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/g1InCSetState.hpp" 36 #include "gc_implementation/g1/g1MonitoringSupport.hpp" 37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 38 #include "gc_implementation/g1/g1YCTypes.hpp" 39 #include "gc_implementation/g1/heapRegionManager.hpp" 40 #include "gc_implementation/g1/heapRegionSet.hpp" 41 #include "gc_implementation/shared/hSpaceCounters.hpp" 42 #include "gc_implementation/shared/parGCAllocBuffer.hpp" 43 #include "memory/barrierSet.hpp" 44 #include "memory/memRegion.hpp" 45 #include "memory/sharedHeap.hpp" 46 #include "utilities/stack.hpp" 47 48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 49 // It uses the "Garbage First" heap organization and algorithm, which 50 // may combine concurrent marking with parallel, incremental compaction of 51 // heap subsets that will yield large amounts of garbage. 52 53 // Forward declarations 54 class HeapRegion; 55 class HRRSCleanupTask; 56 class GenerationSpec; 57 class OopsInHeapRegionClosure; 58 class G1KlassScanClosure; 59 class G1ScanHeapEvacClosure; 60 class ObjectClosure; 61 class SpaceClosure; 62 class CompactibleSpaceClosure; 63 class Space; 64 class G1CollectorPolicy; 65 class GenRemSet; 66 class G1RemSet; 67 class HeapRegionRemSetIterator; 68 class ConcurrentMark; 69 class ConcurrentMarkThread; 70 class ConcurrentG1Refine; 71 class ConcurrentGCTimer; 72 class GenerationCounters; 73 class STWGCTimer; 74 class G1NewTracer; 75 class G1OldTracer; 76 class EvacuationFailedInfo; 77 class nmethod; 78 class Ticks; 79 80 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 81 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 82 83 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 84 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 85 86 class YoungList : public CHeapObj<mtGC> { 87 private: 88 G1CollectedHeap* _g1h; 89 90 HeapRegion* _head; 91 92 HeapRegion* _survivor_head; 93 HeapRegion* _survivor_tail; 94 95 HeapRegion* _curr; 96 97 uint _length; 98 uint _survivor_length; 99 100 size_t _last_sampled_rs_lengths; 101 size_t _sampled_rs_lengths; 102 103 void empty_list(HeapRegion* list); 104 105 public: 106 YoungList(G1CollectedHeap* g1h); 107 108 void push_region(HeapRegion* hr); 109 void add_survivor_region(HeapRegion* hr); 110 111 void empty_list(); 112 bool is_empty() { return _length == 0; } 113 uint length() { return _length; } 114 uint survivor_length() { return _survivor_length; } 115 116 // Currently we do not keep track of the used byte sum for the 117 // young list and the survivors and it'd be quite a lot of work to 118 // do so. When we'll eventually replace the young list with 119 // instances of HeapRegionLinkedList we'll get that for free. So, 120 // we'll report the more accurate information then. 121 size_t eden_used_bytes() { 122 assert(length() >= survivor_length(), "invariant"); 123 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes; 124 } 125 size_t survivor_used_bytes() { 126 return (size_t) survivor_length() * HeapRegion::GrainBytes; 127 } 128 129 void rs_length_sampling_init(); 130 bool rs_length_sampling_more(); 131 void rs_length_sampling_next(); 132 133 void reset_sampled_info() { 134 _last_sampled_rs_lengths = 0; 135 } 136 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } 137 138 // for development purposes 139 void reset_auxilary_lists(); 140 void clear() { _head = NULL; _length = 0; } 141 142 void clear_survivors() { 143 _survivor_head = NULL; 144 _survivor_tail = NULL; 145 _survivor_length = 0; 146 } 147 148 HeapRegion* first_region() { return _head; } 149 HeapRegion* first_survivor_region() { return _survivor_head; } 150 HeapRegion* last_survivor_region() { return _survivor_tail; } 151 152 // debugging 153 bool check_list_well_formed(); 154 bool check_list_empty(bool check_sample = true); 155 void print(); 156 }; 157 158 // The G1 STW is alive closure. 159 // An instance is embedded into the G1CH and used as the 160 // (optional) _is_alive_non_header closure in the STW 161 // reference processor. It is also extensively used during 162 // reference processing during STW evacuation pauses. 163 class G1STWIsAliveClosure: public BoolObjectClosure { 164 G1CollectedHeap* _g1; 165 public: 166 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 167 bool do_object_b(oop p); 168 }; 169 170 class RefineCardTableEntryClosure; 171 172 class G1RegionMappingChangedListener : public G1MappingChangedListener { 173 private: 174 void reset_from_card_cache(uint start_idx, size_t num_regions); 175 public: 176 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 177 }; 178 179 class G1CollectedHeap : public SharedHeap { 180 friend class VM_CollectForMetadataAllocation; 181 friend class VM_G1CollectForAllocation; 182 friend class VM_G1CollectFull; 183 friend class VM_G1IncCollectionPause; 184 friend class VMStructs; 185 friend class MutatorAllocRegion; 186 friend class SurvivorGCAllocRegion; 187 friend class OldGCAllocRegion; 188 friend class G1Allocator; 189 friend class G1DefaultAllocator; 190 friend class G1ResManAllocator; 191 192 // Closures used in implementation. 193 template <G1Barrier barrier, G1Mark do_mark_object> 194 friend class G1ParCopyClosure; 195 friend class G1IsAliveClosure; 196 friend class G1EvacuateFollowersClosure; 197 friend class G1ParScanThreadState; 198 friend class G1ParScanClosureSuper; 199 friend class G1ParEvacuateFollowersClosure; 200 friend class G1ParTask; 201 friend class G1ParGCAllocator; 202 friend class G1DefaultParGCAllocator; 203 friend class G1FreeGarbageRegionClosure; 204 friend class RefineCardTableEntryClosure; 205 friend class G1PrepareCompactClosure; 206 friend class RegionSorter; 207 friend class RegionResetter; 208 friend class CountRCClosure; 209 friend class EvacPopObjClosure; 210 friend class G1ParCleanupCTTask; 211 212 friend class G1FreeHumongousRegionClosure; 213 // Other related classes. 214 friend class G1MarkSweep; 215 216 // Testing classes. 217 friend class G1CheckCSetFastTableClosure; 218 219 private: 220 // The one and only G1CollectedHeap, so static functions can find it. 221 static G1CollectedHeap* _g1h; 222 223 static size_t _humongous_object_threshold_in_words; 224 225 // The secondary free list which contains regions that have been 226 // freed up during the cleanup process. This will be appended to 227 // the master free list when appropriate. 228 FreeRegionList _secondary_free_list; 229 230 // It keeps track of the old regions. 231 HeapRegionSet _old_set; 232 233 // It keeps track of the humongous regions. 234 HeapRegionSet _humongous_set; 235 236 void clear_humongous_is_live_table(); 237 void eagerly_reclaim_humongous_regions(); 238 239 // The number of regions we could create by expansion. 240 uint _expansion_regions; 241 242 // The block offset table for the G1 heap. 243 G1BlockOffsetSharedArray* _bot_shared; 244 245 // Tears down the region sets / lists so that they are empty and the 246 // regions on the heap do not belong to a region set / list. The 247 // only exception is the humongous set which we leave unaltered. If 248 // free_list_only is true, it will only tear down the master free 249 // list. It is called before a Full GC (free_list_only == false) or 250 // before heap shrinking (free_list_only == true). 251 void tear_down_region_sets(bool free_list_only); 252 253 // Rebuilds the region sets / lists so that they are repopulated to 254 // reflect the contents of the heap. The only exception is the 255 // humongous set which was not torn down in the first place. If 256 // free_list_only is true, it will only rebuild the master free 257 // list. It is called after a Full GC (free_list_only == false) or 258 // after heap shrinking (free_list_only == true). 259 void rebuild_region_sets(bool free_list_only); 260 261 // Callback for region mapping changed events. 262 G1RegionMappingChangedListener _listener; 263 264 // The sequence of all heap regions in the heap. 265 HeapRegionManager _hrm; 266 267 // Class that handles the different kinds of allocations. 268 G1Allocator* _allocator; 269 270 // Statistics for each allocation context 271 AllocationContextStats _allocation_context_stats; 272 273 // PLAB sizing policy for survivors. 274 PLABStats _survivor_plab_stats; 275 276 // PLAB sizing policy for tenured objects. 277 PLABStats _old_plab_stats; 278 279 // It specifies whether we should attempt to expand the heap after a 280 // region allocation failure. If heap expansion fails we set this to 281 // false so that we don't re-attempt the heap expansion (it's likely 282 // that subsequent expansion attempts will also fail if one fails). 283 // Currently, it is only consulted during GC and it's reset at the 284 // start of each GC. 285 bool _expand_heap_after_alloc_failure; 286 287 // It resets the mutator alloc region before new allocations can take place. 288 void init_mutator_alloc_region(); 289 290 // It releases the mutator alloc region. 291 void release_mutator_alloc_region(); 292 293 // It initializes the GC alloc regions at the start of a GC. 294 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 295 296 // It releases the GC alloc regions at the end of a GC. 297 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 298 299 // It does any cleanup that needs to be done on the GC alloc regions 300 // before a Full GC. 301 void abandon_gc_alloc_regions(); 302 303 // Helper for monitoring and management support. 304 G1MonitoringSupport* _g1mm; 305 306 // Records whether the region at the given index is kept live by roots or 307 // references from the young generation. 308 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 309 protected: 310 bool default_value() const { return false; } 311 public: 312 void clear() { G1BiasedMappedArray<bool>::clear(); } 313 void set_live(uint region) { 314 set_by_index(region, true); 315 } 316 bool is_live(uint region) { 317 return get_by_index(region); 318 } 319 }; 320 321 HumongousIsLiveBiasedMappedArray _humongous_is_live; 322 // Stores whether during humongous object registration we found candidate regions. 323 // If not, we can skip a few steps. 324 bool _has_humongous_reclaim_candidates; 325 326 volatile unsigned _gc_time_stamp; 327 328 size_t* _surviving_young_words; 329 330 G1HRPrinter _hr_printer; 331 332 void setup_surviving_young_words(); 333 void update_surviving_young_words(size_t* surv_young_words); 334 void cleanup_surviving_young_words(); 335 336 // It decides whether an explicit GC should start a concurrent cycle 337 // instead of doing a STW GC. Currently, a concurrent cycle is 338 // explicitly started if: 339 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 340 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 341 // (c) cause == _g1_humongous_allocation 342 bool should_do_concurrent_full_gc(GCCause::Cause cause); 343 344 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 345 // concurrent cycles) we have started. 346 volatile unsigned int _old_marking_cycles_started; 347 348 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 349 // concurrent cycles) we have completed. 350 volatile unsigned int _old_marking_cycles_completed; 351 352 bool _concurrent_cycle_started; 353 bool _heap_summary_sent; 354 355 // This is a non-product method that is helpful for testing. It is 356 // called at the end of a GC and artificially expands the heap by 357 // allocating a number of dead regions. This way we can induce very 358 // frequent marking cycles and stress the cleanup / concurrent 359 // cleanup code more (as all the regions that will be allocated by 360 // this method will be found dead by the marking cycle). 361 void allocate_dummy_regions() PRODUCT_RETURN; 362 363 // Clear RSets after a compaction. It also resets the GC time stamps. 364 void clear_rsets_post_compaction(); 365 366 // If the HR printer is active, dump the state of the regions in the 367 // heap after a compaction. 368 void print_hrm_post_compaction(); 369 370 double verify(bool guard, const char* msg); 371 void verify_before_gc(); 372 void verify_after_gc(); 373 374 void log_gc_header(); 375 void log_gc_footer(double pause_time_sec); 376 377 // These are macros so that, if the assert fires, we get the correct 378 // line number, file, etc. 379 380 #define heap_locking_asserts_err_msg(_extra_message_) \ 381 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 382 (_extra_message_), \ 383 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 384 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 385 BOOL_TO_STR(Thread::current()->is_VM_thread())) 386 387 #define assert_heap_locked() \ 388 do { \ 389 assert(Heap_lock->owned_by_self(), \ 390 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 391 } while (0) 392 393 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 394 do { \ 395 assert(Heap_lock->owned_by_self() || \ 396 (SafepointSynchronize::is_at_safepoint() && \ 397 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 398 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 399 "should be at a safepoint")); \ 400 } while (0) 401 402 #define assert_heap_locked_and_not_at_safepoint() \ 403 do { \ 404 assert(Heap_lock->owned_by_self() && \ 405 !SafepointSynchronize::is_at_safepoint(), \ 406 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 407 "should not be at a safepoint")); \ 408 } while (0) 409 410 #define assert_heap_not_locked() \ 411 do { \ 412 assert(!Heap_lock->owned_by_self(), \ 413 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 414 } while (0) 415 416 #define assert_heap_not_locked_and_not_at_safepoint() \ 417 do { \ 418 assert(!Heap_lock->owned_by_self() && \ 419 !SafepointSynchronize::is_at_safepoint(), \ 420 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 421 "should not be at a safepoint")); \ 422 } while (0) 423 424 #define assert_at_safepoint(_should_be_vm_thread_) \ 425 do { \ 426 assert(SafepointSynchronize::is_at_safepoint() && \ 427 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 428 heap_locking_asserts_err_msg("should be at a safepoint")); \ 429 } while (0) 430 431 #define assert_not_at_safepoint() \ 432 do { \ 433 assert(!SafepointSynchronize::is_at_safepoint(), \ 434 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 435 } while (0) 436 437 protected: 438 439 // The young region list. 440 YoungList* _young_list; 441 442 // The current policy object for the collector. 443 G1CollectorPolicy* _g1_policy; 444 445 // This is the second level of trying to allocate a new region. If 446 // new_region() didn't find a region on the free_list, this call will 447 // check whether there's anything available on the 448 // secondary_free_list and/or wait for more regions to appear on 449 // that list, if _free_regions_coming is set. 450 HeapRegion* new_region_try_secondary_free_list(bool is_old); 451 452 // Try to allocate a single non-humongous HeapRegion sufficient for 453 // an allocation of the given word_size. If do_expand is true, 454 // attempt to expand the heap if necessary to satisfy the allocation 455 // request. If the region is to be used as an old region or for a 456 // humongous object, set is_old to true. If not, to false. 457 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 458 459 // Initialize a contiguous set of free regions of length num_regions 460 // and starting at index first so that they appear as a single 461 // humongous region. 462 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 463 uint num_regions, 464 size_t word_size, 465 AllocationContext_t context); 466 467 // Attempt to allocate a humongous object of the given size. Return 468 // NULL if unsuccessful. 469 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 470 471 // The following two methods, allocate_new_tlab() and 472 // mem_allocate(), are the two main entry points from the runtime 473 // into the G1's allocation routines. They have the following 474 // assumptions: 475 // 476 // * They should both be called outside safepoints. 477 // 478 // * They should both be called without holding the Heap_lock. 479 // 480 // * All allocation requests for new TLABs should go to 481 // allocate_new_tlab(). 482 // 483 // * All non-TLAB allocation requests should go to mem_allocate(). 484 // 485 // * If either call cannot satisfy the allocation request using the 486 // current allocating region, they will try to get a new one. If 487 // this fails, they will attempt to do an evacuation pause and 488 // retry the allocation. 489 // 490 // * If all allocation attempts fail, even after trying to schedule 491 // an evacuation pause, allocate_new_tlab() will return NULL, 492 // whereas mem_allocate() will attempt a heap expansion and/or 493 // schedule a Full GC. 494 // 495 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 496 // should never be called with word_size being humongous. All 497 // humongous allocation requests should go to mem_allocate() which 498 // will satisfy them with a special path. 499 500 virtual HeapWord* allocate_new_tlab(size_t word_size); 501 502 virtual HeapWord* mem_allocate(size_t word_size, 503 bool* gc_overhead_limit_was_exceeded); 504 505 // The following three methods take a gc_count_before_ret 506 // parameter which is used to return the GC count if the method 507 // returns NULL. Given that we are required to read the GC count 508 // while holding the Heap_lock, and these paths will take the 509 // Heap_lock at some point, it's easier to get them to read the GC 510 // count while holding the Heap_lock before they return NULL instead 511 // of the caller (namely: mem_allocate()) having to also take the 512 // Heap_lock just to read the GC count. 513 514 // First-level mutator allocation attempt: try to allocate out of 515 // the mutator alloc region without taking the Heap_lock. This 516 // should only be used for non-humongous allocations. 517 inline HeapWord* attempt_allocation(size_t word_size, 518 unsigned int* gc_count_before_ret, 519 int* gclocker_retry_count_ret); 520 521 // Second-level mutator allocation attempt: take the Heap_lock and 522 // retry the allocation attempt, potentially scheduling a GC 523 // pause. This should only be used for non-humongous allocations. 524 HeapWord* attempt_allocation_slow(size_t word_size, 525 AllocationContext_t context, 526 unsigned int* gc_count_before_ret, 527 int* gclocker_retry_count_ret); 528 529 // Takes the Heap_lock and attempts a humongous allocation. It can 530 // potentially schedule a GC pause. 531 HeapWord* attempt_allocation_humongous(size_t word_size, 532 unsigned int* gc_count_before_ret, 533 int* gclocker_retry_count_ret); 534 535 // Allocation attempt that should be called during safepoints (e.g., 536 // at the end of a successful GC). expect_null_mutator_alloc_region 537 // specifies whether the mutator alloc region is expected to be NULL 538 // or not. 539 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 540 AllocationContext_t context, 541 bool expect_null_mutator_alloc_region); 542 543 // It dirties the cards that cover the block so that so that the post 544 // write barrier never queues anything when updating objects on this 545 // block. It is assumed (and in fact we assert) that the block 546 // belongs to a young region. 547 inline void dirty_young_block(HeapWord* start, size_t word_size); 548 549 // Allocate blocks during garbage collection. Will ensure an 550 // allocation region, either by picking one or expanding the 551 // heap, and then allocate a block of the given size. The block 552 // may not be a humongous - it must fit into a single heap region. 553 inline HeapWord* par_allocate_during_gc(InCSetState dest, 554 size_t word_size, 555 AllocationContext_t context); 556 // Ensure that no further allocations can happen in "r", bearing in mind 557 // that parallel threads might be attempting allocations. 558 void par_allocate_remaining_space(HeapRegion* r); 559 560 // Allocation attempt during GC for a survivor object / PLAB. 561 inline HeapWord* survivor_attempt_allocation(size_t word_size, 562 AllocationContext_t context); 563 564 // Allocation attempt during GC for an old object / PLAB. 565 inline HeapWord* old_attempt_allocation(size_t word_size, 566 AllocationContext_t context); 567 568 // These methods are the "callbacks" from the G1AllocRegion class. 569 570 // For mutator alloc regions. 571 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 572 void retire_mutator_alloc_region(HeapRegion* alloc_region, 573 size_t allocated_bytes); 574 575 // For GC alloc regions. 576 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 577 InCSetState dest); 578 void retire_gc_alloc_region(HeapRegion* alloc_region, 579 size_t allocated_bytes, InCSetState dest); 580 581 // - if explicit_gc is true, the GC is for a System.gc() or a heap 582 // inspection request and should collect the entire heap 583 // - if clear_all_soft_refs is true, all soft references should be 584 // cleared during the GC 585 // - if explicit_gc is false, word_size describes the allocation that 586 // the GC should attempt (at least) to satisfy 587 // - it returns false if it is unable to do the collection due to the 588 // GC locker being active, true otherwise 589 bool do_collection(bool explicit_gc, 590 bool clear_all_soft_refs, 591 size_t word_size); 592 593 // Callback from VM_G1CollectFull operation. 594 // Perform a full collection. 595 virtual void do_full_collection(bool clear_all_soft_refs); 596 597 // Resize the heap if necessary after a full collection. If this is 598 // after a collect-for allocation, "word_size" is the allocation size, 599 // and will be considered part of the used portion of the heap. 600 void resize_if_necessary_after_full_collection(size_t word_size); 601 602 // Callback from VM_G1CollectForAllocation operation. 603 // This function does everything necessary/possible to satisfy a 604 // failed allocation request (including collection, expansion, etc.) 605 HeapWord* satisfy_failed_allocation(size_t word_size, 606 AllocationContext_t context, 607 bool* succeeded); 608 609 // Attempting to expand the heap sufficiently 610 // to support an allocation of the given "word_size". If 611 // successful, perform the allocation and return the address of the 612 // allocated block, or else "NULL". 613 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 614 615 // Process any reference objects discovered during 616 // an incremental evacuation pause. 617 void process_discovered_references(uint no_of_gc_workers); 618 619 // Enqueue any remaining discovered references 620 // after processing. 621 void enqueue_discovered_references(uint no_of_gc_workers); 622 623 public: 624 625 G1Allocator* allocator() { 626 return _allocator; 627 } 628 629 G1MonitoringSupport* g1mm() { 630 assert(_g1mm != NULL, "should have been initialized"); 631 return _g1mm; 632 } 633 634 // Expand the garbage-first heap by at least the given size (in bytes!). 635 // Returns true if the heap was expanded by the requested amount; 636 // false otherwise. 637 // (Rounds up to a HeapRegion boundary.) 638 bool expand(size_t expand_bytes); 639 640 // Returns the PLAB statistics for a given destination. 641 inline PLABStats* alloc_buffer_stats(InCSetState dest); 642 643 // Determines PLAB size for a given destination. 644 inline size_t desired_plab_sz(InCSetState dest); 645 646 inline AllocationContextStats& allocation_context_stats(); 647 648 // Do anything common to GC's. 649 virtual void gc_prologue(bool full); 650 virtual void gc_epilogue(bool full); 651 652 inline void set_humongous_is_live(oop obj); 653 654 bool humongous_is_live(uint region) { 655 return _humongous_is_live.is_live(region); 656 } 657 658 // Returns whether the given region (which must be a humongous (start) region) 659 // is to be considered conservatively live regardless of any other conditions. 660 bool humongous_region_is_always_live(uint index); 661 // Register the given region to be part of the collection set. 662 inline void register_humongous_region_with_in_cset_fast_test(uint index); 663 // Register regions with humongous objects (actually on the start region) in 664 // the in_cset_fast_test table. 665 void register_humongous_regions_with_in_cset_fast_test(); 666 // We register a region with the fast "in collection set" test. We 667 // simply set to true the array slot corresponding to this region. 668 void register_young_region_with_in_cset_fast_test(HeapRegion* r) { 669 _in_cset_fast_test.set_in_young(r->hrm_index()); 670 } 671 void register_old_region_with_in_cset_fast_test(HeapRegion* r) { 672 _in_cset_fast_test.set_in_old(r->hrm_index()); 673 } 674 675 // This is a fast test on whether a reference points into the 676 // collection set or not. Assume that the reference 677 // points into the heap. 678 inline bool in_cset_fast_test(oop obj); 679 680 void clear_cset_fast_test() { 681 _in_cset_fast_test.clear(); 682 } 683 684 // This is called at the start of either a concurrent cycle or a Full 685 // GC to update the number of old marking cycles started. 686 void increment_old_marking_cycles_started(); 687 688 // This is called at the end of either a concurrent cycle or a Full 689 // GC to update the number of old marking cycles completed. Those two 690 // can happen in a nested fashion, i.e., we start a concurrent 691 // cycle, a Full GC happens half-way through it which ends first, 692 // and then the cycle notices that a Full GC happened and ends 693 // too. The concurrent parameter is a boolean to help us do a bit 694 // tighter consistency checking in the method. If concurrent is 695 // false, the caller is the inner caller in the nesting (i.e., the 696 // Full GC). If concurrent is true, the caller is the outer caller 697 // in this nesting (i.e., the concurrent cycle). Further nesting is 698 // not currently supported. The end of this call also notifies 699 // the FullGCCount_lock in case a Java thread is waiting for a full 700 // GC to happen (e.g., it called System.gc() with 701 // +ExplicitGCInvokesConcurrent). 702 void increment_old_marking_cycles_completed(bool concurrent); 703 704 unsigned int old_marking_cycles_completed() { 705 return _old_marking_cycles_completed; 706 } 707 708 void register_concurrent_cycle_start(const Ticks& start_time); 709 void register_concurrent_cycle_end(); 710 void trace_heap_after_concurrent_cycle(); 711 712 G1YCType yc_type(); 713 714 G1HRPrinter* hr_printer() { return &_hr_printer; } 715 716 // Frees a non-humongous region by initializing its contents and 717 // adding it to the free list that's passed as a parameter (this is 718 // usually a local list which will be appended to the master free 719 // list later). The used bytes of freed regions are accumulated in 720 // pre_used. If par is true, the region's RSet will not be freed 721 // up. The assumption is that this will be done later. 722 // The locked parameter indicates if the caller has already taken 723 // care of proper synchronization. This may allow some optimizations. 724 void free_region(HeapRegion* hr, 725 FreeRegionList* free_list, 726 bool par, 727 bool locked = false); 728 729 // Frees a humongous region by collapsing it into individual regions 730 // and calling free_region() for each of them. The freed regions 731 // will be added to the free list that's passed as a parameter (this 732 // is 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 void free_humongous_region(HeapRegion* hr, 737 FreeRegionList* free_list, 738 bool par); 739 protected: 740 741 // Shrink the garbage-first heap by at most the given size (in bytes!). 742 // (Rounds down to a HeapRegion boundary.) 743 virtual void shrink(size_t expand_bytes); 744 void shrink_helper(size_t expand_bytes); 745 746 #if TASKQUEUE_STATS 747 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 748 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 749 void reset_taskqueue_stats(); 750 #endif // TASKQUEUE_STATS 751 752 // Schedule the VM operation that will do an evacuation pause to 753 // satisfy an allocation request of word_size. *succeeded will 754 // return whether the VM operation was successful (it did do an 755 // evacuation pause) or not (another thread beat us to it or the GC 756 // locker was active). Given that we should not be holding the 757 // Heap_lock when we enter this method, we will pass the 758 // gc_count_before (i.e., total_collections()) as a parameter since 759 // it has to be read while holding the Heap_lock. Currently, both 760 // methods that call do_collection_pause() release the Heap_lock 761 // before the call, so it's easy to read gc_count_before just before. 762 HeapWord* do_collection_pause(size_t word_size, 763 unsigned int gc_count_before, 764 bool* succeeded, 765 GCCause::Cause gc_cause); 766 767 // The guts of the incremental collection pause, executed by the vm 768 // thread. It returns false if it is unable to do the collection due 769 // to the GC locker being active, true otherwise 770 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 771 772 // Actually do the work of evacuating the collection set. 773 void evacuate_collection_set(EvacuationInfo& evacuation_info); 774 775 // The g1 remembered set of the heap. 776 G1RemSet* _g1_rem_set; 777 778 // A set of cards that cover the objects for which the Rsets should be updated 779 // concurrently after the collection. 780 DirtyCardQueueSet _dirty_card_queue_set; 781 782 // The closure used to refine a single card. 783 RefineCardTableEntryClosure* _refine_cte_cl; 784 785 // A function to check the consistency of dirty card logs. 786 void check_ct_logs_at_safepoint(); 787 788 // A DirtyCardQueueSet that is used to hold cards that contain 789 // references into the current collection set. This is used to 790 // update the remembered sets of the regions in the collection 791 // set in the event of an evacuation failure. 792 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 793 794 // After a collection pause, make the regions in the CS into free 795 // regions. 796 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 797 798 // Abandon the current collection set without recording policy 799 // statistics or updating free lists. 800 void abandon_collection_set(HeapRegion* cs_head); 801 802 // The concurrent marker (and the thread it runs in.) 803 ConcurrentMark* _cm; 804 ConcurrentMarkThread* _cmThread; 805 bool _mark_in_progress; 806 807 // The concurrent refiner. 808 ConcurrentG1Refine* _cg1r; 809 810 // The parallel task queues 811 RefToScanQueueSet *_task_queues; 812 813 // True iff a evacuation has failed in the current collection. 814 bool _evacuation_failed; 815 816 EvacuationFailedInfo* _evacuation_failed_info_array; 817 818 // Failed evacuations cause some logical from-space objects to have 819 // forwarding pointers to themselves. Reset them. 820 void remove_self_forwarding_pointers(); 821 822 // Together, these store an object with a preserved mark, and its mark value. 823 Stack<oop, mtGC> _objs_with_preserved_marks; 824 Stack<markOop, mtGC> _preserved_marks_of_objs; 825 826 // Preserve the mark of "obj", if necessary, in preparation for its mark 827 // word being overwritten with a self-forwarding-pointer. 828 void preserve_mark_if_necessary(oop obj, markOop m); 829 830 // The stack of evac-failure objects left to be scanned. 831 GrowableArray<oop>* _evac_failure_scan_stack; 832 // The closure to apply to evac-failure objects. 833 834 OopsInHeapRegionClosure* _evac_failure_closure; 835 // Set the field above. 836 void 837 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 838 _evac_failure_closure = evac_failure_closure; 839 } 840 841 // Push "obj" on the scan stack. 842 void push_on_evac_failure_scan_stack(oop obj); 843 // Process scan stack entries until the stack is empty. 844 void drain_evac_failure_scan_stack(); 845 // True iff an invocation of "drain_scan_stack" is in progress; to 846 // prevent unnecessary recursion. 847 bool _drain_in_progress; 848 849 // Do any necessary initialization for evacuation-failure handling. 850 // "cl" is the closure that will be used to process evac-failure 851 // objects. 852 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 853 // Do any necessary cleanup for evacuation-failure handling data 854 // structures. 855 void finalize_for_evac_failure(); 856 857 // An attempt to evacuate "obj" has failed; take necessary steps. 858 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 859 void handle_evacuation_failure_common(oop obj, markOop m); 860 861 #ifndef PRODUCT 862 // Support for forcing evacuation failures. Analogous to 863 // PromotionFailureALot for the other collectors. 864 865 // Records whether G1EvacuationFailureALot should be in effect 866 // for the current GC 867 bool _evacuation_failure_alot_for_current_gc; 868 869 // Used to record the GC number for interval checking when 870 // determining whether G1EvaucationFailureALot is in effect 871 // for the current GC. 872 size_t _evacuation_failure_alot_gc_number; 873 874 // Count of the number of evacuations between failures. 875 volatile size_t _evacuation_failure_alot_count; 876 877 // Set whether G1EvacuationFailureALot should be in effect 878 // for the current GC (based upon the type of GC and which 879 // command line flags are set); 880 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 881 bool during_initial_mark, 882 bool during_marking); 883 884 inline void set_evacuation_failure_alot_for_current_gc(); 885 886 // Return true if it's time to cause an evacuation failure. 887 inline bool evacuation_should_fail(); 888 889 // Reset the G1EvacuationFailureALot counters. Should be called at 890 // the end of an evacuation pause in which an evacuation failure occurred. 891 inline void reset_evacuation_should_fail(); 892 #endif // !PRODUCT 893 894 // ("Weak") Reference processing support. 895 // 896 // G1 has 2 instances of the reference processor class. One 897 // (_ref_processor_cm) handles reference object discovery 898 // and subsequent processing during concurrent marking cycles. 899 // 900 // The other (_ref_processor_stw) handles reference object 901 // discovery and processing during full GCs and incremental 902 // evacuation pauses. 903 // 904 // During an incremental pause, reference discovery will be 905 // temporarily disabled for _ref_processor_cm and will be 906 // enabled for _ref_processor_stw. At the end of the evacuation 907 // pause references discovered by _ref_processor_stw will be 908 // processed and discovery will be disabled. The previous 909 // setting for reference object discovery for _ref_processor_cm 910 // will be re-instated. 911 // 912 // At the start of marking: 913 // * Discovery by the CM ref processor is verified to be inactive 914 // and it's discovered lists are empty. 915 // * Discovery by the CM ref processor is then enabled. 916 // 917 // At the end of marking: 918 // * Any references on the CM ref processor's discovered 919 // lists are processed (possibly MT). 920 // 921 // At the start of full GC we: 922 // * Disable discovery by the CM ref processor and 923 // empty CM ref processor's discovered lists 924 // (without processing any entries). 925 // * Verify that the STW ref processor is inactive and it's 926 // discovered lists are empty. 927 // * Temporarily set STW ref processor discovery as single threaded. 928 // * Temporarily clear the STW ref processor's _is_alive_non_header 929 // field. 930 // * Finally enable discovery by the STW ref processor. 931 // 932 // The STW ref processor is used to record any discovered 933 // references during the full GC. 934 // 935 // At the end of a full GC we: 936 // * Enqueue any reference objects discovered by the STW ref processor 937 // that have non-live referents. This has the side-effect of 938 // making the STW ref processor inactive by disabling discovery. 939 // * Verify that the CM ref processor is still inactive 940 // and no references have been placed on it's discovered 941 // lists (also checked as a precondition during initial marking). 942 943 // The (stw) reference processor... 944 ReferenceProcessor* _ref_processor_stw; 945 946 STWGCTimer* _gc_timer_stw; 947 ConcurrentGCTimer* _gc_timer_cm; 948 949 G1OldTracer* _gc_tracer_cm; 950 G1NewTracer* _gc_tracer_stw; 951 952 // During reference object discovery, the _is_alive_non_header 953 // closure (if non-null) is applied to the referent object to 954 // determine whether the referent is live. If so then the 955 // reference object does not need to be 'discovered' and can 956 // be treated as a regular oop. This has the benefit of reducing 957 // the number of 'discovered' reference objects that need to 958 // be processed. 959 // 960 // Instance of the is_alive closure for embedding into the 961 // STW reference processor as the _is_alive_non_header field. 962 // Supplying a value for the _is_alive_non_header field is 963 // optional but doing so prevents unnecessary additions to 964 // the discovered lists during reference discovery. 965 G1STWIsAliveClosure _is_alive_closure_stw; 966 967 // The (concurrent marking) reference processor... 968 ReferenceProcessor* _ref_processor_cm; 969 970 // Instance of the concurrent mark is_alive closure for embedding 971 // into the Concurrent Marking reference processor as the 972 // _is_alive_non_header field. Supplying a value for the 973 // _is_alive_non_header field is optional but doing so prevents 974 // unnecessary additions to the discovered lists during reference 975 // discovery. 976 G1CMIsAliveClosure _is_alive_closure_cm; 977 978 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 979 HeapRegion** _worker_cset_start_region; 980 981 // Time stamp to validate the regions recorded in the cache 982 // used by G1CollectedHeap::start_cset_region_for_worker(). 983 // The heap region entry for a given worker is valid iff 984 // the associated time stamp value matches the current value 985 // of G1CollectedHeap::_gc_time_stamp. 986 unsigned int* _worker_cset_start_region_time_stamp; 987 988 volatile bool _free_regions_coming; 989 990 public: 991 992 void set_refine_cte_cl_concurrency(bool concurrent); 993 994 RefToScanQueue *task_queue(int i) const; 995 996 // A set of cards where updates happened during the GC 997 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 998 999 // A DirtyCardQueueSet that is used to hold cards that contain 1000 // references into the current collection set. This is used to 1001 // update the remembered sets of the regions in the collection 1002 // set in the event of an evacuation failure. 1003 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1004 { return _into_cset_dirty_card_queue_set; } 1005 1006 // Create a G1CollectedHeap with the specified policy. 1007 // Must call the initialize method afterwards. 1008 // May not return if something goes wrong. 1009 G1CollectedHeap(G1CollectorPolicy* policy); 1010 1011 // Initialize the G1CollectedHeap to have the initial and 1012 // maximum sizes and remembered and barrier sets 1013 // specified by the policy object. 1014 jint initialize(); 1015 1016 virtual void stop(); 1017 1018 // Return the (conservative) maximum heap alignment for any G1 heap 1019 static size_t conservative_max_heap_alignment(); 1020 1021 // Initialize weak reference processing. 1022 virtual void ref_processing_init(); 1023 1024 // Explicitly import set_par_threads into this scope 1025 using SharedHeap::set_par_threads; 1026 // Set _n_par_threads according to a policy TBD. 1027 void set_par_threads(); 1028 1029 virtual CollectedHeap::Name kind() const { 1030 return CollectedHeap::G1CollectedHeap; 1031 } 1032 1033 // The current policy object for the collector. 1034 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1035 1036 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1037 1038 // Adaptive size policy. No such thing for g1. 1039 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1040 1041 // The rem set and barrier set. 1042 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1043 1044 unsigned get_gc_time_stamp() { 1045 return _gc_time_stamp; 1046 } 1047 1048 inline void reset_gc_time_stamp(); 1049 1050 void check_gc_time_stamps() PRODUCT_RETURN; 1051 1052 inline void increment_gc_time_stamp(); 1053 1054 // Reset the given region's GC timestamp. If it's starts humongous, 1055 // also reset the GC timestamp of its corresponding 1056 // continues humongous regions too. 1057 void reset_gc_time_stamps(HeapRegion* hr); 1058 1059 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1060 DirtyCardQueue* into_cset_dcq, 1061 bool concurrent, uint worker_i); 1062 1063 // The shared block offset table array. 1064 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1065 1066 // Reference Processing accessors 1067 1068 // The STW reference processor.... 1069 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1070 1071 // The Concurrent Marking reference processor... 1072 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1073 1074 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1075 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1076 1077 virtual size_t capacity() const; 1078 virtual size_t used() const; 1079 // This should be called when we're not holding the heap lock. The 1080 // result might be a bit inaccurate. 1081 size_t used_unlocked() const; 1082 size_t recalculate_used() const; 1083 1084 // These virtual functions do the actual allocation. 1085 // Some heaps may offer a contiguous region for shared non-blocking 1086 // allocation, via inlined code (by exporting the address of the top and 1087 // end fields defining the extent of the contiguous allocation region.) 1088 // But G1CollectedHeap doesn't yet support this. 1089 1090 virtual bool is_maximal_no_gc() const { 1091 return _hrm.available() == 0; 1092 } 1093 1094 // The current number of regions in the heap. 1095 uint num_regions() const { return _hrm.length(); } 1096 1097 // The max number of regions in the heap. 1098 uint max_regions() const { return _hrm.max_length(); } 1099 1100 // The number of regions that are completely free. 1101 uint num_free_regions() const { return _hrm.num_free_regions(); } 1102 1103 // The number of regions that are not completely free. 1104 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1105 1106 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1107 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1108 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1109 void verify_dirty_young_regions() PRODUCT_RETURN; 1110 1111 #ifndef PRODUCT 1112 // Make sure that the given bitmap has no marked objects in the 1113 // range [from,limit). If it does, print an error message and return 1114 // false. Otherwise, just return true. bitmap_name should be "prev" 1115 // or "next". 1116 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1117 HeapWord* from, HeapWord* limit); 1118 1119 // Verify that the prev / next bitmap range [tams,end) for the given 1120 // region has no marks. Return true if all is well, false if errors 1121 // are detected. 1122 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1123 #endif // PRODUCT 1124 1125 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1126 // the given region do not have any spurious marks. If errors are 1127 // detected, print appropriate error messages and crash. 1128 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1129 1130 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1131 // have any spurious marks. If errors are detected, print 1132 // appropriate error messages and crash. 1133 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1134 1135 // Do sanity check on the contents of the in-cset fast test table. 1136 bool check_cset_fast_test() PRODUCT_RETURN_( return true; ); 1137 1138 // verify_region_sets() performs verification over the region 1139 // lists. It will be compiled in the product code to be used when 1140 // necessary (i.e., during heap verification). 1141 void verify_region_sets(); 1142 1143 // verify_region_sets_optional() is planted in the code for 1144 // list verification in non-product builds (and it can be enabled in 1145 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1146 #if HEAP_REGION_SET_FORCE_VERIFY 1147 void verify_region_sets_optional() { 1148 verify_region_sets(); 1149 } 1150 #else // HEAP_REGION_SET_FORCE_VERIFY 1151 void verify_region_sets_optional() { } 1152 #endif // HEAP_REGION_SET_FORCE_VERIFY 1153 1154 #ifdef ASSERT 1155 bool is_on_master_free_list(HeapRegion* hr) { 1156 return _hrm.is_free(hr); 1157 } 1158 #endif // ASSERT 1159 1160 // Wrapper for the region list operations that can be called from 1161 // methods outside this class. 1162 1163 void secondary_free_list_add(FreeRegionList* list) { 1164 _secondary_free_list.add_ordered(list); 1165 } 1166 1167 void append_secondary_free_list() { 1168 _hrm.insert_list_into_free_list(&_secondary_free_list); 1169 } 1170 1171 void append_secondary_free_list_if_not_empty_with_lock() { 1172 // If the secondary free list looks empty there's no reason to 1173 // take the lock and then try to append it. 1174 if (!_secondary_free_list.is_empty()) { 1175 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1176 append_secondary_free_list(); 1177 } 1178 } 1179 1180 inline void old_set_remove(HeapRegion* hr); 1181 1182 size_t non_young_capacity_bytes() { 1183 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1184 } 1185 1186 void set_free_regions_coming(); 1187 void reset_free_regions_coming(); 1188 bool free_regions_coming() { return _free_regions_coming; } 1189 void wait_while_free_regions_coming(); 1190 1191 // Determine whether the given region is one that we are using as an 1192 // old GC alloc region. 1193 bool is_old_gc_alloc_region(HeapRegion* hr) { 1194 return _allocator->is_retained_old_region(hr); 1195 } 1196 1197 // Perform a collection of the heap; intended for use in implementing 1198 // "System.gc". This probably implies as full a collection as the 1199 // "CollectedHeap" supports. 1200 virtual void collect(GCCause::Cause cause); 1201 1202 // The same as above but assume that the caller holds the Heap_lock. 1203 void collect_locked(GCCause::Cause cause); 1204 1205 virtual bool copy_allocation_context_stats(const jint* contexts, 1206 jlong* totals, 1207 jbyte* accuracy, 1208 jint len); 1209 1210 // True iff an evacuation has failed in the most-recent collection. 1211 bool evacuation_failed() { return _evacuation_failed; } 1212 1213 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1214 void prepend_to_freelist(FreeRegionList* list); 1215 void decrement_summary_bytes(size_t bytes); 1216 1217 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1218 virtual bool is_in(const void* p) const; 1219 #ifdef ASSERT 1220 // Returns whether p is in one of the available areas of the heap. Slow but 1221 // extensive version. 1222 bool is_in_exact(const void* p) const; 1223 #endif 1224 1225 // Return "TRUE" iff the given object address is within the collection 1226 // set. Slow implementation. 1227 inline bool obj_in_cs(oop obj); 1228 1229 inline bool is_in_cset(oop obj); 1230 1231 inline bool is_in_cset_or_humongous(const oop obj); 1232 1233 private: 1234 // This array is used for a quick test on whether a reference points into 1235 // the collection set or not. Each of the array's elements denotes whether the 1236 // corresponding region is in the collection set or not. 1237 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1238 1239 public: 1240 1241 inline InCSetState in_cset_state(const oop obj); 1242 1243 // Return "TRUE" iff the given object address is in the reserved 1244 // region of g1. 1245 bool is_in_g1_reserved(const void* p) const { 1246 return _hrm.reserved().contains(p); 1247 } 1248 1249 // Returns a MemRegion that corresponds to the space that has been 1250 // reserved for the heap 1251 MemRegion g1_reserved() const { 1252 return _hrm.reserved(); 1253 } 1254 1255 virtual bool is_in_closed_subset(const void* p) const; 1256 1257 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1258 return (G1SATBCardTableLoggingModRefBS*) barrier_set(); 1259 } 1260 1261 // This resets the card table to all zeros. It is used after 1262 // a collection pause which used the card table to claim cards. 1263 void cleanUpCardTable(); 1264 1265 // Iteration functions. 1266 1267 // Iterate over all the ref-containing fields of all objects, calling 1268 // "cl.do_oop" on each. 1269 virtual void oop_iterate(ExtendedOopClosure* cl); 1270 1271 // Iterate over all objects, calling "cl.do_object" on each. 1272 virtual void object_iterate(ObjectClosure* cl); 1273 1274 virtual void safe_object_iterate(ObjectClosure* cl) { 1275 object_iterate(cl); 1276 } 1277 1278 // Iterate over all spaces in use in the heap, in ascending address order. 1279 virtual void space_iterate(SpaceClosure* cl); 1280 1281 // Iterate over heap regions, in address order, terminating the 1282 // iteration early if the "doHeapRegion" method returns "true". 1283 void heap_region_iterate(HeapRegionClosure* blk) const; 1284 1285 // Return the region with the given index. It assumes the index is valid. 1286 inline HeapRegion* region_at(uint index) const; 1287 1288 // Calculate the region index of the given address. Given address must be 1289 // within the heap. 1290 inline uint addr_to_region(HeapWord* addr) const; 1291 1292 inline HeapWord* bottom_addr_for_region(uint index) const; 1293 1294 // Divide the heap region sequence into "chunks" of some size (the number 1295 // of regions divided by the number of parallel threads times some 1296 // overpartition factor, currently 4). Assumes that this will be called 1297 // in parallel by ParallelGCThreads worker threads with discinct worker 1298 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel 1299 // calls will use the same "claim_value", and that that claim value is 1300 // different from the claim_value of any heap region before the start of 1301 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by 1302 // attempting to claim the first region in each chunk, and, if 1303 // successful, applying the closure to each region in the chunk (and 1304 // setting the claim value of the second and subsequent regions of the 1305 // chunk.) For now requires that "doHeapRegion" always returns "false", 1306 // i.e., that a closure never attempt to abort a traversal. 1307 void heap_region_par_iterate_chunked(HeapRegionClosure* cl, 1308 uint worker_id, 1309 uint num_workers, 1310 jint claim_value) const; 1311 1312 // It resets all the region claim values to the default. 1313 void reset_heap_region_claim_values(); 1314 1315 // Resets the claim values of regions in the current 1316 // collection set to the default. 1317 void reset_cset_heap_region_claim_values(); 1318 1319 #ifdef ASSERT 1320 bool check_heap_region_claim_values(jint claim_value); 1321 1322 // Same as the routine above but only checks regions in the 1323 // current collection set. 1324 bool check_cset_heap_region_claim_values(jint claim_value); 1325 #endif // ASSERT 1326 1327 // Clear the cached cset start regions and (more importantly) 1328 // the time stamps. Called when we reset the GC time stamp. 1329 void clear_cset_start_regions(); 1330 1331 // Given the id of a worker, obtain or calculate a suitable 1332 // starting region for iterating over the current collection set. 1333 HeapRegion* start_cset_region_for_worker(uint worker_i); 1334 1335 // Iterate over the regions (if any) in the current collection set. 1336 void collection_set_iterate(HeapRegionClosure* blk); 1337 1338 // As above but starting from region r 1339 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1340 1341 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1342 1343 // A CollectedHeap will contain some number of spaces. This finds the 1344 // space containing a given address, or else returns NULL. 1345 virtual Space* space_containing(const void* addr) const; 1346 1347 // Returns the HeapRegion that contains addr. addr must not be NULL. 1348 template <class T> 1349 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1350 1351 // Returns the HeapRegion that contains addr. addr must not be NULL. 1352 // If addr is within a humongous continues region, it returns its humongous start region. 1353 template <class T> 1354 inline HeapRegion* heap_region_containing(const T addr) const; 1355 1356 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1357 // each address in the (reserved) heap is a member of exactly 1358 // one block. The defining characteristic of a block is that it is 1359 // possible to find its size, and thus to progress forward to the next 1360 // block. (Blocks may be of different sizes.) Thus, blocks may 1361 // represent Java objects, or they might be free blocks in a 1362 // free-list-based heap (or subheap), as long as the two kinds are 1363 // distinguishable and the size of each is determinable. 1364 1365 // Returns the address of the start of the "block" that contains the 1366 // address "addr". We say "blocks" instead of "object" since some heaps 1367 // may not pack objects densely; a chunk may either be an object or a 1368 // non-object. 1369 virtual HeapWord* block_start(const void* addr) const; 1370 1371 // Requires "addr" to be the start of a chunk, and returns its size. 1372 // "addr + size" is required to be the start of a new chunk, or the end 1373 // of the active area of the heap. 1374 virtual size_t block_size(const HeapWord* addr) const; 1375 1376 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1377 // the block is an object. 1378 virtual bool block_is_obj(const HeapWord* addr) const; 1379 1380 // Does this heap support heap inspection? (+PrintClassHistogram) 1381 virtual bool supports_heap_inspection() const { return true; } 1382 1383 // Section on thread-local allocation buffers (TLABs) 1384 // See CollectedHeap for semantics. 1385 1386 bool supports_tlab_allocation() const; 1387 size_t tlab_capacity(Thread* ignored) const; 1388 size_t tlab_used(Thread* ignored) const; 1389 size_t max_tlab_size() const; 1390 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1391 1392 // Can a compiler initialize a new object without store barriers? 1393 // This permission only extends from the creation of a new object 1394 // via a TLAB up to the first subsequent safepoint. If such permission 1395 // is granted for this heap type, the compiler promises to call 1396 // defer_store_barrier() below on any slow path allocation of 1397 // a new object for which such initializing store barriers will 1398 // have been elided. G1, like CMS, allows this, but should be 1399 // ready to provide a compensating write barrier as necessary 1400 // if that storage came out of a non-young region. The efficiency 1401 // of this implementation depends crucially on being able to 1402 // answer very efficiently in constant time whether a piece of 1403 // storage in the heap comes from a young region or not. 1404 // See ReduceInitialCardMarks. 1405 virtual bool can_elide_tlab_store_barriers() const { 1406 return true; 1407 } 1408 1409 virtual bool card_mark_must_follow_store() const { 1410 return true; 1411 } 1412 1413 inline bool is_in_young(const oop obj); 1414 1415 #ifdef ASSERT 1416 virtual bool is_in_partial_collection(const void* p); 1417 #endif 1418 1419 virtual bool is_scavengable(const void* addr); 1420 1421 // We don't need barriers for initializing stores to objects 1422 // in the young gen: for the SATB pre-barrier, there is no 1423 // pre-value that needs to be remembered; for the remembered-set 1424 // update logging post-barrier, we don't maintain remembered set 1425 // information for young gen objects. 1426 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1427 1428 // Returns "true" iff the given word_size is "very large". 1429 static bool isHumongous(size_t word_size) { 1430 // Note this has to be strictly greater-than as the TLABs 1431 // are capped at the humongous thresold and we want to 1432 // ensure that we don't try to allocate a TLAB as 1433 // humongous and that we don't allocate a humongous 1434 // object in a TLAB. 1435 return word_size > _humongous_object_threshold_in_words; 1436 } 1437 1438 // Update mod union table with the set of dirty cards. 1439 void updateModUnion(); 1440 1441 // Set the mod union bits corresponding to the given memRegion. Note 1442 // that this is always a safe operation, since it doesn't clear any 1443 // bits. 1444 void markModUnionRange(MemRegion mr); 1445 1446 // Records the fact that a marking phase is no longer in progress. 1447 void set_marking_complete() { 1448 _mark_in_progress = false; 1449 } 1450 void set_marking_started() { 1451 _mark_in_progress = true; 1452 } 1453 bool mark_in_progress() { 1454 return _mark_in_progress; 1455 } 1456 1457 // Print the maximum heap capacity. 1458 virtual size_t max_capacity() const; 1459 1460 virtual jlong millis_since_last_gc(); 1461 1462 1463 // Convenience function to be used in situations where the heap type can be 1464 // asserted to be this type. 1465 static G1CollectedHeap* heap(); 1466 1467 void set_region_short_lived_locked(HeapRegion* hr); 1468 // add appropriate methods for any other surv rate groups 1469 1470 YoungList* young_list() const { return _young_list; } 1471 1472 // debugging 1473 bool check_young_list_well_formed() { 1474 return _young_list->check_list_well_formed(); 1475 } 1476 1477 bool check_young_list_empty(bool check_heap, 1478 bool check_sample = true); 1479 1480 // *** Stuff related to concurrent marking. It's not clear to me that so 1481 // many of these need to be public. 1482 1483 // The functions below are helper functions that a subclass of 1484 // "CollectedHeap" can use in the implementation of its virtual 1485 // functions. 1486 // This performs a concurrent marking of the live objects in a 1487 // bitmap off to the side. 1488 void doConcurrentMark(); 1489 1490 bool isMarkedPrev(oop obj) const; 1491 bool isMarkedNext(oop obj) const; 1492 1493 // Determine if an object is dead, given the object and also 1494 // the region to which the object belongs. An object is dead 1495 // iff a) it was not allocated since the last mark and b) it 1496 // is not marked. 1497 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1498 return 1499 !hr->obj_allocated_since_prev_marking(obj) && 1500 !isMarkedPrev(obj); 1501 } 1502 1503 // This function returns true when an object has been 1504 // around since the previous marking and hasn't yet 1505 // been marked during this marking. 1506 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1507 return 1508 !hr->obj_allocated_since_next_marking(obj) && 1509 !isMarkedNext(obj); 1510 } 1511 1512 // Determine if an object is dead, given only the object itself. 1513 // This will find the region to which the object belongs and 1514 // then call the region version of the same function. 1515 1516 // Added if it is NULL it isn't dead. 1517 1518 inline bool is_obj_dead(const oop obj) const; 1519 1520 inline bool is_obj_ill(const oop obj) const; 1521 1522 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1523 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1524 bool is_marked(oop obj, VerifyOption vo); 1525 const char* top_at_mark_start_str(VerifyOption vo); 1526 1527 ConcurrentMark* concurrent_mark() const { return _cm; } 1528 1529 // Refinement 1530 1531 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1532 1533 // The dirty cards region list is used to record a subset of regions 1534 // whose cards need clearing. The list if populated during the 1535 // remembered set scanning and drained during the card table 1536 // cleanup. Although the methods are reentrant, population/draining 1537 // phases must not overlap. For synchronization purposes the last 1538 // element on the list points to itself. 1539 HeapRegion* _dirty_cards_region_list; 1540 void push_dirty_cards_region(HeapRegion* hr); 1541 HeapRegion* pop_dirty_cards_region(); 1542 1543 // Optimized nmethod scanning support routines 1544 1545 // Register the given nmethod with the G1 heap 1546 virtual void register_nmethod(nmethod* nm); 1547 1548 // Unregister the given nmethod from the G1 heap 1549 virtual void unregister_nmethod(nmethod* nm); 1550 1551 // Free up superfluous code root memory. 1552 void purge_code_root_memory(); 1553 1554 // Rebuild the stong code root lists for each region 1555 // after a full GC 1556 void rebuild_strong_code_roots(); 1557 1558 // Delete entries for dead interned string and clean up unreferenced symbols 1559 // in symbol table, possibly in parallel. 1560 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1561 1562 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1563 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1564 1565 // Redirty logged cards in the refinement queue. 1566 void redirty_logged_cards(); 1567 // Verification 1568 1569 // The following is just to alert the verification code 1570 // that a full collection has occurred and that the 1571 // remembered sets are no longer up to date. 1572 bool _full_collection; 1573 void set_full_collection() { _full_collection = true;} 1574 void clear_full_collection() {_full_collection = false;} 1575 bool full_collection() {return _full_collection;} 1576 1577 // Perform any cleanup actions necessary before allowing a verification. 1578 virtual void prepare_for_verify(); 1579 1580 // Perform verification. 1581 1582 // vo == UsePrevMarking -> use "prev" marking information, 1583 // vo == UseNextMarking -> use "next" marking information 1584 // vo == UseMarkWord -> use the mark word in the object header 1585 // 1586 // NOTE: Only the "prev" marking information is guaranteed to be 1587 // consistent most of the time, so most calls to this should use 1588 // vo == UsePrevMarking. 1589 // Currently, there is only one case where this is called with 1590 // vo == UseNextMarking, which is to verify the "next" marking 1591 // information at the end of remark. 1592 // Currently there is only one place where this is called with 1593 // vo == UseMarkWord, which is to verify the marking during a 1594 // full GC. 1595 void verify(bool silent, VerifyOption vo); 1596 1597 // Override; it uses the "prev" marking information 1598 virtual void verify(bool silent); 1599 1600 // The methods below are here for convenience and dispatch the 1601 // appropriate method depending on value of the given VerifyOption 1602 // parameter. The values for that parameter, and their meanings, 1603 // are the same as those above. 1604 1605 bool is_obj_dead_cond(const oop obj, 1606 const HeapRegion* hr, 1607 const VerifyOption vo) const; 1608 1609 bool is_obj_dead_cond(const oop obj, 1610 const VerifyOption vo) const; 1611 1612 // Printing 1613 1614 virtual void print_on(outputStream* st) const; 1615 virtual void print_extended_on(outputStream* st) const; 1616 virtual void print_on_error(outputStream* st) const; 1617 1618 virtual void print_gc_threads_on(outputStream* st) const; 1619 virtual void gc_threads_do(ThreadClosure* tc) const; 1620 1621 // Override 1622 void print_tracing_info() const; 1623 1624 // The following two methods are helpful for debugging RSet issues. 1625 void print_cset_rsets() PRODUCT_RETURN; 1626 void print_all_rsets() PRODUCT_RETURN; 1627 1628 public: 1629 size_t pending_card_num(); 1630 size_t cards_scanned(); 1631 1632 protected: 1633 size_t _max_heap_capacity; 1634 }; 1635 1636 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP