1 /* 2 * Copyright (c) 2001, 2017, 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_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc/g1/evacuationInfo.hpp" 29 #include "gc/g1/g1AllocationContext.hpp" 30 #include "gc/g1/g1BiasedArray.hpp" 31 #include "gc/g1/g1CollectionSet.hpp" 32 #include "gc/g1/g1CollectorState.hpp" 33 #include "gc/g1/g1ConcurrentMark.hpp" 34 #include "gc/g1/g1EdenRegions.hpp" 35 #include "gc/g1/g1EvacFailure.hpp" 36 #include "gc/g1/g1EvacStats.hpp" 37 #include "gc/g1/g1HeapVerifier.hpp" 38 #include "gc/g1/g1HRPrinter.hpp" 39 #include "gc/g1/g1InCSetState.hpp" 40 #include "gc/g1/g1MonitoringSupport.hpp" 41 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 42 #include "gc/g1/g1SurvivorRegions.hpp" 43 #include "gc/g1/g1YCTypes.hpp" 44 #include "gc/g1/hSpaceCounters.hpp" 45 #include "gc/g1/heapRegionManager.hpp" 46 #include "gc/g1/heapRegionSet.hpp" 47 #include "gc/shared/barrierSet.hpp" 48 #include "gc/shared/collectedHeap.hpp" 49 #include "gc/shared/plab.hpp" 50 #include "gc/shared/preservedMarks.hpp" 51 #include "memory/memRegion.hpp" 52 #include "utilities/stack.hpp" 53 54 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 55 // It uses the "Garbage First" heap organization and algorithm, which 56 // may combine concurrent marking with parallel, incremental compaction of 57 // heap subsets that will yield large amounts of garbage. 58 59 // Forward declarations 60 class HeapRegion; 61 class HRRSCleanupTask; 62 class GenerationSpec; 63 class OopsInHeapRegionClosure; 64 class G1ParScanThreadState; 65 class G1ParScanThreadStateSet; 66 class G1KlassScanClosure; 67 class G1ParScanThreadState; 68 class ObjectClosure; 69 class SpaceClosure; 70 class CompactibleSpaceClosure; 71 class Space; 72 class G1CollectionSet; 73 class G1CollectorPolicy; 74 class G1Policy; 75 class G1HotCardCache; 76 class G1RemSet; 77 class HeapRegionRemSetIterator; 78 class G1ConcurrentMark; 79 class ConcurrentMarkThread; 80 class ConcurrentG1Refine; 81 class GenerationCounters; 82 class STWGCTimer; 83 class G1NewTracer; 84 class EvacuationFailedInfo; 85 class nmethod; 86 class Ticks; 87 class WorkGang; 88 class G1Allocator; 89 class G1ArchiveAllocator; 90 class G1HeapVerifier; 91 class G1HeapSizingPolicy; 92 93 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 94 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 95 96 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 97 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 98 99 // The G1 STW is alive closure. 100 // An instance is embedded into the G1CH and used as the 101 // (optional) _is_alive_non_header closure in the STW 102 // reference processor. It is also extensively used during 103 // reference processing during STW evacuation pauses. 104 class G1STWIsAliveClosure: public BoolObjectClosure { 105 G1CollectedHeap* _g1; 106 public: 107 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 108 bool do_object_b(oop p); 109 }; 110 111 class RefineCardTableEntryClosure; 112 113 class G1RegionMappingChangedListener : public G1MappingChangedListener { 114 private: 115 void reset_from_card_cache(uint start_idx, size_t num_regions); 116 public: 117 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 118 }; 119 120 class G1CollectedHeap : public CollectedHeap { 121 friend class G1FreeCollectionSetTask; 122 friend class VM_CollectForMetadataAllocation; 123 friend class VM_G1CollectForAllocation; 124 friend class VM_G1CollectFull; 125 friend class VM_G1IncCollectionPause; 126 friend class VMStructs; 127 friend class MutatorAllocRegion; 128 friend class G1GCAllocRegion; 129 friend class G1HeapVerifier; 130 131 // Closures used in implementation. 132 friend class G1ParScanThreadState; 133 friend class G1ParScanThreadStateSet; 134 friend class G1ParTask; 135 friend class G1PLABAllocator; 136 friend class G1PrepareCompactClosure; 137 138 // Other related classes. 139 friend class HeapRegionClaimer; 140 141 // Testing classes. 142 friend class G1CheckCSetFastTableClosure; 143 144 private: 145 WorkGang* _workers; 146 G1CollectorPolicy* _collector_policy; 147 148 static size_t _humongous_object_threshold_in_words; 149 150 // The secondary free list which contains regions that have been 151 // freed up during the cleanup process. This will be appended to 152 // the master free list when appropriate. 153 FreeRegionList _secondary_free_list; 154 155 // It keeps track of the old regions. 156 HeapRegionSet _old_set; 157 158 // It keeps track of the humongous regions. 159 HeapRegionSet _humongous_set; 160 161 void eagerly_reclaim_humongous_regions(); 162 // Start a new incremental collection set for the next pause. 163 void start_new_collection_set(); 164 165 // The number of regions we could create by expansion. 166 uint _expansion_regions; 167 168 // The block offset table for the G1 heap. 169 G1BlockOffsetTable* _bot; 170 171 // Tears down the region sets / lists so that they are empty and the 172 // regions on the heap do not belong to a region set / list. The 173 // only exception is the humongous set which we leave unaltered. If 174 // free_list_only is true, it will only tear down the master free 175 // list. It is called before a Full GC (free_list_only == false) or 176 // before heap shrinking (free_list_only == true). 177 void tear_down_region_sets(bool free_list_only); 178 179 // Rebuilds the region sets / lists so that they are repopulated to 180 // reflect the contents of the heap. The only exception is the 181 // humongous set which was not torn down in the first place. If 182 // free_list_only is true, it will only rebuild the master free 183 // list. It is called after a Full GC (free_list_only == false) or 184 // after heap shrinking (free_list_only == true). 185 void rebuild_region_sets(bool free_list_only); 186 187 // Callback for region mapping changed events. 188 G1RegionMappingChangedListener _listener; 189 190 // The sequence of all heap regions in the heap. 191 HeapRegionManager _hrm; 192 193 // Manages all allocations with regions except humongous object allocations. 194 G1Allocator* _allocator; 195 196 // Manages all heap verification. 197 G1HeapVerifier* _verifier; 198 199 // Outside of GC pauses, the number of bytes used in all regions other 200 // than the current allocation region(s). 201 size_t _summary_bytes_used; 202 203 void increase_used(size_t bytes); 204 void decrease_used(size_t bytes); 205 206 void set_used(size_t bytes); 207 208 // Class that handles archive allocation ranges. 209 G1ArchiveAllocator* _archive_allocator; 210 211 // Statistics for each allocation context 212 AllocationContextStats _allocation_context_stats; 213 214 // GC allocation statistics policy for survivors. 215 G1EvacStats _survivor_evac_stats; 216 217 // GC allocation statistics policy for tenured objects. 218 G1EvacStats _old_evac_stats; 219 220 // It specifies whether we should attempt to expand the heap after a 221 // region allocation failure. If heap expansion fails we set this to 222 // false so that we don't re-attempt the heap expansion (it's likely 223 // that subsequent expansion attempts will also fail if one fails). 224 // Currently, it is only consulted during GC and it's reset at the 225 // start of each GC. 226 bool _expand_heap_after_alloc_failure; 227 228 // Helper for monitoring and management support. 229 G1MonitoringSupport* _g1mm; 230 231 // Records whether the region at the given index is (still) a 232 // candidate for eager reclaim. Only valid for humongous start 233 // regions; other regions have unspecified values. Humongous start 234 // regions are initialized at start of collection pause, with 235 // candidates removed from the set as they are found reachable from 236 // roots or the young generation. 237 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 238 protected: 239 bool default_value() const { return false; } 240 public: 241 void clear() { G1BiasedMappedArray<bool>::clear(); } 242 void set_candidate(uint region, bool value) { 243 set_by_index(region, value); 244 } 245 bool is_candidate(uint region) { 246 return get_by_index(region); 247 } 248 }; 249 250 HumongousReclaimCandidates _humongous_reclaim_candidates; 251 // Stores whether during humongous object registration we found candidate regions. 252 // If not, we can skip a few steps. 253 bool _has_humongous_reclaim_candidates; 254 255 volatile uint _gc_time_stamp; 256 257 G1HRPrinter _hr_printer; 258 259 // It decides whether an explicit GC should start a concurrent cycle 260 // instead of doing a STW GC. Currently, a concurrent cycle is 261 // explicitly started if: 262 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 263 // (b) cause == _g1_humongous_allocation 264 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 265 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 266 // (e) cause == _update_allocation_context_stats_inc 267 // (f) cause == _wb_conc_mark 268 bool should_do_concurrent_full_gc(GCCause::Cause cause); 269 270 // indicates whether we are in young or mixed GC mode 271 G1CollectorState _collector_state; 272 273 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 274 // concurrent cycles) we have started. 275 volatile uint _old_marking_cycles_started; 276 277 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 278 // concurrent cycles) we have completed. 279 volatile uint _old_marking_cycles_completed; 280 281 // This is a non-product method that is helpful for testing. It is 282 // called at the end of a GC and artificially expands the heap by 283 // allocating a number of dead regions. This way we can induce very 284 // frequent marking cycles and stress the cleanup / concurrent 285 // cleanup code more (as all the regions that will be allocated by 286 // this method will be found dead by the marking cycle). 287 void allocate_dummy_regions() PRODUCT_RETURN; 288 289 // Clear RSets after a compaction. It also resets the GC time stamps. 290 void clear_rsets_post_compaction(); 291 292 // If the HR printer is active, dump the state of the regions in the 293 // heap after a compaction. 294 void print_hrm_post_compaction(); 295 296 // Create a memory mapper for auxiliary data structures of the given size and 297 // translation factor. 298 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 299 size_t size, 300 size_t translation_factor); 301 302 static G1Policy* create_g1_policy(); 303 304 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 305 306 void process_weak_jni_handles(); 307 308 // These are macros so that, if the assert fires, we get the correct 309 // line number, file, etc. 310 311 #define heap_locking_asserts_params(_extra_message_) \ 312 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 313 (_extra_message_), \ 314 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 315 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 316 BOOL_TO_STR(Thread::current()->is_VM_thread()) 317 318 #define assert_heap_locked() \ 319 do { \ 320 assert(Heap_lock->owned_by_self(), \ 321 heap_locking_asserts_params("should be holding the Heap_lock")); \ 322 } while (0) 323 324 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 325 do { \ 326 assert(Heap_lock->owned_by_self() || \ 327 (SafepointSynchronize::is_at_safepoint() && \ 328 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 329 heap_locking_asserts_params("should be holding the Heap_lock or " \ 330 "should be at a safepoint")); \ 331 } while (0) 332 333 #define assert_heap_locked_and_not_at_safepoint() \ 334 do { \ 335 assert(Heap_lock->owned_by_self() && \ 336 !SafepointSynchronize::is_at_safepoint(), \ 337 heap_locking_asserts_params("should be holding the Heap_lock and " \ 338 "should not be at a safepoint")); \ 339 } while (0) 340 341 #define assert_heap_not_locked() \ 342 do { \ 343 assert(!Heap_lock->owned_by_self(), \ 344 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 345 } while (0) 346 347 #define assert_heap_not_locked_and_not_at_safepoint() \ 348 do { \ 349 assert(!Heap_lock->owned_by_self() && \ 350 !SafepointSynchronize::is_at_safepoint(), \ 351 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 352 "should not be at a safepoint")); \ 353 } while (0) 354 355 #define assert_at_safepoint(_should_be_vm_thread_) \ 356 do { \ 357 assert(SafepointSynchronize::is_at_safepoint() && \ 358 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 359 heap_locking_asserts_params("should be at a safepoint")); \ 360 } while (0) 361 362 #define assert_not_at_safepoint() \ 363 do { \ 364 assert(!SafepointSynchronize::is_at_safepoint(), \ 365 heap_locking_asserts_params("should not be at a safepoint")); \ 366 } while (0) 367 368 protected: 369 370 // The young region list. 371 G1EdenRegions _eden; 372 G1SurvivorRegions _survivor; 373 374 // The current policy object for the collector. 375 G1Policy* _g1_policy; 376 G1HeapSizingPolicy* _heap_sizing_policy; 377 378 G1CollectionSet _collection_set; 379 380 // This is the second level of trying to allocate a new region. If 381 // new_region() didn't find a region on the free_list, this call will 382 // check whether there's anything available on the 383 // secondary_free_list and/or wait for more regions to appear on 384 // that list, if _free_regions_coming is set. 385 HeapRegion* new_region_try_secondary_free_list(bool is_old); 386 387 // Try to allocate a single non-humongous HeapRegion sufficient for 388 // an allocation of the given word_size. If do_expand is true, 389 // attempt to expand the heap if necessary to satisfy the allocation 390 // request. If the region is to be used as an old region or for a 391 // humongous object, set is_old to true. If not, to false. 392 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 393 394 // Initialize a contiguous set of free regions of length num_regions 395 // and starting at index first so that they appear as a single 396 // humongous region. 397 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 398 uint num_regions, 399 size_t word_size, 400 AllocationContext_t context); 401 402 // Attempt to allocate a humongous object of the given size. Return 403 // NULL if unsuccessful. 404 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 405 406 // The following two methods, allocate_new_tlab() and 407 // mem_allocate(), are the two main entry points from the runtime 408 // into the G1's allocation routines. They have the following 409 // assumptions: 410 // 411 // * They should both be called outside safepoints. 412 // 413 // * They should both be called without holding the Heap_lock. 414 // 415 // * All allocation requests for new TLABs should go to 416 // allocate_new_tlab(). 417 // 418 // * All non-TLAB allocation requests should go to mem_allocate(). 419 // 420 // * If either call cannot satisfy the allocation request using the 421 // current allocating region, they will try to get a new one. If 422 // this fails, they will attempt to do an evacuation pause and 423 // retry the allocation. 424 // 425 // * If all allocation attempts fail, even after trying to schedule 426 // an evacuation pause, allocate_new_tlab() will return NULL, 427 // whereas mem_allocate() will attempt a heap expansion and/or 428 // schedule a Full GC. 429 // 430 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 431 // should never be called with word_size being humongous. All 432 // humongous allocation requests should go to mem_allocate() which 433 // will satisfy them with a special path. 434 435 virtual HeapWord* allocate_new_tlab(size_t word_size); 436 437 virtual HeapWord* mem_allocate(size_t word_size, 438 bool* gc_overhead_limit_was_exceeded); 439 440 // The following three methods take a gc_count_before_ret 441 // parameter which is used to return the GC count if the method 442 // returns NULL. Given that we are required to read the GC count 443 // while holding the Heap_lock, and these paths will take the 444 // Heap_lock at some point, it's easier to get them to read the GC 445 // count while holding the Heap_lock before they return NULL instead 446 // of the caller (namely: mem_allocate()) having to also take the 447 // Heap_lock just to read the GC count. 448 449 // First-level mutator allocation attempt: try to allocate out of 450 // the mutator alloc region without taking the Heap_lock. This 451 // should only be used for non-humongous allocations. 452 inline HeapWord* attempt_allocation(size_t word_size, 453 uint* gc_count_before_ret, 454 uint* gclocker_retry_count_ret); 455 456 // Second-level mutator allocation attempt: take the Heap_lock and 457 // retry the allocation attempt, potentially scheduling a GC 458 // pause. This should only be used for non-humongous allocations. 459 HeapWord* attempt_allocation_slow(size_t word_size, 460 AllocationContext_t context, 461 uint* gc_count_before_ret, 462 uint* gclocker_retry_count_ret); 463 464 // Takes the Heap_lock and attempts a humongous allocation. It can 465 // potentially schedule a GC pause. 466 HeapWord* attempt_allocation_humongous(size_t word_size, 467 uint* gc_count_before_ret, 468 uint* gclocker_retry_count_ret); 469 470 // Allocation attempt that should be called during safepoints (e.g., 471 // at the end of a successful GC). expect_null_mutator_alloc_region 472 // specifies whether the mutator alloc region is expected to be NULL 473 // or not. 474 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 475 AllocationContext_t context, 476 bool expect_null_mutator_alloc_region); 477 478 // These methods are the "callbacks" from the G1AllocRegion class. 479 480 // For mutator alloc regions. 481 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 482 void retire_mutator_alloc_region(HeapRegion* alloc_region, 483 size_t allocated_bytes); 484 485 // For GC alloc regions. 486 bool has_more_regions(InCSetState dest); 487 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest); 488 void retire_gc_alloc_region(HeapRegion* alloc_region, 489 size_t allocated_bytes, InCSetState dest); 490 491 // - if explicit_gc is true, the GC is for a System.gc() etc, 492 // otherwise it's for a failed allocation. 493 // - if clear_all_soft_refs is true, all soft references should be 494 // cleared during the GC. 495 // - it returns false if it is unable to do the collection due to the 496 // GC locker being active, true otherwise. 497 bool do_full_collection(bool explicit_gc, 498 bool clear_all_soft_refs); 499 500 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 501 virtual void do_full_collection(bool clear_all_soft_refs); 502 503 // Resize the heap if necessary after a full collection. 504 void resize_if_necessary_after_full_collection(); 505 506 // Callback from VM_G1CollectForAllocation operation. 507 // This function does everything necessary/possible to satisfy a 508 // failed allocation request (including collection, expansion, etc.) 509 HeapWord* satisfy_failed_allocation(size_t word_size, 510 AllocationContext_t context, 511 bool* succeeded); 512 private: 513 // Helper method for satisfy_failed_allocation() 514 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 515 AllocationContext_t context, 516 bool do_gc, 517 bool clear_all_soft_refs, 518 bool expect_null_mutator_alloc_region, 519 bool* gc_succeeded); 520 521 protected: 522 // Attempting to expand the heap sufficiently 523 // to support an allocation of the given "word_size". If 524 // successful, perform the allocation and return the address of the 525 // allocated block, or else "NULL". 526 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 527 528 // Preserve any referents discovered by concurrent marking that have not yet been 529 // copied by the STW pause. 530 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states); 531 // Process any reference objects discovered during 532 // an incremental evacuation pause. 533 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 534 535 // Enqueue any remaining discovered references 536 // after processing. 537 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 538 539 // Merges the information gathered on a per-thread basis for all worker threads 540 // during GC into global variables. 541 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states); 542 public: 543 WorkGang* workers() const { return _workers; } 544 545 G1Allocator* allocator() { 546 return _allocator; 547 } 548 549 G1HeapVerifier* verifier() { 550 return _verifier; 551 } 552 553 G1MonitoringSupport* g1mm() { 554 assert(_g1mm != NULL, "should have been initialized"); 555 return _g1mm; 556 } 557 558 // Expand the garbage-first heap by at least the given size (in bytes!). 559 // Returns true if the heap was expanded by the requested amount; 560 // false otherwise. 561 // (Rounds up to a HeapRegion boundary.) 562 bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL); 563 564 // Returns the PLAB statistics for a given destination. 565 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 566 567 // Determines PLAB size for a given destination. 568 inline size_t desired_plab_sz(InCSetState dest); 569 570 inline AllocationContextStats& allocation_context_stats(); 571 572 // Do anything common to GC's. 573 void gc_prologue(bool full); 574 void gc_epilogue(bool full); 575 576 // Modify the reclaim candidate set and test for presence. 577 // These are only valid for starts_humongous regions. 578 inline void set_humongous_reclaim_candidate(uint region, bool value); 579 inline bool is_humongous_reclaim_candidate(uint region); 580 581 // Remove from the reclaim candidate set. Also remove from the 582 // collection set so that later encounters avoid the slow path. 583 inline void set_humongous_is_live(oop obj); 584 585 // Register the given region to be part of the collection set. 586 inline void register_humongous_region_with_cset(uint index); 587 // Register regions with humongous objects (actually on the start region) in 588 // the in_cset_fast_test table. 589 void register_humongous_regions_with_cset(); 590 // We register a region with the fast "in collection set" test. We 591 // simply set to true the array slot corresponding to this region. 592 void register_young_region_with_cset(HeapRegion* r) { 593 _in_cset_fast_test.set_in_young(r->hrm_index()); 594 } 595 void register_old_region_with_cset(HeapRegion* r) { 596 _in_cset_fast_test.set_in_old(r->hrm_index()); 597 } 598 inline void register_ext_region_with_cset(HeapRegion* r) { 599 _in_cset_fast_test.set_ext(r->hrm_index()); 600 } 601 void clear_in_cset(const HeapRegion* hr) { 602 _in_cset_fast_test.clear(hr); 603 } 604 605 void clear_cset_fast_test() { 606 _in_cset_fast_test.clear(); 607 } 608 609 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 610 611 // This is called at the start of either a concurrent cycle or a Full 612 // GC to update the number of old marking cycles started. 613 void increment_old_marking_cycles_started(); 614 615 // This is called at the end of either a concurrent cycle or a Full 616 // GC to update the number of old marking cycles completed. Those two 617 // can happen in a nested fashion, i.e., we start a concurrent 618 // cycle, a Full GC happens half-way through it which ends first, 619 // and then the cycle notices that a Full GC happened and ends 620 // too. The concurrent parameter is a boolean to help us do a bit 621 // tighter consistency checking in the method. If concurrent is 622 // false, the caller is the inner caller in the nesting (i.e., the 623 // Full GC). If concurrent is true, the caller is the outer caller 624 // in this nesting (i.e., the concurrent cycle). Further nesting is 625 // not currently supported. The end of this call also notifies 626 // the FullGCCount_lock in case a Java thread is waiting for a full 627 // GC to happen (e.g., it called System.gc() with 628 // +ExplicitGCInvokesConcurrent). 629 void increment_old_marking_cycles_completed(bool concurrent); 630 631 uint old_marking_cycles_completed() { 632 return _old_marking_cycles_completed; 633 } 634 635 G1HRPrinter* hr_printer() { return &_hr_printer; } 636 637 // Allocates a new heap region instance. 638 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 639 640 // Allocate the highest free region in the reserved heap. This will commit 641 // regions as necessary. 642 HeapRegion* alloc_highest_free_region(); 643 644 // Frees a non-humongous region by initializing its contents and 645 // adding it to the free list that's passed as a parameter (this is 646 // usually a local list which will be appended to the master free 647 // list later). The used bytes of freed regions are accumulated in 648 // pre_used. If skip_remset is true, the region's RSet will not be freed 649 // up. If skip_hot_card_cache is true, the region's hot card cache will not 650 // be freed up. The assumption is that this will be done later. 651 // The locked parameter indicates if the caller has already taken 652 // care of proper synchronization. This may allow some optimizations. 653 void free_region(HeapRegion* hr, 654 FreeRegionList* free_list, 655 bool skip_remset, 656 bool skip_hot_card_cache = false, 657 bool locked = false); 658 659 // It dirties the cards that cover the block so that the post 660 // write barrier never queues anything when updating objects on this 661 // block. It is assumed (and in fact we assert) that the block 662 // belongs to a young region. 663 inline void dirty_young_block(HeapWord* start, size_t word_size); 664 665 // Frees a humongous region by collapsing it into individual regions 666 // and calling free_region() for each of them. The freed regions 667 // will be added to the free list that's passed as a parameter (this 668 // is usually a local list which will be appended to the master free 669 // list later). The used bytes of freed regions are accumulated in 670 // pre_used. If skip_remset is true, the region's RSet will not be freed 671 // up. The assumption is that this will be done later. 672 void free_humongous_region(HeapRegion* hr, 673 FreeRegionList* free_list, 674 bool skip_remset); 675 676 // Facility for allocating in 'archive' regions in high heap memory and 677 // recording the allocated ranges. These should all be called from the 678 // VM thread at safepoints, without the heap lock held. They can be used 679 // to create and archive a set of heap regions which can be mapped at the 680 // same fixed addresses in a subsequent JVM invocation. 681 void begin_archive_alloc_range(); 682 683 // Check if the requested size would be too large for an archive allocation. 684 bool is_archive_alloc_too_large(size_t word_size); 685 686 // Allocate memory of the requested size from the archive region. This will 687 // return NULL if the size is too large or if no memory is available. It 688 // does not trigger a garbage collection. 689 HeapWord* archive_mem_allocate(size_t word_size); 690 691 // Optionally aligns the end address and returns the allocated ranges in 692 // an array of MemRegions in order of ascending addresses. 693 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 694 size_t end_alignment_in_bytes = 0); 695 696 // Facility for allocating a fixed range within the heap and marking 697 // the containing regions as 'archive'. For use at JVM init time, when the 698 // caller may mmap archived heap data at the specified range(s). 699 // Verify that the MemRegions specified in the argument array are within the 700 // reserved heap. 701 bool check_archive_addresses(MemRegion* range, size_t count); 702 703 // Commit the appropriate G1 regions containing the specified MemRegions 704 // and mark them as 'archive' regions. The regions in the array must be 705 // non-overlapping and in order of ascending address. 706 bool alloc_archive_regions(MemRegion* range, size_t count); 707 708 // Insert any required filler objects in the G1 regions around the specified 709 // ranges to make the regions parseable. This must be called after 710 // alloc_archive_regions, and after class loading has occurred. 711 void fill_archive_regions(MemRegion* range, size_t count); 712 713 // For each of the specified MemRegions, uncommit the containing G1 regions 714 // which had been allocated by alloc_archive_regions. This should be called 715 // rather than fill_archive_regions at JVM init time if the archive file 716 // mapping failed, with the same non-overlapping and sorted MemRegion array. 717 void dealloc_archive_regions(MemRegion* range, size_t count); 718 719 protected: 720 721 // Shrink the garbage-first heap by at most the given size (in bytes!). 722 // (Rounds down to a HeapRegion boundary.) 723 virtual void shrink(size_t expand_bytes); 724 void shrink_helper(size_t expand_bytes); 725 726 #if TASKQUEUE_STATS 727 static void print_taskqueue_stats_hdr(outputStream* const st); 728 void print_taskqueue_stats() const; 729 void reset_taskqueue_stats(); 730 #endif // TASKQUEUE_STATS 731 732 // Schedule the VM operation that will do an evacuation pause to 733 // satisfy an allocation request of word_size. *succeeded will 734 // return whether the VM operation was successful (it did do an 735 // evacuation pause) or not (another thread beat us to it or the GC 736 // locker was active). Given that we should not be holding the 737 // Heap_lock when we enter this method, we will pass the 738 // gc_count_before (i.e., total_collections()) as a parameter since 739 // it has to be read while holding the Heap_lock. Currently, both 740 // methods that call do_collection_pause() release the Heap_lock 741 // before the call, so it's easy to read gc_count_before just before. 742 HeapWord* do_collection_pause(size_t word_size, 743 uint gc_count_before, 744 bool* succeeded, 745 GCCause::Cause gc_cause); 746 747 void wait_for_root_region_scanning(); 748 749 // The guts of the incremental collection pause, executed by the vm 750 // thread. It returns false if it is unable to do the collection due 751 // to the GC locker being active, true otherwise 752 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 753 754 // Actually do the work of evacuating the collection set. 755 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 756 757 void pre_evacuate_collection_set(); 758 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 759 760 // Print the header for the per-thread termination statistics. 761 static void print_termination_stats_hdr(); 762 // Print actual per-thread termination statistics. 763 void print_termination_stats(uint worker_id, 764 double elapsed_ms, 765 double strong_roots_ms, 766 double term_ms, 767 size_t term_attempts, 768 size_t alloc_buffer_waste, 769 size_t undo_waste) const; 770 // Update object copying statistics. 771 void record_obj_copy_mem_stats(); 772 773 // The hot card cache for remembered set insertion optimization. 774 G1HotCardCache* _hot_card_cache; 775 776 // The g1 remembered set of the heap. 777 G1RemSet* _g1_rem_set; 778 779 // A set of cards that cover the objects for which the Rsets should be updated 780 // concurrently after the collection. 781 DirtyCardQueueSet _dirty_card_queue_set; 782 783 // The closure used to refine a single card. 784 RefineCardTableEntryClosure* _refine_cte_cl; 785 786 // After a collection pause, convert the regions in the collection set into free 787 // regions. 788 void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 789 790 // Abandon the current collection set without recording policy 791 // statistics or updating free lists. 792 void abandon_collection_set(G1CollectionSet* collection_set); 793 794 // The concurrent marker (and the thread it runs in.) 795 G1ConcurrentMark* _cm; 796 ConcurrentMarkThread* _cmThread; 797 798 // The concurrent refiner. 799 ConcurrentG1Refine* _cg1r; 800 801 // The parallel task queues 802 RefToScanQueueSet *_task_queues; 803 804 // True iff a evacuation has failed in the current collection. 805 bool _evacuation_failed; 806 807 EvacuationFailedInfo* _evacuation_failed_info_array; 808 809 // Failed evacuations cause some logical from-space objects to have 810 // forwarding pointers to themselves. Reset them. 811 void remove_self_forwarding_pointers(); 812 813 // Restore the objects in the regions in the collection set after an 814 // evacuation failure. 815 void restore_after_evac_failure(); 816 817 PreservedMarksSet _preserved_marks_set; 818 819 // Preserve the mark of "obj", if necessary, in preparation for its mark 820 // word being overwritten with a self-forwarding-pointer. 821 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 822 823 #ifndef PRODUCT 824 // Support for forcing evacuation failures. Analogous to 825 // PromotionFailureALot for the other collectors. 826 827 // Records whether G1EvacuationFailureALot should be in effect 828 // for the current GC 829 bool _evacuation_failure_alot_for_current_gc; 830 831 // Used to record the GC number for interval checking when 832 // determining whether G1EvaucationFailureALot is in effect 833 // for the current GC. 834 size_t _evacuation_failure_alot_gc_number; 835 836 // Count of the number of evacuations between failures. 837 volatile size_t _evacuation_failure_alot_count; 838 839 // Set whether G1EvacuationFailureALot should be in effect 840 // for the current GC (based upon the type of GC and which 841 // command line flags are set); 842 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 843 bool during_initial_mark, 844 bool during_marking); 845 846 inline void set_evacuation_failure_alot_for_current_gc(); 847 848 // Return true if it's time to cause an evacuation failure. 849 inline bool evacuation_should_fail(); 850 851 // Reset the G1EvacuationFailureALot counters. Should be called at 852 // the end of an evacuation pause in which an evacuation failure occurred. 853 inline void reset_evacuation_should_fail(); 854 #endif // !PRODUCT 855 856 // ("Weak") Reference processing support. 857 // 858 // G1 has 2 instances of the reference processor class. One 859 // (_ref_processor_cm) handles reference object discovery 860 // and subsequent processing during concurrent marking cycles. 861 // 862 // The other (_ref_processor_stw) handles reference object 863 // discovery and processing during full GCs and incremental 864 // evacuation pauses. 865 // 866 // During an incremental pause, reference discovery will be 867 // temporarily disabled for _ref_processor_cm and will be 868 // enabled for _ref_processor_stw. At the end of the evacuation 869 // pause references discovered by _ref_processor_stw will be 870 // processed and discovery will be disabled. The previous 871 // setting for reference object discovery for _ref_processor_cm 872 // will be re-instated. 873 // 874 // At the start of marking: 875 // * Discovery by the CM ref processor is verified to be inactive 876 // and it's discovered lists are empty. 877 // * Discovery by the CM ref processor is then enabled. 878 // 879 // At the end of marking: 880 // * Any references on the CM ref processor's discovered 881 // lists are processed (possibly MT). 882 // 883 // At the start of full GC we: 884 // * Disable discovery by the CM ref processor and 885 // empty CM ref processor's discovered lists 886 // (without processing any entries). 887 // * Verify that the STW ref processor is inactive and it's 888 // discovered lists are empty. 889 // * Temporarily set STW ref processor discovery as single threaded. 890 // * Temporarily clear the STW ref processor's _is_alive_non_header 891 // field. 892 // * Finally enable discovery by the STW ref processor. 893 // 894 // The STW ref processor is used to record any discovered 895 // references during the full GC. 896 // 897 // At the end of a full GC we: 898 // * Enqueue any reference objects discovered by the STW ref processor 899 // that have non-live referents. This has the side-effect of 900 // making the STW ref processor inactive by disabling discovery. 901 // * Verify that the CM ref processor is still inactive 902 // and no references have been placed on it's discovered 903 // lists (also checked as a precondition during initial marking). 904 905 // The (stw) reference processor... 906 ReferenceProcessor* _ref_processor_stw; 907 908 STWGCTimer* _gc_timer_stw; 909 910 G1NewTracer* _gc_tracer_stw; 911 912 // During reference object discovery, the _is_alive_non_header 913 // closure (if non-null) is applied to the referent object to 914 // determine whether the referent is live. If so then the 915 // reference object does not need to be 'discovered' and can 916 // be treated as a regular oop. This has the benefit of reducing 917 // the number of 'discovered' reference objects that need to 918 // be processed. 919 // 920 // Instance of the is_alive closure for embedding into the 921 // STW reference processor as the _is_alive_non_header field. 922 // Supplying a value for the _is_alive_non_header field is 923 // optional but doing so prevents unnecessary additions to 924 // the discovered lists during reference discovery. 925 G1STWIsAliveClosure _is_alive_closure_stw; 926 927 // The (concurrent marking) reference processor... 928 ReferenceProcessor* _ref_processor_cm; 929 930 // Instance of the concurrent mark is_alive closure for embedding 931 // into the Concurrent Marking reference processor as the 932 // _is_alive_non_header field. Supplying a value for the 933 // _is_alive_non_header field is optional but doing so prevents 934 // unnecessary additions to the discovered lists during reference 935 // discovery. 936 G1CMIsAliveClosure _is_alive_closure_cm; 937 938 volatile bool _free_regions_coming; 939 940 public: 941 942 void set_refine_cte_cl_concurrency(bool concurrent); 943 944 RefToScanQueue *task_queue(uint i) const; 945 946 uint num_task_queues() const; 947 948 // A set of cards where updates happened during the GC 949 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 950 951 // Create a G1CollectedHeap with the specified policy. 952 // Must call the initialize method afterwards. 953 // May not return if something goes wrong. 954 G1CollectedHeap(G1CollectorPolicy* policy); 955 956 // Initialize the G1CollectedHeap to have the initial and 957 // maximum sizes and remembered and barrier sets 958 // specified by the policy object. 959 jint initialize(); 960 961 virtual void stop(); 962 963 // Does operations required after initialization has been done. 964 void post_initialize(); 965 966 // Initialize weak reference processing. 967 void ref_processing_init(); 968 969 virtual Name kind() const { 970 return CollectedHeap::G1CollectedHeap; 971 } 972 973 virtual const char* name() const { 974 return "G1"; 975 } 976 977 const G1CollectorState* collector_state() const { return &_collector_state; } 978 G1CollectorState* collector_state() { return &_collector_state; } 979 980 // The current policy object for the collector. 981 G1Policy* g1_policy() const { return _g1_policy; } 982 983 const G1CollectionSet* collection_set() const { return &_collection_set; } 984 G1CollectionSet* collection_set() { return &_collection_set; } 985 986 virtual CollectorPolicy* collector_policy() const; 987 988 // Adaptive size policy. No such thing for g1. 989 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 990 991 // The rem set and barrier set. 992 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 993 994 // Try to minimize the remembered set. 995 void scrub_rem_set(); 996 997 uint get_gc_time_stamp() { 998 return _gc_time_stamp; 999 } 1000 1001 inline void reset_gc_time_stamp(); 1002 1003 void check_gc_time_stamps() PRODUCT_RETURN; 1004 1005 inline void increment_gc_time_stamp(); 1006 1007 // Reset the given region's GC timestamp. If it's starts humongous, 1008 // also reset the GC timestamp of its corresponding 1009 // continues humongous regions too. 1010 void reset_gc_time_stamps(HeapRegion* hr); 1011 1012 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1013 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1014 1015 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1016 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1017 1018 // The shared block offset table array. 1019 G1BlockOffsetTable* bot() const { return _bot; } 1020 1021 // Reference Processing accessors 1022 1023 // The STW reference processor.... 1024 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1025 1026 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1027 1028 // The Concurrent Marking reference processor... 1029 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1030 1031 virtual size_t capacity() const; 1032 virtual size_t used() const; 1033 // This should be called when we're not holding the heap lock. The 1034 // result might be a bit inaccurate. 1035 size_t used_unlocked() const; 1036 size_t recalculate_used() const; 1037 1038 // These virtual functions do the actual allocation. 1039 // Some heaps may offer a contiguous region for shared non-blocking 1040 // allocation, via inlined code (by exporting the address of the top and 1041 // end fields defining the extent of the contiguous allocation region.) 1042 // But G1CollectedHeap doesn't yet support this. 1043 1044 virtual bool is_maximal_no_gc() const { 1045 return _hrm.available() == 0; 1046 } 1047 1048 // The current number of regions in the heap. 1049 uint num_regions() const { return _hrm.length(); } 1050 1051 // The max number of regions in the heap. 1052 uint max_regions() const { return _hrm.max_length(); } 1053 1054 // The number of regions that are completely free. 1055 uint num_free_regions() const { return _hrm.num_free_regions(); } 1056 1057 MemoryUsage get_auxiliary_data_memory_usage() const { 1058 return _hrm.get_auxiliary_data_memory_usage(); 1059 } 1060 1061 // The number of regions that are not completely free. 1062 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1063 1064 #ifdef ASSERT 1065 bool is_on_master_free_list(HeapRegion* hr) { 1066 return _hrm.is_free(hr); 1067 } 1068 #endif // ASSERT 1069 1070 // Wrapper for the region list operations that can be called from 1071 // methods outside this class. 1072 1073 void secondary_free_list_add(FreeRegionList* list) { 1074 _secondary_free_list.add_ordered(list); 1075 } 1076 1077 void append_secondary_free_list() { 1078 _hrm.insert_list_into_free_list(&_secondary_free_list); 1079 } 1080 1081 void append_secondary_free_list_if_not_empty_with_lock() { 1082 // If the secondary free list looks empty there's no reason to 1083 // take the lock and then try to append it. 1084 if (!_secondary_free_list.is_empty()) { 1085 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1086 append_secondary_free_list(); 1087 } 1088 } 1089 1090 inline void old_set_add(HeapRegion* hr); 1091 inline void old_set_remove(HeapRegion* hr); 1092 1093 size_t non_young_capacity_bytes() { 1094 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes; 1095 } 1096 1097 void set_free_regions_coming(); 1098 void reset_free_regions_coming(); 1099 bool free_regions_coming() { return _free_regions_coming; } 1100 void wait_while_free_regions_coming(); 1101 1102 // Determine whether the given region is one that we are using as an 1103 // old GC alloc region. 1104 bool is_old_gc_alloc_region(HeapRegion* hr); 1105 1106 // Perform a collection of the heap; intended for use in implementing 1107 // "System.gc". This probably implies as full a collection as the 1108 // "CollectedHeap" supports. 1109 virtual void collect(GCCause::Cause cause); 1110 1111 virtual bool copy_allocation_context_stats(const jint* contexts, 1112 jlong* totals, 1113 jbyte* accuracy, 1114 jint len); 1115 1116 // True iff an evacuation has failed in the most-recent collection. 1117 bool evacuation_failed() { return _evacuation_failed; } 1118 1119 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed); 1120 void prepend_to_freelist(FreeRegionList* list); 1121 void decrement_summary_bytes(size_t bytes); 1122 1123 virtual bool is_in(const void* p) const; 1124 #ifdef ASSERT 1125 // Returns whether p is in one of the available areas of the heap. Slow but 1126 // extensive version. 1127 bool is_in_exact(const void* p) const; 1128 #endif 1129 1130 // Return "TRUE" iff the given object address is within the collection 1131 // set. Assumes that the reference points into the heap. 1132 inline bool is_in_cset(const HeapRegion *hr); 1133 inline bool is_in_cset(oop obj); 1134 1135 inline bool is_in_cset_or_humongous(const oop obj); 1136 1137 private: 1138 // This array is used for a quick test on whether a reference points into 1139 // the collection set or not. Each of the array's elements denotes whether the 1140 // corresponding region is in the collection set or not. 1141 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1142 1143 public: 1144 1145 inline InCSetState in_cset_state(const oop obj); 1146 1147 // Return "TRUE" iff the given object address is in the reserved 1148 // region of g1. 1149 bool is_in_g1_reserved(const void* p) const { 1150 return _hrm.reserved().contains(p); 1151 } 1152 1153 // Returns a MemRegion that corresponds to the space that has been 1154 // reserved for the heap 1155 MemRegion g1_reserved() const { 1156 return _hrm.reserved(); 1157 } 1158 1159 virtual bool is_in_closed_subset(const void* p) const; 1160 1161 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1162 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1163 } 1164 1165 // Iteration functions. 1166 1167 // Iterate over all objects, calling "cl.do_object" on each. 1168 virtual void object_iterate(ObjectClosure* cl); 1169 1170 virtual void safe_object_iterate(ObjectClosure* cl) { 1171 object_iterate(cl); 1172 } 1173 1174 // Iterate over heap regions, in address order, terminating the 1175 // iteration early if the "doHeapRegion" method returns "true". 1176 void heap_region_iterate(HeapRegionClosure* blk) const; 1177 1178 // Return the region with the given index. It assumes the index is valid. 1179 inline HeapRegion* region_at(uint index) const; 1180 1181 // Return the next region (by index) that is part of the same 1182 // humongous object that hr is part of. 1183 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1184 1185 // Calculate the region index of the given address. Given address must be 1186 // within the heap. 1187 inline uint addr_to_region(HeapWord* addr) const; 1188 1189 inline HeapWord* bottom_addr_for_region(uint index) const; 1190 1191 // Iterate over the heap regions in parallel. Assumes that this will be called 1192 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1193 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1194 // to each of the regions, by attempting to claim the region using the 1195 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1196 // region. The concurrent argument should be set to true if iteration is 1197 // performed concurrently, during which no assumptions are made for consistent 1198 // attributes of the heap regions (as they might be modified while iterating). 1199 void heap_region_par_iterate(HeapRegionClosure* cl, 1200 uint worker_id, 1201 HeapRegionClaimer* hrclaimer, 1202 bool concurrent = false) const; 1203 1204 // Iterate over the regions (if any) in the current collection set. 1205 void collection_set_iterate(HeapRegionClosure* blk); 1206 1207 // Iterate over the regions (if any) in the current collection set. Starts the 1208 // iteration over the entire collection set so that the start regions of a given 1209 // worker id over the set active_workers are evenly spread across the set of 1210 // collection set regions. 1211 void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id); 1212 1213 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1214 1215 // Returns the HeapRegion that contains addr. addr must not be NULL. 1216 template <class T> 1217 inline HeapRegion* heap_region_containing(const T addr) const; 1218 1219 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1220 // each address in the (reserved) heap is a member of exactly 1221 // one block. The defining characteristic of a block is that it is 1222 // possible to find its size, and thus to progress forward to the next 1223 // block. (Blocks may be of different sizes.) Thus, blocks may 1224 // represent Java objects, or they might be free blocks in a 1225 // free-list-based heap (or subheap), as long as the two kinds are 1226 // distinguishable and the size of each is determinable. 1227 1228 // Returns the address of the start of the "block" that contains the 1229 // address "addr". We say "blocks" instead of "object" since some heaps 1230 // may not pack objects densely; a chunk may either be an object or a 1231 // non-object. 1232 virtual HeapWord* block_start(const void* addr) const; 1233 1234 // Requires "addr" to be the start of a chunk, and returns its size. 1235 // "addr + size" is required to be the start of a new chunk, or the end 1236 // of the active area of the heap. 1237 virtual size_t block_size(const HeapWord* addr) const; 1238 1239 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1240 // the block is an object. 1241 virtual bool block_is_obj(const HeapWord* addr) const; 1242 1243 // Section on thread-local allocation buffers (TLABs) 1244 // See CollectedHeap for semantics. 1245 1246 bool supports_tlab_allocation() const; 1247 size_t tlab_capacity(Thread* ignored) const; 1248 size_t tlab_used(Thread* ignored) const; 1249 size_t max_tlab_size() const; 1250 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1251 1252 // Can a compiler initialize a new object without store barriers? 1253 // This permission only extends from the creation of a new object 1254 // via a TLAB up to the first subsequent safepoint. If such permission 1255 // is granted for this heap type, the compiler promises to call 1256 // defer_store_barrier() below on any slow path allocation of 1257 // a new object for which such initializing store barriers will 1258 // have been elided. G1, like CMS, allows this, but should be 1259 // ready to provide a compensating write barrier as necessary 1260 // if that storage came out of a non-young region. The efficiency 1261 // of this implementation depends crucially on being able to 1262 // answer very efficiently in constant time whether a piece of 1263 // storage in the heap comes from a young region or not. 1264 // See ReduceInitialCardMarks. 1265 virtual bool can_elide_tlab_store_barriers() const { 1266 return true; 1267 } 1268 1269 virtual bool card_mark_must_follow_store() const { 1270 return true; 1271 } 1272 1273 inline bool is_in_young(const oop obj); 1274 1275 virtual bool is_scavengable(const void* addr); 1276 1277 // We don't need barriers for initializing stores to objects 1278 // in the young gen: for the SATB pre-barrier, there is no 1279 // pre-value that needs to be remembered; for the remembered-set 1280 // update logging post-barrier, we don't maintain remembered set 1281 // information for young gen objects. 1282 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1283 1284 // Returns "true" iff the given word_size is "very large". 1285 static bool is_humongous(size_t word_size) { 1286 // Note this has to be strictly greater-than as the TLABs 1287 // are capped at the humongous threshold and we want to 1288 // ensure that we don't try to allocate a TLAB as 1289 // humongous and that we don't allocate a humongous 1290 // object in a TLAB. 1291 return word_size > _humongous_object_threshold_in_words; 1292 } 1293 1294 // Returns the humongous threshold for a specific region size 1295 static size_t humongous_threshold_for(size_t region_size) { 1296 return (region_size / 2); 1297 } 1298 1299 // Returns the number of regions the humongous object of the given word size 1300 // requires. 1301 static size_t humongous_obj_size_in_regions(size_t word_size); 1302 1303 // Print the maximum heap capacity. 1304 virtual size_t max_capacity() const; 1305 1306 virtual jlong millis_since_last_gc(); 1307 1308 1309 // Convenience function to be used in situations where the heap type can be 1310 // asserted to be this type. 1311 static G1CollectedHeap* heap(); 1312 1313 void set_region_short_lived_locked(HeapRegion* hr); 1314 // add appropriate methods for any other surv rate groups 1315 1316 const G1SurvivorRegions* survivor() const { return &_survivor; } 1317 1318 uint survivor_regions_count() const { 1319 return _survivor.length(); 1320 } 1321 1322 uint eden_regions_count() const { 1323 return _eden.length(); 1324 } 1325 1326 uint young_regions_count() const { 1327 return _eden.length() + _survivor.length(); 1328 } 1329 1330 uint old_regions_count() const { return _old_set.length(); } 1331 1332 uint humongous_regions_count() const { return _humongous_set.length(); } 1333 1334 #ifdef ASSERT 1335 bool check_young_list_empty(); 1336 #endif 1337 1338 // *** Stuff related to concurrent marking. It's not clear to me that so 1339 // many of these need to be public. 1340 1341 // The functions below are helper functions that a subclass of 1342 // "CollectedHeap" can use in the implementation of its virtual 1343 // functions. 1344 // This performs a concurrent marking of the live objects in a 1345 // bitmap off to the side. 1346 void doConcurrentMark(); 1347 1348 bool isMarkedPrev(oop obj) const; 1349 bool isMarkedNext(oop obj) const; 1350 1351 // Determine if an object is dead, given the object and also 1352 // the region to which the object belongs. An object is dead 1353 // iff a) it was not allocated since the last mark, b) it 1354 // is not marked, and c) it is not in an archive region. 1355 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1356 return 1357 !hr->obj_allocated_since_prev_marking(obj) && 1358 !isMarkedPrev(obj) && 1359 !hr->is_archive(); 1360 } 1361 1362 // This function returns true when an object has been 1363 // around since the previous marking and hasn't yet 1364 // been marked during this marking, and is not in an archive region. 1365 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1366 return 1367 !hr->obj_allocated_since_next_marking(obj) && 1368 !isMarkedNext(obj) && 1369 !hr->is_archive(); 1370 } 1371 1372 // Determine if an object is dead, given only the object itself. 1373 // This will find the region to which the object belongs and 1374 // then call the region version of the same function. 1375 1376 // Added if it is NULL it isn't dead. 1377 1378 inline bool is_obj_dead(const oop obj) const; 1379 1380 inline bool is_obj_ill(const oop obj) const; 1381 1382 G1ConcurrentMark* concurrent_mark() const { return _cm; } 1383 1384 // Refinement 1385 1386 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1387 1388 // Optimized nmethod scanning support routines 1389 1390 // Register the given nmethod with the G1 heap. 1391 virtual void register_nmethod(nmethod* nm); 1392 1393 // Unregister the given nmethod from the G1 heap. 1394 virtual void unregister_nmethod(nmethod* nm); 1395 1396 // Free up superfluous code root memory. 1397 void purge_code_root_memory(); 1398 1399 // Rebuild the strong code root lists for each region 1400 // after a full GC. 1401 void rebuild_strong_code_roots(); 1402 1403 // Partial cleaning used when class unloading is disabled. 1404 // Let the caller choose what structures to clean out: 1405 // - StringTable 1406 // - SymbolTable 1407 // - StringDeduplication structures 1408 void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup); 1409 1410 // Complete cleaning used when class unloading is enabled. 1411 // Cleans out all structures handled by partial_cleaning and also the CodeCache. 1412 void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred); 1413 1414 // Redirty logged cards in the refinement queue. 1415 void redirty_logged_cards(); 1416 // Verification 1417 1418 // Perform any cleanup actions necessary before allowing a verification. 1419 virtual void prepare_for_verify(); 1420 1421 // Perform verification. 1422 1423 // vo == UsePrevMarking -> use "prev" marking information, 1424 // vo == UseNextMarking -> use "next" marking information 1425 // vo == UseMarkWord -> use the mark word in the object header 1426 // 1427 // NOTE: Only the "prev" marking information is guaranteed to be 1428 // consistent most of the time, so most calls to this should use 1429 // vo == UsePrevMarking. 1430 // Currently, there is only one case where this is called with 1431 // vo == UseNextMarking, which is to verify the "next" marking 1432 // information at the end of remark. 1433 // Currently there is only one place where this is called with 1434 // vo == UseMarkWord, which is to verify the marking during a 1435 // full GC. 1436 void verify(VerifyOption vo); 1437 1438 // The methods below are here for convenience and dispatch the 1439 // appropriate method depending on value of the given VerifyOption 1440 // parameter. The values for that parameter, and their meanings, 1441 // are the same as those above. 1442 1443 bool is_obj_dead_cond(const oop obj, 1444 const HeapRegion* hr, 1445 const VerifyOption vo) const; 1446 1447 bool is_obj_dead_cond(const oop obj, 1448 const VerifyOption vo) const; 1449 1450 G1HeapSummary create_g1_heap_summary(); 1451 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1452 1453 // Printing 1454 private: 1455 void print_heap_regions() const; 1456 void print_regions_on(outputStream* st) const; 1457 1458 public: 1459 virtual void print_on(outputStream* st) const; 1460 virtual void print_extended_on(outputStream* st) const; 1461 virtual void print_on_error(outputStream* st) const; 1462 1463 virtual void print_gc_threads_on(outputStream* st) const; 1464 virtual void gc_threads_do(ThreadClosure* tc) const; 1465 1466 // Override 1467 void print_tracing_info() const; 1468 1469 // The following two methods are helpful for debugging RSet issues. 1470 void print_cset_rsets() PRODUCT_RETURN; 1471 void print_all_rsets() PRODUCT_RETURN; 1472 1473 public: 1474 size_t pending_card_num(); 1475 1476 protected: 1477 size_t _max_heap_capacity; 1478 }; 1479 1480 class G1ParEvacuateFollowersClosure : public VoidClosure { 1481 private: 1482 double _start_term; 1483 double _term_time; 1484 size_t _term_attempts; 1485 1486 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1487 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1488 protected: 1489 G1CollectedHeap* _g1h; 1490 G1ParScanThreadState* _par_scan_state; 1491 RefToScanQueueSet* _queues; 1492 ParallelTaskTerminator* _terminator; 1493 1494 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1495 RefToScanQueueSet* queues() { return _queues; } 1496 ParallelTaskTerminator* terminator() { return _terminator; } 1497 1498 public: 1499 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1500 G1ParScanThreadState* par_scan_state, 1501 RefToScanQueueSet* queues, 1502 ParallelTaskTerminator* terminator) 1503 : _g1h(g1h), _par_scan_state(par_scan_state), 1504 _queues(queues), _terminator(terminator), 1505 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1506 1507 void do_void(); 1508 1509 double term_time() const { return _term_time; } 1510 size_t term_attempts() const { return _term_attempts; } 1511 1512 private: 1513 inline bool offer_termination(); 1514 }; 1515 1516 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP