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 G1CollectedHeap : public SharedHeap { 203 friend class VM_CollectForMetadataAllocation; 204 friend class VM_G1CollectForAllocation; 205 friend class VM_G1CollectFull; 206 friend class VM_G1IncCollectionPause; 207 friend class VMStructs; 208 friend class MutatorAllocRegion; 209 friend class SurvivorGCAllocRegion; 210 friend class OldGCAllocRegion; 211 212 // Closures used in implementation. 213 template <G1Barrier barrier, G1Mark do_mark_object> 214 friend class G1ParCopyClosure; 215 friend class G1IsAliveClosure; 216 friend class G1EvacuateFollowersClosure; 217 friend class G1ParScanThreadState; 218 friend class G1ParScanClosureSuper; 219 friend class G1ParEvacuateFollowersClosure; 220 friend class G1ParTask; 221 friend class G1FreeGarbageRegionClosure; 222 friend class RefineCardTableEntryClosure; 223 friend class G1PrepareCompactClosure; 224 friend class RegionSorter; 225 friend class RegionResetter; 226 friend class CountRCClosure; 227 friend class EvacPopObjClosure; 228 friend class G1ParCleanupCTTask; 229 230 friend class G1FreeHumongousRegionClosure; 231 // Other related classes. 232 friend class G1MarkSweep; 233 234 private: 235 // The one and only G1CollectedHeap, so static functions can find it. 236 static G1CollectedHeap* _g1h; 237 238 static size_t _humongous_object_threshold_in_words; 239 240 // Storage for the G1 heap. 241 VirtualSpace _g1_storage; 242 MemRegion _g1_reserved; 243 244 // The part of _g1_storage that is currently committed. 245 MemRegion _g1_committed; 246 247 // The master free list. It will satisfy all new region allocations. 248 FreeRegionList _free_list; 249 250 // The secondary free list which contains regions that have been 251 // freed up during the cleanup process. This will be appended to the 252 // master free list when appropriate. 253 FreeRegionList _secondary_free_list; 254 255 // It keeps track of the old regions. 256 HeapRegionSet _old_set; 257 258 // It keeps track of the humongous regions. 259 HeapRegionSet _humongous_set; 260 261 void clear_humongous_is_live_table(); 262 void eagerly_reclaim_humongous_regions(); 263 264 // The number of regions we could create by expansion. 265 uint _expansion_regions; 266 267 // The block offset table for the G1 heap. 268 G1BlockOffsetSharedArray* _bot_shared; 269 270 // Tears down the region sets / lists so that they are empty and the 271 // regions on the heap do not belong to a region set / list. The 272 // only exception is the humongous set which we leave unaltered. If 273 // free_list_only is true, it will only tear down the master free 274 // list. It is called before a Full GC (free_list_only == false) or 275 // before heap shrinking (free_list_only == true). 276 void tear_down_region_sets(bool free_list_only); 277 278 // Rebuilds the region sets / lists so that they are repopulated to 279 // reflect the contents of the heap. The only exception is the 280 // humongous set which was not torn down in the first place. If 281 // free_list_only is true, it will only rebuild the master free 282 // list. It is called after a Full GC (free_list_only == false) or 283 // after heap shrinking (free_list_only == true). 284 void rebuild_region_sets(bool free_list_only); 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 // Attempt to satisfy a humongous allocation request of the given 517 // size by finding a contiguous set of free regions of num_regions 518 // length and remove them from the master free list. Return the 519 // index of the first region or G1_NULL_HRS_INDEX if the search 520 // was unsuccessful. 521 uint humongous_obj_allocate_find_first(uint num_regions, 522 size_t word_size); 523 524 // Initialize a contiguous set of free regions of length num_regions 525 // and starting at index first so that they appear as a single 526 // humongous region. 527 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 528 uint num_regions, 529 size_t word_size); 530 531 // Attempt to allocate a humongous object of the given size. Return 532 // NULL if unsuccessful. 533 HeapWord* humongous_obj_allocate(size_t word_size); 534 535 // The following two methods, allocate_new_tlab() and 536 // mem_allocate(), are the two main entry points from the runtime 537 // into the G1's allocation routines. They have the following 538 // assumptions: 539 // 540 // * They should both be called outside safepoints. 541 // 542 // * They should both be called without holding the Heap_lock. 543 // 544 // * All allocation requests for new TLABs should go to 545 // allocate_new_tlab(). 546 // 547 // * All non-TLAB allocation requests should go to mem_allocate(). 548 // 549 // * If either call cannot satisfy the allocation request using the 550 // current allocating region, they will try to get a new one. If 551 // this fails, they will attempt to do an evacuation pause and 552 // retry the allocation. 553 // 554 // * If all allocation attempts fail, even after trying to schedule 555 // an evacuation pause, allocate_new_tlab() will return NULL, 556 // whereas mem_allocate() will attempt a heap expansion and/or 557 // schedule a Full GC. 558 // 559 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 560 // should never be called with word_size being humongous. All 561 // humongous allocation requests should go to mem_allocate() which 562 // will satisfy them with a special path. 563 564 virtual HeapWord* allocate_new_tlab(size_t word_size); 565 566 virtual HeapWord* mem_allocate(size_t word_size, 567 bool* gc_overhead_limit_was_exceeded); 568 569 // The following three methods take a gc_count_before_ret 570 // parameter which is used to return the GC count if the method 571 // returns NULL. Given that we are required to read the GC count 572 // while holding the Heap_lock, and these paths will take the 573 // Heap_lock at some point, it's easier to get them to read the GC 574 // count while holding the Heap_lock before they return NULL instead 575 // of the caller (namely: mem_allocate()) having to also take the 576 // Heap_lock just to read the GC count. 577 578 // First-level mutator allocation attempt: try to allocate out of 579 // the mutator alloc region without taking the Heap_lock. This 580 // should only be used for non-humongous allocations. 581 inline HeapWord* attempt_allocation(size_t word_size, 582 unsigned int* gc_count_before_ret, 583 int* gclocker_retry_count_ret); 584 585 // Second-level mutator allocation attempt: take the Heap_lock and 586 // retry the allocation attempt, potentially scheduling a GC 587 // pause. This should only be used for non-humongous allocations. 588 HeapWord* attempt_allocation_slow(size_t word_size, 589 unsigned int* gc_count_before_ret, 590 int* gclocker_retry_count_ret); 591 592 // Takes the Heap_lock and attempts a humongous allocation. It can 593 // potentially schedule a GC pause. 594 HeapWord* attempt_allocation_humongous(size_t word_size, 595 unsigned int* gc_count_before_ret, 596 int* gclocker_retry_count_ret); 597 598 // Allocation attempt that should be called during safepoints (e.g., 599 // at the end of a successful GC). expect_null_mutator_alloc_region 600 // specifies whether the mutator alloc region is expected to be NULL 601 // or not. 602 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 603 bool expect_null_mutator_alloc_region); 604 605 // It dirties the cards that cover the block so that so that the post 606 // write barrier never queues anything when updating objects on this 607 // block. It is assumed (and in fact we assert) that the block 608 // belongs to a young region. 609 inline void dirty_young_block(HeapWord* start, size_t word_size); 610 611 // Allocate blocks during garbage collection. Will ensure an 612 // allocation region, either by picking one or expanding the 613 // heap, and then allocate a block of the given size. The block 614 // may not be a humongous - it must fit into a single heap region. 615 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size); 616 617 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, 618 HeapRegion* alloc_region, 619 bool par, 620 size_t word_size); 621 622 // Ensure that no further allocations can happen in "r", bearing in mind 623 // that parallel threads might be attempting allocations. 624 void par_allocate_remaining_space(HeapRegion* r); 625 626 // Allocation attempt during GC for a survivor object / PLAB. 627 inline HeapWord* survivor_attempt_allocation(size_t word_size); 628 629 // Allocation attempt during GC for an old object / PLAB. 630 inline HeapWord* old_attempt_allocation(size_t word_size); 631 632 // These methods are the "callbacks" from the G1AllocRegion class. 633 634 // For mutator alloc regions. 635 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 636 void retire_mutator_alloc_region(HeapRegion* alloc_region, 637 size_t allocated_bytes); 638 639 // For GC alloc regions. 640 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 641 GCAllocPurpose ap); 642 void retire_gc_alloc_region(HeapRegion* alloc_region, 643 size_t allocated_bytes, GCAllocPurpose ap); 644 645 // - if explicit_gc is true, the GC is for a System.gc() or a heap 646 // inspection request and should collect the entire heap 647 // - if clear_all_soft_refs is true, all soft references should be 648 // cleared during the GC 649 // - if explicit_gc is false, word_size describes the allocation that 650 // the GC should attempt (at least) to satisfy 651 // - it returns false if it is unable to do the collection due to the 652 // GC locker being active, true otherwise 653 bool do_collection(bool explicit_gc, 654 bool clear_all_soft_refs, 655 size_t word_size); 656 657 // Callback from VM_G1CollectFull operation. 658 // Perform a full collection. 659 virtual void do_full_collection(bool clear_all_soft_refs); 660 661 // Resize the heap if necessary after a full collection. If this is 662 // after a collect-for allocation, "word_size" is the allocation size, 663 // and will be considered part of the used portion of the heap. 664 void resize_if_necessary_after_full_collection(size_t word_size); 665 666 // Callback from VM_G1CollectForAllocation operation. 667 // This function does everything necessary/possible to satisfy a 668 // failed allocation request (including collection, expansion, etc.) 669 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded); 670 671 // Attempting to expand the heap sufficiently 672 // to support an allocation of the given "word_size". If 673 // successful, perform the allocation and return the address of the 674 // allocated block, or else "NULL". 675 HeapWord* expand_and_allocate(size_t word_size); 676 677 // Process any reference objects discovered during 678 // an incremental evacuation pause. 679 void process_discovered_references(uint no_of_gc_workers); 680 681 // Enqueue any remaining discovered references 682 // after processing. 683 void enqueue_discovered_references(uint no_of_gc_workers); 684 685 public: 686 687 G1MonitoringSupport* g1mm() { 688 assert(_g1mm != NULL, "should have been initialized"); 689 return _g1mm; 690 } 691 692 // Expand the garbage-first heap by at least the given size (in bytes!). 693 // Returns true if the heap was expanded by the requested amount; 694 // false otherwise. 695 // (Rounds up to a HeapRegion boundary.) 696 bool expand(size_t expand_bytes); 697 698 // Do anything common to GC's. 699 virtual void gc_prologue(bool full); 700 virtual void gc_epilogue(bool full); 701 702 inline void set_humongous_is_live(oop obj); 703 704 bool humongous_is_live(uint region) { 705 return _humongous_is_live.is_live(region); 706 } 707 708 // Returns whether the given region (which must be a humongous (start) region) 709 // is to be considered conservatively live regardless of any other conditions. 710 bool humongous_region_is_always_live(uint index); 711 // Register the given region to be part of the collection set. 712 inline void register_humongous_region_with_in_cset_fast_test(uint index); 713 // Register regions with humongous objects (actually on the start region) in 714 // the in_cset_fast_test table. 715 void register_humongous_regions_with_in_cset_fast_test(); 716 // We register a region with the fast "in collection set" test. We 717 // simply set to true the array slot corresponding to this region. 718 void register_region_with_in_cset_fast_test(HeapRegion* r) { 719 _in_cset_fast_test.set_in_cset(r->hrs_index()); 720 } 721 722 // This is a fast test on whether a reference points into the 723 // collection set or not. Assume that the reference 724 // points into the heap. 725 inline bool in_cset_fast_test(oop obj); 726 727 void clear_cset_fast_test() { 728 _in_cset_fast_test.clear(); 729 } 730 731 // This is called at the start of either a concurrent cycle or a Full 732 // GC to update the number of old marking cycles started. 733 void increment_old_marking_cycles_started(); 734 735 // This is called at the end of either a concurrent cycle or a Full 736 // GC to update the number of old marking cycles completed. Those two 737 // can happen in a nested fashion, i.e., we start a concurrent 738 // cycle, a Full GC happens half-way through it which ends first, 739 // and then the cycle notices that a Full GC happened and ends 740 // too. The concurrent parameter is a boolean to help us do a bit 741 // tighter consistency checking in the method. If concurrent is 742 // false, the caller is the inner caller in the nesting (i.e., the 743 // Full GC). If concurrent is true, the caller is the outer caller 744 // in this nesting (i.e., the concurrent cycle). Further nesting is 745 // not currently supported. The end of this call also notifies 746 // the FullGCCount_lock in case a Java thread is waiting for a full 747 // GC to happen (e.g., it called System.gc() with 748 // +ExplicitGCInvokesConcurrent). 749 void increment_old_marking_cycles_completed(bool concurrent); 750 751 unsigned int old_marking_cycles_completed() { 752 return _old_marking_cycles_completed; 753 } 754 755 void register_concurrent_cycle_start(const Ticks& start_time); 756 void register_concurrent_cycle_end(); 757 void trace_heap_after_concurrent_cycle(); 758 759 G1YCType yc_type(); 760 761 G1HRPrinter* hr_printer() { return &_hr_printer; } 762 763 // Frees a non-humongous region by initializing its contents and 764 // adding it to the free list that's passed as a parameter (this is 765 // usually a local list which will be appended to the master free 766 // list later). The used bytes of freed regions are accumulated in 767 // pre_used. If par is true, the region's RSet will not be freed 768 // up. The assumption is that this will be done later. 769 // The locked parameter indicates if the caller has already taken 770 // care of proper synchronization. This may allow some optimizations. 771 void free_region(HeapRegion* hr, 772 FreeRegionList* free_list, 773 bool par, 774 bool locked = false); 775 776 // Frees a humongous region by collapsing it into individual regions 777 // and calling free_region() for each of them. The freed regions 778 // will be added to the free list that's passed as a parameter (this 779 // is usually a local list which will be appended to the master free 780 // list later). The used bytes of freed regions are accumulated in 781 // pre_used. If par is true, the region's RSet will not be freed 782 // up. The assumption is that this will be done later. 783 void free_humongous_region(HeapRegion* hr, 784 FreeRegionList* free_list, 785 bool par); 786 protected: 787 788 // Shrink the garbage-first heap by at most the given size (in bytes!). 789 // (Rounds down to a HeapRegion boundary.) 790 virtual void shrink(size_t expand_bytes); 791 void shrink_helper(size_t expand_bytes); 792 793 #if TASKQUEUE_STATS 794 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 795 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 796 void reset_taskqueue_stats(); 797 #endif // TASKQUEUE_STATS 798 799 // Schedule the VM operation that will do an evacuation pause to 800 // satisfy an allocation request of word_size. *succeeded will 801 // return whether the VM operation was successful (it did do an 802 // evacuation pause) or not (another thread beat us to it or the GC 803 // locker was active). Given that we should not be holding the 804 // Heap_lock when we enter this method, we will pass the 805 // gc_count_before (i.e., total_collections()) as a parameter since 806 // it has to be read while holding the Heap_lock. Currently, both 807 // methods that call do_collection_pause() release the Heap_lock 808 // before the call, so it's easy to read gc_count_before just before. 809 HeapWord* do_collection_pause(size_t word_size, 810 unsigned int gc_count_before, 811 bool* succeeded, 812 GCCause::Cause gc_cause); 813 814 // The guts of the incremental collection pause, executed by the vm 815 // thread. It returns false if it is unable to do the collection due 816 // to the GC locker being active, true otherwise 817 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 818 819 // Actually do the work of evacuating the collection set. 820 void evacuate_collection_set(EvacuationInfo& evacuation_info); 821 822 // The g1 remembered set of the heap. 823 G1RemSet* _g1_rem_set; 824 825 // A set of cards that cover the objects for which the Rsets should be updated 826 // concurrently after the collection. 827 DirtyCardQueueSet _dirty_card_queue_set; 828 829 // The closure used to refine a single card. 830 RefineCardTableEntryClosure* _refine_cte_cl; 831 832 // A function to check the consistency of dirty card logs. 833 void check_ct_logs_at_safepoint(); 834 835 // A DirtyCardQueueSet that is used to hold cards that contain 836 // references into the current collection set. This is used to 837 // update the remembered sets of the regions in the collection 838 // set in the event of an evacuation failure. 839 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 840 841 // After a collection pause, make the regions in the CS into free 842 // regions. 843 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 844 845 // Abandon the current collection set without recording policy 846 // statistics or updating free lists. 847 void abandon_collection_set(HeapRegion* cs_head); 848 849 // Applies "scan_non_heap_roots" to roots outside the heap, 850 // "scan_rs" to roots inside the heap (having done "set_region" to 851 // indicate the region in which the root resides), 852 // and does "scan_metadata" If "scan_rs" is 853 // NULL, then this step is skipped. The "worker_i" 854 // param is for use with parallel roots processing, and should be 855 // the "i" of the calling parallel worker thread's work(i) function. 856 // In the sequential case this param will be ignored. 857 void g1_process_roots(OopClosure* scan_non_heap_roots, 858 OopClosure* scan_non_heap_weak_roots, 859 OopsInHeapRegionClosure* scan_rs, 860 CLDClosure* scan_strong_clds, 861 CLDClosure* scan_weak_clds, 862 CodeBlobClosure* scan_strong_code, 863 uint worker_i); 864 865 // Notifies all the necessary spaces that the committed space has 866 // been updated (either expanded or shrunk). It should be called 867 // after _g1_storage is updated. 868 void update_committed_space(HeapWord* old_end, HeapWord* new_end); 869 870 // The concurrent marker (and the thread it runs in.) 871 ConcurrentMark* _cm; 872 ConcurrentMarkThread* _cmThread; 873 bool _mark_in_progress; 874 875 // The concurrent refiner. 876 ConcurrentG1Refine* _cg1r; 877 878 // The parallel task queues 879 RefToScanQueueSet *_task_queues; 880 881 // True iff a evacuation has failed in the current collection. 882 bool _evacuation_failed; 883 884 EvacuationFailedInfo* _evacuation_failed_info_array; 885 886 // Failed evacuations cause some logical from-space objects to have 887 // forwarding pointers to themselves. Reset them. 888 void remove_self_forwarding_pointers(); 889 890 // Together, these store an object with a preserved mark, and its mark value. 891 Stack<oop, mtGC> _objs_with_preserved_marks; 892 Stack<markOop, mtGC> _preserved_marks_of_objs; 893 894 // Preserve the mark of "obj", if necessary, in preparation for its mark 895 // word being overwritten with a self-forwarding-pointer. 896 void preserve_mark_if_necessary(oop obj, markOop m); 897 898 // The stack of evac-failure objects left to be scanned. 899 GrowableArray<oop>* _evac_failure_scan_stack; 900 // The closure to apply to evac-failure objects. 901 902 OopsInHeapRegionClosure* _evac_failure_closure; 903 // Set the field above. 904 void 905 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 906 _evac_failure_closure = evac_failure_closure; 907 } 908 909 // Push "obj" on the scan stack. 910 void push_on_evac_failure_scan_stack(oop obj); 911 // Process scan stack entries until the stack is empty. 912 void drain_evac_failure_scan_stack(); 913 // True iff an invocation of "drain_scan_stack" is in progress; to 914 // prevent unnecessary recursion. 915 bool _drain_in_progress; 916 917 // Do any necessary initialization for evacuation-failure handling. 918 // "cl" is the closure that will be used to process evac-failure 919 // objects. 920 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 921 // Do any necessary cleanup for evacuation-failure handling data 922 // structures. 923 void finalize_for_evac_failure(); 924 925 // An attempt to evacuate "obj" has failed; take necessary steps. 926 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 927 void handle_evacuation_failure_common(oop obj, markOop m); 928 929 #ifndef PRODUCT 930 // Support for forcing evacuation failures. Analogous to 931 // PromotionFailureALot for the other collectors. 932 933 // Records whether G1EvacuationFailureALot should be in effect 934 // for the current GC 935 bool _evacuation_failure_alot_for_current_gc; 936 937 // Used to record the GC number for interval checking when 938 // determining whether G1EvaucationFailureALot is in effect 939 // for the current GC. 940 size_t _evacuation_failure_alot_gc_number; 941 942 // Count of the number of evacuations between failures. 943 volatile size_t _evacuation_failure_alot_count; 944 945 // Set whether G1EvacuationFailureALot should be in effect 946 // for the current GC (based upon the type of GC and which 947 // command line flags are set); 948 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 949 bool during_initial_mark, 950 bool during_marking); 951 952 inline void set_evacuation_failure_alot_for_current_gc(); 953 954 // Return true if it's time to cause an evacuation failure. 955 inline bool evacuation_should_fail(); 956 957 // Reset the G1EvacuationFailureALot counters. Should be called at 958 // the end of an evacuation pause in which an evacuation failure occurred. 959 inline void reset_evacuation_should_fail(); 960 #endif // !PRODUCT 961 962 // ("Weak") Reference processing support. 963 // 964 // G1 has 2 instances of the reference processor class. One 965 // (_ref_processor_cm) handles reference object discovery 966 // and subsequent processing during concurrent marking cycles. 967 // 968 // The other (_ref_processor_stw) handles reference object 969 // discovery and processing during full GCs and incremental 970 // evacuation pauses. 971 // 972 // During an incremental pause, reference discovery will be 973 // temporarily disabled for _ref_processor_cm and will be 974 // enabled for _ref_processor_stw. At the end of the evacuation 975 // pause references discovered by _ref_processor_stw will be 976 // processed and discovery will be disabled. The previous 977 // setting for reference object discovery for _ref_processor_cm 978 // will be re-instated. 979 // 980 // At the start of marking: 981 // * Discovery by the CM ref processor is verified to be inactive 982 // and it's discovered lists are empty. 983 // * Discovery by the CM ref processor is then enabled. 984 // 985 // At the end of marking: 986 // * Any references on the CM ref processor's discovered 987 // lists are processed (possibly MT). 988 // 989 // At the start of full GC we: 990 // * Disable discovery by the CM ref processor and 991 // empty CM ref processor's discovered lists 992 // (without processing any entries). 993 // * Verify that the STW ref processor is inactive and it's 994 // discovered lists are empty. 995 // * Temporarily set STW ref processor discovery as single threaded. 996 // * Temporarily clear the STW ref processor's _is_alive_non_header 997 // field. 998 // * Finally enable discovery by the STW ref processor. 999 // 1000 // The STW ref processor is used to record any discovered 1001 // references during the full GC. 1002 // 1003 // At the end of a full GC we: 1004 // * Enqueue any reference objects discovered by the STW ref processor 1005 // that have non-live referents. This has the side-effect of 1006 // making the STW ref processor inactive by disabling discovery. 1007 // * Verify that the CM ref processor is still inactive 1008 // and no references have been placed on it's discovered 1009 // lists (also checked as a precondition during initial marking). 1010 1011 // The (stw) reference processor... 1012 ReferenceProcessor* _ref_processor_stw; 1013 1014 STWGCTimer* _gc_timer_stw; 1015 ConcurrentGCTimer* _gc_timer_cm; 1016 1017 G1OldTracer* _gc_tracer_cm; 1018 G1NewTracer* _gc_tracer_stw; 1019 1020 // During reference object discovery, the _is_alive_non_header 1021 // closure (if non-null) is applied to the referent object to 1022 // determine whether the referent is live. If so then the 1023 // reference object does not need to be 'discovered' and can 1024 // be treated as a regular oop. This has the benefit of reducing 1025 // the number of 'discovered' reference objects that need to 1026 // be processed. 1027 // 1028 // Instance of the is_alive closure for embedding into the 1029 // STW reference processor as the _is_alive_non_header field. 1030 // Supplying a value for the _is_alive_non_header field is 1031 // optional but doing so prevents unnecessary additions to 1032 // the discovered lists during reference discovery. 1033 G1STWIsAliveClosure _is_alive_closure_stw; 1034 1035 // The (concurrent marking) reference processor... 1036 ReferenceProcessor* _ref_processor_cm; 1037 1038 // Instance of the concurrent mark is_alive closure for embedding 1039 // into the Concurrent Marking reference processor as the 1040 // _is_alive_non_header field. Supplying a value for the 1041 // _is_alive_non_header field is optional but doing so prevents 1042 // unnecessary additions to the discovered lists during reference 1043 // discovery. 1044 G1CMIsAliveClosure _is_alive_closure_cm; 1045 1046 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 1047 HeapRegion** _worker_cset_start_region; 1048 1049 // Time stamp to validate the regions recorded in the cache 1050 // used by G1CollectedHeap::start_cset_region_for_worker(). 1051 // The heap region entry for a given worker is valid iff 1052 // the associated time stamp value matches the current value 1053 // of G1CollectedHeap::_gc_time_stamp. 1054 unsigned int* _worker_cset_start_region_time_stamp; 1055 1056 enum G1H_process_roots_tasks { 1057 G1H_PS_filter_satb_buffers, 1058 G1H_PS_refProcessor_oops_do, 1059 // Leave this one last. 1060 G1H_PS_NumElements 1061 }; 1062 1063 SubTasksDone* _process_strong_tasks; 1064 1065 volatile bool _free_regions_coming; 1066 1067 public: 1068 1069 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } 1070 1071 void set_refine_cte_cl_concurrency(bool concurrent); 1072 1073 RefToScanQueue *task_queue(int i) const; 1074 1075 // A set of cards where updates happened during the GC 1076 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1077 1078 // A DirtyCardQueueSet that is used to hold cards that contain 1079 // references into the current collection set. This is used to 1080 // update the remembered sets of the regions in the collection 1081 // set in the event of an evacuation failure. 1082 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1083 { return _into_cset_dirty_card_queue_set; } 1084 1085 // Create a G1CollectedHeap with the specified policy. 1086 // Must call the initialize method afterwards. 1087 // May not return if something goes wrong. 1088 G1CollectedHeap(G1CollectorPolicy* policy); 1089 1090 // Initialize the G1CollectedHeap to have the initial and 1091 // maximum sizes and remembered and barrier sets 1092 // specified by the policy object. 1093 jint initialize(); 1094 1095 virtual void stop(); 1096 1097 // Return the (conservative) maximum heap alignment for any G1 heap 1098 static size_t conservative_max_heap_alignment(); 1099 1100 // Initialize weak reference processing. 1101 virtual void ref_processing_init(); 1102 1103 void set_par_threads(uint t) { 1104 SharedHeap::set_par_threads(t); 1105 // Done in SharedHeap but oddly there are 1106 // two _process_strong_tasks's in a G1CollectedHeap 1107 // so do it here too. 1108 _process_strong_tasks->set_n_threads(t); 1109 } 1110 1111 // Set _n_par_threads according to a policy TBD. 1112 void set_par_threads(); 1113 1114 void set_n_termination(int t) { 1115 _process_strong_tasks->set_n_threads(t); 1116 } 1117 1118 virtual CollectedHeap::Name kind() const { 1119 return CollectedHeap::G1CollectedHeap; 1120 } 1121 1122 // The current policy object for the collector. 1123 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1124 1125 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1126 1127 // Adaptive size policy. No such thing for g1. 1128 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1129 1130 // The rem set and barrier set. 1131 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1132 1133 unsigned get_gc_time_stamp() { 1134 return _gc_time_stamp; 1135 } 1136 1137 inline void reset_gc_time_stamp(); 1138 1139 void check_gc_time_stamps() PRODUCT_RETURN; 1140 1141 inline void increment_gc_time_stamp(); 1142 1143 // Reset the given region's GC timestamp. If it's starts humongous, 1144 // also reset the GC timestamp of its corresponding 1145 // continues humongous regions too. 1146 void reset_gc_time_stamps(HeapRegion* hr); 1147 1148 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1149 DirtyCardQueue* into_cset_dcq, 1150 bool concurrent, uint worker_i); 1151 1152 // The shared block offset table array. 1153 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1154 1155 // Reference Processing accessors 1156 1157 // The STW reference processor.... 1158 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1159 1160 // The Concurrent Marking reference processor... 1161 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1162 1163 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1164 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1165 1166 virtual size_t capacity() const; 1167 virtual size_t used() const; 1168 // This should be called when we're not holding the heap lock. The 1169 // result might be a bit inaccurate. 1170 size_t used_unlocked() const; 1171 size_t recalculate_used() const; 1172 1173 // These virtual functions do the actual allocation. 1174 // Some heaps may offer a contiguous region for shared non-blocking 1175 // allocation, via inlined code (by exporting the address of the top and 1176 // end fields defining the extent of the contiguous allocation region.) 1177 // But G1CollectedHeap doesn't yet support this. 1178 1179 virtual bool is_maximal_no_gc() const { 1180 return _g1_storage.uncommitted_size() == 0; 1181 } 1182 1183 // The total number of regions in the heap. 1184 uint n_regions() { return _hrs.length(); } 1185 1186 // The max number of regions in the heap. 1187 uint max_regions() { return _hrs.max_length(); } 1188 1189 // The number of regions that are completely free. 1190 uint free_regions() { return _free_list.length(); } 1191 1192 // The number of regions that are not completely free. 1193 uint used_regions() { return n_regions() - free_regions(); } 1194 1195 // The number of regions available for "regular" expansion. 1196 uint expansion_regions() { return _expansion_regions; } 1197 1198 // Factory method for HeapRegion instances. It will return NULL if 1199 // the allocation fails. 1200 HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom); 1201 1202 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1203 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1204 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1205 void verify_dirty_young_regions() PRODUCT_RETURN; 1206 1207 #ifndef PRODUCT 1208 // Make sure that the given bitmap has no marked objects in the 1209 // range [from,limit). If it does, print an error message and return 1210 // false. Otherwise, just return true. bitmap_name should be "prev" 1211 // or "next". 1212 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1213 HeapWord* from, HeapWord* limit); 1214 1215 // Verify that the prev / next bitmap range [tams,end) for the given 1216 // region has no marks. Return true if all is well, false if errors 1217 // are detected. 1218 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1219 #endif // PRODUCT 1220 1221 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1222 // the given region do not have any spurious marks. If errors are 1223 // detected, print appropriate error messages and crash. 1224 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1225 1226 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1227 // have any spurious marks. If errors are detected, print 1228 // appropriate error messages and crash. 1229 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1230 1231 // verify_region_sets() performs verification over the region 1232 // lists. It will be compiled in the product code to be used when 1233 // necessary (i.e., during heap verification). 1234 void verify_region_sets(); 1235 1236 // verify_region_sets_optional() is planted in the code for 1237 // list verification in non-product builds (and it can be enabled in 1238 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1239 #if HEAP_REGION_SET_FORCE_VERIFY 1240 void verify_region_sets_optional() { 1241 verify_region_sets(); 1242 } 1243 #else // HEAP_REGION_SET_FORCE_VERIFY 1244 void verify_region_sets_optional() { } 1245 #endif // HEAP_REGION_SET_FORCE_VERIFY 1246 1247 #ifdef ASSERT 1248 bool is_on_master_free_list(HeapRegion* hr) { 1249 return hr->containing_set() == &_free_list; 1250 } 1251 #endif // ASSERT 1252 1253 // Wrapper for the region list operations that can be called from 1254 // methods outside this class. 1255 1256 void secondary_free_list_add(FreeRegionList* list) { 1257 _secondary_free_list.add_ordered(list); 1258 } 1259 1260 void append_secondary_free_list() { 1261 _free_list.add_ordered(&_secondary_free_list); 1262 } 1263 1264 void append_secondary_free_list_if_not_empty_with_lock() { 1265 // If the secondary free list looks empty there's no reason to 1266 // take the lock and then try to append it. 1267 if (!_secondary_free_list.is_empty()) { 1268 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1269 append_secondary_free_list(); 1270 } 1271 } 1272 1273 inline void old_set_remove(HeapRegion* hr); 1274 1275 size_t non_young_capacity_bytes() { 1276 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1277 } 1278 1279 void set_free_regions_coming(); 1280 void reset_free_regions_coming(); 1281 bool free_regions_coming() { return _free_regions_coming; } 1282 void wait_while_free_regions_coming(); 1283 1284 // Determine whether the given region is one that we are using as an 1285 // old GC alloc region. 1286 bool is_old_gc_alloc_region(HeapRegion* hr) { 1287 return hr == _retained_old_gc_alloc_region; 1288 } 1289 1290 // Perform a collection of the heap; intended for use in implementing 1291 // "System.gc". This probably implies as full a collection as the 1292 // "CollectedHeap" supports. 1293 virtual void collect(GCCause::Cause cause); 1294 1295 // The same as above but assume that the caller holds the Heap_lock. 1296 void collect_locked(GCCause::Cause cause); 1297 1298 // True iff an evacuation has failed in the most-recent collection. 1299 bool evacuation_failed() { return _evacuation_failed; } 1300 1301 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1302 void prepend_to_freelist(FreeRegionList* list); 1303 void decrement_summary_bytes(size_t bytes); 1304 1305 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1306 virtual bool is_in(const void* p) const; 1307 1308 // Return "TRUE" iff the given object address is within the collection 1309 // set. Slow implementation. 1310 inline bool obj_in_cs(oop obj); 1311 1312 inline bool is_in_cset(oop obj); 1313 1314 inline bool is_in_cset_or_humongous(const oop obj); 1315 1316 enum in_cset_state_t { 1317 InNeither, // neither in collection set nor humongous 1318 InCSet, // region is in collection set only 1319 IsHumongous // region is a humongous start region 1320 }; 1321 private: 1322 // Instances of this class are used for quick tests on whether a reference points 1323 // into the collection set or is a humongous object (points into a humongous 1324 // object). 1325 // Each of the array's elements denotes whether the corresponding region is in 1326 // the collection set or a humongous region. 1327 // We use this to quickly reclaim humongous objects: by making a humongous region 1328 // succeed this test, we sort-of add it to the collection set. During the reference 1329 // iteration closures, when we see a humongous region, we simply mark it as 1330 // referenced, i.e. live. 1331 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> { 1332 protected: 1333 char default_value() const { return G1CollectedHeap::InNeither; } 1334 public: 1335 void set_humongous(uintptr_t index) { 1336 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values"); 1337 set_by_index(index, G1CollectedHeap::IsHumongous); 1338 } 1339 1340 void clear_humongous(uintptr_t index) { 1341 set_by_index(index, G1CollectedHeap::InNeither); 1342 } 1343 1344 void set_in_cset(uintptr_t index) { 1345 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value"); 1346 set_by_index(index, G1CollectedHeap::InCSet); 1347 } 1348 1349 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; } 1350 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; } 1351 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); } 1352 void clear() { G1BiasedMappedArray<char>::clear(); } 1353 }; 1354 1355 // This array is used for a quick test on whether a reference points into 1356 // the collection set or not. Each of the array's elements denotes whether the 1357 // corresponding region is in the collection set or not. 1358 G1FastCSetBiasedMappedArray _in_cset_fast_test; 1359 1360 public: 1361 1362 inline in_cset_state_t in_cset_state(const oop obj); 1363 1364 // Return "TRUE" iff the given object address is in the reserved 1365 // region of g1. 1366 bool is_in_g1_reserved(const void* p) const { 1367 return _g1_reserved.contains(p); 1368 } 1369 1370 // Returns a MemRegion that corresponds to the space that has been 1371 // reserved for the heap 1372 MemRegion g1_reserved() { 1373 return _g1_reserved; 1374 } 1375 1376 // Returns a MemRegion that corresponds to the space that has been 1377 // committed in the heap 1378 MemRegion g1_committed() { 1379 return _g1_committed; 1380 } 1381 1382 virtual bool is_in_closed_subset(const void* p) const; 1383 1384 G1SATBCardTableModRefBS* g1_barrier_set() { 1385 return (G1SATBCardTableModRefBS*) barrier_set(); 1386 } 1387 1388 // This resets the card table to all zeros. It is used after 1389 // a collection pause which used the card table to claim cards. 1390 void cleanUpCardTable(); 1391 1392 // Iteration functions. 1393 1394 // Iterate over all the ref-containing fields of all objects, calling 1395 // "cl.do_oop" on each. 1396 virtual void oop_iterate(ExtendedOopClosure* cl); 1397 1398 // Same as above, restricted to a memory region. 1399 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl); 1400 1401 // Iterate over all objects, calling "cl.do_object" on each. 1402 virtual void object_iterate(ObjectClosure* cl); 1403 1404 virtual void safe_object_iterate(ObjectClosure* cl) { 1405 object_iterate(cl); 1406 } 1407 1408 // Iterate over all spaces in use in the heap, in ascending address order. 1409 virtual void space_iterate(SpaceClosure* cl); 1410 1411 // Iterate over heap regions, in address order, terminating the 1412 // iteration early if the "doHeapRegion" method returns "true". 1413 void heap_region_iterate(HeapRegionClosure* blk) const; 1414 1415 // Return the region with the given index. It assumes the index is valid. 1416 inline HeapRegion* region_at(uint index) const; 1417 1418 // Calculate the region index of the given address. Given address must be 1419 // within the heap. 1420 inline uint addr_to_region(HeapWord* addr) const; 1421 1422 // Divide the heap region sequence into "chunks" of some size (the number 1423 // of regions divided by the number of parallel threads times some 1424 // overpartition factor, currently 4). Assumes that this will be called 1425 // in parallel by ParallelGCThreads worker threads with distinct worker 1426 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel 1427 // calls will use the same "claim_value", and that that claim value is 1428 // different from the claim_value of any heap region before the start of 1429 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by 1430 // attempting to claim the first region in each chunk, and, if 1431 // successful, applying the closure to each region in the chunk (and 1432 // setting the claim value of the second and subsequent regions of the 1433 // chunk.) For now requires that "doHeapRegion" always returns "false", 1434 // i.e., that a closure never attempt to abort a traversal. 1435 void heap_region_par_iterate_chunked(HeapRegionClosure* blk, 1436 uint worker, 1437 uint no_of_par_workers, 1438 jint claim_value); 1439 1440 // It resets all the region claim values to the default. 1441 void reset_heap_region_claim_values(); 1442 1443 // Resets the claim values of regions in the current 1444 // collection set to the default. 1445 void reset_cset_heap_region_claim_values(); 1446 1447 #ifdef ASSERT 1448 bool check_heap_region_claim_values(jint claim_value); 1449 1450 // Same as the routine above but only checks regions in the 1451 // current collection set. 1452 bool check_cset_heap_region_claim_values(jint claim_value); 1453 #endif // ASSERT 1454 1455 // Clear the cached cset start regions and (more importantly) 1456 // the time stamps. Called when we reset the GC time stamp. 1457 void clear_cset_start_regions(); 1458 1459 // Given the id of a worker, obtain or calculate a suitable 1460 // starting region for iterating over the current collection set. 1461 HeapRegion* start_cset_region_for_worker(uint worker_i); 1462 1463 // This is a convenience method that is used by the 1464 // HeapRegionIterator classes to calculate the starting region for 1465 // each worker so that they do not all start from the same region. 1466 HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers); 1467 1468 // Iterate over the regions (if any) in the current collection set. 1469 void collection_set_iterate(HeapRegionClosure* blk); 1470 1471 // As above but starting from region r 1472 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1473 1474 // Returns the first (lowest address) compactible space in the heap. 1475 virtual CompactibleSpace* first_compactible_space(); 1476 1477 // A CollectedHeap will contain some number of spaces. This finds the 1478 // space containing a given address, or else returns NULL. 1479 virtual Space* space_containing(const void* addr) const; 1480 1481 // Returns the HeapRegion that contains addr. addr must not be NULL. 1482 template <class T> 1483 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1484 1485 // Returns the HeapRegion that contains addr. addr must not be NULL. 1486 // If addr is within a humongous continues region, it returns its humongous start region. 1487 template <class T> 1488 inline HeapRegion* heap_region_containing(const T addr) const; 1489 1490 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1491 // each address in the (reserved) heap is a member of exactly 1492 // one block. The defining characteristic of a block is that it is 1493 // possible to find its size, and thus to progress forward to the next 1494 // block. (Blocks may be of different sizes.) Thus, blocks may 1495 // represent Java objects, or they might be free blocks in a 1496 // free-list-based heap (or subheap), as long as the two kinds are 1497 // distinguishable and the size of each is determinable. 1498 1499 // Returns the address of the start of the "block" that contains the 1500 // address "addr". We say "blocks" instead of "object" since some heaps 1501 // may not pack objects densely; a chunk may either be an object or a 1502 // non-object. 1503 virtual HeapWord* block_start(const void* addr) const; 1504 1505 // Requires "addr" to be the start of a chunk, and returns its size. 1506 // "addr + size" is required to be the start of a new chunk, or the end 1507 // of the active area of the heap. 1508 virtual size_t block_size(const HeapWord* addr) const; 1509 1510 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1511 // the block is an object. 1512 virtual bool block_is_obj(const HeapWord* addr) const; 1513 1514 // Does this heap support heap inspection? (+PrintClassHistogram) 1515 virtual bool supports_heap_inspection() const { return true; } 1516 1517 // Section on thread-local allocation buffers (TLABs) 1518 // See CollectedHeap for semantics. 1519 1520 bool supports_tlab_allocation() const; 1521 size_t tlab_capacity(Thread* ignored) const; 1522 size_t tlab_used(Thread* ignored) const; 1523 size_t max_tlab_size() const; 1524 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1525 1526 // Can a compiler initialize a new object without store barriers? 1527 // This permission only extends from the creation of a new object 1528 // via a TLAB up to the first subsequent safepoint. If such permission 1529 // is granted for this heap type, the compiler promises to call 1530 // defer_store_barrier() below on any slow path allocation of 1531 // a new object for which such initializing store barriers will 1532 // have been elided. G1, like CMS, allows this, but should be 1533 // ready to provide a compensating write barrier as necessary 1534 // if that storage came out of a non-young region. The efficiency 1535 // of this implementation depends crucially on being able to 1536 // answer very efficiently in constant time whether a piece of 1537 // storage in the heap comes from a young region or not. 1538 // See ReduceInitialCardMarks. 1539 virtual bool can_elide_tlab_store_barriers() const { 1540 return true; 1541 } 1542 1543 virtual bool card_mark_must_follow_store() const { 1544 return true; 1545 } 1546 1547 inline bool is_in_young(const oop obj); 1548 1549 #ifdef ASSERT 1550 virtual bool is_in_partial_collection(const void* p); 1551 #endif 1552 1553 virtual bool is_scavengable(const void* addr); 1554 1555 // We don't need barriers for initializing stores to objects 1556 // in the young gen: for the SATB pre-barrier, there is no 1557 // pre-value that needs to be remembered; for the remembered-set 1558 // update logging post-barrier, we don't maintain remembered set 1559 // information for young gen objects. 1560 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1561 1562 // Returns "true" iff the given word_size is "very large". 1563 static bool isHumongous(size_t word_size) { 1564 // Note this has to be strictly greater-than as the TLABs 1565 // are capped at the humongous threshold and we want to 1566 // ensure that we don't try to allocate a TLAB as 1567 // humongous and that we don't allocate a humongous 1568 // object in a TLAB. 1569 return word_size > _humongous_object_threshold_in_words; 1570 } 1571 1572 // Update mod union table with the set of dirty cards. 1573 void updateModUnion(); 1574 1575 // Set the mod union bits corresponding to the given memRegion. Note 1576 // that this is always a safe operation, since it doesn't clear any 1577 // bits. 1578 void markModUnionRange(MemRegion mr); 1579 1580 // Records the fact that a marking phase is no longer in progress. 1581 void set_marking_complete() { 1582 _mark_in_progress = false; 1583 } 1584 void set_marking_started() { 1585 _mark_in_progress = true; 1586 } 1587 bool mark_in_progress() { 1588 return _mark_in_progress; 1589 } 1590 1591 // Print the maximum heap capacity. 1592 virtual size_t max_capacity() const; 1593 1594 virtual jlong millis_since_last_gc(); 1595 1596 1597 // Convenience function to be used in situations where the heap type can be 1598 // asserted to be this type. 1599 static G1CollectedHeap* heap(); 1600 1601 void set_region_short_lived_locked(HeapRegion* hr); 1602 // add appropriate methods for any other surv rate groups 1603 1604 YoungList* young_list() const { return _young_list; } 1605 1606 // debugging 1607 bool check_young_list_well_formed() { 1608 return _young_list->check_list_well_formed(); 1609 } 1610 1611 bool check_young_list_empty(bool check_heap, 1612 bool check_sample = true); 1613 1614 // *** Stuff related to concurrent marking. It's not clear to me that so 1615 // many of these need to be public. 1616 1617 // The functions below are helper functions that a subclass of 1618 // "CollectedHeap" can use in the implementation of its virtual 1619 // functions. 1620 // This performs a concurrent marking of the live objects in a 1621 // bitmap off to the side. 1622 void doConcurrentMark(); 1623 1624 bool isMarkedPrev(oop obj) const; 1625 bool isMarkedNext(oop obj) const; 1626 1627 // Determine if an object is dead, given the object and also 1628 // the region to which the object belongs. An object is dead 1629 // iff a) it was not allocated since the last mark and b) it 1630 // is not marked. 1631 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1632 return 1633 !hr->obj_allocated_since_prev_marking(obj) && 1634 !isMarkedPrev(obj); 1635 } 1636 1637 // This function returns true when an object has been 1638 // around since the previous marking and hasn't yet 1639 // been marked during this marking. 1640 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1641 return 1642 !hr->obj_allocated_since_next_marking(obj) && 1643 !isMarkedNext(obj); 1644 } 1645 1646 // Determine if an object is dead, given only the object itself. 1647 // This will find the region to which the object belongs and 1648 // then call the region version of the same function. 1649 1650 // Added if it is NULL it isn't dead. 1651 1652 inline bool is_obj_dead(const oop obj) const; 1653 1654 inline bool is_obj_ill(const oop obj) const; 1655 1656 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1657 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1658 bool is_marked(oop obj, VerifyOption vo); 1659 const char* top_at_mark_start_str(VerifyOption vo); 1660 1661 ConcurrentMark* concurrent_mark() const { return _cm; } 1662 1663 // Refinement 1664 1665 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1666 1667 // The dirty cards region list is used to record a subset of regions 1668 // whose cards need clearing. The list if populated during the 1669 // remembered set scanning and drained during the card table 1670 // cleanup. Although the methods are reentrant, population/draining 1671 // phases must not overlap. For synchronization purposes the last 1672 // element on the list points to itself. 1673 HeapRegion* _dirty_cards_region_list; 1674 void push_dirty_cards_region(HeapRegion* hr); 1675 HeapRegion* pop_dirty_cards_region(); 1676 1677 // Optimized nmethod scanning support routines 1678 1679 // Register the given nmethod with the G1 heap. 1680 virtual void register_nmethod(nmethod* nm); 1681 1682 // Unregister the given nmethod from the G1 heap. 1683 virtual void unregister_nmethod(nmethod* nm); 1684 1685 // Migrate the nmethods in the code root lists of the regions 1686 // in the collection set to regions in to-space. In the event 1687 // of an evacuation failure, nmethods that reference objects 1688 // that were not successfully evacuated are not migrated. 1689 void migrate_strong_code_roots(); 1690 1691 // Free up superfluous code root memory. 1692 void purge_code_root_memory(); 1693 1694 // Rebuild the strong code root lists for each region 1695 // after a full GC. 1696 void rebuild_strong_code_roots(); 1697 1698 // Delete entries for dead interned string and clean up unreferenced symbols 1699 // in symbol table, possibly in parallel. 1700 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1701 1702 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1703 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1704 1705 // Redirty logged cards in the refinement queue. 1706 void redirty_logged_cards(); 1707 // Verification 1708 1709 // The following is just to alert the verification code 1710 // that a full collection has occurred and that the 1711 // remembered sets are no longer up to date. 1712 bool _full_collection; 1713 void set_full_collection() { _full_collection = true;} 1714 void clear_full_collection() {_full_collection = false;} 1715 bool full_collection() {return _full_collection;} 1716 1717 // Perform any cleanup actions necessary before allowing a verification. 1718 virtual void prepare_for_verify(); 1719 1720 // Perform verification. 1721 1722 // vo == UsePrevMarking -> use "prev" marking information, 1723 // vo == UseNextMarking -> use "next" marking information 1724 // vo == UseMarkWord -> use the mark word in the object header 1725 // 1726 // NOTE: Only the "prev" marking information is guaranteed to be 1727 // consistent most of the time, so most calls to this should use 1728 // vo == UsePrevMarking. 1729 // Currently, there is only one case where this is called with 1730 // vo == UseNextMarking, which is to verify the "next" marking 1731 // information at the end of remark. 1732 // Currently there is only one place where this is called with 1733 // vo == UseMarkWord, which is to verify the marking during a 1734 // full GC. 1735 void verify(bool silent, VerifyOption vo); 1736 1737 // Override; it uses the "prev" marking information 1738 virtual void verify(bool silent); 1739 1740 // The methods below are here for convenience and dispatch the 1741 // appropriate method depending on value of the given VerifyOption 1742 // parameter. The values for that parameter, and their meanings, 1743 // are the same as those above. 1744 1745 bool is_obj_dead_cond(const oop obj, 1746 const HeapRegion* hr, 1747 const VerifyOption vo) const; 1748 1749 bool is_obj_dead_cond(const oop obj, 1750 const VerifyOption vo) const; 1751 1752 // Printing 1753 1754 virtual void print_on(outputStream* st) const; 1755 virtual void print_extended_on(outputStream* st) const; 1756 virtual void print_on_error(outputStream* st) const; 1757 1758 virtual void print_gc_threads_on(outputStream* st) const; 1759 virtual void gc_threads_do(ThreadClosure* tc) const; 1760 1761 // Override 1762 void print_tracing_info() const; 1763 1764 // The following two methods are helpful for debugging RSet issues. 1765 void print_cset_rsets() PRODUCT_RETURN; 1766 void print_all_rsets() PRODUCT_RETURN; 1767 1768 public: 1769 size_t pending_card_num(); 1770 size_t cards_scanned(); 1771 1772 protected: 1773 size_t _max_heap_capacity; 1774 }; 1775 1776 class G1ParGCAllocBuffer: public ParGCAllocBuffer { 1777 private: 1778 bool _retired; 1779 1780 public: 1781 G1ParGCAllocBuffer(size_t gclab_word_size); 1782 virtual ~G1ParGCAllocBuffer() { 1783 guarantee(_retired, "Allocation buffer has not been retired"); 1784 } 1785 1786 virtual void set_buf(HeapWord* buf) { 1787 ParGCAllocBuffer::set_buf(buf); 1788 _retired = false; 1789 } 1790 1791 virtual void retire(bool end_of_gc, bool retain) { 1792 if (_retired) { 1793 return; 1794 } 1795 ParGCAllocBuffer::retire(end_of_gc, retain); 1796 _retired = true; 1797 } 1798 }; 1799 1800 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP