1 /* 2 * Copyright (c) 2001, 2011, 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/g1MarkSweep.hpp" 35 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 36 #include "gc_implementation/g1/g1RemSet.inline.hpp" 37 #include "gc_implementation/g1/heapRegionRemSet.hpp" 38 #include "gc_implementation/g1/heapRegionSeq.inline.hpp" 39 #include "gc_implementation/g1/vm_operations_g1.hpp" 40 #include "gc_implementation/shared/isGCActiveMark.hpp" 41 #include "memory/gcLocker.inline.hpp" 42 #include "memory/genOopClosures.inline.hpp" 43 #include "memory/generationSpec.hpp" 44 #include "oops/oop.inline.hpp" 45 #include "oops/oop.pcgc.inline.hpp" 46 #include "runtime/aprofiler.hpp" 47 #include "runtime/vmThread.hpp" 48 49 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 50 51 // turn it on so that the contents of the young list (scan-only / 52 // to-be-collected) are printed at "strategic" points before / during 53 // / after the collection --- this is useful for debugging 54 #define YOUNG_LIST_VERBOSE 0 55 // CURRENT STATUS 56 // This file is under construction. Search for "FIXME". 57 58 // INVARIANTS/NOTES 59 // 60 // All allocation activity covered by the G1CollectedHeap interface is 61 // serialized by acquiring the HeapLock. This happens in mem_allocate 62 // and allocate_new_tlab, which are the "entry" points to the 63 // allocation code from the rest of the JVM. (Note that this does not 64 // apply to TLAB allocation, which is not part of this interface: it 65 // is done by clients of this interface.) 66 67 // Local to this file. 68 69 class RefineCardTableEntryClosure: public CardTableEntryClosure { 70 SuspendibleThreadSet* _sts; 71 G1RemSet* _g1rs; 72 ConcurrentG1Refine* _cg1r; 73 bool _concurrent; 74 public: 75 RefineCardTableEntryClosure(SuspendibleThreadSet* sts, 76 G1RemSet* g1rs, 77 ConcurrentG1Refine* cg1r) : 78 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true) 79 {} 80 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 81 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false); 82 // This path is executed by the concurrent refine or mutator threads, 83 // concurrently, and so we do not care if card_ptr contains references 84 // that point into the collection set. 85 assert(!oops_into_cset, "should be"); 86 87 if (_concurrent && _sts->should_yield()) { 88 // Caller will actually yield. 89 return false; 90 } 91 // Otherwise, we finished successfully; return true. 92 return true; 93 } 94 void set_concurrent(bool b) { _concurrent = b; } 95 }; 96 97 98 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure { 99 int _calls; 100 G1CollectedHeap* _g1h; 101 CardTableModRefBS* _ctbs; 102 int _histo[256]; 103 public: 104 ClearLoggedCardTableEntryClosure() : 105 _calls(0) 106 { 107 _g1h = G1CollectedHeap::heap(); 108 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 109 for (int i = 0; i < 256; i++) _histo[i] = 0; 110 } 111 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 112 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 113 _calls++; 114 unsigned char* ujb = (unsigned char*)card_ptr; 115 int ind = (int)(*ujb); 116 _histo[ind]++; 117 *card_ptr = -1; 118 } 119 return true; 120 } 121 int calls() { return _calls; } 122 void print_histo() { 123 gclog_or_tty->print_cr("Card table value histogram:"); 124 for (int i = 0; i < 256; i++) { 125 if (_histo[i] != 0) { 126 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]); 127 } 128 } 129 } 130 }; 131 132 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure { 133 int _calls; 134 G1CollectedHeap* _g1h; 135 CardTableModRefBS* _ctbs; 136 public: 137 RedirtyLoggedCardTableEntryClosure() : 138 _calls(0) 139 { 140 _g1h = G1CollectedHeap::heap(); 141 _ctbs = (CardTableModRefBS*)_g1h->barrier_set(); 142 } 143 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 144 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) { 145 _calls++; 146 *card_ptr = 0; 147 } 148 return true; 149 } 150 int calls() { return _calls; } 151 }; 152 153 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure { 154 public: 155 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 156 *card_ptr = CardTableModRefBS::dirty_card_val(); 157 return true; 158 } 159 }; 160 161 YoungList::YoungList(G1CollectedHeap* g1h) 162 : _g1h(g1h), _head(NULL), 163 _length(0), 164 _last_sampled_rs_lengths(0), 165 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) 166 { 167 guarantee( check_list_empty(false), "just making sure..." ); 168 } 169 170 void YoungList::push_region(HeapRegion *hr) { 171 assert(!hr->is_young(), "should not already be young"); 172 assert(hr->get_next_young_region() == NULL, "cause it should!"); 173 174 hr->set_next_young_region(_head); 175 _head = hr; 176 177 hr->set_young(); 178 double yg_surv_rate = _g1h->g1_policy()->predict_yg_surv_rate((int)_length); 179 ++_length; 180 } 181 182 void YoungList::add_survivor_region(HeapRegion* hr) { 183 assert(hr->is_survivor(), "should be flagged as survivor region"); 184 assert(hr->get_next_young_region() == NULL, "cause it should!"); 185 186 hr->set_next_young_region(_survivor_head); 187 if (_survivor_head == NULL) { 188 _survivor_tail = hr; 189 } 190 _survivor_head = hr; 191 192 ++_survivor_length; 193 } 194 195 void YoungList::empty_list(HeapRegion* list) { 196 while (list != NULL) { 197 HeapRegion* next = list->get_next_young_region(); 198 list->set_next_young_region(NULL); 199 list->uninstall_surv_rate_group(); 200 list->set_not_young(); 201 list = next; 202 } 203 } 204 205 void YoungList::empty_list() { 206 assert(check_list_well_formed(), "young list should be well formed"); 207 208 empty_list(_head); 209 _head = NULL; 210 _length = 0; 211 212 empty_list(_survivor_head); 213 _survivor_head = NULL; 214 _survivor_tail = NULL; 215 _survivor_length = 0; 216 217 _last_sampled_rs_lengths = 0; 218 219 assert(check_list_empty(false), "just making sure..."); 220 } 221 222 bool YoungList::check_list_well_formed() { 223 bool ret = true; 224 225 size_t length = 0; 226 HeapRegion* curr = _head; 227 HeapRegion* last = NULL; 228 while (curr != NULL) { 229 if (!curr->is_young()) { 230 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 231 "incorrectly tagged (y: %d, surv: %d)", 232 curr->bottom(), curr->end(), 233 curr->is_young(), curr->is_survivor()); 234 ret = false; 235 } 236 ++length; 237 last = curr; 238 curr = curr->get_next_young_region(); 239 } 240 ret = ret && (length == _length); 241 242 if (!ret) { 243 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 244 gclog_or_tty->print_cr("### list has %d entries, _length is %d", 245 length, _length); 246 } 247 248 return ret; 249 } 250 251 bool YoungList::check_list_empty(bool check_sample) { 252 bool ret = true; 253 254 if (_length != 0) { 255 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d", 256 _length); 257 ret = false; 258 } 259 if (check_sample && _last_sampled_rs_lengths != 0) { 260 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 261 ret = false; 262 } 263 if (_head != NULL) { 264 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 265 ret = false; 266 } 267 if (!ret) { 268 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 269 } 270 271 return ret; 272 } 273 274 void 275 YoungList::rs_length_sampling_init() { 276 _sampled_rs_lengths = 0; 277 _curr = _head; 278 } 279 280 bool 281 YoungList::rs_length_sampling_more() { 282 return _curr != NULL; 283 } 284 285 void 286 YoungList::rs_length_sampling_next() { 287 assert( _curr != NULL, "invariant" ); 288 size_t rs_length = _curr->rem_set()->occupied(); 289 290 _sampled_rs_lengths += rs_length; 291 292 // The current region may not yet have been added to the 293 // incremental collection set (it gets added when it is 294 // retired as the current allocation region). 295 if (_curr->in_collection_set()) { 296 // Update the collection set policy information for this region 297 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 298 } 299 300 _curr = _curr->get_next_young_region(); 301 if (_curr == NULL) { 302 _last_sampled_rs_lengths = _sampled_rs_lengths; 303 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 304 } 305 } 306 307 void 308 YoungList::reset_auxilary_lists() { 309 guarantee( is_empty(), "young list should be empty" ); 310 assert(check_list_well_formed(), "young list should be well formed"); 311 312 // Add survivor regions to SurvRateGroup. 313 _g1h->g1_policy()->note_start_adding_survivor_regions(); 314 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 315 316 for (HeapRegion* curr = _survivor_head; 317 curr != NULL; 318 curr = curr->get_next_young_region()) { 319 _g1h->g1_policy()->set_region_survivors(curr); 320 321 // The region is a non-empty survivor so let's add it to 322 // the incremental collection set for the next evacuation 323 // pause. 324 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 325 } 326 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 327 328 _head = _survivor_head; 329 _length = _survivor_length; 330 if (_survivor_head != NULL) { 331 assert(_survivor_tail != NULL, "cause it shouldn't be"); 332 assert(_survivor_length > 0, "invariant"); 333 _survivor_tail->set_next_young_region(NULL); 334 } 335 336 // Don't clear the survivor list handles until the start of 337 // the next evacuation pause - we need it in order to re-tag 338 // the survivor regions from this evacuation pause as 'young' 339 // at the start of the next. 340 341 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 342 343 assert(check_list_well_formed(), "young list should be well formed"); 344 } 345 346 void YoungList::print() { 347 HeapRegion* lists[] = {_head, _survivor_head}; 348 const char* names[] = {"YOUNG", "SURVIVOR"}; 349 350 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 351 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 352 HeapRegion *curr = lists[list]; 353 if (curr == NULL) 354 gclog_or_tty->print_cr(" empty"); 355 while (curr != NULL) { 356 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, " 357 "age: %4d, y: %d, surv: %d", 358 curr->bottom(), curr->end(), 359 curr->top(), 360 curr->prev_top_at_mark_start(), 361 curr->next_top_at_mark_start(), 362 curr->top_at_conc_mark_count(), 363 curr->age_in_surv_rate_group_cond(), 364 curr->is_young(), 365 curr->is_survivor()); 366 curr = curr->get_next_young_region(); 367 } 368 } 369 370 gclog_or_tty->print_cr(""); 371 } 372 373 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 374 { 375 // Claim the right to put the region on the dirty cards region list 376 // by installing a self pointer. 377 HeapRegion* next = hr->get_next_dirty_cards_region(); 378 if (next == NULL) { 379 HeapRegion* res = (HeapRegion*) 380 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 381 NULL); 382 if (res == NULL) { 383 HeapRegion* head; 384 do { 385 // Put the region to the dirty cards region list. 386 head = _dirty_cards_region_list; 387 next = (HeapRegion*) 388 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 389 if (next == head) { 390 assert(hr->get_next_dirty_cards_region() == hr, 391 "hr->get_next_dirty_cards_region() != hr"); 392 if (next == NULL) { 393 // The last region in the list points to itself. 394 hr->set_next_dirty_cards_region(hr); 395 } else { 396 hr->set_next_dirty_cards_region(next); 397 } 398 } 399 } while (next != head); 400 } 401 } 402 } 403 404 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 405 { 406 HeapRegion* head; 407 HeapRegion* hr; 408 do { 409 head = _dirty_cards_region_list; 410 if (head == NULL) { 411 return NULL; 412 } 413 HeapRegion* new_head = head->get_next_dirty_cards_region(); 414 if (head == new_head) { 415 // The last region. 416 new_head = NULL; 417 } 418 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 419 head); 420 } while (hr != head); 421 assert(hr != NULL, "invariant"); 422 hr->set_next_dirty_cards_region(NULL); 423 return hr; 424 } 425 426 void G1CollectedHeap::stop_conc_gc_threads() { 427 _cg1r->stop(); 428 _cmThread->stop(); 429 } 430 431 #ifdef ASSERT 432 // A region is added to the collection set as it is retired 433 // so an address p can point to a region which will be in the 434 // collection set but has not yet been retired. This method 435 // therefore is only accurate during a GC pause after all 436 // regions have been retired. It is used for debugging 437 // to check if an nmethod has references to objects that can 438 // be move during a partial collection. Though it can be 439 // inaccurate, it is sufficient for G1 because the conservative 440 // implementation of is_scavengable() for G1 will indicate that 441 // all nmethods must be scanned during a partial collection. 442 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 443 HeapRegion* hr = heap_region_containing(p); 444 return hr != NULL && hr->in_collection_set(); 445 } 446 #endif 447 448 // Returns true if the reference points to an object that 449 // can move in an incremental collecction. 450 bool G1CollectedHeap::is_scavengable(const void* p) { 451 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 452 G1CollectorPolicy* g1p = g1h->g1_policy(); 453 HeapRegion* hr = heap_region_containing(p); 454 if (hr == NULL) { 455 // perm gen (or null) 456 return false; 457 } else { 458 return !hr->isHumongous(); 459 } 460 } 461 462 void G1CollectedHeap::check_ct_logs_at_safepoint() { 463 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 464 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 465 466 // Count the dirty cards at the start. 467 CountNonCleanMemRegionClosure count1(this); 468 ct_bs->mod_card_iterate(&count1); 469 int orig_count = count1.n(); 470 471 // First clear the logged cards. 472 ClearLoggedCardTableEntryClosure clear; 473 dcqs.set_closure(&clear); 474 dcqs.apply_closure_to_all_completed_buffers(); 475 dcqs.iterate_closure_all_threads(false); 476 clear.print_histo(); 477 478 // Now ensure that there's no dirty cards. 479 CountNonCleanMemRegionClosure count2(this); 480 ct_bs->mod_card_iterate(&count2); 481 if (count2.n() != 0) { 482 gclog_or_tty->print_cr("Card table has %d entries; %d originally", 483 count2.n(), orig_count); 484 } 485 guarantee(count2.n() == 0, "Card table should be clean."); 486 487 RedirtyLoggedCardTableEntryClosure redirty; 488 JavaThread::dirty_card_queue_set().set_closure(&redirty); 489 dcqs.apply_closure_to_all_completed_buffers(); 490 dcqs.iterate_closure_all_threads(false); 491 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.", 492 clear.calls(), orig_count); 493 guarantee(redirty.calls() == clear.calls(), 494 "Or else mechanism is broken."); 495 496 CountNonCleanMemRegionClosure count3(this); 497 ct_bs->mod_card_iterate(&count3); 498 if (count3.n() != orig_count) { 499 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.", 500 orig_count, count3.n()); 501 guarantee(count3.n() >= orig_count, "Should have restored them all."); 502 } 503 504 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 505 } 506 507 // Private class members. 508 509 G1CollectedHeap* G1CollectedHeap::_g1h; 510 511 // Private methods. 512 513 HeapRegion* 514 G1CollectedHeap::new_region_try_secondary_free_list() { 515 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 516 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 517 if (!_secondary_free_list.is_empty()) { 518 if (G1ConcRegionFreeingVerbose) { 519 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 520 "secondary_free_list has "SIZE_FORMAT" entries", 521 _secondary_free_list.length()); 522 } 523 // It looks as if there are free regions available on the 524 // secondary_free_list. Let's move them to the free_list and try 525 // again to allocate from it. 526 append_secondary_free_list(); 527 528 assert(!_free_list.is_empty(), "if the secondary_free_list was not " 529 "empty we should have moved at least one entry to the free_list"); 530 HeapRegion* res = _free_list.remove_head(); 531 if (G1ConcRegionFreeingVerbose) { 532 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 533 "allocated "HR_FORMAT" from secondary_free_list", 534 HR_FORMAT_PARAMS(res)); 535 } 536 return res; 537 } 538 539 // Wait here until we get notifed either when (a) there are no 540 // more free regions coming or (b) some regions have been moved on 541 // the secondary_free_list. 542 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 543 } 544 545 if (G1ConcRegionFreeingVerbose) { 546 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 547 "could not allocate from secondary_free_list"); 548 } 549 return NULL; 550 } 551 552 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) { 553 assert(!isHumongous(word_size) || 554 word_size <= (size_t) HeapRegion::GrainWords, 555 "the only time we use this to allocate a humongous region is " 556 "when we are allocating a single humongous region"); 557 558 HeapRegion* res; 559 if (G1StressConcRegionFreeing) { 560 if (!_secondary_free_list.is_empty()) { 561 if (G1ConcRegionFreeingVerbose) { 562 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 563 "forced to look at the secondary_free_list"); 564 } 565 res = new_region_try_secondary_free_list(); 566 if (res != NULL) { 567 return res; 568 } 569 } 570 } 571 res = _free_list.remove_head_or_null(); 572 if (res == NULL) { 573 if (G1ConcRegionFreeingVerbose) { 574 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 575 "res == NULL, trying the secondary_free_list"); 576 } 577 res = new_region_try_secondary_free_list(); 578 } 579 if (res == NULL && do_expand) { 580 if (expand(word_size * HeapWordSize)) { 581 // Even though the heap was expanded, it might not have reached 582 // the desired size. So, we cannot assume that the allocation 583 // will succeed. 584 res = _free_list.remove_head_or_null(); 585 } 586 } 587 return res; 588 } 589 590 size_t G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions, 591 size_t word_size) { 592 assert(isHumongous(word_size), "word_size should be humongous"); 593 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 594 595 size_t first = G1_NULL_HRS_INDEX; 596 if (num_regions == 1) { 597 // Only one region to allocate, no need to go through the slower 598 // path. The caller will attempt the expasion if this fails, so 599 // let's not try to expand here too. 600 HeapRegion* hr = new_region(word_size, false /* do_expand */); 601 if (hr != NULL) { 602 first = hr->hrs_index(); 603 } else { 604 first = G1_NULL_HRS_INDEX; 605 } 606 } else { 607 // We can't allocate humongous regions while cleanupComplete() is 608 // running, since some of the regions we find to be empty might not 609 // yet be added to the free list and it is not straightforward to 610 // know which list they are on so that we can remove them. Note 611 // that we only need to do this if we need to allocate more than 612 // one region to satisfy the current humongous allocation 613 // request. If we are only allocating one region we use the common 614 // region allocation code (see above). 615 wait_while_free_regions_coming(); 616 append_secondary_free_list_if_not_empty_with_lock(); 617 618 if (free_regions() >= num_regions) { 619 first = _hrs.find_contiguous(num_regions); 620 if (first != G1_NULL_HRS_INDEX) { 621 for (size_t i = first; i < first + num_regions; ++i) { 622 HeapRegion* hr = region_at(i); 623 assert(hr->is_empty(), "sanity"); 624 assert(is_on_master_free_list(hr), "sanity"); 625 hr->set_pending_removal(true); 626 } 627 _free_list.remove_all_pending(num_regions); 628 } 629 } 630 } 631 return first; 632 } 633 634 HeapWord* 635 G1CollectedHeap::humongous_obj_allocate_initialize_regions(size_t first, 636 size_t num_regions, 637 size_t word_size) { 638 assert(first != G1_NULL_HRS_INDEX, "pre-condition"); 639 assert(isHumongous(word_size), "word_size should be humongous"); 640 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 641 642 // Index of last region in the series + 1. 643 size_t last = first + num_regions; 644 645 // We need to initialize the region(s) we just discovered. This is 646 // a bit tricky given that it can happen concurrently with 647 // refinement threads refining cards on these regions and 648 // potentially wanting to refine the BOT as they are scanning 649 // those cards (this can happen shortly after a cleanup; see CR 650 // 6991377). So we have to set up the region(s) carefully and in 651 // a specific order. 652 653 // The word size sum of all the regions we will allocate. 654 size_t word_size_sum = num_regions * HeapRegion::GrainWords; 655 assert(word_size <= word_size_sum, "sanity"); 656 657 // This will be the "starts humongous" region. 658 HeapRegion* first_hr = region_at(first); 659 // The header of the new object will be placed at the bottom of 660 // the first region. 661 HeapWord* new_obj = first_hr->bottom(); 662 // This will be the new end of the first region in the series that 663 // should also match the end of the last region in the seriers. 664 HeapWord* new_end = new_obj + word_size_sum; 665 // This will be the new top of the first region that will reflect 666 // this allocation. 667 HeapWord* new_top = new_obj + word_size; 668 669 // First, we need to zero the header of the space that we will be 670 // allocating. When we update top further down, some refinement 671 // threads might try to scan the region. By zeroing the header we 672 // ensure that any thread that will try to scan the region will 673 // come across the zero klass word and bail out. 674 // 675 // NOTE: It would not have been correct to have used 676 // CollectedHeap::fill_with_object() and make the space look like 677 // an int array. The thread that is doing the allocation will 678 // later update the object header to a potentially different array 679 // type and, for a very short period of time, the klass and length 680 // fields will be inconsistent. This could cause a refinement 681 // thread to calculate the object size incorrectly. 682 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 683 684 // We will set up the first region as "starts humongous". This 685 // will also update the BOT covering all the regions to reflect 686 // that there is a single object that starts at the bottom of the 687 // first region. 688 first_hr->set_startsHumongous(new_top, new_end); 689 690 // Then, if there are any, we will set up the "continues 691 // humongous" regions. 692 HeapRegion* hr = NULL; 693 for (size_t i = first + 1; i < last; ++i) { 694 hr = region_at(i); 695 hr->set_continuesHumongous(first_hr); 696 } 697 // If we have "continues humongous" regions (hr != NULL), then the 698 // end of the last one should match new_end. 699 assert(hr == NULL || hr->end() == new_end, "sanity"); 700 701 // Up to this point no concurrent thread would have been able to 702 // do any scanning on any region in this series. All the top 703 // fields still point to bottom, so the intersection between 704 // [bottom,top] and [card_start,card_end] will be empty. Before we 705 // update the top fields, we'll do a storestore to make sure that 706 // no thread sees the update to top before the zeroing of the 707 // object header and the BOT initialization. 708 OrderAccess::storestore(); 709 710 // Now that the BOT and the object header have been initialized, 711 // we can update top of the "starts humongous" region. 712 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 713 "new_top should be in this region"); 714 first_hr->set_top(new_top); 715 if (_hr_printer.is_active()) { 716 HeapWord* bottom = first_hr->bottom(); 717 HeapWord* end = first_hr->orig_end(); 718 if ((first + 1) == last) { 719 // the series has a single humongous region 720 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 721 } else { 722 // the series has more than one humongous regions 723 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 724 } 725 } 726 727 // Now, we will update the top fields of the "continues humongous" 728 // regions. The reason we need to do this is that, otherwise, 729 // these regions would look empty and this will confuse parts of 730 // G1. For example, the code that looks for a consecutive number 731 // of empty regions will consider them empty and try to 732 // re-allocate them. We can extend is_empty() to also include 733 // !continuesHumongous(), but it is easier to just update the top 734 // fields here. The way we set top for all regions (i.e., top == 735 // end for all regions but the last one, top == new_top for the 736 // last one) is actually used when we will free up the humongous 737 // region in free_humongous_region(). 738 hr = NULL; 739 for (size_t i = first + 1; i < last; ++i) { 740 hr = region_at(i); 741 if ((i + 1) == last) { 742 // last continues humongous region 743 assert(hr->bottom() < new_top && new_top <= hr->end(), 744 "new_top should fall on this region"); 745 hr->set_top(new_top); 746 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 747 } else { 748 // not last one 749 assert(new_top > hr->end(), "new_top should be above this region"); 750 hr->set_top(hr->end()); 751 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 752 } 753 } 754 // If we have continues humongous regions (hr != NULL), then the 755 // end of the last one should match new_end and its top should 756 // match new_top. 757 assert(hr == NULL || 758 (hr->end() == new_end && hr->top() == new_top), "sanity"); 759 760 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 761 _summary_bytes_used += first_hr->used(); 762 _humongous_set.add(first_hr); 763 764 return new_obj; 765 } 766 767 // If could fit into free regions w/o expansion, try. 768 // Otherwise, if can expand, do so. 769 // Otherwise, if using ex regions might help, try with ex given back. 770 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) { 771 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 772 773 verify_region_sets_optional(); 774 775 size_t num_regions = 776 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords; 777 size_t x_size = expansion_regions(); 778 size_t fs = _hrs.free_suffix(); 779 size_t first = humongous_obj_allocate_find_first(num_regions, word_size); 780 if (first == G1_NULL_HRS_INDEX) { 781 // The only thing we can do now is attempt expansion. 782 if (fs + x_size >= num_regions) { 783 // If the number of regions we're trying to allocate for this 784 // object is at most the number of regions in the free suffix, 785 // then the call to humongous_obj_allocate_find_first() above 786 // should have succeeded and we wouldn't be here. 787 // 788 // We should only be trying to expand when the free suffix is 789 // not sufficient for the object _and_ we have some expansion 790 // room available. 791 assert(num_regions > fs, "earlier allocation should have succeeded"); 792 793 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) { 794 // Even though the heap was expanded, it might not have 795 // reached the desired size. So, we cannot assume that the 796 // allocation will succeed. 797 first = humongous_obj_allocate_find_first(num_regions, word_size); 798 } 799 } 800 } 801 802 HeapWord* result = NULL; 803 if (first != G1_NULL_HRS_INDEX) { 804 result = 805 humongous_obj_allocate_initialize_regions(first, num_regions, word_size); 806 assert(result != NULL, "it should always return a valid result"); 807 } 808 809 verify_region_sets_optional(); 810 811 return result; 812 } 813 814 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 815 assert_heap_not_locked_and_not_at_safepoint(); 816 assert(!isHumongous(word_size), "we do not allow humongous TLABs"); 817 818 unsigned int dummy_gc_count_before; 819 return attempt_allocation(word_size, &dummy_gc_count_before); 820 } 821 822 HeapWord* 823 G1CollectedHeap::mem_allocate(size_t word_size, 824 bool* gc_overhead_limit_was_exceeded) { 825 assert_heap_not_locked_and_not_at_safepoint(); 826 827 // Loop until the allocation is satisified, or unsatisfied after GC. 828 for (int try_count = 1; /* we'll return */; try_count += 1) { 829 unsigned int gc_count_before; 830 831 HeapWord* result = NULL; 832 if (!isHumongous(word_size)) { 833 result = attempt_allocation(word_size, &gc_count_before); 834 } else { 835 result = attempt_allocation_humongous(word_size, &gc_count_before); 836 } 837 if (result != NULL) { 838 return result; 839 } 840 841 // Create the garbage collection operation... 842 VM_G1CollectForAllocation op(gc_count_before, word_size); 843 // ...and get the VM thread to execute it. 844 VMThread::execute(&op); 845 846 if (op.prologue_succeeded() && op.pause_succeeded()) { 847 // If the operation was successful we'll return the result even 848 // if it is NULL. If the allocation attempt failed immediately 849 // after a Full GC, it's unlikely we'll be able to allocate now. 850 HeapWord* result = op.result(); 851 if (result != NULL && !isHumongous(word_size)) { 852 // Allocations that take place on VM operations do not do any 853 // card dirtying and we have to do it here. We only have to do 854 // this for non-humongous allocations, though. 855 dirty_young_block(result, word_size); 856 } 857 return result; 858 } else { 859 assert(op.result() == NULL, 860 "the result should be NULL if the VM op did not succeed"); 861 } 862 863 // Give a warning if we seem to be looping forever. 864 if ((QueuedAllocationWarningCount > 0) && 865 (try_count % QueuedAllocationWarningCount == 0)) { 866 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 867 } 868 } 869 870 ShouldNotReachHere(); 871 return NULL; 872 } 873 874 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 875 unsigned int *gc_count_before_ret) { 876 // Make sure you read the note in attempt_allocation_humongous(). 877 878 assert_heap_not_locked_and_not_at_safepoint(); 879 assert(!isHumongous(word_size), "attempt_allocation_slow() should not " 880 "be called for humongous allocation requests"); 881 882 // We should only get here after the first-level allocation attempt 883 // (attempt_allocation()) failed to allocate. 884 885 // We will loop until a) we manage to successfully perform the 886 // allocation or b) we successfully schedule a collection which 887 // fails to perform the allocation. b) is the only case when we'll 888 // return NULL. 889 HeapWord* result = NULL; 890 for (int try_count = 1; /* we'll return */; try_count += 1) { 891 bool should_try_gc; 892 unsigned int gc_count_before; 893 894 { 895 MutexLockerEx x(Heap_lock); 896 897 result = _mutator_alloc_region.attempt_allocation_locked(word_size, 898 false /* bot_updates */); 899 if (result != NULL) { 900 return result; 901 } 902 903 // If we reach here, attempt_allocation_locked() above failed to 904 // allocate a new region. So the mutator alloc region should be NULL. 905 assert(_mutator_alloc_region.get() == NULL, "only way to get here"); 906 907 if (GC_locker::is_active_and_needs_gc()) { 908 if (g1_policy()->can_expand_young_list()) { 909 result = _mutator_alloc_region.attempt_allocation_force(word_size, 910 false /* bot_updates */); 911 if (result != NULL) { 912 return result; 913 } 914 } 915 should_try_gc = false; 916 } else { 917 // Read the GC count while still holding the Heap_lock. 918 gc_count_before = SharedHeap::heap()->total_collections(); 919 should_try_gc = true; 920 } 921 } 922 923 if (should_try_gc) { 924 bool succeeded; 925 result = do_collection_pause(word_size, gc_count_before, &succeeded); 926 if (result != NULL) { 927 assert(succeeded, "only way to get back a non-NULL result"); 928 return result; 929 } 930 931 if (succeeded) { 932 // If we get here we successfully scheduled a collection which 933 // failed to allocate. No point in trying to allocate 934 // further. We'll just return NULL. 935 MutexLockerEx x(Heap_lock); 936 *gc_count_before_ret = SharedHeap::heap()->total_collections(); 937 return NULL; 938 } 939 } else { 940 GC_locker::stall_until_clear(); 941 } 942 943 // We can reach here if we were unsuccessul in scheduling a 944 // collection (because another thread beat us to it) or if we were 945 // stalled due to the GC locker. In either can we should retry the 946 // allocation attempt in case another thread successfully 947 // performed a collection and reclaimed enough space. We do the 948 // first attempt (without holding the Heap_lock) here and the 949 // follow-on attempt will be at the start of the next loop 950 // iteration (after taking the Heap_lock). 951 result = _mutator_alloc_region.attempt_allocation(word_size, 952 false /* bot_updates */); 953 if (result != NULL ){ 954 return result; 955 } 956 957 // Give a warning if we seem to be looping forever. 958 if ((QueuedAllocationWarningCount > 0) && 959 (try_count % QueuedAllocationWarningCount == 0)) { 960 warning("G1CollectedHeap::attempt_allocation_slow() " 961 "retries %d times", try_count); 962 } 963 } 964 965 ShouldNotReachHere(); 966 return NULL; 967 } 968 969 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 970 unsigned int * gc_count_before_ret) { 971 // The structure of this method has a lot of similarities to 972 // attempt_allocation_slow(). The reason these two were not merged 973 // into a single one is that such a method would require several "if 974 // allocation is not humongous do this, otherwise do that" 975 // conditional paths which would obscure its flow. In fact, an early 976 // version of this code did use a unified method which was harder to 977 // follow and, as a result, it had subtle bugs that were hard to 978 // track down. So keeping these two methods separate allows each to 979 // be more readable. It will be good to keep these two in sync as 980 // much as possible. 981 982 assert_heap_not_locked_and_not_at_safepoint(); 983 assert(isHumongous(word_size), "attempt_allocation_humongous() " 984 "should only be called for humongous allocations"); 985 986 // We will loop until a) we manage to successfully perform the 987 // allocation or b) we successfully schedule a collection which 988 // fails to perform the allocation. b) is the only case when we'll 989 // return NULL. 990 HeapWord* result = NULL; 991 for (int try_count = 1; /* we'll return */; try_count += 1) { 992 bool should_try_gc; 993 unsigned int gc_count_before; 994 995 { 996 MutexLockerEx x(Heap_lock); 997 998 // Given that humongous objects are not allocated in young 999 // regions, we'll first try to do the allocation without doing a 1000 // collection hoping that there's enough space in the heap. 1001 result = humongous_obj_allocate(word_size); 1002 if (result != NULL) { 1003 return result; 1004 } 1005 1006 if (GC_locker::is_active_and_needs_gc()) { 1007 should_try_gc = false; 1008 } else { 1009 // Read the GC count while still holding the Heap_lock. 1010 gc_count_before = SharedHeap::heap()->total_collections(); 1011 should_try_gc = true; 1012 } 1013 } 1014 1015 if (should_try_gc) { 1016 // If we failed to allocate the humongous object, we should try to 1017 // do a collection pause (if we're allowed) in case it reclaims 1018 // enough space for the allocation to succeed after the pause. 1019 1020 bool succeeded; 1021 result = do_collection_pause(word_size, gc_count_before, &succeeded); 1022 if (result != NULL) { 1023 assert(succeeded, "only way to get back a non-NULL result"); 1024 return result; 1025 } 1026 1027 if (succeeded) { 1028 // If we get here we successfully scheduled a collection which 1029 // failed to allocate. No point in trying to allocate 1030 // further. We'll just return NULL. 1031 MutexLockerEx x(Heap_lock); 1032 *gc_count_before_ret = SharedHeap::heap()->total_collections(); 1033 return NULL; 1034 } 1035 } else { 1036 GC_locker::stall_until_clear(); 1037 } 1038 1039 // We can reach here if we were unsuccessul in scheduling a 1040 // collection (because another thread beat us to it) or if we were 1041 // stalled due to the GC locker. In either can we should retry the 1042 // allocation attempt in case another thread successfully 1043 // performed a collection and reclaimed enough space. Give a 1044 // warning if we seem to be looping forever. 1045 1046 if ((QueuedAllocationWarningCount > 0) && 1047 (try_count % QueuedAllocationWarningCount == 0)) { 1048 warning("G1CollectedHeap::attempt_allocation_humongous() " 1049 "retries %d times", try_count); 1050 } 1051 } 1052 1053 ShouldNotReachHere(); 1054 return NULL; 1055 } 1056 1057 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1058 bool expect_null_mutator_alloc_region) { 1059 assert_at_safepoint(true /* should_be_vm_thread */); 1060 assert(_mutator_alloc_region.get() == NULL || 1061 !expect_null_mutator_alloc_region, 1062 "the current alloc region was unexpectedly found to be non-NULL"); 1063 1064 if (!isHumongous(word_size)) { 1065 return _mutator_alloc_region.attempt_allocation_locked(word_size, 1066 false /* bot_updates */); 1067 } else { 1068 return humongous_obj_allocate(word_size); 1069 } 1070 1071 ShouldNotReachHere(); 1072 } 1073 1074 class PostMCRemSetClearClosure: public HeapRegionClosure { 1075 ModRefBarrierSet* _mr_bs; 1076 public: 1077 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {} 1078 bool doHeapRegion(HeapRegion* r) { 1079 r->reset_gc_time_stamp(); 1080 if (r->continuesHumongous()) 1081 return false; 1082 HeapRegionRemSet* hrrs = r->rem_set(); 1083 if (hrrs != NULL) hrrs->clear(); 1084 // You might think here that we could clear just the cards 1085 // corresponding to the used region. But no: if we leave a dirty card 1086 // in a region we might allocate into, then it would prevent that card 1087 // from being enqueued, and cause it to be missed. 1088 // Re: the performance cost: we shouldn't be doing full GC anyway! 1089 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1090 return false; 1091 } 1092 }; 1093 1094 1095 class PostMCRemSetInvalidateClosure: public HeapRegionClosure { 1096 ModRefBarrierSet* _mr_bs; 1097 public: 1098 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {} 1099 bool doHeapRegion(HeapRegion* r) { 1100 if (r->continuesHumongous()) return false; 1101 if (r->used_region().word_size() != 0) { 1102 _mr_bs->invalidate(r->used_region(), true /*whole heap*/); 1103 } 1104 return false; 1105 } 1106 }; 1107 1108 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1109 G1CollectedHeap* _g1h; 1110 UpdateRSOopClosure _cl; 1111 int _worker_i; 1112 public: 1113 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1114 _cl(g1->g1_rem_set(), worker_i), 1115 _worker_i(worker_i), 1116 _g1h(g1) 1117 { } 1118 1119 bool doHeapRegion(HeapRegion* r) { 1120 if (!r->continuesHumongous()) { 1121 _cl.set_from(r); 1122 r->oop_iterate(&_cl); 1123 } 1124 return false; 1125 } 1126 }; 1127 1128 class ParRebuildRSTask: public AbstractGangTask { 1129 G1CollectedHeap* _g1; 1130 public: 1131 ParRebuildRSTask(G1CollectedHeap* g1) 1132 : AbstractGangTask("ParRebuildRSTask"), 1133 _g1(g1) 1134 { } 1135 1136 void work(int i) { 1137 RebuildRSOutOfRegionClosure rebuild_rs(_g1, i); 1138 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i, 1139 HeapRegion::RebuildRSClaimValue); 1140 } 1141 }; 1142 1143 class PostCompactionPrinterClosure: public HeapRegionClosure { 1144 private: 1145 G1HRPrinter* _hr_printer; 1146 public: 1147 bool doHeapRegion(HeapRegion* hr) { 1148 assert(!hr->is_young(), "not expecting to find young regions"); 1149 // We only generate output for non-empty regions. 1150 if (!hr->is_empty()) { 1151 if (!hr->isHumongous()) { 1152 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1153 } else if (hr->startsHumongous()) { 1154 if (hr->capacity() == (size_t) HeapRegion::GrainBytes) { 1155 // single humongous region 1156 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1157 } else { 1158 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1159 } 1160 } else { 1161 assert(hr->continuesHumongous(), "only way to get here"); 1162 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1163 } 1164 } 1165 return false; 1166 } 1167 1168 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1169 : _hr_printer(hr_printer) { } 1170 }; 1171 1172 bool G1CollectedHeap::do_collection(bool explicit_gc, 1173 bool clear_all_soft_refs, 1174 size_t word_size) { 1175 assert_at_safepoint(true /* should_be_vm_thread */); 1176 1177 if (GC_locker::check_active_before_gc()) { 1178 return false; 1179 } 1180 1181 SvcGCMarker sgcm(SvcGCMarker::FULL); 1182 ResourceMark rm; 1183 1184 if (PrintHeapAtGC) { 1185 Universe::print_heap_before_gc(); 1186 } 1187 1188 verify_region_sets_optional(); 1189 1190 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1191 collector_policy()->should_clear_all_soft_refs(); 1192 1193 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1194 1195 { 1196 IsGCActiveMark x; 1197 1198 // Timing 1199 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc); 1200 assert(!system_gc || explicit_gc, "invariant"); 1201 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 1202 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 1203 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC", 1204 PrintGC, true, gclog_or_tty); 1205 1206 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1207 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1208 1209 double start = os::elapsedTime(); 1210 g1_policy()->record_full_collection_start(); 1211 1212 wait_while_free_regions_coming(); 1213 append_secondary_free_list_if_not_empty_with_lock(); 1214 1215 gc_prologue(true); 1216 increment_total_collections(true /* full gc */); 1217 1218 size_t g1h_prev_used = used(); 1219 assert(used() == recalculate_used(), "Should be equal"); 1220 1221 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) { 1222 HandleMark hm; // Discard invalid handles created during verification 1223 gclog_or_tty->print(" VerifyBeforeGC:"); 1224 prepare_for_verify(); 1225 Universe::verify(/* allow dirty */ true, 1226 /* silent */ false, 1227 /* option */ VerifyOption_G1UsePrevMarking); 1228 1229 } 1230 1231 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1232 1233 // We want to discover references, but not process them yet. 1234 // This mode is disabled in 1235 // instanceRefKlass::process_discovered_references if the 1236 // generation does some collection work, or 1237 // instanceRefKlass::enqueue_discovered_references if the 1238 // generation returns without doing any work. 1239 ref_processor()->disable_discovery(); 1240 ref_processor()->abandon_partial_discovery(); 1241 ref_processor()->verify_no_references_recorded(); 1242 1243 // Abandon current iterations of concurrent marking and concurrent 1244 // refinement, if any are in progress. 1245 concurrent_mark()->abort(); 1246 1247 // Make sure we'll choose a new allocation region afterwards. 1248 release_mutator_alloc_region(); 1249 abandon_gc_alloc_regions(); 1250 g1_rem_set()->cleanupHRRS(); 1251 tear_down_region_lists(); 1252 1253 // We should call this after we retire any currently active alloc 1254 // regions so that all the ALLOC / RETIRE events are generated 1255 // before the start GC event. 1256 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1257 1258 // We may have added regions to the current incremental collection 1259 // set between the last GC or pause and now. We need to clear the 1260 // incremental collection set and then start rebuilding it afresh 1261 // after this full GC. 1262 abandon_collection_set(g1_policy()->inc_cset_head()); 1263 g1_policy()->clear_incremental_cset(); 1264 g1_policy()->stop_incremental_cset_building(); 1265 1266 if (g1_policy()->in_young_gc_mode()) { 1267 empty_young_list(); 1268 g1_policy()->set_full_young_gcs(true); 1269 } 1270 1271 // See the comment in G1CollectedHeap::ref_processing_init() about 1272 // how reference processing currently works in G1. 1273 1274 // Temporarily make reference _discovery_ single threaded (non-MT). 1275 ReferenceProcessorMTDiscoveryMutator rp_disc_ser(ref_processor(), false); 1276 1277 // Temporarily make refs discovery atomic 1278 ReferenceProcessorAtomicMutator rp_disc_atomic(ref_processor(), true); 1279 1280 // Temporarily clear _is_alive_non_header 1281 ReferenceProcessorIsAliveMutator rp_is_alive_null(ref_processor(), NULL); 1282 1283 ref_processor()->enable_discovery(); 1284 ref_processor()->setup_policy(do_clear_all_soft_refs); 1285 // Do collection work 1286 { 1287 HandleMark hm; // Discard invalid handles created during gc 1288 G1MarkSweep::invoke_at_safepoint(ref_processor(), do_clear_all_soft_refs); 1289 } 1290 assert(free_regions() == 0, "we should not have added any free regions"); 1291 rebuild_region_lists(); 1292 1293 _summary_bytes_used = recalculate_used(); 1294 1295 ref_processor()->enqueue_discovered_references(); 1296 1297 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1298 1299 MemoryService::track_memory_usage(); 1300 1301 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) { 1302 HandleMark hm; // Discard invalid handles created during verification 1303 gclog_or_tty->print(" VerifyAfterGC:"); 1304 prepare_for_verify(); 1305 Universe::verify(/* allow dirty */ false, 1306 /* silent */ false, 1307 /* option */ VerifyOption_G1UsePrevMarking); 1308 1309 } 1310 NOT_PRODUCT(ref_processor()->verify_no_references_recorded()); 1311 1312 reset_gc_time_stamp(); 1313 // Since everything potentially moved, we will clear all remembered 1314 // sets, and clear all cards. Later we will rebuild remebered 1315 // sets. We will also reset the GC time stamps of the regions. 1316 PostMCRemSetClearClosure rs_clear(mr_bs()); 1317 heap_region_iterate(&rs_clear); 1318 1319 // Resize the heap if necessary. 1320 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1321 1322 if (_hr_printer.is_active()) { 1323 // We should do this after we potentially resize the heap so 1324 // that all the COMMIT / UNCOMMIT events are generated before 1325 // the end GC event. 1326 1327 PostCompactionPrinterClosure cl(hr_printer()); 1328 heap_region_iterate(&cl); 1329 1330 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1331 } 1332 1333 if (_cg1r->use_cache()) { 1334 _cg1r->clear_and_record_card_counts(); 1335 _cg1r->clear_hot_cache(); 1336 } 1337 1338 // Rebuild remembered sets of all regions. 1339 1340 if (G1CollectedHeap::use_parallel_gc_threads()) { 1341 ParRebuildRSTask rebuild_rs_task(this); 1342 assert(check_heap_region_claim_values( 1343 HeapRegion::InitialClaimValue), "sanity check"); 1344 set_par_threads(workers()->total_workers()); 1345 workers()->run_task(&rebuild_rs_task); 1346 set_par_threads(0); 1347 assert(check_heap_region_claim_values( 1348 HeapRegion::RebuildRSClaimValue), "sanity check"); 1349 reset_heap_region_claim_values(); 1350 } else { 1351 RebuildRSOutOfRegionClosure rebuild_rs(this); 1352 heap_region_iterate(&rebuild_rs); 1353 } 1354 1355 if (PrintGC) { 1356 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity()); 1357 } 1358 1359 if (true) { // FIXME 1360 // Ask the permanent generation to adjust size for full collections 1361 perm()->compute_new_size(); 1362 } 1363 1364 // Start a new incremental collection set for the next pause 1365 assert(g1_policy()->collection_set() == NULL, "must be"); 1366 g1_policy()->start_incremental_cset_building(); 1367 1368 // Clear the _cset_fast_test bitmap in anticipation of adding 1369 // regions to the incremental collection set for the next 1370 // evacuation pause. 1371 clear_cset_fast_test(); 1372 1373 init_mutator_alloc_region(); 1374 1375 double end = os::elapsedTime(); 1376 g1_policy()->record_full_collection_end(); 1377 1378 #ifdef TRACESPINNING 1379 ParallelTaskTerminator::print_termination_counts(); 1380 #endif 1381 1382 gc_epilogue(true); 1383 1384 // Discard all rset updates 1385 JavaThread::dirty_card_queue_set().abandon_logs(); 1386 assert(!G1DeferredRSUpdate 1387 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any"); 1388 } 1389 1390 if (g1_policy()->in_young_gc_mode()) { 1391 _young_list->reset_sampled_info(); 1392 // At this point there should be no regions in the 1393 // entire heap tagged as young. 1394 assert( check_young_list_empty(true /* check_heap */), 1395 "young list should be empty at this point"); 1396 } 1397 1398 // Update the number of full collections that have been completed. 1399 increment_full_collections_completed(false /* concurrent */); 1400 1401 _hrs.verify_optional(); 1402 verify_region_sets_optional(); 1403 1404 if (PrintHeapAtGC) { 1405 Universe::print_heap_after_gc(); 1406 } 1407 g1mm()->update_counters(); 1408 1409 return true; 1410 } 1411 1412 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1413 // do_collection() will return whether it succeeded in performing 1414 // the GC. Currently, there is no facility on the 1415 // do_full_collection() API to notify the caller than the collection 1416 // did not succeed (e.g., because it was locked out by the GC 1417 // locker). So, right now, we'll ignore the return value. 1418 bool dummy = do_collection(true, /* explicit_gc */ 1419 clear_all_soft_refs, 1420 0 /* word_size */); 1421 } 1422 1423 // This code is mostly copied from TenuredGeneration. 1424 void 1425 G1CollectedHeap:: 1426 resize_if_necessary_after_full_collection(size_t word_size) { 1427 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check"); 1428 1429 // Include the current allocation, if any, and bytes that will be 1430 // pre-allocated to support collections, as "used". 1431 const size_t used_after_gc = used(); 1432 const size_t capacity_after_gc = capacity(); 1433 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1434 1435 // This is enforced in arguments.cpp. 1436 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1437 "otherwise the code below doesn't make sense"); 1438 1439 // We don't have floating point command-line arguments 1440 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1441 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1442 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1443 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1444 1445 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1446 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1447 1448 // We have to be careful here as these two calculations can overflow 1449 // 32-bit size_t's. 1450 double used_after_gc_d = (double) used_after_gc; 1451 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1452 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1453 1454 // Let's make sure that they are both under the max heap size, which 1455 // by default will make them fit into a size_t. 1456 double desired_capacity_upper_bound = (double) max_heap_size; 1457 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1458 desired_capacity_upper_bound); 1459 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1460 desired_capacity_upper_bound); 1461 1462 // We can now safely turn them into size_t's. 1463 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1464 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1465 1466 // This assert only makes sense here, before we adjust them 1467 // with respect to the min and max heap size. 1468 assert(minimum_desired_capacity <= maximum_desired_capacity, 1469 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1470 "maximum_desired_capacity = "SIZE_FORMAT, 1471 minimum_desired_capacity, maximum_desired_capacity)); 1472 1473 // Should not be greater than the heap max size. No need to adjust 1474 // it with respect to the heap min size as it's a lower bound (i.e., 1475 // we'll try to make the capacity larger than it, not smaller). 1476 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1477 // Should not be less than the heap min size. No need to adjust it 1478 // with respect to the heap max size as it's an upper bound (i.e., 1479 // we'll try to make the capacity smaller than it, not greater). 1480 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1481 1482 if (PrintGC && Verbose) { 1483 const double free_percentage = 1484 (double) free_after_gc / (double) capacity_after_gc; 1485 gclog_or_tty->print_cr("Computing new size after full GC "); 1486 gclog_or_tty->print_cr(" " 1487 " minimum_free_percentage: %6.2f", 1488 minimum_free_percentage); 1489 gclog_or_tty->print_cr(" " 1490 " maximum_free_percentage: %6.2f", 1491 maximum_free_percentage); 1492 gclog_or_tty->print_cr(" " 1493 " capacity: %6.1fK" 1494 " minimum_desired_capacity: %6.1fK" 1495 " maximum_desired_capacity: %6.1fK", 1496 (double) capacity_after_gc / (double) K, 1497 (double) minimum_desired_capacity / (double) K, 1498 (double) maximum_desired_capacity / (double) K); 1499 gclog_or_tty->print_cr(" " 1500 " free_after_gc: %6.1fK" 1501 " used_after_gc: %6.1fK", 1502 (double) free_after_gc / (double) K, 1503 (double) used_after_gc / (double) K); 1504 gclog_or_tty->print_cr(" " 1505 " free_percentage: %6.2f", 1506 free_percentage); 1507 } 1508 if (capacity_after_gc < minimum_desired_capacity) { 1509 // Don't expand unless it's significant 1510 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1511 if (expand(expand_bytes)) { 1512 if (PrintGC && Verbose) { 1513 gclog_or_tty->print_cr(" " 1514 " expanding:" 1515 " max_heap_size: %6.1fK" 1516 " minimum_desired_capacity: %6.1fK" 1517 " expand_bytes: %6.1fK", 1518 (double) max_heap_size / (double) K, 1519 (double) minimum_desired_capacity / (double) K, 1520 (double) expand_bytes / (double) K); 1521 } 1522 } 1523 1524 // No expansion, now see if we want to shrink 1525 } else if (capacity_after_gc > maximum_desired_capacity) { 1526 // Capacity too large, compute shrinking size 1527 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1528 shrink(shrink_bytes); 1529 if (PrintGC && Verbose) { 1530 gclog_or_tty->print_cr(" " 1531 " shrinking:" 1532 " min_heap_size: %6.1fK" 1533 " maximum_desired_capacity: %6.1fK" 1534 " shrink_bytes: %6.1fK", 1535 (double) min_heap_size / (double) K, 1536 (double) maximum_desired_capacity / (double) K, 1537 (double) shrink_bytes / (double) K); 1538 } 1539 } 1540 } 1541 1542 1543 HeapWord* 1544 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1545 bool* succeeded) { 1546 assert_at_safepoint(true /* should_be_vm_thread */); 1547 1548 *succeeded = true; 1549 // Let's attempt the allocation first. 1550 HeapWord* result = 1551 attempt_allocation_at_safepoint(word_size, 1552 false /* expect_null_mutator_alloc_region */); 1553 if (result != NULL) { 1554 assert(*succeeded, "sanity"); 1555 return result; 1556 } 1557 1558 // In a G1 heap, we're supposed to keep allocation from failing by 1559 // incremental pauses. Therefore, at least for now, we'll favor 1560 // expansion over collection. (This might change in the future if we can 1561 // do something smarter than full collection to satisfy a failed alloc.) 1562 result = expand_and_allocate(word_size); 1563 if (result != NULL) { 1564 assert(*succeeded, "sanity"); 1565 return result; 1566 } 1567 1568 // Expansion didn't work, we'll try to do a Full GC. 1569 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1570 false, /* clear_all_soft_refs */ 1571 word_size); 1572 if (!gc_succeeded) { 1573 *succeeded = false; 1574 return NULL; 1575 } 1576 1577 // Retry the allocation 1578 result = attempt_allocation_at_safepoint(word_size, 1579 true /* expect_null_mutator_alloc_region */); 1580 if (result != NULL) { 1581 assert(*succeeded, "sanity"); 1582 return result; 1583 } 1584 1585 // Then, try a Full GC that will collect all soft references. 1586 gc_succeeded = do_collection(false, /* explicit_gc */ 1587 true, /* clear_all_soft_refs */ 1588 word_size); 1589 if (!gc_succeeded) { 1590 *succeeded = false; 1591 return NULL; 1592 } 1593 1594 // Retry the allocation once more 1595 result = attempt_allocation_at_safepoint(word_size, 1596 true /* expect_null_mutator_alloc_region */); 1597 if (result != NULL) { 1598 assert(*succeeded, "sanity"); 1599 return result; 1600 } 1601 1602 assert(!collector_policy()->should_clear_all_soft_refs(), 1603 "Flag should have been handled and cleared prior to this point"); 1604 1605 // What else? We might try synchronous finalization later. If the total 1606 // space available is large enough for the allocation, then a more 1607 // complete compaction phase than we've tried so far might be 1608 // appropriate. 1609 assert(*succeeded, "sanity"); 1610 return NULL; 1611 } 1612 1613 // Attempting to expand the heap sufficiently 1614 // to support an allocation of the given "word_size". If 1615 // successful, perform the allocation and return the address of the 1616 // allocated block, or else "NULL". 1617 1618 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) { 1619 assert_at_safepoint(true /* should_be_vm_thread */); 1620 1621 verify_region_sets_optional(); 1622 1623 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1624 if (expand(expand_bytes)) { 1625 _hrs.verify_optional(); 1626 verify_region_sets_optional(); 1627 return attempt_allocation_at_safepoint(word_size, 1628 false /* expect_null_mutator_alloc_region */); 1629 } 1630 return NULL; 1631 } 1632 1633 void G1CollectedHeap::update_committed_space(HeapWord* old_end, 1634 HeapWord* new_end) { 1635 assert(old_end != new_end, "don't call this otherwise"); 1636 assert((HeapWord*) _g1_storage.high() == new_end, "invariant"); 1637 1638 // Update the committed mem region. 1639 _g1_committed.set_end(new_end); 1640 // Tell the card table about the update. 1641 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed); 1642 // Tell the BOT about the update. 1643 _bot_shared->resize(_g1_committed.word_size()); 1644 } 1645 1646 bool G1CollectedHeap::expand(size_t expand_bytes) { 1647 size_t old_mem_size = _g1_storage.committed_size(); 1648 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1649 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1650 HeapRegion::GrainBytes); 1651 1652 if (Verbose && PrintGC) { 1653 gclog_or_tty->print("Expanding garbage-first heap from %ldK by %ldK", 1654 old_mem_size/K, aligned_expand_bytes/K); 1655 } 1656 1657 // First commit the memory. 1658 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1659 bool successful = _g1_storage.expand_by(aligned_expand_bytes); 1660 if (successful) { 1661 // Then propagate this update to the necessary data structures. 1662 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1663 update_committed_space(old_end, new_end); 1664 1665 FreeRegionList expansion_list("Local Expansion List"); 1666 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list); 1667 assert(mr.start() == old_end, "post-condition"); 1668 // mr might be a smaller region than what was requested if 1669 // expand_by() was unable to allocate the HeapRegion instances 1670 assert(mr.end() <= new_end, "post-condition"); 1671 1672 size_t actual_expand_bytes = mr.byte_size(); 1673 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1674 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(), 1675 "post-condition"); 1676 if (actual_expand_bytes < aligned_expand_bytes) { 1677 // We could not expand _hrs to the desired size. In this case we 1678 // need to shrink the committed space accordingly. 1679 assert(mr.end() < new_end, "invariant"); 1680 1681 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes; 1682 // First uncommit the memory. 1683 _g1_storage.shrink_by(diff_bytes); 1684 // Then propagate this update to the necessary data structures. 1685 update_committed_space(new_end, mr.end()); 1686 } 1687 _free_list.add_as_tail(&expansion_list); 1688 1689 if (_hr_printer.is_active()) { 1690 HeapWord* curr = mr.start(); 1691 while (curr < mr.end()) { 1692 HeapWord* curr_end = curr + HeapRegion::GrainWords; 1693 _hr_printer.commit(curr, curr_end); 1694 curr = curr_end; 1695 } 1696 assert(curr == mr.end(), "post-condition"); 1697 } 1698 } else { 1699 // The expansion of the virtual storage space was unsuccessful. 1700 // Let's see if it was because we ran out of swap. 1701 if (G1ExitOnExpansionFailure && 1702 _g1_storage.uncommitted_size() >= aligned_expand_bytes) { 1703 // We had head room... 1704 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion"); 1705 } 1706 } 1707 1708 if (Verbose && PrintGC) { 1709 size_t new_mem_size = _g1_storage.committed_size(); 1710 gclog_or_tty->print_cr("...%s, expanded to %ldK", 1711 (successful ? "Successful" : "Failed"), 1712 new_mem_size/K); 1713 } 1714 return successful; 1715 } 1716 1717 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1718 size_t old_mem_size = _g1_storage.committed_size(); 1719 size_t aligned_shrink_bytes = 1720 ReservedSpace::page_align_size_down(shrink_bytes); 1721 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1722 HeapRegion::GrainBytes); 1723 size_t num_regions_deleted = 0; 1724 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted); 1725 HeapWord* old_end = (HeapWord*) _g1_storage.high(); 1726 assert(mr.end() == old_end, "post-condition"); 1727 if (mr.byte_size() > 0) { 1728 if (_hr_printer.is_active()) { 1729 HeapWord* curr = mr.end(); 1730 while (curr > mr.start()) { 1731 HeapWord* curr_end = curr; 1732 curr -= HeapRegion::GrainWords; 1733 _hr_printer.uncommit(curr, curr_end); 1734 } 1735 assert(curr == mr.start(), "post-condition"); 1736 } 1737 1738 _g1_storage.shrink_by(mr.byte_size()); 1739 HeapWord* new_end = (HeapWord*) _g1_storage.high(); 1740 assert(mr.start() == new_end, "post-condition"); 1741 1742 _expansion_regions += num_regions_deleted; 1743 update_committed_space(old_end, new_end); 1744 HeapRegionRemSet::shrink_heap(n_regions()); 1745 1746 if (Verbose && PrintGC) { 1747 size_t new_mem_size = _g1_storage.committed_size(); 1748 gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK", 1749 old_mem_size/K, aligned_shrink_bytes/K, 1750 new_mem_size/K); 1751 } 1752 } 1753 } 1754 1755 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1756 verify_region_sets_optional(); 1757 1758 // We should only reach here at the end of a Full GC which means we 1759 // should not not be holding to any GC alloc regions. The method 1760 // below will make sure of that and do any remaining clean up. 1761 abandon_gc_alloc_regions(); 1762 1763 // Instead of tearing down / rebuilding the free lists here, we 1764 // could instead use the remove_all_pending() method on free_list to 1765 // remove only the ones that we need to remove. 1766 tear_down_region_lists(); // We will rebuild them in a moment. 1767 shrink_helper(shrink_bytes); 1768 rebuild_region_lists(); 1769 1770 _hrs.verify_optional(); 1771 verify_region_sets_optional(); 1772 } 1773 1774 // Public methods. 1775 1776 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1777 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1778 #endif // _MSC_VER 1779 1780 1781 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1782 SharedHeap(policy_), 1783 _g1_policy(policy_), 1784 _dirty_card_queue_set(false), 1785 _into_cset_dirty_card_queue_set(false), 1786 _is_alive_closure(this), 1787 _ref_processor(NULL), 1788 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1789 _bot_shared(NULL), 1790 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL), 1791 _evac_failure_scan_stack(NULL) , 1792 _mark_in_progress(false), 1793 _cg1r(NULL), _summary_bytes_used(0), 1794 _refine_cte_cl(NULL), 1795 _full_collection(false), 1796 _free_list("Master Free List"), 1797 _secondary_free_list("Secondary Free List"), 1798 _humongous_set("Master Humongous Set"), 1799 _free_regions_coming(false), 1800 _young_list(new YoungList(this)), 1801 _gc_time_stamp(0), 1802 _retained_old_gc_alloc_region(NULL), 1803 _surviving_young_words(NULL), 1804 _full_collections_completed(0), 1805 _in_cset_fast_test(NULL), 1806 _in_cset_fast_test_base(NULL), 1807 _dirty_cards_region_list(NULL) { 1808 _g1h = this; // To catch bugs. 1809 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1810 vm_exit_during_initialization("Failed necessary allocation."); 1811 } 1812 1813 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1814 1815 int n_queues = MAX2((int)ParallelGCThreads, 1); 1816 _task_queues = new RefToScanQueueSet(n_queues); 1817 1818 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1819 assert(n_rem_sets > 0, "Invariant."); 1820 1821 HeapRegionRemSetIterator** iter_arr = 1822 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues); 1823 for (int i = 0; i < n_queues; i++) { 1824 iter_arr[i] = new HeapRegionRemSetIterator(); 1825 } 1826 _rem_set_iterator = iter_arr; 1827 1828 for (int i = 0; i < n_queues; i++) { 1829 RefToScanQueue* q = new RefToScanQueue(); 1830 q->initialize(); 1831 _task_queues->register_queue(i, q); 1832 } 1833 1834 guarantee(_task_queues != NULL, "task_queues allocation failure."); 1835 } 1836 1837 jint G1CollectedHeap::initialize() { 1838 CollectedHeap::pre_initialize(); 1839 os::enable_vtime(); 1840 1841 // Necessary to satisfy locking discipline assertions. 1842 1843 MutexLocker x(Heap_lock); 1844 1845 // We have to initialize the printer before committing the heap, as 1846 // it will be used then. 1847 _hr_printer.set_active(G1PrintHeapRegions); 1848 1849 // While there are no constraints in the GC code that HeapWordSize 1850 // be any particular value, there are multiple other areas in the 1851 // system which believe this to be true (e.g. oop->object_size in some 1852 // cases incorrectly returns the size in wordSize units rather than 1853 // HeapWordSize). 1854 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1855 1856 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1857 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1858 1859 // Ensure that the sizes are properly aligned. 1860 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1861 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1862 1863 _cg1r = new ConcurrentG1Refine(); 1864 1865 // Reserve the maximum. 1866 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation(); 1867 // Includes the perm-gen. 1868 1869 // When compressed oops are enabled, the preferred heap base 1870 // is calculated by subtracting the requested size from the 1871 // 32Gb boundary and using the result as the base address for 1872 // heap reservation. If the requested size is not aligned to 1873 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1874 // into the ReservedHeapSpace constructor) then the actual 1875 // base of the reserved heap may end up differing from the 1876 // address that was requested (i.e. the preferred heap base). 1877 // If this happens then we could end up using a non-optimal 1878 // compressed oops mode. 1879 1880 // Since max_byte_size is aligned to the size of a heap region (checked 1881 // above), we also need to align the perm gen size as it might not be. 1882 const size_t total_reserved = max_byte_size + 1883 align_size_up(pgs->max_size(), HeapRegion::GrainBytes); 1884 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm"); 1885 1886 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop); 1887 1888 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes, 1889 UseLargePages, addr); 1890 1891 if (UseCompressedOops) { 1892 if (addr != NULL && !heap_rs.is_reserved()) { 1893 // Failed to reserve at specified address - the requested memory 1894 // region is taken already, for example, by 'java' launcher. 1895 // Try again to reserver heap higher. 1896 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop); 1897 1898 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes, 1899 UseLargePages, addr); 1900 1901 if (addr != NULL && !heap_rs0.is_reserved()) { 1902 // Failed to reserve at specified address again - give up. 1903 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop); 1904 assert(addr == NULL, ""); 1905 1906 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes, 1907 UseLargePages, addr); 1908 heap_rs = heap_rs1; 1909 } else { 1910 heap_rs = heap_rs0; 1911 } 1912 } 1913 } 1914 1915 if (!heap_rs.is_reserved()) { 1916 vm_exit_during_initialization("Could not reserve enough space for object heap"); 1917 return JNI_ENOMEM; 1918 } 1919 1920 // It is important to do this in a way such that concurrent readers can't 1921 // temporarily think somethings in the heap. (I've actually seen this 1922 // happen in asserts: DLD.) 1923 _reserved.set_word_size(0); 1924 _reserved.set_start((HeapWord*)heap_rs.base()); 1925 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size())); 1926 1927 _expansion_regions = max_byte_size/HeapRegion::GrainBytes; 1928 1929 // Create the gen rem set (and barrier set) for the entire reserved region. 1930 _rem_set = collector_policy()->create_rem_set(_reserved, 2); 1931 set_barrier_set(rem_set()->bs()); 1932 if (barrier_set()->is_a(BarrierSet::ModRef)) { 1933 _mr_bs = (ModRefBarrierSet*)_barrier_set; 1934 } else { 1935 vm_exit_during_initialization("G1 requires a mod ref bs."); 1936 return JNI_ENOMEM; 1937 } 1938 1939 // Also create a G1 rem set. 1940 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) { 1941 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs()); 1942 } else { 1943 vm_exit_during_initialization("G1 requires a cardtable mod ref bs."); 1944 return JNI_ENOMEM; 1945 } 1946 1947 // Carve out the G1 part of the heap. 1948 1949 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1950 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(), 1951 g1_rs.size()/HeapWordSize); 1952 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size); 1953 1954 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set()); 1955 1956 _g1_storage.initialize(g1_rs, 0); 1957 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0); 1958 _hrs.initialize((HeapWord*) _g1_reserved.start(), 1959 (HeapWord*) _g1_reserved.end(), 1960 _expansion_regions); 1961 1962 // 6843694 - ensure that the maximum region index can fit 1963 // in the remembered set structures. 1964 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1; 1965 guarantee((max_regions() - 1) <= max_region_idx, "too many regions"); 1966 1967 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1; 1968 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized"); 1969 guarantee((size_t) HeapRegion::CardsPerRegion < max_cards_per_region, 1970 "too many cards per region"); 1971 1972 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1); 1973 1974 _bot_shared = new G1BlockOffsetSharedArray(_reserved, 1975 heap_word_size(init_byte_size)); 1976 1977 _g1h = this; 1978 1979 _in_cset_fast_test_length = max_regions(); 1980 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length); 1981 1982 // We're biasing _in_cset_fast_test to avoid subtracting the 1983 // beginning of the heap every time we want to index; basically 1984 // it's the same with what we do with the card table. 1985 _in_cset_fast_test = _in_cset_fast_test_base - 1986 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes); 1987 1988 // Clear the _cset_fast_test bitmap in anticipation of adding 1989 // regions to the incremental collection set for the first 1990 // evacuation pause. 1991 clear_cset_fast_test(); 1992 1993 // Create the ConcurrentMark data structure and thread. 1994 // (Must do this late, so that "max_regions" is defined.) 1995 _cm = new ConcurrentMark(heap_rs, (int) max_regions()); 1996 _cmThread = _cm->cmThread(); 1997 1998 // Initialize the from_card cache structure of HeapRegionRemSet. 1999 HeapRegionRemSet::init_heap(max_regions()); 2000 2001 // Now expand into the initial heap size. 2002 if (!expand(init_byte_size)) { 2003 vm_exit_during_initialization("Failed to allocate initial heap."); 2004 return JNI_ENOMEM; 2005 } 2006 2007 // Perform any initialization actions delegated to the policy. 2008 g1_policy()->init(); 2009 2010 g1_policy()->note_start_of_mark_thread(); 2011 2012 _refine_cte_cl = 2013 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(), 2014 g1_rem_set(), 2015 concurrent_g1_refine()); 2016 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl); 2017 2018 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2019 SATB_Q_FL_lock, 2020 G1SATBProcessCompletedThreshold, 2021 Shared_SATB_Q_lock); 2022 2023 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2024 DirtyCardQ_FL_lock, 2025 concurrent_g1_refine()->yellow_zone(), 2026 concurrent_g1_refine()->red_zone(), 2027 Shared_DirtyCardQ_lock); 2028 2029 if (G1DeferredRSUpdate) { 2030 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon, 2031 DirtyCardQ_FL_lock, 2032 -1, // never trigger processing 2033 -1, // no limit on length 2034 Shared_DirtyCardQ_lock, 2035 &JavaThread::dirty_card_queue_set()); 2036 } 2037 2038 // Initialize the card queue set used to hold cards containing 2039 // references into the collection set. 2040 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon, 2041 DirtyCardQ_FL_lock, 2042 -1, // never trigger processing 2043 -1, // no limit on length 2044 Shared_DirtyCardQ_lock, 2045 &JavaThread::dirty_card_queue_set()); 2046 2047 // In case we're keeping closure specialization stats, initialize those 2048 // counts and that mechanism. 2049 SpecializationStats::clear(); 2050 2051 // Do later initialization work for concurrent refinement. 2052 _cg1r->init(); 2053 2054 // Here we allocate the dummy full region that is required by the 2055 // G1AllocRegion class. If we don't pass an address in the reserved 2056 // space here, lots of asserts fire. 2057 2058 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */, 2059 _g1_reserved.start()); 2060 // We'll re-use the same region whether the alloc region will 2061 // require BOT updates or not and, if it doesn't, then a non-young 2062 // region will complain that it cannot support allocations without 2063 // BOT updates. So we'll tag the dummy region as young to avoid that. 2064 dummy_region->set_young(); 2065 // Make sure it's full. 2066 dummy_region->set_top(dummy_region->end()); 2067 G1AllocRegion::setup(this, dummy_region); 2068 2069 init_mutator_alloc_region(); 2070 2071 // Do create of the monitoring and management support so that 2072 // values in the heap have been properly initialized. 2073 _g1mm = new G1MonitoringSupport(this, &_g1_storage); 2074 2075 return JNI_OK; 2076 } 2077 2078 void G1CollectedHeap::ref_processing_init() { 2079 // Reference processing in G1 currently works as follows: 2080 // 2081 // * There is only one reference processor instance that 2082 // 'spans' the entire heap. It is created by the code 2083 // below. 2084 // * Reference discovery is not enabled during an incremental 2085 // pause (see 6484982). 2086 // * Discoverered refs are not enqueued nor are they processed 2087 // during an incremental pause (see 6484982). 2088 // * Reference discovery is enabled at initial marking. 2089 // * Reference discovery is disabled and the discovered 2090 // references processed etc during remarking. 2091 // * Reference discovery is MT (see below). 2092 // * Reference discovery requires a barrier (see below). 2093 // * Reference processing is currently not MT (see 6608385). 2094 // * A full GC enables (non-MT) reference discovery and 2095 // processes any discovered references. 2096 2097 SharedHeap::ref_processing_init(); 2098 MemRegion mr = reserved_region(); 2099 _ref_processor = 2100 new ReferenceProcessor(mr, // span 2101 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing 2102 (int) ParallelGCThreads, // degree of mt processing 2103 ParallelGCThreads > 1 || ConcGCThreads > 1, // mt discovery 2104 (int) MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery 2105 false, // Reference discovery is not atomic 2106 &_is_alive_closure, // is alive closure for efficiency 2107 true); // Setting next fields of discovered 2108 // lists requires a barrier. 2109 } 2110 2111 size_t G1CollectedHeap::capacity() const { 2112 return _g1_committed.byte_size(); 2113 } 2114 2115 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2116 DirtyCardQueue* into_cset_dcq, 2117 bool concurrent, 2118 int worker_i) { 2119 // Clean cards in the hot card cache 2120 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq); 2121 2122 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2123 int n_completed_buffers = 0; 2124 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2125 n_completed_buffers++; 2126 } 2127 g1_policy()->record_update_rs_processed_buffers(worker_i, 2128 (double) n_completed_buffers); 2129 dcqs.clear_n_completed_buffers(); 2130 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2131 } 2132 2133 2134 // Computes the sum of the storage used by the various regions. 2135 2136 size_t G1CollectedHeap::used() const { 2137 assert(Heap_lock->owner() != NULL, 2138 "Should be owned on this thread's behalf."); 2139 size_t result = _summary_bytes_used; 2140 // Read only once in case it is set to NULL concurrently 2141 HeapRegion* hr = _mutator_alloc_region.get(); 2142 if (hr != NULL) 2143 result += hr->used(); 2144 return result; 2145 } 2146 2147 size_t G1CollectedHeap::used_unlocked() const { 2148 size_t result = _summary_bytes_used; 2149 return result; 2150 } 2151 2152 class SumUsedClosure: public HeapRegionClosure { 2153 size_t _used; 2154 public: 2155 SumUsedClosure() : _used(0) {} 2156 bool doHeapRegion(HeapRegion* r) { 2157 if (!r->continuesHumongous()) { 2158 _used += r->used(); 2159 } 2160 return false; 2161 } 2162 size_t result() { return _used; } 2163 }; 2164 2165 size_t G1CollectedHeap::recalculate_used() const { 2166 SumUsedClosure blk; 2167 heap_region_iterate(&blk); 2168 return blk.result(); 2169 } 2170 2171 size_t G1CollectedHeap::unsafe_max_alloc() { 2172 if (free_regions() > 0) return HeapRegion::GrainBytes; 2173 // otherwise, is there space in the current allocation region? 2174 2175 // We need to store the current allocation region in a local variable 2176 // here. The problem is that this method doesn't take any locks and 2177 // there may be other threads which overwrite the current allocation 2178 // region field. attempt_allocation(), for example, sets it to NULL 2179 // and this can happen *after* the NULL check here but before the call 2180 // to free(), resulting in a SIGSEGV. Note that this doesn't appear 2181 // to be a problem in the optimized build, since the two loads of the 2182 // current allocation region field are optimized away. 2183 HeapRegion* hr = _mutator_alloc_region.get(); 2184 if (hr == NULL) { 2185 return 0; 2186 } 2187 return hr->free(); 2188 } 2189 2190 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2191 return 2192 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) || 2193 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)); 2194 } 2195 2196 #ifndef PRODUCT 2197 void G1CollectedHeap::allocate_dummy_regions() { 2198 // Let's fill up most of the region 2199 size_t word_size = HeapRegion::GrainWords - 1024; 2200 // And as a result the region we'll allocate will be humongous. 2201 guarantee(isHumongous(word_size), "sanity"); 2202 2203 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2204 // Let's use the existing mechanism for the allocation 2205 HeapWord* dummy_obj = humongous_obj_allocate(word_size); 2206 if (dummy_obj != NULL) { 2207 MemRegion mr(dummy_obj, word_size); 2208 CollectedHeap::fill_with_object(mr); 2209 } else { 2210 // If we can't allocate once, we probably cannot allocate 2211 // again. Let's get out of the loop. 2212 break; 2213 } 2214 } 2215 } 2216 #endif // !PRODUCT 2217 2218 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) { 2219 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2220 2221 // We assume that if concurrent == true, then the caller is a 2222 // concurrent thread that was joined the Suspendible Thread 2223 // Set. If there's ever a cheap way to check this, we should add an 2224 // assert here. 2225 2226 // We have already incremented _total_full_collections at the start 2227 // of the GC, so total_full_collections() represents how many full 2228 // collections have been started. 2229 unsigned int full_collections_started = total_full_collections(); 2230 2231 // Given that this method is called at the end of a Full GC or of a 2232 // concurrent cycle, and those can be nested (i.e., a Full GC can 2233 // interrupt a concurrent cycle), the number of full collections 2234 // completed should be either one (in the case where there was no 2235 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2236 // behind the number of full collections started. 2237 2238 // This is the case for the inner caller, i.e. a Full GC. 2239 assert(concurrent || 2240 (full_collections_started == _full_collections_completed + 1) || 2241 (full_collections_started == _full_collections_completed + 2), 2242 err_msg("for inner caller (Full GC): full_collections_started = %u " 2243 "is inconsistent with _full_collections_completed = %u", 2244 full_collections_started, _full_collections_completed)); 2245 2246 // This is the case for the outer caller, i.e. the concurrent cycle. 2247 assert(!concurrent || 2248 (full_collections_started == _full_collections_completed + 1), 2249 err_msg("for outer caller (concurrent cycle): " 2250 "full_collections_started = %u " 2251 "is inconsistent with _full_collections_completed = %u", 2252 full_collections_started, _full_collections_completed)); 2253 2254 _full_collections_completed += 1; 2255 2256 // We need to clear the "in_progress" flag in the CM thread before 2257 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2258 // is set) so that if a waiter requests another System.gc() it doesn't 2259 // incorrectly see that a marking cyle is still in progress. 2260 if (concurrent) { 2261 _cmThread->clear_in_progress(); 2262 } 2263 2264 // This notify_all() will ensure that a thread that called 2265 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2266 // and it's waiting for a full GC to finish will be woken up. It is 2267 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2268 FullGCCount_lock->notify_all(); 2269 } 2270 2271 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) { 2272 assert_at_safepoint(true /* should_be_vm_thread */); 2273 GCCauseSetter gcs(this, cause); 2274 switch (cause) { 2275 case GCCause::_heap_inspection: 2276 case GCCause::_heap_dump: { 2277 HandleMark hm; 2278 do_full_collection(false); // don't clear all soft refs 2279 break; 2280 } 2281 default: // XXX FIX ME 2282 ShouldNotReachHere(); // Unexpected use of this function 2283 } 2284 } 2285 2286 void G1CollectedHeap::collect(GCCause::Cause cause) { 2287 // The caller doesn't have the Heap_lock 2288 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock"); 2289 2290 unsigned int gc_count_before; 2291 unsigned int full_gc_count_before; 2292 { 2293 MutexLocker ml(Heap_lock); 2294 2295 // Read the GC count while holding the Heap_lock 2296 gc_count_before = SharedHeap::heap()->total_collections(); 2297 full_gc_count_before = SharedHeap::heap()->total_full_collections(); 2298 } 2299 2300 if (should_do_concurrent_full_gc(cause)) { 2301 // Schedule an initial-mark evacuation pause that will start a 2302 // concurrent cycle. We're setting word_size to 0 which means that 2303 // we are not requesting a post-GC allocation. 2304 VM_G1IncCollectionPause op(gc_count_before, 2305 0, /* word_size */ 2306 true, /* should_initiate_conc_mark */ 2307 g1_policy()->max_pause_time_ms(), 2308 cause); 2309 VMThread::execute(&op); 2310 } else { 2311 if (cause == GCCause::_gc_locker 2312 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2313 2314 // Schedule a standard evacuation pause. We're setting word_size 2315 // to 0 which means that we are not requesting a post-GC allocation. 2316 VM_G1IncCollectionPause op(gc_count_before, 2317 0, /* word_size */ 2318 false, /* should_initiate_conc_mark */ 2319 g1_policy()->max_pause_time_ms(), 2320 cause); 2321 VMThread::execute(&op); 2322 } else { 2323 // Schedule a Full GC. 2324 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2325 VMThread::execute(&op); 2326 } 2327 } 2328 } 2329 2330 bool G1CollectedHeap::is_in(const void* p) const { 2331 HeapRegion* hr = _hrs.addr_to_region((HeapWord*) p); 2332 if (hr != NULL) { 2333 return hr->is_in(p); 2334 } else { 2335 return _perm_gen->as_gen()->is_in(p); 2336 } 2337 } 2338 2339 // Iteration functions. 2340 2341 // Iterates an OopClosure over all ref-containing fields of objects 2342 // within a HeapRegion. 2343 2344 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2345 MemRegion _mr; 2346 OopClosure* _cl; 2347 public: 2348 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl) 2349 : _mr(mr), _cl(cl) {} 2350 bool doHeapRegion(HeapRegion* r) { 2351 if (! r->continuesHumongous()) { 2352 r->oop_iterate(_cl); 2353 } 2354 return false; 2355 } 2356 }; 2357 2358 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) { 2359 IterateOopClosureRegionClosure blk(_g1_committed, cl); 2360 heap_region_iterate(&blk); 2361 if (do_perm) { 2362 perm_gen()->oop_iterate(cl); 2363 } 2364 } 2365 2366 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) { 2367 IterateOopClosureRegionClosure blk(mr, cl); 2368 heap_region_iterate(&blk); 2369 if (do_perm) { 2370 perm_gen()->oop_iterate(cl); 2371 } 2372 } 2373 2374 // Iterates an ObjectClosure over all objects within a HeapRegion. 2375 2376 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2377 ObjectClosure* _cl; 2378 public: 2379 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2380 bool doHeapRegion(HeapRegion* r) { 2381 if (! r->continuesHumongous()) { 2382 r->object_iterate(_cl); 2383 } 2384 return false; 2385 } 2386 }; 2387 2388 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) { 2389 IterateObjectClosureRegionClosure blk(cl); 2390 heap_region_iterate(&blk); 2391 if (do_perm) { 2392 perm_gen()->object_iterate(cl); 2393 } 2394 } 2395 2396 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) { 2397 // FIXME: is this right? 2398 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap"); 2399 } 2400 2401 // Calls a SpaceClosure on a HeapRegion. 2402 2403 class SpaceClosureRegionClosure: public HeapRegionClosure { 2404 SpaceClosure* _cl; 2405 public: 2406 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2407 bool doHeapRegion(HeapRegion* r) { 2408 _cl->do_space(r); 2409 return false; 2410 } 2411 }; 2412 2413 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2414 SpaceClosureRegionClosure blk(cl); 2415 heap_region_iterate(&blk); 2416 } 2417 2418 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2419 _hrs.iterate(cl); 2420 } 2421 2422 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r, 2423 HeapRegionClosure* cl) const { 2424 _hrs.iterate_from(r, cl); 2425 } 2426 2427 void 2428 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl, 2429 int worker, 2430 jint claim_value) { 2431 const size_t regions = n_regions(); 2432 const size_t worker_num = (G1CollectedHeap::use_parallel_gc_threads() ? ParallelGCThreads : 1); 2433 // try to spread out the starting points of the workers 2434 const size_t start_index = regions / worker_num * (size_t) worker; 2435 2436 // each worker will actually look at all regions 2437 for (size_t count = 0; count < regions; ++count) { 2438 const size_t index = (start_index + count) % regions; 2439 assert(0 <= index && index < regions, "sanity"); 2440 HeapRegion* r = region_at(index); 2441 // we'll ignore "continues humongous" regions (we'll process them 2442 // when we come across their corresponding "start humongous" 2443 // region) and regions already claimed 2444 if (r->claim_value() == claim_value || r->continuesHumongous()) { 2445 continue; 2446 } 2447 // OK, try to claim it 2448 if (r->claimHeapRegion(claim_value)) { 2449 // success! 2450 assert(!r->continuesHumongous(), "sanity"); 2451 if (r->startsHumongous()) { 2452 // If the region is "starts humongous" we'll iterate over its 2453 // "continues humongous" first; in fact we'll do them 2454 // first. The order is important. In on case, calling the 2455 // closure on the "starts humongous" region might de-allocate 2456 // and clear all its "continues humongous" regions and, as a 2457 // result, we might end up processing them twice. So, we'll do 2458 // them first (notice: most closures will ignore them anyway) and 2459 // then we'll do the "starts humongous" region. 2460 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) { 2461 HeapRegion* chr = region_at(ch_index); 2462 2463 // if the region has already been claimed or it's not 2464 // "continues humongous" we're done 2465 if (chr->claim_value() == claim_value || 2466 !chr->continuesHumongous()) { 2467 break; 2468 } 2469 2470 // Noone should have claimed it directly. We can given 2471 // that we claimed its "starts humongous" region. 2472 assert(chr->claim_value() != claim_value, "sanity"); 2473 assert(chr->humongous_start_region() == r, "sanity"); 2474 2475 if (chr->claimHeapRegion(claim_value)) { 2476 // we should always be able to claim it; noone else should 2477 // be trying to claim this region 2478 2479 bool res2 = cl->doHeapRegion(chr); 2480 assert(!res2, "Should not abort"); 2481 2482 // Right now, this holds (i.e., no closure that actually 2483 // does something with "continues humongous" regions 2484 // clears them). We might have to weaken it in the future, 2485 // but let's leave these two asserts here for extra safety. 2486 assert(chr->continuesHumongous(), "should still be the case"); 2487 assert(chr->humongous_start_region() == r, "sanity"); 2488 } else { 2489 guarantee(false, "we should not reach here"); 2490 } 2491 } 2492 } 2493 2494 assert(!r->continuesHumongous(), "sanity"); 2495 bool res = cl->doHeapRegion(r); 2496 assert(!res, "Should not abort"); 2497 } 2498 } 2499 } 2500 2501 class ResetClaimValuesClosure: public HeapRegionClosure { 2502 public: 2503 bool doHeapRegion(HeapRegion* r) { 2504 r->set_claim_value(HeapRegion::InitialClaimValue); 2505 return false; 2506 } 2507 }; 2508 2509 void 2510 G1CollectedHeap::reset_heap_region_claim_values() { 2511 ResetClaimValuesClosure blk; 2512 heap_region_iterate(&blk); 2513 } 2514 2515 #ifdef ASSERT 2516 // This checks whether all regions in the heap have the correct claim 2517 // value. I also piggy-backed on this a check to ensure that the 2518 // humongous_start_region() information on "continues humongous" 2519 // regions is correct. 2520 2521 class CheckClaimValuesClosure : public HeapRegionClosure { 2522 private: 2523 jint _claim_value; 2524 size_t _failures; 2525 HeapRegion* _sh_region; 2526 public: 2527 CheckClaimValuesClosure(jint claim_value) : 2528 _claim_value(claim_value), _failures(0), _sh_region(NULL) { } 2529 bool doHeapRegion(HeapRegion* r) { 2530 if (r->claim_value() != _claim_value) { 2531 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), " 2532 "claim value = %d, should be %d", 2533 r->bottom(), r->end(), r->claim_value(), 2534 _claim_value); 2535 ++_failures; 2536 } 2537 if (!r->isHumongous()) { 2538 _sh_region = NULL; 2539 } else if (r->startsHumongous()) { 2540 _sh_region = r; 2541 } else if (r->continuesHumongous()) { 2542 if (r->humongous_start_region() != _sh_region) { 2543 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), " 2544 "HS = "PTR_FORMAT", should be "PTR_FORMAT, 2545 r->bottom(), r->end(), 2546 r->humongous_start_region(), 2547 _sh_region); 2548 ++_failures; 2549 } 2550 } 2551 return false; 2552 } 2553 size_t failures() { 2554 return _failures; 2555 } 2556 }; 2557 2558 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) { 2559 CheckClaimValuesClosure cl(claim_value); 2560 heap_region_iterate(&cl); 2561 return cl.failures() == 0; 2562 } 2563 #endif // ASSERT 2564 2565 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2566 HeapRegion* r = g1_policy()->collection_set(); 2567 while (r != NULL) { 2568 HeapRegion* next = r->next_in_collection_set(); 2569 if (cl->doHeapRegion(r)) { 2570 cl->incomplete(); 2571 return; 2572 } 2573 r = next; 2574 } 2575 } 2576 2577 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2578 HeapRegionClosure *cl) { 2579 if (r == NULL) { 2580 // The CSet is empty so there's nothing to do. 2581 return; 2582 } 2583 2584 assert(r->in_collection_set(), 2585 "Start region must be a member of the collection set."); 2586 HeapRegion* cur = r; 2587 while (cur != NULL) { 2588 HeapRegion* next = cur->next_in_collection_set(); 2589 if (cl->doHeapRegion(cur) && false) { 2590 cl->incomplete(); 2591 return; 2592 } 2593 cur = next; 2594 } 2595 cur = g1_policy()->collection_set(); 2596 while (cur != r) { 2597 HeapRegion* next = cur->next_in_collection_set(); 2598 if (cl->doHeapRegion(cur) && false) { 2599 cl->incomplete(); 2600 return; 2601 } 2602 cur = next; 2603 } 2604 } 2605 2606 CompactibleSpace* G1CollectedHeap::first_compactible_space() { 2607 return n_regions() > 0 ? region_at(0) : NULL; 2608 } 2609 2610 2611 Space* G1CollectedHeap::space_containing(const void* addr) const { 2612 Space* res = heap_region_containing(addr); 2613 if (res == NULL) 2614 res = perm_gen()->space_containing(addr); 2615 return res; 2616 } 2617 2618 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2619 Space* sp = space_containing(addr); 2620 if (sp != NULL) { 2621 return sp->block_start(addr); 2622 } 2623 return NULL; 2624 } 2625 2626 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2627 Space* sp = space_containing(addr); 2628 assert(sp != NULL, "block_size of address outside of heap"); 2629 return sp->block_size(addr); 2630 } 2631 2632 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2633 Space* sp = space_containing(addr); 2634 return sp->block_is_obj(addr); 2635 } 2636 2637 bool G1CollectedHeap::supports_tlab_allocation() const { 2638 return true; 2639 } 2640 2641 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2642 return HeapRegion::GrainBytes; 2643 } 2644 2645 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2646 // Return the remaining space in the cur alloc region, but not less than 2647 // the min TLAB size. 2648 2649 // Also, this value can be at most the humongous object threshold, 2650 // since we can't allow tlabs to grow big enough to accomodate 2651 // humongous objects. 2652 2653 HeapRegion* hr = _mutator_alloc_region.get(); 2654 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize; 2655 if (hr == NULL) { 2656 return max_tlab_size; 2657 } else { 2658 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size); 2659 } 2660 } 2661 2662 size_t G1CollectedHeap::max_capacity() const { 2663 return _g1_reserved.byte_size(); 2664 } 2665 2666 jlong G1CollectedHeap::millis_since_last_gc() { 2667 // assert(false, "NYI"); 2668 return 0; 2669 } 2670 2671 void G1CollectedHeap::prepare_for_verify() { 2672 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2673 ensure_parsability(false); 2674 } 2675 g1_rem_set()->prepare_for_verify(); 2676 } 2677 2678 class VerifyLivenessOopClosure: public OopClosure { 2679 G1CollectedHeap* _g1h; 2680 VerifyOption _vo; 2681 public: 2682 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2683 _g1h(g1h), _vo(vo) 2684 { } 2685 void do_oop(narrowOop *p) { do_oop_work(p); } 2686 void do_oop( oop *p) { do_oop_work(p); } 2687 2688 template <class T> void do_oop_work(T *p) { 2689 oop obj = oopDesc::load_decode_heap_oop(p); 2690 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2691 "Dead object referenced by a not dead object"); 2692 } 2693 }; 2694 2695 class VerifyObjsInRegionClosure: public ObjectClosure { 2696 private: 2697 G1CollectedHeap* _g1h; 2698 size_t _live_bytes; 2699 HeapRegion *_hr; 2700 VerifyOption _vo; 2701 public: 2702 // _vo == UsePrevMarking -> use "prev" marking information, 2703 // _vo == UseNextMarking -> use "next" marking information, 2704 // _vo == UseMarkWord -> use mark word from object header. 2705 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2706 : _live_bytes(0), _hr(hr), _vo(vo) { 2707 _g1h = G1CollectedHeap::heap(); 2708 } 2709 void do_object(oop o) { 2710 VerifyLivenessOopClosure isLive(_g1h, _vo); 2711 assert(o != NULL, "Huh?"); 2712 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2713 // If the object is alive according to the mark word, 2714 // then verify that the marking information agrees. 2715 // Note we can't verify the contra-positive of the 2716 // above: if the object is dead (according to the mark 2717 // word), it may not be marked, or may have been marked 2718 // but has since became dead, or may have been allocated 2719 // since the last marking. 2720 if (_vo == VerifyOption_G1UseMarkWord) { 2721 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2722 } 2723 2724 o->oop_iterate(&isLive); 2725 if (!_hr->obj_allocated_since_prev_marking(o)) { 2726 size_t obj_size = o->size(); // Make sure we don't overflow 2727 _live_bytes += (obj_size * HeapWordSize); 2728 } 2729 } 2730 } 2731 size_t live_bytes() { return _live_bytes; } 2732 }; 2733 2734 class PrintObjsInRegionClosure : public ObjectClosure { 2735 HeapRegion *_hr; 2736 G1CollectedHeap *_g1; 2737 public: 2738 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 2739 _g1 = G1CollectedHeap::heap(); 2740 }; 2741 2742 void do_object(oop o) { 2743 if (o != NULL) { 2744 HeapWord *start = (HeapWord *) o; 2745 size_t word_sz = o->size(); 2746 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 2747 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 2748 (void*) o, word_sz, 2749 _g1->isMarkedPrev(o), 2750 _g1->isMarkedNext(o), 2751 _hr->obj_allocated_since_prev_marking(o)); 2752 HeapWord *end = start + word_sz; 2753 HeapWord *cur; 2754 int *val; 2755 for (cur = start; cur < end; cur++) { 2756 val = (int *) cur; 2757 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val); 2758 } 2759 } 2760 } 2761 }; 2762 2763 class VerifyRegionClosure: public HeapRegionClosure { 2764 private: 2765 bool _allow_dirty; 2766 bool _par; 2767 VerifyOption _vo; 2768 bool _failures; 2769 public: 2770 // _vo == UsePrevMarking -> use "prev" marking information, 2771 // _vo == UseNextMarking -> use "next" marking information, 2772 // _vo == UseMarkWord -> use mark word from object header. 2773 VerifyRegionClosure(bool allow_dirty, bool par, VerifyOption vo) 2774 : _allow_dirty(allow_dirty), 2775 _par(par), 2776 _vo(vo), 2777 _failures(false) {} 2778 2779 bool failures() { 2780 return _failures; 2781 } 2782 2783 bool doHeapRegion(HeapRegion* r) { 2784 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue, 2785 "Should be unclaimed at verify points."); 2786 if (!r->continuesHumongous()) { 2787 bool failures = false; 2788 r->verify(_allow_dirty, _vo, &failures); 2789 if (failures) { 2790 _failures = true; 2791 } else { 2792 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 2793 r->object_iterate(¬_dead_yet_cl); 2794 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 2795 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 2796 "max_live_bytes "SIZE_FORMAT" " 2797 "< calculated "SIZE_FORMAT, 2798 r->bottom(), r->end(), 2799 r->max_live_bytes(), 2800 not_dead_yet_cl.live_bytes()); 2801 _failures = true; 2802 } 2803 } 2804 } 2805 return false; // stop the region iteration if we hit a failure 2806 } 2807 }; 2808 2809 class VerifyRootsClosure: public OopsInGenClosure { 2810 private: 2811 G1CollectedHeap* _g1h; 2812 VerifyOption _vo; 2813 bool _failures; 2814 public: 2815 // _vo == UsePrevMarking -> use "prev" marking information, 2816 // _vo == UseNextMarking -> use "next" marking information, 2817 // _vo == UseMarkWord -> use mark word from object header. 2818 VerifyRootsClosure(VerifyOption vo) : 2819 _g1h(G1CollectedHeap::heap()), 2820 _vo(vo), 2821 _failures(false) { } 2822 2823 bool failures() { return _failures; } 2824 2825 template <class T> void do_oop_nv(T* p) { 2826 T heap_oop = oopDesc::load_heap_oop(p); 2827 if (!oopDesc::is_null(heap_oop)) { 2828 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2829 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2830 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 2831 "points to dead obj "PTR_FORMAT, p, (void*) obj); 2832 if (_vo == VerifyOption_G1UseMarkWord) { 2833 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 2834 } 2835 obj->print_on(gclog_or_tty); 2836 _failures = true; 2837 } 2838 } 2839 } 2840 2841 void do_oop(oop* p) { do_oop_nv(p); } 2842 void do_oop(narrowOop* p) { do_oop_nv(p); } 2843 }; 2844 2845 // This is the task used for parallel heap verification. 2846 2847 class G1ParVerifyTask: public AbstractGangTask { 2848 private: 2849 G1CollectedHeap* _g1h; 2850 bool _allow_dirty; 2851 VerifyOption _vo; 2852 bool _failures; 2853 2854 public: 2855 // _vo == UsePrevMarking -> use "prev" marking information, 2856 // _vo == UseNextMarking -> use "next" marking information, 2857 // _vo == UseMarkWord -> use mark word from object header. 2858 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty, VerifyOption vo) : 2859 AbstractGangTask("Parallel verify task"), 2860 _g1h(g1h), 2861 _allow_dirty(allow_dirty), 2862 _vo(vo), 2863 _failures(false) { } 2864 2865 bool failures() { 2866 return _failures; 2867 } 2868 2869 void work(int worker_i) { 2870 HandleMark hm; 2871 VerifyRegionClosure blk(_allow_dirty, true, _vo); 2872 _g1h->heap_region_par_iterate_chunked(&blk, worker_i, 2873 HeapRegion::ParVerifyClaimValue); 2874 if (blk.failures()) { 2875 _failures = true; 2876 } 2877 } 2878 }; 2879 2880 void G1CollectedHeap::verify(bool allow_dirty, bool silent) { 2881 verify(allow_dirty, silent, VerifyOption_G1UsePrevMarking); 2882 } 2883 2884 void G1CollectedHeap::verify(bool allow_dirty, 2885 bool silent, 2886 VerifyOption vo) { 2887 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2888 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); } 2889 VerifyRootsClosure rootsCl(vo); 2890 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false); 2891 2892 // We apply the relevant closures to all the oops in the 2893 // system dictionary, the string table and the code cache. 2894 const int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache; 2895 2896 process_strong_roots(true, // activate StrongRootsScope 2897 true, // we set "collecting perm gen" to true, 2898 // so we don't reset the dirty cards in the perm gen. 2899 SharedHeap::ScanningOption(so), // roots scanning options 2900 &rootsCl, 2901 &blobsCl, 2902 &rootsCl); 2903 2904 // If we're verifying after the marking phase of a Full GC then we can't 2905 // treat the perm gen as roots into the G1 heap. Some of the objects in 2906 // the perm gen may be dead and hence not marked. If one of these dead 2907 // objects is considered to be a root then we may end up with a false 2908 // "Root location <x> points to dead ob <y>" failure. 2909 if (vo != VerifyOption_G1UseMarkWord) { 2910 // Since we used "collecting_perm_gen" == true above, we will not have 2911 // checked the refs from perm into the G1-collected heap. We check those 2912 // references explicitly below. Whether the relevant cards are dirty 2913 // is checked further below in the rem set verification. 2914 if (!silent) { gclog_or_tty->print("Permgen roots "); } 2915 perm_gen()->oop_iterate(&rootsCl); 2916 } 2917 bool failures = rootsCl.failures(); 2918 2919 if (vo != VerifyOption_G1UseMarkWord) { 2920 // If we're verifying during a full GC then the region sets 2921 // will have been torn down at the start of the GC. Therefore 2922 // verifying the region sets will fail. So we only verify 2923 // the region sets when not in a full GC. 2924 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 2925 verify_region_sets(); 2926 } 2927 2928 if (!silent) { gclog_or_tty->print("HeapRegions "); } 2929 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 2930 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 2931 "sanity check"); 2932 2933 G1ParVerifyTask task(this, allow_dirty, vo); 2934 int n_workers = workers()->total_workers(); 2935 set_par_threads(n_workers); 2936 workers()->run_task(&task); 2937 set_par_threads(0); 2938 if (task.failures()) { 2939 failures = true; 2940 } 2941 2942 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue), 2943 "sanity check"); 2944 2945 reset_heap_region_claim_values(); 2946 2947 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue), 2948 "sanity check"); 2949 } else { 2950 VerifyRegionClosure blk(allow_dirty, false, vo); 2951 heap_region_iterate(&blk); 2952 if (blk.failures()) { 2953 failures = true; 2954 } 2955 } 2956 if (!silent) gclog_or_tty->print("RemSet "); 2957 rem_set()->verify(); 2958 2959 if (failures) { 2960 gclog_or_tty->print_cr("Heap:"); 2961 print_on(gclog_or_tty, true /* extended */); 2962 gclog_or_tty->print_cr(""); 2963 #ifndef PRODUCT 2964 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 2965 concurrent_mark()->print_reachable("at-verification-failure", 2966 vo, false /* all */); 2967 } 2968 #endif 2969 gclog_or_tty->flush(); 2970 } 2971 guarantee(!failures, "there should not have been any failures"); 2972 } else { 2973 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) "); 2974 } 2975 } 2976 2977 class PrintRegionClosure: public HeapRegionClosure { 2978 outputStream* _st; 2979 public: 2980 PrintRegionClosure(outputStream* st) : _st(st) {} 2981 bool doHeapRegion(HeapRegion* r) { 2982 r->print_on(_st); 2983 return false; 2984 } 2985 }; 2986 2987 void G1CollectedHeap::print() const { print_on(tty); } 2988 2989 void G1CollectedHeap::print_on(outputStream* st) const { 2990 print_on(st, PrintHeapAtGCExtended); 2991 } 2992 2993 void G1CollectedHeap::print_on(outputStream* st, bool extended) const { 2994 st->print(" %-20s", "garbage-first heap"); 2995 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 2996 capacity()/K, used_unlocked()/K); 2997 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 2998 _g1_storage.low_boundary(), 2999 _g1_storage.high(), 3000 _g1_storage.high_boundary()); 3001 st->cr(); 3002 st->print(" region size " SIZE_FORMAT "K, ", 3003 HeapRegion::GrainBytes/K); 3004 size_t young_regions = _young_list->length(); 3005 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ", 3006 young_regions, young_regions * HeapRegion::GrainBytes / K); 3007 size_t survivor_regions = g1_policy()->recorded_survivor_regions(); 3008 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)", 3009 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K); 3010 st->cr(); 3011 perm()->as_gen()->print_on(st); 3012 if (extended) { 3013 st->cr(); 3014 print_on_extended(st); 3015 } 3016 } 3017 3018 void G1CollectedHeap::print_on_extended(outputStream* st) const { 3019 PrintRegionClosure blk(st); 3020 heap_region_iterate(&blk); 3021 } 3022 3023 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3024 if (G1CollectedHeap::use_parallel_gc_threads()) { 3025 workers()->print_worker_threads_on(st); 3026 } 3027 _cmThread->print_on(st); 3028 st->cr(); 3029 _cm->print_worker_threads_on(st); 3030 _cg1r->print_worker_threads_on(st); 3031 st->cr(); 3032 } 3033 3034 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3035 if (G1CollectedHeap::use_parallel_gc_threads()) { 3036 workers()->threads_do(tc); 3037 } 3038 tc->do_thread(_cmThread); 3039 _cg1r->threads_do(tc); 3040 } 3041 3042 void G1CollectedHeap::print_tracing_info() const { 3043 // We'll overload this to mean "trace GC pause statistics." 3044 if (TraceGen0Time || TraceGen1Time) { 3045 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3046 // to that. 3047 g1_policy()->print_tracing_info(); 3048 } 3049 if (G1SummarizeRSetStats) { 3050 g1_rem_set()->print_summary_info(); 3051 } 3052 if (G1SummarizeConcMark) { 3053 concurrent_mark()->print_summary_info(); 3054 } 3055 g1_policy()->print_yg_surv_rate_info(); 3056 SpecializationStats::print(); 3057 } 3058 3059 #ifndef PRODUCT 3060 // Helpful for debugging RSet issues. 3061 3062 class PrintRSetsClosure : public HeapRegionClosure { 3063 private: 3064 const char* _msg; 3065 size_t _occupied_sum; 3066 3067 public: 3068 bool doHeapRegion(HeapRegion* r) { 3069 HeapRegionRemSet* hrrs = r->rem_set(); 3070 size_t occupied = hrrs->occupied(); 3071 _occupied_sum += occupied; 3072 3073 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3074 HR_FORMAT_PARAMS(r)); 3075 if (occupied == 0) { 3076 gclog_or_tty->print_cr(" RSet is empty"); 3077 } else { 3078 hrrs->print(); 3079 } 3080 gclog_or_tty->print_cr("----------"); 3081 return false; 3082 } 3083 3084 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3085 gclog_or_tty->cr(); 3086 gclog_or_tty->print_cr("========================================"); 3087 gclog_or_tty->print_cr(msg); 3088 gclog_or_tty->cr(); 3089 } 3090 3091 ~PrintRSetsClosure() { 3092 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3093 gclog_or_tty->print_cr("========================================"); 3094 gclog_or_tty->cr(); 3095 } 3096 }; 3097 3098 void G1CollectedHeap::print_cset_rsets() { 3099 PrintRSetsClosure cl("Printing CSet RSets"); 3100 collection_set_iterate(&cl); 3101 } 3102 3103 void G1CollectedHeap::print_all_rsets() { 3104 PrintRSetsClosure cl("Printing All RSets");; 3105 heap_region_iterate(&cl); 3106 } 3107 #endif // PRODUCT 3108 3109 G1CollectedHeap* G1CollectedHeap::heap() { 3110 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3111 "not a garbage-first heap"); 3112 return _g1h; 3113 } 3114 3115 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3116 // always_do_update_barrier = false; 3117 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3118 // Call allocation profiler 3119 AllocationProfiler::iterate_since_last_gc(); 3120 // Fill TLAB's and such 3121 ensure_parsability(true); 3122 } 3123 3124 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) { 3125 // FIXME: what is this about? 3126 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3127 // is set. 3128 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3129 "derived pointer present")); 3130 // always_do_update_barrier = true; 3131 } 3132 3133 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3134 unsigned int gc_count_before, 3135 bool* succeeded) { 3136 assert_heap_not_locked_and_not_at_safepoint(); 3137 g1_policy()->record_stop_world_start(); 3138 VM_G1IncCollectionPause op(gc_count_before, 3139 word_size, 3140 false, /* should_initiate_conc_mark */ 3141 g1_policy()->max_pause_time_ms(), 3142 GCCause::_g1_inc_collection_pause); 3143 VMThread::execute(&op); 3144 3145 HeapWord* result = op.result(); 3146 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3147 assert(result == NULL || ret_succeeded, 3148 "the result should be NULL if the VM did not succeed"); 3149 *succeeded = ret_succeeded; 3150 3151 assert_heap_not_locked(); 3152 return result; 3153 } 3154 3155 void 3156 G1CollectedHeap::doConcurrentMark() { 3157 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3158 if (!_cmThread->in_progress()) { 3159 _cmThread->set_started(); 3160 CGC_lock->notify(); 3161 } 3162 } 3163 3164 void G1CollectedHeap::do_sync_mark() { 3165 _cm->checkpointRootsInitial(); 3166 _cm->markFromRoots(); 3167 _cm->checkpointRootsFinal(false); 3168 } 3169 3170 // <NEW PREDICTION> 3171 3172 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr, 3173 bool young) { 3174 return _g1_policy->predict_region_elapsed_time_ms(hr, young); 3175 } 3176 3177 void G1CollectedHeap::check_if_region_is_too_expensive(double 3178 predicted_time_ms) { 3179 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms); 3180 } 3181 3182 size_t G1CollectedHeap::pending_card_num() { 3183 size_t extra_cards = 0; 3184 JavaThread *curr = Threads::first(); 3185 while (curr != NULL) { 3186 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3187 extra_cards += dcq.size(); 3188 curr = curr->next(); 3189 } 3190 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3191 size_t buffer_size = dcqs.buffer_size(); 3192 size_t buffer_num = dcqs.completed_buffers_num(); 3193 return buffer_size * buffer_num + extra_cards; 3194 } 3195 3196 size_t G1CollectedHeap::max_pending_card_num() { 3197 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3198 size_t buffer_size = dcqs.buffer_size(); 3199 size_t buffer_num = dcqs.completed_buffers_num(); 3200 int thread_num = Threads::number_of_threads(); 3201 return (buffer_num + thread_num) * buffer_size; 3202 } 3203 3204 size_t G1CollectedHeap::cards_scanned() { 3205 return g1_rem_set()->cardsScanned(); 3206 } 3207 3208 void 3209 G1CollectedHeap::setup_surviving_young_words() { 3210 guarantee( _surviving_young_words == NULL, "pre-condition" ); 3211 size_t array_length = g1_policy()->young_cset_length(); 3212 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length); 3213 if (_surviving_young_words == NULL) { 3214 vm_exit_out_of_memory(sizeof(size_t) * array_length, 3215 "Not enough space for young surv words summary."); 3216 } 3217 memset(_surviving_young_words, 0, array_length * sizeof(size_t)); 3218 #ifdef ASSERT 3219 for (size_t i = 0; i < array_length; ++i) { 3220 assert( _surviving_young_words[i] == 0, "memset above" ); 3221 } 3222 #endif // !ASSERT 3223 } 3224 3225 void 3226 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3227 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3228 size_t array_length = g1_policy()->young_cset_length(); 3229 for (size_t i = 0; i < array_length; ++i) 3230 _surviving_young_words[i] += surv_young_words[i]; 3231 } 3232 3233 void 3234 G1CollectedHeap::cleanup_surviving_young_words() { 3235 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3236 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words); 3237 _surviving_young_words = NULL; 3238 } 3239 3240 // </NEW PREDICTION> 3241 3242 #ifdef ASSERT 3243 class VerifyCSetClosure: public HeapRegionClosure { 3244 public: 3245 bool doHeapRegion(HeapRegion* hr) { 3246 // Here we check that the CSet region's RSet is ready for parallel 3247 // iteration. The fields that we'll verify are only manipulated 3248 // when the region is part of a CSet and is collected. Afterwards, 3249 // we reset these fields when we clear the region's RSet (when the 3250 // region is freed) so they are ready when the region is 3251 // re-allocated. The only exception to this is if there's an 3252 // evacuation failure and instead of freeing the region we leave 3253 // it in the heap. In that case, we reset these fields during 3254 // evacuation failure handling. 3255 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3256 3257 // Here's a good place to add any other checks we'd like to 3258 // perform on CSet regions. 3259 return false; 3260 } 3261 }; 3262 #endif // ASSERT 3263 3264 #if TASKQUEUE_STATS 3265 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3266 st->print_raw_cr("GC Task Stats"); 3267 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3268 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3269 } 3270 3271 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3272 print_taskqueue_stats_hdr(st); 3273 3274 TaskQueueStats totals; 3275 const int n = workers() != NULL ? workers()->total_workers() : 1; 3276 for (int i = 0; i < n; ++i) { 3277 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3278 totals += task_queue(i)->stats; 3279 } 3280 st->print_raw("tot "); totals.print(st); st->cr(); 3281 3282 DEBUG_ONLY(totals.verify()); 3283 } 3284 3285 void G1CollectedHeap::reset_taskqueue_stats() { 3286 const int n = workers() != NULL ? workers()->total_workers() : 1; 3287 for (int i = 0; i < n; ++i) { 3288 task_queue(i)->stats.reset(); 3289 } 3290 } 3291 #endif // TASKQUEUE_STATS 3292 3293 bool 3294 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3295 assert_at_safepoint(true /* should_be_vm_thread */); 3296 guarantee(!is_gc_active(), "collection is not reentrant"); 3297 3298 if (GC_locker::check_active_before_gc()) { 3299 return false; 3300 } 3301 3302 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3303 ResourceMark rm; 3304 3305 if (PrintHeapAtGC) { 3306 Universe::print_heap_before_gc(); 3307 } 3308 3309 verify_region_sets_optional(); 3310 verify_dirty_young_regions(); 3311 3312 { 3313 // This call will decide whether this pause is an initial-mark 3314 // pause. If it is, during_initial_mark_pause() will return true 3315 // for the duration of this pause. 3316 g1_policy()->decide_on_conc_mark_initiation(); 3317 3318 char verbose_str[128]; 3319 sprintf(verbose_str, "GC pause "); 3320 if (g1_policy()->in_young_gc_mode()) { 3321 if (g1_policy()->full_young_gcs()) 3322 strcat(verbose_str, "(young)"); 3323 else 3324 strcat(verbose_str, "(partial)"); 3325 } 3326 if (g1_policy()->during_initial_mark_pause()) { 3327 strcat(verbose_str, " (initial-mark)"); 3328 // We are about to start a marking cycle, so we increment the 3329 // full collection counter. 3330 increment_total_full_collections(); 3331 } 3332 3333 // if PrintGCDetails is on, we'll print long statistics information 3334 // in the collector policy code, so let's not print this as the output 3335 // is messy if we do. 3336 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); 3337 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); 3338 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty); 3339 3340 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3341 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3342 3343 // If the secondary_free_list is not empty, append it to the 3344 // free_list. No need to wait for the cleanup operation to finish; 3345 // the region allocation code will check the secondary_free_list 3346 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3347 // set, skip this step so that the region allocation code has to 3348 // get entries from the secondary_free_list. 3349 if (!G1StressConcRegionFreeing) { 3350 append_secondary_free_list_if_not_empty_with_lock(); 3351 } 3352 3353 if (g1_policy()->in_young_gc_mode()) { 3354 assert(check_young_list_well_formed(), 3355 "young list should be well formed"); 3356 } 3357 3358 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3359 IsGCActiveMark x; 3360 3361 gc_prologue(false); 3362 increment_total_collections(false /* full gc */); 3363 increment_gc_time_stamp(); 3364 3365 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) { 3366 HandleMark hm; // Discard invalid handles created during verification 3367 gclog_or_tty->print(" VerifyBeforeGC:"); 3368 prepare_for_verify(); 3369 Universe::verify(/* allow dirty */ false, 3370 /* silent */ false, 3371 /* option */ VerifyOption_G1UsePrevMarking); 3372 3373 } 3374 3375 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3376 3377 // Please see comment in G1CollectedHeap::ref_processing_init() 3378 // to see how reference processing currently works in G1. 3379 // 3380 // We want to turn off ref discovery, if necessary, and turn it back on 3381 // on again later if we do. XXX Dubious: why is discovery disabled? 3382 bool was_enabled = ref_processor()->discovery_enabled(); 3383 if (was_enabled) ref_processor()->disable_discovery(); 3384 3385 // Forget the current alloc region (we might even choose it to be part 3386 // of the collection set!). 3387 release_mutator_alloc_region(); 3388 3389 // We should call this after we retire the mutator alloc 3390 // region(s) so that all the ALLOC / RETIRE events are generated 3391 // before the start GC event. 3392 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3393 3394 // The elapsed time induced by the start time below deliberately elides 3395 // the possible verification above. 3396 double start_time_sec = os::elapsedTime(); 3397 size_t start_used_bytes = used(); 3398 3399 #if YOUNG_LIST_VERBOSE 3400 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3401 _young_list->print(); 3402 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3403 #endif // YOUNG_LIST_VERBOSE 3404 3405 g1_policy()->record_collection_pause_start(start_time_sec, 3406 start_used_bytes); 3407 3408 #if YOUNG_LIST_VERBOSE 3409 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3410 _young_list->print(); 3411 #endif // YOUNG_LIST_VERBOSE 3412 3413 if (g1_policy()->during_initial_mark_pause()) { 3414 concurrent_mark()->checkpointRootsInitialPre(); 3415 } 3416 perm_gen()->save_marks(); 3417 3418 // We must do this before any possible evacuation that should propagate 3419 // marks. 3420 if (mark_in_progress()) { 3421 double start_time_sec = os::elapsedTime(); 3422 3423 _cm->drainAllSATBBuffers(); 3424 double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0; 3425 g1_policy()->record_satb_drain_time(finish_mark_ms); 3426 } 3427 // Record the number of elements currently on the mark stack, so we 3428 // only iterate over these. (Since evacuation may add to the mark 3429 // stack, doing more exposes race conditions.) If no mark is in 3430 // progress, this will be zero. 3431 _cm->set_oops_do_bound(); 3432 3433 if (mark_in_progress()) { 3434 concurrent_mark()->newCSet(); 3435 } 3436 3437 #if YOUNG_LIST_VERBOSE 3438 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3439 _young_list->print(); 3440 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3441 #endif // YOUNG_LIST_VERBOSE 3442 3443 g1_policy()->choose_collection_set(target_pause_time_ms); 3444 3445 if (_hr_printer.is_active()) { 3446 HeapRegion* hr = g1_policy()->collection_set(); 3447 while (hr != NULL) { 3448 G1HRPrinter::RegionType type; 3449 if (!hr->is_young()) { 3450 type = G1HRPrinter::Old; 3451 } else if (hr->is_survivor()) { 3452 type = G1HRPrinter::Survivor; 3453 } else { 3454 type = G1HRPrinter::Eden; 3455 } 3456 _hr_printer.cset(hr); 3457 hr = hr->next_in_collection_set(); 3458 } 3459 } 3460 3461 // We have chosen the complete collection set. If marking is 3462 // active then, we clear the region fields of any of the 3463 // concurrent marking tasks whose region fields point into 3464 // the collection set as these values will become stale. This 3465 // will cause the owning marking threads to claim a new region 3466 // when marking restarts. 3467 if (mark_in_progress()) { 3468 concurrent_mark()->reset_active_task_region_fields_in_cset(); 3469 } 3470 3471 #ifdef ASSERT 3472 VerifyCSetClosure cl; 3473 collection_set_iterate(&cl); 3474 #endif // ASSERT 3475 3476 setup_surviving_young_words(); 3477 3478 // Initialize the GC alloc regions. 3479 init_gc_alloc_regions(); 3480 3481 // Actually do the work... 3482 evacuate_collection_set(); 3483 3484 free_collection_set(g1_policy()->collection_set()); 3485 g1_policy()->clear_collection_set(); 3486 3487 cleanup_surviving_young_words(); 3488 3489 // Start a new incremental collection set for the next pause. 3490 g1_policy()->start_incremental_cset_building(); 3491 3492 // Clear the _cset_fast_test bitmap in anticipation of adding 3493 // regions to the incremental collection set for the next 3494 // evacuation pause. 3495 clear_cset_fast_test(); 3496 3497 if (g1_policy()->in_young_gc_mode()) { 3498 _young_list->reset_sampled_info(); 3499 3500 // Don't check the whole heap at this point as the 3501 // GC alloc regions from this pause have been tagged 3502 // as survivors and moved on to the survivor list. 3503 // Survivor regions will fail the !is_young() check. 3504 assert(check_young_list_empty(false /* check_heap */), 3505 "young list should be empty"); 3506 3507 #if YOUNG_LIST_VERBOSE 3508 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3509 _young_list->print(); 3510 #endif // YOUNG_LIST_VERBOSE 3511 3512 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3513 _young_list->first_survivor_region(), 3514 _young_list->last_survivor_region()); 3515 3516 _young_list->reset_auxilary_lists(); 3517 } 3518 3519 if (evacuation_failed()) { 3520 _summary_bytes_used = recalculate_used(); 3521 } else { 3522 // The "used" of the the collection set have already been subtracted 3523 // when they were freed. Add in the bytes evacuated. 3524 _summary_bytes_used += g1_policy()->bytes_copied_during_gc(); 3525 } 3526 3527 if (g1_policy()->in_young_gc_mode() && 3528 g1_policy()->during_initial_mark_pause()) { 3529 concurrent_mark()->checkpointRootsInitialPost(); 3530 set_marking_started(); 3531 // CAUTION: after the doConcurrentMark() call below, 3532 // the concurrent marking thread(s) could be running 3533 // concurrently with us. Make sure that anything after 3534 // this point does not assume that we are the only GC thread 3535 // running. Note: of course, the actual marking work will 3536 // not start until the safepoint itself is released in 3537 // ConcurrentGCThread::safepoint_desynchronize(). 3538 doConcurrentMark(); 3539 } 3540 3541 allocate_dummy_regions(); 3542 3543 #if YOUNG_LIST_VERBOSE 3544 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3545 _young_list->print(); 3546 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3547 #endif // YOUNG_LIST_VERBOSE 3548 3549 init_mutator_alloc_region(); 3550 3551 double end_time_sec = os::elapsedTime(); 3552 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS; 3553 g1_policy()->record_pause_time_ms(pause_time_ms); 3554 g1_policy()->record_collection_pause_end(); 3555 3556 MemoryService::track_memory_usage(); 3557 3558 // In prepare_for_verify() below we'll need to scan the deferred 3559 // update buffers to bring the RSets up-to-date if 3560 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3561 // the update buffers we'll probably need to scan cards on the 3562 // regions we just allocated to (i.e., the GC alloc 3563 // regions). However, during the last GC we called 3564 // set_saved_mark() on all the GC alloc regions, so card 3565 // scanning might skip the [saved_mark_word()...top()] area of 3566 // those regions (i.e., the area we allocated objects into 3567 // during the last GC). But it shouldn't. Given that 3568 // saved_mark_word() is conditional on whether the GC time stamp 3569 // on the region is current or not, by incrementing the GC time 3570 // stamp here we invalidate all the GC time stamps on all the 3571 // regions and saved_mark_word() will simply return top() for 3572 // all the regions. This is a nicer way of ensuring this rather 3573 // than iterating over the regions and fixing them. In fact, the 3574 // GC time stamp increment here also ensures that 3575 // saved_mark_word() will return top() between pauses, i.e., 3576 // during concurrent refinement. So we don't need the 3577 // is_gc_active() check to decided which top to use when 3578 // scanning cards (see CR 7039627). 3579 increment_gc_time_stamp(); 3580 3581 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) { 3582 HandleMark hm; // Discard invalid handles created during verification 3583 gclog_or_tty->print(" VerifyAfterGC:"); 3584 prepare_for_verify(); 3585 Universe::verify(/* allow dirty */ true, 3586 /* silent */ false, 3587 /* option */ VerifyOption_G1UsePrevMarking); 3588 } 3589 3590 if (was_enabled) ref_processor()->enable_discovery(); 3591 3592 { 3593 size_t expand_bytes = g1_policy()->expansion_amount(); 3594 if (expand_bytes > 0) { 3595 size_t bytes_before = capacity(); 3596 if (!expand(expand_bytes)) { 3597 // We failed to expand the heap so let's verify that 3598 // committed/uncommitted amount match the backing store 3599 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch"); 3600 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch"); 3601 } 3602 } 3603 } 3604 3605 // We should do this after we potentially expand the heap so 3606 // that all the COMMIT events are generated before the end GC 3607 // event, and after we retire the GC alloc regions so that all 3608 // RETIRE events are generated before the end GC event. 3609 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 3610 3611 // We have to do this after we decide whether to expand the heap or not. 3612 g1_policy()->print_heap_transition(); 3613 3614 if (mark_in_progress()) { 3615 concurrent_mark()->update_g1_committed(); 3616 } 3617 3618 #ifdef TRACESPINNING 3619 ParallelTaskTerminator::print_termination_counts(); 3620 #endif 3621 3622 gc_epilogue(false); 3623 } 3624 3625 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) { 3626 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum); 3627 print_tracing_info(); 3628 vm_exit(-1); 3629 } 3630 } 3631 3632 _hrs.verify_optional(); 3633 verify_region_sets_optional(); 3634 3635 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats()); 3636 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 3637 3638 if (PrintHeapAtGC) { 3639 Universe::print_heap_after_gc(); 3640 } 3641 g1mm()->update_counters(); 3642 3643 if (G1SummarizeRSetStats && 3644 (G1SummarizeRSetStatsPeriod > 0) && 3645 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3646 g1_rem_set()->print_summary_info(); 3647 } 3648 3649 return true; 3650 } 3651 3652 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 3653 { 3654 size_t gclab_word_size; 3655 switch (purpose) { 3656 case GCAllocForSurvived: 3657 gclab_word_size = YoungPLABSize; 3658 break; 3659 case GCAllocForTenured: 3660 gclab_word_size = OldPLABSize; 3661 break; 3662 default: 3663 assert(false, "unknown GCAllocPurpose"); 3664 gclab_word_size = OldPLABSize; 3665 break; 3666 } 3667 return gclab_word_size; 3668 } 3669 3670 void G1CollectedHeap::init_mutator_alloc_region() { 3671 assert(_mutator_alloc_region.get() == NULL, "pre-condition"); 3672 _mutator_alloc_region.init(); 3673 } 3674 3675 void G1CollectedHeap::release_mutator_alloc_region() { 3676 _mutator_alloc_region.release(); 3677 assert(_mutator_alloc_region.get() == NULL, "post-condition"); 3678 } 3679 3680 void G1CollectedHeap::init_gc_alloc_regions() { 3681 assert_at_safepoint(true /* should_be_vm_thread */); 3682 3683 _survivor_gc_alloc_region.init(); 3684 _old_gc_alloc_region.init(); 3685 HeapRegion* retained_region = _retained_old_gc_alloc_region; 3686 _retained_old_gc_alloc_region = NULL; 3687 3688 // We will discard the current GC alloc region if: 3689 // a) it's in the collection set (it can happen!), 3690 // b) it's already full (no point in using it), 3691 // c) it's empty (this means that it was emptied during 3692 // a cleanup and it should be on the free list now), or 3693 // d) it's humongous (this means that it was emptied 3694 // during a cleanup and was added to the free list, but 3695 // has been subseqently used to allocate a humongous 3696 // object that may be less than the region size). 3697 if (retained_region != NULL && 3698 !retained_region->in_collection_set() && 3699 !(retained_region->top() == retained_region->end()) && 3700 !retained_region->is_empty() && 3701 !retained_region->isHumongous()) { 3702 retained_region->set_saved_mark(); 3703 _old_gc_alloc_region.set(retained_region); 3704 _hr_printer.reuse(retained_region); 3705 } 3706 } 3707 3708 void G1CollectedHeap::release_gc_alloc_regions() { 3709 _survivor_gc_alloc_region.release(); 3710 // If we have an old GC alloc region to release, we'll save it in 3711 // _retained_old_gc_alloc_region. If we don't 3712 // _retained_old_gc_alloc_region will become NULL. This is what we 3713 // want either way so no reason to check explicitly for either 3714 // condition. 3715 _retained_old_gc_alloc_region = _old_gc_alloc_region.release(); 3716 } 3717 3718 void G1CollectedHeap::abandon_gc_alloc_regions() { 3719 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition"); 3720 assert(_old_gc_alloc_region.get() == NULL, "pre-condition"); 3721 _retained_old_gc_alloc_region = NULL; 3722 } 3723 3724 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 3725 _drain_in_progress = false; 3726 set_evac_failure_closure(cl); 3727 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true); 3728 } 3729 3730 void G1CollectedHeap::finalize_for_evac_failure() { 3731 assert(_evac_failure_scan_stack != NULL && 3732 _evac_failure_scan_stack->length() == 0, 3733 "Postcondition"); 3734 assert(!_drain_in_progress, "Postcondition"); 3735 delete _evac_failure_scan_stack; 3736 _evac_failure_scan_stack = NULL; 3737 } 3738 3739 // *** Sequential G1 Evacuation 3740 3741 class G1IsAliveClosure: public BoolObjectClosure { 3742 G1CollectedHeap* _g1; 3743 public: 3744 G1IsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3745 void do_object(oop p) { assert(false, "Do not call."); } 3746 bool do_object_b(oop p) { 3747 // It is reachable if it is outside the collection set, or is inside 3748 // and forwarded. 3749 3750 #ifdef G1_DEBUG 3751 gclog_or_tty->print_cr("is alive "PTR_FORMAT" in CS %d forwarded %d overall %d", 3752 (void*) p, _g1->obj_in_cs(p), p->is_forwarded(), 3753 !_g1->obj_in_cs(p) || p->is_forwarded()); 3754 #endif // G1_DEBUG 3755 3756 return !_g1->obj_in_cs(p) || p->is_forwarded(); 3757 } 3758 }; 3759 3760 class G1KeepAliveClosure: public OopClosure { 3761 G1CollectedHeap* _g1; 3762 public: 3763 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 3764 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 3765 void do_oop( oop* p) { 3766 oop obj = *p; 3767 #ifdef G1_DEBUG 3768 if (PrintGC && Verbose) { 3769 gclog_or_tty->print_cr("keep alive *"PTR_FORMAT" = "PTR_FORMAT" "PTR_FORMAT, 3770 p, (void*) obj, (void*) *p); 3771 } 3772 #endif // G1_DEBUG 3773 3774 if (_g1->obj_in_cs(obj)) { 3775 assert( obj->is_forwarded(), "invariant" ); 3776 *p = obj->forwardee(); 3777 #ifdef G1_DEBUG 3778 gclog_or_tty->print_cr(" in CSet: moved "PTR_FORMAT" -> "PTR_FORMAT, 3779 (void*) obj, (void*) *p); 3780 #endif // G1_DEBUG 3781 } 3782 } 3783 }; 3784 3785 class UpdateRSetDeferred : public OopsInHeapRegionClosure { 3786 private: 3787 G1CollectedHeap* _g1; 3788 DirtyCardQueue *_dcq; 3789 CardTableModRefBS* _ct_bs; 3790 3791 public: 3792 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) : 3793 _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {} 3794 3795 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 3796 virtual void do_oop( oop* p) { do_oop_work(p); } 3797 template <class T> void do_oop_work(T* p) { 3798 assert(_from->is_in_reserved(p), "paranoia"); 3799 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && 3800 !_from->is_survivor()) { 3801 size_t card_index = _ct_bs->index_for(p); 3802 if (_ct_bs->mark_card_deferred(card_index)) { 3803 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index)); 3804 } 3805 } 3806 } 3807 }; 3808 3809 class RemoveSelfPointerClosure: public ObjectClosure { 3810 private: 3811 G1CollectedHeap* _g1; 3812 ConcurrentMark* _cm; 3813 HeapRegion* _hr; 3814 size_t _prev_marked_bytes; 3815 size_t _next_marked_bytes; 3816 OopsInHeapRegionClosure *_cl; 3817 public: 3818 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr, 3819 OopsInHeapRegionClosure* cl) : 3820 _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0), 3821 _next_marked_bytes(0), _cl(cl) {} 3822 3823 size_t prev_marked_bytes() { return _prev_marked_bytes; } 3824 size_t next_marked_bytes() { return _next_marked_bytes; } 3825 3826 // <original comment> 3827 // The original idea here was to coalesce evacuated and dead objects. 3828 // However that caused complications with the block offset table (BOT). 3829 // In particular if there were two TLABs, one of them partially refined. 3830 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~| 3831 // The BOT entries of the unrefined part of TLAB_2 point to the start 3832 // of TLAB_2. If the last object of the TLAB_1 and the first object 3833 // of TLAB_2 are coalesced, then the cards of the unrefined part 3834 // would point into middle of the filler object. 3835 // The current approach is to not coalesce and leave the BOT contents intact. 3836 // </original comment> 3837 // 3838 // We now reset the BOT when we start the object iteration over the 3839 // region and refine its entries for every object we come across. So 3840 // the above comment is not really relevant and we should be able 3841 // to coalesce dead objects if we want to. 3842 void do_object(oop obj) { 3843 HeapWord* obj_addr = (HeapWord*) obj; 3844 assert(_hr->is_in(obj_addr), "sanity"); 3845 size_t obj_size = obj->size(); 3846 _hr->update_bot_for_object(obj_addr, obj_size); 3847 if (obj->is_forwarded() && obj->forwardee() == obj) { 3848 // The object failed to move. 3849 assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs."); 3850 _cm->markPrev(obj); 3851 assert(_cm->isPrevMarked(obj), "Should be marked!"); 3852 _prev_marked_bytes += (obj_size * HeapWordSize); 3853 if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) { 3854 _cm->markAndGrayObjectIfNecessary(obj); 3855 } 3856 obj->set_mark(markOopDesc::prototype()); 3857 // While we were processing RSet buffers during the 3858 // collection, we actually didn't scan any cards on the 3859 // collection set, since we didn't want to update remebered 3860 // sets with entries that point into the collection set, given 3861 // that live objects fromthe collection set are about to move 3862 // and such entries will be stale very soon. This change also 3863 // dealt with a reliability issue which involved scanning a 3864 // card in the collection set and coming across an array that 3865 // was being chunked and looking malformed. The problem is 3866 // that, if evacuation fails, we might have remembered set 3867 // entries missing given that we skipped cards on the 3868 // collection set. So, we'll recreate such entries now. 3869 obj->oop_iterate(_cl); 3870 assert(_cm->isPrevMarked(obj), "Should be marked!"); 3871 } else { 3872 // The object has been either evacuated or is dead. Fill it with a 3873 // dummy object. 3874 MemRegion mr((HeapWord*)obj, obj_size); 3875 CollectedHeap::fill_with_object(mr); 3876 _cm->clearRangeBothMaps(mr); 3877 } 3878 } 3879 }; 3880 3881 void G1CollectedHeap::remove_self_forwarding_pointers() { 3882 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set()); 3883 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set()); 3884 UpdateRSetDeferred deferred_update(_g1h, &dcq); 3885 OopsInHeapRegionClosure *cl; 3886 if (G1DeferredRSUpdate) { 3887 cl = &deferred_update; 3888 } else { 3889 cl = &immediate_update; 3890 } 3891 HeapRegion* cur = g1_policy()->collection_set(); 3892 while (cur != NULL) { 3893 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!"); 3894 assert(!cur->isHumongous(), "sanity"); 3895 3896 if (cur->evacuation_failed()) { 3897 assert(cur->in_collection_set(), "bad CS"); 3898 RemoveSelfPointerClosure rspc(_g1h, cur, cl); 3899 3900 // In the common case we make sure that this is done when the 3901 // region is freed so that it is "ready-to-go" when it's 3902 // re-allocated. However, when evacuation failure happens, a 3903 // region will remain in the heap and might ultimately be added 3904 // to a CSet in the future. So we have to be careful here and 3905 // make sure the region's RSet is ready for parallel iteration 3906 // whenever this might be required in the future. 3907 cur->rem_set()->reset_for_par_iteration(); 3908 cur->reset_bot(); 3909 cl->set_region(cur); 3910 cur->object_iterate(&rspc); 3911 3912 // A number of manipulations to make the TAMS be the current top, 3913 // and the marked bytes be the ones observed in the iteration. 3914 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) { 3915 // The comments below are the postconditions achieved by the 3916 // calls. Note especially the last such condition, which says that 3917 // the count of marked bytes has been properly restored. 3918 cur->note_start_of_marking(false); 3919 // _next_top_at_mark_start == top, _next_marked_bytes == 0 3920 cur->add_to_marked_bytes(rspc.prev_marked_bytes()); 3921 // _next_marked_bytes == prev_marked_bytes. 3922 cur->note_end_of_marking(); 3923 // _prev_top_at_mark_start == top(), 3924 // _prev_marked_bytes == prev_marked_bytes 3925 } 3926 // If there is no mark in progress, we modified the _next variables 3927 // above needlessly, but harmlessly. 3928 if (_g1h->mark_in_progress()) { 3929 cur->note_start_of_marking(false); 3930 // _next_top_at_mark_start == top, _next_marked_bytes == 0 3931 // _next_marked_bytes == next_marked_bytes. 3932 } 3933 3934 // Now make sure the region has the right index in the sorted array. 3935 g1_policy()->note_change_in_marked_bytes(cur); 3936 } 3937 cur = cur->next_in_collection_set(); 3938 } 3939 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!"); 3940 3941 // Now restore saved marks, if any. 3942 if (_objs_with_preserved_marks != NULL) { 3943 assert(_preserved_marks_of_objs != NULL, "Both or none."); 3944 guarantee(_objs_with_preserved_marks->length() == 3945 _preserved_marks_of_objs->length(), "Both or none."); 3946 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) { 3947 oop obj = _objs_with_preserved_marks->at(i); 3948 markOop m = _preserved_marks_of_objs->at(i); 3949 obj->set_mark(m); 3950 } 3951 // Delete the preserved marks growable arrays (allocated on the C heap). 3952 delete _objs_with_preserved_marks; 3953 delete _preserved_marks_of_objs; 3954 _objs_with_preserved_marks = NULL; 3955 _preserved_marks_of_objs = NULL; 3956 } 3957 } 3958 3959 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 3960 _evac_failure_scan_stack->push(obj); 3961 } 3962 3963 void G1CollectedHeap::drain_evac_failure_scan_stack() { 3964 assert(_evac_failure_scan_stack != NULL, "precondition"); 3965 3966 while (_evac_failure_scan_stack->length() > 0) { 3967 oop obj = _evac_failure_scan_stack->pop(); 3968 _evac_failure_closure->set_region(heap_region_containing(obj)); 3969 obj->oop_iterate_backwards(_evac_failure_closure); 3970 } 3971 } 3972 3973 oop 3974 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, 3975 oop old) { 3976 assert(obj_in_cs(old), 3977 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 3978 (HeapWord*) old)); 3979 markOop m = old->mark(); 3980 oop forward_ptr = old->forward_to_atomic(old); 3981 if (forward_ptr == NULL) { 3982 // Forward-to-self succeeded. 3983 if (_evac_failure_closure != cl) { 3984 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 3985 assert(!_drain_in_progress, 3986 "Should only be true while someone holds the lock."); 3987 // Set the global evac-failure closure to the current thread's. 3988 assert(_evac_failure_closure == NULL, "Or locking has failed."); 3989 set_evac_failure_closure(cl); 3990 // Now do the common part. 3991 handle_evacuation_failure_common(old, m); 3992 // Reset to NULL. 3993 set_evac_failure_closure(NULL); 3994 } else { 3995 // The lock is already held, and this is recursive. 3996 assert(_drain_in_progress, "This should only be the recursive case."); 3997 handle_evacuation_failure_common(old, m); 3998 } 3999 return old; 4000 } else { 4001 // Forward-to-self failed. Either someone else managed to allocate 4002 // space for this object (old != forward_ptr) or they beat us in 4003 // self-forwarding it (old == forward_ptr). 4004 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4005 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4006 "should not be in the CSet", 4007 (HeapWord*) old, (HeapWord*) forward_ptr)); 4008 return forward_ptr; 4009 } 4010 } 4011 4012 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4013 set_evacuation_failed(true); 4014 4015 preserve_mark_if_necessary(old, m); 4016 4017 HeapRegion* r = heap_region_containing(old); 4018 if (!r->evacuation_failed()) { 4019 r->set_evacuation_failed(true); 4020 _hr_printer.evac_failure(r); 4021 } 4022 4023 push_on_evac_failure_scan_stack(old); 4024 4025 if (!_drain_in_progress) { 4026 // prevent recursion in copy_to_survivor_space() 4027 _drain_in_progress = true; 4028 drain_evac_failure_scan_stack(); 4029 _drain_in_progress = false; 4030 } 4031 } 4032 4033 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4034 assert(evacuation_failed(), "Oversaving!"); 4035 // We want to call the "for_promotion_failure" version only in the 4036 // case of a promotion failure. 4037 if (m->must_be_preserved_for_promotion_failure(obj)) { 4038 if (_objs_with_preserved_marks == NULL) { 4039 assert(_preserved_marks_of_objs == NULL, "Both or none."); 4040 _objs_with_preserved_marks = 4041 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true); 4042 _preserved_marks_of_objs = 4043 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true); 4044 } 4045 _objs_with_preserved_marks->push(obj); 4046 _preserved_marks_of_objs->push(m); 4047 } 4048 } 4049 4050 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4051 size_t word_size) { 4052 if (purpose == GCAllocForSurvived) { 4053 HeapWord* result = survivor_attempt_allocation(word_size); 4054 if (result != NULL) { 4055 return result; 4056 } else { 4057 // Let's try to allocate in the old gen in case we can fit the 4058 // object there. 4059 return old_attempt_allocation(word_size); 4060 } 4061 } else { 4062 assert(purpose == GCAllocForTenured, "sanity"); 4063 HeapWord* result = old_attempt_allocation(word_size); 4064 if (result != NULL) { 4065 return result; 4066 } else { 4067 // Let's try to allocate in the survivors in case we can fit the 4068 // object there. 4069 return survivor_attempt_allocation(word_size); 4070 } 4071 } 4072 4073 ShouldNotReachHere(); 4074 // Trying to keep some compilers happy. 4075 return NULL; 4076 } 4077 4078 #ifndef PRODUCT 4079 bool GCLabBitMapClosure::do_bit(size_t offset) { 4080 HeapWord* addr = _bitmap->offsetToHeapWord(offset); 4081 guarantee(_cm->isMarked(oop(addr)), "it should be!"); 4082 return true; 4083 } 4084 #endif // PRODUCT 4085 4086 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num) 4087 : _g1h(g1h), 4088 _refs(g1h->task_queue(queue_num)), 4089 _dcq(&g1h->dirty_card_queue_set()), 4090 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()), 4091 _g1_rem(g1h->g1_rem_set()), 4092 _hash_seed(17), _queue_num(queue_num), 4093 _term_attempts(0), 4094 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 4095 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 4096 _age_table(false), 4097 _strong_roots_time(0), _term_time(0), 4098 _alloc_buffer_waste(0), _undo_waste(0) 4099 { 4100 // we allocate G1YoungSurvRateNumRegions plus one entries, since 4101 // we "sacrifice" entry 0 to keep track of surviving bytes for 4102 // non-young regions (where the age is -1) 4103 // We also add a few elements at the beginning and at the end in 4104 // an attempt to eliminate cache contention 4105 size_t real_length = 1 + _g1h->g1_policy()->young_cset_length(); 4106 size_t array_length = PADDING_ELEM_NUM + 4107 real_length + 4108 PADDING_ELEM_NUM; 4109 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length); 4110 if (_surviving_young_words_base == NULL) 4111 vm_exit_out_of_memory(array_length * sizeof(size_t), 4112 "Not enough space for young surv histo."); 4113 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 4114 memset(_surviving_young_words, 0, real_length * sizeof(size_t)); 4115 4116 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 4117 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 4118 4119 _start = os::elapsedTime(); 4120 } 4121 4122 void 4123 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 4124 { 4125 st->print_raw_cr("GC Termination Stats"); 4126 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 4127 " ------waste (KiB)------"); 4128 st->print_raw_cr("thr ms ms % ms % attempts" 4129 " total alloc undo"); 4130 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 4131 " ------- ------- -------"); 4132 } 4133 4134 void 4135 G1ParScanThreadState::print_termination_stats(int i, 4136 outputStream* const st) const 4137 { 4138 const double elapsed_ms = elapsed_time() * 1000.0; 4139 const double s_roots_ms = strong_roots_time() * 1000.0; 4140 const double term_ms = term_time() * 1000.0; 4141 st->print_cr("%3d %9.2f %9.2f %6.2f " 4142 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 4143 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 4144 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 4145 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 4146 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 4147 alloc_buffer_waste() * HeapWordSize / K, 4148 undo_waste() * HeapWordSize / K); 4149 } 4150 4151 #ifdef ASSERT 4152 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 4153 assert(ref != NULL, "invariant"); 4154 assert(UseCompressedOops, "sanity"); 4155 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref)); 4156 oop p = oopDesc::load_decode_heap_oop(ref); 4157 assert(_g1h->is_in_g1_reserved(p), 4158 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4159 return true; 4160 } 4161 4162 bool G1ParScanThreadState::verify_ref(oop* ref) const { 4163 assert(ref != NULL, "invariant"); 4164 if (has_partial_array_mask(ref)) { 4165 // Must be in the collection set--it's already been copied. 4166 oop p = clear_partial_array_mask(ref); 4167 assert(_g1h->obj_in_cs(p), 4168 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4169 } else { 4170 oop p = oopDesc::load_decode_heap_oop(ref); 4171 assert(_g1h->is_in_g1_reserved(p), 4172 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p))); 4173 } 4174 return true; 4175 } 4176 4177 bool G1ParScanThreadState::verify_task(StarTask ref) const { 4178 if (ref.is_narrow()) { 4179 return verify_ref((narrowOop*) ref); 4180 } else { 4181 return verify_ref((oop*) ref); 4182 } 4183 } 4184 #endif // ASSERT 4185 4186 void G1ParScanThreadState::trim_queue() { 4187 StarTask ref; 4188 do { 4189 // Drain the overflow stack first, so other threads can steal. 4190 while (refs()->pop_overflow(ref)) { 4191 deal_with_reference(ref); 4192 } 4193 while (refs()->pop_local(ref)) { 4194 deal_with_reference(ref); 4195 } 4196 } while (!refs()->is_empty()); 4197 } 4198 4199 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) : 4200 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()), 4201 _par_scan_state(par_scan_state) { } 4202 4203 template <class T> void G1ParCopyHelper::mark_forwardee(T* p) { 4204 // This is called _after_ do_oop_work has been called, hence after 4205 // the object has been relocated to its new location and *p points 4206 // to its new location. 4207 4208 T heap_oop = oopDesc::load_heap_oop(p); 4209 if (!oopDesc::is_null(heap_oop)) { 4210 oop obj = oopDesc::decode_heap_oop(heap_oop); 4211 HeapWord* addr = (HeapWord*)obj; 4212 if (_g1->is_in_g1_reserved(addr)) { 4213 _cm->grayRoot(oop(addr)); 4214 } 4215 } 4216 } 4217 4218 oop G1ParCopyHelper::copy_to_survivor_space(oop old) { 4219 size_t word_sz = old->size(); 4220 HeapRegion* from_region = _g1->heap_region_containing_raw(old); 4221 // +1 to make the -1 indexes valid... 4222 int young_index = from_region->young_index_in_cset()+1; 4223 assert( (from_region->is_young() && young_index > 0) || 4224 (!from_region->is_young() && young_index == 0), "invariant" ); 4225 G1CollectorPolicy* g1p = _g1->g1_policy(); 4226 markOop m = old->mark(); 4227 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 4228 : m->age(); 4229 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 4230 word_sz); 4231 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz); 4232 oop obj = oop(obj_ptr); 4233 4234 if (obj_ptr == NULL) { 4235 // This will either forward-to-self, or detect that someone else has 4236 // installed a forwarding pointer. 4237 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4238 return _g1->handle_evacuation_failure_par(cl, old); 4239 } 4240 4241 // We're going to allocate linearly, so might as well prefetch ahead. 4242 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 4243 4244 oop forward_ptr = old->forward_to_atomic(obj); 4245 if (forward_ptr == NULL) { 4246 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 4247 if (g1p->track_object_age(alloc_purpose)) { 4248 // We could simply do obj->incr_age(). However, this causes a 4249 // performance issue. obj->incr_age() will first check whether 4250 // the object has a displaced mark by checking its mark word; 4251 // getting the mark word from the new location of the object 4252 // stalls. So, given that we already have the mark word and we 4253 // are about to install it anyway, it's better to increase the 4254 // age on the mark word, when the object does not have a 4255 // displaced mark word. We're not expecting many objects to have 4256 // a displaced marked word, so that case is not optimized 4257 // further (it could be...) and we simply call obj->incr_age(). 4258 4259 if (m->has_displaced_mark_helper()) { 4260 // in this case, we have to install the mark word first, 4261 // otherwise obj looks to be forwarded (the old mark word, 4262 // which contains the forward pointer, was copied) 4263 obj->set_mark(m); 4264 obj->incr_age(); 4265 } else { 4266 m = m->incr_age(); 4267 obj->set_mark(m); 4268 } 4269 _par_scan_state->age_table()->add(obj, word_sz); 4270 } else { 4271 obj->set_mark(m); 4272 } 4273 4274 // preserve "next" mark bit 4275 if (_g1->mark_in_progress() && !_g1->is_obj_ill(old)) { 4276 if (!use_local_bitmaps || 4277 !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) { 4278 // if we couldn't mark it on the local bitmap (this happens when 4279 // the object was not allocated in the GCLab), we have to bite 4280 // the bullet and do the standard parallel mark 4281 _cm->markAndGrayObjectIfNecessary(obj); 4282 } 4283 #if 1 4284 if (_g1->isMarkedNext(old)) { 4285 _cm->nextMarkBitMap()->parClear((HeapWord*)old); 4286 } 4287 #endif 4288 } 4289 4290 size_t* surv_young_words = _par_scan_state->surviving_young_words(); 4291 surv_young_words[young_index] += word_sz; 4292 4293 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 4294 arrayOop(old)->set_length(0); 4295 oop* old_p = set_partial_array_mask(old); 4296 _par_scan_state->push_on_queue(old_p); 4297 } else { 4298 // No point in using the slower heap_region_containing() method, 4299 // given that we know obj is in the heap. 4300 _scanner->set_region(_g1->heap_region_containing_raw(obj)); 4301 obj->oop_iterate_backwards(_scanner); 4302 } 4303 } else { 4304 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz); 4305 obj = forward_ptr; 4306 } 4307 return obj; 4308 } 4309 4310 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_forwardee> 4311 template <class T> 4312 void G1ParCopyClosure <do_gen_barrier, barrier, do_mark_forwardee> 4313 ::do_oop_work(T* p) { 4314 oop obj = oopDesc::load_decode_heap_oop(p); 4315 assert(barrier != G1BarrierRS || obj != NULL, 4316 "Precondition: G1BarrierRS implies obj is nonNull"); 4317 4318 // here the null check is implicit in the cset_fast_test() test 4319 if (_g1->in_cset_fast_test(obj)) { 4320 if (obj->is_forwarded()) { 4321 oopDesc::encode_store_heap_oop(p, obj->forwardee()); 4322 } else { 4323 oop copy_oop = copy_to_survivor_space(obj); 4324 oopDesc::encode_store_heap_oop(p, copy_oop); 4325 } 4326 // When scanning the RS, we only care about objs in CS. 4327 if (barrier == G1BarrierRS) { 4328 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num()); 4329 } 4330 } 4331 4332 if (barrier == G1BarrierEvac && obj != NULL) { 4333 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num()); 4334 } 4335 4336 if (do_gen_barrier && obj != NULL) { 4337 par_do_barrier(p); 4338 } 4339 } 4340 4341 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p); 4342 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p); 4343 4344 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) { 4345 assert(has_partial_array_mask(p), "invariant"); 4346 oop old = clear_partial_array_mask(p); 4347 assert(old->is_objArray(), "must be obj array"); 4348 assert(old->is_forwarded(), "must be forwarded"); 4349 assert(Universe::heap()->is_in_reserved(old), "must be in heap."); 4350 4351 objArrayOop obj = objArrayOop(old->forwardee()); 4352 assert((void*)old != (void*)old->forwardee(), "self forwarding here?"); 4353 // Process ParGCArrayScanChunk elements now 4354 // and push the remainder back onto queue 4355 int start = arrayOop(old)->length(); 4356 int end = obj->length(); 4357 int remainder = end - start; 4358 assert(start <= end, "just checking"); 4359 if (remainder > 2 * ParGCArrayScanChunk) { 4360 // Test above combines last partial chunk with a full chunk 4361 end = start + ParGCArrayScanChunk; 4362 arrayOop(old)->set_length(end); 4363 // Push remainder. 4364 oop* old_p = set_partial_array_mask(old); 4365 assert(arrayOop(old)->length() < obj->length(), "Empty push?"); 4366 _par_scan_state->push_on_queue(old_p); 4367 } else { 4368 // Restore length so that the heap remains parsable in 4369 // case of evacuation failure. 4370 arrayOop(old)->set_length(end); 4371 } 4372 _scanner.set_region(_g1->heap_region_containing_raw(obj)); 4373 // process our set of indices (include header in first chunk) 4374 obj->oop_iterate_range(&_scanner, start, end); 4375 } 4376 4377 class G1ParEvacuateFollowersClosure : public VoidClosure { 4378 protected: 4379 G1CollectedHeap* _g1h; 4380 G1ParScanThreadState* _par_scan_state; 4381 RefToScanQueueSet* _queues; 4382 ParallelTaskTerminator* _terminator; 4383 4384 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4385 RefToScanQueueSet* queues() { return _queues; } 4386 ParallelTaskTerminator* terminator() { return _terminator; } 4387 4388 public: 4389 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4390 G1ParScanThreadState* par_scan_state, 4391 RefToScanQueueSet* queues, 4392 ParallelTaskTerminator* terminator) 4393 : _g1h(g1h), _par_scan_state(par_scan_state), 4394 _queues(queues), _terminator(terminator) {} 4395 4396 void do_void(); 4397 4398 private: 4399 inline bool offer_termination(); 4400 }; 4401 4402 bool G1ParEvacuateFollowersClosure::offer_termination() { 4403 G1ParScanThreadState* const pss = par_scan_state(); 4404 pss->start_term_time(); 4405 const bool res = terminator()->offer_termination(); 4406 pss->end_term_time(); 4407 return res; 4408 } 4409 4410 void G1ParEvacuateFollowersClosure::do_void() { 4411 StarTask stolen_task; 4412 G1ParScanThreadState* const pss = par_scan_state(); 4413 pss->trim_queue(); 4414 4415 do { 4416 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) { 4417 assert(pss->verify_task(stolen_task), "sanity"); 4418 if (stolen_task.is_narrow()) { 4419 pss->deal_with_reference((narrowOop*) stolen_task); 4420 } else { 4421 pss->deal_with_reference((oop*) stolen_task); 4422 } 4423 4424 // We've just processed a reference and we might have made 4425 // available new entries on the queues. So we have to make sure 4426 // we drain the queues as necessary. 4427 pss->trim_queue(); 4428 } 4429 } while (!offer_termination()); 4430 4431 pss->retire_alloc_buffers(); 4432 } 4433 4434 class G1ParTask : public AbstractGangTask { 4435 protected: 4436 G1CollectedHeap* _g1h; 4437 RefToScanQueueSet *_queues; 4438 ParallelTaskTerminator _terminator; 4439 int _n_workers; 4440 4441 Mutex _stats_lock; 4442 Mutex* stats_lock() { return &_stats_lock; } 4443 4444 size_t getNCards() { 4445 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1) 4446 / G1BlockOffsetSharedArray::N_bytes; 4447 } 4448 4449 public: 4450 G1ParTask(G1CollectedHeap* g1h, int workers, RefToScanQueueSet *task_queues) 4451 : AbstractGangTask("G1 collection"), 4452 _g1h(g1h), 4453 _queues(task_queues), 4454 _terminator(workers, _queues), 4455 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true), 4456 _n_workers(workers) 4457 {} 4458 4459 RefToScanQueueSet* queues() { return _queues; } 4460 4461 RefToScanQueue *work_queue(int i) { 4462 return queues()->queue(i); 4463 } 4464 4465 void work(int i) { 4466 if (i >= _n_workers) return; // no work needed this round 4467 4468 double start_time_ms = os::elapsedTime() * 1000.0; 4469 _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms); 4470 4471 ResourceMark rm; 4472 HandleMark hm; 4473 4474 G1ParScanThreadState pss(_g1h, i); 4475 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss); 4476 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss); 4477 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss); 4478 4479 pss.set_evac_closure(&scan_evac_cl); 4480 pss.set_evac_failure_closure(&evac_failure_cl); 4481 pss.set_partial_scan_closure(&partial_scan_cl); 4482 4483 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss); 4484 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss); 4485 G1ParScanHeapRSClosure only_scan_heap_rs_cl(_g1h, &pss); 4486 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4487 4488 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss); 4489 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss); 4490 G1ParScanAndMarkHeapRSClosure scan_mark_heap_rs_cl(_g1h, &pss); 4491 4492 OopsInHeapRegionClosure *scan_root_cl; 4493 OopsInHeapRegionClosure *scan_perm_cl; 4494 4495 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4496 scan_root_cl = &scan_mark_root_cl; 4497 scan_perm_cl = &scan_mark_perm_cl; 4498 } else { 4499 scan_root_cl = &only_scan_root_cl; 4500 scan_perm_cl = &only_scan_perm_cl; 4501 } 4502 4503 pss.start_strong_roots(); 4504 _g1h->g1_process_strong_roots(/* not collecting perm */ false, 4505 SharedHeap::SO_AllClasses, 4506 scan_root_cl, 4507 &push_heap_rs_cl, 4508 scan_perm_cl, 4509 i); 4510 pss.end_strong_roots(); 4511 4512 { 4513 double start = os::elapsedTime(); 4514 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4515 evac.do_void(); 4516 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4517 double term_ms = pss.term_time()*1000.0; 4518 _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms); 4519 _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts()); 4520 } 4521 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4522 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4523 4524 // Clean up any par-expanded rem sets. 4525 HeapRegionRemSet::par_cleanup(); 4526 4527 if (ParallelGCVerbose) { 4528 MutexLocker x(stats_lock()); 4529 pss.print_termination_stats(i); 4530 } 4531 4532 assert(pss.refs()->is_empty(), "should be empty"); 4533 double end_time_ms = os::elapsedTime() * 1000.0; 4534 _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms); 4535 } 4536 }; 4537 4538 // *** Common G1 Evacuation Stuff 4539 4540 // This method is run in a GC worker. 4541 4542 void 4543 G1CollectedHeap:: 4544 g1_process_strong_roots(bool collecting_perm_gen, 4545 SharedHeap::ScanningOption so, 4546 OopClosure* scan_non_heap_roots, 4547 OopsInHeapRegionClosure* scan_rs, 4548 OopsInGenClosure* scan_perm, 4549 int worker_i) { 4550 // First scan the strong roots, including the perm gen. 4551 double ext_roots_start = os::elapsedTime(); 4552 double closure_app_time_sec = 0.0; 4553 4554 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 4555 BufferingOopsInGenClosure buf_scan_perm(scan_perm); 4556 buf_scan_perm.set_generation(perm_gen()); 4557 4558 // Walk the code cache w/o buffering, because StarTask cannot handle 4559 // unaligned oop locations. 4560 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true); 4561 4562 process_strong_roots(false, // no scoping; this is parallel code 4563 collecting_perm_gen, so, 4564 &buf_scan_non_heap_roots, 4565 &eager_scan_code_roots, 4566 &buf_scan_perm); 4567 4568 // Now the ref_processor roots. 4569 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 4570 // We need to treat the discovered reference lists as roots and 4571 // keep entries (which are added by the marking threads) on them 4572 // live until they can be processed at the end of marking. 4573 ref_processor()->weak_oops_do(&buf_scan_non_heap_roots); 4574 ref_processor()->oops_do(&buf_scan_non_heap_roots); 4575 } 4576 4577 // Finish up any enqueued closure apps (attributed as object copy time). 4578 buf_scan_non_heap_roots.done(); 4579 buf_scan_perm.done(); 4580 4581 double ext_roots_end = os::elapsedTime(); 4582 4583 g1_policy()->reset_obj_copy_time(worker_i); 4584 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() + 4585 buf_scan_non_heap_roots.closure_app_seconds(); 4586 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 4587 4588 double ext_root_time_ms = 4589 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0; 4590 4591 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 4592 4593 // Scan strong roots in mark stack. 4594 if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) { 4595 concurrent_mark()->oops_do(scan_non_heap_roots); 4596 } 4597 double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0; 4598 g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms); 4599 4600 // Now scan the complement of the collection set. 4601 if (scan_rs != NULL) { 4602 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i); 4603 } 4604 4605 _process_strong_tasks->all_tasks_completed(); 4606 } 4607 4608 void 4609 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure, 4610 OopClosure* non_root_closure) { 4611 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false); 4612 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure); 4613 } 4614 4615 void G1CollectedHeap::evacuate_collection_set() { 4616 set_evacuation_failed(false); 4617 4618 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 4619 concurrent_g1_refine()->set_use_cache(false); 4620 concurrent_g1_refine()->clear_hot_cache_claimed_index(); 4621 4622 int n_workers = (ParallelGCThreads > 0 ? workers()->total_workers() : 1); 4623 set_par_threads(n_workers); 4624 G1ParTask g1_par_task(this, n_workers, _task_queues); 4625 4626 init_for_evac_failure(NULL); 4627 4628 rem_set()->prepare_for_younger_refs_iterate(true); 4629 4630 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 4631 double start_par = os::elapsedTime(); 4632 if (G1CollectedHeap::use_parallel_gc_threads()) { 4633 // The individual threads will set their evac-failure closures. 4634 StrongRootsScope srs(this); 4635 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr(); 4636 workers()->run_task(&g1_par_task); 4637 } else { 4638 StrongRootsScope srs(this); 4639 g1_par_task.work(0); 4640 } 4641 4642 double par_time = (os::elapsedTime() - start_par) * 1000.0; 4643 g1_policy()->record_par_time(par_time); 4644 set_par_threads(0); 4645 4646 // Weak root processing. 4647 // Note: when JSR 292 is enabled and code blobs can contain 4648 // non-perm oops then we will need to process the code blobs 4649 // here too. 4650 { 4651 G1IsAliveClosure is_alive(this); 4652 G1KeepAliveClosure keep_alive(this); 4653 JNIHandles::weak_oops_do(&is_alive, &keep_alive); 4654 } 4655 release_gc_alloc_regions(); 4656 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 4657 4658 concurrent_g1_refine()->clear_hot_cache(); 4659 concurrent_g1_refine()->set_use_cache(true); 4660 4661 finalize_for_evac_failure(); 4662 4663 // Must do this before removing self-forwarding pointers, which clears 4664 // the per-region evac-failure flags. 4665 concurrent_mark()->complete_marking_in_collection_set(); 4666 4667 if (evacuation_failed()) { 4668 remove_self_forwarding_pointers(); 4669 if (PrintGCDetails) { 4670 gclog_or_tty->print(" (to-space overflow)"); 4671 } else if (PrintGC) { 4672 gclog_or_tty->print("--"); 4673 } 4674 } 4675 4676 if (G1DeferredRSUpdate) { 4677 RedirtyLoggedCardTableEntryFastClosure redirty; 4678 dirty_card_queue_set().set_closure(&redirty); 4679 dirty_card_queue_set().apply_closure_to_all_completed_buffers(); 4680 4681 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 4682 dcq.merge_bufferlists(&dirty_card_queue_set()); 4683 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 4684 } 4685 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 4686 } 4687 4688 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr, 4689 size_t* pre_used, 4690 FreeRegionList* free_list, 4691 HumongousRegionSet* humongous_proxy_set, 4692 HRRSCleanupTask* hrrs_cleanup_task, 4693 bool par) { 4694 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 4695 if (hr->isHumongous()) { 4696 assert(hr->startsHumongous(), "we should only see starts humongous"); 4697 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par); 4698 } else { 4699 free_region(hr, pre_used, free_list, par); 4700 } 4701 } else { 4702 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task); 4703 } 4704 } 4705 4706 void G1CollectedHeap::free_region(HeapRegion* hr, 4707 size_t* pre_used, 4708 FreeRegionList* free_list, 4709 bool par) { 4710 assert(!hr->isHumongous(), "this is only for non-humongous regions"); 4711 assert(!hr->is_empty(), "the region should not be empty"); 4712 assert(free_list != NULL, "pre-condition"); 4713 4714 *pre_used += hr->used(); 4715 hr->hr_clear(par, true /* clear_space */); 4716 free_list->add_as_head(hr); 4717 } 4718 4719 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 4720 size_t* pre_used, 4721 FreeRegionList* free_list, 4722 HumongousRegionSet* humongous_proxy_set, 4723 bool par) { 4724 assert(hr->startsHumongous(), "this is only for starts humongous regions"); 4725 assert(free_list != NULL, "pre-condition"); 4726 assert(humongous_proxy_set != NULL, "pre-condition"); 4727 4728 size_t hr_used = hr->used(); 4729 size_t hr_capacity = hr->capacity(); 4730 size_t hr_pre_used = 0; 4731 _humongous_set.remove_with_proxy(hr, humongous_proxy_set); 4732 hr->set_notHumongous(); 4733 free_region(hr, &hr_pre_used, free_list, par); 4734 4735 size_t i = hr->hrs_index() + 1; 4736 size_t num = 1; 4737 while (i < n_regions()) { 4738 HeapRegion* curr_hr = region_at(i); 4739 if (!curr_hr->continuesHumongous()) { 4740 break; 4741 } 4742 curr_hr->set_notHumongous(); 4743 free_region(curr_hr, &hr_pre_used, free_list, par); 4744 num += 1; 4745 i += 1; 4746 } 4747 assert(hr_pre_used == hr_used, 4748 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" " 4749 "should be the same", hr_pre_used, hr_used)); 4750 *pre_used += hr_pre_used; 4751 } 4752 4753 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used, 4754 FreeRegionList* free_list, 4755 HumongousRegionSet* humongous_proxy_set, 4756 bool par) { 4757 if (pre_used > 0) { 4758 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL; 4759 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag); 4760 assert(_summary_bytes_used >= pre_used, 4761 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" " 4762 "should be >= pre_used: "SIZE_FORMAT, 4763 _summary_bytes_used, pre_used)); 4764 _summary_bytes_used -= pre_used; 4765 } 4766 if (free_list != NULL && !free_list->is_empty()) { 4767 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 4768 _free_list.add_as_head(free_list); 4769 } 4770 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) { 4771 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 4772 _humongous_set.update_from_proxy(humongous_proxy_set); 4773 } 4774 } 4775 4776 class G1ParCleanupCTTask : public AbstractGangTask { 4777 CardTableModRefBS* _ct_bs; 4778 G1CollectedHeap* _g1h; 4779 HeapRegion* volatile _su_head; 4780 public: 4781 G1ParCleanupCTTask(CardTableModRefBS* ct_bs, 4782 G1CollectedHeap* g1h) : 4783 AbstractGangTask("G1 Par Cleanup CT Task"), 4784 _ct_bs(ct_bs), _g1h(g1h) { } 4785 4786 void work(int i) { 4787 HeapRegion* r; 4788 while (r = _g1h->pop_dirty_cards_region()) { 4789 clear_cards(r); 4790 } 4791 } 4792 4793 void clear_cards(HeapRegion* r) { 4794 // Cards of the survivors should have already been dirtied. 4795 if (!r->is_survivor()) { 4796 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 4797 } 4798 } 4799 }; 4800 4801 #ifndef PRODUCT 4802 class G1VerifyCardTableCleanup: public HeapRegionClosure { 4803 G1CollectedHeap* _g1h; 4804 CardTableModRefBS* _ct_bs; 4805 public: 4806 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs) 4807 : _g1h(g1h), _ct_bs(ct_bs) { } 4808 virtual bool doHeapRegion(HeapRegion* r) { 4809 if (r->is_survivor()) { 4810 _g1h->verify_dirty_region(r); 4811 } else { 4812 _g1h->verify_not_dirty_region(r); 4813 } 4814 return false; 4815 } 4816 }; 4817 4818 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 4819 // All of the region should be clean. 4820 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set(); 4821 MemRegion mr(hr->bottom(), hr->end()); 4822 ct_bs->verify_not_dirty_region(mr); 4823 } 4824 4825 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 4826 // We cannot guarantee that [bottom(),end()] is dirty. Threads 4827 // dirty allocated blocks as they allocate them. The thread that 4828 // retires each region and replaces it with a new one will do a 4829 // maximal allocation to fill in [pre_dummy_top(),end()] but will 4830 // not dirty that area (one less thing to have to do while holding 4831 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 4832 // is dirty. 4833 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 4834 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 4835 ct_bs->verify_dirty_region(mr); 4836 } 4837 4838 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 4839 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set(); 4840 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 4841 verify_dirty_region(hr); 4842 } 4843 } 4844 4845 void G1CollectedHeap::verify_dirty_young_regions() { 4846 verify_dirty_young_list(_young_list->first_region()); 4847 verify_dirty_young_list(_young_list->first_survivor_region()); 4848 } 4849 #endif 4850 4851 void G1CollectedHeap::cleanUpCardTable() { 4852 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set()); 4853 double start = os::elapsedTime(); 4854 4855 // Iterate over the dirty cards region list. 4856 G1ParCleanupCTTask cleanup_task(ct_bs, this); 4857 4858 if (ParallelGCThreads > 0) { 4859 set_par_threads(workers()->total_workers()); 4860 workers()->run_task(&cleanup_task); 4861 set_par_threads(0); 4862 } else { 4863 while (_dirty_cards_region_list) { 4864 HeapRegion* r = _dirty_cards_region_list; 4865 cleanup_task.clear_cards(r); 4866 _dirty_cards_region_list = r->get_next_dirty_cards_region(); 4867 if (_dirty_cards_region_list == r) { 4868 // The last region. 4869 _dirty_cards_region_list = NULL; 4870 } 4871 r->set_next_dirty_cards_region(NULL); 4872 } 4873 } 4874 4875 double elapsed = os::elapsedTime() - start; 4876 g1_policy()->record_clear_ct_time( elapsed * 1000.0); 4877 #ifndef PRODUCT 4878 if (G1VerifyCTCleanup || VerifyAfterGC) { 4879 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 4880 heap_region_iterate(&cleanup_verifier); 4881 } 4882 #endif 4883 } 4884 4885 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) { 4886 size_t pre_used = 0; 4887 FreeRegionList local_free_list("Local List for CSet Freeing"); 4888 4889 double young_time_ms = 0.0; 4890 double non_young_time_ms = 0.0; 4891 4892 // Since the collection set is a superset of the the young list, 4893 // all we need to do to clear the young list is clear its 4894 // head and length, and unlink any young regions in the code below 4895 _young_list->clear(); 4896 4897 G1CollectorPolicy* policy = g1_policy(); 4898 4899 double start_sec = os::elapsedTime(); 4900 bool non_young = true; 4901 4902 HeapRegion* cur = cs_head; 4903 int age_bound = -1; 4904 size_t rs_lengths = 0; 4905 4906 while (cur != NULL) { 4907 assert(!is_on_master_free_list(cur), "sanity"); 4908 4909 if (non_young) { 4910 if (cur->is_young()) { 4911 double end_sec = os::elapsedTime(); 4912 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4913 non_young_time_ms += elapsed_ms; 4914 4915 start_sec = os::elapsedTime(); 4916 non_young = false; 4917 } 4918 } else { 4919 double end_sec = os::elapsedTime(); 4920 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4921 young_time_ms += elapsed_ms; 4922 4923 start_sec = os::elapsedTime(); 4924 non_young = true; 4925 } 4926 4927 rs_lengths += cur->rem_set()->occupied(); 4928 4929 HeapRegion* next = cur->next_in_collection_set(); 4930 assert(cur->in_collection_set(), "bad CS"); 4931 cur->set_next_in_collection_set(NULL); 4932 cur->set_in_collection_set(false); 4933 4934 if (cur->is_young()) { 4935 int index = cur->young_index_in_cset(); 4936 guarantee( index != -1, "invariant" ); 4937 guarantee( (size_t)index < policy->young_cset_length(), "invariant" ); 4938 size_t words_survived = _surviving_young_words[index]; 4939 cur->record_surv_words_in_group(words_survived); 4940 4941 // At this point the we have 'popped' cur from the collection set 4942 // (linked via next_in_collection_set()) but it is still in the 4943 // young list (linked via next_young_region()). Clear the 4944 // _next_young_region field. 4945 cur->set_next_young_region(NULL); 4946 } else { 4947 int index = cur->young_index_in_cset(); 4948 guarantee( index == -1, "invariant" ); 4949 } 4950 4951 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 4952 (!cur->is_young() && cur->young_index_in_cset() == -1), 4953 "invariant" ); 4954 4955 if (!cur->evacuation_failed()) { 4956 // And the region is empty. 4957 assert(!cur->is_empty(), "Should not have empty regions in a CS."); 4958 free_region(cur, &pre_used, &local_free_list, false /* par */); 4959 } else { 4960 cur->uninstall_surv_rate_group(); 4961 if (cur->is_young()) 4962 cur->set_young_index_in_cset(-1); 4963 cur->set_not_young(); 4964 cur->set_evacuation_failed(false); 4965 } 4966 cur = next; 4967 } 4968 4969 policy->record_max_rs_lengths(rs_lengths); 4970 policy->cset_regions_freed(); 4971 4972 double end_sec = os::elapsedTime(); 4973 double elapsed_ms = (end_sec - start_sec) * 1000.0; 4974 if (non_young) 4975 non_young_time_ms += elapsed_ms; 4976 else 4977 young_time_ms += elapsed_ms; 4978 4979 update_sets_after_freeing_regions(pre_used, &local_free_list, 4980 NULL /* humongous_proxy_set */, 4981 false /* par */); 4982 policy->record_young_free_cset_time_ms(young_time_ms); 4983 policy->record_non_young_free_cset_time_ms(non_young_time_ms); 4984 } 4985 4986 // This routine is similar to the above but does not record 4987 // any policy statistics or update free lists; we are abandoning 4988 // the current incremental collection set in preparation of a 4989 // full collection. After the full GC we will start to build up 4990 // the incremental collection set again. 4991 // This is only called when we're doing a full collection 4992 // and is immediately followed by the tearing down of the young list. 4993 4994 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 4995 HeapRegion* cur = cs_head; 4996 4997 while (cur != NULL) { 4998 HeapRegion* next = cur->next_in_collection_set(); 4999 assert(cur->in_collection_set(), "bad CS"); 5000 cur->set_next_in_collection_set(NULL); 5001 cur->set_in_collection_set(false); 5002 cur->set_young_index_in_cset(-1); 5003 cur = next; 5004 } 5005 } 5006 5007 void G1CollectedHeap::set_free_regions_coming() { 5008 if (G1ConcRegionFreeingVerbose) { 5009 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5010 "setting free regions coming"); 5011 } 5012 5013 assert(!free_regions_coming(), "pre-condition"); 5014 _free_regions_coming = true; 5015 } 5016 5017 void G1CollectedHeap::reset_free_regions_coming() { 5018 { 5019 assert(free_regions_coming(), "pre-condition"); 5020 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5021 _free_regions_coming = false; 5022 SecondaryFreeList_lock->notify_all(); 5023 } 5024 5025 if (G1ConcRegionFreeingVerbose) { 5026 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 5027 "reset free regions coming"); 5028 } 5029 } 5030 5031 void G1CollectedHeap::wait_while_free_regions_coming() { 5032 // Most of the time we won't have to wait, so let's do a quick test 5033 // first before we take the lock. 5034 if (!free_regions_coming()) { 5035 return; 5036 } 5037 5038 if (G1ConcRegionFreeingVerbose) { 5039 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5040 "waiting for free regions"); 5041 } 5042 5043 { 5044 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5045 while (free_regions_coming()) { 5046 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 5047 } 5048 } 5049 5050 if (G1ConcRegionFreeingVerbose) { 5051 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 5052 "done waiting for free regions"); 5053 } 5054 } 5055 5056 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 5057 assert(heap_lock_held_for_gc(), 5058 "the heap lock should already be held by or for this thread"); 5059 _young_list->push_region(hr); 5060 g1_policy()->set_region_short_lived(hr); 5061 } 5062 5063 class NoYoungRegionsClosure: public HeapRegionClosure { 5064 private: 5065 bool _success; 5066 public: 5067 NoYoungRegionsClosure() : _success(true) { } 5068 bool doHeapRegion(HeapRegion* r) { 5069 if (r->is_young()) { 5070 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 5071 r->bottom(), r->end()); 5072 _success = false; 5073 } 5074 return false; 5075 } 5076 bool success() { return _success; } 5077 }; 5078 5079 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 5080 bool ret = _young_list->check_list_empty(check_sample); 5081 5082 if (check_heap) { 5083 NoYoungRegionsClosure closure; 5084 heap_region_iterate(&closure); 5085 ret = ret && closure.success(); 5086 } 5087 5088 return ret; 5089 } 5090 5091 void G1CollectedHeap::empty_young_list() { 5092 assert(heap_lock_held_for_gc(), 5093 "the heap lock should already be held by or for this thread"); 5094 assert(g1_policy()->in_young_gc_mode(), "should be in young GC mode"); 5095 5096 _young_list->empty_list(); 5097 } 5098 5099 // Done at the start of full GC. 5100 void G1CollectedHeap::tear_down_region_lists() { 5101 _free_list.remove_all(); 5102 } 5103 5104 class RegionResetter: public HeapRegionClosure { 5105 G1CollectedHeap* _g1h; 5106 FreeRegionList _local_free_list; 5107 5108 public: 5109 RegionResetter() : _g1h(G1CollectedHeap::heap()), 5110 _local_free_list("Local Free List for RegionResetter") { } 5111 5112 bool doHeapRegion(HeapRegion* r) { 5113 if (r->continuesHumongous()) return false; 5114 if (r->top() > r->bottom()) { 5115 if (r->top() < r->end()) { 5116 Copy::fill_to_words(r->top(), 5117 pointer_delta(r->end(), r->top())); 5118 } 5119 } else { 5120 assert(r->is_empty(), "tautology"); 5121 _local_free_list.add_as_tail(r); 5122 } 5123 return false; 5124 } 5125 5126 void update_free_lists() { 5127 _g1h->update_sets_after_freeing_regions(0, &_local_free_list, NULL, 5128 false /* par */); 5129 } 5130 }; 5131 5132 // Done at the end of full GC. 5133 void G1CollectedHeap::rebuild_region_lists() { 5134 // This needs to go at the end of the full GC. 5135 RegionResetter rs; 5136 heap_region_iterate(&rs); 5137 rs.update_free_lists(); 5138 } 5139 5140 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 5141 _refine_cte_cl->set_concurrent(concurrent); 5142 } 5143 5144 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 5145 HeapRegion* hr = heap_region_containing(p); 5146 if (hr == NULL) { 5147 return is_in_permanent(p); 5148 } else { 5149 return hr->is_in(p); 5150 } 5151 } 5152 5153 // Methods for the mutator alloc region 5154 5155 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 5156 bool force) { 5157 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5158 assert(!force || g1_policy()->can_expand_young_list(), 5159 "if force is true we should be able to expand the young list"); 5160 bool young_list_full = g1_policy()->is_young_list_full(); 5161 if (force || !young_list_full) { 5162 HeapRegion* new_alloc_region = new_region(word_size, 5163 false /* do_expand */); 5164 if (new_alloc_region != NULL) { 5165 g1_policy()->update_region_num(true /* next_is_young */); 5166 set_region_short_lived_locked(new_alloc_region); 5167 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 5168 g1mm()->update_eden_counters(); 5169 return new_alloc_region; 5170 } 5171 } 5172 return NULL; 5173 } 5174 5175 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 5176 size_t allocated_bytes) { 5177 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5178 assert(alloc_region->is_young(), "all mutator alloc regions should be young"); 5179 5180 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 5181 _summary_bytes_used += allocated_bytes; 5182 _hr_printer.retire(alloc_region); 5183 } 5184 5185 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size, 5186 bool force) { 5187 return _g1h->new_mutator_alloc_region(word_size, force); 5188 } 5189 5190 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region, 5191 size_t allocated_bytes) { 5192 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes); 5193 } 5194 5195 // Methods for the GC alloc regions 5196 5197 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 5198 size_t count, 5199 GCAllocPurpose ap) { 5200 assert(FreeList_lock->owned_by_self(), "pre-condition"); 5201 5202 if (count < g1_policy()->max_regions(ap)) { 5203 HeapRegion* new_alloc_region = new_region(word_size, 5204 true /* do_expand */); 5205 if (new_alloc_region != NULL) { 5206 // We really only need to do this for old regions given that we 5207 // should never scan survivors. But it doesn't hurt to do it 5208 // for survivors too. 5209 new_alloc_region->set_saved_mark(); 5210 if (ap == GCAllocForSurvived) { 5211 new_alloc_region->set_survivor(); 5212 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 5213 } else { 5214 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 5215 } 5216 return new_alloc_region; 5217 } else { 5218 g1_policy()->note_alloc_region_limit_reached(ap); 5219 } 5220 } 5221 return NULL; 5222 } 5223 5224 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 5225 size_t allocated_bytes, 5226 GCAllocPurpose ap) { 5227 alloc_region->note_end_of_copying(); 5228 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 5229 if (ap == GCAllocForSurvived) { 5230 young_list()->add_survivor_region(alloc_region); 5231 } 5232 _hr_printer.retire(alloc_region); 5233 } 5234 5235 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size, 5236 bool force) { 5237 assert(!force, "not supported for GC alloc regions"); 5238 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived); 5239 } 5240 5241 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region, 5242 size_t allocated_bytes) { 5243 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 5244 GCAllocForSurvived); 5245 } 5246 5247 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size, 5248 bool force) { 5249 assert(!force, "not supported for GC alloc regions"); 5250 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured); 5251 } 5252 5253 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region, 5254 size_t allocated_bytes) { 5255 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, 5256 GCAllocForTenured); 5257 } 5258 // Heap region set verification 5259 5260 class VerifyRegionListsClosure : public HeapRegionClosure { 5261 private: 5262 HumongousRegionSet* _humongous_set; 5263 FreeRegionList* _free_list; 5264 size_t _region_count; 5265 5266 public: 5267 VerifyRegionListsClosure(HumongousRegionSet* humongous_set, 5268 FreeRegionList* free_list) : 5269 _humongous_set(humongous_set), _free_list(free_list), 5270 _region_count(0) { } 5271 5272 size_t region_count() { return _region_count; } 5273 5274 bool doHeapRegion(HeapRegion* hr) { 5275 _region_count += 1; 5276 5277 if (hr->continuesHumongous()) { 5278 return false; 5279 } 5280 5281 if (hr->is_young()) { 5282 // TODO 5283 } else if (hr->startsHumongous()) { 5284 _humongous_set->verify_next_region(hr); 5285 } else if (hr->is_empty()) { 5286 _free_list->verify_next_region(hr); 5287 } 5288 return false; 5289 } 5290 }; 5291 5292 HeapRegion* G1CollectedHeap::new_heap_region(size_t hrs_index, 5293 HeapWord* bottom) { 5294 HeapWord* end = bottom + HeapRegion::GrainWords; 5295 MemRegion mr(bottom, end); 5296 assert(_g1_reserved.contains(mr), "invariant"); 5297 // This might return NULL if the allocation fails 5298 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */); 5299 } 5300 5301 void G1CollectedHeap::verify_region_sets() { 5302 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 5303 5304 // First, check the explicit lists. 5305 _free_list.verify(); 5306 { 5307 // Given that a concurrent operation might be adding regions to 5308 // the secondary free list we have to take the lock before 5309 // verifying it. 5310 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 5311 _secondary_free_list.verify(); 5312 } 5313 _humongous_set.verify(); 5314 5315 // If a concurrent region freeing operation is in progress it will 5316 // be difficult to correctly attributed any free regions we come 5317 // across to the correct free list given that they might belong to 5318 // one of several (free_list, secondary_free_list, any local lists, 5319 // etc.). So, if that's the case we will skip the rest of the 5320 // verification operation. Alternatively, waiting for the concurrent 5321 // operation to complete will have a non-trivial effect on the GC's 5322 // operation (no concurrent operation will last longer than the 5323 // interval between two calls to verification) and it might hide 5324 // any issues that we would like to catch during testing. 5325 if (free_regions_coming()) { 5326 return; 5327 } 5328 5329 // Make sure we append the secondary_free_list on the free_list so 5330 // that all free regions we will come across can be safely 5331 // attributed to the free_list. 5332 append_secondary_free_list_if_not_empty_with_lock(); 5333 5334 // Finally, make sure that the region accounting in the lists is 5335 // consistent with what we see in the heap. 5336 _humongous_set.verify_start(); 5337 _free_list.verify_start(); 5338 5339 VerifyRegionListsClosure cl(&_humongous_set, &_free_list); 5340 heap_region_iterate(&cl); 5341 5342 _humongous_set.verify_end(); 5343 _free_list.verify_end(); 5344 }