1 /* 2 * Copyright (c) 2001, 2015, 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/g1AllocationContext.hpp" 29 #include "gc_implementation/g1/g1Allocator.hpp" 30 #include "gc_implementation/g1/concurrentMark.hpp" 31 #include "gc_implementation/g1/evacuationInfo.hpp" 32 #include "gc_implementation/g1/g1AllocRegion.hpp" 33 #include "gc_implementation/g1/g1BiasedArray.hpp" 34 #include "gc_implementation/g1/g1CollectorState.hpp" 35 #include "gc_implementation/g1/g1HRPrinter.hpp" 36 #include "gc_implementation/g1/g1InCSetState.hpp" 37 #include "gc_implementation/g1/g1MonitoringSupport.hpp" 38 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 39 #include "gc_implementation/g1/g1YCTypes.hpp" 40 #include "gc_implementation/g1/heapRegionManager.hpp" 41 #include "gc_implementation/g1/heapRegionSet.hpp" 42 #include "gc_implementation/shared/hSpaceCounters.hpp" 43 #include "gc_interface/collectedHeap.hpp" 44 #include "memory/barrierSet.hpp" 45 #include "memory/memRegion.hpp" 46 #include "utilities/stack.hpp" 47 48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 49 // It uses the "Garbage First" heap organization and algorithm, which 50 // may combine concurrent marking with parallel, incremental compaction of 51 // heap subsets that will yield large amounts of garbage. 52 53 // Forward declarations 54 class HeapRegion; 55 class HRRSCleanupTask; 56 class GenerationSpec; 57 class OopsInHeapRegionClosure; 58 class G1KlassScanClosure; 59 class G1ParScanThreadState; 60 class ObjectClosure; 61 class SpaceClosure; 62 class CompactibleSpaceClosure; 63 class Space; 64 class G1CollectorPolicy; 65 class GenRemSet; 66 class G1RemSet; 67 class HeapRegionRemSetIterator; 68 class ConcurrentMark; 69 class ConcurrentMarkThread; 70 class ConcurrentG1Refine; 71 class ConcurrentGCTimer; 72 class GenerationCounters; 73 class STWGCTimer; 74 class G1NewTracer; 75 class G1OldTracer; 76 class EvacuationFailedInfo; 77 class nmethod; 78 class Ticks; 79 class FlexibleWorkGang; 80 81 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 82 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 83 84 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 85 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 86 87 class YoungList : public CHeapObj<mtGC> { 88 private: 89 G1CollectedHeap* _g1h; 90 91 HeapRegion* _head; 92 93 HeapRegion* _survivor_head; 94 HeapRegion* _survivor_tail; 95 96 HeapRegion* _curr; 97 98 uint _length; 99 uint _survivor_length; 100 101 size_t _last_sampled_rs_lengths; 102 size_t _sampled_rs_lengths; 103 104 void empty_list(HeapRegion* list); 105 106 public: 107 YoungList(G1CollectedHeap* g1h); 108 109 void push_region(HeapRegion* hr); 110 void add_survivor_region(HeapRegion* hr); 111 112 void empty_list(); 113 bool is_empty() { return _length == 0; } 114 uint length() { return _length; } 115 uint eden_length() { return length() - survivor_length(); } 116 uint survivor_length() { return _survivor_length; } 117 118 // Currently we do not keep track of the used byte sum for the 119 // young list and the survivors and it'd be quite a lot of work to 120 // do so. When we'll eventually replace the young list with 121 // instances of HeapRegionLinkedList we'll get that for free. So, 122 // we'll report the more accurate information then. 123 size_t eden_used_bytes() { 124 assert(length() >= survivor_length(), "invariant"); 125 return (size_t) eden_length() * HeapRegion::GrainBytes; 126 } 127 size_t survivor_used_bytes() { 128 return (size_t) survivor_length() * HeapRegion::GrainBytes; 129 } 130 131 void rs_length_sampling_init(); 132 bool rs_length_sampling_more(); 133 void rs_length_sampling_next(); 134 135 void reset_sampled_info() { 136 _last_sampled_rs_lengths = 0; 137 } 138 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } 139 140 // for development purposes 141 void reset_auxilary_lists(); 142 void clear() { _head = NULL; _length = 0; } 143 144 void clear_survivors() { 145 _survivor_head = NULL; 146 _survivor_tail = NULL; 147 _survivor_length = 0; 148 } 149 150 HeapRegion* first_region() { return _head; } 151 HeapRegion* first_survivor_region() { return _survivor_head; } 152 HeapRegion* last_survivor_region() { return _survivor_tail; } 153 154 // debugging 155 bool check_list_well_formed(); 156 bool check_list_empty(bool check_sample = true); 157 void print(); 158 }; 159 160 // The G1 STW is alive closure. 161 // An instance is embedded into the G1CH and used as the 162 // (optional) _is_alive_non_header closure in the STW 163 // reference processor. It is also extensively used during 164 // reference processing during STW evacuation pauses. 165 class G1STWIsAliveClosure: public BoolObjectClosure { 166 G1CollectedHeap* _g1; 167 public: 168 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 169 bool do_object_b(oop p); 170 }; 171 172 class RefineCardTableEntryClosure; 173 174 class G1RegionMappingChangedListener : public G1MappingChangedListener { 175 private: 176 void reset_from_card_cache(uint start_idx, size_t num_regions); 177 public: 178 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 179 }; 180 181 class G1CollectedHeap : public CollectedHeap { 182 friend class VM_CollectForMetadataAllocation; 183 friend class VM_G1CollectForAllocation; 184 friend class VM_G1CollectFull; 185 friend class VM_G1IncCollectionPause; 186 friend class VMStructs; 187 friend class MutatorAllocRegion; 188 friend class SurvivorGCAllocRegion; 189 friend class OldGCAllocRegion; 190 friend class G1Allocator; 191 192 // Closures used in implementation. 193 friend class G1ParScanThreadState; 194 friend class G1ParTask; 195 friend class G1ParGCAllocator; 196 friend class G1PrepareCompactClosure; 197 198 // Other related classes. 199 friend class HeapRegionClaimer; 200 201 // Testing classes. 202 friend class G1CheckCSetFastTableClosure; 203 204 private: 205 FlexibleWorkGang* _workers; 206 207 static size_t _humongous_object_threshold_in_words; 208 209 // The secondary free list which contains regions that have been 210 // freed up during the cleanup process. This will be appended to 211 // the master free list when appropriate. 212 FreeRegionList _secondary_free_list; 213 214 // It keeps track of the old regions. 215 HeapRegionSet _old_set; 216 217 // It keeps track of the humongous regions. 218 HeapRegionSet _humongous_set; 219 220 void eagerly_reclaim_humongous_regions(); 221 222 // The number of regions we could create by expansion. 223 uint _expansion_regions; 224 225 // The block offset table for the G1 heap. 226 G1BlockOffsetSharedArray* _bot_shared; 227 228 // Tears down the region sets / lists so that they are empty and the 229 // regions on the heap do not belong to a region set / list. The 230 // only exception is the humongous set which we leave unaltered. If 231 // free_list_only is true, it will only tear down the master free 232 // list. It is called before a Full GC (free_list_only == false) or 233 // before heap shrinking (free_list_only == true). 234 void tear_down_region_sets(bool free_list_only); 235 236 // Rebuilds the region sets / lists so that they are repopulated to 237 // reflect the contents of the heap. The only exception is the 238 // humongous set which was not torn down in the first place. If 239 // free_list_only is true, it will only rebuild the master free 240 // list. It is called after a Full GC (free_list_only == false) or 241 // after heap shrinking (free_list_only == true). 242 void rebuild_region_sets(bool free_list_only); 243 244 // Callback for region mapping changed events. 245 G1RegionMappingChangedListener _listener; 246 247 // The sequence of all heap regions in the heap. 248 HeapRegionManager _hrm; 249 250 // Class that handles the different kinds of allocations. 251 G1Allocator* _allocator; 252 253 // Statistics for each allocation context 254 AllocationContextStats _allocation_context_stats; 255 256 // PLAB sizing policy for survivors. 257 PLABStats _survivor_plab_stats; 258 259 // PLAB sizing policy for tenured objects. 260 PLABStats _old_plab_stats; 261 262 // It specifies whether we should attempt to expand the heap after a 263 // region allocation failure. If heap expansion fails we set this to 264 // false so that we don't re-attempt the heap expansion (it's likely 265 // that subsequent expansion attempts will also fail if one fails). 266 // Currently, it is only consulted during GC and it's reset at the 267 // start of each GC. 268 bool _expand_heap_after_alloc_failure; 269 270 // It resets the mutator alloc region before new allocations can take place. 271 void init_mutator_alloc_region(); 272 273 // It releases the mutator alloc region. 274 void release_mutator_alloc_region(); 275 276 // It initializes the GC alloc regions at the start of a GC. 277 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 278 279 // It releases the GC alloc regions at the end of a GC. 280 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 281 282 // It does any cleanup that needs to be done on the GC alloc regions 283 // before a Full GC. 284 void abandon_gc_alloc_regions(); 285 286 // Helper for monitoring and management support. 287 G1MonitoringSupport* _g1mm; 288 289 // Records whether the region at the given index is (still) a 290 // candidate for eager reclaim. Only valid for humongous start 291 // regions; other regions have unspecified values. Humongous start 292 // regions are initialized at start of collection pause, with 293 // candidates removed from the set as they are found reachable from 294 // roots or the young generation. 295 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 296 protected: 297 bool default_value() const { return false; } 298 public: 299 void clear() { G1BiasedMappedArray<bool>::clear(); } 300 void set_candidate(uint region, bool value) { 301 set_by_index(region, value); 302 } 303 bool is_candidate(uint region) { 304 return get_by_index(region); 305 } 306 }; 307 308 HumongousReclaimCandidates _humongous_reclaim_candidates; 309 // Stores whether during humongous object registration we found candidate regions. 310 // If not, we can skip a few steps. 311 bool _has_humongous_reclaim_candidates; 312 313 volatile unsigned _gc_time_stamp; 314 315 size_t* _surviving_young_words; 316 317 G1HRPrinter _hr_printer; 318 319 void setup_surviving_young_words(); 320 void update_surviving_young_words(size_t* surv_young_words); 321 void cleanup_surviving_young_words(); 322 323 // It decides whether an explicit GC should start a concurrent cycle 324 // instead of doing a STW GC. Currently, a concurrent cycle is 325 // explicitly started if: 326 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 327 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 328 // (c) cause == _g1_humongous_allocation 329 bool should_do_concurrent_full_gc(GCCause::Cause cause); 330 331 // indicates whether we are in young or mixed GC mode 332 G1CollectorState _collector_state; 333 334 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 335 // concurrent cycles) we have started. 336 volatile uint _old_marking_cycles_started; 337 338 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 339 // concurrent cycles) we have completed. 340 volatile uint _old_marking_cycles_completed; 341 342 bool _heap_summary_sent; 343 344 // This is a non-product method that is helpful for testing. It is 345 // called at the end of a GC and artificially expands the heap by 346 // allocating a number of dead regions. This way we can induce very 347 // frequent marking cycles and stress the cleanup / concurrent 348 // cleanup code more (as all the regions that will be allocated by 349 // this method will be found dead by the marking cycle). 350 void allocate_dummy_regions() PRODUCT_RETURN; 351 352 // Clear RSets after a compaction. It also resets the GC time stamps. 353 void clear_rsets_post_compaction(); 354 355 // If the HR printer is active, dump the state of the regions in the 356 // heap after a compaction. 357 void print_hrm_post_compaction(); 358 359 // Create a memory mapper for auxiliary data structures of the given size and 360 // translation factor. 361 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 362 size_t size, 363 size_t translation_factor); 364 365 double verify(bool guard, const char* msg); 366 void verify_before_gc(); 367 void verify_after_gc(); 368 369 void log_gc_header(); 370 void log_gc_footer(double pause_time_sec); 371 372 // These are macros so that, if the assert fires, we get the correct 373 // line number, file, etc. 374 375 #define heap_locking_asserts_err_msg(_extra_message_) \ 376 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 377 (_extra_message_), \ 378 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 379 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 380 BOOL_TO_STR(Thread::current()->is_VM_thread())) 381 382 #define assert_heap_locked() \ 383 do { \ 384 assert(Heap_lock->owned_by_self(), \ 385 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 386 } while (0) 387 388 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 389 do { \ 390 assert(Heap_lock->owned_by_self() || \ 391 (SafepointSynchronize::is_at_safepoint() && \ 392 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 393 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 394 "should be at a safepoint")); \ 395 } while (0) 396 397 #define assert_heap_locked_and_not_at_safepoint() \ 398 do { \ 399 assert(Heap_lock->owned_by_self() && \ 400 !SafepointSynchronize::is_at_safepoint(), \ 401 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 402 "should not be at a safepoint")); \ 403 } while (0) 404 405 #define assert_heap_not_locked() \ 406 do { \ 407 assert(!Heap_lock->owned_by_self(), \ 408 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 409 } while (0) 410 411 #define assert_heap_not_locked_and_not_at_safepoint() \ 412 do { \ 413 assert(!Heap_lock->owned_by_self() && \ 414 !SafepointSynchronize::is_at_safepoint(), \ 415 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 416 "should not be at a safepoint")); \ 417 } while (0) 418 419 #define assert_at_safepoint(_should_be_vm_thread_) \ 420 do { \ 421 assert(SafepointSynchronize::is_at_safepoint() && \ 422 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 423 heap_locking_asserts_err_msg("should be at a safepoint")); \ 424 } while (0) 425 426 #define assert_not_at_safepoint() \ 427 do { \ 428 assert(!SafepointSynchronize::is_at_safepoint(), \ 429 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 430 } while (0) 431 432 protected: 433 434 // The young region list. 435 YoungList* _young_list; 436 437 // The current policy object for the collector. 438 G1CollectorPolicy* _g1_policy; 439 440 // This is the second level of trying to allocate a new region. If 441 // new_region() didn't find a region on the free_list, this call will 442 // check whether there's anything available on the 443 // secondary_free_list and/or wait for more regions to appear on 444 // that list, if _free_regions_coming is set. 445 HeapRegion* new_region_try_secondary_free_list(bool is_old); 446 447 // Try to allocate a single non-humongous HeapRegion sufficient for 448 // an allocation of the given word_size. If do_expand is true, 449 // attempt to expand the heap if necessary to satisfy the allocation 450 // request. If the region is to be used as an old region or for a 451 // humongous object, set is_old to true. If not, to false. 452 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 453 454 // Initialize a contiguous set of free regions of length num_regions 455 // and starting at index first so that they appear as a single 456 // humongous region. 457 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 458 uint num_regions, 459 size_t word_size, 460 AllocationContext_t context); 461 462 // Attempt to allocate a humongous object of the given size. Return 463 // NULL if unsuccessful. 464 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 465 466 // The following two methods, allocate_new_tlab() and 467 // mem_allocate(), are the two main entry points from the runtime 468 // into the G1's allocation routines. They have the following 469 // assumptions: 470 // 471 // * They should both be called outside safepoints. 472 // 473 // * They should both be called without holding the Heap_lock. 474 // 475 // * All allocation requests for new TLABs should go to 476 // allocate_new_tlab(). 477 // 478 // * All non-TLAB allocation requests should go to mem_allocate(). 479 // 480 // * If either call cannot satisfy the allocation request using the 481 // current allocating region, they will try to get a new one. If 482 // this fails, they will attempt to do an evacuation pause and 483 // retry the allocation. 484 // 485 // * If all allocation attempts fail, even after trying to schedule 486 // an evacuation pause, allocate_new_tlab() will return NULL, 487 // whereas mem_allocate() will attempt a heap expansion and/or 488 // schedule a Full GC. 489 // 490 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 491 // should never be called with word_size being humongous. All 492 // humongous allocation requests should go to mem_allocate() which 493 // will satisfy them with a special path. 494 495 virtual HeapWord* allocate_new_tlab(size_t word_size); 496 497 virtual HeapWord* mem_allocate(size_t word_size, 498 bool* gc_overhead_limit_was_exceeded); 499 500 // The following three methods take a gc_count_before_ret 501 // parameter which is used to return the GC count if the method 502 // returns NULL. Given that we are required to read the GC count 503 // while holding the Heap_lock, and these paths will take the 504 // Heap_lock at some point, it's easier to get them to read the GC 505 // count while holding the Heap_lock before they return NULL instead 506 // of the caller (namely: mem_allocate()) having to also take the 507 // Heap_lock just to read the GC count. 508 509 // First-level mutator allocation attempt: try to allocate out of 510 // the mutator alloc region without taking the Heap_lock. This 511 // should only be used for non-humongous allocations. 512 inline HeapWord* attempt_allocation(size_t word_size, 513 uint* gc_count_before_ret, 514 uint* gclocker_retry_count_ret); 515 516 // Second-level mutator allocation attempt: take the Heap_lock and 517 // retry the allocation attempt, potentially scheduling a GC 518 // pause. This should only be used for non-humongous allocations. 519 HeapWord* attempt_allocation_slow(size_t word_size, 520 AllocationContext_t context, 521 uint* gc_count_before_ret, 522 uint* gclocker_retry_count_ret); 523 524 // Takes the Heap_lock and attempts a humongous allocation. It can 525 // potentially schedule a GC pause. 526 HeapWord* attempt_allocation_humongous(size_t word_size, 527 uint* gc_count_before_ret, 528 uint* gclocker_retry_count_ret); 529 530 // Allocation attempt that should be called during safepoints (e.g., 531 // at the end of a successful GC). expect_null_mutator_alloc_region 532 // specifies whether the mutator alloc region is expected to be NULL 533 // or not. 534 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 535 AllocationContext_t context, 536 bool expect_null_mutator_alloc_region); 537 538 // It dirties the cards that cover the block so that so that the post 539 // write barrier never queues anything when updating objects on this 540 // block. It is assumed (and in fact we assert) that the block 541 // belongs to a young region. 542 inline void dirty_young_block(HeapWord* start, size_t word_size); 543 544 // Allocate blocks during garbage collection. Will ensure an 545 // allocation region, either by picking one or expanding the 546 // heap, and then allocate a block of the given size. The block 547 // may not be a humongous - it must fit into a single heap region. 548 inline HeapWord* par_allocate_during_gc(InCSetState dest, 549 size_t word_size, 550 AllocationContext_t context); 551 // Ensure that no further allocations can happen in "r", bearing in mind 552 // that parallel threads might be attempting allocations. 553 void par_allocate_remaining_space(HeapRegion* r); 554 555 // Allocation attempt during GC for a survivor object / PLAB. 556 inline HeapWord* survivor_attempt_allocation(size_t word_size, 557 AllocationContext_t context); 558 559 // Allocation attempt during GC for an old object / PLAB. 560 inline HeapWord* old_attempt_allocation(size_t word_size, 561 AllocationContext_t context); 562 563 // These methods are the "callbacks" from the G1AllocRegion class. 564 565 // For mutator alloc regions. 566 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 567 void retire_mutator_alloc_region(HeapRegion* alloc_region, 568 size_t allocated_bytes); 569 570 // For GC alloc regions. 571 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 572 InCSetState dest); 573 void retire_gc_alloc_region(HeapRegion* alloc_region, 574 size_t allocated_bytes, InCSetState dest); 575 576 // - if explicit_gc is true, the GC is for a System.gc() or a heap 577 // inspection request and should collect the entire heap 578 // - if clear_all_soft_refs is true, all soft references should be 579 // cleared during the GC 580 // - if explicit_gc is false, word_size describes the allocation that 581 // the GC should attempt (at least) to satisfy 582 // - it returns false if it is unable to do the collection due to the 583 // GC locker being active, true otherwise 584 bool do_collection(bool explicit_gc, 585 bool clear_all_soft_refs, 586 size_t word_size); 587 588 // Callback from VM_G1CollectFull operation. 589 // Perform a full collection. 590 virtual void do_full_collection(bool clear_all_soft_refs); 591 592 // Resize the heap if necessary after a full collection. If this is 593 // after a collect-for allocation, "word_size" is the allocation size, 594 // and will be considered part of the used portion of the heap. 595 void resize_if_necessary_after_full_collection(size_t word_size); 596 597 // Callback from VM_G1CollectForAllocation operation. 598 // This function does everything necessary/possible to satisfy a 599 // failed allocation request (including collection, expansion, etc.) 600 HeapWord* satisfy_failed_allocation(size_t word_size, 601 AllocationContext_t context, 602 bool* succeeded); 603 604 // Attempting to expand the heap sufficiently 605 // to support an allocation of the given "word_size". If 606 // successful, perform the allocation and return the address of the 607 // allocated block, or else "NULL". 608 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 609 610 // Process any reference objects discovered during 611 // an incremental evacuation pause. 612 void process_discovered_references(uint no_of_gc_workers); 613 614 // Enqueue any remaining discovered references 615 // after processing. 616 void enqueue_discovered_references(uint no_of_gc_workers); 617 618 public: 619 FlexibleWorkGang* workers() const { return _workers; } 620 621 G1Allocator* allocator() { 622 return _allocator; 623 } 624 625 G1MonitoringSupport* g1mm() { 626 assert(_g1mm != NULL, "should have been initialized"); 627 return _g1mm; 628 } 629 630 // Expand the garbage-first heap by at least the given size (in bytes!). 631 // Returns true if the heap was expanded by the requested amount; 632 // false otherwise. 633 // (Rounds up to a HeapRegion boundary.) 634 bool expand(size_t expand_bytes); 635 636 // Returns the PLAB statistics for a given destination. 637 inline PLABStats* alloc_buffer_stats(InCSetState dest); 638 639 // Determines PLAB size for a given destination. 640 inline size_t desired_plab_sz(InCSetState dest); 641 642 inline AllocationContextStats& allocation_context_stats(); 643 644 // Do anything common to GC's. 645 void gc_prologue(bool full); 646 void gc_epilogue(bool full); 647 648 // Modify the reclaim candidate set and test for presence. 649 // These are only valid for starts_humongous regions. 650 inline void set_humongous_reclaim_candidate(uint region, bool value); 651 inline bool is_humongous_reclaim_candidate(uint region); 652 653 // Remove from the reclaim candidate set. Also remove from the 654 // collection set so that later encounters avoid the slow path. 655 inline void set_humongous_is_live(oop obj); 656 657 // Register the given region to be part of the collection set. 658 inline void register_humongous_region_with_cset(uint index); 659 // Register regions with humongous objects (actually on the start region) in 660 // the in_cset_fast_test table. 661 void register_humongous_regions_with_cset(); 662 // We register a region with the fast "in collection set" test. We 663 // simply set to true the array slot corresponding to this region. 664 void register_young_region_with_cset(HeapRegion* r) { 665 _in_cset_fast_test.set_in_young(r->hrm_index()); 666 } 667 void register_old_region_with_cset(HeapRegion* r) { 668 _in_cset_fast_test.set_in_old(r->hrm_index()); 669 } 670 void clear_in_cset(const HeapRegion* hr) { 671 _in_cset_fast_test.clear(hr); 672 } 673 674 void clear_cset_fast_test() { 675 _in_cset_fast_test.clear(); 676 } 677 678 // This is called at the start of either a concurrent cycle or a Full 679 // GC to update the number of old marking cycles started. 680 void increment_old_marking_cycles_started(); 681 682 // This is called at the end of either a concurrent cycle or a Full 683 // GC to update the number of old marking cycles completed. Those two 684 // can happen in a nested fashion, i.e., we start a concurrent 685 // cycle, a Full GC happens half-way through it which ends first, 686 // and then the cycle notices that a Full GC happened and ends 687 // too. The concurrent parameter is a boolean to help us do a bit 688 // tighter consistency checking in the method. If concurrent is 689 // false, the caller is the inner caller in the nesting (i.e., the 690 // Full GC). If concurrent is true, the caller is the outer caller 691 // in this nesting (i.e., the concurrent cycle). Further nesting is 692 // not currently supported. The end of this call also notifies 693 // the FullGCCount_lock in case a Java thread is waiting for a full 694 // GC to happen (e.g., it called System.gc() with 695 // +ExplicitGCInvokesConcurrent). 696 void increment_old_marking_cycles_completed(bool concurrent); 697 698 uint old_marking_cycles_completed() { 699 return _old_marking_cycles_completed; 700 } 701 702 void register_concurrent_cycle_start(const Ticks& start_time); 703 void register_concurrent_cycle_end(); 704 void trace_heap_after_concurrent_cycle(); 705 706 G1YCType yc_type(); 707 708 G1HRPrinter* hr_printer() { return &_hr_printer; } 709 710 // Frees a non-humongous region by initializing its contents and 711 // adding it to the free list that's passed as a parameter (this is 712 // usually a local list which will be appended to the master free 713 // list later). The used bytes of freed regions are accumulated in 714 // pre_used. If par is true, the region's RSet will not be freed 715 // up. The assumption is that this will be done later. 716 // The locked parameter indicates if the caller has already taken 717 // care of proper synchronization. This may allow some optimizations. 718 void free_region(HeapRegion* hr, 719 FreeRegionList* free_list, 720 bool par, 721 bool locked = false); 722 723 // Frees a humongous region by collapsing it into individual regions 724 // and calling free_region() for each of them. The freed regions 725 // will be added to the free list that's passed as a parameter (this 726 // is usually a local list which will be appended to the master free 727 // list later). The used bytes of freed regions are accumulated in 728 // pre_used. If par is true, the region's RSet will not be freed 729 // up. The assumption is that this will be done later. 730 void free_humongous_region(HeapRegion* hr, 731 FreeRegionList* free_list, 732 bool par); 733 protected: 734 735 // Shrink the garbage-first heap by at most the given size (in bytes!). 736 // (Rounds down to a HeapRegion boundary.) 737 virtual void shrink(size_t expand_bytes); 738 void shrink_helper(size_t expand_bytes); 739 740 #if TASKQUEUE_STATS 741 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 742 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 743 void reset_taskqueue_stats(); 744 #endif // TASKQUEUE_STATS 745 746 // Schedule the VM operation that will do an evacuation pause to 747 // satisfy an allocation request of word_size. *succeeded will 748 // return whether the VM operation was successful (it did do an 749 // evacuation pause) or not (another thread beat us to it or the GC 750 // locker was active). Given that we should not be holding the 751 // Heap_lock when we enter this method, we will pass the 752 // gc_count_before (i.e., total_collections()) as a parameter since 753 // it has to be read while holding the Heap_lock. Currently, both 754 // methods that call do_collection_pause() release the Heap_lock 755 // before the call, so it's easy to read gc_count_before just before. 756 HeapWord* do_collection_pause(size_t word_size, 757 uint gc_count_before, 758 bool* succeeded, 759 GCCause::Cause gc_cause); 760 761 // The guts of the incremental collection pause, executed by the vm 762 // thread. It returns false if it is unable to do the collection due 763 // to the GC locker being active, true otherwise 764 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 765 766 // Actually do the work of evacuating the collection set. 767 void evacuate_collection_set(EvacuationInfo& evacuation_info); 768 769 // The g1 remembered set of the heap. 770 G1RemSet* _g1_rem_set; 771 772 // A set of cards that cover the objects for which the Rsets should be updated 773 // concurrently after the collection. 774 DirtyCardQueueSet _dirty_card_queue_set; 775 776 // The closure used to refine a single card. 777 RefineCardTableEntryClosure* _refine_cte_cl; 778 779 // A DirtyCardQueueSet that is used to hold cards that contain 780 // references into the current collection set. This is used to 781 // update the remembered sets of the regions in the collection 782 // set in the event of an evacuation failure. 783 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 784 785 // After a collection pause, make the regions in the CS into free 786 // regions. 787 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 788 789 // Abandon the current collection set without recording policy 790 // statistics or updating free lists. 791 void abandon_collection_set(HeapRegion* cs_head); 792 793 // The concurrent marker (and the thread it runs in.) 794 ConcurrentMark* _cm; 795 ConcurrentMarkThread* _cmThread; 796 797 // The concurrent refiner. 798 ConcurrentG1Refine* _cg1r; 799 800 // The parallel task queues 801 RefToScanQueueSet *_task_queues; 802 803 // True iff a evacuation has failed in the current collection. 804 bool _evacuation_failed; 805 806 EvacuationFailedInfo* _evacuation_failed_info_array; 807 808 // Failed evacuations cause some logical from-space objects to have 809 // forwarding pointers to themselves. Reset them. 810 void remove_self_forwarding_pointers(); 811 812 // Together, these store an object with a preserved mark, and its mark value. 813 Stack<oop, mtGC> _objs_with_preserved_marks; 814 Stack<markOop, mtGC> _preserved_marks_of_objs; 815 816 // Preserve the mark of "obj", if necessary, in preparation for its mark 817 // word being overwritten with a self-forwarding-pointer. 818 void preserve_mark_if_necessary(oop obj, markOop m); 819 820 // The stack of evac-failure objects left to be scanned. 821 GrowableArray<oop>* _evac_failure_scan_stack; 822 // The closure to apply to evac-failure objects. 823 824 OopsInHeapRegionClosure* _evac_failure_closure; 825 // Set the field above. 826 void 827 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 828 _evac_failure_closure = evac_failure_closure; 829 } 830 831 // Push "obj" on the scan stack. 832 void push_on_evac_failure_scan_stack(oop obj); 833 // Process scan stack entries until the stack is empty. 834 void drain_evac_failure_scan_stack(); 835 // True iff an invocation of "drain_scan_stack" is in progress; to 836 // prevent unnecessary recursion. 837 bool _drain_in_progress; 838 839 // Do any necessary initialization for evacuation-failure handling. 840 // "cl" is the closure that will be used to process evac-failure 841 // objects. 842 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 843 // Do any necessary cleanup for evacuation-failure handling data 844 // structures. 845 void finalize_for_evac_failure(); 846 847 // An attempt to evacuate "obj" has failed; take necessary steps. 848 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 849 void handle_evacuation_failure_common(oop obj, markOop m); 850 851 #ifndef PRODUCT 852 // Support for forcing evacuation failures. Analogous to 853 // PromotionFailureALot for the other collectors. 854 855 // Records whether G1EvacuationFailureALot should be in effect 856 // for the current GC 857 bool _evacuation_failure_alot_for_current_gc; 858 859 // Used to record the GC number for interval checking when 860 // determining whether G1EvaucationFailureALot is in effect 861 // for the current GC. 862 size_t _evacuation_failure_alot_gc_number; 863 864 // Count of the number of evacuations between failures. 865 volatile size_t _evacuation_failure_alot_count; 866 867 // Set whether G1EvacuationFailureALot should be in effect 868 // for the current GC (based upon the type of GC and which 869 // command line flags are set); 870 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 871 bool during_initial_mark, 872 bool during_marking); 873 874 inline void set_evacuation_failure_alot_for_current_gc(); 875 876 // Return true if it's time to cause an evacuation failure. 877 inline bool evacuation_should_fail(); 878 879 // Reset the G1EvacuationFailureALot counters. Should be called at 880 // the end of an evacuation pause in which an evacuation failure occurred. 881 inline void reset_evacuation_should_fail(); 882 #endif // !PRODUCT 883 884 // ("Weak") Reference processing support. 885 // 886 // G1 has 2 instances of the reference processor class. One 887 // (_ref_processor_cm) handles reference object discovery 888 // and subsequent processing during concurrent marking cycles. 889 // 890 // The other (_ref_processor_stw) handles reference object 891 // discovery and processing during full GCs and incremental 892 // evacuation pauses. 893 // 894 // During an incremental pause, reference discovery will be 895 // temporarily disabled for _ref_processor_cm and will be 896 // enabled for _ref_processor_stw. At the end of the evacuation 897 // pause references discovered by _ref_processor_stw will be 898 // processed and discovery will be disabled. The previous 899 // setting for reference object discovery for _ref_processor_cm 900 // will be re-instated. 901 // 902 // At the start of marking: 903 // * Discovery by the CM ref processor is verified to be inactive 904 // and it's discovered lists are empty. 905 // * Discovery by the CM ref processor is then enabled. 906 // 907 // At the end of marking: 908 // * Any references on the CM ref processor's discovered 909 // lists are processed (possibly MT). 910 // 911 // At the start of full GC we: 912 // * Disable discovery by the CM ref processor and 913 // empty CM ref processor's discovered lists 914 // (without processing any entries). 915 // * Verify that the STW ref processor is inactive and it's 916 // discovered lists are empty. 917 // * Temporarily set STW ref processor discovery as single threaded. 918 // * Temporarily clear the STW ref processor's _is_alive_non_header 919 // field. 920 // * Finally enable discovery by the STW ref processor. 921 // 922 // The STW ref processor is used to record any discovered 923 // references during the full GC. 924 // 925 // At the end of a full GC we: 926 // * Enqueue any reference objects discovered by the STW ref processor 927 // that have non-live referents. This has the side-effect of 928 // making the STW ref processor inactive by disabling discovery. 929 // * Verify that the CM ref processor is still inactive 930 // and no references have been placed on it's discovered 931 // lists (also checked as a precondition during initial marking). 932 933 // The (stw) reference processor... 934 ReferenceProcessor* _ref_processor_stw; 935 936 STWGCTimer* _gc_timer_stw; 937 ConcurrentGCTimer* _gc_timer_cm; 938 939 G1OldTracer* _gc_tracer_cm; 940 G1NewTracer* _gc_tracer_stw; 941 942 // During reference object discovery, the _is_alive_non_header 943 // closure (if non-null) is applied to the referent object to 944 // determine whether the referent is live. If so then the 945 // reference object does not need to be 'discovered' and can 946 // be treated as a regular oop. This has the benefit of reducing 947 // the number of 'discovered' reference objects that need to 948 // be processed. 949 // 950 // Instance of the is_alive closure for embedding into the 951 // STW reference processor as the _is_alive_non_header field. 952 // Supplying a value for the _is_alive_non_header field is 953 // optional but doing so prevents unnecessary additions to 954 // the discovered lists during reference discovery. 955 G1STWIsAliveClosure _is_alive_closure_stw; 956 957 // The (concurrent marking) reference processor... 958 ReferenceProcessor* _ref_processor_cm; 959 960 // Instance of the concurrent mark is_alive closure for embedding 961 // into the Concurrent Marking reference processor as the 962 // _is_alive_non_header field. Supplying a value for the 963 // _is_alive_non_header field is optional but doing so prevents 964 // unnecessary additions to the discovered lists during reference 965 // discovery. 966 G1CMIsAliveClosure _is_alive_closure_cm; 967 968 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 969 HeapRegion** _worker_cset_start_region; 970 971 // Time stamp to validate the regions recorded in the cache 972 // used by G1CollectedHeap::start_cset_region_for_worker(). 973 // The heap region entry for a given worker is valid iff 974 // the associated time stamp value matches the current value 975 // of G1CollectedHeap::_gc_time_stamp. 976 uint* _worker_cset_start_region_time_stamp; 977 978 volatile bool _free_regions_coming; 979 980 public: 981 982 void set_refine_cte_cl_concurrency(bool concurrent); 983 984 RefToScanQueue *task_queue(uint i) const; 985 986 // A set of cards where updates happened during the GC 987 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 988 989 // A DirtyCardQueueSet that is used to hold cards that contain 990 // references into the current collection set. This is used to 991 // update the remembered sets of the regions in the collection 992 // set in the event of an evacuation failure. 993 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 994 { return _into_cset_dirty_card_queue_set; } 995 996 // Create a G1CollectedHeap with the specified policy. 997 // Must call the initialize method afterwards. 998 // May not return if something goes wrong. 999 G1CollectedHeap(G1CollectorPolicy* policy); 1000 1001 // Initialize the G1CollectedHeap to have the initial and 1002 // maximum sizes and remembered and barrier sets 1003 // specified by the policy object. 1004 jint initialize(); 1005 1006 virtual void stop(); 1007 1008 // Return the (conservative) maximum heap alignment for any G1 heap 1009 static size_t conservative_max_heap_alignment(); 1010 1011 // Does operations required after initialization has been done. 1012 void post_initialize(); 1013 1014 // Initialize weak reference processing. 1015 void ref_processing_init(); 1016 1017 // Explicitly import set_par_threads into this scope 1018 using CollectedHeap::set_par_threads; 1019 // Set _n_par_threads according to a policy TBD. 1020 void set_par_threads(); 1021 1022 virtual Name kind() const { 1023 return CollectedHeap::G1CollectedHeap; 1024 } 1025 1026 G1CollectorState* collector_state() { return &_collector_state; } 1027 1028 // The current policy object for the collector. 1029 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1030 1031 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1032 1033 // Adaptive size policy. No such thing for g1. 1034 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1035 1036 // The rem set and barrier set. 1037 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1038 1039 unsigned get_gc_time_stamp() { 1040 return _gc_time_stamp; 1041 } 1042 1043 inline void reset_gc_time_stamp(); 1044 1045 void check_gc_time_stamps() PRODUCT_RETURN; 1046 1047 inline void increment_gc_time_stamp(); 1048 1049 // Reset the given region's GC timestamp. If it's starts humongous, 1050 // also reset the GC timestamp of its corresponding 1051 // continues humongous regions too. 1052 void reset_gc_time_stamps(HeapRegion* hr); 1053 1054 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1055 DirtyCardQueue* into_cset_dcq, 1056 bool concurrent, uint worker_i); 1057 1058 // The shared block offset table array. 1059 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1060 1061 // Reference Processing accessors 1062 1063 // The STW reference processor.... 1064 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1065 1066 // The Concurrent Marking reference processor... 1067 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1068 1069 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1070 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1071 1072 virtual size_t capacity() const; 1073 virtual size_t used() const; 1074 // This should be called when we're not holding the heap lock. The 1075 // result might be a bit inaccurate. 1076 size_t used_unlocked() const; 1077 size_t recalculate_used() const; 1078 1079 // These virtual functions do the actual allocation. 1080 // Some heaps may offer a contiguous region for shared non-blocking 1081 // allocation, via inlined code (by exporting the address of the top and 1082 // end fields defining the extent of the contiguous allocation region.) 1083 // But G1CollectedHeap doesn't yet support this. 1084 1085 virtual bool is_maximal_no_gc() const { 1086 return _hrm.available() == 0; 1087 } 1088 1089 // The current number of regions in the heap. 1090 uint num_regions() const { return _hrm.length(); } 1091 1092 // The max number of regions in the heap. 1093 uint max_regions() const { return _hrm.max_length(); } 1094 1095 // The number of regions that are completely free. 1096 uint num_free_regions() const { return _hrm.num_free_regions(); } 1097 1098 MemoryUsage get_auxiliary_data_memory_usage() const { 1099 return _hrm.get_auxiliary_data_memory_usage(); 1100 } 1101 1102 // The number of regions that are not completely free. 1103 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1104 1105 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1106 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1107 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1108 void verify_dirty_young_regions() PRODUCT_RETURN; 1109 1110 #ifndef PRODUCT 1111 // Make sure that the given bitmap has no marked objects in the 1112 // range [from,limit). If it does, print an error message and return 1113 // false. Otherwise, just return true. bitmap_name should be "prev" 1114 // or "next". 1115 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1116 HeapWord* from, HeapWord* limit); 1117 1118 // Verify that the prev / next bitmap range [tams,end) for the given 1119 // region has no marks. Return true if all is well, false if errors 1120 // are detected. 1121 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1122 #endif // PRODUCT 1123 1124 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1125 // the given region do not have any spurious marks. If errors are 1126 // detected, print appropriate error messages and crash. 1127 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1128 1129 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1130 // have any spurious marks. If errors are detected, print 1131 // appropriate error messages and crash. 1132 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1133 1134 // Do sanity check on the contents of the in-cset fast test table. 1135 bool check_cset_fast_test() PRODUCT_RETURN_( return true; ); 1136 1137 // verify_region_sets() performs verification over the region 1138 // lists. It will be compiled in the product code to be used when 1139 // necessary (i.e., during heap verification). 1140 void verify_region_sets(); 1141 1142 // verify_region_sets_optional() is planted in the code for 1143 // list verification in non-product builds (and it can be enabled in 1144 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1145 #if HEAP_REGION_SET_FORCE_VERIFY 1146 void verify_region_sets_optional() { 1147 verify_region_sets(); 1148 } 1149 #else // HEAP_REGION_SET_FORCE_VERIFY 1150 void verify_region_sets_optional() { } 1151 #endif // HEAP_REGION_SET_FORCE_VERIFY 1152 1153 #ifdef ASSERT 1154 bool is_on_master_free_list(HeapRegion* hr) { 1155 return _hrm.is_free(hr); 1156 } 1157 #endif // ASSERT 1158 1159 // Wrapper for the region list operations that can be called from 1160 // methods outside this class. 1161 1162 void secondary_free_list_add(FreeRegionList* list) { 1163 _secondary_free_list.add_ordered(list); 1164 } 1165 1166 void append_secondary_free_list() { 1167 _hrm.insert_list_into_free_list(&_secondary_free_list); 1168 } 1169 1170 void append_secondary_free_list_if_not_empty_with_lock() { 1171 // If the secondary free list looks empty there's no reason to 1172 // take the lock and then try to append it. 1173 if (!_secondary_free_list.is_empty()) { 1174 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1175 append_secondary_free_list(); 1176 } 1177 } 1178 1179 inline void old_set_remove(HeapRegion* hr); 1180 1181 size_t non_young_capacity_bytes() { 1182 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1183 } 1184 1185 void set_free_regions_coming(); 1186 void reset_free_regions_coming(); 1187 bool free_regions_coming() { return _free_regions_coming; } 1188 void wait_while_free_regions_coming(); 1189 1190 // Determine whether the given region is one that we are using as an 1191 // old GC alloc region. 1192 bool is_old_gc_alloc_region(HeapRegion* hr) { 1193 return _allocator->is_retained_old_region(hr); 1194 } 1195 1196 // Perform a collection of the heap; intended for use in implementing 1197 // "System.gc". This probably implies as full a collection as the 1198 // "CollectedHeap" supports. 1199 virtual void collect(GCCause::Cause cause); 1200 1201 // The same as above but assume that the caller holds the Heap_lock. 1202 void collect_locked(GCCause::Cause cause); 1203 1204 virtual bool copy_allocation_context_stats(const jint* contexts, 1205 jlong* totals, 1206 jbyte* accuracy, 1207 jint len); 1208 1209 // True iff an evacuation has failed in the most-recent collection. 1210 bool evacuation_failed() { return _evacuation_failed; } 1211 1212 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1213 void prepend_to_freelist(FreeRegionList* list); 1214 void decrement_summary_bytes(size_t bytes); 1215 1216 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1217 virtual bool is_in(const void* p) const; 1218 #ifdef ASSERT 1219 // Returns whether p is in one of the available areas of the heap. Slow but 1220 // extensive version. 1221 bool is_in_exact(const void* p) const; 1222 #endif 1223 1224 // Return "TRUE" iff the given object address is within the collection 1225 // set. Slow implementation. 1226 inline bool obj_in_cs(oop obj); 1227 1228 inline bool is_in_cset(const HeapRegion *hr); 1229 inline bool is_in_cset(oop obj); 1230 1231 inline bool is_in_cset_or_humongous(const oop obj); 1232 1233 private: 1234 // This array is used for a quick test on whether a reference points into 1235 // the collection set or not. Each of the array's elements denotes whether the 1236 // corresponding region is in the collection set or not. 1237 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1238 1239 public: 1240 1241 inline InCSetState in_cset_state(const oop obj); 1242 1243 // Return "TRUE" iff the given object address is in the reserved 1244 // region of g1. 1245 bool is_in_g1_reserved(const void* p) const { 1246 return _hrm.reserved().contains(p); 1247 } 1248 1249 // Returns a MemRegion that corresponds to the space that has been 1250 // reserved for the heap 1251 MemRegion g1_reserved() const { 1252 return _hrm.reserved(); 1253 } 1254 1255 virtual bool is_in_closed_subset(const void* p) const; 1256 1257 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1258 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1259 } 1260 1261 // This resets the card table to all zeros. It is used after 1262 // a collection pause which used the card table to claim cards. 1263 void cleanUpCardTable(); 1264 1265 // Iteration functions. 1266 1267 // Iterate over all objects, calling "cl.do_object" on each. 1268 virtual void object_iterate(ObjectClosure* cl); 1269 1270 virtual void safe_object_iterate(ObjectClosure* cl) { 1271 object_iterate(cl); 1272 } 1273 1274 // Iterate over heap regions, in address order, terminating the 1275 // iteration early if the "doHeapRegion" method returns "true". 1276 void heap_region_iterate(HeapRegionClosure* blk) const; 1277 1278 // Return the region with the given index. It assumes the index is valid. 1279 inline HeapRegion* region_at(uint index) const; 1280 1281 // Calculate the region index of the given address. Given address must be 1282 // within the heap. 1283 inline uint addr_to_region(HeapWord* addr) const; 1284 1285 inline HeapWord* bottom_addr_for_region(uint index) const; 1286 1287 // Iterate over the heap regions in parallel. Assumes that this will be called 1288 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1289 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1290 // to each of the regions, by attempting to claim the region using the 1291 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1292 // region. The concurrent argument should be set to true if iteration is 1293 // performed concurrently, during which no assumptions are made for consistent 1294 // attributes of the heap regions (as they might be modified while iterating). 1295 void heap_region_par_iterate(HeapRegionClosure* cl, 1296 uint worker_id, 1297 HeapRegionClaimer* hrclaimer, 1298 bool concurrent = false) const; 1299 1300 // Clear the cached cset start regions and (more importantly) 1301 // the time stamps. Called when we reset the GC time stamp. 1302 void clear_cset_start_regions(); 1303 1304 // Given the id of a worker, obtain or calculate a suitable 1305 // starting region for iterating over the current collection set. 1306 HeapRegion* start_cset_region_for_worker(uint worker_i); 1307 1308 // Iterate over the regions (if any) in the current collection set. 1309 void collection_set_iterate(HeapRegionClosure* blk); 1310 1311 // As above but starting from region r 1312 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1313 1314 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1315 1316 // Returns the HeapRegion that contains addr. addr must not be NULL. 1317 template <class T> 1318 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1319 1320 // Returns the HeapRegion that contains addr. addr must not be NULL. 1321 // If addr is within a humongous continues region, it returns its humongous start region. 1322 template <class T> 1323 inline HeapRegion* heap_region_containing(const T addr) const; 1324 1325 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1326 // each address in the (reserved) heap is a member of exactly 1327 // one block. The defining characteristic of a block is that it is 1328 // possible to find its size, and thus to progress forward to the next 1329 // block. (Blocks may be of different sizes.) Thus, blocks may 1330 // represent Java objects, or they might be free blocks in a 1331 // free-list-based heap (or subheap), as long as the two kinds are 1332 // distinguishable and the size of each is determinable. 1333 1334 // Returns the address of the start of the "block" that contains the 1335 // address "addr". We say "blocks" instead of "object" since some heaps 1336 // may not pack objects densely; a chunk may either be an object or a 1337 // non-object. 1338 virtual HeapWord* block_start(const void* addr) const; 1339 1340 // Requires "addr" to be the start of a chunk, and returns its size. 1341 // "addr + size" is required to be the start of a new chunk, or the end 1342 // of the active area of the heap. 1343 virtual size_t block_size(const HeapWord* addr) const; 1344 1345 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1346 // the block is an object. 1347 virtual bool block_is_obj(const HeapWord* addr) const; 1348 1349 // Section on thread-local allocation buffers (TLABs) 1350 // See CollectedHeap for semantics. 1351 1352 bool supports_tlab_allocation() const; 1353 size_t tlab_capacity(Thread* ignored) const; 1354 size_t tlab_used(Thread* ignored) const; 1355 size_t max_tlab_size() const; 1356 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1357 1358 // Can a compiler initialize a new object without store barriers? 1359 // This permission only extends from the creation of a new object 1360 // via a TLAB up to the first subsequent safepoint. If such permission 1361 // is granted for this heap type, the compiler promises to call 1362 // defer_store_barrier() below on any slow path allocation of 1363 // a new object for which such initializing store barriers will 1364 // have been elided. G1, like CMS, allows this, but should be 1365 // ready to provide a compensating write barrier as necessary 1366 // if that storage came out of a non-young region. The efficiency 1367 // of this implementation depends crucially on being able to 1368 // answer very efficiently in constant time whether a piece of 1369 // storage in the heap comes from a young region or not. 1370 // See ReduceInitialCardMarks. 1371 virtual bool can_elide_tlab_store_barriers() const { 1372 return true; 1373 } 1374 1375 virtual bool card_mark_must_follow_store() const { 1376 return true; 1377 } 1378 1379 inline bool is_in_young(const oop obj); 1380 1381 virtual bool is_scavengable(const void* addr); 1382 1383 // We don't need barriers for initializing stores to objects 1384 // in the young gen: for the SATB pre-barrier, there is no 1385 // pre-value that needs to be remembered; for the remembered-set 1386 // update logging post-barrier, we don't maintain remembered set 1387 // information for young gen objects. 1388 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1389 1390 // Returns "true" iff the given word_size is "very large". 1391 static bool is_humongous(size_t word_size) { 1392 // Note this has to be strictly greater-than as the TLABs 1393 // are capped at the humongous threshold and we want to 1394 // ensure that we don't try to allocate a TLAB as 1395 // humongous and that we don't allocate a humongous 1396 // object in a TLAB. 1397 return word_size > _humongous_object_threshold_in_words; 1398 } 1399 1400 // Update mod union table with the set of dirty cards. 1401 void updateModUnion(); 1402 1403 // Set the mod union bits corresponding to the given memRegion. Note 1404 // that this is always a safe operation, since it doesn't clear any 1405 // bits. 1406 void markModUnionRange(MemRegion mr); 1407 1408 // Print the maximum heap capacity. 1409 virtual size_t max_capacity() const; 1410 1411 virtual jlong millis_since_last_gc(); 1412 1413 1414 // Convenience function to be used in situations where the heap type can be 1415 // asserted to be this type. 1416 static G1CollectedHeap* heap(); 1417 1418 void set_region_short_lived_locked(HeapRegion* hr); 1419 // add appropriate methods for any other surv rate groups 1420 1421 YoungList* young_list() const { return _young_list; } 1422 1423 // debugging 1424 bool check_young_list_well_formed() { 1425 return _young_list->check_list_well_formed(); 1426 } 1427 1428 bool check_young_list_empty(bool check_heap, 1429 bool check_sample = true); 1430 1431 // *** Stuff related to concurrent marking. It's not clear to me that so 1432 // many of these need to be public. 1433 1434 // The functions below are helper functions that a subclass of 1435 // "CollectedHeap" can use in the implementation of its virtual 1436 // functions. 1437 // This performs a concurrent marking of the live objects in a 1438 // bitmap off to the side. 1439 void doConcurrentMark(); 1440 1441 bool isMarkedPrev(oop obj) const; 1442 bool isMarkedNext(oop obj) const; 1443 1444 // Determine if an object is dead, given the object and also 1445 // the region to which the object belongs. An object is dead 1446 // iff a) it was not allocated since the last mark and b) it 1447 // is not marked. 1448 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1449 return 1450 !hr->obj_allocated_since_prev_marking(obj) && 1451 !isMarkedPrev(obj); 1452 } 1453 1454 // This function returns true when an object has been 1455 // around since the previous marking and hasn't yet 1456 // been marked during this marking. 1457 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1458 return 1459 !hr->obj_allocated_since_next_marking(obj) && 1460 !isMarkedNext(obj); 1461 } 1462 1463 // Determine if an object is dead, given only the object itself. 1464 // This will find the region to which the object belongs and 1465 // then call the region version of the same function. 1466 1467 // Added if it is NULL it isn't dead. 1468 1469 inline bool is_obj_dead(const oop obj) const; 1470 1471 inline bool is_obj_ill(const oop obj) const; 1472 1473 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1474 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1475 bool is_marked(oop obj, VerifyOption vo); 1476 const char* top_at_mark_start_str(VerifyOption vo); 1477 1478 ConcurrentMark* concurrent_mark() const { return _cm; } 1479 1480 // Refinement 1481 1482 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1483 1484 // The dirty cards region list is used to record a subset of regions 1485 // whose cards need clearing. The list if populated during the 1486 // remembered set scanning and drained during the card table 1487 // cleanup. Although the methods are reentrant, population/draining 1488 // phases must not overlap. For synchronization purposes the last 1489 // element on the list points to itself. 1490 HeapRegion* _dirty_cards_region_list; 1491 void push_dirty_cards_region(HeapRegion* hr); 1492 HeapRegion* pop_dirty_cards_region(); 1493 1494 // Optimized nmethod scanning support routines 1495 1496 // Register the given nmethod with the G1 heap. 1497 virtual void register_nmethod(nmethod* nm); 1498 1499 // Unregister the given nmethod from the G1 heap. 1500 virtual void unregister_nmethod(nmethod* nm); 1501 1502 // Free up superfluous code root memory. 1503 void purge_code_root_memory(); 1504 1505 // Rebuild the strong code root lists for each region 1506 // after a full GC. 1507 void rebuild_strong_code_roots(); 1508 1509 // Delete entries for dead interned string and clean up unreferenced symbols 1510 // in symbol table, possibly in parallel. 1511 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1512 1513 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1514 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1515 1516 // Redirty logged cards in the refinement queue. 1517 void redirty_logged_cards(); 1518 // Verification 1519 1520 // The following is just to alert the verification code 1521 // that a full collection has occurred and that the 1522 // remembered sets are no longer up to date. 1523 bool full_collection() { return collector_state()->full_collection(); } 1524 1525 // Perform any cleanup actions necessary before allowing a verification. 1526 virtual void prepare_for_verify(); 1527 1528 // Perform verification. 1529 1530 // vo == UsePrevMarking -> use "prev" marking information, 1531 // vo == UseNextMarking -> use "next" marking information 1532 // vo == UseMarkWord -> use the mark word in the object header 1533 // 1534 // NOTE: Only the "prev" marking information is guaranteed to be 1535 // consistent most of the time, so most calls to this should use 1536 // vo == UsePrevMarking. 1537 // Currently, there is only one case where this is called with 1538 // vo == UseNextMarking, which is to verify the "next" marking 1539 // information at the end of remark. 1540 // Currently there is only one place where this is called with 1541 // vo == UseMarkWord, which is to verify the marking during a 1542 // full GC. 1543 void verify(bool silent, VerifyOption vo); 1544 1545 // Override; it uses the "prev" marking information 1546 virtual void verify(bool silent); 1547 1548 // The methods below are here for convenience and dispatch the 1549 // appropriate method depending on value of the given VerifyOption 1550 // parameter. The values for that parameter, and their meanings, 1551 // are the same as those above. 1552 1553 bool is_obj_dead_cond(const oop obj, 1554 const HeapRegion* hr, 1555 const VerifyOption vo) const; 1556 1557 bool is_obj_dead_cond(const oop obj, 1558 const VerifyOption vo) const; 1559 1560 // Printing 1561 1562 virtual void print_on(outputStream* st) const; 1563 virtual void print_extended_on(outputStream* st) const; 1564 virtual void print_on_error(outputStream* st) const; 1565 1566 virtual void print_gc_threads_on(outputStream* st) const; 1567 virtual void gc_threads_do(ThreadClosure* tc) const; 1568 1569 // Override 1570 void print_tracing_info() const; 1571 1572 // The following two methods are helpful for debugging RSet issues. 1573 void print_cset_rsets() PRODUCT_RETURN; 1574 void print_all_rsets() PRODUCT_RETURN; 1575 1576 public: 1577 size_t pending_card_num(); 1578 size_t cards_scanned(); 1579 1580 protected: 1581 size_t _max_heap_capacity; 1582 }; 1583 1584 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP