1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc_implementation/g1/g1AllocationContext.hpp" 29 #include "gc_implementation/g1/g1Allocator.hpp" 30 #include "gc_implementation/g1/concurrentMark.hpp" 31 #include "gc_implementation/g1/evacuationInfo.hpp" 32 #include "gc_implementation/g1/g1AllocRegion.hpp" 33 #include "gc_implementation/g1/g1BiasedArray.hpp" 34 #include "gc_implementation/g1/g1HRPrinter.hpp" 35 #include "gc_implementation/g1/g1InCSetState.hpp" 36 #include "gc_implementation/g1/g1MonitoringSupport.hpp" 37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 38 #include "gc_implementation/g1/g1YCTypes.hpp" 39 #include "gc_implementation/g1/heapRegionManager.hpp" 40 #include "gc_implementation/g1/heapRegionSet.hpp" 41 #include "gc_implementation/shared/hSpaceCounters.hpp" 42 #include "gc_implementation/shared/parGCAllocBuffer.hpp" 43 #include "memory/barrierSet.hpp" 44 #include "memory/memRegion.hpp" 45 #include "memory/sharedHeap.hpp" 46 #include "utilities/stack.hpp" 47 48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 49 // It uses the "Garbage First" heap organization and algorithm, which 50 // may combine concurrent marking with parallel, incremental compaction of 51 // heap subsets that will yield large amounts of garbage. 52 53 // Forward declarations 54 class HeapRegion; 55 class HRRSCleanupTask; 56 class GenerationSpec; 57 class OopsInHeapRegionClosure; 58 class G1KlassScanClosure; 59 class ObjectClosure; 60 class SpaceClosure; 61 class CompactibleSpaceClosure; 62 class Space; 63 class G1CollectorPolicy; 64 class GenRemSet; 65 class G1RemSet; 66 class HeapRegionRemSetIterator; 67 class ConcurrentMark; 68 class ConcurrentMarkThread; 69 class ConcurrentG1Refine; 70 class ConcurrentGCTimer; 71 class GenerationCounters; 72 class STWGCTimer; 73 class G1NewTracer; 74 class G1OldTracer; 75 class EvacuationFailedInfo; 76 class nmethod; 77 class Ticks; 78 79 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 80 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 81 82 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 83 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 84 85 class YoungList : public CHeapObj<mtGC> { 86 private: 87 G1CollectedHeap* _g1h; 88 89 HeapRegion* _head; 90 91 HeapRegion* _survivor_head; 92 HeapRegion* _survivor_tail; 93 94 HeapRegion* _curr; 95 96 uint _length; 97 uint _survivor_length; 98 99 size_t _last_sampled_rs_lengths; 100 size_t _sampled_rs_lengths; 101 102 void empty_list(HeapRegion* list); 103 104 public: 105 YoungList(G1CollectedHeap* g1h); 106 107 void push_region(HeapRegion* hr); 108 void add_survivor_region(HeapRegion* hr); 109 110 void empty_list(); 111 bool is_empty() { return _length == 0; } 112 uint length() { return _length; } 113 uint eden_length() { return length() - survivor_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) eden_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; 189 190 // Closures used in implementation. 191 friend class G1ParScanThreadState; 192 friend class G1ParTask; 193 friend class G1ParGCAllocator; 194 friend class G1PrepareCompactClosure; 195 196 // Other related classes. 197 friend class HeapRegionClaimer; 198 199 // Testing classes. 200 friend class G1CheckCSetFastTableClosure; 201 202 private: 203 // The one and only G1CollectedHeap, so static functions can find it. 204 static G1CollectedHeap* _g1h; 205 206 static size_t _humongous_object_threshold_in_words; 207 208 // The secondary free list which contains regions that have been 209 // freed up during the cleanup process. This will be appended to 210 // the master free list when appropriate. 211 FreeRegionList _secondary_free_list; 212 213 // It keeps track of the old regions. 214 HeapRegionSet _old_set; 215 216 // It keeps track of the humongous regions. 217 HeapRegionSet _humongous_set; 218 219 void clear_humongous_is_live_table(); 220 void eagerly_reclaim_humongous_regions(); 221 222 // The number of regions we could create by expansion. 223 uint _expansion_regions; 224 225 // The block offset table for the G1 heap. 226 G1BlockOffsetSharedArray* _bot_shared; 227 228 // Tears down the region sets / lists so that they are empty and the 229 // regions on the heap do not belong to a region set / list. The 230 // only exception is the humongous set which we leave unaltered. If 231 // free_list_only is true, it will only tear down the master free 232 // list. It is called before a Full GC (free_list_only == false) or 233 // before heap shrinking (free_list_only == true). 234 void tear_down_region_sets(bool free_list_only); 235 236 // Rebuilds the region sets / lists so that they are repopulated to 237 // reflect the contents of the heap. The only exception is the 238 // humongous set which was not torn down in the first place. If 239 // free_list_only is true, it will only rebuild the master free 240 // list. It is called after a Full GC (free_list_only == false) or 241 // after heap shrinking (free_list_only == true). 242 void rebuild_region_sets(bool free_list_only); 243 244 // Callback for region mapping changed events. 245 G1RegionMappingChangedListener _listener; 246 247 // The sequence of all heap regions in the heap. 248 HeapRegionManager _hrm; 249 250 // Class that handles the different kinds of allocations. 251 G1Allocator* _allocator; 252 253 // Statistics for each allocation context 254 AllocationContextStats _allocation_context_stats; 255 256 // PLAB sizing policy for survivors. 257 PLABStats _survivor_plab_stats; 258 259 // PLAB sizing policy for tenured objects. 260 PLABStats _old_plab_stats; 261 262 // It specifies whether we should attempt to expand the heap after a 263 // region allocation failure. If heap expansion fails we set this to 264 // false so that we don't re-attempt the heap expansion (it's likely 265 // that subsequent expansion attempts will also fail if one fails). 266 // Currently, it is only consulted during GC and it's reset at the 267 // start of each GC. 268 bool _expand_heap_after_alloc_failure; 269 270 // It resets the mutator alloc region before new allocations can take place. 271 void init_mutator_alloc_region(); 272 273 // It releases the mutator alloc region. 274 void release_mutator_alloc_region(); 275 276 // It initializes the GC alloc regions at the start of a GC. 277 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 278 279 // It releases the GC alloc regions at the end of a GC. 280 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 281 282 // It does any cleanup that needs to be done on the GC alloc regions 283 // before a Full GC. 284 void abandon_gc_alloc_regions(); 285 286 // Helper for monitoring and management support. 287 G1MonitoringSupport* _g1mm; 288 289 // Records whether the region at the given index is kept live by roots or 290 // references from the young generation. 291 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 292 protected: 293 bool default_value() const { return false; } 294 public: 295 void clear() { G1BiasedMappedArray<bool>::clear(); } 296 void set_live(uint region) { 297 set_by_index(region, true); 298 } 299 bool is_live(uint region) { 300 return get_by_index(region); 301 } 302 }; 303 304 HumongousIsLiveBiasedMappedArray _humongous_is_live; 305 // Stores whether during humongous object registration we found candidate regions. 306 // If not, we can skip a few steps. 307 bool _has_humongous_reclaim_candidates; 308 309 volatile unsigned _gc_time_stamp; 310 311 size_t* _surviving_young_words; 312 313 G1HRPrinter _hr_printer; 314 315 void setup_surviving_young_words(); 316 void update_surviving_young_words(size_t* surv_young_words); 317 void cleanup_surviving_young_words(); 318 319 // It decides whether an explicit GC should start a concurrent cycle 320 // instead of doing a STW GC. Currently, a concurrent cycle is 321 // explicitly started if: 322 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 323 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 324 // (c) cause == _g1_humongous_allocation 325 bool should_do_concurrent_full_gc(GCCause::Cause cause); 326 327 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 328 // concurrent cycles) we have started. 329 volatile uint _old_marking_cycles_started; 330 331 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 332 // concurrent cycles) we have completed. 333 volatile uint _old_marking_cycles_completed; 334 335 bool _concurrent_cycle_started; 336 bool _heap_summary_sent; 337 338 // This is a non-product method that is helpful for testing. It is 339 // called at the end of a GC and artificially expands the heap by 340 // allocating a number of dead regions. This way we can induce very 341 // frequent marking cycles and stress the cleanup / concurrent 342 // cleanup code more (as all the regions that will be allocated by 343 // this method will be found dead by the marking cycle). 344 void allocate_dummy_regions() PRODUCT_RETURN; 345 346 // Clear RSets after a compaction. It also resets the GC time stamps. 347 void clear_rsets_post_compaction(); 348 349 // If the HR printer is active, dump the state of the regions in the 350 // heap after a compaction. 351 void print_hrm_post_compaction(); 352 353 double verify(bool guard, const char* msg); 354 void verify_before_gc(); 355 void verify_after_gc(); 356 357 void log_gc_header(); 358 void log_gc_footer(double pause_time_sec); 359 360 // These are macros so that, if the assert fires, we get the correct 361 // line number, file, etc. 362 363 #define heap_locking_asserts_err_msg(_extra_message_) \ 364 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 365 (_extra_message_), \ 366 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 367 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 368 BOOL_TO_STR(Thread::current()->is_VM_thread())) 369 370 #define assert_heap_locked() \ 371 do { \ 372 assert(Heap_lock->owned_by_self(), \ 373 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 374 } while (0) 375 376 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 377 do { \ 378 assert(Heap_lock->owned_by_self() || \ 379 (SafepointSynchronize::is_at_safepoint() && \ 380 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 381 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 382 "should be at a safepoint")); \ 383 } while (0) 384 385 #define assert_heap_locked_and_not_at_safepoint() \ 386 do { \ 387 assert(Heap_lock->owned_by_self() && \ 388 !SafepointSynchronize::is_at_safepoint(), \ 389 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 390 "should not be at a safepoint")); \ 391 } while (0) 392 393 #define assert_heap_not_locked() \ 394 do { \ 395 assert(!Heap_lock->owned_by_self(), \ 396 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 397 } while (0) 398 399 #define assert_heap_not_locked_and_not_at_safepoint() \ 400 do { \ 401 assert(!Heap_lock->owned_by_self() && \ 402 !SafepointSynchronize::is_at_safepoint(), \ 403 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 404 "should not be at a safepoint")); \ 405 } while (0) 406 407 #define assert_at_safepoint(_should_be_vm_thread_) \ 408 do { \ 409 assert(SafepointSynchronize::is_at_safepoint() && \ 410 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 411 heap_locking_asserts_err_msg("should be at a safepoint")); \ 412 } while (0) 413 414 #define assert_not_at_safepoint() \ 415 do { \ 416 assert(!SafepointSynchronize::is_at_safepoint(), \ 417 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 418 } while (0) 419 420 protected: 421 422 // The young region list. 423 YoungList* _young_list; 424 425 // The current policy object for the collector. 426 G1CollectorPolicy* _g1_policy; 427 428 // This is the second level of trying to allocate a new region. If 429 // new_region() didn't find a region on the free_list, this call will 430 // check whether there's anything available on the 431 // secondary_free_list and/or wait for more regions to appear on 432 // that list, if _free_regions_coming is set. 433 HeapRegion* new_region_try_secondary_free_list(bool is_old); 434 435 // Try to allocate a single non-humongous HeapRegion sufficient for 436 // an allocation of the given word_size. If do_expand is true, 437 // attempt to expand the heap if necessary to satisfy the allocation 438 // request. If the region is to be used as an old region or for a 439 // humongous object, set is_old to true. If not, to false. 440 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 441 442 // Initialize a contiguous set of free regions of length num_regions 443 // and starting at index first so that they appear as a single 444 // humongous region. 445 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 446 uint num_regions, 447 size_t word_size, 448 AllocationContext_t context); 449 450 // Attempt to allocate a humongous object of the given size. Return 451 // NULL if unsuccessful. 452 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 453 454 // The following two methods, allocate_new_tlab() and 455 // mem_allocate(), are the two main entry points from the runtime 456 // into the G1's allocation routines. They have the following 457 // assumptions: 458 // 459 // * They should both be called outside safepoints. 460 // 461 // * They should both be called without holding the Heap_lock. 462 // 463 // * All allocation requests for new TLABs should go to 464 // allocate_new_tlab(). 465 // 466 // * All non-TLAB allocation requests should go to mem_allocate(). 467 // 468 // * If either call cannot satisfy the allocation request using the 469 // current allocating region, they will try to get a new one. If 470 // this fails, they will attempt to do an evacuation pause and 471 // retry the allocation. 472 // 473 // * If all allocation attempts fail, even after trying to schedule 474 // an evacuation pause, allocate_new_tlab() will return NULL, 475 // whereas mem_allocate() will attempt a heap expansion and/or 476 // schedule a Full GC. 477 // 478 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 479 // should never be called with word_size being humongous. All 480 // humongous allocation requests should go to mem_allocate() which 481 // will satisfy them with a special path. 482 483 virtual HeapWord* allocate_new_tlab(size_t word_size); 484 485 virtual HeapWord* mem_allocate(size_t word_size, 486 bool* gc_overhead_limit_was_exceeded); 487 488 // The following three methods take a gc_count_before_ret 489 // parameter which is used to return the GC count if the method 490 // returns NULL. Given that we are required to read the GC count 491 // while holding the Heap_lock, and these paths will take the 492 // Heap_lock at some point, it's easier to get them to read the GC 493 // count while holding the Heap_lock before they return NULL instead 494 // of the caller (namely: mem_allocate()) having to also take the 495 // Heap_lock just to read the GC count. 496 497 // First-level mutator allocation attempt: try to allocate out of 498 // the mutator alloc region without taking the Heap_lock. This 499 // should only be used for non-humongous allocations. 500 inline HeapWord* attempt_allocation(size_t word_size, 501 uint* gc_count_before_ret, 502 uint* gclocker_retry_count_ret, 503 uint* gc_attempt); 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 uint* gc_attempt); 513 514 // Takes the Heap_lock and attempts a humongous allocation. It can 515 // potentially schedule a GC pause. 516 HeapWord* attempt_allocation_humongous(size_t word_size, 517 uint* gc_count_before_ret, 518 uint* gclocker_retry_count_ret, 519 uint* gc_attempt); 520 521 // Allocation attempt that should be called during safepoints (e.g., 522 // at the end of a successful GC). expect_null_mutator_alloc_region 523 // specifies whether the mutator alloc region is expected to be NULL 524 // or not. 525 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 526 AllocationContext_t context, 527 bool expect_null_mutator_alloc_region); 528 529 // It dirties the cards that cover the block so that so that the post 530 // write barrier never queues anything when updating objects on this 531 // block. It is assumed (and in fact we assert) that the block 532 // belongs to a young region. 533 inline void dirty_young_block(HeapWord* start, size_t word_size); 534 535 // Allocate blocks during garbage collection. Will ensure an 536 // allocation region, either by picking one or expanding the 537 // heap, and then allocate a block of the given size. The block 538 // may not be a humongous - it must fit into a single heap region. 539 inline HeapWord* par_allocate_during_gc(InCSetState dest, 540 size_t word_size, 541 AllocationContext_t context); 542 // Ensure that no further allocations can happen in "r", bearing in mind 543 // that parallel threads might be attempting allocations. 544 void par_allocate_remaining_space(HeapRegion* r); 545 546 // Allocation attempt during GC for a survivor object / PLAB. 547 inline HeapWord* survivor_attempt_allocation(size_t word_size, 548 AllocationContext_t context); 549 550 // Allocation attempt during GC for an old object / PLAB. 551 inline HeapWord* old_attempt_allocation(size_t word_size, 552 AllocationContext_t context); 553 554 // These methods are the "callbacks" from the G1AllocRegion class. 555 556 // For mutator alloc regions. 557 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 558 void retire_mutator_alloc_region(HeapRegion* alloc_region, 559 size_t allocated_bytes); 560 561 // For GC alloc regions. 562 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 563 InCSetState dest); 564 void retire_gc_alloc_region(HeapRegion* alloc_region, 565 size_t allocated_bytes, InCSetState dest); 566 567 // - if explicit_gc is true, the GC is for a System.gc() or a heap 568 // inspection request and should collect the entire heap 569 // - if clear_all_soft_refs is true, all soft references should be 570 // cleared during the GC 571 // - if explicit_gc is false, word_size describes the allocation that 572 // the GC should attempt (at least) to satisfy 573 // - it returns false if it is unable to do the collection due to the 574 // GC locker being active, true otherwise 575 bool do_collection(bool explicit_gc, 576 bool clear_all_soft_refs, 577 size_t word_size); 578 579 // Callback from VM_G1CollectFull operation. 580 // Perform a full collection. 581 virtual void do_full_collection(bool clear_all_soft_refs); 582 583 // Resize the heap if necessary after a full collection. If this is 584 // after a collect-for allocation, "word_size" is the allocation size, 585 // and will be considered part of the used portion of the heap. 586 void resize_if_necessary_after_full_collection(size_t word_size); 587 588 // Callback from VM_G1CollectForAllocation operation. 589 // This function does everything necessary/possible to satisfy a 590 // failed allocation request (including collection, expansion, etc.) 591 HeapWord* satisfy_failed_allocation(size_t word_size, 592 AllocationContext_t context, 593 bool* succeeded); 594 595 // Attempting to expand the heap sufficiently 596 // to support an allocation of the given "word_size". If 597 // successful, perform the allocation and return the address of the 598 // allocated block, or else "NULL". 599 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 600 601 // Process any reference objects discovered during 602 // an incremental evacuation pause. 603 void process_discovered_references(uint no_of_gc_workers); 604 605 // Enqueue any remaining discovered references 606 // after processing. 607 void enqueue_discovered_references(uint no_of_gc_workers); 608 609 public: 610 611 G1Allocator* allocator() { 612 return _allocator; 613 } 614 615 G1MonitoringSupport* g1mm() { 616 assert(_g1mm != NULL, "should have been initialized"); 617 return _g1mm; 618 } 619 620 // Expand the garbage-first heap by at least the given size (in bytes!). 621 // Returns true if the heap was expanded by the requested amount; 622 // false otherwise. 623 // (Rounds up to a HeapRegion boundary.) 624 bool expand(size_t expand_bytes); 625 626 // Returns the PLAB statistics for a given destination. 627 inline PLABStats* alloc_buffer_stats(InCSetState dest); 628 629 // Determines PLAB size for a given destination. 630 inline size_t desired_plab_sz(InCSetState dest); 631 632 inline AllocationContextStats& allocation_context_stats(); 633 634 // Do anything common to GC's. 635 virtual void gc_prologue(bool full); 636 virtual void gc_epilogue(bool full); 637 638 inline void set_humongous_is_live(oop obj); 639 640 bool humongous_is_live(uint region) { 641 return _humongous_is_live.is_live(region); 642 } 643 644 // Returns whether the given region (which must be a humongous (start) region) 645 // is to be considered conservatively live regardless of any other conditions. 646 bool humongous_region_is_always_live(uint index); 647 // Returns whether the given region (which must be a humongous (start) region) 648 // is considered a candidate for eager reclamation. 649 bool humongous_region_is_candidate(uint index); 650 // Register the given region to be part of the collection set. 651 inline void register_humongous_region_with_cset(uint index); 652 // Register regions with humongous objects (actually on the start region) in 653 // the in_cset_fast_test table. 654 void register_humongous_regions_with_cset(); 655 // We register a region with the fast "in collection set" test. We 656 // simply set to true the array slot corresponding to this region. 657 void register_young_region_with_cset(HeapRegion* r) { 658 _in_cset_fast_test.set_in_young(r->hrm_index()); 659 } 660 void register_old_region_with_cset(HeapRegion* r) { 661 _in_cset_fast_test.set_in_old(r->hrm_index()); 662 } 663 void clear_in_cset(const HeapRegion* hr) { 664 _in_cset_fast_test.clear(hr); 665 } 666 667 void clear_cset_fast_test() { 668 _in_cset_fast_test.clear(); 669 } 670 671 // This is called at the start of either a concurrent cycle or a Full 672 // GC to update the number of old marking cycles started. 673 void increment_old_marking_cycles_started(); 674 675 // This is called at the end of either a concurrent cycle or a Full 676 // GC to update the number of old marking cycles completed. Those two 677 // can happen in a nested fashion, i.e., we start a concurrent 678 // cycle, a Full GC happens half-way through it which ends first, 679 // and then the cycle notices that a Full GC happened and ends 680 // too. The concurrent parameter is a boolean to help us do a bit 681 // tighter consistency checking in the method. If concurrent is 682 // false, the caller is the inner caller in the nesting (i.e., the 683 // Full GC). If concurrent is true, the caller is the outer caller 684 // in this nesting (i.e., the concurrent cycle). Further nesting is 685 // not currently supported. The end of this call also notifies 686 // the FullGCCount_lock in case a Java thread is waiting for a full 687 // GC to happen (e.g., it called System.gc() with 688 // +ExplicitGCInvokesConcurrent). 689 void increment_old_marking_cycles_completed(bool concurrent); 690 691 uint old_marking_cycles_completed() { 692 return _old_marking_cycles_completed; 693 } 694 695 void register_concurrent_cycle_start(const Ticks& start_time); 696 void register_concurrent_cycle_end(); 697 void trace_heap_after_concurrent_cycle(); 698 699 G1YCType yc_type(); 700 701 G1HRPrinter* hr_printer() { return &_hr_printer; } 702 703 // Frees a non-humongous region by initializing its contents and 704 // adding it to the free list that's passed as a parameter (this is 705 // usually a local list which will be appended to the master free 706 // list later). The used bytes of freed regions are accumulated in 707 // pre_used. If par is true, the region's RSet will not be freed 708 // up. The assumption is that this will be done later. 709 // The locked parameter indicates if the caller has already taken 710 // care of proper synchronization. This may allow some optimizations. 711 void free_region(HeapRegion* hr, 712 FreeRegionList* free_list, 713 bool par, 714 bool locked = false); 715 716 // Frees a humongous region by collapsing it into individual regions 717 // and calling free_region() for each of them. The freed regions 718 // will be added to the free list that's passed as a parameter (this 719 // is usually a local list which will be appended to the master free 720 // list later). The used bytes of freed regions are accumulated in 721 // pre_used. If par is true, the region's RSet will not be freed 722 // up. The assumption is that this will be done later. 723 void free_humongous_region(HeapRegion* hr, 724 FreeRegionList* free_list, 725 bool par); 726 protected: 727 728 // Shrink the garbage-first heap by at most the given size (in bytes!). 729 // (Rounds down to a HeapRegion boundary.) 730 virtual void shrink(size_t expand_bytes); 731 void shrink_helper(size_t expand_bytes); 732 733 #if TASKQUEUE_STATS 734 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 735 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 736 void reset_taskqueue_stats(); 737 #endif // TASKQUEUE_STATS 738 739 // Schedule the VM operation that will do an evacuation pause to 740 // satisfy an allocation request of word_size. *succeeded will 741 // return whether the VM operation was successful (it did do an 742 // evacuation pause) or not (another thread beat us to it or the GC 743 // locker was active). Given that we should not be holding the 744 // Heap_lock when we enter this method, we will pass the 745 // gc_count_before (i.e., total_collections()) as a parameter since 746 // it has to be read while holding the Heap_lock. Currently, both 747 // methods that call do_collection_pause() release the Heap_lock 748 // before the call, so it's easy to read gc_count_before just before. 749 HeapWord* do_collection_pause(size_t word_size, 750 uint gc_count_before, 751 bool* succeeded, 752 GCCause::Cause gc_cause, 753 uint gc_attempt); 754 755 // The guts of the incremental collection pause, executed by the vm 756 // thread. It returns false if it is unable to do the collection due 757 // to the GC locker being active, true otherwise 758 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 759 760 // Actually do the work of evacuating the collection set. 761 void evacuate_collection_set(EvacuationInfo& evacuation_info); 762 763 // The g1 remembered set of the heap. 764 G1RemSet* _g1_rem_set; 765 766 // A set of cards that cover the objects for which the Rsets should be updated 767 // concurrently after the collection. 768 DirtyCardQueueSet _dirty_card_queue_set; 769 770 // The closure used to refine a single card. 771 RefineCardTableEntryClosure* _refine_cte_cl; 772 773 // A DirtyCardQueueSet that is used to hold cards that contain 774 // references into the current collection set. This is used to 775 // update the remembered sets of the regions in the collection 776 // set in the event of an evacuation failure. 777 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 778 779 // After a collection pause, make the regions in the CS into free 780 // regions. 781 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 782 783 // Abandon the current collection set without recording policy 784 // statistics or updating free lists. 785 void abandon_collection_set(HeapRegion* cs_head); 786 787 // The concurrent marker (and the thread it runs in.) 788 ConcurrentMark* _cm; 789 ConcurrentMarkThread* _cmThread; 790 bool _mark_in_progress; 791 792 // The concurrent refiner. 793 ConcurrentG1Refine* _cg1r; 794 795 // The parallel task queues 796 RefToScanQueueSet *_task_queues; 797 798 // True iff a evacuation has failed in the current collection. 799 bool _evacuation_failed; 800 801 EvacuationFailedInfo* _evacuation_failed_info_array; 802 803 // Failed evacuations cause some logical from-space objects to have 804 // forwarding pointers to themselves. Reset them. 805 void remove_self_forwarding_pointers(); 806 807 // Together, these store an object with a preserved mark, and its mark value. 808 Stack<oop, mtGC> _objs_with_preserved_marks; 809 Stack<markOop, mtGC> _preserved_marks_of_objs; 810 811 // Preserve the mark of "obj", if necessary, in preparation for its mark 812 // word being overwritten with a self-forwarding-pointer. 813 void preserve_mark_if_necessary(oop obj, markOop m); 814 815 // The stack of evac-failure objects left to be scanned. 816 GrowableArray<oop>* _evac_failure_scan_stack; 817 // The closure to apply to evac-failure objects. 818 819 OopsInHeapRegionClosure* _evac_failure_closure; 820 // Set the field above. 821 void 822 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 823 _evac_failure_closure = evac_failure_closure; 824 } 825 826 // Push "obj" on the scan stack. 827 void push_on_evac_failure_scan_stack(oop obj); 828 // Process scan stack entries until the stack is empty. 829 void drain_evac_failure_scan_stack(); 830 // True iff an invocation of "drain_scan_stack" is in progress; to 831 // prevent unnecessary recursion. 832 bool _drain_in_progress; 833 834 // Do any necessary initialization for evacuation-failure handling. 835 // "cl" is the closure that will be used to process evac-failure 836 // objects. 837 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 838 // Do any necessary cleanup for evacuation-failure handling data 839 // structures. 840 void finalize_for_evac_failure(); 841 842 // An attempt to evacuate "obj" has failed; take necessary steps. 843 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 844 void handle_evacuation_failure_common(oop obj, markOop m); 845 846 #ifndef PRODUCT 847 // Support for forcing evacuation failures. Analogous to 848 // PromotionFailureALot for the other collectors. 849 850 // Records whether G1EvacuationFailureALot should be in effect 851 // for the current GC 852 bool _evacuation_failure_alot_for_current_gc; 853 854 // Used to record the GC number for interval checking when 855 // determining whether G1EvaucationFailureALot is in effect 856 // for the current GC. 857 size_t _evacuation_failure_alot_gc_number; 858 859 // Count of the number of evacuations between failures. 860 volatile size_t _evacuation_failure_alot_count; 861 862 // Set whether G1EvacuationFailureALot should be in effect 863 // for the current GC (based upon the type of GC and which 864 // command line flags are set); 865 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 866 bool during_initial_mark, 867 bool during_marking); 868 869 inline void set_evacuation_failure_alot_for_current_gc(); 870 871 // Return true if it's time to cause an evacuation failure. 872 inline bool evacuation_should_fail(); 873 874 // Reset the G1EvacuationFailureALot counters. Should be called at 875 // the end of an evacuation pause in which an evacuation failure occurred. 876 inline void reset_evacuation_should_fail(); 877 #endif // !PRODUCT 878 879 // ("Weak") Reference processing support. 880 // 881 // G1 has 2 instances of the reference processor class. One 882 // (_ref_processor_cm) handles reference object discovery 883 // and subsequent processing during concurrent marking cycles. 884 // 885 // The other (_ref_processor_stw) handles reference object 886 // discovery and processing during full GCs and incremental 887 // evacuation pauses. 888 // 889 // During an incremental pause, reference discovery will be 890 // temporarily disabled for _ref_processor_cm and will be 891 // enabled for _ref_processor_stw. At the end of the evacuation 892 // pause references discovered by _ref_processor_stw will be 893 // processed and discovery will be disabled. The previous 894 // setting for reference object discovery for _ref_processor_cm 895 // will be re-instated. 896 // 897 // At the start of marking: 898 // * Discovery by the CM ref processor is verified to be inactive 899 // and it's discovered lists are empty. 900 // * Discovery by the CM ref processor is then enabled. 901 // 902 // At the end of marking: 903 // * Any references on the CM ref processor's discovered 904 // lists are processed (possibly MT). 905 // 906 // At the start of full GC we: 907 // * Disable discovery by the CM ref processor and 908 // empty CM ref processor's discovered lists 909 // (without processing any entries). 910 // * Verify that the STW ref processor is inactive and it's 911 // discovered lists are empty. 912 // * Temporarily set STW ref processor discovery as single threaded. 913 // * Temporarily clear the STW ref processor's _is_alive_non_header 914 // field. 915 // * Finally enable discovery by the STW ref processor. 916 // 917 // The STW ref processor is used to record any discovered 918 // references during the full GC. 919 // 920 // At the end of a full GC we: 921 // * Enqueue any reference objects discovered by the STW ref processor 922 // that have non-live referents. This has the side-effect of 923 // making the STW ref processor inactive by disabling discovery. 924 // * Verify that the CM ref processor is still inactive 925 // and no references have been placed on it's discovered 926 // lists (also checked as a precondition during initial marking). 927 928 // The (stw) reference processor... 929 ReferenceProcessor* _ref_processor_stw; 930 931 STWGCTimer* _gc_timer_stw; 932 ConcurrentGCTimer* _gc_timer_cm; 933 934 G1OldTracer* _gc_tracer_cm; 935 G1NewTracer* _gc_tracer_stw; 936 937 // During reference object discovery, the _is_alive_non_header 938 // closure (if non-null) is applied to the referent object to 939 // determine whether the referent is live. If so then the 940 // reference object does not need to be 'discovered' and can 941 // be treated as a regular oop. This has the benefit of reducing 942 // the number of 'discovered' reference objects that need to 943 // be processed. 944 // 945 // Instance of the is_alive closure for embedding into the 946 // STW reference processor as the _is_alive_non_header field. 947 // Supplying a value for the _is_alive_non_header field is 948 // optional but doing so prevents unnecessary additions to 949 // the discovered lists during reference discovery. 950 G1STWIsAliveClosure _is_alive_closure_stw; 951 952 // The (concurrent marking) reference processor... 953 ReferenceProcessor* _ref_processor_cm; 954 955 // Instance of the concurrent mark is_alive closure for embedding 956 // into the Concurrent Marking reference processor as the 957 // _is_alive_non_header field. Supplying a value for the 958 // _is_alive_non_header field is optional but doing so prevents 959 // unnecessary additions to the discovered lists during reference 960 // discovery. 961 G1CMIsAliveClosure _is_alive_closure_cm; 962 963 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 964 HeapRegion** _worker_cset_start_region; 965 966 // Time stamp to validate the regions recorded in the cache 967 // used by G1CollectedHeap::start_cset_region_for_worker(). 968 // The heap region entry for a given worker is valid iff 969 // the associated time stamp value matches the current value 970 // of G1CollectedHeap::_gc_time_stamp. 971 uint* _worker_cset_start_region_time_stamp; 972 973 volatile bool _free_regions_coming; 974 975 public: 976 977 void set_refine_cte_cl_concurrency(bool concurrent); 978 979 RefToScanQueue *task_queue(int i) const; 980 981 // A set of cards where updates happened during the GC 982 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 983 984 // A DirtyCardQueueSet that is used to hold cards that contain 985 // references into the current collection set. This is used to 986 // update the remembered sets of the regions in the collection 987 // set in the event of an evacuation failure. 988 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 989 { return _into_cset_dirty_card_queue_set; } 990 991 // Create a G1CollectedHeap with the specified policy. 992 // Must call the initialize method afterwards. 993 // May not return if something goes wrong. 994 G1CollectedHeap(G1CollectorPolicy* policy); 995 996 // Initialize the G1CollectedHeap to have the initial and 997 // maximum sizes and remembered and barrier sets 998 // specified by the policy object. 999 jint initialize(); 1000 1001 virtual void stop(); 1002 1003 // Return the (conservative) maximum heap alignment for any G1 heap 1004 static size_t conservative_max_heap_alignment(); 1005 1006 // Initialize weak reference processing. 1007 virtual 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 CollectedHeap::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 the ref-containing fields of all objects, calling 1258 // "cl.do_oop" on each. 1259 virtual void oop_iterate(ExtendedOopClosure* cl); 1260 1261 // Iterate over all objects, calling "cl.do_object" on each. 1262 virtual void object_iterate(ObjectClosure* cl); 1263 1264 virtual void safe_object_iterate(ObjectClosure* cl) { 1265 object_iterate(cl); 1266 } 1267 1268 // Iterate over all spaces in use in the heap, in ascending address order. 1269 virtual void space_iterate(SpaceClosure* cl); 1270 1271 // Iterate over heap regions, in address order, terminating the 1272 // iteration early if the "doHeapRegion" method returns "true". 1273 void heap_region_iterate(HeapRegionClosure* blk) const; 1274 1275 // Return the region with the given index. It assumes the index is valid. 1276 inline HeapRegion* region_at(uint index) const; 1277 1278 // Calculate the region index of the given address. Given address must be 1279 // within the heap. 1280 inline uint addr_to_region(HeapWord* addr) const; 1281 1282 inline HeapWord* bottom_addr_for_region(uint index) const; 1283 1284 // Iterate over the heap regions in parallel. Assumes that this will be called 1285 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1286 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1287 // to each of the regions, by attempting to claim the region using the 1288 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1289 // region. The concurrent argument should be set to true if iteration is 1290 // performed concurrently, during which no assumptions are made for consistent 1291 // attributes of the heap regions (as they might be modified while iterating). 1292 void heap_region_par_iterate(HeapRegionClosure* cl, 1293 uint worker_id, 1294 HeapRegionClaimer* hrclaimer, 1295 bool concurrent = false) const; 1296 1297 // Clear the cached cset start regions and (more importantly) 1298 // the time stamps. Called when we reset the GC time stamp. 1299 void clear_cset_start_regions(); 1300 1301 // Given the id of a worker, obtain or calculate a suitable 1302 // starting region for iterating over the current collection set. 1303 HeapRegion* start_cset_region_for_worker(uint worker_i); 1304 1305 // Iterate over the regions (if any) in the current collection set. 1306 void collection_set_iterate(HeapRegionClosure* blk); 1307 1308 // As above but starting from region r 1309 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1310 1311 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1312 1313 // A CollectedHeap will contain some number of spaces. This finds the 1314 // space containing a given address, or else returns NULL. 1315 virtual Space* space_containing(const void* addr) const; 1316 1317 // Returns the HeapRegion that contains addr. addr must not be NULL. 1318 template <class T> 1319 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1320 1321 // Returns the HeapRegion that contains addr. addr must not be NULL. 1322 // If addr is within a humongous continues region, it returns its humongous start region. 1323 template <class T> 1324 inline HeapRegion* heap_region_containing(const T addr) const; 1325 1326 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1327 // each address in the (reserved) heap is a member of exactly 1328 // one block. The defining characteristic of a block is that it is 1329 // possible to find its size, and thus to progress forward to the next 1330 // block. (Blocks may be of different sizes.) Thus, blocks may 1331 // represent Java objects, or they might be free blocks in a 1332 // free-list-based heap (or subheap), as long as the two kinds are 1333 // distinguishable and the size of each is determinable. 1334 1335 // Returns the address of the start of the "block" that contains the 1336 // address "addr". We say "blocks" instead of "object" since some heaps 1337 // may not pack objects densely; a chunk may either be an object or a 1338 // non-object. 1339 virtual HeapWord* block_start(const void* addr) const; 1340 1341 // Requires "addr" to be the start of a chunk, and returns its size. 1342 // "addr + size" is required to be the start of a new chunk, or the end 1343 // of the active area of the heap. 1344 virtual size_t block_size(const HeapWord* addr) const; 1345 1346 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1347 // the block is an object. 1348 virtual bool block_is_obj(const HeapWord* addr) const; 1349 1350 // Does this heap support heap inspection? (+PrintClassHistogram) 1351 virtual bool supports_heap_inspection() const { return true; } 1352 1353 // Section on thread-local allocation buffers (TLABs) 1354 // See CollectedHeap for semantics. 1355 1356 bool supports_tlab_allocation() const; 1357 size_t tlab_capacity(Thread* ignored) const; 1358 size_t tlab_used(Thread* ignored) const; 1359 size_t max_tlab_size() const; 1360 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1361 1362 // Can a compiler initialize a new object without store barriers? 1363 // This permission only extends from the creation of a new object 1364 // via a TLAB up to the first subsequent safepoint. If such permission 1365 // is granted for this heap type, the compiler promises to call 1366 // defer_store_barrier() below on any slow path allocation of 1367 // a new object for which such initializing store barriers will 1368 // have been elided. G1, like CMS, allows this, but should be 1369 // ready to provide a compensating write barrier as necessary 1370 // if that storage came out of a non-young region. The efficiency 1371 // of this implementation depends crucially on being able to 1372 // answer very efficiently in constant time whether a piece of 1373 // storage in the heap comes from a young region or not. 1374 // See ReduceInitialCardMarks. 1375 virtual bool can_elide_tlab_store_barriers() const { 1376 return true; 1377 } 1378 1379 virtual bool card_mark_must_follow_store() const { 1380 return true; 1381 } 1382 1383 inline bool is_in_young(const oop obj); 1384 1385 #ifdef ASSERT 1386 virtual bool is_in_partial_collection(const void* p); 1387 #endif 1388 1389 virtual bool is_scavengable(const void* addr); 1390 1391 // We don't need barriers for initializing stores to objects 1392 // in the young gen: for the SATB pre-barrier, there is no 1393 // pre-value that needs to be remembered; for the remembered-set 1394 // update logging post-barrier, we don't maintain remembered set 1395 // information for young gen objects. 1396 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1397 1398 // Returns "true" iff the given word_size is "very large". 1399 static bool is_humongous(size_t word_size) { 1400 // Note this has to be strictly greater-than as the TLABs 1401 // are capped at the humongous threshold and we want to 1402 // ensure that we don't try to allocate a TLAB as 1403 // humongous and that we don't allocate a humongous 1404 // object in a TLAB. 1405 return word_size > _humongous_object_threshold_in_words; 1406 } 1407 1408 // Update mod union table with the set of dirty cards. 1409 void updateModUnion(); 1410 1411 // Set the mod union bits corresponding to the given memRegion. Note 1412 // that this is always a safe operation, since it doesn't clear any 1413 // bits. 1414 void markModUnionRange(MemRegion mr); 1415 1416 // Records the fact that a marking phase is no longer in progress. 1417 void set_marking_complete() { 1418 _mark_in_progress = false; 1419 } 1420 void set_marking_started() { 1421 _mark_in_progress = true; 1422 } 1423 bool mark_in_progress() { 1424 return _mark_in_progress; 1425 } 1426 1427 // Print the maximum heap capacity. 1428 virtual size_t max_capacity() const; 1429 1430 virtual jlong millis_since_last_gc(); 1431 1432 1433 // Convenience function to be used in situations where the heap type can be 1434 // asserted to be this type. 1435 static G1CollectedHeap* heap(); 1436 1437 void set_region_short_lived_locked(HeapRegion* hr); 1438 // add appropriate methods for any other surv rate groups 1439 1440 YoungList* young_list() const { return _young_list; } 1441 1442 // debugging 1443 bool check_young_list_well_formed() { 1444 return _young_list->check_list_well_formed(); 1445 } 1446 1447 bool check_young_list_empty(bool check_heap, 1448 bool check_sample = true); 1449 1450 // *** Stuff related to concurrent marking. It's not clear to me that so 1451 // many of these need to be public. 1452 1453 // The functions below are helper functions that a subclass of 1454 // "CollectedHeap" can use in the implementation of its virtual 1455 // functions. 1456 // This performs a concurrent marking of the live objects in a 1457 // bitmap off to the side. 1458 void doConcurrentMark(); 1459 1460 bool isMarkedPrev(oop obj) const; 1461 bool isMarkedNext(oop obj) const; 1462 1463 // Determine if an object is dead, given the object and also 1464 // the region to which the object belongs. An object is dead 1465 // iff a) it was not allocated since the last mark and b) it 1466 // is not marked. 1467 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1468 return 1469 !hr->obj_allocated_since_prev_marking(obj) && 1470 !isMarkedPrev(obj); 1471 } 1472 1473 // This function returns true when an object has been 1474 // around since the previous marking and hasn't yet 1475 // been marked during this marking. 1476 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1477 return 1478 !hr->obj_allocated_since_next_marking(obj) && 1479 !isMarkedNext(obj); 1480 } 1481 1482 // Determine if an object is dead, given only the object itself. 1483 // This will find the region to which the object belongs and 1484 // then call the region version of the same function. 1485 1486 // Added if it is NULL it isn't dead. 1487 1488 inline bool is_obj_dead(const oop obj) const; 1489 1490 inline bool is_obj_ill(const oop obj) const; 1491 1492 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1493 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1494 bool is_marked(oop obj, VerifyOption vo); 1495 const char* top_at_mark_start_str(VerifyOption vo); 1496 1497 ConcurrentMark* concurrent_mark() const { return _cm; } 1498 1499 // Refinement 1500 1501 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1502 1503 // The dirty cards region list is used to record a subset of regions 1504 // whose cards need clearing. The list if populated during the 1505 // remembered set scanning and drained during the card table 1506 // cleanup. Although the methods are reentrant, population/draining 1507 // phases must not overlap. For synchronization purposes the last 1508 // element on the list points to itself. 1509 HeapRegion* _dirty_cards_region_list; 1510 void push_dirty_cards_region(HeapRegion* hr); 1511 HeapRegion* pop_dirty_cards_region(); 1512 1513 // Optimized nmethod scanning support routines 1514 1515 // Register the given nmethod with the G1 heap. 1516 virtual void register_nmethod(nmethod* nm); 1517 1518 // Unregister the given nmethod from the G1 heap. 1519 virtual void unregister_nmethod(nmethod* nm); 1520 1521 // Free up superfluous code root memory. 1522 void purge_code_root_memory(); 1523 1524 // Rebuild the strong code root lists for each region 1525 // after a full GC. 1526 void rebuild_strong_code_roots(); 1527 1528 // Delete entries for dead interned string and clean up unreferenced symbols 1529 // in symbol table, possibly in parallel. 1530 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1531 1532 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1533 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1534 1535 // Redirty logged cards in the refinement queue. 1536 void redirty_logged_cards(); 1537 // Verification 1538 1539 // The following is just to alert the verification code 1540 // that a full collection has occurred and that the 1541 // remembered sets are no longer up to date. 1542 bool _full_collection; 1543 void set_full_collection() { _full_collection = true;} 1544 void clear_full_collection() {_full_collection = false;} 1545 bool full_collection() {return _full_collection;} 1546 1547 // Perform any cleanup actions necessary before allowing a verification. 1548 virtual void prepare_for_verify(); 1549 1550 // Perform verification. 1551 1552 // vo == UsePrevMarking -> use "prev" marking information, 1553 // vo == UseNextMarking -> use "next" marking information 1554 // vo == UseMarkWord -> use the mark word in the object header 1555 // 1556 // NOTE: Only the "prev" marking information is guaranteed to be 1557 // consistent most of the time, so most calls to this should use 1558 // vo == UsePrevMarking. 1559 // Currently, there is only one case where this is called with 1560 // vo == UseNextMarking, which is to verify the "next" marking 1561 // information at the end of remark. 1562 // Currently there is only one place where this is called with 1563 // vo == UseMarkWord, which is to verify the marking during a 1564 // full GC. 1565 void verify(bool silent, VerifyOption vo); 1566 1567 // Override; it uses the "prev" marking information 1568 virtual void verify(bool silent); 1569 1570 // The methods below are here for convenience and dispatch the 1571 // appropriate method depending on value of the given VerifyOption 1572 // parameter. The values for that parameter, and their meanings, 1573 // are the same as those above. 1574 1575 bool is_obj_dead_cond(const oop obj, 1576 const HeapRegion* hr, 1577 const VerifyOption vo) const; 1578 1579 bool is_obj_dead_cond(const oop obj, 1580 const VerifyOption vo) const; 1581 1582 // Printing 1583 1584 virtual void print_on(outputStream* st) const; 1585 virtual void print_extended_on(outputStream* st) const; 1586 virtual void print_on_error(outputStream* st) const; 1587 1588 virtual void print_gc_threads_on(outputStream* st) const; 1589 virtual void gc_threads_do(ThreadClosure* tc) const; 1590 1591 // Override 1592 void print_tracing_info() const; 1593 1594 // The following two methods are helpful for debugging RSet issues. 1595 void print_cset_rsets() PRODUCT_RETURN; 1596 void print_all_rsets() PRODUCT_RETURN; 1597 1598 public: 1599 size_t pending_card_num(); 1600 size_t cards_scanned(); 1601 1602 protected: 1603 size_t _max_heap_capacity; 1604 }; 1605 1606 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP