1 /* 2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #if !defined(__clang_major__) && defined(__GNUC__) 26 // FIXME, formats have issues. Disable this macro definition, compile, and study warnings for more information. 27 #define ATTRIBUTE_PRINTF(x,y) 28 #endif 29 30 #include "precompiled.hpp" 31 #include "classfile/metadataOnStackMark.hpp" 32 #include "classfile/stringTable.hpp" 33 #include "code/codeCache.hpp" 34 #include "code/icBuffer.hpp" 35 #include "gc_implementation/g1/bufferingOopClosure.hpp" 36 #include "gc_implementation/g1/concurrentG1Refine.hpp" 37 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 38 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp" 39 #include "gc_implementation/g1/g1AllocRegion.inline.hpp" 40 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 41 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 42 #include "gc_implementation/g1/g1ErgoVerbose.hpp" 43 #include "gc_implementation/g1/g1EvacFailure.hpp" 44 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 45 #include "gc_implementation/g1/g1Log.hpp" 46 #include "gc_implementation/g1/g1MarkSweep.hpp" 47 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 48 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp" 49 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp" 50 #include "gc_implementation/g1/g1RemSet.inline.hpp" 51 #include "gc_implementation/g1/g1StringDedup.hpp" 52 #include "gc_implementation/g1/g1YCTypes.hpp" 53 #include "gc_implementation/g1/heapRegion.inline.hpp" 54 #include "gc_implementation/g1/heapRegionRemSet.hpp" 55 #include "gc_implementation/g1/heapRegionSet.inline.hpp" 56 #include "gc_implementation/g1/vm_operations_g1.hpp" 57 #include "gc_implementation/shared/gcHeapSummary.hpp" 58 #include "gc_implementation/shared/gcTimer.hpp" 59 #include "gc_implementation/shared/gcTrace.hpp" 60 #include "gc_implementation/shared/gcTraceTime.hpp" 61 #include "gc_implementation/shared/isGCActiveMark.hpp" 62 #include "memory/allocation.hpp" 63 #include "memory/gcLocker.inline.hpp" 64 #include "memory/generationSpec.hpp" 65 #include "memory/iterator.hpp" 66 #include "memory/referenceProcessor.hpp" 67 #include "oops/oop.inline.hpp" 68 #include "oops/oop.pcgc.inline.hpp" 69 #include "runtime/atomic.inline.hpp" 70 #include "runtime/orderAccess.inline.hpp" 71 #include "runtime/vmThread.hpp" 72 #include "utilities/globalDefinitions.hpp" 73 74 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0; 75 76 // turn it on so that the contents of the young list (scan-only / 77 // to-be-collected) are printed at "strategic" points before / during 78 // / after the collection --- this is useful for debugging 79 #define YOUNG_LIST_VERBOSE 0 80 // CURRENT STATUS 81 // This file is under construction. Search for "FIXME". 82 83 // INVARIANTS/NOTES 84 // 85 // All allocation activity covered by the G1CollectedHeap interface is 86 // serialized by acquiring the HeapLock. This happens in mem_allocate 87 // and allocate_new_tlab, which are the "entry" points to the 88 // allocation code from the rest of the JVM. (Note that this does not 89 // apply to TLAB allocation, which is not part of this interface: it 90 // is done by clients of this interface.) 91 92 // Notes on implementation of parallelism in different tasks. 93 // 94 // G1ParVerifyTask uses heap_region_par_iterate() for parallelism. 95 // The number of GC workers is passed to heap_region_par_iterate(). 96 // It does use run_task() which sets _n_workers in the task. 97 // G1ParTask executes g1_process_roots() -> 98 // SharedHeap::process_roots() which calls eventually to 99 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses 100 // SequentialSubTasksDone. SharedHeap::process_roots() also 101 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap). 102 // 103 104 // Local to this file. 105 106 class RefineCardTableEntryClosure: public CardTableEntryClosure { 107 bool _concurrent; 108 public: 109 RefineCardTableEntryClosure() : _concurrent(true) { } 110 111 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 112 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false); 113 // This path is executed by the concurrent refine or mutator threads, 114 // concurrently, and so we do not care if card_ptr contains references 115 // that point into the collection set. 116 assert(!oops_into_cset, "should be"); 117 118 if (_concurrent && SuspendibleThreadSet::should_yield()) { 119 // Caller will actually yield. 120 return false; 121 } 122 // Otherwise, we finished successfully; return true. 123 return true; 124 } 125 126 void set_concurrent(bool b) { _concurrent = b; } 127 }; 128 129 130 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure { 131 private: 132 size_t _num_processed; 133 134 public: 135 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { } 136 137 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 138 *card_ptr = CardTableModRefBS::dirty_card_val(); 139 _num_processed++; 140 return true; 141 } 142 143 size_t num_processed() const { return _num_processed; } 144 }; 145 146 YoungList::YoungList(G1CollectedHeap* g1h) : 147 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0), 148 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) { 149 guarantee(check_list_empty(false), "just making sure..."); 150 } 151 152 void YoungList::push_region(HeapRegion *hr) { 153 assert(!hr->is_young(), "should not already be young"); 154 assert(hr->get_next_young_region() == NULL, "cause it should!"); 155 156 hr->set_next_young_region(_head); 157 _head = hr; 158 159 _g1h->g1_policy()->set_region_eden(hr, (int) _length); 160 ++_length; 161 } 162 163 void YoungList::add_survivor_region(HeapRegion* hr) { 164 assert(hr->is_survivor(), "should be flagged as survivor region"); 165 assert(hr->get_next_young_region() == NULL, "cause it should!"); 166 167 hr->set_next_young_region(_survivor_head); 168 if (_survivor_head == NULL) { 169 _survivor_tail = hr; 170 } 171 _survivor_head = hr; 172 ++_survivor_length; 173 } 174 175 void YoungList::empty_list(HeapRegion* list) { 176 while (list != NULL) { 177 HeapRegion* next = list->get_next_young_region(); 178 list->set_next_young_region(NULL); 179 list->uninstall_surv_rate_group(); 180 // This is called before a Full GC and all the non-empty / 181 // non-humongous regions at the end of the Full GC will end up as 182 // old anyway. 183 list->set_old(); 184 list = next; 185 } 186 } 187 188 void YoungList::empty_list() { 189 assert(check_list_well_formed(), "young list should be well formed"); 190 191 empty_list(_head); 192 _head = NULL; 193 _length = 0; 194 195 empty_list(_survivor_head); 196 _survivor_head = NULL; 197 _survivor_tail = NULL; 198 _survivor_length = 0; 199 200 _last_sampled_rs_lengths = 0; 201 202 assert(check_list_empty(false), "just making sure..."); 203 } 204 205 bool YoungList::check_list_well_formed() { 206 bool ret = true; 207 208 uint length = 0; 209 HeapRegion* curr = _head; 210 HeapRegion* last = NULL; 211 while (curr != NULL) { 212 if (!curr->is_young()) { 213 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" " 214 "incorrectly tagged (y: %d, surv: %d)", 215 curr->bottom(), curr->end(), 216 curr->is_young(), curr->is_survivor()); 217 ret = false; 218 } 219 ++length; 220 last = curr; 221 curr = curr->get_next_young_region(); 222 } 223 ret = ret && (length == _length); 224 225 if (!ret) { 226 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!"); 227 gclog_or_tty->print_cr("### list has %u entries, _length is %u", 228 length, _length); 229 } 230 231 return ret; 232 } 233 234 bool YoungList::check_list_empty(bool check_sample) { 235 bool ret = true; 236 237 if (_length != 0) { 238 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u", 239 _length); 240 ret = false; 241 } 242 if (check_sample && _last_sampled_rs_lengths != 0) { 243 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths"); 244 ret = false; 245 } 246 if (_head != NULL) { 247 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head"); 248 ret = false; 249 } 250 if (!ret) { 251 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty"); 252 } 253 254 return ret; 255 } 256 257 void 258 YoungList::rs_length_sampling_init() { 259 _sampled_rs_lengths = 0; 260 _curr = _head; 261 } 262 263 bool 264 YoungList::rs_length_sampling_more() { 265 return _curr != NULL; 266 } 267 268 void 269 YoungList::rs_length_sampling_next() { 270 assert( _curr != NULL, "invariant" ); 271 size_t rs_length = _curr->rem_set()->occupied(); 272 273 _sampled_rs_lengths += rs_length; 274 275 // The current region may not yet have been added to the 276 // incremental collection set (it gets added when it is 277 // retired as the current allocation region). 278 if (_curr->in_collection_set()) { 279 // Update the collection set policy information for this region 280 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length); 281 } 282 283 _curr = _curr->get_next_young_region(); 284 if (_curr == NULL) { 285 _last_sampled_rs_lengths = _sampled_rs_lengths; 286 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths); 287 } 288 } 289 290 void 291 YoungList::reset_auxilary_lists() { 292 guarantee( is_empty(), "young list should be empty" ); 293 assert(check_list_well_formed(), "young list should be well formed"); 294 295 // Add survivor regions to SurvRateGroup. 296 _g1h->g1_policy()->note_start_adding_survivor_regions(); 297 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */); 298 299 int young_index_in_cset = 0; 300 for (HeapRegion* curr = _survivor_head; 301 curr != NULL; 302 curr = curr->get_next_young_region()) { 303 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset); 304 305 // The region is a non-empty survivor so let's add it to 306 // the incremental collection set for the next evacuation 307 // pause. 308 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr); 309 young_index_in_cset += 1; 310 } 311 assert((uint) young_index_in_cset == _survivor_length, "post-condition"); 312 _g1h->g1_policy()->note_stop_adding_survivor_regions(); 313 314 _head = _survivor_head; 315 _length = _survivor_length; 316 if (_survivor_head != NULL) { 317 assert(_survivor_tail != NULL, "cause it shouldn't be"); 318 assert(_survivor_length > 0, "invariant"); 319 _survivor_tail->set_next_young_region(NULL); 320 } 321 322 // Don't clear the survivor list handles until the start of 323 // the next evacuation pause - we need it in order to re-tag 324 // the survivor regions from this evacuation pause as 'young' 325 // at the start of the next. 326 327 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */); 328 329 assert(check_list_well_formed(), "young list should be well formed"); 330 } 331 332 void YoungList::print() { 333 HeapRegion* lists[] = {_head, _survivor_head}; 334 const char* names[] = {"YOUNG", "SURVIVOR"}; 335 336 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) { 337 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]); 338 HeapRegion *curr = lists[list]; 339 if (curr == NULL) 340 gclog_or_tty->print_cr(" empty"); 341 while (curr != NULL) { 342 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d", 343 HR_FORMAT_PARAMS(curr), 344 curr->prev_top_at_mark_start(), 345 curr->next_top_at_mark_start(), 346 curr->age_in_surv_rate_group_cond()); 347 curr = curr->get_next_young_region(); 348 } 349 } 350 351 gclog_or_tty->cr(); 352 } 353 354 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) { 355 OtherRegionsTable::invalidate(start_idx, num_regions); 356 } 357 358 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) { 359 // The from card cache is not the memory that is actually committed. So we cannot 360 // take advantage of the zero_filled parameter. 361 reset_from_card_cache(start_idx, num_regions); 362 } 363 364 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr) 365 { 366 // Claim the right to put the region on the dirty cards region list 367 // by installing a self pointer. 368 HeapRegion* next = hr->get_next_dirty_cards_region(); 369 if (next == NULL) { 370 HeapRegion* res = (HeapRegion*) 371 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(), 372 NULL); 373 if (res == NULL) { 374 HeapRegion* head; 375 do { 376 // Put the region to the dirty cards region list. 377 head = _dirty_cards_region_list; 378 next = (HeapRegion*) 379 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head); 380 if (next == head) { 381 assert(hr->get_next_dirty_cards_region() == hr, 382 "hr->get_next_dirty_cards_region() != hr"); 383 if (next == NULL) { 384 // The last region in the list points to itself. 385 hr->set_next_dirty_cards_region(hr); 386 } else { 387 hr->set_next_dirty_cards_region(next); 388 } 389 } 390 } while (next != head); 391 } 392 } 393 } 394 395 HeapRegion* G1CollectedHeap::pop_dirty_cards_region() 396 { 397 HeapRegion* head; 398 HeapRegion* hr; 399 do { 400 head = _dirty_cards_region_list; 401 if (head == NULL) { 402 return NULL; 403 } 404 HeapRegion* new_head = head->get_next_dirty_cards_region(); 405 if (head == new_head) { 406 // The last region. 407 new_head = NULL; 408 } 409 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list, 410 head); 411 } while (hr != head); 412 assert(hr != NULL, "invariant"); 413 hr->set_next_dirty_cards_region(NULL); 414 return hr; 415 } 416 417 #ifdef ASSERT 418 // A region is added to the collection set as it is retired 419 // so an address p can point to a region which will be in the 420 // collection set but has not yet been retired. This method 421 // therefore is only accurate during a GC pause after all 422 // regions have been retired. It is used for debugging 423 // to check if an nmethod has references to objects that can 424 // be move during a partial collection. Though it can be 425 // inaccurate, it is sufficient for G1 because the conservative 426 // implementation of is_scavengable() for G1 will indicate that 427 // all nmethods must be scanned during a partial collection. 428 bool G1CollectedHeap::is_in_partial_collection(const void* p) { 429 if (p == NULL) { 430 return false; 431 } 432 return heap_region_containing(p)->in_collection_set(); 433 } 434 #endif 435 436 // Returns true if the reference points to an object that 437 // can move in an incremental collection. 438 bool G1CollectedHeap::is_scavengable(const void* p) { 439 HeapRegion* hr = heap_region_containing(p); 440 return !hr->is_humongous(); 441 } 442 443 // Private class members. 444 445 G1CollectedHeap* G1CollectedHeap::_g1h; 446 447 // Private methods. 448 449 HeapRegion* 450 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) { 451 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 452 while (!_secondary_free_list.is_empty() || free_regions_coming()) { 453 if (!_secondary_free_list.is_empty()) { 454 if (G1ConcRegionFreeingVerbose) { 455 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 456 "secondary_free_list has %u entries", 457 _secondary_free_list.length()); 458 } 459 // It looks as if there are free regions available on the 460 // secondary_free_list. Let's move them to the free_list and try 461 // again to allocate from it. 462 append_secondary_free_list(); 463 464 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not " 465 "empty we should have moved at least one entry to the free_list"); 466 HeapRegion* res = _hrm.allocate_free_region(is_old); 467 if (G1ConcRegionFreeingVerbose) { 468 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 469 "allocated "HR_FORMAT" from secondary_free_list", 470 HR_FORMAT_PARAMS(res)); 471 } 472 return res; 473 } 474 475 // Wait here until we get notified either when (a) there are no 476 // more free regions coming or (b) some regions have been moved on 477 // the secondary_free_list. 478 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 479 } 480 481 if (G1ConcRegionFreeingVerbose) { 482 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 483 "could not allocate from secondary_free_list"); 484 } 485 return NULL; 486 } 487 488 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) { 489 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords, 490 "the only time we use this to allocate a humongous region is " 491 "when we are allocating a single humongous region"); 492 493 HeapRegion* res; 494 if (G1StressConcRegionFreeing) { 495 if (!_secondary_free_list.is_empty()) { 496 if (G1ConcRegionFreeingVerbose) { 497 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 498 "forced to look at the secondary_free_list"); 499 } 500 res = new_region_try_secondary_free_list(is_old); 501 if (res != NULL) { 502 return res; 503 } 504 } 505 } 506 507 res = _hrm.allocate_free_region(is_old); 508 509 if (res == NULL) { 510 if (G1ConcRegionFreeingVerbose) { 511 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : " 512 "res == NULL, trying the secondary_free_list"); 513 } 514 res = new_region_try_secondary_free_list(is_old); 515 } 516 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) { 517 // Currently, only attempts to allocate GC alloc regions set 518 // do_expand to true. So, we should only reach here during a 519 // safepoint. If this assumption changes we might have to 520 // reconsider the use of _expand_heap_after_alloc_failure. 521 assert(SafepointSynchronize::is_at_safepoint(), "invariant"); 522 523 ergo_verbose1(ErgoHeapSizing, 524 "attempt heap expansion", 525 ergo_format_reason("region allocation request failed") 526 ergo_format_byte("allocation request"), 527 word_size * HeapWordSize); 528 if (expand(word_size * HeapWordSize)) { 529 // Given that expand() succeeded in expanding the heap, and we 530 // always expand the heap by an amount aligned to the heap 531 // region size, the free list should in theory not be empty. 532 // In either case allocate_free_region() will check for NULL. 533 res = _hrm.allocate_free_region(is_old); 534 } else { 535 _expand_heap_after_alloc_failure = false; 536 } 537 } 538 return res; 539 } 540 541 HeapWord* 542 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first, 543 uint num_regions, 544 size_t word_size, 545 AllocationContext_t context) { 546 assert(first != G1_NO_HRM_INDEX, "pre-condition"); 547 assert(is_humongous(word_size), "word_size should be humongous"); 548 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition"); 549 550 // Index of last region in the series + 1. 551 uint last = first + num_regions; 552 553 // We need to initialize the region(s) we just discovered. This is 554 // a bit tricky given that it can happen concurrently with 555 // refinement threads refining cards on these regions and 556 // potentially wanting to refine the BOT as they are scanning 557 // those cards (this can happen shortly after a cleanup; see CR 558 // 6991377). So we have to set up the region(s) carefully and in 559 // a specific order. 560 561 // The word size sum of all the regions we will allocate. 562 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords; 563 assert(word_size <= word_size_sum, "sanity"); 564 565 // This will be the "starts humongous" region. 566 HeapRegion* first_hr = region_at(first); 567 // The header of the new object will be placed at the bottom of 568 // the first region. 569 HeapWord* new_obj = first_hr->bottom(); 570 // This will be the new end of the first region in the series that 571 // should also match the end of the last region in the series. 572 HeapWord* new_end = new_obj + word_size_sum; 573 // This will be the new top of the first region that will reflect 574 // this allocation. 575 HeapWord* new_top = new_obj + word_size; 576 577 // First, we need to zero the header of the space that we will be 578 // allocating. When we update top further down, some refinement 579 // threads might try to scan the region. By zeroing the header we 580 // ensure that any thread that will try to scan the region will 581 // come across the zero klass word and bail out. 582 // 583 // NOTE: It would not have been correct to have used 584 // CollectedHeap::fill_with_object() and make the space look like 585 // an int array. The thread that is doing the allocation will 586 // later update the object header to a potentially different array 587 // type and, for a very short period of time, the klass and length 588 // fields will be inconsistent. This could cause a refinement 589 // thread to calculate the object size incorrectly. 590 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0); 591 592 // We will set up the first region as "starts humongous". This 593 // will also update the BOT covering all the regions to reflect 594 // that there is a single object that starts at the bottom of the 595 // first region. 596 first_hr->set_starts_humongous(new_top, new_end); 597 first_hr->set_allocation_context(context); 598 // Then, if there are any, we will set up the "continues 599 // humongous" regions. 600 HeapRegion* hr = NULL; 601 for (uint i = first + 1; i < last; ++i) { 602 hr = region_at(i); 603 hr->set_continues_humongous(first_hr); 604 hr->set_allocation_context(context); 605 } 606 // If we have "continues humongous" regions (hr != NULL), then the 607 // end of the last one should match new_end. 608 assert(hr == NULL || hr->end() == new_end, "sanity"); 609 610 // Up to this point no concurrent thread would have been able to 611 // do any scanning on any region in this series. All the top 612 // fields still point to bottom, so the intersection between 613 // [bottom,top] and [card_start,card_end] will be empty. Before we 614 // update the top fields, we'll do a storestore to make sure that 615 // no thread sees the update to top before the zeroing of the 616 // object header and the BOT initialization. 617 OrderAccess::storestore(); 618 619 // Now that the BOT and the object header have been initialized, 620 // we can update top of the "starts humongous" region. 621 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(), 622 "new_top should be in this region"); 623 first_hr->set_top(new_top); 624 if (_hr_printer.is_active()) { 625 HeapWord* bottom = first_hr->bottom(); 626 HeapWord* end = first_hr->orig_end(); 627 if ((first + 1) == last) { 628 // the series has a single humongous region 629 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top); 630 } else { 631 // the series has more than one humongous regions 632 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end); 633 } 634 } 635 636 // Now, we will update the top fields of the "continues humongous" 637 // regions. The reason we need to do this is that, otherwise, 638 // these regions would look empty and this will confuse parts of 639 // G1. For example, the code that looks for a consecutive number 640 // of empty regions will consider them empty and try to 641 // re-allocate them. We can extend is_empty() to also include 642 // !is_continues_humongous(), but it is easier to just update the top 643 // fields here. The way we set top for all regions (i.e., top == 644 // end for all regions but the last one, top == new_top for the 645 // last one) is actually used when we will free up the humongous 646 // region in free_humongous_region(). 647 hr = NULL; 648 for (uint i = first + 1; i < last; ++i) { 649 hr = region_at(i); 650 if ((i + 1) == last) { 651 // last continues humongous region 652 assert(hr->bottom() < new_top && new_top <= hr->end(), 653 "new_top should fall on this region"); 654 hr->set_top(new_top); 655 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top); 656 } else { 657 // not last one 658 assert(new_top > hr->end(), "new_top should be above this region"); 659 hr->set_top(hr->end()); 660 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end()); 661 } 662 } 663 // If we have continues humongous regions (hr != NULL), then the 664 // end of the last one should match new_end and its top should 665 // match new_top. 666 assert(hr == NULL || 667 (hr->end() == new_end && hr->top() == new_top), "sanity"); 668 check_bitmaps("Humongous Region Allocation", first_hr); 669 670 assert(first_hr->used() == word_size * HeapWordSize, "invariant"); 671 _allocator->increase_used(first_hr->used()); 672 _humongous_set.add(first_hr); 673 674 return new_obj; 675 } 676 677 // If could fit into free regions w/o expansion, try. 678 // Otherwise, if can expand, do so. 679 // Otherwise, if using ex regions might help, try with ex given back. 680 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) { 681 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 682 683 verify_region_sets_optional(); 684 685 uint first = G1_NO_HRM_INDEX; 686 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords); 687 688 if (obj_regions == 1) { 689 // Only one region to allocate, try to use a fast path by directly allocating 690 // from the free lists. Do not try to expand here, we will potentially do that 691 // later. 692 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */); 693 if (hr != NULL) { 694 first = hr->hrm_index(); 695 } 696 } else { 697 // We can't allocate humongous regions spanning more than one region while 698 // cleanupComplete() is running, since some of the regions we find to be 699 // empty might not yet be added to the free list. It is not straightforward 700 // to know in which list they are on so that we can remove them. We only 701 // need to do this if we need to allocate more than one region to satisfy the 702 // current humongous allocation request. If we are only allocating one region 703 // we use the one-region region allocation code (see above), that already 704 // potentially waits for regions from the secondary free list. 705 wait_while_free_regions_coming(); 706 append_secondary_free_list_if_not_empty_with_lock(); 707 708 // Policy: Try only empty regions (i.e. already committed first). Maybe we 709 // are lucky enough to find some. 710 first = _hrm.find_contiguous_only_empty(obj_regions); 711 if (first != G1_NO_HRM_INDEX) { 712 _hrm.allocate_free_regions_starting_at(first, obj_regions); 713 } 714 } 715 716 if (first == G1_NO_HRM_INDEX) { 717 // Policy: We could not find enough regions for the humongous object in the 718 // free list. Look through the heap to find a mix of free and uncommitted regions. 719 // If so, try expansion. 720 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions); 721 if (first != G1_NO_HRM_INDEX) { 722 // We found something. Make sure these regions are committed, i.e. expand 723 // the heap. Alternatively we could do a defragmentation GC. 724 ergo_verbose1(ErgoHeapSizing, 725 "attempt heap expansion", 726 ergo_format_reason("humongous allocation request failed") 727 ergo_format_byte("allocation request"), 728 word_size * HeapWordSize); 729 730 _hrm.expand_at(first, obj_regions); 731 g1_policy()->record_new_heap_size(num_regions()); 732 733 #ifdef ASSERT 734 for (uint i = first; i < first + obj_regions; ++i) { 735 HeapRegion* hr = region_at(i); 736 assert(hr->is_free(), "sanity"); 737 assert(hr->is_empty(), "sanity"); 738 assert(is_on_master_free_list(hr), "sanity"); 739 } 740 #endif 741 _hrm.allocate_free_regions_starting_at(first, obj_regions); 742 } else { 743 // Policy: Potentially trigger a defragmentation GC. 744 } 745 } 746 747 HeapWord* result = NULL; 748 if (first != G1_NO_HRM_INDEX) { 749 result = humongous_obj_allocate_initialize_regions(first, obj_regions, 750 word_size, context); 751 assert(result != NULL, "it should always return a valid result"); 752 753 // A successful humongous object allocation changes the used space 754 // information of the old generation so we need to recalculate the 755 // sizes and update the jstat counters here. 756 g1mm()->update_sizes(); 757 } 758 759 verify_region_sets_optional(); 760 761 return result; 762 } 763 764 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) { 765 assert_heap_not_locked_and_not_at_safepoint(); 766 assert(!is_humongous(word_size), "we do not allow humongous TLABs"); 767 768 unsigned int dummy_gc_count_before; 769 int dummy_gclocker_retry_count = 0; 770 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count); 771 } 772 773 HeapWord* 774 G1CollectedHeap::mem_allocate(size_t word_size, 775 bool* gc_overhead_limit_was_exceeded) { 776 assert_heap_not_locked_and_not_at_safepoint(); 777 778 // Loop until the allocation is satisfied, or unsatisfied after GC. 779 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) { 780 unsigned int gc_count_before; 781 782 HeapWord* result = NULL; 783 if (!is_humongous(word_size)) { 784 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count); 785 } else { 786 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count); 787 } 788 if (result != NULL) { 789 return result; 790 } 791 792 // Create the garbage collection operation... 793 VM_G1CollectForAllocation op(gc_count_before, word_size); 794 op.set_allocation_context(AllocationContext::current()); 795 796 // ...and get the VM thread to execute it. 797 VMThread::execute(&op); 798 799 if (op.prologue_succeeded() && op.pause_succeeded()) { 800 // If the operation was successful we'll return the result even 801 // if it is NULL. If the allocation attempt failed immediately 802 // after a Full GC, it's unlikely we'll be able to allocate now. 803 HeapWord* result = op.result(); 804 if (result != NULL && !is_humongous(word_size)) { 805 // Allocations that take place on VM operations do not do any 806 // card dirtying and we have to do it here. We only have to do 807 // this for non-humongous allocations, though. 808 dirty_young_block(result, word_size); 809 } 810 return result; 811 } else { 812 if (gclocker_retry_count > GCLockerRetryAllocationCount) { 813 return NULL; 814 } 815 assert(op.result() == NULL, 816 "the result should be NULL if the VM op did not succeed"); 817 } 818 819 // Give a warning if we seem to be looping forever. 820 if ((QueuedAllocationWarningCount > 0) && 821 (try_count % QueuedAllocationWarningCount == 0)) { 822 warning("G1CollectedHeap::mem_allocate retries %d times", try_count); 823 } 824 } 825 826 ShouldNotReachHere(); 827 return NULL; 828 } 829 830 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size, 831 AllocationContext_t context, 832 unsigned int *gc_count_before_ret, 833 int* gclocker_retry_count_ret) { 834 // Make sure you read the note in attempt_allocation_humongous(). 835 836 assert_heap_not_locked_and_not_at_safepoint(); 837 assert(!is_humongous(word_size), "attempt_allocation_slow() should not " 838 "be called for humongous allocation requests"); 839 840 // We should only get here after the first-level allocation attempt 841 // (attempt_allocation()) failed to allocate. 842 843 // We will loop until a) we manage to successfully perform the 844 // allocation or b) we successfully schedule a collection which 845 // fails to perform the allocation. b) is the only case when we'll 846 // return NULL. 847 HeapWord* result = NULL; 848 for (int try_count = 1; /* we'll return */; try_count += 1) { 849 bool should_try_gc; 850 unsigned int gc_count_before; 851 852 { 853 MutexLockerEx x(Heap_lock); 854 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 855 false /* bot_updates */); 856 if (result != NULL) { 857 return result; 858 } 859 860 // If we reach here, attempt_allocation_locked() above failed to 861 // allocate a new region. So the mutator alloc region should be NULL. 862 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here"); 863 864 if (GC_locker::is_active_and_needs_gc()) { 865 if (g1_policy()->can_expand_young_list()) { 866 // No need for an ergo verbose message here, 867 // can_expand_young_list() does this when it returns true. 868 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size, 869 false /* bot_updates */); 870 if (result != NULL) { 871 return result; 872 } 873 } 874 should_try_gc = false; 875 } else { 876 // The GCLocker may not be active but the GCLocker initiated 877 // GC may not yet have been performed (GCLocker::needs_gc() 878 // returns true). In this case we do not try this GC and 879 // wait until the GCLocker initiated GC is performed, and 880 // then retry the allocation. 881 if (GC_locker::needs_gc()) { 882 should_try_gc = false; 883 } else { 884 // Read the GC count while still holding the Heap_lock. 885 gc_count_before = total_collections(); 886 should_try_gc = true; 887 } 888 } 889 } 890 891 if (should_try_gc) { 892 bool succeeded; 893 result = do_collection_pause(word_size, gc_count_before, &succeeded, 894 GCCause::_g1_inc_collection_pause); 895 if (result != NULL) { 896 assert(succeeded, "only way to get back a non-NULL result"); 897 return result; 898 } 899 900 if (succeeded) { 901 // If we get here we successfully scheduled a collection which 902 // failed to allocate. No point in trying to allocate 903 // further. We'll just return NULL. 904 MutexLockerEx x(Heap_lock); 905 *gc_count_before_ret = total_collections(); 906 return NULL; 907 } 908 } else { 909 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 910 MutexLockerEx x(Heap_lock); 911 *gc_count_before_ret = total_collections(); 912 return NULL; 913 } 914 // The GCLocker is either active or the GCLocker initiated 915 // GC has not yet been performed. Stall until it is and 916 // then retry the allocation. 917 GC_locker::stall_until_clear(); 918 (*gclocker_retry_count_ret) += 1; 919 } 920 921 // We can reach here if we were unsuccessful in scheduling a 922 // collection (because another thread beat us to it) or if we were 923 // stalled due to the GC locker. In either can we should retry the 924 // allocation attempt in case another thread successfully 925 // performed a collection and reclaimed enough space. We do the 926 // first attempt (without holding the Heap_lock) here and the 927 // follow-on attempt will be at the start of the next loop 928 // iteration (after taking the Heap_lock). 929 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size, 930 false /* bot_updates */); 931 if (result != NULL) { 932 return result; 933 } 934 935 // Give a warning if we seem to be looping forever. 936 if ((QueuedAllocationWarningCount > 0) && 937 (try_count % QueuedAllocationWarningCount == 0)) { 938 warning("G1CollectedHeap::attempt_allocation_slow() " 939 "retries %d times", try_count); 940 } 941 } 942 943 ShouldNotReachHere(); 944 return NULL; 945 } 946 947 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size, 948 unsigned int * gc_count_before_ret, 949 int* gclocker_retry_count_ret) { 950 // The structure of this method has a lot of similarities to 951 // attempt_allocation_slow(). The reason these two were not merged 952 // into a single one is that such a method would require several "if 953 // allocation is not humongous do this, otherwise do that" 954 // conditional paths which would obscure its flow. In fact, an early 955 // version of this code did use a unified method which was harder to 956 // follow and, as a result, it had subtle bugs that were hard to 957 // track down. So keeping these two methods separate allows each to 958 // be more readable. It will be good to keep these two in sync as 959 // much as possible. 960 961 assert_heap_not_locked_and_not_at_safepoint(); 962 assert(is_humongous(word_size), "attempt_allocation_humongous() " 963 "should only be called for humongous allocations"); 964 965 // Humongous objects can exhaust the heap quickly, so we should check if we 966 // need to start a marking cycle at each humongous object allocation. We do 967 // the check before we do the actual allocation. The reason for doing it 968 // before the allocation is that we avoid having to keep track of the newly 969 // allocated memory while we do a GC. 970 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation", 971 word_size)) { 972 collect(GCCause::_g1_humongous_allocation); 973 } 974 975 // We will loop until a) we manage to successfully perform the 976 // allocation or b) we successfully schedule a collection which 977 // fails to perform the allocation. b) is the only case when we'll 978 // return NULL. 979 HeapWord* result = NULL; 980 for (int try_count = 1; /* we'll return */; try_count += 1) { 981 bool should_try_gc; 982 unsigned int gc_count_before; 983 984 { 985 MutexLockerEx x(Heap_lock); 986 987 // Given that humongous objects are not allocated in young 988 // regions, we'll first try to do the allocation without doing a 989 // collection hoping that there's enough space in the heap. 990 result = humongous_obj_allocate(word_size, AllocationContext::current()); 991 if (result != NULL) { 992 return result; 993 } 994 995 if (GC_locker::is_active_and_needs_gc()) { 996 should_try_gc = false; 997 } else { 998 // The GCLocker may not be active but the GCLocker initiated 999 // GC may not yet have been performed (GCLocker::needs_gc() 1000 // returns true). In this case we do not try this GC and 1001 // wait until the GCLocker initiated GC is performed, and 1002 // then retry the allocation. 1003 if (GC_locker::needs_gc()) { 1004 should_try_gc = false; 1005 } else { 1006 // Read the GC count while still holding the Heap_lock. 1007 gc_count_before = total_collections(); 1008 should_try_gc = true; 1009 } 1010 } 1011 } 1012 1013 if (should_try_gc) { 1014 // If we failed to allocate the humongous object, we should try to 1015 // do a collection pause (if we're allowed) in case it reclaims 1016 // enough space for the allocation to succeed after the pause. 1017 1018 bool succeeded; 1019 result = do_collection_pause(word_size, gc_count_before, &succeeded, 1020 GCCause::_g1_humongous_allocation); 1021 if (result != NULL) { 1022 assert(succeeded, "only way to get back a non-NULL result"); 1023 return result; 1024 } 1025 1026 if (succeeded) { 1027 // If we get here we successfully scheduled a collection which 1028 // failed to allocate. No point in trying to allocate 1029 // further. We'll just return NULL. 1030 MutexLockerEx x(Heap_lock); 1031 *gc_count_before_ret = total_collections(); 1032 return NULL; 1033 } 1034 } else { 1035 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) { 1036 MutexLockerEx x(Heap_lock); 1037 *gc_count_before_ret = total_collections(); 1038 return NULL; 1039 } 1040 // The GCLocker is either active or the GCLocker initiated 1041 // GC has not yet been performed. Stall until it is and 1042 // then retry the allocation. 1043 GC_locker::stall_until_clear(); 1044 (*gclocker_retry_count_ret) += 1; 1045 } 1046 1047 // We can reach here if we were unsuccessful in scheduling a 1048 // collection (because another thread beat us to it) or if we were 1049 // stalled due to the GC locker. In either can we should retry the 1050 // allocation attempt in case another thread successfully 1051 // performed a collection and reclaimed enough space. Give a 1052 // warning if we seem to be looping forever. 1053 1054 if ((QueuedAllocationWarningCount > 0) && 1055 (try_count % QueuedAllocationWarningCount == 0)) { 1056 warning("G1CollectedHeap::attempt_allocation_humongous() " 1057 "retries %d times", try_count); 1058 } 1059 } 1060 1061 ShouldNotReachHere(); 1062 return NULL; 1063 } 1064 1065 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size, 1066 AllocationContext_t context, 1067 bool expect_null_mutator_alloc_region) { 1068 assert_at_safepoint(true /* should_be_vm_thread */); 1069 assert(_allocator->mutator_alloc_region(context)->get() == NULL || 1070 !expect_null_mutator_alloc_region, 1071 "the current alloc region was unexpectedly found to be non-NULL"); 1072 1073 if (!is_humongous(word_size)) { 1074 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size, 1075 false /* bot_updates */); 1076 } else { 1077 HeapWord* result = humongous_obj_allocate(word_size, context); 1078 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) { 1079 g1_policy()->set_initiate_conc_mark_if_possible(); 1080 } 1081 return result; 1082 } 1083 1084 ShouldNotReachHere(); 1085 } 1086 1087 class PostMCRemSetClearClosure: public HeapRegionClosure { 1088 G1CollectedHeap* _g1h; 1089 ModRefBarrierSet* _mr_bs; 1090 public: 1091 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) : 1092 _g1h(g1h), _mr_bs(mr_bs) {} 1093 1094 bool doHeapRegion(HeapRegion* r) { 1095 HeapRegionRemSet* hrrs = r->rem_set(); 1096 1097 if (r->is_continues_humongous()) { 1098 // We'll assert that the strong code root list and RSet is empty 1099 assert(hrrs->strong_code_roots_list_length() == 0, "sanity"); 1100 assert(hrrs->occupied() == 0, "RSet should be empty"); 1101 return false; 1102 } 1103 1104 _g1h->reset_gc_time_stamps(r); 1105 hrrs->clear(); 1106 // You might think here that we could clear just the cards 1107 // corresponding to the used region. But no: if we leave a dirty card 1108 // in a region we might allocate into, then it would prevent that card 1109 // from being enqueued, and cause it to be missed. 1110 // Re: the performance cost: we shouldn't be doing full GC anyway! 1111 _mr_bs->clear(MemRegion(r->bottom(), r->end())); 1112 1113 return false; 1114 } 1115 }; 1116 1117 void G1CollectedHeap::clear_rsets_post_compaction() { 1118 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set()); 1119 heap_region_iterate(&rs_clear); 1120 } 1121 1122 class RebuildRSOutOfRegionClosure: public HeapRegionClosure { 1123 G1CollectedHeap* _g1h; 1124 UpdateRSOopClosure _cl; 1125 int _worker_i; 1126 public: 1127 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) : 1128 _cl(g1->g1_rem_set(), worker_i), 1129 _worker_i(worker_i), 1130 _g1h(g1) 1131 { } 1132 1133 bool doHeapRegion(HeapRegion* r) { 1134 if (!r->is_continues_humongous()) { 1135 _cl.set_from(r); 1136 r->oop_iterate(&_cl); 1137 } 1138 return false; 1139 } 1140 }; 1141 1142 class ParRebuildRSTask: public AbstractGangTask { 1143 G1CollectedHeap* _g1; 1144 HeapRegionClaimer _hrclaimer; 1145 1146 public: 1147 ParRebuildRSTask(G1CollectedHeap* g1) : 1148 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {} 1149 1150 void work(uint worker_id) { 1151 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id); 1152 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer); 1153 } 1154 }; 1155 1156 class PostCompactionPrinterClosure: public HeapRegionClosure { 1157 private: 1158 G1HRPrinter* _hr_printer; 1159 public: 1160 bool doHeapRegion(HeapRegion* hr) { 1161 assert(!hr->is_young(), "not expecting to find young regions"); 1162 if (hr->is_free()) { 1163 // We only generate output for non-empty regions. 1164 } else if (hr->is_starts_humongous()) { 1165 if (hr->region_num() == 1) { 1166 // single humongous region 1167 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous); 1168 } else { 1169 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous); 1170 } 1171 } else if (hr->is_continues_humongous()) { 1172 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous); 1173 } else if (hr->is_old()) { 1174 _hr_printer->post_compaction(hr, G1HRPrinter::Old); 1175 } else { 1176 ShouldNotReachHere(); 1177 } 1178 return false; 1179 } 1180 1181 PostCompactionPrinterClosure(G1HRPrinter* hr_printer) 1182 : _hr_printer(hr_printer) { } 1183 }; 1184 1185 void G1CollectedHeap::print_hrm_post_compaction() { 1186 PostCompactionPrinterClosure cl(hr_printer()); 1187 heap_region_iterate(&cl); 1188 } 1189 1190 bool G1CollectedHeap::do_collection(bool explicit_gc, 1191 bool clear_all_soft_refs, 1192 size_t word_size) { 1193 assert_at_safepoint(true /* should_be_vm_thread */); 1194 1195 if (GC_locker::check_active_before_gc()) { 1196 return false; 1197 } 1198 1199 STWGCTimer* gc_timer = G1MarkSweep::gc_timer(); 1200 gc_timer->register_gc_start(); 1201 1202 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer(); 1203 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start()); 1204 1205 SvcGCMarker sgcm(SvcGCMarker::FULL); 1206 ResourceMark rm; 1207 1208 print_heap_before_gc(); 1209 trace_heap_before_gc(gc_tracer); 1210 1211 size_t metadata_prev_used = MetaspaceAux::used_bytes(); 1212 1213 verify_region_sets_optional(); 1214 1215 const bool do_clear_all_soft_refs = clear_all_soft_refs || 1216 collector_policy()->should_clear_all_soft_refs(); 1217 1218 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy()); 1219 1220 { 1221 IsGCActiveMark x; 1222 1223 // Timing 1224 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant"); 1225 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 1226 1227 { 1228 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id()); 1229 TraceCollectorStats tcs(g1mm()->full_collection_counters()); 1230 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause()); 1231 1232 double start = os::elapsedTime(); 1233 g1_policy()->record_full_collection_start(); 1234 1235 // Note: When we have a more flexible GC logging framework that 1236 // allows us to add optional attributes to a GC log record we 1237 // could consider timing and reporting how long we wait in the 1238 // following two methods. 1239 wait_while_free_regions_coming(); 1240 // If we start the compaction before the CM threads finish 1241 // scanning the root regions we might trip them over as we'll 1242 // be moving objects / updating references. So let's wait until 1243 // they are done. By telling them to abort, they should complete 1244 // early. 1245 _cm->root_regions()->abort(); 1246 _cm->root_regions()->wait_until_scan_finished(); 1247 append_secondary_free_list_if_not_empty_with_lock(); 1248 1249 gc_prologue(true); 1250 increment_total_collections(true /* full gc */); 1251 increment_old_marking_cycles_started(); 1252 1253 assert(used() == recalculate_used(), "Should be equal"); 1254 1255 verify_before_gc(); 1256 1257 check_bitmaps("Full GC Start"); 1258 pre_full_gc_dump(gc_timer); 1259 1260 COMPILER2_PRESENT(DerivedPointerTable::clear()); 1261 1262 // Disable discovery and empty the discovered lists 1263 // for the CM ref processor. 1264 ref_processor_cm()->disable_discovery(); 1265 ref_processor_cm()->abandon_partial_discovery(); 1266 ref_processor_cm()->verify_no_references_recorded(); 1267 1268 // Abandon current iterations of concurrent marking and concurrent 1269 // refinement, if any are in progress. We have to do this before 1270 // wait_until_scan_finished() below. 1271 concurrent_mark()->abort(); 1272 1273 // Make sure we'll choose a new allocation region afterwards. 1274 _allocator->release_mutator_alloc_region(); 1275 _allocator->abandon_gc_alloc_regions(); 1276 g1_rem_set()->cleanupHRRS(); 1277 1278 // We should call this after we retire any currently active alloc 1279 // regions so that all the ALLOC / RETIRE events are generated 1280 // before the start GC event. 1281 _hr_printer.start_gc(true /* full */, (size_t) total_collections()); 1282 1283 // We may have added regions to the current incremental collection 1284 // set between the last GC or pause and now. We need to clear the 1285 // incremental collection set and then start rebuilding it afresh 1286 // after this full GC. 1287 abandon_collection_set(g1_policy()->inc_cset_head()); 1288 g1_policy()->clear_incremental_cset(); 1289 g1_policy()->stop_incremental_cset_building(); 1290 1291 tear_down_region_sets(false /* free_list_only */); 1292 g1_policy()->set_gcs_are_young(true); 1293 1294 // See the comments in g1CollectedHeap.hpp and 1295 // G1CollectedHeap::ref_processing_init() about 1296 // how reference processing currently works in G1. 1297 1298 // Temporarily make discovery by the STW ref processor single threaded (non-MT). 1299 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false); 1300 1301 // Temporarily clear the STW ref processor's _is_alive_non_header field. 1302 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL); 1303 1304 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); 1305 ref_processor_stw()->setup_policy(do_clear_all_soft_refs); 1306 1307 // Do collection work 1308 { 1309 HandleMark hm; // Discard invalid handles created during gc 1310 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs); 1311 } 1312 1313 assert(num_free_regions() == 0, "we should not have added any free regions"); 1314 rebuild_region_sets(false /* free_list_only */); 1315 1316 // Enqueue any discovered reference objects that have 1317 // not been removed from the discovered lists. 1318 ref_processor_stw()->enqueue_discovered_references(); 1319 1320 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 1321 1322 MemoryService::track_memory_usage(); 1323 1324 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 1325 ref_processor_stw()->verify_no_references_recorded(); 1326 1327 // Delete metaspaces for unloaded class loaders and clean up loader_data graph 1328 ClassLoaderDataGraph::purge(); 1329 MetaspaceAux::verify_metrics(); 1330 1331 // Note: since we've just done a full GC, concurrent 1332 // marking is no longer active. Therefore we need not 1333 // re-enable reference discovery for the CM ref processor. 1334 // That will be done at the start of the next marking cycle. 1335 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition"); 1336 ref_processor_cm()->verify_no_references_recorded(); 1337 1338 reset_gc_time_stamp(); 1339 // Since everything potentially moved, we will clear all remembered 1340 // sets, and clear all cards. Later we will rebuild remembered 1341 // sets. We will also reset the GC time stamps of the regions. 1342 clear_rsets_post_compaction(); 1343 check_gc_time_stamps(); 1344 1345 // Resize the heap if necessary. 1346 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size); 1347 1348 if (_hr_printer.is_active()) { 1349 // We should do this after we potentially resize the heap so 1350 // that all the COMMIT / UNCOMMIT events are generated before 1351 // the end GC event. 1352 1353 print_hrm_post_compaction(); 1354 _hr_printer.end_gc(true /* full */, (size_t) total_collections()); 1355 } 1356 1357 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 1358 if (hot_card_cache->use_cache()) { 1359 hot_card_cache->reset_card_counts(); 1360 hot_card_cache->reset_hot_cache(); 1361 } 1362 1363 // Rebuild remembered sets of all regions. 1364 uint n_workers = 1365 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 1366 workers()->active_workers(), 1367 Threads::number_of_non_daemon_threads()); 1368 assert(UseDynamicNumberOfGCThreads || 1369 n_workers == workers()->total_workers(), 1370 "If not dynamic should be using all the workers"); 1371 workers()->set_active_workers(n_workers); 1372 // Set parallel threads in the heap (_n_par_threads) only 1373 // before a parallel phase and always reset it to 0 after 1374 // the phase so that the number of parallel threads does 1375 // no get carried forward to a serial phase where there 1376 // may be code that is "possibly_parallel". 1377 set_par_threads(n_workers); 1378 1379 ParRebuildRSTask rebuild_rs_task(this); 1380 assert(UseDynamicNumberOfGCThreads || 1381 workers()->active_workers() == workers()->total_workers(), 1382 "Unless dynamic should use total workers"); 1383 // Use the most recent number of active workers 1384 assert(workers()->active_workers() > 0, 1385 "Active workers not properly set"); 1386 set_par_threads(workers()->active_workers()); 1387 workers()->run_task(&rebuild_rs_task); 1388 set_par_threads(0); 1389 1390 // Rebuild the strong code root lists for each region 1391 rebuild_strong_code_roots(); 1392 1393 if (true) { // FIXME 1394 MetaspaceGC::compute_new_size(); 1395 } 1396 1397 #ifdef TRACESPINNING 1398 ParallelTaskTerminator::print_termination_counts(); 1399 #endif 1400 1401 // Discard all rset updates 1402 JavaThread::dirty_card_queue_set().abandon_logs(); 1403 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty"); 1404 1405 _young_list->reset_sampled_info(); 1406 // At this point there should be no regions in the 1407 // entire heap tagged as young. 1408 assert(check_young_list_empty(true /* check_heap */), 1409 "young list should be empty at this point"); 1410 1411 // Update the number of full collections that have been completed. 1412 increment_old_marking_cycles_completed(false /* concurrent */); 1413 1414 _hrm.verify_optional(); 1415 verify_region_sets_optional(); 1416 1417 verify_after_gc(); 1418 1419 // Clear the previous marking bitmap, if needed for bitmap verification. 1420 // Note we cannot do this when we clear the next marking bitmap in 1421 // ConcurrentMark::abort() above since VerifyDuringGC verifies the 1422 // objects marked during a full GC against the previous bitmap. 1423 // But we need to clear it before calling check_bitmaps below since 1424 // the full GC has compacted objects and updated TAMS but not updated 1425 // the prev bitmap. 1426 if (G1VerifyBitmaps) { 1427 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll(); 1428 } 1429 check_bitmaps("Full GC End"); 1430 1431 // Start a new incremental collection set for the next pause 1432 assert(g1_policy()->collection_set() == NULL, "must be"); 1433 g1_policy()->start_incremental_cset_building(); 1434 1435 clear_cset_fast_test(); 1436 1437 _allocator->init_mutator_alloc_region(); 1438 1439 double end = os::elapsedTime(); 1440 g1_policy()->record_full_collection_end(); 1441 1442 if (G1Log::fine()) { 1443 g1_policy()->print_heap_transition(); 1444 } 1445 1446 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 1447 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 1448 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 1449 // before any GC notifications are raised. 1450 g1mm()->update_sizes(); 1451 1452 gc_epilogue(true); 1453 } 1454 1455 if (G1Log::finer()) { 1456 g1_policy()->print_detailed_heap_transition(true /* full */); 1457 } 1458 1459 print_heap_after_gc(); 1460 trace_heap_after_gc(gc_tracer); 1461 1462 post_full_gc_dump(gc_timer); 1463 1464 gc_timer->register_gc_end(); 1465 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions()); 1466 } 1467 1468 return true; 1469 } 1470 1471 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) { 1472 // do_collection() will return whether it succeeded in performing 1473 // the GC. Currently, there is no facility on the 1474 // do_full_collection() API to notify the caller than the collection 1475 // did not succeed (e.g., because it was locked out by the GC 1476 // locker). So, right now, we'll ignore the return value. 1477 bool dummy = do_collection(true, /* explicit_gc */ 1478 clear_all_soft_refs, 1479 0 /* word_size */); 1480 } 1481 1482 // This code is mostly copied from TenuredGeneration. 1483 void 1484 G1CollectedHeap:: 1485 resize_if_necessary_after_full_collection(size_t word_size) { 1486 // Include the current allocation, if any, and bytes that will be 1487 // pre-allocated to support collections, as "used". 1488 const size_t used_after_gc = used(); 1489 const size_t capacity_after_gc = capacity(); 1490 const size_t free_after_gc = capacity_after_gc - used_after_gc; 1491 1492 // This is enforced in arguments.cpp. 1493 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, 1494 "otherwise the code below doesn't make sense"); 1495 1496 // We don't have floating point command-line arguments 1497 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0; 1498 const double maximum_used_percentage = 1.0 - minimum_free_percentage; 1499 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0; 1500 const double minimum_used_percentage = 1.0 - maximum_free_percentage; 1501 1502 const size_t min_heap_size = collector_policy()->min_heap_byte_size(); 1503 const size_t max_heap_size = collector_policy()->max_heap_byte_size(); 1504 1505 // We have to be careful here as these two calculations can overflow 1506 // 32-bit size_t's. 1507 double used_after_gc_d = (double) used_after_gc; 1508 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage; 1509 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage; 1510 1511 // Let's make sure that they are both under the max heap size, which 1512 // by default will make them fit into a size_t. 1513 double desired_capacity_upper_bound = (double) max_heap_size; 1514 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d, 1515 desired_capacity_upper_bound); 1516 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d, 1517 desired_capacity_upper_bound); 1518 1519 // We can now safely turn them into size_t's. 1520 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d; 1521 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d; 1522 1523 // This assert only makes sense here, before we adjust them 1524 // with respect to the min and max heap size. 1525 assert(minimum_desired_capacity <= maximum_desired_capacity, 1526 err_msg("minimum_desired_capacity = "SIZE_FORMAT", " 1527 "maximum_desired_capacity = "SIZE_FORMAT, 1528 minimum_desired_capacity, maximum_desired_capacity)); 1529 1530 // Should not be greater than the heap max size. No need to adjust 1531 // it with respect to the heap min size as it's a lower bound (i.e., 1532 // we'll try to make the capacity larger than it, not smaller). 1533 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size); 1534 // Should not be less than the heap min size. No need to adjust it 1535 // with respect to the heap max size as it's an upper bound (i.e., 1536 // we'll try to make the capacity smaller than it, not greater). 1537 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size); 1538 1539 if (capacity_after_gc < minimum_desired_capacity) { 1540 // Don't expand unless it's significant 1541 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc; 1542 ergo_verbose4(ErgoHeapSizing, 1543 "attempt heap expansion", 1544 ergo_format_reason("capacity lower than " 1545 "min desired capacity after Full GC") 1546 ergo_format_byte("capacity") 1547 ergo_format_byte("occupancy") 1548 ergo_format_byte_perc("min desired capacity"), 1549 capacity_after_gc, used_after_gc, 1550 minimum_desired_capacity, (double) MinHeapFreeRatio); 1551 expand(expand_bytes); 1552 1553 // No expansion, now see if we want to shrink 1554 } else if (capacity_after_gc > maximum_desired_capacity) { 1555 // Capacity too large, compute shrinking size 1556 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity; 1557 ergo_verbose4(ErgoHeapSizing, 1558 "attempt heap shrinking", 1559 ergo_format_reason("capacity higher than " 1560 "max desired capacity after Full GC") 1561 ergo_format_byte("capacity") 1562 ergo_format_byte("occupancy") 1563 ergo_format_byte_perc("max desired capacity"), 1564 capacity_after_gc, used_after_gc, 1565 maximum_desired_capacity, (double) MaxHeapFreeRatio); 1566 shrink(shrink_bytes); 1567 } 1568 } 1569 1570 1571 HeapWord* 1572 G1CollectedHeap::satisfy_failed_allocation(size_t word_size, 1573 AllocationContext_t context, 1574 bool* succeeded) { 1575 assert_at_safepoint(true /* should_be_vm_thread */); 1576 1577 *succeeded = true; 1578 // Let's attempt the allocation first. 1579 HeapWord* result = 1580 attempt_allocation_at_safepoint(word_size, 1581 context, 1582 false /* expect_null_mutator_alloc_region */); 1583 if (result != NULL) { 1584 assert(*succeeded, "sanity"); 1585 return result; 1586 } 1587 1588 // In a G1 heap, we're supposed to keep allocation from failing by 1589 // incremental pauses. Therefore, at least for now, we'll favor 1590 // expansion over collection. (This might change in the future if we can 1591 // do something smarter than full collection to satisfy a failed alloc.) 1592 result = expand_and_allocate(word_size, context); 1593 if (result != NULL) { 1594 assert(*succeeded, "sanity"); 1595 return result; 1596 } 1597 1598 // Expansion didn't work, we'll try to do a Full GC. 1599 bool gc_succeeded = do_collection(false, /* explicit_gc */ 1600 false, /* clear_all_soft_refs */ 1601 word_size); 1602 if (!gc_succeeded) { 1603 *succeeded = false; 1604 return NULL; 1605 } 1606 1607 // Retry the allocation 1608 result = attempt_allocation_at_safepoint(word_size, 1609 context, 1610 true /* expect_null_mutator_alloc_region */); 1611 if (result != NULL) { 1612 assert(*succeeded, "sanity"); 1613 return result; 1614 } 1615 1616 // Then, try a Full GC that will collect all soft references. 1617 gc_succeeded = do_collection(false, /* explicit_gc */ 1618 true, /* clear_all_soft_refs */ 1619 word_size); 1620 if (!gc_succeeded) { 1621 *succeeded = false; 1622 return NULL; 1623 } 1624 1625 // Retry the allocation once more 1626 result = attempt_allocation_at_safepoint(word_size, 1627 context, 1628 true /* expect_null_mutator_alloc_region */); 1629 if (result != NULL) { 1630 assert(*succeeded, "sanity"); 1631 return result; 1632 } 1633 1634 assert(!collector_policy()->should_clear_all_soft_refs(), 1635 "Flag should have been handled and cleared prior to this point"); 1636 1637 // What else? We might try synchronous finalization later. If the total 1638 // space available is large enough for the allocation, then a more 1639 // complete compaction phase than we've tried so far might be 1640 // appropriate. 1641 assert(*succeeded, "sanity"); 1642 return NULL; 1643 } 1644 1645 // Attempting to expand the heap sufficiently 1646 // to support an allocation of the given "word_size". If 1647 // successful, perform the allocation and return the address of the 1648 // allocated block, or else "NULL". 1649 1650 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) { 1651 assert_at_safepoint(true /* should_be_vm_thread */); 1652 1653 verify_region_sets_optional(); 1654 1655 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes); 1656 ergo_verbose1(ErgoHeapSizing, 1657 "attempt heap expansion", 1658 ergo_format_reason("allocation request failed") 1659 ergo_format_byte("allocation request"), 1660 word_size * HeapWordSize); 1661 if (expand(expand_bytes)) { 1662 _hrm.verify_optional(); 1663 verify_region_sets_optional(); 1664 return attempt_allocation_at_safepoint(word_size, 1665 context, 1666 false /* expect_null_mutator_alloc_region */); 1667 } 1668 return NULL; 1669 } 1670 1671 bool G1CollectedHeap::expand(size_t expand_bytes) { 1672 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes); 1673 aligned_expand_bytes = align_size_up(aligned_expand_bytes, 1674 HeapRegion::GrainBytes); 1675 ergo_verbose2(ErgoHeapSizing, 1676 "expand the heap", 1677 ergo_format_byte("requested expansion amount") 1678 ergo_format_byte("attempted expansion amount"), 1679 expand_bytes, aligned_expand_bytes); 1680 1681 if (is_maximal_no_gc()) { 1682 ergo_verbose0(ErgoHeapSizing, 1683 "did not expand the heap", 1684 ergo_format_reason("heap already fully expanded")); 1685 return false; 1686 } 1687 1688 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes); 1689 assert(regions_to_expand > 0, "Must expand by at least one region"); 1690 1691 uint expanded_by = _hrm.expand_by(regions_to_expand); 1692 1693 if (expanded_by > 0) { 1694 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes; 1695 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition"); 1696 g1_policy()->record_new_heap_size(num_regions()); 1697 } else { 1698 ergo_verbose0(ErgoHeapSizing, 1699 "did not expand the heap", 1700 ergo_format_reason("heap expansion operation failed")); 1701 // The expansion of the virtual storage space was unsuccessful. 1702 // Let's see if it was because we ran out of swap. 1703 if (G1ExitOnExpansionFailure && 1704 _hrm.available() >= regions_to_expand) { 1705 // We had head room... 1706 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion"); 1707 } 1708 } 1709 return regions_to_expand > 0; 1710 } 1711 1712 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) { 1713 size_t aligned_shrink_bytes = 1714 ReservedSpace::page_align_size_down(shrink_bytes); 1715 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes, 1716 HeapRegion::GrainBytes); 1717 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes); 1718 1719 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove); 1720 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes; 1721 1722 ergo_verbose3(ErgoHeapSizing, 1723 "shrink the heap", 1724 ergo_format_byte("requested shrinking amount") 1725 ergo_format_byte("aligned shrinking amount") 1726 ergo_format_byte("attempted shrinking amount"), 1727 shrink_bytes, aligned_shrink_bytes, shrunk_bytes); 1728 if (num_regions_removed > 0) { 1729 g1_policy()->record_new_heap_size(num_regions()); 1730 } else { 1731 ergo_verbose0(ErgoHeapSizing, 1732 "did not shrink the heap", 1733 ergo_format_reason("heap shrinking operation failed")); 1734 } 1735 } 1736 1737 void G1CollectedHeap::shrink(size_t shrink_bytes) { 1738 verify_region_sets_optional(); 1739 1740 // We should only reach here at the end of a Full GC which means we 1741 // should not not be holding to any GC alloc regions. The method 1742 // below will make sure of that and do any remaining clean up. 1743 _allocator->abandon_gc_alloc_regions(); 1744 1745 // Instead of tearing down / rebuilding the free lists here, we 1746 // could instead use the remove_all_pending() method on free_list to 1747 // remove only the ones that we need to remove. 1748 tear_down_region_sets(true /* free_list_only */); 1749 shrink_helper(shrink_bytes); 1750 rebuild_region_sets(true /* free_list_only */); 1751 1752 _hrm.verify_optional(); 1753 verify_region_sets_optional(); 1754 } 1755 1756 // Public methods. 1757 1758 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 1759 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 1760 #endif // _MSC_VER 1761 1762 1763 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) : 1764 SharedHeap(policy_), 1765 _g1_policy(policy_), 1766 _dirty_card_queue_set(false), 1767 _into_cset_dirty_card_queue_set(false), 1768 _is_alive_closure_cm(this), 1769 _is_alive_closure_stw(this), 1770 _ref_processor_cm(NULL), 1771 _ref_processor_stw(NULL), 1772 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)), 1773 _bot_shared(NULL), 1774 _evac_failure_scan_stack(NULL), 1775 _mark_in_progress(false), 1776 _cg1r(NULL), 1777 _g1mm(NULL), 1778 _refine_cte_cl(NULL), 1779 _full_collection(false), 1780 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()), 1781 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()), 1782 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()), 1783 _humongous_is_live(), 1784 _has_humongous_reclaim_candidates(false), 1785 _free_regions_coming(false), 1786 _young_list(new YoungList(this)), 1787 _gc_time_stamp(0), 1788 _survivor_plab_stats(YoungPLABSize, PLABWeight), 1789 _old_plab_stats(OldPLABSize, PLABWeight), 1790 _expand_heap_after_alloc_failure(true), 1791 _surviving_young_words(NULL), 1792 _old_marking_cycles_started(0), 1793 _old_marking_cycles_completed(0), 1794 _concurrent_cycle_started(false), 1795 _heap_summary_sent(false), 1796 _in_cset_fast_test(), 1797 _dirty_cards_region_list(NULL), 1798 _worker_cset_start_region(NULL), 1799 _worker_cset_start_region_time_stamp(NULL), 1800 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()), 1801 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 1802 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()), 1803 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) { 1804 1805 _g1h = this; 1806 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) { 1807 vm_exit_during_initialization("Failed necessary allocation."); 1808 } 1809 1810 _allocator = G1Allocator::create_allocator(_g1h); 1811 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2; 1812 1813 int n_queues = MAX2((int)ParallelGCThreads, 1); 1814 _task_queues = new RefToScanQueueSet(n_queues); 1815 1816 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets(); 1817 assert(n_rem_sets > 0, "Invariant."); 1818 1819 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC); 1820 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC); 1821 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC); 1822 1823 for (int i = 0; i < n_queues; i++) { 1824 RefToScanQueue* q = new RefToScanQueue(); 1825 q->initialize(); 1826 _task_queues->register_queue(i, q); 1827 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo(); 1828 } 1829 clear_cset_start_regions(); 1830 1831 // Initialize the G1EvacuationFailureALot counters and flags. 1832 NOT_PRODUCT(reset_evacuation_should_fail();) 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 G1Log::init(); 1842 1843 // Necessary to satisfy locking discipline assertions. 1844 1845 MutexLocker x(Heap_lock); 1846 1847 // We have to initialize the printer before committing the heap, as 1848 // it will be used then. 1849 _hr_printer.set_active(G1PrintHeapRegions); 1850 1851 // While there are no constraints in the GC code that HeapWordSize 1852 // be any particular value, there are multiple other areas in the 1853 // system which believe this to be true (e.g. oop->object_size in some 1854 // cases incorrectly returns the size in wordSize units rather than 1855 // HeapWordSize). 1856 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize"); 1857 1858 size_t init_byte_size = collector_policy()->initial_heap_byte_size(); 1859 size_t max_byte_size = collector_policy()->max_heap_byte_size(); 1860 size_t heap_alignment = collector_policy()->heap_alignment(); 1861 1862 // Ensure that the sizes are properly aligned. 1863 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1864 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap"); 1865 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap"); 1866 1867 _refine_cte_cl = new RefineCardTableEntryClosure(); 1868 1869 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl); 1870 1871 // Reserve the maximum. 1872 1873 // When compressed oops are enabled, the preferred heap base 1874 // is calculated by subtracting the requested size from the 1875 // 32Gb boundary and using the result as the base address for 1876 // heap reservation. If the requested size is not aligned to 1877 // HeapRegion::GrainBytes (i.e. the alignment that is passed 1878 // into the ReservedHeapSpace constructor) then the actual 1879 // base of the reserved heap may end up differing from the 1880 // address that was requested (i.e. the preferred heap base). 1881 // If this happens then we could end up using a non-optimal 1882 // compressed oops mode. 1883 1884 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size, 1885 heap_alignment); 1886 1887 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size())); 1888 1889 // Create the gen rem set (and barrier set) for the entire reserved region. 1890 _rem_set = collector_policy()->create_rem_set(reserved_region()); 1891 set_barrier_set(rem_set()->bs()); 1892 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) { 1893 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS"); 1894 return JNI_ENOMEM; 1895 } 1896 1897 // Also create a G1 rem set. 1898 _g1_rem_set = new G1RemSet(this, g1_barrier_set()); 1899 1900 // Carve out the G1 part of the heap. 1901 1902 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size); 1903 G1RegionToSpaceMapper* heap_storage = 1904 G1RegionToSpaceMapper::create_mapper(g1_rs, 1905 UseLargePages ? os::large_page_size() : os::vm_page_size(), 1906 HeapRegion::GrainBytes, 1907 1, 1908 mtJavaHeap); 1909 heap_storage->set_mapping_changed_listener(&_listener); 1910 1911 // Reserve space for the block offset table. We do not support automatic uncommit 1912 // for the card table at this time. BOT only. 1913 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize)); 1914 G1RegionToSpaceMapper* bot_storage = 1915 G1RegionToSpaceMapper::create_mapper(bot_rs, 1916 os::vm_page_size(), 1917 HeapRegion::GrainBytes, 1918 G1BlockOffsetSharedArray::N_bytes, 1919 mtGC); 1920 1921 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize)); 1922 G1RegionToSpaceMapper* cardtable_storage = 1923 G1RegionToSpaceMapper::create_mapper(cardtable_rs, 1924 os::vm_page_size(), 1925 HeapRegion::GrainBytes, 1926 G1BlockOffsetSharedArray::N_bytes, 1927 mtGC); 1928 1929 // Reserve space for the card counts table. 1930 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize)); 1931 G1RegionToSpaceMapper* card_counts_storage = 1932 G1RegionToSpaceMapper::create_mapper(card_counts_rs, 1933 os::vm_page_size(), 1934 HeapRegion::GrainBytes, 1935 G1BlockOffsetSharedArray::N_bytes, 1936 mtGC); 1937 1938 // Reserve space for prev and next bitmap. 1939 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size()); 1940 1941 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size)); 1942 G1RegionToSpaceMapper* prev_bitmap_storage = 1943 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs, 1944 os::vm_page_size(), 1945 HeapRegion::GrainBytes, 1946 CMBitMap::mark_distance(), 1947 mtGC); 1948 1949 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size)); 1950 G1RegionToSpaceMapper* next_bitmap_storage = 1951 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs, 1952 os::vm_page_size(), 1953 HeapRegion::GrainBytes, 1954 CMBitMap::mark_distance(), 1955 mtGC); 1956 1957 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage); 1958 g1_barrier_set()->initialize(cardtable_storage); 1959 // Do later initialization work for concurrent refinement. 1960 _cg1r->init(card_counts_storage); 1961 1962 // 6843694 - ensure that the maximum region index can fit 1963 // in the remembered set structures. 1964 const uint max_region_idx = (1U << (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(HeapRegion::CardsPerRegion < max_cards_per_region, 1970 "too many cards per region"); 1971 1972 FreeRegionList::set_unrealistically_long_length(max_regions() + 1); 1973 1974 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage); 1975 1976 _g1h = this; 1977 1978 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes); 1979 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes); 1980 1981 // Create the ConcurrentMark data structure and thread. 1982 // (Must do this late, so that "max_regions" is defined.) 1983 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage); 1984 if (_cm == NULL || !_cm->completed_initialization()) { 1985 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark"); 1986 return JNI_ENOMEM; 1987 } 1988 _cmThread = _cm->cmThread(); 1989 1990 // Initialize the from_card cache structure of HeapRegionRemSet. 1991 HeapRegionRemSet::init_heap(max_regions()); 1992 1993 // Now expand into the initial heap size. 1994 if (!expand(init_byte_size)) { 1995 vm_shutdown_during_initialization("Failed to allocate initial heap."); 1996 return JNI_ENOMEM; 1997 } 1998 1999 // Perform any initialization actions delegated to the policy. 2000 g1_policy()->init(); 2001 2002 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon, 2003 SATB_Q_FL_lock, 2004 G1SATBProcessCompletedThreshold, 2005 Shared_SATB_Q_lock); 2006 2007 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl, 2008 DirtyCardQ_CBL_mon, 2009 DirtyCardQ_FL_lock, 2010 concurrent_g1_refine()->yellow_zone(), 2011 concurrent_g1_refine()->red_zone(), 2012 Shared_DirtyCardQ_lock); 2013 2014 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code 2015 DirtyCardQ_CBL_mon, 2016 DirtyCardQ_FL_lock, 2017 -1, // never trigger processing 2018 -1, // no limit on length 2019 Shared_DirtyCardQ_lock, 2020 &JavaThread::dirty_card_queue_set()); 2021 2022 // Initialize the card queue set used to hold cards containing 2023 // references into the collection set. 2024 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code 2025 DirtyCardQ_CBL_mon, 2026 DirtyCardQ_FL_lock, 2027 -1, // never trigger processing 2028 -1, // no limit on length 2029 Shared_DirtyCardQ_lock, 2030 &JavaThread::dirty_card_queue_set()); 2031 2032 // In case we're keeping closure specialization stats, initialize those 2033 // counts and that mechanism. 2034 SpecializationStats::clear(); 2035 2036 // Here we allocate the dummy HeapRegion that is required by the 2037 // G1AllocRegion class. 2038 HeapRegion* dummy_region = _hrm.get_dummy_region(); 2039 2040 // We'll re-use the same region whether the alloc region will 2041 // require BOT updates or not and, if it doesn't, then a non-young 2042 // region will complain that it cannot support allocations without 2043 // BOT updates. So we'll tag the dummy region as eden to avoid that. 2044 dummy_region->set_eden(); 2045 // Make sure it's full. 2046 dummy_region->set_top(dummy_region->end()); 2047 G1AllocRegion::setup(this, dummy_region); 2048 2049 _allocator->init_mutator_alloc_region(); 2050 2051 // Do create of the monitoring and management support so that 2052 // values in the heap have been properly initialized. 2053 _g1mm = new G1MonitoringSupport(this); 2054 2055 G1StringDedup::initialize(); 2056 2057 return JNI_OK; 2058 } 2059 2060 void G1CollectedHeap::stop() { 2061 // Stop all concurrent threads. We do this to make sure these threads 2062 // do not continue to execute and access resources (e.g. gclog_or_tty) 2063 // that are destroyed during shutdown. 2064 _cg1r->stop(); 2065 _cmThread->stop(); 2066 if (G1StringDedup::is_enabled()) { 2067 G1StringDedup::stop(); 2068 } 2069 } 2070 2071 void G1CollectedHeap::clear_humongous_is_live_table() { 2072 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true"); 2073 _humongous_is_live.clear(); 2074 } 2075 2076 size_t G1CollectedHeap::conservative_max_heap_alignment() { 2077 return HeapRegion::max_region_size(); 2078 } 2079 2080 void G1CollectedHeap::ref_processing_init() { 2081 // Reference processing in G1 currently works as follows: 2082 // 2083 // * There are two reference processor instances. One is 2084 // used to record and process discovered references 2085 // during concurrent marking; the other is used to 2086 // record and process references during STW pauses 2087 // (both full and incremental). 2088 // * Both ref processors need to 'span' the entire heap as 2089 // the regions in the collection set may be dotted around. 2090 // 2091 // * For the concurrent marking ref processor: 2092 // * Reference discovery is enabled at initial marking. 2093 // * Reference discovery is disabled and the discovered 2094 // references processed etc during remarking. 2095 // * Reference discovery is MT (see below). 2096 // * Reference discovery requires a barrier (see below). 2097 // * Reference processing may or may not be MT 2098 // (depending on the value of ParallelRefProcEnabled 2099 // and ParallelGCThreads). 2100 // * A full GC disables reference discovery by the CM 2101 // ref processor and abandons any entries on it's 2102 // discovered lists. 2103 // 2104 // * For the STW processor: 2105 // * Non MT discovery is enabled at the start of a full GC. 2106 // * Processing and enqueueing during a full GC is non-MT. 2107 // * During a full GC, references are processed after marking. 2108 // 2109 // * Discovery (may or may not be MT) is enabled at the start 2110 // of an incremental evacuation pause. 2111 // * References are processed near the end of a STW evacuation pause. 2112 // * For both types of GC: 2113 // * Discovery is atomic - i.e. not concurrent. 2114 // * Reference discovery will not need a barrier. 2115 2116 SharedHeap::ref_processing_init(); 2117 MemRegion mr = reserved_region(); 2118 2119 // Concurrent Mark ref processor 2120 _ref_processor_cm = 2121 new ReferenceProcessor(mr, // span 2122 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2123 // mt processing 2124 (int) ParallelGCThreads, 2125 // degree of mt processing 2126 (ParallelGCThreads > 1) || (ConcGCThreads > 1), 2127 // mt discovery 2128 (int) MAX2(ParallelGCThreads, ConcGCThreads), 2129 // degree of mt discovery 2130 false, 2131 // Reference discovery is not atomic 2132 &_is_alive_closure_cm); 2133 // is alive closure 2134 // (for efficiency/performance) 2135 2136 // STW ref processor 2137 _ref_processor_stw = 2138 new ReferenceProcessor(mr, // span 2139 ParallelRefProcEnabled && (ParallelGCThreads > 1), 2140 // mt processing 2141 MAX2((int)ParallelGCThreads, 1), 2142 // degree of mt processing 2143 (ParallelGCThreads > 1), 2144 // mt discovery 2145 MAX2((int)ParallelGCThreads, 1), 2146 // degree of mt discovery 2147 true, 2148 // Reference discovery is atomic 2149 &_is_alive_closure_stw); 2150 // is alive closure 2151 // (for efficiency/performance) 2152 } 2153 2154 size_t G1CollectedHeap::capacity() const { 2155 return _hrm.length() * HeapRegion::GrainBytes; 2156 } 2157 2158 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) { 2159 assert(!hr->is_continues_humongous(), "pre-condition"); 2160 hr->reset_gc_time_stamp(); 2161 if (hr->is_starts_humongous()) { 2162 uint first_index = hr->hrm_index() + 1; 2163 uint last_index = hr->last_hc_index(); 2164 for (uint i = first_index; i < last_index; i += 1) { 2165 HeapRegion* chr = region_at(i); 2166 assert(chr->is_continues_humongous(), "sanity"); 2167 chr->reset_gc_time_stamp(); 2168 } 2169 } 2170 } 2171 2172 #ifndef PRODUCT 2173 class CheckGCTimeStampsHRClosure : public HeapRegionClosure { 2174 private: 2175 unsigned _gc_time_stamp; 2176 bool _failures; 2177 2178 public: 2179 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) : 2180 _gc_time_stamp(gc_time_stamp), _failures(false) { } 2181 2182 virtual bool doHeapRegion(HeapRegion* hr) { 2183 unsigned region_gc_time_stamp = hr->get_gc_time_stamp(); 2184 if (_gc_time_stamp != region_gc_time_stamp) { 2185 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, " 2186 "expected %d", HR_FORMAT_PARAMS(hr), 2187 region_gc_time_stamp, _gc_time_stamp); 2188 _failures = true; 2189 } 2190 return false; 2191 } 2192 2193 bool failures() { return _failures; } 2194 }; 2195 2196 void G1CollectedHeap::check_gc_time_stamps() { 2197 CheckGCTimeStampsHRClosure cl(_gc_time_stamp); 2198 heap_region_iterate(&cl); 2199 guarantee(!cl.failures(), "all GC time stamps should have been reset"); 2200 } 2201 #endif // PRODUCT 2202 2203 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, 2204 DirtyCardQueue* into_cset_dcq, 2205 bool concurrent, 2206 uint worker_i) { 2207 // Clean cards in the hot card cache 2208 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 2209 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq); 2210 2211 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 2212 int n_completed_buffers = 0; 2213 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) { 2214 n_completed_buffers++; 2215 } 2216 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers); 2217 dcqs.clear_n_completed_buffers(); 2218 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!"); 2219 } 2220 2221 2222 // Computes the sum of the storage used by the various regions. 2223 size_t G1CollectedHeap::used() const { 2224 return _allocator->used(); 2225 } 2226 2227 size_t G1CollectedHeap::used_unlocked() const { 2228 return _allocator->used_unlocked(); 2229 } 2230 2231 class SumUsedClosure: public HeapRegionClosure { 2232 size_t _used; 2233 public: 2234 SumUsedClosure() : _used(0) {} 2235 bool doHeapRegion(HeapRegion* r) { 2236 if (!r->is_continues_humongous()) { 2237 _used += r->used(); 2238 } 2239 return false; 2240 } 2241 size_t result() { return _used; } 2242 }; 2243 2244 size_t G1CollectedHeap::recalculate_used() const { 2245 double recalculate_used_start = os::elapsedTime(); 2246 2247 SumUsedClosure blk; 2248 heap_region_iterate(&blk); 2249 2250 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0); 2251 return blk.result(); 2252 } 2253 2254 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) { 2255 switch (cause) { 2256 case GCCause::_gc_locker: return GCLockerInvokesConcurrent; 2257 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent; 2258 case GCCause::_g1_humongous_allocation: return true; 2259 case GCCause::_update_allocation_context_stats_inc: return true; 2260 case GCCause::_wb_conc_mark: return true; 2261 default: return false; 2262 } 2263 } 2264 2265 #ifndef PRODUCT 2266 void G1CollectedHeap::allocate_dummy_regions() { 2267 // Let's fill up most of the region 2268 size_t word_size = HeapRegion::GrainWords - 1024; 2269 // And as a result the region we'll allocate will be humongous. 2270 guarantee(is_humongous(word_size), "sanity"); 2271 2272 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) { 2273 // Let's use the existing mechanism for the allocation 2274 HeapWord* dummy_obj = humongous_obj_allocate(word_size, 2275 AllocationContext::system()); 2276 if (dummy_obj != NULL) { 2277 MemRegion mr(dummy_obj, word_size); 2278 CollectedHeap::fill_with_object(mr); 2279 } else { 2280 // If we can't allocate once, we probably cannot allocate 2281 // again. Let's get out of the loop. 2282 break; 2283 } 2284 } 2285 } 2286 #endif // !PRODUCT 2287 2288 void G1CollectedHeap::increment_old_marking_cycles_started() { 2289 assert(_old_marking_cycles_started == _old_marking_cycles_completed || 2290 _old_marking_cycles_started == _old_marking_cycles_completed + 1, 2291 err_msg("Wrong marking cycle count (started: %d, completed: %d)", 2292 _old_marking_cycles_started, _old_marking_cycles_completed)); 2293 2294 _old_marking_cycles_started++; 2295 } 2296 2297 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) { 2298 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag); 2299 2300 // We assume that if concurrent == true, then the caller is a 2301 // concurrent thread that was joined the Suspendible Thread 2302 // Set. If there's ever a cheap way to check this, we should add an 2303 // assert here. 2304 2305 // Given that this method is called at the end of a Full GC or of a 2306 // concurrent cycle, and those can be nested (i.e., a Full GC can 2307 // interrupt a concurrent cycle), the number of full collections 2308 // completed should be either one (in the case where there was no 2309 // nesting) or two (when a Full GC interrupted a concurrent cycle) 2310 // behind the number of full collections started. 2311 2312 // This is the case for the inner caller, i.e. a Full GC. 2313 assert(concurrent || 2314 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) || 2315 (_old_marking_cycles_started == _old_marking_cycles_completed + 2), 2316 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u " 2317 "is inconsistent with _old_marking_cycles_completed = %u", 2318 _old_marking_cycles_started, _old_marking_cycles_completed)); 2319 2320 // This is the case for the outer caller, i.e. the concurrent cycle. 2321 assert(!concurrent || 2322 (_old_marking_cycles_started == _old_marking_cycles_completed + 1), 2323 err_msg("for outer caller (concurrent cycle): " 2324 "_old_marking_cycles_started = %u " 2325 "is inconsistent with _old_marking_cycles_completed = %u", 2326 _old_marking_cycles_started, _old_marking_cycles_completed)); 2327 2328 _old_marking_cycles_completed += 1; 2329 2330 // We need to clear the "in_progress" flag in the CM thread before 2331 // we wake up any waiters (especially when ExplicitInvokesConcurrent 2332 // is set) so that if a waiter requests another System.gc() it doesn't 2333 // incorrectly see that a marking cycle is still in progress. 2334 if (concurrent) { 2335 _cmThread->clear_in_progress(); 2336 } 2337 2338 // This notify_all() will ensure that a thread that called 2339 // System.gc() with (with ExplicitGCInvokesConcurrent set or not) 2340 // and it's waiting for a full GC to finish will be woken up. It is 2341 // waiting in VM_G1IncCollectionPause::doit_epilogue(). 2342 FullGCCount_lock->notify_all(); 2343 } 2344 2345 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) { 2346 _concurrent_cycle_started = true; 2347 _gc_timer_cm->register_gc_start(start_time); 2348 2349 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start()); 2350 trace_heap_before_gc(_gc_tracer_cm); 2351 } 2352 2353 void G1CollectedHeap::register_concurrent_cycle_end() { 2354 if (_concurrent_cycle_started) { 2355 if (_cm->has_aborted()) { 2356 _gc_tracer_cm->report_concurrent_mode_failure(); 2357 } 2358 2359 _gc_timer_cm->register_gc_end(); 2360 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 2361 2362 // Clear state variables to prepare for the next concurrent cycle. 2363 _concurrent_cycle_started = false; 2364 _heap_summary_sent = false; 2365 } 2366 } 2367 2368 void G1CollectedHeap::trace_heap_after_concurrent_cycle() { 2369 if (_concurrent_cycle_started) { 2370 // This function can be called when: 2371 // the cleanup pause is run 2372 // the concurrent cycle is aborted before the cleanup pause. 2373 // the concurrent cycle is aborted after the cleanup pause, 2374 // but before the concurrent cycle end has been registered. 2375 // Make sure that we only send the heap information once. 2376 if (!_heap_summary_sent) { 2377 trace_heap_after_gc(_gc_tracer_cm); 2378 _heap_summary_sent = true; 2379 } 2380 } 2381 } 2382 2383 G1YCType G1CollectedHeap::yc_type() { 2384 bool is_young = g1_policy()->gcs_are_young(); 2385 bool is_initial_mark = g1_policy()->during_initial_mark_pause(); 2386 bool is_during_mark = mark_in_progress(); 2387 2388 if (is_initial_mark) { 2389 return InitialMark; 2390 } else if (is_during_mark) { 2391 return DuringMark; 2392 } else if (is_young) { 2393 return Normal; 2394 } else { 2395 return Mixed; 2396 } 2397 } 2398 2399 void G1CollectedHeap::collect(GCCause::Cause cause) { 2400 assert_heap_not_locked(); 2401 2402 unsigned int gc_count_before; 2403 unsigned int old_marking_count_before; 2404 unsigned int full_gc_count_before; 2405 bool retry_gc; 2406 2407 do { 2408 retry_gc = false; 2409 2410 { 2411 MutexLocker ml(Heap_lock); 2412 2413 // Read the GC count while holding the Heap_lock 2414 gc_count_before = total_collections(); 2415 full_gc_count_before = total_full_collections(); 2416 old_marking_count_before = _old_marking_cycles_started; 2417 } 2418 2419 if (should_do_concurrent_full_gc(cause)) { 2420 // Schedule an initial-mark evacuation pause that will start a 2421 // concurrent cycle. We're setting word_size to 0 which means that 2422 // we are not requesting a post-GC allocation. 2423 VM_G1IncCollectionPause op(gc_count_before, 2424 0, /* word_size */ 2425 true, /* should_initiate_conc_mark */ 2426 g1_policy()->max_pause_time_ms(), 2427 cause); 2428 op.set_allocation_context(AllocationContext::current()); 2429 2430 VMThread::execute(&op); 2431 if (!op.pause_succeeded()) { 2432 if (old_marking_count_before == _old_marking_cycles_started) { 2433 retry_gc = op.should_retry_gc(); 2434 } else { 2435 // A Full GC happened while we were trying to schedule the 2436 // initial-mark GC. No point in starting a new cycle given 2437 // that the whole heap was collected anyway. 2438 } 2439 2440 if (retry_gc) { 2441 if (GC_locker::is_active_and_needs_gc()) { 2442 GC_locker::stall_until_clear(); 2443 } 2444 } 2445 } 2446 } else { 2447 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc 2448 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) { 2449 2450 // Schedule a standard evacuation pause. We're setting word_size 2451 // to 0 which means that we are not requesting a post-GC allocation. 2452 VM_G1IncCollectionPause op(gc_count_before, 2453 0, /* word_size */ 2454 false, /* should_initiate_conc_mark */ 2455 g1_policy()->max_pause_time_ms(), 2456 cause); 2457 VMThread::execute(&op); 2458 } else { 2459 // Schedule a Full GC. 2460 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause); 2461 VMThread::execute(&op); 2462 } 2463 } 2464 } while (retry_gc); 2465 } 2466 2467 bool G1CollectedHeap::is_in(const void* p) const { 2468 if (_hrm.reserved().contains(p)) { 2469 // Given that we know that p is in the reserved space, 2470 // heap_region_containing_raw() should successfully 2471 // return the containing region. 2472 HeapRegion* hr = heap_region_containing_raw(p); 2473 return hr->is_in(p); 2474 } else { 2475 return false; 2476 } 2477 } 2478 2479 #ifdef ASSERT 2480 bool G1CollectedHeap::is_in_exact(const void* p) const { 2481 bool contains = reserved_region().contains(p); 2482 bool available = _hrm.is_available(addr_to_region((HeapWord*)p)); 2483 if (contains && available) { 2484 return true; 2485 } else { 2486 return false; 2487 } 2488 } 2489 #endif 2490 2491 // Iteration functions. 2492 2493 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion. 2494 2495 class IterateOopClosureRegionClosure: public HeapRegionClosure { 2496 ExtendedOopClosure* _cl; 2497 public: 2498 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {} 2499 bool doHeapRegion(HeapRegion* r) { 2500 if (!r->is_continues_humongous()) { 2501 r->oop_iterate(_cl); 2502 } 2503 return false; 2504 } 2505 }; 2506 2507 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) { 2508 IterateOopClosureRegionClosure blk(cl); 2509 heap_region_iterate(&blk); 2510 } 2511 2512 // Iterates an ObjectClosure over all objects within a HeapRegion. 2513 2514 class IterateObjectClosureRegionClosure: public HeapRegionClosure { 2515 ObjectClosure* _cl; 2516 public: 2517 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {} 2518 bool doHeapRegion(HeapRegion* r) { 2519 if (!r->is_continues_humongous()) { 2520 r->object_iterate(_cl); 2521 } 2522 return false; 2523 } 2524 }; 2525 2526 void G1CollectedHeap::object_iterate(ObjectClosure* cl) { 2527 IterateObjectClosureRegionClosure blk(cl); 2528 heap_region_iterate(&blk); 2529 } 2530 2531 // Calls a SpaceClosure on a HeapRegion. 2532 2533 class SpaceClosureRegionClosure: public HeapRegionClosure { 2534 SpaceClosure* _cl; 2535 public: 2536 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {} 2537 bool doHeapRegion(HeapRegion* r) { 2538 _cl->do_space(r); 2539 return false; 2540 } 2541 }; 2542 2543 void G1CollectedHeap::space_iterate(SpaceClosure* cl) { 2544 SpaceClosureRegionClosure blk(cl); 2545 heap_region_iterate(&blk); 2546 } 2547 2548 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const { 2549 _hrm.iterate(cl); 2550 } 2551 2552 void 2553 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl, 2554 uint worker_id, 2555 HeapRegionClaimer *hrclaimer, 2556 bool concurrent) const { 2557 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent); 2558 } 2559 2560 // Clear the cached CSet starting regions and (more importantly) 2561 // the time stamps. Called when we reset the GC time stamp. 2562 void G1CollectedHeap::clear_cset_start_regions() { 2563 assert(_worker_cset_start_region != NULL, "sanity"); 2564 assert(_worker_cset_start_region_time_stamp != NULL, "sanity"); 2565 2566 int n_queues = MAX2((int)ParallelGCThreads, 1); 2567 for (int i = 0; i < n_queues; i++) { 2568 _worker_cset_start_region[i] = NULL; 2569 _worker_cset_start_region_time_stamp[i] = 0; 2570 } 2571 } 2572 2573 // Given the id of a worker, obtain or calculate a suitable 2574 // starting region for iterating over the current collection set. 2575 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) { 2576 assert(get_gc_time_stamp() > 0, "should have been updated by now"); 2577 2578 HeapRegion* result = NULL; 2579 unsigned gc_time_stamp = get_gc_time_stamp(); 2580 2581 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) { 2582 // Cached starting region for current worker was set 2583 // during the current pause - so it's valid. 2584 // Note: the cached starting heap region may be NULL 2585 // (when the collection set is empty). 2586 result = _worker_cset_start_region[worker_i]; 2587 assert(result == NULL || result->in_collection_set(), "sanity"); 2588 return result; 2589 } 2590 2591 // The cached entry was not valid so let's calculate 2592 // a suitable starting heap region for this worker. 2593 2594 // We want the parallel threads to start their collection 2595 // set iteration at different collection set regions to 2596 // avoid contention. 2597 // If we have: 2598 // n collection set regions 2599 // p threads 2600 // Then thread t will start at region floor ((t * n) / p) 2601 2602 result = g1_policy()->collection_set(); 2603 uint cs_size = g1_policy()->cset_region_length(); 2604 uint active_workers = workers()->active_workers(); 2605 assert(UseDynamicNumberOfGCThreads || 2606 active_workers == workers()->total_workers(), 2607 "Unless dynamic should use total workers"); 2608 2609 uint end_ind = (cs_size * worker_i) / active_workers; 2610 uint start_ind = 0; 2611 2612 if (worker_i > 0 && 2613 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) { 2614 // Previous workers starting region is valid 2615 // so let's iterate from there 2616 start_ind = (cs_size * (worker_i - 1)) / active_workers; 2617 result = _worker_cset_start_region[worker_i - 1]; 2618 } 2619 2620 for (uint i = start_ind; i < end_ind; i++) { 2621 result = result->next_in_collection_set(); 2622 } 2623 2624 // Note: the calculated starting heap region may be NULL 2625 // (when the collection set is empty). 2626 assert(result == NULL || result->in_collection_set(), "sanity"); 2627 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp, 2628 "should be updated only once per pause"); 2629 _worker_cset_start_region[worker_i] = result; 2630 OrderAccess::storestore(); 2631 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp; 2632 return result; 2633 } 2634 2635 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) { 2636 HeapRegion* r = g1_policy()->collection_set(); 2637 while (r != NULL) { 2638 HeapRegion* next = r->next_in_collection_set(); 2639 if (cl->doHeapRegion(r)) { 2640 cl->incomplete(); 2641 return; 2642 } 2643 r = next; 2644 } 2645 } 2646 2647 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r, 2648 HeapRegionClosure *cl) { 2649 if (r == NULL) { 2650 // The CSet is empty so there's nothing to do. 2651 return; 2652 } 2653 2654 assert(r->in_collection_set(), 2655 "Start region must be a member of the collection set."); 2656 HeapRegion* cur = r; 2657 while (cur != NULL) { 2658 HeapRegion* next = cur->next_in_collection_set(); 2659 if (cl->doHeapRegion(cur) && false) { 2660 cl->incomplete(); 2661 return; 2662 } 2663 cur = next; 2664 } 2665 cur = g1_policy()->collection_set(); 2666 while (cur != r) { 2667 HeapRegion* next = cur->next_in_collection_set(); 2668 if (cl->doHeapRegion(cur) && false) { 2669 cl->incomplete(); 2670 return; 2671 } 2672 cur = next; 2673 } 2674 } 2675 2676 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const { 2677 HeapRegion* result = _hrm.next_region_in_heap(from); 2678 while (result != NULL && result->is_humongous()) { 2679 result = _hrm.next_region_in_heap(result); 2680 } 2681 return result; 2682 } 2683 2684 Space* G1CollectedHeap::space_containing(const void* addr) const { 2685 return heap_region_containing(addr); 2686 } 2687 2688 HeapWord* G1CollectedHeap::block_start(const void* addr) const { 2689 Space* sp = space_containing(addr); 2690 return sp->block_start(addr); 2691 } 2692 2693 size_t G1CollectedHeap::block_size(const HeapWord* addr) const { 2694 Space* sp = space_containing(addr); 2695 return sp->block_size(addr); 2696 } 2697 2698 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const { 2699 Space* sp = space_containing(addr); 2700 return sp->block_is_obj(addr); 2701 } 2702 2703 bool G1CollectedHeap::supports_tlab_allocation() const { 2704 return true; 2705 } 2706 2707 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const { 2708 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes; 2709 } 2710 2711 size_t G1CollectedHeap::tlab_used(Thread* ignored) const { 2712 return young_list()->eden_used_bytes(); 2713 } 2714 2715 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size 2716 // must be smaller than the humongous object limit. 2717 size_t G1CollectedHeap::max_tlab_size() const { 2718 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment); 2719 } 2720 2721 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const { 2722 // Return the remaining space in the cur alloc region, but not less than 2723 // the min TLAB size. 2724 2725 // Also, this value can be at most the humongous object threshold, 2726 // since we can't allow tlabs to grow big enough to accommodate 2727 // humongous objects. 2728 2729 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get(); 2730 size_t max_tlab = max_tlab_size() * wordSize; 2731 if (hr == NULL) { 2732 return max_tlab; 2733 } else { 2734 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab); 2735 } 2736 } 2737 2738 size_t G1CollectedHeap::max_capacity() const { 2739 return _hrm.reserved().byte_size(); 2740 } 2741 2742 jlong G1CollectedHeap::millis_since_last_gc() { 2743 // assert(false, "NYI"); 2744 return 0; 2745 } 2746 2747 void G1CollectedHeap::prepare_for_verify() { 2748 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) { 2749 ensure_parsability(false); 2750 } 2751 g1_rem_set()->prepare_for_verify(); 2752 } 2753 2754 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr, 2755 VerifyOption vo) { 2756 switch (vo) { 2757 case VerifyOption_G1UsePrevMarking: 2758 return hr->obj_allocated_since_prev_marking(obj); 2759 case VerifyOption_G1UseNextMarking: 2760 return hr->obj_allocated_since_next_marking(obj); 2761 case VerifyOption_G1UseMarkWord: 2762 return false; 2763 default: 2764 ShouldNotReachHere(); 2765 } 2766 return false; // keep some compilers happy 2767 } 2768 2769 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) { 2770 switch (vo) { 2771 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start(); 2772 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start(); 2773 case VerifyOption_G1UseMarkWord: return NULL; 2774 default: ShouldNotReachHere(); 2775 } 2776 return NULL; // keep some compilers happy 2777 } 2778 2779 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) { 2780 switch (vo) { 2781 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj); 2782 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj); 2783 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked(); 2784 default: ShouldNotReachHere(); 2785 } 2786 return false; // keep some compilers happy 2787 } 2788 2789 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) { 2790 switch (vo) { 2791 case VerifyOption_G1UsePrevMarking: return "PTAMS"; 2792 case VerifyOption_G1UseNextMarking: return "NTAMS"; 2793 case VerifyOption_G1UseMarkWord: return "NONE"; 2794 default: ShouldNotReachHere(); 2795 } 2796 return NULL; // keep some compilers happy 2797 } 2798 2799 class VerifyRootsClosure: public OopClosure { 2800 private: 2801 G1CollectedHeap* _g1h; 2802 VerifyOption _vo; 2803 bool _failures; 2804 public: 2805 // _vo == UsePrevMarking -> use "prev" marking information, 2806 // _vo == UseNextMarking -> use "next" marking information, 2807 // _vo == UseMarkWord -> use mark word from object header. 2808 VerifyRootsClosure(VerifyOption vo) : 2809 _g1h(G1CollectedHeap::heap()), 2810 _vo(vo), 2811 _failures(false) { } 2812 2813 bool failures() { return _failures; } 2814 2815 template <class T> void do_oop_nv(T* p) { 2816 T heap_oop = oopDesc::load_heap_oop(p); 2817 if (!oopDesc::is_null(heap_oop)) { 2818 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2819 if (_g1h->is_obj_dead_cond(obj, _vo)) { 2820 gclog_or_tty->print_cr("Root location "PTR_FORMAT" " 2821 "points to dead obj "PTR_FORMAT, p, (void*) obj); 2822 if (_vo == VerifyOption_G1UseMarkWord) { 2823 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark())); 2824 } 2825 obj->print_on(gclog_or_tty); 2826 _failures = true; 2827 } 2828 } 2829 } 2830 2831 void do_oop(oop* p) { do_oop_nv(p); } 2832 void do_oop(narrowOop* p) { do_oop_nv(p); } 2833 }; 2834 2835 class G1VerifyCodeRootOopClosure: public OopClosure { 2836 G1CollectedHeap* _g1h; 2837 OopClosure* _root_cl; 2838 nmethod* _nm; 2839 VerifyOption _vo; 2840 bool _failures; 2841 2842 template <class T> void do_oop_work(T* p) { 2843 // First verify that this root is live 2844 _root_cl->do_oop(p); 2845 2846 if (!G1VerifyHeapRegionCodeRoots) { 2847 // We're not verifying the code roots attached to heap region. 2848 return; 2849 } 2850 2851 // Don't check the code roots during marking verification in a full GC 2852 if (_vo == VerifyOption_G1UseMarkWord) { 2853 return; 2854 } 2855 2856 // Now verify that the current nmethod (which contains p) is 2857 // in the code root list of the heap region containing the 2858 // object referenced by p. 2859 2860 T heap_oop = oopDesc::load_heap_oop(p); 2861 if (!oopDesc::is_null(heap_oop)) { 2862 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 2863 2864 // Now fetch the region containing the object 2865 HeapRegion* hr = _g1h->heap_region_containing(obj); 2866 HeapRegionRemSet* hrrs = hr->rem_set(); 2867 // Verify that the strong code root list for this region 2868 // contains the nmethod 2869 if (!hrrs->strong_code_roots_list_contains(_nm)) { 2870 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" " 2871 "from nmethod "PTR_FORMAT" not in strong " 2872 "code roots for region ["PTR_FORMAT","PTR_FORMAT")", 2873 p, _nm, hr->bottom(), hr->end()); 2874 _failures = true; 2875 } 2876 } 2877 } 2878 2879 public: 2880 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo): 2881 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {} 2882 2883 void do_oop(oop* p) { do_oop_work(p); } 2884 void do_oop(narrowOop* p) { do_oop_work(p); } 2885 2886 void set_nmethod(nmethod* nm) { _nm = nm; } 2887 bool failures() { return _failures; } 2888 }; 2889 2890 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure { 2891 G1VerifyCodeRootOopClosure* _oop_cl; 2892 2893 public: 2894 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl): 2895 _oop_cl(oop_cl) {} 2896 2897 void do_code_blob(CodeBlob* cb) { 2898 nmethod* nm = cb->as_nmethod_or_null(); 2899 if (nm != NULL) { 2900 _oop_cl->set_nmethod(nm); 2901 nm->oops_do(_oop_cl); 2902 } 2903 } 2904 }; 2905 2906 class YoungRefCounterClosure : public OopClosure { 2907 G1CollectedHeap* _g1h; 2908 int _count; 2909 public: 2910 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {} 2911 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } } 2912 void do_oop(narrowOop* p) { ShouldNotReachHere(); } 2913 2914 int count() { return _count; } 2915 void reset_count() { _count = 0; }; 2916 }; 2917 2918 class VerifyKlassClosure: public KlassClosure { 2919 YoungRefCounterClosure _young_ref_counter_closure; 2920 OopClosure *_oop_closure; 2921 public: 2922 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {} 2923 void do_klass(Klass* k) { 2924 k->oops_do(_oop_closure); 2925 2926 _young_ref_counter_closure.reset_count(); 2927 k->oops_do(&_young_ref_counter_closure); 2928 if (_young_ref_counter_closure.count() > 0) { 2929 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k)); 2930 } 2931 } 2932 }; 2933 2934 class VerifyLivenessOopClosure: public OopClosure { 2935 G1CollectedHeap* _g1h; 2936 VerifyOption _vo; 2937 public: 2938 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo): 2939 _g1h(g1h), _vo(vo) 2940 { } 2941 void do_oop(narrowOop *p) { do_oop_work(p); } 2942 void do_oop( oop *p) { do_oop_work(p); } 2943 2944 template <class T> void do_oop_work(T *p) { 2945 oop obj = oopDesc::load_decode_heap_oop(p); 2946 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo), 2947 "Dead object referenced by a not dead object"); 2948 } 2949 }; 2950 2951 class VerifyObjsInRegionClosure: public ObjectClosure { 2952 private: 2953 G1CollectedHeap* _g1h; 2954 size_t _live_bytes; 2955 HeapRegion *_hr; 2956 VerifyOption _vo; 2957 public: 2958 // _vo == UsePrevMarking -> use "prev" marking information, 2959 // _vo == UseNextMarking -> use "next" marking information, 2960 // _vo == UseMarkWord -> use mark word from object header. 2961 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo) 2962 : _live_bytes(0), _hr(hr), _vo(vo) { 2963 _g1h = G1CollectedHeap::heap(); 2964 } 2965 void do_object(oop o) { 2966 VerifyLivenessOopClosure isLive(_g1h, _vo); 2967 assert(o != NULL, "Huh?"); 2968 if (!_g1h->is_obj_dead_cond(o, _vo)) { 2969 // If the object is alive according to the mark word, 2970 // then verify that the marking information agrees. 2971 // Note we can't verify the contra-positive of the 2972 // above: if the object is dead (according to the mark 2973 // word), it may not be marked, or may have been marked 2974 // but has since became dead, or may have been allocated 2975 // since the last marking. 2976 if (_vo == VerifyOption_G1UseMarkWord) { 2977 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch"); 2978 } 2979 2980 o->oop_iterate_no_header(&isLive); 2981 if (!_hr->obj_allocated_since_prev_marking(o)) { 2982 size_t obj_size = o->size(); // Make sure we don't overflow 2983 _live_bytes += (obj_size * HeapWordSize); 2984 } 2985 } 2986 } 2987 size_t live_bytes() { return _live_bytes; } 2988 }; 2989 2990 class PrintObjsInRegionClosure : public ObjectClosure { 2991 HeapRegion *_hr; 2992 G1CollectedHeap *_g1; 2993 public: 2994 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) { 2995 _g1 = G1CollectedHeap::heap(); 2996 }; 2997 2998 void do_object(oop o) { 2999 if (o != NULL) { 3000 HeapWord *start = (HeapWord *) o; 3001 size_t word_sz = o->size(); 3002 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT 3003 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n", 3004 (void*) o, word_sz, 3005 _g1->isMarkedPrev(o), 3006 _g1->isMarkedNext(o), 3007 _hr->obj_allocated_since_prev_marking(o)); 3008 HeapWord *end = start + word_sz; 3009 HeapWord *cur; 3010 int *val; 3011 for (cur = start; cur < end; cur++) { 3012 val = (int *) cur; 3013 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val); 3014 } 3015 } 3016 } 3017 }; 3018 3019 class VerifyRegionClosure: public HeapRegionClosure { 3020 private: 3021 bool _par; 3022 VerifyOption _vo; 3023 bool _failures; 3024 public: 3025 // _vo == UsePrevMarking -> use "prev" marking information, 3026 // _vo == UseNextMarking -> use "next" marking information, 3027 // _vo == UseMarkWord -> use mark word from object header. 3028 VerifyRegionClosure(bool par, VerifyOption vo) 3029 : _par(par), 3030 _vo(vo), 3031 _failures(false) {} 3032 3033 bool failures() { 3034 return _failures; 3035 } 3036 3037 bool doHeapRegion(HeapRegion* r) { 3038 if (!r->is_continues_humongous()) { 3039 bool failures = false; 3040 r->verify(_vo, &failures); 3041 if (failures) { 3042 _failures = true; 3043 } else { 3044 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo); 3045 r->object_iterate(¬_dead_yet_cl); 3046 if (_vo != VerifyOption_G1UseNextMarking) { 3047 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) { 3048 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] " 3049 "max_live_bytes "SIZE_FORMAT" " 3050 "< calculated "SIZE_FORMAT, 3051 r->bottom(), r->end(), 3052 r->max_live_bytes(), 3053 not_dead_yet_cl.live_bytes()); 3054 _failures = true; 3055 } 3056 } else { 3057 // When vo == UseNextMarking we cannot currently do a sanity 3058 // check on the live bytes as the calculation has not been 3059 // finalized yet. 3060 } 3061 } 3062 } 3063 return false; // stop the region iteration if we hit a failure 3064 } 3065 }; 3066 3067 // This is the task used for parallel verification of the heap regions 3068 3069 class G1ParVerifyTask: public AbstractGangTask { 3070 private: 3071 G1CollectedHeap* _g1h; 3072 VerifyOption _vo; 3073 bool _failures; 3074 HeapRegionClaimer _hrclaimer; 3075 3076 public: 3077 // _vo == UsePrevMarking -> use "prev" marking information, 3078 // _vo == UseNextMarking -> use "next" marking information, 3079 // _vo == UseMarkWord -> use mark word from object header. 3080 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) : 3081 AbstractGangTask("Parallel verify task"), 3082 _g1h(g1h), 3083 _vo(vo), 3084 _failures(false), 3085 _hrclaimer(g1h->workers()->active_workers()) {} 3086 3087 bool failures() { 3088 return _failures; 3089 } 3090 3091 void work(uint worker_id) { 3092 HandleMark hm; 3093 VerifyRegionClosure blk(true, _vo); 3094 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer); 3095 if (blk.failures()) { 3096 _failures = true; 3097 } 3098 } 3099 }; 3100 3101 void G1CollectedHeap::verify(bool silent, VerifyOption vo) { 3102 if (SafepointSynchronize::is_at_safepoint()) { 3103 assert(Thread::current()->is_VM_thread(), 3104 "Expected to be executed serially by the VM thread at this point"); 3105 3106 if (!silent) { gclog_or_tty->print("Roots "); } 3107 VerifyRootsClosure rootsCl(vo); 3108 VerifyKlassClosure klassCl(this, &rootsCl); 3109 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false); 3110 3111 // We apply the relevant closures to all the oops in the 3112 // system dictionary, class loader data graph, the string table 3113 // and the nmethods in the code cache. 3114 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo); 3115 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl); 3116 3117 process_all_roots(true, // activate StrongRootsScope 3118 SO_AllCodeCache, // roots scanning options 3119 &rootsCl, 3120 &cldCl, 3121 &blobsCl); 3122 3123 bool failures = rootsCl.failures() || codeRootsCl.failures(); 3124 3125 if (vo != VerifyOption_G1UseMarkWord) { 3126 // If we're verifying during a full GC then the region sets 3127 // will have been torn down at the start of the GC. Therefore 3128 // verifying the region sets will fail. So we only verify 3129 // the region sets when not in a full GC. 3130 if (!silent) { gclog_or_tty->print("HeapRegionSets "); } 3131 verify_region_sets(); 3132 } 3133 3134 if (!silent) { gclog_or_tty->print("HeapRegions "); } 3135 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) { 3136 3137 G1ParVerifyTask task(this, vo); 3138 assert(UseDynamicNumberOfGCThreads || 3139 workers()->active_workers() == workers()->total_workers(), 3140 "If not dynamic should be using all the workers"); 3141 int n_workers = workers()->active_workers(); 3142 set_par_threads(n_workers); 3143 workers()->run_task(&task); 3144 set_par_threads(0); 3145 if (task.failures()) { 3146 failures = true; 3147 } 3148 3149 } else { 3150 VerifyRegionClosure blk(false, vo); 3151 heap_region_iterate(&blk); 3152 if (blk.failures()) { 3153 failures = true; 3154 } 3155 } 3156 if (!silent) gclog_or_tty->print("RemSet "); 3157 rem_set()->verify(); 3158 3159 if (G1StringDedup::is_enabled()) { 3160 if (!silent) gclog_or_tty->print("StrDedup "); 3161 G1StringDedup::verify(); 3162 } 3163 3164 if (failures) { 3165 gclog_or_tty->print_cr("Heap:"); 3166 // It helps to have the per-region information in the output to 3167 // help us track down what went wrong. This is why we call 3168 // print_extended_on() instead of print_on(). 3169 print_extended_on(gclog_or_tty); 3170 gclog_or_tty->cr(); 3171 #ifndef PRODUCT 3172 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) { 3173 concurrent_mark()->print_reachable("at-verification-failure", 3174 vo, false /* all */); 3175 } 3176 #endif 3177 gclog_or_tty->flush(); 3178 } 3179 guarantee(!failures, "there should not have been any failures"); 3180 } else { 3181 if (!silent) { 3182 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet"); 3183 if (G1StringDedup::is_enabled()) { 3184 gclog_or_tty->print(", StrDedup"); 3185 } 3186 gclog_or_tty->print(") "); 3187 } 3188 } 3189 } 3190 3191 void G1CollectedHeap::verify(bool silent) { 3192 verify(silent, VerifyOption_G1UsePrevMarking); 3193 } 3194 3195 double G1CollectedHeap::verify(bool guard, const char* msg) { 3196 double verify_time_ms = 0.0; 3197 3198 if (guard && total_collections() >= VerifyGCStartAt) { 3199 double verify_start = os::elapsedTime(); 3200 HandleMark hm; // Discard invalid handles created during verification 3201 prepare_for_verify(); 3202 Universe::verify(VerifyOption_G1UsePrevMarking, msg); 3203 verify_time_ms = (os::elapsedTime() - verify_start) * 1000; 3204 } 3205 3206 return verify_time_ms; 3207 } 3208 3209 void G1CollectedHeap::verify_before_gc() { 3210 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:"); 3211 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms); 3212 } 3213 3214 void G1CollectedHeap::verify_after_gc() { 3215 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:"); 3216 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms); 3217 } 3218 3219 class PrintRegionClosure: public HeapRegionClosure { 3220 outputStream* _st; 3221 public: 3222 PrintRegionClosure(outputStream* st) : _st(st) {} 3223 bool doHeapRegion(HeapRegion* r) { 3224 r->print_on(_st); 3225 return false; 3226 } 3227 }; 3228 3229 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3230 const HeapRegion* hr, 3231 const VerifyOption vo) const { 3232 switch (vo) { 3233 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr); 3234 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr); 3235 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3236 default: ShouldNotReachHere(); 3237 } 3238 return false; // keep some compilers happy 3239 } 3240 3241 bool G1CollectedHeap::is_obj_dead_cond(const oop obj, 3242 const VerifyOption vo) const { 3243 switch (vo) { 3244 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj); 3245 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj); 3246 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked(); 3247 default: ShouldNotReachHere(); 3248 } 3249 return false; // keep some compilers happy 3250 } 3251 3252 void G1CollectedHeap::print_on(outputStream* st) const { 3253 st->print(" %-20s", "garbage-first heap"); 3254 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K", 3255 capacity()/K, used_unlocked()/K); 3256 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")", 3257 _hrm.reserved().start(), 3258 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords, 3259 _hrm.reserved().end()); 3260 st->cr(); 3261 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K); 3262 uint young_regions = _young_list->length(); 3263 st->print("%u young (" SIZE_FORMAT "K), ", young_regions, 3264 (size_t) young_regions * HeapRegion::GrainBytes / K); 3265 uint survivor_regions = g1_policy()->recorded_survivor_regions(); 3266 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions, 3267 (size_t) survivor_regions * HeapRegion::GrainBytes / K); 3268 st->cr(); 3269 MetaspaceAux::print_on(st); 3270 } 3271 3272 void G1CollectedHeap::print_extended_on(outputStream* st) const { 3273 print_on(st); 3274 3275 // Print the per-region information. 3276 st->cr(); 3277 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), " 3278 "HS=humongous(starts), HC=humongous(continues), " 3279 "CS=collection set, F=free, TS=gc time stamp, " 3280 "PTAMS=previous top-at-mark-start, " 3281 "NTAMS=next top-at-mark-start)"); 3282 PrintRegionClosure blk(st); 3283 heap_region_iterate(&blk); 3284 } 3285 3286 void G1CollectedHeap::print_on_error(outputStream* st) const { 3287 this->CollectedHeap::print_on_error(st); 3288 3289 if (_cm != NULL) { 3290 st->cr(); 3291 _cm->print_on_error(st); 3292 } 3293 } 3294 3295 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const { 3296 workers()->print_worker_threads_on(st); 3297 _cmThread->print_on(st); 3298 st->cr(); 3299 _cm->print_worker_threads_on(st); 3300 _cg1r->print_worker_threads_on(st); 3301 if (G1StringDedup::is_enabled()) { 3302 G1StringDedup::print_worker_threads_on(st); 3303 } 3304 } 3305 3306 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const { 3307 workers()->threads_do(tc); 3308 tc->do_thread(_cmThread); 3309 _cg1r->threads_do(tc); 3310 if (G1StringDedup::is_enabled()) { 3311 G1StringDedup::threads_do(tc); 3312 } 3313 } 3314 3315 void G1CollectedHeap::print_tracing_info() const { 3316 // We'll overload this to mean "trace GC pause statistics." 3317 if (TraceYoungGenTime || TraceOldGenTime) { 3318 // The "G1CollectorPolicy" is keeping track of these stats, so delegate 3319 // to that. 3320 g1_policy()->print_tracing_info(); 3321 } 3322 if (G1SummarizeRSetStats) { 3323 g1_rem_set()->print_summary_info(); 3324 } 3325 if (G1SummarizeConcMark) { 3326 concurrent_mark()->print_summary_info(); 3327 } 3328 g1_policy()->print_yg_surv_rate_info(); 3329 SpecializationStats::print(); 3330 } 3331 3332 #ifndef PRODUCT 3333 // Helpful for debugging RSet issues. 3334 3335 class PrintRSetsClosure : public HeapRegionClosure { 3336 private: 3337 const char* _msg; 3338 size_t _occupied_sum; 3339 3340 public: 3341 bool doHeapRegion(HeapRegion* r) { 3342 HeapRegionRemSet* hrrs = r->rem_set(); 3343 size_t occupied = hrrs->occupied(); 3344 _occupied_sum += occupied; 3345 3346 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT, 3347 HR_FORMAT_PARAMS(r)); 3348 if (occupied == 0) { 3349 gclog_or_tty->print_cr(" RSet is empty"); 3350 } else { 3351 hrrs->print(); 3352 } 3353 gclog_or_tty->print_cr("----------"); 3354 return false; 3355 } 3356 3357 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) { 3358 gclog_or_tty->cr(); 3359 gclog_or_tty->print_cr("========================================"); 3360 gclog_or_tty->print_cr("%s", msg); 3361 gclog_or_tty->cr(); 3362 } 3363 3364 ~PrintRSetsClosure() { 3365 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum); 3366 gclog_or_tty->print_cr("========================================"); 3367 gclog_or_tty->cr(); 3368 } 3369 }; 3370 3371 void G1CollectedHeap::print_cset_rsets() { 3372 PrintRSetsClosure cl("Printing CSet RSets"); 3373 collection_set_iterate(&cl); 3374 } 3375 3376 void G1CollectedHeap::print_all_rsets() { 3377 PrintRSetsClosure cl("Printing All RSets");; 3378 heap_region_iterate(&cl); 3379 } 3380 #endif // PRODUCT 3381 3382 G1CollectedHeap* G1CollectedHeap::heap() { 3383 assert(_sh->kind() == CollectedHeap::G1CollectedHeap, 3384 "not a garbage-first heap"); 3385 return _g1h; 3386 } 3387 3388 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) { 3389 // always_do_update_barrier = false; 3390 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer"); 3391 // Fill TLAB's and such 3392 accumulate_statistics_all_tlabs(); 3393 ensure_parsability(true); 3394 3395 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) && 3396 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) { 3397 g1_rem_set()->print_periodic_summary_info("Before GC RS summary"); 3398 } 3399 } 3400 3401 void G1CollectedHeap::gc_epilogue(bool full) { 3402 3403 if (G1SummarizeRSetStats && 3404 (G1SummarizeRSetStatsPeriod > 0) && 3405 // we are at the end of the GC. Total collections has already been increased. 3406 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) { 3407 g1_rem_set()->print_periodic_summary_info("After GC RS summary"); 3408 } 3409 3410 // FIXME: what is this about? 3411 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled" 3412 // is set. 3413 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(), 3414 "derived pointer present")); 3415 // always_do_update_barrier = true; 3416 3417 resize_all_tlabs(); 3418 allocation_context_stats().update(full); 3419 3420 // We have just completed a GC. Update the soft reference 3421 // policy with the new heap occupancy 3422 Universe::update_heap_info_at_gc(); 3423 } 3424 3425 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size, 3426 unsigned int gc_count_before, 3427 bool* succeeded, 3428 GCCause::Cause gc_cause) { 3429 assert_heap_not_locked_and_not_at_safepoint(); 3430 g1_policy()->record_stop_world_start(); 3431 VM_G1IncCollectionPause op(gc_count_before, 3432 word_size, 3433 false, /* should_initiate_conc_mark */ 3434 g1_policy()->max_pause_time_ms(), 3435 gc_cause); 3436 3437 op.set_allocation_context(AllocationContext::current()); 3438 VMThread::execute(&op); 3439 3440 HeapWord* result = op.result(); 3441 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded(); 3442 assert(result == NULL || ret_succeeded, 3443 "the result should be NULL if the VM did not succeed"); 3444 *succeeded = ret_succeeded; 3445 3446 assert_heap_not_locked(); 3447 return result; 3448 } 3449 3450 void 3451 G1CollectedHeap::doConcurrentMark() { 3452 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); 3453 if (!_cmThread->in_progress()) { 3454 _cmThread->set_started(); 3455 CGC_lock->notify(); 3456 } 3457 } 3458 3459 size_t G1CollectedHeap::pending_card_num() { 3460 size_t extra_cards = 0; 3461 JavaThread *curr = Threads::first(); 3462 while (curr != NULL) { 3463 DirtyCardQueue& dcq = curr->dirty_card_queue(); 3464 extra_cards += dcq.size(); 3465 curr = curr->next(); 3466 } 3467 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 3468 size_t buffer_size = dcqs.buffer_size(); 3469 size_t buffer_num = dcqs.completed_buffers_num(); 3470 3471 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes 3472 // in bytes - not the number of 'entries'. We need to convert 3473 // into a number of cards. 3474 return (buffer_size * buffer_num + extra_cards) / oopSize; 3475 } 3476 3477 size_t G1CollectedHeap::cards_scanned() { 3478 return g1_rem_set()->cardsScanned(); 3479 } 3480 3481 bool G1CollectedHeap::humongous_region_is_always_live(uint index) { 3482 HeapRegion* region = region_at(index); 3483 assert(region->is_starts_humongous(), "Must start a humongous object"); 3484 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty(); 3485 } 3486 3487 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure { 3488 private: 3489 size_t _total_humongous; 3490 size_t _candidate_humongous; 3491 public: 3492 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) { 3493 } 3494 3495 virtual bool doHeapRegion(HeapRegion* r) { 3496 if (!r->is_starts_humongous()) { 3497 return false; 3498 } 3499 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3500 3501 uint region_idx = r->hrm_index(); 3502 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx); 3503 // Is_candidate already filters out humongous regions with some remembered set. 3504 // This will not lead to humongous object that we mistakenly keep alive because 3505 // during young collection the remembered sets will only be added to. 3506 if (is_candidate) { 3507 g1h->register_humongous_region_with_in_cset_fast_test(region_idx); 3508 _candidate_humongous++; 3509 } 3510 _total_humongous++; 3511 3512 return false; 3513 } 3514 3515 size_t total_humongous() const { return _total_humongous; } 3516 size_t candidate_humongous() const { return _candidate_humongous; } 3517 }; 3518 3519 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() { 3520 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) { 3521 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0); 3522 return; 3523 } 3524 3525 RegisterHumongousWithInCSetFastTestClosure cl; 3526 heap_region_iterate(&cl); 3527 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(), 3528 cl.candidate_humongous()); 3529 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0; 3530 3531 if (_has_humongous_reclaim_candidates || G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 3532 clear_humongous_is_live_table(); 3533 } 3534 } 3535 3536 void 3537 G1CollectedHeap::setup_surviving_young_words() { 3538 assert(_surviving_young_words == NULL, "pre-condition"); 3539 uint array_length = g1_policy()->young_cset_region_length(); 3540 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC); 3541 if (_surviving_young_words == NULL) { 3542 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR, 3543 "Not enough space for young surv words summary."); 3544 } 3545 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t)); 3546 #ifdef ASSERT 3547 for (uint i = 0; i < array_length; ++i) { 3548 assert( _surviving_young_words[i] == 0, "memset above" ); 3549 } 3550 #endif // !ASSERT 3551 } 3552 3553 void 3554 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) { 3555 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 3556 uint array_length = g1_policy()->young_cset_region_length(); 3557 for (uint i = 0; i < array_length; ++i) { 3558 _surviving_young_words[i] += surv_young_words[i]; 3559 } 3560 } 3561 3562 void 3563 G1CollectedHeap::cleanup_surviving_young_words() { 3564 guarantee( _surviving_young_words != NULL, "pre-condition" ); 3565 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC); 3566 _surviving_young_words = NULL; 3567 } 3568 3569 #ifdef ASSERT 3570 class VerifyCSetClosure: public HeapRegionClosure { 3571 public: 3572 bool doHeapRegion(HeapRegion* hr) { 3573 // Here we check that the CSet region's RSet is ready for parallel 3574 // iteration. The fields that we'll verify are only manipulated 3575 // when the region is part of a CSet and is collected. Afterwards, 3576 // we reset these fields when we clear the region's RSet (when the 3577 // region is freed) so they are ready when the region is 3578 // re-allocated. The only exception to this is if there's an 3579 // evacuation failure and instead of freeing the region we leave 3580 // it in the heap. In that case, we reset these fields during 3581 // evacuation failure handling. 3582 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification"); 3583 3584 // Here's a good place to add any other checks we'd like to 3585 // perform on CSet regions. 3586 return false; 3587 } 3588 }; 3589 #endif // ASSERT 3590 3591 #if TASKQUEUE_STATS 3592 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) { 3593 st->print_raw_cr("GC Task Stats"); 3594 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); 3595 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); 3596 } 3597 3598 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const { 3599 print_taskqueue_stats_hdr(st); 3600 3601 TaskQueueStats totals; 3602 const int n = workers()->total_workers(); 3603 for (int i = 0; i < n; ++i) { 3604 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr(); 3605 totals += task_queue(i)->stats; 3606 } 3607 st->print_raw("tot "); totals.print(st); st->cr(); 3608 3609 DEBUG_ONLY(totals.verify()); 3610 } 3611 3612 void G1CollectedHeap::reset_taskqueue_stats() { 3613 const int n = workers()->total_workers(); 3614 for (int i = 0; i < n; ++i) { 3615 task_queue(i)->stats.reset(); 3616 } 3617 } 3618 #endif // TASKQUEUE_STATS 3619 3620 void G1CollectedHeap::log_gc_header() { 3621 if (!G1Log::fine()) { 3622 return; 3623 } 3624 3625 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id()); 3626 3627 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause()) 3628 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)") 3629 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : ""); 3630 3631 gclog_or_tty->print("[%s", (const char*)gc_cause_str); 3632 } 3633 3634 void G1CollectedHeap::log_gc_footer(double pause_time_sec) { 3635 if (!G1Log::fine()) { 3636 return; 3637 } 3638 3639 if (G1Log::finer()) { 3640 if (evacuation_failed()) { 3641 gclog_or_tty->print(" (to-space exhausted)"); 3642 } 3643 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3644 g1_policy()->phase_times()->note_gc_end(); 3645 g1_policy()->phase_times()->print(pause_time_sec); 3646 g1_policy()->print_detailed_heap_transition(); 3647 } else { 3648 if (evacuation_failed()) { 3649 gclog_or_tty->print("--"); 3650 } 3651 g1_policy()->print_heap_transition(); 3652 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec); 3653 } 3654 gclog_or_tty->flush(); 3655 } 3656 3657 bool 3658 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) { 3659 assert_at_safepoint(true /* should_be_vm_thread */); 3660 guarantee(!is_gc_active(), "collection is not reentrant"); 3661 3662 if (GC_locker::check_active_before_gc()) { 3663 return false; 3664 } 3665 3666 _gc_timer_stw->register_gc_start(); 3667 3668 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start()); 3669 3670 SvcGCMarker sgcm(SvcGCMarker::MINOR); 3671 ResourceMark rm; 3672 3673 print_heap_before_gc(); 3674 trace_heap_before_gc(_gc_tracer_stw); 3675 3676 verify_region_sets_optional(); 3677 verify_dirty_young_regions(); 3678 3679 // This call will decide whether this pause is an initial-mark 3680 // pause. If it is, during_initial_mark_pause() will return true 3681 // for the duration of this pause. 3682 g1_policy()->decide_on_conc_mark_initiation(); 3683 3684 // We do not allow initial-mark to be piggy-backed on a mixed GC. 3685 assert(!g1_policy()->during_initial_mark_pause() || 3686 g1_policy()->gcs_are_young(), "sanity"); 3687 3688 // We also do not allow mixed GCs during marking. 3689 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity"); 3690 3691 // Record whether this pause is an initial mark. When the current 3692 // thread has completed its logging output and it's safe to signal 3693 // the CM thread, the flag's value in the policy has been reset. 3694 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause(); 3695 3696 // Inner scope for scope based logging, timers, and stats collection 3697 { 3698 EvacuationInfo evacuation_info; 3699 3700 if (g1_policy()->during_initial_mark_pause()) { 3701 // We are about to start a marking cycle, so we increment the 3702 // full collection counter. 3703 increment_old_marking_cycles_started(); 3704 register_concurrent_cycle_start(_gc_timer_stw->gc_start()); 3705 } 3706 3707 _gc_tracer_stw->report_yc_type(yc_type()); 3708 3709 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty); 3710 3711 int active_workers = workers()->active_workers(); 3712 double pause_start_sec = os::elapsedTime(); 3713 g1_policy()->phase_times()->note_gc_start(active_workers); 3714 log_gc_header(); 3715 3716 TraceCollectorStats tcs(g1mm()->incremental_collection_counters()); 3717 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause()); 3718 3719 // If the secondary_free_list is not empty, append it to the 3720 // free_list. No need to wait for the cleanup operation to finish; 3721 // the region allocation code will check the secondary_free_list 3722 // and wait if necessary. If the G1StressConcRegionFreeing flag is 3723 // set, skip this step so that the region allocation code has to 3724 // get entries from the secondary_free_list. 3725 if (!G1StressConcRegionFreeing) { 3726 append_secondary_free_list_if_not_empty_with_lock(); 3727 } 3728 3729 assert(check_young_list_well_formed(), "young list should be well formed"); 3730 3731 // Don't dynamically change the number of GC threads this early. A value of 3732 // 0 is used to indicate serial work. When parallel work is done, 3733 // it will be set. 3734 3735 { // Call to jvmpi::post_class_unload_events must occur outside of active GC 3736 IsGCActiveMark x; 3737 3738 gc_prologue(false); 3739 increment_total_collections(false /* full gc */); 3740 increment_gc_time_stamp(); 3741 3742 verify_before_gc(); 3743 3744 check_bitmaps("GC Start"); 3745 3746 COMPILER2_PRESENT(DerivedPointerTable::clear()); 3747 3748 // Please see comment in g1CollectedHeap.hpp and 3749 // G1CollectedHeap::ref_processing_init() to see how 3750 // reference processing currently works in G1. 3751 3752 // Enable discovery in the STW reference processor 3753 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, 3754 true /*verify_no_refs*/); 3755 3756 { 3757 // We want to temporarily turn off discovery by the 3758 // CM ref processor, if necessary, and turn it back on 3759 // on again later if we do. Using a scoped 3760 // NoRefDiscovery object will do this. 3761 NoRefDiscovery no_cm_discovery(ref_processor_cm()); 3762 3763 // Forget the current alloc region (we might even choose it to be part 3764 // of the collection set!). 3765 _allocator->release_mutator_alloc_region(); 3766 3767 // We should call this after we retire the mutator alloc 3768 // region(s) so that all the ALLOC / RETIRE events are generated 3769 // before the start GC event. 3770 _hr_printer.start_gc(false /* full */, (size_t) total_collections()); 3771 3772 // This timing is only used by the ergonomics to handle our pause target. 3773 // It is unclear why this should not include the full pause. We will 3774 // investigate this in CR 7178365. 3775 // 3776 // Preserving the old comment here if that helps the investigation: 3777 // 3778 // The elapsed time induced by the start time below deliberately elides 3779 // the possible verification above. 3780 double sample_start_time_sec = os::elapsedTime(); 3781 3782 #if YOUNG_LIST_VERBOSE 3783 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:"); 3784 _young_list->print(); 3785 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3786 #endif // YOUNG_LIST_VERBOSE 3787 3788 g1_policy()->record_collection_pause_start(sample_start_time_sec); 3789 3790 double scan_wait_start = os::elapsedTime(); 3791 // We have to wait until the CM threads finish scanning the 3792 // root regions as it's the only way to ensure that all the 3793 // objects on them have been correctly scanned before we start 3794 // moving them during the GC. 3795 bool waited = _cm->root_regions()->wait_until_scan_finished(); 3796 double wait_time_ms = 0.0; 3797 if (waited) { 3798 double scan_wait_end = os::elapsedTime(); 3799 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0; 3800 } 3801 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms); 3802 3803 #if YOUNG_LIST_VERBOSE 3804 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:"); 3805 _young_list->print(); 3806 #endif // YOUNG_LIST_VERBOSE 3807 3808 if (g1_policy()->during_initial_mark_pause()) { 3809 concurrent_mark()->checkpointRootsInitialPre(); 3810 } 3811 3812 #if YOUNG_LIST_VERBOSE 3813 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:"); 3814 _young_list->print(); 3815 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3816 #endif // YOUNG_LIST_VERBOSE 3817 3818 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info); 3819 3820 register_humongous_regions_with_in_cset_fast_test(); 3821 3822 _cm->note_start_of_gc(); 3823 // We should not verify the per-thread SATB buffers given that 3824 // we have not filtered them yet (we'll do so during the 3825 // GC). We also call this after finalize_cset() to 3826 // ensure that the CSet has been finalized. 3827 _cm->verify_no_cset_oops(true /* verify_stacks */, 3828 true /* verify_enqueued_buffers */, 3829 false /* verify_thread_buffers */, 3830 true /* verify_fingers */); 3831 3832 if (_hr_printer.is_active()) { 3833 HeapRegion* hr = g1_policy()->collection_set(); 3834 while (hr != NULL) { 3835 _hr_printer.cset(hr); 3836 hr = hr->next_in_collection_set(); 3837 } 3838 } 3839 3840 #ifdef ASSERT 3841 VerifyCSetClosure cl; 3842 collection_set_iterate(&cl); 3843 #endif // ASSERT 3844 3845 setup_surviving_young_words(); 3846 3847 // Initialize the GC alloc regions. 3848 _allocator->init_gc_alloc_regions(evacuation_info); 3849 3850 // Actually do the work... 3851 evacuate_collection_set(evacuation_info); 3852 3853 // We do this to mainly verify the per-thread SATB buffers 3854 // (which have been filtered by now) since we didn't verify 3855 // them earlier. No point in re-checking the stacks / enqueued 3856 // buffers given that the CSet has not changed since last time 3857 // we checked. 3858 _cm->verify_no_cset_oops(false /* verify_stacks */, 3859 false /* verify_enqueued_buffers */, 3860 true /* verify_thread_buffers */, 3861 true /* verify_fingers */); 3862 3863 free_collection_set(g1_policy()->collection_set(), evacuation_info); 3864 3865 eagerly_reclaim_humongous_regions(); 3866 3867 g1_policy()->clear_collection_set(); 3868 3869 cleanup_surviving_young_words(); 3870 3871 // Start a new incremental collection set for the next pause. 3872 g1_policy()->start_incremental_cset_building(); 3873 3874 clear_cset_fast_test(); 3875 3876 _young_list->reset_sampled_info(); 3877 3878 // Don't check the whole heap at this point as the 3879 // GC alloc regions from this pause have been tagged 3880 // as survivors and moved on to the survivor list. 3881 // Survivor regions will fail the !is_young() check. 3882 assert(check_young_list_empty(false /* check_heap */), 3883 "young list should be empty"); 3884 3885 #if YOUNG_LIST_VERBOSE 3886 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:"); 3887 _young_list->print(); 3888 #endif // YOUNG_LIST_VERBOSE 3889 3890 g1_policy()->record_survivor_regions(_young_list->survivor_length(), 3891 _young_list->first_survivor_region(), 3892 _young_list->last_survivor_region()); 3893 3894 _young_list->reset_auxilary_lists(); 3895 3896 if (evacuation_failed()) { 3897 _allocator->set_used(recalculate_used()); 3898 uint n_queues = MAX2((int)ParallelGCThreads, 1); 3899 for (uint i = 0; i < n_queues; i++) { 3900 if (_evacuation_failed_info_array[i].has_failed()) { 3901 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]); 3902 } 3903 } 3904 } else { 3905 // The "used" of the the collection set have already been subtracted 3906 // when they were freed. Add in the bytes evacuated. 3907 _allocator->increase_used(g1_policy()->bytes_copied_during_gc()); 3908 } 3909 3910 if (g1_policy()->during_initial_mark_pause()) { 3911 // We have to do this before we notify the CM threads that 3912 // they can start working to make sure that all the 3913 // appropriate initialization is done on the CM object. 3914 concurrent_mark()->checkpointRootsInitialPost(); 3915 set_marking_started(); 3916 // Note that we don't actually trigger the CM thread at 3917 // this point. We do that later when we're sure that 3918 // the current thread has completed its logging output. 3919 } 3920 3921 allocate_dummy_regions(); 3922 3923 #if YOUNG_LIST_VERBOSE 3924 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:"); 3925 _young_list->print(); 3926 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty); 3927 #endif // YOUNG_LIST_VERBOSE 3928 3929 _allocator->init_mutator_alloc_region(); 3930 3931 { 3932 size_t expand_bytes = g1_policy()->expansion_amount(); 3933 if (expand_bytes > 0) { 3934 size_t bytes_before = capacity(); 3935 // No need for an ergo verbose message here, 3936 // expansion_amount() does this when it returns a value > 0. 3937 if (!expand(expand_bytes)) { 3938 // We failed to expand the heap. Cannot do anything about it. 3939 } 3940 } 3941 } 3942 3943 // We redo the verification but now wrt to the new CSet which 3944 // has just got initialized after the previous CSet was freed. 3945 _cm->verify_no_cset_oops(true /* verify_stacks */, 3946 true /* verify_enqueued_buffers */, 3947 true /* verify_thread_buffers */, 3948 true /* verify_fingers */); 3949 _cm->note_end_of_gc(); 3950 3951 // This timing is only used by the ergonomics to handle our pause target. 3952 // It is unclear why this should not include the full pause. We will 3953 // investigate this in CR 7178365. 3954 double sample_end_time_sec = os::elapsedTime(); 3955 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS; 3956 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info); 3957 3958 MemoryService::track_memory_usage(); 3959 3960 // In prepare_for_verify() below we'll need to scan the deferred 3961 // update buffers to bring the RSets up-to-date if 3962 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning 3963 // the update buffers we'll probably need to scan cards on the 3964 // regions we just allocated to (i.e., the GC alloc 3965 // regions). However, during the last GC we called 3966 // set_saved_mark() on all the GC alloc regions, so card 3967 // scanning might skip the [saved_mark_word()...top()] area of 3968 // those regions (i.e., the area we allocated objects into 3969 // during the last GC). But it shouldn't. Given that 3970 // saved_mark_word() is conditional on whether the GC time stamp 3971 // on the region is current or not, by incrementing the GC time 3972 // stamp here we invalidate all the GC time stamps on all the 3973 // regions and saved_mark_word() will simply return top() for 3974 // all the regions. This is a nicer way of ensuring this rather 3975 // than iterating over the regions and fixing them. In fact, the 3976 // GC time stamp increment here also ensures that 3977 // saved_mark_word() will return top() between pauses, i.e., 3978 // during concurrent refinement. So we don't need the 3979 // is_gc_active() check to decided which top to use when 3980 // scanning cards (see CR 7039627). 3981 increment_gc_time_stamp(); 3982 3983 verify_after_gc(); 3984 check_bitmaps("GC End"); 3985 3986 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition"); 3987 ref_processor_stw()->verify_no_references_recorded(); 3988 3989 // CM reference discovery will be re-enabled if necessary. 3990 } 3991 3992 // We should do this after we potentially expand the heap so 3993 // that all the COMMIT events are generated before the end GC 3994 // event, and after we retire the GC alloc regions so that all 3995 // RETIRE events are generated before the end GC event. 3996 _hr_printer.end_gc(false /* full */, (size_t) total_collections()); 3997 3998 #ifdef TRACESPINNING 3999 ParallelTaskTerminator::print_termination_counts(); 4000 #endif 4001 4002 gc_epilogue(false); 4003 } 4004 4005 // Print the remainder of the GC log output. 4006 log_gc_footer(os::elapsedTime() - pause_start_sec); 4007 4008 // It is not yet to safe to tell the concurrent mark to 4009 // start as we have some optional output below. We don't want the 4010 // output from the concurrent mark thread interfering with this 4011 // logging output either. 4012 4013 _hrm.verify_optional(); 4014 verify_region_sets_optional(); 4015 4016 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats()); 4017 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats()); 4018 4019 print_heap_after_gc(); 4020 trace_heap_after_gc(_gc_tracer_stw); 4021 4022 // We must call G1MonitoringSupport::update_sizes() in the same scoping level 4023 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the 4024 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated 4025 // before any GC notifications are raised. 4026 g1mm()->update_sizes(); 4027 4028 _gc_tracer_stw->report_evacuation_info(&evacuation_info); 4029 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold()); 4030 _gc_timer_stw->register_gc_end(); 4031 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions()); 4032 } 4033 // It should now be safe to tell the concurrent mark thread to start 4034 // without its logging output interfering with the logging output 4035 // that came from the pause. 4036 4037 if (should_start_conc_mark) { 4038 // CAUTION: after the doConcurrentMark() call below, 4039 // the concurrent marking thread(s) could be running 4040 // concurrently with us. Make sure that anything after 4041 // this point does not assume that we are the only GC thread 4042 // running. Note: of course, the actual marking work will 4043 // not start until the safepoint itself is released in 4044 // SuspendibleThreadSet::desynchronize(). 4045 doConcurrentMark(); 4046 } 4047 4048 return true; 4049 } 4050 4051 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose) 4052 { 4053 size_t gclab_word_size; 4054 switch (purpose) { 4055 case GCAllocForSurvived: 4056 gclab_word_size = _survivor_plab_stats.desired_plab_sz(); 4057 break; 4058 case GCAllocForTenured: 4059 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4060 break; 4061 default: 4062 assert(false, "unknown GCAllocPurpose"); 4063 gclab_word_size = _old_plab_stats.desired_plab_sz(); 4064 break; 4065 } 4066 4067 // Prevent humongous PLAB sizes for two reasons: 4068 // * PLABs are allocated using a similar paths as oops, but should 4069 // never be in a humongous region 4070 // * Allowing humongous PLABs needlessly churns the region free lists 4071 return MIN2(_humongous_object_threshold_in_words, gclab_word_size); 4072 } 4073 4074 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) { 4075 _drain_in_progress = false; 4076 set_evac_failure_closure(cl); 4077 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true); 4078 } 4079 4080 void G1CollectedHeap::finalize_for_evac_failure() { 4081 assert(_evac_failure_scan_stack != NULL && 4082 _evac_failure_scan_stack->length() == 0, 4083 "Postcondition"); 4084 assert(!_drain_in_progress, "Postcondition"); 4085 delete _evac_failure_scan_stack; 4086 _evac_failure_scan_stack = NULL; 4087 } 4088 4089 void G1CollectedHeap::remove_self_forwarding_pointers() { 4090 double remove_self_forwards_start = os::elapsedTime(); 4091 4092 set_par_threads(); 4093 G1ParRemoveSelfForwardPtrsTask rsfp_task(this); 4094 workers()->run_task(&rsfp_task); 4095 set_par_threads(0); 4096 4097 // Now restore saved marks, if any. 4098 assert(_objs_with_preserved_marks.size() == 4099 _preserved_marks_of_objs.size(), "Both or none."); 4100 while (!_objs_with_preserved_marks.is_empty()) { 4101 oop obj = _objs_with_preserved_marks.pop(); 4102 markOop m = _preserved_marks_of_objs.pop(); 4103 obj->set_mark(m); 4104 } 4105 _objs_with_preserved_marks.clear(true); 4106 _preserved_marks_of_objs.clear(true); 4107 4108 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0); 4109 } 4110 4111 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) { 4112 _evac_failure_scan_stack->push(obj); 4113 } 4114 4115 void G1CollectedHeap::drain_evac_failure_scan_stack() { 4116 assert(_evac_failure_scan_stack != NULL, "precondition"); 4117 4118 while (_evac_failure_scan_stack->length() > 0) { 4119 oop obj = _evac_failure_scan_stack->pop(); 4120 _evac_failure_closure->set_region(heap_region_containing(obj)); 4121 obj->oop_iterate_backwards(_evac_failure_closure); 4122 } 4123 } 4124 4125 oop 4126 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, 4127 oop old) { 4128 assert(obj_in_cs(old), 4129 err_msg("obj: "PTR_FORMAT" should still be in the CSet", 4130 (HeapWord*) old)); 4131 markOop m = old->mark(); 4132 oop forward_ptr = old->forward_to_atomic(old); 4133 if (forward_ptr == NULL) { 4134 // Forward-to-self succeeded. 4135 assert(_par_scan_state != NULL, "par scan state"); 4136 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure(); 4137 uint queue_num = _par_scan_state->queue_num(); 4138 4139 _evacuation_failed = true; 4140 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size()); 4141 if (_evac_failure_closure != cl) { 4142 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag); 4143 assert(!_drain_in_progress, 4144 "Should only be true while someone holds the lock."); 4145 // Set the global evac-failure closure to the current thread's. 4146 assert(_evac_failure_closure == NULL, "Or locking has failed."); 4147 set_evac_failure_closure(cl); 4148 // Now do the common part. 4149 handle_evacuation_failure_common(old, m); 4150 // Reset to NULL. 4151 set_evac_failure_closure(NULL); 4152 } else { 4153 // The lock is already held, and this is recursive. 4154 assert(_drain_in_progress, "This should only be the recursive case."); 4155 handle_evacuation_failure_common(old, m); 4156 } 4157 return old; 4158 } else { 4159 // Forward-to-self failed. Either someone else managed to allocate 4160 // space for this object (old != forward_ptr) or they beat us in 4161 // self-forwarding it (old == forward_ptr). 4162 assert(old == forward_ptr || !obj_in_cs(forward_ptr), 4163 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" " 4164 "should not be in the CSet", 4165 (HeapWord*) old, (HeapWord*) forward_ptr)); 4166 return forward_ptr; 4167 } 4168 } 4169 4170 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) { 4171 preserve_mark_if_necessary(old, m); 4172 4173 HeapRegion* r = heap_region_containing(old); 4174 if (!r->evacuation_failed()) { 4175 r->set_evacuation_failed(true); 4176 _hr_printer.evac_failure(r); 4177 } 4178 4179 push_on_evac_failure_scan_stack(old); 4180 4181 if (!_drain_in_progress) { 4182 // prevent recursion in copy_to_survivor_space() 4183 _drain_in_progress = true; 4184 drain_evac_failure_scan_stack(); 4185 _drain_in_progress = false; 4186 } 4187 } 4188 4189 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) { 4190 assert(evacuation_failed(), "Oversaving!"); 4191 // We want to call the "for_promotion_failure" version only in the 4192 // case of a promotion failure. 4193 if (m->must_be_preserved_for_promotion_failure(obj)) { 4194 _objs_with_preserved_marks.push(obj); 4195 _preserved_marks_of_objs.push(m); 4196 } 4197 } 4198 4199 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose, 4200 size_t word_size, 4201 AllocationContext_t context) { 4202 if (purpose == GCAllocForSurvived) { 4203 HeapWord* result = survivor_attempt_allocation(word_size, context); 4204 if (result != NULL) { 4205 return result; 4206 } else { 4207 // Let's try to allocate in the old gen in case we can fit the 4208 // object there. 4209 return old_attempt_allocation(word_size, context); 4210 } 4211 } else { 4212 assert(purpose == GCAllocForTenured, "sanity"); 4213 HeapWord* result = old_attempt_allocation(word_size, context); 4214 if (result != NULL) { 4215 return result; 4216 } else { 4217 // Let's try to allocate in the survivors in case we can fit the 4218 // object there. 4219 return survivor_attempt_allocation(word_size, context); 4220 } 4221 } 4222 4223 ShouldNotReachHere(); 4224 // Trying to keep some compilers happy. 4225 return NULL; 4226 } 4227 4228 void G1ParCopyHelper::mark_object(oop obj) { 4229 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet"); 4230 4231 // We know that the object is not moving so it's safe to read its size. 4232 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id); 4233 } 4234 4235 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) { 4236 assert(from_obj->is_forwarded(), "from obj should be forwarded"); 4237 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee"); 4238 assert(from_obj != to_obj, "should not be self-forwarded"); 4239 4240 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet"); 4241 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet"); 4242 4243 // The object might be in the process of being copied by another 4244 // worker so we cannot trust that its to-space image is 4245 // well-formed. So we have to read its size from its from-space 4246 // image which we know should not be changing. 4247 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id); 4248 } 4249 4250 template <class T> 4251 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) { 4252 if (_g1->heap_region_containing_raw(new_obj)->is_young()) { 4253 _scanned_klass->record_modified_oops(); 4254 } 4255 } 4256 4257 template <G1Barrier barrier, G1Mark do_mark_object> 4258 template <class T> 4259 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) { 4260 T heap_oop = oopDesc::load_heap_oop(p); 4261 4262 if (oopDesc::is_null(heap_oop)) { 4263 return; 4264 } 4265 4266 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 4267 4268 assert(_worker_id == _par_scan_state->queue_num(), "sanity"); 4269 4270 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj); 4271 4272 if (state == G1CollectedHeap::InCSet) { 4273 oop forwardee; 4274 markOop m = obj->mark(); 4275 if (m->is_marked()) { 4276 forwardee = (oop) m->decode_pointer(); 4277 } else { 4278 forwardee = _par_scan_state->copy_to_survivor_space(obj, m); 4279 } 4280 assert(forwardee != NULL, "forwardee should not be NULL"); 4281 oopDesc::encode_store_heap_oop(p, forwardee); 4282 if (do_mark_object != G1MarkNone && forwardee != obj) { 4283 // If the object is self-forwarded we don't need to explicitly 4284 // mark it, the evacuation failure protocol will do so. 4285 mark_forwarded_object(obj, forwardee); 4286 } 4287 4288 if (barrier == G1BarrierKlass) { 4289 do_klass_barrier(p, forwardee); 4290 } 4291 } else { 4292 if (state == G1CollectedHeap::IsHumongous) { 4293 _g1->set_humongous_is_live(obj); 4294 } 4295 // The object is not in collection set. If we're a root scanning 4296 // closure during an initial mark pause then attempt to mark the object. 4297 if (do_mark_object == G1MarkFromRoot) { 4298 mark_object(obj); 4299 } 4300 } 4301 4302 if (barrier == G1BarrierEvac) { 4303 _par_scan_state->update_rs(_from, p, _worker_id); 4304 } 4305 } 4306 4307 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p); 4308 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p); 4309 4310 class G1ParEvacuateFollowersClosure : public VoidClosure { 4311 protected: 4312 G1CollectedHeap* _g1h; 4313 G1ParScanThreadState* _par_scan_state; 4314 RefToScanQueueSet* _queues; 4315 ParallelTaskTerminator* _terminator; 4316 4317 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 4318 RefToScanQueueSet* queues() { return _queues; } 4319 ParallelTaskTerminator* terminator() { return _terminator; } 4320 4321 public: 4322 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 4323 G1ParScanThreadState* par_scan_state, 4324 RefToScanQueueSet* queues, 4325 ParallelTaskTerminator* terminator) 4326 : _g1h(g1h), _par_scan_state(par_scan_state), 4327 _queues(queues), _terminator(terminator) {} 4328 4329 void do_void(); 4330 4331 private: 4332 inline bool offer_termination(); 4333 }; 4334 4335 bool G1ParEvacuateFollowersClosure::offer_termination() { 4336 G1ParScanThreadState* const pss = par_scan_state(); 4337 pss->start_term_time(); 4338 const bool res = terminator()->offer_termination(); 4339 pss->end_term_time(); 4340 return res; 4341 } 4342 4343 void G1ParEvacuateFollowersClosure::do_void() { 4344 G1ParScanThreadState* const pss = par_scan_state(); 4345 pss->trim_queue(); 4346 do { 4347 pss->steal_and_trim_queue(queues()); 4348 } while (!offer_termination()); 4349 } 4350 4351 class G1KlassScanClosure : public KlassClosure { 4352 G1ParCopyHelper* _closure; 4353 bool _process_only_dirty; 4354 int _count; 4355 public: 4356 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty) 4357 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {} 4358 void do_klass(Klass* klass) { 4359 // If the klass has not been dirtied we know that there's 4360 // no references into the young gen and we can skip it. 4361 if (!_process_only_dirty || klass->has_modified_oops()) { 4362 // Clean the klass since we're going to scavenge all the metadata. 4363 klass->clear_modified_oops(); 4364 4365 // Tell the closure that this klass is the Klass to scavenge 4366 // and is the one to dirty if oops are left pointing into the young gen. 4367 _closure->set_scanned_klass(klass); 4368 4369 klass->oops_do(_closure); 4370 4371 _closure->set_scanned_klass(NULL); 4372 } 4373 _count++; 4374 } 4375 }; 4376 4377 class G1CodeBlobClosure : public CodeBlobClosure { 4378 class HeapRegionGatheringOopClosure : public OopClosure { 4379 G1CollectedHeap* _g1h; 4380 OopClosure* _work; 4381 nmethod* _nm; 4382 4383 template <typename T> 4384 void do_oop_work(T* p) { 4385 _work->do_oop(p); 4386 T oop_or_narrowoop = oopDesc::load_heap_oop(p); 4387 if (!oopDesc::is_null(oop_or_narrowoop)) { 4388 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop); 4389 HeapRegion* hr = _g1h->heap_region_containing_raw(o); 4390 assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset"); 4391 hr->add_strong_code_root(_nm); 4392 } 4393 } 4394 4395 public: 4396 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {} 4397 4398 void do_oop(oop* o) { 4399 do_oop_work(o); 4400 } 4401 4402 void do_oop(narrowOop* o) { 4403 do_oop_work(o); 4404 } 4405 4406 void set_nm(nmethod* nm) { 4407 _nm = nm; 4408 } 4409 }; 4410 4411 HeapRegionGatheringOopClosure _oc; 4412 public: 4413 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {} 4414 4415 void do_code_blob(CodeBlob* cb) { 4416 nmethod* nm = cb->as_nmethod_or_null(); 4417 if (nm != NULL) { 4418 if (!nm->test_set_oops_do_mark()) { 4419 _oc.set_nm(nm); 4420 nm->oops_do(&_oc); 4421 nm->fix_oop_relocations(); 4422 } 4423 } 4424 } 4425 }; 4426 4427 class G1ParTask : public AbstractGangTask { 4428 protected: 4429 G1CollectedHeap* _g1h; 4430 RefToScanQueueSet *_queues; 4431 ParallelTaskTerminator _terminator; 4432 uint _n_workers; 4433 4434 Mutex _stats_lock; 4435 Mutex* stats_lock() { return &_stats_lock; } 4436 4437 public: 4438 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues) 4439 : AbstractGangTask("G1 collection"), 4440 _g1h(g1h), 4441 _queues(task_queues), 4442 _terminator(0, _queues), 4443 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true) 4444 {} 4445 4446 RefToScanQueueSet* queues() { return _queues; } 4447 4448 RefToScanQueue *work_queue(int i) { 4449 return queues()->queue(i); 4450 } 4451 4452 ParallelTaskTerminator* terminator() { return &_terminator; } 4453 4454 virtual void set_for_termination(int active_workers) { 4455 // This task calls set_n_termination() in par_non_clean_card_iterate_work() 4456 // in the young space (_par_seq_tasks) in the G1 heap 4457 // for SequentialSubTasksDone. 4458 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap 4459 // both of which need setting by set_n_termination(). 4460 _g1h->SharedHeap::set_n_termination(active_workers); 4461 _g1h->set_n_termination(active_workers); 4462 terminator()->reset_for_reuse(active_workers); 4463 _n_workers = active_workers; 4464 } 4465 4466 // Helps out with CLD processing. 4467 // 4468 // During InitialMark we need to: 4469 // 1) Scavenge all CLDs for the young GC. 4470 // 2) Mark all objects directly reachable from strong CLDs. 4471 template <G1Mark do_mark_object> 4472 class G1CLDClosure : public CLDClosure { 4473 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure; 4474 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure; 4475 G1KlassScanClosure _klass_in_cld_closure; 4476 bool _claim; 4477 4478 public: 4479 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure, 4480 bool only_young, bool claim) 4481 : _oop_closure(oop_closure), 4482 _oop_in_klass_closure(oop_closure->g1(), 4483 oop_closure->pss(), 4484 oop_closure->rp()), 4485 _klass_in_cld_closure(&_oop_in_klass_closure, only_young), 4486 _claim(claim) { 4487 4488 } 4489 4490 void do_cld(ClassLoaderData* cld) { 4491 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim); 4492 } 4493 }; 4494 4495 void work(uint worker_id) { 4496 if (worker_id >= _n_workers) return; // no work needed this round 4497 4498 double start_time_ms = os::elapsedTime() * 1000.0; 4499 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms); 4500 4501 { 4502 ResourceMark rm; 4503 HandleMark hm; 4504 4505 ReferenceProcessor* rp = _g1h->ref_processor_stw(); 4506 4507 G1ParScanThreadState pss(_g1h, worker_id, rp); 4508 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp); 4509 4510 pss.set_evac_failure_closure(&evac_failure_cl); 4511 4512 bool only_young = _g1h->g1_policy()->gcs_are_young(); 4513 4514 // Non-IM young GC. 4515 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp); 4516 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl, 4517 only_young, // Only process dirty klasses. 4518 false); // No need to claim CLDs. 4519 // IM young GC. 4520 // Strong roots closures. 4521 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp); 4522 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl, 4523 false, // Process all klasses. 4524 true); // Need to claim CLDs. 4525 // Weak roots closures. 4526 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp); 4527 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl, 4528 false, // Process all klasses. 4529 true); // Need to claim CLDs. 4530 4531 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl); 4532 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl); 4533 // IM Weak code roots are handled later. 4534 4535 OopClosure* strong_root_cl; 4536 OopClosure* weak_root_cl; 4537 CLDClosure* strong_cld_cl; 4538 CLDClosure* weak_cld_cl; 4539 CodeBlobClosure* strong_code_cl; 4540 4541 if (_g1h->g1_policy()->during_initial_mark_pause()) { 4542 // We also need to mark copied objects. 4543 strong_root_cl = &scan_mark_root_cl; 4544 strong_cld_cl = &scan_mark_cld_cl; 4545 strong_code_cl = &scan_mark_code_cl; 4546 if (ClassUnloadingWithConcurrentMark) { 4547 weak_root_cl = &scan_mark_weak_root_cl; 4548 weak_cld_cl = &scan_mark_weak_cld_cl; 4549 } else { 4550 weak_root_cl = &scan_mark_root_cl; 4551 weak_cld_cl = &scan_mark_cld_cl; 4552 } 4553 } else { 4554 strong_root_cl = &scan_only_root_cl; 4555 weak_root_cl = &scan_only_root_cl; 4556 strong_cld_cl = &scan_only_cld_cl; 4557 weak_cld_cl = &scan_only_cld_cl; 4558 strong_code_cl = &scan_only_code_cl; 4559 } 4560 4561 4562 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss); 4563 4564 pss.start_strong_roots(); 4565 _g1h->g1_process_roots(strong_root_cl, 4566 weak_root_cl, 4567 &push_heap_rs_cl, 4568 strong_cld_cl, 4569 weak_cld_cl, 4570 strong_code_cl, 4571 worker_id); 4572 4573 pss.end_strong_roots(); 4574 4575 { 4576 double start = os::elapsedTime(); 4577 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator); 4578 evac.do_void(); 4579 double elapsed_ms = (os::elapsedTime()-start)*1000.0; 4580 double term_ms = pss.term_time()*1000.0; 4581 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms); 4582 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts()); 4583 } 4584 _g1h->g1_policy()->record_thread_age_table(pss.age_table()); 4585 _g1h->update_surviving_young_words(pss.surviving_young_words()+1); 4586 4587 if (PrintTerminationStats) { 4588 MutexLocker x(stats_lock()); 4589 pss.print_termination_stats(worker_id); 4590 } 4591 4592 assert(pss.queue_is_empty(), "should be empty"); 4593 4594 // Close the inner scope so that the ResourceMark and HandleMark 4595 // destructors are executed here and are included as part of the 4596 // "GC Worker Time". 4597 } 4598 4599 double end_time_ms = os::elapsedTime() * 1000.0; 4600 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms); 4601 } 4602 }; 4603 4604 // *** Common G1 Evacuation Stuff 4605 4606 // This method is run in a GC worker. 4607 4608 void 4609 G1CollectedHeap:: 4610 g1_process_roots(OopClosure* scan_non_heap_roots, 4611 OopClosure* scan_non_heap_weak_roots, 4612 OopsInHeapRegionClosure* scan_rs, 4613 CLDClosure* scan_strong_clds, 4614 CLDClosure* scan_weak_clds, 4615 CodeBlobClosure* scan_strong_code, 4616 uint worker_i) { 4617 4618 // First scan the shared roots. 4619 double ext_roots_start = os::elapsedTime(); 4620 double closure_app_time_sec = 0.0; 4621 4622 bool during_im = _g1h->g1_policy()->during_initial_mark_pause(); 4623 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark; 4624 4625 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots); 4626 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots); 4627 4628 process_roots(false, // no scoping; this is parallel code 4629 SharedHeap::SO_None, 4630 &buf_scan_non_heap_roots, 4631 &buf_scan_non_heap_weak_roots, 4632 scan_strong_clds, 4633 // Unloading Initial Marks handle the weak CLDs separately. 4634 (trace_metadata ? NULL : scan_weak_clds), 4635 scan_strong_code); 4636 4637 // Now the CM ref_processor roots. 4638 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) { 4639 // We need to treat the discovered reference lists of the 4640 // concurrent mark ref processor as roots and keep entries 4641 // (which are added by the marking threads) on them live 4642 // until they can be processed at the end of marking. 4643 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots); 4644 } 4645 4646 if (trace_metadata) { 4647 // Barrier to make sure all workers passed 4648 // the strong CLD and strong nmethods phases. 4649 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads()); 4650 4651 // Now take the complement of the strong CLDs. 4652 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds); 4653 } 4654 4655 // Finish up any enqueued closure apps (attributed as object copy time). 4656 buf_scan_non_heap_roots.done(); 4657 buf_scan_non_heap_weak_roots.done(); 4658 4659 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds() 4660 + buf_scan_non_heap_weak_roots.closure_app_seconds(); 4661 4662 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0); 4663 4664 double ext_root_time_ms = 4665 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0; 4666 4667 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms); 4668 4669 // During conc marking we have to filter the per-thread SATB buffers 4670 // to make sure we remove any oops into the CSet (which will show up 4671 // as implicitly live). 4672 double satb_filtering_ms = 0.0; 4673 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) { 4674 if (mark_in_progress()) { 4675 double satb_filter_start = os::elapsedTime(); 4676 4677 JavaThread::satb_mark_queue_set().filter_thread_buffers(); 4678 4679 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0; 4680 } 4681 } 4682 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms); 4683 4684 // Now scan the complement of the collection set. 4685 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots); 4686 4687 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i); 4688 4689 _process_strong_tasks->all_tasks_completed(); 4690 } 4691 4692 class G1StringSymbolTableUnlinkTask : public AbstractGangTask { 4693 private: 4694 BoolObjectClosure* _is_alive; 4695 int _initial_string_table_size; 4696 int _initial_symbol_table_size; 4697 4698 bool _process_strings; 4699 int _strings_processed; 4700 int _strings_removed; 4701 4702 bool _process_symbols; 4703 int _symbols_processed; 4704 int _symbols_removed; 4705 4706 public: 4707 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) : 4708 AbstractGangTask("String/Symbol Unlinking"), 4709 _is_alive(is_alive), 4710 _process_strings(process_strings), _strings_processed(0), _strings_removed(0), 4711 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) { 4712 4713 _initial_string_table_size = StringTable::the_table()->table_size(); 4714 _initial_symbol_table_size = SymbolTable::the_table()->table_size(); 4715 if (process_strings) { 4716 StringTable::clear_parallel_claimed_index(); 4717 } 4718 if (process_symbols) { 4719 SymbolTable::clear_parallel_claimed_index(); 4720 } 4721 } 4722 4723 ~G1StringSymbolTableUnlinkTask() { 4724 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size, 4725 err_msg("claim value %d after unlink less than initial string table size %d", 4726 StringTable::parallel_claimed_index(), _initial_string_table_size)); 4727 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size, 4728 err_msg("claim value %d after unlink less than initial symbol table size %d", 4729 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size)); 4730 4731 if (G1TraceStringSymbolTableScrubbing) { 4732 gclog_or_tty->print_cr("Cleaned string and symbol table, " 4733 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, " 4734 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed", 4735 strings_processed(), strings_removed(), 4736 symbols_processed(), symbols_removed()); 4737 } 4738 } 4739 4740 void work(uint worker_id) { 4741 int strings_processed = 0; 4742 int strings_removed = 0; 4743 int symbols_processed = 0; 4744 int symbols_removed = 0; 4745 if (_process_strings) { 4746 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed); 4747 Atomic::add(strings_processed, &_strings_processed); 4748 Atomic::add(strings_removed, &_strings_removed); 4749 } 4750 if (_process_symbols) { 4751 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed); 4752 Atomic::add(symbols_processed, &_symbols_processed); 4753 Atomic::add(symbols_removed, &_symbols_removed); 4754 } 4755 } 4756 4757 size_t strings_processed() const { return (size_t)_strings_processed; } 4758 size_t strings_removed() const { return (size_t)_strings_removed; } 4759 4760 size_t symbols_processed() const { return (size_t)_symbols_processed; } 4761 size_t symbols_removed() const { return (size_t)_symbols_removed; } 4762 }; 4763 4764 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC { 4765 private: 4766 static Monitor* _lock; 4767 4768 BoolObjectClosure* const _is_alive; 4769 const bool _unloading_occurred; 4770 const uint _num_workers; 4771 4772 // Variables used to claim nmethods. 4773 nmethod* _first_nmethod; 4774 volatile nmethod* _claimed_nmethod; 4775 4776 // The list of nmethods that need to be processed by the second pass. 4777 volatile nmethod* _postponed_list; 4778 volatile uint _num_entered_barrier; 4779 4780 public: 4781 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) : 4782 _is_alive(is_alive), 4783 _unloading_occurred(unloading_occurred), 4784 _num_workers(num_workers), 4785 _first_nmethod(NULL), 4786 _claimed_nmethod(NULL), 4787 _postponed_list(NULL), 4788 _num_entered_barrier(0) 4789 { 4790 nmethod::increase_unloading_clock(); 4791 // Get first alive nmethod 4792 NMethodIterator iter = NMethodIterator(); 4793 if(iter.next_alive()) { 4794 _first_nmethod = iter.method(); 4795 } 4796 _claimed_nmethod = (volatile nmethod*)_first_nmethod; 4797 } 4798 4799 ~G1CodeCacheUnloadingTask() { 4800 CodeCache::verify_clean_inline_caches(); 4801 4802 CodeCache::set_needs_cache_clean(false); 4803 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be"); 4804 4805 CodeCache::verify_icholder_relocations(); 4806 } 4807 4808 private: 4809 void add_to_postponed_list(nmethod* nm) { 4810 nmethod* old; 4811 do { 4812 old = (nmethod*)_postponed_list; 4813 nm->set_unloading_next(old); 4814 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old); 4815 } 4816 4817 void clean_nmethod(nmethod* nm) { 4818 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred); 4819 4820 if (postponed) { 4821 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet. 4822 add_to_postponed_list(nm); 4823 } 4824 4825 // Mark that this thread has been cleaned/unloaded. 4826 // After this call, it will be safe to ask if this nmethod was unloaded or not. 4827 nm->set_unloading_clock(nmethod::global_unloading_clock()); 4828 } 4829 4830 void clean_nmethod_postponed(nmethod* nm) { 4831 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred); 4832 } 4833 4834 static const int MaxClaimNmethods = 16; 4835 4836 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) { 4837 nmethod* first; 4838 NMethodIterator last; 4839 4840 do { 4841 *num_claimed_nmethods = 0; 4842 4843 first = (nmethod*)_claimed_nmethod; 4844 last = NMethodIterator(first); 4845 4846 if (first != NULL) { 4847 4848 for (int i = 0; i < MaxClaimNmethods; i++) { 4849 if (!last.next_alive()) { 4850 break; 4851 } 4852 claimed_nmethods[i] = last.method(); 4853 (*num_claimed_nmethods)++; 4854 } 4855 } 4856 4857 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first); 4858 } 4859 4860 nmethod* claim_postponed_nmethod() { 4861 nmethod* claim; 4862 nmethod* next; 4863 4864 do { 4865 claim = (nmethod*)_postponed_list; 4866 if (claim == NULL) { 4867 return NULL; 4868 } 4869 4870 next = claim->unloading_next(); 4871 4872 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim); 4873 4874 return claim; 4875 } 4876 4877 public: 4878 // Mark that we're done with the first pass of nmethod cleaning. 4879 void barrier_mark(uint worker_id) { 4880 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4881 _num_entered_barrier++; 4882 if (_num_entered_barrier == _num_workers) { 4883 ml.notify_all(); 4884 } 4885 } 4886 4887 // See if we have to wait for the other workers to 4888 // finish their first-pass nmethod cleaning work. 4889 void barrier_wait(uint worker_id) { 4890 if (_num_entered_barrier < _num_workers) { 4891 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag); 4892 while (_num_entered_barrier < _num_workers) { 4893 ml.wait(Mutex::_no_safepoint_check_flag, 0, false); 4894 } 4895 } 4896 } 4897 4898 // Cleaning and unloading of nmethods. Some work has to be postponed 4899 // to the second pass, when we know which nmethods survive. 4900 void work_first_pass(uint worker_id) { 4901 // The first nmethods is claimed by the first worker. 4902 if (worker_id == 0 && _first_nmethod != NULL) { 4903 clean_nmethod(_first_nmethod); 4904 _first_nmethod = NULL; 4905 } 4906 4907 int num_claimed_nmethods; 4908 nmethod* claimed_nmethods[MaxClaimNmethods]; 4909 4910 while (true) { 4911 claim_nmethods(claimed_nmethods, &num_claimed_nmethods); 4912 4913 if (num_claimed_nmethods == 0) { 4914 break; 4915 } 4916 4917 for (int i = 0; i < num_claimed_nmethods; i++) { 4918 clean_nmethod(claimed_nmethods[i]); 4919 } 4920 } 4921 4922 // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark. 4923 // Need to retire the buffers now that this thread has stopped cleaning nmethods. 4924 MetadataOnStackMark::retire_buffer_for_thread(Thread::current()); 4925 } 4926 4927 void work_second_pass(uint worker_id) { 4928 nmethod* nm; 4929 // Take care of postponed nmethods. 4930 while ((nm = claim_postponed_nmethod()) != NULL) { 4931 clean_nmethod_postponed(nm); 4932 } 4933 } 4934 }; 4935 4936 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock"); 4937 4938 class G1KlassCleaningTask : public StackObj { 4939 BoolObjectClosure* _is_alive; 4940 volatile jint _clean_klass_tree_claimed; 4941 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator; 4942 4943 public: 4944 G1KlassCleaningTask(BoolObjectClosure* is_alive) : 4945 _is_alive(is_alive), 4946 _clean_klass_tree_claimed(0), 4947 _klass_iterator() { 4948 } 4949 4950 private: 4951 bool claim_clean_klass_tree_task() { 4952 if (_clean_klass_tree_claimed) { 4953 return false; 4954 } 4955 4956 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0; 4957 } 4958 4959 InstanceKlass* claim_next_klass() { 4960 Klass* klass; 4961 do { 4962 klass =_klass_iterator.next_klass(); 4963 } while (klass != NULL && !klass->oop_is_instance()); 4964 4965 return (InstanceKlass*)klass; 4966 } 4967 4968 public: 4969 4970 void clean_klass(InstanceKlass* ik) { 4971 ik->clean_implementors_list(_is_alive); 4972 ik->clean_method_data(_is_alive); 4973 4974 // G1 specific cleanup work that has 4975 // been moved here to be done in parallel. 4976 ik->clean_dependent_nmethods(); 4977 if (JvmtiExport::has_redefined_a_class()) { 4978 InstanceKlass::purge_previous_versions(ik); 4979 } 4980 } 4981 4982 void work() { 4983 ResourceMark rm; 4984 4985 // One worker will clean the subklass/sibling klass tree. 4986 if (claim_clean_klass_tree_task()) { 4987 Klass::clean_subklass_tree(_is_alive); 4988 } 4989 4990 // All workers will help cleaning the classes, 4991 InstanceKlass* klass; 4992 while ((klass = claim_next_klass()) != NULL) { 4993 clean_klass(klass); 4994 } 4995 } 4996 }; 4997 4998 // To minimize the remark pause times, the tasks below are done in parallel. 4999 class G1ParallelCleaningTask : public AbstractGangTask { 5000 private: 5001 G1StringSymbolTableUnlinkTask _string_symbol_task; 5002 G1CodeCacheUnloadingTask _code_cache_task; 5003 G1KlassCleaningTask _klass_cleaning_task; 5004 5005 public: 5006 // The constructor is run in the VMThread. 5007 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) : 5008 AbstractGangTask("Parallel Cleaning"), 5009 _string_symbol_task(is_alive, process_strings, process_symbols), 5010 _code_cache_task(num_workers, is_alive, unloading_occurred), 5011 _klass_cleaning_task(is_alive) { 5012 } 5013 5014 void pre_work_verification() { 5015 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty"); 5016 } 5017 5018 void post_work_verification() { 5019 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty"); 5020 } 5021 5022 // The parallel work done by all worker threads. 5023 void work(uint worker_id) { 5024 pre_work_verification(); 5025 5026 // Do first pass of code cache cleaning. 5027 _code_cache_task.work_first_pass(worker_id); 5028 5029 // Let the threads mark that the first pass is done. 5030 _code_cache_task.barrier_mark(worker_id); 5031 5032 // Clean the Strings and Symbols. 5033 _string_symbol_task.work(worker_id); 5034 5035 // Wait for all workers to finish the first code cache cleaning pass. 5036 _code_cache_task.barrier_wait(worker_id); 5037 5038 // Do the second code cache cleaning work, which realize on 5039 // the liveness information gathered during the first pass. 5040 _code_cache_task.work_second_pass(worker_id); 5041 5042 // Clean all klasses that were not unloaded. 5043 _klass_cleaning_task.work(); 5044 5045 post_work_verification(); 5046 } 5047 }; 5048 5049 5050 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive, 5051 bool process_strings, 5052 bool process_symbols, 5053 bool class_unloading_occurred) { 5054 uint n_workers = workers()->active_workers(); 5055 5056 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, 5057 n_workers, class_unloading_occurred); 5058 set_par_threads(n_workers); 5059 workers()->run_task(&g1_unlink_task); 5060 set_par_threads(0); 5061 } 5062 5063 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive, 5064 bool process_strings, bool process_symbols) { 5065 { 5066 uint n_workers = _g1h->workers()->active_workers(); 5067 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols); 5068 set_par_threads(n_workers); 5069 workers()->run_task(&g1_unlink_task); 5070 set_par_threads(0); 5071 } 5072 5073 if (G1StringDedup::is_enabled()) { 5074 G1StringDedup::unlink(is_alive); 5075 } 5076 } 5077 5078 class G1RedirtyLoggedCardsTask : public AbstractGangTask { 5079 private: 5080 DirtyCardQueueSet* _queue; 5081 public: 5082 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { } 5083 5084 virtual void work(uint worker_id) { 5085 double start_time = os::elapsedTime(); 5086 5087 RedirtyLoggedCardTableEntryClosure cl; 5088 _queue->par_apply_closure_to_all_completed_buffers(&cl); 5089 5090 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times(); 5091 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0); 5092 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed()); 5093 } 5094 }; 5095 5096 void G1CollectedHeap::redirty_logged_cards() { 5097 double redirty_logged_cards_start = os::elapsedTime(); 5098 5099 uint n_workers = _g1h->workers()->active_workers(); 5100 5101 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set()); 5102 dirty_card_queue_set().reset_for_par_iteration(); 5103 set_par_threads(n_workers); 5104 workers()->run_task(&redirty_task); 5105 set_par_threads(0); 5106 5107 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set(); 5108 dcq.merge_bufferlists(&dirty_card_queue_set()); 5109 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 5110 5111 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0); 5112 } 5113 5114 // Weak Reference Processing support 5115 5116 // An always "is_alive" closure that is used to preserve referents. 5117 // If the object is non-null then it's alive. Used in the preservation 5118 // of referent objects that are pointed to by reference objects 5119 // discovered by the CM ref processor. 5120 class G1AlwaysAliveClosure: public BoolObjectClosure { 5121 G1CollectedHeap* _g1; 5122 public: 5123 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5124 bool do_object_b(oop p) { 5125 if (p != NULL) { 5126 return true; 5127 } 5128 return false; 5129 } 5130 }; 5131 5132 bool G1STWIsAliveClosure::do_object_b(oop p) { 5133 // An object is reachable if it is outside the collection set, 5134 // or is inside and copied. 5135 return !_g1->obj_in_cs(p) || p->is_forwarded(); 5136 } 5137 5138 // Non Copying Keep Alive closure 5139 class G1KeepAliveClosure: public OopClosure { 5140 G1CollectedHeap* _g1; 5141 public: 5142 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 5143 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); } 5144 void do_oop(oop* p) { 5145 oop obj = *p; 5146 assert(obj != NULL, "the caller should have filtered out NULL values"); 5147 5148 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj); 5149 if (cset_state == G1CollectedHeap::InNeither) { 5150 return; 5151 } 5152 if (cset_state == G1CollectedHeap::InCSet) { 5153 assert( obj->is_forwarded(), "invariant" ); 5154 *p = obj->forwardee(); 5155 } else { 5156 assert(!obj->is_forwarded(), "invariant" ); 5157 assert(cset_state == G1CollectedHeap::IsHumongous, 5158 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state)); 5159 _g1->set_humongous_is_live(obj); 5160 } 5161 } 5162 }; 5163 5164 // Copying Keep Alive closure - can be called from both 5165 // serial and parallel code as long as different worker 5166 // threads utilize different G1ParScanThreadState instances 5167 // and different queues. 5168 5169 class G1CopyingKeepAliveClosure: public OopClosure { 5170 G1CollectedHeap* _g1h; 5171 OopClosure* _copy_non_heap_obj_cl; 5172 G1ParScanThreadState* _par_scan_state; 5173 5174 public: 5175 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h, 5176 OopClosure* non_heap_obj_cl, 5177 G1ParScanThreadState* pss): 5178 _g1h(g1h), 5179 _copy_non_heap_obj_cl(non_heap_obj_cl), 5180 _par_scan_state(pss) 5181 {} 5182 5183 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 5184 virtual void do_oop( oop* p) { do_oop_work(p); } 5185 5186 template <class T> void do_oop_work(T* p) { 5187 oop obj = oopDesc::load_decode_heap_oop(p); 5188 5189 if (_g1h->is_in_cset_or_humongous(obj)) { 5190 // If the referent object has been forwarded (either copied 5191 // to a new location or to itself in the event of an 5192 // evacuation failure) then we need to update the reference 5193 // field and, if both reference and referent are in the G1 5194 // heap, update the RSet for the referent. 5195 // 5196 // If the referent has not been forwarded then we have to keep 5197 // it alive by policy. Therefore we have copy the referent. 5198 // 5199 // If the reference field is in the G1 heap then we can push 5200 // on the PSS queue. When the queue is drained (after each 5201 // phase of reference processing) the object and it's followers 5202 // will be copied, the reference field set to point to the 5203 // new location, and the RSet updated. Otherwise we need to 5204 // use the the non-heap or metadata closures directly to copy 5205 // the referent object and update the pointer, while avoiding 5206 // updating the RSet. 5207 5208 if (_g1h->is_in_g1_reserved(p)) { 5209 _par_scan_state->push_on_queue(p); 5210 } else { 5211 assert(!Metaspace::contains((const void*)p), 5212 err_msg("Unexpectedly found a pointer from metadata: " 5213 PTR_FORMAT, p)); 5214 _copy_non_heap_obj_cl->do_oop(p); 5215 } 5216 } 5217 } 5218 }; 5219 5220 // Serial drain queue closure. Called as the 'complete_gc' 5221 // closure for each discovered list in some of the 5222 // reference processing phases. 5223 5224 class G1STWDrainQueueClosure: public VoidClosure { 5225 protected: 5226 G1CollectedHeap* _g1h; 5227 G1ParScanThreadState* _par_scan_state; 5228 5229 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 5230 5231 public: 5232 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) : 5233 _g1h(g1h), 5234 _par_scan_state(pss) 5235 { } 5236 5237 void do_void() { 5238 G1ParScanThreadState* const pss = par_scan_state(); 5239 pss->trim_queue(); 5240 } 5241 }; 5242 5243 // Parallel Reference Processing closures 5244 5245 // Implementation of AbstractRefProcTaskExecutor for parallel reference 5246 // processing during G1 evacuation pauses. 5247 5248 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 5249 private: 5250 G1CollectedHeap* _g1h; 5251 RefToScanQueueSet* _queues; 5252 FlexibleWorkGang* _workers; 5253 int _active_workers; 5254 5255 public: 5256 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h, 5257 FlexibleWorkGang* workers, 5258 RefToScanQueueSet *task_queues, 5259 int n_workers) : 5260 _g1h(g1h), 5261 _queues(task_queues), 5262 _workers(workers), 5263 _active_workers(n_workers) 5264 { 5265 assert(n_workers > 0, "shouldn't call this otherwise"); 5266 } 5267 5268 // Executes the given task using concurrent marking worker threads. 5269 virtual void execute(ProcessTask& task); 5270 virtual void execute(EnqueueTask& task); 5271 }; 5272 5273 // Gang task for possibly parallel reference processing 5274 5275 class G1STWRefProcTaskProxy: public AbstractGangTask { 5276 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 5277 ProcessTask& _proc_task; 5278 G1CollectedHeap* _g1h; 5279 RefToScanQueueSet *_task_queues; 5280 ParallelTaskTerminator* _terminator; 5281 5282 public: 5283 G1STWRefProcTaskProxy(ProcessTask& proc_task, 5284 G1CollectedHeap* g1h, 5285 RefToScanQueueSet *task_queues, 5286 ParallelTaskTerminator* terminator) : 5287 AbstractGangTask("Process reference objects in parallel"), 5288 _proc_task(proc_task), 5289 _g1h(g1h), 5290 _task_queues(task_queues), 5291 _terminator(terminator) 5292 {} 5293 5294 virtual void work(uint worker_id) { 5295 // The reference processing task executed by a single worker. 5296 ResourceMark rm; 5297 HandleMark hm; 5298 5299 G1STWIsAliveClosure is_alive(_g1h); 5300 5301 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5302 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5303 5304 pss.set_evac_failure_closure(&evac_failure_cl); 5305 5306 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5307 5308 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5309 5310 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5311 5312 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5313 // We also need to mark copied objects. 5314 copy_non_heap_cl = ©_mark_non_heap_cl; 5315 } 5316 5317 // Keep alive closure. 5318 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5319 5320 // Complete GC closure 5321 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator); 5322 5323 // Call the reference processing task's work routine. 5324 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue); 5325 5326 // Note we cannot assert that the refs array is empty here as not all 5327 // of the processing tasks (specifically phase2 - pp2_work) execute 5328 // the complete_gc closure (which ordinarily would drain the queue) so 5329 // the queue may not be empty. 5330 } 5331 }; 5332 5333 // Driver routine for parallel reference processing. 5334 // Creates an instance of the ref processing gang 5335 // task and has the worker threads execute it. 5336 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) { 5337 assert(_workers != NULL, "Need parallel worker threads."); 5338 5339 ParallelTaskTerminator terminator(_active_workers, _queues); 5340 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator); 5341 5342 _g1h->set_par_threads(_active_workers); 5343 _workers->run_task(&proc_task_proxy); 5344 _g1h->set_par_threads(0); 5345 } 5346 5347 // Gang task for parallel reference enqueueing. 5348 5349 class G1STWRefEnqueueTaskProxy: public AbstractGangTask { 5350 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 5351 EnqueueTask& _enq_task; 5352 5353 public: 5354 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) : 5355 AbstractGangTask("Enqueue reference objects in parallel"), 5356 _enq_task(enq_task) 5357 { } 5358 5359 virtual void work(uint worker_id) { 5360 _enq_task.work(worker_id); 5361 } 5362 }; 5363 5364 // Driver routine for parallel reference enqueueing. 5365 // Creates an instance of the ref enqueueing gang 5366 // task and has the worker threads execute it. 5367 5368 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 5369 assert(_workers != NULL, "Need parallel worker threads."); 5370 5371 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task); 5372 5373 _g1h->set_par_threads(_active_workers); 5374 _workers->run_task(&enq_task_proxy); 5375 _g1h->set_par_threads(0); 5376 } 5377 5378 // End of weak reference support closures 5379 5380 // Abstract task used to preserve (i.e. copy) any referent objects 5381 // that are in the collection set and are pointed to by reference 5382 // objects discovered by the CM ref processor. 5383 5384 class G1ParPreserveCMReferentsTask: public AbstractGangTask { 5385 protected: 5386 G1CollectedHeap* _g1h; 5387 RefToScanQueueSet *_queues; 5388 ParallelTaskTerminator _terminator; 5389 uint _n_workers; 5390 5391 public: 5392 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) : 5393 AbstractGangTask("ParPreserveCMReferents"), 5394 _g1h(g1h), 5395 _queues(task_queues), 5396 _terminator(workers, _queues), 5397 _n_workers(workers) 5398 { } 5399 5400 void work(uint worker_id) { 5401 ResourceMark rm; 5402 HandleMark hm; 5403 5404 G1ParScanThreadState pss(_g1h, worker_id, NULL); 5405 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL); 5406 5407 pss.set_evac_failure_closure(&evac_failure_cl); 5408 5409 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5410 5411 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL); 5412 5413 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL); 5414 5415 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5416 5417 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5418 // We also need to mark copied objects. 5419 copy_non_heap_cl = ©_mark_non_heap_cl; 5420 } 5421 5422 // Is alive closure 5423 G1AlwaysAliveClosure always_alive(_g1h); 5424 5425 // Copying keep alive closure. Applied to referent objects that need 5426 // to be copied. 5427 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss); 5428 5429 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 5430 5431 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q(); 5432 uint stride = MIN2(MAX2(_n_workers, 1U), limit); 5433 5434 // limit is set using max_num_q() - which was set using ParallelGCThreads. 5435 // So this must be true - but assert just in case someone decides to 5436 // change the worker ids. 5437 assert(0 <= worker_id && worker_id < limit, "sanity"); 5438 assert(!rp->discovery_is_atomic(), "check this code"); 5439 5440 // Select discovered lists [i, i+stride, i+2*stride,...,limit) 5441 for (uint idx = worker_id; idx < limit; idx += stride) { 5442 DiscoveredList& ref_list = rp->discovered_refs()[idx]; 5443 5444 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive); 5445 while (iter.has_next()) { 5446 // Since discovery is not atomic for the CM ref processor, we 5447 // can see some null referent objects. 5448 iter.load_ptrs(DEBUG_ONLY(true)); 5449 oop ref = iter.obj(); 5450 5451 // This will filter nulls. 5452 if (iter.is_referent_alive()) { 5453 iter.make_referent_alive(); 5454 } 5455 iter.move_to_next(); 5456 } 5457 } 5458 5459 // Drain the queue - which may cause stealing 5460 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator); 5461 drain_queue.do_void(); 5462 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure 5463 assert(pss.queue_is_empty(), "should be"); 5464 } 5465 }; 5466 5467 // Weak Reference processing during an evacuation pause (part 1). 5468 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) { 5469 double ref_proc_start = os::elapsedTime(); 5470 5471 ReferenceProcessor* rp = _ref_processor_stw; 5472 assert(rp->discovery_enabled(), "should have been enabled"); 5473 5474 // Any reference objects, in the collection set, that were 'discovered' 5475 // by the CM ref processor should have already been copied (either by 5476 // applying the external root copy closure to the discovered lists, or 5477 // by following an RSet entry). 5478 // 5479 // But some of the referents, that are in the collection set, that these 5480 // reference objects point to may not have been copied: the STW ref 5481 // processor would have seen that the reference object had already 5482 // been 'discovered' and would have skipped discovering the reference, 5483 // but would not have treated the reference object as a regular oop. 5484 // As a result the copy closure would not have been applied to the 5485 // referent object. 5486 // 5487 // We need to explicitly copy these referent objects - the references 5488 // will be processed at the end of remarking. 5489 // 5490 // We also need to do this copying before we process the reference 5491 // objects discovered by the STW ref processor in case one of these 5492 // referents points to another object which is also referenced by an 5493 // object discovered by the STW ref processor. 5494 5495 assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers"); 5496 5497 set_par_threads(no_of_gc_workers); 5498 G1ParPreserveCMReferentsTask keep_cm_referents(this, 5499 no_of_gc_workers, 5500 _task_queues); 5501 5502 workers()->run_task(&keep_cm_referents); 5503 5504 set_par_threads(0); 5505 5506 // Closure to test whether a referent is alive. 5507 G1STWIsAliveClosure is_alive(this); 5508 5509 // Even when parallel reference processing is enabled, the processing 5510 // of JNI refs is serial and performed serially by the current thread 5511 // rather than by a worker. The following PSS will be used for processing 5512 // JNI refs. 5513 5514 // Use only a single queue for this PSS. 5515 G1ParScanThreadState pss(this, 0, NULL); 5516 5517 // We do not embed a reference processor in the copying/scanning 5518 // closures while we're actually processing the discovered 5519 // reference objects. 5520 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL); 5521 5522 pss.set_evac_failure_closure(&evac_failure_cl); 5523 5524 assert(pss.queue_is_empty(), "pre-condition"); 5525 5526 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL); 5527 5528 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL); 5529 5530 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl; 5531 5532 if (_g1h->g1_policy()->during_initial_mark_pause()) { 5533 // We also need to mark copied objects. 5534 copy_non_heap_cl = ©_mark_non_heap_cl; 5535 } 5536 5537 // Keep alive closure. 5538 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss); 5539 5540 // Serial Complete GC closure 5541 G1STWDrainQueueClosure drain_queue(this, &pss); 5542 5543 // Setup the soft refs policy... 5544 rp->setup_policy(false); 5545 5546 ReferenceProcessorStats stats; 5547 if (!rp->processing_is_mt()) { 5548 // Serial reference processing... 5549 stats = rp->process_discovered_references(&is_alive, 5550 &keep_alive, 5551 &drain_queue, 5552 NULL, 5553 _gc_timer_stw, 5554 _gc_tracer_stw->gc_id()); 5555 } else { 5556 // Parallel reference processing 5557 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5558 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5559 5560 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5561 stats = rp->process_discovered_references(&is_alive, 5562 &keep_alive, 5563 &drain_queue, 5564 &par_task_executor, 5565 _gc_timer_stw, 5566 _gc_tracer_stw->gc_id()); 5567 } 5568 5569 _gc_tracer_stw->report_gc_reference_stats(stats); 5570 5571 // We have completed copying any necessary live referent objects. 5572 assert(pss.queue_is_empty(), "both queue and overflow should be empty"); 5573 5574 double ref_proc_time = os::elapsedTime() - ref_proc_start; 5575 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0); 5576 } 5577 5578 // Weak Reference processing during an evacuation pause (part 2). 5579 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) { 5580 double ref_enq_start = os::elapsedTime(); 5581 5582 ReferenceProcessor* rp = _ref_processor_stw; 5583 assert(!rp->discovery_enabled(), "should have been disabled as part of processing"); 5584 5585 // Now enqueue any remaining on the discovered lists on to 5586 // the pending list. 5587 if (!rp->processing_is_mt()) { 5588 // Serial reference processing... 5589 rp->enqueue_discovered_references(); 5590 } else { 5591 // Parallel reference enqueueing 5592 5593 assert(no_of_gc_workers == workers()->active_workers(), 5594 "Need to reset active workers"); 5595 assert(rp->num_q() == no_of_gc_workers, "sanity"); 5596 assert(no_of_gc_workers <= rp->max_num_q(), "sanity"); 5597 5598 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers); 5599 rp->enqueue_discovered_references(&par_task_executor); 5600 } 5601 5602 rp->verify_no_references_recorded(); 5603 assert(!rp->discovery_enabled(), "should have been disabled"); 5604 5605 // FIXME 5606 // CM's reference processing also cleans up the string and symbol tables. 5607 // Should we do that here also? We could, but it is a serial operation 5608 // and could significantly increase the pause time. 5609 5610 double ref_enq_time = os::elapsedTime() - ref_enq_start; 5611 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0); 5612 } 5613 5614 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) { 5615 _expand_heap_after_alloc_failure = true; 5616 _evacuation_failed = false; 5617 5618 // Should G1EvacuationFailureALot be in effect for this GC? 5619 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();) 5620 5621 g1_rem_set()->prepare_for_oops_into_collection_set_do(); 5622 5623 // Disable the hot card cache. 5624 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 5625 hot_card_cache->reset_hot_cache_claimed_index(); 5626 hot_card_cache->set_use_cache(false); 5627 5628 uint n_workers; 5629 n_workers = 5630 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(), 5631 workers()->active_workers(), 5632 Threads::number_of_non_daemon_threads()); 5633 assert(UseDynamicNumberOfGCThreads || 5634 n_workers == workers()->total_workers(), 5635 "If not dynamic should be using all the workers"); 5636 workers()->set_active_workers(n_workers); 5637 set_par_threads(n_workers); 5638 5639 G1ParTask g1_par_task(this, _task_queues); 5640 5641 init_for_evac_failure(NULL); 5642 5643 rem_set()->prepare_for_younger_refs_iterate(true); 5644 5645 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty"); 5646 double start_par_time_sec = os::elapsedTime(); 5647 double end_par_time_sec; 5648 5649 { 5650 StrongRootsScope srs(this); 5651 // InitialMark needs claim bits to keep track of the marked-through CLDs. 5652 if (g1_policy()->during_initial_mark_pause()) { 5653 ClassLoaderDataGraph::clear_claimed_marks(); 5654 } 5655 5656 // The individual threads will set their evac-failure closures. 5657 if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr(); 5658 // These tasks use ShareHeap::_process_strong_tasks 5659 assert(UseDynamicNumberOfGCThreads || 5660 workers()->active_workers() == workers()->total_workers(), 5661 "If not dynamic should be using all the workers"); 5662 workers()->run_task(&g1_par_task); 5663 end_par_time_sec = os::elapsedTime(); 5664 5665 // Closing the inner scope will execute the destructor 5666 // for the StrongRootsScope object. We record the current 5667 // elapsed time before closing the scope so that time 5668 // taken for the SRS destructor is NOT included in the 5669 // reported parallel time. 5670 } 5671 5672 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0; 5673 g1_policy()->phase_times()->record_par_time(par_time_ms); 5674 5675 double code_root_fixup_time_ms = 5676 (os::elapsedTime() - end_par_time_sec) * 1000.0; 5677 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms); 5678 5679 set_par_threads(0); 5680 5681 // Process any discovered reference objects - we have 5682 // to do this _before_ we retire the GC alloc regions 5683 // as we may have to copy some 'reachable' referent 5684 // objects (and their reachable sub-graphs) that were 5685 // not copied during the pause. 5686 process_discovered_references(n_workers); 5687 5688 if (G1StringDedup::is_enabled()) { 5689 G1STWIsAliveClosure is_alive(this); 5690 G1KeepAliveClosure keep_alive(this); 5691 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive); 5692 } 5693 5694 _allocator->release_gc_alloc_regions(n_workers, evacuation_info); 5695 g1_rem_set()->cleanup_after_oops_into_collection_set_do(); 5696 5697 // Reset and re-enable the hot card cache. 5698 // Note the counts for the cards in the regions in the 5699 // collection set are reset when the collection set is freed. 5700 hot_card_cache->reset_hot_cache(); 5701 hot_card_cache->set_use_cache(true); 5702 5703 purge_code_root_memory(); 5704 5705 finalize_for_evac_failure(); 5706 5707 if (evacuation_failed()) { 5708 remove_self_forwarding_pointers(); 5709 5710 // Reset the G1EvacuationFailureALot counters and flags 5711 // Note: the values are reset only when an actual 5712 // evacuation failure occurs. 5713 NOT_PRODUCT(reset_evacuation_should_fail();) 5714 } 5715 5716 // Enqueue any remaining references remaining on the STW 5717 // reference processor's discovered lists. We need to do 5718 // this after the card table is cleaned (and verified) as 5719 // the act of enqueueing entries on to the pending list 5720 // will log these updates (and dirty their associated 5721 // cards). We need these updates logged to update any 5722 // RSets. 5723 enqueue_discovered_references(n_workers); 5724 5725 redirty_logged_cards(); 5726 COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); 5727 } 5728 5729 void G1CollectedHeap::free_region(HeapRegion* hr, 5730 FreeRegionList* free_list, 5731 bool par, 5732 bool locked) { 5733 assert(!hr->is_free(), "the region should not be free"); 5734 assert(!hr->is_empty(), "the region should not be empty"); 5735 assert(_hrm.is_available(hr->hrm_index()), "region should be committed"); 5736 assert(free_list != NULL, "pre-condition"); 5737 5738 if (G1VerifyBitmaps) { 5739 MemRegion mr(hr->bottom(), hr->end()); 5740 concurrent_mark()->clearRangePrevBitmap(mr); 5741 } 5742 5743 // Clear the card counts for this region. 5744 // Note: we only need to do this if the region is not young 5745 // (since we don't refine cards in young regions). 5746 if (!hr->is_young()) { 5747 _cg1r->hot_card_cache()->reset_card_counts(hr); 5748 } 5749 hr->hr_clear(par, true /* clear_space */, locked /* locked */); 5750 free_list->add_ordered(hr); 5751 } 5752 5753 void G1CollectedHeap::free_humongous_region(HeapRegion* hr, 5754 FreeRegionList* free_list, 5755 bool par) { 5756 assert(hr->is_starts_humongous(), "this is only for starts humongous regions"); 5757 assert(free_list != NULL, "pre-condition"); 5758 5759 size_t hr_capacity = hr->capacity(); 5760 // We need to read this before we make the region non-humongous, 5761 // otherwise the information will be gone. 5762 uint last_index = hr->last_hc_index(); 5763 hr->clear_humongous(); 5764 free_region(hr, free_list, par); 5765 5766 uint i = hr->hrm_index() + 1; 5767 while (i < last_index) { 5768 HeapRegion* curr_hr = region_at(i); 5769 assert(curr_hr->is_continues_humongous(), "invariant"); 5770 curr_hr->clear_humongous(); 5771 free_region(curr_hr, free_list, par); 5772 i += 1; 5773 } 5774 } 5775 5776 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, 5777 const HeapRegionSetCount& humongous_regions_removed) { 5778 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) { 5779 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag); 5780 _old_set.bulk_remove(old_regions_removed); 5781 _humongous_set.bulk_remove(humongous_regions_removed); 5782 } 5783 5784 } 5785 5786 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) { 5787 assert(list != NULL, "list can't be null"); 5788 if (!list->is_empty()) { 5789 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag); 5790 _hrm.insert_list_into_free_list(list); 5791 } 5792 } 5793 5794 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) { 5795 _allocator->decrease_used(bytes); 5796 } 5797 5798 class G1ParCleanupCTTask : public AbstractGangTask { 5799 G1SATBCardTableModRefBS* _ct_bs; 5800 G1CollectedHeap* _g1h; 5801 HeapRegion* volatile _su_head; 5802 public: 5803 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs, 5804 G1CollectedHeap* g1h) : 5805 AbstractGangTask("G1 Par Cleanup CT Task"), 5806 _ct_bs(ct_bs), _g1h(g1h) { } 5807 5808 void work(uint worker_id) { 5809 HeapRegion* r; 5810 while (r = _g1h->pop_dirty_cards_region()) { 5811 clear_cards(r); 5812 } 5813 } 5814 5815 void clear_cards(HeapRegion* r) { 5816 // Cards of the survivors should have already been dirtied. 5817 if (!r->is_survivor()) { 5818 _ct_bs->clear(MemRegion(r->bottom(), r->end())); 5819 } 5820 } 5821 }; 5822 5823 #ifndef PRODUCT 5824 class G1VerifyCardTableCleanup: public HeapRegionClosure { 5825 G1CollectedHeap* _g1h; 5826 G1SATBCardTableModRefBS* _ct_bs; 5827 public: 5828 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs) 5829 : _g1h(g1h), _ct_bs(ct_bs) { } 5830 virtual bool doHeapRegion(HeapRegion* r) { 5831 if (r->is_survivor()) { 5832 _g1h->verify_dirty_region(r); 5833 } else { 5834 _g1h->verify_not_dirty_region(r); 5835 } 5836 return false; 5837 } 5838 }; 5839 5840 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) { 5841 // All of the region should be clean. 5842 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5843 MemRegion mr(hr->bottom(), hr->end()); 5844 ct_bs->verify_not_dirty_region(mr); 5845 } 5846 5847 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) { 5848 // We cannot guarantee that [bottom(),end()] is dirty. Threads 5849 // dirty allocated blocks as they allocate them. The thread that 5850 // retires each region and replaces it with a new one will do a 5851 // maximal allocation to fill in [pre_dummy_top(),end()] but will 5852 // not dirty that area (one less thing to have to do while holding 5853 // a lock). So we can only verify that [bottom(),pre_dummy_top()] 5854 // is dirty. 5855 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5856 MemRegion mr(hr->bottom(), hr->pre_dummy_top()); 5857 if (hr->is_young()) { 5858 ct_bs->verify_g1_young_region(mr); 5859 } else { 5860 ct_bs->verify_dirty_region(mr); 5861 } 5862 } 5863 5864 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) { 5865 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5866 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) { 5867 verify_dirty_region(hr); 5868 } 5869 } 5870 5871 void G1CollectedHeap::verify_dirty_young_regions() { 5872 verify_dirty_young_list(_young_list->first_region()); 5873 } 5874 5875 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 5876 HeapWord* tams, HeapWord* end) { 5877 guarantee(tams <= end, 5878 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end)); 5879 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end); 5880 if (result < end) { 5881 gclog_or_tty->cr(); 5882 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT, 5883 bitmap_name, result); 5884 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT, 5885 bitmap_name, tams, end); 5886 return false; 5887 } 5888 return true; 5889 } 5890 5891 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) { 5892 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap(); 5893 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap(); 5894 5895 HeapWord* bottom = hr->bottom(); 5896 HeapWord* ptams = hr->prev_top_at_mark_start(); 5897 HeapWord* ntams = hr->next_top_at_mark_start(); 5898 HeapWord* end = hr->end(); 5899 5900 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end); 5901 5902 bool res_n = true; 5903 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window 5904 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap 5905 // if we happen to be in that state. 5906 if (mark_in_progress() || !_cmThread->in_progress()) { 5907 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end); 5908 } 5909 if (!res_p || !res_n) { 5910 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT, 5911 HR_FORMAT_PARAMS(hr)); 5912 gclog_or_tty->print_cr("#### Caller: %s", caller); 5913 return false; 5914 } 5915 return true; 5916 } 5917 5918 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) { 5919 if (!G1VerifyBitmaps) return; 5920 5921 guarantee(verify_bitmaps(caller, hr), "bitmap verification"); 5922 } 5923 5924 class G1VerifyBitmapClosure : public HeapRegionClosure { 5925 private: 5926 const char* _caller; 5927 G1CollectedHeap* _g1h; 5928 bool _failures; 5929 5930 public: 5931 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) : 5932 _caller(caller), _g1h(g1h), _failures(false) { } 5933 5934 bool failures() { return _failures; } 5935 5936 virtual bool doHeapRegion(HeapRegion* hr) { 5937 if (hr->is_continues_humongous()) return false; 5938 5939 bool result = _g1h->verify_bitmaps(_caller, hr); 5940 if (!result) { 5941 _failures = true; 5942 } 5943 return false; 5944 } 5945 }; 5946 5947 void G1CollectedHeap::check_bitmaps(const char* caller) { 5948 if (!G1VerifyBitmaps) return; 5949 5950 G1VerifyBitmapClosure cl(caller, this); 5951 heap_region_iterate(&cl); 5952 guarantee(!cl.failures(), "bitmap verification"); 5953 } 5954 #endif // PRODUCT 5955 5956 void G1CollectedHeap::cleanUpCardTable() { 5957 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set(); 5958 double start = os::elapsedTime(); 5959 5960 { 5961 // Iterate over the dirty cards region list. 5962 G1ParCleanupCTTask cleanup_task(ct_bs, this); 5963 5964 set_par_threads(); 5965 workers()->run_task(&cleanup_task); 5966 set_par_threads(0); 5967 #ifndef PRODUCT 5968 if (G1VerifyCTCleanup || VerifyAfterGC) { 5969 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs); 5970 heap_region_iterate(&cleanup_verifier); 5971 } 5972 #endif 5973 } 5974 5975 double elapsed = os::elapsedTime() - start; 5976 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0); 5977 } 5978 5979 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) { 5980 size_t pre_used = 0; 5981 FreeRegionList local_free_list("Local List for CSet Freeing"); 5982 5983 double young_time_ms = 0.0; 5984 double non_young_time_ms = 0.0; 5985 5986 // Since the collection set is a superset of the the young list, 5987 // all we need to do to clear the young list is clear its 5988 // head and length, and unlink any young regions in the code below 5989 _young_list->clear(); 5990 5991 G1CollectorPolicy* policy = g1_policy(); 5992 5993 double start_sec = os::elapsedTime(); 5994 bool non_young = true; 5995 5996 HeapRegion* cur = cs_head; 5997 int age_bound = -1; 5998 size_t rs_lengths = 0; 5999 6000 while (cur != NULL) { 6001 assert(!is_on_master_free_list(cur), "sanity"); 6002 if (non_young) { 6003 if (cur->is_young()) { 6004 double end_sec = os::elapsedTime(); 6005 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6006 non_young_time_ms += elapsed_ms; 6007 6008 start_sec = os::elapsedTime(); 6009 non_young = false; 6010 } 6011 } else { 6012 if (!cur->is_young()) { 6013 double end_sec = os::elapsedTime(); 6014 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6015 young_time_ms += elapsed_ms; 6016 6017 start_sec = os::elapsedTime(); 6018 non_young = true; 6019 } 6020 } 6021 6022 rs_lengths += cur->rem_set()->occupied_locked(); 6023 6024 HeapRegion* next = cur->next_in_collection_set(); 6025 assert(cur->in_collection_set(), "bad CS"); 6026 cur->set_next_in_collection_set(NULL); 6027 cur->set_in_collection_set(false); 6028 6029 if (cur->is_young()) { 6030 int index = cur->young_index_in_cset(); 6031 assert(index != -1, "invariant"); 6032 assert((uint) index < policy->young_cset_region_length(), "invariant"); 6033 size_t words_survived = _surviving_young_words[index]; 6034 cur->record_surv_words_in_group(words_survived); 6035 6036 // At this point the we have 'popped' cur from the collection set 6037 // (linked via next_in_collection_set()) but it is still in the 6038 // young list (linked via next_young_region()). Clear the 6039 // _next_young_region field. 6040 cur->set_next_young_region(NULL); 6041 } else { 6042 int index = cur->young_index_in_cset(); 6043 assert(index == -1, "invariant"); 6044 } 6045 6046 assert( (cur->is_young() && cur->young_index_in_cset() > -1) || 6047 (!cur->is_young() && cur->young_index_in_cset() == -1), 6048 "invariant" ); 6049 6050 if (!cur->evacuation_failed()) { 6051 MemRegion used_mr = cur->used_region(); 6052 6053 // And the region is empty. 6054 assert(!used_mr.is_empty(), "Should not have empty regions in a CS."); 6055 pre_used += cur->used(); 6056 free_region(cur, &local_free_list, false /* par */, true /* locked */); 6057 } else { 6058 cur->uninstall_surv_rate_group(); 6059 if (cur->is_young()) { 6060 cur->set_young_index_in_cset(-1); 6061 } 6062 cur->set_evacuation_failed(false); 6063 // The region is now considered to be old. 6064 cur->set_old(); 6065 _old_set.add(cur); 6066 evacuation_info.increment_collectionset_used_after(cur->used()); 6067 } 6068 cur = next; 6069 } 6070 6071 evacuation_info.set_regions_freed(local_free_list.length()); 6072 policy->record_max_rs_lengths(rs_lengths); 6073 policy->cset_regions_freed(); 6074 6075 double end_sec = os::elapsedTime(); 6076 double elapsed_ms = (end_sec - start_sec) * 1000.0; 6077 6078 if (non_young) { 6079 non_young_time_ms += elapsed_ms; 6080 } else { 6081 young_time_ms += elapsed_ms; 6082 } 6083 6084 prepend_to_freelist(&local_free_list); 6085 decrement_summary_bytes(pre_used); 6086 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms); 6087 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms); 6088 } 6089 6090 class G1FreeHumongousRegionClosure : public HeapRegionClosure { 6091 private: 6092 FreeRegionList* _free_region_list; 6093 HeapRegionSet* _proxy_set; 6094 HeapRegionSetCount _humongous_regions_removed; 6095 size_t _freed_bytes; 6096 public: 6097 6098 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) : 6099 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) { 6100 } 6101 6102 virtual bool doHeapRegion(HeapRegion* r) { 6103 if (!r->is_starts_humongous()) { 6104 return false; 6105 } 6106 6107 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 6108 6109 oop obj = (oop)r->bottom(); 6110 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap(); 6111 6112 // The following checks whether the humongous object is live are sufficient. 6113 // The main additional check (in addition to having a reference from the roots 6114 // or the young gen) is whether the humongous object has a remembered set entry. 6115 // 6116 // A humongous object cannot be live if there is no remembered set for it 6117 // because: 6118 // - there can be no references from within humongous starts regions referencing 6119 // the object because we never allocate other objects into them. 6120 // (I.e. there are no intra-region references that may be missed by the 6121 // remembered set) 6122 // - as soon there is a remembered set entry to the humongous starts region 6123 // (i.e. it has "escaped" to an old object) this remembered set entry will stay 6124 // until the end of a concurrent mark. 6125 // 6126 // It is not required to check whether the object has been found dead by marking 6127 // or not, in fact it would prevent reclamation within a concurrent cycle, as 6128 // all objects allocated during that time are considered live. 6129 // SATB marking is even more conservative than the remembered set. 6130 // So if at this point in the collection there is no remembered set entry, 6131 // nobody has a reference to it. 6132 // At the start of collection we flush all refinement logs, and remembered sets 6133 // are completely up-to-date wrt to references to the humongous object. 6134 // 6135 // Other implementation considerations: 6136 // - never consider object arrays: while they are a valid target, they have not 6137 // been observed to be used as temporary objects. 6138 // - they would also pose considerable effort for cleaning up the the remembered 6139 // sets. 6140 // While this cleanup is not strictly necessary to be done (or done instantly), 6141 // given that their occurrence is very low, this saves us this additional 6142 // complexity. 6143 uint region_idx = r->hrm_index(); 6144 if (g1h->humongous_is_live(region_idx) || 6145 g1h->humongous_region_is_always_live(region_idx)) { 6146 6147 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 6148 gclog_or_tty->print_cr("Live humongous %d region %d size "SIZE_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d", 6149 r->is_humongous(), 6150 region_idx, 6151 obj->size()*HeapWordSize, 6152 r->rem_set()->occupied(), 6153 r->rem_set()->strong_code_roots_list_length(), 6154 next_bitmap->isMarked(r->bottom()), 6155 g1h->humongous_is_live(region_idx), 6156 obj->is_objArray() 6157 ); 6158 } 6159 6160 return false; 6161 } 6162 6163 guarantee(!obj->is_objArray(), 6164 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.", 6165 r->bottom())); 6166 6167 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) { 6168 gclog_or_tty->print_cr("Reclaim humongous region %d size "SIZE_FORMAT" start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d", 6169 r->is_humongous(), 6170 obj->size()*HeapWordSize, 6171 r->bottom(), 6172 region_idx, 6173 r->region_num(), 6174 r->rem_set()->occupied(), 6175 r->rem_set()->strong_code_roots_list_length(), 6176 next_bitmap->isMarked(r->bottom()), 6177 g1h->humongous_is_live(region_idx), 6178 obj->is_objArray() 6179 ); 6180 } 6181 // Need to clear mark bit of the humongous object if already set. 6182 if (next_bitmap->isMarked(r->bottom())) { 6183 next_bitmap->clear(r->bottom()); 6184 } 6185 _freed_bytes += r->used(); 6186 r->set_containing_set(NULL); 6187 _humongous_regions_removed.increment(1u, r->capacity()); 6188 g1h->free_humongous_region(r, _free_region_list, false); 6189 6190 return false; 6191 } 6192 6193 HeapRegionSetCount& humongous_free_count() { 6194 return _humongous_regions_removed; 6195 } 6196 6197 size_t bytes_freed() const { 6198 return _freed_bytes; 6199 } 6200 6201 size_t humongous_reclaimed() const { 6202 return _humongous_regions_removed.length(); 6203 } 6204 }; 6205 6206 void G1CollectedHeap::eagerly_reclaim_humongous_regions() { 6207 assert_at_safepoint(true); 6208 6209 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || 6210 (!_has_humongous_reclaim_candidates && !G1TraceReclaimDeadHumongousObjectsAtYoungGC)) { 6211 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0); 6212 return; 6213 } 6214 6215 double start_time = os::elapsedTime(); 6216 6217 FreeRegionList local_cleanup_list("Local Humongous Cleanup List"); 6218 6219 G1FreeHumongousRegionClosure cl(&local_cleanup_list); 6220 heap_region_iterate(&cl); 6221 6222 HeapRegionSetCount empty_set; 6223 remove_from_old_sets(empty_set, cl.humongous_free_count()); 6224 6225 G1HRPrinter* hr_printer = _g1h->hr_printer(); 6226 if (hr_printer->is_active()) { 6227 FreeRegionListIterator iter(&local_cleanup_list); 6228 while (iter.more_available()) { 6229 HeapRegion* hr = iter.get_next(); 6230 hr_printer->cleanup(hr); 6231 } 6232 } 6233 6234 prepend_to_freelist(&local_cleanup_list); 6235 decrement_summary_bytes(cl.bytes_freed()); 6236 6237 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0, 6238 cl.humongous_reclaimed()); 6239 } 6240 6241 // This routine is similar to the above but does not record 6242 // any policy statistics or update free lists; we are abandoning 6243 // the current incremental collection set in preparation of a 6244 // full collection. After the full GC we will start to build up 6245 // the incremental collection set again. 6246 // This is only called when we're doing a full collection 6247 // and is immediately followed by the tearing down of the young list. 6248 6249 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) { 6250 HeapRegion* cur = cs_head; 6251 6252 while (cur != NULL) { 6253 HeapRegion* next = cur->next_in_collection_set(); 6254 assert(cur->in_collection_set(), "bad CS"); 6255 cur->set_next_in_collection_set(NULL); 6256 cur->set_in_collection_set(false); 6257 cur->set_young_index_in_cset(-1); 6258 cur = next; 6259 } 6260 } 6261 6262 void G1CollectedHeap::set_free_regions_coming() { 6263 if (G1ConcRegionFreeingVerbose) { 6264 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6265 "setting free regions coming"); 6266 } 6267 6268 assert(!free_regions_coming(), "pre-condition"); 6269 _free_regions_coming = true; 6270 } 6271 6272 void G1CollectedHeap::reset_free_regions_coming() { 6273 assert(free_regions_coming(), "pre-condition"); 6274 6275 { 6276 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6277 _free_regions_coming = false; 6278 SecondaryFreeList_lock->notify_all(); 6279 } 6280 6281 if (G1ConcRegionFreeingVerbose) { 6282 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : " 6283 "reset free regions coming"); 6284 } 6285 } 6286 6287 void G1CollectedHeap::wait_while_free_regions_coming() { 6288 // Most of the time we won't have to wait, so let's do a quick test 6289 // first before we take the lock. 6290 if (!free_regions_coming()) { 6291 return; 6292 } 6293 6294 if (G1ConcRegionFreeingVerbose) { 6295 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6296 "waiting for free regions"); 6297 } 6298 6299 { 6300 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6301 while (free_regions_coming()) { 6302 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag); 6303 } 6304 } 6305 6306 if (G1ConcRegionFreeingVerbose) { 6307 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : " 6308 "done waiting for free regions"); 6309 } 6310 } 6311 6312 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) { 6313 assert(heap_lock_held_for_gc(), 6314 "the heap lock should already be held by or for this thread"); 6315 _young_list->push_region(hr); 6316 } 6317 6318 class NoYoungRegionsClosure: public HeapRegionClosure { 6319 private: 6320 bool _success; 6321 public: 6322 NoYoungRegionsClosure() : _success(true) { } 6323 bool doHeapRegion(HeapRegion* r) { 6324 if (r->is_young()) { 6325 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young", 6326 r->bottom(), r->end()); 6327 _success = false; 6328 } 6329 return false; 6330 } 6331 bool success() { return _success; } 6332 }; 6333 6334 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) { 6335 bool ret = _young_list->check_list_empty(check_sample); 6336 6337 if (check_heap) { 6338 NoYoungRegionsClosure closure; 6339 heap_region_iterate(&closure); 6340 ret = ret && closure.success(); 6341 } 6342 6343 return ret; 6344 } 6345 6346 class TearDownRegionSetsClosure : public HeapRegionClosure { 6347 private: 6348 HeapRegionSet *_old_set; 6349 6350 public: 6351 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { } 6352 6353 bool doHeapRegion(HeapRegion* r) { 6354 if (r->is_old()) { 6355 _old_set->remove(r); 6356 } else { 6357 // We ignore free regions, we'll empty the free list afterwards. 6358 // We ignore young regions, we'll empty the young list afterwards. 6359 // We ignore humongous regions, we're not tearing down the 6360 // humongous regions set. 6361 assert(r->is_free() || r->is_young() || r->is_humongous(), 6362 "it cannot be another type"); 6363 } 6364 return false; 6365 } 6366 6367 ~TearDownRegionSetsClosure() { 6368 assert(_old_set->is_empty(), "post-condition"); 6369 } 6370 }; 6371 6372 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) { 6373 assert_at_safepoint(true /* should_be_vm_thread */); 6374 6375 if (!free_list_only) { 6376 TearDownRegionSetsClosure cl(&_old_set); 6377 heap_region_iterate(&cl); 6378 6379 // Note that emptying the _young_list is postponed and instead done as 6380 // the first step when rebuilding the regions sets again. The reason for 6381 // this is that during a full GC string deduplication needs to know if 6382 // a collected region was young or old when the full GC was initiated. 6383 } 6384 _hrm.remove_all_free_regions(); 6385 } 6386 6387 class RebuildRegionSetsClosure : public HeapRegionClosure { 6388 private: 6389 bool _free_list_only; 6390 HeapRegionSet* _old_set; 6391 HeapRegionManager* _hrm; 6392 size_t _total_used; 6393 6394 public: 6395 RebuildRegionSetsClosure(bool free_list_only, 6396 HeapRegionSet* old_set, HeapRegionManager* hrm) : 6397 _free_list_only(free_list_only), 6398 _old_set(old_set), _hrm(hrm), _total_used(0) { 6399 assert(_hrm->num_free_regions() == 0, "pre-condition"); 6400 if (!free_list_only) { 6401 assert(_old_set->is_empty(), "pre-condition"); 6402 } 6403 } 6404 6405 bool doHeapRegion(HeapRegion* r) { 6406 if (r->is_continues_humongous()) { 6407 return false; 6408 } 6409 6410 if (r->is_empty()) { 6411 // Add free regions to the free list 6412 r->set_free(); 6413 r->set_allocation_context(AllocationContext::system()); 6414 _hrm->insert_into_free_list(r); 6415 } else if (!_free_list_only) { 6416 assert(!r->is_young(), "we should not come across young regions"); 6417 6418 if (r->is_humongous()) { 6419 // We ignore humongous regions, we left the humongous set unchanged 6420 } else { 6421 // Objects that were compacted would have ended up on regions 6422 // that were previously old or free. 6423 assert(r->is_free() || r->is_old(), "invariant"); 6424 // We now consider them old, so register as such. 6425 r->set_old(); 6426 _old_set->add(r); 6427 } 6428 _total_used += r->used(); 6429 } 6430 6431 return false; 6432 } 6433 6434 size_t total_used() { 6435 return _total_used; 6436 } 6437 }; 6438 6439 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) { 6440 assert_at_safepoint(true /* should_be_vm_thread */); 6441 6442 if (!free_list_only) { 6443 _young_list->empty_list(); 6444 } 6445 6446 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm); 6447 heap_region_iterate(&cl); 6448 6449 if (!free_list_only) { 6450 _allocator->set_used(cl.total_used()); 6451 } 6452 assert(_allocator->used_unlocked() == recalculate_used(), 6453 err_msg("inconsistent _allocator->used_unlocked(), " 6454 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT, 6455 _allocator->used_unlocked(), recalculate_used())); 6456 } 6457 6458 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) { 6459 _refine_cte_cl->set_concurrent(concurrent); 6460 } 6461 6462 bool G1CollectedHeap::is_in_closed_subset(const void* p) const { 6463 HeapRegion* hr = heap_region_containing(p); 6464 return hr->is_in(p); 6465 } 6466 6467 // Methods for the mutator alloc region 6468 6469 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size, 6470 bool force) { 6471 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6472 assert(!force || g1_policy()->can_expand_young_list(), 6473 "if force is true we should be able to expand the young list"); 6474 bool young_list_full = g1_policy()->is_young_list_full(); 6475 if (force || !young_list_full) { 6476 HeapRegion* new_alloc_region = new_region(word_size, 6477 false /* is_old */, 6478 false /* do_expand */); 6479 if (new_alloc_region != NULL) { 6480 set_region_short_lived_locked(new_alloc_region); 6481 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full); 6482 check_bitmaps("Mutator Region Allocation", new_alloc_region); 6483 return new_alloc_region; 6484 } 6485 } 6486 return NULL; 6487 } 6488 6489 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region, 6490 size_t allocated_bytes) { 6491 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6492 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden"); 6493 6494 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region); 6495 _allocator->increase_used(allocated_bytes); 6496 _hr_printer.retire(alloc_region); 6497 // We update the eden sizes here, when the region is retired, 6498 // instead of when it's allocated, since this is the point that its 6499 // used space has been recored in _summary_bytes_used. 6500 g1mm()->update_eden_size(); 6501 } 6502 6503 void G1CollectedHeap::set_par_threads() { 6504 // Don't change the number of workers. Use the value previously set 6505 // in the workgroup. 6506 uint n_workers = workers()->active_workers(); 6507 assert(UseDynamicNumberOfGCThreads || 6508 n_workers == workers()->total_workers(), 6509 "Otherwise should be using the total number of workers"); 6510 if (n_workers == 0) { 6511 assert(false, "Should have been set in prior evacuation pause."); 6512 n_workers = ParallelGCThreads; 6513 workers()->set_active_workers(n_workers); 6514 } 6515 set_par_threads(n_workers); 6516 } 6517 6518 // Methods for the GC alloc regions 6519 6520 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, 6521 uint count, 6522 GCAllocPurpose ap) { 6523 assert(FreeList_lock->owned_by_self(), "pre-condition"); 6524 6525 if (count < g1_policy()->max_regions(ap)) { 6526 bool survivor = (ap == GCAllocForSurvived); 6527 HeapRegion* new_alloc_region = new_region(word_size, 6528 !survivor, 6529 true /* do_expand */); 6530 if (new_alloc_region != NULL) { 6531 // We really only need to do this for old regions given that we 6532 // should never scan survivors. But it doesn't hurt to do it 6533 // for survivors too. 6534 new_alloc_region->record_timestamp(); 6535 if (survivor) { 6536 new_alloc_region->set_survivor(); 6537 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor); 6538 check_bitmaps("Survivor Region Allocation", new_alloc_region); 6539 } else { 6540 new_alloc_region->set_old(); 6541 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old); 6542 check_bitmaps("Old Region Allocation", new_alloc_region); 6543 } 6544 bool during_im = g1_policy()->during_initial_mark_pause(); 6545 new_alloc_region->note_start_of_copying(during_im); 6546 return new_alloc_region; 6547 } else { 6548 g1_policy()->note_alloc_region_limit_reached(ap); 6549 } 6550 } 6551 return NULL; 6552 } 6553 6554 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region, 6555 size_t allocated_bytes, 6556 GCAllocPurpose ap) { 6557 bool during_im = g1_policy()->during_initial_mark_pause(); 6558 alloc_region->note_end_of_copying(during_im); 6559 g1_policy()->record_bytes_copied_during_gc(allocated_bytes); 6560 if (ap == GCAllocForSurvived) { 6561 young_list()->add_survivor_region(alloc_region); 6562 } else { 6563 _old_set.add(alloc_region); 6564 } 6565 _hr_printer.retire(alloc_region); 6566 } 6567 6568 // Heap region set verification 6569 6570 class VerifyRegionListsClosure : public HeapRegionClosure { 6571 private: 6572 HeapRegionSet* _old_set; 6573 HeapRegionSet* _humongous_set; 6574 HeapRegionManager* _hrm; 6575 6576 public: 6577 HeapRegionSetCount _old_count; 6578 HeapRegionSetCount _humongous_count; 6579 HeapRegionSetCount _free_count; 6580 6581 VerifyRegionListsClosure(HeapRegionSet* old_set, 6582 HeapRegionSet* humongous_set, 6583 HeapRegionManager* hrm) : 6584 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm), 6585 _old_count(), _humongous_count(), _free_count(){ } 6586 6587 bool doHeapRegion(HeapRegion* hr) { 6588 if (hr->is_continues_humongous()) { 6589 return false; 6590 } 6591 6592 if (hr->is_young()) { 6593 // TODO 6594 } else if (hr->is_starts_humongous()) { 6595 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index())); 6596 _humongous_count.increment(1u, hr->capacity()); 6597 } else if (hr->is_empty()) { 6598 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index())); 6599 _free_count.increment(1u, hr->capacity()); 6600 } else if (hr->is_old()) { 6601 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index())); 6602 _old_count.increment(1u, hr->capacity()); 6603 } else { 6604 ShouldNotReachHere(); 6605 } 6606 return false; 6607 } 6608 6609 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) { 6610 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length())); 6611 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6612 old_set->total_capacity_bytes(), _old_count.capacity())); 6613 6614 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length())); 6615 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6616 humongous_set->total_capacity_bytes(), _humongous_count.capacity())); 6617 6618 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length())); 6619 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT, 6620 free_list->total_capacity_bytes(), _free_count.capacity())); 6621 } 6622 }; 6623 6624 void G1CollectedHeap::verify_region_sets() { 6625 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */); 6626 6627 // First, check the explicit lists. 6628 _hrm.verify(); 6629 { 6630 // Given that a concurrent operation might be adding regions to 6631 // the secondary free list we have to take the lock before 6632 // verifying it. 6633 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 6634 _secondary_free_list.verify_list(); 6635 } 6636 6637 // If a concurrent region freeing operation is in progress it will 6638 // be difficult to correctly attributed any free regions we come 6639 // across to the correct free list given that they might belong to 6640 // one of several (free_list, secondary_free_list, any local lists, 6641 // etc.). So, if that's the case we will skip the rest of the 6642 // verification operation. Alternatively, waiting for the concurrent 6643 // operation to complete will have a non-trivial effect on the GC's 6644 // operation (no concurrent operation will last longer than the 6645 // interval between two calls to verification) and it might hide 6646 // any issues that we would like to catch during testing. 6647 if (free_regions_coming()) { 6648 return; 6649 } 6650 6651 // Make sure we append the secondary_free_list on the free_list so 6652 // that all free regions we will come across can be safely 6653 // attributed to the free_list. 6654 append_secondary_free_list_if_not_empty_with_lock(); 6655 6656 // Finally, make sure that the region accounting in the lists is 6657 // consistent with what we see in the heap. 6658 6659 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm); 6660 heap_region_iterate(&cl); 6661 cl.verify_counts(&_old_set, &_humongous_set, &_hrm); 6662 } 6663 6664 // Optimized nmethod scanning 6665 6666 class RegisterNMethodOopClosure: public OopClosure { 6667 G1CollectedHeap* _g1h; 6668 nmethod* _nm; 6669 6670 template <class T> void do_oop_work(T* p) { 6671 T heap_oop = oopDesc::load_heap_oop(p); 6672 if (!oopDesc::is_null(heap_oop)) { 6673 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6674 HeapRegion* hr = _g1h->heap_region_containing(obj); 6675 assert(!hr->is_continues_humongous(), 6676 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6677 " starting at "HR_FORMAT, 6678 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6679 6680 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries. 6681 hr->add_strong_code_root_locked(_nm); 6682 } 6683 } 6684 6685 public: 6686 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6687 _g1h(g1h), _nm(nm) {} 6688 6689 void do_oop(oop* p) { do_oop_work(p); } 6690 void do_oop(narrowOop* p) { do_oop_work(p); } 6691 }; 6692 6693 class UnregisterNMethodOopClosure: public OopClosure { 6694 G1CollectedHeap* _g1h; 6695 nmethod* _nm; 6696 6697 template <class T> void do_oop_work(T* p) { 6698 T heap_oop = oopDesc::load_heap_oop(p); 6699 if (!oopDesc::is_null(heap_oop)) { 6700 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); 6701 HeapRegion* hr = _g1h->heap_region_containing(obj); 6702 assert(!hr->is_continues_humongous(), 6703 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT 6704 " starting at "HR_FORMAT, 6705 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()))); 6706 6707 hr->remove_strong_code_root(_nm); 6708 } 6709 } 6710 6711 public: 6712 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) : 6713 _g1h(g1h), _nm(nm) {} 6714 6715 void do_oop(oop* p) { do_oop_work(p); } 6716 void do_oop(narrowOop* p) { do_oop_work(p); } 6717 }; 6718 6719 void G1CollectedHeap::register_nmethod(nmethod* nm) { 6720 CollectedHeap::register_nmethod(nm); 6721 6722 guarantee(nm != NULL, "sanity"); 6723 RegisterNMethodOopClosure reg_cl(this, nm); 6724 nm->oops_do(®_cl); 6725 } 6726 6727 void G1CollectedHeap::unregister_nmethod(nmethod* nm) { 6728 CollectedHeap::unregister_nmethod(nm); 6729 6730 guarantee(nm != NULL, "sanity"); 6731 UnregisterNMethodOopClosure reg_cl(this, nm); 6732 nm->oops_do(®_cl, true); 6733 } 6734 6735 void G1CollectedHeap::purge_code_root_memory() { 6736 double purge_start = os::elapsedTime(); 6737 G1CodeRootSet::purge(); 6738 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0; 6739 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms); 6740 } 6741 6742 class RebuildStrongCodeRootClosure: public CodeBlobClosure { 6743 G1CollectedHeap* _g1h; 6744 6745 public: 6746 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) : 6747 _g1h(g1h) {} 6748 6749 void do_code_blob(CodeBlob* cb) { 6750 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL; 6751 if (nm == NULL) { 6752 return; 6753 } 6754 6755 if (ScavengeRootsInCode) { 6756 _g1h->register_nmethod(nm); 6757 } 6758 } 6759 }; 6760 6761 void G1CollectedHeap::rebuild_strong_code_roots() { 6762 RebuildStrongCodeRootClosure blob_cl(this); 6763 CodeCache::blobs_do(&blob_cl); 6764 }