1 /* 2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc_implementation/g1/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/g1MonitoringSupport.hpp" 36 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 37 #include "gc_implementation/g1/g1YCTypes.hpp" 38 #include "gc_implementation/g1/heapRegionManager.hpp" 39 #include "gc_implementation/g1/heapRegionSet.hpp" 40 #include "gc_implementation/shared/hSpaceCounters.hpp" 41 #include "gc_implementation/shared/parGCAllocBuffer.hpp" 42 #include "memory/barrierSet.hpp" 43 #include "memory/memRegion.hpp" 44 #include "memory/sharedHeap.hpp" 45 #include "utilities/stack.hpp" 46 47 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 48 // It uses the "Garbage First" heap organization and algorithm, which 49 // may combine concurrent marking with parallel, incremental compaction of 50 // heap subsets that will yield large amounts of garbage. 51 52 // Forward declarations 53 class HeapRegion; 54 class HRRSCleanupTask; 55 class GenerationSpec; 56 class OopsInHeapRegionClosure; 57 class G1KlassScanClosure; 58 class G1ScanHeapEvacClosure; 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); 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 friend class G1DefaultAllocator; 189 friend class G1ResManAllocator; 190 191 // Closures used in implementation. 192 template <G1Barrier barrier, G1Mark do_mark_object> 193 friend class G1ParCopyClosure; 194 friend class G1IsAliveClosure; 195 friend class G1EvacuateFollowersClosure; 196 friend class G1ParScanThreadState; 197 friend class G1ParScanClosureSuper; 198 friend class G1ParEvacuateFollowersClosure; 199 friend class G1ParTask; 200 friend class G1ParGCAllocator; 201 friend class G1DefaultParGCAllocator; 202 friend class G1FreeGarbageRegionClosure; 203 friend class RefineCardTableEntryClosure; 204 friend class G1PrepareCompactClosure; 205 friend class RegionSorter; 206 friend class RegionResetter; 207 friend class CountRCClosure; 208 friend class EvacPopObjClosure; 209 friend class G1ParCleanupCTTask; 210 211 friend class G1FreeHumongousRegionClosure; 212 // Other related classes. 213 friend class G1MarkSweep; 214 215 private: 216 // The one and only G1CollectedHeap, so static functions can find it. 217 static G1CollectedHeap* _g1h; 218 219 static size_t _humongous_object_threshold_in_words; 220 221 // The secondary free list which contains regions that have been 222 // freed up during the cleanup process. This will be appended to 223 // the master free list when appropriate. 224 FreeRegionList _secondary_free_list; 225 226 // It keeps track of the old regions. 227 HeapRegionSet _old_set; 228 229 // It keeps track of the humongous regions. 230 HeapRegionSet _humongous_set; 231 232 void clear_humongous_is_live_table(); 233 void eagerly_reclaim_humongous_regions(); 234 235 // The number of regions we could create by expansion. 236 uint _expansion_regions; 237 238 // The block offset table for the G1 heap. 239 G1BlockOffsetSharedArray* _bot_shared; 240 241 // Tears down the region sets / lists so that they are empty and the 242 // regions on the heap do not belong to a region set / list. The 243 // only exception is the humongous set which we leave unaltered. If 244 // free_list_only is true, it will only tear down the master free 245 // list. It is called before a Full GC (free_list_only == false) or 246 // before heap shrinking (free_list_only == true). 247 void tear_down_region_sets(bool free_list_only); 248 249 // Rebuilds the region sets / lists so that they are repopulated to 250 // reflect the contents of the heap. The only exception is the 251 // humongous set which was not torn down in the first place. If 252 // free_list_only is true, it will only rebuild the master free 253 // list. It is called after a Full GC (free_list_only == false) or 254 // after heap shrinking (free_list_only == true). 255 void rebuild_region_sets(bool free_list_only); 256 257 // Callback for region mapping changed events. 258 G1RegionMappingChangedListener _listener; 259 260 // The sequence of all heap regions in the heap. 261 HeapRegionManager _hrm; 262 263 // Class that handles the different kinds of allocations. 264 G1Allocator* _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(uint no_of_gc_workers, 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 kept live by roots or 303 // references from the young generation. 304 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 305 protected: 306 bool default_value() const { return false; } 307 public: 308 void clear() { G1BiasedMappedArray<bool>::clear(); } 309 void set_live(uint region) { 310 set_by_index(region, true); 311 } 312 bool is_live(uint region) { 313 return get_by_index(region); 314 } 315 }; 316 317 HumongousIsLiveBiasedMappedArray _humongous_is_live; 318 // Stores whether during humongous object registration we found candidate regions. 319 // If not, we can skip a few steps. 320 bool _has_humongous_reclaim_candidates; 321 322 volatile unsigned _gc_time_stamp; 323 324 size_t* _surviving_young_words; 325 326 G1HRPrinter _hr_printer; 327 328 void setup_surviving_young_words(); 329 void update_surviving_young_words(size_t* surv_young_words); 330 void cleanup_surviving_young_words(); 331 332 // It decides whether an explicit GC should start a concurrent cycle 333 // instead of doing a STW GC. Currently, a concurrent cycle is 334 // explicitly started if: 335 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 336 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 337 // (c) cause == _g1_humongous_allocation 338 bool should_do_concurrent_full_gc(GCCause::Cause cause); 339 340 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 341 // concurrent cycles) we have started. 342 volatile unsigned int _old_marking_cycles_started; 343 344 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 345 // concurrent cycles) we have completed. 346 volatile unsigned int _old_marking_cycles_completed; 347 348 bool _concurrent_cycle_started; 349 bool _heap_summary_sent; 350 351 // This is a non-product method that is helpful for testing. It is 352 // called at the end of a GC and artificially expands the heap by 353 // allocating a number of dead regions. This way we can induce very 354 // frequent marking cycles and stress the cleanup / concurrent 355 // cleanup code more (as all the regions that will be allocated by 356 // this method will be found dead by the marking cycle). 357 void allocate_dummy_regions() PRODUCT_RETURN; 358 359 // Clear RSets after a compaction. It also resets the GC time stamps. 360 void clear_rsets_post_compaction(); 361 362 // If the HR printer is active, dump the state of the regions in the 363 // heap after a compaction. 364 void print_hrm_post_compaction(); 365 366 double verify(bool guard, const char* msg); 367 void verify_before_gc(); 368 void verify_after_gc(); 369 370 void log_gc_header(); 371 void log_gc_footer(double pause_time_sec); 372 373 // These are macros so that, if the assert fires, we get the correct 374 // line number, file, etc. 375 376 #define heap_locking_asserts_err_msg(_extra_message_) \ 377 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 378 (_extra_message_), \ 379 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 380 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 381 BOOL_TO_STR(Thread::current()->is_VM_thread())) 382 383 #define assert_heap_locked() \ 384 do { \ 385 assert(Heap_lock->owned_by_self(), \ 386 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 387 } while (0) 388 389 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 390 do { \ 391 assert(Heap_lock->owned_by_self() || \ 392 (SafepointSynchronize::is_at_safepoint() && \ 393 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 394 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 395 "should be at a safepoint")); \ 396 } while (0) 397 398 #define assert_heap_locked_and_not_at_safepoint() \ 399 do { \ 400 assert(Heap_lock->owned_by_self() && \ 401 !SafepointSynchronize::is_at_safepoint(), \ 402 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 403 "should not be at a safepoint")); \ 404 } while (0) 405 406 #define assert_heap_not_locked() \ 407 do { \ 408 assert(!Heap_lock->owned_by_self(), \ 409 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 410 } while (0) 411 412 #define assert_heap_not_locked_and_not_at_safepoint() \ 413 do { \ 414 assert(!Heap_lock->owned_by_self() && \ 415 !SafepointSynchronize::is_at_safepoint(), \ 416 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 417 "should not be at a safepoint")); \ 418 } while (0) 419 420 #define assert_at_safepoint(_should_be_vm_thread_) \ 421 do { \ 422 assert(SafepointSynchronize::is_at_safepoint() && \ 423 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 424 heap_locking_asserts_err_msg("should be at a safepoint")); \ 425 } while (0) 426 427 #define assert_not_at_safepoint() \ 428 do { \ 429 assert(!SafepointSynchronize::is_at_safepoint(), \ 430 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 431 } while (0) 432 433 protected: 434 435 // The young region list. 436 YoungList* _young_list; 437 438 // The current policy object for the collector. 439 G1CollectorPolicy* _g1_policy; 440 441 // This is the second level of trying to allocate a new region. If 442 // new_region() didn't find a region on the free_list, this call will 443 // check whether there's anything available on the 444 // secondary_free_list and/or wait for more regions to appear on 445 // that list, if _free_regions_coming is set. 446 HeapRegion* new_region_try_secondary_free_list(bool is_old); 447 448 // Try to allocate a single non-humongous HeapRegion sufficient for 449 // an allocation of the given word_size. If do_expand is true, 450 // attempt to expand the heap if necessary to satisfy the allocation 451 // request. If the region is to be used as an old region or for a 452 // humongous object, set is_old to true. If not, to false. 453 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 454 455 // Initialize a contiguous set of free regions of length num_regions 456 // and starting at index first so that they appear as a single 457 // humongous region. 458 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 459 uint num_regions, 460 size_t word_size, 461 AllocationContext_t context); 462 463 // Attempt to allocate a humongous object of the given size. Return 464 // NULL if unsuccessful. 465 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 466 467 // The following two methods, allocate_new_tlab() and 468 // mem_allocate(), are the two main entry points from the runtime 469 // into the G1's allocation routines. They have the following 470 // assumptions: 471 // 472 // * They should both be called outside safepoints. 473 // 474 // * They should both be called without holding the Heap_lock. 475 // 476 // * All allocation requests for new TLABs should go to 477 // allocate_new_tlab(). 478 // 479 // * All non-TLAB allocation requests should go to mem_allocate(). 480 // 481 // * If either call cannot satisfy the allocation request using the 482 // current allocating region, they will try to get a new one. If 483 // this fails, they will attempt to do an evacuation pause and 484 // retry the allocation. 485 // 486 // * If all allocation attempts fail, even after trying to schedule 487 // an evacuation pause, allocate_new_tlab() will return NULL, 488 // whereas mem_allocate() will attempt a heap expansion and/or 489 // schedule a Full GC. 490 // 491 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 492 // should never be called with word_size being humongous. All 493 // humongous allocation requests should go to mem_allocate() which 494 // will satisfy them with a special path. 495 496 virtual HeapWord* allocate_new_tlab(size_t word_size); 497 498 virtual HeapWord* mem_allocate(size_t word_size, 499 bool* gc_overhead_limit_was_exceeded); 500 501 // The following three methods take a gc_count_before_ret 502 // parameter which is used to return the GC count if the method 503 // returns NULL. Given that we are required to read the GC count 504 // while holding the Heap_lock, and these paths will take the 505 // Heap_lock at some point, it's easier to get them to read the GC 506 // count while holding the Heap_lock before they return NULL instead 507 // of the caller (namely: mem_allocate()) having to also take the 508 // Heap_lock just to read the GC count. 509 510 // First-level mutator allocation attempt: try to allocate out of 511 // the mutator alloc region without taking the Heap_lock. This 512 // should only be used for non-humongous allocations. 513 inline HeapWord* attempt_allocation(size_t word_size, 514 unsigned int* gc_count_before_ret, 515 int* gclocker_retry_count_ret); 516 517 // Second-level mutator allocation attempt: take the Heap_lock and 518 // retry the allocation attempt, potentially scheduling a GC 519 // pause. This should only be used for non-humongous allocations. 520 HeapWord* attempt_allocation_slow(size_t word_size, 521 AllocationContext_t context, 522 unsigned int* gc_count_before_ret, 523 int* gclocker_retry_count_ret); 524 525 // Takes the Heap_lock and attempts a humongous allocation. It can 526 // potentially schedule a GC pause. 527 HeapWord* attempt_allocation_humongous(size_t word_size, 528 unsigned int* gc_count_before_ret, 529 int* gclocker_retry_count_ret); 530 531 // Allocation attempt that should be called during safepoints (e.g., 532 // at the end of a successful GC). expect_null_mutator_alloc_region 533 // specifies whether the mutator alloc region is expected to be NULL 534 // or not. 535 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 536 AllocationContext_t context, 537 bool expect_null_mutator_alloc_region); 538 539 // It dirties the cards that cover the block so that so that the post 540 // write barrier never queues anything when updating objects on this 541 // block. It is assumed (and in fact we assert) that the block 542 // belongs to a young region. 543 inline void dirty_young_block(HeapWord* start, size_t word_size); 544 545 // Allocate blocks during garbage collection. Will ensure an 546 // allocation region, either by picking one or expanding the 547 // heap, and then allocate a block of the given size. The block 548 // may not be a humongous - it must fit into a single heap region. 549 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, 550 size_t word_size, 551 AllocationContext_t context); 552 553 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, 554 HeapRegion* alloc_region, 555 bool par, 556 size_t word_size); 557 558 // Ensure that no further allocations can happen in "r", bearing in mind 559 // that parallel threads might be attempting allocations. 560 void par_allocate_remaining_space(HeapRegion* r); 561 562 // Allocation attempt during GC for a survivor object / PLAB. 563 inline HeapWord* survivor_attempt_allocation(size_t word_size, 564 AllocationContext_t context); 565 566 // Allocation attempt during GC for an old object / PLAB. 567 inline HeapWord* old_attempt_allocation(size_t word_size, 568 AllocationContext_t context); 569 570 // These methods are the "callbacks" from the G1AllocRegion class. 571 572 // For mutator alloc regions. 573 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 574 void retire_mutator_alloc_region(HeapRegion* alloc_region, 575 size_t allocated_bytes); 576 577 // For GC alloc regions. 578 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 579 GCAllocPurpose ap); 580 void retire_gc_alloc_region(HeapRegion* alloc_region, 581 size_t allocated_bytes, GCAllocPurpose ap); 582 583 // - if explicit_gc is true, the GC is for a System.gc() or a heap 584 // inspection request and should collect the entire heap 585 // - if clear_all_soft_refs is true, all soft references should be 586 // cleared during the GC 587 // - if explicit_gc is false, word_size describes the allocation that 588 // the GC should attempt (at least) to satisfy 589 // - it returns false if it is unable to do the collection due to the 590 // GC locker being active, true otherwise 591 bool do_collection(bool explicit_gc, 592 bool clear_all_soft_refs, 593 size_t word_size); 594 595 // Callback from VM_G1CollectFull operation. 596 // Perform a full collection. 597 virtual void do_full_collection(bool clear_all_soft_refs); 598 599 // Resize the heap if necessary after a full collection. If this is 600 // after a collect-for allocation, "word_size" is the allocation size, 601 // and will be considered part of the used portion of the heap. 602 void resize_if_necessary_after_full_collection(size_t word_size); 603 604 // Callback from VM_G1CollectForAllocation operation. 605 // This function does everything necessary/possible to satisfy a 606 // failed allocation request (including collection, expansion, etc.) 607 HeapWord* satisfy_failed_allocation(size_t word_size, 608 AllocationContext_t context, 609 bool* succeeded); 610 611 // Attempting to expand the heap sufficiently 612 // to support an allocation of the given "word_size". If 613 // successful, perform the allocation and return the address of the 614 // allocated block, or else "NULL". 615 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 616 617 // Process any reference objects discovered during 618 // an incremental evacuation pause. 619 void process_discovered_references(uint no_of_gc_workers); 620 621 // Enqueue any remaining discovered references 622 // after processing. 623 void enqueue_discovered_references(uint no_of_gc_workers); 624 625 public: 626 627 G1Allocator* allocator() { 628 return _allocator; 629 } 630 631 G1MonitoringSupport* g1mm() { 632 assert(_g1mm != NULL, "should have been initialized"); 633 return _g1mm; 634 } 635 636 // Expand the garbage-first heap by at least the given size (in bytes!). 637 // Returns true if the heap was expanded by the requested amount; 638 // false otherwise. 639 // (Rounds up to a HeapRegion boundary.) 640 bool expand(size_t expand_bytes); 641 642 // Returns the PLAB statistics given a purpose. 643 PLABStats* stats_for_purpose(GCAllocPurpose purpose) { 644 PLABStats* stats = NULL; 645 646 switch (purpose) { 647 case GCAllocForSurvived: 648 stats = &_survivor_plab_stats; 649 break; 650 case GCAllocForTenured: 651 stats = &_old_plab_stats; 652 break; 653 default: 654 assert(false, "unrecognized GCAllocPurpose"); 655 } 656 657 return stats; 658 } 659 660 // Determines PLAB size for a particular allocation purpose. 661 size_t desired_plab_sz(GCAllocPurpose purpose); 662 663 inline AllocationContextStats& allocation_context_stats(); 664 665 // Do anything common to GC's. 666 virtual void gc_prologue(bool full); 667 virtual void gc_epilogue(bool full); 668 669 inline void set_humongous_is_live(oop obj); 670 671 bool humongous_is_live(uint region) { 672 return _humongous_is_live.is_live(region); 673 } 674 675 // Returns whether the given region (which must be a humongous (start) region) 676 // is to be considered conservatively live regardless of any other conditions. 677 bool humongous_region_is_always_live(uint index); 678 // Register the given region to be part of the collection set. 679 inline void register_humongous_region_with_in_cset_fast_test(uint index); 680 // Register regions with humongous objects (actually on the start region) in 681 // the in_cset_fast_test table. 682 void register_humongous_regions_with_in_cset_fast_test(); 683 // We register a region with the fast "in collection set" test. We 684 // simply set to true the array slot corresponding to this region. 685 void register_region_with_in_cset_fast_test(HeapRegion* r) { 686 _in_cset_fast_test.set_in_cset(r->hrm_index()); 687 } 688 689 // This is a fast test on whether a reference points into the 690 // collection set or not. Assume that the reference 691 // points into the heap. 692 inline bool in_cset_fast_test(oop obj); 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 unsigned int 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 G1YCType yc_type(); 727 728 G1HRPrinter* hr_printer() { return &_hr_printer; } 729 730 // Frees a non-humongous region by initializing its contents and 731 // adding it to the free list that's passed as a parameter (this is 732 // usually a local list which will be appended to the master free 733 // list later). The used bytes of freed regions are accumulated in 734 // pre_used. If par is true, the region's RSet will not be freed 735 // up. The assumption is that this will be done later. 736 // The locked parameter indicates if the caller has already taken 737 // care of proper synchronization. This may allow some optimizations. 738 void free_region(HeapRegion* hr, 739 FreeRegionList* free_list, 740 bool par, 741 bool locked = false); 742 743 // Frees a humongous region by collapsing it into individual regions 744 // and calling free_region() for each of them. The freed regions 745 // will be added to the free list that's passed as a parameter (this 746 // is usually a local list which will be appended to the master free 747 // list later). The used bytes of freed regions are accumulated in 748 // pre_used. If par is true, the region's RSet will not be freed 749 // up. The assumption is that this will be done later. 750 void free_humongous_region(HeapRegion* hr, 751 FreeRegionList* free_list, 752 bool par); 753 protected: 754 755 // Shrink the garbage-first heap by at most the given size (in bytes!). 756 // (Rounds down to a HeapRegion boundary.) 757 virtual void shrink(size_t expand_bytes); 758 void shrink_helper(size_t expand_bytes); 759 760 #if TASKQUEUE_STATS 761 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 762 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 763 void reset_taskqueue_stats(); 764 #endif // TASKQUEUE_STATS 765 766 // Schedule the VM operation that will do an evacuation pause to 767 // satisfy an allocation request of word_size. *succeeded will 768 // return whether the VM operation was successful (it did do an 769 // evacuation pause) or not (another thread beat us to it or the GC 770 // locker was active). Given that we should not be holding the 771 // Heap_lock when we enter this method, we will pass the 772 // gc_count_before (i.e., total_collections()) as a parameter since 773 // it has to be read while holding the Heap_lock. Currently, both 774 // methods that call do_collection_pause() release the Heap_lock 775 // before the call, so it's easy to read gc_count_before just before. 776 HeapWord* do_collection_pause(size_t word_size, 777 unsigned int gc_count_before, 778 bool* succeeded, 779 GCCause::Cause gc_cause); 780 781 // The guts of the incremental collection pause, executed by the vm 782 // thread. It returns false if it is unable to do the collection due 783 // to the GC locker being active, true otherwise 784 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 785 786 // Actually do the work of evacuating the collection set. 787 void evacuate_collection_set(EvacuationInfo& evacuation_info); 788 789 // The g1 remembered set of the heap. 790 G1RemSet* _g1_rem_set; 791 792 // A set of cards that cover the objects for which the Rsets should be updated 793 // concurrently after the collection. 794 DirtyCardQueueSet _dirty_card_queue_set; 795 796 // The closure used to refine a single card. 797 RefineCardTableEntryClosure* _refine_cte_cl; 798 799 // A function to check the consistency of dirty card logs. 800 void check_ct_logs_at_safepoint(); 801 802 // A DirtyCardQueueSet that is used to hold cards that contain 803 // references into the current collection set. This is used to 804 // update the remembered sets of the regions in the collection 805 // set in the event of an evacuation failure. 806 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 807 808 // After a collection pause, make the regions in the CS into free 809 // regions. 810 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 811 812 // Abandon the current collection set without recording policy 813 // statistics or updating free lists. 814 void abandon_collection_set(HeapRegion* cs_head); 815 816 // Applies "scan_non_heap_roots" to roots outside the heap, 817 // "scan_rs" to roots inside the heap (having done "set_region" to 818 // indicate the region in which the root resides), 819 // and does "scan_metadata" If "scan_rs" is 820 // NULL, then this step is skipped. The "worker_i" 821 // param is for use with parallel roots processing, and should be 822 // the "i" of the calling parallel worker thread's work(i) function. 823 // In the sequential case this param will be ignored. 824 void g1_process_roots(OopClosure* scan_non_heap_roots, 825 OopClosure* scan_non_heap_weak_roots, 826 OopsInHeapRegionClosure* scan_rs, 827 CLDClosure* scan_strong_clds, 828 CLDClosure* scan_weak_clds, 829 CodeBlobClosure* scan_strong_code, 830 uint worker_i); 831 832 // The concurrent marker (and the thread it runs in.) 833 ConcurrentMark* _cm; 834 ConcurrentMarkThread* _cmThread; 835 bool _mark_in_progress; 836 837 // The concurrent refiner. 838 ConcurrentG1Refine* _cg1r; 839 840 // The parallel task queues 841 RefToScanQueueSet *_task_queues; 842 843 // True iff a evacuation has failed in the current collection. 844 bool _evacuation_failed; 845 846 EvacuationFailedInfo* _evacuation_failed_info_array; 847 848 // Failed evacuations cause some logical from-space objects to have 849 // forwarding pointers to themselves. Reset them. 850 void remove_self_forwarding_pointers(); 851 852 // Together, these store an object with a preserved mark, and its mark value. 853 Stack<oop, mtGC> _objs_with_preserved_marks; 854 Stack<markOop, mtGC> _preserved_marks_of_objs; 855 856 // Preserve the mark of "obj", if necessary, in preparation for its mark 857 // word being overwritten with a self-forwarding-pointer. 858 void preserve_mark_if_necessary(oop obj, markOop m); 859 860 // The stack of evac-failure objects left to be scanned. 861 GrowableArray<oop>* _evac_failure_scan_stack; 862 // The closure to apply to evac-failure objects. 863 864 OopsInHeapRegionClosure* _evac_failure_closure; 865 // Set the field above. 866 void 867 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 868 _evac_failure_closure = evac_failure_closure; 869 } 870 871 // Push "obj" on the scan stack. 872 void push_on_evac_failure_scan_stack(oop obj); 873 // Process scan stack entries until the stack is empty. 874 void drain_evac_failure_scan_stack(); 875 // True iff an invocation of "drain_scan_stack" is in progress; to 876 // prevent unnecessary recursion. 877 bool _drain_in_progress; 878 879 // Do any necessary initialization for evacuation-failure handling. 880 // "cl" is the closure that will be used to process evac-failure 881 // objects. 882 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 883 // Do any necessary cleanup for evacuation-failure handling data 884 // structures. 885 void finalize_for_evac_failure(); 886 887 // An attempt to evacuate "obj" has failed; take necessary steps. 888 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 889 void handle_evacuation_failure_common(oop obj, markOop m); 890 891 #ifndef PRODUCT 892 // Support for forcing evacuation failures. Analogous to 893 // PromotionFailureALot for the other collectors. 894 895 // Records whether G1EvacuationFailureALot should be in effect 896 // for the current GC 897 bool _evacuation_failure_alot_for_current_gc; 898 899 // Used to record the GC number for interval checking when 900 // determining whether G1EvaucationFailureALot is in effect 901 // for the current GC. 902 size_t _evacuation_failure_alot_gc_number; 903 904 // Count of the number of evacuations between failures. 905 volatile size_t _evacuation_failure_alot_count; 906 907 // Set whether G1EvacuationFailureALot should be in effect 908 // for the current GC (based upon the type of GC and which 909 // command line flags are set); 910 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 911 bool during_initial_mark, 912 bool during_marking); 913 914 inline void set_evacuation_failure_alot_for_current_gc(); 915 916 // Return true if it's time to cause an evacuation failure. 917 inline bool evacuation_should_fail(); 918 919 // Reset the G1EvacuationFailureALot counters. Should be called at 920 // the end of an evacuation pause in which an evacuation failure occurred. 921 inline void reset_evacuation_should_fail(); 922 #endif // !PRODUCT 923 924 // ("Weak") Reference processing support. 925 // 926 // G1 has 2 instances of the reference processor class. One 927 // (_ref_processor_cm) handles reference object discovery 928 // and subsequent processing during concurrent marking cycles. 929 // 930 // The other (_ref_processor_stw) handles reference object 931 // discovery and processing during full GCs and incremental 932 // evacuation pauses. 933 // 934 // During an incremental pause, reference discovery will be 935 // temporarily disabled for _ref_processor_cm and will be 936 // enabled for _ref_processor_stw. At the end of the evacuation 937 // pause references discovered by _ref_processor_stw will be 938 // processed and discovery will be disabled. The previous 939 // setting for reference object discovery for _ref_processor_cm 940 // will be re-instated. 941 // 942 // At the start of marking: 943 // * Discovery by the CM ref processor is verified to be inactive 944 // and it's discovered lists are empty. 945 // * Discovery by the CM ref processor is then enabled. 946 // 947 // At the end of marking: 948 // * Any references on the CM ref processor's discovered 949 // lists are processed (possibly MT). 950 // 951 // At the start of full GC we: 952 // * Disable discovery by the CM ref processor and 953 // empty CM ref processor's discovered lists 954 // (without processing any entries). 955 // * Verify that the STW ref processor is inactive and it's 956 // discovered lists are empty. 957 // * Temporarily set STW ref processor discovery as single threaded. 958 // * Temporarily clear the STW ref processor's _is_alive_non_header 959 // field. 960 // * Finally enable discovery by the STW ref processor. 961 // 962 // The STW ref processor is used to record any discovered 963 // references during the full GC. 964 // 965 // At the end of a full GC we: 966 // * Enqueue any reference objects discovered by the STW ref processor 967 // that have non-live referents. This has the side-effect of 968 // making the STW ref processor inactive by disabling discovery. 969 // * Verify that the CM ref processor is still inactive 970 // and no references have been placed on it's discovered 971 // lists (also checked as a precondition during initial marking). 972 973 // The (stw) reference processor... 974 ReferenceProcessor* _ref_processor_stw; 975 976 STWGCTimer* _gc_timer_stw; 977 ConcurrentGCTimer* _gc_timer_cm; 978 979 G1OldTracer* _gc_tracer_cm; 980 G1NewTracer* _gc_tracer_stw; 981 982 // During reference object discovery, the _is_alive_non_header 983 // closure (if non-null) is applied to the referent object to 984 // determine whether the referent is live. If so then the 985 // reference object does not need to be 'discovered' and can 986 // be treated as a regular oop. This has the benefit of reducing 987 // the number of 'discovered' reference objects that need to 988 // be processed. 989 // 990 // Instance of the is_alive closure for embedding into the 991 // STW reference processor as the _is_alive_non_header field. 992 // Supplying a value for the _is_alive_non_header field is 993 // optional but doing so prevents unnecessary additions to 994 // the discovered lists during reference discovery. 995 G1STWIsAliveClosure _is_alive_closure_stw; 996 997 // The (concurrent marking) reference processor... 998 ReferenceProcessor* _ref_processor_cm; 999 1000 // Instance of the concurrent mark is_alive closure for embedding 1001 // into the Concurrent Marking reference processor as the 1002 // _is_alive_non_header field. Supplying a value for the 1003 // _is_alive_non_header field is optional but doing so prevents 1004 // unnecessary additions to the discovered lists during reference 1005 // discovery. 1006 G1CMIsAliveClosure _is_alive_closure_cm; 1007 1008 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 1009 HeapRegion** _worker_cset_start_region; 1010 1011 // Time stamp to validate the regions recorded in the cache 1012 // used by G1CollectedHeap::start_cset_region_for_worker(). 1013 // The heap region entry for a given worker is valid iff 1014 // the associated time stamp value matches the current value 1015 // of G1CollectedHeap::_gc_time_stamp. 1016 unsigned int* _worker_cset_start_region_time_stamp; 1017 1018 enum G1H_process_roots_tasks { 1019 G1H_PS_filter_satb_buffers, 1020 G1H_PS_refProcessor_oops_do, 1021 // Leave this one last. 1022 G1H_PS_NumElements 1023 }; 1024 1025 SubTasksDone* _process_strong_tasks; 1026 1027 volatile bool _free_regions_coming; 1028 1029 public: 1030 1031 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } 1032 1033 void set_refine_cte_cl_concurrency(bool concurrent); 1034 1035 RefToScanQueue *task_queue(int i) const; 1036 1037 // A set of cards where updates happened during the GC 1038 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1039 1040 // A DirtyCardQueueSet that is used to hold cards that contain 1041 // references into the current collection set. This is used to 1042 // update the remembered sets of the regions in the collection 1043 // set in the event of an evacuation failure. 1044 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1045 { return _into_cset_dirty_card_queue_set; } 1046 1047 // Create a G1CollectedHeap with the specified policy. 1048 // Must call the initialize method afterwards. 1049 // May not return if something goes wrong. 1050 G1CollectedHeap(G1CollectorPolicy* policy); 1051 1052 // Initialize the G1CollectedHeap to have the initial and 1053 // maximum sizes and remembered and barrier sets 1054 // specified by the policy object. 1055 jint initialize(); 1056 1057 virtual void stop(); 1058 1059 // Return the (conservative) maximum heap alignment for any G1 heap 1060 static size_t conservative_max_heap_alignment(); 1061 1062 // Initialize weak reference processing. 1063 virtual void ref_processing_init(); 1064 1065 void set_par_threads(uint t) { 1066 SharedHeap::set_par_threads(t); 1067 // Done in SharedHeap but oddly there are 1068 // two _process_strong_tasks's in a G1CollectedHeap 1069 // so do it here too. 1070 _process_strong_tasks->set_n_threads(t); 1071 } 1072 1073 // Set _n_par_threads according to a policy TBD. 1074 void set_par_threads(); 1075 1076 void set_n_termination(int t) { 1077 _process_strong_tasks->set_n_threads(t); 1078 } 1079 1080 virtual CollectedHeap::Name kind() const { 1081 return CollectedHeap::G1CollectedHeap; 1082 } 1083 1084 // The current policy object for the collector. 1085 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1086 1087 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1088 1089 // Adaptive size policy. No such thing for g1. 1090 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1091 1092 // The rem set and barrier set. 1093 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1094 1095 unsigned get_gc_time_stamp() { 1096 return _gc_time_stamp; 1097 } 1098 1099 inline void reset_gc_time_stamp(); 1100 1101 void check_gc_time_stamps() PRODUCT_RETURN; 1102 1103 inline void increment_gc_time_stamp(); 1104 1105 // Reset the given region's GC timestamp. If it's starts humongous, 1106 // also reset the GC timestamp of its corresponding 1107 // continues humongous regions too. 1108 void reset_gc_time_stamps(HeapRegion* hr); 1109 1110 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1111 DirtyCardQueue* into_cset_dcq, 1112 bool concurrent, uint worker_i); 1113 1114 // The shared block offset table array. 1115 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1116 1117 // Reference Processing accessors 1118 1119 // The STW reference processor.... 1120 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1121 1122 // The Concurrent Marking reference processor... 1123 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1124 1125 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1126 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1127 1128 virtual size_t capacity() const; 1129 virtual size_t used() const; 1130 // This should be called when we're not holding the heap lock. The 1131 // result might be a bit inaccurate. 1132 size_t used_unlocked() const; 1133 size_t recalculate_used() const; 1134 1135 // These virtual functions do the actual allocation. 1136 // Some heaps may offer a contiguous region for shared non-blocking 1137 // allocation, via inlined code (by exporting the address of the top and 1138 // end fields defining the extent of the contiguous allocation region.) 1139 // But G1CollectedHeap doesn't yet support this. 1140 1141 virtual bool is_maximal_no_gc() const { 1142 return _hrm.available() == 0; 1143 } 1144 1145 // The current number of regions in the heap. 1146 uint num_regions() const { return _hrm.length(); } 1147 1148 // The max number of regions in the heap. 1149 uint max_regions() const { return _hrm.max_length(); } 1150 1151 // The number of regions that are completely free. 1152 uint num_free_regions() const { return _hrm.num_free_regions(); } 1153 1154 // The number of regions that are not completely free. 1155 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1156 1157 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1158 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1159 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1160 void verify_dirty_young_regions() PRODUCT_RETURN; 1161 1162 #ifndef PRODUCT 1163 // Make sure that the given bitmap has no marked objects in the 1164 // range [from,limit). If it does, print an error message and return 1165 // false. Otherwise, just return true. bitmap_name should be "prev" 1166 // or "next". 1167 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1168 HeapWord* from, HeapWord* limit); 1169 1170 // Verify that the prev / next bitmap range [tams,end) for the given 1171 // region has no marks. Return true if all is well, false if errors 1172 // are detected. 1173 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1174 #endif // PRODUCT 1175 1176 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1177 // the given region do not have any spurious marks. If errors are 1178 // detected, print appropriate error messages and crash. 1179 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1180 1181 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1182 // have any spurious marks. If errors are detected, print 1183 // appropriate error messages and crash. 1184 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1185 1186 // verify_region_sets() performs verification over the region 1187 // lists. It will be compiled in the product code to be used when 1188 // necessary (i.e., during heap verification). 1189 void verify_region_sets(); 1190 1191 // verify_region_sets_optional() is planted in the code for 1192 // list verification in non-product builds (and it can be enabled in 1193 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1194 #if HEAP_REGION_SET_FORCE_VERIFY 1195 void verify_region_sets_optional() { 1196 verify_region_sets(); 1197 } 1198 #else // HEAP_REGION_SET_FORCE_VERIFY 1199 void verify_region_sets_optional() { } 1200 #endif // HEAP_REGION_SET_FORCE_VERIFY 1201 1202 #ifdef ASSERT 1203 bool is_on_master_free_list(HeapRegion* hr) { 1204 return _hrm.is_free(hr); 1205 } 1206 #endif // ASSERT 1207 1208 // Wrapper for the region list operations that can be called from 1209 // methods outside this class. 1210 1211 void secondary_free_list_add(FreeRegionList* list) { 1212 _secondary_free_list.add_ordered(list); 1213 } 1214 1215 void append_secondary_free_list() { 1216 _hrm.insert_list_into_free_list(&_secondary_free_list); 1217 } 1218 1219 void append_secondary_free_list_if_not_empty_with_lock() { 1220 // If the secondary free list looks empty there's no reason to 1221 // take the lock and then try to append it. 1222 if (!_secondary_free_list.is_empty()) { 1223 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1224 append_secondary_free_list(); 1225 } 1226 } 1227 1228 inline void old_set_remove(HeapRegion* hr); 1229 1230 size_t non_young_capacity_bytes() { 1231 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1232 } 1233 1234 void set_free_regions_coming(); 1235 void reset_free_regions_coming(); 1236 bool free_regions_coming() { return _free_regions_coming; } 1237 void wait_while_free_regions_coming(); 1238 1239 // Determine whether the given region is one that we are using as an 1240 // old GC alloc region. 1241 bool is_old_gc_alloc_region(HeapRegion* hr) { 1242 return _allocator->is_retained_old_region(hr); 1243 } 1244 1245 // Perform a collection of the heap; intended for use in implementing 1246 // "System.gc". This probably implies as full a collection as the 1247 // "CollectedHeap" supports. 1248 virtual void collect(GCCause::Cause cause); 1249 1250 // The same as above but assume that the caller holds the Heap_lock. 1251 void collect_locked(GCCause::Cause cause); 1252 1253 virtual void copy_allocation_context_stats(const jint* contexts, 1254 jlong* totals, 1255 jbyte* accuracy, 1256 jint len); 1257 1258 // True iff an evacuation has failed in the most-recent collection. 1259 bool evacuation_failed() { return _evacuation_failed; } 1260 1261 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1262 void prepend_to_freelist(FreeRegionList* list); 1263 void decrement_summary_bytes(size_t bytes); 1264 1265 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1266 virtual bool is_in(const void* p) const; 1267 #ifdef ASSERT 1268 // Returns whether p is in one of the available areas of the heap. Slow but 1269 // extensive version. 1270 bool is_in_exact(const void* p) const; 1271 #endif 1272 1273 // Return "TRUE" iff the given object address is within the collection 1274 // set. Slow implementation. 1275 inline bool obj_in_cs(oop obj); 1276 1277 inline bool is_in_cset(oop obj); 1278 1279 inline bool is_in_cset_or_humongous(const oop obj); 1280 1281 enum in_cset_state_t { 1282 InNeither, // neither in collection set nor humongous 1283 InCSet, // region is in collection set only 1284 IsHumongous // region is a humongous start region 1285 }; 1286 private: 1287 // Instances of this class are used for quick tests on whether a reference points 1288 // into the collection set or is a humongous object (points into a humongous 1289 // object). 1290 // Each of the array's elements denotes whether the corresponding region is in 1291 // the collection set or a humongous region. 1292 // We use this to quickly reclaim humongous objects: by making a humongous region 1293 // succeed this test, we sort-of add it to the collection set. During the reference 1294 // iteration closures, when we see a humongous region, we simply mark it as 1295 // referenced, i.e. live. 1296 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> { 1297 protected: 1298 char default_value() const { return G1CollectedHeap::InNeither; } 1299 public: 1300 void set_humongous(uintptr_t index) { 1301 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values"); 1302 set_by_index(index, G1CollectedHeap::IsHumongous); 1303 } 1304 1305 void clear_humongous(uintptr_t index) { 1306 set_by_index(index, G1CollectedHeap::InNeither); 1307 } 1308 1309 void set_in_cset(uintptr_t index) { 1310 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value"); 1311 set_by_index(index, G1CollectedHeap::InCSet); 1312 } 1313 1314 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; } 1315 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; } 1316 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); } 1317 void clear() { G1BiasedMappedArray<char>::clear(); } 1318 }; 1319 1320 // This array is used for a quick test on whether a reference points into 1321 // the collection set or not. Each of the array's elements denotes whether the 1322 // corresponding region is in the collection set or not. 1323 G1FastCSetBiasedMappedArray _in_cset_fast_test; 1324 1325 public: 1326 1327 inline in_cset_state_t in_cset_state(const oop obj); 1328 1329 // Return "TRUE" iff the given object address is in the reserved 1330 // region of g1. 1331 bool is_in_g1_reserved(const void* p) const { 1332 return _hrm.reserved().contains(p); 1333 } 1334 1335 // Returns a MemRegion that corresponds to the space that has been 1336 // reserved for the heap 1337 MemRegion g1_reserved() const { 1338 return _hrm.reserved(); 1339 } 1340 1341 virtual bool is_in_closed_subset(const void* p) const; 1342 1343 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1344 return (G1SATBCardTableLoggingModRefBS*) barrier_set(); 1345 } 1346 1347 // This resets the card table to all zeros. It is used after 1348 // a collection pause which used the card table to claim cards. 1349 void cleanUpCardTable(); 1350 1351 // Iteration functions. 1352 1353 // Iterate over all the ref-containing fields of all objects, calling 1354 // "cl.do_oop" on each. 1355 virtual void oop_iterate(ExtendedOopClosure* cl); 1356 1357 // Iterate over all objects, calling "cl.do_object" on each. 1358 virtual void object_iterate(ObjectClosure* cl); 1359 1360 virtual void safe_object_iterate(ObjectClosure* cl) { 1361 object_iterate(cl); 1362 } 1363 1364 // Iterate over all spaces in use in the heap, in ascending address order. 1365 virtual void space_iterate(SpaceClosure* cl); 1366 1367 // Iterate over heap regions, in address order, terminating the 1368 // iteration early if the "doHeapRegion" method returns "true". 1369 void heap_region_iterate(HeapRegionClosure* blk) const; 1370 1371 // Return the region with the given index. It assumes the index is valid. 1372 inline HeapRegion* region_at(uint index) const; 1373 1374 // Calculate the region index of the given address. Given address must be 1375 // within the heap. 1376 inline uint addr_to_region(HeapWord* addr) const; 1377 1378 inline HeapWord* bottom_addr_for_region(uint index) const; 1379 1380 // Divide the heap region sequence into "chunks" of some size (the number 1381 // of regions divided by the number of parallel threads times some 1382 // overpartition factor, currently 4). Assumes that this will be called 1383 // in parallel by ParallelGCThreads worker threads with distinct worker 1384 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel 1385 // calls will use the same "claim_value", and that that claim value is 1386 // different from the claim_value of any heap region before the start of 1387 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by 1388 // attempting to claim the first region in each chunk, and, if 1389 // successful, applying the closure to each region in the chunk (and 1390 // setting the claim value of the second and subsequent regions of the 1391 // chunk.) For now requires that "doHeapRegion" always returns "false", 1392 // i.e., that a closure never attempt to abort a traversal. 1393 void heap_region_par_iterate_chunked(HeapRegionClosure* cl, 1394 uint worker_id, 1395 uint num_workers, 1396 jint claim_value) const; 1397 1398 // It resets all the region claim values to the default. 1399 void reset_heap_region_claim_values(); 1400 1401 // Resets the claim values of regions in the current 1402 // collection set to the default. 1403 void reset_cset_heap_region_claim_values(); 1404 1405 #ifdef ASSERT 1406 bool check_heap_region_claim_values(jint claim_value); 1407 1408 // Same as the routine above but only checks regions in the 1409 // current collection set. 1410 bool check_cset_heap_region_claim_values(jint claim_value); 1411 #endif // ASSERT 1412 1413 // Clear the cached cset start regions and (more importantly) 1414 // the time stamps. Called when we reset the GC time stamp. 1415 void clear_cset_start_regions(); 1416 1417 // Given the id of a worker, obtain or calculate a suitable 1418 // starting region for iterating over the current collection set. 1419 HeapRegion* start_cset_region_for_worker(uint worker_i); 1420 1421 // Iterate over the regions (if any) in the current collection set. 1422 void collection_set_iterate(HeapRegionClosure* blk); 1423 1424 // As above but starting from region r 1425 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1426 1427 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1428 1429 // A CollectedHeap will contain some number of spaces. This finds the 1430 // space containing a given address, or else returns NULL. 1431 virtual Space* space_containing(const void* addr) const; 1432 1433 // Returns the HeapRegion that contains addr. addr must not be NULL. 1434 template <class T> 1435 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1436 1437 // Returns the HeapRegion that contains addr. addr must not be NULL. 1438 // If addr is within a humongous continues region, it returns its humongous start region. 1439 template <class T> 1440 inline HeapRegion* heap_region_containing(const T addr) const; 1441 1442 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1443 // each address in the (reserved) heap is a member of exactly 1444 // one block. The defining characteristic of a block is that it is 1445 // possible to find its size, and thus to progress forward to the next 1446 // block. (Blocks may be of different sizes.) Thus, blocks may 1447 // represent Java objects, or they might be free blocks in a 1448 // free-list-based heap (or subheap), as long as the two kinds are 1449 // distinguishable and the size of each is determinable. 1450 1451 // Returns the address of the start of the "block" that contains the 1452 // address "addr". We say "blocks" instead of "object" since some heaps 1453 // may not pack objects densely; a chunk may either be an object or a 1454 // non-object. 1455 virtual HeapWord* block_start(const void* addr) const; 1456 1457 // Requires "addr" to be the start of a chunk, and returns its size. 1458 // "addr + size" is required to be the start of a new chunk, or the end 1459 // of the active area of the heap. 1460 virtual size_t block_size(const HeapWord* addr) const; 1461 1462 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1463 // the block is an object. 1464 virtual bool block_is_obj(const HeapWord* addr) const; 1465 1466 // Does this heap support heap inspection? (+PrintClassHistogram) 1467 virtual bool supports_heap_inspection() const { return true; } 1468 1469 // Section on thread-local allocation buffers (TLABs) 1470 // See CollectedHeap for semantics. 1471 1472 bool supports_tlab_allocation() const; 1473 size_t tlab_capacity(Thread* ignored) const; 1474 size_t tlab_used(Thread* ignored) const; 1475 size_t max_tlab_size() const; 1476 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1477 1478 // Can a compiler initialize a new object without store barriers? 1479 // This permission only extends from the creation of a new object 1480 // via a TLAB up to the first subsequent safepoint. If such permission 1481 // is granted for this heap type, the compiler promises to call 1482 // defer_store_barrier() below on any slow path allocation of 1483 // a new object for which such initializing store barriers will 1484 // have been elided. G1, like CMS, allows this, but should be 1485 // ready to provide a compensating write barrier as necessary 1486 // if that storage came out of a non-young region. The efficiency 1487 // of this implementation depends crucially on being able to 1488 // answer very efficiently in constant time whether a piece of 1489 // storage in the heap comes from a young region or not. 1490 // See ReduceInitialCardMarks. 1491 virtual bool can_elide_tlab_store_barriers() const { 1492 return true; 1493 } 1494 1495 virtual bool card_mark_must_follow_store() const { 1496 return true; 1497 } 1498 1499 inline bool is_in_young(const oop obj); 1500 1501 #ifdef ASSERT 1502 virtual bool is_in_partial_collection(const void* p); 1503 #endif 1504 1505 virtual bool is_scavengable(const void* addr); 1506 1507 // We don't need barriers for initializing stores to objects 1508 // in the young gen: for the SATB pre-barrier, there is no 1509 // pre-value that needs to be remembered; for the remembered-set 1510 // update logging post-barrier, we don't maintain remembered set 1511 // information for young gen objects. 1512 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1513 1514 // Returns "true" iff the given word_size is "very large". 1515 static bool is_humongous(size_t word_size) { 1516 // Note this has to be strictly greater-than as the TLABs 1517 // are capped at the humongous threshold and we want to 1518 // ensure that we don't try to allocate a TLAB as 1519 // humongous and that we don't allocate a humongous 1520 // object in a TLAB. 1521 return word_size > _humongous_object_threshold_in_words; 1522 } 1523 1524 // Update mod union table with the set of dirty cards. 1525 void updateModUnion(); 1526 1527 // Set the mod union bits corresponding to the given memRegion. Note 1528 // that this is always a safe operation, since it doesn't clear any 1529 // bits. 1530 void markModUnionRange(MemRegion mr); 1531 1532 // Records the fact that a marking phase is no longer in progress. 1533 void set_marking_complete() { 1534 _mark_in_progress = false; 1535 } 1536 void set_marking_started() { 1537 _mark_in_progress = true; 1538 } 1539 bool mark_in_progress() { 1540 return _mark_in_progress; 1541 } 1542 1543 // Print the maximum heap capacity. 1544 virtual size_t max_capacity() const; 1545 1546 virtual jlong millis_since_last_gc(); 1547 1548 1549 // Convenience function to be used in situations where the heap type can be 1550 // asserted to be this type. 1551 static G1CollectedHeap* heap(); 1552 1553 void set_region_short_lived_locked(HeapRegion* hr); 1554 // add appropriate methods for any other surv rate groups 1555 1556 YoungList* young_list() const { return _young_list; } 1557 1558 // debugging 1559 bool check_young_list_well_formed() { 1560 return _young_list->check_list_well_formed(); 1561 } 1562 1563 bool check_young_list_empty(bool check_heap, 1564 bool check_sample = true); 1565 1566 // *** Stuff related to concurrent marking. It's not clear to me that so 1567 // many of these need to be public. 1568 1569 // The functions below are helper functions that a subclass of 1570 // "CollectedHeap" can use in the implementation of its virtual 1571 // functions. 1572 // This performs a concurrent marking of the live objects in a 1573 // bitmap off to the side. 1574 void doConcurrentMark(); 1575 1576 bool isMarkedPrev(oop obj) const; 1577 bool isMarkedNext(oop obj) const; 1578 1579 // Determine if an object is dead, given the object and also 1580 // the region to which the object belongs. An object is dead 1581 // iff a) it was not allocated since the last mark and b) it 1582 // is not marked. 1583 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1584 return 1585 !hr->obj_allocated_since_prev_marking(obj) && 1586 !isMarkedPrev(obj); 1587 } 1588 1589 // This function returns true when an object has been 1590 // around since the previous marking and hasn't yet 1591 // been marked during this marking. 1592 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1593 return 1594 !hr->obj_allocated_since_next_marking(obj) && 1595 !isMarkedNext(obj); 1596 } 1597 1598 // Determine if an object is dead, given only the object itself. 1599 // This will find the region to which the object belongs and 1600 // then call the region version of the same function. 1601 1602 // Added if it is NULL it isn't dead. 1603 1604 inline bool is_obj_dead(const oop obj) const; 1605 1606 inline bool is_obj_ill(const oop obj) const; 1607 1608 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1609 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1610 bool is_marked(oop obj, VerifyOption vo); 1611 const char* top_at_mark_start_str(VerifyOption vo); 1612 1613 ConcurrentMark* concurrent_mark() const { return _cm; } 1614 1615 // Refinement 1616 1617 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1618 1619 // The dirty cards region list is used to record a subset of regions 1620 // whose cards need clearing. The list if populated during the 1621 // remembered set scanning and drained during the card table 1622 // cleanup. Although the methods are reentrant, population/draining 1623 // phases must not overlap. For synchronization purposes the last 1624 // element on the list points to itself. 1625 HeapRegion* _dirty_cards_region_list; 1626 void push_dirty_cards_region(HeapRegion* hr); 1627 HeapRegion* pop_dirty_cards_region(); 1628 1629 // Optimized nmethod scanning support routines 1630 1631 // Register the given nmethod with the G1 heap. 1632 virtual void register_nmethod(nmethod* nm); 1633 1634 // Unregister the given nmethod from the G1 heap. 1635 virtual void unregister_nmethod(nmethod* nm); 1636 1637 // Free up superfluous code root memory. 1638 void purge_code_root_memory(); 1639 1640 // Rebuild the strong code root lists for each region 1641 // after a full GC. 1642 void rebuild_strong_code_roots(); 1643 1644 // Delete entries for dead interned string and clean up unreferenced symbols 1645 // in symbol table, possibly in parallel. 1646 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1647 1648 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1649 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1650 1651 // Redirty logged cards in the refinement queue. 1652 void redirty_logged_cards(); 1653 // Verification 1654 1655 // The following is just to alert the verification code 1656 // that a full collection has occurred and that the 1657 // remembered sets are no longer up to date. 1658 bool _full_collection; 1659 void set_full_collection() { _full_collection = true;} 1660 void clear_full_collection() {_full_collection = false;} 1661 bool full_collection() {return _full_collection;} 1662 1663 // Perform any cleanup actions necessary before allowing a verification. 1664 virtual void prepare_for_verify(); 1665 1666 // Perform verification. 1667 1668 // vo == UsePrevMarking -> use "prev" marking information, 1669 // vo == UseNextMarking -> use "next" marking information 1670 // vo == UseMarkWord -> use the mark word in the object header 1671 // 1672 // NOTE: Only the "prev" marking information is guaranteed to be 1673 // consistent most of the time, so most calls to this should use 1674 // vo == UsePrevMarking. 1675 // Currently, there is only one case where this is called with 1676 // vo == UseNextMarking, which is to verify the "next" marking 1677 // information at the end of remark. 1678 // Currently there is only one place where this is called with 1679 // vo == UseMarkWord, which is to verify the marking during a 1680 // full GC. 1681 void verify(bool silent, VerifyOption vo); 1682 1683 // Override; it uses the "prev" marking information 1684 virtual void verify(bool silent); 1685 1686 // The methods below are here for convenience and dispatch the 1687 // appropriate method depending on value of the given VerifyOption 1688 // parameter. The values for that parameter, and their meanings, 1689 // are the same as those above. 1690 1691 bool is_obj_dead_cond(const oop obj, 1692 const HeapRegion* hr, 1693 const VerifyOption vo) const; 1694 1695 bool is_obj_dead_cond(const oop obj, 1696 const VerifyOption vo) const; 1697 1698 // Printing 1699 1700 virtual void print_on(outputStream* st) const; 1701 virtual void print_extended_on(outputStream* st) const; 1702 virtual void print_on_error(outputStream* st) const; 1703 1704 virtual void print_gc_threads_on(outputStream* st) const; 1705 virtual void gc_threads_do(ThreadClosure* tc) const; 1706 1707 // Override 1708 void print_tracing_info() const; 1709 1710 // The following two methods are helpful for debugging RSet issues. 1711 void print_cset_rsets() PRODUCT_RETURN; 1712 void print_all_rsets() PRODUCT_RETURN; 1713 1714 public: 1715 size_t pending_card_num(); 1716 size_t cards_scanned(); 1717 1718 protected: 1719 size_t _max_heap_capacity; 1720 }; 1721 1722 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP