1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc_implementation/g1/g1AllocationContext.hpp" 29 #include "gc_implementation/g1/g1Allocator.hpp" 30 #include "gc_implementation/g1/concurrentMark.hpp" 31 #include "gc_implementation/g1/evacuationInfo.hpp" 32 #include "gc_implementation/g1/g1AllocRegion.hpp" 33 #include "gc_implementation/g1/g1BiasedArray.hpp" 34 #include "gc_implementation/g1/g1HRPrinter.hpp" 35 #include "gc_implementation/g1/g1InCSetState.hpp" 36 #include "gc_implementation/g1/g1MonitoringSupport.hpp" 37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 38 #include "gc_implementation/g1/g1YCTypes.hpp" 39 #include "gc_implementation/g1/heapRegionManager.hpp" 40 #include "gc_implementation/g1/heapRegionSet.hpp" 41 #include "gc_implementation/shared/hSpaceCounters.hpp" 42 #include "gc_implementation/shared/parGCAllocBuffer.hpp" 43 #include "memory/barrierSet.hpp" 44 #include "memory/memRegion.hpp" 45 #include "memory/sharedHeap.hpp" 46 #include "utilities/stack.hpp" 47 48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 49 // It uses the "Garbage First" heap organization and algorithm, which 50 // may combine concurrent marking with parallel, incremental compaction of 51 // heap subsets that will yield large amounts of garbage. 52 53 // Forward declarations 54 class HeapRegion; 55 class HRRSCleanupTask; 56 class GenerationSpec; 57 class OopsInHeapRegionClosure; 58 class G1KlassScanClosure; 59 class G1ParScanThreadState; 60 class ObjectClosure; 61 class SpaceClosure; 62 class CompactibleSpaceClosure; 63 class Space; 64 class G1CollectorPolicy; 65 class GenRemSet; 66 class G1RemSet; 67 class HeapRegionRemSetIterator; 68 class ConcurrentMark; 69 class ConcurrentMarkThread; 70 class ConcurrentG1Refine; 71 class ConcurrentGCTimer; 72 class GenerationCounters; 73 class STWGCTimer; 74 class G1NewTracer; 75 class G1OldTracer; 76 class EvacuationFailedInfo; 77 class nmethod; 78 class Ticks; 79 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 eden_length() { return length() - survivor_length(); } 115 uint survivor_length() { return _survivor_length; } 116 117 // Currently we do not keep track of the used byte sum for the 118 // young list and the survivors and it'd be quite a lot of work to 119 // do so. When we'll eventually replace the young list with 120 // instances of HeapRegionLinkedList we'll get that for free. So, 121 // we'll report the more accurate information then. 122 size_t eden_used_bytes() { 123 assert(length() >= survivor_length(), "invariant"); 124 return (size_t) eden_length() * HeapRegion::GrainBytes; 125 } 126 size_t survivor_used_bytes() { 127 return (size_t) survivor_length() * HeapRegion::GrainBytes; 128 } 129 130 void rs_length_sampling_init(); 131 bool rs_length_sampling_more(); 132 void rs_length_sampling_next(); 133 134 void reset_sampled_info() { 135 _last_sampled_rs_lengths = 0; 136 } 137 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } 138 139 // for development purposes 140 void reset_auxilary_lists(); 141 void clear() { _head = NULL; _length = 0; } 142 143 void clear_survivors() { 144 _survivor_head = NULL; 145 _survivor_tail = NULL; 146 _survivor_length = 0; 147 } 148 149 HeapRegion* first_region() { return _head; } 150 HeapRegion* first_survivor_region() { return _survivor_head; } 151 HeapRegion* last_survivor_region() { return _survivor_tail; } 152 153 // debugging 154 bool check_list_well_formed(); 155 bool check_list_empty(bool check_sample = true); 156 void print(); 157 }; 158 159 // The G1 STW is alive closure. 160 // An instance is embedded into the G1CH and used as the 161 // (optional) _is_alive_non_header closure in the STW 162 // reference processor. It is also extensively used during 163 // reference processing during STW evacuation pauses. 164 class G1STWIsAliveClosure: public BoolObjectClosure { 165 G1CollectedHeap* _g1; 166 public: 167 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 168 bool do_object_b(oop p); 169 }; 170 171 class RefineCardTableEntryClosure; 172 173 class G1RegionMappingChangedListener : public G1MappingChangedListener { 174 private: 175 void reset_from_card_cache(uint start_idx, size_t num_regions); 176 public: 177 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 178 }; 179 180 class G1CollectedHeap : public SharedHeap { 181 friend class VM_CollectForMetadataAllocation; 182 friend class VM_G1CollectForAllocation; 183 friend class VM_G1CollectFull; 184 friend class VM_G1IncCollectionPause; 185 friend class VMStructs; 186 friend class MutatorAllocRegion; 187 friend class SurvivorGCAllocRegion; 188 friend class OldGCAllocRegion; 189 friend class G1Allocator; 190 191 // Closures used in implementation. 192 friend class G1ParScanThreadState; 193 friend class G1ParTask; 194 friend class G1ParGCAllocator; 195 friend class G1PrepareCompactClosure; 196 197 // Other related classes. 198 friend class HeapRegionClaimer; 199 200 // Testing classes. 201 friend class G1CheckCSetFastTableClosure; 202 203 private: 204 // The one and only G1CollectedHeap, so static functions can find it. 205 static G1CollectedHeap* _g1h; 206 207 static size_t _humongous_object_threshold_in_words; 208 209 // The secondary free list which contains regions that have been 210 // freed up during the cleanup process. This will be appended to 211 // the master free list when appropriate. 212 FreeRegionList _secondary_free_list; 213 214 // It keeps track of the old regions. 215 HeapRegionSet _old_set; 216 217 // It keeps track of the humongous regions. 218 HeapRegionSet _humongous_set; 219 220 void clear_humongous_is_live_table(); 221 void eagerly_reclaim_humongous_regions(); 222 223 // The number of regions we could create by expansion. 224 uint _expansion_regions; 225 226 // The block offset table for the G1 heap. 227 G1BlockOffsetSharedArray* _bot_shared; 228 229 // Tears down the region sets / lists so that they are empty and the 230 // regions on the heap do not belong to a region set / list. The 231 // only exception is the humongous set which we leave unaltered. If 232 // free_list_only is true, it will only tear down the master free 233 // list. It is called before a Full GC (free_list_only == false) or 234 // before heap shrinking (free_list_only == true). 235 void tear_down_region_sets(bool free_list_only); 236 237 // Rebuilds the region sets / lists so that they are repopulated to 238 // reflect the contents of the heap. The only exception is the 239 // humongous set which was not torn down in the first place. If 240 // free_list_only is true, it will only rebuild the master free 241 // list. It is called after a Full GC (free_list_only == false) or 242 // after heap shrinking (free_list_only == true). 243 void rebuild_region_sets(bool free_list_only); 244 245 // Callback for region mapping changed events. 246 G1RegionMappingChangedListener _listener; 247 248 // The sequence of all heap regions in the heap. 249 HeapRegionManager _hrm; 250 251 // Class that handles the different kinds of allocations. 252 G1Allocator* _allocator; 253 254 // Statistics for each allocation context 255 AllocationContextStats _allocation_context_stats; 256 257 // PLAB sizing policy for survivors. 258 PLABStats _survivor_plab_stats; 259 260 // PLAB sizing policy for tenured objects. 261 PLABStats _old_plab_stats; 262 263 // It specifies whether we should attempt to expand the heap after a 264 // region allocation failure. If heap expansion fails we set this to 265 // false so that we don't re-attempt the heap expansion (it's likely 266 // that subsequent expansion attempts will also fail if one fails). 267 // Currently, it is only consulted during GC and it's reset at the 268 // start of each GC. 269 bool _expand_heap_after_alloc_failure; 270 271 // It resets the mutator alloc region before new allocations can take place. 272 void init_mutator_alloc_region(); 273 274 // It releases the mutator alloc region. 275 void release_mutator_alloc_region(); 276 277 // It initializes the GC alloc regions at the start of a GC. 278 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 279 280 // It releases the GC alloc regions at the end of a GC. 281 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 282 283 // It does any cleanup that needs to be done on the GC alloc regions 284 // before a Full GC. 285 void abandon_gc_alloc_regions(); 286 287 // Helper for monitoring and management support. 288 G1MonitoringSupport* _g1mm; 289 290 // Records whether the region at the given index is kept live by roots or 291 // references from the young generation. 292 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 293 protected: 294 bool default_value() const { return false; } 295 public: 296 void clear() { G1BiasedMappedArray<bool>::clear(); } 297 void set_live(uint region) { 298 set_by_index(region, true); 299 } 300 bool is_live(uint region) { 301 return get_by_index(region); 302 } 303 }; 304 305 HumongousIsLiveBiasedMappedArray _humongous_is_live; 306 // Stores whether during humongous object registration we found candidate regions. 307 // If not, we can skip a few steps. 308 bool _has_humongous_reclaim_candidates; 309 310 volatile unsigned _gc_time_stamp; 311 312 size_t* _surviving_young_words; 313 314 G1HRPrinter _hr_printer; 315 316 void setup_surviving_young_words(); 317 void update_surviving_young_words(size_t* surv_young_words); 318 void cleanup_surviving_young_words(); 319 320 // It decides whether an explicit GC should start a concurrent cycle 321 // instead of doing a STW GC. Currently, a concurrent cycle is 322 // explicitly started if: 323 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 324 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 325 // (c) cause == _g1_humongous_allocation 326 bool should_do_concurrent_full_gc(GCCause::Cause cause); 327 328 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 329 // concurrent cycles) we have started. 330 volatile uint _old_marking_cycles_started; 331 332 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 333 // concurrent cycles) we have completed. 334 volatile uint _old_marking_cycles_completed; 335 336 bool _concurrent_cycle_started; 337 bool _heap_summary_sent; 338 339 // This is a non-product method that is helpful for testing. It is 340 // called at the end of a GC and artificially expands the heap by 341 // allocating a number of dead regions. This way we can induce very 342 // frequent marking cycles and stress the cleanup / concurrent 343 // cleanup code more (as all the regions that will be allocated by 344 // this method will be found dead by the marking cycle). 345 void allocate_dummy_regions() PRODUCT_RETURN; 346 347 // Clear RSets after a compaction. It also resets the GC time stamps. 348 void clear_rsets_post_compaction(); 349 350 // If the HR printer is active, dump the state of the regions in the 351 // heap after a compaction. 352 void print_hrm_post_compaction(); 353 354 double verify(bool guard, const char* msg); 355 void verify_before_gc(); 356 void verify_after_gc(); 357 358 void log_gc_header(); 359 void log_gc_footer(double pause_time_sec); 360 361 // These are macros so that, if the assert fires, we get the correct 362 // line number, file, etc. 363 364 #define heap_locking_asserts_err_msg(_extra_message_) \ 365 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 366 (_extra_message_), \ 367 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 368 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 369 BOOL_TO_STR(Thread::current()->is_VM_thread())) 370 371 #define assert_heap_locked() \ 372 do { \ 373 assert(Heap_lock->owned_by_self(), \ 374 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 375 } while (0) 376 377 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 378 do { \ 379 assert(Heap_lock->owned_by_self() || \ 380 (SafepointSynchronize::is_at_safepoint() && \ 381 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 382 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 383 "should be at a safepoint")); \ 384 } while (0) 385 386 #define assert_heap_locked_and_not_at_safepoint() \ 387 do { \ 388 assert(Heap_lock->owned_by_self() && \ 389 !SafepointSynchronize::is_at_safepoint(), \ 390 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 391 "should not be at a safepoint")); \ 392 } while (0) 393 394 #define assert_heap_not_locked() \ 395 do { \ 396 assert(!Heap_lock->owned_by_self(), \ 397 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 398 } while (0) 399 400 #define assert_heap_not_locked_and_not_at_safepoint() \ 401 do { \ 402 assert(!Heap_lock->owned_by_self() && \ 403 !SafepointSynchronize::is_at_safepoint(), \ 404 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 405 "should not be at a safepoint")); \ 406 } while (0) 407 408 #define assert_at_safepoint(_should_be_vm_thread_) \ 409 do { \ 410 assert(SafepointSynchronize::is_at_safepoint() && \ 411 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 412 heap_locking_asserts_err_msg("should be at a safepoint")); \ 413 } while (0) 414 415 #define assert_not_at_safepoint() \ 416 do { \ 417 assert(!SafepointSynchronize::is_at_safepoint(), \ 418 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 419 } while (0) 420 421 protected: 422 423 // The young region list. 424 YoungList* _young_list; 425 426 // The current policy object for the collector. 427 G1CollectorPolicy* _g1_policy; 428 429 // This is the second level of trying to allocate a new region. If 430 // new_region() didn't find a region on the free_list, this call will 431 // check whether there's anything available on the 432 // secondary_free_list and/or wait for more regions to appear on 433 // that list, if _free_regions_coming is set. 434 HeapRegion* new_region_try_secondary_free_list(bool is_old); 435 436 // Try to allocate a single non-humongous HeapRegion sufficient for 437 // an allocation of the given word_size. If do_expand is true, 438 // attempt to expand the heap if necessary to satisfy the allocation 439 // request. If the region is to be used as an old region or for a 440 // humongous object, set is_old to true. If not, to false. 441 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 442 443 // Initialize a contiguous set of free regions of length num_regions 444 // and starting at index first so that they appear as a single 445 // humongous region. 446 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 447 uint num_regions, 448 size_t word_size, 449 AllocationContext_t context); 450 451 // Attempt to allocate a humongous object of the given size. Return 452 // NULL if unsuccessful. 453 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 454 455 // The following two methods, allocate_new_tlab() and 456 // mem_allocate(), are the two main entry points from the runtime 457 // into the G1's allocation routines. They have the following 458 // assumptions: 459 // 460 // * They should both be called outside safepoints. 461 // 462 // * They should both be called without holding the Heap_lock. 463 // 464 // * All allocation requests for new TLABs should go to 465 // allocate_new_tlab(). 466 // 467 // * All non-TLAB allocation requests should go to mem_allocate(). 468 // 469 // * If either call cannot satisfy the allocation request using the 470 // current allocating region, they will try to get a new one. If 471 // this fails, they will attempt to do an evacuation pause and 472 // retry the allocation. 473 // 474 // * If all allocation attempts fail, even after trying to schedule 475 // an evacuation pause, allocate_new_tlab() will return NULL, 476 // whereas mem_allocate() will attempt a heap expansion and/or 477 // schedule a Full GC. 478 // 479 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 480 // should never be called with word_size being humongous. All 481 // humongous allocation requests should go to mem_allocate() which 482 // will satisfy them with a special path. 483 484 virtual HeapWord* allocate_new_tlab(size_t word_size); 485 486 virtual HeapWord* mem_allocate(size_t word_size, 487 bool* gc_overhead_limit_was_exceeded); 488 489 // The following three methods take a gc_count_before_ret 490 // parameter which is used to return the GC count if the method 491 // returns NULL. Given that we are required to read the GC count 492 // while holding the Heap_lock, and these paths will take the 493 // Heap_lock at some point, it's easier to get them to read the GC 494 // count while holding the Heap_lock before they return NULL instead 495 // of the caller (namely: mem_allocate()) having to also take the 496 // Heap_lock just to read the GC count. 497 498 // First-level mutator allocation attempt: try to allocate out of 499 // the mutator alloc region without taking the Heap_lock. This 500 // should only be used for non-humongous allocations. 501 inline HeapWord* attempt_allocation(size_t word_size, 502 uint* gc_count_before_ret, 503 uint* gclocker_retry_count_ret); 504 505 // Second-level mutator allocation attempt: take the Heap_lock and 506 // retry the allocation attempt, potentially scheduling a GC 507 // pause. This should only be used for non-humongous allocations. 508 HeapWord* attempt_allocation_slow(size_t word_size, 509 AllocationContext_t context, 510 uint* gc_count_before_ret, 511 uint* gclocker_retry_count_ret); 512 513 // Takes the Heap_lock and attempts a humongous allocation. It can 514 // potentially schedule a GC pause. 515 HeapWord* attempt_allocation_humongous(size_t word_size, 516 uint* gc_count_before_ret, 517 uint* gclocker_retry_count_ret); 518 519 // Allocation attempt that should be called during safepoints (e.g., 520 // at the end of a successful GC). expect_null_mutator_alloc_region 521 // specifies whether the mutator alloc region is expected to be NULL 522 // or not. 523 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 524 AllocationContext_t context, 525 bool expect_null_mutator_alloc_region); 526 527 // It dirties the cards that cover the block so that so that the post 528 // write barrier never queues anything when updating objects on this 529 // block. It is assumed (and in fact we assert) that the block 530 // belongs to a young region. 531 inline void dirty_young_block(HeapWord* start, size_t word_size); 532 533 // Allocate blocks during garbage collection. Will ensure an 534 // allocation region, either by picking one or expanding the 535 // heap, and then allocate a block of the given size. The block 536 // may not be a humongous - it must fit into a single heap region. 537 inline HeapWord* par_allocate_during_gc(InCSetState dest, 538 size_t word_size, 539 AllocationContext_t context); 540 // Ensure that no further allocations can happen in "r", bearing in mind 541 // that parallel threads might be attempting allocations. 542 void par_allocate_remaining_space(HeapRegion* r); 543 544 // Allocation attempt during GC for a survivor object / PLAB. 545 inline HeapWord* survivor_attempt_allocation(size_t word_size, 546 AllocationContext_t context); 547 548 // Allocation attempt during GC for an old object / PLAB. 549 inline HeapWord* old_attempt_allocation(size_t word_size, 550 AllocationContext_t context); 551 552 // These methods are the "callbacks" from the G1AllocRegion class. 553 554 // For mutator alloc regions. 555 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 556 void retire_mutator_alloc_region(HeapRegion* alloc_region, 557 size_t allocated_bytes); 558 559 // For GC alloc regions. 560 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 561 InCSetState dest); 562 void retire_gc_alloc_region(HeapRegion* alloc_region, 563 size_t allocated_bytes, InCSetState dest); 564 565 // - if explicit_gc is true, the GC is for a System.gc() or a heap 566 // inspection request and should collect the entire heap 567 // - if clear_all_soft_refs is true, all soft references should be 568 // cleared during the GC 569 // - if explicit_gc is false, word_size describes the allocation that 570 // the GC should attempt (at least) to satisfy 571 // - it returns false if it is unable to do the collection due to the 572 // GC locker being active, true otherwise 573 bool do_collection(bool explicit_gc, 574 bool clear_all_soft_refs, 575 size_t word_size); 576 577 // Callback from VM_G1CollectFull operation. 578 // Perform a full collection. 579 virtual void do_full_collection(bool clear_all_soft_refs); 580 581 // Resize the heap if necessary after a full collection. If this is 582 // after a collect-for allocation, "word_size" is the allocation size, 583 // and will be considered part of the used portion of the heap. 584 void resize_if_necessary_after_full_collection(size_t word_size); 585 586 // Callback from VM_G1CollectForAllocation operation. 587 // This function does everything necessary/possible to satisfy a 588 // failed allocation request (including collection, expansion, etc.) 589 HeapWord* satisfy_failed_allocation(size_t word_size, 590 AllocationContext_t context, 591 bool* succeeded); 592 593 // Attempting to expand the heap sufficiently 594 // to support an allocation of the given "word_size". If 595 // successful, perform the allocation and return the address of the 596 // allocated block, or else "NULL". 597 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 598 599 // Process any reference objects discovered during 600 // an incremental evacuation pause. 601 void process_discovered_references(uint no_of_gc_workers); 602 603 // Enqueue any remaining discovered references 604 // after processing. 605 void enqueue_discovered_references(uint no_of_gc_workers); 606 607 public: 608 609 G1Allocator* allocator() { 610 return _allocator; 611 } 612 613 G1MonitoringSupport* g1mm() { 614 assert(_g1mm != NULL, "should have been initialized"); 615 return _g1mm; 616 } 617 618 // Expand the garbage-first heap by at least the given size (in bytes!). 619 // Returns true if the heap was expanded by the requested amount; 620 // false otherwise. 621 // (Rounds up to a HeapRegion boundary.) 622 bool expand(size_t expand_bytes); 623 624 // Returns the PLAB statistics for a given destination. 625 inline PLABStats* alloc_buffer_stats(InCSetState dest); 626 627 // Determines PLAB size for a given destination. 628 inline size_t desired_plab_sz(InCSetState dest); 629 630 inline AllocationContextStats& allocation_context_stats(); 631 632 // Do anything common to GC's. 633 void gc_prologue(bool full); 634 void gc_epilogue(bool full); 635 636 inline void set_humongous_is_live(oop obj); 637 638 bool humongous_is_live(uint region) { 639 return _humongous_is_live.is_live(region); 640 } 641 642 // Returns whether the given region (which must be a humongous (start) region) 643 // is to be considered conservatively live regardless of any other conditions. 644 bool humongous_region_is_always_live(uint index); 645 // Returns whether the given region (which must be a humongous (start) region) 646 // is considered a candidate for eager reclamation. 647 bool humongous_region_is_candidate(uint index); 648 // Register the given region to be part of the collection set. 649 inline void register_humongous_region_with_cset(uint index); 650 // Register regions with humongous objects (actually on the start region) in 651 // the in_cset_fast_test table. 652 void register_humongous_regions_with_cset(); 653 // We register a region with the fast "in collection set" test. We 654 // simply set to true the array slot corresponding to this region. 655 void register_young_region_with_cset(HeapRegion* r) { 656 _in_cset_fast_test.set_in_young(r->hrm_index()); 657 } 658 void register_old_region_with_cset(HeapRegion* r) { 659 _in_cset_fast_test.set_in_old(r->hrm_index()); 660 } 661 void clear_in_cset(const HeapRegion* hr) { 662 _in_cset_fast_test.clear(hr); 663 } 664 665 void clear_cset_fast_test() { 666 _in_cset_fast_test.clear(); 667 } 668 669 // This is called at the start of either a concurrent cycle or a Full 670 // GC to update the number of old marking cycles started. 671 void increment_old_marking_cycles_started(); 672 673 // This is called at the end of either a concurrent cycle or a Full 674 // GC to update the number of old marking cycles completed. Those two 675 // can happen in a nested fashion, i.e., we start a concurrent 676 // cycle, a Full GC happens half-way through it which ends first, 677 // and then the cycle notices that a Full GC happened and ends 678 // too. The concurrent parameter is a boolean to help us do a bit 679 // tighter consistency checking in the method. If concurrent is 680 // false, the caller is the inner caller in the nesting (i.e., the 681 // Full GC). If concurrent is true, the caller is the outer caller 682 // in this nesting (i.e., the concurrent cycle). Further nesting is 683 // not currently supported. The end of this call also notifies 684 // the FullGCCount_lock in case a Java thread is waiting for a full 685 // GC to happen (e.g., it called System.gc() with 686 // +ExplicitGCInvokesConcurrent). 687 void increment_old_marking_cycles_completed(bool concurrent); 688 689 uint old_marking_cycles_completed() { 690 return _old_marking_cycles_completed; 691 } 692 693 void register_concurrent_cycle_start(const Ticks& start_time); 694 void register_concurrent_cycle_end(); 695 void trace_heap_after_concurrent_cycle(); 696 697 G1YCType yc_type(); 698 699 G1HRPrinter* hr_printer() { return &_hr_printer; } 700 701 // Frees a non-humongous region by initializing its contents and 702 // adding it to the free list that's passed as a parameter (this is 703 // usually a local list which will be appended to the master free 704 // list later). The used bytes of freed regions are accumulated in 705 // pre_used. If par is true, the region's RSet will not be freed 706 // up. The assumption is that this will be done later. 707 // The locked parameter indicates if the caller has already taken 708 // care of proper synchronization. This may allow some optimizations. 709 void free_region(HeapRegion* hr, 710 FreeRegionList* free_list, 711 bool par, 712 bool locked = false); 713 714 // Frees a humongous region by collapsing it into individual regions 715 // and calling free_region() for each of them. The freed regions 716 // will be added to the free list that's passed as a parameter (this 717 // is usually a local list which will be appended to the master free 718 // list later). The used bytes of freed regions are accumulated in 719 // pre_used. If par is true, the region's RSet will not be freed 720 // up. The assumption is that this will be done later. 721 void free_humongous_region(HeapRegion* hr, 722 FreeRegionList* free_list, 723 bool par); 724 protected: 725 726 // Shrink the garbage-first heap by at most the given size (in bytes!). 727 // (Rounds down to a HeapRegion boundary.) 728 virtual void shrink(size_t expand_bytes); 729 void shrink_helper(size_t expand_bytes); 730 731 #if TASKQUEUE_STATS 732 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 733 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 734 void reset_taskqueue_stats(); 735 #endif // TASKQUEUE_STATS 736 737 // Schedule the VM operation that will do an evacuation pause to 738 // satisfy an allocation request of word_size. *succeeded will 739 // return whether the VM operation was successful (it did do an 740 // evacuation pause) or not (another thread beat us to it or the GC 741 // locker was active). Given that we should not be holding the 742 // Heap_lock when we enter this method, we will pass the 743 // gc_count_before (i.e., total_collections()) as a parameter since 744 // it has to be read while holding the Heap_lock. Currently, both 745 // methods that call do_collection_pause() release the Heap_lock 746 // before the call, so it's easy to read gc_count_before just before. 747 HeapWord* do_collection_pause(size_t word_size, 748 uint gc_count_before, 749 bool* succeeded, 750 GCCause::Cause gc_cause); 751 752 // The guts of the incremental collection pause, executed by the vm 753 // thread. It returns false if it is unable to do the collection due 754 // to the GC locker being active, true otherwise 755 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 756 757 // Actually do the work of evacuating the collection set. 758 void evacuate_collection_set(EvacuationInfo& evacuation_info); 759 760 // The g1 remembered set of the heap. 761 G1RemSet* _g1_rem_set; 762 763 // A set of cards that cover the objects for which the Rsets should be updated 764 // concurrently after the collection. 765 DirtyCardQueueSet _dirty_card_queue_set; 766 767 // The closure used to refine a single card. 768 RefineCardTableEntryClosure* _refine_cte_cl; 769 770 // A DirtyCardQueueSet that is used to hold cards that contain 771 // references into the current collection set. This is used to 772 // update the remembered sets of the regions in the collection 773 // set in the event of an evacuation failure. 774 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 775 776 // After a collection pause, make the regions in the CS into free 777 // regions. 778 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 779 780 // Abandon the current collection set without recording policy 781 // statistics or updating free lists. 782 void abandon_collection_set(HeapRegion* cs_head); 783 784 // The concurrent marker (and the thread it runs in.) 785 ConcurrentMark* _cm; 786 ConcurrentMarkThread* _cmThread; 787 bool _mark_in_progress; 788 789 // The concurrent refiner. 790 ConcurrentG1Refine* _cg1r; 791 792 // The parallel task queues 793 RefToScanQueueSet *_task_queues; 794 795 // True iff a evacuation has failed in the current collection. 796 bool _evacuation_failed; 797 798 EvacuationFailedInfo* _evacuation_failed_info_array; 799 800 // Failed evacuations cause some logical from-space objects to have 801 // forwarding pointers to themselves. Reset them. 802 void remove_self_forwarding_pointers(); 803 804 // Together, these store an object with a preserved mark, and its mark value. 805 Stack<oop, mtGC> _objs_with_preserved_marks; 806 Stack<markOop, mtGC> _preserved_marks_of_objs; 807 808 // Preserve the mark of "obj", if necessary, in preparation for its mark 809 // word being overwritten with a self-forwarding-pointer. 810 void preserve_mark_if_necessary(oop obj, markOop m); 811 812 // The stack of evac-failure objects left to be scanned. 813 GrowableArray<oop>* _evac_failure_scan_stack; 814 // The closure to apply to evac-failure objects. 815 816 OopsInHeapRegionClosure* _evac_failure_closure; 817 // Set the field above. 818 void 819 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 820 _evac_failure_closure = evac_failure_closure; 821 } 822 823 // Push "obj" on the scan stack. 824 void push_on_evac_failure_scan_stack(oop obj); 825 // Process scan stack entries until the stack is empty. 826 void drain_evac_failure_scan_stack(); 827 // True iff an invocation of "drain_scan_stack" is in progress; to 828 // prevent unnecessary recursion. 829 bool _drain_in_progress; 830 831 // Do any necessary initialization for evacuation-failure handling. 832 // "cl" is the closure that will be used to process evac-failure 833 // objects. 834 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 835 // Do any necessary cleanup for evacuation-failure handling data 836 // structures. 837 void finalize_for_evac_failure(); 838 839 // An attempt to evacuate "obj" has failed; take necessary steps. 840 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 841 void handle_evacuation_failure_common(oop obj, markOop m); 842 843 #ifndef PRODUCT 844 // Support for forcing evacuation failures. Analogous to 845 // PromotionFailureALot for the other collectors. 846 847 // Records whether G1EvacuationFailureALot should be in effect 848 // for the current GC 849 bool _evacuation_failure_alot_for_current_gc; 850 851 // Used to record the GC number for interval checking when 852 // determining whether G1EvaucationFailureALot is in effect 853 // for the current GC. 854 size_t _evacuation_failure_alot_gc_number; 855 856 // Count of the number of evacuations between failures. 857 volatile size_t _evacuation_failure_alot_count; 858 859 // Set whether G1EvacuationFailureALot should be in effect 860 // for the current GC (based upon the type of GC and which 861 // command line flags are set); 862 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 863 bool during_initial_mark, 864 bool during_marking); 865 866 inline void set_evacuation_failure_alot_for_current_gc(); 867 868 // Return true if it's time to cause an evacuation failure. 869 inline bool evacuation_should_fail(); 870 871 // Reset the G1EvacuationFailureALot counters. Should be called at 872 // the end of an evacuation pause in which an evacuation failure occurred. 873 inline void reset_evacuation_should_fail(); 874 #endif // !PRODUCT 875 876 // ("Weak") Reference processing support. 877 // 878 // G1 has 2 instances of the reference processor class. One 879 // (_ref_processor_cm) handles reference object discovery 880 // and subsequent processing during concurrent marking cycles. 881 // 882 // The other (_ref_processor_stw) handles reference object 883 // discovery and processing during full GCs and incremental 884 // evacuation pauses. 885 // 886 // During an incremental pause, reference discovery will be 887 // temporarily disabled for _ref_processor_cm and will be 888 // enabled for _ref_processor_stw. At the end of the evacuation 889 // pause references discovered by _ref_processor_stw will be 890 // processed and discovery will be disabled. The previous 891 // setting for reference object discovery for _ref_processor_cm 892 // will be re-instated. 893 // 894 // At the start of marking: 895 // * Discovery by the CM ref processor is verified to be inactive 896 // and it's discovered lists are empty. 897 // * Discovery by the CM ref processor is then enabled. 898 // 899 // At the end of marking: 900 // * Any references on the CM ref processor's discovered 901 // lists are processed (possibly MT). 902 // 903 // At the start of full GC we: 904 // * Disable discovery by the CM ref processor and 905 // empty CM ref processor's discovered lists 906 // (without processing any entries). 907 // * Verify that the STW ref processor is inactive and it's 908 // discovered lists are empty. 909 // * Temporarily set STW ref processor discovery as single threaded. 910 // * Temporarily clear the STW ref processor's _is_alive_non_header 911 // field. 912 // * Finally enable discovery by the STW ref processor. 913 // 914 // The STW ref processor is used to record any discovered 915 // references during the full GC. 916 // 917 // At the end of a full GC we: 918 // * Enqueue any reference objects discovered by the STW ref processor 919 // that have non-live referents. This has the side-effect of 920 // making the STW ref processor inactive by disabling discovery. 921 // * Verify that the CM ref processor is still inactive 922 // and no references have been placed on it's discovered 923 // lists (also checked as a precondition during initial marking). 924 925 // The (stw) reference processor... 926 ReferenceProcessor* _ref_processor_stw; 927 928 STWGCTimer* _gc_timer_stw; 929 ConcurrentGCTimer* _gc_timer_cm; 930 931 G1OldTracer* _gc_tracer_cm; 932 G1NewTracer* _gc_tracer_stw; 933 934 // During reference object discovery, the _is_alive_non_header 935 // closure (if non-null) is applied to the referent object to 936 // determine whether the referent is live. If so then the 937 // reference object does not need to be 'discovered' and can 938 // be treated as a regular oop. This has the benefit of reducing 939 // the number of 'discovered' reference objects that need to 940 // be processed. 941 // 942 // Instance of the is_alive closure for embedding into the 943 // STW reference processor as the _is_alive_non_header field. 944 // Supplying a value for the _is_alive_non_header field is 945 // optional but doing so prevents unnecessary additions to 946 // the discovered lists during reference discovery. 947 G1STWIsAliveClosure _is_alive_closure_stw; 948 949 // The (concurrent marking) reference processor... 950 ReferenceProcessor* _ref_processor_cm; 951 952 // Instance of the concurrent mark is_alive closure for embedding 953 // into the Concurrent Marking reference processor as the 954 // _is_alive_non_header field. Supplying a value for the 955 // _is_alive_non_header field is optional but doing so prevents 956 // unnecessary additions to the discovered lists during reference 957 // discovery. 958 G1CMIsAliveClosure _is_alive_closure_cm; 959 960 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 961 HeapRegion** _worker_cset_start_region; 962 963 // Time stamp to validate the regions recorded in the cache 964 // used by G1CollectedHeap::start_cset_region_for_worker(). 965 // The heap region entry for a given worker is valid iff 966 // the associated time stamp value matches the current value 967 // of G1CollectedHeap::_gc_time_stamp. 968 uint* _worker_cset_start_region_time_stamp; 969 970 volatile bool _free_regions_coming; 971 972 public: 973 974 void set_refine_cte_cl_concurrency(bool concurrent); 975 976 RefToScanQueue *task_queue(int i) const; 977 978 // A set of cards where updates happened during the GC 979 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 980 981 // A DirtyCardQueueSet that is used to hold cards that contain 982 // references into the current collection set. This is used to 983 // update the remembered sets of the regions in the collection 984 // set in the event of an evacuation failure. 985 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 986 { return _into_cset_dirty_card_queue_set; } 987 988 // Create a G1CollectedHeap with the specified policy. 989 // Must call the initialize method afterwards. 990 // May not return if something goes wrong. 991 G1CollectedHeap(G1CollectorPolicy* policy); 992 993 // Initialize the G1CollectedHeap to have the initial and 994 // maximum sizes and remembered and barrier sets 995 // specified by the policy object. 996 jint initialize(); 997 998 virtual void stop(); 999 1000 // Return the (conservative) maximum heap alignment for any G1 heap 1001 static size_t conservative_max_heap_alignment(); 1002 1003 // Does operations required after initialization has been done. 1004 void post_initialize(); 1005 1006 // Initialize weak reference processing. 1007 void ref_processing_init(); 1008 1009 // Explicitly import set_par_threads into this scope 1010 using SharedHeap::set_par_threads; 1011 // Set _n_par_threads according to a policy TBD. 1012 void set_par_threads(); 1013 1014 virtual Name kind() const { 1015 return CollectedHeap::G1CollectedHeap; 1016 } 1017 1018 // The current policy object for the collector. 1019 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1020 1021 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1022 1023 // Adaptive size policy. No such thing for g1. 1024 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1025 1026 // The rem set and barrier set. 1027 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1028 1029 unsigned get_gc_time_stamp() { 1030 return _gc_time_stamp; 1031 } 1032 1033 inline void reset_gc_time_stamp(); 1034 1035 void check_gc_time_stamps() PRODUCT_RETURN; 1036 1037 inline void increment_gc_time_stamp(); 1038 1039 // Reset the given region's GC timestamp. If it's starts humongous, 1040 // also reset the GC timestamp of its corresponding 1041 // continues humongous regions too. 1042 void reset_gc_time_stamps(HeapRegion* hr); 1043 1044 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1045 DirtyCardQueue* into_cset_dcq, 1046 bool concurrent, uint worker_i); 1047 1048 // The shared block offset table array. 1049 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1050 1051 // Reference Processing accessors 1052 1053 // The STW reference processor.... 1054 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1055 1056 // The Concurrent Marking reference processor... 1057 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1058 1059 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1060 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1061 1062 virtual size_t capacity() const; 1063 virtual size_t used() const; 1064 // This should be called when we're not holding the heap lock. The 1065 // result might be a bit inaccurate. 1066 size_t used_unlocked() const; 1067 size_t recalculate_used() const; 1068 1069 // These virtual functions do the actual allocation. 1070 // Some heaps may offer a contiguous region for shared non-blocking 1071 // allocation, via inlined code (by exporting the address of the top and 1072 // end fields defining the extent of the contiguous allocation region.) 1073 // But G1CollectedHeap doesn't yet support this. 1074 1075 virtual bool is_maximal_no_gc() const { 1076 return _hrm.available() == 0; 1077 } 1078 1079 // The current number of regions in the heap. 1080 uint num_regions() const { return _hrm.length(); } 1081 1082 // The max number of regions in the heap. 1083 uint max_regions() const { return _hrm.max_length(); } 1084 1085 // The number of regions that are completely free. 1086 uint num_free_regions() const { return _hrm.num_free_regions(); } 1087 1088 MemoryUsage get_auxiliary_data_memory_usage() const { 1089 return _hrm.get_auxiliary_data_memory_usage(); 1090 } 1091 1092 // The number of regions that are not completely free. 1093 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1094 1095 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1096 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1097 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1098 void verify_dirty_young_regions() PRODUCT_RETURN; 1099 1100 #ifndef PRODUCT 1101 // Make sure that the given bitmap has no marked objects in the 1102 // range [from,limit). If it does, print an error message and return 1103 // false. Otherwise, just return true. bitmap_name should be "prev" 1104 // or "next". 1105 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1106 HeapWord* from, HeapWord* limit); 1107 1108 // Verify that the prev / next bitmap range [tams,end) for the given 1109 // region has no marks. Return true if all is well, false if errors 1110 // are detected. 1111 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1112 #endif // PRODUCT 1113 1114 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1115 // the given region do not have any spurious marks. If errors are 1116 // detected, print appropriate error messages and crash. 1117 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1118 1119 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1120 // have any spurious marks. If errors are detected, print 1121 // appropriate error messages and crash. 1122 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1123 1124 // Do sanity check on the contents of the in-cset fast test table. 1125 bool check_cset_fast_test() PRODUCT_RETURN_( return true; ); 1126 1127 // verify_region_sets() performs verification over the region 1128 // lists. It will be compiled in the product code to be used when 1129 // necessary (i.e., during heap verification). 1130 void verify_region_sets(); 1131 1132 // verify_region_sets_optional() is planted in the code for 1133 // list verification in non-product builds (and it can be enabled in 1134 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1135 #if HEAP_REGION_SET_FORCE_VERIFY 1136 void verify_region_sets_optional() { 1137 verify_region_sets(); 1138 } 1139 #else // HEAP_REGION_SET_FORCE_VERIFY 1140 void verify_region_sets_optional() { } 1141 #endif // HEAP_REGION_SET_FORCE_VERIFY 1142 1143 #ifdef ASSERT 1144 bool is_on_master_free_list(HeapRegion* hr) { 1145 return _hrm.is_free(hr); 1146 } 1147 #endif // ASSERT 1148 1149 // Wrapper for the region list operations that can be called from 1150 // methods outside this class. 1151 1152 void secondary_free_list_add(FreeRegionList* list) { 1153 _secondary_free_list.add_ordered(list); 1154 } 1155 1156 void append_secondary_free_list() { 1157 _hrm.insert_list_into_free_list(&_secondary_free_list); 1158 } 1159 1160 void append_secondary_free_list_if_not_empty_with_lock() { 1161 // If the secondary free list looks empty there's no reason to 1162 // take the lock and then try to append it. 1163 if (!_secondary_free_list.is_empty()) { 1164 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1165 append_secondary_free_list(); 1166 } 1167 } 1168 1169 inline void old_set_remove(HeapRegion* hr); 1170 1171 size_t non_young_capacity_bytes() { 1172 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1173 } 1174 1175 void set_free_regions_coming(); 1176 void reset_free_regions_coming(); 1177 bool free_regions_coming() { return _free_regions_coming; } 1178 void wait_while_free_regions_coming(); 1179 1180 // Determine whether the given region is one that we are using as an 1181 // old GC alloc region. 1182 bool is_old_gc_alloc_region(HeapRegion* hr) { 1183 return _allocator->is_retained_old_region(hr); 1184 } 1185 1186 // Perform a collection of the heap; intended for use in implementing 1187 // "System.gc". This probably implies as full a collection as the 1188 // "CollectedHeap" supports. 1189 virtual void collect(GCCause::Cause cause); 1190 1191 // The same as above but assume that the caller holds the Heap_lock. 1192 void collect_locked(GCCause::Cause cause); 1193 1194 virtual bool copy_allocation_context_stats(const jint* contexts, 1195 jlong* totals, 1196 jbyte* accuracy, 1197 jint len); 1198 1199 // True iff an evacuation has failed in the most-recent collection. 1200 bool evacuation_failed() { return _evacuation_failed; } 1201 1202 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1203 void prepend_to_freelist(FreeRegionList* list); 1204 void decrement_summary_bytes(size_t bytes); 1205 1206 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1207 virtual bool is_in(const void* p) const; 1208 #ifdef ASSERT 1209 // Returns whether p is in one of the available areas of the heap. Slow but 1210 // extensive version. 1211 bool is_in_exact(const void* p) const; 1212 #endif 1213 1214 // Return "TRUE" iff the given object address is within the collection 1215 // set. Slow implementation. 1216 inline bool obj_in_cs(oop obj); 1217 1218 inline bool is_in_cset(const HeapRegion *hr); 1219 inline bool is_in_cset(oop obj); 1220 1221 inline bool is_in_cset_or_humongous(const oop obj); 1222 1223 private: 1224 // This array is used for a quick test on whether a reference points into 1225 // the collection set or not. Each of the array's elements denotes whether the 1226 // corresponding region is in the collection set or not. 1227 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1228 1229 public: 1230 1231 inline InCSetState in_cset_state(const oop obj); 1232 1233 // Return "TRUE" iff the given object address is in the reserved 1234 // region of g1. 1235 bool is_in_g1_reserved(const void* p) const { 1236 return _hrm.reserved().contains(p); 1237 } 1238 1239 // Returns a MemRegion that corresponds to the space that has been 1240 // reserved for the heap 1241 MemRegion g1_reserved() const { 1242 return _hrm.reserved(); 1243 } 1244 1245 virtual bool is_in_closed_subset(const void* p) const; 1246 1247 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1248 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1249 } 1250 1251 // This resets the card table to all zeros. It is used after 1252 // a collection pause which used the card table to claim cards. 1253 void cleanUpCardTable(); 1254 1255 // Iteration functions. 1256 1257 // Iterate over all objects, calling "cl.do_object" on each. 1258 virtual void object_iterate(ObjectClosure* cl); 1259 1260 virtual void safe_object_iterate(ObjectClosure* cl) { 1261 object_iterate(cl); 1262 } 1263 1264 // Iterate over heap regions, in address order, terminating the 1265 // iteration early if the "doHeapRegion" method returns "true". 1266 void heap_region_iterate(HeapRegionClosure* blk) const; 1267 1268 // Return the region with the given index. It assumes the index is valid. 1269 inline HeapRegion* region_at(uint index) const; 1270 1271 // Calculate the region index of the given address. Given address must be 1272 // within the heap. 1273 inline uint addr_to_region(HeapWord* addr) const; 1274 1275 inline HeapWord* bottom_addr_for_region(uint index) const; 1276 1277 // Iterate over the heap regions in parallel. Assumes that this will be called 1278 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1279 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1280 // to each of the regions, by attempting to claim the region using the 1281 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1282 // region. The concurrent argument should be set to true if iteration is 1283 // performed concurrently, during which no assumptions are made for consistent 1284 // attributes of the heap regions (as they might be modified while iterating). 1285 void heap_region_par_iterate(HeapRegionClosure* cl, 1286 uint worker_id, 1287 HeapRegionClaimer* hrclaimer, 1288 bool concurrent = false) const; 1289 1290 // Clear the cached cset start regions and (more importantly) 1291 // the time stamps. Called when we reset the GC time stamp. 1292 void clear_cset_start_regions(); 1293 1294 // Given the id of a worker, obtain or calculate a suitable 1295 // starting region for iterating over the current collection set. 1296 HeapRegion* start_cset_region_for_worker(uint worker_i); 1297 1298 // Iterate over the regions (if any) in the current collection set. 1299 void collection_set_iterate(HeapRegionClosure* blk); 1300 1301 // As above but starting from region r 1302 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1303 1304 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1305 1306 // A CollectedHeap will contain some number of spaces. This finds the 1307 // space containing a given address, or else returns NULL. 1308 virtual Space* space_containing(const void* addr) const; 1309 1310 // Returns the HeapRegion that contains addr. addr must not be NULL. 1311 template <class T> 1312 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1313 1314 // Returns the HeapRegion that contains addr. addr must not be NULL. 1315 // If addr is within a humongous continues region, it returns its humongous start region. 1316 template <class T> 1317 inline HeapRegion* heap_region_containing(const T addr) const; 1318 1319 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1320 // each address in the (reserved) heap is a member of exactly 1321 // one block. The defining characteristic of a block is that it is 1322 // possible to find its size, and thus to progress forward to the next 1323 // block. (Blocks may be of different sizes.) Thus, blocks may 1324 // represent Java objects, or they might be free blocks in a 1325 // free-list-based heap (or subheap), as long as the two kinds are 1326 // distinguishable and the size of each is determinable. 1327 1328 // Returns the address of the start of the "block" that contains the 1329 // address "addr". We say "blocks" instead of "object" since some heaps 1330 // may not pack objects densely; a chunk may either be an object or a 1331 // non-object. 1332 virtual HeapWord* block_start(const void* addr) const; 1333 1334 // Requires "addr" to be the start of a chunk, and returns its size. 1335 // "addr + size" is required to be the start of a new chunk, or the end 1336 // of the active area of the heap. 1337 virtual size_t block_size(const HeapWord* addr) const; 1338 1339 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1340 // the block is an object. 1341 virtual bool block_is_obj(const HeapWord* addr) const; 1342 1343 // Does this heap support heap inspection? (+PrintClassHistogram) 1344 virtual bool supports_heap_inspection() const { return true; } 1345 1346 // Section on thread-local allocation buffers (TLABs) 1347 // See CollectedHeap for semantics. 1348 1349 bool supports_tlab_allocation() const; 1350 size_t tlab_capacity(Thread* ignored) const; 1351 size_t tlab_used(Thread* ignored) const; 1352 size_t max_tlab_size() const; 1353 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1354 1355 // Can a compiler initialize a new object without store barriers? 1356 // This permission only extends from the creation of a new object 1357 // via a TLAB up to the first subsequent safepoint. If such permission 1358 // is granted for this heap type, the compiler promises to call 1359 // defer_store_barrier() below on any slow path allocation of 1360 // a new object for which such initializing store barriers will 1361 // have been elided. G1, like CMS, allows this, but should be 1362 // ready to provide a compensating write barrier as necessary 1363 // if that storage came out of a non-young region. The efficiency 1364 // of this implementation depends crucially on being able to 1365 // answer very efficiently in constant time whether a piece of 1366 // storage in the heap comes from a young region or not. 1367 // See ReduceInitialCardMarks. 1368 virtual bool can_elide_tlab_store_barriers() const { 1369 return true; 1370 } 1371 1372 virtual bool card_mark_must_follow_store() const { 1373 return true; 1374 } 1375 1376 inline bool is_in_young(const oop obj); 1377 1378 virtual bool is_scavengable(const void* addr); 1379 1380 // We don't need barriers for initializing stores to objects 1381 // in the young gen: for the SATB pre-barrier, there is no 1382 // pre-value that needs to be remembered; for the remembered-set 1383 // update logging post-barrier, we don't maintain remembered set 1384 // information for young gen objects. 1385 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1386 1387 // Returns "true" iff the given word_size is "very large". 1388 static bool is_humongous(size_t word_size) { 1389 // Note this has to be strictly greater-than as the TLABs 1390 // are capped at the humongous threshold and we want to 1391 // ensure that we don't try to allocate a TLAB as 1392 // humongous and that we don't allocate a humongous 1393 // object in a TLAB. 1394 return word_size > _humongous_object_threshold_in_words; 1395 } 1396 1397 // Update mod union table with the set of dirty cards. 1398 void updateModUnion(); 1399 1400 // Set the mod union bits corresponding to the given memRegion. Note 1401 // that this is always a safe operation, since it doesn't clear any 1402 // bits. 1403 void markModUnionRange(MemRegion mr); 1404 1405 // Records the fact that a marking phase is no longer in progress. 1406 void set_marking_complete() { 1407 _mark_in_progress = false; 1408 } 1409 void set_marking_started() { 1410 _mark_in_progress = true; 1411 } 1412 bool mark_in_progress() { 1413 return _mark_in_progress; 1414 } 1415 1416 // Print the maximum heap capacity. 1417 virtual size_t max_capacity() const; 1418 1419 virtual jlong millis_since_last_gc(); 1420 1421 1422 // Convenience function to be used in situations where the heap type can be 1423 // asserted to be this type. 1424 static G1CollectedHeap* heap(); 1425 1426 void set_region_short_lived_locked(HeapRegion* hr); 1427 // add appropriate methods for any other surv rate groups 1428 1429 YoungList* young_list() const { return _young_list; } 1430 1431 // debugging 1432 bool check_young_list_well_formed() { 1433 return _young_list->check_list_well_formed(); 1434 } 1435 1436 bool check_young_list_empty(bool check_heap, 1437 bool check_sample = true); 1438 1439 // *** Stuff related to concurrent marking. It's not clear to me that so 1440 // many of these need to be public. 1441 1442 // The functions below are helper functions that a subclass of 1443 // "CollectedHeap" can use in the implementation of its virtual 1444 // functions. 1445 // This performs a concurrent marking of the live objects in a 1446 // bitmap off to the side. 1447 void doConcurrentMark(); 1448 1449 bool isMarkedPrev(oop obj) const; 1450 bool isMarkedNext(oop obj) const; 1451 1452 // Determine if an object is dead, given the object and also 1453 // the region to which the object belongs. An object is dead 1454 // iff a) it was not allocated since the last mark and b) it 1455 // is not marked. 1456 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1457 return 1458 !hr->obj_allocated_since_prev_marking(obj) && 1459 !isMarkedPrev(obj); 1460 } 1461 1462 // This function returns true when an object has been 1463 // around since the previous marking and hasn't yet 1464 // been marked during this marking. 1465 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1466 return 1467 !hr->obj_allocated_since_next_marking(obj) && 1468 !isMarkedNext(obj); 1469 } 1470 1471 // Determine if an object is dead, given only the object itself. 1472 // This will find the region to which the object belongs and 1473 // then call the region version of the same function. 1474 1475 // Added if it is NULL it isn't dead. 1476 1477 inline bool is_obj_dead(const oop obj) const; 1478 1479 inline bool is_obj_ill(const oop obj) const; 1480 1481 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1482 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1483 bool is_marked(oop obj, VerifyOption vo); 1484 const char* top_at_mark_start_str(VerifyOption vo); 1485 1486 ConcurrentMark* concurrent_mark() const { return _cm; } 1487 1488 // Refinement 1489 1490 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1491 1492 // The dirty cards region list is used to record a subset of regions 1493 // whose cards need clearing. The list if populated during the 1494 // remembered set scanning and drained during the card table 1495 // cleanup. Although the methods are reentrant, population/draining 1496 // phases must not overlap. For synchronization purposes the last 1497 // element on the list points to itself. 1498 HeapRegion* _dirty_cards_region_list; 1499 void push_dirty_cards_region(HeapRegion* hr); 1500 HeapRegion* pop_dirty_cards_region(); 1501 1502 // Optimized nmethod scanning support routines 1503 1504 // Register the given nmethod with the G1 heap. 1505 virtual void register_nmethod(nmethod* nm); 1506 1507 // Unregister the given nmethod from the G1 heap. 1508 virtual void unregister_nmethod(nmethod* nm); 1509 1510 // Free up superfluous code root memory. 1511 void purge_code_root_memory(); 1512 1513 // Rebuild the strong code root lists for each region 1514 // after a full GC. 1515 void rebuild_strong_code_roots(); 1516 1517 // Delete entries for dead interned string and clean up unreferenced symbols 1518 // in symbol table, possibly in parallel. 1519 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1520 1521 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1522 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1523 1524 // Redirty logged cards in the refinement queue. 1525 void redirty_logged_cards(); 1526 // Verification 1527 1528 // The following is just to alert the verification code 1529 // that a full collection has occurred and that the 1530 // remembered sets are no longer up to date. 1531 bool _full_collection; 1532 void set_full_collection() { _full_collection = true;} 1533 void clear_full_collection() {_full_collection = false;} 1534 bool full_collection() {return _full_collection;} 1535 1536 // Perform any cleanup actions necessary before allowing a verification. 1537 virtual void prepare_for_verify(); 1538 1539 // Perform verification. 1540 1541 // vo == UsePrevMarking -> use "prev" marking information, 1542 // vo == UseNextMarking -> use "next" marking information 1543 // vo == UseMarkWord -> use the mark word in the object header 1544 // 1545 // NOTE: Only the "prev" marking information is guaranteed to be 1546 // consistent most of the time, so most calls to this should use 1547 // vo == UsePrevMarking. 1548 // Currently, there is only one case where this is called with 1549 // vo == UseNextMarking, which is to verify the "next" marking 1550 // information at the end of remark. 1551 // Currently there is only one place where this is called with 1552 // vo == UseMarkWord, which is to verify the marking during a 1553 // full GC. 1554 void verify(bool silent, VerifyOption vo); 1555 1556 // Override; it uses the "prev" marking information 1557 virtual void verify(bool silent); 1558 1559 // The methods below are here for convenience and dispatch the 1560 // appropriate method depending on value of the given VerifyOption 1561 // parameter. The values for that parameter, and their meanings, 1562 // are the same as those above. 1563 1564 bool is_obj_dead_cond(const oop obj, 1565 const HeapRegion* hr, 1566 const VerifyOption vo) const; 1567 1568 bool is_obj_dead_cond(const oop obj, 1569 const VerifyOption vo) const; 1570 1571 // Printing 1572 1573 virtual void print_on(outputStream* st) const; 1574 virtual void print_extended_on(outputStream* st) const; 1575 virtual void print_on_error(outputStream* st) const; 1576 1577 virtual void print_gc_threads_on(outputStream* st) const; 1578 virtual void gc_threads_do(ThreadClosure* tc) const; 1579 1580 // Override 1581 void print_tracing_info() const; 1582 1583 // The following two methods are helpful for debugging RSet issues. 1584 void print_cset_rsets() PRODUCT_RETURN; 1585 void print_all_rsets() PRODUCT_RETURN; 1586 1587 public: 1588 size_t pending_card_num(); 1589 size_t cards_scanned(); 1590 1591 protected: 1592 size_t _max_heap_capacity; 1593 }; 1594 1595 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP