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, 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 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 friend class HeapRegionClaimer; 215 216 private: 217 // The one and only G1CollectedHeap, so static functions can find it. 218 static G1CollectedHeap* _g1h; 219 220 static size_t _humongous_object_threshold_in_words; 221 222 // The secondary free list which contains regions that have been 223 // freed up during the cleanup process. This will be appended to 224 // the master free list when appropriate. 225 FreeRegionList _secondary_free_list; 226 227 // It keeps track of the old regions. 228 HeapRegionSet _old_set; 229 230 // It keeps track of the humongous regions. 231 HeapRegionSet _humongous_set; 232 233 void clear_humongous_is_live_table(); 234 void eagerly_reclaim_humongous_regions(); 235 236 // The number of regions we could create by expansion. 237 uint _expansion_regions; 238 239 // The block offset table for the G1 heap. 240 G1BlockOffsetSharedArray* _bot_shared; 241 242 // Tears down the region sets / lists so that they are empty and the 243 // regions on the heap do not belong to a region set / list. The 244 // only exception is the humongous set which we leave unaltered. If 245 // free_list_only is true, it will only tear down the master free 246 // list. It is called before a Full GC (free_list_only == false) or 247 // before heap shrinking (free_list_only == true). 248 void tear_down_region_sets(bool free_list_only); 249 250 // Rebuilds the region sets / lists so that they are repopulated to 251 // reflect the contents of the heap. The only exception is the 252 // humongous set which was not torn down in the first place. If 253 // free_list_only is true, it will only rebuild the master free 254 // list. It is called after a Full GC (free_list_only == false) or 255 // after heap shrinking (free_list_only == true). 256 void rebuild_region_sets(bool free_list_only); 257 258 // Callback for region mapping changed events. 259 G1RegionMappingChangedListener _listener; 260 261 // The sequence of all heap regions in the heap. 262 HeapRegionManager _hrm; 263 264 // Class that handles the different kinds of allocations. 265 G1Allocator* _allocator; 266 267 // Statistics for each allocation context 268 AllocationContextStats _allocation_context_stats; 269 270 // PLAB sizing policy for survivors. 271 PLABStats _survivor_plab_stats; 272 273 // PLAB sizing policy for tenured objects. 274 PLABStats _old_plab_stats; 275 276 // It specifies whether we should attempt to expand the heap after a 277 // region allocation failure. If heap expansion fails we set this to 278 // false so that we don't re-attempt the heap expansion (it's likely 279 // that subsequent expansion attempts will also fail if one fails). 280 // Currently, it is only consulted during GC and it's reset at the 281 // start of each GC. 282 bool _expand_heap_after_alloc_failure; 283 284 // It resets the mutator alloc region before new allocations can take place. 285 void init_mutator_alloc_region(); 286 287 // It releases the mutator alloc region. 288 void release_mutator_alloc_region(); 289 290 // It initializes the GC alloc regions at the start of a GC. 291 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 292 293 // It releases the GC alloc regions at the end of a GC. 294 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 295 296 // It does any cleanup that needs to be done on the GC alloc regions 297 // before a Full GC. 298 void abandon_gc_alloc_regions(); 299 300 // Helper for monitoring and management support. 301 G1MonitoringSupport* _g1mm; 302 303 // Records whether the region at the given index is kept live by roots or 304 // references from the young generation. 305 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 306 protected: 307 bool default_value() const { return false; } 308 public: 309 void clear() { G1BiasedMappedArray<bool>::clear(); } 310 void set_live(uint region) { 311 set_by_index(region, true); 312 } 313 bool is_live(uint region) { 314 return get_by_index(region); 315 } 316 }; 317 318 HumongousIsLiveBiasedMappedArray _humongous_is_live; 319 // Stores whether during humongous object registration we found candidate regions. 320 // If not, we can skip a few steps. 321 bool _has_humongous_reclaim_candidates; 322 323 volatile unsigned _gc_time_stamp; 324 325 size_t* _surviving_young_words; 326 327 G1HRPrinter _hr_printer; 328 329 void setup_surviving_young_words(); 330 void update_surviving_young_words(size_t* surv_young_words); 331 void cleanup_surviving_young_words(); 332 333 // It decides whether an explicit GC should start a concurrent cycle 334 // instead of doing a STW GC. Currently, a concurrent cycle is 335 // explicitly started if: 336 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 337 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 338 // (c) cause == _g1_humongous_allocation 339 bool should_do_concurrent_full_gc(GCCause::Cause cause); 340 341 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 342 // concurrent cycles) we have started. 343 volatile unsigned int _old_marking_cycles_started; 344 345 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 346 // concurrent cycles) we have completed. 347 volatile unsigned int _old_marking_cycles_completed; 348 349 bool _concurrent_cycle_started; 350 bool _heap_summary_sent; 351 352 // This is a non-product method that is helpful for testing. It is 353 // called at the end of a GC and artificially expands the heap by 354 // allocating a number of dead regions. This way we can induce very 355 // frequent marking cycles and stress the cleanup / concurrent 356 // cleanup code more (as all the regions that will be allocated by 357 // this method will be found dead by the marking cycle). 358 void allocate_dummy_regions() PRODUCT_RETURN; 359 360 // Clear RSets after a compaction. It also resets the GC time stamps. 361 void clear_rsets_post_compaction(); 362 363 // If the HR printer is active, dump the state of the regions in the 364 // heap after a compaction. 365 void print_hrm_post_compaction(); 366 367 double verify(bool guard, const char* msg); 368 void verify_before_gc(); 369 void verify_after_gc(); 370 371 void log_gc_header(); 372 void log_gc_footer(double pause_time_sec); 373 374 // These are macros so that, if the assert fires, we get the correct 375 // line number, file, etc. 376 377 #define heap_locking_asserts_err_msg(_extra_message_) \ 378 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 379 (_extra_message_), \ 380 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 381 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 382 BOOL_TO_STR(Thread::current()->is_VM_thread())) 383 384 #define assert_heap_locked() \ 385 do { \ 386 assert(Heap_lock->owned_by_self(), \ 387 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 388 } while (0) 389 390 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 391 do { \ 392 assert(Heap_lock->owned_by_self() || \ 393 (SafepointSynchronize::is_at_safepoint() && \ 394 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 395 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 396 "should be at a safepoint")); \ 397 } while (0) 398 399 #define assert_heap_locked_and_not_at_safepoint() \ 400 do { \ 401 assert(Heap_lock->owned_by_self() && \ 402 !SafepointSynchronize::is_at_safepoint(), \ 403 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 404 "should not be at a safepoint")); \ 405 } while (0) 406 407 #define assert_heap_not_locked() \ 408 do { \ 409 assert(!Heap_lock->owned_by_self(), \ 410 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 411 } while (0) 412 413 #define assert_heap_not_locked_and_not_at_safepoint() \ 414 do { \ 415 assert(!Heap_lock->owned_by_self() && \ 416 !SafepointSynchronize::is_at_safepoint(), \ 417 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 418 "should not be at a safepoint")); \ 419 } while (0) 420 421 #define assert_at_safepoint(_should_be_vm_thread_) \ 422 do { \ 423 assert(SafepointSynchronize::is_at_safepoint() && \ 424 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 425 heap_locking_asserts_err_msg("should be at a safepoint")); \ 426 } while (0) 427 428 #define assert_not_at_safepoint() \ 429 do { \ 430 assert(!SafepointSynchronize::is_at_safepoint(), \ 431 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 432 } while (0) 433 434 protected: 435 436 // The young region list. 437 YoungList* _young_list; 438 439 // The current policy object for the collector. 440 G1CollectorPolicy* _g1_policy; 441 442 // This is the second level of trying to allocate a new region. If 443 // new_region() didn't find a region on the free_list, this call will 444 // check whether there's anything available on the 445 // secondary_free_list and/or wait for more regions to appear on 446 // that list, if _free_regions_coming is set. 447 HeapRegion* new_region_try_secondary_free_list(bool is_old); 448 449 // Try to allocate a single non-humongous HeapRegion sufficient for 450 // an allocation of the given word_size. If do_expand is true, 451 // attempt to expand the heap if necessary to satisfy the allocation 452 // request. If the region is to be used as an old region or for a 453 // humongous object, set is_old to true. If not, to false. 454 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 455 456 // Initialize a contiguous set of free regions of length num_regions 457 // and starting at index first so that they appear as a single 458 // humongous region. 459 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 460 uint num_regions, 461 size_t word_size, 462 AllocationContext_t context); 463 464 // Attempt to allocate a humongous object of the given size. Return 465 // NULL if unsuccessful. 466 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 467 468 // The following two methods, allocate_new_tlab() and 469 // mem_allocate(), are the two main entry points from the runtime 470 // into the G1's allocation routines. They have the following 471 // assumptions: 472 // 473 // * They should both be called outside safepoints. 474 // 475 // * They should both be called without holding the Heap_lock. 476 // 477 // * All allocation requests for new TLABs should go to 478 // allocate_new_tlab(). 479 // 480 // * All non-TLAB allocation requests should go to mem_allocate(). 481 // 482 // * If either call cannot satisfy the allocation request using the 483 // current allocating region, they will try to get a new one. If 484 // this fails, they will attempt to do an evacuation pause and 485 // retry the allocation. 486 // 487 // * If all allocation attempts fail, even after trying to schedule 488 // an evacuation pause, allocate_new_tlab() will return NULL, 489 // whereas mem_allocate() will attempt a heap expansion and/or 490 // schedule a Full GC. 491 // 492 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 493 // should never be called with word_size being humongous. All 494 // humongous allocation requests should go to mem_allocate() which 495 // will satisfy them with a special path. 496 497 virtual HeapWord* allocate_new_tlab(size_t word_size); 498 499 virtual HeapWord* mem_allocate(size_t word_size, 500 bool* gc_overhead_limit_was_exceeded); 501 502 // The following three methods take a gc_count_before_ret 503 // parameter which is used to return the GC count if the method 504 // returns NULL. Given that we are required to read the GC count 505 // while holding the Heap_lock, and these paths will take the 506 // Heap_lock at some point, it's easier to get them to read the GC 507 // count while holding the Heap_lock before they return NULL instead 508 // of the caller (namely: mem_allocate()) having to also take the 509 // Heap_lock just to read the GC count. 510 511 // First-level mutator allocation attempt: try to allocate out of 512 // the mutator alloc region without taking the Heap_lock. This 513 // should only be used for non-humongous allocations. 514 inline HeapWord* attempt_allocation(size_t word_size, 515 unsigned int* gc_count_before_ret, 516 int* gclocker_retry_count_ret); 517 518 // Second-level mutator allocation attempt: take the Heap_lock and 519 // retry the allocation attempt, potentially scheduling a GC 520 // pause. This should only be used for non-humongous allocations. 521 HeapWord* attempt_allocation_slow(size_t word_size, 522 AllocationContext_t context, 523 unsigned int* gc_count_before_ret, 524 int* gclocker_retry_count_ret); 525 526 // Takes the Heap_lock and attempts a humongous allocation. It can 527 // potentially schedule a GC pause. 528 HeapWord* attempt_allocation_humongous(size_t word_size, 529 unsigned int* gc_count_before_ret, 530 int* gclocker_retry_count_ret); 531 532 // Allocation attempt that should be called during safepoints (e.g., 533 // at the end of a successful GC). expect_null_mutator_alloc_region 534 // specifies whether the mutator alloc region is expected to be NULL 535 // or not. 536 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 537 AllocationContext_t context, 538 bool expect_null_mutator_alloc_region); 539 540 // It dirties the cards that cover the block so that so that the post 541 // write barrier never queues anything when updating objects on this 542 // block. It is assumed (and in fact we assert) that the block 543 // belongs to a young region. 544 inline void dirty_young_block(HeapWord* start, size_t word_size); 545 546 // Allocate blocks during garbage collection. Will ensure an 547 // allocation region, either by picking one or expanding the 548 // heap, and then allocate a block of the given size. The block 549 // may not be a humongous - it must fit into a single heap region. 550 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, 551 size_t word_size, 552 AllocationContext_t context); 553 554 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, 555 HeapRegion* alloc_region, 556 bool par, 557 size_t word_size); 558 559 // Ensure that no further allocations can happen in "r", bearing in mind 560 // that parallel threads might be attempting allocations. 561 void par_allocate_remaining_space(HeapRegion* r); 562 563 // Allocation attempt during GC for a survivor object / PLAB. 564 inline HeapWord* survivor_attempt_allocation(size_t word_size, 565 AllocationContext_t context); 566 567 // Allocation attempt during GC for an old object / PLAB. 568 inline HeapWord* old_attempt_allocation(size_t word_size, 569 AllocationContext_t context); 570 571 // These methods are the "callbacks" from the G1AllocRegion class. 572 573 // For mutator alloc regions. 574 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 575 void retire_mutator_alloc_region(HeapRegion* alloc_region, 576 size_t allocated_bytes); 577 578 // For GC alloc regions. 579 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 580 GCAllocPurpose ap); 581 void retire_gc_alloc_region(HeapRegion* alloc_region, 582 size_t allocated_bytes, GCAllocPurpose ap); 583 584 // - if explicit_gc is true, the GC is for a System.gc() or a heap 585 // inspection request and should collect the entire heap 586 // - if clear_all_soft_refs is true, all soft references should be 587 // cleared during the GC 588 // - if explicit_gc is false, word_size describes the allocation that 589 // the GC should attempt (at least) to satisfy 590 // - it returns false if it is unable to do the collection due to the 591 // GC locker being active, true otherwise 592 bool do_collection(bool explicit_gc, 593 bool clear_all_soft_refs, 594 size_t word_size); 595 596 // Callback from VM_G1CollectFull operation. 597 // Perform a full collection. 598 virtual void do_full_collection(bool clear_all_soft_refs); 599 600 // Resize the heap if necessary after a full collection. If this is 601 // after a collect-for allocation, "word_size" is the allocation size, 602 // and will be considered part of the used portion of the heap. 603 void resize_if_necessary_after_full_collection(size_t word_size); 604 605 // Callback from VM_G1CollectForAllocation operation. 606 // This function does everything necessary/possible to satisfy a 607 // failed allocation request (including collection, expansion, etc.) 608 HeapWord* satisfy_failed_allocation(size_t word_size, 609 AllocationContext_t context, 610 bool* succeeded); 611 612 // Attempting to expand the heap sufficiently 613 // to support an allocation of the given "word_size". If 614 // successful, perform the allocation and return the address of the 615 // allocated block, or else "NULL". 616 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 617 618 // Process any reference objects discovered during 619 // an incremental evacuation pause. 620 void process_discovered_references(uint no_of_gc_workers); 621 622 // Enqueue any remaining discovered references 623 // after processing. 624 void enqueue_discovered_references(uint no_of_gc_workers); 625 626 public: 627 628 G1Allocator* allocator() { 629 return _allocator; 630 } 631 632 G1MonitoringSupport* g1mm() { 633 assert(_g1mm != NULL, "should have been initialized"); 634 return _g1mm; 635 } 636 637 // Expand the garbage-first heap by at least the given size (in bytes!). 638 // Returns true if the heap was expanded by the requested amount; 639 // false otherwise. 640 // (Rounds up to a HeapRegion boundary.) 641 bool expand(size_t expand_bytes); 642 643 // Returns the PLAB statistics given a purpose. 644 PLABStats* stats_for_purpose(GCAllocPurpose purpose) { 645 PLABStats* stats = NULL; 646 647 switch (purpose) { 648 case GCAllocForSurvived: 649 stats = &_survivor_plab_stats; 650 break; 651 case GCAllocForTenured: 652 stats = &_old_plab_stats; 653 break; 654 default: 655 assert(false, "unrecognized GCAllocPurpose"); 656 } 657 658 return stats; 659 } 660 661 // Determines PLAB size for a particular allocation purpose. 662 size_t desired_plab_sz(GCAllocPurpose purpose); 663 664 inline AllocationContextStats& allocation_context_stats(); 665 666 // Do anything common to GC's. 667 virtual void gc_prologue(bool full); 668 virtual void gc_epilogue(bool full); 669 670 inline void set_humongous_is_live(oop obj); 671 672 bool humongous_is_live(uint region) { 673 return _humongous_is_live.is_live(region); 674 } 675 676 // Returns whether the given region (which must be a humongous (start) region) 677 // is to be considered conservatively live regardless of any other conditions. 678 bool humongous_region_is_always_live(uint index); 679 // Register the given region to be part of the collection set. 680 inline void register_humongous_region_with_in_cset_fast_test(uint index); 681 // Register regions with humongous objects (actually on the start region) in 682 // the in_cset_fast_test table. 683 void register_humongous_regions_with_in_cset_fast_test(); 684 // We register a region with the fast "in collection set" test. We 685 // simply set to true the array slot corresponding to this region. 686 void register_region_with_in_cset_fast_test(HeapRegion* r) { 687 _in_cset_fast_test.set_in_cset(r->hrm_index()); 688 } 689 690 // This is a fast test on whether a reference points into the 691 // collection set or not. Assume that the reference 692 // points into the heap. 693 inline bool in_cset_fast_test(oop obj); 694 695 void clear_cset_fast_test() { 696 _in_cset_fast_test.clear(); 697 } 698 699 // This is called at the start of either a concurrent cycle or a Full 700 // GC to update the number of old marking cycles started. 701 void increment_old_marking_cycles_started(); 702 703 // This is called at the end of either a concurrent cycle or a Full 704 // GC to update the number of old marking cycles completed. Those two 705 // can happen in a nested fashion, i.e., we start a concurrent 706 // cycle, a Full GC happens half-way through it which ends first, 707 // and then the cycle notices that a Full GC happened and ends 708 // too. The concurrent parameter is a boolean to help us do a bit 709 // tighter consistency checking in the method. If concurrent is 710 // false, the caller is the inner caller in the nesting (i.e., the 711 // Full GC). If concurrent is true, the caller is the outer caller 712 // in this nesting (i.e., the concurrent cycle). Further nesting is 713 // not currently supported. The end of this call also notifies 714 // the FullGCCount_lock in case a Java thread is waiting for a full 715 // GC to happen (e.g., it called System.gc() with 716 // +ExplicitGCInvokesConcurrent). 717 void increment_old_marking_cycles_completed(bool concurrent); 718 719 unsigned int old_marking_cycles_completed() { 720 return _old_marking_cycles_completed; 721 } 722 723 void register_concurrent_cycle_start(const Ticks& start_time); 724 void register_concurrent_cycle_end(); 725 void trace_heap_after_concurrent_cycle(); 726 727 G1YCType yc_type(); 728 729 G1HRPrinter* hr_printer() { return &_hr_printer; } 730 731 // Frees a non-humongous region by initializing its contents and 732 // adding it to the free list that's passed as a parameter (this is 733 // usually a local list which will be appended to the master free 734 // list later). The used bytes of freed regions are accumulated in 735 // pre_used. If par is true, the region's RSet will not be freed 736 // up. The assumption is that this will be done later. 737 // The locked parameter indicates if the caller has already taken 738 // care of proper synchronization. This may allow some optimizations. 739 void free_region(HeapRegion* hr, 740 FreeRegionList* free_list, 741 bool par, 742 bool locked = false); 743 744 // Frees a humongous region by collapsing it into individual regions 745 // and calling free_region() for each of them. The freed regions 746 // will be added to the free list that's passed as a parameter (this 747 // is usually a local list which will be appended to the master free 748 // list later). The used bytes of freed regions are accumulated in 749 // pre_used. If par is true, the region's RSet will not be freed 750 // up. The assumption is that this will be done later. 751 void free_humongous_region(HeapRegion* hr, 752 FreeRegionList* free_list, 753 bool par); 754 protected: 755 756 // Shrink the garbage-first heap by at most the given size (in bytes!). 757 // (Rounds down to a HeapRegion boundary.) 758 virtual void shrink(size_t expand_bytes); 759 void shrink_helper(size_t expand_bytes); 760 761 #if TASKQUEUE_STATS 762 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 763 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 764 void reset_taskqueue_stats(); 765 #endif // TASKQUEUE_STATS 766 767 // Schedule the VM operation that will do an evacuation pause to 768 // satisfy an allocation request of word_size. *succeeded will 769 // return whether the VM operation was successful (it did do an 770 // evacuation pause) or not (another thread beat us to it or the GC 771 // locker was active). Given that we should not be holding the 772 // Heap_lock when we enter this method, we will pass the 773 // gc_count_before (i.e., total_collections()) as a parameter since 774 // it has to be read while holding the Heap_lock. Currently, both 775 // methods that call do_collection_pause() release the Heap_lock 776 // before the call, so it's easy to read gc_count_before just before. 777 HeapWord* do_collection_pause(size_t word_size, 778 unsigned int gc_count_before, 779 bool* succeeded, 780 GCCause::Cause gc_cause); 781 782 // The guts of the incremental collection pause, executed by the vm 783 // thread. It returns false if it is unable to do the collection due 784 // to the GC locker being active, true otherwise 785 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 786 787 // Actually do the work of evacuating the collection set. 788 void evacuate_collection_set(EvacuationInfo& evacuation_info); 789 790 // The g1 remembered set of the heap. 791 G1RemSet* _g1_rem_set; 792 793 // A set of cards that cover the objects for which the Rsets should be updated 794 // concurrently after the collection. 795 DirtyCardQueueSet _dirty_card_queue_set; 796 797 // The closure used to refine a single card. 798 RefineCardTableEntryClosure* _refine_cte_cl; 799 800 // A DirtyCardQueueSet that is used to hold cards that contain 801 // references into the current collection set. This is used to 802 // update the remembered sets of the regions in the collection 803 // set in the event of an evacuation failure. 804 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 805 806 // After a collection pause, make the regions in the CS into free 807 // regions. 808 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 809 810 // Abandon the current collection set without recording policy 811 // statistics or updating free lists. 812 void abandon_collection_set(HeapRegion* cs_head); 813 814 // Applies "scan_non_heap_roots" to roots outside the heap, 815 // "scan_rs" to roots inside the heap (having done "set_region" to 816 // indicate the region in which the root resides), 817 // and does "scan_metadata" If "scan_rs" is 818 // NULL, then this step is skipped. The "worker_i" 819 // param is for use with parallel roots processing, and should be 820 // the "i" of the calling parallel worker thread's work(i) function. 821 // In the sequential case this param will be ignored. 822 void g1_process_roots(OopClosure* scan_non_heap_roots, 823 OopClosure* scan_non_heap_weak_roots, 824 OopsInHeapRegionClosure* scan_rs, 825 CLDClosure* scan_strong_clds, 826 CLDClosure* scan_weak_clds, 827 CodeBlobClosure* scan_strong_code, 828 uint worker_i); 829 830 // The concurrent marker (and the thread it runs in.) 831 ConcurrentMark* _cm; 832 ConcurrentMarkThread* _cmThread; 833 bool _mark_in_progress; 834 835 // The concurrent refiner. 836 ConcurrentG1Refine* _cg1r; 837 838 // The parallel task queues 839 RefToScanQueueSet *_task_queues; 840 841 // True iff a evacuation has failed in the current collection. 842 bool _evacuation_failed; 843 844 EvacuationFailedInfo* _evacuation_failed_info_array; 845 846 // Failed evacuations cause some logical from-space objects to have 847 // forwarding pointers to themselves. Reset them. 848 void remove_self_forwarding_pointers(); 849 850 // Together, these store an object with a preserved mark, and its mark value. 851 Stack<oop, mtGC> _objs_with_preserved_marks; 852 Stack<markOop, mtGC> _preserved_marks_of_objs; 853 854 // Preserve the mark of "obj", if necessary, in preparation for its mark 855 // word being overwritten with a self-forwarding-pointer. 856 void preserve_mark_if_necessary(oop obj, markOop m); 857 858 // The stack of evac-failure objects left to be scanned. 859 GrowableArray<oop>* _evac_failure_scan_stack; 860 // The closure to apply to evac-failure objects. 861 862 OopsInHeapRegionClosure* _evac_failure_closure; 863 // Set the field above. 864 void 865 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 866 _evac_failure_closure = evac_failure_closure; 867 } 868 869 // Push "obj" on the scan stack. 870 void push_on_evac_failure_scan_stack(oop obj); 871 // Process scan stack entries until the stack is empty. 872 void drain_evac_failure_scan_stack(); 873 // True iff an invocation of "drain_scan_stack" is in progress; to 874 // prevent unnecessary recursion. 875 bool _drain_in_progress; 876 877 // Do any necessary initialization for evacuation-failure handling. 878 // "cl" is the closure that will be used to process evac-failure 879 // objects. 880 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 881 // Do any necessary cleanup for evacuation-failure handling data 882 // structures. 883 void finalize_for_evac_failure(); 884 885 // An attempt to evacuate "obj" has failed; take necessary steps. 886 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 887 void handle_evacuation_failure_common(oop obj, markOop m); 888 889 #ifndef PRODUCT 890 // Support for forcing evacuation failures. Analogous to 891 // PromotionFailureALot for the other collectors. 892 893 // Records whether G1EvacuationFailureALot should be in effect 894 // for the current GC 895 bool _evacuation_failure_alot_for_current_gc; 896 897 // Used to record the GC number for interval checking when 898 // determining whether G1EvaucationFailureALot is in effect 899 // for the current GC. 900 size_t _evacuation_failure_alot_gc_number; 901 902 // Count of the number of evacuations between failures. 903 volatile size_t _evacuation_failure_alot_count; 904 905 // Set whether G1EvacuationFailureALot should be in effect 906 // for the current GC (based upon the type of GC and which 907 // command line flags are set); 908 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 909 bool during_initial_mark, 910 bool during_marking); 911 912 inline void set_evacuation_failure_alot_for_current_gc(); 913 914 // Return true if it's time to cause an evacuation failure. 915 inline bool evacuation_should_fail(); 916 917 // Reset the G1EvacuationFailureALot counters. Should be called at 918 // the end of an evacuation pause in which an evacuation failure occurred. 919 inline void reset_evacuation_should_fail(); 920 #endif // !PRODUCT 921 922 // ("Weak") Reference processing support. 923 // 924 // G1 has 2 instances of the reference processor class. One 925 // (_ref_processor_cm) handles reference object discovery 926 // and subsequent processing during concurrent marking cycles. 927 // 928 // The other (_ref_processor_stw) handles reference object 929 // discovery and processing during full GCs and incremental 930 // evacuation pauses. 931 // 932 // During an incremental pause, reference discovery will be 933 // temporarily disabled for _ref_processor_cm and will be 934 // enabled for _ref_processor_stw. At the end of the evacuation 935 // pause references discovered by _ref_processor_stw will be 936 // processed and discovery will be disabled. The previous 937 // setting for reference object discovery for _ref_processor_cm 938 // will be re-instated. 939 // 940 // At the start of marking: 941 // * Discovery by the CM ref processor is verified to be inactive 942 // and it's discovered lists are empty. 943 // * Discovery by the CM ref processor is then enabled. 944 // 945 // At the end of marking: 946 // * Any references on the CM ref processor's discovered 947 // lists are processed (possibly MT). 948 // 949 // At the start of full GC we: 950 // * Disable discovery by the CM ref processor and 951 // empty CM ref processor's discovered lists 952 // (without processing any entries). 953 // * Verify that the STW ref processor is inactive and it's 954 // discovered lists are empty. 955 // * Temporarily set STW ref processor discovery as single threaded. 956 // * Temporarily clear the STW ref processor's _is_alive_non_header 957 // field. 958 // * Finally enable discovery by the STW ref processor. 959 // 960 // The STW ref processor is used to record any discovered 961 // references during the full GC. 962 // 963 // At the end of a full GC we: 964 // * Enqueue any reference objects discovered by the STW ref processor 965 // that have non-live referents. This has the side-effect of 966 // making the STW ref processor inactive by disabling discovery. 967 // * Verify that the CM ref processor is still inactive 968 // and no references have been placed on it's discovered 969 // lists (also checked as a precondition during initial marking). 970 971 // The (stw) reference processor... 972 ReferenceProcessor* _ref_processor_stw; 973 974 STWGCTimer* _gc_timer_stw; 975 ConcurrentGCTimer* _gc_timer_cm; 976 977 G1OldTracer* _gc_tracer_cm; 978 G1NewTracer* _gc_tracer_stw; 979 980 // During reference object discovery, the _is_alive_non_header 981 // closure (if non-null) is applied to the referent object to 982 // determine whether the referent is live. If so then the 983 // reference object does not need to be 'discovered' and can 984 // be treated as a regular oop. This has the benefit of reducing 985 // the number of 'discovered' reference objects that need to 986 // be processed. 987 // 988 // Instance of the is_alive closure for embedding into the 989 // STW reference processor as the _is_alive_non_header field. 990 // Supplying a value for the _is_alive_non_header field is 991 // optional but doing so prevents unnecessary additions to 992 // the discovered lists during reference discovery. 993 G1STWIsAliveClosure _is_alive_closure_stw; 994 995 // The (concurrent marking) reference processor... 996 ReferenceProcessor* _ref_processor_cm; 997 998 // Instance of the concurrent mark is_alive closure for embedding 999 // into the Concurrent Marking reference processor as the 1000 // _is_alive_non_header field. Supplying a value for the 1001 // _is_alive_non_header field is optional but doing so prevents 1002 // unnecessary additions to the discovered lists during reference 1003 // discovery. 1004 G1CMIsAliveClosure _is_alive_closure_cm; 1005 1006 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 1007 HeapRegion** _worker_cset_start_region; 1008 1009 // Time stamp to validate the regions recorded in the cache 1010 // used by G1CollectedHeap::start_cset_region_for_worker(). 1011 // The heap region entry for a given worker is valid iff 1012 // the associated time stamp value matches the current value 1013 // of G1CollectedHeap::_gc_time_stamp. 1014 unsigned int* _worker_cset_start_region_time_stamp; 1015 1016 enum G1H_process_roots_tasks { 1017 G1H_PS_filter_satb_buffers, 1018 G1H_PS_refProcessor_oops_do, 1019 // Leave this one last. 1020 G1H_PS_NumElements 1021 }; 1022 1023 SubTasksDone* _process_strong_tasks; 1024 1025 volatile bool _free_regions_coming; 1026 1027 public: 1028 1029 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } 1030 1031 void set_refine_cte_cl_concurrency(bool concurrent); 1032 1033 RefToScanQueue *task_queue(int i) const; 1034 1035 // A set of cards where updates happened during the GC 1036 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1037 1038 // A DirtyCardQueueSet that is used to hold cards that contain 1039 // references into the current collection set. This is used to 1040 // update the remembered sets of the regions in the collection 1041 // set in the event of an evacuation failure. 1042 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1043 { return _into_cset_dirty_card_queue_set; } 1044 1045 // Create a G1CollectedHeap with the specified policy. 1046 // Must call the initialize method afterwards. 1047 // May not return if something goes wrong. 1048 G1CollectedHeap(G1CollectorPolicy* policy); 1049 1050 // Initialize the G1CollectedHeap to have the initial and 1051 // maximum sizes and remembered and barrier sets 1052 // specified by the policy object. 1053 jint initialize(); 1054 1055 virtual void stop(); 1056 1057 // Return the (conservative) maximum heap alignment for any G1 heap 1058 static size_t conservative_max_heap_alignment(); 1059 1060 // Initialize weak reference processing. 1061 virtual void ref_processing_init(); 1062 1063 void set_par_threads(uint t) { 1064 SharedHeap::set_par_threads(t); 1065 // Done in SharedHeap but oddly there are 1066 // two _process_strong_tasks's in a G1CollectedHeap 1067 // so do it here too. 1068 _process_strong_tasks->set_n_threads(t); 1069 } 1070 1071 // Set _n_par_threads according to a policy TBD. 1072 void set_par_threads(); 1073 1074 void set_n_termination(int t) { 1075 _process_strong_tasks->set_n_threads(t); 1076 } 1077 1078 virtual CollectedHeap::Name kind() const { 1079 return CollectedHeap::G1CollectedHeap; 1080 } 1081 1082 // The current policy object for the collector. 1083 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1084 1085 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1086 1087 // Adaptive size policy. No such thing for g1. 1088 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1089 1090 // The rem set and barrier set. 1091 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1092 1093 unsigned get_gc_time_stamp() { 1094 return _gc_time_stamp; 1095 } 1096 1097 inline void reset_gc_time_stamp(); 1098 1099 void check_gc_time_stamps() PRODUCT_RETURN; 1100 1101 inline void increment_gc_time_stamp(); 1102 1103 // Reset the given region's GC timestamp. If it's starts humongous, 1104 // also reset the GC timestamp of its corresponding 1105 // continues humongous regions too. 1106 void reset_gc_time_stamps(HeapRegion* hr); 1107 1108 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1109 DirtyCardQueue* into_cset_dcq, 1110 bool concurrent, uint worker_i); 1111 1112 // The shared block offset table array. 1113 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1114 1115 // Reference Processing accessors 1116 1117 // The STW reference processor.... 1118 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1119 1120 // The Concurrent Marking reference processor... 1121 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1122 1123 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1124 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1125 1126 virtual size_t capacity() const; 1127 virtual size_t used() const; 1128 // This should be called when we're not holding the heap lock. The 1129 // result might be a bit inaccurate. 1130 size_t used_unlocked() const; 1131 size_t recalculate_used() const; 1132 1133 // These virtual functions do the actual allocation. 1134 // Some heaps may offer a contiguous region for shared non-blocking 1135 // allocation, via inlined code (by exporting the address of the top and 1136 // end fields defining the extent of the contiguous allocation region.) 1137 // But G1CollectedHeap doesn't yet support this. 1138 1139 virtual bool is_maximal_no_gc() const { 1140 return _hrm.available() == 0; 1141 } 1142 1143 // The current number of regions in the heap. 1144 uint num_regions() const { return _hrm.length(); } 1145 1146 // The max number of regions in the heap. 1147 uint max_regions() const { return _hrm.max_length(); } 1148 1149 // The number of regions that are completely free. 1150 uint num_free_regions() const { return _hrm.num_free_regions(); } 1151 1152 // The number of regions that are not completely free. 1153 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1154 1155 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1156 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1157 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1158 void verify_dirty_young_regions() PRODUCT_RETURN; 1159 1160 #ifndef PRODUCT 1161 // Make sure that the given bitmap has no marked objects in the 1162 // range [from,limit). If it does, print an error message and return 1163 // false. Otherwise, just return true. bitmap_name should be "prev" 1164 // or "next". 1165 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1166 HeapWord* from, HeapWord* limit); 1167 1168 // Verify that the prev / next bitmap range [tams,end) for the given 1169 // region has no marks. Return true if all is well, false if errors 1170 // are detected. 1171 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1172 #endif // PRODUCT 1173 1174 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1175 // the given region do not have any spurious marks. If errors are 1176 // detected, print appropriate error messages and crash. 1177 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1178 1179 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1180 // have any spurious marks. If errors are detected, print 1181 // appropriate error messages and crash. 1182 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1183 1184 // verify_region_sets() performs verification over the region 1185 // lists. It will be compiled in the product code to be used when 1186 // necessary (i.e., during heap verification). 1187 void verify_region_sets(); 1188 1189 // verify_region_sets_optional() is planted in the code for 1190 // list verification in non-product builds (and it can be enabled in 1191 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1192 #if HEAP_REGION_SET_FORCE_VERIFY 1193 void verify_region_sets_optional() { 1194 verify_region_sets(); 1195 } 1196 #else // HEAP_REGION_SET_FORCE_VERIFY 1197 void verify_region_sets_optional() { } 1198 #endif // HEAP_REGION_SET_FORCE_VERIFY 1199 1200 #ifdef ASSERT 1201 bool is_on_master_free_list(HeapRegion* hr) { 1202 return _hrm.is_free(hr); 1203 } 1204 #endif // ASSERT 1205 1206 // Wrapper for the region list operations that can be called from 1207 // methods outside this class. 1208 1209 void secondary_free_list_add(FreeRegionList* list) { 1210 _secondary_free_list.add_ordered(list); 1211 } 1212 1213 void append_secondary_free_list() { 1214 _hrm.insert_list_into_free_list(&_secondary_free_list); 1215 } 1216 1217 void append_secondary_free_list_if_not_empty_with_lock() { 1218 // If the secondary free list looks empty there's no reason to 1219 // take the lock and then try to append it. 1220 if (!_secondary_free_list.is_empty()) { 1221 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1222 append_secondary_free_list(); 1223 } 1224 } 1225 1226 inline void old_set_remove(HeapRegion* hr); 1227 1228 size_t non_young_capacity_bytes() { 1229 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1230 } 1231 1232 void set_free_regions_coming(); 1233 void reset_free_regions_coming(); 1234 bool free_regions_coming() { return _free_regions_coming; } 1235 void wait_while_free_regions_coming(); 1236 1237 // Determine whether the given region is one that we are using as an 1238 // old GC alloc region. 1239 bool is_old_gc_alloc_region(HeapRegion* hr) { 1240 return _allocator->is_retained_old_region(hr); 1241 } 1242 1243 // Perform a collection of the heap; intended for use in implementing 1244 // "System.gc". This probably implies as full a collection as the 1245 // "CollectedHeap" supports. 1246 virtual void collect(GCCause::Cause cause); 1247 1248 // The same as above but assume that the caller holds the Heap_lock. 1249 void collect_locked(GCCause::Cause cause); 1250 1251 virtual bool copy_allocation_context_stats(const jint* contexts, 1252 jlong* totals, 1253 jbyte* accuracy, 1254 jint len); 1255 1256 // True iff an evacuation has failed in the most-recent collection. 1257 bool evacuation_failed() { return _evacuation_failed; } 1258 1259 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1260 void prepend_to_freelist(FreeRegionList* list); 1261 void decrement_summary_bytes(size_t bytes); 1262 1263 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1264 virtual bool is_in(const void* p) const; 1265 #ifdef ASSERT 1266 // Returns whether p is in one of the available areas of the heap. Slow but 1267 // extensive version. 1268 bool is_in_exact(const void* p) const; 1269 #endif 1270 1271 // Return "TRUE" iff the given object address is within the collection 1272 // set. Slow implementation. 1273 inline bool obj_in_cs(oop obj); 1274 1275 inline bool is_in_cset(oop obj); 1276 1277 inline bool is_in_cset_or_humongous(const oop obj); 1278 1279 enum in_cset_state_t { 1280 InNeither, // neither in collection set nor humongous 1281 InCSet, // region is in collection set only 1282 IsHumongous // region is a humongous start region 1283 }; 1284 private: 1285 // Instances of this class are used for quick tests on whether a reference points 1286 // into the collection set or is a humongous object (points into a humongous 1287 // object). 1288 // Each of the array's elements denotes whether the corresponding region is in 1289 // the collection set or a humongous region. 1290 // We use this to quickly reclaim humongous objects: by making a humongous region 1291 // succeed this test, we sort-of add it to the collection set. During the reference 1292 // iteration closures, when we see a humongous region, we simply mark it as 1293 // referenced, i.e. live. 1294 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> { 1295 protected: 1296 char default_value() const { return G1CollectedHeap::InNeither; } 1297 public: 1298 void set_humongous(uintptr_t index) { 1299 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values"); 1300 set_by_index(index, G1CollectedHeap::IsHumongous); 1301 } 1302 1303 void clear_humongous(uintptr_t index) { 1304 set_by_index(index, G1CollectedHeap::InNeither); 1305 } 1306 1307 void set_in_cset(uintptr_t index) { 1308 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value"); 1309 set_by_index(index, G1CollectedHeap::InCSet); 1310 } 1311 1312 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; } 1313 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; } 1314 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); } 1315 void clear() { G1BiasedMappedArray<char>::clear(); } 1316 }; 1317 1318 // This array is used for a quick test on whether a reference points into 1319 // the collection set or not. Each of the array's elements denotes whether the 1320 // corresponding region is in the collection set or not. 1321 G1FastCSetBiasedMappedArray _in_cset_fast_test; 1322 1323 public: 1324 1325 inline in_cset_state_t in_cset_state(const oop obj); 1326 1327 // Return "TRUE" iff the given object address is in the reserved 1328 // region of g1. 1329 bool is_in_g1_reserved(const void* p) const { 1330 return _hrm.reserved().contains(p); 1331 } 1332 1333 // Returns a MemRegion that corresponds to the space that has been 1334 // reserved for the heap 1335 MemRegion g1_reserved() const { 1336 return _hrm.reserved(); 1337 } 1338 1339 virtual bool is_in_closed_subset(const void* p) const; 1340 1341 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1342 return (G1SATBCardTableLoggingModRefBS*) barrier_set(); 1343 } 1344 1345 // This resets the card table to all zeros. It is used after 1346 // a collection pause which used the card table to claim cards. 1347 void cleanUpCardTable(); 1348 1349 // Iteration functions. 1350 1351 // Iterate over all the ref-containing fields of all objects, calling 1352 // "cl.do_oop" on each. 1353 virtual void oop_iterate(ExtendedOopClosure* cl); 1354 1355 // Iterate over all objects, calling "cl.do_object" on each. 1356 virtual void object_iterate(ObjectClosure* cl); 1357 1358 virtual void safe_object_iterate(ObjectClosure* cl) { 1359 object_iterate(cl); 1360 } 1361 1362 // Iterate over all spaces in use in the heap, in ascending address order. 1363 virtual void space_iterate(SpaceClosure* cl); 1364 1365 // Iterate over heap regions, in address order, terminating the 1366 // iteration early if the "doHeapRegion" method returns "true". 1367 void heap_region_iterate(HeapRegionClosure* blk) const; 1368 1369 // Return the region with the given index. It assumes the index is valid. 1370 inline HeapRegion* region_at(uint index) const; 1371 1372 // Calculate the region index of the given address. Given address must be 1373 // within the heap. 1374 inline uint addr_to_region(HeapWord* addr) const; 1375 1376 inline HeapWord* bottom_addr_for_region(uint index) const; 1377 1378 // Iterate over the heap regions in parallel. Assumes that this will be called 1379 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1380 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1381 // to each of the regions, by attempting to claim the region using the 1382 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1383 // region. The concurrent argument should be set to true if iteration is 1384 // performed concurrently, during which no assumptions are made for consistent 1385 // attributes of the heap regions (as they might be modified while iterating). 1386 void heap_region_par_iterate(HeapRegionClosure* cl, 1387 uint worker_id, 1388 HeapRegionClaimer* hrclaimer, 1389 bool concurrent = false) const; 1390 1391 // Clear the cached cset start regions and (more importantly) 1392 // the time stamps. Called when we reset the GC time stamp. 1393 void clear_cset_start_regions(); 1394 1395 // Given the id of a worker, obtain or calculate a suitable 1396 // starting region for iterating over the current collection set. 1397 HeapRegion* start_cset_region_for_worker(uint worker_i); 1398 1399 // Iterate over the regions (if any) in the current collection set. 1400 void collection_set_iterate(HeapRegionClosure* blk); 1401 1402 // As above but starting from region r 1403 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1404 1405 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1406 1407 // A CollectedHeap will contain some number of spaces. This finds the 1408 // space containing a given address, or else returns NULL. 1409 virtual Space* space_containing(const void* addr) const; 1410 1411 // Returns the HeapRegion that contains addr. addr must not be NULL. 1412 template <class T> 1413 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1414 1415 // Returns the HeapRegion that contains addr. addr must not be NULL. 1416 // If addr is within a humongous continues region, it returns its humongous start region. 1417 template <class T> 1418 inline HeapRegion* heap_region_containing(const T addr) const; 1419 1420 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1421 // each address in the (reserved) heap is a member of exactly 1422 // one block. The defining characteristic of a block is that it is 1423 // possible to find its size, and thus to progress forward to the next 1424 // block. (Blocks may be of different sizes.) Thus, blocks may 1425 // represent Java objects, or they might be free blocks in a 1426 // free-list-based heap (or subheap), as long as the two kinds are 1427 // distinguishable and the size of each is determinable. 1428 1429 // Returns the address of the start of the "block" that contains the 1430 // address "addr". We say "blocks" instead of "object" since some heaps 1431 // may not pack objects densely; a chunk may either be an object or a 1432 // non-object. 1433 virtual HeapWord* block_start(const void* addr) const; 1434 1435 // Requires "addr" to be the start of a chunk, and returns its size. 1436 // "addr + size" is required to be the start of a new chunk, or the end 1437 // of the active area of the heap. 1438 virtual size_t block_size(const HeapWord* addr) const; 1439 1440 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1441 // the block is an object. 1442 virtual bool block_is_obj(const HeapWord* addr) const; 1443 1444 // Does this heap support heap inspection? (+PrintClassHistogram) 1445 virtual bool supports_heap_inspection() const { return true; } 1446 1447 // Section on thread-local allocation buffers (TLABs) 1448 // See CollectedHeap for semantics. 1449 1450 bool supports_tlab_allocation() const; 1451 size_t tlab_capacity(Thread* ignored) const; 1452 size_t tlab_used(Thread* ignored) const; 1453 size_t max_tlab_size() const; 1454 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1455 1456 // Can a compiler initialize a new object without store barriers? 1457 // This permission only extends from the creation of a new object 1458 // via a TLAB up to the first subsequent safepoint. If such permission 1459 // is granted for this heap type, the compiler promises to call 1460 // defer_store_barrier() below on any slow path allocation of 1461 // a new object for which such initializing store barriers will 1462 // have been elided. G1, like CMS, allows this, but should be 1463 // ready to provide a compensating write barrier as necessary 1464 // if that storage came out of a non-young region. The efficiency 1465 // of this implementation depends crucially on being able to 1466 // answer very efficiently in constant time whether a piece of 1467 // storage in the heap comes from a young region or not. 1468 // See ReduceInitialCardMarks. 1469 virtual bool can_elide_tlab_store_barriers() const { 1470 return true; 1471 } 1472 1473 virtual bool card_mark_must_follow_store() const { 1474 return true; 1475 } 1476 1477 inline bool is_in_young(const oop obj); 1478 1479 #ifdef ASSERT 1480 virtual bool is_in_partial_collection(const void* p); 1481 #endif 1482 1483 virtual bool is_scavengable(const void* addr); 1484 1485 // We don't need barriers for initializing stores to objects 1486 // in the young gen: for the SATB pre-barrier, there is no 1487 // pre-value that needs to be remembered; for the remembered-set 1488 // update logging post-barrier, we don't maintain remembered set 1489 // information for young gen objects. 1490 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1491 1492 // Returns "true" iff the given word_size is "very large". 1493 static bool is_humongous(size_t word_size) { 1494 // Note this has to be strictly greater-than as the TLABs 1495 // are capped at the humongous threshold and we want to 1496 // ensure that we don't try to allocate a TLAB as 1497 // humongous and that we don't allocate a humongous 1498 // object in a TLAB. 1499 return word_size > _humongous_object_threshold_in_words; 1500 } 1501 1502 // Update mod union table with the set of dirty cards. 1503 void updateModUnion(); 1504 1505 // Set the mod union bits corresponding to the given memRegion. Note 1506 // that this is always a safe operation, since it doesn't clear any 1507 // bits. 1508 void markModUnionRange(MemRegion mr); 1509 1510 // Records the fact that a marking phase is no longer in progress. 1511 void set_marking_complete() { 1512 _mark_in_progress = false; 1513 } 1514 void set_marking_started() { 1515 _mark_in_progress = true; 1516 } 1517 bool mark_in_progress() { 1518 return _mark_in_progress; 1519 } 1520 1521 // Print the maximum heap capacity. 1522 virtual size_t max_capacity() const; 1523 1524 virtual jlong millis_since_last_gc(); 1525 1526 1527 // Convenience function to be used in situations where the heap type can be 1528 // asserted to be this type. 1529 static G1CollectedHeap* heap(); 1530 1531 void set_region_short_lived_locked(HeapRegion* hr); 1532 // add appropriate methods for any other surv rate groups 1533 1534 YoungList* young_list() const { return _young_list; } 1535 1536 // debugging 1537 bool check_young_list_well_formed() { 1538 return _young_list->check_list_well_formed(); 1539 } 1540 1541 bool check_young_list_empty(bool check_heap, 1542 bool check_sample = true); 1543 1544 // *** Stuff related to concurrent marking. It's not clear to me that so 1545 // many of these need to be public. 1546 1547 // The functions below are helper functions that a subclass of 1548 // "CollectedHeap" can use in the implementation of its virtual 1549 // functions. 1550 // This performs a concurrent marking of the live objects in a 1551 // bitmap off to the side. 1552 void doConcurrentMark(); 1553 1554 bool isMarkedPrev(oop obj) const; 1555 bool isMarkedNext(oop obj) const; 1556 1557 // Determine if an object is dead, given the object and also 1558 // the region to which the object belongs. An object is dead 1559 // iff a) it was not allocated since the last mark and b) it 1560 // is not marked. 1561 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1562 return 1563 !hr->obj_allocated_since_prev_marking(obj) && 1564 !isMarkedPrev(obj); 1565 } 1566 1567 // This function returns true when an object has been 1568 // around since the previous marking and hasn't yet 1569 // been marked during this marking. 1570 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1571 return 1572 !hr->obj_allocated_since_next_marking(obj) && 1573 !isMarkedNext(obj); 1574 } 1575 1576 // Determine if an object is dead, given only the object itself. 1577 // This will find the region to which the object belongs and 1578 // then call the region version of the same function. 1579 1580 // Added if it is NULL it isn't dead. 1581 1582 inline bool is_obj_dead(const oop obj) const; 1583 1584 inline bool is_obj_ill(const oop obj) const; 1585 1586 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1587 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1588 bool is_marked(oop obj, VerifyOption vo); 1589 const char* top_at_mark_start_str(VerifyOption vo); 1590 1591 ConcurrentMark* concurrent_mark() const { return _cm; } 1592 1593 // Refinement 1594 1595 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1596 1597 // The dirty cards region list is used to record a subset of regions 1598 // whose cards need clearing. The list if populated during the 1599 // remembered set scanning and drained during the card table 1600 // cleanup. Although the methods are reentrant, population/draining 1601 // phases must not overlap. For synchronization purposes the last 1602 // element on the list points to itself. 1603 HeapRegion* _dirty_cards_region_list; 1604 void push_dirty_cards_region(HeapRegion* hr); 1605 HeapRegion* pop_dirty_cards_region(); 1606 1607 // Optimized nmethod scanning support routines 1608 1609 // Register the given nmethod with the G1 heap. 1610 virtual void register_nmethod(nmethod* nm); 1611 1612 // Unregister the given nmethod from the G1 heap. 1613 virtual void unregister_nmethod(nmethod* nm); 1614 1615 // Free up superfluous code root memory. 1616 void purge_code_root_memory(); 1617 1618 // Rebuild the strong code root lists for each region 1619 // after a full GC. 1620 void rebuild_strong_code_roots(); 1621 1622 // Delete entries for dead interned string and clean up unreferenced symbols 1623 // in symbol table, possibly in parallel. 1624 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1625 1626 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1627 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1628 1629 // Redirty logged cards in the refinement queue. 1630 void redirty_logged_cards(); 1631 // Verification 1632 1633 // The following is just to alert the verification code 1634 // that a full collection has occurred and that the 1635 // remembered sets are no longer up to date. 1636 bool _full_collection; 1637 void set_full_collection() { _full_collection = true;} 1638 void clear_full_collection() {_full_collection = false;} 1639 bool full_collection() {return _full_collection;} 1640 1641 // Perform any cleanup actions necessary before allowing a verification. 1642 virtual void prepare_for_verify(); 1643 1644 // Perform verification. 1645 1646 // vo == UsePrevMarking -> use "prev" marking information, 1647 // vo == UseNextMarking -> use "next" marking information 1648 // vo == UseMarkWord -> use the mark word in the object header 1649 // 1650 // NOTE: Only the "prev" marking information is guaranteed to be 1651 // consistent most of the time, so most calls to this should use 1652 // vo == UsePrevMarking. 1653 // Currently, there is only one case where this is called with 1654 // vo == UseNextMarking, which is to verify the "next" marking 1655 // information at the end of remark. 1656 // Currently there is only one place where this is called with 1657 // vo == UseMarkWord, which is to verify the marking during a 1658 // full GC. 1659 void verify(bool silent, VerifyOption vo); 1660 1661 // Override; it uses the "prev" marking information 1662 virtual void verify(bool silent); 1663 1664 // The methods below are here for convenience and dispatch the 1665 // appropriate method depending on value of the given VerifyOption 1666 // parameter. The values for that parameter, and their meanings, 1667 // are the same as those above. 1668 1669 bool is_obj_dead_cond(const oop obj, 1670 const HeapRegion* hr, 1671 const VerifyOption vo) const; 1672 1673 bool is_obj_dead_cond(const oop obj, 1674 const VerifyOption vo) const; 1675 1676 // Printing 1677 1678 virtual void print_on(outputStream* st) const; 1679 virtual void print_extended_on(outputStream* st) const; 1680 virtual void print_on_error(outputStream* st) const; 1681 1682 virtual void print_gc_threads_on(outputStream* st) const; 1683 virtual void gc_threads_do(ThreadClosure* tc) const; 1684 1685 // Override 1686 void print_tracing_info() const; 1687 1688 // The following two methods are helpful for debugging RSet issues. 1689 void print_cset_rsets() PRODUCT_RETURN; 1690 void print_all_rsets() PRODUCT_RETURN; 1691 1692 public: 1693 size_t pending_card_num(); 1694 size_t cards_scanned(); 1695 1696 protected: 1697 size_t _max_heap_capacity; 1698 }; 1699 1700 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP