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/g1HRPrinter.hpp" 35 #include "gc_implementation/g1/g1InCSetState.hpp" 36 #include "gc_implementation/g1/g1MonitoringSupport.hpp" 37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 38 #include "gc_implementation/g1/g1YCTypes.hpp" 39 #include "gc_implementation/g1/heapRegionManager.hpp" 40 #include "gc_implementation/g1/heapRegionSet.hpp" 41 #include "gc_implementation/shared/hSpaceCounters.hpp" 42 #include "gc_implementation/shared/parGCAllocBuffer.hpp" 43 #include "memory/barrierSet.hpp" 44 #include "memory/memRegion.hpp" 45 #include "memory/sharedHeap.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 ObjectClosure; 60 class SpaceClosure; 61 class CompactibleSpaceClosure; 62 class Space; 63 class G1CollectorPolicy; 64 class GenRemSet; 65 class G1RemSet; 66 class HeapRegionRemSetIterator; 67 class ConcurrentMark; 68 class ConcurrentMarkThread; 69 class ConcurrentG1Refine; 70 class ConcurrentGCTimer; 71 class GenerationCounters; 72 class STWGCTimer; 73 class G1NewTracer; 74 class G1OldTracer; 75 class EvacuationFailedInfo; 76 class nmethod; 77 class Ticks; 78 79 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 80 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 81 82 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 83 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 84 85 class YoungList : public CHeapObj<mtGC> { 86 private: 87 G1CollectedHeap* _g1h; 88 89 HeapRegion* _head; 90 91 HeapRegion* _survivor_head; 92 HeapRegion* _survivor_tail; 93 94 HeapRegion* _curr; 95 96 uint _length; 97 uint _survivor_length; 98 99 size_t _last_sampled_rs_lengths; 100 size_t _sampled_rs_lengths; 101 102 void empty_list(HeapRegion* list); 103 104 public: 105 YoungList(G1CollectedHeap* g1h); 106 107 void push_region(HeapRegion* hr); 108 void add_survivor_region(HeapRegion* hr); 109 110 void empty_list(); 111 bool is_empty() { return _length == 0; } 112 uint length() { return _length; } 113 uint survivor_length() { return _survivor_length; } 114 115 // Currently we do not keep track of the used byte sum for the 116 // young list and the survivors and it'd be quite a lot of work to 117 // do so. When we'll eventually replace the young list with 118 // instances of HeapRegionLinkedList we'll get that for free. So, 119 // we'll report the more accurate information then. 120 size_t eden_used_bytes() { 121 assert(length() >= survivor_length(), "invariant"); 122 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes; 123 } 124 size_t survivor_used_bytes() { 125 return (size_t) survivor_length() * HeapRegion::GrainBytes; 126 } 127 128 void rs_length_sampling_init(); 129 bool rs_length_sampling_more(); 130 void rs_length_sampling_next(); 131 132 void reset_sampled_info() { 133 _last_sampled_rs_lengths = 0; 134 } 135 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } 136 137 // for development purposes 138 void reset_auxilary_lists(); 139 void clear() { _head = NULL; _length = 0; } 140 141 void clear_survivors() { 142 _survivor_head = NULL; 143 _survivor_tail = NULL; 144 _survivor_length = 0; 145 } 146 147 HeapRegion* first_region() { return _head; } 148 HeapRegion* first_survivor_region() { return _survivor_head; } 149 HeapRegion* last_survivor_region() { return _survivor_tail; } 150 151 // debugging 152 bool check_list_well_formed(); 153 bool check_list_empty(bool check_sample = true); 154 void print(); 155 }; 156 157 // The G1 STW is alive closure. 158 // An instance is embedded into the G1CH and used as the 159 // (optional) _is_alive_non_header closure in the STW 160 // reference processor. It is also extensively used during 161 // reference processing during STW evacuation pauses. 162 class G1STWIsAliveClosure: public BoolObjectClosure { 163 G1CollectedHeap* _g1; 164 public: 165 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 166 bool do_object_b(oop p); 167 }; 168 169 class RefineCardTableEntryClosure; 170 171 class G1RegionMappingChangedListener : public G1MappingChangedListener { 172 private: 173 void reset_from_card_cache(uint start_idx, size_t num_regions); 174 public: 175 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 176 }; 177 178 class G1CollectedHeap : public SharedHeap { 179 friend class VM_CollectForMetadataAllocation; 180 friend class VM_G1CollectForAllocation; 181 friend class VM_G1CollectFull; 182 friend class VM_G1IncCollectionPause; 183 friend class VMStructs; 184 friend class MutatorAllocRegion; 185 friend class SurvivorGCAllocRegion; 186 friend class OldGCAllocRegion; 187 friend class G1Allocator; 188 189 // Closures used in implementation. 190 friend class G1ParScanThreadState; 191 friend class G1ParTask; 192 friend class G1ParGCAllocator; 193 friend class G1PrepareCompactClosure; 194 195 // Other related classes. 196 friend class HeapRegionClaimer; 197 198 // Testing classes. 199 friend class G1CheckCSetFastTableClosure; 200 201 private: 202 // The one and only G1CollectedHeap, so static functions can find it. 203 static G1CollectedHeap* _g1h; 204 205 static size_t _humongous_object_threshold_in_words; 206 207 // The secondary free list which contains regions that have been 208 // freed up during the cleanup process. This will be appended to 209 // the master free list when appropriate. 210 FreeRegionList _secondary_free_list; 211 212 // It keeps track of the old regions. 213 HeapRegionSet _old_set; 214 215 // It keeps track of the humongous regions. 216 HeapRegionSet _humongous_set; 217 218 void clear_humongous_is_live_table(); 219 void eagerly_reclaim_humongous_regions(); 220 221 // The number of regions we could create by expansion. 222 uint _expansion_regions; 223 224 // The block offset table for the G1 heap. 225 G1BlockOffsetSharedArray* _bot_shared; 226 227 // Tears down the region sets / lists so that they are empty and the 228 // regions on the heap do not belong to a region set / list. The 229 // only exception is the humongous set which we leave unaltered. If 230 // free_list_only is true, it will only tear down the master free 231 // list. It is called before a Full GC (free_list_only == false) or 232 // before heap shrinking (free_list_only == true). 233 void tear_down_region_sets(bool free_list_only); 234 235 // Rebuilds the region sets / lists so that they are repopulated to 236 // reflect the contents of the heap. The only exception is the 237 // humongous set which was not torn down in the first place. If 238 // free_list_only is true, it will only rebuild the master free 239 // list. It is called after a Full GC (free_list_only == false) or 240 // after heap shrinking (free_list_only == true). 241 void rebuild_region_sets(bool free_list_only); 242 243 // Callback for region mapping changed events. 244 G1RegionMappingChangedListener _listener; 245 246 // The sequence of all heap regions in the heap. 247 HeapRegionManager _hrm; 248 249 // Class that handles the different kinds of allocations. 250 G1Allocator* _allocator; 251 252 // Statistics for each allocation context 253 AllocationContextStats _allocation_context_stats; 254 255 // PLAB sizing policy for survivors. 256 PLABStats _survivor_plab_stats; 257 258 // PLAB sizing policy for tenured objects. 259 PLABStats _old_plab_stats; 260 261 // It specifies whether we should attempt to expand the heap after a 262 // region allocation failure. If heap expansion fails we set this to 263 // false so that we don't re-attempt the heap expansion (it's likely 264 // that subsequent expansion attempts will also fail if one fails). 265 // Currently, it is only consulted during GC and it's reset at the 266 // start of each GC. 267 bool _expand_heap_after_alloc_failure; 268 269 // It resets the mutator alloc region before new allocations can take place. 270 void init_mutator_alloc_region(); 271 272 // It releases the mutator alloc region. 273 void release_mutator_alloc_region(); 274 275 // It initializes the GC alloc regions at the start of a GC. 276 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 277 278 // It releases the GC alloc regions at the end of a GC. 279 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 280 281 // It does any cleanup that needs to be done on the GC alloc regions 282 // before a Full GC. 283 void abandon_gc_alloc_regions(); 284 285 // Helper for monitoring and management support. 286 G1MonitoringSupport* _g1mm; 287 288 // Records whether the region at the given index is kept live by roots or 289 // references from the young generation. 290 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 291 protected: 292 bool default_value() const { return false; } 293 public: 294 void clear() { G1BiasedMappedArray<bool>::clear(); } 295 void set_live(uint region) { 296 set_by_index(region, true); 297 } 298 bool is_live(uint region) { 299 return get_by_index(region); 300 } 301 }; 302 303 HumongousIsLiveBiasedMappedArray _humongous_is_live; 304 // Stores whether during humongous object registration we found candidate regions. 305 // If not, we can skip a few steps. 306 bool _has_humongous_reclaim_candidates; 307 308 volatile unsigned _gc_time_stamp; 309 310 size_t* _surviving_young_words; 311 312 G1HRPrinter _hr_printer; 313 314 void setup_surviving_young_words(); 315 void update_surviving_young_words(size_t* surv_young_words); 316 void cleanup_surviving_young_words(); 317 318 // It decides whether an explicit GC should start a concurrent cycle 319 // instead of doing a STW GC. Currently, a concurrent cycle is 320 // explicitly started if: 321 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 322 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 323 // (c) cause == _g1_humongous_allocation 324 bool should_do_concurrent_full_gc(GCCause::Cause cause); 325 326 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 327 // concurrent cycles) we have started. 328 volatile unsigned int _old_marking_cycles_started; 329 330 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 331 // concurrent cycles) we have completed. 332 volatile unsigned int _old_marking_cycles_completed; 333 334 bool _concurrent_cycle_started; 335 bool _heap_summary_sent; 336 337 // This is a non-product method that is helpful for testing. It is 338 // called at the end of a GC and artificially expands the heap by 339 // allocating a number of dead regions. This way we can induce very 340 // frequent marking cycles and stress the cleanup / concurrent 341 // cleanup code more (as all the regions that will be allocated by 342 // this method will be found dead by the marking cycle). 343 void allocate_dummy_regions() PRODUCT_RETURN; 344 345 // Clear RSets after a compaction. It also resets the GC time stamps. 346 void clear_rsets_post_compaction(); 347 348 // If the HR printer is active, dump the state of the regions in the 349 // heap after a compaction. 350 void print_hrm_post_compaction(); 351 352 // Create a memory mapper for auxiliary data structures of the given size and 353 // translation factor. 354 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 355 size_t size, 356 size_t translation_factor); 357 358 double verify(bool guard, const char* msg); 359 void verify_before_gc(); 360 void verify_after_gc(); 361 362 void log_gc_header(); 363 void log_gc_footer(double pause_time_sec); 364 365 // These are macros so that, if the assert fires, we get the correct 366 // line number, file, etc. 367 368 #define heap_locking_asserts_err_msg(_extra_message_) \ 369 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 370 (_extra_message_), \ 371 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 372 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 373 BOOL_TO_STR(Thread::current()->is_VM_thread())) 374 375 #define assert_heap_locked() \ 376 do { \ 377 assert(Heap_lock->owned_by_self(), \ 378 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 379 } while (0) 380 381 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 382 do { \ 383 assert(Heap_lock->owned_by_self() || \ 384 (SafepointSynchronize::is_at_safepoint() && \ 385 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 386 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 387 "should be at a safepoint")); \ 388 } while (0) 389 390 #define assert_heap_locked_and_not_at_safepoint() \ 391 do { \ 392 assert(Heap_lock->owned_by_self() && \ 393 !SafepointSynchronize::is_at_safepoint(), \ 394 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 395 "should not be at a safepoint")); \ 396 } while (0) 397 398 #define assert_heap_not_locked() \ 399 do { \ 400 assert(!Heap_lock->owned_by_self(), \ 401 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 402 } while (0) 403 404 #define assert_heap_not_locked_and_not_at_safepoint() \ 405 do { \ 406 assert(!Heap_lock->owned_by_self() && \ 407 !SafepointSynchronize::is_at_safepoint(), \ 408 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 409 "should not be at a safepoint")); \ 410 } while (0) 411 412 #define assert_at_safepoint(_should_be_vm_thread_) \ 413 do { \ 414 assert(SafepointSynchronize::is_at_safepoint() && \ 415 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 416 heap_locking_asserts_err_msg("should be at a safepoint")); \ 417 } while (0) 418 419 #define assert_not_at_safepoint() \ 420 do { \ 421 assert(!SafepointSynchronize::is_at_safepoint(), \ 422 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 423 } while (0) 424 425 protected: 426 427 // The young region list. 428 YoungList* _young_list; 429 430 // The current policy object for the collector. 431 G1CollectorPolicy* _g1_policy; 432 433 // This is the second level of trying to allocate a new region. If 434 // new_region() didn't find a region on the free_list, this call will 435 // check whether there's anything available on the 436 // secondary_free_list and/or wait for more regions to appear on 437 // that list, if _free_regions_coming is set. 438 HeapRegion* new_region_try_secondary_free_list(bool is_old); 439 440 // Try to allocate a single non-humongous HeapRegion sufficient for 441 // an allocation of the given word_size. If do_expand is true, 442 // attempt to expand the heap if necessary to satisfy the allocation 443 // request. If the region is to be used as an old region or for a 444 // humongous object, set is_old to true. If not, to false. 445 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 446 447 // Initialize a contiguous set of free regions of length num_regions 448 // and starting at index first so that they appear as a single 449 // humongous region. 450 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 451 uint num_regions, 452 size_t word_size, 453 AllocationContext_t context); 454 455 // Attempt to allocate a humongous object of the given size. Return 456 // NULL if unsuccessful. 457 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 458 459 // The following two methods, allocate_new_tlab() and 460 // mem_allocate(), are the two main entry points from the runtime 461 // into the G1's allocation routines. They have the following 462 // assumptions: 463 // 464 // * They should both be called outside safepoints. 465 // 466 // * They should both be called without holding the Heap_lock. 467 // 468 // * All allocation requests for new TLABs should go to 469 // allocate_new_tlab(). 470 // 471 // * All non-TLAB allocation requests should go to mem_allocate(). 472 // 473 // * If either call cannot satisfy the allocation request using the 474 // current allocating region, they will try to get a new one. If 475 // this fails, they will attempt to do an evacuation pause and 476 // retry the allocation. 477 // 478 // * If all allocation attempts fail, even after trying to schedule 479 // an evacuation pause, allocate_new_tlab() will return NULL, 480 // whereas mem_allocate() will attempt a heap expansion and/or 481 // schedule a Full GC. 482 // 483 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 484 // should never be called with word_size being humongous. All 485 // humongous allocation requests should go to mem_allocate() which 486 // will satisfy them with a special path. 487 488 virtual HeapWord* allocate_new_tlab(size_t word_size); 489 490 virtual HeapWord* mem_allocate(size_t word_size, 491 bool* gc_overhead_limit_was_exceeded); 492 493 // The following three methods take a gc_count_before_ret 494 // parameter which is used to return the GC count if the method 495 // returns NULL. Given that we are required to read the GC count 496 // while holding the Heap_lock, and these paths will take the 497 // Heap_lock at some point, it's easier to get them to read the GC 498 // count while holding the Heap_lock before they return NULL instead 499 // of the caller (namely: mem_allocate()) having to also take the 500 // Heap_lock just to read the GC count. 501 502 // First-level mutator allocation attempt: try to allocate out of 503 // the mutator alloc region without taking the Heap_lock. This 504 // should only be used for non-humongous allocations. 505 inline HeapWord* attempt_allocation(size_t word_size, 506 unsigned int* gc_count_before_ret, 507 int* gclocker_retry_count_ret); 508 509 // Second-level mutator allocation attempt: take the Heap_lock and 510 // retry the allocation attempt, potentially scheduling a GC 511 // pause. This should only be used for non-humongous allocations. 512 HeapWord* attempt_allocation_slow(size_t word_size, 513 AllocationContext_t context, 514 unsigned int* gc_count_before_ret, 515 int* gclocker_retry_count_ret); 516 517 // Takes the Heap_lock and attempts a humongous allocation. It can 518 // potentially schedule a GC pause. 519 HeapWord* attempt_allocation_humongous(size_t word_size, 520 unsigned int* gc_count_before_ret, 521 int* gclocker_retry_count_ret); 522 523 // Allocation attempt that should be called during safepoints (e.g., 524 // at the end of a successful GC). expect_null_mutator_alloc_region 525 // specifies whether the mutator alloc region is expected to be NULL 526 // or not. 527 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 528 AllocationContext_t context, 529 bool expect_null_mutator_alloc_region); 530 531 // It dirties the cards that cover the block so that so that the post 532 // write barrier never queues anything when updating objects on this 533 // block. It is assumed (and in fact we assert) that the block 534 // belongs to a young region. 535 inline void dirty_young_block(HeapWord* start, size_t word_size); 536 537 // Allocate blocks during garbage collection. Will ensure an 538 // allocation region, either by picking one or expanding the 539 // heap, and then allocate a block of the given size. The block 540 // may not be a humongous - it must fit into a single heap region. 541 inline HeapWord* par_allocate_during_gc(InCSetState dest, 542 size_t word_size, 543 AllocationContext_t context); 544 // Ensure that no further allocations can happen in "r", bearing in mind 545 // that parallel threads might be attempting allocations. 546 void par_allocate_remaining_space(HeapRegion* r); 547 548 // Allocation attempt during GC for a survivor object / PLAB. 549 inline HeapWord* survivor_attempt_allocation(size_t word_size, 550 AllocationContext_t context); 551 552 // Allocation attempt during GC for an old object / PLAB. 553 inline HeapWord* old_attempt_allocation(size_t word_size, 554 AllocationContext_t context); 555 556 // These methods are the "callbacks" from the G1AllocRegion class. 557 558 // For mutator alloc regions. 559 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 560 void retire_mutator_alloc_region(HeapRegion* alloc_region, 561 size_t allocated_bytes); 562 563 // For GC alloc regions. 564 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 565 InCSetState dest); 566 void retire_gc_alloc_region(HeapRegion* alloc_region, 567 size_t allocated_bytes, InCSetState dest); 568 569 // - if explicit_gc is true, the GC is for a System.gc() or a heap 570 // inspection request and should collect the entire heap 571 // - if clear_all_soft_refs is true, all soft references should be 572 // cleared during the GC 573 // - if explicit_gc is false, word_size describes the allocation that 574 // the GC should attempt (at least) to satisfy 575 // - it returns false if it is unable to do the collection due to the 576 // GC locker being active, true otherwise 577 bool do_collection(bool explicit_gc, 578 bool clear_all_soft_refs, 579 size_t word_size); 580 581 // Callback from VM_G1CollectFull operation. 582 // Perform a full collection. 583 virtual void do_full_collection(bool clear_all_soft_refs); 584 585 // Resize the heap if necessary after a full collection. If this is 586 // after a collect-for allocation, "word_size" is the allocation size, 587 // and will be considered part of the used portion of the heap. 588 void resize_if_necessary_after_full_collection(size_t word_size); 589 590 // Callback from VM_G1CollectForAllocation operation. 591 // This function does everything necessary/possible to satisfy a 592 // failed allocation request (including collection, expansion, etc.) 593 HeapWord* satisfy_failed_allocation(size_t word_size, 594 AllocationContext_t context, 595 bool* succeeded); 596 597 // Attempting to expand the heap sufficiently 598 // to support an allocation of the given "word_size". If 599 // successful, perform the allocation and return the address of the 600 // allocated block, or else "NULL". 601 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 602 603 // Process any reference objects discovered during 604 // an incremental evacuation pause. 605 void process_discovered_references(uint no_of_gc_workers); 606 607 // Enqueue any remaining discovered references 608 // after processing. 609 void enqueue_discovered_references(uint no_of_gc_workers); 610 611 public: 612 613 G1Allocator* allocator() { 614 return _allocator; 615 } 616 617 G1MonitoringSupport* g1mm() { 618 assert(_g1mm != NULL, "should have been initialized"); 619 return _g1mm; 620 } 621 622 // Expand the garbage-first heap by at least the given size (in bytes!). 623 // Returns true if the heap was expanded by the requested amount; 624 // false otherwise. 625 // (Rounds up to a HeapRegion boundary.) 626 bool expand(size_t expand_bytes); 627 628 // Returns the PLAB statistics for a given destination. 629 inline PLABStats* alloc_buffer_stats(InCSetState dest); 630 631 // Determines PLAB size for a given destination. 632 inline size_t desired_plab_sz(InCSetState dest); 633 634 inline AllocationContextStats& allocation_context_stats(); 635 636 // Do anything common to GC's. 637 virtual void gc_prologue(bool full); 638 virtual void gc_epilogue(bool full); 639 640 inline void set_humongous_is_live(oop obj); 641 642 bool humongous_is_live(uint region) { 643 return _humongous_is_live.is_live(region); 644 } 645 646 // Returns whether the given region (which must be a humongous (start) region) 647 // is to be considered conservatively live regardless of any other conditions. 648 bool humongous_region_is_always_live(uint index); 649 // Returns whether the given region (which must be a humongous (start) region) 650 // is considered a candidate for eager reclamation. 651 bool humongous_region_is_candidate(uint index); 652 // Register the given region to be part of the collection set. 653 inline void register_humongous_region_with_in_cset_fast_test(uint index); 654 // Register regions with humongous objects (actually on the start region) in 655 // the in_cset_fast_test table. 656 void register_humongous_regions_with_in_cset_fast_test(); 657 // We register a region with the fast "in collection set" test. We 658 // simply set to true the array slot corresponding to this region. 659 void register_young_region_with_in_cset_fast_test(HeapRegion* r) { 660 _in_cset_fast_test.set_in_young(r->hrm_index()); 661 } 662 void register_old_region_with_in_cset_fast_test(HeapRegion* r) { 663 _in_cset_fast_test.set_in_old(r->hrm_index()); 664 } 665 666 // This is a fast test on whether a reference points into the 667 // collection set or not. Assume that the reference 668 // points into the heap. 669 inline bool in_cset_fast_test(oop obj); 670 671 void clear_cset_fast_test() { 672 _in_cset_fast_test.clear(); 673 } 674 675 // This is called at the start of either a concurrent cycle or a Full 676 // GC to update the number of old marking cycles started. 677 void increment_old_marking_cycles_started(); 678 679 // This is called at the end of either a concurrent cycle or a Full 680 // GC to update the number of old marking cycles completed. Those two 681 // can happen in a nested fashion, i.e., we start a concurrent 682 // cycle, a Full GC happens half-way through it which ends first, 683 // and then the cycle notices that a Full GC happened and ends 684 // too. The concurrent parameter is a boolean to help us do a bit 685 // tighter consistency checking in the method. If concurrent is 686 // false, the caller is the inner caller in the nesting (i.e., the 687 // Full GC). If concurrent is true, the caller is the outer caller 688 // in this nesting (i.e., the concurrent cycle). Further nesting is 689 // not currently supported. The end of this call also notifies 690 // the FullGCCount_lock in case a Java thread is waiting for a full 691 // GC to happen (e.g., it called System.gc() with 692 // +ExplicitGCInvokesConcurrent). 693 void increment_old_marking_cycles_completed(bool concurrent); 694 695 unsigned int old_marking_cycles_completed() { 696 return _old_marking_cycles_completed; 697 } 698 699 void register_concurrent_cycle_start(const Ticks& start_time); 700 void register_concurrent_cycle_end(); 701 void trace_heap_after_concurrent_cycle(); 702 703 G1YCType yc_type(); 704 705 G1HRPrinter* hr_printer() { return &_hr_printer; } 706 707 // Frees a non-humongous region by initializing its contents and 708 // adding it to the free list that's passed as a parameter (this is 709 // usually a local list which will be appended to the master free 710 // list later). The used bytes of freed regions are accumulated in 711 // pre_used. If par is true, the region's RSet will not be freed 712 // up. The assumption is that this will be done later. 713 // The locked parameter indicates if the caller has already taken 714 // care of proper synchronization. This may allow some optimizations. 715 void free_region(HeapRegion* hr, 716 FreeRegionList* free_list, 717 bool par, 718 bool locked = false); 719 720 // Frees a humongous region by collapsing it into individual regions 721 // and calling free_region() for each of them. The freed regions 722 // will be added to the free list that's passed as a parameter (this 723 // is usually a local list which will be appended to the master free 724 // list later). The used bytes of freed regions are accumulated in 725 // pre_used. If par is true, the region's RSet will not be freed 726 // up. The assumption is that this will be done later. 727 void free_humongous_region(HeapRegion* hr, 728 FreeRegionList* free_list, 729 bool par); 730 protected: 731 732 // Shrink the garbage-first heap by at most the given size (in bytes!). 733 // (Rounds down to a HeapRegion boundary.) 734 virtual void shrink(size_t expand_bytes); 735 void shrink_helper(size_t expand_bytes); 736 737 #if TASKQUEUE_STATS 738 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 739 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 740 void reset_taskqueue_stats(); 741 #endif // TASKQUEUE_STATS 742 743 // Schedule the VM operation that will do an evacuation pause to 744 // satisfy an allocation request of word_size. *succeeded will 745 // return whether the VM operation was successful (it did do an 746 // evacuation pause) or not (another thread beat us to it or the GC 747 // locker was active). Given that we should not be holding the 748 // Heap_lock when we enter this method, we will pass the 749 // gc_count_before (i.e., total_collections()) as a parameter since 750 // it has to be read while holding the Heap_lock. Currently, both 751 // methods that call do_collection_pause() release the Heap_lock 752 // before the call, so it's easy to read gc_count_before just before. 753 HeapWord* do_collection_pause(size_t word_size, 754 unsigned int gc_count_before, 755 bool* succeeded, 756 GCCause::Cause gc_cause); 757 758 // The guts of the incremental collection pause, executed by the vm 759 // thread. It returns false if it is unable to do the collection due 760 // to the GC locker being active, true otherwise 761 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 762 763 // Actually do the work of evacuating the collection set. 764 void evacuate_collection_set(EvacuationInfo& evacuation_info); 765 766 // The g1 remembered set of the heap. 767 G1RemSet* _g1_rem_set; 768 769 // A set of cards that cover the objects for which the Rsets should be updated 770 // concurrently after the collection. 771 DirtyCardQueueSet _dirty_card_queue_set; 772 773 // The closure used to refine a single card. 774 RefineCardTableEntryClosure* _refine_cte_cl; 775 776 // A DirtyCardQueueSet that is used to hold cards that contain 777 // references into the current collection set. This is used to 778 // update the remembered sets of the regions in the collection 779 // set in the event of an evacuation failure. 780 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 781 782 // After a collection pause, make the regions in the CS into free 783 // regions. 784 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 785 786 // Abandon the current collection set without recording policy 787 // statistics or updating free lists. 788 void abandon_collection_set(HeapRegion* cs_head); 789 790 // Applies "scan_non_heap_roots" to roots outside the heap, 791 // "scan_rs" to roots inside the heap (having done "set_region" to 792 // indicate the region in which the root resides), 793 // and does "scan_metadata" If "scan_rs" is 794 // NULL, then this step is skipped. The "worker_i" 795 // param is for use with parallel roots processing, and should be 796 // the "i" of the calling parallel worker thread's work(i) function. 797 // In the sequential case this param will be ignored. 798 void g1_process_roots(OopClosure* scan_non_heap_roots, 799 OopClosure* scan_non_heap_weak_roots, 800 G1ParPushHeapRSClosure* scan_rs, 801 CLDClosure* scan_strong_clds, 802 CLDClosure* scan_weak_clds, 803 CodeBlobClosure* scan_strong_code, 804 uint worker_i); 805 806 // The concurrent marker (and the thread it runs in.) 807 ConcurrentMark* _cm; 808 ConcurrentMarkThread* _cmThread; 809 bool _mark_in_progress; 810 811 // The concurrent refiner. 812 ConcurrentG1Refine* _cg1r; 813 814 // The parallel task queues 815 RefToScanQueueSet *_task_queues; 816 817 // True iff a evacuation has failed in the current collection. 818 bool _evacuation_failed; 819 820 EvacuationFailedInfo* _evacuation_failed_info_array; 821 822 // Failed evacuations cause some logical from-space objects to have 823 // forwarding pointers to themselves. Reset them. 824 void remove_self_forwarding_pointers(); 825 826 // Together, these store an object with a preserved mark, and its mark value. 827 Stack<oop, mtGC> _objs_with_preserved_marks; 828 Stack<markOop, mtGC> _preserved_marks_of_objs; 829 830 // Preserve the mark of "obj", if necessary, in preparation for its mark 831 // word being overwritten with a self-forwarding-pointer. 832 void preserve_mark_if_necessary(oop obj, markOop m); 833 834 // The stack of evac-failure objects left to be scanned. 835 GrowableArray<oop>* _evac_failure_scan_stack; 836 // The closure to apply to evac-failure objects. 837 838 OopsInHeapRegionClosure* _evac_failure_closure; 839 // Set the field above. 840 void 841 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 842 _evac_failure_closure = evac_failure_closure; 843 } 844 845 // Push "obj" on the scan stack. 846 void push_on_evac_failure_scan_stack(oop obj); 847 // Process scan stack entries until the stack is empty. 848 void drain_evac_failure_scan_stack(); 849 // True iff an invocation of "drain_scan_stack" is in progress; to 850 // prevent unnecessary recursion. 851 bool _drain_in_progress; 852 853 // Do any necessary initialization for evacuation-failure handling. 854 // "cl" is the closure that will be used to process evac-failure 855 // objects. 856 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 857 // Do any necessary cleanup for evacuation-failure handling data 858 // structures. 859 void finalize_for_evac_failure(); 860 861 // An attempt to evacuate "obj" has failed; take necessary steps. 862 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 863 void handle_evacuation_failure_common(oop obj, markOop m); 864 865 #ifndef PRODUCT 866 // Support for forcing evacuation failures. Analogous to 867 // PromotionFailureALot for the other collectors. 868 869 // Records whether G1EvacuationFailureALot should be in effect 870 // for the current GC 871 bool _evacuation_failure_alot_for_current_gc; 872 873 // Used to record the GC number for interval checking when 874 // determining whether G1EvaucationFailureALot is in effect 875 // for the current GC. 876 size_t _evacuation_failure_alot_gc_number; 877 878 // Count of the number of evacuations between failures. 879 volatile size_t _evacuation_failure_alot_count; 880 881 // Set whether G1EvacuationFailureALot should be in effect 882 // for the current GC (based upon the type of GC and which 883 // command line flags are set); 884 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 885 bool during_initial_mark, 886 bool during_marking); 887 888 inline void set_evacuation_failure_alot_for_current_gc(); 889 890 // Return true if it's time to cause an evacuation failure. 891 inline bool evacuation_should_fail(); 892 893 // Reset the G1EvacuationFailureALot counters. Should be called at 894 // the end of an evacuation pause in which an evacuation failure occurred. 895 inline void reset_evacuation_should_fail(); 896 #endif // !PRODUCT 897 898 // ("Weak") Reference processing support. 899 // 900 // G1 has 2 instances of the reference processor class. One 901 // (_ref_processor_cm) handles reference object discovery 902 // and subsequent processing during concurrent marking cycles. 903 // 904 // The other (_ref_processor_stw) handles reference object 905 // discovery and processing during full GCs and incremental 906 // evacuation pauses. 907 // 908 // During an incremental pause, reference discovery will be 909 // temporarily disabled for _ref_processor_cm and will be 910 // enabled for _ref_processor_stw. At the end of the evacuation 911 // pause references discovered by _ref_processor_stw will be 912 // processed and discovery will be disabled. The previous 913 // setting for reference object discovery for _ref_processor_cm 914 // will be re-instated. 915 // 916 // At the start of marking: 917 // * Discovery by the CM ref processor is verified to be inactive 918 // and it's discovered lists are empty. 919 // * Discovery by the CM ref processor is then enabled. 920 // 921 // At the end of marking: 922 // * Any references on the CM ref processor's discovered 923 // lists are processed (possibly MT). 924 // 925 // At the start of full GC we: 926 // * Disable discovery by the CM ref processor and 927 // empty CM ref processor's discovered lists 928 // (without processing any entries). 929 // * Verify that the STW ref processor is inactive and it's 930 // discovered lists are empty. 931 // * Temporarily set STW ref processor discovery as single threaded. 932 // * Temporarily clear the STW ref processor's _is_alive_non_header 933 // field. 934 // * Finally enable discovery by the STW ref processor. 935 // 936 // The STW ref processor is used to record any discovered 937 // references during the full GC. 938 // 939 // At the end of a full GC we: 940 // * Enqueue any reference objects discovered by the STW ref processor 941 // that have non-live referents. This has the side-effect of 942 // making the STW ref processor inactive by disabling discovery. 943 // * Verify that the CM ref processor is still inactive 944 // and no references have been placed on it's discovered 945 // lists (also checked as a precondition during initial marking). 946 947 // The (stw) reference processor... 948 ReferenceProcessor* _ref_processor_stw; 949 950 STWGCTimer* _gc_timer_stw; 951 ConcurrentGCTimer* _gc_timer_cm; 952 953 G1OldTracer* _gc_tracer_cm; 954 G1NewTracer* _gc_tracer_stw; 955 956 // During reference object discovery, the _is_alive_non_header 957 // closure (if non-null) is applied to the referent object to 958 // determine whether the referent is live. If so then the 959 // reference object does not need to be 'discovered' and can 960 // be treated as a regular oop. This has the benefit of reducing 961 // the number of 'discovered' reference objects that need to 962 // be processed. 963 // 964 // Instance of the is_alive closure for embedding into the 965 // STW reference processor as the _is_alive_non_header field. 966 // Supplying a value for the _is_alive_non_header field is 967 // optional but doing so prevents unnecessary additions to 968 // the discovered lists during reference discovery. 969 G1STWIsAliveClosure _is_alive_closure_stw; 970 971 // The (concurrent marking) reference processor... 972 ReferenceProcessor* _ref_processor_cm; 973 974 // Instance of the concurrent mark is_alive closure for embedding 975 // into the Concurrent Marking reference processor as the 976 // _is_alive_non_header field. Supplying a value for the 977 // _is_alive_non_header field is optional but doing so prevents 978 // unnecessary additions to the discovered lists during reference 979 // discovery. 980 G1CMIsAliveClosure _is_alive_closure_cm; 981 982 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 983 HeapRegion** _worker_cset_start_region; 984 985 // Time stamp to validate the regions recorded in the cache 986 // used by G1CollectedHeap::start_cset_region_for_worker(). 987 // The heap region entry for a given worker is valid iff 988 // the associated time stamp value matches the current value 989 // of G1CollectedHeap::_gc_time_stamp. 990 unsigned int* _worker_cset_start_region_time_stamp; 991 992 enum G1H_process_roots_tasks { 993 G1H_PS_filter_satb_buffers, 994 G1H_PS_refProcessor_oops_do, 995 // Leave this one last. 996 G1H_PS_NumElements 997 }; 998 999 SubTasksDone* _process_strong_tasks; 1000 1001 volatile bool _free_regions_coming; 1002 1003 public: 1004 1005 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } 1006 1007 void set_refine_cte_cl_concurrency(bool concurrent); 1008 1009 RefToScanQueue *task_queue(int i) const; 1010 1011 // A set of cards where updates happened during the GC 1012 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1013 1014 // A DirtyCardQueueSet that is used to hold cards that contain 1015 // references into the current collection set. This is used to 1016 // update the remembered sets of the regions in the collection 1017 // set in the event of an evacuation failure. 1018 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1019 { return _into_cset_dirty_card_queue_set; } 1020 1021 // Create a G1CollectedHeap with the specified policy. 1022 // Must call the initialize method afterwards. 1023 // May not return if something goes wrong. 1024 G1CollectedHeap(G1CollectorPolicy* policy); 1025 1026 // Initialize the G1CollectedHeap to have the initial and 1027 // maximum sizes and remembered and barrier sets 1028 // specified by the policy object. 1029 jint initialize(); 1030 1031 virtual void stop(); 1032 1033 // Return the (conservative) maximum heap alignment for any G1 heap 1034 static size_t conservative_max_heap_alignment(); 1035 1036 // Initialize weak reference processing. 1037 virtual void ref_processing_init(); 1038 1039 void set_par_threads(uint t) { 1040 SharedHeap::set_par_threads(t); 1041 // Done in SharedHeap but oddly there are 1042 // two _process_strong_tasks's in a G1CollectedHeap 1043 // so do it here too. 1044 _process_strong_tasks->set_n_threads(t); 1045 } 1046 1047 // Set _n_par_threads according to a policy TBD. 1048 void set_par_threads(); 1049 1050 void set_n_termination(int t) { 1051 _process_strong_tasks->set_n_threads(t); 1052 } 1053 1054 virtual CollectedHeap::Name kind() const { 1055 return CollectedHeap::G1CollectedHeap; 1056 } 1057 1058 // The current policy object for the collector. 1059 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1060 1061 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1062 1063 // Adaptive size policy. No such thing for g1. 1064 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1065 1066 // The rem set and barrier set. 1067 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1068 1069 unsigned get_gc_time_stamp() { 1070 return _gc_time_stamp; 1071 } 1072 1073 inline void reset_gc_time_stamp(); 1074 1075 void check_gc_time_stamps() PRODUCT_RETURN; 1076 1077 inline void increment_gc_time_stamp(); 1078 1079 // Reset the given region's GC timestamp. If it's starts humongous, 1080 // also reset the GC timestamp of its corresponding 1081 // continues humongous regions too. 1082 void reset_gc_time_stamps(HeapRegion* hr); 1083 1084 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1085 DirtyCardQueue* into_cset_dcq, 1086 bool concurrent, uint worker_i); 1087 1088 // The shared block offset table array. 1089 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1090 1091 // Reference Processing accessors 1092 1093 // The STW reference processor.... 1094 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1095 1096 // The Concurrent Marking reference processor... 1097 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1098 1099 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1100 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1101 1102 virtual size_t capacity() const; 1103 virtual size_t used() const; 1104 // This should be called when we're not holding the heap lock. The 1105 // result might be a bit inaccurate. 1106 size_t used_unlocked() const; 1107 size_t recalculate_used() const; 1108 1109 // These virtual functions do the actual allocation. 1110 // Some heaps may offer a contiguous region for shared non-blocking 1111 // allocation, via inlined code (by exporting the address of the top and 1112 // end fields defining the extent of the contiguous allocation region.) 1113 // But G1CollectedHeap doesn't yet support this. 1114 1115 virtual bool is_maximal_no_gc() const { 1116 return _hrm.available() == 0; 1117 } 1118 1119 // The current number of regions in the heap. 1120 uint num_regions() const { return _hrm.length(); } 1121 1122 // The max number of regions in the heap. 1123 uint max_regions() const { return _hrm.max_length(); } 1124 1125 // The number of regions that are completely free. 1126 uint num_free_regions() const { return _hrm.num_free_regions(); } 1127 1128 // The number of regions that are not completely free. 1129 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1130 1131 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1132 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1133 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1134 void verify_dirty_young_regions() PRODUCT_RETURN; 1135 1136 #ifndef PRODUCT 1137 // Make sure that the given bitmap has no marked objects in the 1138 // range [from,limit). If it does, print an error message and return 1139 // false. Otherwise, just return true. bitmap_name should be "prev" 1140 // or "next". 1141 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1142 HeapWord* from, HeapWord* limit); 1143 1144 // Verify that the prev / next bitmap range [tams,end) for the given 1145 // region has no marks. Return true if all is well, false if errors 1146 // are detected. 1147 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1148 #endif // PRODUCT 1149 1150 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1151 // the given region do not have any spurious marks. If errors are 1152 // detected, print appropriate error messages and crash. 1153 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1154 1155 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1156 // have any spurious marks. If errors are detected, print 1157 // appropriate error messages and crash. 1158 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1159 1160 // Do sanity check on the contents of the in-cset fast test table. 1161 bool check_cset_fast_test() PRODUCT_RETURN_( return true; ); 1162 1163 // verify_region_sets() performs verification over the region 1164 // lists. It will be compiled in the product code to be used when 1165 // necessary (i.e., during heap verification). 1166 void verify_region_sets(); 1167 1168 // verify_region_sets_optional() is planted in the code for 1169 // list verification in non-product builds (and it can be enabled in 1170 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1171 #if HEAP_REGION_SET_FORCE_VERIFY 1172 void verify_region_sets_optional() { 1173 verify_region_sets(); 1174 } 1175 #else // HEAP_REGION_SET_FORCE_VERIFY 1176 void verify_region_sets_optional() { } 1177 #endif // HEAP_REGION_SET_FORCE_VERIFY 1178 1179 #ifdef ASSERT 1180 bool is_on_master_free_list(HeapRegion* hr) { 1181 return _hrm.is_free(hr); 1182 } 1183 #endif // ASSERT 1184 1185 // Wrapper for the region list operations that can be called from 1186 // methods outside this class. 1187 1188 void secondary_free_list_add(FreeRegionList* list) { 1189 _secondary_free_list.add_ordered(list); 1190 } 1191 1192 void append_secondary_free_list() { 1193 _hrm.insert_list_into_free_list(&_secondary_free_list); 1194 } 1195 1196 void append_secondary_free_list_if_not_empty_with_lock() { 1197 // If the secondary free list looks empty there's no reason to 1198 // take the lock and then try to append it. 1199 if (!_secondary_free_list.is_empty()) { 1200 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1201 append_secondary_free_list(); 1202 } 1203 } 1204 1205 inline void old_set_remove(HeapRegion* hr); 1206 1207 size_t non_young_capacity_bytes() { 1208 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1209 } 1210 1211 void set_free_regions_coming(); 1212 void reset_free_regions_coming(); 1213 bool free_regions_coming() { return _free_regions_coming; } 1214 void wait_while_free_regions_coming(); 1215 1216 // Determine whether the given region is one that we are using as an 1217 // old GC alloc region. 1218 bool is_old_gc_alloc_region(HeapRegion* hr) { 1219 return _allocator->is_retained_old_region(hr); 1220 } 1221 1222 // Perform a collection of the heap; intended for use in implementing 1223 // "System.gc". This probably implies as full a collection as the 1224 // "CollectedHeap" supports. 1225 virtual void collect(GCCause::Cause cause); 1226 1227 // The same as above but assume that the caller holds the Heap_lock. 1228 void collect_locked(GCCause::Cause cause); 1229 1230 virtual bool copy_allocation_context_stats(const jint* contexts, 1231 jlong* totals, 1232 jbyte* accuracy, 1233 jint len); 1234 1235 // True iff an evacuation has failed in the most-recent collection. 1236 bool evacuation_failed() { return _evacuation_failed; } 1237 1238 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1239 void prepend_to_freelist(FreeRegionList* list); 1240 void decrement_summary_bytes(size_t bytes); 1241 1242 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1243 virtual bool is_in(const void* p) const; 1244 #ifdef ASSERT 1245 // Returns whether p is in one of the available areas of the heap. Slow but 1246 // extensive version. 1247 bool is_in_exact(const void* p) const; 1248 #endif 1249 1250 // Return "TRUE" iff the given object address is within the collection 1251 // set. Slow implementation. 1252 inline bool obj_in_cs(oop obj); 1253 1254 inline bool is_in_cset(oop obj); 1255 1256 inline bool is_in_cset_or_humongous(const oop obj); 1257 1258 private: 1259 // This array is used for a quick test on whether a reference points into 1260 // the collection set or not. Each of the array's elements denotes whether the 1261 // corresponding region is in the collection set or not. 1262 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1263 1264 public: 1265 1266 inline InCSetState in_cset_state(const oop obj); 1267 1268 // Return "TRUE" iff the given object address is in the reserved 1269 // region of g1. 1270 bool is_in_g1_reserved(const void* p) const { 1271 return _hrm.reserved().contains(p); 1272 } 1273 1274 // Returns a MemRegion that corresponds to the space that has been 1275 // reserved for the heap 1276 MemRegion g1_reserved() const { 1277 return _hrm.reserved(); 1278 } 1279 1280 virtual bool is_in_closed_subset(const void* p) const; 1281 1282 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1283 return (G1SATBCardTableLoggingModRefBS*) barrier_set(); 1284 } 1285 1286 // This resets the card table to all zeros. It is used after 1287 // a collection pause which used the card table to claim cards. 1288 void cleanUpCardTable(); 1289 1290 // Iteration functions. 1291 1292 // Iterate over all the ref-containing fields of all objects, calling 1293 // "cl.do_oop" on each. 1294 virtual void oop_iterate(ExtendedOopClosure* cl); 1295 1296 // Iterate over all objects, calling "cl.do_object" on each. 1297 virtual void object_iterate(ObjectClosure* cl); 1298 1299 virtual void safe_object_iterate(ObjectClosure* cl) { 1300 object_iterate(cl); 1301 } 1302 1303 // Iterate over all spaces in use in the heap, in ascending address order. 1304 virtual void space_iterate(SpaceClosure* cl); 1305 1306 // Iterate over heap regions, in address order, terminating the 1307 // iteration early if the "doHeapRegion" method returns "true". 1308 void heap_region_iterate(HeapRegionClosure* blk) const; 1309 1310 // Return the region with the given index. It assumes the index is valid. 1311 inline HeapRegion* region_at(uint index) const; 1312 1313 // Calculate the region index of the given address. Given address must be 1314 // within the heap. 1315 inline uint addr_to_region(HeapWord* addr) const; 1316 1317 inline HeapWord* bottom_addr_for_region(uint index) const; 1318 1319 // Iterate over the heap regions in parallel. Assumes that this will be called 1320 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1321 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1322 // to each of the regions, by attempting to claim the region using the 1323 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1324 // region. The concurrent argument should be set to true if iteration is 1325 // performed concurrently, during which no assumptions are made for consistent 1326 // attributes of the heap regions (as they might be modified while iterating). 1327 void heap_region_par_iterate(HeapRegionClosure* cl, 1328 uint worker_id, 1329 HeapRegionClaimer* hrclaimer, 1330 bool concurrent = false) const; 1331 1332 // Clear the cached cset start regions and (more importantly) 1333 // the time stamps. Called when we reset the GC time stamp. 1334 void clear_cset_start_regions(); 1335 1336 // Given the id of a worker, obtain or calculate a suitable 1337 // starting region for iterating over the current collection set. 1338 HeapRegion* start_cset_region_for_worker(uint worker_i); 1339 1340 // Iterate over the regions (if any) in the current collection set. 1341 void collection_set_iterate(HeapRegionClosure* blk); 1342 1343 // As above but starting from region r 1344 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1345 1346 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1347 1348 // A CollectedHeap will contain some number of spaces. This finds the 1349 // space containing a given address, or else returns NULL. 1350 virtual Space* space_containing(const void* addr) const; 1351 1352 // Returns the HeapRegion that contains addr. addr must not be NULL. 1353 template <class T> 1354 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1355 1356 // Returns the HeapRegion that contains addr. addr must not be NULL. 1357 // If addr is within a humongous continues region, it returns its humongous start region. 1358 template <class T> 1359 inline HeapRegion* heap_region_containing(const T addr) const; 1360 1361 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1362 // each address in the (reserved) heap is a member of exactly 1363 // one block. The defining characteristic of a block is that it is 1364 // possible to find its size, and thus to progress forward to the next 1365 // block. (Blocks may be of different sizes.) Thus, blocks may 1366 // represent Java objects, or they might be free blocks in a 1367 // free-list-based heap (or subheap), as long as the two kinds are 1368 // distinguishable and the size of each is determinable. 1369 1370 // Returns the address of the start of the "block" that contains the 1371 // address "addr". We say "blocks" instead of "object" since some heaps 1372 // may not pack objects densely; a chunk may either be an object or a 1373 // non-object. 1374 virtual HeapWord* block_start(const void* addr) const; 1375 1376 // Requires "addr" to be the start of a chunk, and returns its size. 1377 // "addr + size" is required to be the start of a new chunk, or the end 1378 // of the active area of the heap. 1379 virtual size_t block_size(const HeapWord* addr) const; 1380 1381 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1382 // the block is an object. 1383 virtual bool block_is_obj(const HeapWord* addr) const; 1384 1385 // Does this heap support heap inspection? (+PrintClassHistogram) 1386 virtual bool supports_heap_inspection() const { return true; } 1387 1388 // Section on thread-local allocation buffers (TLABs) 1389 // See CollectedHeap for semantics. 1390 1391 bool supports_tlab_allocation() const; 1392 size_t tlab_capacity(Thread* ignored) const; 1393 size_t tlab_used(Thread* ignored) const; 1394 size_t max_tlab_size() const; 1395 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1396 1397 // Can a compiler initialize a new object without store barriers? 1398 // This permission only extends from the creation of a new object 1399 // via a TLAB up to the first subsequent safepoint. If such permission 1400 // is granted for this heap type, the compiler promises to call 1401 // defer_store_barrier() below on any slow path allocation of 1402 // a new object for which such initializing store barriers will 1403 // have been elided. G1, like CMS, allows this, but should be 1404 // ready to provide a compensating write barrier as necessary 1405 // if that storage came out of a non-young region. The efficiency 1406 // of this implementation depends crucially on being able to 1407 // answer very efficiently in constant time whether a piece of 1408 // storage in the heap comes from a young region or not. 1409 // See ReduceInitialCardMarks. 1410 virtual bool can_elide_tlab_store_barriers() const { 1411 return true; 1412 } 1413 1414 virtual bool card_mark_must_follow_store() const { 1415 return true; 1416 } 1417 1418 inline bool is_in_young(const oop obj); 1419 1420 #ifdef ASSERT 1421 virtual bool is_in_partial_collection(const void* p); 1422 #endif 1423 1424 virtual bool is_scavengable(const void* addr); 1425 1426 // We don't need barriers for initializing stores to objects 1427 // in the young gen: for the SATB pre-barrier, there is no 1428 // pre-value that needs to be remembered; for the remembered-set 1429 // update logging post-barrier, we don't maintain remembered set 1430 // information for young gen objects. 1431 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1432 1433 // Returns "true" iff the given word_size is "very large". 1434 static bool is_humongous(size_t word_size) { 1435 // Note this has to be strictly greater-than as the TLABs 1436 // are capped at the humongous threshold and we want to 1437 // ensure that we don't try to allocate a TLAB as 1438 // humongous and that we don't allocate a humongous 1439 // object in a TLAB. 1440 return word_size > _humongous_object_threshold_in_words; 1441 } 1442 1443 // Update mod union table with the set of dirty cards. 1444 void updateModUnion(); 1445 1446 // Set the mod union bits corresponding to the given memRegion. Note 1447 // that this is always a safe operation, since it doesn't clear any 1448 // bits. 1449 void markModUnionRange(MemRegion mr); 1450 1451 // Records the fact that a marking phase is no longer in progress. 1452 void set_marking_complete() { 1453 _mark_in_progress = false; 1454 } 1455 void set_marking_started() { 1456 _mark_in_progress = true; 1457 } 1458 bool mark_in_progress() { 1459 return _mark_in_progress; 1460 } 1461 1462 // Print the maximum heap capacity. 1463 virtual size_t max_capacity() const; 1464 1465 virtual jlong millis_since_last_gc(); 1466 1467 1468 // Convenience function to be used in situations where the heap type can be 1469 // asserted to be this type. 1470 static G1CollectedHeap* heap(); 1471 1472 void set_region_short_lived_locked(HeapRegion* hr); 1473 // add appropriate methods for any other surv rate groups 1474 1475 YoungList* young_list() const { return _young_list; } 1476 1477 // debugging 1478 bool check_young_list_well_formed() { 1479 return _young_list->check_list_well_formed(); 1480 } 1481 1482 bool check_young_list_empty(bool check_heap, 1483 bool check_sample = true); 1484 1485 // *** Stuff related to concurrent marking. It's not clear to me that so 1486 // many of these need to be public. 1487 1488 // The functions below are helper functions that a subclass of 1489 // "CollectedHeap" can use in the implementation of its virtual 1490 // functions. 1491 // This performs a concurrent marking of the live objects in a 1492 // bitmap off to the side. 1493 void doConcurrentMark(); 1494 1495 bool isMarkedPrev(oop obj) const; 1496 bool isMarkedNext(oop obj) const; 1497 1498 // Determine if an object is dead, given the object and also 1499 // the region to which the object belongs. An object is dead 1500 // iff a) it was not allocated since the last mark and b) it 1501 // is not marked. 1502 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1503 return 1504 !hr->obj_allocated_since_prev_marking(obj) && 1505 !isMarkedPrev(obj); 1506 } 1507 1508 // This function returns true when an object has been 1509 // around since the previous marking and hasn't yet 1510 // been marked during this marking. 1511 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1512 return 1513 !hr->obj_allocated_since_next_marking(obj) && 1514 !isMarkedNext(obj); 1515 } 1516 1517 // Determine if an object is dead, given only the object itself. 1518 // This will find the region to which the object belongs and 1519 // then call the region version of the same function. 1520 1521 // Added if it is NULL it isn't dead. 1522 1523 inline bool is_obj_dead(const oop obj) const; 1524 1525 inline bool is_obj_ill(const oop obj) const; 1526 1527 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1528 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1529 bool is_marked(oop obj, VerifyOption vo); 1530 const char* top_at_mark_start_str(VerifyOption vo); 1531 1532 ConcurrentMark* concurrent_mark() const { return _cm; } 1533 1534 // Refinement 1535 1536 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1537 1538 // The dirty cards region list is used to record a subset of regions 1539 // whose cards need clearing. The list if populated during the 1540 // remembered set scanning and drained during the card table 1541 // cleanup. Although the methods are reentrant, population/draining 1542 // phases must not overlap. For synchronization purposes the last 1543 // element on the list points to itself. 1544 HeapRegion* _dirty_cards_region_list; 1545 void push_dirty_cards_region(HeapRegion* hr); 1546 HeapRegion* pop_dirty_cards_region(); 1547 1548 // Optimized nmethod scanning support routines 1549 1550 // Register the given nmethod with the G1 heap. 1551 virtual void register_nmethod(nmethod* nm); 1552 1553 // Unregister the given nmethod from the G1 heap. 1554 virtual void unregister_nmethod(nmethod* nm); 1555 1556 // Free up superfluous code root memory. 1557 void purge_code_root_memory(); 1558 1559 // Rebuild the strong code root lists for each region 1560 // after a full GC. 1561 void rebuild_strong_code_roots(); 1562 1563 // Delete entries for dead interned string and clean up unreferenced symbols 1564 // in symbol table, possibly in parallel. 1565 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1566 1567 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1568 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1569 1570 // Redirty logged cards in the refinement queue. 1571 void redirty_logged_cards(); 1572 // Verification 1573 1574 // The following is just to alert the verification code 1575 // that a full collection has occurred and that the 1576 // remembered sets are no longer up to date. 1577 bool _full_collection; 1578 void set_full_collection() { _full_collection = true;} 1579 void clear_full_collection() {_full_collection = false;} 1580 bool full_collection() {return _full_collection;} 1581 1582 // Perform any cleanup actions necessary before allowing a verification. 1583 virtual void prepare_for_verify(); 1584 1585 // Perform verification. 1586 1587 // vo == UsePrevMarking -> use "prev" marking information, 1588 // vo == UseNextMarking -> use "next" marking information 1589 // vo == UseMarkWord -> use the mark word in the object header 1590 // 1591 // NOTE: Only the "prev" marking information is guaranteed to be 1592 // consistent most of the time, so most calls to this should use 1593 // vo == UsePrevMarking. 1594 // Currently, there is only one case where this is called with 1595 // vo == UseNextMarking, which is to verify the "next" marking 1596 // information at the end of remark. 1597 // Currently there is only one place where this is called with 1598 // vo == UseMarkWord, which is to verify the marking during a 1599 // full GC. 1600 void verify(bool silent, VerifyOption vo); 1601 1602 // Override; it uses the "prev" marking information 1603 virtual void verify(bool silent); 1604 1605 // The methods below are here for convenience and dispatch the 1606 // appropriate method depending on value of the given VerifyOption 1607 // parameter. The values for that parameter, and their meanings, 1608 // are the same as those above. 1609 1610 bool is_obj_dead_cond(const oop obj, 1611 const HeapRegion* hr, 1612 const VerifyOption vo) const; 1613 1614 bool is_obj_dead_cond(const oop obj, 1615 const VerifyOption vo) const; 1616 1617 // Printing 1618 1619 virtual void print_on(outputStream* st) const; 1620 virtual void print_extended_on(outputStream* st) const; 1621 virtual void print_on_error(outputStream* st) const; 1622 1623 virtual void print_gc_threads_on(outputStream* st) const; 1624 virtual void gc_threads_do(ThreadClosure* tc) const; 1625 1626 // Override 1627 void print_tracing_info() const; 1628 1629 // The following two methods are helpful for debugging RSet issues. 1630 void print_cset_rsets() PRODUCT_RETURN; 1631 void print_all_rsets() PRODUCT_RETURN; 1632 1633 public: 1634 size_t pending_card_num(); 1635 size_t cards_scanned(); 1636 1637 protected: 1638 size_t _max_heap_capacity; 1639 }; 1640 1641 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP