1 /* 2 * Copyright (c) 2001, 2013, 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 #include "precompiled.hpp" 26 #include "code/icBuffer.hpp" 27 #include "gc_implementation/g1/bufferingOopClosure.hpp" 28 #include "gc_implementation/g1/concurrentG1Refine.hpp" 29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp" 32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 33 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 34 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 35 #include "gc_implementation/g1/g1EvacFailure.hpp" 36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 37 #include "gc_implementation/g1/g1Log.hpp" 38 #include "gc_implementation/g1/g1MarkSweep.hpp" 39 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 40 #include "gc_implementation/g1/g1RemSet.inline.hpp" 41 #include "gc_implementation/g1/heapRegion.inline.hpp" 42 #include "gc_implementation/g1/heapRegionRemSet.hpp" 43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp" 44 #include "gc_implementation/g1/vm_operations_g1.hpp" 45 #include "gc_implementation/shared/isGCActiveMark.hpp" 46 #include "memory/gcLocker.inline.hpp" 47 #include "memory/genOopClosures.inline.hpp" 48 #include "memory/generationSpec.hpp" 49 #include "memory/referenceProcessor.hpp" 50 #include "oops/oop.inline.hpp" 51 #include "oops/oop.pcgc.inline.hpp" 52 #include "runtime/aprofiler.hpp" 53 #include "runtime/vmThread.hpp" 54 55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 56 57 // turn it on so that the contents of the young list (scan-only / 58 // to-be-collected) are printed at "strategic" points before / during 59 // / after the collection --- this is useful for debugging 60 #define YOUNG_LIST_VERBOSE 0 61 // CURRENT STATUS 62 // This file is under construction. Search for "FIXME". 63 64 // INVARIANTS/NOTES 65 // 66 // All allocation activity covered by the G1CollectedHeap interface is 67 // serialized by acquiring the HeapLock. This happens in mem_allocate 68 // and allocate_new_tlab, which are the "entry" points to the 69 // allocation code from the rest of the JVM. (Note that this does not 70 // apply to TLAB allocation, which is not part of this interface: it 71 // is done by clients of this interface.) 72 73 // Notes on implementation of parallelism in different tasks. 74 // 75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism. 76 // The number of GC workers is passed to heap_region_par_iterate_chunked(). 77 // It does use run_task() which sets _n_workers in the task. 78 // G1ParTask executes g1_process_strong_roots() -> 79 // SharedHeap::process_strong_roots() which calls eventuall to 80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses 81 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also 82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). 83 // 84 85 // Local to this file. 86 87 class RefineCardTableEntryClosure: public CardTableEntryClosure { 88 SuspendibleThreadSet* _sts; 89 G1RemSet* _g1rs; 90 ConcurrentG1Refine* _cg1r; 91 bool _concurrent; 92 public: 93 RefineCardTableEntryClosure(SuspendibleThreadSet* sts, 94 G1RemSet* g1rs, 95 ConcurrentG1Refine* cg1r) : 96 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true) 97 {} 98 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 99 bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false); 100 // This path is executed by the concurrent refine or mutator threads, 101 // concurrently, and so we do not care if card_ptr contains references 102 // that point into the collection set. 103 assert(!oops_into_cset, "should be"); 104 105 if (_concurrent && _sts->should_yield()) { 106 // Caller will actually yield. 107 return false; 108 } 109 // Otherwise, we finished successfully; return true. 110 return true; 111 } 112 void set_concurrent(bool b) { _concurrent = b; } 113 }; 114 115 116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 117 int _calls; 118 G1CollectedHeap* _g1h; 119 CardTableModRefBS* _ctbs; 120 int _histo[256]; 121 public: 122 ClearLoggedCardTableEntryClosure() : 123 _calls(0) 124 { 125 _g1h = G1CollectedHeap::heap(); 126 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 127 for (int i = 0; i < 256; i++) _histo[i] = 0; 128 } 129 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 130 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 131 _calls++; 132 unsigned char* ujb = (unsigned char*)card_ptr; 133 int ind = (int)(*ujb); 134 _histo[ind]++; 135 *card_ptr = -1; 136 } 137 return true; 138 } 139 int calls() { return _calls; } 140 void print_histo() { 141 gclog_or_tty->print_cr("Card table value histogram:"); 142 for (int i = 0; i < 256; i++) { 143 if (_histo[i] != 0) { 144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 145 } 146 } 147 } 148 }; 149 150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure { 151 int _calls; 152 G1CollectedHeap* _g1h; 153 CardTableModRefBS* _ctbs; 154 public: 155 RedirtyLoggedCardTableEntryClosure() : 156 _calls(0) 157 { 158 _g1h = G1CollectedHeap::heap(); 159 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 160 } 161 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 162 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 163 _calls++; 164 *card_ptr = 0; 165 } 166 return true; 167 } 168 int calls() { return _calls; } 169 }; 170 171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure { 172 public: 173 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 174 *card_ptr = CardTableModRefBS::dirty_card_val(); 175 return true; 176 } 177 }; 178 179 YoungList::YoungList(G1CollectedHeap* g1h) : 180 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 181 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 182 guarantee(check_list_empty(false), "just making sure..."); 183 } 184 185 void YoungList::push_region(HeapRegion *hr) { 186 assert(!hr->is_young(), "should not already be young"); 187 assert(hr->get_next_young_region() == NULL, "cause it should!"); 188 189 hr->set_next_young_region(_head); 190 _head = hr; 191 192 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 193 ++_length; 194 } 195 196 void YoungList::add_survivor_region(HeapRegion* hr) { 197 assert(hr->is_survivor(), "should be flagged as survivor region"); 198 assert(hr->get_next_young_region() == NULL, "cause it should!"); 199 200 hr->set_next_young_region(_survivor_head); 201 if (_survivor_head == NULL) { 202 _survivor_tail = hr; 203 } 204 _survivor_head = hr; 205 ++_survivor_length; 206 } 207 208 void YoungList::empty_list(HeapRegion* list) { 209 while (list != NULL) { 210 HeapRegion* next = list->get_next_young_region(); 211 list->set_next_young_region(NULL); 212 list->uninstall_surv_rate_group(); 213 list->set_not_young(); 214 list = next; 215 } 216 } 217 218 void YoungList::empty_list() { 219 assert(check_list_well_formed(), "young list should be well formed"); 220 221 empty_list(_head); 222 _head = NULL; 223 _length = 0; 224 225 empty_list(_survivor_head); 226 _survivor_head = NULL; 227 _survivor_tail = NULL; 228 _survivor_length = 0; 229 230 _last_sampled_rs_lengths = 0; 231 232 assert(check_list_empty(false), "just making sure..."); 233 } 234 235 bool YoungList::check_list_well_formed() { 236 bool ret = true; 237 238 uint length = 0; 239 HeapRegion* curr = _head; 240 HeapRegion* last = NULL; 241 while (curr != NULL) { 242 if (!curr->is_young()) { 243 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 244 "incorrectly tagged (y: %d, surv: %d)", 245 curr->bottom(), curr->end(), 246 curr->is_young(), curr->is_survivor()); 247 ret = false; 248 } 249 ++length; 250 last = curr; 251 curr = curr->get_next_young_region(); 252 } 253 ret = ret && (length == _length); 254 255 if (!ret) { 256 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 257 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 258 length, _length); 259 } 260 261 return ret; 262 } 263 264 bool YoungList::check_list_empty(bool check_sample) { 265 bool ret = true; 266 267 if (_length != 0) { 268 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 269 _length); 270 ret = false; 271 } 272 if (check_sample && _last_sampled_rs_lengths != 0) { 273 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 274 ret = false; 275 } 276 if (_head != NULL) { 277 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 278 ret = false; 279 } 280 if (!ret) { 281 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 282 } 283 284 return ret; 285 } 286 287 void 288 YoungList::rs_length_sampling_init() { 289 _sampled_rs_lengths = 0; 290 _curr = _head; 291 } 292 293 bool 294 YoungList::rs_length_sampling_more() { 295 return _curr != NULL; 296 } 297 298 void 299 YoungList::rs_length_sampling_next() { 300 assert( _curr != NULL, "invariant" ); 301 size_t rs_length = _curr->rem_set()->occupied(); 302 303 _sampled_rs_lengths += rs_length; 304 305 // The current region may not yet have been added to the 306 // incremental collection set (it gets added when it is 307 // retired as the current allocation region). 308 if (_curr->in_collection_set()) { 309 // Update the collection set policy information for this region 310 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 311 } 312 313 _curr = _curr->get_next_young_region(); 314 if (_curr == NULL) { 315 _last_sampled_rs_lengths = _sampled_rs_lengths; 316 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 317 } 318 } 319 320 void 321 YoungList::reset_auxilary_lists() { 322 guarantee( is_empty(), "young list should be empty" ); 323 assert(check_list_well_formed(), "young list should be well formed"); 324 325 // Add survivor regions to SurvRateGroup. 326 _g1h->g1_policy()->note_start_adding_survivor_regions(); 327 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 328 329 int young_index_in_cset = 0; 330 for (HeapRegion* curr = _survivor_head; 331 curr != NULL; 332 curr = curr->get_next_young_region()) { 333 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 334 335 // The region is a non-empty survivor so let's add it to 336 // the incremental collection set for the next evacuation 337 // pause. 338 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 339 young_index_in_cset += 1; 340 } 341 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 342 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 343 344 _head = _survivor_head; 345 _length = _survivor_length; 346 if (_survivor_head != NULL) { 347 assert(_survivor_tail != NULL, "cause it shouldn't be"); 348 assert(_survivor_length > 0, "invariant"); 349 _survivor_tail->set_next_young_region(NULL); 350 } 351 352 // Don't clear the survivor list handles until the start of 353 // the next evacuation pause - we need it in order to re-tag 354 // the survivor regions from this evacuation pause as 'young' 355 // at the start of the next. 356 357 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 358 359 assert(check_list_well_formed(), "young list should be well formed"); 360 } 361 362 void YoungList::print() { 363 HeapRegion* lists[] = {_head, _survivor_head}; 364 const char* names[] = {"YOUNG", "SURVIVOR"}; 365 366 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 367 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 368 HeapRegion *curr = lists[list]; 369 if (curr == NULL) 370 gclog_or_tty->print_cr(" empty"); 371 while (curr != NULL) { 372 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d", 373 HR_FORMAT_PARAMS(curr), 374 curr->prev_top_at_mark_start(), 375 curr->next_top_at_mark_start(), 376 curr->age_in_surv_rate_group_cond()); 377 curr = curr->get_next_young_region(); 378 } 379 } 380 381 gclog_or_tty->print_cr(""); 382 } 383 384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 385 { 386 // Claim the right to put the region on the dirty cards region list 387 // by installing a self pointer. 388 HeapRegion* next = hr->get_next_dirty_cards_region(); 389 if (next == NULL) { 390 HeapRegion* res = (HeapRegion*) 391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 392 NULL); 393 if (res == NULL) { 394 HeapRegion* head; 395 do { 396 // Put the region to the dirty cards region list. 397 head = _dirty_cards_region_list; 398 next = (HeapRegion*) 399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 400 if (next == head) { 401 assert(hr->get_next_dirty_cards_region() == hr, 402 "hr->get_next_dirty_cards_region() != hr"); 403 if (next == NULL) { 404 // The last region in the list points to itself. 405 hr->set_next_dirty_cards_region(hr); 406 } else { 407 hr->set_next_dirty_cards_region(next); 408 } 409 } 410 } while (next != head); 411 } 412 } 413 } 414 415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 416 { 417 HeapRegion* head; 418 HeapRegion* hr; 419 do { 420 head = _dirty_cards_region_list; 421 if (head == NULL) { 422 return NULL; 423 } 424 HeapRegion* new_head = head->get_next_dirty_cards_region(); 425 if (head == new_head) { 426 // The last region. 427 new_head = NULL; 428 } 429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 430 head); 431 } while (hr != head); 432 assert(hr != NULL, "invariant"); 433 hr->set_next_dirty_cards_region(NULL); 434 return hr; 435 } 436 437 void G1CollectedHeap::stop_conc_gc_threads() { 438 _cg1r->stop(); 439 _cmThread->stop(); 440 } 441 442 #ifdef ASSERT 443 // A region is added to the collection set as it is retired 444 // so an address p can point to a region which will be in the 445 // collection set but has not yet been retired. This method 446 // therefore is only accurate during a GC pause after all 447 // regions have been retired. It is used for debugging 448 // to check if an nmethod has references to objects that can 449 // be move during a partial collection. Though it can be 450 // inaccurate, it is sufficient for G1 because the conservative 451 // implementation of is_scavengable() for G1 will indicate that 452 // all nmethods must be scanned during a partial collection. 453 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 454 HeapRegion* hr = heap_region_containing(p); 455 return hr != NULL && hr->in_collection_set(); 456 } 457 #endif 458 459 // Returns true if the reference points to an object that 460 // can move in an incremental collecction. 461 bool G1CollectedHeap::is_scavengable(const void* p) { 462 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 463 G1CollectorPolicy* g1p = g1h->g1_policy(); 464 HeapRegion* hr = heap_region_containing(p); 465 if (hr == NULL) { 466 // null 467 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p)); 468 return false; 469 } else { 470 return !hr->isHumongous(); 471 } 472 } 473 474 void G1CollectedHeap::check_ct_logs_at_safepoint() { 475 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 476 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 477 478 // Count the dirty cards at the start. 479 CountNonCleanMemRegionClosure count1(this); 480 ct_bs->mod_card_iterate(&count1); 481 int orig_count = count1.n(); 482 483 // First clear the logged cards. 484 ClearLoggedCardTableEntryClosure clear; 485 dcqs.set_closure(&clear); 486 dcqs.apply_closure_to_all_completed_buffers(); 487 dcqs.iterate_closure_all_threads(false); 488 clear.print_histo(); 489 490 // Now ensure that there's no dirty cards. 491 CountNonCleanMemRegionClosure count2(this); 492 ct_bs->mod_card_iterate(&count2); 493 if (count2.n() != 0) { 494 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 495 count2.n(), orig_count); 496 } 497 guarantee(count2.n() == 0, "Card table should be clean."); 498 499 RedirtyLoggedCardTableEntryClosure redirty; 500 JavaThread::dirty_card_queue_set().set_closure(&redirty); 501 dcqs.apply_closure_to_all_completed_buffers(); 502 dcqs.iterate_closure_all_threads(false); 503 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 504 clear.calls(), orig_count); 505 guarantee(redirty.calls() == clear.calls(), 506 "Or else mechanism is broken."); 507 508 CountNonCleanMemRegionClosure count3(this); 509 ct_bs->mod_card_iterate(&count3); 510 if (count3.n() != orig_count) { 511 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 512 orig_count, count3.n()); 513 guarantee(count3.n() >= orig_count, "Should have restored them all."); 514 } 515 516 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 517 } 518 519 // Private class members. 520 521 G1CollectedHeap* G1CollectedHeap::_g1h; 522 523 // Private methods. 524 525 HeapRegion* 526 G1CollectedHeap::new_region_try_secondary_free_list() { 527 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 528 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 529 if (!_secondary_free_list.is_empty()) { 530 if (G1ConcRegionFreeingVerbose) { 531 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 532 "secondary_free_list has %u entries", 533 _secondary_free_list.length()); 534 } 535 // It looks as if there are free regions available on the 536 // secondary_free_list. Let's move them to the free_list and try 537 // again to allocate from it. 538 append_secondary_free_list(); 539 540 assert(!_free_list.is_empty(), "if the secondary_free_list was not " 541 "empty we should have moved at least one entry to the free_list"); 542 HeapRegion* res = _free_list.remove_head(); 543 if (G1ConcRegionFreeingVerbose) { 544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 545 "allocated "HR_FORMAT" from secondary_free_list", 546 HR_FORMAT_PARAMS(res)); 547 } 548 return res; 549 } 550 551 // Wait here until we get notifed either when (a) there are no 552 // more free regions coming or (b) some regions have been moved on 553 // the secondary_free_list. 554 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 555 } 556 557 if (G1ConcRegionFreeingVerbose) { 558 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 559 "could not allocate from secondary_free_list"); 560 } 561 return NULL; 562 } 563 564 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) { 565 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords, 566 "the only time we use this to allocate a humongous region is " 567 "when we are allocating a single humongous region"); 568 569 HeapRegion* res; 570 if (G1StressConcRegionFreeing) { 571 if (!_secondary_free_list.is_empty()) { 572 if (G1ConcRegionFreeingVerbose) { 573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 574 "forced to look at the secondary_free_list"); 575 } 576 res = new_region_try_secondary_free_list(); 577 if (res != NULL) { 578 return res; 579 } 580 } 581 } 582 res = _free_list.remove_head_or_null(); 583 if (res == NULL) { 584 if (G1ConcRegionFreeingVerbose) { 585 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 586 "res == NULL, trying the secondary_free_list"); 587 } 588 res = new_region_try_secondary_free_list(); 589 } 590 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 591 // Currently, only attempts to allocate GC alloc regions set 592 // do_expand to true. So, we should only reach here during a 593 // safepoint. If this assumption changes we might have to 594 // reconsider the use of _expand_heap_after_alloc_failure. 595 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 596 597 ergo_verbose1(ErgoHeapSizing, 598 "attempt heap expansion", 599 ergo_format_reason("region allocation request failed") 600 ergo_format_byte("allocation request"), 601 word_size * HeapWordSize); 602 if (expand(word_size * HeapWordSize)) { 603 // Given that expand() succeeded in expanding the heap, and we 604 // always expand the heap by an amount aligned to the heap 605 // region size, the free list should in theory not be empty. So 606 // it would probably be OK to use remove_head(). But the extra 607 // check for NULL is unlikely to be a performance issue here (we 608 // just expanded the heap!) so let's just be conservative and 609 // use remove_head_or_null(). 610 res = _free_list.remove_head_or_null(); 611 } else { 612 _expand_heap_after_alloc_failure = false; 613 } 614 } 615 return res; 616 } 617 618 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions, 619 size_t word_size) { 620 assert(isHumongous(word_size), "word_size should be humongous"); 621 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 622 623 uint first = G1_NULL_HRS_INDEX; 624 if (num_regions == 1) { 625 // Only one region to allocate, no need to go through the slower 626 // path. The caller will attempt the expasion if this fails, so 627 // let's not try to expand here too. 628 HeapRegion* hr = new_region(word_size, false /* do_expand */); 629 if (hr != NULL) { 630 first = hr->hrs_index(); 631 } else { 632 first = G1_NULL_HRS_INDEX; 633 } 634 } else { 635 // We can't allocate humongous regions while cleanupComplete() is 636 // running, since some of the regions we find to be empty might not 637 // yet be added to the free list and it is not straightforward to 638 // know which list they are on so that we can remove them. Note 639 // that we only need to do this if we need to allocate more than 640 // one region to satisfy the current humongous allocation 641 // request. If we are only allocating one region we use the common 642 // region allocation code (see above). 643 wait_while_free_regions_coming(); 644 append_secondary_free_list_if_not_empty_with_lock(); 645 646 if (free_regions() >= num_regions) { 647 first = _hrs.find_contiguous(num_regions); 648 if (first != G1_NULL_HRS_INDEX) { 649 for (uint i = first; i < first + num_regions; ++i) { 650 HeapRegion* hr = region_at(i); 651 assert(hr->is_empty(), "sanity"); 652 assert(is_on_master_free_list(hr), "sanity"); 653 hr->set_pending_removal(true); 654 } 655 _free_list.remove_all_pending(num_regions); 656 } 657 } 658 } 659 return first; 660 } 661 662 HeapWord* 663 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 664 uint num_regions, 665 size_t word_size) { 666 assert(first != G1_NULL_HRS_INDEX, "pre-condition"); 667 assert(isHumongous(word_size), "word_size should be humongous"); 668 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 669 670 // Index of last region in the series + 1. 671 uint last = first + num_regions; 672 673 // We need to initialize the region(s) we just discovered. This is 674 // a bit tricky given that it can happen concurrently with 675 // refinement threads refining cards on these regions and 676 // potentially wanting to refine the BOT as they are scanning 677 // those cards (this can happen shortly after a cleanup; see CR 678 // 6991377). So we have to set up the region(s) carefully and in 679 // a specific order. 680 681 // The word size sum of all the regions we will allocate. 682 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 683 assert(word_size <= word_size_sum, "sanity"); 684 685 // This will be the "starts humongous" region. 686 HeapRegion* first_hr = region_at(first); 687 // The header of the new object will be placed at the bottom of 688 // the first region. 689 HeapWord* new_obj = first_hr->bottom(); 690 // This will be the new end of the first region in the series that 691 // should also match the end of the last region in the seriers. 692 HeapWord* new_end = new_obj + word_size_sum; 693 // This will be the new top of the first region that will reflect 694 // this allocation. 695 HeapWord* new_top = new_obj + word_size; 696 697 // First, we need to zero the header of the space that we will be 698 // allocating. When we update top further down, some refinement 699 // threads might try to scan the region. By zeroing the header we 700 // ensure that any thread that will try to scan the region will 701 // come across the zero klass word and bail out. 702 // 703 // NOTE: It would not have been correct to have used 704 // CollectedHeap::fill_with_object() and make the space look like 705 // an int array. The thread that is doing the allocation will 706 // later update the object header to a potentially different array 707 // type and, for a very short period of time, the klass and length 708 // fields will be inconsistent. This could cause a refinement 709 // thread to calculate the object size incorrectly. 710 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 711 712 // We will set up the first region as "starts humongous". This 713 // will also update the BOT covering all the regions to reflect 714 // that there is a single object that starts at the bottom of the 715 // first region. 716 first_hr->set_startsHumongous(new_top, new_end); 717 718 // Then, if there are any, we will set up the "continues 719 // humongous" regions. 720 HeapRegion* hr = NULL; 721 for (uint i = first + 1; i < last; ++i) { 722 hr = region_at(i); 723 hr->set_continuesHumongous(first_hr); 724 } 725 // If we have "continues humongous" regions (hr != NULL), then the 726 // end of the last one should match new_end. 727 assert(hr == NULL || hr->end() == new_end, "sanity"); 728 729 // Up to this point no concurrent thread would have been able to 730 // do any scanning on any region in this series. All the top 731 // fields still point to bottom, so the intersection between 732 // [bottom,top] and [card_start,card_end] will be empty. Before we 733 // update the top fields, we'll do a storestore to make sure that 734 // no thread sees the update to top before the zeroing of the 735 // object header and the BOT initialization. 736 OrderAccess::storestore(); 737 738 // Now that the BOT and the object header have been initialized, 739 // we can update top of the "starts humongous" region. 740 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 741 "new_top should be in this region"); 742 first_hr->set_top(new_top); 743 if (_hr_printer.is_active()) { 744 HeapWord* bottom = first_hr->bottom(); 745 HeapWord* end = first_hr->orig_end(); 746 if ((first + 1) == last) { 747 // the series has a single humongous region 748 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 749 } else { 750 // the series has more than one humongous regions 751 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 752 } 753 } 754 755 // Now, we will update the top fields of the "continues humongous" 756 // regions. The reason we need to do this is that, otherwise, 757 // these regions would look empty and this will confuse parts of 758 // G1. For example, the code that looks for a consecutive number 759 // of empty regions will consider them empty and try to 760 // re-allocate them. We can extend is_empty() to also include 761 // !continuesHumongous(), but it is easier to just update the top 762 // fields here. The way we set top for all regions (i.e., top == 763 // end for all regions but the last one, top == new_top for the 764 // last one) is actually used when we will free up the humongous 765 // region in free_humongous_region(). 766 hr = NULL; 767 for (uint i = first + 1; i < last; ++i) { 768 hr = region_at(i); 769 if ((i + 1) == last) { 770 // last continues humongous region 771 assert(hr->bottom() < new_top && new_top <= hr->end(), 772 "new_top should fall on this region"); 773 hr->set_top(new_top); 774 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 775 } else { 776 // not last one 777 assert(new_top > hr->end(), "new_top should be above this region"); 778 hr->set_top(hr->end()); 779 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 780 } 781 } 782 // If we have continues humongous regions (hr != NULL), then the 783 // end of the last one should match new_end and its top should 784 // match new_top. 785 assert(hr == NULL || 786 (hr->end() == new_end && hr->top() == new_top), "sanity"); 787 788 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 789 _summary_bytes_used += first_hr->used(); 790 _humongous_set.add(first_hr); 791 792 return new_obj; 793 } 794 795 // If could fit into free regions w/o expansion, try. 796 // Otherwise, if can expand, do so. 797 // Otherwise, if using ex regions might help, try with ex given back. 798 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 799 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 800 801 verify_region_sets_optional(); 802 803 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords); 804 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords); 805 uint x_num = expansion_regions(); 806 uint fs = _hrs.free_suffix(); 807 uint first = humongous_obj_allocate_find_first(num_regions, word_size); 808 if (first == G1_NULL_HRS_INDEX) { 809 // The only thing we can do now is attempt expansion. 810 if (fs + x_num >= num_regions) { 811 // If the number of regions we're trying to allocate for this 812 // object is at most the number of regions in the free suffix, 813 // then the call to humongous_obj_allocate_find_first() above 814 // should have succeeded and we wouldn't be here. 815 // 816 // We should only be trying to expand when the free suffix is 817 // not sufficient for the object _and_ we have some expansion 818 // room available. 819 assert(num_regions > fs, "earlier allocation should have succeeded"); 820 821 ergo_verbose1(ErgoHeapSizing, 822 "attempt heap expansion", 823 ergo_format_reason("humongous allocation request failed") 824 ergo_format_byte("allocation request"), 825 word_size * HeapWordSize); 826 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) { 827 // Even though the heap was expanded, it might not have 828 // reached the desired size. So, we cannot assume that the 829 // allocation will succeed. 830 first = humongous_obj_allocate_find_first(num_regions, word_size); 831 } 832 } 833 } 834 835 HeapWord* result = NULL; 836 if (first != G1_NULL_HRS_INDEX) { 837 result = 838 humongous_obj_allocate_initialize_regions(first, num_regions, word_size); 839 assert(result != NULL, "it should always return a valid result"); 840 841 // A successful humongous object allocation changes the used space 842 // information of the old generation so we need to recalculate the 843 // sizes and update the jstat counters here. 844 g1mm()->update_sizes(); 845 } 846 847 verify_region_sets_optional(); 848 849 return result; 850 } 851 852 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 853 assert_heap_not_locked_and_not_at_safepoint(); 854 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 855 856 unsigned int dummy_gc_count_before; 857 int dummy_gclocker_retry_count = 0; 858 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 859 } 860 861 HeapWord* 862 G1CollectedHeap::mem_allocate(size_t word_size, 863 bool* gc_overhead_limit_was_exceeded) { 864 assert_heap_not_locked_and_not_at_safepoint(); 865 866 // Loop until the allocation is satisified, or unsatisfied after GC. 867 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 868 unsigned int gc_count_before; 869 870 HeapWord* result = NULL; 871 if (!isHumongous(word_size)) { 872 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 873 } else { 874 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 875 } 876 if (result != NULL) { 877 return result; 878 } 879 880 // Create the garbage collection operation... 881 VM_G1CollectForAllocation op(gc_count_before, word_size); 882 // ...and get the VM thread to execute it. 883 VMThread::execute(&op); 884 885 if (op.prologue_succeeded() && op.pause_succeeded()) { 886 // If the operation was successful we'll return the result even 887 // if it is NULL. If the allocation attempt failed immediately 888 // after a Full GC, it's unlikely we'll be able to allocate now. 889 HeapWord* result = op.result(); 890 if (result != NULL && !isHumongous(word_size)) { 891 // Allocations that take place on VM operations do not do any 892 // card dirtying and we have to do it here. We only have to do 893 // this for non-humongous allocations, though. 894 dirty_young_block(result, word_size); 895 } 896 return result; 897 } else { 898 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 899 return NULL; 900 } 901 assert(op.result() == NULL, 902 "the result should be NULL if the VM op did not succeed"); 903 } 904 905 // Give a warning if we seem to be looping forever. 906 if ((QueuedAllocationWarningCount > 0) && 907 (try_count % QueuedAllocationWarningCount == 0)) { 908 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 909 } 910 } 911 912 ShouldNotReachHere(); 913 return NULL; 914 } 915 916 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 917 unsigned int *gc_count_before_ret, 918 int* gclocker_retry_count_ret) { 919 // Make sure you read the note in attempt_allocation_humongous(). 920 921 assert_heap_not_locked_and_not_at_safepoint(); 922 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 923 "be called for humongous allocation requests"); 924 925 // We should only get here after the first-level allocation attempt 926 // (attempt_allocation()) failed to allocate. 927 928 // We will loop until a) we manage to successfully perform the 929 // allocation or b) we successfully schedule a collection which 930 // fails to perform the allocation. b) is the only case when we'll 931 // return NULL. 932 HeapWord* result = NULL; 933 for (int try_count = 1; /* we'll return */; try_count += 1) { 934 bool should_try_gc; 935 unsigned int gc_count_before; 936 937 { 938 MutexLockerEx x(Heap_lock); 939 940 result = _mutator_alloc_region.attempt_allocation_locked(word_size, 941 false /* bot_updates */); 942 if (result != NULL) { 943 return result; 944 } 945 946 // If we reach here, attempt_allocation_locked() above failed to 947 // allocate a new region. So the mutator alloc region should be NULL. 948 assert(_mutator_alloc_region.get() == NULL, "only way to get here"); 949 950 if (GC_locker::is_active_and_needs_gc()) { 951 if (g1_policy()->can_expand_young_list()) { 952 // No need for an ergo verbose message here, 953 // can_expand_young_list() does this when it returns true. 954 result = _mutator_alloc_region.attempt_allocation_force(word_size, 955 false /* bot_updates */); 956 if (result != NULL) { 957 return result; 958 } 959 } 960 should_try_gc = false; 961 } else { 962 // The GCLocker may not be active but the GCLocker initiated 963 // GC may not yet have been performed (GCLocker::needs_gc() 964 // returns true). In this case we do not try this GC and 965 // wait until the GCLocker initiated GC is performed, and 966 // then retry the allocation. 967 if (GC_locker::needs_gc()) { 968 should_try_gc = false; 969 } else { 970 // Read the GC count while still holding the Heap_lock. 971 gc_count_before = total_collections(); 972 should_try_gc = true; 973 } 974 } 975 } 976 977 if (should_try_gc) { 978 bool succeeded; 979 result = do_collection_pause(word_size, gc_count_before, &succeeded); 980 if (result != NULL) { 981 assert(succeeded, "only way to get back a non-NULL result"); 982 return result; 983 } 984 985 if (succeeded) { 986 // If we get here we successfully scheduled a collection which 987 // failed to allocate. No point in trying to allocate 988 // further. We'll just return NULL. 989 MutexLockerEx x(Heap_lock); 990 *gc_count_before_ret = total_collections(); 991 return NULL; 992 } 993 } else { 994 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 995 MutexLockerEx x(Heap_lock); 996 *gc_count_before_ret = total_collections(); 997 return NULL; 998 } 999 // The GCLocker is either active or the GCLocker initiated 1000 // GC has not yet been performed. Stall until it is and 1001 // then retry the allocation. 1002 GC_locker::stall_until_clear(); 1003 (*gclocker_retry_count_ret) += 1; 1004 } 1005 1006 // We can reach here if we were unsuccessul in scheduling a 1007 // collection (because another thread beat us to it) or if we were 1008 // stalled due to the GC locker. In either can we should retry the 1009 // allocation attempt in case another thread successfully 1010 // performed a collection and reclaimed enough space. We do the 1011 // first attempt (without holding the Heap_lock) here and the 1012 // follow-on attempt will be at the start of the next loop 1013 // iteration (after taking the Heap_lock). 1014 result = _mutator_alloc_region.attempt_allocation(word_size, 1015 false /* bot_updates */); 1016 if (result != NULL) { 1017 return result; 1018 } 1019 1020 // Give a warning if we seem to be looping forever. 1021 if ((QueuedAllocationWarningCount > 0) && 1022 (try_count % QueuedAllocationWarningCount == 0)) { 1023 warning("G1CollectedHeap::attempt_allocation_slow() " 1024 "retries %d times", try_count); 1025 } 1026 } 1027 1028 ShouldNotReachHere(); 1029 return NULL; 1030 } 1031 1032 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 1033 unsigned int * gc_count_before_ret, 1034 int* gclocker_retry_count_ret) { 1035 // The structure of this method has a lot of similarities to 1036 // attempt_allocation_slow(). The reason these two were not merged 1037 // into a single one is that such a method would require several "if 1038 // allocation is not humongous do this, otherwise do that" 1039 // conditional paths which would obscure its flow. In fact, an early 1040 // version of this code did use a unified method which was harder to 1041 // follow and, as a result, it had subtle bugs that were hard to 1042 // track down. So keeping these two methods separate allows each to 1043 // be more readable. It will be good to keep these two in sync as 1044 // much as possible. 1045 1046 assert_heap_not_locked_and_not_at_safepoint(); 1047 assert(isHumongous(word_size), "attempt_allocation_humongous() " 1048 "should only be called for humongous allocations"); 1049 1050 // Humongous objects can exhaust the heap quickly, so we should check if we 1051 // need to start a marking cycle at each humongous object allocation. We do 1052 // the check before we do the actual allocation. The reason for doing it 1053 // before the allocation is that we avoid having to keep track of the newly 1054 // allocated memory while we do a GC. 1055 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 1056 word_size)) { 1057 collect(GCCause::_g1_humongous_allocation); 1058 } 1059 1060 // We will loop until a) we manage to successfully perform the 1061 // allocation or b) we successfully schedule a collection which 1062 // fails to perform the allocation. b) is the only case when we'll 1063 // return NULL. 1064 HeapWord* result = NULL; 1065 for (int try_count = 1; /* we'll return */; try_count += 1) { 1066 bool should_try_gc; 1067 unsigned int gc_count_before; 1068 1069 { 1070 MutexLockerEx x(Heap_lock); 1071 1072 // Given that humongous objects are not allocated in young 1073 // regions, we'll first try to do the allocation without doing a 1074 // collection hoping that there's enough space in the heap. 1075 result = humongous_obj_allocate(word_size); 1076 if (result != NULL) { 1077 return result; 1078 } 1079 1080 if (GC_locker::is_active_and_needs_gc()) { 1081 should_try_gc = false; 1082 } else { 1083 // The GCLocker may not be active but the GCLocker initiated 1084 // GC may not yet have been performed (GCLocker::needs_gc() 1085 // returns true). In this case we do not try this GC and 1086 // wait until the GCLocker initiated GC is performed, and 1087 // then retry the allocation. 1088 if (GC_locker::needs_gc()) { 1089 should_try_gc = false; 1090 } else { 1091 // Read the GC count while still holding the Heap_lock. 1092 gc_count_before = total_collections(); 1093 should_try_gc = true; 1094 } 1095 } 1096 } 1097 1098 if (should_try_gc) { 1099 // If we failed to allocate the humongous object, we should try to 1100 // do a collection pause (if we're allowed) in case it reclaims 1101 // enough space for the allocation to succeed after the pause. 1102 1103 bool succeeded; 1104 result = do_collection_pause(word_size, gc_count_before, &succeeded); 1105 if (result != NULL) { 1106 assert(succeeded, "only way to get back a non-NULL result"); 1107 return result; 1108 } 1109 1110 if (succeeded) { 1111 // If we get here we successfully scheduled a collection which 1112 // failed to allocate. No point in trying to allocate 1113 // further. We'll just return NULL. 1114 MutexLockerEx x(Heap_lock); 1115 *gc_count_before_ret = total_collections(); 1116 return NULL; 1117 } 1118 } else { 1119 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1120 MutexLockerEx x(Heap_lock); 1121 *gc_count_before_ret = total_collections(); 1122 return NULL; 1123 } 1124 // The GCLocker is either active or the GCLocker initiated 1125 // GC has not yet been performed. Stall until it is and 1126 // then retry the allocation. 1127 GC_locker::stall_until_clear(); 1128 (*gclocker_retry_count_ret) += 1; 1129 } 1130 1131 // We can reach here if we were unsuccessul in scheduling a 1132 // collection (because another thread beat us to it) or if we were 1133 // stalled due to the GC locker. In either can we should retry the 1134 // allocation attempt in case another thread successfully 1135 // performed a collection and reclaimed enough space. Give a 1136 // warning if we seem to be looping forever. 1137 1138 if ((QueuedAllocationWarningCount > 0) && 1139 (try_count % QueuedAllocationWarningCount == 0)) { 1140 warning("G1CollectedHeap::attempt_allocation_humongous() " 1141 "retries %d times", try_count); 1142 } 1143 } 1144 1145 ShouldNotReachHere(); 1146 return NULL; 1147 } 1148 1149 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1150 bool expect_null_mutator_alloc_region) { 1151 assert_at_safepoint(true /* should_be_vm_thread */); 1152 assert(_mutator_alloc_region.get() == NULL || 1153 !expect_null_mutator_alloc_region, 1154 "the current alloc region was unexpectedly found to be non-NULL"); 1155 1156 if (!isHumongous(word_size)) { 1157 return _mutator_alloc_region.attempt_allocation_locked(word_size, 1158 false /* bot_updates */); 1159 } else { 1160 HeapWord* result = humongous_obj_allocate(word_size); 1161 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1162 g1_policy()->set_initiate_conc_mark_if_possible(); 1163 } 1164 return result; 1165 } 1166 1167 ShouldNotReachHere(); 1168 } 1169 1170 class PostMCRemSetClearClosure: public HeapRegionClosure { 1171 G1CollectedHeap* _g1h; 1172 ModRefBarrierSet* _mr_bs; 1173 public: 1174 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1175 _g1h(g1h), _mr_bs(mr_bs) { } 1176 bool doHeapRegion(HeapRegion* r) { 1177 if (r->continuesHumongous()) { 1178 return false; 1179 } 1180 _g1h->reset_gc_time_stamps(r); 1181 HeapRegionRemSet* hrrs = r->rem_set(); 1182 if (hrrs != NULL) hrrs->clear(); 1183 // You might think here that we could clear just the cards 1184 // corresponding to the used region. But no: if we leave a dirty card 1185 // in a region we might allocate into, then it would prevent that card 1186 // from being enqueued, and cause it to be missed. 1187 // Re: the performance cost: we shouldn't be doing full GC anyway! 1188 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1189 return false; 1190 } 1191 }; 1192 1193 void G1CollectedHeap::clear_rsets_post_compaction() { 1194 PostMCRemSetClearClosure rs_clear(this, mr_bs()); 1195 heap_region_iterate(&rs_clear); 1196 } 1197 1198 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1199 G1CollectedHeap* _g1h; 1200 UpdateRSOopClosure _cl; 1201 int _worker_i; 1202 public: 1203 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1204 _cl(g1->g1_rem_set(), worker_i), 1205 _worker_i(worker_i), 1206 _g1h(g1) 1207 { } 1208 1209 bool doHeapRegion(HeapRegion* r) { 1210 if (!r->continuesHumongous()) { 1211 _cl.set_from(r); 1212 r->oop_iterate(&_cl); 1213 } 1214 return false; 1215 } 1216 }; 1217 1218 class ParRebuildRSTask: public AbstractGangTask { 1219 G1CollectedHeap* _g1; 1220 public: 1221 ParRebuildRSTask(G1CollectedHeap* g1) 1222 : AbstractGangTask("ParRebuildRSTask"), 1223 _g1(g1) 1224 { } 1225 1226 void work(uint worker_id) { 1227 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1228 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id, 1229 _g1->workers()->active_workers(), 1230 HeapRegion::RebuildRSClaimValue); 1231 } 1232 }; 1233 1234 class PostCompactionPrinterClosure: public HeapRegionClosure { 1235 private: 1236 G1HRPrinter* _hr_printer; 1237 public: 1238 bool doHeapRegion(HeapRegion* hr) { 1239 assert(!hr->is_young(), "not expecting to find young regions"); 1240 // We only generate output for non-empty regions. 1241 if (!hr->is_empty()) { 1242 if (!hr->isHumongous()) { 1243 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1244 } else if (hr->startsHumongous()) { 1245 if (hr->region_num() == 1) { 1246 // single humongous region 1247 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1248 } else { 1249 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1250 } 1251 } else { 1252 assert(hr->continuesHumongous(), "only way to get here"); 1253 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1254 } 1255 } 1256 return false; 1257 } 1258 1259 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1260 : _hr_printer(hr_printer) { } 1261 }; 1262 1263 void G1CollectedHeap::print_hrs_post_compaction() { 1264 PostCompactionPrinterClosure cl(hr_printer()); 1265 heap_region_iterate(&cl); 1266 } 1267 1268 double G1CollectedHeap::verify(bool guard, const char* msg) { 1269 double verify_time_ms = 0.0; 1270 1271 if (guard && total_collections() >= VerifyGCStartAt) { 1272 double verify_start = os::elapsedTime(); 1273 HandleMark hm; // Discard invalid handles created during verification 1274 prepare_for_verify(); 1275 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 1276 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 1277 } 1278 1279 return verify_time_ms; 1280 } 1281 1282 void G1CollectedHeap::verify_before_gc() { 1283 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 1284 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 1285 } 1286 1287 void G1CollectedHeap::verify_after_gc() { 1288 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 1289 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 1290 } 1291 1292 bool G1CollectedHeap::do_collection(bool explicit_gc, 1293 bool clear_all_soft_refs, 1294 size_t word_size) { 1295 assert_at_safepoint(true /* should_be_vm_thread */); 1296 1297 if (GC_locker::check_active_before_gc()) { 1298 return false; 1299 } 1300 1301 SvcGCMarker sgcm(SvcGCMarker::FULL); 1302 ResourceMark rm; 1303 1304 print_heap_before_gc(); 1305 1306 size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes(); 1307 1308 HRSPhaseSetter x(HRSPhaseFullGC); 1309 verify_region_sets_optional(); 1310 1311 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1312 collector_policy()->should_clear_all_soft_refs(); 1313 1314 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1315 1316 { 1317 IsGCActiveMark x; 1318 1319 // Timing 1320 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1321 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps); 1322 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1323 1324 { 1325 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty); 1326 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1327 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1328 1329 double start = os::elapsedTime(); 1330 g1_policy()->record_full_collection_start(); 1331 1332 // Note: When we have a more flexible GC logging framework that 1333 // allows us to add optional attributes to a GC log record we 1334 // could consider timing and reporting how long we wait in the 1335 // following two methods. 1336 wait_while_free_regions_coming(); 1337 // If we start the compaction before the CM threads finish 1338 // scanning the root regions we might trip them over as we'll 1339 // be moving objects / updating references. So let's wait until 1340 // they are done. By telling them to abort, they should complete 1341 // early. 1342 _cm->root_regions()->abort(); 1343 _cm->root_regions()->wait_until_scan_finished(); 1344 append_secondary_free_list_if_not_empty_with_lock(); 1345 1346 gc_prologue(true); 1347 increment_total_collections(true /* full gc */); 1348 increment_old_marking_cycles_started(); 1349 1350 assert(used() == recalculate_used(), "Should be equal"); 1351 1352 verify_before_gc(); 1353 1354 pre_full_gc_dump(); 1355 1356 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1357 1358 // Disable discovery and empty the discovered lists 1359 // for the CM ref processor. 1360 ref_processor_cm()->disable_discovery(); 1361 ref_processor_cm()->abandon_partial_discovery(); 1362 ref_processor_cm()->verify_no_references_recorded(); 1363 1364 // Abandon current iterations of concurrent marking and concurrent 1365 // refinement, if any are in progress. We have to do this before 1366 // wait_until_scan_finished() below. 1367 concurrent_mark()->abort(); 1368 1369 // Make sure we'll choose a new allocation region afterwards. 1370 release_mutator_alloc_region(); 1371 abandon_gc_alloc_regions(); 1372 g1_rem_set()->cleanupHRRS(); 1373 1374 // We should call this after we retire any currently active alloc 1375 // regions so that all the ALLOC / RETIRE events are generated 1376 // before the start GC event. 1377 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1378 1379 // We may have added regions to the current incremental collection 1380 // set between the last GC or pause and now. We need to clear the 1381 // incremental collection set and then start rebuilding it afresh 1382 // after this full GC. 1383 abandon_collection_set(g1_policy()->inc_cset_head()); 1384 g1_policy()->clear_incremental_cset(); 1385 g1_policy()->stop_incremental_cset_building(); 1386 1387 tear_down_region_sets(false /* free_list_only */); 1388 g1_policy()->set_gcs_are_young(true); 1389 1390 // See the comments in g1CollectedHeap.hpp and 1391 // G1CollectedHeap::ref_processing_init() about 1392 // how reference processing currently works in G1. 1393 1394 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1395 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1396 1397 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1398 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1399 1400 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1401 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1402 1403 // Do collection work 1404 { 1405 HandleMark hm; // Discard invalid handles created during gc 1406 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1407 } 1408 1409 assert(free_regions() == 0, "we should not have added any free regions"); 1410 rebuild_region_sets(false /* free_list_only */); 1411 1412 // Enqueue any discovered reference objects that have 1413 // not been removed from the discovered lists. 1414 ref_processor_stw()->enqueue_discovered_references(); 1415 1416 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1417 1418 MemoryService::track_memory_usage(); 1419 1420 verify_after_gc(); 1421 1422 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1423 ref_processor_stw()->verify_no_references_recorded(); 1424 1425 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1426 ClassLoaderDataGraph::purge(); 1427 MetaspaceAux::verify_metrics(); 1428 1429 // Note: since we've just done a full GC, concurrent 1430 // marking is no longer active. Therefore we need not 1431 // re-enable reference discovery for the CM ref processor. 1432 // That will be done at the start of the next marking cycle. 1433 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1434 ref_processor_cm()->verify_no_references_recorded(); 1435 1436 reset_gc_time_stamp(); 1437 // Since everything potentially moved, we will clear all remembered 1438 // sets, and clear all cards. Later we will rebuild remebered 1439 // sets. We will also reset the GC time stamps of the regions. 1440 clear_rsets_post_compaction(); 1441 check_gc_time_stamps(); 1442 1443 // Resize the heap if necessary. 1444 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1445 1446 if (_hr_printer.is_active()) { 1447 // We should do this after we potentially resize the heap so 1448 // that all the COMMIT / UNCOMMIT events are generated before 1449 // the end GC event. 1450 1451 print_hrs_post_compaction(); 1452 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1453 } 1454 1455 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1456 if (hot_card_cache->use_cache()) { 1457 hot_card_cache->reset_card_counts(); 1458 hot_card_cache->reset_hot_cache(); 1459 } 1460 1461 // Rebuild remembered sets of all regions. 1462 if (G1CollectedHeap::use_parallel_gc_threads()) { 1463 uint n_workers = 1464 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1465 workers()->active_workers(), 1466 Threads::number_of_non_daemon_threads()); 1467 assert(UseDynamicNumberOfGCThreads || 1468 n_workers == workers()->total_workers(), 1469 "If not dynamic should be using all the workers"); 1470 workers()->set_active_workers(n_workers); 1471 // Set parallel threads in the heap (_n_par_threads) only 1472 // before a parallel phase and always reset it to 0 after 1473 // the phase so that the number of parallel threads does 1474 // no get carried forward to a serial phase where there 1475 // may be code that is "possibly_parallel". 1476 set_par_threads(n_workers); 1477 1478 ParRebuildRSTask rebuild_rs_task(this); 1479 assert(check_heap_region_claim_values( 1480 HeapRegion::InitialClaimValue), "sanity check"); 1481 assert(UseDynamicNumberOfGCThreads || 1482 workers()->active_workers() == workers()->total_workers(), 1483 "Unless dynamic should use total workers"); 1484 // Use the most recent number of active workers 1485 assert(workers()->active_workers() > 0, 1486 "Active workers not properly set"); 1487 set_par_threads(workers()->active_workers()); 1488 workers()->run_task(&rebuild_rs_task); 1489 set_par_threads(0); 1490 assert(check_heap_region_claim_values( 1491 HeapRegion::RebuildRSClaimValue), "sanity check"); 1492 reset_heap_region_claim_values(); 1493 } else { 1494 RebuildRSOutOfRegionClosure rebuild_rs(this); 1495 heap_region_iterate(&rebuild_rs); 1496 } 1497 1498 if (true) { // FIXME 1499 MetaspaceGC::compute_new_size(); 1500 } 1501 1502 #ifdef TRACESPINNING 1503 ParallelTaskTerminator::print_termination_counts(); 1504 #endif 1505 1506 // Discard all rset updates 1507 JavaThread::dirty_card_queue_set().abandon_logs(); 1508 assert(!G1DeferredRSUpdate 1509 || (G1DeferredRSUpdate && 1510 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1511 1512 _young_list->reset_sampled_info(); 1513 // At this point there should be no regions in the 1514 // entire heap tagged as young. 1515 assert(check_young_list_empty(true /* check_heap */), 1516 "young list should be empty at this point"); 1517 1518 // Update the number of full collections that have been completed. 1519 increment_old_marking_cycles_completed(false /* concurrent */); 1520 1521 _hrs.verify_optional(); 1522 verify_region_sets_optional(); 1523 1524 // Start a new incremental collection set for the next pause 1525 assert(g1_policy()->collection_set() == NULL, "must be"); 1526 g1_policy()->start_incremental_cset_building(); 1527 1528 // Clear the _cset_fast_test bitmap in anticipation of adding 1529 // regions to the incremental collection set for the next 1530 // evacuation pause. 1531 clear_cset_fast_test(); 1532 1533 init_mutator_alloc_region(); 1534 1535 double end = os::elapsedTime(); 1536 g1_policy()->record_full_collection_end(); 1537 1538 if (G1Log::fine()) { 1539 g1_policy()->print_heap_transition(); 1540 } 1541 1542 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1543 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1544 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1545 // before any GC notifications are raised. 1546 g1mm()->update_sizes(); 1547 1548 gc_epilogue(true); 1549 } 1550 1551 if (G1Log::finer()) { 1552 g1_policy()->print_detailed_heap_transition(true /* full */); 1553 } 1554 1555 print_heap_after_gc(); 1556 1557 post_full_gc_dump(); 1558 } 1559 1560 return true; 1561 } 1562 1563 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1564 // do_collection() will return whether it succeeded in performing 1565 // the GC. Currently, there is no facility on the 1566 // do_full_collection() API to notify the caller than the collection 1567 // did not succeed (e.g., because it was locked out by the GC 1568 // locker). So, right now, we'll ignore the return value. 1569 bool dummy = do_collection(true, /* explicit_gc */ 1570 clear_all_soft_refs, 1571 0 /* word_size */); 1572 } 1573 1574 // This code is mostly copied from TenuredGeneration. 1575 void 1576 G1CollectedHeap:: 1577 resize_if_necessary_after_full_collection(size_t word_size) { 1578 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check"); 1579 1580 // Include the current allocation, if any, and bytes that will be 1581 // pre-allocated to support collections, as "used". 1582 const size_t used_after_gc = used(); 1583 const size_t capacity_after_gc = capacity(); 1584 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1585 1586 // This is enforced in arguments.cpp. 1587 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1588 "otherwise the code below doesn't make sense"); 1589 1590 // We don't have floating point command-line arguments 1591 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1592 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1593 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1594 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1595 1596 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1597 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1598 1599 // We have to be careful here as these two calculations can overflow 1600 // 32-bit size_t's. 1601 double used_after_gc_d = (double) used_after_gc; 1602 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1603 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1604 1605 // Let's make sure that they are both under the max heap size, which 1606 // by default will make them fit into a size_t. 1607 double desired_capacity_upper_bound = (double) max_heap_size; 1608 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1609 desired_capacity_upper_bound); 1610 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1611 desired_capacity_upper_bound); 1612 1613 // We can now safely turn them into size_t's. 1614 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1615 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1616 1617 // This assert only makes sense here, before we adjust them 1618 // with respect to the min and max heap size. 1619 assert(minimum_desired_capacity <= maximum_desired_capacity, 1620 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1621 "maximum_desired_capacity = "SIZE_FORMAT, 1622 minimum_desired_capacity, maximum_desired_capacity)); 1623 1624 // Should not be greater than the heap max size. No need to adjust 1625 // it with respect to the heap min size as it's a lower bound (i.e., 1626 // we'll try to make the capacity larger than it, not smaller). 1627 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1628 // Should not be less than the heap min size. No need to adjust it 1629 // with respect to the heap max size as it's an upper bound (i.e., 1630 // we'll try to make the capacity smaller than it, not greater). 1631 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1632 1633 if (capacity_after_gc < minimum_desired_capacity) { 1634 // Don't expand unless it's significant 1635 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1636 ergo_verbose4(ErgoHeapSizing, 1637 "attempt heap expansion", 1638 ergo_format_reason("capacity lower than " 1639 "min desired capacity after Full GC") 1640 ergo_format_byte("capacity") 1641 ergo_format_byte("occupancy") 1642 ergo_format_byte_perc("min desired capacity"), 1643 capacity_after_gc, used_after_gc, 1644 minimum_desired_capacity, (double) MinHeapFreeRatio); 1645 expand(expand_bytes); 1646 1647 // No expansion, now see if we want to shrink 1648 } else if (capacity_after_gc > maximum_desired_capacity) { 1649 // Capacity too large, compute shrinking size 1650 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1651 ergo_verbose4(ErgoHeapSizing, 1652 "attempt heap shrinking", 1653 ergo_format_reason("capacity higher than " 1654 "max desired capacity after Full GC") 1655 ergo_format_byte("capacity") 1656 ergo_format_byte("occupancy") 1657 ergo_format_byte_perc("max desired capacity"), 1658 capacity_after_gc, used_after_gc, 1659 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1660 shrink(shrink_bytes); 1661 } 1662 } 1663 1664 1665 HeapWord* 1666 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1667 bool* succeeded) { 1668 assert_at_safepoint(true /* should_be_vm_thread */); 1669 1670 *succeeded = true; 1671 // Let's attempt the allocation first. 1672 HeapWord* result = 1673 attempt_allocation_at_safepoint(word_size, 1674 false /* expect_null_mutator_alloc_region */); 1675 if (result != NULL) { 1676 assert(*succeeded, "sanity"); 1677 return result; 1678 } 1679 1680 // In a G1 heap, we're supposed to keep allocation from failing by 1681 // incremental pauses. Therefore, at least for now, we'll favor 1682 // expansion over collection. (This might change in the future if we can 1683 // do something smarter than full collection to satisfy a failed alloc.) 1684 result = expand_and_allocate(word_size); 1685 if (result != NULL) { 1686 assert(*succeeded, "sanity"); 1687 return result; 1688 } 1689 1690 // Expansion didn't work, we'll try to do a Full GC. 1691 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1692 false, /* clear_all_soft_refs */ 1693 word_size); 1694 if (!gc_succeeded) { 1695 *succeeded = false; 1696 return NULL; 1697 } 1698 1699 // Retry the allocation 1700 result = attempt_allocation_at_safepoint(word_size, 1701 true /* expect_null_mutator_alloc_region */); 1702 if (result != NULL) { 1703 assert(*succeeded, "sanity"); 1704 return result; 1705 } 1706 1707 // Then, try a Full GC that will collect all soft references. 1708 gc_succeeded = do_collection(false, /* explicit_gc */ 1709 true, /* clear_all_soft_refs */ 1710 word_size); 1711 if (!gc_succeeded) { 1712 *succeeded = false; 1713 return NULL; 1714 } 1715 1716 // Retry the allocation once more 1717 result = attempt_allocation_at_safepoint(word_size, 1718 true /* expect_null_mutator_alloc_region */); 1719 if (result != NULL) { 1720 assert(*succeeded, "sanity"); 1721 return result; 1722 } 1723 1724 assert(!collector_policy()->should_clear_all_soft_refs(), 1725 "Flag should have been handled and cleared prior to this point"); 1726 1727 // What else? We might try synchronous finalization later. If the total 1728 // space available is large enough for the allocation, then a more 1729 // complete compaction phase than we've tried so far might be 1730 // appropriate. 1731 assert(*succeeded, "sanity"); 1732 return NULL; 1733 } 1734 1735 // Attempting to expand the heap sufficiently 1736 // to support an allocation of the given "word_size". If 1737 // successful, perform the allocation and return the address of the 1738 // allocated block, or else "NULL". 1739 1740 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1741 assert_at_safepoint(true /* should_be_vm_thread */); 1742 1743 verify_region_sets_optional(); 1744 1745 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1746 ergo_verbose1(ErgoHeapSizing, 1747 "attempt heap expansion", 1748 ergo_format_reason("allocation request failed") 1749 ergo_format_byte("allocation request"), 1750 word_size * HeapWordSize); 1751 if (expand(expand_bytes)) { 1752 _hrs.verify_optional(); 1753 verify_region_sets_optional(); 1754 return attempt_allocation_at_safepoint(word_size, 1755 false /* expect_null_mutator_alloc_region */); 1756 } 1757 return NULL; 1758 } 1759 1760 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1761 HeapWord* new_end) { 1762 assert(old_end != new_end, "don't call this otherwise"); 1763 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1764 1765 // Update the committed mem region. 1766 _g1_committed.set_end(new_end); 1767 // Tell the card table about the update. 1768 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1769 // Tell the BOT about the update. 1770 _bot_shared->resize(_g1_committed.word_size()); 1771 // Tell the hot card cache about the update 1772 _cg1r->hot_card_cache()->resize_card_counts(capacity()); 1773 } 1774 1775 bool G1CollectedHeap::expand(size_t expand_bytes) { 1776 size_t old_mem_size = _g1_storage.committed_size(); 1777 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1778 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1779 HeapRegion::GrainBytes); 1780 ergo_verbose2(ErgoHeapSizing, 1781 "expand the heap", 1782 ergo_format_byte("requested expansion amount") 1783 ergo_format_byte("attempted expansion amount"), 1784 expand_bytes, aligned_expand_bytes); 1785 1786 // First commit the memory. 1787 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1788 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1789 if (successful) { 1790 // Then propagate this update to the necessary data structures. 1791 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1792 update_committed_space(old_end, new_end); 1793 1794 FreeRegionList expansion_list("Local Expansion List"); 1795 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1796 assert(mr.start() == old_end, "post-condition"); 1797 // mr might be a smaller region than what was requested if 1798 // expand_by() was unable to allocate the HeapRegion instances 1799 assert(mr.end() <= new_end, "post-condition"); 1800 1801 size_t actual_expand_bytes = mr.byte_size(); 1802 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1803 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1804 "post-condition"); 1805 if (actual_expand_bytes < aligned_expand_bytes) { 1806 // We could not expand _hrs to the desired size. In this case we 1807 // need to shrink the committed space accordingly. 1808 assert(mr.end() < new_end, "invariant"); 1809 1810 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1811 // First uncommit the memory. 1812 _g1_storage.shrink_by(diff_bytes); 1813 // Then propagate this update to the necessary data structures. 1814 update_committed_space(new_end, mr.end()); 1815 } 1816 _free_list.add_as_tail(&expansion_list); 1817 1818 if (_hr_printer.is_active()) { 1819 HeapWord* curr = mr.start(); 1820 while (curr < mr.end()) { 1821 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1822 _hr_printer.commit(curr, curr_end); 1823 curr = curr_end; 1824 } 1825 assert(curr == mr.end(), "post-condition"); 1826 } 1827 g1_policy()->record_new_heap_size(n_regions()); 1828 } else { 1829 ergo_verbose0(ErgoHeapSizing, 1830 "did not expand the heap", 1831 ergo_format_reason("heap expansion operation failed")); 1832 // The expansion of the virtual storage space was unsuccessful. 1833 // Let's see if it was because we ran out of swap. 1834 if (G1ExitOnExpansionFailure && 1835 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1836 // We had head room... 1837 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1838 } 1839 } 1840 return successful; 1841 } 1842 1843 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1844 size_t old_mem_size = _g1_storage.committed_size(); 1845 size_t aligned_shrink_bytes = 1846 ReservedSpace::page_align_size_down(shrink_bytes); 1847 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1848 HeapRegion::GrainBytes); 1849 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1850 1851 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove); 1852 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1853 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1854 1855 ergo_verbose3(ErgoHeapSizing, 1856 "shrink the heap", 1857 ergo_format_byte("requested shrinking amount") 1858 ergo_format_byte("aligned shrinking amount") 1859 ergo_format_byte("attempted shrinking amount"), 1860 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1861 if (num_regions_removed > 0) { 1862 _g1_storage.shrink_by(shrunk_bytes); 1863 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1864 1865 if (_hr_printer.is_active()) { 1866 HeapWord* curr = old_end; 1867 while (curr > new_end) { 1868 HeapWord* curr_end = curr; 1869 curr -= HeapRegion::GrainWords; 1870 _hr_printer.uncommit(curr, curr_end); 1871 } 1872 } 1873 1874 _expansion_regions += num_regions_removed; 1875 update_committed_space(old_end, new_end); 1876 HeapRegionRemSet::shrink_heap(n_regions()); 1877 g1_policy()->record_new_heap_size(n_regions()); 1878 } else { 1879 ergo_verbose0(ErgoHeapSizing, 1880 "did not shrink the heap", 1881 ergo_format_reason("heap shrinking operation failed")); 1882 } 1883 } 1884 1885 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1886 verify_region_sets_optional(); 1887 1888 // We should only reach here at the end of a Full GC which means we 1889 // should not not be holding to any GC alloc regions. The method 1890 // below will make sure of that and do any remaining clean up. 1891 abandon_gc_alloc_regions(); 1892 1893 // Instead of tearing down / rebuilding the free lists here, we 1894 // could instead use the remove_all_pending() method on free_list to 1895 // remove only the ones that we need to remove. 1896 tear_down_region_sets(true /* free_list_only */); 1897 shrink_helper(shrink_bytes); 1898 rebuild_region_sets(true /* free_list_only */); 1899 1900 _hrs.verify_optional(); 1901 verify_region_sets_optional(); 1902 } 1903 1904 // Public methods. 1905 1906 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1907 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1908 #endif // _MSC_VER 1909 1910 1911 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1912 SharedHeap(policy_), 1913 _g1_policy(policy_), 1914 _dirty_card_queue_set(false), 1915 _into_cset_dirty_card_queue_set(false), 1916 _is_alive_closure_cm(this), 1917 _is_alive_closure_stw(this), 1918 _ref_processor_cm(NULL), 1919 _ref_processor_stw(NULL), 1920 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1921 _bot_shared(NULL), 1922 _evac_failure_scan_stack(NULL) , 1923 _mark_in_progress(false), 1924 _cg1r(NULL), _summary_bytes_used(0), 1925 _g1mm(NULL), 1926 _refine_cte_cl(NULL), 1927 _full_collection(false), 1928 _free_list("Master Free List"), 1929 _secondary_free_list("Secondary Free List"), 1930 _old_set("Old Set"), 1931 _humongous_set("Master Humongous Set"), 1932 _free_regions_coming(false), 1933 _young_list(new YoungList(this)), 1934 _gc_time_stamp(0), 1935 _retained_old_gc_alloc_region(NULL), 1936 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1937 _old_plab_stats(OldPLABSize, PLABWeight), 1938 _expand_heap_after_alloc_failure(true), 1939 _surviving_young_words(NULL), 1940 _old_marking_cycles_started(0), 1941 _old_marking_cycles_completed(0), 1942 _in_cset_fast_test(NULL), 1943 _in_cset_fast_test_base(NULL), 1944 _dirty_cards_region_list(NULL), 1945 _worker_cset_start_region(NULL), 1946 _worker_cset_start_region_time_stamp(NULL) { 1947 _g1h = this; // To catch bugs. 1948 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1949 vm_exit_during_initialization("Failed necessary allocation."); 1950 } 1951 1952 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1953 1954 int n_queues = MAX2((int)ParallelGCThreads, 1); 1955 _task_queues = new RefToScanQueueSet(n_queues); 1956 1957 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1958 assert(n_rem_sets > 0, "Invariant."); 1959 1960 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1961 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1962 1963 for (int i = 0; i < n_queues; i++) { 1964 RefToScanQueue* q = new RefToScanQueue(); 1965 q->initialize(); 1966 _task_queues->register_queue(i, q); 1967 } 1968 1969 clear_cset_start_regions(); 1970 1971 // Initialize the G1EvacuationFailureALot counters and flags. 1972 NOT_PRODUCT(reset_evacuation_should_fail();) 1973 1974 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1975 } 1976 1977 jint G1CollectedHeap::initialize() { 1978 CollectedHeap::pre_initialize(); 1979 os::enable_vtime(); 1980 1981 G1Log::init(); 1982 1983 // Necessary to satisfy locking discipline assertions. 1984 1985 MutexLocker x(Heap_lock); 1986 1987 // We have to initialize the printer before committing the heap, as 1988 // it will be used then. 1989 _hr_printer.set_active(G1PrintHeapRegions); 1990 1991 // While there are no constraints in the GC code that HeapWordSize 1992 // be any particular value, there are multiple other areas in the 1993 // system which believe this to be true (e.g. oop->object_size in some 1994 // cases incorrectly returns the size in wordSize units rather than 1995 // HeapWordSize). 1996 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1997 1998 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1999 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 2000 2001 // Ensure that the sizes are properly aligned. 2002 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2003 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2004 2005 _cg1r = new ConcurrentG1Refine(this); 2006 2007 // Reserve the maximum. 2008 2009 // When compressed oops are enabled, the preferred heap base 2010 // is calculated by subtracting the requested size from the 2011 // 32Gb boundary and using the result as the base address for 2012 // heap reservation. If the requested size is not aligned to 2013 // HeapRegion::GrainBytes (i.e. the alignment that is passed 2014 // into the ReservedHeapSpace constructor) then the actual 2015 // base of the reserved heap may end up differing from the 2016 // address that was requested (i.e. the preferred heap base). 2017 // If this happens then we could end up using a non-optimal 2018 // compressed oops mode. 2019 2020 // Since max_byte_size is aligned to the size of a heap region (checked 2021 // above). 2022 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 2023 2024 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 2025 HeapRegion::GrainBytes); 2026 2027 // It is important to do this in a way such that concurrent readers can't 2028 // temporarily think somethings in the heap. (I've actually seen this 2029 // happen in asserts: DLD.) 2030 _reserved.set_word_size(0); 2031 _reserved.set_start((HeapWord*)heap_rs.base()); 2032 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 2033 2034 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes); 2035 2036 // Create the gen rem set (and barrier set) for the entire reserved region. 2037 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 2038 set_barrier_set(rem_set()->bs()); 2039 if (barrier_set()->is_a(BarrierSet::ModRef)) { 2040 _mr_bs = (ModRefBarrierSet*)_barrier_set; 2041 } else { 2042 vm_exit_during_initialization("G1 requires a mod ref bs."); 2043 return JNI_ENOMEM; 2044 } 2045 2046 // Also create a G1 rem set. 2047 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) { 2048 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs()); 2049 } else { 2050 vm_exit_during_initialization("G1 requires a cardtable mod ref bs."); 2051 return JNI_ENOMEM; 2052 } 2053 2054 // Carve out the G1 part of the heap. 2055 2056 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 2057 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 2058 g1_rs.size()/HeapWordSize); 2059 2060 _g1_storage.initialize(g1_rs, 0); 2061 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 2062 _hrs.initialize((HeapWord*) _g1_reserved.start(), 2063 (HeapWord*) _g1_reserved.end(), 2064 _expansion_regions); 2065 2066 // Do later initialization work for concurrent refinement. 2067 _cg1r->init(); 2068 2069 // 6843694 - ensure that the maximum region index can fit 2070 // in the remembered set structures. 2071 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 2072 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 2073 2074 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 2075 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 2076 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region, 2077 "too many cards per region"); 2078 2079 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1); 2080 2081 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 2082 heap_word_size(init_byte_size)); 2083 2084 _g1h = this; 2085 2086 _in_cset_fast_test_length = max_regions(); 2087 _in_cset_fast_test_base = 2088 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC); 2089 2090 // We're biasing _in_cset_fast_test to avoid subtracting the 2091 // beginning of the heap every time we want to index; basically 2092 // it's the same with what we do with the card table. 2093 _in_cset_fast_test = _in_cset_fast_test_base - 2094 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); 2095 2096 // Clear the _cset_fast_test bitmap in anticipation of adding 2097 // regions to the incremental collection set for the first 2098 // evacuation pause. 2099 clear_cset_fast_test(); 2100 2101 // Create the ConcurrentMark data structure and thread. 2102 // (Must do this late, so that "max_regions" is defined.) 2103 _cm = new ConcurrentMark(this, heap_rs); 2104 if (_cm == NULL || !_cm->completed_initialization()) { 2105 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 2106 return JNI_ENOMEM; 2107 } 2108 _cmThread = _cm->cmThread(); 2109 2110 // Initialize the from_card cache structure of HeapRegionRemSet. 2111 HeapRegionRemSet::init_heap(max_regions()); 2112 2113 // Now expand into the initial heap size. 2114 if (!expand(init_byte_size)) { 2115 vm_shutdown_during_initialization("Failed to allocate initial heap."); 2116 return JNI_ENOMEM; 2117 } 2118 2119 // Perform any initialization actions delegated to the policy. 2120 g1_policy()->init(); 2121 2122 _refine_cte_cl = 2123 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(), 2124 g1_rem_set(), 2125 concurrent_g1_refine()); 2126 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 2127 2128 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2129 SATB_Q_FL_lock, 2130 G1SATBProcessCompletedThreshold, 2131 Shared_SATB_Q_lock); 2132 2133 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2134 DirtyCardQ_FL_lock, 2135 concurrent_g1_refine()->yellow_zone(), 2136 concurrent_g1_refine()->red_zone(), 2137 Shared_DirtyCardQ_lock); 2138 2139 if (G1DeferredRSUpdate) { 2140 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2141 DirtyCardQ_FL_lock, 2142 -1, // never trigger processing 2143 -1, // no limit on length 2144 Shared_DirtyCardQ_lock, 2145 &JavaThread::dirty_card_queue_set()); 2146 } 2147 2148 // Initialize the card queue set used to hold cards containing 2149 // references into the collection set. 2150 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, 2151 DirtyCardQ_FL_lock, 2152 -1, // never trigger processing 2153 -1, // no limit on length 2154 Shared_DirtyCardQ_lock, 2155 &JavaThread::dirty_card_queue_set()); 2156 2157 // In case we're keeping closure specialization stats, initialize those 2158 // counts and that mechanism. 2159 SpecializationStats::clear(); 2160 2161 // Here we allocate the dummy full region that is required by the 2162 // G1AllocRegion class. If we don't pass an address in the reserved 2163 // space here, lots of asserts fire. 2164 2165 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2166 _g1_reserved.start()); 2167 // We'll re-use the same region whether the alloc region will 2168 // require BOT updates or not and, if it doesn't, then a non-young 2169 // region will complain that it cannot support allocations without 2170 // BOT updates. So we'll tag the dummy region as young to avoid that. 2171 dummy_region->set_young(); 2172 // Make sure it's full. 2173 dummy_region->set_top(dummy_region->end()); 2174 G1AllocRegion::setup(this, dummy_region); 2175 2176 init_mutator_alloc_region(); 2177 2178 // Do create of the monitoring and management support so that 2179 // values in the heap have been properly initialized. 2180 _g1mm = new G1MonitoringSupport(this); 2181 2182 return JNI_OK; 2183 } 2184 2185 size_t G1CollectedHeap::max_heap_alignment() { 2186 return HeapRegion::max_heap_alignment(); 2187 } 2188 2189 void G1CollectedHeap::ref_processing_init() { 2190 // Reference processing in G1 currently works as follows: 2191 // 2192 // * There are two reference processor instances. One is 2193 // used to record and process discovered references 2194 // during concurrent marking; the other is used to 2195 // record and process references during STW pauses 2196 // (both full and incremental). 2197 // * Both ref processors need to 'span' the entire heap as 2198 // the regions in the collection set may be dotted around. 2199 // 2200 // * For the concurrent marking ref processor: 2201 // * Reference discovery is enabled at initial marking. 2202 // * Reference discovery is disabled and the discovered 2203 // references processed etc during remarking. 2204 // * Reference discovery is MT (see below). 2205 // * Reference discovery requires a barrier (see below). 2206 // * Reference processing may or may not be MT 2207 // (depending on the value of ParallelRefProcEnabled 2208 // and ParallelGCThreads). 2209 // * A full GC disables reference discovery by the CM 2210 // ref processor and abandons any entries on it's 2211 // discovered lists. 2212 // 2213 // * For the STW processor: 2214 // * Non MT discovery is enabled at the start of a full GC. 2215 // * Processing and enqueueing during a full GC is non-MT. 2216 // * During a full GC, references are processed after marking. 2217 // 2218 // * Discovery (may or may not be MT) is enabled at the start 2219 // of an incremental evacuation pause. 2220 // * References are processed near the end of a STW evacuation pause. 2221 // * For both types of GC: 2222 // * Discovery is atomic - i.e. not concurrent. 2223 // * Reference discovery will not need a barrier. 2224 2225 SharedHeap::ref_processing_init(); 2226 MemRegion mr = reserved_region(); 2227 2228 // Concurrent Mark ref processor 2229 _ref_processor_cm = 2230 new ReferenceProcessor(mr, // span 2231 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2232 // mt processing 2233 (int) ParallelGCThreads, 2234 // degree of mt processing 2235 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2236 // mt discovery 2237 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2238 // degree of mt discovery 2239 false, 2240 // Reference discovery is not atomic 2241 &_is_alive_closure_cm, 2242 // is alive closure 2243 // (for efficiency/performance) 2244 true); 2245 // Setting next fields of discovered 2246 // lists requires a barrier. 2247 2248 // STW ref processor 2249 _ref_processor_stw = 2250 new ReferenceProcessor(mr, // span 2251 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2252 // mt processing 2253 MAX2((int)ParallelGCThreads, 1), 2254 // degree of mt processing 2255 (ParallelGCThreads > 1), 2256 // mt discovery 2257 MAX2((int)ParallelGCThreads, 1), 2258 // degree of mt discovery 2259 true, 2260 // Reference discovery is atomic 2261 &_is_alive_closure_stw, 2262 // is alive closure 2263 // (for efficiency/performance) 2264 false); 2265 // Setting next fields of discovered 2266 // lists requires a barrier. 2267 } 2268 2269 size_t G1CollectedHeap::capacity() const { 2270 return _g1_committed.byte_size(); 2271 } 2272 2273 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2274 assert(!hr->continuesHumongous(), "pre-condition"); 2275 hr->reset_gc_time_stamp(); 2276 if (hr->startsHumongous()) { 2277 uint first_index = hr->hrs_index() + 1; 2278 uint last_index = hr->last_hc_index(); 2279 for (uint i = first_index; i < last_index; i += 1) { 2280 HeapRegion* chr = region_at(i); 2281 assert(chr->continuesHumongous(), "sanity"); 2282 chr->reset_gc_time_stamp(); 2283 } 2284 } 2285 } 2286 2287 #ifndef PRODUCT 2288 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2289 private: 2290 unsigned _gc_time_stamp; 2291 bool _failures; 2292 2293 public: 2294 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2295 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2296 2297 virtual bool doHeapRegion(HeapRegion* hr) { 2298 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2299 if (_gc_time_stamp != region_gc_time_stamp) { 2300 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2301 "expected %d", HR_FORMAT_PARAMS(hr), 2302 region_gc_time_stamp, _gc_time_stamp); 2303 _failures = true; 2304 } 2305 return false; 2306 } 2307 2308 bool failures() { return _failures; } 2309 }; 2310 2311 void G1CollectedHeap::check_gc_time_stamps() { 2312 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2313 heap_region_iterate(&cl); 2314 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2315 } 2316 #endif // PRODUCT 2317 2318 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2319 DirtyCardQueue* into_cset_dcq, 2320 bool concurrent, 2321 int worker_i) { 2322 // Clean cards in the hot card cache 2323 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2324 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2325 2326 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2327 int n_completed_buffers = 0; 2328 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2329 n_completed_buffers++; 2330 } 2331 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2332 dcqs.clear_n_completed_buffers(); 2333 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2334 } 2335 2336 2337 // Computes the sum of the storage used by the various regions. 2338 2339 size_t G1CollectedHeap::used() const { 2340 assert(Heap_lock->owner() != NULL, 2341 "Should be owned on this thread's behalf."); 2342 size_t result = _summary_bytes_used; 2343 // Read only once in case it is set to NULL concurrently 2344 HeapRegion* hr = _mutator_alloc_region.get(); 2345 if (hr != NULL) 2346 result += hr->used(); 2347 return result; 2348 } 2349 2350 size_t G1CollectedHeap::used_unlocked() const { 2351 size_t result = _summary_bytes_used; 2352 return result; 2353 } 2354 2355 class SumUsedClosure: public HeapRegionClosure { 2356 size_t _used; 2357 public: 2358 SumUsedClosure() : _used(0) {} 2359 bool doHeapRegion(HeapRegion* r) { 2360 if (!r->continuesHumongous()) { 2361 _used += r->used(); 2362 } 2363 return false; 2364 } 2365 size_t result() { return _used; } 2366 }; 2367 2368 size_t G1CollectedHeap::recalculate_used() const { 2369 SumUsedClosure blk; 2370 heap_region_iterate(&blk); 2371 return blk.result(); 2372 } 2373 2374 size_t G1CollectedHeap::unsafe_max_alloc() { 2375 if (free_regions() > 0) return HeapRegion::GrainBytes; 2376 // otherwise, is there space in the current allocation region? 2377 2378 // We need to store the current allocation region in a local variable 2379 // here. The problem is that this method doesn't take any locks and 2380 // there may be other threads which overwrite the current allocation 2381 // region field. attempt_allocation(), for example, sets it to NULL 2382 // and this can happen *after* the NULL check here but before the call 2383 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2384 // to be a problem in the optimized build, since the two loads of the 2385 // current allocation region field are optimized away. 2386 HeapRegion* hr = _mutator_alloc_region.get(); 2387 if (hr == NULL) { 2388 return 0; 2389 } 2390 return hr->free(); 2391 } 2392 2393 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2394 switch (cause) { 2395 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2396 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2397 case GCCause::_g1_humongous_allocation: return true; 2398 default: return false; 2399 } 2400 } 2401 2402 #ifndef PRODUCT 2403 void G1CollectedHeap::allocate_dummy_regions() { 2404 // Let's fill up most of the region 2405 size_t word_size = HeapRegion::GrainWords - 1024; 2406 // And as a result the region we'll allocate will be humongous. 2407 guarantee(isHumongous(word_size), "sanity"); 2408 2409 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2410 // Let's use the existing mechanism for the allocation 2411 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2412 if (dummy_obj != NULL) { 2413 MemRegion mr(dummy_obj, word_size); 2414 CollectedHeap::fill_with_object(mr); 2415 } else { 2416 // If we can't allocate once, we probably cannot allocate 2417 // again. Let's get out of the loop. 2418 break; 2419 } 2420 } 2421 } 2422 #endif // !PRODUCT 2423 2424 void G1CollectedHeap::increment_old_marking_cycles_started() { 2425 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2426 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2427 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2428 _old_marking_cycles_started, _old_marking_cycles_completed)); 2429 2430 _old_marking_cycles_started++; 2431 } 2432 2433 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2434 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2435 2436 // We assume that if concurrent == true, then the caller is a 2437 // concurrent thread that was joined the Suspendible Thread 2438 // Set. If there's ever a cheap way to check this, we should add an 2439 // assert here. 2440 2441 // Given that this method is called at the end of a Full GC or of a 2442 // concurrent cycle, and those can be nested (i.e., a Full GC can 2443 // interrupt a concurrent cycle), the number of full collections 2444 // completed should be either one (in the case where there was no 2445 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2446 // behind the number of full collections started. 2447 2448 // This is the case for the inner caller, i.e. a Full GC. 2449 assert(concurrent || 2450 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2451 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2452 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2453 "is inconsistent with _old_marking_cycles_completed = %u", 2454 _old_marking_cycles_started, _old_marking_cycles_completed)); 2455 2456 // This is the case for the outer caller, i.e. the concurrent cycle. 2457 assert(!concurrent || 2458 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2459 err_msg("for outer caller (concurrent cycle): " 2460 "_old_marking_cycles_started = %u " 2461 "is inconsistent with _old_marking_cycles_completed = %u", 2462 _old_marking_cycles_started, _old_marking_cycles_completed)); 2463 2464 _old_marking_cycles_completed += 1; 2465 2466 // We need to clear the "in_progress" flag in the CM thread before 2467 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2468 // is set) so that if a waiter requests another System.gc() it doesn't 2469 // incorrectly see that a marking cyle is still in progress. 2470 if (concurrent) { 2471 _cmThread->clear_in_progress(); 2472 } 2473 2474 // This notify_all() will ensure that a thread that called 2475 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2476 // and it's waiting for a full GC to finish will be woken up. It is 2477 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2478 FullGCCount_lock->notify_all(); 2479 } 2480 2481 void G1CollectedHeap::collect(GCCause::Cause cause) { 2482 assert_heap_not_locked(); 2483 2484 unsigned int gc_count_before; 2485 unsigned int old_marking_count_before; 2486 bool retry_gc; 2487 2488 do { 2489 retry_gc = false; 2490 2491 { 2492 MutexLocker ml(Heap_lock); 2493 2494 // Read the GC count while holding the Heap_lock 2495 gc_count_before = total_collections(); 2496 old_marking_count_before = _old_marking_cycles_started; 2497 } 2498 2499 if (should_do_concurrent_full_gc(cause)) { 2500 // Schedule an initial-mark evacuation pause that will start a 2501 // concurrent cycle. We're setting word_size to 0 which means that 2502 // we are not requesting a post-GC allocation. 2503 VM_G1IncCollectionPause op(gc_count_before, 2504 0, /* word_size */ 2505 true, /* should_initiate_conc_mark */ 2506 g1_policy()->max_pause_time_ms(), 2507 cause); 2508 2509 VMThread::execute(&op); 2510 if (!op.pause_succeeded()) { 2511 if (old_marking_count_before == _old_marking_cycles_started) { 2512 retry_gc = op.should_retry_gc(); 2513 } else { 2514 // A Full GC happened while we were trying to schedule the 2515 // initial-mark GC. No point in starting a new cycle given 2516 // that the whole heap was collected anyway. 2517 } 2518 2519 if (retry_gc) { 2520 if (GC_locker::is_active_and_needs_gc()) { 2521 GC_locker::stall_until_clear(); 2522 } 2523 } 2524 } 2525 } else { 2526 if (cause == GCCause::_gc_locker 2527 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2528 2529 // Schedule a standard evacuation pause. We're setting word_size 2530 // to 0 which means that we are not requesting a post-GC allocation. 2531 VM_G1IncCollectionPause op(gc_count_before, 2532 0, /* word_size */ 2533 false, /* should_initiate_conc_mark */ 2534 g1_policy()->max_pause_time_ms(), 2535 cause); 2536 VMThread::execute(&op); 2537 } else { 2538 // Schedule a Full GC. 2539 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause); 2540 VMThread::execute(&op); 2541 } 2542 } 2543 } while (retry_gc); 2544 } 2545 2546 bool G1CollectedHeap::is_in(const void* p) const { 2547 if (_g1_committed.contains(p)) { 2548 // Given that we know that p is in the committed space, 2549 // heap_region_containing_raw() should successfully 2550 // return the containing region. 2551 HeapRegion* hr = heap_region_containing_raw(p); 2552 return hr->is_in(p); 2553 } else { 2554 return false; 2555 } 2556 } 2557 2558 // Iteration functions. 2559 2560 // Iterates an OopClosure over all ref-containing fields of objects 2561 // within a HeapRegion. 2562 2563 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2564 MemRegion _mr; 2565 ExtendedOopClosure* _cl; 2566 public: 2567 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl) 2568 : _mr(mr), _cl(cl) {} 2569 bool doHeapRegion(HeapRegion* r) { 2570 if (!r->continuesHumongous()) { 2571 r->oop_iterate(_cl); 2572 } 2573 return false; 2574 } 2575 }; 2576 2577 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2578 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2579 heap_region_iterate(&blk); 2580 } 2581 2582 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) { 2583 IterateOopClosureRegionClosure blk(mr, cl); 2584 heap_region_iterate(&blk); 2585 } 2586 2587 // Iterates an ObjectClosure over all objects within a HeapRegion. 2588 2589 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2590 ObjectClosure* _cl; 2591 public: 2592 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2593 bool doHeapRegion(HeapRegion* r) { 2594 if (! r->continuesHumongous()) { 2595 r->object_iterate(_cl); 2596 } 2597 return false; 2598 } 2599 }; 2600 2601 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2602 IterateObjectClosureRegionClosure blk(cl); 2603 heap_region_iterate(&blk); 2604 } 2605 2606 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) { 2607 // FIXME: is this right? 2608 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap"); 2609 } 2610 2611 // Calls a SpaceClosure on a HeapRegion. 2612 2613 class SpaceClosureRegionClosure: public HeapRegionClosure { 2614 SpaceClosure* _cl; 2615 public: 2616 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2617 bool doHeapRegion(HeapRegion* r) { 2618 _cl->do_space(r); 2619 return false; 2620 } 2621 }; 2622 2623 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2624 SpaceClosureRegionClosure blk(cl); 2625 heap_region_iterate(&blk); 2626 } 2627 2628 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2629 _hrs.iterate(cl); 2630 } 2631 2632 void 2633 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2634 uint worker_id, 2635 uint no_of_par_workers, 2636 jint claim_value) { 2637 const uint regions = n_regions(); 2638 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 2639 no_of_par_workers : 2640 1); 2641 assert(UseDynamicNumberOfGCThreads || 2642 no_of_par_workers == workers()->total_workers(), 2643 "Non dynamic should use fixed number of workers"); 2644 // try to spread out the starting points of the workers 2645 const HeapRegion* start_hr = 2646 start_region_for_worker(worker_id, no_of_par_workers); 2647 const uint start_index = start_hr->hrs_index(); 2648 2649 // each worker will actually look at all regions 2650 for (uint count = 0; count < regions; ++count) { 2651 const uint index = (start_index + count) % regions; 2652 assert(0 <= index && index < regions, "sanity"); 2653 HeapRegion* r = region_at(index); 2654 // we'll ignore "continues humongous" regions (we'll process them 2655 // when we come across their corresponding "start humongous" 2656 // region) and regions already claimed 2657 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2658 continue; 2659 } 2660 // OK, try to claim it 2661 if (r->claimHeapRegion(claim_value)) { 2662 // success! 2663 assert(!r->continuesHumongous(), "sanity"); 2664 if (r->startsHumongous()) { 2665 // If the region is "starts humongous" we'll iterate over its 2666 // "continues humongous" first; in fact we'll do them 2667 // first. The order is important. In on case, calling the 2668 // closure on the "starts humongous" region might de-allocate 2669 // and clear all its "continues humongous" regions and, as a 2670 // result, we might end up processing them twice. So, we'll do 2671 // them first (notice: most closures will ignore them anyway) and 2672 // then we'll do the "starts humongous" region. 2673 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) { 2674 HeapRegion* chr = region_at(ch_index); 2675 2676 // if the region has already been claimed or it's not 2677 // "continues humongous" we're done 2678 if (chr->claim_value() == claim_value || 2679 !chr->continuesHumongous()) { 2680 break; 2681 } 2682 2683 // Noone should have claimed it directly. We can given 2684 // that we claimed its "starts humongous" region. 2685 assert(chr->claim_value() != claim_value, "sanity"); 2686 assert(chr->humongous_start_region() == r, "sanity"); 2687 2688 if (chr->claimHeapRegion(claim_value)) { 2689 // we should always be able to claim it; noone else should 2690 // be trying to claim this region 2691 2692 bool res2 = cl->doHeapRegion(chr); 2693 assert(!res2, "Should not abort"); 2694 2695 // Right now, this holds (i.e., no closure that actually 2696 // does something with "continues humongous" regions 2697 // clears them). We might have to weaken it in the future, 2698 // but let's leave these two asserts here for extra safety. 2699 assert(chr->continuesHumongous(), "should still be the case"); 2700 assert(chr->humongous_start_region() == r, "sanity"); 2701 } else { 2702 guarantee(false, "we should not reach here"); 2703 } 2704 } 2705 } 2706 2707 assert(!r->continuesHumongous(), "sanity"); 2708 bool res = cl->doHeapRegion(r); 2709 assert(!res, "Should not abort"); 2710 } 2711 } 2712 } 2713 2714 class ResetClaimValuesClosure: public HeapRegionClosure { 2715 public: 2716 bool doHeapRegion(HeapRegion* r) { 2717 r->set_claim_value(HeapRegion::InitialClaimValue); 2718 return false; 2719 } 2720 }; 2721 2722 void G1CollectedHeap::reset_heap_region_claim_values() { 2723 ResetClaimValuesClosure blk; 2724 heap_region_iterate(&blk); 2725 } 2726 2727 void G1CollectedHeap::reset_cset_heap_region_claim_values() { 2728 ResetClaimValuesClosure blk; 2729 collection_set_iterate(&blk); 2730 } 2731 2732 #ifdef ASSERT 2733 // This checks whether all regions in the heap have the correct claim 2734 // value. I also piggy-backed on this a check to ensure that the 2735 // humongous_start_region() information on "continues humongous" 2736 // regions is correct. 2737 2738 class CheckClaimValuesClosure : public HeapRegionClosure { 2739 private: 2740 jint _claim_value; 2741 uint _failures; 2742 HeapRegion* _sh_region; 2743 2744 public: 2745 CheckClaimValuesClosure(jint claim_value) : 2746 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2747 bool doHeapRegion(HeapRegion* r) { 2748 if (r->claim_value() != _claim_value) { 2749 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2750 "claim value = %d, should be %d", 2751 HR_FORMAT_PARAMS(r), 2752 r->claim_value(), _claim_value); 2753 ++_failures; 2754 } 2755 if (!r->isHumongous()) { 2756 _sh_region = NULL; 2757 } else if (r->startsHumongous()) { 2758 _sh_region = r; 2759 } else if (r->continuesHumongous()) { 2760 if (r->humongous_start_region() != _sh_region) { 2761 gclog_or_tty->print_cr("Region " HR_FORMAT ", " 2762 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2763 HR_FORMAT_PARAMS(r), 2764 r->humongous_start_region(), 2765 _sh_region); 2766 ++_failures; 2767 } 2768 } 2769 return false; 2770 } 2771 uint failures() { return _failures; } 2772 }; 2773 2774 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2775 CheckClaimValuesClosure cl(claim_value); 2776 heap_region_iterate(&cl); 2777 return cl.failures() == 0; 2778 } 2779 2780 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure { 2781 private: 2782 jint _claim_value; 2783 uint _failures; 2784 2785 public: 2786 CheckClaimValuesInCSetHRClosure(jint claim_value) : 2787 _claim_value(claim_value), _failures(0) { } 2788 2789 uint failures() { return _failures; } 2790 2791 bool doHeapRegion(HeapRegion* hr) { 2792 assert(hr->in_collection_set(), "how?"); 2793 assert(!hr->isHumongous(), "H-region in CSet"); 2794 if (hr->claim_value() != _claim_value) { 2795 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", " 2796 "claim value = %d, should be %d", 2797 HR_FORMAT_PARAMS(hr), 2798 hr->claim_value(), _claim_value); 2799 _failures += 1; 2800 } 2801 return false; 2802 } 2803 }; 2804 2805 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) { 2806 CheckClaimValuesInCSetHRClosure cl(claim_value); 2807 collection_set_iterate(&cl); 2808 return cl.failures() == 0; 2809 } 2810 #endif // ASSERT 2811 2812 // Clear the cached CSet starting regions and (more importantly) 2813 // the time stamps. Called when we reset the GC time stamp. 2814 void G1CollectedHeap::clear_cset_start_regions() { 2815 assert(_worker_cset_start_region != NULL, "sanity"); 2816 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2817 2818 int n_queues = MAX2((int)ParallelGCThreads, 1); 2819 for (int i = 0; i < n_queues; i++) { 2820 _worker_cset_start_region[i] = NULL; 2821 _worker_cset_start_region_time_stamp[i] = 0; 2822 } 2823 } 2824 2825 // Given the id of a worker, obtain or calculate a suitable 2826 // starting region for iterating over the current collection set. 2827 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) { 2828 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2829 2830 HeapRegion* result = NULL; 2831 unsigned gc_time_stamp = get_gc_time_stamp(); 2832 2833 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2834 // Cached starting region for current worker was set 2835 // during the current pause - so it's valid. 2836 // Note: the cached starting heap region may be NULL 2837 // (when the collection set is empty). 2838 result = _worker_cset_start_region[worker_i]; 2839 assert(result == NULL || result->in_collection_set(), "sanity"); 2840 return result; 2841 } 2842 2843 // The cached entry was not valid so let's calculate 2844 // a suitable starting heap region for this worker. 2845 2846 // We want the parallel threads to start their collection 2847 // set iteration at different collection set regions to 2848 // avoid contention. 2849 // If we have: 2850 // n collection set regions 2851 // p threads 2852 // Then thread t will start at region floor ((t * n) / p) 2853 2854 result = g1_policy()->collection_set(); 2855 if (G1CollectedHeap::use_parallel_gc_threads()) { 2856 uint cs_size = g1_policy()->cset_region_length(); 2857 uint active_workers = workers()->active_workers(); 2858 assert(UseDynamicNumberOfGCThreads || 2859 active_workers == workers()->total_workers(), 2860 "Unless dynamic should use total workers"); 2861 2862 uint end_ind = (cs_size * worker_i) / active_workers; 2863 uint start_ind = 0; 2864 2865 if (worker_i > 0 && 2866 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2867 // Previous workers starting region is valid 2868 // so let's iterate from there 2869 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2870 result = _worker_cset_start_region[worker_i - 1]; 2871 } 2872 2873 for (uint i = start_ind; i < end_ind; i++) { 2874 result = result->next_in_collection_set(); 2875 } 2876 } 2877 2878 // Note: the calculated starting heap region may be NULL 2879 // (when the collection set is empty). 2880 assert(result == NULL || result->in_collection_set(), "sanity"); 2881 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2882 "should be updated only once per pause"); 2883 _worker_cset_start_region[worker_i] = result; 2884 OrderAccess::storestore(); 2885 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2886 return result; 2887 } 2888 2889 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i, 2890 uint no_of_par_workers) { 2891 uint worker_num = 2892 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U; 2893 assert(UseDynamicNumberOfGCThreads || 2894 no_of_par_workers == workers()->total_workers(), 2895 "Non dynamic should use fixed number of workers"); 2896 const uint start_index = n_regions() * worker_i / worker_num; 2897 return region_at(start_index); 2898 } 2899 2900 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2901 HeapRegion* r = g1_policy()->collection_set(); 2902 while (r != NULL) { 2903 HeapRegion* next = r->next_in_collection_set(); 2904 if (cl->doHeapRegion(r)) { 2905 cl->incomplete(); 2906 return; 2907 } 2908 r = next; 2909 } 2910 } 2911 2912 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2913 HeapRegionClosure *cl) { 2914 if (r == NULL) { 2915 // The CSet is empty so there's nothing to do. 2916 return; 2917 } 2918 2919 assert(r->in_collection_set(), 2920 "Start region must be a member of the collection set."); 2921 HeapRegion* cur = r; 2922 while (cur != NULL) { 2923 HeapRegion* next = cur->next_in_collection_set(); 2924 if (cl->doHeapRegion(cur) && false) { 2925 cl->incomplete(); 2926 return; 2927 } 2928 cur = next; 2929 } 2930 cur = g1_policy()->collection_set(); 2931 while (cur != r) { 2932 HeapRegion* next = cur->next_in_collection_set(); 2933 if (cl->doHeapRegion(cur) && false) { 2934 cl->incomplete(); 2935 return; 2936 } 2937 cur = next; 2938 } 2939 } 2940 2941 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2942 return n_regions() > 0 ? region_at(0) : NULL; 2943 } 2944 2945 2946 Space* G1CollectedHeap::space_containing(const void* addr) const { 2947 Space* res = heap_region_containing(addr); 2948 return res; 2949 } 2950 2951 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2952 Space* sp = space_containing(addr); 2953 if (sp != NULL) { 2954 return sp->block_start(addr); 2955 } 2956 return NULL; 2957 } 2958 2959 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2960 Space* sp = space_containing(addr); 2961 assert(sp != NULL, "block_size of address outside of heap"); 2962 return sp->block_size(addr); 2963 } 2964 2965 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2966 Space* sp = space_containing(addr); 2967 return sp->block_is_obj(addr); 2968 } 2969 2970 bool G1CollectedHeap::supports_tlab_allocation() const { 2971 return true; 2972 } 2973 2974 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2975 return HeapRegion::GrainBytes; 2976 } 2977 2978 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2979 // Return the remaining space in the cur alloc region, but not less than 2980 // the min TLAB size. 2981 2982 // Also, this value can be at most the humongous object threshold, 2983 // since we can't allow tlabs to grow big enough to accomodate 2984 // humongous objects. 2985 2986 HeapRegion* hr = _mutator_alloc_region.get(); 2987 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize; 2988 if (hr == NULL) { 2989 return max_tlab_size; 2990 } else { 2991 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size); 2992 } 2993 } 2994 2995 size_t G1CollectedHeap::max_capacity() const { 2996 return _g1_reserved.byte_size(); 2997 } 2998 2999 jlong G1CollectedHeap::millis_since_last_gc() { 3000 // assert(false, "NYI"); 3001 return 0; 3002 } 3003 3004 void G1CollectedHeap::prepare_for_verify() { 3005 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 3006 ensure_parsability(false); 3007 } 3008 g1_rem_set()->prepare_for_verify(); 3009 } 3010 3011 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 3012 VerifyOption vo) { 3013 switch (vo) { 3014 case VerifyOption_G1UsePrevMarking: 3015 return hr->obj_allocated_since_prev_marking(obj); 3016 case VerifyOption_G1UseNextMarking: 3017 return hr->obj_allocated_since_next_marking(obj); 3018 case VerifyOption_G1UseMarkWord: 3019 return false; 3020 default: 3021 ShouldNotReachHere(); 3022 } 3023 return false; // keep some compilers happy 3024 } 3025 3026 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 3027 switch (vo) { 3028 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 3029 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 3030 case VerifyOption_G1UseMarkWord: return NULL; 3031 default: ShouldNotReachHere(); 3032 } 3033 return NULL; // keep some compilers happy 3034 } 3035 3036 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 3037 switch (vo) { 3038 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 3039 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 3040 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 3041 default: ShouldNotReachHere(); 3042 } 3043 return false; // keep some compilers happy 3044 } 3045 3046 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 3047 switch (vo) { 3048 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 3049 case VerifyOption_G1UseNextMarking: return "NTAMS"; 3050 case VerifyOption_G1UseMarkWord: return "NONE"; 3051 default: ShouldNotReachHere(); 3052 } 3053 return NULL; // keep some compilers happy 3054 } 3055 3056 class VerifyLivenessOopClosure: public OopClosure { 3057 G1CollectedHeap* _g1h; 3058 VerifyOption _vo; 3059 public: 3060 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 3061 _g1h(g1h), _vo(vo) 3062 { } 3063 void do_oop(narrowOop *p) { do_oop_work(p); } 3064 void do_oop( oop *p) { do_oop_work(p); } 3065 3066 template <class T> void do_oop_work(T *p) { 3067 oop obj = oopDesc::load_decode_heap_oop(p); 3068 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 3069 "Dead object referenced by a not dead object"); 3070 } 3071 }; 3072 3073 class VerifyObjsInRegionClosure: public ObjectClosure { 3074 private: 3075 G1CollectedHeap* _g1h; 3076 size_t _live_bytes; 3077 HeapRegion *_hr; 3078 VerifyOption _vo; 3079 public: 3080 // _vo == UsePrevMarking -> use "prev" marking information, 3081 // _vo == UseNextMarking -> use "next" marking information, 3082 // _vo == UseMarkWord -> use mark word from object header. 3083 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 3084 : _live_bytes(0), _hr(hr), _vo(vo) { 3085 _g1h = G1CollectedHeap::heap(); 3086 } 3087 void do_object(oop o) { 3088 VerifyLivenessOopClosure isLive(_g1h, _vo); 3089 assert(o != NULL, "Huh?"); 3090 if (!_g1h->is_obj_dead_cond(o, _vo)) { 3091 // If the object is alive according to the mark word, 3092 // then verify that the marking information agrees. 3093 // Note we can't verify the contra-positive of the 3094 // above: if the object is dead (according to the mark 3095 // word), it may not be marked, or may have been marked 3096 // but has since became dead, or may have been allocated 3097 // since the last marking. 3098 if (_vo == VerifyOption_G1UseMarkWord) { 3099 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 3100 } 3101 3102 o->oop_iterate_no_header(&isLive); 3103 if (!_hr->obj_allocated_since_prev_marking(o)) { 3104 size_t obj_size = o->size(); // Make sure we don't overflow 3105 _live_bytes += (obj_size * HeapWordSize); 3106 } 3107 } 3108 } 3109 size_t live_bytes() { return _live_bytes; } 3110 }; 3111 3112 class PrintObjsInRegionClosure : public ObjectClosure { 3113 HeapRegion *_hr; 3114 G1CollectedHeap *_g1; 3115 public: 3116 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 3117 _g1 = G1CollectedHeap::heap(); 3118 }; 3119 3120 void do_object(oop o) { 3121 if (o != NULL) { 3122 HeapWord *start = (HeapWord *) o; 3123 size_t word_sz = o->size(); 3124 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3125 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3126 (void*) o, word_sz, 3127 _g1->isMarkedPrev(o), 3128 _g1->isMarkedNext(o), 3129 _hr->obj_allocated_since_prev_marking(o)); 3130 HeapWord *end = start + word_sz; 3131 HeapWord *cur; 3132 int *val; 3133 for (cur = start; cur < end; cur++) { 3134 val = (int *) cur; 3135 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 3136 } 3137 } 3138 } 3139 }; 3140 3141 class VerifyRegionClosure: public HeapRegionClosure { 3142 private: 3143 bool _par; 3144 VerifyOption _vo; 3145 bool _failures; 3146 public: 3147 // _vo == UsePrevMarking -> use "prev" marking information, 3148 // _vo == UseNextMarking -> use "next" marking information, 3149 // _vo == UseMarkWord -> use mark word from object header. 3150 VerifyRegionClosure(bool par, VerifyOption vo) 3151 : _par(par), 3152 _vo(vo), 3153 _failures(false) {} 3154 3155 bool failures() { 3156 return _failures; 3157 } 3158 3159 bool doHeapRegion(HeapRegion* r) { 3160 if (!r->continuesHumongous()) { 3161 bool failures = false; 3162 r->verify(_vo, &failures); 3163 if (failures) { 3164 _failures = true; 3165 } else { 3166 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3167 r->object_iterate(¬_dead_yet_cl); 3168 if (_vo != VerifyOption_G1UseNextMarking) { 3169 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3170 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3171 "max_live_bytes "SIZE_FORMAT" " 3172 "< calculated "SIZE_FORMAT, 3173 r->bottom(), r->end(), 3174 r->max_live_bytes(), 3175 not_dead_yet_cl.live_bytes()); 3176 _failures = true; 3177 } 3178 } else { 3179 // When vo == UseNextMarking we cannot currently do a sanity 3180 // check on the live bytes as the calculation has not been 3181 // finalized yet. 3182 } 3183 } 3184 } 3185 return false; // stop the region iteration if we hit a failure 3186 } 3187 }; 3188 3189 class YoungRefCounterClosure : public OopClosure { 3190 G1CollectedHeap* _g1h; 3191 int _count; 3192 public: 3193 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 3194 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 3195 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 3196 3197 int count() { return _count; } 3198 void reset_count() { _count = 0; }; 3199 }; 3200 3201 class VerifyKlassClosure: public KlassClosure { 3202 YoungRefCounterClosure _young_ref_counter_closure; 3203 OopClosure *_oop_closure; 3204 public: 3205 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 3206 void do_klass(Klass* k) { 3207 k->oops_do(_oop_closure); 3208 3209 _young_ref_counter_closure.reset_count(); 3210 k->oops_do(&_young_ref_counter_closure); 3211 if (_young_ref_counter_closure.count() > 0) { 3212 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k)); 3213 } 3214 } 3215 }; 3216 3217 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can 3218 // pass it as the perm_blk to SharedHeap::process_strong_roots. 3219 // When process_strong_roots stop calling perm_blk->younger_refs_iterate 3220 // we can change this closure to extend the simpler OopClosure. 3221 class VerifyRootsClosure: public OopsInGenClosure { 3222 private: 3223 G1CollectedHeap* _g1h; 3224 VerifyOption _vo; 3225 bool _failures; 3226 public: 3227 // _vo == UsePrevMarking -> use "prev" marking information, 3228 // _vo == UseNextMarking -> use "next" marking information, 3229 // _vo == UseMarkWord -> use mark word from object header. 3230 VerifyRootsClosure(VerifyOption vo) : 3231 _g1h(G1CollectedHeap::heap()), 3232 _vo(vo), 3233 _failures(false) { } 3234 3235 bool failures() { return _failures; } 3236 3237 template <class T> void do_oop_nv(T* p) { 3238 T heap_oop = oopDesc::load_heap_oop(p); 3239 if (!oopDesc::is_null(heap_oop)) { 3240 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 3241 if (_g1h->is_obj_dead_cond(obj, _vo)) { 3242 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 3243 "points to dead obj "PTR_FORMAT, p, (void*) obj); 3244 if (_vo == VerifyOption_G1UseMarkWord) { 3245 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 3246 } 3247 obj->print_on(gclog_or_tty); 3248 _failures = true; 3249 } 3250 } 3251 } 3252 3253 void do_oop(oop* p) { do_oop_nv(p); } 3254 void do_oop(narrowOop* p) { do_oop_nv(p); } 3255 }; 3256 3257 // This is the task used for parallel heap verification. 3258 3259 class G1ParVerifyTask: public AbstractGangTask { 3260 private: 3261 G1CollectedHeap* _g1h; 3262 VerifyOption _vo; 3263 bool _failures; 3264 3265 public: 3266 // _vo == UsePrevMarking -> use "prev" marking information, 3267 // _vo == UseNextMarking -> use "next" marking information, 3268 // _vo == UseMarkWord -> use mark word from object header. 3269 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3270 AbstractGangTask("Parallel verify task"), 3271 _g1h(g1h), 3272 _vo(vo), 3273 _failures(false) { } 3274 3275 bool failures() { 3276 return _failures; 3277 } 3278 3279 void work(uint worker_id) { 3280 HandleMark hm; 3281 VerifyRegionClosure blk(true, _vo); 3282 _g1h->heap_region_par_iterate_chunked(&blk, worker_id, 3283 _g1h->workers()->active_workers(), 3284 HeapRegion::ParVerifyClaimValue); 3285 if (blk.failures()) { 3286 _failures = true; 3287 } 3288 } 3289 }; 3290 3291 void G1CollectedHeap::verify(bool silent) { 3292 verify(silent, VerifyOption_G1UsePrevMarking); 3293 } 3294 3295 void G1CollectedHeap::verify(bool silent, 3296 VerifyOption vo) { 3297 if (SafepointSynchronize::is_at_safepoint()) { 3298 if (!silent) { gclog_or_tty->print("Roots "); } 3299 VerifyRootsClosure rootsCl(vo); 3300 3301 assert(Thread::current()->is_VM_thread(), 3302 "Expected to be executed serially by the VM thread at this point"); 3303 3304 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false); 3305 VerifyKlassClosure klassCl(this, &rootsCl); 3306 3307 // We apply the relevant closures to all the oops in the 3308 // system dictionary, the string table and the code cache. 3309 const int so = SO_AllClasses | SO_Strings | SO_CodeCache; 3310 3311 // Need cleared claim bits for the strong roots processing 3312 ClassLoaderDataGraph::clear_claimed_marks(); 3313 3314 process_strong_roots(true, // activate StrongRootsScope 3315 false, // we set "is scavenging" to false, 3316 // so we don't reset the dirty cards. 3317 ScanningOption(so), // roots scanning options 3318 &rootsCl, 3319 &blobsCl, 3320 &klassCl 3321 ); 3322 3323 bool failures = rootsCl.failures(); 3324 3325 if (vo != VerifyOption_G1UseMarkWord) { 3326 // If we're verifying during a full GC then the region sets 3327 // will have been torn down at the start of the GC. Therefore 3328 // verifying the region sets will fail. So we only verify 3329 // the region sets when not in a full GC. 3330 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3331 verify_region_sets(); 3332 } 3333 3334 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3335 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3336 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3337 "sanity check"); 3338 3339 G1ParVerifyTask task(this, vo); 3340 assert(UseDynamicNumberOfGCThreads || 3341 workers()->active_workers() == workers()->total_workers(), 3342 "If not dynamic should be using all the workers"); 3343 int n_workers = workers()->active_workers(); 3344 set_par_threads(n_workers); 3345 workers()->run_task(&task); 3346 set_par_threads(0); 3347 if (task.failures()) { 3348 failures = true; 3349 } 3350 3351 // Checks that the expected amount of parallel work was done. 3352 // The implication is that n_workers is > 0. 3353 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 3354 "sanity check"); 3355 3356 reset_heap_region_claim_values(); 3357 3358 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 3359 "sanity check"); 3360 } else { 3361 VerifyRegionClosure blk(false, vo); 3362 heap_region_iterate(&blk); 3363 if (blk.failures()) { 3364 failures = true; 3365 } 3366 } 3367 if (!silent) gclog_or_tty->print("RemSet "); 3368 rem_set()->verify(); 3369 3370 if (failures) { 3371 gclog_or_tty->print_cr("Heap:"); 3372 // It helps to have the per-region information in the output to 3373 // help us track down what went wrong. This is why we call 3374 // print_extended_on() instead of print_on(). 3375 print_extended_on(gclog_or_tty); 3376 gclog_or_tty->print_cr(""); 3377 #ifndef PRODUCT 3378 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3379 concurrent_mark()->print_reachable("at-verification-failure", 3380 vo, false /* all */); 3381 } 3382 #endif 3383 gclog_or_tty->flush(); 3384 } 3385 guarantee(!failures, "there should not have been any failures"); 3386 } else { 3387 if (!silent) 3388 gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) "); 3389 } 3390 } 3391 3392 class PrintRegionClosure: public HeapRegionClosure { 3393 outputStream* _st; 3394 public: 3395 PrintRegionClosure(outputStream* st) : _st(st) {} 3396 bool doHeapRegion(HeapRegion* r) { 3397 r->print_on(_st); 3398 return false; 3399 } 3400 }; 3401 3402 void G1CollectedHeap::print_on(outputStream* st) const { 3403 st->print(" %-20s", "garbage-first heap"); 3404 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3405 capacity()/K, used_unlocked()/K); 3406 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3407 _g1_storage.low_boundary(), 3408 _g1_storage.high(), 3409 _g1_storage.high_boundary()); 3410 st->cr(); 3411 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3412 uint young_regions = _young_list->length(); 3413 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3414 (size_t) young_regions * HeapRegion::GrainBytes / K); 3415 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3416 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3417 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3418 st->cr(); 3419 MetaspaceAux::print_on(st); 3420 } 3421 3422 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3423 print_on(st); 3424 3425 // Print the per-region information. 3426 st->cr(); 3427 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3428 "HS=humongous(starts), HC=humongous(continues), " 3429 "CS=collection set, F=free, TS=gc time stamp, " 3430 "PTAMS=previous top-at-mark-start, " 3431 "NTAMS=next top-at-mark-start)"); 3432 PrintRegionClosure blk(st); 3433 heap_region_iterate(&blk); 3434 } 3435 3436 void G1CollectedHeap::print_on_error(outputStream* st) const { 3437 this->CollectedHeap::print_on_error(st); 3438 3439 if (_cm != NULL) { 3440 st->cr(); 3441 _cm->print_on_error(st); 3442 } 3443 } 3444 3445 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3446 if (G1CollectedHeap::use_parallel_gc_threads()) { 3447 workers()->print_worker_threads_on(st); 3448 } 3449 _cmThread->print_on(st); 3450 st->cr(); 3451 _cm->print_worker_threads_on(st); 3452 _cg1r->print_worker_threads_on(st); 3453 } 3454 3455 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3456 if (G1CollectedHeap::use_parallel_gc_threads()) { 3457 workers()->threads_do(tc); 3458 } 3459 tc->do_thread(_cmThread); 3460 _cg1r->threads_do(tc); 3461 } 3462 3463 void G1CollectedHeap::print_tracing_info() const { 3464 // We'll overload this to mean "trace GC pause statistics." 3465 if (TraceGen0Time || TraceGen1Time) { 3466 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3467 // to that. 3468 g1_policy()->print_tracing_info(); 3469 } 3470 if (G1SummarizeRSetStats) { 3471 g1_rem_set()->print_summary_info(); 3472 } 3473 if (G1SummarizeConcMark) { 3474 concurrent_mark()->print_summary_info(); 3475 } 3476 g1_policy()->print_yg_surv_rate_info(); 3477 SpecializationStats::print(); 3478 } 3479 3480 #ifndef PRODUCT 3481 // Helpful for debugging RSet issues. 3482 3483 class PrintRSetsClosure : public HeapRegionClosure { 3484 private: 3485 const char* _msg; 3486 size_t _occupied_sum; 3487 3488 public: 3489 bool doHeapRegion(HeapRegion* r) { 3490 HeapRegionRemSet* hrrs = r->rem_set(); 3491 size_t occupied = hrrs->occupied(); 3492 _occupied_sum += occupied; 3493 3494 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3495 HR_FORMAT_PARAMS(r)); 3496 if (occupied == 0) { 3497 gclog_or_tty->print_cr(" RSet is empty"); 3498 } else { 3499 hrrs->print(); 3500 } 3501 gclog_or_tty->print_cr("----------"); 3502 return false; 3503 } 3504 3505 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3506 gclog_or_tty->cr(); 3507 gclog_or_tty->print_cr("========================================"); 3508 gclog_or_tty->print_cr(msg); 3509 gclog_or_tty->cr(); 3510 } 3511 3512 ~PrintRSetsClosure() { 3513 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3514 gclog_or_tty->print_cr("========================================"); 3515 gclog_or_tty->cr(); 3516 } 3517 }; 3518 3519 void G1CollectedHeap::print_cset_rsets() { 3520 PrintRSetsClosure cl("Printing CSet RSets"); 3521 collection_set_iterate(&cl); 3522 } 3523 3524 void G1CollectedHeap::print_all_rsets() { 3525 PrintRSetsClosure cl("Printing All RSets");; 3526 heap_region_iterate(&cl); 3527 } 3528 #endif // PRODUCT 3529 3530 G1CollectedHeap* G1CollectedHeap::heap() { 3531 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3532 "not a garbage-first heap"); 3533 return _g1h; 3534 } 3535 3536 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3537 // always_do_update_barrier = false; 3538 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3539 // Call allocation profiler 3540 AllocationProfiler::iterate_since_last_gc(); 3541 // Fill TLAB's and such 3542 ensure_parsability(true); 3543 } 3544 3545 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3546 3547 if (G1SummarizeRSetStats && 3548 (G1SummarizeRSetStatsPeriod > 0) && 3549 // we are at the end of the GC. Total collections has already been increased. 3550 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3551 g1_rem_set()->print_periodic_summary_info(); 3552 } 3553 3554 // FIXME: what is this about? 3555 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3556 // is set. 3557 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3558 "derived pointer present")); 3559 // always_do_update_barrier = true; 3560 3561 // We have just completed a GC. Update the soft reference 3562 // policy with the new heap occupancy 3563 Universe::update_heap_info_at_gc(); 3564 } 3565 3566 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3567 unsigned int gc_count_before, 3568 bool* succeeded) { 3569 assert_heap_not_locked_and_not_at_safepoint(); 3570 g1_policy()->record_stop_world_start(); 3571 VM_G1IncCollectionPause op(gc_count_before, 3572 word_size, 3573 false, /* should_initiate_conc_mark */ 3574 g1_policy()->max_pause_time_ms(), 3575 GCCause::_g1_inc_collection_pause); 3576 VMThread::execute(&op); 3577 3578 HeapWord* result = op.result(); 3579 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3580 assert(result == NULL || ret_succeeded, 3581 "the result should be NULL if the VM did not succeed"); 3582 *succeeded = ret_succeeded; 3583 3584 assert_heap_not_locked(); 3585 return result; 3586 } 3587 3588 void 3589 G1CollectedHeap::doConcurrentMark() { 3590 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3591 if (!_cmThread->in_progress()) { 3592 _cmThread->set_started(); 3593 CGC_lock->notify(); 3594 } 3595 } 3596 3597 size_t G1CollectedHeap::pending_card_num() { 3598 size_t extra_cards = 0; 3599 JavaThread *curr = Threads::first(); 3600 while (curr != NULL) { 3601 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3602 extra_cards += dcq.size(); 3603 curr = curr->next(); 3604 } 3605 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3606 size_t buffer_size = dcqs.buffer_size(); 3607 size_t buffer_num = dcqs.completed_buffers_num(); 3608 3609 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3610 // in bytes - not the number of 'entries'. We need to convert 3611 // into a number of cards. 3612 return (buffer_size * buffer_num + extra_cards) / oopSize; 3613 } 3614 3615 size_t G1CollectedHeap::cards_scanned() { 3616 return g1_rem_set()->cardsScanned(); 3617 } 3618 3619 void 3620 G1CollectedHeap::setup_surviving_young_words() { 3621 assert(_surviving_young_words == NULL, "pre-condition"); 3622 uint array_length = g1_policy()->young_cset_region_length(); 3623 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3624 if (_surviving_young_words == NULL) { 3625 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3626 "Not enough space for young surv words summary."); 3627 } 3628 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3629 #ifdef ASSERT 3630 for (uint i = 0; i < array_length; ++i) { 3631 assert( _surviving_young_words[i] == 0, "memset above" ); 3632 } 3633 #endif // !ASSERT 3634 } 3635 3636 void 3637 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3638 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3639 uint array_length = g1_policy()->young_cset_region_length(); 3640 for (uint i = 0; i < array_length; ++i) { 3641 _surviving_young_words[i] += surv_young_words[i]; 3642 } 3643 } 3644 3645 void 3646 G1CollectedHeap::cleanup_surviving_young_words() { 3647 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3648 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3649 _surviving_young_words = NULL; 3650 } 3651 3652 #ifdef ASSERT 3653 class VerifyCSetClosure: public HeapRegionClosure { 3654 public: 3655 bool doHeapRegion(HeapRegion* hr) { 3656 // Here we check that the CSet region's RSet is ready for parallel 3657 // iteration. The fields that we'll verify are only manipulated 3658 // when the region is part of a CSet and is collected. Afterwards, 3659 // we reset these fields when we clear the region's RSet (when the 3660 // region is freed) so they are ready when the region is 3661 // re-allocated. The only exception to this is if there's an 3662 // evacuation failure and instead of freeing the region we leave 3663 // it in the heap. In that case, we reset these fields during 3664 // evacuation failure handling. 3665 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3666 3667 // Here's a good place to add any other checks we'd like to 3668 // perform on CSet regions. 3669 return false; 3670 } 3671 }; 3672 #endif // ASSERT 3673 3674 #if TASKQUEUE_STATS 3675 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3676 st->print_raw_cr("GC Task Stats"); 3677 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3678 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3679 } 3680 3681 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3682 print_taskqueue_stats_hdr(st); 3683 3684 TaskQueueStats totals; 3685 const int n = workers() != NULL ? workers()->total_workers() : 1; 3686 for (int i = 0; i < n; ++i) { 3687 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3688 totals += task_queue(i)->stats; 3689 } 3690 st->print_raw("tot "); totals.print(st); st->cr(); 3691 3692 DEBUG_ONLY(totals.verify()); 3693 } 3694 3695 void G1CollectedHeap::reset_taskqueue_stats() { 3696 const int n = workers() != NULL ? workers()->total_workers() : 1; 3697 for (int i = 0; i < n; ++i) { 3698 task_queue(i)->stats.reset(); 3699 } 3700 } 3701 #endif // TASKQUEUE_STATS 3702 3703 void G1CollectedHeap::log_gc_header() { 3704 if (!G1Log::fine()) { 3705 return; 3706 } 3707 3708 gclog_or_tty->date_stamp(PrintGCDateStamps); 3709 gclog_or_tty->stamp(PrintGCTimeStamps); 3710 3711 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3712 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3713 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3714 3715 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3716 } 3717 3718 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3719 if (!G1Log::fine()) { 3720 return; 3721 } 3722 3723 if (G1Log::finer()) { 3724 if (evacuation_failed()) { 3725 gclog_or_tty->print(" (to-space exhausted)"); 3726 } 3727 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3728 g1_policy()->phase_times()->note_gc_end(); 3729 g1_policy()->phase_times()->print(pause_time_sec); 3730 g1_policy()->print_detailed_heap_transition(); 3731 } else { 3732 if (evacuation_failed()) { 3733 gclog_or_tty->print("--"); 3734 } 3735 g1_policy()->print_heap_transition(); 3736 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3737 } 3738 gclog_or_tty->flush(); 3739 } 3740 3741 bool 3742 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3743 assert_at_safepoint(true /* should_be_vm_thread */); 3744 guarantee(!is_gc_active(), "collection is not reentrant"); 3745 3746 if (GC_locker::check_active_before_gc()) { 3747 return false; 3748 } 3749 3750 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3751 ResourceMark rm; 3752 3753 print_heap_before_gc(); 3754 3755 HRSPhaseSetter x(HRSPhaseEvacuation); 3756 verify_region_sets_optional(); 3757 verify_dirty_young_regions(); 3758 3759 // This call will decide whether this pause is an initial-mark 3760 // pause. If it is, during_initial_mark_pause() will return true 3761 // for the duration of this pause. 3762 g1_policy()->decide_on_conc_mark_initiation(); 3763 3764 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3765 assert(!g1_policy()->during_initial_mark_pause() || 3766 g1_policy()->gcs_are_young(), "sanity"); 3767 3768 // We also do not allow mixed GCs during marking. 3769 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3770 3771 // Record whether this pause is an initial mark. When the current 3772 // thread has completed its logging output and it's safe to signal 3773 // the CM thread, the flag's value in the policy has been reset. 3774 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3775 3776 // Inner scope for scope based logging, timers, and stats collection 3777 { 3778 if (g1_policy()->during_initial_mark_pause()) { 3779 // We are about to start a marking cycle, so we increment the 3780 // full collection counter. 3781 increment_old_marking_cycles_started(); 3782 } 3783 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3784 3785 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ? 3786 workers()->active_workers() : 1); 3787 double pause_start_sec = os::elapsedTime(); 3788 g1_policy()->phase_times()->note_gc_start(active_workers); 3789 log_gc_header(); 3790 3791 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3792 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3793 3794 // If the secondary_free_list is not empty, append it to the 3795 // free_list. No need to wait for the cleanup operation to finish; 3796 // the region allocation code will check the secondary_free_list 3797 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3798 // set, skip this step so that the region allocation code has to 3799 // get entries from the secondary_free_list. 3800 if (!G1StressConcRegionFreeing) { 3801 append_secondary_free_list_if_not_empty_with_lock(); 3802 } 3803 3804 assert(check_young_list_well_formed(), 3805 "young list should be well formed"); 3806 3807 // Don't dynamically change the number of GC threads this early. A value of 3808 // 0 is used to indicate serial work. When parallel work is done, 3809 // it will be set. 3810 3811 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3812 IsGCActiveMark x; 3813 3814 gc_prologue(false); 3815 increment_total_collections(false /* full gc */); 3816 increment_gc_time_stamp(); 3817 3818 verify_before_gc(); 3819 3820 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3821 3822 // Please see comment in g1CollectedHeap.hpp and 3823 // G1CollectedHeap::ref_processing_init() to see how 3824 // reference processing currently works in G1. 3825 3826 // Enable discovery in the STW reference processor 3827 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3828 true /*verify_no_refs*/); 3829 3830 { 3831 // We want to temporarily turn off discovery by the 3832 // CM ref processor, if necessary, and turn it back on 3833 // on again later if we do. Using a scoped 3834 // NoRefDiscovery object will do this. 3835 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3836 3837 // Forget the current alloc region (we might even choose it to be part 3838 // of the collection set!). 3839 release_mutator_alloc_region(); 3840 3841 // We should call this after we retire the mutator alloc 3842 // region(s) so that all the ALLOC / RETIRE events are generated 3843 // before the start GC event. 3844 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3845 3846 // This timing is only used by the ergonomics to handle our pause target. 3847 // It is unclear why this should not include the full pause. We will 3848 // investigate this in CR 7178365. 3849 // 3850 // Preserving the old comment here if that helps the investigation: 3851 // 3852 // The elapsed time induced by the start time below deliberately elides 3853 // the possible verification above. 3854 double sample_start_time_sec = os::elapsedTime(); 3855 3856 #if YOUNG_LIST_VERBOSE 3857 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3858 _young_list->print(); 3859 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3860 #endif // YOUNG_LIST_VERBOSE 3861 3862 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3863 3864 double scan_wait_start = os::elapsedTime(); 3865 // We have to wait until the CM threads finish scanning the 3866 // root regions as it's the only way to ensure that all the 3867 // objects on them have been correctly scanned before we start 3868 // moving them during the GC. 3869 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3870 double wait_time_ms = 0.0; 3871 if (waited) { 3872 double scan_wait_end = os::elapsedTime(); 3873 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3874 } 3875 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3876 3877 #if YOUNG_LIST_VERBOSE 3878 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3879 _young_list->print(); 3880 #endif // YOUNG_LIST_VERBOSE 3881 3882 if (g1_policy()->during_initial_mark_pause()) { 3883 concurrent_mark()->checkpointRootsInitialPre(); 3884 } 3885 3886 #if YOUNG_LIST_VERBOSE 3887 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3888 _young_list->print(); 3889 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3890 #endif // YOUNG_LIST_VERBOSE 3891 3892 g1_policy()->finalize_cset(target_pause_time_ms); 3893 3894 _cm->note_start_of_gc(); 3895 // We should not verify the per-thread SATB buffers given that 3896 // we have not filtered them yet (we'll do so during the 3897 // GC). We also call this after finalize_cset() to 3898 // ensure that the CSet has been finalized. 3899 _cm->verify_no_cset_oops(true /* verify_stacks */, 3900 true /* verify_enqueued_buffers */, 3901 false /* verify_thread_buffers */, 3902 true /* verify_fingers */); 3903 3904 if (_hr_printer.is_active()) { 3905 HeapRegion* hr = g1_policy()->collection_set(); 3906 while (hr != NULL) { 3907 G1HRPrinter::RegionType type; 3908 if (!hr->is_young()) { 3909 type = G1HRPrinter::Old; 3910 } else if (hr->is_survivor()) { 3911 type = G1HRPrinter::Survivor; 3912 } else { 3913 type = G1HRPrinter::Eden; 3914 } 3915 _hr_printer.cset(hr); 3916 hr = hr->next_in_collection_set(); 3917 } 3918 } 3919 3920 #ifdef ASSERT 3921 VerifyCSetClosure cl; 3922 collection_set_iterate(&cl); 3923 #endif // ASSERT 3924 3925 setup_surviving_young_words(); 3926 3927 // Initialize the GC alloc regions. 3928 init_gc_alloc_regions(); 3929 3930 // Actually do the work... 3931 evacuate_collection_set(); 3932 3933 // We do this to mainly verify the per-thread SATB buffers 3934 // (which have been filtered by now) since we didn't verify 3935 // them earlier. No point in re-checking the stacks / enqueued 3936 // buffers given that the CSet has not changed since last time 3937 // we checked. 3938 _cm->verify_no_cset_oops(false /* verify_stacks */, 3939 false /* verify_enqueued_buffers */, 3940 true /* verify_thread_buffers */, 3941 true /* verify_fingers */); 3942 3943 free_collection_set(g1_policy()->collection_set()); 3944 g1_policy()->clear_collection_set(); 3945 3946 cleanup_surviving_young_words(); 3947 3948 // Start a new incremental collection set for the next pause. 3949 g1_policy()->start_incremental_cset_building(); 3950 3951 // Clear the _cset_fast_test bitmap in anticipation of adding 3952 // regions to the incremental collection set for the next 3953 // evacuation pause. 3954 clear_cset_fast_test(); 3955 3956 _young_list->reset_sampled_info(); 3957 3958 // Don't check the whole heap at this point as the 3959 // GC alloc regions from this pause have been tagged 3960 // as survivors and moved on to the survivor list. 3961 // Survivor regions will fail the !is_young() check. 3962 assert(check_young_list_empty(false /* check_heap */), 3963 "young list should be empty"); 3964 3965 #if YOUNG_LIST_VERBOSE 3966 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3967 _young_list->print(); 3968 #endif // YOUNG_LIST_VERBOSE 3969 3970 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3971 _young_list->first_survivor_region(), 3972 _young_list->last_survivor_region()); 3973 3974 _young_list->reset_auxilary_lists(); 3975 3976 if (evacuation_failed()) { 3977 _summary_bytes_used = recalculate_used(); 3978 } else { 3979 // The "used" of the the collection set have already been subtracted 3980 // when they were freed. Add in the bytes evacuated. 3981 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 3982 } 3983 3984 if (g1_policy()->during_initial_mark_pause()) { 3985 // We have to do this before we notify the CM threads that 3986 // they can start working to make sure that all the 3987 // appropriate initialization is done on the CM object. 3988 concurrent_mark()->checkpointRootsInitialPost(); 3989 set_marking_started(); 3990 // Note that we don't actually trigger the CM thread at 3991 // this point. We do that later when we're sure that 3992 // the current thread has completed its logging output. 3993 } 3994 3995 allocate_dummy_regions(); 3996 3997 #if YOUNG_LIST_VERBOSE 3998 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3999 _young_list->print(); 4000 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 4001 #endif // YOUNG_LIST_VERBOSE 4002 4003 init_mutator_alloc_region(); 4004 4005 { 4006 size_t expand_bytes = g1_policy()->expansion_amount(); 4007 if (expand_bytes > 0) { 4008 size_t bytes_before = capacity(); 4009 // No need for an ergo verbose message here, 4010 // expansion_amount() does this when it returns a value > 0. 4011 if (!expand(expand_bytes)) { 4012 // We failed to expand the heap so let's verify that 4013 // committed/uncommitted amount match the backing store 4014 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 4015 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 4016 } 4017 } 4018 } 4019 4020 // We redo the verificaiton but now wrt to the new CSet which 4021 // has just got initialized after the previous CSet was freed. 4022 _cm->verify_no_cset_oops(true /* verify_stacks */, 4023 true /* verify_enqueued_buffers */, 4024 true /* verify_thread_buffers */, 4025 true /* verify_fingers */); 4026 _cm->note_end_of_gc(); 4027 4028 // This timing is only used by the ergonomics to handle our pause target. 4029 // It is unclear why this should not include the full pause. We will 4030 // investigate this in CR 7178365. 4031 double sample_end_time_sec = os::elapsedTime(); 4032 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 4033 g1_policy()->record_collection_pause_end(pause_time_ms); 4034 4035 MemoryService::track_memory_usage(); 4036 4037 // In prepare_for_verify() below we'll need to scan the deferred 4038 // update buffers to bring the RSets up-to-date if 4039 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 4040 // the update buffers we'll probably need to scan cards on the 4041 // regions we just allocated to (i.e., the GC alloc 4042 // regions). However, during the last GC we called 4043 // set_saved_mark() on all the GC alloc regions, so card 4044 // scanning might skip the [saved_mark_word()...top()] area of 4045 // those regions (i.e., the area we allocated objects into 4046 // during the last GC). But it shouldn't. Given that 4047 // saved_mark_word() is conditional on whether the GC time stamp 4048 // on the region is current or not, by incrementing the GC time 4049 // stamp here we invalidate all the GC time stamps on all the 4050 // regions and saved_mark_word() will simply return top() for 4051 // all the regions. This is a nicer way of ensuring this rather 4052 // than iterating over the regions and fixing them. In fact, the 4053 // GC time stamp increment here also ensures that 4054 // saved_mark_word() will return top() between pauses, i.e., 4055 // during concurrent refinement. So we don't need the 4056 // is_gc_active() check to decided which top to use when 4057 // scanning cards (see CR 7039627). 4058 increment_gc_time_stamp(); 4059 4060 verify_after_gc(); 4061 4062 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 4063 ref_processor_stw()->verify_no_references_recorded(); 4064 4065 // CM reference discovery will be re-enabled if necessary. 4066 } 4067 4068 // We should do this after we potentially expand the heap so 4069 // that all the COMMIT events are generated before the end GC 4070 // event, and after we retire the GC alloc regions so that all 4071 // RETIRE events are generated before the end GC event. 4072 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 4073 4074 if (mark_in_progress()) { 4075 concurrent_mark()->update_g1_committed(); 4076 } 4077 4078 #ifdef TRACESPINNING 4079 ParallelTaskTerminator::print_termination_counts(); 4080 #endif 4081 4082 gc_epilogue(false); 4083 } 4084 4085 // Print the remainder of the GC log output. 4086 log_gc_footer(os::elapsedTime() - pause_start_sec); 4087 4088 // It is not yet to safe to tell the concurrent mark to 4089 // start as we have some optional output below. We don't want the 4090 // output from the concurrent mark thread interfering with this 4091 // logging output either. 4092 4093 _hrs.verify_optional(); 4094 verify_region_sets_optional(); 4095 4096 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 4097 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4098 4099 print_heap_after_gc(); 4100 4101 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4102 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4103 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4104 // before any GC notifications are raised. 4105 g1mm()->update_sizes(); 4106 } 4107 4108 // It should now be safe to tell the concurrent mark thread to start 4109 // without its logging output interfering with the logging output 4110 // that came from the pause. 4111 4112 if (should_start_conc_mark) { 4113 // CAUTION: after the doConcurrentMark() call below, 4114 // the concurrent marking thread(s) could be running 4115 // concurrently with us. Make sure that anything after 4116 // this point does not assume that we are the only GC thread 4117 // running. Note: of course, the actual marking work will 4118 // not start until the safepoint itself is released in 4119 // ConcurrentGCThread::safepoint_desynchronize(). 4120 doConcurrentMark(); 4121 } 4122 4123 return true; 4124 } 4125 4126 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4127 { 4128 size_t gclab_word_size; 4129 switch (purpose) { 4130 case GCAllocForSurvived: 4131 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4132 break; 4133 case GCAllocForTenured: 4134 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4135 break; 4136 default: 4137 assert(false, "unknown GCAllocPurpose"); 4138 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4139 break; 4140 } 4141 4142 // Prevent humongous PLAB sizes for two reasons: 4143 // * PLABs are allocated using a similar paths as oops, but should 4144 // never be in a humongous region 4145 // * Allowing humongous PLABs needlessly churns the region free lists 4146 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4147 } 4148 4149 void G1CollectedHeap::init_mutator_alloc_region() { 4150 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 4151 _mutator_alloc_region.init(); 4152 } 4153 4154 void G1CollectedHeap::release_mutator_alloc_region() { 4155 _mutator_alloc_region.release(); 4156 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 4157 } 4158 4159 void G1CollectedHeap::init_gc_alloc_regions() { 4160 assert_at_safepoint(true /* should_be_vm_thread */); 4161 4162 _survivor_gc_alloc_region.init(); 4163 _old_gc_alloc_region.init(); 4164 HeapRegion* retained_region = _retained_old_gc_alloc_region; 4165 _retained_old_gc_alloc_region = NULL; 4166 4167 // We will discard the current GC alloc region if: 4168 // a) it's in the collection set (it can happen!), 4169 // b) it's already full (no point in using it), 4170 // c) it's empty (this means that it was emptied during 4171 // a cleanup and it should be on the free list now), or 4172 // d) it's humongous (this means that it was emptied 4173 // during a cleanup and was added to the free list, but 4174 // has been subseqently used to allocate a humongous 4175 // object that may be less than the region size). 4176 if (retained_region != NULL && 4177 !retained_region->in_collection_set() && 4178 !(retained_region->top() == retained_region->end()) && 4179 !retained_region->is_empty() && 4180 !retained_region->isHumongous()) { 4181 retained_region->set_saved_mark(); 4182 // The retained region was added to the old region set when it was 4183 // retired. We have to remove it now, since we don't allow regions 4184 // we allocate to in the region sets. We'll re-add it later, when 4185 // it's retired again. 4186 _old_set.remove(retained_region); 4187 bool during_im = g1_policy()->during_initial_mark_pause(); 4188 retained_region->note_start_of_copying(during_im); 4189 _old_gc_alloc_region.set(retained_region); 4190 _hr_printer.reuse(retained_region); 4191 } 4192 } 4193 4194 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers) { 4195 _survivor_gc_alloc_region.release(); 4196 // If we have an old GC alloc region to release, we'll save it in 4197 // _retained_old_gc_alloc_region. If we don't 4198 // _retained_old_gc_alloc_region will become NULL. This is what we 4199 // want either way so no reason to check explicitly for either 4200 // condition. 4201 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 4202 4203 if (ResizePLAB) { 4204 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4205 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers); 4206 } 4207 } 4208 4209 void G1CollectedHeap::abandon_gc_alloc_regions() { 4210 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 4211 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 4212 _retained_old_gc_alloc_region = NULL; 4213 } 4214 4215 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4216 _drain_in_progress = false; 4217 set_evac_failure_closure(cl); 4218 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4219 } 4220 4221 void G1CollectedHeap::finalize_for_evac_failure() { 4222 assert(_evac_failure_scan_stack != NULL && 4223 _evac_failure_scan_stack->length() == 0, 4224 "Postcondition"); 4225 assert(!_drain_in_progress, "Postcondition"); 4226 delete _evac_failure_scan_stack; 4227 _evac_failure_scan_stack = NULL; 4228 } 4229 4230 void G1CollectedHeap::remove_self_forwarding_pointers() { 4231 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4232 4233 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4234 4235 if (G1CollectedHeap::use_parallel_gc_threads()) { 4236 set_par_threads(); 4237 workers()->run_task(&rsfp_task); 4238 set_par_threads(0); 4239 } else { 4240 rsfp_task.work(0); 4241 } 4242 4243 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity"); 4244 4245 // Reset the claim values in the regions in the collection set. 4246 reset_cset_heap_region_claim_values(); 4247 4248 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity"); 4249 4250 // Now restore saved marks, if any. 4251 assert(_objs_with_preserved_marks.size() == 4252 _preserved_marks_of_objs.size(), "Both or none."); 4253 while (!_objs_with_preserved_marks.is_empty()) { 4254 oop obj = _objs_with_preserved_marks.pop(); 4255 markOop m = _preserved_marks_of_objs.pop(); 4256 obj->set_mark(m); 4257 } 4258 _objs_with_preserved_marks.clear(true); 4259 _preserved_marks_of_objs.clear(true); 4260 } 4261 4262 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4263 _evac_failure_scan_stack->push(obj); 4264 } 4265 4266 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4267 assert(_evac_failure_scan_stack != NULL, "precondition"); 4268 4269 while (_evac_failure_scan_stack->length() > 0) { 4270 oop obj = _evac_failure_scan_stack->pop(); 4271 _evac_failure_closure->set_region(heap_region_containing(obj)); 4272 obj->oop_iterate_backwards(_evac_failure_closure); 4273 } 4274 } 4275 4276 oop 4277 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, 4278 oop old) { 4279 assert(obj_in_cs(old), 4280 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4281 (HeapWord*) old)); 4282 markOop m = old->mark(); 4283 oop forward_ptr = old->forward_to_atomic(old); 4284 if (forward_ptr == NULL) { 4285 // Forward-to-self succeeded. 4286 4287 if (_evac_failure_closure != cl) { 4288 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4289 assert(!_drain_in_progress, 4290 "Should only be true while someone holds the lock."); 4291 // Set the global evac-failure closure to the current thread's. 4292 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4293 set_evac_failure_closure(cl); 4294 // Now do the common part. 4295 handle_evacuation_failure_common(old, m); 4296 // Reset to NULL. 4297 set_evac_failure_closure(NULL); 4298 } else { 4299 // The lock is already held, and this is recursive. 4300 assert(_drain_in_progress, "This should only be the recursive case."); 4301 handle_evacuation_failure_common(old, m); 4302 } 4303 return old; 4304 } else { 4305 // Forward-to-self failed. Either someone else managed to allocate 4306 // space for this object (old != forward_ptr) or they beat us in 4307 // self-forwarding it (old == forward_ptr). 4308 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4309 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4310 "should not be in the CSet", 4311 (HeapWord*) old, (HeapWord*) forward_ptr)); 4312 return forward_ptr; 4313 } 4314 } 4315 4316 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4317 set_evacuation_failed(true); 4318 4319 preserve_mark_if_necessary(old, m); 4320 4321 HeapRegion* r = heap_region_containing(old); 4322 if (!r->evacuation_failed()) { 4323 r->set_evacuation_failed(true); 4324 _hr_printer.evac_failure(r); 4325 } 4326 4327 push_on_evac_failure_scan_stack(old); 4328 4329 if (!_drain_in_progress) { 4330 // prevent recursion in copy_to_survivor_space() 4331 _drain_in_progress = true; 4332 drain_evac_failure_scan_stack(); 4333 _drain_in_progress = false; 4334 } 4335 } 4336 4337 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4338 assert(evacuation_failed(), "Oversaving!"); 4339 // We want to call the "for_promotion_failure" version only in the 4340 // case of a promotion failure. 4341 if (m->must_be_preserved_for_promotion_failure(obj)) { 4342 _objs_with_preserved_marks.push(obj); 4343 _preserved_marks_of_objs.push(m); 4344 } 4345 } 4346 4347 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4348 size_t word_size) { 4349 if (purpose == GCAllocForSurvived) { 4350 HeapWord* result = survivor_attempt_allocation(word_size); 4351 if (result != NULL) { 4352 return result; 4353 } else { 4354 // Let's try to allocate in the old gen in case we can fit the 4355 // object there. 4356 return old_attempt_allocation(word_size); 4357 } 4358 } else { 4359 assert(purpose == GCAllocForTenured, "sanity"); 4360 HeapWord* result = old_attempt_allocation(word_size); 4361 if (result != NULL) { 4362 return result; 4363 } else { 4364 // Let's try to allocate in the survivors in case we can fit the 4365 // object there. 4366 return survivor_attempt_allocation(word_size); 4367 } 4368 } 4369 4370 ShouldNotReachHere(); 4371 // Trying to keep some compilers happy. 4372 return NULL; 4373 } 4374 4375 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) : 4376 ParGCAllocBuffer(gclab_word_size), _retired(false) { } 4377 4378 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num) 4379 : _g1h(g1h), 4380 _refs(g1h->task_queue(queue_num)), 4381 _dcq(&g1h->dirty_card_queue_set()), 4382 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()), 4383 _g1_rem(g1h->g1_rem_set()), 4384 _hash_seed(17), _queue_num(queue_num), 4385 _term_attempts(0), 4386 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4387 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4388 _age_table(false), 4389 _strong_roots_time(0), _term_time(0), 4390 _alloc_buffer_waste(0), _undo_waste(0) { 4391 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4392 // we "sacrifice" entry 0 to keep track of surviving bytes for 4393 // non-young regions (where the age is -1) 4394 // We also add a few elements at the beginning and at the end in 4395 // an attempt to eliminate cache contention 4396 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 4397 uint array_length = PADDING_ELEM_NUM + 4398 real_length + 4399 PADDING_ELEM_NUM; 4400 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); 4401 if (_surviving_young_words_base == NULL) 4402 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR, 4403 "Not enough space for young surv histo."); 4404 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4405 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); 4406 4407 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4408 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4409 4410 _start = os::elapsedTime(); 4411 } 4412 4413 void 4414 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4415 { 4416 st->print_raw_cr("GC Termination Stats"); 4417 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4418 " ------waste (KiB)------"); 4419 st->print_raw_cr("thr ms ms % ms % attempts" 4420 " total alloc undo"); 4421 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4422 " ------- ------- -------"); 4423 } 4424 4425 void 4426 G1ParScanThreadState::print_termination_stats(int i, 4427 outputStream* const st) const 4428 { 4429 const double elapsed_ms = elapsed_time() * 1000.0; 4430 const double s_roots_ms = strong_roots_time() * 1000.0; 4431 const double term_ms = term_time() * 1000.0; 4432 st->print_cr("%3d %9.2f %9.2f %6.2f " 4433 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4434 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4435 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4436 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4437 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4438 alloc_buffer_waste() * HeapWordSize / K, 4439 undo_waste() * HeapWordSize / K); 4440 } 4441 4442 #ifdef ASSERT 4443 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4444 assert(ref != NULL, "invariant"); 4445 assert(UseCompressedOops, "sanity"); 4446 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4447 oop p = oopDesc::load_decode_heap_oop(ref); 4448 assert(_g1h->is_in_g1_reserved(p), 4449 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4450 return true; 4451 } 4452 4453 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4454 assert(ref != NULL, "invariant"); 4455 if (has_partial_array_mask(ref)) { 4456 // Must be in the collection set--it's already been copied. 4457 oop p = clear_partial_array_mask(ref); 4458 assert(_g1h->obj_in_cs(p), 4459 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4460 } else { 4461 oop p = oopDesc::load_decode_heap_oop(ref); 4462 assert(_g1h->is_in_g1_reserved(p), 4463 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4464 } 4465 return true; 4466 } 4467 4468 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4469 if (ref.is_narrow()) { 4470 return verify_ref((narrowOop*) ref); 4471 } else { 4472 return verify_ref((oop*) ref); 4473 } 4474 } 4475 #endif // ASSERT 4476 4477 void G1ParScanThreadState::trim_queue() { 4478 assert(_evac_cl != NULL, "not set"); 4479 assert(_evac_failure_cl != NULL, "not set"); 4480 assert(_partial_scan_cl != NULL, "not set"); 4481 4482 StarTask ref; 4483 do { 4484 // Drain the overflow stack first, so other threads can steal. 4485 while (refs()->pop_overflow(ref)) { 4486 deal_with_reference(ref); 4487 } 4488 4489 while (refs()->pop_local(ref)) { 4490 deal_with_reference(ref); 4491 } 4492 } while (!refs()->is_empty()); 4493 } 4494 4495 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, 4496 G1ParScanThreadState* par_scan_state) : 4497 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()), 4498 _par_scan_state(par_scan_state), 4499 _worker_id(par_scan_state->queue_num()), 4500 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()), 4501 _mark_in_progress(_g1->mark_in_progress()) { } 4502 4503 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4504 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) { 4505 #ifdef ASSERT 4506 HeapRegion* hr = _g1->heap_region_containing(obj); 4507 assert(hr != NULL, "sanity"); 4508 assert(!hr->in_collection_set(), "should not mark objects in the CSet"); 4509 #endif // ASSERT 4510 4511 // We know that the object is not moving so it's safe to read its size. 4512 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4513 } 4514 4515 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4516 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4517 ::mark_forwarded_object(oop from_obj, oop to_obj) { 4518 #ifdef ASSERT 4519 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4520 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4521 assert(from_obj != to_obj, "should not be self-forwarded"); 4522 4523 HeapRegion* from_hr = _g1->heap_region_containing(from_obj); 4524 assert(from_hr != NULL, "sanity"); 4525 assert(from_hr->in_collection_set(), "from obj should be in the CSet"); 4526 4527 HeapRegion* to_hr = _g1->heap_region_containing(to_obj); 4528 assert(to_hr != NULL, "sanity"); 4529 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet"); 4530 #endif // ASSERT 4531 4532 // The object might be in the process of being copied by another 4533 // worker so we cannot trust that its to-space image is 4534 // well-formed. So we have to read its size from its from-space 4535 // image which we know should not be changing. 4536 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4537 } 4538 4539 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4540 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4541 ::copy_to_survivor_space(oop old) { 4542 size_t word_sz = old->size(); 4543 HeapRegion* from_region = _g1->heap_region_containing_raw(old); 4544 // +1 to make the -1 indexes valid... 4545 int young_index = from_region->young_index_in_cset()+1; 4546 assert( (from_region->is_young() && young_index > 0) || 4547 (!from_region->is_young() && young_index == 0), "invariant" ); 4548 G1CollectorPolicy* g1p = _g1->g1_policy(); 4549 markOop m = old->mark(); 4550 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4551 : m->age(); 4552 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4553 word_sz); 4554 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz); 4555 #ifndef PRODUCT 4556 // Should this evacuation fail? 4557 if (_g1->evacuation_should_fail()) { 4558 if (obj_ptr != NULL) { 4559 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4560 obj_ptr = NULL; 4561 } 4562 } 4563 #endif // !PRODUCT 4564 4565 if (obj_ptr == NULL) { 4566 // This will either forward-to-self, or detect that someone else has 4567 // installed a forwarding pointer. 4568 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4569 return _g1->handle_evacuation_failure_par(cl, old); 4570 } 4571 4572 oop obj = oop(obj_ptr); 4573 4574 // We're going to allocate linearly, so might as well prefetch ahead. 4575 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4576 4577 oop forward_ptr = old->forward_to_atomic(obj); 4578 if (forward_ptr == NULL) { 4579 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4580 if (g1p->track_object_age(alloc_purpose)) { 4581 // We could simply do obj->incr_age(). However, this causes a 4582 // performance issue. obj->incr_age() will first check whether 4583 // the object has a displaced mark by checking its mark word; 4584 // getting the mark word from the new location of the object 4585 // stalls. So, given that we already have the mark word and we 4586 // are about to install it anyway, it's better to increase the 4587 // age on the mark word, when the object does not have a 4588 // displaced mark word. We're not expecting many objects to have 4589 // a displaced marked word, so that case is not optimized 4590 // further (it could be...) and we simply call obj->incr_age(). 4591 4592 if (m->has_displaced_mark_helper()) { 4593 // in this case, we have to install the mark word first, 4594 // otherwise obj looks to be forwarded (the old mark word, 4595 // which contains the forward pointer, was copied) 4596 obj->set_mark(m); 4597 obj->incr_age(); 4598 } else { 4599 m = m->incr_age(); 4600 obj->set_mark(m); 4601 } 4602 _par_scan_state->age_table()->add(obj, word_sz); 4603 } else { 4604 obj->set_mark(m); 4605 } 4606 4607 size_t* surv_young_words = _par_scan_state->surviving_young_words(); 4608 surv_young_words[young_index] += word_sz; 4609 4610 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4611 // We keep track of the next start index in the length field of 4612 // the to-space object. The actual length can be found in the 4613 // length field of the from-space object. 4614 arrayOop(obj)->set_length(0); 4615 oop* old_p = set_partial_array_mask(old); 4616 _par_scan_state->push_on_queue(old_p); 4617 } else { 4618 // No point in using the slower heap_region_containing() method, 4619 // given that we know obj is in the heap. 4620 _scanner.set_region(_g1->heap_region_containing_raw(obj)); 4621 obj->oop_iterate_backwards(&_scanner); 4622 } 4623 } else { 4624 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4625 obj = forward_ptr; 4626 } 4627 return obj; 4628 } 4629 4630 template <class T> 4631 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4632 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4633 _scanned_klass->record_modified_oops(); 4634 } 4635 } 4636 4637 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object> 4638 template <class T> 4639 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object> 4640 ::do_oop_work(T* p) { 4641 oop obj = oopDesc::load_decode_heap_oop(p); 4642 assert(barrier != G1BarrierRS || obj != NULL, 4643 "Precondition: G1BarrierRS implies obj is non-NULL"); 4644 4645 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4646 4647 // here the null check is implicit in the cset_fast_test() test 4648 if (_g1->in_cset_fast_test(obj)) { 4649 oop forwardee; 4650 if (obj->is_forwarded()) { 4651 forwardee = obj->forwardee(); 4652 } else { 4653 forwardee = copy_to_survivor_space(obj); 4654 } 4655 assert(forwardee != NULL, "forwardee should not be NULL"); 4656 oopDesc::encode_store_heap_oop(p, forwardee); 4657 if (do_mark_object && forwardee != obj) { 4658 // If the object is self-forwarded we don't need to explicitly 4659 // mark it, the evacuation failure protocol will do so. 4660 mark_forwarded_object(obj, forwardee); 4661 } 4662 4663 // When scanning the RS, we only care about objs in CS. 4664 if (barrier == G1BarrierRS) { 4665 _par_scan_state->update_rs(_from, p, _worker_id); 4666 } else if (barrier == G1BarrierKlass) { 4667 do_klass_barrier(p, forwardee); 4668 } 4669 } else { 4670 // The object is not in collection set. If we're a root scanning 4671 // closure during an initial mark pause (i.e. do_mark_object will 4672 // be true) then attempt to mark the object. 4673 if (do_mark_object && _g1->is_in_g1_reserved(obj)) { 4674 mark_object(obj); 4675 } 4676 } 4677 4678 if (barrier == G1BarrierEvac && obj != NULL) { 4679 _par_scan_state->update_rs(_from, p, _worker_id); 4680 } 4681 4682 if (do_gen_barrier && obj != NULL) { 4683 par_do_barrier(p); 4684 } 4685 } 4686 4687 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p); 4688 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4689 4690 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) { 4691 assert(has_partial_array_mask(p), "invariant"); 4692 oop from_obj = clear_partial_array_mask(p); 4693 4694 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap."); 4695 assert(from_obj->is_objArray(), "must be obj array"); 4696 objArrayOop from_obj_array = objArrayOop(from_obj); 4697 // The from-space object contains the real length. 4698 int length = from_obj_array->length(); 4699 4700 assert(from_obj->is_forwarded(), "must be forwarded"); 4701 oop to_obj = from_obj->forwardee(); 4702 assert(from_obj != to_obj, "should not be chunking self-forwarded objects"); 4703 objArrayOop to_obj_array = objArrayOop(to_obj); 4704 // We keep track of the next start index in the length field of the 4705 // to-space object. 4706 int next_index = to_obj_array->length(); 4707 assert(0 <= next_index && next_index < length, 4708 err_msg("invariant, next index: %d, length: %d", next_index, length)); 4709 4710 int start = next_index; 4711 int end = length; 4712 int remainder = end - start; 4713 // We'll try not to push a range that's smaller than ParGCArrayScanChunk. 4714 if (remainder > 2 * ParGCArrayScanChunk) { 4715 end = start + ParGCArrayScanChunk; 4716 to_obj_array->set_length(end); 4717 // Push the remainder before we process the range in case another 4718 // worker has run out of things to do and can steal it. 4719 oop* from_obj_p = set_partial_array_mask(from_obj); 4720 _par_scan_state->push_on_queue(from_obj_p); 4721 } else { 4722 assert(length == end, "sanity"); 4723 // We'll process the final range for this object. Restore the length 4724 // so that the heap remains parsable in case of evacuation failure. 4725 to_obj_array->set_length(end); 4726 } 4727 _scanner.set_region(_g1->heap_region_containing_raw(to_obj)); 4728 // Process indexes [start,end). It will also process the header 4729 // along with the first chunk (i.e., the chunk with start == 0). 4730 // Note that at this point the length field of to_obj_array is not 4731 // correct given that we are using it to keep track of the next 4732 // start index. oop_iterate_range() (thankfully!) ignores the length 4733 // field and only relies on the start / end parameters. It does 4734 // however return the size of the object which will be incorrect. So 4735 // we have to ignore it even if we wanted to use it. 4736 to_obj_array->oop_iterate_range(&_scanner, start, end); 4737 } 4738 4739 class G1ParEvacuateFollowersClosure : public VoidClosure { 4740 protected: 4741 G1CollectedHeap* _g1h; 4742 G1ParScanThreadState* _par_scan_state; 4743 RefToScanQueueSet* _queues; 4744 ParallelTaskTerminator* _terminator; 4745 4746 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4747 RefToScanQueueSet* queues() { return _queues; } 4748 ParallelTaskTerminator* terminator() { return _terminator; } 4749 4750 public: 4751 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4752 G1ParScanThreadState* par_scan_state, 4753 RefToScanQueueSet* queues, 4754 ParallelTaskTerminator* terminator) 4755 : _g1h(g1h), _par_scan_state(par_scan_state), 4756 _queues(queues), _terminator(terminator) {} 4757 4758 void do_void(); 4759 4760 private: 4761 inline bool offer_termination(); 4762 }; 4763 4764 bool G1ParEvacuateFollowersClosure::offer_termination() { 4765 G1ParScanThreadState* const pss = par_scan_state(); 4766 pss->start_term_time(); 4767 const bool res = terminator()->offer_termination(); 4768 pss->end_term_time(); 4769 return res; 4770 } 4771 4772 void G1ParEvacuateFollowersClosure::do_void() { 4773 StarTask stolen_task; 4774 G1ParScanThreadState* const pss = par_scan_state(); 4775 pss->trim_queue(); 4776 4777 do { 4778 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4779 assert(pss->verify_task(stolen_task), "sanity"); 4780 if (stolen_task.is_narrow()) { 4781 pss->deal_with_reference((narrowOop*) stolen_task); 4782 } else { 4783 pss->deal_with_reference((oop*) stolen_task); 4784 } 4785 4786 // We've just processed a reference and we might have made 4787 // available new entries on the queues. So we have to make sure 4788 // we drain the queues as necessary. 4789 pss->trim_queue(); 4790 } 4791 } while (!offer_termination()); 4792 4793 pss->retire_alloc_buffers(); 4794 } 4795 4796 class G1KlassScanClosure : public KlassClosure { 4797 G1ParCopyHelper* _closure; 4798 bool _process_only_dirty; 4799 int _count; 4800 public: 4801 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4802 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4803 void do_klass(Klass* klass) { 4804 // If the klass has not been dirtied we know that there's 4805 // no references into the young gen and we can skip it. 4806 if (!_process_only_dirty || klass->has_modified_oops()) { 4807 // Clean the klass since we're going to scavenge all the metadata. 4808 klass->clear_modified_oops(); 4809 4810 // Tell the closure that this klass is the Klass to scavenge 4811 // and is the one to dirty if oops are left pointing into the young gen. 4812 _closure->set_scanned_klass(klass); 4813 4814 klass->oops_do(_closure); 4815 4816 _closure->set_scanned_klass(NULL); 4817 } 4818 _count++; 4819 } 4820 }; 4821 4822 class G1ParTask : public AbstractGangTask { 4823 protected: 4824 G1CollectedHeap* _g1h; 4825 RefToScanQueueSet *_queues; 4826 ParallelTaskTerminator _terminator; 4827 uint _n_workers; 4828 4829 Mutex _stats_lock; 4830 Mutex* stats_lock() { return &_stats_lock; } 4831 4832 size_t getNCards() { 4833 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 4834 / G1BlockOffsetSharedArray::N_bytes; 4835 } 4836 4837 public: 4838 G1ParTask(G1CollectedHeap* g1h, 4839 RefToScanQueueSet *task_queues) 4840 : AbstractGangTask("G1 collection"), 4841 _g1h(g1h), 4842 _queues(task_queues), 4843 _terminator(0, _queues), 4844 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4845 {} 4846 4847 RefToScanQueueSet* queues() { return _queues; } 4848 4849 RefToScanQueue *work_queue(int i) { 4850 return queues()->queue(i); 4851 } 4852 4853 ParallelTaskTerminator* terminator() { return &_terminator; } 4854 4855 virtual void set_for_termination(int active_workers) { 4856 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4857 // in the young space (_par_seq_tasks) in the G1 heap 4858 // for SequentialSubTasksDone. 4859 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4860 // both of which need setting by set_n_termination(). 4861 _g1h->SharedHeap::set_n_termination(active_workers); 4862 _g1h->set_n_termination(active_workers); 4863 terminator()->reset_for_reuse(active_workers); 4864 _n_workers = active_workers; 4865 } 4866 4867 void work(uint worker_id) { 4868 if (worker_id >= _n_workers) return; // no work needed this round 4869 4870 double start_time_ms = os::elapsedTime() * 1000.0; 4871 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 4872 4873 { 4874 ResourceMark rm; 4875 HandleMark hm; 4876 4877 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4878 4879 G1ParScanThreadState pss(_g1h, worker_id); 4880 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp); 4881 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4882 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp); 4883 4884 pss.set_evac_closure(&scan_evac_cl); 4885 pss.set_evac_failure_closure(&evac_failure_cl); 4886 pss.set_partial_scan_closure(&partial_scan_cl); 4887 4888 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp); 4889 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp); 4890 4891 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp); 4892 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp); 4893 4894 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4895 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false); 4896 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young); 4897 4898 OopClosure* scan_root_cl = &only_scan_root_cl; 4899 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s; 4900 4901 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4902 // We also need to mark copied objects. 4903 scan_root_cl = &scan_mark_root_cl; 4904 scan_klasses_cl = &scan_mark_klasses_cl_s; 4905 } 4906 4907 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4908 4909 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 4910 4911 pss.start_strong_roots(); 4912 _g1h->g1_process_strong_roots(/* is scavenging */ true, 4913 SharedHeap::ScanningOption(so), 4914 scan_root_cl, 4915 &push_heap_rs_cl, 4916 scan_klasses_cl, 4917 worker_id); 4918 pss.end_strong_roots(); 4919 4920 { 4921 double start = os::elapsedTime(); 4922 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4923 evac.do_void(); 4924 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4925 double term_ms = pss.term_time()*1000.0; 4926 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 4927 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 4928 } 4929 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4930 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4931 4932 if (ParallelGCVerbose) { 4933 MutexLocker x(stats_lock()); 4934 pss.print_termination_stats(worker_id); 4935 } 4936 4937 assert(pss.refs()->is_empty(), "should be empty"); 4938 4939 // Close the inner scope so that the ResourceMark and HandleMark 4940 // destructors are executed here and are included as part of the 4941 // "GC Worker Time". 4942 } 4943 4944 double end_time_ms = os::elapsedTime() * 1000.0; 4945 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 4946 } 4947 }; 4948 4949 // *** Common G1 Evacuation Stuff 4950 4951 // Closures that support the filtering of CodeBlobs scanned during 4952 // external root scanning. 4953 4954 // Closure applied to reference fields in code blobs (specifically nmethods) 4955 // to determine whether an nmethod contains references that point into 4956 // the collection set. Used as a predicate when walking code roots so 4957 // that only nmethods that point into the collection set are added to the 4958 // 'marked' list. 4959 4960 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure { 4961 4962 class G1PointsIntoCSOopClosure : public OopClosure { 4963 G1CollectedHeap* _g1; 4964 bool _points_into_cs; 4965 public: 4966 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) : 4967 _g1(g1), _points_into_cs(false) { } 4968 4969 bool points_into_cs() const { return _points_into_cs; } 4970 4971 template <class T> 4972 void do_oop_nv(T* p) { 4973 if (!_points_into_cs) { 4974 T heap_oop = oopDesc::load_heap_oop(p); 4975 if (!oopDesc::is_null(heap_oop) && 4976 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) { 4977 _points_into_cs = true; 4978 } 4979 } 4980 } 4981 4982 virtual void do_oop(oop* p) { do_oop_nv(p); } 4983 virtual void do_oop(narrowOop* p) { do_oop_nv(p); } 4984 }; 4985 4986 G1CollectedHeap* _g1; 4987 4988 public: 4989 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) : 4990 CodeBlobToOopClosure(cl, true), _g1(g1) { } 4991 4992 virtual void do_code_blob(CodeBlob* cb) { 4993 nmethod* nm = cb->as_nmethod_or_null(); 4994 if (nm != NULL && !(nm->test_oops_do_mark())) { 4995 G1PointsIntoCSOopClosure predicate_cl(_g1); 4996 nm->oops_do(&predicate_cl); 4997 4998 if (predicate_cl.points_into_cs()) { 4999 // At least one of the reference fields or the oop relocations 5000 // in the nmethod points into the collection set. We have to 5001 // 'mark' this nmethod. 5002 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob() 5003 // or MarkingCodeBlobClosure::do_code_blob() change. 5004 if (!nm->test_set_oops_do_mark()) { 5005 do_newly_marked_nmethod(nm); 5006 } 5007 } 5008 } 5009 } 5010 }; 5011 5012 // This method is run in a GC worker. 5013 5014 void 5015 G1CollectedHeap:: 5016 g1_process_strong_roots(bool is_scavenging, 5017 ScanningOption so, 5018 OopClosure* scan_non_heap_roots, 5019 OopsInHeapRegionClosure* scan_rs, 5020 G1KlassScanClosure* scan_klasses, 5021 int worker_i) { 5022 5023 // First scan the strong roots 5024 double ext_roots_start = os::elapsedTime(); 5025 double closure_app_time_sec = 0.0; 5026 5027 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 5028 5029 // Walk the code cache w/o buffering, because StarTask cannot handle 5030 // unaligned oop locations. 5031 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots); 5032 5033 process_strong_roots(false, // no scoping; this is parallel code 5034 is_scavenging, so, 5035 &buf_scan_non_heap_roots, 5036 &eager_scan_code_roots, 5037 scan_klasses 5038 ); 5039 5040 // Now the CM ref_processor roots. 5041 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 5042 // We need to treat the discovered reference lists of the 5043 // concurrent mark ref processor as roots and keep entries 5044 // (which are added by the marking threads) on them live 5045 // until they can be processed at the end of marking. 5046 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 5047 } 5048 5049 // Finish up any enqueued closure apps (attributed as object copy time). 5050 buf_scan_non_heap_roots.done(); 5051 5052 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds(); 5053 5054 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 5055 5056 double ext_root_time_ms = 5057 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 5058 5059 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 5060 5061 // During conc marking we have to filter the per-thread SATB buffers 5062 // to make sure we remove any oops into the CSet (which will show up 5063 // as implicitly live). 5064 double satb_filtering_ms = 0.0; 5065 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 5066 if (mark_in_progress()) { 5067 double satb_filter_start = os::elapsedTime(); 5068 5069 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 5070 5071 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 5072 } 5073 } 5074 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 5075 5076 // Now scan the complement of the collection set. 5077 if (scan_rs != NULL) { 5078 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i); 5079 } 5080 _process_strong_tasks->all_tasks_completed(); 5081 } 5082 5083 void 5084 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) { 5085 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 5086 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs); 5087 } 5088 5089 // Weak Reference Processing support 5090 5091 // An always "is_alive" closure that is used to preserve referents. 5092 // If the object is non-null then it's alive. Used in the preservation 5093 // of referent objects that are pointed to by reference objects 5094 // discovered by the CM ref processor. 5095 class G1AlwaysAliveClosure: public BoolObjectClosure { 5096 G1CollectedHeap* _g1; 5097 public: 5098 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5099 bool do_object_b(oop p) { 5100 if (p != NULL) { 5101 return true; 5102 } 5103 return false; 5104 } 5105 }; 5106 5107 bool G1STWIsAliveClosure::do_object_b(oop p) { 5108 // An object is reachable if it is outside the collection set, 5109 // or is inside and copied. 5110 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5111 } 5112 5113 // Non Copying Keep Alive closure 5114 class G1KeepAliveClosure: public OopClosure { 5115 G1CollectedHeap* _g1; 5116 public: 5117 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5118 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5119 void do_oop( oop* p) { 5120 oop obj = *p; 5121 5122 if (_g1->obj_in_cs(obj)) { 5123 assert( obj->is_forwarded(), "invariant" ); 5124 *p = obj->forwardee(); 5125 } 5126 } 5127 }; 5128 5129 // Copying Keep Alive closure - can be called from both 5130 // serial and parallel code as long as different worker 5131 // threads utilize different G1ParScanThreadState instances 5132 // and different queues. 5133 5134 class G1CopyingKeepAliveClosure: public OopClosure { 5135 G1CollectedHeap* _g1h; 5136 OopClosure* _copy_non_heap_obj_cl; 5137 OopsInHeapRegionClosure* _copy_metadata_obj_cl; 5138 G1ParScanThreadState* _par_scan_state; 5139 5140 public: 5141 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5142 OopClosure* non_heap_obj_cl, 5143 OopsInHeapRegionClosure* metadata_obj_cl, 5144 G1ParScanThreadState* pss): 5145 _g1h(g1h), 5146 _copy_non_heap_obj_cl(non_heap_obj_cl), 5147 _copy_metadata_obj_cl(metadata_obj_cl), 5148 _par_scan_state(pss) 5149 {} 5150 5151 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5152 virtual void do_oop( oop* p) { do_oop_work(p); } 5153 5154 template <class T> void do_oop_work(T* p) { 5155 oop obj = oopDesc::load_decode_heap_oop(p); 5156 5157 if (_g1h->obj_in_cs(obj)) { 5158 // If the referent object has been forwarded (either copied 5159 // to a new location or to itself in the event of an 5160 // evacuation failure) then we need to update the reference 5161 // field and, if both reference and referent are in the G1 5162 // heap, update the RSet for the referent. 5163 // 5164 // If the referent has not been forwarded then we have to keep 5165 // it alive by policy. Therefore we have copy the referent. 5166 // 5167 // If the reference field is in the G1 heap then we can push 5168 // on the PSS queue. When the queue is drained (after each 5169 // phase of reference processing) the object and it's followers 5170 // will be copied, the reference field set to point to the 5171 // new location, and the RSet updated. Otherwise we need to 5172 // use the the non-heap or metadata closures directly to copy 5173 // the refernt object and update the pointer, while avoiding 5174 // updating the RSet. 5175 5176 if (_g1h->is_in_g1_reserved(p)) { 5177 _par_scan_state->push_on_queue(p); 5178 } else { 5179 assert(!ClassLoaderDataGraph::contains((address)p), 5180 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) " 5181 PTR_FORMAT, p)); 5182 _copy_non_heap_obj_cl->do_oop(p); 5183 } 5184 } 5185 } 5186 }; 5187 5188 // Serial drain queue closure. Called as the 'complete_gc' 5189 // closure for each discovered list in some of the 5190 // reference processing phases. 5191 5192 class G1STWDrainQueueClosure: public VoidClosure { 5193 protected: 5194 G1CollectedHeap* _g1h; 5195 G1ParScanThreadState* _par_scan_state; 5196 5197 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5198 5199 public: 5200 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5201 _g1h(g1h), 5202 _par_scan_state(pss) 5203 { } 5204 5205 void do_void() { 5206 G1ParScanThreadState* const pss = par_scan_state(); 5207 pss->trim_queue(); 5208 } 5209 }; 5210 5211 // Parallel Reference Processing closures 5212 5213 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5214 // processing during G1 evacuation pauses. 5215 5216 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5217 private: 5218 G1CollectedHeap* _g1h; 5219 RefToScanQueueSet* _queues; 5220 FlexibleWorkGang* _workers; 5221 int _active_workers; 5222 5223 public: 5224 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5225 FlexibleWorkGang* workers, 5226 RefToScanQueueSet *task_queues, 5227 int n_workers) : 5228 _g1h(g1h), 5229 _queues(task_queues), 5230 _workers(workers), 5231 _active_workers(n_workers) 5232 { 5233 assert(n_workers > 0, "shouldn't call this otherwise"); 5234 } 5235 5236 // Executes the given task using concurrent marking worker threads. 5237 virtual void execute(ProcessTask& task); 5238 virtual void execute(EnqueueTask& task); 5239 }; 5240 5241 // Gang task for possibly parallel reference processing 5242 5243 class G1STWRefProcTaskProxy: public AbstractGangTask { 5244 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5245 ProcessTask& _proc_task; 5246 G1CollectedHeap* _g1h; 5247 RefToScanQueueSet *_task_queues; 5248 ParallelTaskTerminator* _terminator; 5249 5250 public: 5251 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5252 G1CollectedHeap* g1h, 5253 RefToScanQueueSet *task_queues, 5254 ParallelTaskTerminator* terminator) : 5255 AbstractGangTask("Process reference objects in parallel"), 5256 _proc_task(proc_task), 5257 _g1h(g1h), 5258 _task_queues(task_queues), 5259 _terminator(terminator) 5260 {} 5261 5262 virtual void work(uint worker_id) { 5263 // The reference processing task executed by a single worker. 5264 ResourceMark rm; 5265 HandleMark hm; 5266 5267 G1STWIsAliveClosure is_alive(_g1h); 5268 5269 G1ParScanThreadState pss(_g1h, worker_id); 5270 5271 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5272 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5273 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5274 5275 pss.set_evac_closure(&scan_evac_cl); 5276 pss.set_evac_failure_closure(&evac_failure_cl); 5277 pss.set_partial_scan_closure(&partial_scan_cl); 5278 5279 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5280 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5281 5282 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5283 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5284 5285 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5286 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5287 5288 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5289 // We also need to mark copied objects. 5290 copy_non_heap_cl = ©_mark_non_heap_cl; 5291 copy_metadata_cl = ©_mark_metadata_cl; 5292 } 5293 5294 // Keep alive closure. 5295 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5296 5297 // Complete GC closure 5298 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5299 5300 // Call the reference processing task's work routine. 5301 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5302 5303 // Note we cannot assert that the refs array is empty here as not all 5304 // of the processing tasks (specifically phase2 - pp2_work) execute 5305 // the complete_gc closure (which ordinarily would drain the queue) so 5306 // the queue may not be empty. 5307 } 5308 }; 5309 5310 // Driver routine for parallel reference processing. 5311 // Creates an instance of the ref processing gang 5312 // task and has the worker threads execute it. 5313 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5314 assert(_workers != NULL, "Need parallel worker threads."); 5315 5316 ParallelTaskTerminator terminator(_active_workers, _queues); 5317 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5318 5319 _g1h->set_par_threads(_active_workers); 5320 _workers->run_task(&proc_task_proxy); 5321 _g1h->set_par_threads(0); 5322 } 5323 5324 // Gang task for parallel reference enqueueing. 5325 5326 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5327 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5328 EnqueueTask& _enq_task; 5329 5330 public: 5331 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5332 AbstractGangTask("Enqueue reference objects in parallel"), 5333 _enq_task(enq_task) 5334 { } 5335 5336 virtual void work(uint worker_id) { 5337 _enq_task.work(worker_id); 5338 } 5339 }; 5340 5341 // Driver routine for parallel reference enqueing. 5342 // Creates an instance of the ref enqueueing gang 5343 // task and has the worker threads execute it. 5344 5345 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5346 assert(_workers != NULL, "Need parallel worker threads."); 5347 5348 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5349 5350 _g1h->set_par_threads(_active_workers); 5351 _workers->run_task(&enq_task_proxy); 5352 _g1h->set_par_threads(0); 5353 } 5354 5355 // End of weak reference support closures 5356 5357 // Abstract task used to preserve (i.e. copy) any referent objects 5358 // that are in the collection set and are pointed to by reference 5359 // objects discovered by the CM ref processor. 5360 5361 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5362 protected: 5363 G1CollectedHeap* _g1h; 5364 RefToScanQueueSet *_queues; 5365 ParallelTaskTerminator _terminator; 5366 uint _n_workers; 5367 5368 public: 5369 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5370 AbstractGangTask("ParPreserveCMReferents"), 5371 _g1h(g1h), 5372 _queues(task_queues), 5373 _terminator(workers, _queues), 5374 _n_workers(workers) 5375 { } 5376 5377 void work(uint worker_id) { 5378 ResourceMark rm; 5379 HandleMark hm; 5380 5381 G1ParScanThreadState pss(_g1h, worker_id); 5382 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL); 5383 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5384 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL); 5385 5386 pss.set_evac_closure(&scan_evac_cl); 5387 pss.set_evac_failure_closure(&evac_failure_cl); 5388 pss.set_partial_scan_closure(&partial_scan_cl); 5389 5390 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5391 5392 5393 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5394 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL); 5395 5396 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5397 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL); 5398 5399 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5400 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5401 5402 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5403 // We also need to mark copied objects. 5404 copy_non_heap_cl = ©_mark_non_heap_cl; 5405 copy_metadata_cl = ©_mark_metadata_cl; 5406 } 5407 5408 // Is alive closure 5409 G1AlwaysAliveClosure always_alive(_g1h); 5410 5411 // Copying keep alive closure. Applied to referent objects that need 5412 // to be copied. 5413 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss); 5414 5415 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5416 5417 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5418 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5419 5420 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5421 // So this must be true - but assert just in case someone decides to 5422 // change the worker ids. 5423 assert(0 <= worker_id && worker_id < limit, "sanity"); 5424 assert(!rp->discovery_is_atomic(), "check this code"); 5425 5426 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5427 for (uint idx = worker_id; idx < limit; idx += stride) { 5428 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5429 5430 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5431 while (iter.has_next()) { 5432 // Since discovery is not atomic for the CM ref processor, we 5433 // can see some null referent objects. 5434 iter.load_ptrs(DEBUG_ONLY(true)); 5435 oop ref = iter.obj(); 5436 5437 // This will filter nulls. 5438 if (iter.is_referent_alive()) { 5439 iter.make_referent_alive(); 5440 } 5441 iter.move_to_next(); 5442 } 5443 } 5444 5445 // Drain the queue - which may cause stealing 5446 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5447 drain_queue.do_void(); 5448 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5449 assert(pss.refs()->is_empty(), "should be"); 5450 } 5451 }; 5452 5453 // Weak Reference processing during an evacuation pause (part 1). 5454 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5455 double ref_proc_start = os::elapsedTime(); 5456 5457 ReferenceProcessor* rp = _ref_processor_stw; 5458 assert(rp->discovery_enabled(), "should have been enabled"); 5459 5460 // Any reference objects, in the collection set, that were 'discovered' 5461 // by the CM ref processor should have already been copied (either by 5462 // applying the external root copy closure to the discovered lists, or 5463 // by following an RSet entry). 5464 // 5465 // But some of the referents, that are in the collection set, that these 5466 // reference objects point to may not have been copied: the STW ref 5467 // processor would have seen that the reference object had already 5468 // been 'discovered' and would have skipped discovering the reference, 5469 // but would not have treated the reference object as a regular oop. 5470 // As a reult the copy closure would not have been applied to the 5471 // referent object. 5472 // 5473 // We need to explicitly copy these referent objects - the references 5474 // will be processed at the end of remarking. 5475 // 5476 // We also need to do this copying before we process the reference 5477 // objects discovered by the STW ref processor in case one of these 5478 // referents points to another object which is also referenced by an 5479 // object discovered by the STW ref processor. 5480 5481 assert(!G1CollectedHeap::use_parallel_gc_threads() || 5482 no_of_gc_workers == workers()->active_workers(), 5483 "Need to reset active GC workers"); 5484 5485 set_par_threads(no_of_gc_workers); 5486 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5487 no_of_gc_workers, 5488 _task_queues); 5489 5490 if (G1CollectedHeap::use_parallel_gc_threads()) { 5491 workers()->run_task(&keep_cm_referents); 5492 } else { 5493 keep_cm_referents.work(0); 5494 } 5495 5496 set_par_threads(0); 5497 5498 // Closure to test whether a referent is alive. 5499 G1STWIsAliveClosure is_alive(this); 5500 5501 // Even when parallel reference processing is enabled, the processing 5502 // of JNI refs is serial and performed serially by the current thread 5503 // rather than by a worker. The following PSS will be used for processing 5504 // JNI refs. 5505 5506 // Use only a single queue for this PSS. 5507 G1ParScanThreadState pss(this, 0); 5508 5509 // We do not embed a reference processor in the copying/scanning 5510 // closures while we're actually processing the discovered 5511 // reference objects. 5512 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL); 5513 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5514 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL); 5515 5516 pss.set_evac_closure(&scan_evac_cl); 5517 pss.set_evac_failure_closure(&evac_failure_cl); 5518 pss.set_partial_scan_closure(&partial_scan_cl); 5519 5520 assert(pss.refs()->is_empty(), "pre-condition"); 5521 5522 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5523 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL); 5524 5525 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5526 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL); 5527 5528 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5529 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl; 5530 5531 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5532 // We also need to mark copied objects. 5533 copy_non_heap_cl = ©_mark_non_heap_cl; 5534 copy_metadata_cl = ©_mark_metadata_cl; 5535 } 5536 5537 // Keep alive closure. 5538 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss); 5539 5540 // Serial Complete GC closure 5541 G1STWDrainQueueClosure drain_queue(this, &pss); 5542 5543 // Setup the soft refs policy... 5544 rp->setup_policy(false); 5545 5546 if (!rp->processing_is_mt()) { 5547 // Serial reference processing... 5548 rp->process_discovered_references(&is_alive, 5549 &keep_alive, 5550 &drain_queue, 5551 NULL); 5552 } else { 5553 // Parallel reference processing 5554 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5555 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5556 5557 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5558 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor); 5559 } 5560 5561 // We have completed copying any necessary live referent objects 5562 // (that were not copied during the actual pause) so we can 5563 // retire any active alloc buffers 5564 pss.retire_alloc_buffers(); 5565 assert(pss.refs()->is_empty(), "both queue and overflow should be empty"); 5566 5567 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5568 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5569 } 5570 5571 // Weak Reference processing during an evacuation pause (part 2). 5572 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5573 double ref_enq_start = os::elapsedTime(); 5574 5575 ReferenceProcessor* rp = _ref_processor_stw; 5576 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5577 5578 // Now enqueue any remaining on the discovered lists on to 5579 // the pending list. 5580 if (!rp->processing_is_mt()) { 5581 // Serial reference processing... 5582 rp->enqueue_discovered_references(); 5583 } else { 5584 // Parallel reference enqueuing 5585 5586 assert(no_of_gc_workers == workers()->active_workers(), 5587 "Need to reset active workers"); 5588 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5589 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5590 5591 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5592 rp->enqueue_discovered_references(&par_task_executor); 5593 } 5594 5595 rp->verify_no_references_recorded(); 5596 assert(!rp->discovery_enabled(), "should have been disabled"); 5597 5598 // FIXME 5599 // CM's reference processing also cleans up the string and symbol tables. 5600 // Should we do that here also? We could, but it is a serial operation 5601 // and could signicantly increase the pause time. 5602 5603 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5604 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5605 } 5606 5607 void G1CollectedHeap::evacuate_collection_set() { 5608 _expand_heap_after_alloc_failure = true; 5609 set_evacuation_failed(false); 5610 5611 // Should G1EvacuationFailureALot be in effect for this GC? 5612 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5613 5614 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5615 5616 // Disable the hot card cache. 5617 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5618 hot_card_cache->reset_hot_cache_claimed_index(); 5619 hot_card_cache->set_use_cache(false); 5620 5621 uint n_workers; 5622 if (G1CollectedHeap::use_parallel_gc_threads()) { 5623 n_workers = 5624 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5625 workers()->active_workers(), 5626 Threads::number_of_non_daemon_threads()); 5627 assert(UseDynamicNumberOfGCThreads || 5628 n_workers == workers()->total_workers(), 5629 "If not dynamic should be using all the workers"); 5630 workers()->set_active_workers(n_workers); 5631 set_par_threads(n_workers); 5632 } else { 5633 assert(n_par_threads() == 0, 5634 "Should be the original non-parallel value"); 5635 n_workers = 1; 5636 } 5637 5638 G1ParTask g1_par_task(this, _task_queues); 5639 5640 init_for_evac_failure(NULL); 5641 5642 rem_set()->prepare_for_younger_refs_iterate(true); 5643 5644 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5645 double start_par_time_sec = os::elapsedTime(); 5646 double end_par_time_sec; 5647 5648 { 5649 StrongRootsScope srs(this); 5650 5651 if (G1CollectedHeap::use_parallel_gc_threads()) { 5652 // The individual threads will set their evac-failure closures. 5653 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 5654 // These tasks use ShareHeap::_process_strong_tasks 5655 assert(UseDynamicNumberOfGCThreads || 5656 workers()->active_workers() == workers()->total_workers(), 5657 "If not dynamic should be using all the workers"); 5658 workers()->run_task(&g1_par_task); 5659 } else { 5660 g1_par_task.set_for_termination(n_workers); 5661 g1_par_task.work(0); 5662 } 5663 end_par_time_sec = os::elapsedTime(); 5664 5665 // Closing the inner scope will execute the destructor 5666 // for the StrongRootsScope object. We record the current 5667 // elapsed time before closing the scope so that time 5668 // taken for the SRS destructor is NOT included in the 5669 // reported parallel time. 5670 } 5671 5672 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5673 g1_policy()->phase_times()->record_par_time(par_time_ms); 5674 5675 double code_root_fixup_time_ms = 5676 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5677 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5678 5679 set_par_threads(0); 5680 5681 // Process any discovered reference objects - we have 5682 // to do this _before_ we retire the GC alloc regions 5683 // as we may have to copy some 'reachable' referent 5684 // objects (and their reachable sub-graphs) that were 5685 // not copied during the pause. 5686 process_discovered_references(n_workers); 5687 5688 // Weak root processing. 5689 // Note: when JSR 292 is enabled and code blobs can contain 5690 // non-perm oops then we will need to process the code blobs 5691 // here too. 5692 { 5693 G1STWIsAliveClosure is_alive(this); 5694 G1KeepAliveClosure keep_alive(this); 5695 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 5696 } 5697 5698 release_gc_alloc_regions(n_workers); 5699 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5700 5701 // Reset and re-enable the hot card cache. 5702 // Note the counts for the cards in the regions in the 5703 // collection set are reset when the collection set is freed. 5704 hot_card_cache->reset_hot_cache(); 5705 hot_card_cache->set_use_cache(true); 5706 5707 finalize_for_evac_failure(); 5708 5709 if (evacuation_failed()) { 5710 remove_self_forwarding_pointers(); 5711 5712 // Reset the G1EvacuationFailureALot counters and flags 5713 // Note: the values are reset only when an actual 5714 // evacuation failure occurs. 5715 NOT_PRODUCT(reset_evacuation_should_fail();) 5716 } 5717 5718 // Enqueue any remaining references remaining on the STW 5719 // reference processor's discovered lists. We need to do 5720 // this after the card table is cleaned (and verified) as 5721 // the act of enqueuing entries on to the pending list 5722 // will log these updates (and dirty their associated 5723 // cards). We need these updates logged to update any 5724 // RSets. 5725 enqueue_discovered_references(n_workers); 5726 5727 if (G1DeferredRSUpdate) { 5728 RedirtyLoggedCardTableEntryFastClosure redirty; 5729 dirty_card_queue_set().set_closure(&redirty); 5730 dirty_card_queue_set().apply_closure_to_all_completed_buffers(); 5731 5732 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5733 dcq.merge_bufferlists(&dirty_card_queue_set()); 5734 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5735 } 5736 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5737 } 5738 5739 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr, 5740 size_t* pre_used, 5741 FreeRegionList* free_list, 5742 OldRegionSet* old_proxy_set, 5743 HumongousRegionSet* humongous_proxy_set, 5744 HRRSCleanupTask* hrrs_cleanup_task, 5745 bool par) { 5746 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 5747 if (hr->isHumongous()) { 5748 assert(hr->startsHumongous(), "we should only see starts humongous"); 5749 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par); 5750 } else { 5751 _old_set.remove_with_proxy(hr, old_proxy_set); 5752 free_region(hr, pre_used, free_list, par); 5753 } 5754 } else { 5755 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task); 5756 } 5757 } 5758 5759 void G1CollectedHeap::free_region(HeapRegion* hr, 5760 size_t* pre_used, 5761 FreeRegionList* free_list, 5762 bool par) { 5763 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 5764 assert(!hr->is_empty(), "the region should not be empty"); 5765 assert(free_list != NULL, "pre-condition"); 5766 5767 // Clear the card counts for this region. 5768 // Note: we only need to do this if the region is not young 5769 // (since we don't refine cards in young regions). 5770 if (!hr->is_young()) { 5771 _cg1r->hot_card_cache()->reset_card_counts(hr); 5772 } 5773 *pre_used += hr->used(); 5774 hr->hr_clear(par, true /* clear_space */); 5775 free_list->add_as_head(hr); 5776 } 5777 5778 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5779 size_t* pre_used, 5780 FreeRegionList* free_list, 5781 HumongousRegionSet* humongous_proxy_set, 5782 bool par) { 5783 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 5784 assert(free_list != NULL, "pre-condition"); 5785 assert(humongous_proxy_set != NULL, "pre-condition"); 5786 5787 size_t hr_used = hr->used(); 5788 size_t hr_capacity = hr->capacity(); 5789 size_t hr_pre_used = 0; 5790 _humongous_set.remove_with_proxy(hr, humongous_proxy_set); 5791 // We need to read this before we make the region non-humongous, 5792 // otherwise the information will be gone. 5793 uint last_index = hr->last_hc_index(); 5794 hr->set_notHumongous(); 5795 free_region(hr, &hr_pre_used, free_list, par); 5796 5797 uint i = hr->hrs_index() + 1; 5798 while (i < last_index) { 5799 HeapRegion* curr_hr = region_at(i); 5800 assert(curr_hr->continuesHumongous(), "invariant"); 5801 curr_hr->set_notHumongous(); 5802 free_region(curr_hr, &hr_pre_used, free_list, par); 5803 i += 1; 5804 } 5805 assert(hr_pre_used == hr_used, 5806 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" " 5807 "should be the same", hr_pre_used, hr_used)); 5808 *pre_used += hr_pre_used; 5809 } 5810 5811 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used, 5812 FreeRegionList* free_list, 5813 OldRegionSet* old_proxy_set, 5814 HumongousRegionSet* humongous_proxy_set, 5815 bool par) { 5816 if (pre_used > 0) { 5817 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL; 5818 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 5819 assert(_summary_bytes_used >= pre_used, 5820 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" " 5821 "should be >= pre_used: "SIZE_FORMAT, 5822 _summary_bytes_used, pre_used)); 5823 _summary_bytes_used -= pre_used; 5824 } 5825 if (free_list != NULL && !free_list->is_empty()) { 5826 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5827 _free_list.add_as_head(free_list); 5828 } 5829 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) { 5830 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5831 _old_set.update_from_proxy(old_proxy_set); 5832 } 5833 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) { 5834 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5835 _humongous_set.update_from_proxy(humongous_proxy_set); 5836 } 5837 } 5838 5839 class G1ParCleanupCTTask : public AbstractGangTask { 5840 CardTableModRefBS* _ct_bs; 5841 G1CollectedHeap* _g1h; 5842 HeapRegion* volatile _su_head; 5843 public: 5844 G1ParCleanupCTTask(CardTableModRefBS* ct_bs, 5845 G1CollectedHeap* g1h) : 5846 AbstractGangTask("G1 Par Cleanup CT Task"), 5847 _ct_bs(ct_bs), _g1h(g1h) { } 5848 5849 void work(uint worker_id) { 5850 HeapRegion* r; 5851 while (r = _g1h->pop_dirty_cards_region()) { 5852 clear_cards(r); 5853 } 5854 } 5855 5856 void clear_cards(HeapRegion* r) { 5857 // Cards of the survivors should have already been dirtied. 5858 if (!r->is_survivor()) { 5859 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5860 } 5861 } 5862 }; 5863 5864 #ifndef PRODUCT 5865 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5866 G1CollectedHeap* _g1h; 5867 CardTableModRefBS* _ct_bs; 5868 public: 5869 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs) 5870 : _g1h(g1h), _ct_bs(ct_bs) { } 5871 virtual bool doHeapRegion(HeapRegion* r) { 5872 if (r->is_survivor()) { 5873 _g1h->verify_dirty_region(r); 5874 } else { 5875 _g1h->verify_not_dirty_region(r); 5876 } 5877 return false; 5878 } 5879 }; 5880 5881 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5882 // All of the region should be clean. 5883 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 5884 MemRegion mr(hr->bottom(), hr->end()); 5885 ct_bs->verify_not_dirty_region(mr); 5886 } 5887 5888 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5889 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5890 // dirty allocated blocks as they allocate them. The thread that 5891 // retires each region and replaces it with a new one will do a 5892 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5893 // not dirty that area (one less thing to have to do while holding 5894 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5895 // is dirty. 5896 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5897 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5898 ct_bs->verify_dirty_region(mr); 5899 } 5900 5901 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5902 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 5903 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5904 verify_dirty_region(hr); 5905 } 5906 } 5907 5908 void G1CollectedHeap::verify_dirty_young_regions() { 5909 verify_dirty_young_list(_young_list->first_region()); 5910 } 5911 #endif 5912 5913 void G1CollectedHeap::cleanUpCardTable() { 5914 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set()); 5915 double start = os::elapsedTime(); 5916 5917 { 5918 // Iterate over the dirty cards region list. 5919 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5920 5921 if (G1CollectedHeap::use_parallel_gc_threads()) { 5922 set_par_threads(); 5923 workers()->run_task(&cleanup_task); 5924 set_par_threads(0); 5925 } else { 5926 while (_dirty_cards_region_list) { 5927 HeapRegion* r = _dirty_cards_region_list; 5928 cleanup_task.clear_cards(r); 5929 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 5930 if (_dirty_cards_region_list == r) { 5931 // The last region. 5932 _dirty_cards_region_list = NULL; 5933 } 5934 r->set_next_dirty_cards_region(NULL); 5935 } 5936 } 5937 #ifndef PRODUCT 5938 if (G1VerifyCTCleanup || VerifyAfterGC) { 5939 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5940 heap_region_iterate(&cleanup_verifier); 5941 } 5942 #endif 5943 } 5944 5945 double elapsed = os::elapsedTime() - start; 5946 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5947 } 5948 5949 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) { 5950 size_t pre_used = 0; 5951 FreeRegionList local_free_list("Local List for CSet Freeing"); 5952 5953 double young_time_ms = 0.0; 5954 double non_young_time_ms = 0.0; 5955 5956 // Since the collection set is a superset of the the young list, 5957 // all we need to do to clear the young list is clear its 5958 // head and length, and unlink any young regions in the code below 5959 _young_list->clear(); 5960 5961 G1CollectorPolicy* policy = g1_policy(); 5962 5963 double start_sec = os::elapsedTime(); 5964 bool non_young = true; 5965 5966 HeapRegion* cur = cs_head; 5967 int age_bound = -1; 5968 size_t rs_lengths = 0; 5969 5970 while (cur != NULL) { 5971 assert(!is_on_master_free_list(cur), "sanity"); 5972 if (non_young) { 5973 if (cur->is_young()) { 5974 double end_sec = os::elapsedTime(); 5975 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5976 non_young_time_ms += elapsed_ms; 5977 5978 start_sec = os::elapsedTime(); 5979 non_young = false; 5980 } 5981 } else { 5982 if (!cur->is_young()) { 5983 double end_sec = os::elapsedTime(); 5984 double elapsed_ms = (end_sec - start_sec) * 1000.0; 5985 young_time_ms += elapsed_ms; 5986 5987 start_sec = os::elapsedTime(); 5988 non_young = true; 5989 } 5990 } 5991 5992 rs_lengths += cur->rem_set()->occupied(); 5993 5994 HeapRegion* next = cur->next_in_collection_set(); 5995 assert(cur->in_collection_set(), "bad CS"); 5996 cur->set_next_in_collection_set(NULL); 5997 cur->set_in_collection_set(false); 5998 5999 if (cur->is_young()) { 6000 int index = cur->young_index_in_cset(); 6001 assert(index != -1, "invariant"); 6002 assert((uint) index < policy->young_cset_region_length(), "invariant"); 6003 size_t words_survived = _surviving_young_words[index]; 6004 cur->record_surv_words_in_group(words_survived); 6005 6006 // At this point the we have 'popped' cur from the collection set 6007 // (linked via next_in_collection_set()) but it is still in the 6008 // young list (linked via next_young_region()). Clear the 6009 // _next_young_region field. 6010 cur->set_next_young_region(NULL); 6011 } else { 6012 int index = cur->young_index_in_cset(); 6013 assert(index == -1, "invariant"); 6014 } 6015 6016 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6017 (!cur->is_young() && cur->young_index_in_cset() == -1), 6018 "invariant" ); 6019 6020 if (!cur->evacuation_failed()) { 6021 MemRegion used_mr = cur->used_region(); 6022 6023 // And the region is empty. 6024 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6025 free_region(cur, &pre_used, &local_free_list, false /* par */); 6026 } else { 6027 cur->uninstall_surv_rate_group(); 6028 if (cur->is_young()) { 6029 cur->set_young_index_in_cset(-1); 6030 } 6031 cur->set_not_young(); 6032 cur->set_evacuation_failed(false); 6033 // The region is now considered to be old. 6034 _old_set.add(cur); 6035 } 6036 cur = next; 6037 } 6038 6039 policy->record_max_rs_lengths(rs_lengths); 6040 policy->cset_regions_freed(); 6041 6042 double end_sec = os::elapsedTime(); 6043 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6044 6045 if (non_young) { 6046 non_young_time_ms += elapsed_ms; 6047 } else { 6048 young_time_ms += elapsed_ms; 6049 } 6050 6051 update_sets_after_freeing_regions(pre_used, &local_free_list, 6052 NULL /* old_proxy_set */, 6053 NULL /* humongous_proxy_set */, 6054 false /* par */); 6055 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6056 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6057 } 6058 6059 // This routine is similar to the above but does not record 6060 // any policy statistics or update free lists; we are abandoning 6061 // the current incremental collection set in preparation of a 6062 // full collection. After the full GC we will start to build up 6063 // the incremental collection set again. 6064 // This is only called when we're doing a full collection 6065 // and is immediately followed by the tearing down of the young list. 6066 6067 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6068 HeapRegion* cur = cs_head; 6069 6070 while (cur != NULL) { 6071 HeapRegion* next = cur->next_in_collection_set(); 6072 assert(cur->in_collection_set(), "bad CS"); 6073 cur->set_next_in_collection_set(NULL); 6074 cur->set_in_collection_set(false); 6075 cur->set_young_index_in_cset(-1); 6076 cur = next; 6077 } 6078 } 6079 6080 void G1CollectedHeap::set_free_regions_coming() { 6081 if (G1ConcRegionFreeingVerbose) { 6082 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6083 "setting free regions coming"); 6084 } 6085 6086 assert(!free_regions_coming(), "pre-condition"); 6087 _free_regions_coming = true; 6088 } 6089 6090 void G1CollectedHeap::reset_free_regions_coming() { 6091 assert(free_regions_coming(), "pre-condition"); 6092 6093 { 6094 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6095 _free_regions_coming = false; 6096 SecondaryFreeList_lock->notify_all(); 6097 } 6098 6099 if (G1ConcRegionFreeingVerbose) { 6100 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6101 "reset free regions coming"); 6102 } 6103 } 6104 6105 void G1CollectedHeap::wait_while_free_regions_coming() { 6106 // Most of the time we won't have to wait, so let's do a quick test 6107 // first before we take the lock. 6108 if (!free_regions_coming()) { 6109 return; 6110 } 6111 6112 if (G1ConcRegionFreeingVerbose) { 6113 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6114 "waiting for free regions"); 6115 } 6116 6117 { 6118 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6119 while (free_regions_coming()) { 6120 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6121 } 6122 } 6123 6124 if (G1ConcRegionFreeingVerbose) { 6125 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6126 "done waiting for free regions"); 6127 } 6128 } 6129 6130 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6131 assert(heap_lock_held_for_gc(), 6132 "the heap lock should already be held by or for this thread"); 6133 _young_list->push_region(hr); 6134 } 6135 6136 class NoYoungRegionsClosure: public HeapRegionClosure { 6137 private: 6138 bool _success; 6139 public: 6140 NoYoungRegionsClosure() : _success(true) { } 6141 bool doHeapRegion(HeapRegion* r) { 6142 if (r->is_young()) { 6143 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6144 r->bottom(), r->end()); 6145 _success = false; 6146 } 6147 return false; 6148 } 6149 bool success() { return _success; } 6150 }; 6151 6152 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6153 bool ret = _young_list->check_list_empty(check_sample); 6154 6155 if (check_heap) { 6156 NoYoungRegionsClosure closure; 6157 heap_region_iterate(&closure); 6158 ret = ret && closure.success(); 6159 } 6160 6161 return ret; 6162 } 6163 6164 class TearDownRegionSetsClosure : public HeapRegionClosure { 6165 private: 6166 OldRegionSet *_old_set; 6167 6168 public: 6169 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { } 6170 6171 bool doHeapRegion(HeapRegion* r) { 6172 if (r->is_empty()) { 6173 // We ignore empty regions, we'll empty the free list afterwards 6174 } else if (r->is_young()) { 6175 // We ignore young regions, we'll empty the young list afterwards 6176 } else if (r->isHumongous()) { 6177 // We ignore humongous regions, we're not tearing down the 6178 // humongous region set 6179 } else { 6180 // The rest should be old 6181 _old_set->remove(r); 6182 } 6183 return false; 6184 } 6185 6186 ~TearDownRegionSetsClosure() { 6187 assert(_old_set->is_empty(), "post-condition"); 6188 } 6189 }; 6190 6191 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6192 assert_at_safepoint(true /* should_be_vm_thread */); 6193 6194 if (!free_list_only) { 6195 TearDownRegionSetsClosure cl(&_old_set); 6196 heap_region_iterate(&cl); 6197 6198 // Need to do this after the heap iteration to be able to 6199 // recognize the young regions and ignore them during the iteration. 6200 _young_list->empty_list(); 6201 } 6202 _free_list.remove_all(); 6203 } 6204 6205 class RebuildRegionSetsClosure : public HeapRegionClosure { 6206 private: 6207 bool _free_list_only; 6208 OldRegionSet* _old_set; 6209 FreeRegionList* _free_list; 6210 size_t _total_used; 6211 6212 public: 6213 RebuildRegionSetsClosure(bool free_list_only, 6214 OldRegionSet* old_set, FreeRegionList* free_list) : 6215 _free_list_only(free_list_only), 6216 _old_set(old_set), _free_list(free_list), _total_used(0) { 6217 assert(_free_list->is_empty(), "pre-condition"); 6218 if (!free_list_only) { 6219 assert(_old_set->is_empty(), "pre-condition"); 6220 } 6221 } 6222 6223 bool doHeapRegion(HeapRegion* r) { 6224 if (r->continuesHumongous()) { 6225 return false; 6226 } 6227 6228 if (r->is_empty()) { 6229 // Add free regions to the free list 6230 _free_list->add_as_tail(r); 6231 } else if (!_free_list_only) { 6232 assert(!r->is_young(), "we should not come across young regions"); 6233 6234 if (r->isHumongous()) { 6235 // We ignore humongous regions, we left the humongous set unchanged 6236 } else { 6237 // The rest should be old, add them to the old set 6238 _old_set->add(r); 6239 } 6240 _total_used += r->used(); 6241 } 6242 6243 return false; 6244 } 6245 6246 size_t total_used() { 6247 return _total_used; 6248 } 6249 }; 6250 6251 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6252 assert_at_safepoint(true /* should_be_vm_thread */); 6253 6254 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list); 6255 heap_region_iterate(&cl); 6256 6257 if (!free_list_only) { 6258 _summary_bytes_used = cl.total_used(); 6259 } 6260 assert(_summary_bytes_used == recalculate_used(), 6261 err_msg("inconsistent _summary_bytes_used, " 6262 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6263 _summary_bytes_used, recalculate_used())); 6264 } 6265 6266 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6267 _refine_cte_cl->set_concurrent(concurrent); 6268 } 6269 6270 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6271 HeapRegion* hr = heap_region_containing(p); 6272 if (hr == NULL) { 6273 return false; 6274 } else { 6275 return hr->is_in(p); 6276 } 6277 } 6278 6279 // Methods for the mutator alloc region 6280 6281 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6282 bool force) { 6283 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6284 assert(!force || g1_policy()->can_expand_young_list(), 6285 "if force is true we should be able to expand the young list"); 6286 bool young_list_full = g1_policy()->is_young_list_full(); 6287 if (force || !young_list_full) { 6288 HeapRegion* new_alloc_region = new_region(word_size, 6289 false /* do_expand */); 6290 if (new_alloc_region != NULL) { 6291 set_region_short_lived_locked(new_alloc_region); 6292 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6293 return new_alloc_region; 6294 } 6295 } 6296 return NULL; 6297 } 6298 6299 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6300 size_t allocated_bytes) { 6301 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6302 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 6303 6304 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6305 _summary_bytes_used += allocated_bytes; 6306 _hr_printer.retire(alloc_region); 6307 // We update the eden sizes here, when the region is retired, 6308 // instead of when it's allocated, since this is the point that its 6309 // used space has been recored in _summary_bytes_used. 6310 g1mm()->update_eden_size(); 6311 } 6312 6313 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 6314 bool force) { 6315 return _g1h->new_mutator_alloc_region(word_size, force); 6316 } 6317 6318 void G1CollectedHeap::set_par_threads() { 6319 // Don't change the number of workers. Use the value previously set 6320 // in the workgroup. 6321 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise"); 6322 uint n_workers = workers()->active_workers(); 6323 assert(UseDynamicNumberOfGCThreads || 6324 n_workers == workers()->total_workers(), 6325 "Otherwise should be using the total number of workers"); 6326 if (n_workers == 0) { 6327 assert(false, "Should have been set in prior evacuation pause."); 6328 n_workers = ParallelGCThreads; 6329 workers()->set_active_workers(n_workers); 6330 } 6331 set_par_threads(n_workers); 6332 } 6333 6334 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 6335 size_t allocated_bytes) { 6336 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 6337 } 6338 6339 // Methods for the GC alloc regions 6340 6341 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6342 uint count, 6343 GCAllocPurpose ap) { 6344 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6345 6346 if (count < g1_policy()->max_regions(ap)) { 6347 HeapRegion* new_alloc_region = new_region(word_size, 6348 true /* do_expand */); 6349 if (new_alloc_region != NULL) { 6350 // We really only need to do this for old regions given that we 6351 // should never scan survivors. But it doesn't hurt to do it 6352 // for survivors too. 6353 new_alloc_region->set_saved_mark(); 6354 if (ap == GCAllocForSurvived) { 6355 new_alloc_region->set_survivor(); 6356 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6357 } else { 6358 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6359 } 6360 bool during_im = g1_policy()->during_initial_mark_pause(); 6361 new_alloc_region->note_start_of_copying(during_im); 6362 return new_alloc_region; 6363 } else { 6364 g1_policy()->note_alloc_region_limit_reached(ap); 6365 } 6366 } 6367 return NULL; 6368 } 6369 6370 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6371 size_t allocated_bytes, 6372 GCAllocPurpose ap) { 6373 bool during_im = g1_policy()->during_initial_mark_pause(); 6374 alloc_region->note_end_of_copying(during_im); 6375 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6376 if (ap == GCAllocForSurvived) { 6377 young_list()->add_survivor_region(alloc_region); 6378 } else { 6379 _old_set.add(alloc_region); 6380 } 6381 _hr_printer.retire(alloc_region); 6382 } 6383 6384 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 6385 bool force) { 6386 assert(!force, "not supported for GC alloc regions"); 6387 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 6388 } 6389 6390 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 6391 size_t allocated_bytes) { 6392 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6393 GCAllocForSurvived); 6394 } 6395 6396 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 6397 bool force) { 6398 assert(!force, "not supported for GC alloc regions"); 6399 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 6400 } 6401 6402 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 6403 size_t allocated_bytes) { 6404 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 6405 GCAllocForTenured); 6406 } 6407 // Heap region set verification 6408 6409 class VerifyRegionListsClosure : public HeapRegionClosure { 6410 private: 6411 FreeRegionList* _free_list; 6412 OldRegionSet* _old_set; 6413 HumongousRegionSet* _humongous_set; 6414 uint _region_count; 6415 6416 public: 6417 VerifyRegionListsClosure(OldRegionSet* old_set, 6418 HumongousRegionSet* humongous_set, 6419 FreeRegionList* free_list) : 6420 _old_set(old_set), _humongous_set(humongous_set), 6421 _free_list(free_list), _region_count(0) { } 6422 6423 uint region_count() { return _region_count; } 6424 6425 bool doHeapRegion(HeapRegion* hr) { 6426 _region_count += 1; 6427 6428 if (hr->continuesHumongous()) { 6429 return false; 6430 } 6431 6432 if (hr->is_young()) { 6433 // TODO 6434 } else if (hr->startsHumongous()) { 6435 _humongous_set->verify_next_region(hr); 6436 } else if (hr->is_empty()) { 6437 _free_list->verify_next_region(hr); 6438 } else { 6439 _old_set->verify_next_region(hr); 6440 } 6441 return false; 6442 } 6443 }; 6444 6445 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index, 6446 HeapWord* bottom) { 6447 HeapWord* end = bottom + HeapRegion::GrainWords; 6448 MemRegion mr(bottom, end); 6449 assert(_g1_reserved.contains(mr), "invariant"); 6450 // This might return NULL if the allocation fails 6451 return new HeapRegion(hrs_index, _bot_shared, mr); 6452 } 6453 6454 void G1CollectedHeap::verify_region_sets() { 6455 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6456 6457 // First, check the explicit lists. 6458 _free_list.verify(); 6459 { 6460 // Given that a concurrent operation might be adding regions to 6461 // the secondary free list we have to take the lock before 6462 // verifying it. 6463 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6464 _secondary_free_list.verify(); 6465 } 6466 _old_set.verify(); 6467 _humongous_set.verify(); 6468 6469 // If a concurrent region freeing operation is in progress it will 6470 // be difficult to correctly attributed any free regions we come 6471 // across to the correct free list given that they might belong to 6472 // one of several (free_list, secondary_free_list, any local lists, 6473 // etc.). So, if that's the case we will skip the rest of the 6474 // verification operation. Alternatively, waiting for the concurrent 6475 // operation to complete will have a non-trivial effect on the GC's 6476 // operation (no concurrent operation will last longer than the 6477 // interval between two calls to verification) and it might hide 6478 // any issues that we would like to catch during testing. 6479 if (free_regions_coming()) { 6480 return; 6481 } 6482 6483 // Make sure we append the secondary_free_list on the free_list so 6484 // that all free regions we will come across can be safely 6485 // attributed to the free_list. 6486 append_secondary_free_list_if_not_empty_with_lock(); 6487 6488 // Finally, make sure that the region accounting in the lists is 6489 // consistent with what we see in the heap. 6490 _old_set.verify_start(); 6491 _humongous_set.verify_start(); 6492 _free_list.verify_start(); 6493 6494 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list); 6495 heap_region_iterate(&cl); 6496 6497 _old_set.verify_end(); 6498 _humongous_set.verify_end(); 6499 _free_list.verify_end(); 6500 }