1 /* 2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc_implementation/g1/concurrentMark.hpp" 29 #include "gc_implementation/g1/evacuationInfo.hpp" 30 #include "gc_implementation/g1/g1AllocRegion.hpp" 31 #include "gc_implementation/g1/g1BiasedArray.hpp" 32 #include "gc_implementation/g1/g1HRPrinter.hpp" 33 #include "gc_implementation/g1/g1MonitoringSupport.hpp" 34 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp" 35 #include "gc_implementation/g1/g1YCTypes.hpp" 36 #include "gc_implementation/g1/heapRegionSeq.hpp" 37 #include "gc_implementation/g1/heapRegionSet.hpp" 38 #include "gc_implementation/shared/hSpaceCounters.hpp" 39 #include "gc_implementation/shared/parGCAllocBuffer.hpp" 40 #include "memory/barrierSet.hpp" 41 #include "memory/memRegion.hpp" 42 #include "memory/sharedHeap.hpp" 43 #include "utilities/stack.hpp" 44 45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 46 // It uses the "Garbage First" heap organization and algorithm, which 47 // may combine concurrent marking with parallel, incremental compaction of 48 // heap subsets that will yield large amounts of garbage. 49 50 // Forward declarations 51 class HeapRegion; 52 class HRRSCleanupTask; 53 class GenerationSpec; 54 class OopsInHeapRegionClosure; 55 class G1KlassScanClosure; 56 class G1ScanHeapEvacClosure; 57 class ObjectClosure; 58 class SpaceClosure; 59 class CompactibleSpaceClosure; 60 class Space; 61 class G1CollectorPolicy; 62 class GenRemSet; 63 class G1RemSet; 64 class HeapRegionRemSetIterator; 65 class ConcurrentMark; 66 class ConcurrentMarkThread; 67 class ConcurrentG1Refine; 68 class ConcurrentGCTimer; 69 class GenerationCounters; 70 class STWGCTimer; 71 class G1NewTracer; 72 class G1OldTracer; 73 class EvacuationFailedInfo; 74 class nmethod; 75 class Ticks; 76 77 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 79 80 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 81 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 82 83 enum GCAllocPurpose { 84 GCAllocForTenured, 85 GCAllocForSurvived, 86 GCAllocPurposeCount 87 }; 88 89 class YoungList : public CHeapObj<mtGC> { 90 private: 91 G1CollectedHeap* _g1h; 92 93 HeapRegion* _head; 94 95 HeapRegion* _survivor_head; 96 HeapRegion* _survivor_tail; 97 98 HeapRegion* _curr; 99 100 uint _length; 101 uint _survivor_length; 102 103 size_t _last_sampled_rs_lengths; 104 size_t _sampled_rs_lengths; 105 106 void empty_list(HeapRegion* list); 107 108 public: 109 YoungList(G1CollectedHeap* g1h); 110 111 void push_region(HeapRegion* hr); 112 void add_survivor_region(HeapRegion* hr); 113 114 void empty_list(); 115 bool is_empty() { return _length == 0; } 116 uint length() { return _length; } 117 uint survivor_length() { return _survivor_length; } 118 119 // Currently we do not keep track of the used byte sum for the 120 // young list and the survivors and it'd be quite a lot of work to 121 // do so. When we'll eventually replace the young list with 122 // instances of HeapRegionLinkedList we'll get that for free. So, 123 // we'll report the more accurate information then. 124 size_t eden_used_bytes() { 125 assert(length() >= survivor_length(), "invariant"); 126 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes; 127 } 128 size_t survivor_used_bytes() { 129 return (size_t) survivor_length() * HeapRegion::GrainBytes; 130 } 131 132 void rs_length_sampling_init(); 133 bool rs_length_sampling_more(); 134 void rs_length_sampling_next(); 135 136 void reset_sampled_info() { 137 _last_sampled_rs_lengths = 0; 138 } 139 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; } 140 141 // for development purposes 142 void reset_auxilary_lists(); 143 void clear() { _head = NULL; _length = 0; } 144 145 void clear_survivors() { 146 _survivor_head = NULL; 147 _survivor_tail = NULL; 148 _survivor_length = 0; 149 } 150 151 HeapRegion* first_region() { return _head; } 152 HeapRegion* first_survivor_region() { return _survivor_head; } 153 HeapRegion* last_survivor_region() { return _survivor_tail; } 154 155 // debugging 156 bool check_list_well_formed(); 157 bool check_list_empty(bool check_sample = true); 158 void print(); 159 }; 160 161 class MutatorAllocRegion : public G1AllocRegion { 162 protected: 163 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 164 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 165 public: 166 MutatorAllocRegion() 167 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { } 168 }; 169 170 class SurvivorGCAllocRegion : public G1AllocRegion { 171 protected: 172 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 173 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 174 public: 175 SurvivorGCAllocRegion() 176 : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { } 177 }; 178 179 class OldGCAllocRegion : public G1AllocRegion { 180 protected: 181 virtual HeapRegion* allocate_new_region(size_t word_size, bool force); 182 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes); 183 public: 184 OldGCAllocRegion() 185 : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { } 186 }; 187 188 // The G1 STW is alive closure. 189 // An instance is embedded into the G1CH and used as the 190 // (optional) _is_alive_non_header closure in the STW 191 // reference processor. It is also extensively used during 192 // reference processing during STW evacuation pauses. 193 class G1STWIsAliveClosure: public BoolObjectClosure { 194 G1CollectedHeap* _g1; 195 public: 196 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 197 bool do_object_b(oop p); 198 }; 199 200 // Instances of this class are used for quick tests on whether a reference points 201 // into the collection set or is a humongous object (points into a humongous 202 // object). 203 // Each of the array's elements denotes whether the corresponding region is in 204 // the collection set or a humongous region. 205 // We use this to quickly reclaim humongous objects: by making a humongous region 206 // succeed this test, we sort-of add it to the collection set which objects are 207 // supposed to be evacuated. However, since the region is humongous, evacuation 208 // will automatically fail the test to allocate it into a PLAB. We catch this 209 // condition (in this slow-path), and mark that region as "live" in a side table. 210 // At the end of GC, we use this information, among other, to determine whether 211 // we can reclaim the humongous object or not. 212 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> { 213 public: 214 enum in_cset_state_t { 215 InNeither, // neither in collection set nor humongous 216 InCSet, // region is in collection set only 217 IsHumongous // region is a humongous start region 218 }; 219 protected: 220 char default_value() const { return InNeither; } 221 public: 222 void set_humongous(uintptr_t index) { assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values"); set_by_index(index, IsHumongous); } 223 void clear_humongous(uintptr_t index) { 224 set_by_index(index, InNeither); 225 } 226 void set_in_cset(uintptr_t index) { assert(get_by_index(index) != IsHumongous, "Should not overwrite IsHumongous value"); set_by_index(index, InCSet); } 227 228 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != InNeither; } 229 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == InCSet; } 230 in_cset_state_t at(HeapWord* addr) const { return (in_cset_state_t)get_by_address(addr); } 231 void clear() { G1BiasedMappedArray<char>::clear(); } 232 }; 233 234 class RefineCardTableEntryClosure; 235 236 class G1CollectedHeap : public SharedHeap { 237 friend class VM_CollectForMetadataAllocation; 238 friend class VM_G1CollectForAllocation; 239 friend class VM_G1CollectFull; 240 friend class VM_G1IncCollectionPause; 241 friend class VMStructs; 242 friend class MutatorAllocRegion; 243 friend class SurvivorGCAllocRegion; 244 friend class OldGCAllocRegion; 245 246 // Closures used in implementation. 247 template <G1Barrier barrier, G1Mark do_mark_object> 248 friend class G1ParCopyClosure; 249 friend class G1IsAliveClosure; 250 friend class G1EvacuateFollowersClosure; 251 friend class G1ParScanThreadState; 252 friend class G1ParScanClosureSuper; 253 friend class G1ParEvacuateFollowersClosure; 254 friend class G1ParTask; 255 friend class G1FreeGarbageRegionClosure; 256 friend class RefineCardTableEntryClosure; 257 friend class G1PrepareCompactClosure; 258 friend class RegionSorter; 259 friend class RegionResetter; 260 friend class CountRCClosure; 261 friend class EvacPopObjClosure; 262 friend class G1ParCleanupCTTask; 263 264 friend class G1FreeHumongousRegionClosure; 265 // Other related classes. 266 friend class G1MarkSweep; 267 268 private: 269 // The one and only G1CollectedHeap, so static functions can find it. 270 static G1CollectedHeap* _g1h; 271 272 static size_t _humongous_object_threshold_in_words; 273 274 // Storage for the G1 heap. 275 VirtualSpace _g1_storage; 276 MemRegion _g1_reserved; 277 278 // The part of _g1_storage that is currently committed. 279 MemRegion _g1_committed; 280 281 // The master free list. It will satisfy all new region allocations. 282 FreeRegionList _free_list; 283 284 // The secondary free list which contains regions that have been 285 // freed up during the cleanup process. This will be appended to the 286 // master free list when appropriate. 287 FreeRegionList _secondary_free_list; 288 289 // It keeps track of the old regions. 290 HeapRegionSet _old_set; 291 292 // It keeps track of the humongous regions. 293 HeapRegionSet _humongous_set; 294 295 void clear_humongous_is_live_table(); 296 void eagerly_reclaim_humongous_regions(); 297 298 // The number of regions we could create by expansion. 299 uint _expansion_regions; 300 301 // The block offset table for the G1 heap. 302 G1BlockOffsetSharedArray* _bot_shared; 303 304 // Tears down the region sets / lists so that they are empty and the 305 // regions on the heap do not belong to a region set / list. The 306 // only exception is the humongous set which we leave unaltered. If 307 // free_list_only is true, it will only tear down the master free 308 // list. It is called before a Full GC (free_list_only == false) or 309 // before heap shrinking (free_list_only == true). 310 void tear_down_region_sets(bool free_list_only); 311 312 // Rebuilds the region sets / lists so that they are repopulated to 313 // reflect the contents of the heap. The only exception is the 314 // humongous set which was not torn down in the first place. If 315 // free_list_only is true, it will only rebuild the master free 316 // list. It is called after a Full GC (free_list_only == false) or 317 // after heap shrinking (free_list_only == true). 318 void rebuild_region_sets(bool free_list_only); 319 320 // The sequence of all heap regions in the heap. 321 HeapRegionSeq _hrs; 322 323 // Alloc region used to satisfy mutator allocation requests. 324 MutatorAllocRegion _mutator_alloc_region; 325 326 // Alloc region used to satisfy allocation requests by the GC for 327 // survivor objects. 328 SurvivorGCAllocRegion _survivor_gc_alloc_region; 329 330 // PLAB sizing policy for survivors. 331 PLABStats _survivor_plab_stats; 332 333 // Alloc region used to satisfy allocation requests by the GC for 334 // old objects. 335 OldGCAllocRegion _old_gc_alloc_region; 336 337 // PLAB sizing policy for tenured objects. 338 PLABStats _old_plab_stats; 339 340 PLABStats* stats_for_purpose(GCAllocPurpose purpose) { 341 PLABStats* stats = NULL; 342 343 switch (purpose) { 344 case GCAllocForSurvived: 345 stats = &_survivor_plab_stats; 346 break; 347 case GCAllocForTenured: 348 stats = &_old_plab_stats; 349 break; 350 default: 351 assert(false, "unrecognized GCAllocPurpose"); 352 } 353 354 return stats; 355 } 356 357 // The last old region we allocated to during the last GC. 358 // Typically, it is not full so we should re-use it during the next GC. 359 HeapRegion* _retained_old_gc_alloc_region; 360 361 // It specifies whether we should attempt to expand the heap after a 362 // region allocation failure. If heap expansion fails we set this to 363 // false so that we don't re-attempt the heap expansion (it's likely 364 // that subsequent expansion attempts will also fail if one fails). 365 // Currently, it is only consulted during GC and it's reset at the 366 // start of each GC. 367 bool _expand_heap_after_alloc_failure; 368 369 // It resets the mutator alloc region before new allocations can take place. 370 void init_mutator_alloc_region(); 371 372 // It releases the mutator alloc region. 373 void release_mutator_alloc_region(); 374 375 // It initializes the GC alloc regions at the start of a GC. 376 void init_gc_alloc_regions(EvacuationInfo& evacuation_info); 377 378 // Setup the retained old gc alloc region as the currrent old gc alloc region. 379 void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info); 380 381 // It releases the GC alloc regions at the end of a GC. 382 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info); 383 384 // It does any cleanup that needs to be done on the GC alloc regions 385 // before a Full GC. 386 void abandon_gc_alloc_regions(); 387 388 // Helper for monitoring and management support. 389 G1MonitoringSupport* _g1mm; 390 391 // Determines PLAB size for a particular allocation purpose. 392 size_t desired_plab_sz(GCAllocPurpose purpose); 393 394 // Outside of GC pauses, the number of bytes used in all regions other 395 // than the current allocation region. 396 size_t _summary_bytes_used; 397 398 // This array is used for a quick test on whether a reference points into 399 // the collection set or not. Each of the array's elements denotes whether the 400 // corresponding region is in the collection set or not. 401 G1FastCSetBiasedMappedArray _in_cset_fast_test; 402 403 // Records whether the region at the given index is kept live by roots or 404 // references from the young generation. 405 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> { 406 protected: 407 bool default_value() const { return false; } 408 public: 409 void clear() { G1BiasedMappedArray<bool>::clear(); } 410 void set_live(uint region) { 411 set_by_index(region, true); 412 } 413 bool is_live(uint region) { 414 return get_by_index(region); 415 } 416 }; 417 418 HumongousIsLiveBiasedMappedArray _humongous_is_live; 419 // Stores whether during humongous object registration we found candidate regions. 420 // If not, we can skip a few steps. 421 bool _has_humongous_reclaim_candidates; 422 423 volatile unsigned _gc_time_stamp; 424 425 size_t* _surviving_young_words; 426 427 G1HRPrinter _hr_printer; 428 429 void setup_surviving_young_words(); 430 void update_surviving_young_words(size_t* surv_young_words); 431 void cleanup_surviving_young_words(); 432 433 // It decides whether an explicit GC should start a concurrent cycle 434 // instead of doing a STW GC. Currently, a concurrent cycle is 435 // explicitly started if: 436 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 437 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 438 // (c) cause == _g1_humongous_allocation 439 bool should_do_concurrent_full_gc(GCCause::Cause cause); 440 441 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 442 // concurrent cycles) we have started. 443 volatile unsigned int _old_marking_cycles_started; 444 445 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 446 // concurrent cycles) we have completed. 447 volatile unsigned int _old_marking_cycles_completed; 448 449 bool _concurrent_cycle_started; 450 451 // This is a non-product method that is helpful for testing. It is 452 // called at the end of a GC and artificially expands the heap by 453 // allocating a number of dead regions. This way we can induce very 454 // frequent marking cycles and stress the cleanup / concurrent 455 // cleanup code more (as all the regions that will be allocated by 456 // this method will be found dead by the marking cycle). 457 void allocate_dummy_regions() PRODUCT_RETURN; 458 459 // Clear RSets after a compaction. It also resets the GC time stamps. 460 void clear_rsets_post_compaction(); 461 462 // If the HR printer is active, dump the state of the regions in the 463 // heap after a compaction. 464 void print_hrs_post_compaction(); 465 466 double verify(bool guard, const char* msg); 467 void verify_before_gc(); 468 void verify_after_gc(); 469 470 void log_gc_header(); 471 void log_gc_footer(double pause_time_sec); 472 473 // These are macros so that, if the assert fires, we get the correct 474 // line number, file, etc. 475 476 #define heap_locking_asserts_err_msg(_extra_message_) \ 477 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 478 (_extra_message_), \ 479 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 480 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 481 BOOL_TO_STR(Thread::current()->is_VM_thread())) 482 483 #define assert_heap_locked() \ 484 do { \ 485 assert(Heap_lock->owned_by_self(), \ 486 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \ 487 } while (0) 488 489 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 490 do { \ 491 assert(Heap_lock->owned_by_self() || \ 492 (SafepointSynchronize::is_at_safepoint() && \ 493 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 494 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \ 495 "should be at a safepoint")); \ 496 } while (0) 497 498 #define assert_heap_locked_and_not_at_safepoint() \ 499 do { \ 500 assert(Heap_lock->owned_by_self() && \ 501 !SafepointSynchronize::is_at_safepoint(), \ 502 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \ 503 "should not be at a safepoint")); \ 504 } while (0) 505 506 #define assert_heap_not_locked() \ 507 do { \ 508 assert(!Heap_lock->owned_by_self(), \ 509 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \ 510 } while (0) 511 512 #define assert_heap_not_locked_and_not_at_safepoint() \ 513 do { \ 514 assert(!Heap_lock->owned_by_self() && \ 515 !SafepointSynchronize::is_at_safepoint(), \ 516 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \ 517 "should not be at a safepoint")); \ 518 } while (0) 519 520 #define assert_at_safepoint(_should_be_vm_thread_) \ 521 do { \ 522 assert(SafepointSynchronize::is_at_safepoint() && \ 523 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 524 heap_locking_asserts_err_msg("should be at a safepoint")); \ 525 } while (0) 526 527 #define assert_not_at_safepoint() \ 528 do { \ 529 assert(!SafepointSynchronize::is_at_safepoint(), \ 530 heap_locking_asserts_err_msg("should not be at a safepoint")); \ 531 } while (0) 532 533 protected: 534 535 // The young region list. 536 YoungList* _young_list; 537 538 // The current policy object for the collector. 539 G1CollectorPolicy* _g1_policy; 540 541 // This is the second level of trying to allocate a new region. If 542 // new_region() didn't find a region on the free_list, this call will 543 // check whether there's anything available on the 544 // secondary_free_list and/or wait for more regions to appear on 545 // that list, if _free_regions_coming is set. 546 HeapRegion* new_region_try_secondary_free_list(bool is_old); 547 548 // Try to allocate a single non-humongous HeapRegion sufficient for 549 // an allocation of the given word_size. If do_expand is true, 550 // attempt to expand the heap if necessary to satisfy the allocation 551 // request. If the region is to be used as an old region or for a 552 // humongous object, set is_old to true. If not, to false. 553 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 554 555 // Attempt to satisfy a humongous allocation request of the given 556 // size by finding a contiguous set of free regions of num_regions 557 // length and remove them from the master free list. Return the 558 // index of the first region or G1_NULL_HRS_INDEX if the search 559 // was unsuccessful. 560 uint humongous_obj_allocate_find_first(uint num_regions, 561 size_t word_size); 562 563 // Initialize a contiguous set of free regions of length num_regions 564 // and starting at index first so that they appear as a single 565 // humongous region. 566 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 567 uint num_regions, 568 size_t word_size); 569 570 // Attempt to allocate a humongous object of the given size. Return 571 // NULL if unsuccessful. 572 HeapWord* humongous_obj_allocate(size_t word_size); 573 574 // The following two methods, allocate_new_tlab() and 575 // mem_allocate(), are the two main entry points from the runtime 576 // into the G1's allocation routines. They have the following 577 // assumptions: 578 // 579 // * They should both be called outside safepoints. 580 // 581 // * They should both be called without holding the Heap_lock. 582 // 583 // * All allocation requests for new TLABs should go to 584 // allocate_new_tlab(). 585 // 586 // * All non-TLAB allocation requests should go to mem_allocate(). 587 // 588 // * If either call cannot satisfy the allocation request using the 589 // current allocating region, they will try to get a new one. If 590 // this fails, they will attempt to do an evacuation pause and 591 // retry the allocation. 592 // 593 // * If all allocation attempts fail, even after trying to schedule 594 // an evacuation pause, allocate_new_tlab() will return NULL, 595 // whereas mem_allocate() will attempt a heap expansion and/or 596 // schedule a Full GC. 597 // 598 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 599 // should never be called with word_size being humongous. All 600 // humongous allocation requests should go to mem_allocate() which 601 // will satisfy them with a special path. 602 603 virtual HeapWord* allocate_new_tlab(size_t word_size); 604 605 virtual HeapWord* mem_allocate(size_t word_size, 606 bool* gc_overhead_limit_was_exceeded); 607 608 // The following three methods take a gc_count_before_ret 609 // parameter which is used to return the GC count if the method 610 // returns NULL. Given that we are required to read the GC count 611 // while holding the Heap_lock, and these paths will take the 612 // Heap_lock at some point, it's easier to get them to read the GC 613 // count while holding the Heap_lock before they return NULL instead 614 // of the caller (namely: mem_allocate()) having to also take the 615 // Heap_lock just to read the GC count. 616 617 // First-level mutator allocation attempt: try to allocate out of 618 // the mutator alloc region without taking the Heap_lock. This 619 // should only be used for non-humongous allocations. 620 inline HeapWord* attempt_allocation(size_t word_size, 621 unsigned int* gc_count_before_ret, 622 int* gclocker_retry_count_ret); 623 624 // Second-level mutator allocation attempt: take the Heap_lock and 625 // retry the allocation attempt, potentially scheduling a GC 626 // pause. This should only be used for non-humongous allocations. 627 HeapWord* attempt_allocation_slow(size_t word_size, 628 unsigned int* gc_count_before_ret, 629 int* gclocker_retry_count_ret); 630 631 // Takes the Heap_lock and attempts a humongous allocation. It can 632 // potentially schedule a GC pause. 633 HeapWord* attempt_allocation_humongous(size_t word_size, 634 unsigned int* gc_count_before_ret, 635 int* gclocker_retry_count_ret); 636 637 // Allocation attempt that should be called during safepoints (e.g., 638 // at the end of a successful GC). expect_null_mutator_alloc_region 639 // specifies whether the mutator alloc region is expected to be NULL 640 // or not. 641 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 642 bool expect_null_mutator_alloc_region); 643 644 // It dirties the cards that cover the block so that so that the post 645 // write barrier never queues anything when updating objects on this 646 // block. It is assumed (and in fact we assert) that the block 647 // belongs to a young region. 648 inline void dirty_young_block(HeapWord* start, size_t word_size); 649 650 // Allocate blocks during garbage collection. Will ensure an 651 // allocation region, either by picking one or expanding the 652 // heap, and then allocate a block of the given size. The block 653 // may not be a humongous - it must fit into a single heap region. 654 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size); 655 656 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose, 657 HeapRegion* alloc_region, 658 bool par, 659 size_t word_size); 660 661 // Ensure that no further allocations can happen in "r", bearing in mind 662 // that parallel threads might be attempting allocations. 663 void par_allocate_remaining_space(HeapRegion* r); 664 665 // Allocation attempt during GC for a survivor object / PLAB. 666 inline HeapWord* survivor_attempt_allocation(size_t word_size); 667 668 // Allocation attempt during GC for an old object / PLAB. 669 inline HeapWord* old_attempt_allocation(size_t word_size); 670 671 // These methods are the "callbacks" from the G1AllocRegion class. 672 673 // For mutator alloc regions. 674 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 675 void retire_mutator_alloc_region(HeapRegion* alloc_region, 676 size_t allocated_bytes); 677 678 // For GC alloc regions. 679 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 680 GCAllocPurpose ap); 681 void retire_gc_alloc_region(HeapRegion* alloc_region, 682 size_t allocated_bytes, GCAllocPurpose ap); 683 684 // - if explicit_gc is true, the GC is for a System.gc() or a heap 685 // inspection request and should collect the entire heap 686 // - if clear_all_soft_refs is true, all soft references should be 687 // cleared during the GC 688 // - if explicit_gc is false, word_size describes the allocation that 689 // the GC should attempt (at least) to satisfy 690 // - it returns false if it is unable to do the collection due to the 691 // GC locker being active, true otherwise 692 bool do_collection(bool explicit_gc, 693 bool clear_all_soft_refs, 694 size_t word_size); 695 696 // Callback from VM_G1CollectFull operation. 697 // Perform a full collection. 698 virtual void do_full_collection(bool clear_all_soft_refs); 699 700 // Resize the heap if necessary after a full collection. If this is 701 // after a collect-for allocation, "word_size" is the allocation size, 702 // and will be considered part of the used portion of the heap. 703 void resize_if_necessary_after_full_collection(size_t word_size); 704 705 // Callback from VM_G1CollectForAllocation operation. 706 // This function does everything necessary/possible to satisfy a 707 // failed allocation request (including collection, expansion, etc.) 708 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded); 709 710 // Attempting to expand the heap sufficiently 711 // to support an allocation of the given "word_size". If 712 // successful, perform the allocation and return the address of the 713 // allocated block, or else "NULL". 714 HeapWord* expand_and_allocate(size_t word_size); 715 716 // Process any reference objects discovered during 717 // an incremental evacuation pause. 718 void process_discovered_references(uint no_of_gc_workers); 719 720 // Enqueue any remaining discovered references 721 // after processing. 722 void enqueue_discovered_references(uint no_of_gc_workers); 723 724 public: 725 726 G1MonitoringSupport* g1mm() { 727 assert(_g1mm != NULL, "should have been initialized"); 728 return _g1mm; 729 } 730 731 // Expand the garbage-first heap by at least the given size (in bytes!). 732 // Returns true if the heap was expanded by the requested amount; 733 // false otherwise. 734 // (Rounds up to a HeapRegion boundary.) 735 bool expand(size_t expand_bytes); 736 737 // Do anything common to GC's. 738 virtual void gc_prologue(bool full); 739 virtual void gc_epilogue(bool full); 740 741 inline void set_humongous_is_live(oop obj); 742 743 bool humongous_is_live(uint region) { 744 return _humongous_is_live.is_live(region); 745 } 746 747 // Returns whether the given region (which must be a humongous (start) region) 748 // is to be considered conservatively live regardless of any other conditions. 749 bool humongous_region_is_always_live(uint index); 750 // Register the given region to be part of the collection set. 751 inline void register_humongous_region_with_in_cset_fast_test(uint index); 752 // Register regions with humongous objects (actually on the start region) in 753 // the in_cset_fast_test table. 754 void register_humongous_regions_with_in_cset_fast_test(); 755 // We register a region with the fast "in collection set" test. We 756 // simply set to true the array slot corresponding to this region. 757 void register_region_with_in_cset_fast_test(HeapRegion* r) { 758 _in_cset_fast_test.set_in_cset(r->hrs_index()); 759 } 760 761 // This is a fast test on whether a reference points into the 762 // collection set or not. Assume that the reference 763 // points into the heap. 764 inline bool in_cset_fast_test(oop obj); 765 766 void clear_cset_fast_test() { 767 _in_cset_fast_test.clear(); 768 } 769 770 // This is called at the start of either a concurrent cycle or a Full 771 // GC to update the number of old marking cycles started. 772 void increment_old_marking_cycles_started(); 773 774 // This is called at the end of either a concurrent cycle or a Full 775 // GC to update the number of old marking cycles completed. Those two 776 // can happen in a nested fashion, i.e., we start a concurrent 777 // cycle, a Full GC happens half-way through it which ends first, 778 // and then the cycle notices that a Full GC happened and ends 779 // too. The concurrent parameter is a boolean to help us do a bit 780 // tighter consistency checking in the method. If concurrent is 781 // false, the caller is the inner caller in the nesting (i.e., the 782 // Full GC). If concurrent is true, the caller is the outer caller 783 // in this nesting (i.e., the concurrent cycle). Further nesting is 784 // not currently supported. The end of this call also notifies 785 // the FullGCCount_lock in case a Java thread is waiting for a full 786 // GC to happen (e.g., it called System.gc() with 787 // +ExplicitGCInvokesConcurrent). 788 void increment_old_marking_cycles_completed(bool concurrent); 789 790 unsigned int old_marking_cycles_completed() { 791 return _old_marking_cycles_completed; 792 } 793 794 void register_concurrent_cycle_start(const Ticks& start_time); 795 void register_concurrent_cycle_end(); 796 void trace_heap_after_concurrent_cycle(); 797 798 G1YCType yc_type(); 799 800 G1HRPrinter* hr_printer() { return &_hr_printer; } 801 802 // Frees a non-humongous region by initializing its contents and 803 // adding it to the free list that's passed as a parameter (this is 804 // usually a local list which will be appended to the master free 805 // list later). The used bytes of freed regions are accumulated in 806 // pre_used. If par is true, the region's RSet will not be freed 807 // up. The assumption is that this will be done later. 808 // The locked parameter indicates if the caller has already taken 809 // care of proper synchronization. This may allow some optimizations. 810 void free_region(HeapRegion* hr, 811 FreeRegionList* free_list, 812 bool par, 813 bool locked = false); 814 815 // Frees a humongous region by collapsing it into individual regions 816 // and calling free_region() for each of them. The freed regions 817 // will be added to the free list that's passed as a parameter (this 818 // is usually a local list which will be appended to the master free 819 // list later). The used bytes of freed regions are accumulated in 820 // pre_used. If par is true, the region's RSet will not be freed 821 // up. The assumption is that this will be done later. 822 void free_humongous_region(HeapRegion* hr, 823 FreeRegionList* free_list, 824 bool par); 825 protected: 826 827 // Shrink the garbage-first heap by at most the given size (in bytes!). 828 // (Rounds down to a HeapRegion boundary.) 829 virtual void shrink(size_t expand_bytes); 830 void shrink_helper(size_t expand_bytes); 831 832 #if TASKQUEUE_STATS 833 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 834 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 835 void reset_taskqueue_stats(); 836 #endif // TASKQUEUE_STATS 837 838 // Schedule the VM operation that will do an evacuation pause to 839 // satisfy an allocation request of word_size. *succeeded will 840 // return whether the VM operation was successful (it did do an 841 // evacuation pause) or not (another thread beat us to it or the GC 842 // locker was active). Given that we should not be holding the 843 // Heap_lock when we enter this method, we will pass the 844 // gc_count_before (i.e., total_collections()) as a parameter since 845 // it has to be read while holding the Heap_lock. Currently, both 846 // methods that call do_collection_pause() release the Heap_lock 847 // before the call, so it's easy to read gc_count_before just before. 848 HeapWord* do_collection_pause(size_t word_size, 849 unsigned int gc_count_before, 850 bool* succeeded, 851 GCCause::Cause gc_cause); 852 853 // The guts of the incremental collection pause, executed by the vm 854 // thread. It returns false if it is unable to do the collection due 855 // to the GC locker being active, true otherwise 856 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 857 858 // Actually do the work of evacuating the collection set. 859 void evacuate_collection_set(EvacuationInfo& evacuation_info); 860 861 // The g1 remembered set of the heap. 862 G1RemSet* _g1_rem_set; 863 864 // A set of cards that cover the objects for which the Rsets should be updated 865 // concurrently after the collection. 866 DirtyCardQueueSet _dirty_card_queue_set; 867 868 // The closure used to refine a single card. 869 RefineCardTableEntryClosure* _refine_cte_cl; 870 871 // A function to check the consistency of dirty card logs. 872 void check_ct_logs_at_safepoint(); 873 874 // A DirtyCardQueueSet that is used to hold cards that contain 875 // references into the current collection set. This is used to 876 // update the remembered sets of the regions in the collection 877 // set in the event of an evacuation failure. 878 DirtyCardQueueSet _into_cset_dirty_card_queue_set; 879 880 // After a collection pause, make the regions in the CS into free 881 // regions. 882 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info); 883 884 // Abandon the current collection set without recording policy 885 // statistics or updating free lists. 886 void abandon_collection_set(HeapRegion* cs_head); 887 888 // Applies "scan_non_heap_roots" to roots outside the heap, 889 // "scan_rs" to roots inside the heap (having done "set_region" to 890 // indicate the region in which the root resides), 891 // and does "scan_metadata" If "scan_rs" is 892 // NULL, then this step is skipped. The "worker_i" 893 // param is for use with parallel roots processing, and should be 894 // the "i" of the calling parallel worker thread's work(i) function. 895 // In the sequential case this param will be ignored. 896 void g1_process_roots(OopClosure* scan_non_heap_roots, 897 OopClosure* scan_non_heap_weak_roots, 898 OopsInHeapRegionClosure* scan_rs, 899 CLDClosure* scan_strong_clds, 900 CLDClosure* scan_weak_clds, 901 CodeBlobClosure* scan_strong_code, 902 uint worker_i); 903 904 // Notifies all the necessary spaces that the committed space has 905 // been updated (either expanded or shrunk). It should be called 906 // after _g1_storage is updated. 907 void update_committed_space(HeapWord* old_end, HeapWord* new_end); 908 909 // The concurrent marker (and the thread it runs in.) 910 ConcurrentMark* _cm; 911 ConcurrentMarkThread* _cmThread; 912 bool _mark_in_progress; 913 914 // The concurrent refiner. 915 ConcurrentG1Refine* _cg1r; 916 917 // The parallel task queues 918 RefToScanQueueSet *_task_queues; 919 920 // True iff a evacuation has failed in the current collection. 921 bool _evacuation_failed; 922 923 EvacuationFailedInfo* _evacuation_failed_info_array; 924 925 // Failed evacuations cause some logical from-space objects to have 926 // forwarding pointers to themselves. Reset them. 927 void remove_self_forwarding_pointers(); 928 929 // Together, these store an object with a preserved mark, and its mark value. 930 Stack<oop, mtGC> _objs_with_preserved_marks; 931 Stack<markOop, mtGC> _preserved_marks_of_objs; 932 933 // Preserve the mark of "obj", if necessary, in preparation for its mark 934 // word being overwritten with a self-forwarding-pointer. 935 void preserve_mark_if_necessary(oop obj, markOop m); 936 937 // The stack of evac-failure objects left to be scanned. 938 GrowableArray<oop>* _evac_failure_scan_stack; 939 // The closure to apply to evac-failure objects. 940 941 OopsInHeapRegionClosure* _evac_failure_closure; 942 // Set the field above. 943 void 944 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) { 945 _evac_failure_closure = evac_failure_closure; 946 } 947 948 // Push "obj" on the scan stack. 949 void push_on_evac_failure_scan_stack(oop obj); 950 // Process scan stack entries until the stack is empty. 951 void drain_evac_failure_scan_stack(); 952 // True iff an invocation of "drain_scan_stack" is in progress; to 953 // prevent unnecessary recursion. 954 bool _drain_in_progress; 955 956 // Do any necessary initialization for evacuation-failure handling. 957 // "cl" is the closure that will be used to process evac-failure 958 // objects. 959 void init_for_evac_failure(OopsInHeapRegionClosure* cl); 960 // Do any necessary cleanup for evacuation-failure handling data 961 // structures. 962 void finalize_for_evac_failure(); 963 964 // An attempt to evacuate "obj" has failed; take necessary steps. 965 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj); 966 void handle_evacuation_failure_common(oop obj, markOop m); 967 968 #ifndef PRODUCT 969 // Support for forcing evacuation failures. Analogous to 970 // PromotionFailureALot for the other collectors. 971 972 // Records whether G1EvacuationFailureALot should be in effect 973 // for the current GC 974 bool _evacuation_failure_alot_for_current_gc; 975 976 // Used to record the GC number for interval checking when 977 // determining whether G1EvaucationFailureALot is in effect 978 // for the current GC. 979 size_t _evacuation_failure_alot_gc_number; 980 981 // Count of the number of evacuations between failures. 982 volatile size_t _evacuation_failure_alot_count; 983 984 // Set whether G1EvacuationFailureALot should be in effect 985 // for the current GC (based upon the type of GC and which 986 // command line flags are set); 987 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 988 bool during_initial_mark, 989 bool during_marking); 990 991 inline void set_evacuation_failure_alot_for_current_gc(); 992 993 // Return true if it's time to cause an evacuation failure. 994 inline bool evacuation_should_fail(); 995 996 // Reset the G1EvacuationFailureALot counters. Should be called at 997 // the end of an evacuation pause in which an evacuation failure occurred. 998 inline void reset_evacuation_should_fail(); 999 #endif // !PRODUCT 1000 1001 // ("Weak") Reference processing support. 1002 // 1003 // G1 has 2 instances of the reference processor class. One 1004 // (_ref_processor_cm) handles reference object discovery 1005 // and subsequent processing during concurrent marking cycles. 1006 // 1007 // The other (_ref_processor_stw) handles reference object 1008 // discovery and processing during full GCs and incremental 1009 // evacuation pauses. 1010 // 1011 // During an incremental pause, reference discovery will be 1012 // temporarily disabled for _ref_processor_cm and will be 1013 // enabled for _ref_processor_stw. At the end of the evacuation 1014 // pause references discovered by _ref_processor_stw will be 1015 // processed and discovery will be disabled. The previous 1016 // setting for reference object discovery for _ref_processor_cm 1017 // will be re-instated. 1018 // 1019 // At the start of marking: 1020 // * Discovery by the CM ref processor is verified to be inactive 1021 // and it's discovered lists are empty. 1022 // * Discovery by the CM ref processor is then enabled. 1023 // 1024 // At the end of marking: 1025 // * Any references on the CM ref processor's discovered 1026 // lists are processed (possibly MT). 1027 // 1028 // At the start of full GC we: 1029 // * Disable discovery by the CM ref processor and 1030 // empty CM ref processor's discovered lists 1031 // (without processing any entries). 1032 // * Verify that the STW ref processor is inactive and it's 1033 // discovered lists are empty. 1034 // * Temporarily set STW ref processor discovery as single threaded. 1035 // * Temporarily clear the STW ref processor's _is_alive_non_header 1036 // field. 1037 // * Finally enable discovery by the STW ref processor. 1038 // 1039 // The STW ref processor is used to record any discovered 1040 // references during the full GC. 1041 // 1042 // At the end of a full GC we: 1043 // * Enqueue any reference objects discovered by the STW ref processor 1044 // that have non-live referents. This has the side-effect of 1045 // making the STW ref processor inactive by disabling discovery. 1046 // * Verify that the CM ref processor is still inactive 1047 // and no references have been placed on it's discovered 1048 // lists (also checked as a precondition during initial marking). 1049 1050 // The (stw) reference processor... 1051 ReferenceProcessor* _ref_processor_stw; 1052 1053 STWGCTimer* _gc_timer_stw; 1054 ConcurrentGCTimer* _gc_timer_cm; 1055 1056 G1OldTracer* _gc_tracer_cm; 1057 G1NewTracer* _gc_tracer_stw; 1058 1059 // During reference object discovery, the _is_alive_non_header 1060 // closure (if non-null) is applied to the referent object to 1061 // determine whether the referent is live. If so then the 1062 // reference object does not need to be 'discovered' and can 1063 // be treated as a regular oop. This has the benefit of reducing 1064 // the number of 'discovered' reference objects that need to 1065 // be processed. 1066 // 1067 // Instance of the is_alive closure for embedding into the 1068 // STW reference processor as the _is_alive_non_header field. 1069 // Supplying a value for the _is_alive_non_header field is 1070 // optional but doing so prevents unnecessary additions to 1071 // the discovered lists during reference discovery. 1072 G1STWIsAliveClosure _is_alive_closure_stw; 1073 1074 // The (concurrent marking) reference processor... 1075 ReferenceProcessor* _ref_processor_cm; 1076 1077 // Instance of the concurrent mark is_alive closure for embedding 1078 // into the Concurrent Marking reference processor as the 1079 // _is_alive_non_header field. Supplying a value for the 1080 // _is_alive_non_header field is optional but doing so prevents 1081 // unnecessary additions to the discovered lists during reference 1082 // discovery. 1083 G1CMIsAliveClosure _is_alive_closure_cm; 1084 1085 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 1086 HeapRegion** _worker_cset_start_region; 1087 1088 // Time stamp to validate the regions recorded in the cache 1089 // used by G1CollectedHeap::start_cset_region_for_worker(). 1090 // The heap region entry for a given worker is valid iff 1091 // the associated time stamp value matches the current value 1092 // of G1CollectedHeap::_gc_time_stamp. 1093 unsigned int* _worker_cset_start_region_time_stamp; 1094 1095 enum G1H_process_roots_tasks { 1096 G1H_PS_filter_satb_buffers, 1097 G1H_PS_refProcessor_oops_do, 1098 // Leave this one last. 1099 G1H_PS_NumElements 1100 }; 1101 1102 SubTasksDone* _process_strong_tasks; 1103 1104 volatile bool _free_regions_coming; 1105 1106 public: 1107 1108 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; } 1109 1110 void set_refine_cte_cl_concurrency(bool concurrent); 1111 1112 RefToScanQueue *task_queue(int i) const; 1113 1114 // A set of cards where updates happened during the GC 1115 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 1116 1117 // A DirtyCardQueueSet that is used to hold cards that contain 1118 // references into the current collection set. This is used to 1119 // update the remembered sets of the regions in the collection 1120 // set in the event of an evacuation failure. 1121 DirtyCardQueueSet& into_cset_dirty_card_queue_set() 1122 { return _into_cset_dirty_card_queue_set; } 1123 1124 // Create a G1CollectedHeap with the specified policy. 1125 // Must call the initialize method afterwards. 1126 // May not return if something goes wrong. 1127 G1CollectedHeap(G1CollectorPolicy* policy); 1128 1129 // Initialize the G1CollectedHeap to have the initial and 1130 // maximum sizes and remembered and barrier sets 1131 // specified by the policy object. 1132 jint initialize(); 1133 1134 virtual void stop(); 1135 1136 // Return the (conservative) maximum heap alignment for any G1 heap 1137 static size_t conservative_max_heap_alignment(); 1138 1139 // Initialize weak reference processing. 1140 virtual void ref_processing_init(); 1141 1142 void set_par_threads(uint t) { 1143 SharedHeap::set_par_threads(t); 1144 // Done in SharedHeap but oddly there are 1145 // two _process_strong_tasks's in a G1CollectedHeap 1146 // so do it here too. 1147 _process_strong_tasks->set_n_threads(t); 1148 } 1149 1150 // Set _n_par_threads according to a policy TBD. 1151 void set_par_threads(); 1152 1153 void set_n_termination(int t) { 1154 _process_strong_tasks->set_n_threads(t); 1155 } 1156 1157 virtual CollectedHeap::Name kind() const { 1158 return CollectedHeap::G1CollectedHeap; 1159 } 1160 1161 // The current policy object for the collector. 1162 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 1163 1164 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); } 1165 1166 // Adaptive size policy. No such thing for g1. 1167 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1168 1169 // The rem set and barrier set. 1170 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1171 1172 unsigned get_gc_time_stamp() { 1173 return _gc_time_stamp; 1174 } 1175 1176 inline void reset_gc_time_stamp(); 1177 1178 void check_gc_time_stamps() PRODUCT_RETURN; 1179 1180 inline void increment_gc_time_stamp(); 1181 1182 // Reset the given region's GC timestamp. If it's starts humongous, 1183 // also reset the GC timestamp of its corresponding 1184 // continues humongous regions too. 1185 void reset_gc_time_stamps(HeapRegion* hr); 1186 1187 void iterate_dirty_card_closure(CardTableEntryClosure* cl, 1188 DirtyCardQueue* into_cset_dcq, 1189 bool concurrent, uint worker_i); 1190 1191 // The shared block offset table array. 1192 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1193 1194 // Reference Processing accessors 1195 1196 // The STW reference processor.... 1197 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1198 1199 // The Concurrent Marking reference processor... 1200 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1201 1202 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1203 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1204 1205 virtual size_t capacity() const; 1206 virtual size_t used() const; 1207 // This should be called when we're not holding the heap lock. The 1208 // result might be a bit inaccurate. 1209 size_t used_unlocked() const; 1210 size_t recalculate_used() const; 1211 1212 // These virtual functions do the actual allocation. 1213 // Some heaps may offer a contiguous region for shared non-blocking 1214 // allocation, via inlined code (by exporting the address of the top and 1215 // end fields defining the extent of the contiguous allocation region.) 1216 // But G1CollectedHeap doesn't yet support this. 1217 1218 virtual bool is_maximal_no_gc() const { 1219 return _g1_storage.uncommitted_size() == 0; 1220 } 1221 1222 // The total number of regions in the heap. 1223 uint n_regions() { return _hrs.length(); } 1224 1225 // The max number of regions in the heap. 1226 uint max_regions() { return _hrs.max_length(); } 1227 1228 // The number of regions that are completely free. 1229 uint free_regions() { return _free_list.length(); } 1230 1231 // The number of regions that are not completely free. 1232 uint used_regions() { return n_regions() - free_regions(); } 1233 1234 // The number of regions available for "regular" expansion. 1235 uint expansion_regions() { return _expansion_regions; } 1236 1237 // Factory method for HeapRegion instances. It will return NULL if 1238 // the allocation fails. 1239 HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom); 1240 1241 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1242 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1243 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1244 void verify_dirty_young_regions() PRODUCT_RETURN; 1245 1246 #ifndef PRODUCT 1247 // Make sure that the given bitmap has no marked objects in the 1248 // range [from,limit). If it does, print an error message and return 1249 // false. Otherwise, just return true. bitmap_name should be "prev" 1250 // or "next". 1251 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1252 HeapWord* from, HeapWord* limit); 1253 1254 // Verify that the prev / next bitmap range [tams,end) for the given 1255 // region has no marks. Return true if all is well, false if errors 1256 // are detected. 1257 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1258 #endif // PRODUCT 1259 1260 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1261 // the given region do not have any spurious marks. If errors are 1262 // detected, print appropriate error messages and crash. 1263 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1264 1265 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1266 // have any spurious marks. If errors are detected, print 1267 // appropriate error messages and crash. 1268 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1269 1270 // verify_region_sets() performs verification over the region 1271 // lists. It will be compiled in the product code to be used when 1272 // necessary (i.e., during heap verification). 1273 void verify_region_sets(); 1274 1275 // verify_region_sets_optional() is planted in the code for 1276 // list verification in non-product builds (and it can be enabled in 1277 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1278 #if HEAP_REGION_SET_FORCE_VERIFY 1279 void verify_region_sets_optional() { 1280 verify_region_sets(); 1281 } 1282 #else // HEAP_REGION_SET_FORCE_VERIFY 1283 void verify_region_sets_optional() { } 1284 #endif // HEAP_REGION_SET_FORCE_VERIFY 1285 1286 #ifdef ASSERT 1287 bool is_on_master_free_list(HeapRegion* hr) { 1288 return hr->containing_set() == &_free_list; 1289 } 1290 #endif // ASSERT 1291 1292 // Wrapper for the region list operations that can be called from 1293 // methods outside this class. 1294 1295 void secondary_free_list_add(FreeRegionList* list) { 1296 _secondary_free_list.add_ordered(list); 1297 } 1298 1299 void append_secondary_free_list() { 1300 _free_list.add_ordered(&_secondary_free_list); 1301 } 1302 1303 void append_secondary_free_list_if_not_empty_with_lock() { 1304 // If the secondary free list looks empty there's no reason to 1305 // take the lock and then try to append it. 1306 if (!_secondary_free_list.is_empty()) { 1307 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1308 append_secondary_free_list(); 1309 } 1310 } 1311 1312 inline void old_set_remove(HeapRegion* hr); 1313 1314 size_t non_young_capacity_bytes() { 1315 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1316 } 1317 1318 void set_free_regions_coming(); 1319 void reset_free_regions_coming(); 1320 bool free_regions_coming() { return _free_regions_coming; } 1321 void wait_while_free_regions_coming(); 1322 1323 // Determine whether the given region is one that we are using as an 1324 // old GC alloc region. 1325 bool is_old_gc_alloc_region(HeapRegion* hr) { 1326 return hr == _retained_old_gc_alloc_region; 1327 } 1328 1329 // Perform a collection of the heap; intended for use in implementing 1330 // "System.gc". This probably implies as full a collection as the 1331 // "CollectedHeap" supports. 1332 virtual void collect(GCCause::Cause cause); 1333 1334 // The same as above but assume that the caller holds the Heap_lock. 1335 void collect_locked(GCCause::Cause cause); 1336 1337 // True iff an evacuation has failed in the most-recent collection. 1338 bool evacuation_failed() { return _evacuation_failed; } 1339 1340 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1341 void prepend_to_freelist(FreeRegionList* list); 1342 void decrement_summary_bytes(size_t bytes); 1343 1344 // Returns "TRUE" iff "p" points into the committed areas of the heap. 1345 virtual bool is_in(const void* p) const; 1346 1347 // Return "TRUE" iff the given object address is within the collection 1348 // set. Slow implementation. 1349 inline bool obj_in_cs(oop obj); 1350 1351 inline bool is_in_cset(oop obj); 1352 1353 inline bool is_in_cset_or_humongous(const oop obj); 1354 1355 inline G1FastCSetBiasedMappedArray::in_cset_state_t in_cset_state(const oop obj); 1356 1357 // Return "TRUE" iff the given object address is in the reserved 1358 // region of g1. 1359 bool is_in_g1_reserved(const void* p) const { 1360 return _g1_reserved.contains(p); 1361 } 1362 1363 // Returns a MemRegion that corresponds to the space that has been 1364 // reserved for the heap 1365 MemRegion g1_reserved() { 1366 return _g1_reserved; 1367 } 1368 1369 // Returns a MemRegion that corresponds to the space that has been 1370 // committed in the heap 1371 MemRegion g1_committed() { 1372 return _g1_committed; 1373 } 1374 1375 virtual bool is_in_closed_subset(const void* p) const; 1376 1377 G1SATBCardTableModRefBS* g1_barrier_set() { 1378 return (G1SATBCardTableModRefBS*) barrier_set(); 1379 } 1380 1381 // This resets the card table to all zeros. It is used after 1382 // a collection pause which used the card table to claim cards. 1383 void cleanUpCardTable(); 1384 1385 // Iteration functions. 1386 1387 // Iterate over all the ref-containing fields of all objects, calling 1388 // "cl.do_oop" on each. 1389 virtual void oop_iterate(ExtendedOopClosure* cl); 1390 1391 // Same as above, restricted to a memory region. 1392 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl); 1393 1394 // Iterate over all objects, calling "cl.do_object" on each. 1395 virtual void object_iterate(ObjectClosure* cl); 1396 1397 virtual void safe_object_iterate(ObjectClosure* cl) { 1398 object_iterate(cl); 1399 } 1400 1401 // Iterate over all spaces in use in the heap, in ascending address order. 1402 virtual void space_iterate(SpaceClosure* cl); 1403 1404 // Iterate over heap regions, in address order, terminating the 1405 // iteration early if the "doHeapRegion" method returns "true". 1406 void heap_region_iterate(HeapRegionClosure* blk) const; 1407 1408 // Return the region with the given index. It assumes the index is valid. 1409 inline HeapRegion* region_at(uint index) const; 1410 1411 // Calculate the region index of the given address. Given address must be 1412 // within the heap. 1413 inline uint addr_to_region(HeapWord* addr) const; 1414 1415 // Divide the heap region sequence into "chunks" of some size (the number 1416 // of regions divided by the number of parallel threads times some 1417 // overpartition factor, currently 4). Assumes that this will be called 1418 // in parallel by ParallelGCThreads worker threads with distinct worker 1419 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel 1420 // calls will use the same "claim_value", and that that claim value is 1421 // different from the claim_value of any heap region before the start of 1422 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by 1423 // attempting to claim the first region in each chunk, and, if 1424 // successful, applying the closure to each region in the chunk (and 1425 // setting the claim value of the second and subsequent regions of the 1426 // chunk.) For now requires that "doHeapRegion" always returns "false", 1427 // i.e., that a closure never attempt to abort a traversal. 1428 void heap_region_par_iterate_chunked(HeapRegionClosure* blk, 1429 uint worker, 1430 uint no_of_par_workers, 1431 jint claim_value); 1432 1433 // It resets all the region claim values to the default. 1434 void reset_heap_region_claim_values(); 1435 1436 // Resets the claim values of regions in the current 1437 // collection set to the default. 1438 void reset_cset_heap_region_claim_values(); 1439 1440 #ifdef ASSERT 1441 bool check_heap_region_claim_values(jint claim_value); 1442 1443 // Same as the routine above but only checks regions in the 1444 // current collection set. 1445 bool check_cset_heap_region_claim_values(jint claim_value); 1446 #endif // ASSERT 1447 1448 // Clear the cached cset start regions and (more importantly) 1449 // the time stamps. Called when we reset the GC time stamp. 1450 void clear_cset_start_regions(); 1451 1452 // Given the id of a worker, obtain or calculate a suitable 1453 // starting region for iterating over the current collection set. 1454 HeapRegion* start_cset_region_for_worker(uint worker_i); 1455 1456 // This is a convenience method that is used by the 1457 // HeapRegionIterator classes to calculate the starting region for 1458 // each worker so that they do not all start from the same region. 1459 HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers); 1460 1461 // Iterate over the regions (if any) in the current collection set. 1462 void collection_set_iterate(HeapRegionClosure* blk); 1463 1464 // As above but starting from region r 1465 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1466 1467 // Returns the first (lowest address) compactible space in the heap. 1468 virtual CompactibleSpace* first_compactible_space(); 1469 1470 // A CollectedHeap will contain some number of spaces. This finds the 1471 // space containing a given address, or else returns NULL. 1472 virtual Space* space_containing(const void* addr) const; 1473 1474 // Returns the HeapRegion that contains addr. addr must not be NULL. 1475 template <class T> 1476 inline HeapRegion* heap_region_containing_raw(const T addr) const; 1477 1478 // Returns the HeapRegion that contains addr. addr must not be NULL. 1479 // If addr is within a humongous continues region, it returns its humongous start region. 1480 template <class T> 1481 inline HeapRegion* heap_region_containing(const T addr) const; 1482 1483 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1484 // each address in the (reserved) heap is a member of exactly 1485 // one block. The defining characteristic of a block is that it is 1486 // possible to find its size, and thus to progress forward to the next 1487 // block. (Blocks may be of different sizes.) Thus, blocks may 1488 // represent Java objects, or they might be free blocks in a 1489 // free-list-based heap (or subheap), as long as the two kinds are 1490 // distinguishable and the size of each is determinable. 1491 1492 // Returns the address of the start of the "block" that contains the 1493 // address "addr". We say "blocks" instead of "object" since some heaps 1494 // may not pack objects densely; a chunk may either be an object or a 1495 // non-object. 1496 virtual HeapWord* block_start(const void* addr) const; 1497 1498 // Requires "addr" to be the start of a chunk, and returns its size. 1499 // "addr + size" is required to be the start of a new chunk, or the end 1500 // of the active area of the heap. 1501 virtual size_t block_size(const HeapWord* addr) const; 1502 1503 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1504 // the block is an object. 1505 virtual bool block_is_obj(const HeapWord* addr) const; 1506 1507 // Does this heap support heap inspection? (+PrintClassHistogram) 1508 virtual bool supports_heap_inspection() const { return true; } 1509 1510 // Section on thread-local allocation buffers (TLABs) 1511 // See CollectedHeap for semantics. 1512 1513 bool supports_tlab_allocation() const; 1514 size_t tlab_capacity(Thread* ignored) const; 1515 size_t tlab_used(Thread* ignored) const; 1516 size_t max_tlab_size() const; 1517 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1518 1519 // Can a compiler initialize a new object without store barriers? 1520 // This permission only extends from the creation of a new object 1521 // via a TLAB up to the first subsequent safepoint. If such permission 1522 // is granted for this heap type, the compiler promises to call 1523 // defer_store_barrier() below on any slow path allocation of 1524 // a new object for which such initializing store barriers will 1525 // have been elided. G1, like CMS, allows this, but should be 1526 // ready to provide a compensating write barrier as necessary 1527 // if that storage came out of a non-young region. The efficiency 1528 // of this implementation depends crucially on being able to 1529 // answer very efficiently in constant time whether a piece of 1530 // storage in the heap comes from a young region or not. 1531 // See ReduceInitialCardMarks. 1532 virtual bool can_elide_tlab_store_barriers() const { 1533 return true; 1534 } 1535 1536 virtual bool card_mark_must_follow_store() const { 1537 return true; 1538 } 1539 1540 inline bool is_in_young(const oop obj); 1541 1542 #ifdef ASSERT 1543 virtual bool is_in_partial_collection(const void* p); 1544 #endif 1545 1546 virtual bool is_scavengable(const void* addr); 1547 1548 // We don't need barriers for initializing stores to objects 1549 // in the young gen: for the SATB pre-barrier, there is no 1550 // pre-value that needs to be remembered; for the remembered-set 1551 // update logging post-barrier, we don't maintain remembered set 1552 // information for young gen objects. 1553 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1554 1555 // Returns "true" iff the given word_size is "very large". 1556 static bool isHumongous(size_t word_size) { 1557 // Note this has to be strictly greater-than as the TLABs 1558 // are capped at the humongous threshold and we want to 1559 // ensure that we don't try to allocate a TLAB as 1560 // humongous and that we don't allocate a humongous 1561 // object in a TLAB. 1562 return word_size > _humongous_object_threshold_in_words; 1563 } 1564 1565 // Update mod union table with the set of dirty cards. 1566 void updateModUnion(); 1567 1568 // Set the mod union bits corresponding to the given memRegion. Note 1569 // that this is always a safe operation, since it doesn't clear any 1570 // bits. 1571 void markModUnionRange(MemRegion mr); 1572 1573 // Records the fact that a marking phase is no longer in progress. 1574 void set_marking_complete() { 1575 _mark_in_progress = false; 1576 } 1577 void set_marking_started() { 1578 _mark_in_progress = true; 1579 } 1580 bool mark_in_progress() { 1581 return _mark_in_progress; 1582 } 1583 1584 // Print the maximum heap capacity. 1585 virtual size_t max_capacity() const; 1586 1587 virtual jlong millis_since_last_gc(); 1588 1589 1590 // Convenience function to be used in situations where the heap type can be 1591 // asserted to be this type. 1592 static G1CollectedHeap* heap(); 1593 1594 void set_region_short_lived_locked(HeapRegion* hr); 1595 // add appropriate methods for any other surv rate groups 1596 1597 YoungList* young_list() const { return _young_list; } 1598 1599 // debugging 1600 bool check_young_list_well_formed() { 1601 return _young_list->check_list_well_formed(); 1602 } 1603 1604 bool check_young_list_empty(bool check_heap, 1605 bool check_sample = true); 1606 1607 // *** Stuff related to concurrent marking. It's not clear to me that so 1608 // many of these need to be public. 1609 1610 // The functions below are helper functions that a subclass of 1611 // "CollectedHeap" can use in the implementation of its virtual 1612 // functions. 1613 // This performs a concurrent marking of the live objects in a 1614 // bitmap off to the side. 1615 void doConcurrentMark(); 1616 1617 bool isMarkedPrev(oop obj) const; 1618 bool isMarkedNext(oop obj) const; 1619 1620 // Determine if an object is dead, given the object and also 1621 // the region to which the object belongs. An object is dead 1622 // iff a) it was not allocated since the last mark and b) it 1623 // is not marked. 1624 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1625 return 1626 !hr->obj_allocated_since_prev_marking(obj) && 1627 !isMarkedPrev(obj); 1628 } 1629 1630 // This function returns true when an object has been 1631 // around since the previous marking and hasn't yet 1632 // been marked during this marking. 1633 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1634 return 1635 !hr->obj_allocated_since_next_marking(obj) && 1636 !isMarkedNext(obj); 1637 } 1638 1639 // Determine if an object is dead, given only the object itself. 1640 // This will find the region to which the object belongs and 1641 // then call the region version of the same function. 1642 1643 // Added if it is NULL it isn't dead. 1644 1645 inline bool is_obj_dead(const oop obj) const; 1646 1647 inline bool is_obj_ill(const oop obj) const; 1648 1649 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1650 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1651 bool is_marked(oop obj, VerifyOption vo); 1652 const char* top_at_mark_start_str(VerifyOption vo); 1653 1654 ConcurrentMark* concurrent_mark() const { return _cm; } 1655 1656 // Refinement 1657 1658 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1659 1660 // The dirty cards region list is used to record a subset of regions 1661 // whose cards need clearing. The list if populated during the 1662 // remembered set scanning and drained during the card table 1663 // cleanup. Although the methods are reentrant, population/draining 1664 // phases must not overlap. For synchronization purposes the last 1665 // element on the list points to itself. 1666 HeapRegion* _dirty_cards_region_list; 1667 void push_dirty_cards_region(HeapRegion* hr); 1668 HeapRegion* pop_dirty_cards_region(); 1669 1670 // Optimized nmethod scanning support routines 1671 1672 // Register the given nmethod with the G1 heap. 1673 virtual void register_nmethod(nmethod* nm); 1674 1675 // Unregister the given nmethod from the G1 heap. 1676 virtual void unregister_nmethod(nmethod* nm); 1677 1678 // Migrate the nmethods in the code root lists of the regions 1679 // in the collection set to regions in to-space. In the event 1680 // of an evacuation failure, nmethods that reference objects 1681 // that were not successfully evacuated are not migrated. 1682 void migrate_strong_code_roots(); 1683 1684 // Free up superfluous code root memory. 1685 void purge_code_root_memory(); 1686 1687 // Rebuild the strong code root lists for each region 1688 // after a full GC. 1689 void rebuild_strong_code_roots(); 1690 1691 // Delete entries for dead interned string and clean up unreferenced symbols 1692 // in symbol table, possibly in parallel. 1693 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1694 1695 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1696 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1697 1698 // Redirty logged cards in the refinement queue. 1699 void redirty_logged_cards(); 1700 // Verification 1701 1702 // The following is just to alert the verification code 1703 // that a full collection has occurred and that the 1704 // remembered sets are no longer up to date. 1705 bool _full_collection; 1706 void set_full_collection() { _full_collection = true;} 1707 void clear_full_collection() {_full_collection = false;} 1708 bool full_collection() {return _full_collection;} 1709 1710 // Perform any cleanup actions necessary before allowing a verification. 1711 virtual void prepare_for_verify(); 1712 1713 // Perform verification. 1714 1715 // vo == UsePrevMarking -> use "prev" marking information, 1716 // vo == UseNextMarking -> use "next" marking information 1717 // vo == UseMarkWord -> use the mark word in the object header 1718 // 1719 // NOTE: Only the "prev" marking information is guaranteed to be 1720 // consistent most of the time, so most calls to this should use 1721 // vo == UsePrevMarking. 1722 // Currently, there is only one case where this is called with 1723 // vo == UseNextMarking, which is to verify the "next" marking 1724 // information at the end of remark. 1725 // Currently there is only one place where this is called with 1726 // vo == UseMarkWord, which is to verify the marking during a 1727 // full GC. 1728 void verify(bool silent, VerifyOption vo); 1729 1730 // Override; it uses the "prev" marking information 1731 virtual void verify(bool silent); 1732 1733 // The methods below are here for convenience and dispatch the 1734 // appropriate method depending on value of the given VerifyOption 1735 // parameter. The values for that parameter, and their meanings, 1736 // are the same as those above. 1737 1738 bool is_obj_dead_cond(const oop obj, 1739 const HeapRegion* hr, 1740 const VerifyOption vo) const; 1741 1742 bool is_obj_dead_cond(const oop obj, 1743 const VerifyOption vo) const; 1744 1745 // Printing 1746 1747 virtual void print_on(outputStream* st) const; 1748 virtual void print_extended_on(outputStream* st) const; 1749 virtual void print_on_error(outputStream* st) const; 1750 1751 virtual void print_gc_threads_on(outputStream* st) const; 1752 virtual void gc_threads_do(ThreadClosure* tc) const; 1753 1754 // Override 1755 void print_tracing_info() const; 1756 1757 // The following two methods are helpful for debugging RSet issues. 1758 void print_cset_rsets() PRODUCT_RETURN; 1759 void print_all_rsets() PRODUCT_RETURN; 1760 1761 public: 1762 size_t pending_card_num(); 1763 size_t cards_scanned(); 1764 1765 protected: 1766 size_t _max_heap_capacity; 1767 }; 1768 1769 class G1ParGCAllocBuffer: public ParGCAllocBuffer { 1770 private: 1771 bool _retired; 1772 1773 public: 1774 G1ParGCAllocBuffer(size_t gclab_word_size); 1775 virtual ~G1ParGCAllocBuffer() { 1776 guarantee(_retired, "Allocation buffer has not been retired"); 1777 } 1778 1779 virtual void set_buf(HeapWord* buf) { 1780 ParGCAllocBuffer::set_buf(buf); 1781 _retired = false; 1782 } 1783 1784 virtual void retire(bool end_of_gc, bool retain) { 1785 if (_retired) { 1786 return; 1787 } 1788 ParGCAllocBuffer::retire(end_of_gc, retain); 1789 _retired = true; 1790 } 1791 }; 1792 1793 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP