("G1CollectedHeap::attempt_allocation_humongous() " 1130 "retries %d times", try_count); 1131 } 1132 } 1133 1134 ShouldNotReachHere(); 1135 return NULL; 1136 } 1137 1138 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1139 bool expect_null_mutator_alloc_region) { 1140 assert_at_safepoint(true /* should_be_vm_thread */); 1141 assert(_mutator_alloc_region.get() == NULL || 1142 !expect_null_mutator_alloc_region, 1143 "the current alloc region was unexpectedly found to be non-NULL"); 1144 1145 if (!isHumongous(word_size)) { 1146 return _mutator_alloc_region.attempt_allocation_locked(word_size, 1147 false /* bot_updates */); 1148 } else { 1149 HeapWord* result = humongous_obj_allocate(word_size); 1150 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1151 g1_policy()->set_initiate_conc_mark_if_possible(); 1152 } 1153 return result; 1154 } 1155 1156 ShouldNotReachHere(); 1157 } 1158 1159 class PostMCRemSetClearClosure: public HeapRegionClosure { 1160 G1CollectedHeap* _g1h; 1161 ModRefBarrierSet* _mr_bs; 1162 public: 1163 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1164 _g1h(g1h), _mr_bs(mr_bs) {} 1165 1166 bool doHeapRegion(HeapRegion* r) { 1167 HeapRegionRemSet* hrrs = r->rem_set(); 1168 1169 if (r->continuesHumongous()) { 1170 // We'll assert that the strong code root list and RSet is empty 1171 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1172 assert(hrrs->occupied() == 0, "RSet should be empty"); 1173 return false; 1174 } 1175 1176 _g1h->reset_gc_time_stamps(r); 1177 hrrs->clear(); 1178 // You might think here that we could clear just the cards 1179 // corresponding to the used region. But no: if we leave a dirty card 1180 // in a region we might allocate into, then it would prevent that card 1181 // from being enqueued, and cause it to be missed. 1182 // Re: the performance cost: we shouldn't be doing full GC anyway! 1183 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1184 1185 return false; 1186 } 1187 }; 1188 1189 void G1CollectedHeap::clear_rsets_post_compaction() { 1190 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1191 heap_region_iterate(&rs_clear); 1192 } 1193 1194 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1195 G1CollectedHeap* _g1h; 1196 UpdateRSOopClosure _cl; 1197 int _worker_i; 1198 public: 1199 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1200 _cl(g1->g1_rem_set(), worker_i), 1201 _worker_i(worker_i), 1202 _g1h(g1) 1203 { } 1204 1205 bool doHeapRegion(HeapRegion* r) { 1206 if (!r->continuesHumongous()) { 1207 _cl.set_from(r); 1208 r->oop_iterate(&_cl); 1209 } 1210 return false; 1211 } 1212 }; 1213 1214 class ParRebuildRSTask: public AbstractGangTask { 1215 G1CollectedHeap* _g1; 1216 public: 1217 ParRebuildRSTask(G1CollectedHeap* g1) 1218 : AbstractGangTask("ParRebuildRSTask"), 1219 _g1(g1) 1220 { } 1221 1222 void work(uint worker_id) { 1223 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1224 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, 1225 _g1->workers()->active_workers(), 1226 HeapRegion::RebuildRSClaimValue); 1227 } 1228 }; 1229 1230 class PostCompactionPrinterClosure: public HeapRegionClosure { 1231 private: 1232 G1HRPrinter* _hr_printer; 1233 public: 1234 bool doHeapRegion(HeapRegion* hr) { 1235 assert(!hr->is_young(), "not expecting to find young regions"); 1236 // We only generate output for non-empty regions. 1237 if (!hr->is_empty()) { 1238 if (!hr->isHumongous()) { 1239 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1240 } else if (hr->startsHumongous()) { 1241 if (hr->region_num() == 1) { 1242 // single humongous region 1243 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1244 } else { 1245 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1246 } 1247 } else { 1248 assert(hr->continuesHumongous(), "only way to get here"); 1249 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1250 } 1251 } 1252 return false; 1253 } 1254 1255 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1256 : _hr_printer(hr_printer) { } 1257 }; 1258 1259 void G1CollectedHeap::print_hrs_post_compaction() { 1260 PostCompactionPrinterClosure cl(hr_printer()); 1261 heap_region_iterate(&cl); 1262 } 1263 1264 bool G1CollectedHeap::do_collection(bool explicit_gc, 1265 bool clear_all_soft_refs, 1266 size_t word_size) { 1267 assert_at_safepoint(true /* should_be_vm_thread */); 1268 1269 if (GC_locker::check_active_before_gc()) { 1270 return false; 1271 } 1272 1273 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1274 gc_timer->register_gc_start(); 1275 1276 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1277 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1278 1279 SvcGCMarker sgcm(SvcGCMarker::FULL); 1280 ResourceMark rm; 1281 1282 print_heap_before_gc(); 1283 trace_heap_before_gc(gc_tracer); 1284 1285 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1286 1287 verify_region_sets_optional(); 1288 1289 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1290 collector_policy()->should_clear_all_soft_refs(); 1291 1292 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1293 1294 { 1295 IsGCActiveMark x; 1296 1297 // Timing 1298 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1299 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); 1300 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1301 1302 { 1303 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id()); 1304 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1305 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1306 1307 double start = os::elapsedTime(); 1308 g1_policy()->record_full_collection_start(); 1309 1310 // Note: When we have a more flexible GC logging framework that 1311 // allows us to add optional attributes to a GC log record we 1312 // could consider timing and reporting how long we wait in the 1313 // following two methods. 1314 wait_while_free_regions_coming(); 1315 // If we start the compaction before the CM threads finish 1316 // scanning the root regions we might trip them over as we'll 1317 // be moving objects / updating references. So let's wait until 1318 // they are done. By telling them to abort, they should complete 1319 // early. 1320 _cm->root_regions()->abort(); 1321 _cm->root_regions()->wait_until_scan_finished(); 1322 append_secondary_free_list_if_not_empty_with_lock(); 1323 1324 gc_prologue(true); 1325 increment_total_collections(true /* full gc */); 1326 increment_old_marking_cycles_started(); 1327 1328 assert(used() == recalculate_used(), "Should be equal"); 1329 1330 verify_before_gc(); 1331 1332 pre_full_gc_dump(gc_timer); 1333 1334 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1335 1336 // Disable discovery and empty the discovered lists 1337 // for the CM ref processor. 1338 ref_processor_cm()->disable_discovery(); 1339 ref_processor_cm()->abandon_partial_discovery(); 1340 ref_processor_cm()->verify_no_references_recorded(); 1341 1342 // Abandon current iterations of concurrent marking and concurrent 1343 // refinement, if any are in progress. We have to do this before 1344 // wait_until_scan_finished() below. 1345 concurrent_mark()->abort(); 1346 1347 // Make sure we'll choose a new allocation region afterwards. 1348 release_mutator_alloc_region(); 1349 abandon_gc_alloc_regions(); 1350 g1_rem_set()->cleanupHRRS(); 1351 1352 // We should call this after we retire any currently active alloc 1353 // regions so that all the ALLOC / RETIRE events are generated 1354 // before the start GC event. 1355 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1356 1357 // We may have added regions to the current incremental collection 1358 // set between the last GC or pause and now. We need to clear the 1359 // incremental collection set and then start rebuilding it afresh 1360 // after this full GC. 1361 abandon_collection_set(g1_policy()->inc_cset_head()); 1362 g1_policy()->clear_incremental_cset(); 1363 g1_policy()->stop_incremental_cset_building(); 1364 1365 tear_down_region_sets(false /* free_list_only */); 1366 g1_policy()->set_gcs_are_young(true); 1367 1368 // See the comments in g1CollectedHeap.hpp and 1369 // G1CollectedHeap::ref_processing_init() about 1370 // how reference processing currently works in G1. 1371 1372 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1373 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1374 1375 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1376 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1377 1378 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1379 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1380 1381 // Do collection work 1382 { 1383 HandleMark hm; // Discard invalid handles created during gc 1384 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1385 } 1386 1387 assert(free_regions() == 0, "we should not have added any free regions"); 1388 rebuild_region_sets(false /* free_list_only */); 1389 1390 // Enqueue any discovered reference objects that have 1391 // not been removed from the discovered lists. 1392 ref_processor_stw()->enqueue_discovered_references(); 1393 1394 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1395 1396 MemoryService::track_memory_usage(); 1397 1398 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1399 ref_processor_stw()->verify_no_references_recorded(); 1400 1401 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1402 ClassLoaderDataGraph::purge(); 1403 MetaspaceAux::verify_metrics(); 1404 1405 // Note: since we've just done a full GC, concurrent 1406 // marking is no longer active. Therefore we need not 1407 // re-enable reference discovery for the CM ref processor. 1408 // That will be done at the start of the next marking cycle. 1409 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1410 ref_processor_cm()->verify_no_references_recorded(); 1411 1412 reset_gc_time_stamp(); 1413 // Since everything potentially moved, we will clear all remembered 1414 // sets, and clear all cards. Later we will rebuild remembered 1415 // sets. We will also reset the GC time stamps of the regions. 1416 clear_rsets_post_compaction(); 1417 check_gc_time_stamps(); 1418 1419 // Resize the heap if necessary. 1420 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1421 1422 if (_hr_printer.is_active()) { 1423 // We should do this after we potentially resize the heap so 1424 // that all the COMMIT / UNCOMMIT events are generated before 1425 // the end GC event. 1426 1427 print_hrs_post_compaction(); 1428 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1429 } 1430 1431 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1432 if (hot_card_cache->use_cache()) { 1433 hot_card_cache->reset_card_counts(); 1434 hot_card_cache->reset_hot_cache(); 1435 } 1436 1437 // Rebuild remembered sets of all regions. 1438 if (G1CollectedHeap::use_parallel_gc_threads()) { 1439 uint n_workers = 1440 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1441 workers()->active_workers(), 1442 Threads::number_of_non_daemon_threads()); 1443 assert(UseDynamicNumberOfGCThreads || 1444 n_workers == workers()->total_workers(), 1445 "If not dynamic should be using all the workers"); 1446 workers()->set_active_workers(n_workers); 1447 // Set parallel threads in the heap (_n_par_threads) only 1448 // before a parallel phase and always reset it to 0 after 1449 // the phase so that the number of parallel threads does 1450 // no get carried forward to a serial phase where there 1451 // may be code that is "possibly_parallel". 1452 set_par_threads(n_workers); 1453 1454 ParRebuildRSTask rebuild_rs_task(this); 1455 assert(check_heap_region_claim_values( 1456 HeapRegion::InitialClaimValue), "sanity check"); 1457 assert(UseDynamicNumberOfGCThreads || 1458 workers()->active_workers() == workers()->total_workers(), 1459 "Unless dynamic should use total workers"); 1460 // Use the most recent number of active workers 1461 assert(workers()->active_workers() > 0, 1462 "Active workers not properly set"); 1463 set_par_threads(workers()->active_workers()); 1464 workers()->run_task(&rebuild_rs_task); 1465 set_par_threads(0); 1466 assert(check_heap_region_claim_values( 1467 HeapRegion::RebuildRSClaimValue), "sanity check"); 1468 reset_heap_region_claim_values(); 1469 } else { 1470 RebuildRSOutOfRegionClosure rebuild_rs(this); 1471 heap_region_iterate(&rebuild_rs); 1472 } 1473 1474 // Rebuild the strong code root lists for each region 1475 rebuild_strong_code_roots(); 1476 1477 if (true) { // FIXME 1478 MetaspaceGC::compute_new_size(); 1479 } 1480 1481 #ifdef TRACESPINNING 1482 ParallelTaskTerminator::print_termination_counts(); 1483 #endif 1484 1485 // Discard all rset updates 1486 JavaThread::dirty_card_queue_set().abandon_logs(); 1487 assert(!G1DeferredRSUpdate 1488 || (G1DeferredRSUpdate && 1489 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1490 1491 _young_list->reset_sampled_info(); 1492 // At this point there should be no regions in the 1493 // entire heap tagged as young. 1494 assert(check_young_list_empty(true /* check_heap */), 1495 "young list should be empty at this point"); 1496 1497 // Update the number of full collections that have been completed. 1498 increment_old_marking_cycles_completed(false /* concurrent */); 1499 1500 _hrs.verify_optional(); 1501 verify_region_sets_optional(); 1502 1503 verify_after_gc(); 1504 1505 // Start a new incremental collection set for the next pause 1506 assert(g1_policy()->collection_set() == NULL, "must be"); 1507 g1_policy()->start_incremental_cset_building(); 1508 1509 clear_cset_fast_test(); 1510 1511 init_mutator_alloc_region(); 1512 1513 double end = os::elapsedTime(); 1514 g1_policy()->record_full_collection_end(); 1515 1516 if (G1Log::fine()) { 1517 g1_policy()->print_heap_transition(); 1518 } 1519 1520 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1521 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1522 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1523 // before any GC notifications are raised. 1524 g1mm()->update_sizes(); 1525 1526 gc_epilogue(true); 1527 } 1528 1529 if (G1Log::finer()) { 1530 g1_policy()->print_detailed_heap_transition(true /* full */); 1531 } 1532 1533 print_heap_after_gc(); 1534 trace_heap_after_gc(gc_tracer); 1535 1536 post_full_gc_dump(gc_timer); 1537 1538 gc_timer->register_gc_end(); 1539 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1540 } 1541 1542 return true; 1543 } 1544 1545 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1546 // do_collection() will return whether it succeeded in performing 1547 // the GC. Currently, there is no facility on the 1548 // do_full_collection() API to notify the caller than the collection 1549 // did not succeed (e.g., because it was locked out by the GC 1550 // locker). So, right now, we'll ignore the return value. 1551 bool dummy = do_collection(true, /* explicit_gc */ 1552 clear_all_soft_refs, 1553 0 /* word_size */); 1554 } 1555 1556 // This code is mostly copied from TenuredGeneration. 1557 void 1558 G1CollectedHeap:: 1559 resize_if_necessary_after_full_collection(size_t word_size) { 1560 // Include the current allocation, if any, and bytes that will be 1561 // pre-allocated to support collections, as "used". 1562 const size_t used_after_gc = used(); 1563 const size_t capacity_after_gc = capacity(); 1564 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1565 1566 // This is enforced in arguments.cpp. 1567 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1568 "otherwise the code below doesn't make sense"); 1569 1570 // We don't have floating point command-line arguments 1571 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1572 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1573 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1574 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1575 1576 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1577 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1578 1579 // We have to be careful here as these two calculations can overflow 1580 // 32-bit size_t's. 1581 double used_after_gc_d = (double) used_after_gc; 1582 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1583 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1584 1585 // Let's make sure that they are both under the max heap size, which 1586 // by default will make them fit into a size_t. 1587 double desired_capacity_upper_bound = (double) max_heap_size; 1588 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1589 desired_capacity_upper_bound); 1590 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1591 desired_capacity_upper_bound); 1592 1593 // We can now safely turn them into size_t's. 1594 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1595 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1596 1597 // This assert only makes sense here, before we adjust them 1598 // with respect to the min and max heap size. 1599 assert(minimum_desired_capacity <= maximum_desired_capacity, 1600 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1601 "maximum_desired_capacity = "SIZE_FORMAT, 1602 minimum_desired_capacity, maximum_desired_capacity)); 1603 1604 // Should not be greater than the heap max size. No need to adjust 1605 // it with respect to the heap min size as it's a lower bound (i.e., 1606 // we'll try to make the capacity larger than it, not smaller). 1607 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1608 // Should not be less than the heap min size. No need to adjust it 1609 // with respect to the heap max size as it's an upper bound (i.e., 1610 // we'll try to make the capacity smaller than it, not greater). 1611 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1612 1613 if (capacity_after_gc < minimum_desired_capacity) { 1614 // Don't expand unless it's significant 1615 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1616 ergo_verbose4(ErgoHeapSizing, 1617 "attempt heap expansion", 1618 ergo_format_reason("capacity lower than " 1619 "min desired capacity after Full GC") 1620 ergo_format_byte("capacity") 1621 ergo_format_byte("occupancy") 1622 ergo_format_byte_perc("min desired capacity"), 1623 capacity_after_gc, used_after_gc, 1624 minimum_desired_capacity, (double) MinHeapFreeRatio); 1625 expand(expand_bytes); 1626 1627 // No expansion, now see if we want to shrink 1628 } else if (capacity_after_gc > maximum_desired_capacity) { 1629 // Capacity too large, compute shrinking size 1630 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1631 ergo_verbose4(ErgoHeapSizing, 1632 "attempt heap shrinking", 1633 ergo_format_reason("capacity higher than " 1634 "max desired capacity after Full GC") 1635 ergo_format_byte("capacity") 1636 ergo_format_byte("occupancy") 1637 ergo_format_byte_perc("max desired capacity"), 1638 capacity_after_gc, used_after_gc, 1639 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1640 shrink(shrink_bytes); 1641 } 1642 } 1643 1644 1645 HeapWord* 1646 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1647 bool* succeeded) { 1648 assert_at_safepoint(true /* should_be_vm_thread */); 1649 1650 *succeeded = true; 1651 // Let's attempt the allocation first. 1652 HeapWord* result = 1653 attempt_allocation_at_safepoint(word_size, 1654 false /* expect_null_mutator_alloc_region */); 1655 if (result != NULL) { 1656 assert(*succeeded, "sanity"); 1657 return result; 1658 } 1659 1660 // In a G1 heap, we're supposed to keep allocation from failing by 1661 // incremental pauses. Therefore, at least for now, we'll favor 1662 // expansion over collection. (This might change in the future if we can 1663 // do something smarter than full collection to satisfy a failed alloc.) 1664 result = expand_and_allocate(word_size); 1665 if (result != NULL) { 1666 assert(*succeeded, "sanity"); 1667 return result; 1668 } 1669 1670 // Expansion didn't work, we'll try to do a Full GC. 1671 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1672 false, /* clear_all_soft_refs */ 1673 word_size); 1674 if (!gc_succeeded) { 1675 *succeeded = false; 1676 return NULL; 1677 } 1678 1679 // Retry the allocation 1680 result = attempt_allocation_at_safepoint(word_size, 1681 true /* expect_null_mutator_alloc_region */); 1682 if (result != NULL) { 1683 assert(*succeeded, "sanity"); 1684 return result; 1685 } 1686 1687 // Then, try a Full GC that will collect all soft references. 1688 gc_succeeded = do_collection(false, /* explicit_gc */ 1689 true, /* clear_all_soft_refs */ 1690 word_size); 1691 if (!gc_succeeded) { 1692 *succeeded = false; 1693 return NULL; 1694 } 1695 1696 // Retry the allocation once more 1697 result = attempt_allocation_at_safepoint(word_size, 1698 true /* expect_null_mutator_alloc_region */); 1699 if (result != NULL) { 1700 assert(*succeeded, "sanity"); 1701 return result; 1702 } 1703 1704 assert(!collector_policy()->should_clear_all_soft_refs(), 1705 "Flag should have been handled and cleared prior to this point"); 1706 1707 // What else? We might try synchronous finalization later. If the total 1708 // space available is large enough for the allocation, then a more 1709 // complete compaction phase than we've tried so far might be 1710 // appropriate. 1711 assert(*succeeded, "sanity"); 1712 return NULL; 1713 } 1714 1715 // Attempting to expand the heap sufficiently 1716 // to support an allocation of the given "word_size". If 1717 // successful, perform the allocation and return the address of the 1718 // allocated block, or else "NULL". 1719 1720 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1721 assert_at_safepoint(true /* should_be_vm_thread */); 1722 1723 verify_region_sets_optional(); 1724 1725 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1726 ergo_verbose1(ErgoHeapSizing, 1727 "attempt heap expansion", 1728 ergo_format_reason("allocation request failed") 1729 ergo_format_byte("allocation request"), 1730 word_size * HeapWordSize); 1731 if (expand(expand_bytes)) { 1732 _hrs.verify_optional(); 1733 verify_region_sets_optional(); 1734 return attempt_allocation_at_safepoint(word_size, 1735 false /* expect_null_mutator_alloc_region */); 1736 } 1737 return NULL; 1738 } 1739 1740 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1741 HeapWord* new_end) { 1742 assert(old_end != new_end, "don't call this otherwise"); 1743 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1744 1745 // Update the committed mem region. 1746 _g1_committed.set_end(new_end); 1747 // Tell the card table about the update. 1748 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1749 // Tell the BOT about the update. 1750 _bot_shared->resize(_g1_committed.word_size()); 1751 // Tell the hot card cache about the update 1752 _cg1r->hot_card_cache()->resize_card_counts(capacity()); 1753 } 1754 1755 bool G1CollectedHeap::expand(size_t expand_bytes) { 1756 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1757 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1758 HeapRegion::GrainBytes); 1759 ergo_verbose2(ErgoHeapSizing, 1760 "expand the heap", 1761 ergo_format_byte("requested expansion amount") 1762 ergo_format_byte("attempted expansion amount"), 1763 expand_bytes, aligned_expand_bytes); 1764 1765 if (_g1_storage.uncommitted_size() == 0) { 1766 ergo_verbose0(ErgoHeapSizing, 1767 "did not expand the heap", 1768 ergo_format_reason("heap already fully expanded")); 1769 return false; 1770 } 1771 1772 // First commit the memory. 1773 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1774 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1775 if (successful) { 1776 // Then propagate this update to the necessary data structures. 1777 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1778 update_committed_space(old_end, new_end); 1779 1780 FreeRegionList expansion_list("Local Expansion List"); 1781 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1782 assert(mr.start() == old_end, "post-condition"); 1783 // mr might be a smaller region than what was requested if 1784 // expand_by() was unable to allocate the HeapRegion instances 1785 assert(mr.end() <= new_end, "post-condition"); 1786 1787 size_t actual_expand_bytes = mr.byte_size(); 1788 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1789 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1790 "post-condition"); 1791 if (actual_expand_bytes < aligned_expand_bytes) { 1792 // We could not expand _hrs to the desired size. In this case we 1793 // need to shrink the committed space accordingly. 1794 assert(mr.end() < new_end, "invariant"); 1795 1796 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1797 // First uncommit the memory. 1798 _g1_storage.shrink_by(diff_bytes); 1799 // Then propagate this update to the necessary data structures. 1800 update_committed_space(new_end, mr.end()); 1801 } 1802 _free_list.add_as_tail(&expansion_list); 1803 1804 if (_hr_printer.is_active()) { 1805 HeapWord* curr = mr.start(); 1806 while (curr < mr.end()) { 1807 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1808 _hr_printer.commit(curr, curr_end); 1809 curr = curr_end; 1810 } 1811 assert(curr == mr.end(), "post-condition"); 1812 } 1813 g1_policy()->record_new_heap_size(n_regions()); 1814 } else { 1815 ergo_verbose0(ErgoHeapSizing, 1816 "did not expand the heap", 1817 ergo_format_reason("heap expansion operation failed")); 1818 // The expansion of the virtual storage space was unsuccessful. 1819 // Let's see if it was because we ran out of swap. 1820 if (G1ExitOnExpansionFailure && 1821 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1822 // We had head room... 1823 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1824 } 1825 } 1826 return successful; 1827 } 1828 1829 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1830 size_t aligned_shrink_bytes = 1831 ReservedSpace::page_align_size_down(shrink_bytes); 1832 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1833 HeapRegion::GrainBytes); 1834 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1835 1836 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove); 1837 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1838 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1839 1840 ergo_verbose3(ErgoHeapSizing, 1841 "shrink the heap", 1842 ergo_format_byte("requested shrinking amount") 1843 ergo_format_byte("aligned shrinking amount") 1844 ergo_format_byte("attempted shrinking amount"), 1845 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1846 if (num_regions_removed > 0) { 1847 _g1_storage.shrink_by(shrunk_bytes); 1848 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1849 1850 if (_hr_printer.is_active()) { 1851 HeapWord* curr = old_end; 1852 while (curr > new_end) { 1853 HeapWord* curr_end = curr; 1854 curr -= HeapRegion::GrainWords; 1855 _hr_printer.uncommit(curr, curr_end); 1856 } 1857 } 1858 1859 _expansion_regions += num_regions_removed; 1860 update_committed_space(old_end, new_end); 1861 HeapRegionRemSet::shrink_heap(n_regions()); 1862 g1_policy()->record_new_heap_size(n_regions()); 1863 } else { 1864 ergo_verbose0(ErgoHeapSizing, 1865 "did not shrink the heap", 1866 ergo_format_reason("heap shrinking operation failed")); 1867 } 1868 } 1869 1870 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1871 verify_region_sets_optional(); 1872 1873 // We should only reach here at the end of a Full GC which means we 1874 // should not not be holding to any GC alloc regions. The method 1875 // below will make sure of that and do any remaining clean up. 1876 abandon_gc_alloc_regions(); 1877 1878 // Instead of tearing down / rebuilding the free lists here, we 1879 // could instead use the remove_all_pending() method on free_list to 1880 // remove only the ones that we need to remove. 1881 tear_down_region_sets(true /* free_list_only */); 1882 shrink_helper(shrink_bytes); 1883 rebuild_region_sets(true /* free_list_only */); 1884 1885 _hrs.verify_optional(); 1886 verify_region_sets_optional(); 1887 } 1888 1889 // Public methods. 1890 1891 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1892 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1893 #endif // _MSC_VER 1894 1895 1896 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1897 SharedHeap(policy_), 1898 _g1_policy(policy_), 1899 _dirty_card_queue_set(false), 1900 _into_cset_dirty_card_queue_set(false), 1901 _is_alive_closure_cm(this), 1902 _is_alive_closure_stw(this), 1903 _ref_processor_cm(NULL), 1904 _ref_processor_stw(NULL), 1905 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1906 _bot_shared(NULL), 1907 _evac_failure_scan_stack(NULL), 1908 _mark_in_progress(false), 1909 _cg1r(NULL), _summary_bytes_used(0), 1910 _g1mm(NULL), 1911 _refine_cte_cl(NULL), 1912 _full_collection(false), 1913 _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()), 1914 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1915 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1916 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1917 _free_regions_coming(false), 1918 _young_list(new YoungList(this)), 1919 _gc_time_stamp(0), 1920 _retained_old_gc_alloc_region(NULL), 1921 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1922 _old_plab_stats(OldPLABSize, PLABWeight), 1923 _expand_heap_after_alloc_failure(true), 1924 _surviving_young_words(NULL), 1925 _old_marking_cycles_started(0), 1926 _old_marking_cycles_completed(0), 1927 _concurrent_cycle_started(false), 1928 _in_cset_fast_test(), 1929 _dirty_cards_region_list(NULL), 1930 _worker_cset_start_region(NULL), 1931 _worker_cset_start_region_time_stamp(NULL), 1932 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1933 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1934 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1935 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1936 1937 _g1h = this; 1938 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1939 vm_exit_during_initialization("Failed necessary allocation."); 1940 } 1941 1942 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1943 1944 int n_queues = MAX2((int)ParallelGCThreads, 1); 1945 _task_queues = new RefToScanQueueSet(n_queues); 1946 1947 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1948 assert(n_rem_sets > 0, "Invariant."); 1949 1950 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1951 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1952 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1953 1954 for (int i = 0; i < n_queues; i++) { 1955 RefToScanQueue* q = new RefToScanQueue(); 1956 q->initialize(); 1957 _task_queues->register_queue(i, q); 1958 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1959 } 1960 clear_cset_start_regions(); 1961 1962 // Initialize the G1EvacuationFailureALot counters and flags. 1963 NOT_PRODUCT(reset_evacuation_should_fail();) 1964 1965 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1966 } 1967 1968 jint G1CollectedHeap::initialize() { 1969 CollectedHeap::pre_initialize(); 1970 os::enable_vtime(); 1971 1972 G1Log::init(); 1973 1974 // Necessary to satisfy locking discipline assertions. 1975 1976 MutexLocker x(Heap_lock); 1977 1978 // We have to initialize the printer before committing the heap, as 1979 // it will be used then. 1980 _hr_printer.set_active(G1PrintHeapRegions); 1981 1982 // While there are no constraints in the GC code that HeapWordSize 1983 // be any particular value, there are multiple other areas in the 1984 // system which believe this to be true (e.g. oop->object_size in some 1985 // cases incorrectly returns the size in wordSize units rather than 1986 // HeapWordSize). 1987 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1988 1989 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1990 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1991 size_t heap_alignment = collector_policy()->heap_alignment(); 1992 1993 // Ensure that the sizes are properly aligned. 1994 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1995 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1996 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1997 1998 _refine_cte_cl = new RefineCardTableEntryClosure(); 1999 2000 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl); 2001 2002 // Reserve the maximum. 2003 2004 // When compressed oops are enabled, the preferred heap base 2005 // is calculated by subtracting the requested size from the 2006 // 32Gb boundary and using the result as the base address for 2007 // heap reservation. If the requested size is not aligned to 2008 // HeapRegion::GrainBytes (i.e. the alignment that is passed 2009 // into the ReservedHeapSpace constructor) then the actual 2010 // base of the reserved heap may end up differing from the 2011 // address that was requested (i.e. the preferred heap base). 2012 // If this happens then we could end up using a non-optimal 2013 // compressed oops mode. 2014 2015 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 2016 heap_alignment); 2017 2018 // It is important to do this in a way such that concurrent readers can't 2019 // temporarily think something is in the heap. (I've actually seen this 2020 // happen in asserts: DLD.) 2021 _reserved.set_word_size(0); 2022 _reserved.set_start((HeapWord*)heap_rs.base()); 2023 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 2024 2025 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes); 2026 2027 // Create the gen rem set (and barrier set) for the entire reserved region. 2028 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 2029 set_barrier_set(rem_set()->bs()); 2030 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) { 2031 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS"); 2032 return JNI_ENOMEM; 2033 } 2034 2035 // Also create a G1 rem set. 2036 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 2037 2038 // Carve out the G1 part of the heap. 2039 2040 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 2041 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 2042 g1_rs.size()/HeapWordSize); 2043 2044 _g1_storage.initialize(g1_rs, 0); 2045 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 2046 _hrs.initialize((HeapWord*) _g1_reserved.start(), 2047 (HeapWord*) _g1_reserved.end()); 2048 assert(_hrs.max_length() == _expansion_regions, 2049 err_msg("max length: %u expansion regions: %u", 2050 _hrs.max_length(), _expansion_regions)); 2051 2052 // Do later initialization work for concurrent refinement. 2053 _cg1r->init(); 2054 2055 // 6843694 - ensure that the maximum region index can fit 2056 // in the remembered set structures. 2057 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2058 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2059 2060 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2061 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2062 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2063 "too many cards per region"); 2064 2065 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 2066 2067 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 2068 heap_word_size(init_byte_size)); 2069 2070 _g1h = this; 2071 2072 _in_cset_fast_test.initialize(_g1_reserved.start(), _g1_reserved.end(), HeapRegion::GrainBytes); 2073 2074 // Create the ConcurrentMark data structure and thread. 2075 // (Must do this late, so that "max_regions" is defined.) 2076 _cm = new ConcurrentMark(this, heap_rs); 2077 if (_cm == NULL || !_cm->completed_initialization()) { 2078 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2079 return JNI_ENOMEM; 2080 } 2081 _cmThread = _cm->cmThread(); 2082 2083 // Initialize the from_card cache structure of HeapRegionRemSet. 2084 HeapRegionRemSet::init_heap(max_regions()); 2085 2086 // Now expand into the initial heap size. 2087 if (!expand(init_byte_size)) { 2088 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2089 return JNI_ENOMEM; 2090 } 2091 2092 // Perform any initialization actions delegated to the policy. 2093 g1_policy()->init(); 2094 2095 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2096 SATB_Q_FL_lock, 2097 G1SATBProcessCompletedThreshold, 2098 Shared_SATB_Q_lock); 2099 2100 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2101 DirtyCardQ_CBL_mon, 2102 DirtyCardQ_FL_lock, 2103 concurrent_g1_refine()->yellow_zone(), 2104 concurrent_g1_refine()->red_zone(), 2105 Shared_DirtyCardQ_lock); 2106 2107 if (G1DeferredRSUpdate) { 2108 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2109 DirtyCardQ_CBL_mon, 2110 DirtyCardQ_FL_lock, 2111 -1, // never trigger processing 2112 -1, // no limit on length 2113 Shared_DirtyCardQ_lock, 2114 &JavaThread::dirty_card_queue_set()); 2115 } 2116 2117 // Initialize the card queue set used to hold cards containing 2118 // references into the collection set. 2119 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code 2120 DirtyCardQ_CBL_mon, 2121 DirtyCardQ_FL_lock, 2122 -1, // never trigger processing 2123 -1, // no limit on length 2124 Shared_DirtyCardQ_lock, 2125 &JavaThread::dirty_card_queue_set()); 2126 2127 // In case we're keeping closure specialization stats, initialize those 2128 // counts and that mechanism. 2129 SpecializationStats::clear(); 2130 2131 // Here we allocate the dummy full region that is required by the 2132 // G1AllocRegion class. If we don't pass an address in the reserved 2133 // space here, lots of asserts fire. 2134 2135 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2136 _g1_reserved.start()); 2137 // We'll re-use the same region whether the alloc region will 2138 // require BOT updates or not and, if it doesn't, then a non-young 2139 // region will complain that it cannot support allocations without 2140 // BOT updates. So we'll tag the dummy region as young to avoid that. 2141 dummy_region->set_young(); 2142 // Make sure it's full. 2143 dummy_region->set_top(dummy_region->end()); 2144 G1AllocRegion::setup(this, dummy_region); 2145 2146 init_mutator_alloc_region(); 2147 2148 // Do create of the monitoring and management support so that 2149 // values in the heap have been properly initialized. 2150 _g1mm = new G1MonitoringSupport(this); 2151 2152 G1StringDedup::initialize(); 2153 2154 return JNI_OK; 2155 } 2156 2157 void G1CollectedHeap::stop() { 2158 // Stop all concurrent threads. We do this to make sure these threads 2159 // do not continue to execute and access resources (e.g. gclog_or_tty) 2160 // that are destroyed during shutdown. 2161 _cg1r->stop(); 2162 _cmThread->stop(); 2163 if (G1StringDedup::is_enabled()) { 2164 G1StringDedup::stop(); 2165 } 2166 } 2167 2168 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2169 return HeapRegion::max_region_size(); 2170 } 2171 2172 void G1CollectedHeap::ref_processing_init() { 2173 // Reference processing in G1 currently works as follows: 2174 // 2175 // * There are two reference processor instances. One is 2176 // used to record and process discovered references 2177 // during concurrent marking; the other is used to 2178 // record and process references during STW pauses 2179 // (both full and incremental). 2180 // * Both ref processors need to 'span' the entire heap as 2181 // the regions in the collection set may be dotted around. 2182 // 2183 // * For the concurrent marking ref processor: 2184 // * Reference discovery is enabled at initial marking. 2185 // * Reference discovery is disabled and the discovered 2186 // references processed etc during remarking. 2187 // * Reference discovery is MT (see below). 2188 // * Reference discovery requires a barrier (see below). 2189 // * Reference processing may or may not be MT 2190 // (depending on the value of ParallelRefProcEnabled 2191 // and ParallelGCThreads). 2192 // * A full GC disables reference discovery by the CM 2193 // ref processor and abandons any entries on it's 2194 // discovered lists. 2195 // 2196 // * For the STW processor: 2197 // * Non MT discovery is enabled at the start of a full GC. 2198 // * Processing and enqueueing during a full GC is non-MT. 2199 // * During a full GC, references are processed after marking. 2200 // 2201 // * Discovery (may or may not be MT) is enabled at the start 2202 // of an incremental evacuation pause. 2203 // * References are processed near the end of a STW evacuation pause. 2204 // * For both types of GC: 2205 // * Discovery is atomic - i.e. not concurrent. 2206 // * Reference discovery will not need a barrier. 2207 2208 SharedHeap::ref_processing_init(); 2209 MemRegion mr = reserved_region(); 2210 2211 // Concurrent Mark ref processor 2212 _ref_processor_cm = 2213 new ReferenceProcessor(mr, // span 2214 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2215 // mt processing 2216 (int) ParallelGCThreads, 2217 // degree of mt processing 2218 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2219 // mt discovery 2220 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2221 // degree of mt discovery 2222 false, 2223 // Reference discovery is not atomic 2224 &_is_alive_closure_cm); 2225 // is alive closure 2226 // (for efficiency/performance) 2227 2228 // STW ref processor 2229 _ref_processor_stw = 2230 new ReferenceProcessor(mr, // span 2231 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2232 // mt processing 2233 MAX2((int)ParallelGCThreads, 1), 2234 // degree of mt processing 2235 (ParallelGCThreads > 1), 2236 // mt discovery 2237 MAX2((int)ParallelGCThreads, 1), 2238 // degree of mt discovery 2239 true, 2240 // Reference discovery is atomic 2241 &_is_alive_closure_stw); 2242 // is alive closure 2243 // (for efficiency/performance) 2244 } 2245 2246 size_t G1CollectedHeap::capacity() const { 2247 return _g1_committed.byte_size(); 2248 } 2249 2250 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2251 assert(!hr->continuesHumongous(), "pre-condition"); 2252 hr->reset_gc_time_stamp(); 2253 if (hr->startsHumongous()) { 2254 uint first_index = hr->hrs_index() + 1; 2255 uint last_index = hr->last_hc_index(); 2256 for (uint i = first_index; i < last_index; i += 1) { 2257 HeapRegion* chr = region_at(i); 2258 assert(chr->continuesHumongous(), "sanity"); 2259 chr->reset_gc_time_stamp(); 2260 } 2261 } 2262 } 2263 2264 #ifndef PRODUCT 2265 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2266 private: 2267 unsigned _gc_time_stamp; 2268 bool _failures; 2269 2270 public: 2271 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2272 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2273 2274 virtual bool doHeapRegion(HeapRegion* hr) { 2275 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2276 if (_gc_time_stamp != region_gc_time_stamp) { 2277 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2278 "expected %d", HR_FORMAT_PARAMS(hr), 2279 region_gc_time_stamp, _gc_time_stamp); 2280 _failures = true; 2281 } 2282 return false; 2283 } 2284 2285 bool failures() { return _failures; } 2286 }; 2287 2288 void G1CollectedHeap::check_gc_time_stamps() { 2289 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2290 heap_region_iterate(&cl); 2291 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2292 } 2293 #endif // PRODUCT 2294 2295 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2296 DirtyCardQueue* into_cset_dcq, 2297 bool concurrent, 2298 uint worker_i) { 2299 // Clean cards in the hot card cache 2300 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2301 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2302 2303 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2304 int n_completed_buffers = 0; 2305 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2306 n_completed_buffers++; 2307 } 2308 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2309 dcqs.clear_n_completed_buffers(); 2310 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2311 } 2312 2313 2314 // Computes the sum of the storage used by the various regions. 2315 2316 size_t G1CollectedHeap::used() const { 2317 assert(Heap_lock->owner() != NULL, 2318 "Should be owned on this thread's behalf."); 2319 size_t result = _summary_bytes_used; 2320 // Read only once in case it is set to NULL concurrently 2321 HeapRegion* hr = _mutator_alloc_region.get(); 2322 if (hr != NULL) 2323 result += hr->used(); 2324 return result; 2325 } 2326 2327 size_t G1CollectedHeap::used_unlocked() const { 2328 size_t result = _summary_bytes_used; 2329 return result; 2330 } 2331 2332 class SumUsedClosure: public HeapRegionClosure { 2333 size_t _used; 2334 public: 2335 SumUsedClosure() : _used(0) {} 2336 bool doHeapRegion(HeapRegion* r) { 2337 if (!r->continuesHumongous()) { 2338 _used += r->used(); 2339 } 2340 return false; 2341 } 2342 size_t result() { return _used; } 2343 }; 2344 2345 size_t G1CollectedHeap::recalculate_used() const { 2346 double recalculate_used_start = os::elapsedTime(); 2347 2348 SumUsedClosure blk; 2349 heap_region_iterate(&blk); 2350 2351 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2352 return blk.result(); 2353 } 2354 2355 size_t G1CollectedHeap::unsafe_max_alloc() { 2356 if (free_regions() > 0) return HeapRegion::GrainBytes; 2357 // otherwise, is there space in the current allocation region? 2358 2359 // We need to store the current allocation region in a local variable 2360 // here. The problem is that this method doesn't take any locks and 2361 // there may be other threads which overwrite the current allocation 2362 // region field. attempt_allocation(), for example, sets it to NULL 2363 // and this can happen *after* the NULL check here but before the call 2364 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2365 // to be a problem in the optimized build, since the two loads of the 2366 // current allocation region field are optimized away. 2367 HeapRegion* hr = _mutator_alloc_region.get(); 2368 if (hr == NULL) { 2369 return 0; 2370 } 2371 return hr->free(); 2372 } 2373 2374 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2375 switch (cause) { 2376 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2377 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2378 case GCCause::_g1_humongous_allocation: return true; 2379 default: return false; 2380 } 2381 } 2382 2383 #ifndef PRODUCT 2384 void G1CollectedHeap::allocate_dummy_regions() { 2385 // Let's fill up most of the region 2386 size_t word_size = HeapRegion::GrainWords - 1024; 2387 // And as a result the region we'll allocate will be humongous. 2388 guarantee(isHumongous(word_size), "sanity"); 2389 2390 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2391 // Let's use the existing mechanism for the allocation 2392 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2393 if (dummy_obj != NULL) { 2394 MemRegion mr(dummy_obj, word_size); 2395 CollectedHeap::fill_with_object(mr); 2396 } else { 2397 // If we can't allocate once, we probably cannot allocate 2398 // again. Let's get out of the loop. 2399 break; 2400 } 2401 } 2402 } 2403 #endif // !PRODUCT 2404 2405 void G1CollectedHeap::increment_old_marking_cycles_started() { 2406 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2407 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2408 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2409 _old_marking_cycles_started, _old_marking_cycles_completed)); 2410 2411 _old_marking_cycles_started++; 2412 } 2413 2414 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2415 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2416 2417 // We assume that if concurrent == true, then the caller is a 2418 // concurrent thread that was joined the Suspendible Thread 2419 // Set. If there's ever a cheap way to check this, we should add an 2420 // assert here. 2421 2422 // Given that this method is called at the end of a Full GC or of a 2423 // concurrent cycle, and those can be nested (i.e., a Full GC can 2424 // interrupt a concurrent cycle), the number of full collections 2425 // completed should be either one (in the case where there was no 2426 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2427 // behind the number of full collections started. 2428 2429 // This is the case for the inner caller, i.e. a Full GC. 2430 assert(concurrent || 2431 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2432 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2433 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2434 "is inconsistent with _old_marking_cycles_completed = %u", 2435 _old_marking_cycles_started, _old_marking_cycles_completed)); 2436 2437 // This is the case for the outer caller, i.e. the concurrent cycle. 2438 assert(!concurrent || 2439 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2440 err_msg("for outer caller (concurrent cycle): " 2441 "_old_marking_cycles_started = %u " 2442 "is inconsistent with _old_marking_cycles_completed = %u", 2443 _old_marking_cycles_started, _old_marking_cycles_completed)); 2444 2445 _old_marking_cycles_completed += 1; 2446 2447 // We need to clear the "in_progress" flag in the CM thread before 2448 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2449 // is set) so that if a waiter requests another System.gc() it doesn't 2450 // incorrectly see that a marking cycle is still in progress. 2451 if (concurrent) { 2452 _cmThread->clear_in_progress(); 2453 } 2454 2455 // This notify_all() will ensure that a thread that called 2456 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2457 // and it's waiting for a full GC to finish will be woken up. It is 2458 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2459 FullGCCount_lock->notify_all(); 2460 } 2461 2462 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2463 _concurrent_cycle_started = true; 2464 _gc_timer_cm->register_gc_start(start_time); 2465 2466 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2467 trace_heap_before_gc(_gc_tracer_cm); 2468 } 2469 2470 void G1CollectedHeap::register_concurrent_cycle_end() { 2471 if (_concurrent_cycle_started) { 2472 if (_cm->has_aborted()) { 2473 _gc_tracer_cm->report_concurrent_mode_failure(); 2474 } 2475 2476 _gc_timer_cm->register_gc_end(); 2477 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2478 2479 _concurrent_cycle_started = false; 2480 } 2481 } 2482 2483 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2484 if (_concurrent_cycle_started) { 2485 trace_heap_after_gc(_gc_tracer_cm); 2486 } 2487 } 2488 2489 G1YCType G1CollectedHeap::yc_type() { 2490 bool is_young = g1_policy()->gcs_are_young(); 2491 bool is_initial_mark = g1_policy()->during_initial_mark_pause(); 2492 bool is_during_mark = mark_in_progress(); 2493 2494 if (is_initial_mark) { 2495 return InitialMark; 2496 } else if (is_during_mark) { 2497 return DuringMark; 2498 } else if (is_young) { 2499 return Normal; 2500 } else { 2501 return Mixed; 2502 } 2503 } 2504 2505 void G1CollectedHeap::collect(GCCause::Cause cause) { 2506 assert_heap_not_locked(); 2507 2508 unsigned int gc_count_before; 2509 unsigned int old_marking_count_before; 2510 bool retry_gc; 2511 2512 do { 2513 retry_gc = false; 2514 2515 { 2516 MutexLocker ml(Heap_lock); 2517 2518 // Read the GC count while holding the Heap_lock 2519 gc_count_before = total_collections(); 2520 old_marking_count_before = _old_marking_cycles_started; 2521 } 2522 2523 if (should_do_concurrent_full_gc(cause)) { 2524 // Schedule an initial-mark evacuation pause that will start a 2525 // concurrent cycle. We're setting word_size to 0 which means that 2526 // we are not requesting a post-GC allocation. 2527 VM_G1IncCollectionPause op(gc_count_before, 2528 0, /* word_size */ 2529 true, /* should_initiate_conc_mark */ 2530 g1_policy()->max_pause_time_ms(), 2531 cause); 2532 2533 VMThread::execute(&op); 2534 if (!op.pause_succeeded()) { 2535 if (old_marking_count_before == _old_marking_cycles_started) { 2536 retry_gc = op.should_retry_gc(); 2537 } else { 2538 // A Full GC happened while we were trying to schedule the 2539 // initial-mark GC. No point in starting a new cycle given 2540 // that the whole heap was collected anyway. 2541 } 2542 2543 if (retry_gc) { 2544 if (GC_locker::is_active_and_needs_gc()) { 2545 GC_locker::stall_until_clear(); 2546 } 2547 } 2548 } 2549 } else { 2550 if (cause == GCCause::_gc_locker 2551 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2552 2553 // Schedule a standard evacuation pause. We're setting word_size 2554 // to 0 which means that we are not requesting a post-GC allocation. 2555 VM_G1IncCollectionPause op(gc_count_before, 2556 0, /* word_size */ 2557 false, /* should_initiate_conc_mark */ 2558 g1_policy()->max_pause_time_ms(), 2559 cause); 2560 VMThread::execute(&op); 2561 } else { 2562 // Schedule a Full GC. 2563 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); 2564 VMThread::execute(&op); 2565 } 2566 } 2567 } while (retry_gc); 2568 } 2569 2570 bool G1CollectedHeap::is_in(const void* p) const { 2571 if (_g1_committed.contains(p)) { 2572 // Given that we know that p is in the committed space, 2573 // heap_region_containing_raw() should successfully 2574 // return the containing region. 2575 HeapRegion* hr = heap_region_containing_raw(p); 2576 return hr->is_in(p); 2577 } else { 2578 return false; 2579 } 2580 } 2581 2582 // Iteration functions. 2583 2584 // Iterates an OopClosure over all ref-containing fields of objects 2585 // within a HeapRegion. 2586 2587 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2588 MemRegion _mr; 2589 ExtendedOopClosure* _cl; 2590 public: 2591 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl) 2592 : _mr(mr), _cl(cl) {} 2593 bool doHeapRegion(HeapRegion* r) { 2594 if (!r->continuesHumongous()) { 2595 r->oop_iterate(_cl); 2596 } 2597 return false; 2598 } 2599 }; 2600 2601 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2602 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2603 heap_region_iterate(&blk); 2604 } 2605 2606 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { 2607 IterateOopClosureRegionClosure blk(mr, cl); 2608 heap_region_iterate(&blk); 2609 } 2610 2611 // Iterates an ObjectClosure over all objects within a HeapRegion. 2612 2613 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2614 ObjectClosure* _cl; 2615 public: 2616 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2617 bool doHeapRegion(HeapRegion* r) { 2618 if (! r->continuesHumongous()) { 2619 r->object_iterate(_cl); 2620 } 2621 return false; 2622 } 2623 }; 2624 2625 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2626 IterateObjectClosureRegionClosure blk(cl); 2627 heap_region_iterate(&blk); 2628 } 2629 2630 // Calls a SpaceClosure on a HeapRegion. 2631 2632 class SpaceClosureRegionClosure: public HeapRegionClosure { 2633 SpaceClosure* _cl; 2634 public: 2635 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2636 bool doHeapRegion(HeapRegion* r) { 2637 _cl->do_space(r); 2638 return false; 2639 } 2640 }; 2641 2642 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2643 SpaceClosureRegionClosure blk(cl); 2644 heap_region_iterate(&blk); 2645 } 2646 2647 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2648 _hrs.iterate(cl); 2649 } 2650 2651 void 2652 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2653 uint worker_id, 2654 uint no_of_par_workers, 2655 jint claim_value) { 2656 const uint regions = n_regions(); 2657 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 2658 no_of_par_workers : 2659 1); 2660 assert(UseDynamicNumberOfGCThreads || 2661 no_of_par_workers == workers()->total_workers(), 2662 "Non dynamic should use fixed number of workers"); 2663 // try to spread out the starting points of the workers 2664 const HeapRegion* start_hr = 2665 start_region_for_worker(worker_id, no_of_par_workers); 2666 const uint start_index = start_hr->hrs_index(); 2667 2668 // each worker will actually look at all regions 2669 for (uint count = 0; count < regions; ++count) { 2670 const uint index = (start_index + count) % regions; 2671 assert(0 <= index && index < regions, "sanity"); 2672 HeapRegion* r = region_at(index); 2673 // we'll ignore "continues humongous" regions (we'll process them 2674 // when we come across their corresponding "start humongous" 2675 // region) and regions already claimed 2676 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2677 continue; 2678 } 2679 // OK, try to claim it 2680 if (r->claimHeapRegion(claim_value)) { 2681 // success! 2682 assert(!r->continuesHumongous(), "sanity"); 2683 if (r->startsHumongous()) { 2684 // If the region is "starts humongous" we'll iterate over its 2685 // "continues humongous" first; in fact we'll do them 2686 // first. The order is important. In on case, calling the 2687 // closure on the "starts humongous" region might de-allocate 2688 // and clear all its "continues humongous" regions and, as a 2689 // result, we might end up processing them twice. So, we'll do 2690 // them first (notice: most closures will ignore them anyway) and 2691 // then we'll do the "starts humongous" region. 2692 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) { 2693 HeapRegion* chr = region_at(ch_index); 2694 2695 // if the region has already been claimed or it's not 2696 // "continues humongous" we're done 2697 if (chr->claim_value() == claim_value || 2698 !chr->continuesHumongous()) { 2699 break; 2700 } 2701 2702 // No one should have claimed it directly. We can given 2703 // that we claimed its "starts humongous" region. 2704 assert(chr->claim_value() != claim_value, "sanity"); 2705 assert(chr->humongous_start_region() == r, "sanity"); 2706 2707 if (chr->claimHeapRegion(claim_value)) { 2708 // we should always be able to claim it; no one else should 2709 // be trying to claim this region 2710 2711 bool res2 = cl->doHeapRegion(chr); 2712 assert(!res2, "Should not abort"); 2713 2714 // Right now, this holds (i.e., no closure that actually 2715 // does something with "continues humongous" regions 2716 // clears them). We might have to weaken it in the future, 2717 // but let's leave these two asserts here for extra safety. 2718 assert(chr->continuesHumongous(), "should still be the case"); 2719 assert(chr->humongous_start_region() == r, "sanity"); 2720 } else { 2721 guarantee(false, "we should not reach here"); 2722 } 2723 } 2724 } 2725 2726 assert(!r->continuesHumongous(), "sanity"); 2727 bool res = cl->doHeapRegion(r); 2728 assert(!res, "Should not abort"); 2729 } 2730 } 2731 } 2732 2733 class ResetClaimValuesClosure: public HeapRegionClosure { 2734 public: 2735 bool doHeapRegion(HeapRegion* r) { 2736 r->set_claim_value(HeapRegion::InitialClaimValue); 2737 return false; 2738 } 2739 }; 2740 2741 void G1CollectedHeap::reset_heap_region_claim_values() { 2742 ResetClaimValuesClosure blk; 2743 heap_region_iterate(&blk); 2744 } 2745 2746 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2747 ResetClaimValuesClosure blk; 2748 collection_set_iterate(&blk); 2749 } 2750 2751 #ifdef ASSERT 2752 // This checks whether all regions in the heap have the correct claim 2753 // value. I also piggy-backed on this a check to ensure that the 2754 // humongous_start_region() information on "continues humongous" 2755 // regions is correct. 2756 2757 class CheckClaimValuesClosure : public HeapRegionClosure { 2758 private: 2759 jint _claim_value; 2760 uint _failures; 2761 HeapRegion* _sh_region; 2762 2763 public: 2764 CheckClaimValuesClosure(jint claim_value) : 2765 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2766 bool doHeapRegion(HeapRegion* r) { 2767 if (r->claim_value() != _claim_value) { 2768 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2769 "claim value = %d, should be %d", 2770 HR_FORMAT_PARAMS(r), 2771 r->claim_value(), _claim_value); 2772 ++_failures; 2773 } 2774 if (!r->isHumongous()) { 2775 _sh_region = NULL; 2776 } else if (r->startsHumongous()) { 2777 _sh_region = r; 2778 } else if (r->continuesHumongous()) { 2779 if (r->humongous_start_region() != _sh_region) { 2780 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2781 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2782 HR_FORMAT_PARAMS(r), 2783 r->humongous_start_region(), 2784 _sh_region); 2785 ++_failures; 2786 } 2787 } 2788 return false; 2789 } 2790 uint failures() { return _failures; } 2791 }; 2792 2793 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2794 CheckClaimValuesClosure cl(claim_value); 2795 heap_region_iterate(&cl); 2796 return cl.failures() == 0; 2797 } 2798 2799 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2800 private: 2801 jint _claim_value; 2802 uint _failures; 2803 2804 public: 2805 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2806 _claim_value(claim_value), _failures(0) { } 2807 2808 uint failures() { return _failures; } 2809 2810 bool doHeapRegion(HeapRegion* hr) { 2811 assert(hr->in_collection_set(), "how?"); 2812 assert(!hr->isHumongous(), "H-region in CSet"); 2813 if (hr->claim_value() != _claim_value) { 2814 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2815 "claim value = %d, should be %d", 2816 HR_FORMAT_PARAMS(hr), 2817 hr->claim_value(), _claim_value); 2818 _failures += 1; 2819 } 2820 return false; 2821 } 2822 }; 2823 2824 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2825 CheckClaimValuesInCSetHRClosure cl(claim_value); 2826 collection_set_iterate(&cl); 2827 return cl.failures() == 0; 2828 } 2829 #endif // ASSERT 2830 2831 // Clear the cached CSet starting regions and (more importantly) 2832 // the time stamps. Called when we reset the GC time stamp. 2833 void G1CollectedHeap::clear_cset_start_regions() { 2834 assert(_worker_cset_start_region != NULL, "sanity"); 2835 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2836 2837 int n_queues = MAX2((int)ParallelGCThreads, 1); 2838 for (int i = 0; i < n_queues; i++) { 2839 _worker_cset_start_region[i] = NULL; 2840 _worker_cset_start_region_time_stamp[i] = 0; 2841 } 2842 } 2843 2844 // Given the id of a worker, obtain or calculate a suitable 2845 // starting region for iterating over the current collection set. 2846 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2847 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2848 2849 HeapRegion* result = NULL; 2850 unsigned gc_time_stamp = get_gc_time_stamp(); 2851 2852 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2853 // Cached starting region for current worker was set 2854 // during the current pause - so it's valid. 2855 // Note: the cached starting heap region may be NULL 2856 // (when the collection set is empty). 2857 result = _worker_cset_start_region[worker_i]; 2858 assert(result == NULL || result->in_collection_set(), "sanity"); 2859 return result; 2860 } 2861 2862 // The cached entry was not valid so let's calculate 2863 // a suitable starting heap region for this worker. 2864 2865 // We want the parallel threads to start their collection 2866 // set iteration at different collection set regions to 2867 // avoid contention. 2868 // If we have: 2869 // n collection set regions 2870 // p threads 2871 // Then thread t will start at region floor ((t * n) / p) 2872 2873 result = g1_policy()->collection_set(); 2874 if (G1CollectedHeap::use_parallel_gc_threads()) { 2875 uint cs_size = g1_policy()->cset_region_length(); 2876 uint active_workers = workers()->active_workers(); 2877 assert(UseDynamicNumberOfGCThreads || 2878 active_workers == workers()->total_workers(), 2879 "Unless dynamic should use total workers"); 2880 2881 uint end_ind = (cs_size * worker_i) / active_workers; 2882 uint start_ind = 0; 2883 2884 if (worker_i > 0 && 2885 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2886 // Previous workers starting region is valid 2887 // so let's iterate from there 2888 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2889 result = _worker_cset_start_region[worker_i - 1]; 2890 } 2891 2892 for (uint i = start_ind; i < end_ind; i++) { 2893 result = result->next_in_collection_set(); 2894 } 2895 } 2896 2897 // Note: the calculated starting heap region may be NULL 2898 // (when the collection set is empty). 2899 assert(result == NULL || result->in_collection_set(), "sanity"); 2900 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2901 "should be updated only once per pause"); 2902 _worker_cset_start_region[worker_i] = result; 2903 OrderAccess::storestore(); 2904 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2905 return result; 2906 } 2907 2908 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i, 2909 uint no_of_par_workers) { 2910 uint worker_num = 2911 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U; 2912 assert(UseDynamicNumberOfGCThreads || 2913 no_of_par_workers == workers()->total_workers(), 2914 "Non dynamic should use fixed number of workers"); 2915 const uint start_index = n_regions() * worker_i / worker_num; 2916 return region_at(start_index); 2917 } 2918 2919 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2920 HeapRegion* r = g1_policy()->collection_set(); 2921 while (r != NULL) { 2922 HeapRegion* next = r->next_in_collection_set(); 2923 if (cl->doHeapRegion(r)) { 2924 cl->incomplete(); 2925 return; 2926 } 2927 r = next; 2928 } 2929 } 2930 2931 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2932 HeapRegionClosure *cl) { 2933 if (r == NULL) { 2934 // The CSet is empty so there's nothing to do. 2935 return; 2936 } 2937 2938 assert(r->in_collection_set(), 2939 "Start region must be a member of the collection set."); 2940 HeapRegion* cur = r; 2941 while (cur != NULL) { 2942 HeapRegion* next = cur->next_in_collection_set(); 2943 if (cl->doHeapRegion(cur) && false) { 2944 cl->incomplete(); 2945 return; 2946 } 2947 cur = next; 2948 } 2949 cur = g1_policy()->collection_set(); 2950 while (cur != r) { 2951 HeapRegion* next = cur->next_in_collection_set(); 2952 if (cl->doHeapRegion(cur) && false) { 2953 cl->incomplete(); 2954 return; 2955 } 2956 cur = next; 2957 } 2958 } 2959 2960 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2961 return n_regions() > 0 ? region_at(0) : NULL; 2962 } 2963 2964 2965 Space* G1CollectedHeap::space_containing(const void* addr) const { 2966 Space* res = heap_region_containing(addr); 2967 return res; 2968 } 2969 2970 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2971 Space* sp = space_containing(addr); 2972 if (sp != NULL) { 2973 return sp->block_start(addr); 2974 } 2975 return NULL; 2976 } 2977 2978 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2979 Space* sp = space_containing(addr); 2980 assert(sp != NULL, "block_size of address outside of heap"); 2981 return sp->block_size(addr); 2982 } 2983 2984 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2985 Space* sp = space_containing(addr); 2986 return sp->block_is_obj(addr); 2987 } 2988 2989 bool G1CollectedHeap::supports_tlab_allocation() const { 2990 return true; 2991 } 2992 2993 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2994 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2995 } 2996 2997 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2998 return young_list()->eden_used_bytes(); 2999 } 3000 3001 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 3002 // must be smaller than the humongous object limit. 3003 size_t G1CollectedHeap::max_tlab_size() const { 3004 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment); 3005 } 3006 3007 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 3008 // Return the remaining space in the cur alloc region, but not less than 3009 // the min TLAB size. 3010 3011 // Also, this value can be at most the humongous object threshold, 3012 // since we can't allow tlabs to grow big enough to accommodate 3013 // humongous objects. 3014 3015 HeapRegion* hr = _mutator_alloc_region.get(); 3016 size_t max_tlab = max_tlab_size() * wordSize; 3017 if (hr == NULL) { 3018 return max_tlab; 3019 } else { 3020 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab); 3021 } 3022 } 3023 3024 size_t G1CollectedHeap::max_capacity() const { 3025 return _g1_reserved.byte_size(); 3026 } 3027 3028 jlong G1CollectedHeap::millis_since_last_gc() { 3029 // assert(false, "NYI"); 3030 return 0; 3031 } 3032 3033 void G1CollectedHeap::prepare_for_verify() { 3034 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 3035 ensure_parsability(false); 3036 } 3037 g1_rem_set()->prepare_for_verify(); 3038 } 3039 3040 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 3041 VerifyOption vo) { 3042 switch (vo) { 3043 case VerifyOption_G1UsePrevMarking: 3044 return hr->obj_allocated_since_prev_marking(obj); 3045 case VerifyOption_G1UseNextMarking: 3046 return hr->obj_allocated_since_next_marking(obj); 3047 case VerifyOption_G1UseMarkWord: 3048 return false; 3049 default: 3050 ShouldNotReachHere(); 3051 } 3052 return false; // keep some compilers happy 3053 } 3054 3055 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 3056 switch (vo) { 3057 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 3058 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 3059 case VerifyOption_G1UseMarkWord: return NULL; 3060 default: ShouldNotReachHere(); 3061 } 3062 return NULL; // keep some compilers happy 3063 } 3064 3065 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 3066 switch (vo) { 3067 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 3068 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 3069 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 3070 default: ShouldNotReachHere(); 3071 } 3072 return false; // keep some compilers happy 3073 } 3074 3075 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 3076 switch (vo) { 3077 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 3078 case VerifyOption_G1UseNextMarking: return "NTAMS"; 3079 case VerifyOption_G1UseMarkWord: return "NONE"; 3080 default: ShouldNotReachHere(); 3081 } 3082 return NULL; // keep some compilers happy 3083 } 3084 3085 class VerifyRootsClosure: public OopClosure { 3086 private: 3087 G1CollectedHeap* _g1h; 3088 VerifyOption _vo; 3089 bool _failures; 3090 public: 3091 // _vo == UsePrevMarking -> use "prev" marking information, 3092 // _vo == UseNextMarking -> use "next" marking information, 3093 // _vo == UseMarkWord -> use mark word from object header. 3094 VerifyRootsClosure(VerifyOption vo) : 3095 _g1h(G1CollectedHeap::heap()), 3096 _vo(vo), 3097 _failures(false) { } 3098 3099 bool failures() { return _failures; } 3100 3101 template <class T> void do_oop_nv(T* p) { 3102 T heap_oop = oopDesc::load_heap_oop(p); 3103 if (!oopDesc::is_null(heap_oop)) { 3104 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3105 if (_g1h->is_obj_dead_cond(obj, _vo)) { 3106 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 3107 "points to dead obj "PTR_FORMAT, p, (void*) obj); 3108 if (_vo == VerifyOption_G1UseMarkWord) { 3109 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3110 } 3111 obj->print_on(gclog_or_tty); 3112 _failures = true; 3113 } 3114 } 3115 } 3116 3117 void do_oop(oop* p) { do_oop_nv(p); } 3118 void do_oop(narrowOop* p) { do_oop_nv(p); } 3119 }; 3120 3121 class G1VerifyCodeRootOopClosure: public OopClosure { 3122 G1CollectedHeap* _g1h; 3123 OopClosure* _root_cl; 3124 nmethod* _nm; 3125 VerifyOption _vo; 3126 bool _failures; 3127 3128 template <class T> void do_oop_work(T* p) { 3129 // First verify that this root is live 3130 _root_cl->do_oop(p); 3131 3132 if (!G1VerifyHeapRegionCodeRoots) { 3133 // We're not verifying the code roots attached to heap region. 3134 return; 3135 } 3136 3137 // Don't check the code roots during marking verification in a full GC 3138 if (_vo == VerifyOption_G1UseMarkWord) { 3139 return; 3140 } 3141 3142 // Now verify that the current nmethod (which contains p) is 3143 // in the code root list of the heap region containing the 3144 // object referenced by p. 3145 3146 T heap_oop = oopDesc::load_heap_oop(p); 3147 if (!oopDesc::is_null(heap_oop)) { 3148 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3149 3150 // Now fetch the region containing the object 3151 HeapRegion* hr = _g1h->heap_region_containing(obj); 3152 HeapRegionRemSet* hrrs = hr->rem_set(); 3153 // Verify that the strong code root list for this region 3154 // contains the nmethod 3155 if (!hrrs->strong_code_roots_list_contains(_nm)) { 3156 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" " 3157 "from nmethod "PTR_FORMAT" not in strong " 3158 "code roots for region ["PTR_FORMAT","PTR_FORMAT")", 3159 p, _nm, hr->bottom(), hr->end()); 3160 _failures = true; 3161 } 3162 } 3163 } 3164 3165 public: 3166 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 3167 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 3168 3169 void do_oop(oop* p) { do_oop_work(p); } 3170 void do_oop(narrowOop* p) { do_oop_work(p); } 3171 3172 void set_nmethod(nmethod* nm) { _nm = nm; } 3173 bool failures() { return _failures; } 3174 }; 3175 3176 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 3177 G1VerifyCodeRootOopClosure* _oop_cl; 3178 3179 public: 3180 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 3181 _oop_cl(oop_cl) {} 3182 3183 void do_code_blob(CodeBlob* cb) { 3184 nmethod* nm = cb->as_nmethod_or_null(); 3185 if (nm != NULL) { 3186 _oop_cl->set_nmethod(nm); 3187 nm->oops_do(_oop_cl); 3188 } 3189 } 3190 }; 3191 3192 class YoungRefCounterClosure : public OopClosure { 3193 G1CollectedHeap* _g1h; 3194 int _count; 3195 public: 3196 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3197 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3198 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3199 3200 int count() { return _count; } 3201 void reset_count() { _count = 0; }; 3202 }; 3203 3204 class VerifyKlassClosure: public KlassClosure { 3205 YoungRefCounterClosure _young_ref_counter_closure; 3206 OopClosure *_oop_closure; 3207 public: 3208 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3209 void do_klass(Klass* k) { 3210 k->oops_do(_oop_closure); 3211 3212 _young_ref_counter_closure.reset_count(); 3213 k->oops_do(&_young_ref_counter_closure); 3214 if (_young_ref_counter_closure.count() > 0) { 3215 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3216 } 3217 } 3218 }; 3219 3220 class VerifyLivenessOopClosure: public OopClosure { 3221 G1CollectedHeap* _g1h; 3222 VerifyOption _vo; 3223 public: 3224 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3225 _g1h(g1h), _vo(vo) 3226 { } 3227 void do_oop(narrowOop *p) { do_oop_work(p); } 3228 void do_oop( oop *p) { do_oop_work(p); } 3229 3230 template <class T> void do_oop_work(T *p) { 3231 oop obj = oopDesc::load_decode_heap_oop(p); 3232 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3233 "Dead object referenced by a not dead object"); 3234 } 3235 }; 3236 3237 class VerifyObjsInRegionClosure: public ObjectClosure { 3238 private: 3239 G1CollectedHeap* _g1h; 3240 size_t _live_bytes; 3241 HeapRegion *_hr; 3242 VerifyOption _vo; 3243 public: 3244 // _vo == UsePrevMarking -> use "prev" marking information, 3245 // _vo == UseNextMarking -> use "next" marking information, 3246 // _vo == UseMarkWord -> use mark word from object header. 3247 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3248 : _live_bytes(0), _hr(hr), _vo(vo) { 3249 _g1h = G1CollectedHeap::heap(); 3250 } 3251 void do_object(oop o) { 3252 VerifyLivenessOopClosure isLive(_g1h, _vo); 3253 assert(o != NULL, "Huh?"); 3254 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3255 // If the object is alive according to the mark word, 3256 // then verify that the marking information agrees. 3257 // Note we can't verify the contra-positive of the 3258 // above: if the object is dead (according to the mark 3259 // word), it may not be marked, or may have been marked 3260 // but has since became dead, or may have been allocated 3261 // since the last marking. 3262 if (_vo == VerifyOption_G1UseMarkWord) { 3263 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3264 } 3265 3266 o->oop_iterate_no_header(&isLive); 3267 if (!_hr->obj_allocated_since_prev_marking(o)) { 3268 size_t obj_size = o->size(); // Make sure we don't overflow 3269 _live_bytes += (obj_size * HeapWordSize); 3270 } 3271 } 3272 } 3273 size_t live_bytes() { return _live_bytes; } 3274 }; 3275 3276 class PrintObjsInRegionClosure : public ObjectClosure { 3277 HeapRegion *_hr; 3278 G1CollectedHeap *_g1; 3279 public: 3280 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3281 _g1 = G1CollectedHeap::heap(); 3282 }; 3283 3284 void do_object(oop o) { 3285 if (o != NULL) { 3286 HeapWord *start = (HeapWord *) o; 3287 size_t word_sz = o->size(); 3288 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3289 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3290 (void*) o, word_sz, 3291 _g1->isMarkedPrev(o), 3292 _g1->isMarkedNext(o), 3293 _hr->obj_allocated_since_prev_marking(o)); 3294 HeapWord *end = start + word_sz; 3295 HeapWord *cur; 3296 int *val; 3297 for (cur = start; cur < end; cur++) { 3298 val = (int *) cur; 3299 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 3300 } 3301 } 3302 } 3303 }; 3304 3305 class VerifyRegionClosure: public HeapRegionClosure { 3306 private: 3307 bool _par; 3308 VerifyOption _vo; 3309 bool _failures; 3310 public: 3311 // _vo == UsePrevMarking -> use "prev" marking information, 3312 // _vo == UseNextMarking -> use "next" marking information, 3313 // _vo == UseMarkWord -> use mark word from object header. 3314 VerifyRegionClosure(bool par, VerifyOption vo) 3315 : _par(par), 3316 _vo(vo), 3317 _failures(false) {} 3318 3319 bool failures() { 3320 return _failures; 3321 } 3322 3323 bool doHeapRegion(HeapRegion* r) { 3324 if (!r->continuesHumongous()) { 3325 bool failures = false; 3326 r->verify(_vo, &failures); 3327 if (failures) { 3328 _failures = true; 3329 } else { 3330 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3331 r->object_iterate(¬_dead_yet_cl); 3332 if (_vo != VerifyOption_G1UseNextMarking) { 3333 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3334 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3335 "max_live_bytes "SIZE_FORMAT" " 3336 "< calculated "SIZE_FORMAT, 3337 r->bottom(), r->end(), 3338 r->max_live_bytes(), 3339 not_dead_yet_cl.live_bytes()); 3340 _failures = true; 3341 } 3342 } else { 3343 // When vo == UseNextMarking we cannot currently do a sanity 3344 // check on the live bytes as the calculation has not been 3345 // finalized yet. 3346 } 3347 } 3348 } 3349 return false; // stop the region iteration if we hit a failure 3350 } 3351 }; 3352 3353 // This is the task used for parallel verification of the heap regions 3354 3355 class G1ParVerifyTask: public AbstractGangTask { 3356 private: 3357 G1CollectedHeap* _g1h; 3358 VerifyOption _vo; 3359 bool _failures; 3360 3361 public: 3362 // _vo == UsePrevMarking -> use "prev" marking information, 3363 // _vo == UseNextMarking -> use "next" marking information, 3364 // _vo == UseMarkWord -> use mark word from object header. 3365 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3366 AbstractGangTask("Parallel verify task"), 3367 _g1h(g1h), 3368 _vo(vo), 3369 _failures(false) { } 3370 3371 bool failures() { 3372 return _failures; 3373 } 3374 3375 void work(uint worker_id) { 3376 HandleMark hm; 3377 VerifyRegionClosure blk(true, _vo); 3378 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3379 _g1h->workers()->active_workers(), 3380 HeapRegion::ParVerifyClaimValue); 3381 if (blk.failures()) { 3382 _failures = true; 3383 } 3384 } 3385 }; 3386 3387 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3388 if (SafepointSynchronize::is_at_safepoint()) { 3389 assert(Thread::current()->is_VM_thread(), 3390 "Expected to be executed serially by the VM thread at this point"); 3391 3392 if (!silent) { gclog_or_tty->print("Roots "); } 3393 VerifyRootsClosure rootsCl(vo); 3394 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3395 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3396 VerifyKlassClosure klassCl(this, &rootsCl); 3397 3398 // We apply the relevant closures to all the oops in the 3399 // system dictionary, the string table and the code cache. 3400 const int so = SO_AllClasses | SO_Strings | SO_CodeCache; 3401 3402 // Need cleared claim bits for the strong roots processing 3403 ClassLoaderDataGraph::clear_claimed_marks(); 3404 3405 process_strong_roots(true, // activate StrongRootsScope 3406 false, // we set "is scavenging" to false, 3407 // so we don't reset the dirty cards. 3408 ScanningOption(so), // roots scanning options 3409 &rootsCl, 3410 &blobsCl, 3411 &klassCl 3412 ); 3413 3414 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3415 3416 if (vo != VerifyOption_G1UseMarkWord) { 3417 // If we're verifying during a full GC then the region sets 3418 // will have been torn down at the start of the GC. Therefore 3419 // verifying the region sets will fail. So we only verify 3420 // the region sets when not in a full GC. 3421 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3422 verify_region_sets(); 3423 } 3424 3425 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3426 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3427 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3428 "sanity check"); 3429 3430 G1ParVerifyTask task(this, vo); 3431 assert(UseDynamicNumberOfGCThreads || 3432 workers()->active_workers() == workers()->total_workers(), 3433 "If not dynamic should be using all the workers"); 3434 int n_workers = workers()->active_workers(); 3435 set_par_threads(n_workers); 3436 workers()->run_task(&task); 3437 set_par_threads(0); 3438 if (task.failures()) { 3439 failures = true; 3440 } 3441 3442 // Checks that the expected amount of parallel work was done. 3443 // The implication is that n_workers is > 0. 3444 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3445 "sanity check"); 3446 3447 reset_heap_region_claim_values(); 3448 3449 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3450 "sanity check"); 3451 } else { 3452 VerifyRegionClosure blk(false, vo); 3453 heap_region_iterate(&blk); 3454 if (blk.failures()) { 3455 failures = true; 3456 } 3457 } 3458 if (!silent) gclog_or_tty->print("RemSet "); 3459 rem_set()->verify(); 3460 3461 if (G1StringDedup::is_enabled()) { 3462 if (!silent) gclog_or_tty->print("StrDedup "); 3463 G1StringDedup::verify(); 3464 } 3465 3466 if (failures) { 3467 gclog_or_tty->print_cr("Heap:"); 3468 // It helps to have the per-region information in the output to 3469 // help us track down what went wrong. This is why we call 3470 // print_extended_on() instead of print_on(). 3471 print_extended_on(gclog_or_tty); 3472 gclog_or_tty->cr(); 3473 #ifndef PRODUCT 3474 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3475 concurrent_mark()->print_reachable("at-verification-failure", 3476 vo, false /* all */); 3477 } 3478 #endif 3479 gclog_or_tty->flush(); 3480 } 3481 guarantee(!failures, "there should not have been any failures"); 3482 } else { 3483 if (!silent) { 3484 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3485 if (G1StringDedup::is_enabled()) { 3486 gclog_or_tty->print(", StrDedup"); 3487 } 3488 gclog_or_tty->print(") "); 3489 } 3490 } 3491 } 3492 3493 void G1CollectedHeap::verify(bool silent) { 3494 verify(silent, VerifyOption_G1UsePrevMarking); 3495 } 3496 3497 double G1CollectedHeap::verify(bool guard, const char* msg) { 3498 double verify_time_ms = 0.0; 3499 3500 if (guard && total_collections() >= VerifyGCStartAt) { 3501 double verify_start = os::elapsedTime(); 3502 HandleMark hm; // Discard invalid handles created during verification 3503 prepare_for_verify(); 3504 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3505 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3506 } 3507 3508 return verify_time_ms; 3509 } 3510 3511 void G1CollectedHeap::verify_before_gc() { 3512 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3513 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3514 } 3515 3516 void G1CollectedHeap::verify_after_gc() { 3517 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3518 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3519 } 3520 3521 class PrintRegionClosure: public HeapRegionClosure { 3522 outputStream* _st; 3523 public: 3524 PrintRegionClosure(outputStream* st) : _st(st) {} 3525 bool doHeapRegion(HeapRegion* r) { 3526 r->print_on(_st); 3527 return false; 3528 } 3529 }; 3530 3531 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3532 const HeapRegion* hr, 3533 const VerifyOption vo) const { 3534 switch (vo) { 3535 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3536 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3537 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3538 default: ShouldNotReachHere(); 3539 } 3540 return false; // keep some compilers happy 3541 } 3542 3543 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3544 const VerifyOption vo) const { 3545 switch (vo) { 3546 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3547 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3548 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3549 default: ShouldNotReachHere(); 3550 } 3551 return false; // keep some compilers happy 3552 } 3553 3554 void G1CollectedHeap::print_on(outputStream* st) const { 3555 st->print(" %-20s", "garbage-first heap"); 3556 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3557 capacity()/K, used_unlocked()/K); 3558 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3559 _g1_storage.low_boundary(), 3560 _g1_storage.high(), 3561 _g1_storage.high_boundary()); 3562 st->cr(); 3563 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3564 uint young_regions = _young_list->length(); 3565 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3566 (size_t) young_regions * HeapRegion::GrainBytes / K); 3567 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3568 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3569 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3570 st->cr(); 3571 MetaspaceAux::print_on(st); 3572 } 3573 3574 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3575 print_on(st); 3576 3577 // Print the per-region information. 3578 st->cr(); 3579 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3580 "HS=humongous(starts), HC=humongous(continues), " 3581 "CS=collection set, F=free, TS=gc time stamp, " 3582 "PTAMS=previous top-at-mark-start, " 3583 "NTAMS=next top-at-mark-start)"); 3584 PrintRegionClosure blk(st); 3585 heap_region_iterate(&blk); 3586 } 3587 3588 void G1CollectedHeap::print_on_error(outputStream* st) const { 3589 this->CollectedHeap::print_on_error(st); 3590 3591 if (_cm != NULL) { 3592 st->cr(); 3593 _cm->print_on_error(st); 3594 } 3595 } 3596 3597 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3598 if (G1CollectedHeap::use_parallel_gc_threads()) { 3599 workers()->print_worker_threads_on(st); 3600 } 3601 _cmThread->print_on(st); 3602 st->cr(); 3603 _cm->print_worker_threads_on(st); 3604 _cg1r->print_worker_threads_on(st); 3605 if (G1StringDedup::is_enabled()) { 3606 G1StringDedup::print_worker_threads_on(st); 3607 } 3608 } 3609 3610 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3611 if (G1CollectedHeap::use_parallel_gc_threads()) { 3612 workers()->threads_do(tc); 3613 } 3614 tc->do_thread(_cmThread); 3615 _cg1r->threads_do(tc); 3616 if (G1StringDedup::is_enabled()) { 3617 G1StringDedup::threads_do(tc); 3618 } 3619 } 3620 3621 void G1CollectedHeap::print_tracing_info() const { 3622 // We'll overload this to mean "trace GC pause statistics." 3623 if (TraceGen0Time || TraceGen1Time) { 3624 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3625 // to that. 3626 g1_policy()->print_tracing_info(); 3627 } 3628 if (G1SummarizeRSetStats) { 3629 g1_rem_set()->print_summary_info(); 3630 } 3631 if (G1SummarizeConcMark) { 3632 concurrent_mark()->print_summary_info(); 3633 } 3634 g1_policy()->print_yg_surv_rate_info(); 3635 SpecializationStats::print(); 3636 } 3637 3638 #ifndef PRODUCT 3639 // Helpful for debugging RSet issues. 3640 3641 class PrintRSetsClosure : public HeapRegionClosure { 3642 private: 3643 const char* _msg; 3644 size_t _occupied_sum; 3645 3646 public: 3647 bool doHeapRegion(HeapRegion* r) { 3648 HeapRegionRemSet* hrrs = r->rem_set(); 3649 size_t occupied = hrrs->occupied(); 3650 _occupied_sum += occupied; 3651 3652 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3653 HR_FORMAT_PARAMS(r)); 3654 if (occupied == 0) { 3655 gclog_or_tty->print_cr(" RSet is empty"); 3656 } else { 3657 hrrs->print(); 3658 } 3659 gclog_or_tty->print_cr("----------"); 3660 return false; 3661 } 3662 3663 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3664 gclog_or_tty->cr(); 3665 gclog_or_tty->print_cr("========================================"); 3666 gclog_or_tty->print_cr("%s", msg); 3667 gclog_or_tty->cr(); 3668 } 3669 3670 ~PrintRSetsClosure() { 3671 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3672 gclog_or_tty->print_cr("========================================"); 3673 gclog_or_tty->cr(); 3674 } 3675 }; 3676 3677 void G1CollectedHeap::print_cset_rsets() { 3678 PrintRSetsClosure cl("Printing CSet RSets"); 3679 collection_set_iterate(&cl); 3680 } 3681 3682 void G1CollectedHeap::print_all_rsets() { 3683 PrintRSetsClosure cl("Printing All RSets");; 3684 heap_region_iterate(&cl); 3685 } 3686 #endif // PRODUCT 3687 3688 G1CollectedHeap* G1CollectedHeap::heap() { 3689 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3690 "not a garbage-first heap"); 3691 return _g1h; 3692 } 3693 3694 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3695 // always_do_update_barrier = false; 3696 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3697 // Fill TLAB's and such 3698 accumulate_statistics_all_tlabs(); 3699 ensure_parsability(true); 3700 3701 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3702 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3703 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3704 } 3705 } 3706 3707 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3708 3709 if (G1SummarizeRSetStats && 3710 (G1SummarizeRSetStatsPeriod > 0) && 3711 // we are at the end of the GC. Total collections has already been increased. 3712 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3713 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3714 } 3715 3716 // FIXME: what is this about? 3717 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3718 // is set. 3719 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3720 "derived pointer present")); 3721 // always_do_update_barrier = true; 3722 3723 resize_all_tlabs(); 3724 3725 // We have just completed a GC. Update the soft reference 3726 // policy with the new heap occupancy 3727 Universe::update_heap_info_at_gc(); 3728 } 3729 3730 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3731 unsigned int gc_count_before, 3732 bool* succeeded, 3733 GCCause::Cause gc_cause) { 3734 assert_heap_not_locked_and_not_at_safepoint(); 3735 g1_policy()->record_stop_world_start(); 3736 VM_G1IncCollectionPause op(gc_count_before, 3737 word_size, 3738 false, /* should_initiate_conc_mark */ 3739 g1_policy()->max_pause_time_ms(), 3740 gc_cause); 3741 VMThread::execute(&op); 3742 3743 HeapWord* result = op.result(); 3744 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3745 assert(result == NULL || ret_succeeded, 3746 "the result should be NULL if the VM did not succeed"); 3747 *succeeded = ret_succeeded; 3748 3749 assert_heap_not_locked(); 3750 return result; 3751 } 3752 3753 void 3754 G1CollectedHeap::doConcurrentMark() { 3755 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3756 if (!_cmThread->in_progress()) { 3757 _cmThread->set_started(); 3758 CGC_lock->notify(); 3759 } 3760 } 3761 3762 size_t G1CollectedHeap::pending_card_num() { 3763 size_t extra_cards = 0; 3764 JavaThread *curr = Threads::first(); 3765 while (curr != NULL) { 3766 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3767 extra_cards += dcq.size(); 3768 curr = curr->next(); 3769 } 3770 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3771 size_t buffer_size = dcqs.buffer_size(); 3772 size_t buffer_num = dcqs.completed_buffers_num(); 3773 3774 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3775 // in bytes - not the number of 'entries'. We need to convert 3776 // into a number of cards. 3777 return (buffer_size * buffer_num + extra_cards) / oopSize; 3778 } 3779 3780 size_t G1CollectedHeap::cards_scanned() { 3781 return g1_rem_set()->cardsScanned(); 3782 } 3783 3784 void 3785 G1CollectedHeap::setup_surviving_young_words() { 3786 assert(_surviving_young_words == NULL, "pre-condition"); 3787 uint array_length = g1_policy()->young_cset_region_length(); 3788 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3789 if (_surviving_young_words == NULL) { 3790 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3791 "Not enough space for young surv words summary."); 3792 } 3793 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3794 #ifdef ASSERT 3795 for (uint i = 0; i < array_length; ++i) { 3796 assert( _surviving_young_words[i] == 0, "memset above" ); 3797 } 3798 #endif // !ASSERT 3799 } 3800 3801 void 3802 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3803 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3804 uint array_length = g1_policy()->young_cset_region_length(); 3805 for (uint i = 0; i < array_length; ++i) { 3806 _surviving_young_words[i] += surv_young_words[i]; 3807 } 3808 } 3809 3810 void 3811 G1CollectedHeap::cleanup_surviving_young_words() { 3812 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3813 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3814 _surviving_young_words = NULL; 3815 } 3816 3817 #ifdef ASSERT 3818 class VerifyCSetClosure: public HeapRegionClosure { 3819 public: 3820 bool doHeapRegion(HeapRegion* hr) { 3821 // Here we check that the CSet region's RSet is ready for parallel 3822 // iteration. The fields that we'll verify are only manipulated 3823 // when the region is part of a CSet and is collected. Afterwards, 3824 // we reset these fields when we clear the region's RSet (when the 3825 // region is freed) so they are ready when the region is 3826 // re-allocated. The only exception to this is if there's an 3827 // evacuation failure and instead of freeing the region we leave 3828 // it in the heap. In that case, we reset these fields during 3829 // evacuation failure handling. 3830 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3831 3832 // Here's a good place to add any other checks we'd like to 3833 // perform on CSet regions. 3834 return false; 3835 } 3836 }; 3837 #endif // ASSERT 3838 3839 #if TASKQUEUE_STATS 3840 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3841 st->print_raw_cr("GC Task Stats"); 3842 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3843 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3844 } 3845 3846 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3847 print_taskqueue_stats_hdr(st); 3848 3849 TaskQueueStats totals; 3850 const int n = workers() != NULL ? workers()->total_workers() : 1; 3851 for (int i = 0; i < n; ++i) { 3852 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3853 totals += task_queue(i)->stats; 3854 } 3855 st->print_raw("tot "); totals.print(st); st->cr(); 3856 3857 DEBUG_ONLY(totals.verify()); 3858 } 3859 3860 void G1CollectedHeap::reset_taskqueue_stats() { 3861 const int n = workers() != NULL ? workers()->total_workers() : 1; 3862 for (int i = 0; i < n; ++i) { 3863 task_queue(i)->stats.reset(); 3864 } 3865 } 3866 #endif // TASKQUEUE_STATS 3867 3868 void G1CollectedHeap::log_gc_header() { 3869 if (!G1Log::fine()) { 3870 return; 3871 } 3872 3873 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id()); 3874 3875 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3876 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3877 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3878 3879 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3880 } 3881 3882 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3883 if (!G1Log::fine()) { 3884 return; 3885 } 3886 3887 if (G1Log::finer()) { 3888 if (evacuation_failed()) { 3889 gclog_or_tty->print(" (to-space exhausted)"); 3890 } 3891 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3892 g1_policy()->phase_times()->note_gc_end(); 3893 g1_policy()->phase_times()->print(pause_time_sec); 3894 g1_policy()->print_detailed_heap_transition(); 3895 } else { 3896 if (evacuation_failed()) { 3897 gclog_or_tty->print("--"); 3898 } 3899 g1_policy()->print_heap_transition(); 3900 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3901 } 3902 gclog_or_tty->flush(); 3903 } 3904 3905 bool 3906 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3907 assert_at_safepoint(true /* should_be_vm_thread */); 3908 guarantee(!is_gc_active(), "collection is not reentrant"); 3909 3910 if (GC_locker::check_active_before_gc()) { 3911 return false; 3912 } 3913 3914 _gc_timer_stw->register_gc_start(); 3915 3916 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3917 3918 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3919 ResourceMark rm; 3920 3921 print_heap_before_gc(); 3922 trace_heap_before_gc(_gc_tracer_stw); 3923 3924 verify_region_sets_optional(); 3925 verify_dirty_young_regions(); 3926 3927 // This call will decide whether this pause is an initial-mark 3928 // pause. If it is, during_initial_mark_pause() will return true 3929 // for the duration of this pause. 3930 g1_policy()->decide_on_conc_mark_initiation(); 3931 3932 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3933 assert(!g1_policy()->during_initial_mark_pause() || 3934 g1_policy()->gcs_are_young(), "sanity"); 3935 3936 // We also do not allow mixed GCs during marking. 3937 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3938 3939 // Record whether this pause is an initial mark. When the current 3940 // thread has completed its logging output and it's safe to signal 3941 // the CM thread, the flag's value in the policy has been reset. 3942 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3943 3944 // Inner scope for scope based logging, timers, and stats collection 3945 { 3946 EvacuationInfo evacuation_info; 3947 3948 if (g1_policy()->during_initial_mark_pause()) { 3949 // We are about to start a marking cycle, so we increment the 3950 // full collection counter. 3951 increment_old_marking_cycles_started(); 3952 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3953 } 3954 3955 _gc_tracer_stw->report_yc_type(yc_type()); 3956 3957 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3958 3959 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3960 workers()->active_workers() : 1); 3961 double pause_start_sec = os::elapsedTime(); 3962 g1_policy()->phase_times()->note_gc_start(active_workers); 3963 log_gc_header(); 3964 3965 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3966 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3967 3968 // If the secondary_free_list is not empty, append it to the 3969 // free_list. No need to wait for the cleanup operation to finish; 3970 // the region allocation code will check the secondary_free_list 3971 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3972 // set, skip this step so that the region allocation code has to 3973 // get entries from the secondary_free_list. 3974 if (!G1StressConcRegionFreeing) { 3975 append_secondary_free_list_if_not_empty_with_lock(); 3976 } 3977 3978 assert(check_young_list_well_formed(), "young list should be well formed"); 3979 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3980 "sanity check"); 3981 3982 // Don't dynamically change the number of GC threads this early. A value of 3983 // 0 is used to indicate serial work. When parallel work is done, 3984 // it will be set. 3985 3986 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3987 IsGCActiveMark x; 3988 3989 gc_prologue(false); 3990 increment_total_collections(false /* full gc */); 3991 increment_gc_time_stamp(); 3992 3993 verify_before_gc(); 3994 3995 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3996 3997 // Please see comment in g1CollectedHeap.hpp and 3998 // G1CollectedHeap::ref_processing_init() to see how 3999 // reference processing currently works in G1. 4000 4001 // Enable discovery in the STW reference processor 4002 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 4003 true /*verify_no_refs*/); 4004 4005 { 4006 // We want to temporarily turn off discovery by the 4007 // CM ref processor, if necessary, and turn it back on 4008 // on again later if we do. Using a scoped 4009 // NoRefDiscovery object will do this. 4010 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 4011 4012 // Forget the current alloc region (we might even choose it to be part 4013 // of the collection set!). 4014 release_mutator_alloc_region(); 4015 4016 // We should call this after we retire the mutator alloc 4017 // region(s) so that all the ALLOC / RETIRE events are generated 4018 // before the start GC event. 4019 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 4020 4021 // This timing is only used by the ergonomics to handle our pause target. 4022 // It is unclear why this should not include the full pause. We will 4023 // investigate this in CR 7178365. 4024 // 4025 // Preserving the old comment here if that helps the investigation: 4026 // 4027 // The elapsed time induced by the start time below deliberately elides 4028 // the possible verification above. 4029 double sample_start_time_sec = os::elapsedTime(); 4030 4031 #if YOUNG_LIST_VERBOSE 4032 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 4033 _young_list->print(); 4034 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4035 #endif // YOUNG_LIST_VERBOSE 4036 4037 g1_policy()->record_collection_pause_start(sample_start_time_sec); 4038 4039 double scan_wait_start = os::elapsedTime(); 4040 // We have to wait until the CM threads finish scanning the 4041 // root regions as it's the only way to ensure that all the 4042 // objects on them have been correctly scanned before we start 4043 // moving them during the GC. 4044 bool waited = _cm->root_regions()->wait_until_scan_finished(); 4045 double wait_time_ms = 0.0; 4046 if (waited) { 4047 double scan_wait_end = os::elapsedTime(); 4048 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 4049 } 4050 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 4051 4052 #if YOUNG_LIST_VERBOSE 4053 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 4054 _young_list->print(); 4055 #endif // YOUNG_LIST_VERBOSE 4056 4057 if (g1_policy()->during_initial_mark_pause()) { 4058 concurrent_mark()->checkpointRootsInitialPre(); 4059 } 4060 4061 #if YOUNG_LIST_VERBOSE 4062 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 4063 _young_list->print(); 4064 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4065 #endif // YOUNG_LIST_VERBOSE 4066 4067 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info); 4068 4069 _cm->note_start_of_gc(); 4070 // We should not verify the per-thread SATB buffers given that 4071 // we have not filtered them yet (we'll do so during the 4072 // GC). We also call this after finalize_cset() to 4073 // ensure that the CSet has been finalized. 4074 _cm->verify_no_cset_oops(true /* verify_stacks */, 4075 true /* verify_enqueued_buffers */, 4076 false /* verify_thread_buffers */, 4077 true /* verify_fingers */); 4078 4079 if (_hr_printer.is_active()) { 4080 HeapRegion* hr = g1_policy()->collection_set(); 4081 while (hr != NULL) { 4082 G1HRPrinter::RegionType type; 4083 if (!hr->is_young()) { 4084 type = G1HRPrinter::Old; 4085 } else if (hr->is_survivor()) { 4086 type = G1HRPrinter::Survivor; 4087 } else { 4088 type = G1HRPrinter::Eden; 4089 } 4090 _hr_printer.cset(hr); 4091 hr = hr->next_in_collection_set(); 4092 } 4093 } 4094 4095 #ifdef ASSERT 4096 VerifyCSetClosure cl; 4097 collection_set_iterate(&cl); 4098 #endif // ASSERT 4099 4100 setup_surviving_young_words(); 4101 4102 // Initialize the GC alloc regions. 4103 init_gc_alloc_regions(evacuation_info); 4104 4105 // Actually do the work... 4106 evacuate_collection_set(evacuation_info); 4107 4108 // We do this to mainly verify the per-thread SATB buffers 4109 // (which have been filtered by now) since we didn't verify 4110 // them earlier. No point in re-checking the stacks / enqueued 4111 // buffers given that the CSet has not changed since last time 4112 // we checked. 4113 _cm->verify_no_cset_oops(false /* verify_stacks */, 4114 false /* verify_enqueued_buffers */, 4115 true /* verify_thread_buffers */, 4116 true /* verify_fingers */); 4117 4118 free_collection_set(g1_policy()->collection_set(), evacuation_info); 4119 g1_policy()->clear_collection_set(); 4120 4121 cleanup_surviving_young_words(); 4122 4123 // Start a new incremental collection set for the next pause. 4124 g1_policy()->start_incremental_cset_building(); 4125 4126 clear_cset_fast_test(); 4127 4128 _young_list->reset_sampled_info(); 4129 4130 // Don't check the whole heap at this point as the 4131 // GC alloc regions from this pause have been tagged 4132 // as survivors and moved on to the survivor list. 4133 // Survivor regions will fail the !is_young() check. 4134 assert(check_young_list_empty(false /* check_heap */), 4135 "young list should be empty"); 4136 4137 #if YOUNG_LIST_VERBOSE 4138 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 4139 _young_list->print(); 4140 #endif // YOUNG_LIST_VERBOSE 4141 4142 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 4143 _young_list->first_survivor_region(), 4144 _young_list->last_survivor_region()); 4145 4146 _young_list->reset_auxilary_lists(); 4147 4148 if (evacuation_failed()) { 4149 _summary_bytes_used = recalculate_used(); 4150 uint n_queues = MAX2((int)ParallelGCThreads, 1); 4151 for (uint i = 0; i < n_queues; i++) { 4152 if (_evacuation_failed_info_array[i].has_failed()) { 4153 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 4154 } 4155 } 4156 } else { 4157 // The "used" of the the collection set have already been subtracted 4158 // when they were freed. Add in the bytes evacuated. 4159 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 4160 } 4161 4162 if (g1_policy()->during_initial_mark_pause()) { 4163 // We have to do this before we notify the CM threads that 4164 // they can start working to make sure that all the 4165 // appropriate initialization is done on the CM object. 4166 concurrent_mark()->checkpointRootsInitialPost(); 4167 set_marking_started(); 4168 // Note that we don't actually trigger the CM thread at 4169 // this point. We do that later when we're sure that 4170 // the current thread has completed its logging output. 4171 } 4172 4173 allocate_dummy_regions(); 4174 4175 #if YOUNG_LIST_VERBOSE 4176 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 4177 _young_list->print(); 4178 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4179 #endif // YOUNG_LIST_VERBOSE 4180 4181 init_mutator_alloc_region(); 4182 4183 { 4184 size_t expand_bytes = g1_policy()->expansion_amount(); 4185 if (expand_bytes > 0) { 4186 size_t bytes_before = capacity(); 4187 // No need for an ergo verbose message here, 4188 // expansion_amount() does this when it returns a value > 0. 4189 if (!expand(expand_bytes)) { 4190 // We failed to expand the heap so let's verify that 4191 // committed/uncommitted amount match the backing store 4192 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 4193 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 4194 } 4195 } 4196 } 4197 4198 // We redo the verification but now wrt to the new CSet which 4199 // has just got initialized after the previous CSet was freed. 4200 _cm->verify_no_cset_oops(true /* verify_stacks */, 4201 true /* verify_enqueued_buffers */, 4202 true /* verify_thread_buffers */, 4203 true /* verify_fingers */); 4204 _cm->note_end_of_gc(); 4205 4206 // This timing is only used by the ergonomics to handle our pause target. 4207 // It is unclear why this should not include the full pause. We will 4208 // investigate this in CR 7178365. 4209 double sample_end_time_sec = os::elapsedTime(); 4210 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4211 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info); 4212 4213 MemoryService::track_memory_usage(); 4214 4215 // In prepare_for_verify() below we'll need to scan the deferred 4216 // update buffers to bring the RSets up-to-date if 4217 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4218 // the update buffers we'll probably need to scan cards on the 4219 // regions we just allocated to (i.e., the GC alloc 4220 // regions). However, during the last GC we called 4221 // set_saved_mark() on all the GC alloc regions, so card 4222 // scanning might skip the [saved_mark_word()...top()] area of 4223 // those regions (i.e., the area we allocated objects into 4224 // during the last GC). But it shouldn't. Given that 4225 // saved_mark_word() is conditional on whether the GC time stamp 4226 // on the region is current or not, by incrementing the GC time 4227 // stamp here we invalidate all the GC time stamps on all the 4228 // regions and saved_mark_word() will simply return top() for 4229 // all the regions. This is a nicer way of ensuring this rather 4230 // than iterating over the regions and fixing them. In fact, the 4231 // GC time stamp increment here also ensures that 4232 // saved_mark_word() will return top() between pauses, i.e., 4233 // during concurrent refinement. So we don't need the 4234 // is_gc_active() check to decided which top to use when 4235 // scanning cards (see CR 7039627). 4236 increment_gc_time_stamp(); 4237 4238 verify_after_gc(); 4239 4240 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4241 ref_processor_stw()->verify_no_references_recorded(); 4242 4243 // CM reference discovery will be re-enabled if necessary. 4244 } 4245 4246 // We should do this after we potentially expand the heap so 4247 // that all the COMMIT events are generated before the end GC 4248 // event, and after we retire the GC alloc regions so that all 4249 // RETIRE events are generated before the end GC event. 4250 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4251 4252 if (mark_in_progress()) { 4253 concurrent_mark()->update_g1_committed(); 4254 } 4255 4256 #ifdef TRACESPINNING 4257 ParallelTaskTerminator::print_termination_counts(); 4258 #endif 4259 4260 gc_epilogue(false); 4261 } 4262 4263 // Print the remainder of the GC log output. 4264 log_gc_footer(os::elapsedTime() - pause_start_sec); 4265 4266 // It is not yet to safe to tell the concurrent mark to 4267 // start as we have some optional output below. We don't want the 4268 // output from the concurrent mark thread interfering with this 4269 // logging output either. 4270 4271 _hrs.verify_optional(); 4272 verify_region_sets_optional(); 4273 4274 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4275 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4276 4277 print_heap_after_gc(); 4278 trace_heap_after_gc(_gc_tracer_stw); 4279 4280 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4281 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4282 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4283 // before any GC notifications are raised. 4284 g1mm()->update_sizes(); 4285 4286 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4287 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4288 _gc_timer_stw->register_gc_end(); 4289 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4290 } 4291 // It should now be safe to tell the concurrent mark thread to start 4292 // without its logging output interfering with the logging output 4293 // that came from the pause. 4294 4295 if (should_start_conc_mark) { 4296 // CAUTION: after the doConcurrentMark() call below, 4297 // the concurrent marking thread(s) could be running 4298 // concurrently with us. Make sure that anything after 4299 // this point does not assume that we are the only GC thread 4300 // running. Note: of course, the actual marking work will 4301 // not start until the safepoint itself is released in 4302 // SuspendibleThreadSet::desynchronize(). 4303 doConcurrentMark(); 4304 } 4305 4306 return true; 4307 } 4308 4309 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4310 { 4311 size_t gclab_word_size; 4312 switch (purpose) { 4313 case GCAllocForSurvived: 4314 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4315 break; 4316 case GCAllocForTenured: 4317 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4318 break; 4319 default: 4320 assert(false, "unknown GCAllocPurpose"); 4321 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4322 break; 4323 } 4324 4325 // Prevent humongous PLAB sizes for two reasons: 4326 // * PLABs are allocated using a similar paths as oops, but should 4327 // never be in a humongous region 4328 // * Allowing humongous PLABs needlessly churns the region free lists 4329 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4330 } 4331 4332 void G1CollectedHeap::init_mutator_alloc_region() { 4333 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 4334 _mutator_alloc_region.init(); 4335 } 4336 4337 void G1CollectedHeap::release_mutator_alloc_region() { 4338 _mutator_alloc_region.release(); 4339 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 4340 } 4341 4342 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) { 4343 assert_at_safepoint(true /* should_be_vm_thread */); 4344 4345 _survivor_gc_alloc_region.init(); 4346 _old_gc_alloc_region.init(); 4347 HeapRegion* retained_region = _retained_old_gc_alloc_region; 4348 _retained_old_gc_alloc_region = NULL; 4349 4350 // We will discard the current GC alloc region if: 4351 // a) it's in the collection set (it can happen!), 4352 // b) it's already full (no point in using it), 4353 // c) it's empty (this means that it was emptied during 4354 // a cleanup and it should be on the free list now), or 4355 // d) it's humongous (this means that it was emptied 4356 // during a cleanup and was added to the free list, but 4357 // has been subsequently used to allocate a humongous 4358 // object that may be less than the region size). 4359 if (retained_region != NULL && 4360 !retained_region->in_collection_set() && 4361 !(retained_region->top() == retained_region->end()) && 4362 !retained_region->is_empty() && 4363 !retained_region->isHumongous()) { 4364 retained_region->set_saved_mark(); 4365 // The retained region was added to the old region set when it was 4366 // retired. We have to remove it now, since we don't allow regions 4367 // we allocate to in the region sets. We'll re-add it later, when 4368 // it's retired again. 4369 _old_set.remove(retained_region); 4370 bool during_im = g1_policy()->during_initial_mark_pause(); 4371 retained_region->note_start_of_copying(during_im); 4372 _old_gc_alloc_region.set(retained_region); 4373 _hr_printer.reuse(retained_region); 4374 evacuation_info.set_alloc_regions_used_before(retained_region->used()); 4375 } 4376 } 4377 4378 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) { 4379 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() + 4380 _old_gc_alloc_region.count()); 4381 _survivor_gc_alloc_region.release(); 4382 // If we have an old GC alloc region to release, we'll save it in 4383 // _retained_old_gc_alloc_region. If we don't 4384 // _retained_old_gc_alloc_region will become NULL. This is what we 4385 // want either way so no reason to check explicitly for either 4386 // condition. 4387 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 4388 4389 if (ResizePLAB) { 4390 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4391 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4392 } 4393 } 4394 4395 void G1CollectedHeap::abandon_gc_alloc_regions() { 4396 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 4397 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 4398 _retained_old_gc_alloc_region = NULL; 4399 } 4400 4401 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4402 _drain_in_progress = false; 4403 set_evac_failure_closure(cl); 4404 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4405 } 4406 4407 void G1CollectedHeap::finalize_for_evac_failure() { 4408 assert(_evac_failure_scan_stack != NULL && 4409 _evac_failure_scan_stack->length() == 0, 4410 "Postcondition"); 4411 assert(!_drain_in_progress, "Postcondition"); 4412 delete _evac_failure_scan_stack; 4413 _evac_failure_scan_stack = NULL; 4414 } 4415 4416 void G1CollectedHeap::remove_self_forwarding_pointers() { 4417 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4418 4419 double remove_self_forwards_start = os::elapsedTime(); 4420 4421 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4422 4423 if (G1CollectedHeap::use_parallel_gc_threads()) { 4424 set_par_threads(); 4425 workers()->run_task(&rsfp_task); 4426 set_par_threads(0); 4427 } else { 4428 rsfp_task.work(0); 4429 } 4430 4431 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4432 4433 // Reset the claim values in the regions in the collection set. 4434 reset_cset_heap_region_claim_values(); 4435 4436 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4437 4438 // Now restore saved marks, if any. 4439 assert(_objs_with_preserved_marks.size() == 4440 _preserved_marks_of_objs.size(), "Both or none."); 4441 while (!_objs_with_preserved_marks.is_empty()) { 4442 oop obj = _objs_with_preserved_marks.pop(); 4443 markOop m = _preserved_marks_of_objs.pop(); 4444 obj->set_mark(m); 4445 } 4446 _objs_with_preserved_marks.clear(true); 4447 _preserved_marks_of_objs.clear(true); 4448 4449 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4450 } 4451 4452 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4453 _evac_failure_scan_stack->push(obj); 4454 } 4455 4456 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4457 assert(_evac_failure_scan_stack != NULL, "precondition"); 4458 4459 while (_evac_failure_scan_stack->length() > 0) { 4460 oop obj = _evac_failure_scan_stack->pop(); 4461 _evac_failure_closure->set_region(heap_region_containing(obj)); 4462 obj->oop_iterate_backwards(_evac_failure_closure); 4463 } 4464 } 4465 4466 oop 4467 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, 4468 oop old) { 4469 assert(obj_in_cs(old), 4470 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4471 (HeapWord*) old)); 4472 markOop m = old->mark(); 4473 oop forward_ptr = old->forward_to_atomic(old); 4474 if (forward_ptr == NULL) { 4475 // Forward-to-self succeeded. 4476 assert(_par_scan_state != NULL, "par scan state"); 4477 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4478 uint queue_num = _par_scan_state->queue_num(); 4479 4480 _evacuation_failed = true; 4481 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size()); 4482 if (_evac_failure_closure != cl) { 4483 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4484 assert(!_drain_in_progress, 4485 "Should only be true while someone holds the lock."); 4486 // Set the global evac-failure closure to the current thread's. 4487 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4488 set_evac_failure_closure(cl); 4489 // Now do the common part. 4490 handle_evacuation_failure_common(old, m); 4491 // Reset to NULL. 4492 set_evac_failure_closure(NULL); 4493 } else { 4494 // The lock is already held, and this is recursive. 4495 assert(_drain_in_progress, "This should only be the recursive case."); 4496 handle_evacuation_failure_common(old, m); 4497 } 4498 return old; 4499 } else { 4500 // Forward-to-self failed. Either someone else managed to allocate 4501 // space for this object (old != forward_ptr) or they beat us in 4502 // self-forwarding it (old == forward_ptr). 4503 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4504 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4505 "should not be in the CSet", 4506 (HeapWord*) old, (HeapWord*) forward_ptr)); 4507 return forward_ptr; 4508 } 4509 } 4510 4511 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4512 preserve_mark_if_necessary(old, m); 4513 4514 HeapRegion* r = heap_region_containing(old); 4515 if (!r->evacuation_failed()) { 4516 r->set_evacuation_failed(true); 4517 _hr_printer.evac_failure(r); 4518 } 4519 4520 push_on_evac_failure_scan_stack(old); 4521 4522 if (!_drain_in_progress) { 4523 // prevent recursion in copy_to_survivor_space() 4524 _drain_in_progress = true; 4525 drain_evac_failure_scan_stack(); 4526 _drain_in_progress = false; 4527 } 4528 } 4529 4530 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4531 assert(evacuation_failed(), "Oversaving!"); 4532 // We want to call the "for_promotion_failure" version only in the 4533 // case of a promotion failure. 4534 if (m->must_be_preserved_for_promotion_failure(obj)) { 4535 _objs_with_preserved_marks.push(obj); 4536 _preserved_marks_of_objs.push(m); 4537 } 4538 } 4539 4540 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4541 size_t word_size) { 4542 if (purpose == GCAllocForSurvived) { 4543 HeapWord* result = survivor_attempt_allocation(word_size); 4544 if (result != NULL) { 4545 return result; 4546 } else { 4547 // Let's try to allocate in the old gen in case we can fit the 4548 // object there. 4549 return old_attempt_allocation(word_size); 4550 } 4551 } else { 4552 assert(purpose == GCAllocForTenured, "sanity"); 4553 HeapWord* result = old_attempt_allocation(word_size); 4554 if (result != NULL) { 4555 return result; 4556 } else { 4557 // Let's try to allocate in the survivors in case we can fit the 4558 // object there. 4559 return survivor_attempt_allocation(word_size); 4560 } 4561 } 4562 4563 ShouldNotReachHere(); 4564 // Trying to keep some compilers happy. 4565 return NULL; 4566 } 4567 4568 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : 4569 ParGCAllocBuffer(gclab_word_size), _retired(true) { } 4570 4571 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp) 4572 : _g1h(g1h), 4573 _refs(g1h->task_queue(queue_num)), 4574 _dcq(&g1h->dirty_card_queue_set()), 4575 _ct_bs(g1h->g1_barrier_set()), 4576 _g1_rem(g1h->g1_rem_set()), 4577 _hash_seed(17), _queue_num(queue_num), 4578 _term_attempts(0), 4579 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4580 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4581 _age_table(false), _scanner(g1h, this, rp), 4582 _strong_roots_time(0), _term_time(0), 4583 _alloc_buffer_waste(0), _undo_waste(0) { 4584 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4585 // we "sacrifice" entry 0 to keep track of surviving bytes for 4586 // non-young regions (where the age is -1) 4587 // We also add a few elements at the beginning and at the end in 4588 // an attempt to eliminate cache contention 4589 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 4590 uint array_length = PADDING_ELEM_NUM + 4591 real_length + 4592 PADDING_ELEM_NUM; 4593 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); 4594 if (_surviving_young_words_base == NULL) 4595 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR, 4596 "Not enough space for young surv histo."); 4597 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4598 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); 4599 4600 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4601 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4602 4603 _start = os::elapsedTime(); 4604 } 4605 4606 void 4607 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4608 { 4609 st->print_raw_cr("GC Termination Stats"); 4610 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4611 " ------waste (KiB)------"); 4612 st->print_raw_cr("thr ms ms % ms % attempts" 4613 " total alloc undo"); 4614 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4615 " ------- ------- -------"); 4616 } 4617 4618 void 4619 G1ParScanThreadState::print_termination_stats(int i, 4620 outputStream* const st) const 4621 { 4622 const double elapsed_ms = elapsed_time() * 1000.0; 4623 const double s_roots_ms = strong_roots_time() * 1000.0; 4624 const double term_ms = term_time() * 1000.0; 4625 st->print_cr("%3d %9.2f %9.2f %6.2f " 4626 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4627 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4628 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4629 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4630 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4631 alloc_buffer_waste() * HeapWordSize / K, 4632 undo_waste() * HeapWordSize / K); 4633 } 4634 4635 #ifdef ASSERT 4636 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4637 assert(ref != NULL, "invariant"); 4638 assert(UseCompressedOops, "sanity"); 4639 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4640 oop p = oopDesc::load_decode_heap_oop(ref); 4641 assert(_g1h->is_in_g1_reserved(p), 4642 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p)); 4643 return true; 4644 } 4645 4646 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4647 assert(ref != NULL, "invariant"); 4648 if (has_partial_array_mask(ref)) { 4649 // Must be in the collection set--it's already been copied. 4650 oop p = clear_partial_array_mask(ref); 4651 assert(_g1h->obj_in_cs(p), 4652 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p)); 4653 } else { 4654 oop p = oopDesc::load_decode_heap_oop(ref); 4655 assert(_g1h->is_in_g1_reserved(p), 4656 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p)); 4657 } 4658 return true; 4659 } 4660 4661 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4662 if (ref.is_narrow()) { 4663 return verify_ref((narrowOop*) ref); 4664 } else { 4665 return verify_ref((oop*) ref); 4666 } 4667 } 4668 #endif // ASSERT 4669 4670 void G1ParScanThreadState::trim_queue() { 4671 assert(_evac_failure_cl != NULL, "not set"); 4672 4673 StarTask ref; 4674 do { 4675 // Drain the overflow stack first, so other threads can steal. 4676 while (refs()->pop_overflow(ref)) { 4677 deal_with_reference(ref); 4678 } 4679 4680 while (refs()->pop_local(ref)) { 4681 deal_with_reference(ref); 4682 } 4683 } while (!refs()->is_empty()); 4684 } 4685 4686 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, 4687 G1ParScanThreadState* par_scan_state) : 4688 _g1(g1), _par_scan_state(par_scan_state), 4689 _worker_id(par_scan_state->queue_num()) { } 4690 4691 void G1ParCopyHelper::mark_object(oop obj) { 4692 #ifdef ASSERT 4693 HeapRegion* hr = _g1->heap_region_containing(obj); 4694 assert(hr != NULL, "sanity"); 4695 assert(!hr->in_collection_set(), "should not mark objects in the CSet"); 4696 #endif // ASSERT 4697 4698 // We know that the object is not moving so it's safe to read its size. 4699 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4700 } 4701 4702 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) { 4703 #ifdef ASSERT 4704 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4705 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4706 assert(from_obj != to_obj, "should not be self-forwarded"); 4707 4708 HeapRegion* from_hr = _g1->heap_region_containing(from_obj); 4709 assert(from_hr != NULL, "sanity"); 4710 assert(from_hr->in_collection_set(), "from obj should be in the CSet"); 4711 4712 HeapRegion* to_hr = _g1->heap_region_containing(to_obj); 4713 assert(to_hr != NULL, "sanity"); 4714 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet"); 4715 #endif // ASSERT 4716 4717 // The object might be in the process of being copied by another 4718 // worker so we cannot trust that its to-space image is 4719 // well-formed. So we have to read its size from its from-space 4720 // image which we know should not be changing. 4721 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4722 } 4723 4724 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) { 4725 size_t word_sz = old->size(); 4726 HeapRegion* from_region = _g1h->heap_region_containing_raw(old); 4727 // +1 to make the -1 indexes valid... 4728 int young_index = from_region->young_index_in_cset()+1; 4729 assert( (from_region->is_young() && young_index > 0) || 4730 (!from_region->is_young() && young_index == 0), "invariant" ); 4731 G1CollectorPolicy* g1p = _g1h->g1_policy(); 4732 markOop m = old->mark(); 4733 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4734 : m->age(); 4735 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4736 word_sz); 4737 HeapWord* obj_ptr = allocate(alloc_purpose, word_sz); 4738 #ifndef PRODUCT 4739 // Should this evacuation fail? 4740 if (_g1h->evacuation_should_fail()) { 4741 if (obj_ptr != NULL) { 4742 undo_allocation(alloc_purpose, obj_ptr, word_sz); 4743 obj_ptr = NULL; 4744 } 4745 } 4746 #endif // !PRODUCT 4747 4748 if (obj_ptr == NULL) { 4749 // This will either forward-to-self, or detect that someone else has 4750 // installed a forwarding pointer. 4751 return _g1h->handle_evacuation_failure_par(this, old); 4752 } 4753 4754 oop obj = oop(obj_ptr); 4755 4756 // We're going to allocate linearly, so might as well prefetch ahead. 4757 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4758 4759 oop forward_ptr = old->forward_to_atomic(obj); 4760 if (forward_ptr == NULL) { 4761 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4762 4763 // alloc_purpose is just a hint to allocate() above, recheck the type of region 4764 // we actually allocated from and update alloc_purpose accordingly 4765 HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr); 4766 alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured; 4767 4768 if (g1p->track_object_age(alloc_purpose)) { 4769 // We could simply do obj->incr_age(). However, this causes a 4770 // performance issue. obj->incr_age() will first check whether 4771 // the object has a displaced mark by checking its mark word; 4772 // getting the mark word from the new location of the object 4773 // stalls. So, given that we already have the mark word and we 4774 // are about to install it anyway, it's better to increase the 4775 // age on the mark word, when the object does not have a 4776 // displaced mark word. We're not expecting many objects to have 4777 // a displaced marked word, so that case is not optimized 4778 // further (it could be...) and we simply call obj->incr_age(). 4779 4780 if (m->has_displaced_mark_helper()) { 4781 // in this case, we have to install the mark word first, 4782 // otherwise obj looks to be forwarded (the old mark word, 4783 // which contains the forward pointer, was copied) 4784 obj->set_mark(m); 4785 obj->incr_age(); 4786 } else { 4787 m = m->incr_age(); 4788 obj->set_mark(m); 4789 } 4790 age_table()->add(obj, word_sz); 4791 } else { 4792 obj->set_mark(m); 4793 } 4794 4795 if (G1StringDedup::is_enabled()) { 4796 G1StringDedup::enqueue_from_evacuation(from_region->is_young(), 4797 to_region->is_young(), 4798 queue_num(), 4799 obj); 4800 } 4801 4802 size_t* surv_young_words = surviving_young_words(); 4803 surv_young_words[young_index] += word_sz; 4804 4805 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4806 // We keep track of the next start index in the length field of 4807 // the to-space object. The actual length can be found in the 4808 // length field of the from-space object. 4809 arrayOop(obj)->set_length(0); 4810 oop* old_p = set_partial_array_mask(old); 4811 push_on_queue(old_p); 4812 } else { 4813 // No point in using the slower heap_region_containing() method, 4814 // given that we know obj is in the heap. 4815 _scanner.set_region(_g1h->heap_region_containing_raw(obj)); 4816 obj->oop_iterate_backwards(&_scanner); 4817 } 4818 } else { 4819 undo_allocation(alloc_purpose, obj_ptr, word_sz); 4820 obj = forward_ptr; 4821 } 4822 return obj; 4823 } 4824 4825 template <class T> 4826 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4827 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4828 _scanned_klass->record_modified_oops(); 4829 } 4830 } 4831 4832 template <G1Barrier barrier, bool do_mark_object> 4833 template <class T> 4834 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) { 4835 T heap_oop = oopDesc::load_heap_oop(p); 4836 4837 if (oopDesc::is_null(heap_oop)) { 4838 return; 4839 } 4840 4841 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 4842 4843 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4844 4845 if (_g1->in_cset_fast_test(obj)) { 4846 oop forwardee; 4847 if (obj->is_forwarded()) { 4848 forwardee = obj->forwardee(); 4849 } else { 4850 forwardee = _par_scan_state->copy_to_survivor_space(obj); 4851 } 4852 assert(forwardee != NULL, "forwardee should not be NULL"); 4853 oopDesc::encode_store_heap_oop(p, forwardee); 4854 if (do_mark_object && forwardee != obj) { 4855 // If the object is self-forwarded we don't need to explicitly 4856 // mark it, the evacuation failure protocol will do so. 4857 mark_forwarded_object(obj, forwardee); 4858 } 4859 4860 if (barrier == G1BarrierKlass) { 4861 do_klass_barrier(p, forwardee); 4862 } 4863 } else { 4864 // The object is not in collection set. If we're a root scanning 4865 // closure during an initial mark pause (i.e. do_mark_object will 4866 // be true) then attempt to mark the object. 4867 if (do_mark_object) { 4868 mark_object(obj); 4869 } 4870 } 4871 4872 if (barrier == G1BarrierEvac) { 4873 _par_scan_state->update_rs(_from, p, _worker_id); 4874 } 4875 } 4876 4877 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p); 4878 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4879 4880 class G1ParEvacuateFollowersClosure : public VoidClosure { 4881 protected: 4882 G1CollectedHeap* _g1h; 4883 G1ParScanThreadState* _par_scan_state; 4884 RefToScanQueueSet* _queues; 4885 ParallelTaskTerminator* _terminator; 4886 4887 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4888 RefToScanQueueSet* queues() { return _queues; } 4889 ParallelTaskTerminator* terminator() { return _terminator; } 4890 4891 public: 4892 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4893 G1ParScanThreadState* par_scan_state, 4894 RefToScanQueueSet* queues, 4895 ParallelTaskTerminator* terminator) 4896 : _g1h(g1h), _par_scan_state(par_scan_state), 4897 _queues(queues), _terminator(terminator) {} 4898 4899 void do_void(); 4900 4901 private: 4902 inline bool offer_termination(); 4903 }; 4904 4905 bool G1ParEvacuateFollowersClosure::offer_termination() { 4906 G1ParScanThreadState* const pss = par_scan_state(); 4907 pss->start_term_time(); 4908 const bool res = terminator()->offer_termination(); 4909 pss->end_term_time(); 4910 return res; 4911 } 4912 4913 void G1ParEvacuateFollowersClosure::do_void() { 4914 StarTask stolen_task; 4915 G1ParScanThreadState* const pss = par_scan_state(); 4916 pss->trim_queue(); 4917 4918 do { 4919 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4920 assert(pss->verify_task(stolen_task), "sanity"); 4921 if (stolen_task.is_narrow()) { 4922 pss->deal_with_reference((narrowOop*) stolen_task); 4923 } else { 4924 pss->deal_with_reference((oop*) stolen_task); 4925 } 4926 4927 // We've just processed a reference and we might have made 4928 // available new entries on the queues. So we have to make sure 4929 // we drain the queues as necessary. 4930 pss->trim_queue(); 4931 } 4932 } while (!offer_termination()); 4933 } 4934 4935 class G1KlassScanClosure : public KlassClosure { 4936 G1ParCopyHelper* _closure; 4937 bool _process_only_dirty; 4938 int _count; 4939 public: 4940 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4941 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4942 void do_klass(Klass* klass) { 4943 // If the klass has not been dirtied we know that there's 4944 // no references into the young gen and we can skip it. 4945 if (!_process_only_dirty || klass->has_modified_oops()) { 4946 // Clean the klass since we're going to scavenge all the metadata. 4947 klass->clear_modified_oops(); 4948 4949 // Tell the closure that this klass is the Klass to scavenge 4950 // and is the one to dirty if oops are left pointing into the young gen. 4951 _closure->set_scanned_klass(klass); 4952 4953 klass->oops_do(_closure); 4954 4955 _closure->set_scanned_klass(NULL); 4956 } 4957 _count++; 4958 } 4959 }; 4960 4961 class G1ParTask : public AbstractGangTask { 4962 protected: 4963 G1CollectedHeap* _g1h; 4964 RefToScanQueueSet *_queues; 4965 ParallelTaskTerminator _terminator; 4966 uint _n_workers; 4967 4968 Mutex _stats_lock; 4969 Mutex* stats_lock() { return &_stats_lock; } 4970 4971 size_t getNCards() { 4972 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 4973 / G1BlockOffsetSharedArray::N_bytes; 4974 } 4975 4976 public: 4977 G1ParTask(G1CollectedHeap* g1h, 4978 RefToScanQueueSet *task_queues) 4979 : AbstractGangTask("G1 collection"), 4980 _g1h(g1h), 4981 _queues(task_queues), 4982 _terminator(0, _queues), 4983 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4984 {} 4985 4986 RefToScanQueueSet* queues() { return _queues; } 4987 4988 RefToScanQueue *work_queue(int i) { 4989 return queues()->queue(i); 4990 } 4991 4992 ParallelTaskTerminator* terminator() { return &_terminator; } 4993 4994 virtual void set_for_termination(int active_workers) { 4995 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4996 // in the young space (_par_seq_tasks) in the G1 heap 4997 // for SequentialSubTasksDone. 4998 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4999 // both of which need setting by set_n_termination(). 5000 _g1h->SharedHeap::set_n_termination(active_workers); 5001 _g1h->set_n_termination(active_workers); 5002 terminator()->reset_for_reuse(active_workers); 5003 _n_workers = active_workers; 5004 } 5005 5006 void work(uint worker_id) { 5007 if (worker_id >= _n_workers) return; // no work needed this round 5008 5009 double start_time_ms = os::elapsedTime() * 1000.0; 5010 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 5011 5012 { 5013 ResourceMark rm; 5014 HandleMark hm; 5015 5016 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 5017 5018 G1ParScanThreadState pss(_g1h, worker_id, rp); 5019 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 5020 5021 pss.set_evac_failure_closure(&evac_failure_cl); 5022 5023 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); 5024 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp); 5025 5026 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); 5027 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp); 5028 5029 bool only_young = _g1h->g1_policy()->gcs_are_young(); 5030 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false); 5031 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young); 5032 5033 OopClosure* scan_root_cl = &only_scan_root_cl; 5034 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s; 5035 5036 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5037 // We also need to mark copied objects. 5038 scan_root_cl = &scan_mark_root_cl; 5039 scan_klasses_cl = &scan_mark_klasses_cl_s; 5040 } 5041 5042 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 5043 5044 // Don't scan the scavengable methods in the code cache as part 5045 // of strong root scanning. The code roots that point into a 5046 // region in the collection set are scanned when we scan the 5047 // region's RSet. 5048 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings; 5049 5050 pss.start_strong_roots(); 5051 _g1h->g1_process_strong_roots(/* is scavenging */ true, 5052 SharedHeap::ScanningOption(so), 5053 scan_root_cl, 5054 &push_heap_rs_cl, 5055 scan_klasses_cl, 5056 worker_id); 5057 pss.end_strong_roots(); 5058 5059 { 5060 double start = os::elapsedTime(); 5061 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 5062 evac.do_void(); 5063 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 5064 double term_ms = pss.term_time()*1000.0; 5065 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 5066 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 5067 } 5068 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 5069 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 5070 5071 if (ParallelGCVerbose) { 5072 MutexLocker x(stats_lock()); 5073 pss.print_termination_stats(worker_id); 5074 } 5075 5076 assert(pss.refs()->is_empty(), "should be empty"); 5077 5078 // Close the inner scope so that the ResourceMark and HandleMark 5079 // destructors are executed here and are included as part of the 5080 // "GC Worker Time". 5081 } 5082 5083 double end_time_ms = os::elapsedTime() * 1000.0; 5084 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 5085 } 5086 }; 5087 5088 // *** Common G1 Evacuation Stuff 5089 5090 // This method is run in a GC worker. 5091 5092 void 5093 G1CollectedHeap:: 5094 g1_process_strong_roots(bool is_scavenging, 5095 ScanningOption so, 5096 OopClosure* scan_non_heap_roots, 5097 OopsInHeapRegionClosure* scan_rs, 5098 G1KlassScanClosure* scan_klasses, 5099 uint worker_i) { 5100 5101 // First scan the strong roots 5102 double ext_roots_start = os::elapsedTime(); 5103 double closure_app_time_sec = 0.0; 5104 5105 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 5106 5107 assert(so & SO_CodeCache || scan_rs != NULL, "must scan code roots somehow"); 5108 // Walk the code cache/strong code roots w/o buffering, because StarTask 5109 // cannot handle unaligned oop locations. 5110 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */); 5111 5112 process_strong_roots(false, // no scoping; this is parallel code 5113 is_scavenging, so, 5114 &buf_scan_non_heap_roots, 5115 &eager_scan_code_roots, 5116 scan_klasses 5117 ); 5118 5119 // Now the CM ref_processor roots. 5120 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 5121 // We need to treat the discovered reference lists of the 5122 // concurrent mark ref processor as roots and keep entries 5123 // (which are added by the marking threads) on them live 5124 // until they can be processed at the end of marking. 5125 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 5126 } 5127 5128 // Finish up any enqueued closure apps (attributed as object copy time). 5129 buf_scan_non_heap_roots.done(); 5130 5131 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds(); 5132 5133 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 5134 5135 double ext_root_time_ms = 5136 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 5137 5138 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 5139 5140 // During conc marking we have to filter the per-thread SATB buffers 5141 // to make sure we remove any oops into the CSet (which will show up 5142 // as implicitly live). 5143 double satb_filtering_ms = 0.0; 5144 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 5145 if (mark_in_progress()) { 5146 double satb_filter_start = os::elapsedTime(); 5147 5148 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 5149 5150 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 5151 } 5152 } 5153 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 5154 5155 // If this is an initial mark pause, and we're not scanning 5156 // the entire code cache, we need to mark the oops in the 5157 // strong code root lists for the regions that are not in 5158 // the collection set. 5159 // Note all threads participate in this set of root tasks. 5160 double mark_strong_code_roots_ms = 0.0; 5161 if (g1_policy()->during_initial_mark_pause() && !(so & SO_CodeCache)) { 5162 double mark_strong_roots_start = os::elapsedTime(); 5163 mark_strong_code_roots(worker_i); 5164 mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0; 5165 } 5166 g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms); 5167 5168 // Now scan the complement of the collection set. 5169 if (scan_rs != NULL) { 5170 g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i); 5171 } 5172 _process_strong_tasks->all_tasks_completed(); 5173 } 5174 5175 void 5176 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) { 5177 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 5178 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs); 5179 } 5180 5181 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 5182 private: 5183 BoolObjectClosure* _is_alive; 5184 int _initial_string_table_size; 5185 int _initial_symbol_table_size; 5186 5187 bool _process_strings; 5188 int _strings_processed; 5189 int _strings_removed; 5190 5191 bool _process_symbols; 5192 int _symbols_processed; 5193 int _symbols_removed; 5194 5195 bool _do_in_parallel; 5196 public: 5197 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 5198 AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive), 5199 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()), 5200 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 5201 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 5202 5203 _initial_string_table_size = StringTable::the_table()->table_size(); 5204 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 5205 if (process_strings) { 5206 StringTable::clear_parallel_claimed_index(); 5207 } 5208 if (process_symbols) { 5209 SymbolTable::clear_parallel_claimed_index(); 5210 } 5211 } 5212 5213 ~G1StringSymbolTableUnlinkTask() { 5214 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size, 5215 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT, 5216 StringTable::parallel_claimed_index(), _initial_string_table_size)); 5217 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 5218 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT, 5219 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size)); 5220 } 5221 5222 void work(uint worker_id) { 5223 if (_do_in_parallel) { 5224 int strings_processed = 0; 5225 int strings_removed = 0; 5226 int symbols_processed = 0; 5227 int symbols_removed = 0; 5228 if (_process_strings) { 5229 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 5230 Atomic::add(strings_processed, &_strings_processed); 5231 Atomic::add(strings_removed, &_strings_removed); 5232 } 5233 if (_process_symbols) { 5234 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 5235 Atomic::add(symbols_processed, &_symbols_processed); 5236 Atomic::add(symbols_removed, &_symbols_removed); 5237 } 5238 } else { 5239 if (_process_strings) { 5240 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed); 5241 } 5242 if (_process_symbols) { 5243 SymbolTable::unlink(&_symbols_processed, &_symbols_removed); 5244 } 5245 } 5246 } 5247 5248 size_t strings_processed() const { return (size_t)_strings_processed; } 5249 size_t strings_removed() const { return (size_t)_strings_removed; } 5250 5251 size_t symbols_processed() const { return (size_t)_symbols_processed; } 5252 size_t symbols_removed() const { return (size_t)_symbols_removed; } 5253 }; 5254 5255 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 5256 bool process_strings, bool process_symbols) { 5257 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5258 _g1h->workers()->active_workers() : 1); 5259 5260 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 5261 if (G1CollectedHeap::use_parallel_gc_threads()) { 5262 set_par_threads(n_workers); 5263 workers()->run_task(&g1_unlink_task); 5264 set_par_threads(0); 5265 } else { 5266 g1_unlink_task.work(0); 5267 } 5268 if (G1TraceStringSymbolTableScrubbing) { 5269 gclog_or_tty->print_cr("Cleaned string and symbol table, " 5270 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, " 5271 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed", 5272 g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(), 5273 g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed()); 5274 } 5275 5276 if (G1StringDedup::is_enabled()) { 5277 G1StringDedup::unlink(is_alive); 5278 } 5279 } 5280 5281 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 5282 private: 5283 DirtyCardQueueSet* _queue; 5284 public: 5285 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 5286 5287 virtual void work(uint worker_id) { 5288 double start_time = os::elapsedTime(); 5289 5290 RedirtyLoggedCardTableEntryClosure cl; 5291 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) { 5292 _queue->par_apply_closure_to_all_completed_buffers(&cl); 5293 } else { 5294 _queue->apply_closure_to_all_completed_buffers(&cl); 5295 } 5296 5297 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 5298 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0); 5299 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed()); 5300 } 5301 }; 5302 5303 void G1CollectedHeap::redirty_logged_cards() { 5304 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates."); 5305 double redirty_logged_cards_start = os::elapsedTime(); 5306 5307 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 5308 _g1h->workers()->active_workers() : 1); 5309 5310 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 5311 dirty_card_queue_set().reset_for_par_iteration(); 5312 if (use_parallel_gc_threads()) { 5313 set_par_threads(n_workers); 5314 workers()->run_task(&redirty_task); 5315 set_par_threads(0); 5316 } else { 5317 redirty_task.work(0); 5318 } 5319 5320 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5321 dcq.merge_bufferlists(&dirty_card_queue_set()); 5322 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5323 5324 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 5325 } 5326 5327 // Weak Reference Processing support 5328 5329 // An always "is_alive" closure that is used to preserve referents. 5330 // If the object is non-null then it's alive. Used in the preservation 5331 // of referent objects that are pointed to by reference objects 5332 // discovered by the CM ref processor. 5333 class G1AlwaysAliveClosure: public BoolObjectClosure { 5334 G1CollectedHeap* _g1; 5335 public: 5336 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5337 bool do_object_b(oop p) { 5338 if (p != NULL) { 5339 return true; 5340 } 5341 return false; 5342 } 5343 }; 5344 5345 bool G1STWIsAliveClosure::do_object_b(oop p) { 5346 // An object is reachable if it is outside the collection set, 5347 // or is inside and copied. 5348 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5349 } 5350 5351 // Non Copying Keep Alive closure 5352 class G1KeepAliveClosure: public OopClosure { 5353 G1CollectedHeap* _g1; 5354 public: 5355 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5356 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5357 void do_oop( oop* p) { 5358 oop obj = *p; 5359 5360 if (_g1->obj_in_cs(obj)) { 5361 assert( obj->is_forwarded(), "invariant" ); 5362 *p = obj->forwardee(); 5363 } 5364 } 5365 }; 5366 5367 // Copying Keep Alive closure - can be called from both 5368 // serial and parallel code as long as different worker 5369 // threads utilize different G1ParScanThreadState instances 5370 // and different queues. 5371 5372 class G1CopyingKeepAliveClosure: public OopClosure { 5373 G1CollectedHeap* _g1h; 5374 OopClosure* _copy_non_heap_obj_cl; 5375 OopsInHeapRegionClosure* _copy_metadata_obj_cl; 5376 G1ParScanThreadState* _par_scan_state; 5377 5378 public: 5379 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5380 OopClosure* non_heap_obj_cl, 5381 OopsInHeapRegionClosure* metadata_obj_cl, 5382 G1ParScanThreadState* pss): 5383 _g1h(g1h), 5384 _copy_non_heap_obj_cl(non_heap_obj_cl), 5385 _copy_metadata_obj_cl(metadata_obj_cl), 5386 _par_scan_state(pss) 5387 {} 5388 5389 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5390 virtual void do_oop( oop* p) { do_oop_work(p); } 5391 5392 template <class T> void do_oop_work(T* p) { 5393 oop obj = oopDesc::load_decode_heap_oop(p); 5394 5395 if (_g1h->obj_in_cs(obj)) { 5396 // If the referent object has been forwarded (either copied 5397 // to a new location or to itself in the event of an 5398 // evacuation failure) then we need to update the reference 5399 // field and, if both reference and referent are in the G1 5400 // heap, update the RSet for the referent. 5401 // 5402 // If the referent has not been forwarded then we have to keep 5403 // it alive by policy. Therefore we have copy the referent. 5404 // 5405 // If the reference field is in the G1 heap then we can push 5406 // on the PSS queue. When the queue is drained (after each 5407 // phase of reference processing) the object and it's followers 5408 // will be copied, the reference field set to point to the 5409 // new location, and the RSet updated. Otherwise we need to 5410 // use the the non-heap or metadata closures directly to copy 5411 // the referent object and update the pointer, while avoiding 5412 // updating the RSet. 5413 5414 if (_g1h->is_in_g1_reserved(p)) { 5415 _par_scan_state->push_on_queue(p); 5416 } else { 5417 assert(!Metaspace::contains((const void*)p), 5418 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) " 5419 PTR_FORMAT, p)); 5420 _copy_non_heap_obj_cl->do_oop(p); 5421 } 5422 } 5423 } 5424 }; 5425 5426 // Serial drain queue closure. Called as the 'complete_gc' 5427 // closure for each discovered list in some of the 5428 // reference processing phases. 5429 5430 class G1STWDrainQueueClosure: public VoidClosure { 5431 protected: 5432 G1CollectedHeap* _g1h; 5433 G1ParScanThreadState* _par_scan_state; 5434 5435 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5436 5437 public: 5438 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5439 _g1h(g1h), 5440 _par_scan_state(pss) 5441 { } 5442 5443 void do_void() { 5444 G1ParScanThreadState* const pss = par_scan_state(); 5445 pss->trim_queue(); 5446 } 5447 }; 5448 5449 // Parallel Reference Processing closures 5450 5451 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5452 // processing during G1 evacuation pauses. 5453 5454 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5455 private: 5456 G1CollectedHeap* _g1h; 5457 RefToScanQueueSet* _queues; 5458 FlexibleWorkGang* _workers; 5459 int _active_workers; 5460 5461 public: 5462 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5463 FlexibleWorkGang* workers, 5464 RefToScanQueueSet *task_queues, 5465 int n_workers) : 5466 _g1h(g1h), 5467 _queues(task_queues), 5468 _workers(workers), 5469 _active_workers(n_workers) 5470 { 5471 assert(n_workers > 0, "shouldn't call this otherwise"); 5472 } 5473 5474 // Executes the given task using concurrent marking worker threads. 5475 virtual void execute(ProcessTask& task); 5476 virtual void execute(EnqueueTask& task); 5477 }; 5478 5479 // Gang task for possibly parallel reference processing 5480 5481 class G1STWRefProcTaskProxy: public AbstractGangTask { 5482 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5483 ProcessTask& _proc_task; 5484 G1CollectedHeap* _g1h; 5485 RefToScanQueueSet *_task_queues; 5486 ParallelTaskTerminator* _terminator; 5487 5488 public: 5489 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5490 G1CollectedHeap* g1h, 5491 RefToScanQueueSet *task_queues, 5492 ParallelTaskTerminator* terminator) : 5493 AbstractGangTask("Process reference objects in parallel"), 5494 _proc_task(proc_task), 5495 _g1h(g1h), 5496 _task_queues(task_queues), 5497 _terminator(terminator) 5498 {} 5499 5500 virtual void work(uint worker_id) { 5501 // The reference processing task executed by a single worker. 5502 ResourceMark rm; 5503 HandleMark hm; 5504 5505 G1STWIsAliveClosure is_alive(_g1h); 5506 5507 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5508 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5509 5510 pss.set_evac_failure_closure(&evac_failure_cl); 5511 5512 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5513 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5514 5515 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5516 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5517 5518 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5519 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5520 5521 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5522 // We also need to mark copied objects. 5523 copy_non_heap_cl = ©_mark_non_heap_cl; 5524 copy_metadata_cl = ©_mark_metadata_cl; 5525 } 5526 5527 // Keep alive closure. 5528 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5529 5530 // Complete GC closure 5531 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5532 5533 // Call the reference processing task's work routine. 5534 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5535 5536 // Note we cannot assert that the refs array is empty here as not all 5537 // of the processing tasks (specifically phase2 - pp2_work) execute 5538 // the complete_gc closure (which ordinarily would drain the queue) so 5539 // the queue may not be empty. 5540 } 5541 }; 5542 5543 // Driver routine for parallel reference processing. 5544 // Creates an instance of the ref processing gang 5545 // task and has the worker threads execute it. 5546 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5547 assert(_workers != NULL, "Need parallel worker threads."); 5548 5549 ParallelTaskTerminator terminator(_active_workers, _queues); 5550 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5551 5552 _g1h->set_par_threads(_active_workers); 5553 _workers->run_task(&proc_task_proxy); 5554 _g1h->set_par_threads(0); 5555 } 5556 5557 // Gang task for parallel reference enqueueing. 5558 5559 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5560 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5561 EnqueueTask& _enq_task; 5562 5563 public: 5564 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5565 AbstractGangTask("Enqueue reference objects in parallel"), 5566 _enq_task(enq_task) 5567 { } 5568 5569 virtual void work(uint worker_id) { 5570 _enq_task.work(worker_id); 5571 } 5572 }; 5573 5574 // Driver routine for parallel reference enqueueing. 5575 // Creates an instance of the ref enqueueing gang 5576 // task and has the worker threads execute it. 5577 5578 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5579 assert(_workers != NULL, "Need parallel worker threads."); 5580 5581 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5582 5583 _g1h->set_par_threads(_active_workers); 5584 _workers->run_task(&enq_task_proxy); 5585 _g1h->set_par_threads(0); 5586 } 5587 5588 // End of weak reference support closures 5589 5590 // Abstract task used to preserve (i.e. copy) any referent objects 5591 // that are in the collection set and are pointed to by reference 5592 // objects discovered by the CM ref processor. 5593 5594 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5595 protected: 5596 G1CollectedHeap* _g1h; 5597 RefToScanQueueSet *_queues; 5598 ParallelTaskTerminator _terminator; 5599 uint _n_workers; 5600 5601 public: 5602 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5603 AbstractGangTask("ParPreserveCMReferents"), 5604 _g1h(g1h), 5605 _queues(task_queues), 5606 _terminator(workers, _queues), 5607 _n_workers(workers) 5608 { } 5609 5610 void work(uint worker_id) { 5611 ResourceMark rm; 5612 HandleMark hm; 5613 5614 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5615 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5616 5617 pss.set_evac_failure_closure(&evac_failure_cl); 5618 5619 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5620 5621 5622 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5623 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5624 5625 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5626 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5627 5628 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5629 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5630 5631 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5632 // We also need to mark copied objects. 5633 copy_non_heap_cl = ©_mark_non_heap_cl; 5634 copy_metadata_cl = ©_mark_metadata_cl; 5635 } 5636 5637 // Is alive closure 5638 G1AlwaysAliveClosure always_alive(_g1h); 5639 5640 // Copying keep alive closure. Applied to referent objects that need 5641 // to be copied. 5642 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5643 5644 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5645 5646 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5647 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5648 5649 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5650 // So this must be true - but assert just in case someone decides to 5651 // change the worker ids. 5652 assert(0 <= worker_id && worker_id < limit, "sanity"); 5653 assert(!rp->discovery_is_atomic(), "check this code"); 5654 5655 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5656 for (uint idx = worker_id; idx < limit; idx += stride) { 5657 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5658 5659 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5660 while (iter.has_next()) { 5661 // Since discovery is not atomic for the CM ref processor, we 5662 // can see some null referent objects. 5663 iter.load_ptrs(DEBUG_ONLY(true)); 5664 oop ref = iter.obj(); 5665 5666 // This will filter nulls. 5667 if (iter.is_referent_alive()) { 5668 iter.make_referent_alive(); 5669 } 5670 iter.move_to_next(); 5671 } 5672 } 5673 5674 // Drain the queue - which may cause stealing 5675 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5676 drain_queue.do_void(); 5677 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5678 assert(pss.refs()->is_empty(), "should be"); 5679 } 5680 }; 5681 5682 // Weak Reference processing during an evacuation pause (part 1). 5683 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5684 double ref_proc_start = os::elapsedTime(); 5685 5686 ReferenceProcessor* rp = _ref_processor_stw; 5687 assert(rp->discovery_enabled(), "should have been enabled"); 5688 5689 // Any reference objects, in the collection set, that were 'discovered' 5690 // by the CM ref processor should have already been copied (either by 5691 // applying the external root copy closure to the discovered lists, or 5692 // by following an RSet entry). 5693 // 5694 // But some of the referents, that are in the collection set, that these 5695 // reference objects point to may not have been copied: the STW ref 5696 // processor would have seen that the reference object had already 5697 // been 'discovered' and would have skipped discovering the reference, 5698 // but would not have treated the reference object as a regular oop. 5699 // As a result the copy closure would not have been applied to the 5700 // referent object. 5701 // 5702 // We need to explicitly copy these referent objects - the references 5703 // will be processed at the end of remarking. 5704 // 5705 // We also need to do this copying before we process the reference 5706 // objects discovered by the STW ref processor in case one of these 5707 // referents points to another object which is also referenced by an 5708 // object discovered by the STW ref processor. 5709 5710 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5711 no_of_gc_workers == workers()->active_workers(), 5712 "Need to reset active GC workers"); 5713 5714 set_par_threads(no_of_gc_workers); 5715 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5716 no_of_gc_workers, 5717 _task_queues); 5718 5719 if (G1CollectedHeap::use_parallel_gc_threads()) { 5720 workers()->run_task(&keep_cm_referents); 5721 } else { 5722 keep_cm_referents.work(0); 5723 } 5724 5725 set_par_threads(0); 5726 5727 // Closure to test whether a referent is alive. 5728 G1STWIsAliveClosure is_alive(this); 5729 5730 // Even when parallel reference processing is enabled, the processing 5731 // of JNI refs is serial and performed serially by the current thread 5732 // rather than by a worker. The following PSS will be used for processing 5733 // JNI refs. 5734 5735 // Use only a single queue for this PSS. 5736 G1ParScanThreadState pss(this, 0, NULL); 5737 5738 // We do not embed a reference processor in the copying/scanning 5739 // closures while we're actually processing the discovered 5740 // reference objects. 5741 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5742 5743 pss.set_evac_failure_closure(&evac_failure_cl); 5744 5745 assert(pss.refs()->is_empty(), "pre-condition"); 5746 5747 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5748 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL); 5749 5750 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5751 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL); 5752 5753 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5754 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5755 5756 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5757 // We also need to mark copied objects. 5758 copy_non_heap_cl = ©_mark_non_heap_cl; 5759 copy_metadata_cl = ©_mark_metadata_cl; 5760 } 5761 5762 // Keep alive closure. 5763 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss); 5764 5765 // Serial Complete GC closure 5766 G1STWDrainQueueClosure drain_queue(this, &pss); 5767 5768 // Setup the soft refs policy... 5769 rp->setup_policy(false); 5770 5771 ReferenceProcessorStats stats; 5772 if (!rp->processing_is_mt()) { 5773 // Serial reference processing... 5774 stats = rp->process_discovered_references(&is_alive, 5775 &keep_alive, 5776 &drain_queue, 5777 NULL, 5778 _gc_timer_stw, 5779 _gc_tracer_stw->gc_id()); 5780 } else { 5781 // Parallel reference processing 5782 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5783 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5784 5785 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5786 stats = rp->process_discovered_references(&is_alive, 5787 &keep_alive, 5788 &drain_queue, 5789 &par_task_executor, 5790 _gc_timer_stw, 5791 _gc_tracer_stw->gc_id()); 5792 } 5793 5794 _gc_tracer_stw->report_gc_reference_stats(stats); 5795 5796 // We have completed copying any necessary live referent objects. 5797 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5798 5799 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5800 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5801 } 5802 5803 // Weak Reference processing during an evacuation pause (part 2). 5804 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5805 double ref_enq_start = os::elapsedTime(); 5806 5807 ReferenceProcessor* rp = _ref_processor_stw; 5808 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5809 5810 // Now enqueue any remaining on the discovered lists on to 5811 // the pending list. 5812 if (!rp->processing_is_mt()) { 5813 // Serial reference processing... 5814 rp->enqueue_discovered_references(); 5815 } else { 5816 // Parallel reference enqueueing 5817 5818 assert(no_of_gc_workers == workers()->active_workers(), 5819 "Need to reset active workers"); 5820 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5821 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5822 5823 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5824 rp->enqueue_discovered_references(&par_task_executor); 5825 } 5826 5827 rp->verify_no_references_recorded(); 5828 assert(!rp->discovery_enabled(), "should have been disabled"); 5829 5830 // FIXME 5831 // CM's reference processing also cleans up the string and symbol tables. 5832 // Should we do that here also? We could, but it is a serial operation 5833 // and could significantly increase the pause time. 5834 5835 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5836 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5837 } 5838 5839 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) { 5840 _expand_heap_after_alloc_failure = true; 5841 _evacuation_failed = false; 5842 5843 // Should G1EvacuationFailureALot be in effect for this GC? 5844 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5845 5846 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5847 5848 // Disable the hot card cache. 5849 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5850 hot_card_cache->reset_hot_cache_claimed_index(); 5851 hot_card_cache->set_use_cache(false); 5852 5853 uint n_workers; 5854 if (G1CollectedHeap::use_parallel_gc_threads()) { 5855 n_workers = 5856 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5857 workers()->active_workers(), 5858 Threads::number_of_non_daemon_threads()); 5859 assert(UseDynamicNumberOfGCThreads || 5860 n_workers == workers()->total_workers(), 5861 "If not dynamic should be using all the workers"); 5862 workers()->set_active_workers(n_workers); 5863 set_par_threads(n_workers); 5864 } else { 5865 assert(n_par_threads() == 0, 5866 "Should be the original non-parallel value"); 5867 n_workers = 1; 5868 } 5869 5870 G1ParTask g1_par_task(this, _task_queues); 5871 5872 init_for_evac_failure(NULL); 5873 5874 rem_set()->prepare_for_younger_refs_iterate(true); 5875 5876 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5877 double start_par_time_sec = os::elapsedTime(); 5878 double end_par_time_sec; 5879 5880 { 5881 StrongRootsScope srs(this); 5882 5883 if (G1CollectedHeap::use_parallel_gc_threads()) { 5884 // The individual threads will set their evac-failure closures. 5885 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5886 // These tasks use ShareHeap::_process_strong_tasks 5887 assert(UseDynamicNumberOfGCThreads || 5888 workers()->active_workers() == workers()->total_workers(), 5889 "If not dynamic should be using all the workers"); 5890 workers()->run_task(&g1_par_task); 5891 } else { 5892 g1_par_task.set_for_termination(n_workers); 5893 g1_par_task.work(0); 5894 } 5895 end_par_time_sec = os::elapsedTime(); 5896 5897 // Closing the inner scope will execute the destructor 5898 // for the StrongRootsScope object. We record the current 5899 // elapsed time before closing the scope so that time 5900 // taken for the SRS destructor is NOT included in the 5901 // reported parallel time. 5902 } 5903 5904 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5905 g1_policy()->phase_times()->record_par_time(par_time_ms); 5906 5907 double code_root_fixup_time_ms = 5908 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5909 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5910 5911 set_par_threads(0); 5912 5913 // Process any discovered reference objects - we have 5914 // to do this _before_ we retire the GC alloc regions 5915 // as we may have to copy some 'reachable' referent 5916 // objects (and their reachable sub-graphs) that were 5917 // not copied during the pause. 5918 process_discovered_references(n_workers); 5919 5920 // Weak root processing. 5921 { 5922 G1STWIsAliveClosure is_alive(this); 5923 G1KeepAliveClosure keep_alive(this); 5924 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5925 if (G1StringDedup::is_enabled()) { 5926 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive); 5927 } 5928 } 5929 5930 release_gc_alloc_regions(n_workers, evacuation_info); 5931 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5932 5933 // Reset and re-enable the hot card cache. 5934 // Note the counts for the cards in the regions in the 5935 // collection set are reset when the collection set is freed. 5936 hot_card_cache->reset_hot_cache(); 5937 hot_card_cache->set_use_cache(true); 5938 5939 // Migrate the strong code roots attached to each region in 5940 // the collection set. Ideally we would like to do this 5941 // after we have finished the scanning/evacuation of the 5942 // strong code roots for a particular heap region. 5943 migrate_strong_code_roots(); 5944 5945 purge_code_root_memory(); 5946 5947 if (g1_policy()->during_initial_mark_pause()) { 5948 // Reset the claim values set during marking the strong code roots 5949 reset_heap_region_claim_values(); 5950 } 5951 5952 finalize_for_evac_failure(); 5953 5954 if (evacuation_failed()) { 5955 remove_self_forwarding_pointers(); 5956 5957 // Reset the G1EvacuationFailureALot counters and flags 5958 // Note: the values are reset only when an actual 5959 // evacuation failure occurs. 5960 NOT_PRODUCT(reset_evacuation_should_fail();) 5961 } 5962 5963 // Enqueue any remaining references remaining on the STW 5964 // reference processor's discovered lists. We need to do 5965 // this after the card table is cleaned (and verified) as 5966 // the act of enqueueing entries on to the pending list 5967 // will log these updates (and dirty their associated 5968 // cards). We need these updates logged to update any 5969 // RSets. 5970 enqueue_discovered_references(n_workers); 5971 5972 if (G1DeferredRSUpdate) { 5973 redirty_logged_cards(); 5974 } 5975 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5976 } 5977 5978 void G1CollectedHeap::free_region(HeapRegion* hr, 5979 FreeRegionList* free_list, 5980 bool par, 5981 bool locked) { 5982 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 5983 assert(!hr->is_empty(), "the region should not be empty"); 5984 assert(free_list != NULL, "pre-condition"); 5985 5986 // Clear the card counts for this region. 5987 // Note: we only need to do this if the region is not young 5988 // (since we don't refine cards in young regions). 5989 if (!hr->is_young()) { 5990 _cg1r->hot_card_cache()->reset_card_counts(hr); 5991 } 5992 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5993 free_list->add_ordered(hr); 5994 } 5995 5996 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5997 FreeRegionList* free_list, 5998 bool par) { 5999 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 6000 assert(free_list != NULL, "pre-condition"); 6001 6002 size_t hr_capacity = hr->capacity(); 6003 // We need to read this before we make the region non-humongous, 6004 // otherwise the information will be gone. 6005 uint last_index = hr->last_hc_index(); 6006 hr->set_notHumongous(); 6007 free_region(hr, free_list, par); 6008 6009 uint i = hr->hrs_index() + 1; 6010 while (i < last_index) { 6011 HeapRegion* curr_hr = region_at(i); 6012 assert(curr_hr->continuesHumongous(), "invariant"); 6013 curr_hr->set_notHumongous(); 6014 free_region(curr_hr, free_list, par); 6015 i += 1; 6016 } 6017 } 6018 6019 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 6020 const HeapRegionSetCount& humongous_regions_removed) { 6021 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 6022 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 6023 _old_set.bulk_remove(old_regions_removed); 6024 _humongous_set.bulk_remove(humongous_regions_removed); 6025 } 6026 6027 } 6028 6029 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 6030 assert(list != NULL, "list can't be null"); 6031 if (!list->is_empty()) { 6032 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 6033 _free_list.add_ordered(list); 6034 } 6035 } 6036 6037 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 6038 assert(_summary_bytes_used >= bytes, 6039 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT, 6040 _summary_bytes_used, bytes)); 6041 _summary_bytes_used -= bytes; 6042 } 6043 6044 class G1ParCleanupCTTask : public AbstractGangTask { 6045 G1SATBCardTableModRefBS* _ct_bs; 6046 G1CollectedHeap* _g1h; 6047 HeapRegion* volatile _su_head; 6048 public: 6049 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 6050 G1CollectedHeap* g1h) : 6051 AbstractGangTask("G1 Par Cleanup CT Task"), 6052 _ct_bs(ct_bs), _g1h(g1h) { } 6053 6054 void work(uint worker_id) { 6055 HeapRegion* r; 6056 while (r = _g1h->pop_dirty_cards_region()) { 6057 clear_cards(r); 6058 } 6059 } 6060 6061 void clear_cards(HeapRegion* r) { 6062 // Cards of the survivors should have already been dirtied. 6063 if (!r->is_survivor()) { 6064 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 6065 } 6066 } 6067 }; 6068 6069 #ifndef PRODUCT 6070 class G1VerifyCardTableCleanup: public HeapRegionClosure { 6071 G1CollectedHeap* _g1h; 6072 G1SATBCardTableModRefBS* _ct_bs; 6073 public: 6074 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 6075 : _g1h(g1h), _ct_bs(ct_bs) { } 6076 virtual bool doHeapRegion(HeapRegion* r) { 6077 if (r->is_survivor()) { 6078 _g1h->verify_dirty_region(r); 6079 } else { 6080 _g1h->verify_not_dirty_region(r); 6081 } 6082 return false; 6083 } 6084 }; 6085 6086 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 6087 // All of the region should be clean. 6088 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6089 MemRegion mr(hr->bottom(), hr->end()); 6090 ct_bs->verify_not_dirty_region(mr); 6091 } 6092 6093 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 6094 // We cannot guarantee that [bottom(),end()] is dirty. Threads 6095 // dirty allocated blocks as they allocate them. The thread that 6096 // retires each region and replaces it with a new one will do a 6097 // maximal allocation to fill in [pre_dummy_top(),end()] but will 6098 // not dirty that area (one less thing to have to do while holding 6099 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 6100 // is dirty. 6101 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6102 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 6103 if (hr->is_young()) { 6104 ct_bs->verify_g1_young_region(mr); 6105 } else { 6106 ct_bs->verify_dirty_region(mr); 6107 } 6108 } 6109 6110 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 6111 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6112 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 6113 verify_dirty_region(hr); 6114 } 6115 } 6116 6117 void G1CollectedHeap::verify_dirty_young_regions() { 6118 verify_dirty_young_list(_young_list->first_region()); 6119 } 6120 #endif 6121 6122 void G1CollectedHeap::cleanUpCardTable() { 6123 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 6124 double start = os::elapsedTime(); 6125 6126 { 6127 // Iterate over the dirty cards region list. 6128 G1ParCleanupCTTask cleanup_task(ct_bs, this); 6129 6130 if (G1CollectedHeap::use_parallel_gc_threads()) { 6131 set_par_threads(); 6132 workers()->run_task(&cleanup_task); 6133 set_par_threads(0); 6134 } else { 6135 while (_dirty_cards_region_list) { 6136 HeapRegion* r = _dirty_cards_region_list; 6137 cleanup_task.clear_cards(r); 6138 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 6139 if (_dirty_cards_region_list == r) { 6140 // The last region. 6141 _dirty_cards_region_list = NULL; 6142 } 6143 r->set_next_dirty_cards_region(NULL); 6144 } 6145 } 6146 #ifndef PRODUCT 6147 if (G1VerifyCTCleanup || VerifyAfterGC) { 6148 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 6149 heap_region_iterate(&cleanup_verifier); 6150 } 6151 #endif 6152 } 6153 6154 double elapsed = os::elapsedTime() - start; 6155 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 6156 } 6157 6158 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) { 6159 size_t pre_used = 0; 6160 FreeRegionList local_free_list("Local List for CSet Freeing"); 6161 6162 double young_time_ms = 0.0; 6163 double non_young_time_ms = 0.0; 6164 6165 // Since the collection set is a superset of the the young list, 6166 // all we need to do to clear the young list is clear its 6167 // head and length, and unlink any young regions in the code below 6168 _young_list->clear(); 6169 6170 G1CollectorPolicy* policy = g1_policy(); 6171 6172 double start_sec = os::elapsedTime(); 6173 bool non_young = true; 6174 6175 HeapRegion* cur = cs_head; 6176 int age_bound = -1; 6177 size_t rs_lengths = 0; 6178 6179 while (cur != NULL) { 6180 assert(!is_on_master_free_list(cur), "sanity"); 6181 if (non_young) { 6182 if (cur->is_young()) { 6183 double end_sec = os::elapsedTime(); 6184 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6185 non_young_time_ms += elapsed_ms; 6186 6187 start_sec = os::elapsedTime(); 6188 non_young = false; 6189 } 6190 } else { 6191 if (!cur->is_young()) { 6192 double end_sec = os::elapsedTime(); 6193 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6194 young_time_ms += elapsed_ms; 6195 6196 start_sec = os::elapsedTime(); 6197 non_young = true; 6198 } 6199 } 6200 6201 rs_lengths += cur->rem_set()->occupied_locked(); 6202 6203 HeapRegion* next = cur->next_in_collection_set(); 6204 assert(cur->in_collection_set(), "bad CS"); 6205 cur->set_next_in_collection_set(NULL); 6206 cur->set_in_collection_set(false); 6207 6208 if (cur->is_young()) { 6209 int index = cur->young_index_in_cset(); 6210 assert(index != -1, "invariant"); 6211 assert((uint) index < policy->young_cset_region_length(), "invariant"); 6212 size_t words_survived = _surviving_young_words[index]; 6213 cur->record_surv_words_in_group(words_survived); 6214 6215 // At this point the we have 'popped' cur from the collection set 6216 // (linked via next_in_collection_set()) but it is still in the 6217 // young list (linked via next_young_region()). Clear the 6218 // _next_young_region field. 6219 cur->set_next_young_region(NULL); 6220 } else { 6221 int index = cur->young_index_in_cset(); 6222 assert(index == -1, "invariant"); 6223 } 6224 6225 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6226 (!cur->is_young() && cur->young_index_in_cset() == -1), 6227 "invariant" ); 6228 6229 if (!cur->evacuation_failed()) { 6230 MemRegion used_mr = cur->used_region(); 6231 6232 // And the region is empty. 6233 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6234 pre_used += cur->used(); 6235 free_region(cur, &local_free_list, false /* par */, true /* locked */); 6236 } else { 6237 cur->uninstall_surv_rate_group(); 6238 if (cur->is_young()) { 6239 cur->set_young_index_in_cset(-1); 6240 } 6241 cur->set_not_young(); 6242 cur->set_evacuation_failed(false); 6243 // The region is now considered to be old. 6244 _old_set.add(cur); 6245 evacuation_info.increment_collectionset_used_after(cur->used()); 6246 } 6247 cur = next; 6248 } 6249 6250 evacuation_info.set_regions_freed(local_free_list.length()); 6251 policy->record_max_rs_lengths(rs_lengths); 6252 policy->cset_regions_freed(); 6253 6254 double end_sec = os::elapsedTime(); 6255 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6256 6257 if (non_young) { 6258 non_young_time_ms += elapsed_ms; 6259 } else { 6260 young_time_ms += elapsed_ms; 6261 } 6262 6263 prepend_to_freelist(&local_free_list); 6264 decrement_summary_bytes(pre_used); 6265 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6266 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6267 } 6268 6269 // This routine is similar to the above but does not record 6270 // any policy statistics or update free lists; we are abandoning 6271 // the current incremental collection set in preparation of a 6272 // full collection. After the full GC we will start to build up 6273 // the incremental collection set again. 6274 // This is only called when we're doing a full collection 6275 // and is immediately followed by the tearing down of the young list. 6276 6277 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6278 HeapRegion* cur = cs_head; 6279 6280 while (cur != NULL) { 6281 HeapRegion* next = cur->next_in_collection_set(); 6282 assert(cur->in_collection_set(), "bad CS"); 6283 cur->set_next_in_collection_set(NULL); 6284 cur->set_in_collection_set(false); 6285 cur->set_young_index_in_cset(-1); 6286 cur = next; 6287 } 6288 } 6289 6290 void G1CollectedHeap::set_free_regions_coming() { 6291 if (G1ConcRegionFreeingVerbose) { 6292 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6293 "setting free regions coming"); 6294 } 6295 6296 assert(!free_regions_coming(), "pre-condition"); 6297 _free_regions_coming = true; 6298 } 6299 6300 void G1CollectedHeap::reset_free_regions_coming() { 6301 assert(free_regions_coming(), "pre-condition"); 6302 6303 { 6304 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6305 _free_regions_coming = false; 6306 SecondaryFreeList_lock->notify_all(); 6307 } 6308 6309 if (G1ConcRegionFreeingVerbose) { 6310 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6311 "reset free regions coming"); 6312 } 6313 } 6314 6315 void G1CollectedHeap::wait_while_free_regions_coming() { 6316 // Most of the time we won't have to wait, so let's do a quick test 6317 // first before we take the lock. 6318 if (!free_regions_coming()) { 6319 return; 6320 } 6321 6322 if (G1ConcRegionFreeingVerbose) { 6323 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6324 "waiting for free regions"); 6325 } 6326 6327 { 6328 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6329 while (free_regions_coming()) { 6330 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6331 } 6332 } 6333 6334 if (G1ConcRegionFreeingVerbose) { 6335 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6336 "done waiting for free regions"); 6337 } 6338 } 6339 6340 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6341 assert(heap_lock_held_for_gc(), 6342 "the heap lock should already be held by or for this thread"); 6343 _young_list->push_region(hr); 6344 } 6345 6346 class NoYoungRegionsClosure: public HeapRegionClosure { 6347 private: 6348 bool _success; 6349 public: 6350 NoYoungRegionsClosure() : _success(true) { } 6351 bool doHeapRegion(HeapRegion* r) { 6352 if (r->is_young()) { 6353 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6354 r->bottom(), r->end()); 6355 _success = false; 6356 } 6357 return false; 6358 } 6359 bool success() { return _success; } 6360 }; 6361 6362 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6363 bool ret = _young_list->check_list_empty(check_sample); 6364 6365 if (check_heap) { 6366 NoYoungRegionsClosure closure; 6367 heap_region_iterate(&closure); 6368 ret = ret && closure.success(); 6369 } 6370 6371 return ret; 6372 } 6373 6374 class TearDownRegionSetsClosure : public HeapRegionClosure { 6375 private: 6376 HeapRegionSet *_old_set; 6377 6378 public: 6379 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 6380 6381 bool doHeapRegion(HeapRegion* r) { 6382 if (r->is_empty()) { 6383 // We ignore empty regions, we'll empty the free list afterwards 6384 } else if (r->is_young()) { 6385 // We ignore young regions, we'll empty the young list afterwards 6386 } else if (r->isHumongous()) { 6387 // We ignore humongous regions, we're not tearing down the 6388 // humongous region set 6389 } else { 6390 // The rest should be old 6391 _old_set->remove(r); 6392 } 6393 return false; 6394 } 6395 6396 ~TearDownRegionSetsClosure() { 6397 assert(_old_set->is_empty(), "post-condition"); 6398 } 6399 }; 6400 6401 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6402 assert_at_safepoint(true /* should_be_vm_thread */); 6403 6404 if (!free_list_only) { 6405 TearDownRegionSetsClosure cl(&_old_set); 6406 heap_region_iterate(&cl); 6407 6408 // Note that emptying the _young_list is postponed and instead done as 6409 // the first step when rebuilding the regions sets again. The reason for 6410 // this is that during a full GC string deduplication needs to know if 6411 // a collected region was young or old when the full GC was initiated. 6412 } 6413 _free_list.remove_all(); 6414 } 6415 6416 class RebuildRegionSetsClosure : public HeapRegionClosure { 6417 private: 6418 bool _free_list_only; 6419 HeapRegionSet* _old_set; 6420 FreeRegionList* _free_list; 6421 size_t _total_used; 6422 6423 public: 6424 RebuildRegionSetsClosure(bool free_list_only, 6425 HeapRegionSet* old_set, FreeRegionList* free_list) : 6426 _free_list_only(free_list_only), 6427 _old_set(old_set), _free_list(free_list), _total_used(0) { 6428 assert(_free_list->is_empty(), "pre-condition"); 6429 if (!free_list_only) { 6430 assert(_old_set->is_empty(), "pre-condition"); 6431 } 6432 } 6433 6434 bool doHeapRegion(HeapRegion* r) { 6435 if (r->continuesHumongous()) { 6436 return false; 6437 } 6438 6439 if (r->is_empty()) { 6440 // Add free regions to the free list 6441 _free_list->add_as_tail(r); 6442 } else if (!_free_list_only) { 6443 assert(!r->is_young(), "we should not come across young regions"); 6444 6445 if (r->isHumongous()) { 6446 // We ignore humongous regions, we left the humongous set unchanged 6447 } else { 6448 // The rest should be old, add them to the old set 6449 _old_set->add(r); 6450 } 6451 _total_used += r->used(); 6452 } 6453 6454 return false; 6455 } 6456 6457 size_t total_used() { 6458 return _total_used; 6459 } 6460 }; 6461 6462 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6463 assert_at_safepoint(true /* should_be_vm_thread */); 6464 6465 if (!free_list_only) { 6466 _young_list->empty_list(); 6467 } 6468 6469 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); 6470 heap_region_iterate(&cl); 6471 6472 if (!free_list_only) { 6473 _summary_bytes_used = cl.total_used(); 6474 } 6475 assert(_summary_bytes_used == recalculate_used(), 6476 err_msg("inconsistent _summary_bytes_used, " 6477 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6478 _summary_bytes_used, recalculate_used())); 6479 } 6480 6481 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6482 _refine_cte_cl->set_concurrent(concurrent); 6483 } 6484 6485 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6486 HeapRegion* hr = heap_region_containing(p); 6487 if (hr == NULL) { 6488 return false; 6489 } else { 6490 return hr->is_in(p); 6491 } 6492 } 6493 6494 // Methods for the mutator alloc region 6495 6496 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6497 bool force) { 6498 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6499 assert(!force || g1_policy()->can_expand_young_list(), 6500 "if force is true we should be able to expand the young list"); 6501 bool young_list_full = g1_policy()->is_young_list_full(); 6502 if (force || !young_list_full) { 6503 HeapRegion* new_alloc_region = new_region(word_size, 6504 false /* is_old */, 6505 false /* do_expand */); 6506 if (new_alloc_region != NULL) { 6507 set_region_short_lived_locked(new_alloc_region); 6508 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6509 return new_alloc_region; 6510 } 6511 } 6512 return NULL; 6513 } 6514 6515 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6516 size_t allocated_bytes) { 6517 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6518 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 6519 6520 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6521 _summary_bytes_used += allocated_bytes; 6522 _hr_printer.retire(alloc_region); 6523 // We update the eden sizes here, when the region is retired, 6524 // instead of when it's allocated, since this is the point that its 6525 // used space has been recored in _summary_bytes_used. 6526 g1mm()->update_eden_size(); 6527 } 6528 6529 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 6530 bool force) { 6531 return _g1h->new_mutator_alloc_region(word_size, force); 6532 } 6533 6534 void G1CollectedHeap::set_par_threads() { 6535 // Don't change the number of workers. Use the value previously set 6536 // in the workgroup. 6537 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6538 uint n_workers = workers()->active_workers(); 6539 assert(UseDynamicNumberOfGCThreads || 6540 n_workers == workers()->total_workers(), 6541 "Otherwise should be using the total number of workers"); 6542 if (n_workers == 0) { 6543 assert(false, "Should have been set in prior evacuation pause."); 6544 n_workers = ParallelGCThreads; 6545 workers()->set_active_workers(n_workers); 6546 } 6547 set_par_threads(n_workers); 6548 } 6549 6550 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 6551 size_t allocated_bytes) { 6552 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 6553 } 6554 6555 // Methods for the GC alloc regions 6556 6557 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6558 uint count, 6559 GCAllocPurpose ap) { 6560 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6561 6562 if (count < g1_policy()->max_regions(ap)) { 6563 bool survivor = (ap == GCAllocForSurvived); 6564 HeapRegion* new_alloc_region = new_region(word_size, 6565 !survivor, 6566 true /* do_expand */); 6567 if (new_alloc_region != NULL) { 6568 // We really only need to do this for old regions given that we 6569 // should never scan survivors. But it doesn't hurt to do it 6570 // for survivors too. 6571 new_alloc_region->set_saved_mark(); 6572 if (survivor) { 6573 new_alloc_region->set_survivor(); 6574 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6575 } else { 6576 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6577 } 6578 bool during_im = g1_policy()->during_initial_mark_pause(); 6579 new_alloc_region->note_start_of_copying(during_im); 6580 return new_alloc_region; 6581 } else { 6582 g1_policy()->note_alloc_region_limit_reached(ap); 6583 } 6584 } 6585 return NULL; 6586 } 6587 6588 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6589 size_t allocated_bytes, 6590 GCAllocPurpose ap) { 6591 bool during_im = g1_policy()->during_initial_mark_pause(); 6592 alloc_region->note_end_of_copying(during_im); 6593 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6594 if (ap == GCAllocForSurvived) { 6595 young_list()->add_survivor_region(alloc_region); 6596 } else { 6597 _old_set.add(alloc_region); 6598 } 6599 _hr_printer.retire(alloc_region); 6600 } 6601 6602 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 6603 bool force) { 6604 assert(!force, "not supported for GC alloc regions"); 6605 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 6606 } 6607 6608 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 6609 size_t allocated_bytes) { 6610 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6611 GCAllocForSurvived); 6612 } 6613 6614 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 6615 bool force) { 6616 assert(!force, "not supported for GC alloc regions"); 6617 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 6618 } 6619 6620 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 6621 size_t allocated_bytes) { 6622 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6623 GCAllocForTenured); 6624 } 6625 // Heap region set verification 6626 6627 class VerifyRegionListsClosure : public HeapRegionClosure { 6628 private: 6629 HeapRegionSet* _old_set; 6630 HeapRegionSet* _humongous_set; 6631 FreeRegionList* _free_list; 6632 6633 public: 6634 HeapRegionSetCount _old_count; 6635 HeapRegionSetCount _humongous_count; 6636 HeapRegionSetCount _free_count; 6637 6638 VerifyRegionListsClosure(HeapRegionSet* old_set, 6639 HeapRegionSet* humongous_set, 6640 FreeRegionList* free_list) : 6641 _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list), 6642 _old_count(), _humongous_count(), _free_count(){ } 6643 6644 bool doHeapRegion(HeapRegion* hr) { 6645 if (hr->continuesHumongous()) { 6646 return false; 6647 } 6648 6649 if (hr->is_young()) { 6650 // TODO 6651 } else if (hr->startsHumongous()) { 6652 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->region_num())); 6653 _humongous_count.increment(1u, hr->capacity()); 6654 } else if (hr->is_empty()) { 6655 assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->region_num())); 6656 _free_count.increment(1u, hr->capacity()); 6657 } else { 6658 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->region_num())); 6659 _old_count.increment(1u, hr->capacity()); 6660 } 6661 return false; 6662 } 6663 6664 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) { 6665 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length())); 6666 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6667 old_set->total_capacity_bytes(), _old_count.capacity())); 6668 6669 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length())); 6670 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6671 humongous_set->total_capacity_bytes(), _humongous_count.capacity())); 6672 6673 guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length())); 6674 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6675 free_list->total_capacity_bytes(), _free_count.capacity())); 6676 } 6677 }; 6678 6679 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 6680 HeapWord* bottom) { 6681 HeapWord* end = bottom + HeapRegion::GrainWords; 6682 MemRegion mr(bottom, end); 6683 assert(_g1_reserved.contains(mr), "invariant"); 6684 // This might return NULL if the allocation fails 6685 return new HeapRegion(hrs_index, _bot_shared, mr); 6686 } 6687 6688 void G1CollectedHeap::verify_region_sets() { 6689 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6690 6691 // First, check the explicit lists. 6692 _free_list.verify_list(); 6693 { 6694 // Given that a concurrent operation might be adding regions to 6695 // the secondary free list we have to take the lock before 6696 // verifying it. 6697 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6698 _secondary_free_list.verify_list(); 6699 } 6700 6701 // If a concurrent region freeing operation is in progress it will 6702 // be difficult to correctly attributed any free regions we come 6703 // across to the correct free list given that they might belong to 6704 // one of several (free_list, secondary_free_list, any local lists, 6705 // etc.). So, if that's the case we will skip the rest of the 6706 // verification operation. Alternatively, waiting for the concurrent 6707 // operation to complete will have a non-trivial effect on the GC's 6708 // operation (no concurrent operation will last longer than the 6709 // interval between two calls to verification) and it might hide 6710 // any issues that we would like to catch during testing. 6711 if (free_regions_coming()) { 6712 return; 6713 } 6714 6715 // Make sure we append the secondary_free_list on the free_list so 6716 // that all free regions we will come across can be safely 6717 // attributed to the free_list. 6718 append_secondary_free_list_if_not_empty_with_lock(); 6719 6720 // Finally, make sure that the region accounting in the lists is 6721 // consistent with what we see in the heap. 6722 6723 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); 6724 heap_region_iterate(&cl); 6725 cl.verify_counts(&_old_set, &_humongous_set, &_free_list); 6726 } 6727 6728 // Optimized nmethod scanning 6729 6730 class RegisterNMethodOopClosure: public OopClosure { 6731 G1CollectedHeap* _g1h; 6732 nmethod* _nm; 6733 6734 template <class T> void do_oop_work(T* p) { 6735 T heap_oop = oopDesc::load_heap_oop(p); 6736 if (!oopDesc::is_null(heap_oop)) { 6737 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6738 HeapRegion* hr = _g1h->heap_region_containing(obj); 6739 assert(!hr->continuesHumongous(), 6740 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6741 " starting at "HR_FORMAT, 6742 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6743 6744 // HeapRegion::add_strong_code_root() avoids adding duplicate 6745 // entries but having duplicates is OK since we "mark" nmethods 6746 // as visited when we scan the strong code root lists during the GC. 6747 hr->add_strong_code_root(_nm); 6748 assert(hr->rem_set()->strong_code_roots_list_contains(_nm), 6749 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT, 6750 _nm, HR_FORMAT_PARAMS(hr))); 6751 } 6752 } 6753 6754 public: 6755 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6756 _g1h(g1h), _nm(nm) {} 6757 6758 void do_oop(oop* p) { do_oop_work(p); } 6759 void do_oop(narrowOop* p) { do_oop_work(p); } 6760 }; 6761 6762 class UnregisterNMethodOopClosure: public OopClosure { 6763 G1CollectedHeap* _g1h; 6764 nmethod* _nm; 6765 6766 template <class T> void do_oop_work(T* p) { 6767 T heap_oop = oopDesc::load_heap_oop(p); 6768 if (!oopDesc::is_null(heap_oop)) { 6769 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6770 HeapRegion* hr = _g1h->heap_region_containing(obj); 6771 assert(!hr->continuesHumongous(), 6772 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6773 " starting at "HR_FORMAT, 6774 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6775 6776 hr->remove_strong_code_root(_nm); 6777 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm), 6778 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT, 6779 _nm, HR_FORMAT_PARAMS(hr))); 6780 } 6781 } 6782 6783 public: 6784 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6785 _g1h(g1h), _nm(nm) {} 6786 6787 void do_oop(oop* p) { do_oop_work(p); } 6788 void do_oop(narrowOop* p) { do_oop_work(p); } 6789 }; 6790 6791 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6792 CollectedHeap::register_nmethod(nm); 6793 6794 guarantee(nm != NULL, "sanity"); 6795 RegisterNMethodOopClosure reg_cl(this, nm); 6796 nm->oops_do(®_cl); 6797 } 6798 6799 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6800 CollectedHeap::unregister_nmethod(nm); 6801 6802 guarantee(nm != NULL, "sanity"); 6803 UnregisterNMethodOopClosure reg_cl(this, nm); 6804 nm->oops_do(®_cl, true); 6805 } 6806 6807 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure { 6808 public: 6809 bool doHeapRegion(HeapRegion *hr) { 6810 assert(!hr->isHumongous(), 6811 err_msg("humongous region "HR_FORMAT" should not have been added to collection set", 6812 HR_FORMAT_PARAMS(hr))); 6813 hr->migrate_strong_code_roots(); 6814 return false; 6815 } 6816 }; 6817 6818 void G1CollectedHeap::migrate_strong_code_roots() { 6819 MigrateCodeRootsHeapRegionClosure cl; 6820 double migrate_start = os::elapsedTime(); 6821 collection_set_iterate(&cl); 6822 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0; 6823 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms); 6824 } 6825 6826 void G1CollectedHeap::purge_code_root_memory() { 6827 double purge_start = os::elapsedTime(); 6828 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent); 6829 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6830 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6831 } 6832 6833 // Mark all the code roots that point into regions *not* in the 6834 // collection set. 6835 // 6836 // Note we do not want to use a "marking" CodeBlobToOopClosure while 6837 // walking the the code roots lists of regions not in the collection 6838 // set. Suppose we have an nmethod (M) that points to objects in two 6839 // separate regions - one in the collection set (R1) and one not (R2). 6840 // Using a "marking" CodeBlobToOopClosure here would result in "marking" 6841 // nmethod M when walking the code roots for R1. When we come to scan 6842 // the code roots for R2, we would see that M is already marked and it 6843 // would be skipped and the objects in R2 that are referenced from M 6844 // would not be evacuated. 6845 6846 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure { 6847 6848 class MarkStrongCodeRootOopClosure: public OopClosure { 6849 ConcurrentMark* _cm; 6850 HeapRegion* _hr; 6851 uint _worker_id; 6852 6853 template <class T> void do_oop_work(T* p) { 6854 T heap_oop = oopDesc::load_heap_oop(p); 6855 if (!oopDesc::is_null(heap_oop)) { 6856 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6857 // Only mark objects in the region (which is assumed 6858 // to be not in the collection set). 6859 if (_hr->is_in(obj)) { 6860 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 6861 } 6862 } 6863 } 6864 6865 public: 6866 MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) : 6867 _cm(cm), _hr(hr), _worker_id(worker_id) { 6868 assert(!_hr->in_collection_set(), "sanity"); 6869 } 6870 6871 void do_oop(narrowOop* p) { do_oop_work(p); } 6872 void do_oop(oop* p) { do_oop_work(p); } 6873 }; 6874 6875 MarkStrongCodeRootOopClosure _oop_cl; 6876 6877 public: 6878 MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id): 6879 _oop_cl(cm, hr, worker_id) {} 6880 6881 void do_code_blob(CodeBlob* cb) { 6882 nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null(); 6883 if (nm != NULL) { 6884 nm->oops_do(&_oop_cl); 6885 } 6886 } 6887 }; 6888 6889 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure { 6890 G1CollectedHeap* _g1h; 6891 uint _worker_id; 6892 6893 public: 6894 MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) : 6895 _g1h(g1h), _worker_id(worker_id) {} 6896 6897 bool doHeapRegion(HeapRegion *hr) { 6898 HeapRegionRemSet* hrrs = hr->rem_set(); 6899 if (hr->continuesHumongous()) { 6900 // Code roots should never be attached to a continuation of a humongous region 6901 assert(hrrs->strong_code_roots_list_length() == 0, 6902 err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT 6903 " starting at "HR_FORMAT", but has "SIZE_FORMAT, 6904 HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()), 6905 hrrs->strong_code_roots_list_length())); 6906 return false; 6907 } 6908 6909 if (hr->in_collection_set()) { 6910 // Don't mark code roots into regions in the collection set here. 6911 // They will be marked when we scan them. 6912 return false; 6913 } 6914 6915 MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id); 6916 hr->strong_code_roots_do(&cb_cl); 6917 return false; 6918 } 6919 }; 6920 6921 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) { 6922 MarkStrongCodeRootsHRClosure cl(this, worker_id); 6923 if (G1CollectedHeap::use_parallel_gc_threads()) { 6924 heap_region_par_iterate_chunked(&cl, 6925 worker_id, 6926 workers()->active_workers(), 6927 HeapRegion::ParMarkRootClaimValue); 6928 } else { 6929 heap_region_iterate(&cl); 6930 } 6931 } 6932 6933 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6934 G1CollectedHeap* _g1h; 6935 6936 public: 6937 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6938 _g1h(g1h) {} 6939 6940 void do_code_blob(CodeBlob* cb) { 6941 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6942 if (nm == NULL) { 6943 return; 6944 } 6945 6946 if (ScavengeRootsInCode) { 6947 _g1h->register_nmethod(nm); 6948 } 6949 } 6950 }; 6951 6952 void G1CollectedHeap::rebuild_strong_code_roots() { 6953 RebuildStrongCodeRootClosure blob_cl(this); 6954 CodeCache::blobs_do(&blob_cl); 6955 }