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/heapRegionSeq.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 }; 187 188 // The G1 STW is alive closure. 189 // An instance is embedded into the G1CH and used as the 190 // (optional) _is_alive_non_header closure in the STW 191 // reference processor. It is also extensively used during 192 // reference processing during STW evacuation pauses. 193 class G1STWIsAliveClosure: public BoolObjectClosure { 194 G1CollectedHeap* _g1; 195 public: 196 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 197 bool do_object_b(oop p); 198 }; 199 200 class RefineCardTableEntryClosure; 201 202 class G1RegionMappingChangedListener : public G1MappingChangedListener { 203 private: 204 void reset_from_card_cache(uint start_idx, size_t num_regions); 205 public: 206 virtual void on_commit(uint start_idx, size_t num_regions); 207 }; 208 209 class G1CollectedHeap : public SharedHeap { 210 friend class VM_CollectForMetadataAllocation; 211 friend class VM_G1CollectForAllocation; 212 friend class VM_G1CollectFull; 213 friend class VM_G1IncCollectionPause; 214 friend class VMStructs; 215 friend class MutatorAllocRegion; 216 friend class SurvivorGCAllocRegion; 217 friend class OldGCAllocRegion; 218 219 // Closures used in implementation. 220 template <G1Barrier barrier, G1Mark do_mark_object> 221 friend class G1ParCopyClosure; 222 friend class G1IsAliveClosure; 223 friend class G1EvacuateFollowersClosure; 224 friend class G1ParScanThreadState; 225 friend class G1ParScanClosureSuper; 226 friend class G1ParEvacuateFollowersClosure; 227 friend class G1ParTask; 228 friend class G1FreeGarbageRegionClosure; 229 friend class RefineCardTableEntryClosure; 230 friend class G1PrepareCompactClosure; 231 friend class RegionSorter; 232 friend class RegionResetter; 233 friend class CountRCClosure; 234 friend class EvacPopObjClosure; 235 friend class G1ParCleanupCTTask; 236 237 friend class G1FreeHumongousRegionClosure; 238 // Other related classes. 239 friend class G1MarkSweep; 240 241 private: 242 // The one and only G1CollectedHeap, so static functions can find it. 243 static G1CollectedHeap* _g1h; 244 245 static size_t _humongous_object_threshold_in_words; 246 247 // The secondary free list which contains regions that have been 248 // freed up during the cleanup process. This will be appended to 249 // the master free list when appropriate. 250 FreeRegionList _secondary_free_list; 251 252 // It keeps track of the old regions. 253 HeapRegionSet _old_set; 254 255 // It keeps track of the humongous regions. 256 HeapRegionSet _humongous_set; 257 258 void clear_humongous_is_live_table(); 259 void eagerly_reclaim_humongous_regions(); 260 261 // The number of regions we could create by expansion. 262 uint _expansion_regions; 263 264 // The block offset table for the G1 heap. 265 G1BlockOffsetSharedArray* _bot_shared; 266 267 // Tears down the region sets / lists so that they are empty and the 268 // regions on the heap do not belong to a region set / list. The 269 // only exception is the humongous set which we leave unaltered. If 270 // free_list_only is true, it will only tear down the master free 271 // list. It is called before a Full GC (free_list_only == false) or 272 // before heap shrinking (free_list_only == true). 273 void tear_down_region_sets(bool free_list_only); 274 275 // Rebuilds the region sets / lists so that they are repopulated to 276 // reflect the contents of the heap. The only exception is the 277 // humongous set which was not torn down in the first place. If 278 // free_list_only is true, it will only rebuild the master free 279 // list. It is called after a Full GC (free_list_only == false) or 280 // after heap shrinking (free_list_only == true). 281 void rebuild_region_sets(bool free_list_only); 282 283 // Callback for region mapping changed events. 284 G1RegionMappingChangedListener _listener; 285 286 // The sequence of all heap regions in the heap. 287 HeapRegionSeq _hrs; 288 289 // Alloc region used to satisfy mutator allocation requests. 290 MutatorAllocRegion _mutator_alloc_region; 291 292 // Alloc region used to satisfy allocation requests by the GC for 293 // survivor objects. 294 SurvivorGCAllocRegion _survivor_gc_alloc_region; 295 296 // PLAB sizing policy for survivors. 297 PLABStats _survivor_plab_stats; 298 299 // Alloc region used to satisfy allocation requests by the GC for 300 // old objects. 301 OldGCAllocRegion _old_gc_alloc_region; 302 303 // PLAB sizing policy for tenured objects. 304 PLABStats _old_plab_stats; 305 306 PLABStats* stats_for_purpose(GCAllocPurpose purpose) { 307 PLABStats* stats = NULL; 308 309 switch (purpose) { 310 case GCAllocForSurvived: 311 stats = &_survivor_plab_stats; 312 break; 313 case GCAllocForTenured: 314 stats = &_old_plab_stats; 315 break; 316 default: 317 assert(false, "unrecognized GCAllocPurpose"); 318 } 319 320 return stats; 321 } 322 323 // The last old region we allocated to during the last GC. 324 // Typically, it is not full so we should re-use it during the next GC. 325 HeapRegion* _retained_old_gc_alloc_region; 326 327 // It specifies whether we should attempt to expand the heap after a 328 // region allocation failure. If heap expansion fails we set this to 329 // false so that we don't re-attempt the heap expansion (it's likely 330 // that subsequent expansion attempts will also fail if one fails). 331 // Currently, it is only consulted during GC and it's reset at the 332 // start of each GC. 333 bool _expand_heap_after_alloc_failure; 334 335 // It resets the mutator alloc region before new allocations can take place. 336 void init_mutator_alloc_region(); 337 338 // It releases the mutator alloc region. 339 void release_mutator_alloc_region(); 340 341 // It initializes the GC alloc regions at the start of a GC. 342 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 343 344 // Setup the retained old gc alloc region as the currrent old gc alloc region. 345 void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info); 346 347 // It releases the GC alloc regions at the end of a GC. 348 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 349 350 // It does any cleanup that needs to be done on the GC alloc regions 351 // before a Full GC. 352 void abandon_gc_alloc_regions(); 353 354 // Helper for monitoring and management support. 355 G1MonitoringSupport* _g1mm; 356 357 // Determines PLAB size for a particular allocation purpose. 358 size_t desired_plab_sz(GCAllocPurpose purpose); 359 360 // Outside of GC pauses, the number of bytes used in all regions other 361 // than the current allocation region. 362 size_t _summary_bytes_used; 363 364 // Records whether the region at the given index is kept live by roots or 365 // references from the young generation. 366 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 367 protected: 368 bool default_value() const { return false; } 369 public: 370 void clear() { G1BiasedMappedArray<bool>::clear(); } 371 void set_live(uint region) { 372 set_by_index(region, true); 373 } 374 bool is_live(uint region) { 375 return get_by_index(region); 376 } 377 }; 378 379 HumongousIsLiveBiasedMappedArray _humongous_is_live; 380 // Stores whether during humongous object registration we found candidate regions. 381 // If not, we can skip a few steps. 382 bool _has_humongous_reclaim_candidates; 383 384 volatile unsigned _gc_time_stamp; 385 386 size_t* _surviving_young_words; 387 388 G1HRPrinter _hr_printer; 389 390 void setup_surviving_young_words(); 391 void update_surviving_young_words(size_t* surv_young_words); 392 void cleanup_surviving_young_words(); 393 394 // It decides whether an explicit GC should start a concurrent cycle 395 // instead of doing a STW GC. Currently, a concurrent cycle is 396 // explicitly started if: 397 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 398 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 399 // (c) cause == _g1_humongous_allocation 400 bool should_do_concurrent_full_gc(GCCause::Cause cause); 401 402 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 403 // concurrent cycles) we have started. 404 volatile unsigned int _old_marking_cycles_started; 405 406 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 407 // concurrent cycles) we have completed. 408 volatile unsigned int _old_marking_cycles_completed; 409 410 bool _concurrent_cycle_started; 411 412 // This is a non-product method that is helpful for testing. It is 413 // called at the end of a GC and artificially expands the heap by 414 // allocating a number of dead regions. This way we can induce very 415 // frequent marking cycles and stress the cleanup / concurrent 416 // cleanup code more (as all the regions that will be allocated by 417 // this method will be found dead by the marking cycle). 418 void allocate_dummy_regions() PRODUCT_RETURN; 419 420 // Clear RSets after a compaction. It also resets the GC time stamps. 421 void clear_rsets_post_compaction(); 422 423 // If the HR printer is active, dump the state of the regions in the 424 // heap after a compaction. 425 void print_hrs_post_compaction(); 426 427 double verify(bool guard, const char* msg); 428 void verify_before_gc(); 429 void verify_after_gc(); 430 431 void log_gc_header(); 432 void log_gc_footer(double pause_time_sec); 433 434 // These are macros so that, if the assert fires, we get the correct 435 // line number, file, etc. 436 437 #define heap_locking_asserts_err_msg(_extra_message_) \ 438 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 439 (_extra_message_), \ 440 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 441 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 442 BOOL_TO_STR(Thread::current()->is_VM_thread())) 443 444 #define assert_heap_locked() \ 445 do { \ 446 assert(Heap_lock->owned_by_self(), \ 447 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 448 } while (0) 449 450 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 451 do { \ 452 assert(Heap_lock->owned_by_self() || \ 453 (SafepointSynchronize::is_at_safepoint() && \ 454 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 455 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 456 "should be at a safepoint")); \ 457 } while (0) 458 459 #define assert_heap_locked_and_not_at_safepoint() \ 460 do { \ 461 assert(Heap_lock->owned_by_self() && \ 462 !SafepointSynchronize::is_at_safepoint(), \ 463 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 464 "should not be at a safepoint")); \ 465 } while (0) 466 467 #define assert_heap_not_locked() \ 468 do { \ 469 assert(!Heap_lock->owned_by_self(), \ 470 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 471 } while (0) 472 473 #define assert_heap_not_locked_and_not_at_safepoint() \ 474 do { \ 475 assert(!Heap_lock->owned_by_self() && \ 476 !SafepointSynchronize::is_at_safepoint(), \ 477 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 478 "should not be at a safepoint")); \ 479 } while (0) 480 481 #define assert_at_safepoint(_should_be_vm_thread_) \ 482 do { \ 483 assert(SafepointSynchronize::is_at_safepoint() && \ 484 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 485 heap_locking_asserts_err_msg("should be at a safepoint")); \ 486 } while (0) 487 488 #define assert_not_at_safepoint() \ 489 do { \ 490 assert(!SafepointSynchronize::is_at_safepoint(), \ 491 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 492 } while (0) 493 494 protected: 495 496 // The young region list. 497 YoungList* _young_list; 498 499 // The current policy object for the collector. 500 G1CollectorPolicy* _g1_policy; 501 502 // This is the second level of trying to allocate a new region. If 503 // new_region() didn't find a region on the free_list, this call will 504 // check whether there's anything available on the 505 // secondary_free_list and/or wait for more regions to appear on 506 // that list, if _free_regions_coming is set. 507 HeapRegion* new_region_try_secondary_free_list(bool is_old); 508 509 // Try to allocate a single non-humongous HeapRegion sufficient for 510 // an allocation of the given word_size. If do_expand is true, 511 // attempt to expand the heap if necessary to satisfy the allocation 512 // request. If the region is to be used as an old region or for a 513 // humongous object, set is_old to true. If not, to false. 514 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 515 516 // Initialize a contiguous set of free regions of length num_regions 517 // and starting at index first so that they appear as a single 518 // humongous region. 519 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 520 uint num_regions, 521 size_t word_size); 522 523 // Attempt to allocate a humongous object of the given size. Return 524 // NULL if unsuccessful. 525 HeapWord* humongous_obj_allocate(size_t word_size); 526 527 // The following two methods, allocate_new_tlab() and 528 // mem_allocate(), are the two main entry points from the runtime 529 // into the G1's allocation routines. They have the following 530 // assumptions: 531 // 532 // * They should both be called outside safepoints. 533 // 534 // * They should both be called without holding the Heap_lock. 535 // 536 // * All allocation requests for new TLABs should go to 537 // allocate_new_tlab(). 538 // 539 // * All non-TLAB allocation requests should go to mem_allocate(). 540 // 541 // * If either call cannot satisfy the allocation request using the 542 // current allocating region, they will try to get a new one. If 543 // this fails, they will attempt to do an evacuation pause and 544 // retry the allocation. 545 // 546 // * If all allocation attempts fail, even after trying to schedule 547 // an evacuation pause, allocate_new_tlab() will return NULL, 548 // whereas mem_allocate() will attempt a heap expansion and/or 549 // schedule a Full GC. 550 // 551 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 552 // should never be called with word_size being humongous. All 553 // humongous allocation requests should go to mem_allocate() which 554 // will satisfy them with a special path. 555 556 virtual HeapWord* allocate_new_tlab(size_t word_size); 557 558 virtual HeapWord* mem_allocate(size_t word_size, 559 bool* gc_overhead_limit_was_exceeded); 560 561 // The following three methods take a gc_count_before_ret 562 // parameter which is used to return the GC count if the method 563 // returns NULL. Given that we are required to read the GC count 564 // while holding the Heap_lock, and these paths will take the 565 // Heap_lock at some point, it's easier to get them to read the GC 566 // count while holding the Heap_lock before they return NULL instead 567 // of the caller (namely: mem_allocate()) having to also take the 568 // Heap_lock just to read the GC count. 569 570 // First-level mutator allocation attempt: try to allocate out of 571 // the mutator alloc region without taking the Heap_lock. This 572 // should only be used for non-humongous allocations. 573 inline HeapWord* attempt_allocation(size_t word_size, 574 unsigned int* gc_count_before_ret, 575 int* gclocker_retry_count_ret); 576 577 // Second-level mutator allocation attempt: take the Heap_lock and 578 // retry the allocation attempt, potentially scheduling a GC 579 // pause. This should only be used for non-humongous allocations. 580 HeapWord* attempt_allocation_slow(size_t word_size, 581 unsigned int* gc_count_before_ret, 582 int* gclocker_retry_count_ret); 583 584 // Takes the Heap_lock and attempts a humongous allocation. It can 585 // potentially schedule a GC pause. 586 HeapWord* attempt_allocation_humongous(size_t word_size, 587 unsigned int* gc_count_before_ret, 588 int* gclocker_retry_count_ret); 589 590 // Allocation attempt that should be called during safepoints (e.g., 591 // at the end of a successful GC). expect_null_mutator_alloc_region 592 // specifies whether the mutator alloc region is expected to be NULL 593 // or not. 594 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 595 bool expect_null_mutator_alloc_region); 596 597 // It dirties the cards that cover the block so that so that the post 598 // write barrier never queues anything when updating objects on this 599 // block. It is assumed (and in fact we assert) that the block 600 // belongs to a young region. 601 inline void dirty_young_block(HeapWord* start, size_t word_size); 602 603 // Allocate blocks during garbage collection. Will ensure an 604 // allocation region, either by picking one or expanding the 605 // heap, and then allocate a block of the given size. The block 606 // may not be a humongous - it must fit into a single heap region. 607 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size); 608 609 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, 610 HeapRegion* alloc_region, 611 bool par, 612 size_t word_size); 613 614 // Ensure that no further allocations can happen in "r", bearing in mind 615 // that parallel threads might be attempting allocations. 616 void par_allocate_remaining_space(HeapRegion* r); 617 618 // Allocation attempt during GC for a survivor object / PLAB. 619 inline HeapWord* survivor_attempt_allocation(size_t word_size); 620 621 // Allocation attempt during GC for an old object / PLAB. 622 inline HeapWord* old_attempt_allocation(size_t word_size); 623 624 // These methods are the "callbacks" from the G1AllocRegion class. 625 626 // For mutator alloc regions. 627 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 628 void retire_mutator_alloc_region(HeapRegion* alloc_region, 629 size_t allocated_bytes); 630 631 // For GC alloc regions. 632 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 633 GCAllocPurpose ap); 634 void retire_gc_alloc_region(HeapRegion* alloc_region, 635 size_t allocated_bytes, GCAllocPurpose ap); 636 637 // - if explicit_gc is true, the GC is for a System.gc() or a heap 638 // inspection request and should collect the entire heap 639 // - if clear_all_soft_refs is true, all soft references should be 640 // cleared during the GC 641 // - if explicit_gc is false, word_size describes the allocation that 642 // the GC should attempt (at least) to satisfy 643 // - it returns false if it is unable to do the collection due to the 644 // GC locker being active, true otherwise 645 bool do_collection(bool explicit_gc, 646 bool clear_all_soft_refs, 647 size_t word_size); 648 649 // Callback from VM_G1CollectFull operation. 650 // Perform a full collection. 651 virtual void do_full_collection(bool clear_all_soft_refs); 652 653 // Resize the heap if necessary after a full collection. If this is 654 // after a collect-for allocation, "word_size" is the allocation size, 655 // and will be considered part of the used portion of the heap. 656 void resize_if_necessary_after_full_collection(size_t word_size); 657 658 // Callback from VM_G1CollectForAllocation operation. 659 // This function does everything necessary/possible to satisfy a 660 // failed allocation request (including collection, expansion, etc.) 661 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded); 662 663 // Attempting to expand the heap sufficiently 664 // to support an allocation of the given "word_size". If 665 // successful, perform the allocation and return the address of the 666 // allocated block, or else "NULL". 667 HeapWord* expand_and_allocate(size_t word_size); 668 669 // Process any reference objects discovered during 670 // an incremental evacuation pause. 671 void process_discovered_references(uint no_of_gc_workers); 672 673 // Enqueue any remaining discovered references 674 // after processing. 675 void enqueue_discovered_references(uint no_of_gc_workers); 676 677 public: 678 679 G1MonitoringSupport* g1mm() { 680 assert(_g1mm != NULL, "should have been initialized"); 681 return _g1mm; 682 } 683 684 // Expand the garbage-first heap by at least the given size (in bytes!). 685 // Returns true if the heap was expanded by the requested amount; 686 // false otherwise. 687 // (Rounds up to a HeapRegion boundary.) 688 bool expand(size_t expand_bytes); 689 690 // Do anything common to GC's. 691 virtual void gc_prologue(bool full); 692 virtual void gc_epilogue(bool full); 693 694 inline void set_humongous_is_live(oop obj); 695 696 bool humongous_is_live(uint region) { 697 return _humongous_is_live.is_live(region); 698 } 699 700 // Returns whether the given region (which must be a humongous (start) region) 701 // is to be considered conservatively live regardless of any other conditions. 702 bool humongous_region_is_always_live(uint index); 703 // Register the given region to be part of the collection set. 704 inline void register_humongous_region_with_in_cset_fast_test(uint index); 705 // Register regions with humongous objects (actually on the start region) in 706 // the in_cset_fast_test table. 707 void register_humongous_regions_with_in_cset_fast_test(); 708 // We register a region with the fast "in collection set" test. We 709 // simply set to true the array slot corresponding to this region. 710 void register_region_with_in_cset_fast_test(HeapRegion* r) { 711 _in_cset_fast_test.set_in_cset(r->hrs_index()); 712 } 713 714 // This is a fast test on whether a reference points into the 715 // collection set or not. Assume that the reference 716 // points into the heap. 717 inline bool in_cset_fast_test(oop obj); 718 719 void clear_cset_fast_test() { 720 _in_cset_fast_test.clear(); 721 } 722 723 // This is called at the start of either a concurrent cycle or a Full 724 // GC to update the number of old marking cycles started. 725 void increment_old_marking_cycles_started(); 726 727 // This is called at the end of either a concurrent cycle or a Full 728 // GC to update the number of old marking cycles completed. Those two 729 // can happen in a nested fashion, i.e., we start a concurrent 730 // cycle, a Full GC happens half-way through it which ends first, 731 // and then the cycle notices that a Full GC happened and ends 732 // too. The concurrent parameter is a boolean to help us do a bit 733 // tighter consistency checking in the method. If concurrent is 734 // false, the caller is the inner caller in the nesting (i.e., the 735 // Full GC). If concurrent is true, the caller is the outer caller 736 // in this nesting (i.e., the concurrent cycle). Further nesting is 737 // not currently supported. The end of this call also notifies 738 // the FullGCCount_lock in case a Java thread is waiting for a full 739 // GC to happen (e.g., it called System.gc() with 740 // +ExplicitGCInvokesConcurrent). 741 void increment_old_marking_cycles_completed(bool concurrent); 742 743 unsigned int old_marking_cycles_completed() { 744 return _old_marking_cycles_completed; 745 } 746 747 void register_concurrent_cycle_start(const Ticks& start_time); 748 void register_concurrent_cycle_end(); 749 void trace_heap_after_concurrent_cycle(); 750 751 G1YCType yc_type(); 752 753 G1HRPrinter* hr_printer() { return &_hr_printer; } 754 755 // Frees a non-humongous region by initializing its contents and 756 // adding it to the free list that's passed as a parameter (this is 757 // usually a local list which will be appended to the master free 758 // list later). The used bytes of freed regions are accumulated in 759 // pre_used. If par is true, the region's RSet will not be freed 760 // up. The assumption is that this will be done later. 761 // The locked parameter indicates if the caller has already taken 762 // care of proper synchronization. This may allow some optimizations. 763 void free_region(HeapRegion* hr, 764 FreeRegionList* free_list, 765 bool par, 766 bool locked = false); 767 768 // Frees a humongous region by collapsing it into individual regions 769 // and calling free_region() for each of them. The freed regions 770 // will be added to the free list that's passed as a parameter (this 771 // is usually a local list which will be appended to the master free 772 // list later). The used bytes of freed regions are accumulated in 773 // pre_used. If par is true, the region's RSet will not be freed 774 // up. The assumption is that this will be done later. 775 void free_humongous_region(HeapRegion* hr, 776 FreeRegionList* free_list, 777 bool par); 778 protected: 779 780 // Shrink the garbage-first heap by at most the given size (in bytes!). 781 // (Rounds down to a HeapRegion boundary.) 782 virtual void shrink(size_t expand_bytes); 783 void shrink_helper(size_t expand_bytes); 784 785 #if TASKQUEUE_STATS 786 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 787 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 788 void reset_taskqueue_stats(); 789 #endif // TASKQUEUE_STATS 790 791 // Schedule the VM operation that will do an evacuation pause to 792 // satisfy an allocation request of word_size. *succeeded will 793 // return whether the VM operation was successful (it did do an 794 // evacuation pause) or not (another thread beat us to it or the GC 795 // locker was active). Given that we should not be holding the 796 // Heap_lock when we enter this method, we will pass the 797 // gc_count_before (i.e., total_collections()) as a parameter since 798 // it has to be read while holding the Heap_lock. Currently, both 799 // methods that call do_collection_pause() release the Heap_lock 800 // before the call, so it's easy to read gc_count_before just before. 801 HeapWord* do_collection_pause(size_t word_size, 802 unsigned int gc_count_before, 803 bool* succeeded, 804 GCCause::Cause gc_cause); 805 806 // The guts of the incremental collection pause, executed by the vm 807 // thread. It returns false if it is unable to do the collection due 808 // to the GC locker being active, true otherwise 809 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 810 811 // Actually do the work of evacuating the collection set. 812 void evacuate_collection_set(EvacuationInfo& evacuation_info); 813 814 // The g1 remembered set of the heap. 815 G1RemSet* _g1_rem_set; 816 817 // A set of cards that cover the objects for which the Rsets should be updated 818 // concurrently after the collection. 819 DirtyCardQueueSet _dirty_card_queue_set; 820 821 // The closure used to refine a single card. 822 RefineCardTableEntryClosure* _refine_cte_cl; 823 824 // A function to check the consistency of dirty card logs. 825 void check_ct_logs_at_safepoint(); 826 827 // A DirtyCardQueueSet that is used to hold cards that contain 828 // references into the current collection set. This is used to 829 // update the remembered sets of the regions in the collection 830 // set in the event of an evacuation failure. 831 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 832 833 // After a collection pause, make the regions in the CS into free 834 // regions. 835 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 836 837 // Abandon the current collection set without recording policy 838 // statistics or updating free lists. 839 void abandon_collection_set(HeapRegion* cs_head); 840 841 // Applies "scan_non_heap_roots" to roots outside the heap, 842 // "scan_rs" to roots inside the heap (having done "set_region" to 843 // indicate the region in which the root resides), 844 // and does "scan_metadata" If "scan_rs" is 845 // NULL, then this step is skipped. The "worker_i" 846 // param is for use with parallel roots processing, and should be 847 // the "i" of the calling parallel worker thread's work(i) function. 848 // In the sequential case this param will be ignored. 849 void g1_process_roots(OopClosure* scan_non_heap_roots, 850 OopClosure* scan_non_heap_weak_roots, 851 OopsInHeapRegionClosure* scan_rs, 852 CLDClosure* scan_strong_clds, 853 CLDClosure* scan_weak_clds, 854 CodeBlobClosure* scan_strong_code, 855 uint worker_i); 856 857 // The concurrent marker (and the thread it runs in.) 858 ConcurrentMark* _cm; 859 ConcurrentMarkThread* _cmThread; 860 bool _mark_in_progress; 861 862 // The concurrent refiner. 863 ConcurrentG1Refine* _cg1r; 864 865 // The parallel task queues 866 RefToScanQueueSet *_task_queues; 867 868 // True iff a evacuation has failed in the current collection. 869 bool _evacuation_failed; 870 871 EvacuationFailedInfo* _evacuation_failed_info_array; 872 873 // Failed evacuations cause some logical from-space objects to have 874 // forwarding pointers to themselves. Reset them. 875 void remove_self_forwarding_pointers(); 876 877 // Together, these store an object with a preserved mark, and its mark value. 878 Stack<oop, mtGC> _objs_with_preserved_marks; 879 Stack<markOop, mtGC> _preserved_marks_of_objs; 880 881 // Preserve the mark of "obj", if necessary, in preparation for its mark 882 // word being overwritten with a self-forwarding-pointer. 883 void preserve_mark_if_necessary(oop obj, markOop m); 884 885 // The stack of evac-failure objects left to be scanned. 886 GrowableArray<oop>* _evac_failure_scan_stack; 887 // The closure to apply to evac-failure objects. 888 889 OopsInHeapRegionClosure* _evac_failure_closure; 890 // Set the field above. 891 void 892 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 893 _evac_failure_closure = evac_failure_closure; 894 } 895 896 // Push "obj" on the scan stack. 897 void push_on_evac_failure_scan_stack(oop obj); 898 // Process scan stack entries until the stack is empty. 899 void drain_evac_failure_scan_stack(); 900 // True iff an invocation of "drain_scan_stack" is in progress; to 901 // prevent unnecessary recursion. 902 bool _drain_in_progress; 903 904 // Do any necessary initialization for evacuation-failure handling. 905 // "cl" is the closure that will be used to process evac-failure 906 // objects. 907 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 908 // Do any necessary cleanup for evacuation-failure handling data 909 // structures. 910 void finalize_for_evac_failure(); 911 912 // An attempt to evacuate "obj" has failed; take necessary steps. 913 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 914 void handle_evacuation_failure_common(oop obj, markOop m); 915 916 #ifndef PRODUCT 917 // Support for forcing evacuation failures. Analogous to 918 // PromotionFailureALot for the other collectors. 919 920 // Records whether G1EvacuationFailureALot should be in effect 921 // for the current GC 922 bool _evacuation_failure_alot_for_current_gc; 923 924 // Used to record the GC number for interval checking when 925 // determining whether G1EvaucationFailureALot is in effect 926 // for the current GC. 927 size_t _evacuation_failure_alot_gc_number; 928 929 // Count of the number of evacuations between failures. 930 volatile size_t _evacuation_failure_alot_count; 931 932 // Set whether G1EvacuationFailureALot should be in effect 933 // for the current GC (based upon the type of GC and which 934 // command line flags are set); 935 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 936 bool during_initial_mark, 937 bool during_marking); 938 939 inline void set_evacuation_failure_alot_for_current_gc(); 940 941 // Return true if it's time to cause an evacuation failure. 942 inline bool evacuation_should_fail(); 943 944 // Reset the G1EvacuationFailureALot counters. Should be called at 945 // the end of an evacuation pause in which an evacuation failure occurred. 946 inline void reset_evacuation_should_fail(); 947 #endif // !PRODUCT 948 949 // ("Weak") Reference processing support. 950 // 951 // G1 has 2 instances of the reference processor class. One 952 // (_ref_processor_cm) handles reference object discovery 953 // and subsequent processing during concurrent marking cycles. 954 // 955 // The other (_ref_processor_stw) handles reference object 956 // discovery and processing during full GCs and incremental 957 // evacuation pauses. 958 // 959 // During an incremental pause, reference discovery will be 960 // temporarily disabled for _ref_processor_cm and will be 961 // enabled for _ref_processor_stw. At the end of the evacuation 962 // pause references discovered by _ref_processor_stw will be 963 // processed and discovery will be disabled. The previous 964 // setting for reference object discovery for _ref_processor_cm 965 // will be re-instated. 966 // 967 // At the start of marking: 968 // * Discovery by the CM ref processor is verified to be inactive 969 // and it's discovered lists are empty. 970 // * Discovery by the CM ref processor is then enabled. 971 // 972 // At the end of marking: 973 // * Any references on the CM ref processor's discovered 974 // lists are processed (possibly MT). 975 // 976 // At the start of full GC we: 977 // * Disable discovery by the CM ref processor and 978 // empty CM ref processor's discovered lists 979 // (without processing any entries). 980 // * Verify that the STW ref processor is inactive and it's 981 // discovered lists are empty. 982 // * Temporarily set STW ref processor discovery as single threaded. 983 // * Temporarily clear the STW ref processor's _is_alive_non_header 984 // field. 985 // * Finally enable discovery by the STW ref processor. 986 // 987 // The STW ref processor is used to record any discovered 988 // references during the full GC. 989 // 990 // At the end of a full GC we: 991 // * Enqueue any reference objects discovered by the STW ref processor 992 // that have non-live referents. This has the side-effect of 993 // making the STW ref processor inactive by disabling discovery. 994 // * Verify that the CM ref processor is still inactive 995 // and no references have been placed on it's discovered 996 // lists (also checked as a precondition during initial marking). 997 998 // The (stw) reference processor... 999 ReferenceProcessor* _ref_processor_stw; 1000 1001 STWGCTimer* _gc_timer_stw; 1002 ConcurrentGCTimer* _gc_timer_cm; 1003 1004 G1OldTracer* _gc_tracer_cm; 1005 G1NewTracer* _gc_tracer_stw; 1006 1007 // During reference object discovery, the _is_alive_non_header 1008 // closure (if non-null) is applied to the referent object to 1009 // determine whether the referent is live. If so then the 1010 // reference object does not need to be 'discovered' and can 1011 // be treated as a regular oop. This has the benefit of reducing 1012 // the number of 'discovered' reference objects that need to 1013 // be processed. 1014 // 1015 // Instance of the is_alive closure for embedding into the 1016 // STW reference processor as the _is_alive_non_header field. 1017 // Supplying a value for the _is_alive_non_header field is 1018 // optional but doing so prevents unnecessary additions to 1019 // the discovered lists during reference discovery. 1020 G1STWIsAliveClosure _is_alive_closure_stw; 1021 1022 // The (concurrent marking) reference processor... 1023 ReferenceProcessor* _ref_processor_cm; 1024 1025 // Instance of the concurrent mark is_alive closure for embedding 1026 // into the Concurrent Marking reference processor as the 1027 // _is_alive_non_header field. Supplying a value for the 1028 // _is_alive_non_header field is optional but doing so prevents 1029 // unnecessary additions to the discovered lists during reference 1030 // discovery. 1031 G1CMIsAliveClosure _is_alive_closure_cm; 1032 1033 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 1034 HeapRegion** _worker_cset_start_region; 1035 1036 // Time stamp to validate the regions recorded in the cache 1037 // used by G1CollectedHeap::start_cset_region_for_worker(). 1038 // The heap region entry for a given worker is valid iff 1039 // the associated time stamp value matches the current value 1040 // of G1CollectedHeap::_gc_time_stamp. 1041 unsigned int* _worker_cset_start_region_time_stamp; 1042 1043 enum G1H_process_roots_tasks { 1044 G1H_PS_filter_satb_buffers, 1045 G1H_PS_refProcessor_oops_do, 1046 // Leave this one last. 1047 G1H_PS_NumElements 1048 }; 1049 1050 SubTasksDone* _process_strong_tasks; 1051 1052 volatile bool _free_regions_coming; 1053 1054 public: 1055 1056 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } 1057 1058 void set_refine_cte_cl_concurrency(bool concurrent); 1059 1060 RefToScanQueue *task_queue(int i) const; 1061 1062 // A set of cards where updates happened during the GC 1063 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1064 1065 // A DirtyCardQueueSet that is used to hold cards that contain 1066 // references into the current collection set. This is used to 1067 // update the remembered sets of the regions in the collection 1068 // set in the event of an evacuation failure. 1069 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1070 { return _into_cset_dirty_card_queue_set; } 1071 1072 // Create a G1CollectedHeap with the specified policy. 1073 // Must call the initialize method afterwards. 1074 // May not return if something goes wrong. 1075 G1CollectedHeap(G1CollectorPolicy* policy); 1076 1077 // Initialize the G1CollectedHeap to have the initial and 1078 // maximum sizes and remembered and barrier sets 1079 // specified by the policy object. 1080 jint initialize(); 1081 1082 virtual void stop(); 1083 1084 // Return the (conservative) maximum heap alignment for any G1 heap 1085 static size_t conservative_max_heap_alignment(); 1086 1087 // Initialize weak reference processing. 1088 virtual void ref_processing_init(); 1089 1090 void set_par_threads(uint t) { 1091 SharedHeap::set_par_threads(t); 1092 // Done in SharedHeap but oddly there are 1093 // two _process_strong_tasks's in a G1CollectedHeap 1094 // so do it here too. 1095 _process_strong_tasks->set_n_threads(t); 1096 } 1097 1098 // Set _n_par_threads according to a policy TBD. 1099 void set_par_threads(); 1100 1101 void set_n_termination(int t) { 1102 _process_strong_tasks->set_n_threads(t); 1103 } 1104 1105 virtual CollectedHeap::Name kind() const { 1106 return CollectedHeap::G1CollectedHeap; 1107 } 1108 1109 // The current policy object for the collector. 1110 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1111 1112 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1113 1114 // Adaptive size policy. No such thing for g1. 1115 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1116 1117 // The rem set and barrier set. 1118 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1119 1120 unsigned get_gc_time_stamp() { 1121 return _gc_time_stamp; 1122 } 1123 1124 inline void reset_gc_time_stamp(); 1125 1126 void check_gc_time_stamps() PRODUCT_RETURN; 1127 1128 inline void increment_gc_time_stamp(); 1129 1130 // Reset the given region's GC timestamp. If it's starts humongous, 1131 // also reset the GC timestamp of its corresponding 1132 // continues humongous regions too. 1133 void reset_gc_time_stamps(HeapRegion* hr); 1134 1135 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1136 DirtyCardQueue* into_cset_dcq, 1137 bool concurrent, uint worker_i); 1138 1139 // The shared block offset table array. 1140 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1141 1142 // Reference Processing accessors 1143 1144 // The STW reference processor.... 1145 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1146 1147 // The Concurrent Marking reference processor... 1148 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1149 1150 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1151 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1152 1153 virtual size_t capacity() const; 1154 virtual size_t used() const; 1155 // This should be called when we're not holding the heap lock. The 1156 // result might be a bit inaccurate. 1157 size_t used_unlocked() const; 1158 size_t recalculate_used() const; 1159 1160 // These virtual functions do the actual allocation. 1161 // Some heaps may offer a contiguous region for shared non-blocking 1162 // allocation, via inlined code (by exporting the address of the top and 1163 // end fields defining the extent of the contiguous allocation region.) 1164 // But G1CollectedHeap doesn't yet support this. 1165 1166 virtual bool is_maximal_no_gc() const { 1167 return _hrs.available() == 0; 1168 } 1169 1170 // The current number of regions in the heap. 1171 uint num_regions() const { return _hrs.length(); } 1172 1173 // The max number of regions in the heap. 1174 uint max_regions() const { return _hrs.max_length(); } 1175 1176 // The number of regions that are completely free. 1177 uint num_free_regions() const { return _hrs.num_free_regions(); } 1178 1179 // The number of regions that are not completely free. 1180 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1181 1182 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1183 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1184 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1185 void verify_dirty_young_regions() PRODUCT_RETURN; 1186 1187 #ifndef PRODUCT 1188 // Make sure that the given bitmap has no marked objects in the 1189 // range [from,limit). If it does, print an error message and return 1190 // false. Otherwise, just return true. bitmap_name should be "prev" 1191 // or "next". 1192 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1193 HeapWord* from, HeapWord* limit); 1194 1195 // Verify that the prev / next bitmap range [tams,end) for the given 1196 // region has no marks. Return true if all is well, false if errors 1197 // are detected. 1198 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1199 #endif // PRODUCT 1200 1201 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1202 // the given region do not have any spurious marks. If errors are 1203 // detected, print appropriate error messages and crash. 1204 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1205 1206 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1207 // have any spurious marks. If errors are detected, print 1208 // appropriate error messages and crash. 1209 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1210 1211 // verify_region_sets() performs verification over the region 1212 // lists. It will be compiled in the product code to be used when 1213 // necessary (i.e., during heap verification). 1214 void verify_region_sets(); 1215 1216 // verify_region_sets_optional() is planted in the code for 1217 // list verification in non-product builds (and it can be enabled in 1218 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1219 #if HEAP_REGION_SET_FORCE_VERIFY 1220 void verify_region_sets_optional() { 1221 verify_region_sets(); 1222 } 1223 #else // HEAP_REGION_SET_FORCE_VERIFY 1224 void verify_region_sets_optional() { } 1225 #endif // HEAP_REGION_SET_FORCE_VERIFY 1226 1227 #ifdef ASSERT 1228 bool is_on_master_free_list(HeapRegion* hr) { 1229 return _hrs.is_free(hr); 1230 } 1231 #endif // ASSERT 1232 1233 // Wrapper for the region list operations that can be called from 1234 // methods outside this class. 1235 1236 void secondary_free_list_add(FreeRegionList* list) { 1237 _secondary_free_list.add_ordered(list); 1238 } 1239 1240 void append_secondary_free_list() { 1241 _hrs.insert_list_into_free_list(&_secondary_free_list); 1242 } 1243 1244 void append_secondary_free_list_if_not_empty_with_lock() { 1245 // If the secondary free list looks empty there's no reason to 1246 // take the lock and then try to append it. 1247 if (!_secondary_free_list.is_empty()) { 1248 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1249 append_secondary_free_list(); 1250 } 1251 } 1252 1253 inline void old_set_remove(HeapRegion* hr); 1254 1255 size_t non_young_capacity_bytes() { 1256 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1257 } 1258 1259 void set_free_regions_coming(); 1260 void reset_free_regions_coming(); 1261 bool free_regions_coming() { return _free_regions_coming; } 1262 void wait_while_free_regions_coming(); 1263 1264 // Determine whether the given region is one that we are using as an 1265 // old GC alloc region. 1266 bool is_old_gc_alloc_region(HeapRegion* hr) { 1267 return hr == _retained_old_gc_alloc_region; 1268 } 1269 1270 // Perform a collection of the heap; intended for use in implementing 1271 // "System.gc". This probably implies as full a collection as the 1272 // "CollectedHeap" supports. 1273 virtual void collect(GCCause::Cause cause); 1274 1275 // The same as above but assume that the caller holds the Heap_lock. 1276 void collect_locked(GCCause::Cause cause); 1277 1278 // True iff an evacuation has failed in the most-recent collection. 1279 bool evacuation_failed() { return _evacuation_failed; } 1280 1281 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1282 void prepend_to_freelist(FreeRegionList* list); 1283 void decrement_summary_bytes(size_t bytes); 1284 1285 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1286 virtual bool is_in(const void* p) const; 1287 #ifdef ASSERT 1288 // Returns whether p is in one of the available areas of the heap. Slow but 1289 // extensive version. 1290 bool is_in_exact(const void* p) const; 1291 #endif 1292 1293 // Return "TRUE" iff the given object address is within the collection 1294 // set. Slow implementation. 1295 inline bool obj_in_cs(oop obj); 1296 1297 inline bool is_in_cset(oop obj); 1298 1299 inline bool is_in_cset_or_humongous(const oop obj); 1300 1301 enum in_cset_state_t { 1302 InNeither, // neither in collection set nor humongous 1303 InCSet, // region is in collection set only 1304 IsHumongous // region is a humongous start region 1305 }; 1306 private: 1307 // Instances of this class are used for quick tests on whether a reference points 1308 // into the collection set or is a humongous object (points into a humongous 1309 // object). 1310 // Each of the array's elements denotes whether the corresponding region is in 1311 // the collection set or a humongous region. 1312 // We use this to quickly reclaim humongous objects: by making a humongous region 1313 // succeed this test, we sort-of add it to the collection set. During the reference 1314 // iteration closures, when we see a humongous region, we simply mark it as 1315 // referenced, i.e. live. 1316 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> { 1317 protected: 1318 char default_value() const { return G1CollectedHeap::InNeither; } 1319 public: 1320 void set_humongous(uintptr_t index) { 1321 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values"); 1322 set_by_index(index, G1CollectedHeap::IsHumongous); 1323 } 1324 1325 void clear_humongous(uintptr_t index) { 1326 set_by_index(index, G1CollectedHeap::InNeither); 1327 } 1328 1329 void set_in_cset(uintptr_t index) { 1330 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value"); 1331 set_by_index(index, G1CollectedHeap::InCSet); 1332 } 1333 1334 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; } 1335 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; } 1336 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); } 1337 void clear() { G1BiasedMappedArray<char>::clear(); } 1338 }; 1339 1340 // This array is used for a quick test on whether a reference points into 1341 // the collection set or not. Each of the array's elements denotes whether the 1342 // corresponding region is in the collection set or not. 1343 G1FastCSetBiasedMappedArray _in_cset_fast_test; 1344 1345 public: 1346 1347 inline in_cset_state_t in_cset_state(const oop obj); 1348 1349 // Return "TRUE" iff the given object address is in the reserved 1350 // region of g1. 1351 bool is_in_g1_reserved(const void* p) const { 1352 return _hrs.reserved().contains(p); 1353 } 1354 1355 // Returns a MemRegion that corresponds to the space that has been 1356 // reserved for the heap 1357 MemRegion g1_reserved() const { 1358 return _hrs.reserved(); 1359 } 1360 1361 virtual bool is_in_closed_subset(const void* p) const; 1362 1363 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1364 return (G1SATBCardTableLoggingModRefBS*) barrier_set(); 1365 } 1366 1367 // This resets the card table to all zeros. It is used after 1368 // a collection pause which used the card table to claim cards. 1369 void cleanUpCardTable(); 1370 1371 // Iteration functions. 1372 1373 // Iterate over all the ref-containing fields of all objects, calling 1374 // "cl.do_oop" on each. 1375 virtual void oop_iterate(ExtendedOopClosure* cl); 1376 1377 // Iterate over all objects, calling "cl.do_object" on each. 1378 virtual void object_iterate(ObjectClosure* cl); 1379 1380 virtual void safe_object_iterate(ObjectClosure* cl) { 1381 object_iterate(cl); 1382 } 1383 1384 // Iterate over all spaces in use in the heap, in ascending address order. 1385 virtual void space_iterate(SpaceClosure* cl); 1386 1387 // Iterate over heap regions, in address order, terminating the 1388 // iteration early if the "doHeapRegion" method returns "true". 1389 void heap_region_iterate(HeapRegionClosure* blk) const; 1390 1391 // Return the region with the given index. It assumes the index is valid. 1392 inline HeapRegion* region_at(uint index) const; 1393 1394 // Calculate the region index of the given address. Given address must be 1395 // within the heap. 1396 inline uint addr_to_region(HeapWord* addr) const; 1397 1398 inline HeapWord* bottom_addr_for_region(uint index) const; 1399 1400 // Divide the heap region sequence into "chunks" of some size (the number 1401 // of regions divided by the number of parallel threads times some 1402 // overpartition factor, currently 4). Assumes that this will be called 1403 // in parallel by ParallelGCThreads worker threads with distinct worker 1404 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel 1405 // calls will use the same "claim_value", and that that claim value is 1406 // different from the claim_value of any heap region before the start of 1407 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by 1408 // attempting to claim the first region in each chunk, and, if 1409 // successful, applying the closure to each region in the chunk (and 1410 // setting the claim value of the second and subsequent regions of the 1411 // chunk.) For now requires that "doHeapRegion" always returns "false", 1412 // i.e., that a closure never attempt to abort a traversal. 1413 void heap_region_par_iterate_chunked(HeapRegionClosure* cl, 1414 uint worker_id, 1415 uint num_workers, 1416 jint claim_value) const; 1417 1418 // It resets all the region claim values to the default. 1419 void reset_heap_region_claim_values(); 1420 1421 // Resets the claim values of regions in the current 1422 // collection set to the default. 1423 void reset_cset_heap_region_claim_values(); 1424 1425 #ifdef ASSERT 1426 bool check_heap_region_claim_values(jint claim_value); 1427 1428 // Same as the routine above but only checks regions in the 1429 // current collection set. 1430 bool check_cset_heap_region_claim_values(jint claim_value); 1431 #endif // ASSERT 1432 1433 // Clear the cached cset start regions and (more importantly) 1434 // the time stamps. Called when we reset the GC time stamp. 1435 void clear_cset_start_regions(); 1436 1437 // Given the id of a worker, obtain or calculate a suitable 1438 // starting region for iterating over the current collection set. 1439 HeapRegion* start_cset_region_for_worker(uint worker_i); 1440 1441 // Iterate over the regions (if any) in the current collection set. 1442 void collection_set_iterate(HeapRegionClosure* blk); 1443 1444 // As above but starting from region r 1445 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1446 1447 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1448 1449 // A CollectedHeap will contain some number of spaces. This finds the 1450 // space containing a given address, or else returns NULL. 1451 virtual Space* space_containing(const void* addr) const; 1452 1453 // Returns the HeapRegion that contains addr. addr must not be NULL. 1454 template <class T> 1455 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1456 1457 // Returns the HeapRegion that contains addr. addr must not be NULL. 1458 // If addr is within a humongous continues region, it returns its humongous start region. 1459 template <class T> 1460 inline HeapRegion* heap_region_containing(const T addr) const; 1461 1462 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1463 // each address in the (reserved) heap is a member of exactly 1464 // one block. The defining characteristic of a block is that it is 1465 // possible to find its size, and thus to progress forward to the next 1466 // block. (Blocks may be of different sizes.) Thus, blocks may 1467 // represent Java objects, or they might be free blocks in a 1468 // free-list-based heap (or subheap), as long as the two kinds are 1469 // distinguishable and the size of each is determinable. 1470 1471 // Returns the address of the start of the "block" that contains the 1472 // address "addr". We say "blocks" instead of "object" since some heaps 1473 // may not pack objects densely; a chunk may either be an object or a 1474 // non-object. 1475 virtual HeapWord* block_start(const void* addr) const; 1476 1477 // Requires "addr" to be the start of a chunk, and returns its size. 1478 // "addr + size" is required to be the start of a new chunk, or the end 1479 // of the active area of the heap. 1480 virtual size_t block_size(const HeapWord* addr) const; 1481 1482 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1483 // the block is an object. 1484 virtual bool block_is_obj(const HeapWord* addr) const; 1485 1486 // Does this heap support heap inspection? (+PrintClassHistogram) 1487 virtual bool supports_heap_inspection() const { return true; } 1488 1489 // Section on thread-local allocation buffers (TLABs) 1490 // See CollectedHeap for semantics. 1491 1492 bool supports_tlab_allocation() const; 1493 size_t tlab_capacity(Thread* ignored) const; 1494 size_t tlab_used(Thread* ignored) const; 1495 size_t max_tlab_size() const; 1496 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1497 1498 // Can a compiler initialize a new object without store barriers? 1499 // This permission only extends from the creation of a new object 1500 // via a TLAB up to the first subsequent safepoint. If such permission 1501 // is granted for this heap type, the compiler promises to call 1502 // defer_store_barrier() below on any slow path allocation of 1503 // a new object for which such initializing store barriers will 1504 // have been elided. G1, like CMS, allows this, but should be 1505 // ready to provide a compensating write barrier as necessary 1506 // if that storage came out of a non-young region. The efficiency 1507 // of this implementation depends crucially on being able to 1508 // answer very efficiently in constant time whether a piece of 1509 // storage in the heap comes from a young region or not. 1510 // See ReduceInitialCardMarks. 1511 virtual bool can_elide_tlab_store_barriers() const { 1512 return true; 1513 } 1514 1515 virtual bool card_mark_must_follow_store() const { 1516 return true; 1517 } 1518 1519 inline bool is_in_young(const oop obj); 1520 1521 #ifdef ASSERT 1522 virtual bool is_in_partial_collection(const void* p); 1523 #endif 1524 1525 virtual bool is_scavengable(const void* addr); 1526 1527 // We don't need barriers for initializing stores to objects 1528 // in the young gen: for the SATB pre-barrier, there is no 1529 // pre-value that needs to be remembered; for the remembered-set 1530 // update logging post-barrier, we don't maintain remembered set 1531 // information for young gen objects. 1532 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1533 1534 // Returns "true" iff the given word_size is "very large". 1535 static bool isHumongous(size_t word_size) { 1536 // Note this has to be strictly greater-than as the TLABs 1537 // are capped at the humongous threshold and we want to 1538 // ensure that we don't try to allocate a TLAB as 1539 // humongous and that we don't allocate a humongous 1540 // object in a TLAB. 1541 return word_size > _humongous_object_threshold_in_words; 1542 } 1543 1544 // Update mod union table with the set of dirty cards. 1545 void updateModUnion(); 1546 1547 // Set the mod union bits corresponding to the given memRegion. Note 1548 // that this is always a safe operation, since it doesn't clear any 1549 // bits. 1550 void markModUnionRange(MemRegion mr); 1551 1552 // Records the fact that a marking phase is no longer in progress. 1553 void set_marking_complete() { 1554 _mark_in_progress = false; 1555 } 1556 void set_marking_started() { 1557 _mark_in_progress = true; 1558 } 1559 bool mark_in_progress() { 1560 return _mark_in_progress; 1561 } 1562 1563 // Print the maximum heap capacity. 1564 virtual size_t max_capacity() const; 1565 1566 virtual jlong millis_since_last_gc(); 1567 1568 1569 // Convenience function to be used in situations where the heap type can be 1570 // asserted to be this type. 1571 static G1CollectedHeap* heap(); 1572 1573 void set_region_short_lived_locked(HeapRegion* hr); 1574 // add appropriate methods for any other surv rate groups 1575 1576 YoungList* young_list() const { return _young_list; } 1577 1578 // debugging 1579 bool check_young_list_well_formed() { 1580 return _young_list->check_list_well_formed(); 1581 } 1582 1583 bool check_young_list_empty(bool check_heap, 1584 bool check_sample = true); 1585 1586 // *** Stuff related to concurrent marking. It's not clear to me that so 1587 // many of these need to be public. 1588 1589 // The functions below are helper functions that a subclass of 1590 // "CollectedHeap" can use in the implementation of its virtual 1591 // functions. 1592 // This performs a concurrent marking of the live objects in a 1593 // bitmap off to the side. 1594 void doConcurrentMark(); 1595 1596 bool isMarkedPrev(oop obj) const; 1597 bool isMarkedNext(oop obj) const; 1598 1599 // Determine if an object is dead, given the object and also 1600 // the region to which the object belongs. An object is dead 1601 // iff a) it was not allocated since the last mark and b) it 1602 // is not marked. 1603 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1604 return 1605 !hr->obj_allocated_since_prev_marking(obj) && 1606 !isMarkedPrev(obj); 1607 } 1608 1609 // This function returns true when an object has been 1610 // around since the previous marking and hasn't yet 1611 // been marked during this marking. 1612 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1613 return 1614 !hr->obj_allocated_since_next_marking(obj) && 1615 !isMarkedNext(obj); 1616 } 1617 1618 // Determine if an object is dead, given only the object itself. 1619 // This will find the region to which the object belongs and 1620 // then call the region version of the same function. 1621 1622 // Added if it is NULL it isn't dead. 1623 1624 inline bool is_obj_dead(const oop obj) const; 1625 1626 inline bool is_obj_ill(const oop obj) const; 1627 1628 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1629 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1630 bool is_marked(oop obj, VerifyOption vo); 1631 const char* top_at_mark_start_str(VerifyOption vo); 1632 1633 ConcurrentMark* concurrent_mark() const { return _cm; } 1634 1635 // Refinement 1636 1637 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1638 1639 // The dirty cards region list is used to record a subset of regions 1640 // whose cards need clearing. The list if populated during the 1641 // remembered set scanning and drained during the card table 1642 // cleanup. Although the methods are reentrant, population/draining 1643 // phases must not overlap. For synchronization purposes the last 1644 // element on the list points to itself. 1645 HeapRegion* _dirty_cards_region_list; 1646 void push_dirty_cards_region(HeapRegion* hr); 1647 HeapRegion* pop_dirty_cards_region(); 1648 1649 // Optimized nmethod scanning support routines 1650 1651 // Register the given nmethod with the G1 heap. 1652 virtual void register_nmethod(nmethod* nm); 1653 1654 // Unregister the given nmethod from the G1 heap. 1655 virtual void unregister_nmethod(nmethod* nm); 1656 1657 // Migrate the nmethods in the code root lists of the regions 1658 // in the collection set to regions in to-space. In the event 1659 // of an evacuation failure, nmethods that reference objects 1660 // that were not successfully evacuated are not migrated. 1661 void migrate_strong_code_roots(); 1662 1663 // Free up superfluous code root memory. 1664 void purge_code_root_memory(); 1665 1666 // Rebuild the strong code root lists for each region 1667 // after a full GC. 1668 void rebuild_strong_code_roots(); 1669 1670 // Delete entries for dead interned string and clean up unreferenced symbols 1671 // in symbol table, possibly in parallel. 1672 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1673 1674 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1675 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1676 1677 // Redirty logged cards in the refinement queue. 1678 void redirty_logged_cards(); 1679 // Verification 1680 1681 // The following is just to alert the verification code 1682 // that a full collection has occurred and that the 1683 // remembered sets are no longer up to date. 1684 bool _full_collection; 1685 void set_full_collection() { _full_collection = true;} 1686 void clear_full_collection() {_full_collection = false;} 1687 bool full_collection() {return _full_collection;} 1688 1689 // Perform any cleanup actions necessary before allowing a verification. 1690 virtual void prepare_for_verify(); 1691 1692 // Perform verification. 1693 1694 // vo == UsePrevMarking -> use "prev" marking information, 1695 // vo == UseNextMarking -> use "next" marking information 1696 // vo == UseMarkWord -> use the mark word in the object header 1697 // 1698 // NOTE: Only the "prev" marking information is guaranteed to be 1699 // consistent most of the time, so most calls to this should use 1700 // vo == UsePrevMarking. 1701 // Currently, there is only one case where this is called with 1702 // vo == UseNextMarking, which is to verify the "next" marking 1703 // information at the end of remark. 1704 // Currently there is only one place where this is called with 1705 // vo == UseMarkWord, which is to verify the marking during a 1706 // full GC. 1707 void verify(bool silent, VerifyOption vo); 1708 1709 // Override; it uses the "prev" marking information 1710 virtual void verify(bool silent); 1711 1712 // The methods below are here for convenience and dispatch the 1713 // appropriate method depending on value of the given VerifyOption 1714 // parameter. The values for that parameter, and their meanings, 1715 // are the same as those above. 1716 1717 bool is_obj_dead_cond(const oop obj, 1718 const HeapRegion* hr, 1719 const VerifyOption vo) const; 1720 1721 bool is_obj_dead_cond(const oop obj, 1722 const VerifyOption vo) const; 1723 1724 // Printing 1725 1726 virtual void print_on(outputStream* st) const; 1727 virtual void print_extended_on(outputStream* st) const; 1728 virtual void print_on_error(outputStream* st) const; 1729 1730 virtual void print_gc_threads_on(outputStream* st) const; 1731 virtual void gc_threads_do(ThreadClosure* tc) const; 1732 1733 // Override 1734 void print_tracing_info() const; 1735 1736 // The following two methods are helpful for debugging RSet issues. 1737 void print_cset_rsets() PRODUCT_RETURN; 1738 void print_all_rsets() PRODUCT_RETURN; 1739 1740 public: 1741 size_t pending_card_num(); 1742 size_t cards_scanned(); 1743 1744 protected: 1745 size_t _max_heap_capacity; 1746 }; 1747 1748 class G1ParGCAllocBuffer: public ParGCAllocBuffer { 1749 private: 1750 bool _retired; 1751 1752 public: 1753 G1ParGCAllocBuffer(size_t gclab_word_size); 1754 virtual ~G1ParGCAllocBuffer() { 1755 guarantee(_retired, "Allocation buffer has not been retired"); 1756 } 1757 1758 virtual void set_buf(HeapWord* buf) { 1759 ParGCAllocBuffer::set_buf(buf); 1760 _retired = false; 1761 } 1762 1763 virtual void retire(bool end_of_gc, bool retain) { 1764 if (_retired) { 1765 return; 1766 } 1767 ParGCAllocBuffer::retire(end_of_gc, retain); 1768 _retired = true; 1769 } 1770 }; 1771 1772 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP