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(); 162 163 // The number of regions we could create by expansion. 164 uint _expansion_regions; 165 166 // The block offset table for the G1 heap. 167 G1BlockOffsetTable* _bot; 168 169 // Tears down the region sets / lists so that they are empty and the 170 // regions on the heap do not belong to a region set / list. The 171 // only exception is the humongous set which we leave unaltered. If 172 // free_list_only is true, it will only tear down the master free 173 // list. It is called before a Full GC (free_list_only == false) or 174 // before heap shrinking (free_list_only == true). 175 void tear_down_region_sets(bool free_list_only); 176 177 // Rebuilds the region sets / lists so that they are repopulated to 178 // reflect the contents of the heap. The only exception is the 179 // humongous set which was not torn down in the first place. If 180 // free_list_only is true, it will only rebuild the master free 181 // list. It is called after a Full GC (free_list_only == false) or 182 // after heap shrinking (free_list_only == true). 183 void rebuild_region_sets(bool free_list_only); 184 185 // Callback for region mapping changed events. 186 G1RegionMappingChangedListener _listener; 187 188 // The sequence of all heap regions in the heap. 189 HeapRegionManager _hrm; 190 191 // Manages all allocations with regions except humongous object allocations. 192 G1Allocator* _allocator; 193 194 // Manages all heap verification. 195 G1HeapVerifier* _verifier; 196 197 // Outside of GC pauses, the number of bytes used in all regions other 198 // than the current allocation region(s). 199 size_t _summary_bytes_used; 200 201 void increase_used(size_t bytes); 202 void decrease_used(size_t bytes); 203 204 void set_used(size_t bytes); 205 206 // Class that handles archive allocation ranges. 207 G1ArchiveAllocator* _archive_allocator; 208 209 // Statistics for each allocation context 210 AllocationContextStats _allocation_context_stats; 211 212 // GC allocation statistics policy for survivors. 213 G1EvacStats _survivor_evac_stats; 214 215 // GC allocation statistics policy for tenured objects. 216 G1EvacStats _old_evac_stats; 217 218 // It specifies whether we should attempt to expand the heap after a 219 // region allocation failure. If heap expansion fails we set this to 220 // false so that we don't re-attempt the heap expansion (it's likely 221 // that subsequent expansion attempts will also fail if one fails). 222 // Currently, it is only consulted during GC and it's reset at the 223 // start of each GC. 224 bool _expand_heap_after_alloc_failure; 225 226 // Helper for monitoring and management support. 227 G1MonitoringSupport* _g1mm; 228 229 // Records whether the region at the given index is (still) a 230 // candidate for eager reclaim. Only valid for humongous start 231 // regions; other regions have unspecified values. Humongous start 232 // regions are initialized at start of collection pause, with 233 // candidates removed from the set as they are found reachable from 234 // roots or the young generation. 235 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 236 protected: 237 bool default_value() const { return false; } 238 public: 239 void clear() { G1BiasedMappedArray<bool>::clear(); } 240 void set_candidate(uint region, bool value) { 241 set_by_index(region, value); 242 } 243 bool is_candidate(uint region) { 244 return get_by_index(region); 245 } 246 }; 247 248 HumongousReclaimCandidates _humongous_reclaim_candidates; 249 // Stores whether during humongous object registration we found candidate regions. 250 // If not, we can skip a few steps. 251 bool _has_humongous_reclaim_candidates; 252 253 volatile uint _gc_time_stamp; 254 255 G1HRPrinter _hr_printer; 256 257 // It decides whether an explicit GC should start a concurrent cycle 258 // instead of doing a STW GC. Currently, a concurrent cycle is 259 // explicitly started if: 260 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 261 // (b) cause == _g1_humongous_allocation 262 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 263 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 264 // (e) cause == _update_allocation_context_stats_inc 265 // (f) cause == _wb_conc_mark 266 bool should_do_concurrent_full_gc(GCCause::Cause cause); 267 268 // indicates whether we are in young or mixed GC mode 269 G1CollectorState _collector_state; 270 271 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 272 // concurrent cycles) we have started. 273 volatile uint _old_marking_cycles_started; 274 275 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 276 // concurrent cycles) we have completed. 277 volatile uint _old_marking_cycles_completed; 278 279 // This is a non-product method that is helpful for testing. It is 280 // called at the end of a GC and artificially expands the heap by 281 // allocating a number of dead regions. This way we can induce very 282 // frequent marking cycles and stress the cleanup / concurrent 283 // cleanup code more (as all the regions that will be allocated by 284 // this method will be found dead by the marking cycle). 285 void allocate_dummy_regions() PRODUCT_RETURN; 286 287 // Clear RSets after a compaction. It also resets the GC time stamps. 288 void clear_rsets_post_compaction(); 289 290 // If the HR printer is active, dump the state of the regions in the 291 // heap after a compaction. 292 void print_hrm_post_compaction(); 293 294 // Create a memory mapper for auxiliary data structures of the given size and 295 // translation factor. 296 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 297 size_t size, 298 size_t translation_factor); 299 300 static G1Policy* create_g1_policy(); 301 302 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 303 304 void process_weak_jni_handles(); 305 306 // These are macros so that, if the assert fires, we get the correct 307 // line number, file, etc. 308 309 #define heap_locking_asserts_params(_extra_message_) \ 310 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 311 (_extra_message_), \ 312 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 313 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 314 BOOL_TO_STR(Thread::current()->is_VM_thread()) 315 316 #define assert_heap_locked() \ 317 do { \ 318 assert(Heap_lock->owned_by_self(), \ 319 heap_locking_asserts_params("should be holding the Heap_lock")); \ 320 } while (0) 321 322 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 323 do { \ 324 assert(Heap_lock->owned_by_self() || \ 325 (SafepointSynchronize::is_at_safepoint() && \ 326 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 327 heap_locking_asserts_params("should be holding the Heap_lock or " \ 328 "should be at a safepoint")); \ 329 } while (0) 330 331 #define assert_heap_locked_and_not_at_safepoint() \ 332 do { \ 333 assert(Heap_lock->owned_by_self() && \ 334 !SafepointSynchronize::is_at_safepoint(), \ 335 heap_locking_asserts_params("should be holding the Heap_lock and " \ 336 "should not be at a safepoint")); \ 337 } while (0) 338 339 #define assert_heap_not_locked() \ 340 do { \ 341 assert(!Heap_lock->owned_by_self(), \ 342 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 343 } while (0) 344 345 #define assert_heap_not_locked_and_not_at_safepoint() \ 346 do { \ 347 assert(!Heap_lock->owned_by_self() && \ 348 !SafepointSynchronize::is_at_safepoint(), \ 349 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 350 "should not be at a safepoint")); \ 351 } while (0) 352 353 #define assert_at_safepoint(_should_be_vm_thread_) \ 354 do { \ 355 assert(SafepointSynchronize::is_at_safepoint() && \ 356 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 357 heap_locking_asserts_params("should be at a safepoint")); \ 358 } while (0) 359 360 #define assert_not_at_safepoint() \ 361 do { \ 362 assert(!SafepointSynchronize::is_at_safepoint(), \ 363 heap_locking_asserts_params("should not be at a safepoint")); \ 364 } while (0) 365 366 protected: 367 368 // The young region list. 369 G1EdenRegions _eden; 370 G1SurvivorRegions _survivor; 371 372 // The current policy object for the collector. 373 G1Policy* _g1_policy; 374 G1HeapSizingPolicy* _heap_sizing_policy; 375 376 G1CollectionSet _collection_set; 377 378 // This is the second level of trying to allocate a new region. If 379 // new_region() didn't find a region on the free_list, this call will 380 // check whether there's anything available on the 381 // secondary_free_list and/or wait for more regions to appear on 382 // that list, if _free_regions_coming is set. 383 HeapRegion* new_region_try_secondary_free_list(bool is_old); 384 385 // Try to allocate a single non-humongous HeapRegion sufficient for 386 // an allocation of the given word_size. If do_expand is true, 387 // attempt to expand the heap if necessary to satisfy the allocation 388 // request. If the region is to be used as an old region or for a 389 // humongous object, set is_old to true. If not, to false. 390 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 391 392 // Initialize a contiguous set of free regions of length num_regions 393 // and starting at index first so that they appear as a single 394 // humongous region. 395 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 396 uint num_regions, 397 size_t word_size, 398 AllocationContext_t context); 399 400 // Attempt to allocate a humongous object of the given size. Return 401 // NULL if unsuccessful. 402 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 403 404 // The following two methods, allocate_new_tlab() and 405 // mem_allocate(), are the two main entry points from the runtime 406 // into the G1's allocation routines. They have the following 407 // assumptions: 408 // 409 // * They should both be called outside safepoints. 410 // 411 // * They should both be called without holding the Heap_lock. 412 // 413 // * All allocation requests for new TLABs should go to 414 // allocate_new_tlab(). 415 // 416 // * All non-TLAB allocation requests should go to mem_allocate(). 417 // 418 // * If either call cannot satisfy the allocation request using the 419 // current allocating region, they will try to get a new one. If 420 // this fails, they will attempt to do an evacuation pause and 421 // retry the allocation. 422 // 423 // * If all allocation attempts fail, even after trying to schedule 424 // an evacuation pause, allocate_new_tlab() will return NULL, 425 // whereas mem_allocate() will attempt a heap expansion and/or 426 // schedule a Full GC. 427 // 428 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 429 // should never be called with word_size being humongous. All 430 // humongous allocation requests should go to mem_allocate() which 431 // will satisfy them with a special path. 432 433 virtual HeapWord* allocate_new_tlab(size_t word_size); 434 435 virtual HeapWord* mem_allocate(size_t word_size, 436 bool* gc_overhead_limit_was_exceeded); 437 438 // The following three methods take a gc_count_before_ret 439 // parameter which is used to return the GC count if the method 440 // returns NULL. Given that we are required to read the GC count 441 // while holding the Heap_lock, and these paths will take the 442 // Heap_lock at some point, it's easier to get them to read the GC 443 // count while holding the Heap_lock before they return NULL instead 444 // of the caller (namely: mem_allocate()) having to also take the 445 // Heap_lock just to read the GC count. 446 447 // First-level mutator allocation attempt: try to allocate out of 448 // the mutator alloc region without taking the Heap_lock. This 449 // should only be used for non-humongous allocations. 450 inline HeapWord* attempt_allocation(size_t word_size, 451 uint* gc_count_before_ret, 452 uint* gclocker_retry_count_ret); 453 454 // Second-level mutator allocation attempt: take the Heap_lock and 455 // retry the allocation attempt, potentially scheduling a GC 456 // pause. This should only be used for non-humongous allocations. 457 HeapWord* attempt_allocation_slow(size_t word_size, 458 AllocationContext_t context, 459 uint* gc_count_before_ret, 460 uint* gclocker_retry_count_ret); 461 462 // Takes the Heap_lock and attempts a humongous allocation. It can 463 // potentially schedule a GC pause. 464 HeapWord* attempt_allocation_humongous(size_t word_size, 465 uint* gc_count_before_ret, 466 uint* gclocker_retry_count_ret); 467 468 // Allocation attempt that should be called during safepoints (e.g., 469 // at the end of a successful GC). expect_null_mutator_alloc_region 470 // specifies whether the mutator alloc region is expected to be NULL 471 // or not. 472 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 473 AllocationContext_t context, 474 bool expect_null_mutator_alloc_region); 475 476 // These methods are the "callbacks" from the G1AllocRegion class. 477 478 // For mutator alloc regions. 479 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 480 void retire_mutator_alloc_region(HeapRegion* alloc_region, 481 size_t allocated_bytes); 482 483 // For GC alloc regions. 484 bool has_more_regions(InCSetState dest); 485 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest); 486 void retire_gc_alloc_region(HeapRegion* alloc_region, 487 size_t allocated_bytes, InCSetState dest); 488 489 // - if explicit_gc is true, the GC is for a System.gc() etc, 490 // otherwise it's for a failed allocation. 491 // - if clear_all_soft_refs is true, all soft references should be 492 // cleared during the GC. 493 // - it returns false if it is unable to do the collection due to the 494 // GC locker being active, true otherwise. 495 bool do_full_collection(bool explicit_gc, 496 bool clear_all_soft_refs); 497 498 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 499 virtual void do_full_collection(bool clear_all_soft_refs); 500 501 // Resize the heap if necessary after a full collection. 502 void resize_if_necessary_after_full_collection(); 503 504 // Callback from VM_G1CollectForAllocation operation. 505 // This function does everything necessary/possible to satisfy a 506 // failed allocation request (including collection, expansion, etc.) 507 HeapWord* satisfy_failed_allocation(size_t word_size, 508 AllocationContext_t context, 509 bool* succeeded); 510 private: 511 // Helper method for satisfy_failed_allocation() 512 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 513 AllocationContext_t context, 514 bool do_gc, 515 bool clear_all_soft_refs, 516 bool expect_null_mutator_alloc_region, 517 bool* gc_succeeded); 518 519 protected: 520 // Attempting to expand the heap sufficiently 521 // to support an allocation of the given "word_size". If 522 // successful, perform the allocation and return the address of the 523 // allocated block, or else "NULL". 524 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 525 526 // Preserve any referents discovered by concurrent marking that have not yet been 527 // copied by the STW pause. 528 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states); 529 // Process any reference objects discovered during 530 // an incremental evacuation pause. 531 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 532 533 // Enqueue any remaining discovered references 534 // after processing. 535 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 536 537 // Merges the information gathered on a per-thread basis for all worker threads 538 // during GC into global variables. 539 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states); 540 public: 541 WorkGang* workers() const { return _workers; } 542 543 G1Allocator* allocator() { 544 return _allocator; 545 } 546 547 G1HeapVerifier* verifier() { 548 return _verifier; 549 } 550 551 G1MonitoringSupport* g1mm() { 552 assert(_g1mm != NULL, "should have been initialized"); 553 return _g1mm; 554 } 555 556 // Expand the garbage-first heap by at least the given size (in bytes!). 557 // Returns true if the heap was expanded by the requested amount; 558 // false otherwise. 559 // (Rounds up to a HeapRegion boundary.) 560 bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL); 561 562 // Returns the PLAB statistics for a given destination. 563 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 564 565 // Determines PLAB size for a given destination. 566 inline size_t desired_plab_sz(InCSetState dest); 567 568 inline AllocationContextStats& allocation_context_stats(); 569 570 // Do anything common to GC's. 571 void gc_prologue(bool full); 572 void gc_epilogue(bool full); 573 574 // Modify the reclaim candidate set and test for presence. 575 // These are only valid for starts_humongous regions. 576 inline void set_humongous_reclaim_candidate(uint region, bool value); 577 inline bool is_humongous_reclaim_candidate(uint region); 578 579 // Remove from the reclaim candidate set. Also remove from the 580 // collection set so that later encounters avoid the slow path. 581 inline void set_humongous_is_live(oop obj); 582 583 // Register the given region to be part of the collection set. 584 inline void register_humongous_region_with_cset(uint index); 585 // Register regions with humongous objects (actually on the start region) in 586 // the in_cset_fast_test table. 587 void register_humongous_regions_with_cset(); 588 // We register a region with the fast "in collection set" test. We 589 // simply set to true the array slot corresponding to this region. 590 void register_young_region_with_cset(HeapRegion* r) { 591 _in_cset_fast_test.set_in_young(r->hrm_index()); 592 } 593 void register_old_region_with_cset(HeapRegion* r) { 594 _in_cset_fast_test.set_in_old(r->hrm_index()); 595 } 596 inline void register_ext_region_with_cset(HeapRegion* r) { 597 _in_cset_fast_test.set_ext(r->hrm_index()); 598 } 599 void clear_in_cset(const HeapRegion* hr) { 600 _in_cset_fast_test.clear(hr); 601 } 602 603 void clear_cset_fast_test() { 604 _in_cset_fast_test.clear(); 605 } 606 607 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 608 609 // This is called at the start of either a concurrent cycle or a Full 610 // GC to update the number of old marking cycles started. 611 void increment_old_marking_cycles_started(); 612 613 // This is called at the end of either a concurrent cycle or a Full 614 // GC to update the number of old marking cycles completed. Those two 615 // can happen in a nested fashion, i.e., we start a concurrent 616 // cycle, a Full GC happens half-way through it which ends first, 617 // and then the cycle notices that a Full GC happened and ends 618 // too. The concurrent parameter is a boolean to help us do a bit 619 // tighter consistency checking in the method. If concurrent is 620 // false, the caller is the inner caller in the nesting (i.e., the 621 // Full GC). If concurrent is true, the caller is the outer caller 622 // in this nesting (i.e., the concurrent cycle). Further nesting is 623 // not currently supported. The end of this call also notifies 624 // the FullGCCount_lock in case a Java thread is waiting for a full 625 // GC to happen (e.g., it called System.gc() with 626 // +ExplicitGCInvokesConcurrent). 627 void increment_old_marking_cycles_completed(bool concurrent); 628 629 uint old_marking_cycles_completed() { 630 return _old_marking_cycles_completed; 631 } 632 633 G1HRPrinter* hr_printer() { return &_hr_printer; } 634 635 // Allocates a new heap region instance. 636 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 637 638 // Allocate the highest free region in the reserved heap. This will commit 639 // regions as necessary. 640 HeapRegion* alloc_highest_free_region(); 641 642 // Frees a non-humongous region by initializing its contents and 643 // adding it to the free list that's passed as a parameter (this is 644 // usually a local list which will be appended to the master free 645 // list later). The used bytes of freed regions are accumulated in 646 // pre_used. If skip_remset is true, the region's RSet will not be freed 647 // up. If skip_hot_card_cache is true, the region's hot card cache will not 648 // be freed up. The assumption is that this will be done later. 649 // The locked parameter indicates if the caller has already taken 650 // care of proper synchronization. This may allow some optimizations. 651 void free_region(HeapRegion* hr, 652 FreeRegionList* free_list, 653 bool skip_remset, 654 bool skip_hot_card_cache = false, 655 bool locked = false); 656 657 // It dirties the cards that cover the block so that the post 658 // write barrier never queues anything when updating objects on this 659 // block. It is assumed (and in fact we assert) that the block 660 // belongs to a young region. 661 inline void dirty_young_block(HeapWord* start, size_t word_size); 662 663 // Frees a humongous region by collapsing it into individual regions 664 // and calling free_region() for each of them. The freed regions 665 // will be added to the free list that's passed as a parameter (this 666 // is usually a local list which will be appended to the master free 667 // list later). The used bytes of freed regions are accumulated in 668 // pre_used. If skip_remset is true, the region's RSet will not be freed 669 // up. The assumption is that this will be done later. 670 void free_humongous_region(HeapRegion* hr, 671 FreeRegionList* free_list, 672 bool skip_remset); 673 674 // Facility for allocating in 'archive' regions in high heap memory and 675 // recording the allocated ranges. These should all be called from the 676 // VM thread at safepoints, without the heap lock held. They can be used 677 // to create and archive a set of heap regions which can be mapped at the 678 // same fixed addresses in a subsequent JVM invocation. 679 void begin_archive_alloc_range(); 680 681 // Check if the requested size would be too large for an archive allocation. 682 bool is_archive_alloc_too_large(size_t word_size); 683 684 // Allocate memory of the requested size from the archive region. This will 685 // return NULL if the size is too large or if no memory is available. It 686 // does not trigger a garbage collection. 687 HeapWord* archive_mem_allocate(size_t word_size); 688 689 // Optionally aligns the end address and returns the allocated ranges in 690 // an array of MemRegions in order of ascending addresses. 691 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 692 size_t end_alignment_in_bytes = 0); 693 694 // Facility for allocating a fixed range within the heap and marking 695 // the containing regions as 'archive'. For use at JVM init time, when the 696 // caller may mmap archived heap data at the specified range(s). 697 // Verify that the MemRegions specified in the argument array are within the 698 // reserved heap. 699 bool check_archive_addresses(MemRegion* range, size_t count); 700 701 // Commit the appropriate G1 regions containing the specified MemRegions 702 // and mark them as 'archive' regions. The regions in the array must be 703 // non-overlapping and in order of ascending address. 704 bool alloc_archive_regions(MemRegion* range, size_t count); 705 706 // Insert any required filler objects in the G1 regions around the specified 707 // ranges to make the regions parseable. This must be called after 708 // alloc_archive_regions, and after class loading has occurred. 709 void fill_archive_regions(MemRegion* range, size_t count); 710 711 // For each of the specified MemRegions, uncommit the containing G1 regions 712 // which had been allocated by alloc_archive_regions. This should be called 713 // rather than fill_archive_regions at JVM init time if the archive file 714 // mapping failed, with the same non-overlapping and sorted MemRegion array. 715 void dealloc_archive_regions(MemRegion* range, size_t count); 716 717 protected: 718 719 // Shrink the garbage-first heap by at most the given size (in bytes!). 720 // (Rounds down to a HeapRegion boundary.) 721 virtual void shrink(size_t expand_bytes); 722 void shrink_helper(size_t expand_bytes); 723 724 #if TASKQUEUE_STATS 725 static void print_taskqueue_stats_hdr(outputStream* const st); 726 void print_taskqueue_stats() const; 727 void reset_taskqueue_stats(); 728 #endif // TASKQUEUE_STATS 729 730 // Schedule the VM operation that will do an evacuation pause to 731 // satisfy an allocation request of word_size. *succeeded will 732 // return whether the VM operation was successful (it did do an 733 // evacuation pause) or not (another thread beat us to it or the GC 734 // locker was active). Given that we should not be holding the 735 // Heap_lock when we enter this method, we will pass the 736 // gc_count_before (i.e., total_collections()) as a parameter since 737 // it has to be read while holding the Heap_lock. Currently, both 738 // methods that call do_collection_pause() release the Heap_lock 739 // before the call, so it's easy to read gc_count_before just before. 740 HeapWord* do_collection_pause(size_t word_size, 741 uint gc_count_before, 742 bool* succeeded, 743 GCCause::Cause gc_cause); 744 745 void wait_for_root_region_scanning(); 746 747 // The guts of the incremental collection pause, executed by the vm 748 // thread. It returns false if it is unable to do the collection due 749 // to the GC locker being active, true otherwise 750 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 751 752 // Actually do the work of evacuating the collection set. 753 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 754 755 void pre_evacuate_collection_set(); 756 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 757 758 // Print the header for the per-thread termination statistics. 759 static void print_termination_stats_hdr(); 760 // Print actual per-thread termination statistics. 761 void print_termination_stats(uint worker_id, 762 double elapsed_ms, 763 double strong_roots_ms, 764 double term_ms, 765 size_t term_attempts, 766 size_t alloc_buffer_waste, 767 size_t undo_waste) const; 768 // Update object copying statistics. 769 void record_obj_copy_mem_stats(); 770 771 // The hot card cache for remembered set insertion optimization. 772 G1HotCardCache* _hot_card_cache; 773 774 // The g1 remembered set of the heap. 775 G1RemSet* _g1_rem_set; 776 777 // A set of cards that cover the objects for which the Rsets should be updated 778 // concurrently after the collection. 779 DirtyCardQueueSet _dirty_card_queue_set; 780 781 // The closure used to refine a single card. 782 RefineCardTableEntryClosure* _refine_cte_cl; 783 784 // After a collection pause, convert the regions in the collection set into free 785 // regions. 786 void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 787 788 // Abandon the current collection set without recording policy 789 // statistics or updating free lists. 790 void abandon_collection_set(G1CollectionSet* collection_set); 791 792 // The concurrent marker (and the thread it runs in.) 793 G1ConcurrentMark* _cm; 794 ConcurrentMarkThread* _cmThread; 795 796 // The concurrent refiner. 797 ConcurrentG1Refine* _cg1r; 798 799 // The parallel task queues 800 RefToScanQueueSet *_task_queues; 801 802 // True iff a evacuation has failed in the current collection. 803 bool _evacuation_failed; 804 805 EvacuationFailedInfo* _evacuation_failed_info_array; 806 807 // Failed evacuations cause some logical from-space objects to have 808 // forwarding pointers to themselves. Reset them. 809 void remove_self_forwarding_pointers(); 810 811 // Restore the objects in the regions in the collection set after an 812 // evacuation failure. 813 void restore_after_evac_failure(); 814 815 PreservedMarksSet _preserved_marks_set; 816 817 // Preserve the mark of "obj", if necessary, in preparation for its mark 818 // word being overwritten with a self-forwarding-pointer. 819 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 820 821 #ifndef PRODUCT 822 // Support for forcing evacuation failures. Analogous to 823 // PromotionFailureALot for the other collectors. 824 825 // Records whether G1EvacuationFailureALot should be in effect 826 // for the current GC 827 bool _evacuation_failure_alot_for_current_gc; 828 829 // Used to record the GC number for interval checking when 830 // determining whether G1EvaucationFailureALot is in effect 831 // for the current GC. 832 size_t _evacuation_failure_alot_gc_number; 833 834 // Count of the number of evacuations between failures. 835 volatile size_t _evacuation_failure_alot_count; 836 837 // Set whether G1EvacuationFailureALot should be in effect 838 // for the current GC (based upon the type of GC and which 839 // command line flags are set); 840 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 841 bool during_initial_mark, 842 bool during_marking); 843 844 inline void set_evacuation_failure_alot_for_current_gc(); 845 846 // Return true if it's time to cause an evacuation failure. 847 inline bool evacuation_should_fail(); 848 849 // Reset the G1EvacuationFailureALot counters. Should be called at 850 // the end of an evacuation pause in which an evacuation failure occurred. 851 inline void reset_evacuation_should_fail(); 852 #endif // !PRODUCT 853 854 // ("Weak") Reference processing support. 855 // 856 // G1 has 2 instances of the reference processor class. One 857 // (_ref_processor_cm) handles reference object discovery 858 // and subsequent processing during concurrent marking cycles. 859 // 860 // The other (_ref_processor_stw) handles reference object 861 // discovery and processing during full GCs and incremental 862 // evacuation pauses. 863 // 864 // During an incremental pause, reference discovery will be 865 // temporarily disabled for _ref_processor_cm and will be 866 // enabled for _ref_processor_stw. At the end of the evacuation 867 // pause references discovered by _ref_processor_stw will be 868 // processed and discovery will be disabled. The previous 869 // setting for reference object discovery for _ref_processor_cm 870 // will be re-instated. 871 // 872 // At the start of marking: 873 // * Discovery by the CM ref processor is verified to be inactive 874 // and it's discovered lists are empty. 875 // * Discovery by the CM ref processor is then enabled. 876 // 877 // At the end of marking: 878 // * Any references on the CM ref processor's discovered 879 // lists are processed (possibly MT). 880 // 881 // At the start of full GC we: 882 // * Disable discovery by the CM ref processor and 883 // empty CM ref processor's discovered lists 884 // (without processing any entries). 885 // * Verify that the STW ref processor is inactive and it's 886 // discovered lists are empty. 887 // * Temporarily set STW ref processor discovery as single threaded. 888 // * Temporarily clear the STW ref processor's _is_alive_non_header 889 // field. 890 // * Finally enable discovery by the STW ref processor. 891 // 892 // The STW ref processor is used to record any discovered 893 // references during the full GC. 894 // 895 // At the end of a full GC we: 896 // * Enqueue any reference objects discovered by the STW ref processor 897 // that have non-live referents. This has the side-effect of 898 // making the STW ref processor inactive by disabling discovery. 899 // * Verify that the CM ref processor is still inactive 900 // and no references have been placed on it's discovered 901 // lists (also checked as a precondition during initial marking). 902 903 // The (stw) reference processor... 904 ReferenceProcessor* _ref_processor_stw; 905 906 STWGCTimer* _gc_timer_stw; 907 908 G1NewTracer* _gc_tracer_stw; 909 910 // During reference object discovery, the _is_alive_non_header 911 // closure (if non-null) is applied to the referent object to 912 // determine whether the referent is live. If so then the 913 // reference object does not need to be 'discovered' and can 914 // be treated as a regular oop. This has the benefit of reducing 915 // the number of 'discovered' reference objects that need to 916 // be processed. 917 // 918 // Instance of the is_alive closure for embedding into the 919 // STW reference processor as the _is_alive_non_header field. 920 // Supplying a value for the _is_alive_non_header field is 921 // optional but doing so prevents unnecessary additions to 922 // the discovered lists during reference discovery. 923 G1STWIsAliveClosure _is_alive_closure_stw; 924 925 // The (concurrent marking) reference processor... 926 ReferenceProcessor* _ref_processor_cm; 927 928 // Instance of the concurrent mark is_alive closure for embedding 929 // into the Concurrent Marking reference processor as the 930 // _is_alive_non_header field. Supplying a value for the 931 // _is_alive_non_header field is optional but doing so prevents 932 // unnecessary additions to the discovered lists during reference 933 // discovery. 934 G1CMIsAliveClosure _is_alive_closure_cm; 935 936 volatile bool _free_regions_coming; 937 938 public: 939 940 void set_refine_cte_cl_concurrency(bool concurrent); 941 942 RefToScanQueue *task_queue(uint i) const; 943 944 uint num_task_queues() const; 945 946 // A set of cards where updates happened during the GC 947 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 948 949 // Create a G1CollectedHeap with the specified policy. 950 // Must call the initialize method afterwards. 951 // May not return if something goes wrong. 952 G1CollectedHeap(G1CollectorPolicy* policy); 953 954 // Initialize the G1CollectedHeap to have the initial and 955 // maximum sizes and remembered and barrier sets 956 // specified by the policy object. 957 jint initialize(); 958 959 virtual void stop(); 960 961 // Return the (conservative) maximum heap alignment for any G1 heap 962 static size_t conservative_max_heap_alignment(); 963 964 // Does operations required after initialization has been done. 965 void post_initialize(); 966 967 // Initialize weak reference processing. 968 void ref_processing_init(); 969 970 virtual Name kind() const { 971 return CollectedHeap::G1CollectedHeap; 972 } 973 974 virtual const char* name() const { 975 return "G1"; 976 } 977 978 const G1CollectorState* collector_state() const { return &_collector_state; } 979 G1CollectorState* collector_state() { return &_collector_state; } 980 981 // The current policy object for the collector. 982 G1Policy* g1_policy() const { return _g1_policy; } 983 984 const G1CollectionSet* collection_set() const { return &_collection_set; } 985 G1CollectionSet* collection_set() { return &_collection_set; } 986 987 virtual CollectorPolicy* collector_policy() const; 988 989 // Adaptive size policy. No such thing for g1. 990 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 991 992 // The rem set and barrier set. 993 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 994 995 // Try to minimize the remembered set. 996 void scrub_rem_set(); 997 998 uint get_gc_time_stamp() { 999 return _gc_time_stamp; 1000 } 1001 1002 inline void reset_gc_time_stamp(); 1003 1004 void check_gc_time_stamps() PRODUCT_RETURN; 1005 1006 inline void increment_gc_time_stamp(); 1007 1008 // Reset the given region's GC timestamp. If it's starts humongous, 1009 // also reset the GC timestamp of its corresponding 1010 // continues humongous regions too. 1011 void reset_gc_time_stamps(HeapRegion* hr); 1012 1013 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1014 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1015 1016 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1017 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1018 1019 // The shared block offset table array. 1020 G1BlockOffsetTable* bot() const { return _bot; } 1021 1022 // Reference Processing accessors 1023 1024 // The STW reference processor.... 1025 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1026 1027 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1028 1029 // The Concurrent Marking reference processor... 1030 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1031 1032 virtual size_t capacity() const; 1033 virtual size_t used() const; 1034 // This should be called when we're not holding the heap lock. The 1035 // result might be a bit inaccurate. 1036 size_t used_unlocked() const; 1037 size_t recalculate_used() const; 1038 1039 // These virtual functions do the actual allocation. 1040 // Some heaps may offer a contiguous region for shared non-blocking 1041 // allocation, via inlined code (by exporting the address of the top and 1042 // end fields defining the extent of the contiguous allocation region.) 1043 // But G1CollectedHeap doesn't yet support this. 1044 1045 virtual bool is_maximal_no_gc() const { 1046 return _hrm.available() == 0; 1047 } 1048 1049 // The current number of regions in the heap. 1050 uint num_regions() const { return _hrm.length(); } 1051 1052 // The max number of regions in the heap. 1053 uint max_regions() const { return _hrm.max_length(); } 1054 1055 // The number of regions that are completely free. 1056 uint num_free_regions() const { return _hrm.num_free_regions(); } 1057 1058 MemoryUsage get_auxiliary_data_memory_usage() const { 1059 return _hrm.get_auxiliary_data_memory_usage(); 1060 } 1061 1062 // The number of regions that are not completely free. 1063 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1064 1065 #ifdef ASSERT 1066 bool is_on_master_free_list(HeapRegion* hr) { 1067 return _hrm.is_free(hr); 1068 } 1069 #endif // ASSERT 1070 1071 // Wrapper for the region list operations that can be called from 1072 // methods outside this class. 1073 1074 void secondary_free_list_add(FreeRegionList* list) { 1075 _secondary_free_list.add_ordered(list); 1076 } 1077 1078 void append_secondary_free_list() { 1079 _hrm.insert_list_into_free_list(&_secondary_free_list); 1080 } 1081 1082 void append_secondary_free_list_if_not_empty_with_lock() { 1083 // If the secondary free list looks empty there's no reason to 1084 // take the lock and then try to append it. 1085 if (!_secondary_free_list.is_empty()) { 1086 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1087 append_secondary_free_list(); 1088 } 1089 } 1090 1091 inline void old_set_add(HeapRegion* hr); 1092 inline void old_set_remove(HeapRegion* hr); 1093 1094 size_t non_young_capacity_bytes() { 1095 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes; 1096 } 1097 1098 void set_free_regions_coming(); 1099 void reset_free_regions_coming(); 1100 bool free_regions_coming() { return _free_regions_coming; } 1101 void wait_while_free_regions_coming(); 1102 1103 // Determine whether the given region is one that we are using as an 1104 // old GC alloc region. 1105 bool is_old_gc_alloc_region(HeapRegion* hr); 1106 1107 // Perform a collection of the heap; intended for use in implementing 1108 // "System.gc". This probably implies as full a collection as the 1109 // "CollectedHeap" supports. 1110 virtual void collect(GCCause::Cause cause); 1111 1112 virtual bool copy_allocation_context_stats(const jint* contexts, 1113 jlong* totals, 1114 jbyte* accuracy, 1115 jint len); 1116 1117 // True iff an evacuation has failed in the most-recent collection. 1118 bool evacuation_failed() { return _evacuation_failed; } 1119 1120 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed); 1121 void prepend_to_freelist(FreeRegionList* list); 1122 void decrement_summary_bytes(size_t bytes); 1123 1124 virtual bool is_in(const void* p) const; 1125 #ifdef ASSERT 1126 // Returns whether p is in one of the available areas of the heap. Slow but 1127 // extensive version. 1128 bool is_in_exact(const void* p) const; 1129 #endif 1130 1131 // Return "TRUE" iff the given object address is within the collection 1132 // set. Slow implementation. 1133 bool obj_in_cs(oop obj); 1134 1135 inline bool is_in_cset(const HeapRegion *hr); 1136 inline bool is_in_cset(oop obj); 1137 1138 inline bool is_in_cset_or_humongous(const oop obj); 1139 1140 private: 1141 // This array is used for a quick test on whether a reference points into 1142 // the collection set or not. Each of the array's elements denotes whether the 1143 // corresponding region is in the collection set or not. 1144 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1145 1146 public: 1147 1148 inline InCSetState in_cset_state(const oop obj); 1149 1150 // Return "TRUE" iff the given object address is in the reserved 1151 // region of g1. 1152 bool is_in_g1_reserved(const void* p) const { 1153 return _hrm.reserved().contains(p); 1154 } 1155 1156 // Returns a MemRegion that corresponds to the space that has been 1157 // reserved for the heap 1158 MemRegion g1_reserved() const { 1159 return _hrm.reserved(); 1160 } 1161 1162 virtual bool is_in_closed_subset(const void* p) const; 1163 1164 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1165 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1166 } 1167 1168 // Iteration functions. 1169 1170 // Iterate over all objects, calling "cl.do_object" on each. 1171 virtual void object_iterate(ObjectClosure* cl); 1172 1173 virtual void safe_object_iterate(ObjectClosure* cl) { 1174 object_iterate(cl); 1175 } 1176 1177 // Iterate over heap regions, in address order, terminating the 1178 // iteration early if the "doHeapRegion" method returns "true". 1179 void heap_region_iterate(HeapRegionClosure* blk) const; 1180 1181 // Return the region with the given index. It assumes the index is valid. 1182 inline HeapRegion* region_at(uint index) const; 1183 1184 // Return the next region (by index) that is part of the same 1185 // humongous object that hr is part of. 1186 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1187 1188 // Calculate the region index of the given address. Given address must be 1189 // within the heap. 1190 inline uint addr_to_region(HeapWord* addr) const; 1191 1192 inline HeapWord* bottom_addr_for_region(uint index) const; 1193 1194 // Iterate over the heap regions in parallel. Assumes that this will be called 1195 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1196 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1197 // to each of the regions, by attempting to claim the region using the 1198 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1199 // region. The concurrent argument should be set to true if iteration is 1200 // performed concurrently, during which no assumptions are made for consistent 1201 // attributes of the heap regions (as they might be modified while iterating). 1202 void heap_region_par_iterate(HeapRegionClosure* cl, 1203 uint worker_id, 1204 HeapRegionClaimer* hrclaimer, 1205 bool concurrent = false) const; 1206 1207 // Iterate over the regions (if any) in the current collection set. 1208 void collection_set_iterate(HeapRegionClosure* blk); 1209 1210 // Iterate over the regions (if any) in the current collection set. Starts the 1211 // iteration over the entire collection set so that the start regions of a given 1212 // worker id over the set active_workers are evenly spread across the set of 1213 // collection set regions. 1214 void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id); 1215 1216 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1217 1218 // Returns the HeapRegion that contains addr. addr must not be NULL. 1219 template <class T> 1220 inline HeapRegion* heap_region_containing(const T addr) const; 1221 1222 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1223 // each address in the (reserved) heap is a member of exactly 1224 // one block. The defining characteristic of a block is that it is 1225 // possible to find its size, and thus to progress forward to the next 1226 // block. (Blocks may be of different sizes.) Thus, blocks may 1227 // represent Java objects, or they might be free blocks in a 1228 // free-list-based heap (or subheap), as long as the two kinds are 1229 // distinguishable and the size of each is determinable. 1230 1231 // Returns the address of the start of the "block" that contains the 1232 // address "addr". We say "blocks" instead of "object" since some heaps 1233 // may not pack objects densely; a chunk may either be an object or a 1234 // non-object. 1235 virtual HeapWord* block_start(const void* addr) const; 1236 1237 // Requires "addr" to be the start of a chunk, and returns its size. 1238 // "addr + size" is required to be the start of a new chunk, or the end 1239 // of the active area of the heap. 1240 virtual size_t block_size(const HeapWord* addr) const; 1241 1242 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1243 // the block is an object. 1244 virtual bool block_is_obj(const HeapWord* addr) const; 1245 1246 // Section on thread-local allocation buffers (TLABs) 1247 // See CollectedHeap for semantics. 1248 1249 bool supports_tlab_allocation() const; 1250 size_t tlab_capacity(Thread* ignored) const; 1251 size_t tlab_used(Thread* ignored) const; 1252 size_t max_tlab_size() const; 1253 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1254 1255 // Can a compiler initialize a new object without store barriers? 1256 // This permission only extends from the creation of a new object 1257 // via a TLAB up to the first subsequent safepoint. If such permission 1258 // is granted for this heap type, the compiler promises to call 1259 // defer_store_barrier() below on any slow path allocation of 1260 // a new object for which such initializing store barriers will 1261 // have been elided. G1, like CMS, allows this, but should be 1262 // ready to provide a compensating write barrier as necessary 1263 // if that storage came out of a non-young region. The efficiency 1264 // of this implementation depends crucially on being able to 1265 // answer very efficiently in constant time whether a piece of 1266 // storage in the heap comes from a young region or not. 1267 // See ReduceInitialCardMarks. 1268 virtual bool can_elide_tlab_store_barriers() const { 1269 return true; 1270 } 1271 1272 virtual bool card_mark_must_follow_store() const { 1273 return true; 1274 } 1275 1276 inline bool is_in_young(const oop obj); 1277 1278 virtual bool is_scavengable(const void* addr); 1279 1280 // We don't need barriers for initializing stores to objects 1281 // in the young gen: for the SATB pre-barrier, there is no 1282 // pre-value that needs to be remembered; for the remembered-set 1283 // update logging post-barrier, we don't maintain remembered set 1284 // information for young gen objects. 1285 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1286 1287 // Returns "true" iff the given word_size is "very large". 1288 static bool is_humongous(size_t word_size) { 1289 // Note this has to be strictly greater-than as the TLABs 1290 // are capped at the humongous threshold and we want to 1291 // ensure that we don't try to allocate a TLAB as 1292 // humongous and that we don't allocate a humongous 1293 // object in a TLAB. 1294 return word_size > _humongous_object_threshold_in_words; 1295 } 1296 1297 // Returns the humongous threshold for a specific region size 1298 static size_t humongous_threshold_for(size_t region_size) { 1299 return (region_size / 2); 1300 } 1301 1302 // Returns the number of regions the humongous object of the given word size 1303 // requires. 1304 static size_t humongous_obj_size_in_regions(size_t word_size); 1305 1306 // Print the maximum heap capacity. 1307 virtual size_t max_capacity() const; 1308 1309 virtual jlong millis_since_last_gc(); 1310 1311 1312 // Convenience function to be used in situations where the heap type can be 1313 // asserted to be this type. 1314 static G1CollectedHeap* heap(); 1315 1316 void set_region_short_lived_locked(HeapRegion* hr); 1317 // add appropriate methods for any other surv rate groups 1318 1319 const G1SurvivorRegions* survivor() const { return &_survivor; } 1320 1321 uint survivor_regions_count() const { 1322 return _survivor.length(); 1323 } 1324 1325 uint eden_regions_count() const { 1326 return _eden.length(); 1327 } 1328 1329 uint young_regions_count() const { 1330 return _eden.length() + _survivor.length(); 1331 } 1332 1333 uint old_regions_count() const { return _old_set.length(); } 1334 1335 uint humongous_regions_count() const { return _humongous_set.length(); } 1336 1337 #ifdef ASSERT 1338 bool check_young_list_empty(); 1339 #endif 1340 1341 // *** Stuff related to concurrent marking. It's not clear to me that so 1342 // many of these need to be public. 1343 1344 // The functions below are helper functions that a subclass of 1345 // "CollectedHeap" can use in the implementation of its virtual 1346 // functions. 1347 // This performs a concurrent marking of the live objects in a 1348 // bitmap off to the side. 1349 void doConcurrentMark(); 1350 1351 bool isMarkedPrev(oop obj) const; 1352 bool isMarkedNext(oop obj) const; 1353 1354 // Determine if an object is dead, given the object and also 1355 // the region to which the object belongs. An object is dead 1356 // iff a) it was not allocated since the last mark, b) it 1357 // is not marked, and c) it is not in an archive region. 1358 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1359 return 1360 !hr->obj_allocated_since_prev_marking(obj) && 1361 !isMarkedPrev(obj) && 1362 !hr->is_archive(); 1363 } 1364 1365 // This function returns true when an object has been 1366 // around since the previous marking and hasn't yet 1367 // been marked during this marking, and is not in an archive region. 1368 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1369 return 1370 !hr->obj_allocated_since_next_marking(obj) && 1371 !isMarkedNext(obj) && 1372 !hr->is_archive(); 1373 } 1374 1375 // Determine if an object is dead, given only the object itself. 1376 // This will find the region to which the object belongs and 1377 // then call the region version of the same function. 1378 1379 // Added if it is NULL it isn't dead. 1380 1381 inline bool is_obj_dead(const oop obj) const; 1382 1383 inline bool is_obj_ill(const oop obj) const; 1384 1385 G1ConcurrentMark* concurrent_mark() const { return _cm; } 1386 1387 // Refinement 1388 1389 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1390 1391 // Optimized nmethod scanning support routines 1392 1393 // Register the given nmethod with the G1 heap. 1394 virtual void register_nmethod(nmethod* nm); 1395 1396 // Unregister the given nmethod from the G1 heap. 1397 virtual void unregister_nmethod(nmethod* nm); 1398 1399 // Free up superfluous code root memory. 1400 void purge_code_root_memory(); 1401 1402 // Rebuild the strong code root lists for each region 1403 // after a full GC. 1404 void rebuild_strong_code_roots(); 1405 1406 // Delete entries for dead interned string and clean up unreferenced symbols 1407 // in symbol table, possibly in parallel. 1408 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1409 1410 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1411 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1412 1413 // Redirty logged cards in the refinement queue. 1414 void redirty_logged_cards(); 1415 // Verification 1416 1417 // Perform any cleanup actions necessary before allowing a verification. 1418 virtual void prepare_for_verify(); 1419 1420 // Perform verification. 1421 1422 // vo == UsePrevMarking -> use "prev" marking information, 1423 // vo == UseNextMarking -> use "next" marking information 1424 // vo == UseMarkWord -> use the mark word in the object header 1425 // 1426 // NOTE: Only the "prev" marking information is guaranteed to be 1427 // consistent most of the time, so most calls to this should use 1428 // vo == UsePrevMarking. 1429 // Currently, there is only one case where this is called with 1430 // vo == UseNextMarking, which is to verify the "next" marking 1431 // information at the end of remark. 1432 // Currently there is only one place where this is called with 1433 // vo == UseMarkWord, which is to verify the marking during a 1434 // full GC. 1435 void verify(VerifyOption vo); 1436 1437 // WhiteBox testing support. 1438 virtual bool supports_concurrent_phase_control() const; 1439 virtual const char* const* concurrent_phases() const; 1440 virtual bool request_concurrent_phase(const char* phase); 1441 1442 // The methods below are here for convenience and dispatch the 1443 // appropriate method depending on value of the given VerifyOption 1444 // parameter. The values for that parameter, and their meanings, 1445 // are the same as those above. 1446 1447 bool is_obj_dead_cond(const oop obj, 1448 const HeapRegion* hr, 1449 const VerifyOption vo) const; 1450 1451 bool is_obj_dead_cond(const oop obj, 1452 const VerifyOption vo) const; 1453 1454 G1HeapSummary create_g1_heap_summary(); 1455 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1456 1457 // Printing 1458 private: 1459 void print_heap_regions() const; 1460 void print_regions_on(outputStream* st) const; 1461 1462 public: 1463 virtual void print_on(outputStream* st) const; 1464 virtual void print_extended_on(outputStream* st) const; 1465 virtual void print_on_error(outputStream* st) const; 1466 1467 virtual void print_gc_threads_on(outputStream* st) const; 1468 virtual void gc_threads_do(ThreadClosure* tc) const; 1469 1470 // Override 1471 void print_tracing_info() const; 1472 1473 // The following two methods are helpful for debugging RSet issues. 1474 void print_cset_rsets() PRODUCT_RETURN; 1475 void print_all_rsets() PRODUCT_RETURN; 1476 1477 public: 1478 size_t pending_card_num(); 1479 1480 protected: 1481 size_t _max_heap_capacity; 1482 }; 1483 1484 class G1ParEvacuateFollowersClosure : public VoidClosure { 1485 private: 1486 double _start_term; 1487 double _term_time; 1488 size_t _term_attempts; 1489 1490 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1491 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1492 protected: 1493 G1CollectedHeap* _g1h; 1494 G1ParScanThreadState* _par_scan_state; 1495 RefToScanQueueSet* _queues; 1496 ParallelTaskTerminator* _terminator; 1497 1498 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1499 RefToScanQueueSet* queues() { return _queues; } 1500 ParallelTaskTerminator* terminator() { return _terminator; } 1501 1502 public: 1503 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1504 G1ParScanThreadState* par_scan_state, 1505 RefToScanQueueSet* queues, 1506 ParallelTaskTerminator* terminator) 1507 : _g1h(g1h), _par_scan_state(par_scan_state), 1508 _queues(queues), _terminator(terminator), 1509 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1510 1511 void do_void(); 1512 1513 double term_time() const { return _term_time; } 1514 size_t term_attempts() const { return _term_attempts; } 1515 1516 private: 1517 inline bool offer_termination(); 1518 }; 1519 1520 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP