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_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc/g1/concurrentMark.hpp" 29 #include "gc/g1/evacuationInfo.hpp" 30 #include "gc/g1/g1AllocRegion.hpp" 31 #include "gc/g1/g1AllocationContext.hpp" 32 #include "gc/g1/g1Allocator.hpp" 33 #include "gc/g1/g1BiasedArray.hpp" 34 #include "gc/g1/g1CollectorState.hpp" 35 #include "gc/g1/g1HRPrinter.hpp" 36 #include "gc/g1/g1InCSetState.hpp" 37 #include "gc/g1/g1MonitoringSupport.hpp" 38 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 39 #include "gc/g1/g1YCTypes.hpp" 40 #include "gc/g1/hSpaceCounters.hpp" 41 #include "gc/g1/heapRegionManager.hpp" 42 #include "gc/g1/heapRegionSet.hpp" 43 #include "gc/shared/barrierSet.hpp" 44 #include "gc/shared/collectedHeap.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 friend class G1ArchiveAllocator; 192 193 // Closures used in implementation. 194 friend class G1ParScanThreadState; 195 friend class G1ParTask; 196 friend class G1ParGCAllocator; 197 friend class G1PrepareCompactClosure; 198 199 // Other related classes. 200 friend class HeapRegionClaimer; 201 202 // Testing classes. 203 friend class G1CheckCSetFastTableClosure; 204 205 private: 206 FlexibleWorkGang* _workers; 207 208 static size_t _humongous_object_threshold_in_words; 209 210 // The secondary free list which contains regions that have been 211 // freed up during the cleanup process. This will be appended to 212 // the master free list when appropriate. 213 FreeRegionList _secondary_free_list; 214 215 // It keeps track of the old regions. 216 HeapRegionSet _old_set; 217 218 // It keeps track of the humongous regions. 219 HeapRegionSet _humongous_set; 220 221 void eagerly_reclaim_humongous_regions(); 222 223 // The number of regions we could create by expansion. 224 uint _expansion_regions; 225 226 // The block offset table for the G1 heap. 227 G1BlockOffsetSharedArray* _bot_shared; 228 229 // Tears down the region sets / lists so that they are empty and the 230 // regions on the heap do not belong to a region set / list. The 231 // only exception is the humongous set which we leave unaltered. If 232 // free_list_only is true, it will only tear down the master free 233 // list. It is called before a Full GC (free_list_only == false) or 234 // before heap shrinking (free_list_only == true). 235 void tear_down_region_sets(bool free_list_only); 236 237 // Rebuilds the region sets / lists so that they are repopulated to 238 // reflect the contents of the heap. The only exception is the 239 // humongous set which was not torn down in the first place. If 240 // free_list_only is true, it will only rebuild the master free 241 // list. It is called after a Full GC (free_list_only == false) or 242 // after heap shrinking (free_list_only == true). 243 void rebuild_region_sets(bool free_list_only); 244 245 // Callback for region mapping changed events. 246 G1RegionMappingChangedListener _listener; 247 248 // The sequence of all heap regions in the heap. 249 HeapRegionManager _hrm; 250 251 // Class that handles the different kinds of allocations. 252 G1Allocator* _allocator; 253 254 // Outside of GC pauses, the number of bytes used in all regions other 255 // than the current allocation region(s). 256 size_t _summary_bytes_used; 257 258 void increase_used(size_t bytes); 259 void decrease_used(size_t bytes); 260 261 void set_used(size_t bytes); 262 263 // Class that handles archive allocation ranges. 264 G1ArchiveAllocator* _archive_allocator; 265 266 // Statistics for each allocation context 267 AllocationContextStats _allocation_context_stats; 268 269 // PLAB sizing policy for survivors. 270 PLABStats _survivor_plab_stats; 271 272 // PLAB sizing policy for tenured objects. 273 PLABStats _old_plab_stats; 274 275 // It specifies whether we should attempt to expand the heap after a 276 // region allocation failure. If heap expansion fails we set this to 277 // false so that we don't re-attempt the heap expansion (it's likely 278 // that subsequent expansion attempts will also fail if one fails). 279 // Currently, it is only consulted during GC and it's reset at the 280 // start of each GC. 281 bool _expand_heap_after_alloc_failure; 282 283 // It resets the mutator alloc region before new allocations can take place. 284 void init_mutator_alloc_region(); 285 286 // It releases the mutator alloc region. 287 void release_mutator_alloc_region(); 288 289 // It initializes the GC alloc regions at the start of a GC. 290 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 291 292 // It releases the GC alloc regions at the end of a GC. 293 void release_gc_alloc_regions(EvacuationInfo& evacuation_info); 294 295 // It does any cleanup that needs to be done on the GC alloc regions 296 // before a Full GC. 297 void abandon_gc_alloc_regions(); 298 299 // Helper for monitoring and management support. 300 G1MonitoringSupport* _g1mm; 301 302 // Records whether the region at the given index is (still) a 303 // candidate for eager reclaim. Only valid for humongous start 304 // regions; other regions have unspecified values. Humongous start 305 // regions are initialized at start of collection pause, with 306 // candidates removed from the set as they are found reachable from 307 // roots or the young generation. 308 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 309 protected: 310 bool default_value() const { return false; } 311 public: 312 void clear() { G1BiasedMappedArray<bool>::clear(); } 313 void set_candidate(uint region, bool value) { 314 set_by_index(region, value); 315 } 316 bool is_candidate(uint region) { 317 return get_by_index(region); 318 } 319 }; 320 321 HumongousReclaimCandidates _humongous_reclaim_candidates; 322 // Stores whether during humongous object registration we found candidate regions. 323 // If not, we can skip a few steps. 324 bool _has_humongous_reclaim_candidates; 325 326 volatile unsigned _gc_time_stamp; 327 328 size_t* _surviving_young_words; 329 330 G1HRPrinter _hr_printer; 331 332 void setup_surviving_young_words(); 333 void update_surviving_young_words(size_t* surv_young_words); 334 void cleanup_surviving_young_words(); 335 336 // It decides whether an explicit GC should start a concurrent cycle 337 // instead of doing a STW GC. Currently, a concurrent cycle is 338 // explicitly started if: 339 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 340 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 341 // (c) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 342 // (d) cause == _g1_humongous_allocation 343 bool should_do_concurrent_full_gc(GCCause::Cause cause); 344 345 // indicates whether we are in young or mixed GC mode 346 G1CollectorState _collector_state; 347 348 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 349 // concurrent cycles) we have started. 350 volatile uint _old_marking_cycles_started; 351 352 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 353 // concurrent cycles) we have completed. 354 volatile uint _old_marking_cycles_completed; 355 356 bool _heap_summary_sent; 357 358 // This is a non-product method that is helpful for testing. It is 359 // called at the end of a GC and artificially expands the heap by 360 // allocating a number of dead regions. This way we can induce very 361 // frequent marking cycles and stress the cleanup / concurrent 362 // cleanup code more (as all the regions that will be allocated by 363 // this method will be found dead by the marking cycle). 364 void allocate_dummy_regions() PRODUCT_RETURN; 365 366 // Clear RSets after a compaction. It also resets the GC time stamps. 367 void clear_rsets_post_compaction(); 368 369 // If the HR printer is active, dump the state of the regions in the 370 // heap after a compaction. 371 void print_hrm_post_compaction(); 372 373 // Create a memory mapper for auxiliary data structures of the given size and 374 // translation factor. 375 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 376 size_t size, 377 size_t translation_factor); 378 379 double verify(bool guard, const char* msg); 380 void verify_before_gc(); 381 void verify_after_gc(); 382 383 void log_gc_header(); 384 void log_gc_footer(double pause_time_sec); 385 386 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 387 388 // These are macros so that, if the assert fires, we get the correct 389 // line number, file, etc. 390 391 #define heap_locking_asserts_err_msg(_extra_message_) \ 392 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 393 (_extra_message_), \ 394 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 395 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 396 BOOL_TO_STR(Thread::current()->is_VM_thread())) 397 398 #define assert_heap_locked() \ 399 do { \ 400 assert(Heap_lock->owned_by_self(), \ 401 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 402 } while (0) 403 404 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 405 do { \ 406 assert(Heap_lock->owned_by_self() || \ 407 (SafepointSynchronize::is_at_safepoint() && \ 408 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 409 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 410 "should be at a safepoint")); \ 411 } while (0) 412 413 #define assert_heap_locked_and_not_at_safepoint() \ 414 do { \ 415 assert(Heap_lock->owned_by_self() && \ 416 !SafepointSynchronize::is_at_safepoint(), \ 417 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 418 "should not be at a safepoint")); \ 419 } while (0) 420 421 #define assert_heap_not_locked() \ 422 do { \ 423 assert(!Heap_lock->owned_by_self(), \ 424 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 425 } while (0) 426 427 #define assert_heap_not_locked_and_not_at_safepoint() \ 428 do { \ 429 assert(!Heap_lock->owned_by_self() && \ 430 !SafepointSynchronize::is_at_safepoint(), \ 431 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 432 "should not be at a safepoint")); \ 433 } while (0) 434 435 #define assert_at_safepoint(_should_be_vm_thread_) \ 436 do { \ 437 assert(SafepointSynchronize::is_at_safepoint() && \ 438 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 439 heap_locking_asserts_err_msg("should be at a safepoint")); \ 440 } while (0) 441 442 #define assert_not_at_safepoint() \ 443 do { \ 444 assert(!SafepointSynchronize::is_at_safepoint(), \ 445 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 446 } while (0) 447 448 protected: 449 450 // The young region list. 451 YoungList* _young_list; 452 453 // The current policy object for the collector. 454 G1CollectorPolicy* _g1_policy; 455 456 // This is the second level of trying to allocate a new region. If 457 // new_region() didn't find a region on the free_list, this call will 458 // check whether there's anything available on the 459 // secondary_free_list and/or wait for more regions to appear on 460 // that list, if _free_regions_coming is set. 461 HeapRegion* new_region_try_secondary_free_list(bool is_old); 462 463 // Try to allocate a single non-humongous HeapRegion sufficient for 464 // an allocation of the given word_size. If do_expand is true, 465 // attempt to expand the heap if necessary to satisfy the allocation 466 // request. If the region is to be used as an old region or for a 467 // humongous object, set is_old to true. If not, to false. 468 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 469 470 // Initialize a contiguous set of free regions of length num_regions 471 // and starting at index first so that they appear as a single 472 // humongous region. 473 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 474 uint num_regions, 475 size_t word_size, 476 AllocationContext_t context); 477 478 // Attempt to allocate a humongous object of the given size. Return 479 // NULL if unsuccessful. 480 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 481 482 // The following two methods, allocate_new_tlab() and 483 // mem_allocate(), are the two main entry points from the runtime 484 // into the G1's allocation routines. They have the following 485 // assumptions: 486 // 487 // * They should both be called outside safepoints. 488 // 489 // * They should both be called without holding the Heap_lock. 490 // 491 // * All allocation requests for new TLABs should go to 492 // allocate_new_tlab(). 493 // 494 // * All non-TLAB allocation requests should go to mem_allocate(). 495 // 496 // * If either call cannot satisfy the allocation request using the 497 // current allocating region, they will try to get a new one. If 498 // this fails, they will attempt to do an evacuation pause and 499 // retry the allocation. 500 // 501 // * If all allocation attempts fail, even after trying to schedule 502 // an evacuation pause, allocate_new_tlab() will return NULL, 503 // whereas mem_allocate() will attempt a heap expansion and/or 504 // schedule a Full GC. 505 // 506 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 507 // should never be called with word_size being humongous. All 508 // humongous allocation requests should go to mem_allocate() which 509 // will satisfy them with a special path. 510 511 virtual HeapWord* allocate_new_tlab(size_t word_size); 512 513 virtual HeapWord* mem_allocate(size_t word_size, 514 bool* gc_overhead_limit_was_exceeded); 515 516 // The following three methods take a gc_count_before_ret 517 // parameter which is used to return the GC count if the method 518 // returns NULL. Given that we are required to read the GC count 519 // while holding the Heap_lock, and these paths will take the 520 // Heap_lock at some point, it's easier to get them to read the GC 521 // count while holding the Heap_lock before they return NULL instead 522 // of the caller (namely: mem_allocate()) having to also take the 523 // Heap_lock just to read the GC count. 524 525 // First-level mutator allocation attempt: try to allocate out of 526 // the mutator alloc region without taking the Heap_lock. This 527 // should only be used for non-humongous allocations. 528 inline HeapWord* attempt_allocation(size_t word_size, 529 uint* gc_count_before_ret, 530 uint* gclocker_retry_count_ret); 531 532 // Second-level mutator allocation attempt: take the Heap_lock and 533 // retry the allocation attempt, potentially scheduling a GC 534 // pause. This should only be used for non-humongous allocations. 535 HeapWord* attempt_allocation_slow(size_t word_size, 536 AllocationContext_t context, 537 uint* gc_count_before_ret, 538 uint* gclocker_retry_count_ret); 539 540 // Takes the Heap_lock and attempts a humongous allocation. It can 541 // potentially schedule a GC pause. 542 HeapWord* attempt_allocation_humongous(size_t word_size, 543 uint* gc_count_before_ret, 544 uint* gclocker_retry_count_ret); 545 546 // Allocation attempt that should be called during safepoints (e.g., 547 // at the end of a successful GC). expect_null_mutator_alloc_region 548 // specifies whether the mutator alloc region is expected to be NULL 549 // or not. 550 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 551 AllocationContext_t context, 552 bool expect_null_mutator_alloc_region); 553 554 // It dirties the cards that cover the block so that so that the post 555 // write barrier never queues anything when updating objects on this 556 // block. It is assumed (and in fact we assert) that the block 557 // belongs to a young region. 558 inline void dirty_young_block(HeapWord* start, size_t word_size); 559 560 // Allocate blocks during garbage collection. Will ensure an 561 // allocation region, either by picking one or expanding the 562 // heap, and then allocate a block of the given size. The block 563 // may not be a humongous - it must fit into a single heap region. 564 inline HeapWord* par_allocate_during_gc(InCSetState dest, 565 size_t word_size, 566 AllocationContext_t context); 567 // Ensure that no further allocations can happen in "r", bearing in mind 568 // that parallel threads might be attempting allocations. 569 void par_allocate_remaining_space(HeapRegion* r); 570 571 // Allocation attempt during GC for a survivor object / PLAB. 572 inline HeapWord* survivor_attempt_allocation(size_t word_size, 573 AllocationContext_t context); 574 575 // Allocation attempt during GC for an old object / PLAB. 576 inline HeapWord* old_attempt_allocation(size_t word_size, 577 AllocationContext_t context); 578 579 // These methods are the "callbacks" from the G1AllocRegion class. 580 581 // For mutator alloc regions. 582 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 583 void retire_mutator_alloc_region(HeapRegion* alloc_region, 584 size_t allocated_bytes); 585 586 // For GC alloc regions. 587 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 588 InCSetState dest); 589 void retire_gc_alloc_region(HeapRegion* alloc_region, 590 size_t allocated_bytes, InCSetState dest); 591 592 // Allocate the highest free region in the reserved heap. This will commit 593 // regions as necessary. 594 HeapRegion* alloc_highest_free_region(); 595 596 // - if explicit_gc is true, the GC is for a System.gc() or a heap 597 // inspection request and should collect the entire heap 598 // - if clear_all_soft_refs is true, all soft references should be 599 // cleared during the GC 600 // - if explicit_gc is false, word_size describes the allocation that 601 // the GC should attempt (at least) to satisfy 602 // - it returns false if it is unable to do the collection due to the 603 // GC locker being active, true otherwise 604 bool do_collection(bool explicit_gc, 605 bool clear_all_soft_refs, 606 size_t word_size); 607 608 // Callback from VM_G1CollectFull operation. 609 // Perform a full collection. 610 virtual void do_full_collection(bool clear_all_soft_refs); 611 612 // Resize the heap if necessary after a full collection. If this is 613 // after a collect-for allocation, "word_size" is the allocation size, 614 // and will be considered part of the used portion of the heap. 615 void resize_if_necessary_after_full_collection(size_t word_size); 616 617 // Callback from VM_G1CollectForAllocation operation. 618 // This function does everything necessary/possible to satisfy a 619 // failed allocation request (including collection, expansion, etc.) 620 HeapWord* satisfy_failed_allocation(size_t word_size, 621 AllocationContext_t context, 622 bool* succeeded); 623 624 // Attempting to expand the heap sufficiently 625 // to support an allocation of the given "word_size". If 626 // successful, perform the allocation and return the address of the 627 // allocated block, or else "NULL". 628 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 629 630 // Process any reference objects discovered during 631 // an incremental evacuation pause. 632 void process_discovered_references(); 633 634 // Enqueue any remaining discovered references 635 // after processing. 636 void enqueue_discovered_references(); 637 638 public: 639 FlexibleWorkGang* workers() const { return _workers; } 640 641 G1Allocator* allocator() { 642 return _allocator; 643 } 644 645 G1MonitoringSupport* g1mm() { 646 assert(_g1mm != NULL, "should have been initialized"); 647 return _g1mm; 648 } 649 650 // Expand the garbage-first heap by at least the given size (in bytes!). 651 // Returns true if the heap was expanded by the requested amount; 652 // false otherwise. 653 // (Rounds up to a HeapRegion boundary.) 654 bool expand(size_t expand_bytes); 655 656 // Returns the PLAB statistics for a given destination. 657 inline PLABStats* alloc_buffer_stats(InCSetState dest); 658 659 // Determines PLAB size for a given destination. 660 inline size_t desired_plab_sz(InCSetState dest); 661 662 inline AllocationContextStats& allocation_context_stats(); 663 664 // Do anything common to GC's. 665 void gc_prologue(bool full); 666 void gc_epilogue(bool full); 667 668 // Modify the reclaim candidate set and test for presence. 669 // These are only valid for starts_humongous regions. 670 inline void set_humongous_reclaim_candidate(uint region, bool value); 671 inline bool is_humongous_reclaim_candidate(uint region); 672 673 // Remove from the reclaim candidate set. Also remove from the 674 // collection set so that later encounters avoid the slow path. 675 inline void set_humongous_is_live(oop obj); 676 677 // Register the given region to be part of the collection set. 678 inline void register_humongous_region_with_cset(uint index); 679 // Register regions with humongous objects (actually on the start region) in 680 // the in_cset_fast_test table. 681 void register_humongous_regions_with_cset(); 682 // We register a region with the fast "in collection set" test. We 683 // simply set to true the array slot corresponding to this region. 684 void register_young_region_with_cset(HeapRegion* r) { 685 _in_cset_fast_test.set_in_young(r->hrm_index()); 686 } 687 void register_old_region_with_cset(HeapRegion* r) { 688 _in_cset_fast_test.set_in_old(r->hrm_index()); 689 } 690 void clear_in_cset(const HeapRegion* hr) { 691 _in_cset_fast_test.clear(hr); 692 } 693 694 void clear_cset_fast_test() { 695 _in_cset_fast_test.clear(); 696 } 697 698 // This is called at the start of either a concurrent cycle or a Full 699 // GC to update the number of old marking cycles started. 700 void increment_old_marking_cycles_started(); 701 702 // This is called at the end of either a concurrent cycle or a Full 703 // GC to update the number of old marking cycles completed. Those two 704 // can happen in a nested fashion, i.e., we start a concurrent 705 // cycle, a Full GC happens half-way through it which ends first, 706 // and then the cycle notices that a Full GC happened and ends 707 // too. The concurrent parameter is a boolean to help us do a bit 708 // tighter consistency checking in the method. If concurrent is 709 // false, the caller is the inner caller in the nesting (i.e., the 710 // Full GC). If concurrent is true, the caller is the outer caller 711 // in this nesting (i.e., the concurrent cycle). Further nesting is 712 // not currently supported. The end of this call also notifies 713 // the FullGCCount_lock in case a Java thread is waiting for a full 714 // GC to happen (e.g., it called System.gc() with 715 // +ExplicitGCInvokesConcurrent). 716 void increment_old_marking_cycles_completed(bool concurrent); 717 718 uint old_marking_cycles_completed() { 719 return _old_marking_cycles_completed; 720 } 721 722 void register_concurrent_cycle_start(const Ticks& start_time); 723 void register_concurrent_cycle_end(); 724 void trace_heap_after_concurrent_cycle(); 725 726 G1HRPrinter* hr_printer() { return &_hr_printer; } 727 728 // Frees a non-humongous region by initializing its contents and 729 // adding it to the free list that's passed as a parameter (this is 730 // usually a local list which will be appended to the master free 731 // list later). The used bytes of freed regions are accumulated in 732 // pre_used. If par is true, the region's RSet will not be freed 733 // up. The assumption is that this will be done later. 734 // The locked parameter indicates if the caller has already taken 735 // care of proper synchronization. This may allow some optimizations. 736 void free_region(HeapRegion* hr, 737 FreeRegionList* free_list, 738 bool par, 739 bool locked = false); 740 741 // Frees a humongous region by collapsing it into individual regions 742 // and calling free_region() for each of them. The freed regions 743 // will be added to the free list that's passed as a parameter (this 744 // is usually a local list which will be appended to the master free 745 // list later). The used bytes of freed regions are accumulated in 746 // pre_used. If par is true, the region's RSet will not be freed 747 // up. The assumption is that this will be done later. 748 void free_humongous_region(HeapRegion* hr, 749 FreeRegionList* free_list, 750 bool par); 751 752 // Facility for allocating in 'archive' regions in high heap memory and 753 // recording the allocated ranges. These should all be called from the 754 // VM thread at safepoints, without the heap lock held. They can be used 755 // to create and archive a set of heap regions which can be mapped at the 756 // same fixed addresses in a subsequent JVM invocation. 757 void begin_archive_alloc_range(); 758 759 // Check if the requested size would be too large for an archive allocation. 760 bool is_archive_alloc_too_large(size_t word_size); 761 762 // Allocate memory of the requested size from the archive region. This will 763 // return NULL if the size is too large or if no memory is available. It 764 // does not trigger a garbage collection. 765 HeapWord* archive_mem_allocate(size_t word_size); 766 767 // Optionally aligns the end address and returns the allocated ranges in 768 // an array of MemRegions in order of ascending addresses. 769 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 770 size_t end_alignment_in_bytes = 0); 771 772 // Facility for allocating a fixed range within the heap and marking 773 // the containing regions as 'archive'. For use at JVM init time, when the 774 // caller may mmap archived heap data at the specified range(s). 775 // Verify that the MemRegions specified in the argument array are within the 776 // reserved heap. 777 bool check_archive_addresses(MemRegion* range, size_t count); 778 779 // Commit the appropriate G1 regions containing the specified MemRegions 780 // and mark them as 'archive' regions. The regions in the array must be 781 // non-overlapping and in order of ascending address. 782 bool alloc_archive_regions(MemRegion* range, size_t count); 783 784 // Insert any required filler objects in the G1 regions around the specified 785 // ranges to make the regions parseable. This must be called after 786 // alloc_archive_regions, and after class loading has occurred. 787 void fill_archive_regions(MemRegion* range, size_t count); 788 789 // For each of the specified MemRegions, free the containing G1 regions 790 // which had been allocated by alloc_archive_regions. This should be called 791 // rather than fill_archive_regions at JVM init time if the archive file 792 // mapping failed. 793 void free_archive_regions(MemRegion* range, size_t count); 794 795 protected: 796 797 // Shrink the garbage-first heap by at most the given size (in bytes!). 798 // (Rounds down to a HeapRegion boundary.) 799 virtual void shrink(size_t expand_bytes); 800 void shrink_helper(size_t expand_bytes); 801 802 #if TASKQUEUE_STATS 803 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 804 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 805 void reset_taskqueue_stats(); 806 #endif // TASKQUEUE_STATS 807 808 // Schedule the VM operation that will do an evacuation pause to 809 // satisfy an allocation request of word_size. *succeeded will 810 // return whether the VM operation was successful (it did do an 811 // evacuation pause) or not (another thread beat us to it or the GC 812 // locker was active). Given that we should not be holding the 813 // Heap_lock when we enter this method, we will pass the 814 // gc_count_before (i.e., total_collections()) as a parameter since 815 // it has to be read while holding the Heap_lock. Currently, both 816 // methods that call do_collection_pause() release the Heap_lock 817 // before the call, so it's easy to read gc_count_before just before. 818 HeapWord* do_collection_pause(size_t word_size, 819 uint gc_count_before, 820 bool* succeeded, 821 GCCause::Cause gc_cause); 822 823 void wait_for_root_region_scanning(); 824 825 // The guts of the incremental collection pause, executed by the vm 826 // thread. It returns false if it is unable to do the collection due 827 // to the GC locker being active, true otherwise 828 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 829 830 // Actually do the work of evacuating the collection set. 831 void evacuate_collection_set(EvacuationInfo& evacuation_info); 832 833 // The g1 remembered set of the heap. 834 G1RemSet* _g1_rem_set; 835 836 // A set of cards that cover the objects for which the Rsets should be updated 837 // concurrently after the collection. 838 DirtyCardQueueSet _dirty_card_queue_set; 839 840 // The closure used to refine a single card. 841 RefineCardTableEntryClosure* _refine_cte_cl; 842 843 // A DirtyCardQueueSet that is used to hold cards that contain 844 // references into the current collection set. This is used to 845 // update the remembered sets of the regions in the collection 846 // set in the event of an evacuation failure. 847 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 848 849 // After a collection pause, make the regions in the CS into free 850 // regions. 851 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 852 853 // Abandon the current collection set without recording policy 854 // statistics or updating free lists. 855 void abandon_collection_set(HeapRegion* cs_head); 856 857 // The concurrent marker (and the thread it runs in.) 858 ConcurrentMark* _cm; 859 ConcurrentMarkThread* _cmThread; 860 861 // The concurrent refiner. 862 ConcurrentG1Refine* _cg1r; 863 864 // The parallel task queues 865 RefToScanQueueSet *_task_queues; 866 867 // True iff a evacuation has failed in the current collection. 868 bool _evacuation_failed; 869 870 EvacuationFailedInfo* _evacuation_failed_info_array; 871 872 // Failed evacuations cause some logical from-space objects to have 873 // forwarding pointers to themselves. Reset them. 874 void remove_self_forwarding_pointers(); 875 876 struct OopAndMarkOop { 877 private: 878 oop _o; 879 markOop _m; 880 public: 881 OopAndMarkOop(oop obj, markOop m) : _o(obj), _m(m) { 882 } 883 884 void set_mark() { 885 _o->set_mark(_m); 886 } 887 }; 888 889 typedef Stack<OopAndMarkOop,mtGC> OopAndMarkOopStack; 890 // Stores marks with the corresponding oop that we need to preserve during evacuation 891 // failure. 892 OopAndMarkOopStack* _preserved_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_during_evac_failure(uint queue, oop obj, markOop m); 897 898 #ifndef PRODUCT 899 // Support for forcing evacuation failures. Analogous to 900 // PromotionFailureALot for the other collectors. 901 902 // Records whether G1EvacuationFailureALot should be in effect 903 // for the current GC 904 bool _evacuation_failure_alot_for_current_gc; 905 906 // Used to record the GC number for interval checking when 907 // determining whether G1EvaucationFailureALot is in effect 908 // for the current GC. 909 size_t _evacuation_failure_alot_gc_number; 910 911 // Count of the number of evacuations between failures. 912 volatile size_t _evacuation_failure_alot_count; 913 914 // Set whether G1EvacuationFailureALot should be in effect 915 // for the current GC (based upon the type of GC and which 916 // command line flags are set); 917 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 918 bool during_initial_mark, 919 bool during_marking); 920 921 inline void set_evacuation_failure_alot_for_current_gc(); 922 923 // Return true if it's time to cause an evacuation failure. 924 inline bool evacuation_should_fail(); 925 926 // Reset the G1EvacuationFailureALot counters. Should be called at 927 // the end of an evacuation pause in which an evacuation failure occurred. 928 inline void reset_evacuation_should_fail(); 929 #endif // !PRODUCT 930 931 // ("Weak") Reference processing support. 932 // 933 // G1 has 2 instances of the reference processor class. One 934 // (_ref_processor_cm) handles reference object discovery 935 // and subsequent processing during concurrent marking cycles. 936 // 937 // The other (_ref_processor_stw) handles reference object 938 // discovery and processing during full GCs and incremental 939 // evacuation pauses. 940 // 941 // During an incremental pause, reference discovery will be 942 // temporarily disabled for _ref_processor_cm and will be 943 // enabled for _ref_processor_stw. At the end of the evacuation 944 // pause references discovered by _ref_processor_stw will be 945 // processed and discovery will be disabled. The previous 946 // setting for reference object discovery for _ref_processor_cm 947 // will be re-instated. 948 // 949 // At the start of marking: 950 // * Discovery by the CM ref processor is verified to be inactive 951 // and it's discovered lists are empty. 952 // * Discovery by the CM ref processor is then enabled. 953 // 954 // At the end of marking: 955 // * Any references on the CM ref processor's discovered 956 // lists are processed (possibly MT). 957 // 958 // At the start of full GC we: 959 // * Disable discovery by the CM ref processor and 960 // empty CM ref processor's discovered lists 961 // (without processing any entries). 962 // * Verify that the STW ref processor is inactive and it's 963 // discovered lists are empty. 964 // * Temporarily set STW ref processor discovery as single threaded. 965 // * Temporarily clear the STW ref processor's _is_alive_non_header 966 // field. 967 // * Finally enable discovery by the STW ref processor. 968 // 969 // The STW ref processor is used to record any discovered 970 // references during the full GC. 971 // 972 // At the end of a full GC we: 973 // * Enqueue any reference objects discovered by the STW ref processor 974 // that have non-live referents. This has the side-effect of 975 // making the STW ref processor inactive by disabling discovery. 976 // * Verify that the CM ref processor is still inactive 977 // and no references have been placed on it's discovered 978 // lists (also checked as a precondition during initial marking). 979 980 // The (stw) reference processor... 981 ReferenceProcessor* _ref_processor_stw; 982 983 STWGCTimer* _gc_timer_stw; 984 ConcurrentGCTimer* _gc_timer_cm; 985 986 G1OldTracer* _gc_tracer_cm; 987 G1NewTracer* _gc_tracer_stw; 988 989 // During reference object discovery, the _is_alive_non_header 990 // closure (if non-null) is applied to the referent object to 991 // determine whether the referent is live. If so then the 992 // reference object does not need to be 'discovered' and can 993 // be treated as a regular oop. This has the benefit of reducing 994 // the number of 'discovered' reference objects that need to 995 // be processed. 996 // 997 // Instance of the is_alive closure for embedding into the 998 // STW reference processor as the _is_alive_non_header field. 999 // Supplying a value for the _is_alive_non_header field is 1000 // optional but doing so prevents unnecessary additions to 1001 // the discovered lists during reference discovery. 1002 G1STWIsAliveClosure _is_alive_closure_stw; 1003 1004 // The (concurrent marking) reference processor... 1005 ReferenceProcessor* _ref_processor_cm; 1006 1007 // Instance of the concurrent mark is_alive closure for embedding 1008 // into the Concurrent Marking reference processor as the 1009 // _is_alive_non_header field. Supplying a value for the 1010 // _is_alive_non_header field is optional but doing so prevents 1011 // unnecessary additions to the discovered lists during reference 1012 // discovery. 1013 G1CMIsAliveClosure _is_alive_closure_cm; 1014 1015 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 1016 HeapRegion** _worker_cset_start_region; 1017 1018 // Time stamp to validate the regions recorded in the cache 1019 // used by G1CollectedHeap::start_cset_region_for_worker(). 1020 // The heap region entry for a given worker is valid iff 1021 // the associated time stamp value matches the current value 1022 // of G1CollectedHeap::_gc_time_stamp. 1023 uint* _worker_cset_start_region_time_stamp; 1024 1025 volatile bool _free_regions_coming; 1026 1027 public: 1028 1029 void set_refine_cte_cl_concurrency(bool concurrent); 1030 1031 RefToScanQueue *task_queue(uint i) const; 1032 1033 uint num_task_queues() const; 1034 1035 // A set of cards where updates happened during the GC 1036 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1037 1038 // A DirtyCardQueueSet that is used to hold cards that contain 1039 // references into the current collection set. This is used to 1040 // update the remembered sets of the regions in the collection 1041 // set in the event of an evacuation failure. 1042 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1043 { return _into_cset_dirty_card_queue_set; } 1044 1045 // Create a G1CollectedHeap with the specified policy. 1046 // Must call the initialize method afterwards. 1047 // May not return if something goes wrong. 1048 G1CollectedHeap(G1CollectorPolicy* policy); 1049 1050 // Initialize the G1CollectedHeap to have the initial and 1051 // maximum sizes and remembered and barrier sets 1052 // specified by the policy object. 1053 jint initialize(); 1054 1055 virtual void stop(); 1056 1057 // Return the (conservative) maximum heap alignment for any G1 heap 1058 static size_t conservative_max_heap_alignment(); 1059 1060 // Does operations required after initialization has been done. 1061 void post_initialize(); 1062 1063 // Initialize weak reference processing. 1064 void ref_processing_init(); 1065 1066 virtual Name kind() const { 1067 return CollectedHeap::G1CollectedHeap; 1068 } 1069 1070 G1CollectorState* collector_state() { return &_collector_state; } 1071 1072 // The current policy object for the collector. 1073 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1074 1075 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1076 1077 // Adaptive size policy. No such thing for g1. 1078 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1079 1080 // The rem set and barrier set. 1081 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1082 1083 unsigned get_gc_time_stamp() { 1084 return _gc_time_stamp; 1085 } 1086 1087 inline void reset_gc_time_stamp(); 1088 1089 void check_gc_time_stamps() PRODUCT_RETURN; 1090 1091 inline void increment_gc_time_stamp(); 1092 1093 // Reset the given region's GC timestamp. If it's starts humongous, 1094 // also reset the GC timestamp of its corresponding 1095 // continues humongous regions too. 1096 void reset_gc_time_stamps(HeapRegion* hr); 1097 1098 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1099 DirtyCardQueue* into_cset_dcq, 1100 bool concurrent, uint worker_i); 1101 1102 // The shared block offset table array. 1103 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1104 1105 // Reference Processing accessors 1106 1107 // The STW reference processor.... 1108 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1109 1110 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1111 1112 // The Concurrent Marking reference processor... 1113 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1114 1115 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1116 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1117 1118 virtual size_t capacity() const; 1119 virtual size_t used() const; 1120 // This should be called when we're not holding the heap lock. The 1121 // result might be a bit inaccurate. 1122 size_t used_unlocked() const; 1123 size_t recalculate_used() const; 1124 1125 // These virtual functions do the actual allocation. 1126 // Some heaps may offer a contiguous region for shared non-blocking 1127 // allocation, via inlined code (by exporting the address of the top and 1128 // end fields defining the extent of the contiguous allocation region.) 1129 // But G1CollectedHeap doesn't yet support this. 1130 1131 virtual bool is_maximal_no_gc() const { 1132 return _hrm.available() == 0; 1133 } 1134 1135 // The current number of regions in the heap. 1136 uint num_regions() const { return _hrm.length(); } 1137 1138 // The max number of regions in the heap. 1139 uint max_regions() const { return _hrm.max_length(); } 1140 1141 // The number of regions that are completely free. 1142 uint num_free_regions() const { return _hrm.num_free_regions(); } 1143 1144 MemoryUsage get_auxiliary_data_memory_usage() const { 1145 return _hrm.get_auxiliary_data_memory_usage(); 1146 } 1147 1148 // The number of regions that are not completely free. 1149 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1150 1151 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1152 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1153 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1154 void verify_dirty_young_regions() PRODUCT_RETURN; 1155 1156 #ifndef PRODUCT 1157 // Make sure that the given bitmap has no marked objects in the 1158 // range [from,limit). If it does, print an error message and return 1159 // false. Otherwise, just return true. bitmap_name should be "prev" 1160 // or "next". 1161 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1162 HeapWord* from, HeapWord* limit); 1163 1164 // Verify that the prev / next bitmap range [tams,end) for the given 1165 // region has no marks. Return true if all is well, false if errors 1166 // are detected. 1167 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1168 #endif // PRODUCT 1169 1170 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1171 // the given region do not have any spurious marks. If errors are 1172 // detected, print appropriate error messages and crash. 1173 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1174 1175 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1176 // have any spurious marks. If errors are detected, print 1177 // appropriate error messages and crash. 1178 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1179 1180 // Do sanity check on the contents of the in-cset fast test table. 1181 bool check_cset_fast_test() PRODUCT_RETURN_( return true; ); 1182 1183 // verify_region_sets() performs verification over the region 1184 // lists. It will be compiled in the product code to be used when 1185 // necessary (i.e., during heap verification). 1186 void verify_region_sets(); 1187 1188 // verify_region_sets_optional() is planted in the code for 1189 // list verification in non-product builds (and it can be enabled in 1190 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1191 #if HEAP_REGION_SET_FORCE_VERIFY 1192 void verify_region_sets_optional() { 1193 verify_region_sets(); 1194 } 1195 #else // HEAP_REGION_SET_FORCE_VERIFY 1196 void verify_region_sets_optional() { } 1197 #endif // HEAP_REGION_SET_FORCE_VERIFY 1198 1199 #ifdef ASSERT 1200 bool is_on_master_free_list(HeapRegion* hr) { 1201 return _hrm.is_free(hr); 1202 } 1203 #endif // ASSERT 1204 1205 // Wrapper for the region list operations that can be called from 1206 // methods outside this class. 1207 1208 void secondary_free_list_add(FreeRegionList* list) { 1209 _secondary_free_list.add_ordered(list); 1210 } 1211 1212 void append_secondary_free_list() { 1213 _hrm.insert_list_into_free_list(&_secondary_free_list); 1214 } 1215 1216 void append_secondary_free_list_if_not_empty_with_lock() { 1217 // If the secondary free list looks empty there's no reason to 1218 // take the lock and then try to append it. 1219 if (!_secondary_free_list.is_empty()) { 1220 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1221 append_secondary_free_list(); 1222 } 1223 } 1224 1225 inline void old_set_remove(HeapRegion* hr); 1226 1227 size_t non_young_capacity_bytes() { 1228 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1229 } 1230 1231 void set_free_regions_coming(); 1232 void reset_free_regions_coming(); 1233 bool free_regions_coming() { return _free_regions_coming; } 1234 void wait_while_free_regions_coming(); 1235 1236 // Determine whether the given region is one that we are using as an 1237 // old GC alloc region. 1238 bool is_old_gc_alloc_region(HeapRegion* hr) { 1239 return _allocator->is_retained_old_region(hr); 1240 } 1241 1242 // Perform a collection of the heap; intended for use in implementing 1243 // "System.gc". This probably implies as full a collection as the 1244 // "CollectedHeap" supports. 1245 virtual void collect(GCCause::Cause cause); 1246 1247 // The same as above but assume that the caller holds the Heap_lock. 1248 void collect_locked(GCCause::Cause cause); 1249 1250 virtual bool copy_allocation_context_stats(const jint* contexts, 1251 jlong* totals, 1252 jbyte* accuracy, 1253 jint len); 1254 1255 // True iff an evacuation has failed in the most-recent collection. 1256 bool evacuation_failed() { return _evacuation_failed; } 1257 1258 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1259 void prepend_to_freelist(FreeRegionList* list); 1260 void decrement_summary_bytes(size_t bytes); 1261 1262 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1263 virtual bool is_in(const void* p) const; 1264 #ifdef ASSERT 1265 // Returns whether p is in one of the available areas of the heap. Slow but 1266 // extensive version. 1267 bool is_in_exact(const void* p) const; 1268 #endif 1269 1270 // Return "TRUE" iff the given object address is within the collection 1271 // set. Slow implementation. 1272 inline bool obj_in_cs(oop obj); 1273 1274 inline bool is_in_cset(const HeapRegion *hr); 1275 inline bool is_in_cset(oop obj); 1276 1277 inline bool is_in_cset_or_humongous(const oop obj); 1278 1279 private: 1280 // This array is used for a quick test on whether a reference points into 1281 // the collection set or not. Each of the array's elements denotes whether the 1282 // corresponding region is in the collection set or not. 1283 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1284 1285 public: 1286 1287 inline InCSetState in_cset_state(const oop obj); 1288 1289 // Return "TRUE" iff the given object address is in the reserved 1290 // region of g1. 1291 bool is_in_g1_reserved(const void* p) const { 1292 return _hrm.reserved().contains(p); 1293 } 1294 1295 // Returns a MemRegion that corresponds to the space that has been 1296 // reserved for the heap 1297 MemRegion g1_reserved() const { 1298 return _hrm.reserved(); 1299 } 1300 1301 virtual bool is_in_closed_subset(const void* p) const; 1302 1303 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1304 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1305 } 1306 1307 // This resets the card table to all zeros. It is used after 1308 // a collection pause which used the card table to claim cards. 1309 void cleanUpCardTable(); 1310 1311 // Iteration functions. 1312 1313 // Iterate over all objects, calling "cl.do_object" on each. 1314 virtual void object_iterate(ObjectClosure* cl); 1315 1316 virtual void safe_object_iterate(ObjectClosure* cl) { 1317 object_iterate(cl); 1318 } 1319 1320 // Iterate over heap regions, in address order, terminating the 1321 // iteration early if the "doHeapRegion" method returns "true". 1322 void heap_region_iterate(HeapRegionClosure* blk) const; 1323 1324 // Return the region with the given index. It assumes the index is valid. 1325 inline HeapRegion* region_at(uint index) const; 1326 1327 // Calculate the region index of the given address. Given address must be 1328 // within the heap. 1329 inline uint addr_to_region(HeapWord* addr) const; 1330 1331 inline HeapWord* bottom_addr_for_region(uint index) const; 1332 1333 // Iterate over the heap regions in parallel. Assumes that this will be called 1334 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1335 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1336 // to each of the regions, by attempting to claim the region using the 1337 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1338 // region. The concurrent argument should be set to true if iteration is 1339 // performed concurrently, during which no assumptions are made for consistent 1340 // attributes of the heap regions (as they might be modified while iterating). 1341 void heap_region_par_iterate(HeapRegionClosure* cl, 1342 uint worker_id, 1343 HeapRegionClaimer* hrclaimer, 1344 bool concurrent = false) const; 1345 1346 // Clear the cached cset start regions and (more importantly) 1347 // the time stamps. Called when we reset the GC time stamp. 1348 void clear_cset_start_regions(); 1349 1350 // Given the id of a worker, obtain or calculate a suitable 1351 // starting region for iterating over the current collection set. 1352 HeapRegion* start_cset_region_for_worker(uint worker_i); 1353 1354 // Iterate over the regions (if any) in the current collection set. 1355 void collection_set_iterate(HeapRegionClosure* blk); 1356 1357 // As above but starting from region r 1358 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1359 1360 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1361 1362 // Returns the HeapRegion that contains addr. addr must not be NULL. 1363 template <class T> 1364 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1365 1366 // Returns the HeapRegion that contains addr. addr must not be NULL. 1367 // If addr is within a humongous continues region, it returns its humongous start region. 1368 template <class T> 1369 inline HeapRegion* heap_region_containing(const T addr) const; 1370 1371 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1372 // each address in the (reserved) heap is a member of exactly 1373 // one block. The defining characteristic of a block is that it is 1374 // possible to find its size, and thus to progress forward to the next 1375 // block. (Blocks may be of different sizes.) Thus, blocks may 1376 // represent Java objects, or they might be free blocks in a 1377 // free-list-based heap (or subheap), as long as the two kinds are 1378 // distinguishable and the size of each is determinable. 1379 1380 // Returns the address of the start of the "block" that contains the 1381 // address "addr". We say "blocks" instead of "object" since some heaps 1382 // may not pack objects densely; a chunk may either be an object or a 1383 // non-object. 1384 virtual HeapWord* block_start(const void* addr) const; 1385 1386 // Requires "addr" to be the start of a chunk, and returns its size. 1387 // "addr + size" is required to be the start of a new chunk, or the end 1388 // of the active area of the heap. 1389 virtual size_t block_size(const HeapWord* addr) const; 1390 1391 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1392 // the block is an object. 1393 virtual bool block_is_obj(const HeapWord* addr) const; 1394 1395 // Section on thread-local allocation buffers (TLABs) 1396 // See CollectedHeap for semantics. 1397 1398 bool supports_tlab_allocation() const; 1399 size_t tlab_capacity(Thread* ignored) const; 1400 size_t tlab_used(Thread* ignored) const; 1401 size_t max_tlab_size() const; 1402 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1403 1404 // Can a compiler initialize a new object without store barriers? 1405 // This permission only extends from the creation of a new object 1406 // via a TLAB up to the first subsequent safepoint. If such permission 1407 // is granted for this heap type, the compiler promises to call 1408 // defer_store_barrier() below on any slow path allocation of 1409 // a new object for which such initializing store barriers will 1410 // have been elided. G1, like CMS, allows this, but should be 1411 // ready to provide a compensating write barrier as necessary 1412 // if that storage came out of a non-young region. The efficiency 1413 // of this implementation depends crucially on being able to 1414 // answer very efficiently in constant time whether a piece of 1415 // storage in the heap comes from a young region or not. 1416 // See ReduceInitialCardMarks. 1417 virtual bool can_elide_tlab_store_barriers() const { 1418 return true; 1419 } 1420 1421 virtual bool card_mark_must_follow_store() const { 1422 return true; 1423 } 1424 1425 inline bool is_in_young(const oop obj); 1426 1427 virtual bool is_scavengable(const void* addr); 1428 1429 // We don't need barriers for initializing stores to objects 1430 // in the young gen: for the SATB pre-barrier, there is no 1431 // pre-value that needs to be remembered; for the remembered-set 1432 // update logging post-barrier, we don't maintain remembered set 1433 // information for young gen objects. 1434 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1435 1436 // Returns "true" iff the given word_size is "very large". 1437 static bool is_humongous(size_t word_size) { 1438 // Note this has to be strictly greater-than as the TLABs 1439 // are capped at the humongous threshold and we want to 1440 // ensure that we don't try to allocate a TLAB as 1441 // humongous and that we don't allocate a humongous 1442 // object in a TLAB. 1443 return word_size > _humongous_object_threshold_in_words; 1444 } 1445 1446 // Returns the humongous threshold for a specific region size 1447 static size_t humongous_threshold_for(size_t region_size) { 1448 return (region_size / 2); 1449 } 1450 1451 // Update mod union table with the set of dirty cards. 1452 void updateModUnion(); 1453 1454 // Set the mod union bits corresponding to the given memRegion. Note 1455 // that this is always a safe operation, since it doesn't clear any 1456 // bits. 1457 void markModUnionRange(MemRegion mr); 1458 1459 // Print the maximum heap capacity. 1460 virtual size_t max_capacity() const; 1461 1462 virtual jlong millis_since_last_gc(); 1463 1464 1465 // Convenience function to be used in situations where the heap type can be 1466 // asserted to be this type. 1467 static G1CollectedHeap* heap(); 1468 1469 void set_region_short_lived_locked(HeapRegion* hr); 1470 // add appropriate methods for any other surv rate groups 1471 1472 YoungList* young_list() const { return _young_list; } 1473 1474 // debugging 1475 bool check_young_list_well_formed() { 1476 return _young_list->check_list_well_formed(); 1477 } 1478 1479 bool check_young_list_empty(bool check_heap, 1480 bool check_sample = true); 1481 1482 // *** Stuff related to concurrent marking. It's not clear to me that so 1483 // many of these need to be public. 1484 1485 // The functions below are helper functions that a subclass of 1486 // "CollectedHeap" can use in the implementation of its virtual 1487 // functions. 1488 // This performs a concurrent marking of the live objects in a 1489 // bitmap off to the side. 1490 void doConcurrentMark(); 1491 1492 bool isMarkedPrev(oop obj) const; 1493 bool isMarkedNext(oop obj) const; 1494 1495 // Determine if an object is dead, given the object and also 1496 // the region to which the object belongs. An object is dead 1497 // iff a) it was not allocated since the last mark, b) it 1498 // is not marked, and c) it is not in an archive region. 1499 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1500 return 1501 !hr->obj_allocated_since_prev_marking(obj) && 1502 !isMarkedPrev(obj) && 1503 !hr->is_archive(); 1504 } 1505 1506 // This function returns true when an object has been 1507 // around since the previous marking and hasn't yet 1508 // been marked during this marking, and is not in an archive region. 1509 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1510 return 1511 !hr->obj_allocated_since_next_marking(obj) && 1512 !isMarkedNext(obj) && 1513 !hr->is_archive(); 1514 } 1515 1516 // Determine if an object is dead, given only the object itself. 1517 // This will find the region to which the object belongs and 1518 // then call the region version of the same function. 1519 1520 // Added if it is NULL it isn't dead. 1521 1522 inline bool is_obj_dead(const oop obj) const; 1523 1524 inline bool is_obj_ill(const oop obj) const; 1525 1526 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1527 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1528 bool is_marked(oop obj, VerifyOption vo); 1529 const char* top_at_mark_start_str(VerifyOption vo); 1530 1531 ConcurrentMark* concurrent_mark() const { return _cm; } 1532 1533 // Refinement 1534 1535 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1536 1537 // The dirty cards region list is used to record a subset of regions 1538 // whose cards need clearing. The list if populated during the 1539 // remembered set scanning and drained during the card table 1540 // cleanup. Although the methods are reentrant, population/draining 1541 // phases must not overlap. For synchronization purposes the last 1542 // element on the list points to itself. 1543 HeapRegion* _dirty_cards_region_list; 1544 void push_dirty_cards_region(HeapRegion* hr); 1545 HeapRegion* pop_dirty_cards_region(); 1546 1547 // Optimized nmethod scanning support routines 1548 1549 // Register the given nmethod with the G1 heap. 1550 virtual void register_nmethod(nmethod* nm); 1551 1552 // Unregister the given nmethod from the G1 heap. 1553 virtual void unregister_nmethod(nmethod* nm); 1554 1555 // Free up superfluous code root memory. 1556 void purge_code_root_memory(); 1557 1558 // Rebuild the strong code root lists for each region 1559 // after a full GC. 1560 void rebuild_strong_code_roots(); 1561 1562 // Delete entries for dead interned string and clean up unreferenced symbols 1563 // in symbol table, possibly in parallel. 1564 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1565 1566 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1567 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1568 1569 // Redirty logged cards in the refinement queue. 1570 void redirty_logged_cards(); 1571 // Verification 1572 1573 // Perform any cleanup actions necessary before allowing a verification. 1574 virtual void prepare_for_verify(); 1575 1576 // Perform verification. 1577 1578 // vo == UsePrevMarking -> use "prev" marking information, 1579 // vo == UseNextMarking -> use "next" marking information 1580 // vo == UseMarkWord -> use the mark word in the object header 1581 // 1582 // NOTE: Only the "prev" marking information is guaranteed to be 1583 // consistent most of the time, so most calls to this should use 1584 // vo == UsePrevMarking. 1585 // Currently, there is only one case where this is called with 1586 // vo == UseNextMarking, which is to verify the "next" marking 1587 // information at the end of remark. 1588 // Currently there is only one place where this is called with 1589 // vo == UseMarkWord, which is to verify the marking during a 1590 // full GC. 1591 void verify(bool silent, VerifyOption vo); 1592 1593 // Override; it uses the "prev" marking information 1594 virtual void verify(bool silent); 1595 1596 // The methods below are here for convenience and dispatch the 1597 // appropriate method depending on value of the given VerifyOption 1598 // parameter. The values for that parameter, and their meanings, 1599 // are the same as those above. 1600 1601 bool is_obj_dead_cond(const oop obj, 1602 const HeapRegion* hr, 1603 const VerifyOption vo) const; 1604 1605 bool is_obj_dead_cond(const oop obj, 1606 const VerifyOption vo) const; 1607 1608 G1HeapSummary create_g1_heap_summary(); 1609 1610 // Printing 1611 1612 virtual void print_on(outputStream* st) const; 1613 virtual void print_extended_on(outputStream* st) const; 1614 virtual void print_on_error(outputStream* st) const; 1615 1616 virtual void print_gc_threads_on(outputStream* st) const; 1617 virtual void gc_threads_do(ThreadClosure* tc) const; 1618 1619 // Override 1620 void print_tracing_info() const; 1621 1622 // The following two methods are helpful for debugging RSet issues. 1623 void print_cset_rsets() PRODUCT_RETURN; 1624 void print_all_rsets() PRODUCT_RETURN; 1625 1626 public: 1627 size_t pending_card_num(); 1628 size_t cards_scanned(); 1629 1630 protected: 1631 size_t _max_heap_capacity; 1632 }; 1633 1634 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP