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 G1ParScanThreadState; 64 class G1ParScanThreadStateSet; 65 class G1KlassScanClosure; 66 class G1ParScanThreadState; 67 class ObjectClosure; 68 class SpaceClosure; 69 class CompactibleSpaceClosure; 70 class Space; 71 class G1CollectionSet; 72 class G1CollectorPolicy; 73 class G1Policy; 74 class G1HotCardCache; 75 class G1RemSet; 76 class HeapRegionRemSetIterator; 77 class G1ConcurrentMark; 78 class ConcurrentMarkThread; 79 class ConcurrentG1Refine; 80 class GenerationCounters; 81 class STWGCTimer; 82 class G1NewTracer; 83 class EvacuationFailedInfo; 84 class nmethod; 85 class Ticks; 86 class WorkGang; 87 class G1Allocator; 88 class G1ArchiveAllocator; 89 class G1HeapVerifier; 90 class G1HeapSizingPolicy; 91 class G1HeapSummary; 92 class G1EvacSummary; 93 94 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 95 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 96 97 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 98 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 99 100 // The G1 STW is alive closure. 101 // An instance is embedded into the G1CH and used as the 102 // (optional) _is_alive_non_header closure in the STW 103 // reference processor. It is also extensively used during 104 // reference processing during STW evacuation pauses. 105 class G1STWIsAliveClosure: public BoolObjectClosure { 106 G1CollectedHeap* _g1; 107 public: 108 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 109 bool do_object_b(oop p); 110 }; 111 112 class G1RegionMappingChangedListener : public G1MappingChangedListener { 113 private: 114 void reset_from_card_cache(uint start_idx, size_t num_regions); 115 public: 116 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 117 }; 118 119 class G1CollectedHeap : public CollectedHeap { 120 friend class G1FreeCollectionSetTask; 121 friend class VM_CollectForMetadataAllocation; 122 friend class VM_G1CollectForAllocation; 123 friend class VM_G1CollectFull; 124 friend class VM_G1IncCollectionPause; 125 friend class VMStructs; 126 friend class MutatorAllocRegion; 127 friend class G1GCAllocRegion; 128 friend class G1HeapVerifier; 129 130 // Closures used in implementation. 131 friend class G1ParScanThreadState; 132 friend class G1ParScanThreadStateSet; 133 friend class G1ParTask; 134 friend class G1PLABAllocator; 135 friend class G1PrepareCompactClosure; 136 137 // Other related classes. 138 friend class HeapRegionClaimer; 139 140 // Testing classes. 141 friend class G1CheckCSetFastTableClosure; 142 143 private: 144 WorkGang* _workers; 145 G1CollectorPolicy* _collector_policy; 146 147 static size_t _humongous_object_threshold_in_words; 148 149 // The secondary free list which contains regions that have been 150 // freed up during the cleanup process. This will be appended to 151 // the master free list when appropriate. 152 FreeRegionList _secondary_free_list; 153 154 // It keeps track of the old regions. 155 HeapRegionSet _old_set; 156 157 // It keeps track of the humongous regions. 158 HeapRegionSet _humongous_set; 159 160 void eagerly_reclaim_humongous_regions(); 161 // Start a new incremental collection set for the next pause. 162 void start_new_collection_set(); 163 164 // The number of regions we could create by expansion. 165 uint _expansion_regions; 166 167 // The block offset table for the G1 heap. 168 G1BlockOffsetTable* _bot; 169 170 // Tears down the region sets / lists so that they are empty and the 171 // regions on the heap do not belong to a region set / list. The 172 // only exception is the humongous set which we leave unaltered. If 173 // free_list_only is true, it will only tear down the master free 174 // list. It is called before a Full GC (free_list_only == false) or 175 // before heap shrinking (free_list_only == true). 176 void tear_down_region_sets(bool free_list_only); 177 178 // Rebuilds the region sets / lists so that they are repopulated to 179 // reflect the contents of the heap. The only exception is the 180 // humongous set which was not torn down in the first place. If 181 // free_list_only is true, it will only rebuild the master free 182 // list. It is called after a Full GC (free_list_only == false) or 183 // after heap shrinking (free_list_only == true). 184 void rebuild_region_sets(bool free_list_only); 185 186 // Callback for region mapping changed events. 187 G1RegionMappingChangedListener _listener; 188 189 // The sequence of all heap regions in the heap. 190 HeapRegionManager _hrm; 191 192 // Manages all allocations with regions except humongous object allocations. 193 G1Allocator* _allocator; 194 195 // Manages all heap verification. 196 G1HeapVerifier* _verifier; 197 198 // Outside of GC pauses, the number of bytes used in all regions other 199 // than the current allocation region(s). 200 size_t _summary_bytes_used; 201 202 void increase_used(size_t bytes); 203 void decrease_used(size_t bytes); 204 205 void set_used(size_t bytes); 206 207 // Class that handles archive allocation ranges. 208 G1ArchiveAllocator* _archive_allocator; 209 210 // Statistics for each allocation context 211 AllocationContextStats _allocation_context_stats; 212 213 // GC allocation statistics policy for survivors. 214 G1EvacStats _survivor_evac_stats; 215 216 // GC allocation statistics policy for tenured objects. 217 G1EvacStats _old_evac_stats; 218 219 // It specifies whether we should attempt to expand the heap after a 220 // region allocation failure. If heap expansion fails we set this to 221 // false so that we don't re-attempt the heap expansion (it's likely 222 // that subsequent expansion attempts will also fail if one fails). 223 // Currently, it is only consulted during GC and it's reset at the 224 // start of each GC. 225 bool _expand_heap_after_alloc_failure; 226 227 // Helper for monitoring and management support. 228 G1MonitoringSupport* _g1mm; 229 230 // Records whether the region at the given index is (still) a 231 // candidate for eager reclaim. Only valid for humongous start 232 // regions; other regions have unspecified values. Humongous start 233 // regions are initialized at start of collection pause, with 234 // candidates removed from the set as they are found reachable from 235 // roots or the young generation. 236 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 237 protected: 238 bool default_value() const { return false; } 239 public: 240 void clear() { G1BiasedMappedArray<bool>::clear(); } 241 void set_candidate(uint region, bool value) { 242 set_by_index(region, value); 243 } 244 bool is_candidate(uint region) { 245 return get_by_index(region); 246 } 247 }; 248 249 HumongousReclaimCandidates _humongous_reclaim_candidates; 250 // Stores whether during humongous object registration we found candidate regions. 251 // If not, we can skip a few steps. 252 bool _has_humongous_reclaim_candidates; 253 254 volatile uint _gc_time_stamp; 255 256 G1HRPrinter _hr_printer; 257 258 // It decides whether an explicit GC should start a concurrent cycle 259 // instead of doing a STW GC. Currently, a concurrent cycle is 260 // explicitly started if: 261 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 262 // (b) cause == _g1_humongous_allocation 263 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 264 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 265 // (e) cause == _update_allocation_context_stats_inc 266 // (f) cause == _wb_conc_mark 267 bool should_do_concurrent_full_gc(GCCause::Cause cause); 268 269 // indicates whether we are in young or mixed GC mode 270 G1CollectorState _collector_state; 271 272 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 273 // concurrent cycles) we have started. 274 volatile uint _old_marking_cycles_started; 275 276 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 277 // concurrent cycles) we have completed. 278 volatile uint _old_marking_cycles_completed; 279 280 // This is a non-product method that is helpful for testing. It is 281 // called at the end of a GC and artificially expands the heap by 282 // allocating a number of dead regions. This way we can induce very 283 // frequent marking cycles and stress the cleanup / concurrent 284 // cleanup code more (as all the regions that will be allocated by 285 // this method will be found dead by the marking cycle). 286 void allocate_dummy_regions() PRODUCT_RETURN; 287 288 // Clear RSets after a compaction. It also resets the GC time stamps. 289 void clear_rsets_post_compaction(); 290 291 // If the HR printer is active, dump the state of the regions in the 292 // heap after a compaction. 293 void print_hrm_post_compaction(); 294 295 // Create a memory mapper for auxiliary data structures of the given size and 296 // translation factor. 297 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 298 size_t size, 299 size_t translation_factor); 300 301 static G1Policy* create_g1_policy(); 302 303 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 304 305 void process_weak_jni_handles(); 306 307 // These are macros so that, if the assert fires, we get the correct 308 // line number, file, etc. 309 310 #define heap_locking_asserts_params(_extra_message_) \ 311 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 312 (_extra_message_), \ 313 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 314 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 315 BOOL_TO_STR(Thread::current()->is_VM_thread()) 316 317 #define assert_heap_locked() \ 318 do { \ 319 assert(Heap_lock->owned_by_self(), \ 320 heap_locking_asserts_params("should be holding the Heap_lock")); \ 321 } while (0) 322 323 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 324 do { \ 325 assert(Heap_lock->owned_by_self() || \ 326 (SafepointSynchronize::is_at_safepoint() && \ 327 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 328 heap_locking_asserts_params("should be holding the Heap_lock or " \ 329 "should be at a safepoint")); \ 330 } while (0) 331 332 #define assert_heap_locked_and_not_at_safepoint() \ 333 do { \ 334 assert(Heap_lock->owned_by_self() && \ 335 !SafepointSynchronize::is_at_safepoint(), \ 336 heap_locking_asserts_params("should be holding the Heap_lock and " \ 337 "should not be at a safepoint")); \ 338 } while (0) 339 340 #define assert_heap_not_locked() \ 341 do { \ 342 assert(!Heap_lock->owned_by_self(), \ 343 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 344 } while (0) 345 346 #define assert_heap_not_locked_and_not_at_safepoint() \ 347 do { \ 348 assert(!Heap_lock->owned_by_self() && \ 349 !SafepointSynchronize::is_at_safepoint(), \ 350 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 351 "should not be at a safepoint")); \ 352 } while (0) 353 354 #define assert_at_safepoint(_should_be_vm_thread_) \ 355 do { \ 356 assert(SafepointSynchronize::is_at_safepoint() && \ 357 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 358 heap_locking_asserts_params("should be at a safepoint")); \ 359 } while (0) 360 361 #define assert_not_at_safepoint() \ 362 do { \ 363 assert(!SafepointSynchronize::is_at_safepoint(), \ 364 heap_locking_asserts_params("should not be at a safepoint")); \ 365 } while (0) 366 367 protected: 368 369 // The young region list. 370 G1EdenRegions _eden; 371 G1SurvivorRegions _survivor; 372 373 // The current policy object for the collector. 374 G1Policy* _g1_policy; 375 G1HeapSizingPolicy* _heap_sizing_policy; 376 377 G1CollectionSet _collection_set; 378 379 // This is the second level of trying to allocate a new region. If 380 // new_region() didn't find a region on the free_list, this call will 381 // check whether there's anything available on the 382 // secondary_free_list and/or wait for more regions to appear on 383 // that list, if _free_regions_coming is set. 384 HeapRegion* new_region_try_secondary_free_list(bool is_old); 385 386 // Try to allocate a single non-humongous HeapRegion sufficient for 387 // an allocation of the given word_size. If do_expand is true, 388 // attempt to expand the heap if necessary to satisfy the allocation 389 // request. If the region is to be used as an old region or for a 390 // humongous object, set is_old to true. If not, to false. 391 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 392 393 // Initialize a contiguous set of free regions of length num_regions 394 // and starting at index first so that they appear as a single 395 // humongous region. 396 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 397 uint num_regions, 398 size_t word_size, 399 AllocationContext_t context); 400 401 // Attempt to allocate a humongous object of the given size. Return 402 // NULL if unsuccessful. 403 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 404 405 // The following two methods, allocate_new_tlab() and 406 // mem_allocate(), are the two main entry points from the runtime 407 // into the G1's allocation routines. They have the following 408 // assumptions: 409 // 410 // * They should both be called outside safepoints. 411 // 412 // * They should both be called without holding the Heap_lock. 413 // 414 // * All allocation requests for new TLABs should go to 415 // allocate_new_tlab(). 416 // 417 // * All non-TLAB allocation requests should go to mem_allocate(). 418 // 419 // * If either call cannot satisfy the allocation request using the 420 // current allocating region, they will try to get a new one. If 421 // this fails, they will attempt to do an evacuation pause and 422 // retry the allocation. 423 // 424 // * If all allocation attempts fail, even after trying to schedule 425 // an evacuation pause, allocate_new_tlab() will return NULL, 426 // whereas mem_allocate() will attempt a heap expansion and/or 427 // schedule a Full GC. 428 // 429 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 430 // should never be called with word_size being humongous. All 431 // humongous allocation requests should go to mem_allocate() which 432 // will satisfy them with a special path. 433 434 virtual HeapWord* allocate_new_tlab(size_t word_size); 435 436 virtual HeapWord* mem_allocate(size_t word_size, 437 bool* gc_overhead_limit_was_exceeded); 438 439 // The following three methods take a gc_count_before_ret 440 // parameter which is used to return the GC count if the method 441 // returns NULL. Given that we are required to read the GC count 442 // while holding the Heap_lock, and these paths will take the 443 // Heap_lock at some point, it's easier to get them to read the GC 444 // count while holding the Heap_lock before they return NULL instead 445 // of the caller (namely: mem_allocate()) having to also take the 446 // Heap_lock just to read the GC count. 447 448 // First-level mutator allocation attempt: try to allocate out of 449 // the mutator alloc region without taking the Heap_lock. This 450 // should only be used for non-humongous allocations. 451 inline HeapWord* attempt_allocation(size_t word_size, 452 uint* gc_count_before_ret, 453 uint* gclocker_retry_count_ret); 454 455 // Second-level mutator allocation attempt: take the Heap_lock and 456 // retry the allocation attempt, potentially scheduling a GC 457 // pause. This should only be used for non-humongous allocations. 458 HeapWord* attempt_allocation_slow(size_t word_size, 459 AllocationContext_t context, 460 uint* gc_count_before_ret, 461 uint* gclocker_retry_count_ret); 462 463 // Takes the Heap_lock and attempts a humongous allocation. It can 464 // potentially schedule a GC pause. 465 HeapWord* attempt_allocation_humongous(size_t word_size, 466 uint* gc_count_before_ret, 467 uint* gclocker_retry_count_ret); 468 469 // Allocation attempt that should be called during safepoints (e.g., 470 // at the end of a successful GC). expect_null_mutator_alloc_region 471 // specifies whether the mutator alloc region is expected to be NULL 472 // or not. 473 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 474 AllocationContext_t context, 475 bool expect_null_mutator_alloc_region); 476 477 // These methods are the "callbacks" from the G1AllocRegion class. 478 479 // For mutator alloc regions. 480 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 481 void retire_mutator_alloc_region(HeapRegion* alloc_region, 482 size_t allocated_bytes); 483 484 // For GC alloc regions. 485 bool has_more_regions(InCSetState dest); 486 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest); 487 void retire_gc_alloc_region(HeapRegion* alloc_region, 488 size_t allocated_bytes, InCSetState dest); 489 490 // - if explicit_gc is true, the GC is for a System.gc() etc, 491 // otherwise it's for a failed allocation. 492 // - if clear_all_soft_refs is true, all soft references should be 493 // cleared during the GC. 494 // - it returns false if it is unable to do the collection due to the 495 // GC locker being active, true otherwise. 496 bool do_full_collection(bool explicit_gc, 497 bool clear_all_soft_refs); 498 499 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 500 virtual void do_full_collection(bool clear_all_soft_refs); 501 502 // Resize the heap if necessary after a full collection. 503 void resize_if_necessary_after_full_collection(); 504 505 // Callback from VM_G1CollectForAllocation operation. 506 // This function does everything necessary/possible to satisfy a 507 // failed allocation request (including collection, expansion, etc.) 508 HeapWord* satisfy_failed_allocation(size_t word_size, 509 AllocationContext_t context, 510 bool* succeeded); 511 private: 512 // Helper method for satisfy_failed_allocation() 513 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 514 AllocationContext_t context, 515 bool do_gc, 516 bool clear_all_soft_refs, 517 bool expect_null_mutator_alloc_region, 518 bool* gc_succeeded); 519 520 protected: 521 // Attempting to expand the heap sufficiently 522 // to support an allocation of the given "word_size". If 523 // successful, perform the allocation and return the address of the 524 // allocated block, or else "NULL". 525 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 526 527 // Preserve any referents discovered by concurrent marking that have not yet been 528 // copied by the STW pause. 529 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states); 530 // Process any reference objects discovered during 531 // an incremental evacuation pause. 532 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 533 534 // Enqueue any remaining discovered references 535 // after processing. 536 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 537 538 // Merges the information gathered on a per-thread basis for all worker threads 539 // during GC into global variables. 540 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states); 541 public: 542 WorkGang* workers() const { return _workers; } 543 544 G1Allocator* allocator() { 545 return _allocator; 546 } 547 548 G1HeapVerifier* verifier() { 549 return _verifier; 550 } 551 552 G1MonitoringSupport* g1mm() { 553 assert(_g1mm != NULL, "should have been initialized"); 554 return _g1mm; 555 } 556 557 // Expand the garbage-first heap by at least the given size (in bytes!). 558 // Returns true if the heap was expanded by the requested amount; 559 // false otherwise. 560 // (Rounds up to a HeapRegion boundary.) 561 bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL); 562 563 // Returns the PLAB statistics for a given destination. 564 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 565 566 // Determines PLAB size for a given destination. 567 inline size_t desired_plab_sz(InCSetState dest); 568 569 inline AllocationContextStats& allocation_context_stats(); 570 571 // Do anything common to GC's. 572 void gc_prologue(bool full); 573 void gc_epilogue(bool full); 574 575 // Modify the reclaim candidate set and test for presence. 576 // These are only valid for starts_humongous regions. 577 inline void set_humongous_reclaim_candidate(uint region, bool value); 578 inline bool is_humongous_reclaim_candidate(uint region); 579 580 // Remove from the reclaim candidate set. Also remove from the 581 // collection set so that later encounters avoid the slow path. 582 inline void set_humongous_is_live(oop obj); 583 584 // Register the given region to be part of the collection set. 585 inline void register_humongous_region_with_cset(uint index); 586 // Register regions with humongous objects (actually on the start region) in 587 // the in_cset_fast_test table. 588 void register_humongous_regions_with_cset(); 589 // We register a region with the fast "in collection set" test. We 590 // simply set to true the array slot corresponding to this region. 591 void register_young_region_with_cset(HeapRegion* r) { 592 _in_cset_fast_test.set_in_young(r->hrm_index()); 593 } 594 void register_old_region_with_cset(HeapRegion* r) { 595 _in_cset_fast_test.set_in_old(r->hrm_index()); 596 } 597 inline void register_ext_region_with_cset(HeapRegion* r) { 598 _in_cset_fast_test.set_ext(r->hrm_index()); 599 } 600 void clear_in_cset(const HeapRegion* hr) { 601 _in_cset_fast_test.clear(hr); 602 } 603 604 void clear_cset_fast_test() { 605 _in_cset_fast_test.clear(); 606 } 607 608 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 609 610 // This is called at the start of either a concurrent cycle or a Full 611 // GC to update the number of old marking cycles started. 612 void increment_old_marking_cycles_started(); 613 614 // This is called at the end of either a concurrent cycle or a Full 615 // GC to update the number of old marking cycles completed. Those two 616 // can happen in a nested fashion, i.e., we start a concurrent 617 // cycle, a Full GC happens half-way through it which ends first, 618 // and then the cycle notices that a Full GC happened and ends 619 // too. The concurrent parameter is a boolean to help us do a bit 620 // tighter consistency checking in the method. If concurrent is 621 // false, the caller is the inner caller in the nesting (i.e., the 622 // Full GC). If concurrent is true, the caller is the outer caller 623 // in this nesting (i.e., the concurrent cycle). Further nesting is 624 // not currently supported. The end of this call also notifies 625 // the FullGCCount_lock in case a Java thread is waiting for a full 626 // GC to happen (e.g., it called System.gc() with 627 // +ExplicitGCInvokesConcurrent). 628 void increment_old_marking_cycles_completed(bool concurrent); 629 630 uint old_marking_cycles_completed() { 631 return _old_marking_cycles_completed; 632 } 633 634 G1HRPrinter* hr_printer() { return &_hr_printer; } 635 636 // Allocates a new heap region instance. 637 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 638 639 // Allocate the highest free region in the reserved heap. This will commit 640 // regions as necessary. 641 HeapRegion* alloc_highest_free_region(); 642 643 // Frees a non-humongous region by initializing its contents and 644 // adding it to the free list that's passed as a parameter (this is 645 // usually a local list which will be appended to the master free 646 // list later). The used bytes of freed regions are accumulated in 647 // pre_used. If skip_remset is true, the region's RSet will not be freed 648 // up. If skip_hot_card_cache is true, the region's hot card cache will not 649 // be freed up. The assumption is that this will be done later. 650 // The locked parameter indicates if the caller has already taken 651 // care of proper synchronization. This may allow some optimizations. 652 void free_region(HeapRegion* hr, 653 FreeRegionList* free_list, 654 bool skip_remset, 655 bool skip_hot_card_cache = false, 656 bool locked = false); 657 658 // It dirties the cards that cover the block so that the post 659 // write barrier never queues anything when updating objects on this 660 // block. It is assumed (and in fact we assert) that the block 661 // belongs to a young region. 662 inline void dirty_young_block(HeapWord* start, size_t word_size); 663 664 // Frees a humongous region by collapsing it into individual regions 665 // and calling free_region() for each of them. The freed regions 666 // will be added to the free list that's passed as a parameter (this 667 // is usually a local list which will be appended to the master free 668 // list later). The used bytes of freed regions are accumulated in 669 // pre_used. If skip_remset is true, the region's RSet will not be freed 670 // up. The assumption is that this will be done later. 671 void free_humongous_region(HeapRegion* hr, 672 FreeRegionList* free_list, 673 bool skip_remset); 674 675 // Facility for allocating in 'archive' regions in high heap memory and 676 // recording the allocated ranges. These should all be called from the 677 // VM thread at safepoints, without the heap lock held. They can be used 678 // to create and archive a set of heap regions which can be mapped at the 679 // same fixed addresses in a subsequent JVM invocation. 680 void begin_archive_alloc_range(); 681 682 // Check if the requested size would be too large for an archive allocation. 683 bool is_archive_alloc_too_large(size_t word_size); 684 685 // Allocate memory of the requested size from the archive region. This will 686 // return NULL if the size is too large or if no memory is available. It 687 // does not trigger a garbage collection. 688 HeapWord* archive_mem_allocate(size_t word_size); 689 690 // Optionally aligns the end address and returns the allocated ranges in 691 // an array of MemRegions in order of ascending addresses. 692 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 693 size_t end_alignment_in_bytes = 0); 694 695 // Facility for allocating a fixed range within the heap and marking 696 // the containing regions as 'archive'. For use at JVM init time, when the 697 // caller may mmap archived heap data at the specified range(s). 698 // Verify that the MemRegions specified in the argument array are within the 699 // reserved heap. 700 bool check_archive_addresses(MemRegion* range, size_t count); 701 702 // Commit the appropriate G1 regions containing the specified MemRegions 703 // and mark them as 'archive' regions. The regions in the array must be 704 // non-overlapping and in order of ascending address. 705 bool alloc_archive_regions(MemRegion* range, size_t count); 706 707 // Insert any required filler objects in the G1 regions around the specified 708 // ranges to make the regions parseable. This must be called after 709 // alloc_archive_regions, and after class loading has occurred. 710 void fill_archive_regions(MemRegion* range, size_t count); 711 712 // For each of the specified MemRegions, uncommit the containing G1 regions 713 // which had been allocated by alloc_archive_regions. This should be called 714 // rather than fill_archive_regions at JVM init time if the archive file 715 // mapping failed, with the same non-overlapping and sorted MemRegion array. 716 void dealloc_archive_regions(MemRegion* range, size_t count); 717 718 protected: 719 720 // Shrink the garbage-first heap by at most the given size (in bytes!). 721 // (Rounds down to a HeapRegion boundary.) 722 virtual void shrink(size_t expand_bytes); 723 void shrink_helper(size_t expand_bytes); 724 725 #if TASKQUEUE_STATS 726 static void print_taskqueue_stats_hdr(outputStream* const st); 727 void print_taskqueue_stats() const; 728 void reset_taskqueue_stats(); 729 #endif // TASKQUEUE_STATS 730 731 // Schedule the VM operation that will do an evacuation pause to 732 // satisfy an allocation request of word_size. *succeeded will 733 // return whether the VM operation was successful (it did do an 734 // evacuation pause) or not (another thread beat us to it or the GC 735 // locker was active). Given that we should not be holding the 736 // Heap_lock when we enter this method, we will pass the 737 // gc_count_before (i.e., total_collections()) as a parameter since 738 // it has to be read while holding the Heap_lock. Currently, both 739 // methods that call do_collection_pause() release the Heap_lock 740 // before the call, so it's easy to read gc_count_before just before. 741 HeapWord* do_collection_pause(size_t word_size, 742 uint gc_count_before, 743 bool* succeeded, 744 GCCause::Cause gc_cause); 745 746 void wait_for_root_region_scanning(); 747 748 // The guts of the incremental collection pause, executed by the vm 749 // thread. It returns false if it is unable to do the collection due 750 // to the GC locker being active, true otherwise 751 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 752 753 // Actually do the work of evacuating the collection set. 754 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 755 756 void pre_evacuate_collection_set(); 757 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 758 759 // Print the header for the per-thread termination statistics. 760 static void print_termination_stats_hdr(); 761 // Print actual per-thread termination statistics. 762 void print_termination_stats(uint worker_id, 763 double elapsed_ms, 764 double strong_roots_ms, 765 double term_ms, 766 size_t term_attempts, 767 size_t alloc_buffer_waste, 768 size_t undo_waste) const; 769 // Update object copying statistics. 770 void record_obj_copy_mem_stats(); 771 772 // The hot card cache for remembered set insertion optimization. 773 G1HotCardCache* _hot_card_cache; 774 775 // The g1 remembered set of the heap. 776 G1RemSet* _g1_rem_set; 777 778 // A set of cards that cover the objects for which the Rsets should be updated 779 // concurrently after the collection. 780 DirtyCardQueueSet _dirty_card_queue_set; 781 782 // After a collection pause, convert the regions in the collection set into free 783 // regions. 784 void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 785 786 // Abandon the current collection set without recording policy 787 // statistics or updating free lists. 788 void abandon_collection_set(G1CollectionSet* collection_set); 789 790 // The concurrent marker (and the thread it runs in.) 791 G1ConcurrentMark* _cm; 792 ConcurrentMarkThread* _cmThread; 793 794 // The concurrent refiner. 795 ConcurrentG1Refine* _cg1r; 796 797 // The parallel task queues 798 RefToScanQueueSet *_task_queues; 799 800 // True iff a evacuation has failed in the current collection. 801 bool _evacuation_failed; 802 803 EvacuationFailedInfo* _evacuation_failed_info_array; 804 805 // Failed evacuations cause some logical from-space objects to have 806 // forwarding pointers to themselves. Reset them. 807 void remove_self_forwarding_pointers(); 808 809 // Restore the objects in the regions in the collection set after an 810 // evacuation failure. 811 void restore_after_evac_failure(); 812 813 PreservedMarksSet _preserved_marks_set; 814 815 // Preserve the mark of "obj", if necessary, in preparation for its mark 816 // word being overwritten with a self-forwarding-pointer. 817 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 818 819 #ifndef PRODUCT 820 // Support for forcing evacuation failures. Analogous to 821 // PromotionFailureALot for the other collectors. 822 823 // Records whether G1EvacuationFailureALot should be in effect 824 // for the current GC 825 bool _evacuation_failure_alot_for_current_gc; 826 827 // Used to record the GC number for interval checking when 828 // determining whether G1EvaucationFailureALot is in effect 829 // for the current GC. 830 size_t _evacuation_failure_alot_gc_number; 831 832 // Count of the number of evacuations between failures. 833 volatile size_t _evacuation_failure_alot_count; 834 835 // Set whether G1EvacuationFailureALot should be in effect 836 // for the current GC (based upon the type of GC and which 837 // command line flags are set); 838 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 839 bool during_initial_mark, 840 bool during_marking); 841 842 inline void set_evacuation_failure_alot_for_current_gc(); 843 844 // Return true if it's time to cause an evacuation failure. 845 inline bool evacuation_should_fail(); 846 847 // Reset the G1EvacuationFailureALot counters. Should be called at 848 // the end of an evacuation pause in which an evacuation failure occurred. 849 inline void reset_evacuation_should_fail(); 850 #endif // !PRODUCT 851 852 // ("Weak") Reference processing support. 853 // 854 // G1 has 2 instances of the reference processor class. One 855 // (_ref_processor_cm) handles reference object discovery 856 // and subsequent processing during concurrent marking cycles. 857 // 858 // The other (_ref_processor_stw) handles reference object 859 // discovery and processing during full GCs and incremental 860 // evacuation pauses. 861 // 862 // During an incremental pause, reference discovery will be 863 // temporarily disabled for _ref_processor_cm and will be 864 // enabled for _ref_processor_stw. At the end of the evacuation 865 // pause references discovered by _ref_processor_stw will be 866 // processed and discovery will be disabled. The previous 867 // setting for reference object discovery for _ref_processor_cm 868 // will be re-instated. 869 // 870 // At the start of marking: 871 // * Discovery by the CM ref processor is verified to be inactive 872 // and it's discovered lists are empty. 873 // * Discovery by the CM ref processor is then enabled. 874 // 875 // At the end of marking: 876 // * Any references on the CM ref processor's discovered 877 // lists are processed (possibly MT). 878 // 879 // At the start of full GC we: 880 // * Disable discovery by the CM ref processor and 881 // empty CM ref processor's discovered lists 882 // (without processing any entries). 883 // * Verify that the STW ref processor is inactive and it's 884 // discovered lists are empty. 885 // * Temporarily set STW ref processor discovery as single threaded. 886 // * Temporarily clear the STW ref processor's _is_alive_non_header 887 // field. 888 // * Finally enable discovery by the STW ref processor. 889 // 890 // The STW ref processor is used to record any discovered 891 // references during the full GC. 892 // 893 // At the end of a full GC we: 894 // * Enqueue any reference objects discovered by the STW ref processor 895 // that have non-live referents. This has the side-effect of 896 // making the STW ref processor inactive by disabling discovery. 897 // * Verify that the CM ref processor is still inactive 898 // and no references have been placed on it's discovered 899 // lists (also checked as a precondition during initial marking). 900 901 // The (stw) reference processor... 902 ReferenceProcessor* _ref_processor_stw; 903 904 STWGCTimer* _gc_timer_stw; 905 906 G1NewTracer* _gc_tracer_stw; 907 908 // During reference object discovery, the _is_alive_non_header 909 // closure (if non-null) is applied to the referent object to 910 // determine whether the referent is live. If so then the 911 // reference object does not need to be 'discovered' and can 912 // be treated as a regular oop. This has the benefit of reducing 913 // the number of 'discovered' reference objects that need to 914 // be processed. 915 // 916 // Instance of the is_alive closure for embedding into the 917 // STW reference processor as the _is_alive_non_header field. 918 // Supplying a value for the _is_alive_non_header field is 919 // optional but doing so prevents unnecessary additions to 920 // the discovered lists during reference discovery. 921 G1STWIsAliveClosure _is_alive_closure_stw; 922 923 // The (concurrent marking) reference processor... 924 ReferenceProcessor* _ref_processor_cm; 925 926 // Instance of the concurrent mark is_alive closure for embedding 927 // into the Concurrent Marking reference processor as the 928 // _is_alive_non_header field. Supplying a value for the 929 // _is_alive_non_header field is optional but doing so prevents 930 // unnecessary additions to the discovered lists during reference 931 // discovery. 932 G1CMIsAliveClosure _is_alive_closure_cm; 933 934 volatile bool _free_regions_coming; 935 936 public: 937 938 RefToScanQueue *task_queue(uint i) const; 939 940 uint num_task_queues() const; 941 942 // A set of cards where updates happened during the GC 943 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 944 945 // Create a G1CollectedHeap with the specified policy. 946 // Must call the initialize method afterwards. 947 // May not return if something goes wrong. 948 G1CollectedHeap(G1CollectorPolicy* policy); 949 950 private: 951 jint initialize_concurrent_refinement(); 952 public: 953 // Initialize the G1CollectedHeap to have the initial and 954 // maximum sizes and remembered and barrier sets 955 // specified by the policy object. 956 jint initialize(); 957 958 virtual void stop(); 959 960 // Return the (conservative) maximum heap alignment for any G1 heap 961 static size_t conservative_max_heap_alignment(); 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 inline bool is_in_cset(HeapWord* addr); 1135 1136 inline bool is_in_cset_or_humongous(const oop obj); 1137 1138 private: 1139 // This array is used for a quick test on whether a reference points into 1140 // the collection set or not. Each of the array's elements denotes whether the 1141 // corresponding region is in the collection set or not. 1142 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1143 1144 public: 1145 1146 inline InCSetState in_cset_state(const oop obj); 1147 1148 // Return "TRUE" iff the given object address is in the reserved 1149 // region of g1. 1150 bool is_in_g1_reserved(const void* p) const { 1151 return _hrm.reserved().contains(p); 1152 } 1153 1154 // Returns a MemRegion that corresponds to the space that has been 1155 // reserved for the heap 1156 MemRegion g1_reserved() const { 1157 return _hrm.reserved(); 1158 } 1159 1160 virtual bool is_in_closed_subset(const void* p) const; 1161 1162 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1163 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1164 } 1165 1166 // Iteration functions. 1167 1168 // Iterate over all objects, calling "cl.do_object" on each. 1169 virtual void object_iterate(ObjectClosure* cl); 1170 1171 virtual void safe_object_iterate(ObjectClosure* cl) { 1172 object_iterate(cl); 1173 } 1174 1175 // Iterate over heap regions, in address order, terminating the 1176 // iteration early if the "doHeapRegion" method returns "true". 1177 void heap_region_iterate(HeapRegionClosure* blk) const; 1178 1179 // Return the region with the given index. It assumes the index is valid. 1180 inline HeapRegion* region_at(uint index) const; 1181 1182 // Return the next region (by index) that is part of the same 1183 // humongous object that hr is part of. 1184 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1185 1186 // Calculate the region index of the given address. Given address must be 1187 // within the heap. 1188 inline uint addr_to_region(HeapWord* addr) const; 1189 1190 inline HeapWord* bottom_addr_for_region(uint index) const; 1191 1192 // Iterate over the heap regions in parallel. Assumes that this will be called 1193 // in parallel by a number of worker threads with distinct worker ids 1194 // in the range passed to the HeapRegionClaimer. Applies "blk->doHeapRegion" 1195 // to each of the regions, by attempting to claim the region using the 1196 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1197 // region. 1198 void heap_region_par_iterate(HeapRegionClosure* cl, 1199 uint worker_id, 1200 HeapRegionClaimer* hrclaimer) const; 1201 1202 // Iterate over the regions (if any) in the current collection set. 1203 void collection_set_iterate(HeapRegionClosure* blk); 1204 1205 // Iterate over the regions (if any) in the current collection set. Starts the 1206 // iteration over the entire collection set so that the start regions of a given 1207 // worker id over the set active_workers are evenly spread across the set of 1208 // collection set regions. 1209 void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id); 1210 1211 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1212 1213 // Returns the HeapRegion that contains addr. addr must not be NULL. 1214 template <class T> 1215 inline HeapRegion* heap_region_containing(const T addr) const; 1216 1217 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1218 // each address in the (reserved) heap is a member of exactly 1219 // one block. The defining characteristic of a block is that it is 1220 // possible to find its size, and thus to progress forward to the next 1221 // block. (Blocks may be of different sizes.) Thus, blocks may 1222 // represent Java objects, or they might be free blocks in a 1223 // free-list-based heap (or subheap), as long as the two kinds are 1224 // distinguishable and the size of each is determinable. 1225 1226 // Returns the address of the start of the "block" that contains the 1227 // address "addr". We say "blocks" instead of "object" since some heaps 1228 // may not pack objects densely; a chunk may either be an object or a 1229 // non-object. 1230 virtual HeapWord* block_start(const void* addr) const; 1231 1232 // Requires "addr" to be the start of a chunk, and returns its size. 1233 // "addr + size" is required to be the start of a new chunk, or the end 1234 // of the active area of the heap. 1235 virtual size_t block_size(const HeapWord* addr) const; 1236 1237 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1238 // the block is an object. 1239 virtual bool block_is_obj(const HeapWord* addr) const; 1240 1241 // Section on thread-local allocation buffers (TLABs) 1242 // See CollectedHeap for semantics. 1243 1244 bool supports_tlab_allocation() const; 1245 size_t tlab_capacity(Thread* ignored) const; 1246 size_t tlab_used(Thread* ignored) const; 1247 size_t max_tlab_size() const; 1248 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1249 1250 // Can a compiler initialize a new object without store barriers? 1251 // This permission only extends from the creation of a new object 1252 // via a TLAB up to the first subsequent safepoint. If such permission 1253 // is granted for this heap type, the compiler promises to call 1254 // defer_store_barrier() below on any slow path allocation of 1255 // a new object for which such initializing store barriers will 1256 // have been elided. G1, like CMS, allows this, but should be 1257 // ready to provide a compensating write barrier as necessary 1258 // if that storage came out of a non-young region. The efficiency 1259 // of this implementation depends crucially on being able to 1260 // answer very efficiently in constant time whether a piece of 1261 // storage in the heap comes from a young region or not. 1262 // See ReduceInitialCardMarks. 1263 virtual bool can_elide_tlab_store_barriers() const { 1264 return true; 1265 } 1266 1267 virtual bool card_mark_must_follow_store() const { 1268 return true; 1269 } 1270 1271 inline bool is_in_young(const oop obj); 1272 1273 virtual bool is_scavengable(const void* addr); 1274 1275 // We don't need barriers for initializing stores to objects 1276 // in the young gen: for the SATB pre-barrier, there is no 1277 // pre-value that needs to be remembered; for the remembered-set 1278 // update logging post-barrier, we don't maintain remembered set 1279 // information for young gen objects. 1280 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1281 1282 // Returns "true" iff the given word_size is "very large". 1283 static bool is_humongous(size_t word_size) { 1284 // Note this has to be strictly greater-than as the TLABs 1285 // are capped at the humongous threshold and we want to 1286 // ensure that we don't try to allocate a TLAB as 1287 // humongous and that we don't allocate a humongous 1288 // object in a TLAB. 1289 return word_size > _humongous_object_threshold_in_words; 1290 } 1291 1292 // Returns the humongous threshold for a specific region size 1293 static size_t humongous_threshold_for(size_t region_size) { 1294 return (region_size / 2); 1295 } 1296 1297 // Returns the number of regions the humongous object of the given word size 1298 // requires. 1299 static size_t humongous_obj_size_in_regions(size_t word_size); 1300 1301 // Print the maximum heap capacity. 1302 virtual size_t max_capacity() const; 1303 1304 virtual jlong millis_since_last_gc(); 1305 1306 1307 // Convenience function to be used in situations where the heap type can be 1308 // asserted to be this type. 1309 static G1CollectedHeap* heap(); 1310 1311 void set_region_short_lived_locked(HeapRegion* hr); 1312 // add appropriate methods for any other surv rate groups 1313 1314 const G1SurvivorRegions* survivor() const { return &_survivor; } 1315 1316 uint survivor_regions_count() const { 1317 return _survivor.length(); 1318 } 1319 1320 uint eden_regions_count() const { 1321 return _eden.length(); 1322 } 1323 1324 uint young_regions_count() const { 1325 return _eden.length() + _survivor.length(); 1326 } 1327 1328 uint old_regions_count() const { return _old_set.length(); } 1329 1330 uint humongous_regions_count() const { return _humongous_set.length(); } 1331 1332 #ifdef ASSERT 1333 bool check_young_list_empty(); 1334 #endif 1335 1336 // *** Stuff related to concurrent marking. It's not clear to me that so 1337 // many of these need to be public. 1338 1339 // The functions below are helper functions that a subclass of 1340 // "CollectedHeap" can use in the implementation of its virtual 1341 // functions. 1342 // This performs a concurrent marking of the live objects in a 1343 // bitmap off to the side. 1344 void doConcurrentMark(); 1345 1346 bool isMarkedNext(oop obj) const; 1347 1348 // Determine if an object is dead, given the object and also 1349 // the region to which the object belongs. An object is dead 1350 // iff a) it was not allocated since the last mark, b) it 1351 // is not marked, and c) it is not in an archive region. 1352 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1353 return 1354 hr->is_obj_dead(obj, _cm->prevMarkBitMap()) && 1355 !hr->is_archive(); 1356 } 1357 1358 // This function returns true when an object has been 1359 // around since the previous marking and hasn't yet 1360 // been marked during this marking, and is not in an archive region. 1361 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1362 return 1363 !hr->obj_allocated_since_next_marking(obj) && 1364 !isMarkedNext(obj) && 1365 !hr->is_archive(); 1366 } 1367 1368 // Determine if an object is dead, given only the object itself. 1369 // This will find the region to which the object belongs and 1370 // then call the region version of the same function. 1371 1372 // Added if it is NULL it isn't dead. 1373 1374 inline bool is_obj_dead(const oop obj) const; 1375 1376 inline bool is_obj_ill(const oop obj) const; 1377 1378 G1ConcurrentMark* concurrent_mark() const { return _cm; } 1379 1380 // Refinement 1381 1382 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1383 1384 // Optimized nmethod scanning support routines 1385 1386 // Register the given nmethod with the G1 heap. 1387 virtual void register_nmethod(nmethod* nm); 1388 1389 // Unregister the given nmethod from the G1 heap. 1390 virtual void unregister_nmethod(nmethod* nm); 1391 1392 // Free up superfluous code root memory. 1393 void purge_code_root_memory(); 1394 1395 // Rebuild the strong code root lists for each region 1396 // after a full GC. 1397 void rebuild_strong_code_roots(); 1398 1399 // Partial cleaning used when class unloading is disabled. 1400 // Let the caller choose what structures to clean out: 1401 // - StringTable 1402 // - SymbolTable 1403 // - StringDeduplication structures 1404 void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup); 1405 1406 // Complete cleaning used when class unloading is enabled. 1407 // Cleans out all structures handled by partial_cleaning and also the CodeCache. 1408 void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred); 1409 1410 // Redirty logged cards in the refinement queue. 1411 void redirty_logged_cards(); 1412 // Verification 1413 1414 // Perform any cleanup actions necessary before allowing a verification. 1415 virtual void prepare_for_verify(); 1416 1417 // Perform verification. 1418 1419 // vo == UsePrevMarking -> use "prev" marking information, 1420 // vo == UseNextMarking -> use "next" marking information 1421 // vo == UseMarkWord -> use the mark word in the object header 1422 // 1423 // NOTE: Only the "prev" marking information is guaranteed to be 1424 // consistent most of the time, so most calls to this should use 1425 // vo == UsePrevMarking. 1426 // Currently, there is only one case where this is called with 1427 // vo == UseNextMarking, which is to verify the "next" marking 1428 // information at the end of remark. 1429 // Currently there is only one place where this is called with 1430 // vo == UseMarkWord, which is to verify the marking during a 1431 // full GC. 1432 void verify(VerifyOption vo); 1433 1434 // WhiteBox testing support. 1435 virtual bool supports_concurrent_phase_control() const; 1436 virtual const char* const* concurrent_phases() const; 1437 virtual bool request_concurrent_phase(const char* phase); 1438 1439 // The methods below are here for convenience and dispatch the 1440 // appropriate method depending on value of the given VerifyOption 1441 // parameter. The values for that parameter, and their meanings, 1442 // are the same as those above. 1443 1444 bool is_obj_dead_cond(const oop obj, 1445 const HeapRegion* hr, 1446 const VerifyOption vo) const; 1447 1448 bool is_obj_dead_cond(const oop obj, 1449 const VerifyOption vo) const; 1450 1451 G1HeapSummary create_g1_heap_summary(); 1452 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1453 1454 // Printing 1455 private: 1456 void print_heap_regions() const; 1457 void print_regions_on(outputStream* st) const; 1458 1459 public: 1460 virtual void print_on(outputStream* st) const; 1461 virtual void print_extended_on(outputStream* st) const; 1462 virtual void print_on_error(outputStream* st) const; 1463 1464 virtual void print_gc_threads_on(outputStream* st) const; 1465 virtual void gc_threads_do(ThreadClosure* tc) const; 1466 1467 // Override 1468 void print_tracing_info() const; 1469 1470 // The following two methods are helpful for debugging RSet issues. 1471 void print_cset_rsets() PRODUCT_RETURN; 1472 void print_all_rsets() PRODUCT_RETURN; 1473 1474 public: 1475 size_t pending_card_num(); 1476 1477 protected: 1478 size_t _max_heap_capacity; 1479 }; 1480 1481 class G1ParEvacuateFollowersClosure : public VoidClosure { 1482 private: 1483 double _start_term; 1484 double _term_time; 1485 size_t _term_attempts; 1486 1487 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1488 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1489 protected: 1490 G1CollectedHeap* _g1h; 1491 G1ParScanThreadState* _par_scan_state; 1492 RefToScanQueueSet* _queues; 1493 ParallelTaskTerminator* _terminator; 1494 1495 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1496 RefToScanQueueSet* queues() { return _queues; } 1497 ParallelTaskTerminator* terminator() { return _terminator; } 1498 1499 public: 1500 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1501 G1ParScanThreadState* par_scan_state, 1502 RefToScanQueueSet* queues, 1503 ParallelTaskTerminator* terminator) 1504 : _g1h(g1h), _par_scan_state(par_scan_state), 1505 _queues(queues), _terminator(terminator), 1506 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1507 1508 void do_void(); 1509 1510 double term_time() const { return _term_time; } 1511 size_t term_attempts() const { return _term_attempts; } 1512 1513 private: 1514 inline bool offer_termination(); 1515 }; 1516 1517 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP