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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc_implementation/g1/concurrentMark.hpp" 29 #include "gc_implementation/g1/evacuationInfo.hpp" 30 #include "gc_implementation/g1/g1AllocRegion.hpp" 31 #include "gc_implementation/g1/g1BiasedArray.hpp" 32 #include "gc_implementation/g1/g1HRPrinter.hpp" 33 #include "gc_implementation/g1/g1MonitoringSupport.hpp" 34 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 35 #include "gc_implementation/g1/g1YCTypes.hpp" 36 #include "gc_implementation/g1/heapRegionManager.hpp" 37 #include "gc_implementation/g1/heapRegionSet.hpp" 38 #include "gc_implementation/shared/hSpaceCounters.hpp" 39 #include "gc_implementation/shared/parGCAllocBuffer.hpp" 40 #include "memory/barrierSet.hpp" 41 #include "memory/memRegion.hpp" 42 #include "memory/sharedHeap.hpp" 43 #include "utilities/stack.hpp" 44 45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 46 // It uses the "Garbage First" heap organization and algorithm, which 47 // may combine concurrent marking with parallel, incremental compaction of 48 // heap subsets that will yield large amounts of garbage. 49 50 // Forward declarations 51 class HeapRegion; 52 class HRRSCleanupTask; 53 class GenerationSpec; 54 class OopsInHeapRegionClosure; 55 class G1KlassScanClosure; 56 class G1ScanHeapEvacClosure; 57 class ObjectClosure; 58 class SpaceClosure; 59 class CompactibleSpaceClosure; 60 class Space; 61 class G1CollectorPolicy; 62 class GenRemSet; 63 class G1RemSet; 64 class HeapRegionRemSetIterator; 65 class ConcurrentMark; 66 class ConcurrentMarkThread; 67 class ConcurrentG1Refine; 68 class ConcurrentGCTimer; 69 class GenerationCounters; 70 class STWGCTimer; 71 class G1NewTracer; 72 class G1OldTracer; 73 class EvacuationFailedInfo; 74 class nmethod; 75 class Ticks; 76 77 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 79 80 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 81 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 82 83 enum GCAllocPurpose { 84 GCAllocForTenured, 85 GCAllocForSurvived, 86 GCAllocPurposeCount 87 }; 88 89 class YoungList : public CHeapObj<mtGC> { 90 private: 91 G1CollectedHeap* _g1h; 92 93 HeapRegion* _head; 94 95 HeapRegion* _survivor_head; 96 HeapRegion* _survivor_tail; 97 98 HeapRegion* _curr; 99 100 uint _length; 101 uint _survivor_length; 102 103 size_t _last_sampled_rs_lengths; 104 size_t _sampled_rs_lengths; 105 106 void empty_list(HeapRegion* list); 107 108 public: 109 YoungList(G1CollectedHeap* g1h); 110 111 void push_region(HeapRegion* hr); 112 void add_survivor_region(HeapRegion* hr); 113 114 void empty_list(); 115 bool is_empty() { return _length == 0; } 116 uint length() { return _length; } 117 uint survivor_length() { return _survivor_length; } 118 119 // Currently we do not keep track of the used byte sum for the 120 // young list and the survivors and it'd be quite a lot of work to 121 // do so. When we'll eventually replace the young list with 122 // instances of HeapRegionLinkedList we'll get that for free. So, 123 // we'll report the more accurate information then. 124 size_t eden_used_bytes() { 125 assert(length() >= survivor_length(), "invariant"); 126 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes; 127 } 128 size_t survivor_used_bytes() { 129 return (size_t) survivor_length() * HeapRegion::GrainBytes; 130 } 131 132 void rs_length_sampling_init(); 133 bool rs_length_sampling_more(); 134 void rs_length_sampling_next(); 135 136 void reset_sampled_info() { 137 _last_sampled_rs_lengths = 0; 138 } 139 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } 140 141 // for development purposes 142 void reset_auxilary_lists(); 143 void clear() { _head = NULL; _length = 0; } 144 145 void clear_survivors() { 146 _survivor_head = NULL; 147 _survivor_tail = NULL; 148 _survivor_length = 0; 149 } 150 151 HeapRegion* first_region() { return _head; } 152 HeapRegion* first_survivor_region() { return _survivor_head; } 153 HeapRegion* last_survivor_region() { return _survivor_tail; } 154 155 // debugging 156 bool check_list_well_formed(); 157 bool check_list_empty(bool check_sample = true); 158 void print(); 159 }; 160 161 class MutatorAllocRegion : public G1AllocRegion { 162 protected: 163 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 164 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 165 public: 166 MutatorAllocRegion() 167 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { } 168 }; 169 170 class SurvivorGCAllocRegion : public G1AllocRegion { 171 protected: 172 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 173 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 174 public: 175 SurvivorGCAllocRegion() 176 : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { } 177 }; 178 179 class OldGCAllocRegion : public G1AllocRegion { 180 protected: 181 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 182 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 183 public: 184 OldGCAllocRegion() 185 : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { } 186 187 // This specialization of release() makes sure that the last card that has been 188 // allocated into has been completely filled by a dummy object. 189 // This avoids races when remembered set scanning wants to update the BOT of the 190 // last card in the retained old gc alloc region, and allocation threads 191 // allocating into that card at the same time. 192 virtual HeapRegion* release(); 193 }; 194 195 // The G1 STW is alive closure. 196 // An instance is embedded into the G1CH and used as the 197 // (optional) _is_alive_non_header closure in the STW 198 // reference processor. It is also extensively used during 199 // reference processing during STW evacuation pauses. 200 class G1STWIsAliveClosure: public BoolObjectClosure { 201 G1CollectedHeap* _g1; 202 public: 203 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 204 bool do_object_b(oop p); 205 }; 206 207 class RefineCardTableEntryClosure; 208 209 class G1RegionMappingChangedListener : public G1MappingChangedListener { 210 private: 211 void reset_from_card_cache(uint start_idx, size_t num_regions); 212 public: 213 virtual void on_commit(uint start_idx, size_t num_regions); 214 }; 215 216 class G1CollectedHeap : public SharedHeap { 217 friend class VM_CollectForMetadataAllocation; 218 friend class VM_G1CollectForAllocation; 219 friend class VM_G1CollectFull; 220 friend class VM_G1IncCollectionPause; 221 friend class VMStructs; 222 friend class MutatorAllocRegion; 223 friend class SurvivorGCAllocRegion; 224 friend class OldGCAllocRegion; 225 226 // Closures used in implementation. 227 template <G1Barrier barrier, G1Mark do_mark_object> 228 friend class G1ParCopyClosure; 229 friend class G1IsAliveClosure; 230 friend class G1EvacuateFollowersClosure; 231 friend class G1ParScanThreadState; 232 friend class G1ParScanClosureSuper; 233 friend class G1ParEvacuateFollowersClosure; 234 friend class G1ParTask; 235 friend class G1FreeGarbageRegionClosure; 236 friend class RefineCardTableEntryClosure; 237 friend class G1PrepareCompactClosure; 238 friend class RegionSorter; 239 friend class RegionResetter; 240 friend class CountRCClosure; 241 friend class EvacPopObjClosure; 242 friend class G1ParCleanupCTTask; 243 244 friend class G1FreeHumongousRegionClosure; 245 // Other related classes. 246 friend class G1MarkSweep; 247 friend class HeapRegionClaimer; 248 249 private: 250 // The one and only G1CollectedHeap, so static functions can find it. 251 static G1CollectedHeap* _g1h; 252 253 static size_t _humongous_object_threshold_in_words; 254 255 // The secondary free list which contains regions that have been 256 // freed up during the cleanup process. This will be appended to 257 // the master free list when appropriate. 258 FreeRegionList _secondary_free_list; 259 260 // It keeps track of the old regions. 261 HeapRegionSet _old_set; 262 263 // It keeps track of the humongous regions. 264 HeapRegionSet _humongous_set; 265 266 void clear_humongous_is_live_table(); 267 void eagerly_reclaim_humongous_regions(); 268 269 // The number of regions we could create by expansion. 270 uint _expansion_regions; 271 272 // The block offset table for the G1 heap. 273 G1BlockOffsetSharedArray* _bot_shared; 274 275 // Tears down the region sets / lists so that they are empty and the 276 // regions on the heap do not belong to a region set / list. The 277 // only exception is the humongous set which we leave unaltered. If 278 // free_list_only is true, it will only tear down the master free 279 // list. It is called before a Full GC (free_list_only == false) or 280 // before heap shrinking (free_list_only == true). 281 void tear_down_region_sets(bool free_list_only); 282 283 // Rebuilds the region sets / lists so that they are repopulated to 284 // reflect the contents of the heap. The only exception is the 285 // humongous set which was not torn down in the first place. If 286 // free_list_only is true, it will only rebuild the master free 287 // list. It is called after a Full GC (free_list_only == false) or 288 // after heap shrinking (free_list_only == true). 289 void rebuild_region_sets(bool free_list_only); 290 291 // Callback for region mapping changed events. 292 G1RegionMappingChangedListener _listener; 293 294 // The sequence of all heap regions in the heap. 295 HeapRegionManager _hrm; 296 297 // Alloc region used to satisfy mutator allocation requests. 298 MutatorAllocRegion _mutator_alloc_region; 299 300 // Alloc region used to satisfy allocation requests by the GC for 301 // survivor objects. 302 SurvivorGCAllocRegion _survivor_gc_alloc_region; 303 304 // PLAB sizing policy for survivors. 305 PLABStats _survivor_plab_stats; 306 307 // Alloc region used to satisfy allocation requests by the GC for 308 // old objects. 309 OldGCAllocRegion _old_gc_alloc_region; 310 311 // PLAB sizing policy for tenured objects. 312 PLABStats _old_plab_stats; 313 314 PLABStats* stats_for_purpose(GCAllocPurpose purpose) { 315 PLABStats* stats = NULL; 316 317 switch (purpose) { 318 case GCAllocForSurvived: 319 stats = &_survivor_plab_stats; 320 break; 321 case GCAllocForTenured: 322 stats = &_old_plab_stats; 323 break; 324 default: 325 assert(false, "unrecognized GCAllocPurpose"); 326 } 327 328 return stats; 329 } 330 331 // The last old region we allocated to during the last GC. 332 // Typically, it is not full so we should re-use it during the next GC. 333 HeapRegion* _retained_old_gc_alloc_region; 334 335 // It specifies whether we should attempt to expand the heap after a 336 // region allocation failure. If heap expansion fails we set this to 337 // false so that we don't re-attempt the heap expansion (it's likely 338 // that subsequent expansion attempts will also fail if one fails). 339 // Currently, it is only consulted during GC and it's reset at the 340 // start of each GC. 341 bool _expand_heap_after_alloc_failure; 342 343 // It resets the mutator alloc region before new allocations can take place. 344 void init_mutator_alloc_region(); 345 346 // It releases the mutator alloc region. 347 void release_mutator_alloc_region(); 348 349 // It initializes the GC alloc regions at the start of a GC. 350 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 351 352 // Setup the retained old gc alloc region as the currrent old gc alloc region. 353 void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info); 354 355 // It releases the GC alloc regions at the end of a GC. 356 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 357 358 // It does any cleanup that needs to be done on the GC alloc regions 359 // before a Full GC. 360 void abandon_gc_alloc_regions(); 361 362 // Helper for monitoring and management support. 363 G1MonitoringSupport* _g1mm; 364 365 // Determines PLAB size for a particular allocation purpose. 366 size_t desired_plab_sz(GCAllocPurpose purpose); 367 368 // Outside of GC pauses, the number of bytes used in all regions other 369 // than the current allocation region. 370 size_t _summary_bytes_used; 371 372 // Records whether the region at the given index is kept live by roots or 373 // references from the young generation. 374 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 375 protected: 376 bool default_value() const { return false; } 377 public: 378 void clear() { G1BiasedMappedArray<bool>::clear(); } 379 void set_live(uint region) { 380 set_by_index(region, true); 381 } 382 bool is_live(uint region) { 383 return get_by_index(region); 384 } 385 }; 386 387 HumongousIsLiveBiasedMappedArray _humongous_is_live; 388 // Stores whether during humongous object registration we found candidate regions. 389 // If not, we can skip a few steps. 390 bool _has_humongous_reclaim_candidates; 391 392 volatile unsigned _gc_time_stamp; 393 394 size_t* _surviving_young_words; 395 396 G1HRPrinter _hr_printer; 397 398 void setup_surviving_young_words(); 399 void update_surviving_young_words(size_t* surv_young_words); 400 void cleanup_surviving_young_words(); 401 402 // It decides whether an explicit GC should start a concurrent cycle 403 // instead of doing a STW GC. Currently, a concurrent cycle is 404 // explicitly started if: 405 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 406 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 407 // (c) cause == _g1_humongous_allocation 408 bool should_do_concurrent_full_gc(GCCause::Cause cause); 409 410 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 411 // concurrent cycles) we have started. 412 volatile unsigned int _old_marking_cycles_started; 413 414 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 415 // concurrent cycles) we have completed. 416 volatile unsigned int _old_marking_cycles_completed; 417 418 bool _concurrent_cycle_started; 419 bool _heap_summary_sent; 420 421 // This is a non-product method that is helpful for testing. It is 422 // called at the end of a GC and artificially expands the heap by 423 // allocating a number of dead regions. This way we can induce very 424 // frequent marking cycles and stress the cleanup / concurrent 425 // cleanup code more (as all the regions that will be allocated by 426 // this method will be found dead by the marking cycle). 427 void allocate_dummy_regions() PRODUCT_RETURN; 428 429 // Clear RSets after a compaction. It also resets the GC time stamps. 430 void clear_rsets_post_compaction(); 431 432 // If the HR printer is active, dump the state of the regions in the 433 // heap after a compaction. 434 void print_hrm_post_compaction(); 435 436 double verify(bool guard, const char* msg); 437 void verify_before_gc(); 438 void verify_after_gc(); 439 440 void log_gc_header(); 441 void log_gc_footer(double pause_time_sec); 442 443 // These are macros so that, if the assert fires, we get the correct 444 // line number, file, etc. 445 446 #define heap_locking_asserts_err_msg(_extra_message_) \ 447 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 448 (_extra_message_), \ 449 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 450 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 451 BOOL_TO_STR(Thread::current()->is_VM_thread())) 452 453 #define assert_heap_locked() \ 454 do { \ 455 assert(Heap_lock->owned_by_self(), \ 456 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 457 } while (0) 458 459 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 460 do { \ 461 assert(Heap_lock->owned_by_self() || \ 462 (SafepointSynchronize::is_at_safepoint() && \ 463 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 464 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 465 "should be at a safepoint")); \ 466 } while (0) 467 468 #define assert_heap_locked_and_not_at_safepoint() \ 469 do { \ 470 assert(Heap_lock->owned_by_self() && \ 471 !SafepointSynchronize::is_at_safepoint(), \ 472 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 473 "should not be at a safepoint")); \ 474 } while (0) 475 476 #define assert_heap_not_locked() \ 477 do { \ 478 assert(!Heap_lock->owned_by_self(), \ 479 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 480 } while (0) 481 482 #define assert_heap_not_locked_and_not_at_safepoint() \ 483 do { \ 484 assert(!Heap_lock->owned_by_self() && \ 485 !SafepointSynchronize::is_at_safepoint(), \ 486 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 487 "should not be at a safepoint")); \ 488 } while (0) 489 490 #define assert_at_safepoint(_should_be_vm_thread_) \ 491 do { \ 492 assert(SafepointSynchronize::is_at_safepoint() && \ 493 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 494 heap_locking_asserts_err_msg("should be at a safepoint")); \ 495 } while (0) 496 497 #define assert_not_at_safepoint() \ 498 do { \ 499 assert(!SafepointSynchronize::is_at_safepoint(), \ 500 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 501 } while (0) 502 503 protected: 504 505 // The young region list. 506 YoungList* _young_list; 507 508 // The current policy object for the collector. 509 G1CollectorPolicy* _g1_policy; 510 511 // This is the second level of trying to allocate a new region. If 512 // new_region() didn't find a region on the free_list, this call will 513 // check whether there's anything available on the 514 // secondary_free_list and/or wait for more regions to appear on 515 // that list, if _free_regions_coming is set. 516 HeapRegion* new_region_try_secondary_free_list(bool is_old); 517 518 // Try to allocate a single non-humongous HeapRegion sufficient for 519 // an allocation of the given word_size. If do_expand is true, 520 // attempt to expand the heap if necessary to satisfy the allocation 521 // request. If the region is to be used as an old region or for a 522 // humongous object, set is_old to true. If not, to false. 523 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 524 525 // Initialize a contiguous set of free regions of length num_regions 526 // and starting at index first so that they appear as a single 527 // humongous region. 528 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 529 uint num_regions, 530 size_t word_size); 531 532 // Attempt to allocate a humongous object of the given size. Return 533 // NULL if unsuccessful. 534 HeapWord* humongous_obj_allocate(size_t word_size); 535 536 // The following two methods, allocate_new_tlab() and 537 // mem_allocate(), are the two main entry points from the runtime 538 // into the G1's allocation routines. They have the following 539 // assumptions: 540 // 541 // * They should both be called outside safepoints. 542 // 543 // * They should both be called without holding the Heap_lock. 544 // 545 // * All allocation requests for new TLABs should go to 546 // allocate_new_tlab(). 547 // 548 // * All non-TLAB allocation requests should go to mem_allocate(). 549 // 550 // * If either call cannot satisfy the allocation request using the 551 // current allocating region, they will try to get a new one. If 552 // this fails, they will attempt to do an evacuation pause and 553 // retry the allocation. 554 // 555 // * If all allocation attempts fail, even after trying to schedule 556 // an evacuation pause, allocate_new_tlab() will return NULL, 557 // whereas mem_allocate() will attempt a heap expansion and/or 558 // schedule a Full GC. 559 // 560 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 561 // should never be called with word_size being humongous. All 562 // humongous allocation requests should go to mem_allocate() which 563 // will satisfy them with a special path. 564 565 virtual HeapWord* allocate_new_tlab(size_t word_size); 566 567 virtual HeapWord* mem_allocate(size_t word_size, 568 bool* gc_overhead_limit_was_exceeded); 569 570 // The following three methods take a gc_count_before_ret 571 // parameter which is used to return the GC count if the method 572 // returns NULL. Given that we are required to read the GC count 573 // while holding the Heap_lock, and these paths will take the 574 // Heap_lock at some point, it's easier to get them to read the GC 575 // count while holding the Heap_lock before they return NULL instead 576 // of the caller (namely: mem_allocate()) having to also take the 577 // Heap_lock just to read the GC count. 578 579 // First-level mutator allocation attempt: try to allocate out of 580 // the mutator alloc region without taking the Heap_lock. This 581 // should only be used for non-humongous allocations. 582 inline HeapWord* attempt_allocation(size_t word_size, 583 unsigned int* gc_count_before_ret, 584 int* gclocker_retry_count_ret); 585 586 // Second-level mutator allocation attempt: take the Heap_lock and 587 // retry the allocation attempt, potentially scheduling a GC 588 // pause. This should only be used for non-humongous allocations. 589 HeapWord* attempt_allocation_slow(size_t word_size, 590 unsigned int* gc_count_before_ret, 591 int* gclocker_retry_count_ret); 592 593 // Takes the Heap_lock and attempts a humongous allocation. It can 594 // potentially schedule a GC pause. 595 HeapWord* attempt_allocation_humongous(size_t word_size, 596 unsigned int* gc_count_before_ret, 597 int* gclocker_retry_count_ret); 598 599 // Allocation attempt that should be called during safepoints (e.g., 600 // at the end of a successful GC). expect_null_mutator_alloc_region 601 // specifies whether the mutator alloc region is expected to be NULL 602 // or not. 603 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 604 bool expect_null_mutator_alloc_region); 605 606 // It dirties the cards that cover the block so that so that the post 607 // write barrier never queues anything when updating objects on this 608 // block. It is assumed (and in fact we assert) that the block 609 // belongs to a young region. 610 inline void dirty_young_block(HeapWord* start, size_t word_size); 611 612 // Allocate blocks during garbage collection. Will ensure an 613 // allocation region, either by picking one or expanding the 614 // heap, and then allocate a block of the given size. The block 615 // may not be a humongous - it must fit into a single heap region. 616 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size); 617 618 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, 619 HeapRegion* alloc_region, 620 bool par, 621 size_t word_size); 622 623 // Ensure that no further allocations can happen in "r", bearing in mind 624 // that parallel threads might be attempting allocations. 625 void par_allocate_remaining_space(HeapRegion* r); 626 627 // Allocation attempt during GC for a survivor object / PLAB. 628 inline HeapWord* survivor_attempt_allocation(size_t word_size); 629 630 // Allocation attempt during GC for an old object / PLAB. 631 inline HeapWord* old_attempt_allocation(size_t word_size); 632 633 // These methods are the "callbacks" from the G1AllocRegion class. 634 635 // For mutator alloc regions. 636 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 637 void retire_mutator_alloc_region(HeapRegion* alloc_region, 638 size_t allocated_bytes); 639 640 // For GC alloc regions. 641 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 642 GCAllocPurpose ap); 643 void retire_gc_alloc_region(HeapRegion* alloc_region, 644 size_t allocated_bytes, GCAllocPurpose ap); 645 646 // - if explicit_gc is true, the GC is for a System.gc() or a heap 647 // inspection request and should collect the entire heap 648 // - if clear_all_soft_refs is true, all soft references should be 649 // cleared during the GC 650 // - if explicit_gc is false, word_size describes the allocation that 651 // the GC should attempt (at least) to satisfy 652 // - it returns false if it is unable to do the collection due to the 653 // GC locker being active, true otherwise 654 bool do_collection(bool explicit_gc, 655 bool clear_all_soft_refs, 656 size_t word_size); 657 658 // Callback from VM_G1CollectFull operation. 659 // Perform a full collection. 660 virtual void do_full_collection(bool clear_all_soft_refs); 661 662 // Resize the heap if necessary after a full collection. If this is 663 // after a collect-for allocation, "word_size" is the allocation size, 664 // and will be considered part of the used portion of the heap. 665 void resize_if_necessary_after_full_collection(size_t word_size); 666 667 // Callback from VM_G1CollectForAllocation operation. 668 // This function does everything necessary/possible to satisfy a 669 // failed allocation request (including collection, expansion, etc.) 670 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded); 671 672 // Attempting to expand the heap sufficiently 673 // to support an allocation of the given "word_size". If 674 // successful, perform the allocation and return the address of the 675 // allocated block, or else "NULL". 676 HeapWord* expand_and_allocate(size_t word_size); 677 678 // Process any reference objects discovered during 679 // an incremental evacuation pause. 680 void process_discovered_references(uint no_of_gc_workers); 681 682 // Enqueue any remaining discovered references 683 // after processing. 684 void enqueue_discovered_references(uint no_of_gc_workers); 685 686 public: 687 688 G1MonitoringSupport* g1mm() { 689 assert(_g1mm != NULL, "should have been initialized"); 690 return _g1mm; 691 } 692 693 // Expand the garbage-first heap by at least the given size (in bytes!). 694 // Returns true if the heap was expanded by the requested amount; 695 // false otherwise. 696 // (Rounds up to a HeapRegion boundary.) 697 bool expand(size_t expand_bytes); 698 699 // Do anything common to GC's. 700 virtual void gc_prologue(bool full); 701 virtual void gc_epilogue(bool full); 702 703 inline void set_humongous_is_live(oop obj); 704 705 bool humongous_is_live(uint region) { 706 return _humongous_is_live.is_live(region); 707 } 708 709 // Returns whether the given region (which must be a humongous (start) region) 710 // is to be considered conservatively live regardless of any other conditions. 711 bool humongous_region_is_always_live(uint index); 712 // Register the given region to be part of the collection set. 713 inline void register_humongous_region_with_in_cset_fast_test(uint index); 714 // Register regions with humongous objects (actually on the start region) in 715 // the in_cset_fast_test table. 716 void register_humongous_regions_with_in_cset_fast_test(); 717 // We register a region with the fast "in collection set" test. We 718 // simply set to true the array slot corresponding to this region. 719 void register_region_with_in_cset_fast_test(HeapRegion* r) { 720 _in_cset_fast_test.set_in_cset(r->hrm_index()); 721 } 722 723 // This is a fast test on whether a reference points into the 724 // collection set or not. Assume that the reference 725 // points into the heap. 726 inline bool in_cset_fast_test(oop obj); 727 728 void clear_cset_fast_test() { 729 _in_cset_fast_test.clear(); 730 } 731 732 // This is called at the start of either a concurrent cycle or a Full 733 // GC to update the number of old marking cycles started. 734 void increment_old_marking_cycles_started(); 735 736 // This is called at the end of either a concurrent cycle or a Full 737 // GC to update the number of old marking cycles completed. Those two 738 // can happen in a nested fashion, i.e., we start a concurrent 739 // cycle, a Full GC happens half-way through it which ends first, 740 // and then the cycle notices that a Full GC happened and ends 741 // too. The concurrent parameter is a boolean to help us do a bit 742 // tighter consistency checking in the method. If concurrent is 743 // false, the caller is the inner caller in the nesting (i.e., the 744 // Full GC). If concurrent is true, the caller is the outer caller 745 // in this nesting (i.e., the concurrent cycle). Further nesting is 746 // not currently supported. The end of this call also notifies 747 // the FullGCCount_lock in case a Java thread is waiting for a full 748 // GC to happen (e.g., it called System.gc() with 749 // +ExplicitGCInvokesConcurrent). 750 void increment_old_marking_cycles_completed(bool concurrent); 751 752 unsigned int old_marking_cycles_completed() { 753 return _old_marking_cycles_completed; 754 } 755 756 void register_concurrent_cycle_start(const Ticks& start_time); 757 void register_concurrent_cycle_end(); 758 void trace_heap_after_concurrent_cycle(); 759 760 G1YCType yc_type(); 761 762 G1HRPrinter* hr_printer() { return &_hr_printer; } 763 764 // Frees a non-humongous region by initializing its contents and 765 // adding it to the free list that's passed as a parameter (this is 766 // usually a local list which will be appended to the master free 767 // list later). The used bytes of freed regions are accumulated in 768 // pre_used. If par is true, the region's RSet will not be freed 769 // up. The assumption is that this will be done later. 770 // The locked parameter indicates if the caller has already taken 771 // care of proper synchronization. This may allow some optimizations. 772 void free_region(HeapRegion* hr, 773 FreeRegionList* free_list, 774 bool par, 775 bool locked = false); 776 777 // Frees a humongous region by collapsing it into individual regions 778 // and calling free_region() for each of them. The freed regions 779 // will be added to the free list that's passed as a parameter (this 780 // is usually a local list which will be appended to the master free 781 // list later). The used bytes of freed regions are accumulated in 782 // pre_used. If par is true, the region's RSet will not be freed 783 // up. The assumption is that this will be done later. 784 void free_humongous_region(HeapRegion* hr, 785 FreeRegionList* free_list, 786 bool par); 787 protected: 788 789 // Shrink the garbage-first heap by at most the given size (in bytes!). 790 // (Rounds down to a HeapRegion boundary.) 791 virtual void shrink(size_t expand_bytes); 792 void shrink_helper(size_t expand_bytes); 793 794 #if TASKQUEUE_STATS 795 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 796 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 797 void reset_taskqueue_stats(); 798 #endif // TASKQUEUE_STATS 799 800 // Schedule the VM operation that will do an evacuation pause to 801 // satisfy an allocation request of word_size. *succeeded will 802 // return whether the VM operation was successful (it did do an 803 // evacuation pause) or not (another thread beat us to it or the GC 804 // locker was active). Given that we should not be holding the 805 // Heap_lock when we enter this method, we will pass the 806 // gc_count_before (i.e., total_collections()) as a parameter since 807 // it has to be read while holding the Heap_lock. Currently, both 808 // methods that call do_collection_pause() release the Heap_lock 809 // before the call, so it's easy to read gc_count_before just before. 810 HeapWord* do_collection_pause(size_t word_size, 811 unsigned int gc_count_before, 812 bool* succeeded, 813 GCCause::Cause gc_cause); 814 815 // The guts of the incremental collection pause, executed by the vm 816 // thread. It returns false if it is unable to do the collection due 817 // to the GC locker being active, true otherwise 818 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 819 820 // Actually do the work of evacuating the collection set. 821 void evacuate_collection_set(EvacuationInfo& evacuation_info); 822 823 // The g1 remembered set of the heap. 824 G1RemSet* _g1_rem_set; 825 826 // A set of cards that cover the objects for which the Rsets should be updated 827 // concurrently after the collection. 828 DirtyCardQueueSet _dirty_card_queue_set; 829 830 // The closure used to refine a single card. 831 RefineCardTableEntryClosure* _refine_cte_cl; 832 833 // A function to check the consistency of dirty card logs. 834 void check_ct_logs_at_safepoint(); 835 836 // A DirtyCardQueueSet that is used to hold cards that contain 837 // references into the current collection set. This is used to 838 // update the remembered sets of the regions in the collection 839 // set in the event of an evacuation failure. 840 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 841 842 // After a collection pause, make the regions in the CS into free 843 // regions. 844 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 845 846 // Abandon the current collection set without recording policy 847 // statistics or updating free lists. 848 void abandon_collection_set(HeapRegion* cs_head); 849 850 // Applies "scan_non_heap_roots" to roots outside the heap, 851 // "scan_rs" to roots inside the heap (having done "set_region" to 852 // indicate the region in which the root resides), 853 // and does "scan_metadata" If "scan_rs" is 854 // NULL, then this step is skipped. The "worker_i" 855 // param is for use with parallel roots processing, and should be 856 // the "i" of the calling parallel worker thread's work(i) function. 857 // In the sequential case this param will be ignored. 858 void g1_process_roots(OopClosure* scan_non_heap_roots, 859 OopClosure* scan_non_heap_weak_roots, 860 OopsInHeapRegionClosure* scan_rs, 861 CLDClosure* scan_strong_clds, 862 CLDClosure* scan_weak_clds, 863 CodeBlobClosure* scan_strong_code, 864 uint worker_i); 865 866 // The concurrent marker (and the thread it runs in.) 867 ConcurrentMark* _cm; 868 ConcurrentMarkThread* _cmThread; 869 bool _mark_in_progress; 870 871 // The concurrent refiner. 872 ConcurrentG1Refine* _cg1r; 873 874 // The parallel task queues 875 RefToScanQueueSet *_task_queues; 876 877 // True iff a evacuation has failed in the current collection. 878 bool _evacuation_failed; 879 880 EvacuationFailedInfo* _evacuation_failed_info_array; 881 882 // Failed evacuations cause some logical from-space objects to have 883 // forwarding pointers to themselves. Reset them. 884 void remove_self_forwarding_pointers(); 885 886 // Together, these store an object with a preserved mark, and its mark value. 887 Stack<oop, mtGC> _objs_with_preserved_marks; 888 Stack<markOop, mtGC> _preserved_marks_of_objs; 889 890 // Preserve the mark of "obj", if necessary, in preparation for its mark 891 // word being overwritten with a self-forwarding-pointer. 892 void preserve_mark_if_necessary(oop obj, markOop m); 893 894 // The stack of evac-failure objects left to be scanned. 895 GrowableArray<oop>* _evac_failure_scan_stack; 896 // The closure to apply to evac-failure objects. 897 898 OopsInHeapRegionClosure* _evac_failure_closure; 899 // Set the field above. 900 void 901 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 902 _evac_failure_closure = evac_failure_closure; 903 } 904 905 // Push "obj" on the scan stack. 906 void push_on_evac_failure_scan_stack(oop obj); 907 // Process scan stack entries until the stack is empty. 908 void drain_evac_failure_scan_stack(); 909 // True iff an invocation of "drain_scan_stack" is in progress; to 910 // prevent unnecessary recursion. 911 bool _drain_in_progress; 912 913 // Do any necessary initialization for evacuation-failure handling. 914 // "cl" is the closure that will be used to process evac-failure 915 // objects. 916 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 917 // Do any necessary cleanup for evacuation-failure handling data 918 // structures. 919 void finalize_for_evac_failure(); 920 921 // An attempt to evacuate "obj" has failed; take necessary steps. 922 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 923 void handle_evacuation_failure_common(oop obj, markOop m); 924 925 #ifndef PRODUCT 926 // Support for forcing evacuation failures. Analogous to 927 // PromotionFailureALot for the other collectors. 928 929 // Records whether G1EvacuationFailureALot should be in effect 930 // for the current GC 931 bool _evacuation_failure_alot_for_current_gc; 932 933 // Used to record the GC number for interval checking when 934 // determining whether G1EvaucationFailureALot is in effect 935 // for the current GC. 936 size_t _evacuation_failure_alot_gc_number; 937 938 // Count of the number of evacuations between failures. 939 volatile size_t _evacuation_failure_alot_count; 940 941 // Set whether G1EvacuationFailureALot should be in effect 942 // for the current GC (based upon the type of GC and which 943 // command line flags are set); 944 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 945 bool during_initial_mark, 946 bool during_marking); 947 948 inline void set_evacuation_failure_alot_for_current_gc(); 949 950 // Return true if it's time to cause an evacuation failure. 951 inline bool evacuation_should_fail(); 952 953 // Reset the G1EvacuationFailureALot counters. Should be called at 954 // the end of an evacuation pause in which an evacuation failure occurred. 955 inline void reset_evacuation_should_fail(); 956 #endif // !PRODUCT 957 958 // ("Weak") Reference processing support. 959 // 960 // G1 has 2 instances of the reference processor class. One 961 // (_ref_processor_cm) handles reference object discovery 962 // and subsequent processing during concurrent marking cycles. 963 // 964 // The other (_ref_processor_stw) handles reference object 965 // discovery and processing during full GCs and incremental 966 // evacuation pauses. 967 // 968 // During an incremental pause, reference discovery will be 969 // temporarily disabled for _ref_processor_cm and will be 970 // enabled for _ref_processor_stw. At the end of the evacuation 971 // pause references discovered by _ref_processor_stw will be 972 // processed and discovery will be disabled. The previous 973 // setting for reference object discovery for _ref_processor_cm 974 // will be re-instated. 975 // 976 // At the start of marking: 977 // * Discovery by the CM ref processor is verified to be inactive 978 // and it's discovered lists are empty. 979 // * Discovery by the CM ref processor is then enabled. 980 // 981 // At the end of marking: 982 // * Any references on the CM ref processor's discovered 983 // lists are processed (possibly MT). 984 // 985 // At the start of full GC we: 986 // * Disable discovery by the CM ref processor and 987 // empty CM ref processor's discovered lists 988 // (without processing any entries). 989 // * Verify that the STW ref processor is inactive and it's 990 // discovered lists are empty. 991 // * Temporarily set STW ref processor discovery as single threaded. 992 // * Temporarily clear the STW ref processor's _is_alive_non_header 993 // field. 994 // * Finally enable discovery by the STW ref processor. 995 // 996 // The STW ref processor is used to record any discovered 997 // references during the full GC. 998 // 999 // At the end of a full GC we: 1000 // * Enqueue any reference objects discovered by the STW ref processor 1001 // that have non-live referents. This has the side-effect of 1002 // making the STW ref processor inactive by disabling discovery. 1003 // * Verify that the CM ref processor is still inactive 1004 // and no references have been placed on it's discovered 1005 // lists (also checked as a precondition during initial marking). 1006 1007 // The (stw) reference processor... 1008 ReferenceProcessor* _ref_processor_stw; 1009 1010 STWGCTimer* _gc_timer_stw; 1011 ConcurrentGCTimer* _gc_timer_cm; 1012 1013 G1OldTracer* _gc_tracer_cm; 1014 G1NewTracer* _gc_tracer_stw; 1015 1016 // During reference object discovery, the _is_alive_non_header 1017 // closure (if non-null) is applied to the referent object to 1018 // determine whether the referent is live. If so then the 1019 // reference object does not need to be 'discovered' and can 1020 // be treated as a regular oop. This has the benefit of reducing 1021 // the number of 'discovered' reference objects that need to 1022 // be processed. 1023 // 1024 // Instance of the is_alive closure for embedding into the 1025 // STW reference processor as the _is_alive_non_header field. 1026 // Supplying a value for the _is_alive_non_header field is 1027 // optional but doing so prevents unnecessary additions to 1028 // the discovered lists during reference discovery. 1029 G1STWIsAliveClosure _is_alive_closure_stw; 1030 1031 // The (concurrent marking) reference processor... 1032 ReferenceProcessor* _ref_processor_cm; 1033 1034 // Instance of the concurrent mark is_alive closure for embedding 1035 // into the Concurrent Marking reference processor as the 1036 // _is_alive_non_header field. Supplying a value for the 1037 // _is_alive_non_header field is optional but doing so prevents 1038 // unnecessary additions to the discovered lists during reference 1039 // discovery. 1040 G1CMIsAliveClosure _is_alive_closure_cm; 1041 1042 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 1043 HeapRegion** _worker_cset_start_region; 1044 1045 // Time stamp to validate the regions recorded in the cache 1046 // used by G1CollectedHeap::start_cset_region_for_worker(). 1047 // The heap region entry for a given worker is valid iff 1048 // the associated time stamp value matches the current value 1049 // of G1CollectedHeap::_gc_time_stamp. 1050 unsigned int* _worker_cset_start_region_time_stamp; 1051 1052 enum G1H_process_roots_tasks { 1053 G1H_PS_filter_satb_buffers, 1054 G1H_PS_refProcessor_oops_do, 1055 // Leave this one last. 1056 G1H_PS_NumElements 1057 }; 1058 1059 SubTasksDone* _process_strong_tasks; 1060 1061 volatile bool _free_regions_coming; 1062 1063 public: 1064 1065 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } 1066 1067 void set_refine_cte_cl_concurrency(bool concurrent); 1068 1069 RefToScanQueue *task_queue(int i) const; 1070 1071 // A set of cards where updates happened during the GC 1072 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1073 1074 // A DirtyCardQueueSet that is used to hold cards that contain 1075 // references into the current collection set. This is used to 1076 // update the remembered sets of the regions in the collection 1077 // set in the event of an evacuation failure. 1078 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1079 { return _into_cset_dirty_card_queue_set; } 1080 1081 // Create a G1CollectedHeap with the specified policy. 1082 // Must call the initialize method afterwards. 1083 // May not return if something goes wrong. 1084 G1CollectedHeap(G1CollectorPolicy* policy); 1085 1086 // Initialize the G1CollectedHeap to have the initial and 1087 // maximum sizes and remembered and barrier sets 1088 // specified by the policy object. 1089 jint initialize(); 1090 1091 virtual void stop(); 1092 1093 // Return the (conservative) maximum heap alignment for any G1 heap 1094 static size_t conservative_max_heap_alignment(); 1095 1096 // Initialize weak reference processing. 1097 virtual void ref_processing_init(); 1098 1099 void set_par_threads(uint t) { 1100 SharedHeap::set_par_threads(t); 1101 // Done in SharedHeap but oddly there are 1102 // two _process_strong_tasks's in a G1CollectedHeap 1103 // so do it here too. 1104 _process_strong_tasks->set_n_threads(t); 1105 } 1106 1107 // Set _n_par_threads according to a policy TBD. 1108 void set_par_threads(); 1109 1110 void set_n_termination(int t) { 1111 _process_strong_tasks->set_n_threads(t); 1112 } 1113 1114 virtual CollectedHeap::Name kind() const { 1115 return CollectedHeap::G1CollectedHeap; 1116 } 1117 1118 // The current policy object for the collector. 1119 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1120 1121 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1122 1123 // Adaptive size policy. No such thing for g1. 1124 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1125 1126 // The rem set and barrier set. 1127 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1128 1129 unsigned get_gc_time_stamp() { 1130 return _gc_time_stamp; 1131 } 1132 1133 inline void reset_gc_time_stamp(); 1134 1135 void check_gc_time_stamps() PRODUCT_RETURN; 1136 1137 inline void increment_gc_time_stamp(); 1138 1139 // Reset the given region's GC timestamp. If it's starts humongous, 1140 // also reset the GC timestamp of its corresponding 1141 // continues humongous regions too. 1142 void reset_gc_time_stamps(HeapRegion* hr); 1143 1144 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1145 DirtyCardQueue* into_cset_dcq, 1146 bool concurrent, uint worker_i); 1147 1148 // The shared block offset table array. 1149 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1150 1151 // Reference Processing accessors 1152 1153 // The STW reference processor.... 1154 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1155 1156 // The Concurrent Marking reference processor... 1157 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1158 1159 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1160 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1161 1162 virtual size_t capacity() const; 1163 virtual size_t used() const; 1164 // This should be called when we're not holding the heap lock. The 1165 // result might be a bit inaccurate. 1166 size_t used_unlocked() const; 1167 size_t recalculate_used() const; 1168 1169 // These virtual functions do the actual allocation. 1170 // Some heaps may offer a contiguous region for shared non-blocking 1171 // allocation, via inlined code (by exporting the address of the top and 1172 // end fields defining the extent of the contiguous allocation region.) 1173 // But G1CollectedHeap doesn't yet support this. 1174 1175 virtual bool is_maximal_no_gc() const { 1176 return _hrm.available() == 0; 1177 } 1178 1179 // The current number of regions in the heap. 1180 uint num_regions() const { return _hrm.length(); } 1181 1182 // The max number of regions in the heap. 1183 uint max_regions() const { return _hrm.max_length(); } 1184 1185 // The number of regions that are completely free. 1186 uint num_free_regions() const { return _hrm.num_free_regions(); } 1187 1188 // The number of regions that are not completely free. 1189 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1190 1191 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1192 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1193 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1194 void verify_dirty_young_regions() PRODUCT_RETURN; 1195 1196 #ifndef PRODUCT 1197 // Make sure that the given bitmap has no marked objects in the 1198 // range [from,limit). If it does, print an error message and return 1199 // false. Otherwise, just return true. bitmap_name should be "prev" 1200 // or "next". 1201 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1202 HeapWord* from, HeapWord* limit); 1203 1204 // Verify that the prev / next bitmap range [tams,end) for the given 1205 // region has no marks. Return true if all is well, false if errors 1206 // are detected. 1207 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1208 #endif // PRODUCT 1209 1210 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1211 // the given region do not have any spurious marks. If errors are 1212 // detected, print appropriate error messages and crash. 1213 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1214 1215 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1216 // have any spurious marks. If errors are detected, print 1217 // appropriate error messages and crash. 1218 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1219 1220 // verify_region_sets() performs verification over the region 1221 // lists. It will be compiled in the product code to be used when 1222 // necessary (i.e., during heap verification). 1223 void verify_region_sets(); 1224 1225 // verify_region_sets_optional() is planted in the code for 1226 // list verification in non-product builds (and it can be enabled in 1227 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1228 #if HEAP_REGION_SET_FORCE_VERIFY 1229 void verify_region_sets_optional() { 1230 verify_region_sets(); 1231 } 1232 #else // HEAP_REGION_SET_FORCE_VERIFY 1233 void verify_region_sets_optional() { } 1234 #endif // HEAP_REGION_SET_FORCE_VERIFY 1235 1236 #ifdef ASSERT 1237 bool is_on_master_free_list(HeapRegion* hr) { 1238 return _hrm.is_free(hr); 1239 } 1240 #endif // ASSERT 1241 1242 // Wrapper for the region list operations that can be called from 1243 // methods outside this class. 1244 1245 void secondary_free_list_add(FreeRegionList* list) { 1246 _secondary_free_list.add_ordered(list); 1247 } 1248 1249 void append_secondary_free_list() { 1250 _hrm.insert_list_into_free_list(&_secondary_free_list); 1251 } 1252 1253 void append_secondary_free_list_if_not_empty_with_lock() { 1254 // If the secondary free list looks empty there's no reason to 1255 // take the lock and then try to append it. 1256 if (!_secondary_free_list.is_empty()) { 1257 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1258 append_secondary_free_list(); 1259 } 1260 } 1261 1262 inline void old_set_remove(HeapRegion* hr); 1263 1264 size_t non_young_capacity_bytes() { 1265 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1266 } 1267 1268 void set_free_regions_coming(); 1269 void reset_free_regions_coming(); 1270 bool free_regions_coming() { return _free_regions_coming; } 1271 void wait_while_free_regions_coming(); 1272 1273 // Determine whether the given region is one that we are using as an 1274 // old GC alloc region. 1275 bool is_old_gc_alloc_region(HeapRegion* hr) { 1276 return hr == _retained_old_gc_alloc_region; 1277 } 1278 1279 // Perform a collection of the heap; intended for use in implementing 1280 // "System.gc". This probably implies as full a collection as the 1281 // "CollectedHeap" supports. 1282 virtual void collect(GCCause::Cause cause); 1283 1284 // The same as above but assume that the caller holds the Heap_lock. 1285 void collect_locked(GCCause::Cause cause); 1286 1287 // True iff an evacuation has failed in the most-recent collection. 1288 bool evacuation_failed() { return _evacuation_failed; } 1289 1290 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1291 void prepend_to_freelist(FreeRegionList* list); 1292 void decrement_summary_bytes(size_t bytes); 1293 1294 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1295 virtual bool is_in(const void* p) const; 1296 #ifdef ASSERT 1297 // Returns whether p is in one of the available areas of the heap. Slow but 1298 // extensive version. 1299 bool is_in_exact(const void* p) const; 1300 #endif 1301 1302 // Return "TRUE" iff the given object address is within the collection 1303 // set. Slow implementation. 1304 inline bool obj_in_cs(oop obj); 1305 1306 inline bool is_in_cset(oop obj); 1307 1308 inline bool is_in_cset_or_humongous(const oop obj); 1309 1310 enum in_cset_state_t { 1311 InNeither, // neither in collection set nor humongous 1312 InCSet, // region is in collection set only 1313 IsHumongous // region is a humongous start region 1314 }; 1315 private: 1316 // Instances of this class are used for quick tests on whether a reference points 1317 // into the collection set or is a humongous object (points into a humongous 1318 // object). 1319 // Each of the array's elements denotes whether the corresponding region is in 1320 // the collection set or a humongous region. 1321 // We use this to quickly reclaim humongous objects: by making a humongous region 1322 // succeed this test, we sort-of add it to the collection set. During the reference 1323 // iteration closures, when we see a humongous region, we simply mark it as 1324 // referenced, i.e. live. 1325 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> { 1326 protected: 1327 char default_value() const { return G1CollectedHeap::InNeither; } 1328 public: 1329 void set_humongous(uintptr_t index) { 1330 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values"); 1331 set_by_index(index, G1CollectedHeap::IsHumongous); 1332 } 1333 1334 void clear_humongous(uintptr_t index) { 1335 set_by_index(index, G1CollectedHeap::InNeither); 1336 } 1337 1338 void set_in_cset(uintptr_t index) { 1339 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value"); 1340 set_by_index(index, G1CollectedHeap::InCSet); 1341 } 1342 1343 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; } 1344 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; } 1345 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); } 1346 void clear() { G1BiasedMappedArray<char>::clear(); } 1347 }; 1348 1349 // This array is used for a quick test on whether a reference points into 1350 // the collection set or not. Each of the array's elements denotes whether the 1351 // corresponding region is in the collection set or not. 1352 G1FastCSetBiasedMappedArray _in_cset_fast_test; 1353 1354 public: 1355 1356 inline in_cset_state_t in_cset_state(const oop obj); 1357 1358 // Return "TRUE" iff the given object address is in the reserved 1359 // region of g1. 1360 bool is_in_g1_reserved(const void* p) const { 1361 return _hrm.reserved().contains(p); 1362 } 1363 1364 // Returns a MemRegion that corresponds to the space that has been 1365 // reserved for the heap 1366 MemRegion g1_reserved() const { 1367 return _hrm.reserved(); 1368 } 1369 1370 virtual bool is_in_closed_subset(const void* p) const; 1371 1372 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1373 return (G1SATBCardTableLoggingModRefBS*) barrier_set(); 1374 } 1375 1376 // This resets the card table to all zeros. It is used after 1377 // a collection pause which used the card table to claim cards. 1378 void cleanUpCardTable(); 1379 1380 // Iteration functions. 1381 1382 // Iterate over all the ref-containing fields of all objects, calling 1383 // "cl.do_oop" on each. 1384 virtual void oop_iterate(ExtendedOopClosure* cl); 1385 1386 // Iterate over all objects, calling "cl.do_object" on each. 1387 virtual void object_iterate(ObjectClosure* cl); 1388 1389 virtual void safe_object_iterate(ObjectClosure* cl) { 1390 object_iterate(cl); 1391 } 1392 1393 // Iterate over all spaces in use in the heap, in ascending address order. 1394 virtual void space_iterate(SpaceClosure* cl); 1395 1396 // Iterate over heap regions, in address order, terminating the 1397 // iteration early if the "doHeapRegion" method returns "true". 1398 void heap_region_iterate(HeapRegionClosure* blk) const; 1399 1400 // Return the region with the given index. It assumes the index is valid. 1401 inline HeapRegion* region_at(uint index) const; 1402 1403 // Calculate the region index of the given address. Given address must be 1404 // within the heap. 1405 inline uint addr_to_region(HeapWord* addr) const; 1406 1407 inline HeapWord* bottom_addr_for_region(uint index) const; 1408 1409 // Iterate over the heap regions in parallel. Assumes that this will be called 1410 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1411 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1412 // to each of the regions, by attempting to claim the region using the 1413 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1414 // region. 1415 void heap_region_par_iterate(HeapRegionClosure* cl, 1416 uint worker_id, 1417 HeapRegionClaimer* hrclaimer) const; 1418 1419 // Clear the cached cset start regions and (more importantly) 1420 // the time stamps. Called when we reset the GC time stamp. 1421 void clear_cset_start_regions(); 1422 1423 // Given the id of a worker, obtain or calculate a suitable 1424 // starting region for iterating over the current collection set. 1425 HeapRegion* start_cset_region_for_worker(uint worker_i); 1426 1427 // Iterate over the regions (if any) in the current collection set. 1428 void collection_set_iterate(HeapRegionClosure* blk); 1429 1430 // As above but starting from region r 1431 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1432 1433 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1434 1435 // A CollectedHeap will contain some number of spaces. This finds the 1436 // space containing a given address, or else returns NULL. 1437 virtual Space* space_containing(const void* addr) const; 1438 1439 // Returns the HeapRegion that contains addr. addr must not be NULL. 1440 template <class T> 1441 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1442 1443 // Returns the HeapRegion that contains addr. addr must not be NULL. 1444 // If addr is within a humongous continues region, it returns its humongous start region. 1445 template <class T> 1446 inline HeapRegion* heap_region_containing(const T addr) const; 1447 1448 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1449 // each address in the (reserved) heap is a member of exactly 1450 // one block. The defining characteristic of a block is that it is 1451 // possible to find its size, and thus to progress forward to the next 1452 // block. (Blocks may be of different sizes.) Thus, blocks may 1453 // represent Java objects, or they might be free blocks in a 1454 // free-list-based heap (or subheap), as long as the two kinds are 1455 // distinguishable and the size of each is determinable. 1456 1457 // Returns the address of the start of the "block" that contains the 1458 // address "addr". We say "blocks" instead of "object" since some heaps 1459 // may not pack objects densely; a chunk may either be an object or a 1460 // non-object. 1461 virtual HeapWord* block_start(const void* addr) const; 1462 1463 // Requires "addr" to be the start of a chunk, and returns its size. 1464 // "addr + size" is required to be the start of a new chunk, or the end 1465 // of the active area of the heap. 1466 virtual size_t block_size(const HeapWord* addr) const; 1467 1468 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1469 // the block is an object. 1470 virtual bool block_is_obj(const HeapWord* addr) const; 1471 1472 // Does this heap support heap inspection? (+PrintClassHistogram) 1473 virtual bool supports_heap_inspection() const { return true; } 1474 1475 // Section on thread-local allocation buffers (TLABs) 1476 // See CollectedHeap for semantics. 1477 1478 bool supports_tlab_allocation() const; 1479 size_t tlab_capacity(Thread* ignored) const; 1480 size_t tlab_used(Thread* ignored) const; 1481 size_t max_tlab_size() const; 1482 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1483 1484 // Can a compiler initialize a new object without store barriers? 1485 // This permission only extends from the creation of a new object 1486 // via a TLAB up to the first subsequent safepoint. If such permission 1487 // is granted for this heap type, the compiler promises to call 1488 // defer_store_barrier() below on any slow path allocation of 1489 // a new object for which such initializing store barriers will 1490 // have been elided. G1, like CMS, allows this, but should be 1491 // ready to provide a compensating write barrier as necessary 1492 // if that storage came out of a non-young region. The efficiency 1493 // of this implementation depends crucially on being able to 1494 // answer very efficiently in constant time whether a piece of 1495 // storage in the heap comes from a young region or not. 1496 // See ReduceInitialCardMarks. 1497 virtual bool can_elide_tlab_store_barriers() const { 1498 return true; 1499 } 1500 1501 virtual bool card_mark_must_follow_store() const { 1502 return true; 1503 } 1504 1505 inline bool is_in_young(const oop obj); 1506 1507 #ifdef ASSERT 1508 virtual bool is_in_partial_collection(const void* p); 1509 #endif 1510 1511 virtual bool is_scavengable(const void* addr); 1512 1513 // We don't need barriers for initializing stores to objects 1514 // in the young gen: for the SATB pre-barrier, there is no 1515 // pre-value that needs to be remembered; for the remembered-set 1516 // update logging post-barrier, we don't maintain remembered set 1517 // information for young gen objects. 1518 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1519 1520 // Returns "true" iff the given word_size is "very large". 1521 static bool isHumongous(size_t word_size) { 1522 // Note this has to be strictly greater-than as the TLABs 1523 // are capped at the humongous threshold and we want to 1524 // ensure that we don't try to allocate a TLAB as 1525 // humongous and that we don't allocate a humongous 1526 // object in a TLAB. 1527 return word_size > _humongous_object_threshold_in_words; 1528 } 1529 1530 // Update mod union table with the set of dirty cards. 1531 void updateModUnion(); 1532 1533 // Set the mod union bits corresponding to the given memRegion. Note 1534 // that this is always a safe operation, since it doesn't clear any 1535 // bits. 1536 void markModUnionRange(MemRegion mr); 1537 1538 // Records the fact that a marking phase is no longer in progress. 1539 void set_marking_complete() { 1540 _mark_in_progress = false; 1541 } 1542 void set_marking_started() { 1543 _mark_in_progress = true; 1544 } 1545 bool mark_in_progress() { 1546 return _mark_in_progress; 1547 } 1548 1549 // Print the maximum heap capacity. 1550 virtual size_t max_capacity() const; 1551 1552 virtual jlong millis_since_last_gc(); 1553 1554 1555 // Convenience function to be used in situations where the heap type can be 1556 // asserted to be this type. 1557 static G1CollectedHeap* heap(); 1558 1559 void set_region_short_lived_locked(HeapRegion* hr); 1560 // add appropriate methods for any other surv rate groups 1561 1562 YoungList* young_list() const { return _young_list; } 1563 1564 // debugging 1565 bool check_young_list_well_formed() { 1566 return _young_list->check_list_well_formed(); 1567 } 1568 1569 bool check_young_list_empty(bool check_heap, 1570 bool check_sample = true); 1571 1572 // *** Stuff related to concurrent marking. It's not clear to me that so 1573 // many of these need to be public. 1574 1575 // The functions below are helper functions that a subclass of 1576 // "CollectedHeap" can use in the implementation of its virtual 1577 // functions. 1578 // This performs a concurrent marking of the live objects in a 1579 // bitmap off to the side. 1580 void doConcurrentMark(); 1581 1582 bool isMarkedPrev(oop obj) const; 1583 bool isMarkedNext(oop obj) const; 1584 1585 // Determine if an object is dead, given the object and also 1586 // the region to which the object belongs. An object is dead 1587 // iff a) it was not allocated since the last mark and b) it 1588 // is not marked. 1589 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1590 return 1591 !hr->obj_allocated_since_prev_marking(obj) && 1592 !isMarkedPrev(obj); 1593 } 1594 1595 // This function returns true when an object has been 1596 // around since the previous marking and hasn't yet 1597 // been marked during this marking. 1598 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1599 return 1600 !hr->obj_allocated_since_next_marking(obj) && 1601 !isMarkedNext(obj); 1602 } 1603 1604 // Determine if an object is dead, given only the object itself. 1605 // This will find the region to which the object belongs and 1606 // then call the region version of the same function. 1607 1608 // Added if it is NULL it isn't dead. 1609 1610 inline bool is_obj_dead(const oop obj) const; 1611 1612 inline bool is_obj_ill(const oop obj) const; 1613 1614 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1615 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1616 bool is_marked(oop obj, VerifyOption vo); 1617 const char* top_at_mark_start_str(VerifyOption vo); 1618 1619 ConcurrentMark* concurrent_mark() const { return _cm; } 1620 1621 // Refinement 1622 1623 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1624 1625 // The dirty cards region list is used to record a subset of regions 1626 // whose cards need clearing. The list if populated during the 1627 // remembered set scanning and drained during the card table 1628 // cleanup. Although the methods are reentrant, population/draining 1629 // phases must not overlap. For synchronization purposes the last 1630 // element on the list points to itself. 1631 HeapRegion* _dirty_cards_region_list; 1632 void push_dirty_cards_region(HeapRegion* hr); 1633 HeapRegion* pop_dirty_cards_region(); 1634 1635 // Optimized nmethod scanning support routines 1636 1637 // Register the given nmethod with the G1 heap. 1638 virtual void register_nmethod(nmethod* nm); 1639 1640 // Unregister the given nmethod from the G1 heap. 1641 virtual void unregister_nmethod(nmethod* nm); 1642 1643 // Free up superfluous code root memory. 1644 void purge_code_root_memory(); 1645 1646 // Rebuild the strong code root lists for each region 1647 // after a full GC. 1648 void rebuild_strong_code_roots(); 1649 1650 // Delete entries for dead interned string and clean up unreferenced symbols 1651 // in symbol table, possibly in parallel. 1652 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1653 1654 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1655 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1656 1657 // Redirty logged cards in the refinement queue. 1658 void redirty_logged_cards(); 1659 // Verification 1660 1661 // The following is just to alert the verification code 1662 // that a full collection has occurred and that the 1663 // remembered sets are no longer up to date. 1664 bool _full_collection; 1665 void set_full_collection() { _full_collection = true;} 1666 void clear_full_collection() {_full_collection = false;} 1667 bool full_collection() {return _full_collection;} 1668 1669 // Perform any cleanup actions necessary before allowing a verification. 1670 virtual void prepare_for_verify(); 1671 1672 // Perform verification. 1673 1674 // vo == UsePrevMarking -> use "prev" marking information, 1675 // vo == UseNextMarking -> use "next" marking information 1676 // vo == UseMarkWord -> use the mark word in the object header 1677 // 1678 // NOTE: Only the "prev" marking information is guaranteed to be 1679 // consistent most of the time, so most calls to this should use 1680 // vo == UsePrevMarking. 1681 // Currently, there is only one case where this is called with 1682 // vo == UseNextMarking, which is to verify the "next" marking 1683 // information at the end of remark. 1684 // Currently there is only one place where this is called with 1685 // vo == UseMarkWord, which is to verify the marking during a 1686 // full GC. 1687 void verify(bool silent, VerifyOption vo); 1688 1689 // Override; it uses the "prev" marking information 1690 virtual void verify(bool silent); 1691 1692 // The methods below are here for convenience and dispatch the 1693 // appropriate method depending on value of the given VerifyOption 1694 // parameter. The values for that parameter, and their meanings, 1695 // are the same as those above. 1696 1697 bool is_obj_dead_cond(const oop obj, 1698 const HeapRegion* hr, 1699 const VerifyOption vo) const; 1700 1701 bool is_obj_dead_cond(const oop obj, 1702 const VerifyOption vo) const; 1703 1704 // Printing 1705 1706 virtual void print_on(outputStream* st) const; 1707 virtual void print_extended_on(outputStream* st) const; 1708 virtual void print_on_error(outputStream* st) const; 1709 1710 virtual void print_gc_threads_on(outputStream* st) const; 1711 virtual void gc_threads_do(ThreadClosure* tc) const; 1712 1713 // Override 1714 void print_tracing_info() const; 1715 1716 // The following two methods are helpful for debugging RSet issues. 1717 void print_cset_rsets() PRODUCT_RETURN; 1718 void print_all_rsets() PRODUCT_RETURN; 1719 1720 public: 1721 size_t pending_card_num(); 1722 size_t cards_scanned(); 1723 1724 protected: 1725 size_t _max_heap_capacity; 1726 }; 1727 1728 class G1ParGCAllocBuffer: public ParGCAllocBuffer { 1729 private: 1730 bool _retired; 1731 1732 public: 1733 G1ParGCAllocBuffer(size_t gclab_word_size); 1734 virtual ~G1ParGCAllocBuffer() { 1735 guarantee(_retired, "Allocation buffer has not been retired"); 1736 } 1737 1738 virtual void set_buf(HeapWord* buf) { 1739 ParGCAllocBuffer::set_buf(buf); 1740 _retired = false; 1741 } 1742 1743 virtual void retire(bool end_of_gc, bool retain) { 1744 if (_retired) { 1745 return; 1746 } 1747 ParGCAllocBuffer::retire(end_of_gc, retain); 1748 _retired = true; 1749 } 1750 }; 1751 1752 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP