1 /* 2 * Copyright (c) 2001, 2016, 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/g1HRPrinter.hpp" 35 #include "gc/g1/g1InCSetState.hpp" 36 #include "gc/g1/g1MonitoringSupport.hpp" 37 #include "gc/g1/g1EvacFailure.hpp" 38 #include "gc/g1/g1EvacStats.hpp" 39 #include "gc/g1/g1HeapVerifier.hpp" 40 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 41 #include "gc/g1/g1YCTypes.hpp" 42 #include "gc/g1/hSpaceCounters.hpp" 43 #include "gc/g1/heapRegionManager.hpp" 44 #include "gc/g1/heapRegionSet.hpp" 45 #include "gc/g1/youngList.hpp" 46 #include "gc/shared/barrierSet.hpp" 47 #include "gc/shared/collectedHeap.hpp" 48 #include "gc/shared/plab.hpp" 49 #include "gc/shared/preservedMarks.hpp" 50 #include "memory/memRegion.hpp" 51 #include "utilities/stack.hpp" 52 53 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 54 // It uses the "Garbage First" heap organization and algorithm, which 55 // may combine concurrent marking with parallel, incremental compaction of 56 // heap subsets that will yield large amounts of garbage. 57 58 // Forward declarations 59 class HeapRegion; 60 class HRRSCleanupTask; 61 class GenerationSpec; 62 class OopsInHeapRegionClosure; 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 G1RemSet; 75 class HeapRegionRemSetIterator; 76 class G1ConcurrentMark; 77 class ConcurrentMarkThread; 78 class ConcurrentG1Refine; 79 class GenerationCounters; 80 class STWGCTimer; 81 class G1NewTracer; 82 class EvacuationFailedInfo; 83 class nmethod; 84 class Ticks; 85 class WorkGang; 86 class G1Allocator; 87 class G1ArchiveAllocator; 88 class G1HeapVerifier; 89 class G1HeapSizingPolicy; 90 91 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 92 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 93 94 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 95 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 96 97 // The G1 STW is alive closure. 98 // An instance is embedded into the G1CH and used as the 99 // (optional) _is_alive_non_header closure in the STW 100 // reference processor. It is also extensively used during 101 // reference processing during STW evacuation pauses. 102 class G1STWIsAliveClosure: public BoolObjectClosure { 103 G1CollectedHeap* _g1; 104 public: 105 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 106 bool do_object_b(oop p); 107 }; 108 109 class RefineCardTableEntryClosure; 110 111 class G1RegionMappingChangedListener : public G1MappingChangedListener { 112 private: 113 void reset_from_card_cache(uint start_idx, size_t num_regions); 114 public: 115 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 116 }; 117 118 class G1CollectedHeap : public CollectedHeap { 119 friend class VM_CollectForMetadataAllocation; 120 friend class VM_G1CollectForAllocation; 121 friend class VM_G1CollectFull; 122 friend class VM_G1IncCollectionPause; 123 friend class VMStructs; 124 friend class MutatorAllocRegion; 125 friend class G1GCAllocRegion; 126 friend class G1HeapVerifier; 127 128 // Closures used in implementation. 129 friend class G1ParScanThreadState; 130 friend class G1ParScanThreadStateSet; 131 friend class G1ParTask; 132 friend class G1PLABAllocator; 133 friend class G1PrepareCompactClosure; 134 135 // Other related classes. 136 friend class HeapRegionClaimer; 137 138 // Testing classes. 139 friend class G1CheckCSetFastTableClosure; 140 141 private: 142 WorkGang* _workers; 143 G1CollectorPolicy* _collector_policy; 144 145 static size_t _humongous_object_threshold_in_words; 146 147 // The secondary free list which contains regions that have been 148 // freed up during the cleanup process. This will be appended to 149 // the master free list when appropriate. 150 FreeRegionList _secondary_free_list; 151 152 // It keeps track of the old regions. 153 HeapRegionSet _old_set; 154 155 // It keeps track of the humongous regions. 156 HeapRegionSet _humongous_set; 157 158 void eagerly_reclaim_humongous_regions(); 159 160 // The number of regions we could create by expansion. 161 uint _expansion_regions; 162 163 // The block offset table for the G1 heap. 164 G1BlockOffsetTable* _bot; 165 166 // Tears down the region sets / lists so that they are empty and the 167 // regions on the heap do not belong to a region set / list. The 168 // only exception is the humongous set which we leave unaltered. If 169 // free_list_only is true, it will only tear down the master free 170 // list. It is called before a Full GC (free_list_only == false) or 171 // before heap shrinking (free_list_only == true). 172 void tear_down_region_sets(bool free_list_only); 173 174 // Rebuilds the region sets / lists so that they are repopulated to 175 // reflect the contents of the heap. The only exception is the 176 // humongous set which was not torn down in the first place. If 177 // free_list_only is true, it will only rebuild the master free 178 // list. It is called after a Full GC (free_list_only == false) or 179 // after heap shrinking (free_list_only == true). 180 void rebuild_region_sets(bool free_list_only); 181 182 // Callback for region mapping changed events. 183 G1RegionMappingChangedListener _listener; 184 185 // The sequence of all heap regions in the heap. 186 HeapRegionManager _hrm; 187 188 // Manages all allocations with regions except humongous object allocations. 189 G1Allocator* _allocator; 190 191 // Manages all heap verification. 192 G1HeapVerifier* _verifier; 193 194 // Outside of GC pauses, the number of bytes used in all regions other 195 // than the current allocation region(s). 196 size_t _summary_bytes_used; 197 198 void increase_used(size_t bytes); 199 void decrease_used(size_t bytes); 200 201 void set_used(size_t bytes); 202 203 // Class that handles archive allocation ranges. 204 G1ArchiveAllocator* _archive_allocator; 205 206 // Statistics for each allocation context 207 AllocationContextStats _allocation_context_stats; 208 209 // GC allocation statistics policy for survivors. 210 G1EvacStats _survivor_evac_stats; 211 212 // GC allocation statistics policy for tenured objects. 213 G1EvacStats _old_evac_stats; 214 215 // It specifies whether we should attempt to expand the heap after a 216 // region allocation failure. If heap expansion fails we set this to 217 // false so that we don't re-attempt the heap expansion (it's likely 218 // that subsequent expansion attempts will also fail if one fails). 219 // Currently, it is only consulted during GC and it's reset at the 220 // start of each GC. 221 bool _expand_heap_after_alloc_failure; 222 223 // Helper for monitoring and management support. 224 G1MonitoringSupport* _g1mm; 225 226 // Records whether the region at the given index is (still) a 227 // candidate for eager reclaim. Only valid for humongous start 228 // regions; other regions have unspecified values. Humongous start 229 // regions are initialized at start of collection pause, with 230 // candidates removed from the set as they are found reachable from 231 // roots or the young generation. 232 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 233 protected: 234 bool default_value() const { return false; } 235 public: 236 void clear() { G1BiasedMappedArray<bool>::clear(); } 237 void set_candidate(uint region, bool value) { 238 set_by_index(region, value); 239 } 240 bool is_candidate(uint region) { 241 return get_by_index(region); 242 } 243 }; 244 245 HumongousReclaimCandidates _humongous_reclaim_candidates; 246 // Stores whether during humongous object registration we found candidate regions. 247 // If not, we can skip a few steps. 248 bool _has_humongous_reclaim_candidates; 249 250 volatile uint _gc_time_stamp; 251 252 G1HRPrinter _hr_printer; 253 254 // It decides whether an explicit GC should start a concurrent cycle 255 // instead of doing a STW GC. Currently, a concurrent cycle is 256 // explicitly started if: 257 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 258 // (b) cause == _g1_humongous_allocation 259 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 260 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 261 // (e) cause == _update_allocation_context_stats_inc 262 // (f) cause == _wb_conc_mark 263 bool should_do_concurrent_full_gc(GCCause::Cause cause); 264 265 // indicates whether we are in young or mixed GC mode 266 G1CollectorState _collector_state; 267 268 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 269 // concurrent cycles) we have started. 270 volatile uint _old_marking_cycles_started; 271 272 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 273 // concurrent cycles) we have completed. 274 volatile uint _old_marking_cycles_completed; 275 276 // This is a non-product method that is helpful for testing. It is 277 // called at the end of a GC and artificially expands the heap by 278 // allocating a number of dead regions. This way we can induce very 279 // frequent marking cycles and stress the cleanup / concurrent 280 // cleanup code more (as all the regions that will be allocated by 281 // this method will be found dead by the marking cycle). 282 void allocate_dummy_regions() PRODUCT_RETURN; 283 284 // Clear RSets after a compaction. It also resets the GC time stamps. 285 void clear_rsets_post_compaction(); 286 287 // If the HR printer is active, dump the state of the regions in the 288 // heap after a compaction. 289 void print_hrm_post_compaction(); 290 291 // Create a memory mapper for auxiliary data structures of the given size and 292 // translation factor. 293 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 294 size_t size, 295 size_t translation_factor); 296 297 static G1Policy* create_g1_policy(); 298 299 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 300 301 void process_weak_jni_handles(); 302 303 // These are macros so that, if the assert fires, we get the correct 304 // line number, file, etc. 305 306 #define heap_locking_asserts_params(_extra_message_) \ 307 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 308 (_extra_message_), \ 309 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 310 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 311 BOOL_TO_STR(Thread::current()->is_VM_thread()) 312 313 #define assert_heap_locked() \ 314 do { \ 315 assert(Heap_lock->owned_by_self(), \ 316 heap_locking_asserts_params("should be holding the Heap_lock")); \ 317 } while (0) 318 319 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 320 do { \ 321 assert(Heap_lock->owned_by_self() || \ 322 (SafepointSynchronize::is_at_safepoint() && \ 323 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 324 heap_locking_asserts_params("should be holding the Heap_lock or " \ 325 "should be at a safepoint")); \ 326 } while (0) 327 328 #define assert_heap_locked_and_not_at_safepoint() \ 329 do { \ 330 assert(Heap_lock->owned_by_self() && \ 331 !SafepointSynchronize::is_at_safepoint(), \ 332 heap_locking_asserts_params("should be holding the Heap_lock and " \ 333 "should not be at a safepoint")); \ 334 } while (0) 335 336 #define assert_heap_not_locked() \ 337 do { \ 338 assert(!Heap_lock->owned_by_self(), \ 339 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 340 } while (0) 341 342 #define assert_heap_not_locked_and_not_at_safepoint() \ 343 do { \ 344 assert(!Heap_lock->owned_by_self() && \ 345 !SafepointSynchronize::is_at_safepoint(), \ 346 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 347 "should not be at a safepoint")); \ 348 } while (0) 349 350 #define assert_at_safepoint(_should_be_vm_thread_) \ 351 do { \ 352 assert(SafepointSynchronize::is_at_safepoint() && \ 353 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 354 heap_locking_asserts_params("should be at a safepoint")); \ 355 } while (0) 356 357 #define assert_not_at_safepoint() \ 358 do { \ 359 assert(!SafepointSynchronize::is_at_safepoint(), \ 360 heap_locking_asserts_params("should not be at a safepoint")); \ 361 } while (0) 362 363 protected: 364 365 // The young region list. 366 YoungList* _young_list; 367 368 // The current policy object for the collector. 369 G1Policy* _g1_policy; 370 G1HeapSizingPolicy* _heap_sizing_policy; 371 372 G1CollectionSet _collection_set; 373 374 // This is the second level of trying to allocate a new region. If 375 // new_region() didn't find a region on the free_list, this call will 376 // check whether there's anything available on the 377 // secondary_free_list and/or wait for more regions to appear on 378 // that list, if _free_regions_coming is set. 379 HeapRegion* new_region_try_secondary_free_list(bool is_old); 380 381 // Try to allocate a single non-humongous HeapRegion sufficient for 382 // an allocation of the given word_size. If do_expand is true, 383 // attempt to expand the heap if necessary to satisfy the allocation 384 // request. If the region is to be used as an old region or for a 385 // humongous object, set is_old to true. If not, to false. 386 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 387 388 // Initialize a contiguous set of free regions of length num_regions 389 // and starting at index first so that they appear as a single 390 // humongous region. 391 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 392 uint num_regions, 393 size_t word_size, 394 AllocationContext_t context); 395 396 // Attempt to allocate a humongous object of the given size. Return 397 // NULL if unsuccessful. 398 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 399 400 // The following two methods, allocate_new_tlab() and 401 // mem_allocate(), are the two main entry points from the runtime 402 // into the G1's allocation routines. They have the following 403 // assumptions: 404 // 405 // * They should both be called outside safepoints. 406 // 407 // * They should both be called without holding the Heap_lock. 408 // 409 // * All allocation requests for new TLABs should go to 410 // allocate_new_tlab(). 411 // 412 // * All non-TLAB allocation requests should go to mem_allocate(). 413 // 414 // * If either call cannot satisfy the allocation request using the 415 // current allocating region, they will try to get a new one. If 416 // this fails, they will attempt to do an evacuation pause and 417 // retry the allocation. 418 // 419 // * If all allocation attempts fail, even after trying to schedule 420 // an evacuation pause, allocate_new_tlab() will return NULL, 421 // whereas mem_allocate() will attempt a heap expansion and/or 422 // schedule a Full GC. 423 // 424 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 425 // should never be called with word_size being humongous. All 426 // humongous allocation requests should go to mem_allocate() which 427 // will satisfy them with a special path. 428 429 virtual HeapWord* allocate_new_tlab(size_t word_size); 430 431 virtual HeapWord* mem_allocate(size_t word_size, 432 bool* gc_overhead_limit_was_exceeded); 433 434 // The following three methods take a gc_count_before_ret 435 // parameter which is used to return the GC count if the method 436 // returns NULL. Given that we are required to read the GC count 437 // while holding the Heap_lock, and these paths will take the 438 // Heap_lock at some point, it's easier to get them to read the GC 439 // count while holding the Heap_lock before they return NULL instead 440 // of the caller (namely: mem_allocate()) having to also take the 441 // Heap_lock just to read the GC count. 442 443 // First-level mutator allocation attempt: try to allocate out of 444 // the mutator alloc region without taking the Heap_lock. This 445 // should only be used for non-humongous allocations. 446 inline HeapWord* attempt_allocation(size_t word_size, 447 uint* gc_count_before_ret, 448 uint* gclocker_retry_count_ret); 449 450 // Second-level mutator allocation attempt: take the Heap_lock and 451 // retry the allocation attempt, potentially scheduling a GC 452 // pause. This should only be used for non-humongous allocations. 453 HeapWord* attempt_allocation_slow(size_t word_size, 454 AllocationContext_t context, 455 uint* gc_count_before_ret, 456 uint* gclocker_retry_count_ret); 457 458 // Takes the Heap_lock and attempts a humongous allocation. It can 459 // potentially schedule a GC pause. 460 HeapWord* attempt_allocation_humongous(size_t word_size, 461 uint* gc_count_before_ret, 462 uint* gclocker_retry_count_ret); 463 464 // Allocation attempt that should be called during safepoints (e.g., 465 // at the end of a successful GC). expect_null_mutator_alloc_region 466 // specifies whether the mutator alloc region is expected to be NULL 467 // or not. 468 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 469 AllocationContext_t context, 470 bool expect_null_mutator_alloc_region); 471 472 // These methods are the "callbacks" from the G1AllocRegion class. 473 474 // For mutator alloc regions. 475 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 476 void retire_mutator_alloc_region(HeapRegion* alloc_region, 477 size_t allocated_bytes); 478 479 // For GC alloc regions. 480 bool has_more_regions(InCSetState dest); 481 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest); 482 void retire_gc_alloc_region(HeapRegion* alloc_region, 483 size_t allocated_bytes, InCSetState dest); 484 485 // - if explicit_gc is true, the GC is for a System.gc() etc, 486 // otherwise it's for a failed allocation. 487 // - if clear_all_soft_refs is true, all soft references should be 488 // cleared during the GC. 489 // - it returns false if it is unable to do the collection due to the 490 // GC locker being active, true otherwise. 491 bool do_full_collection(bool explicit_gc, 492 bool clear_all_soft_refs); 493 494 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 495 virtual void do_full_collection(bool clear_all_soft_refs); 496 497 // Resize the heap if necessary after a full collection. 498 void resize_if_necessary_after_full_collection(); 499 500 // Callback from VM_G1CollectForAllocation operation. 501 // This function does everything necessary/possible to satisfy a 502 // failed allocation request (including collection, expansion, etc.) 503 HeapWord* satisfy_failed_allocation(size_t word_size, 504 AllocationContext_t context, 505 bool* succeeded); 506 private: 507 // Helper method for satisfy_failed_allocation() 508 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 509 AllocationContext_t context, 510 bool do_gc, 511 bool clear_all_soft_refs, 512 bool expect_null_mutator_alloc_region, 513 bool* gc_succeeded); 514 515 protected: 516 // Attempting to expand the heap sufficiently 517 // to support an allocation of the given "word_size". If 518 // successful, perform the allocation and return the address of the 519 // allocated block, or else "NULL". 520 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 521 522 // Preserve any referents discovered by concurrent marking that have not yet been 523 // copied by the STW pause. 524 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states); 525 // Process any reference objects discovered during 526 // an incremental evacuation pause. 527 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 528 529 // Enqueue any remaining discovered references 530 // after processing. 531 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 532 533 // Merges the information gathered on a per-thread basis for all worker threads 534 // during GC into global variables. 535 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states); 536 public: 537 WorkGang* workers() const { return _workers; } 538 539 G1Allocator* allocator() { 540 return _allocator; 541 } 542 543 G1HeapVerifier* verifier() { 544 return _verifier; 545 } 546 547 G1MonitoringSupport* g1mm() { 548 assert(_g1mm != NULL, "should have been initialized"); 549 return _g1mm; 550 } 551 552 // Expand the garbage-first heap by at least the given size (in bytes!). 553 // Returns true if the heap was expanded by the requested amount; 554 // false otherwise. 555 // (Rounds up to a HeapRegion boundary.) 556 bool expand(size_t expand_bytes, double* expand_time_ms = NULL); 557 558 // Returns the PLAB statistics for a given destination. 559 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 560 561 // Determines PLAB size for a given destination. 562 inline size_t desired_plab_sz(InCSetState dest); 563 564 inline AllocationContextStats& allocation_context_stats(); 565 566 // Do anything common to GC's. 567 void gc_prologue(bool full); 568 void gc_epilogue(bool full); 569 570 // Modify the reclaim candidate set and test for presence. 571 // These are only valid for starts_humongous regions. 572 inline void set_humongous_reclaim_candidate(uint region, bool value); 573 inline bool is_humongous_reclaim_candidate(uint region); 574 575 // Remove from the reclaim candidate set. Also remove from the 576 // collection set so that later encounters avoid the slow path. 577 inline void set_humongous_is_live(oop obj); 578 579 // Register the given region to be part of the collection set. 580 inline void register_humongous_region_with_cset(uint index); 581 // Register regions with humongous objects (actually on the start region) in 582 // the in_cset_fast_test table. 583 void register_humongous_regions_with_cset(); 584 // We register a region with the fast "in collection set" test. We 585 // simply set to true the array slot corresponding to this region. 586 void register_young_region_with_cset(HeapRegion* r) { 587 _in_cset_fast_test.set_in_young(r->hrm_index()); 588 } 589 void register_old_region_with_cset(HeapRegion* r) { 590 _in_cset_fast_test.set_in_old(r->hrm_index()); 591 } 592 inline void register_ext_region_with_cset(HeapRegion* r) { 593 _in_cset_fast_test.set_ext(r->hrm_index()); 594 } 595 void clear_in_cset(const HeapRegion* hr) { 596 _in_cset_fast_test.clear(hr); 597 } 598 599 void clear_cset_fast_test() { 600 _in_cset_fast_test.clear(); 601 } 602 603 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 604 605 // This is called at the start of either a concurrent cycle or a Full 606 // GC to update the number of old marking cycles started. 607 void increment_old_marking_cycles_started(); 608 609 // This is called at the end of either a concurrent cycle or a Full 610 // GC to update the number of old marking cycles completed. Those two 611 // can happen in a nested fashion, i.e., we start a concurrent 612 // cycle, a Full GC happens half-way through it which ends first, 613 // and then the cycle notices that a Full GC happened and ends 614 // too. The concurrent parameter is a boolean to help us do a bit 615 // tighter consistency checking in the method. If concurrent is 616 // false, the caller is the inner caller in the nesting (i.e., the 617 // Full GC). If concurrent is true, the caller is the outer caller 618 // in this nesting (i.e., the concurrent cycle). Further nesting is 619 // not currently supported. The end of this call also notifies 620 // the FullGCCount_lock in case a Java thread is waiting for a full 621 // GC to happen (e.g., it called System.gc() with 622 // +ExplicitGCInvokesConcurrent). 623 void increment_old_marking_cycles_completed(bool concurrent); 624 625 uint old_marking_cycles_completed() { 626 return _old_marking_cycles_completed; 627 } 628 629 G1HRPrinter* hr_printer() { return &_hr_printer; } 630 631 // Allocates a new heap region instance. 632 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 633 634 // Allocate the highest free region in the reserved heap. This will commit 635 // regions as necessary. 636 HeapRegion* alloc_highest_free_region(); 637 638 // Frees a non-humongous region by initializing its contents and 639 // adding it to the free list that's passed as a parameter (this is 640 // usually a local list which will be appended to the master free 641 // list later). The used bytes of freed regions are accumulated in 642 // pre_used. If par is true, the region's RSet will not be freed 643 // up. The assumption is that this will be done later. 644 // The locked parameter indicates if the caller has already taken 645 // care of proper synchronization. This may allow some optimizations. 646 void free_region(HeapRegion* hr, 647 FreeRegionList* free_list, 648 bool par, 649 bool locked = false); 650 651 // It dirties the cards that cover the block so that the post 652 // write barrier never queues anything when updating objects on this 653 // block. It is assumed (and in fact we assert) that the block 654 // belongs to a young region. 655 inline void dirty_young_block(HeapWord* start, size_t word_size); 656 657 // Frees a humongous region by collapsing it into individual regions 658 // and calling free_region() for each of them. The freed regions 659 // will be added to the free list that's passed as a parameter (this 660 // is usually a local list which will be appended to the master free 661 // list later). The used bytes of freed regions are accumulated in 662 // pre_used. If par is true, the region's RSet will not be freed 663 // up. The assumption is that this will be done later. 664 void free_humongous_region(HeapRegion* hr, 665 FreeRegionList* free_list, 666 bool par); 667 668 // Facility for allocating in 'archive' regions in high heap memory and 669 // recording the allocated ranges. These should all be called from the 670 // VM thread at safepoints, without the heap lock held. They can be used 671 // to create and archive a set of heap regions which can be mapped at the 672 // same fixed addresses in a subsequent JVM invocation. 673 void begin_archive_alloc_range(); 674 675 // Check if the requested size would be too large for an archive allocation. 676 bool is_archive_alloc_too_large(size_t word_size); 677 678 // Allocate memory of the requested size from the archive region. This will 679 // return NULL if the size is too large or if no memory is available. It 680 // does not trigger a garbage collection. 681 HeapWord* archive_mem_allocate(size_t word_size); 682 683 // Optionally aligns the end address and returns the allocated ranges in 684 // an array of MemRegions in order of ascending addresses. 685 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 686 size_t end_alignment_in_bytes = 0); 687 688 // Facility for allocating a fixed range within the heap and marking 689 // the containing regions as 'archive'. For use at JVM init time, when the 690 // caller may mmap archived heap data at the specified range(s). 691 // Verify that the MemRegions specified in the argument array are within the 692 // reserved heap. 693 bool check_archive_addresses(MemRegion* range, size_t count); 694 695 // Commit the appropriate G1 regions containing the specified MemRegions 696 // and mark them as 'archive' regions. The regions in the array must be 697 // non-overlapping and in order of ascending address. 698 bool alloc_archive_regions(MemRegion* range, size_t count); 699 700 // Insert any required filler objects in the G1 regions around the specified 701 // ranges to make the regions parseable. This must be called after 702 // alloc_archive_regions, and after class loading has occurred. 703 void fill_archive_regions(MemRegion* range, size_t count); 704 705 // For each of the specified MemRegions, uncommit the containing G1 regions 706 // which had been allocated by alloc_archive_regions. This should be called 707 // rather than fill_archive_regions at JVM init time if the archive file 708 // mapping failed, with the same non-overlapping and sorted MemRegion array. 709 void dealloc_archive_regions(MemRegion* range, size_t count); 710 711 protected: 712 713 // Shrink the garbage-first heap by at most the given size (in bytes!). 714 // (Rounds down to a HeapRegion boundary.) 715 virtual void shrink(size_t expand_bytes); 716 void shrink_helper(size_t expand_bytes); 717 718 #if TASKQUEUE_STATS 719 static void print_taskqueue_stats_hdr(outputStream* const st); 720 void print_taskqueue_stats() const; 721 void reset_taskqueue_stats(); 722 #endif // TASKQUEUE_STATS 723 724 // Schedule the VM operation that will do an evacuation pause to 725 // satisfy an allocation request of word_size. *succeeded will 726 // return whether the VM operation was successful (it did do an 727 // evacuation pause) or not (another thread beat us to it or the GC 728 // locker was active). Given that we should not be holding the 729 // Heap_lock when we enter this method, we will pass the 730 // gc_count_before (i.e., total_collections()) as a parameter since 731 // it has to be read while holding the Heap_lock. Currently, both 732 // methods that call do_collection_pause() release the Heap_lock 733 // before the call, so it's easy to read gc_count_before just before. 734 HeapWord* do_collection_pause(size_t word_size, 735 uint gc_count_before, 736 bool* succeeded, 737 GCCause::Cause gc_cause); 738 739 void wait_for_root_region_scanning(); 740 741 // The guts of the incremental collection pause, executed by the vm 742 // thread. It returns false if it is unable to do the collection due 743 // to the GC locker being active, true otherwise 744 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 745 746 // Actually do the work of evacuating the collection set. 747 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 748 749 void pre_evacuate_collection_set(); 750 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 751 752 // Print the header for the per-thread termination statistics. 753 static void print_termination_stats_hdr(); 754 // Print actual per-thread termination statistics. 755 void print_termination_stats(uint worker_id, 756 double elapsed_ms, 757 double strong_roots_ms, 758 double term_ms, 759 size_t term_attempts, 760 size_t alloc_buffer_waste, 761 size_t undo_waste) const; 762 // Update object copying statistics. 763 void record_obj_copy_mem_stats(); 764 765 // The g1 remembered set of the heap. 766 G1RemSet* _g1_rem_set; 767 768 // A set of cards that cover the objects for which the Rsets should be updated 769 // concurrently after the collection. 770 DirtyCardQueueSet _dirty_card_queue_set; 771 772 // The closure used to refine a single card. 773 RefineCardTableEntryClosure* _refine_cte_cl; 774 775 // After a collection pause, make the regions in the CS into free 776 // regions. 777 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 778 779 // Abandon the current collection set without recording policy 780 // statistics or updating free lists. 781 void abandon_collection_set(HeapRegion* cs_head); 782 783 // The concurrent marker (and the thread it runs in.) 784 G1ConcurrentMark* _cm; 785 ConcurrentMarkThread* _cmThread; 786 787 // The concurrent refiner. 788 ConcurrentG1Refine* _cg1r; 789 790 // The parallel task queues 791 RefToScanQueueSet *_task_queues; 792 793 // True iff a evacuation has failed in the current collection. 794 bool _evacuation_failed; 795 796 EvacuationFailedInfo* _evacuation_failed_info_array; 797 798 // Failed evacuations cause some logical from-space objects to have 799 // forwarding pointers to themselves. Reset them. 800 void remove_self_forwarding_pointers(); 801 802 // Restore the objects in the regions in the collection set after an 803 // evacuation failure. 804 void restore_after_evac_failure(); 805 806 PreservedMarksSet _preserved_marks_set; 807 808 // Preserve the mark of "obj", if necessary, in preparation for its mark 809 // word being overwritten with a self-forwarding-pointer. 810 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 811 812 #ifndef PRODUCT 813 // Support for forcing evacuation failures. Analogous to 814 // PromotionFailureALot for the other collectors. 815 816 // Records whether G1EvacuationFailureALot should be in effect 817 // for the current GC 818 bool _evacuation_failure_alot_for_current_gc; 819 820 // Used to record the GC number for interval checking when 821 // determining whether G1EvaucationFailureALot is in effect 822 // for the current GC. 823 size_t _evacuation_failure_alot_gc_number; 824 825 // Count of the number of evacuations between failures. 826 volatile size_t _evacuation_failure_alot_count; 827 828 // Set whether G1EvacuationFailureALot should be in effect 829 // for the current GC (based upon the type of GC and which 830 // command line flags are set); 831 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 832 bool during_initial_mark, 833 bool during_marking); 834 835 inline void set_evacuation_failure_alot_for_current_gc(); 836 837 // Return true if it's time to cause an evacuation failure. 838 inline bool evacuation_should_fail(); 839 840 // Reset the G1EvacuationFailureALot counters. Should be called at 841 // the end of an evacuation pause in which an evacuation failure occurred. 842 inline void reset_evacuation_should_fail(); 843 #endif // !PRODUCT 844 845 // ("Weak") Reference processing support. 846 // 847 // G1 has 2 instances of the reference processor class. One 848 // (_ref_processor_cm) handles reference object discovery 849 // and subsequent processing during concurrent marking cycles. 850 // 851 // The other (_ref_processor_stw) handles reference object 852 // discovery and processing during full GCs and incremental 853 // evacuation pauses. 854 // 855 // During an incremental pause, reference discovery will be 856 // temporarily disabled for _ref_processor_cm and will be 857 // enabled for _ref_processor_stw. At the end of the evacuation 858 // pause references discovered by _ref_processor_stw will be 859 // processed and discovery will be disabled. The previous 860 // setting for reference object discovery for _ref_processor_cm 861 // will be re-instated. 862 // 863 // At the start of marking: 864 // * Discovery by the CM ref processor is verified to be inactive 865 // and it's discovered lists are empty. 866 // * Discovery by the CM ref processor is then enabled. 867 // 868 // At the end of marking: 869 // * Any references on the CM ref processor's discovered 870 // lists are processed (possibly MT). 871 // 872 // At the start of full GC we: 873 // * Disable discovery by the CM ref processor and 874 // empty CM ref processor's discovered lists 875 // (without processing any entries). 876 // * Verify that the STW ref processor is inactive and it's 877 // discovered lists are empty. 878 // * Temporarily set STW ref processor discovery as single threaded. 879 // * Temporarily clear the STW ref processor's _is_alive_non_header 880 // field. 881 // * Finally enable discovery by the STW ref processor. 882 // 883 // The STW ref processor is used to record any discovered 884 // references during the full GC. 885 // 886 // At the end of a full GC we: 887 // * Enqueue any reference objects discovered by the STW ref processor 888 // that have non-live referents. This has the side-effect of 889 // making the STW ref processor inactive by disabling discovery. 890 // * Verify that the CM ref processor is still inactive 891 // and no references have been placed on it's discovered 892 // lists (also checked as a precondition during initial marking). 893 894 // The (stw) reference processor... 895 ReferenceProcessor* _ref_processor_stw; 896 897 STWGCTimer* _gc_timer_stw; 898 899 G1NewTracer* _gc_tracer_stw; 900 901 // During reference object discovery, the _is_alive_non_header 902 // closure (if non-null) is applied to the referent object to 903 // determine whether the referent is live. If so then the 904 // reference object does not need to be 'discovered' and can 905 // be treated as a regular oop. This has the benefit of reducing 906 // the number of 'discovered' reference objects that need to 907 // be processed. 908 // 909 // Instance of the is_alive closure for embedding into the 910 // STW reference processor as the _is_alive_non_header field. 911 // Supplying a value for the _is_alive_non_header field is 912 // optional but doing so prevents unnecessary additions to 913 // the discovered lists during reference discovery. 914 G1STWIsAliveClosure _is_alive_closure_stw; 915 916 // The (concurrent marking) reference processor... 917 ReferenceProcessor* _ref_processor_cm; 918 919 // Instance of the concurrent mark is_alive closure for embedding 920 // into the Concurrent Marking reference processor as the 921 // _is_alive_non_header field. Supplying a value for the 922 // _is_alive_non_header field is optional but doing so prevents 923 // unnecessary additions to the discovered lists during reference 924 // discovery. 925 G1CMIsAliveClosure _is_alive_closure_cm; 926 927 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 928 HeapRegion** _worker_cset_start_region; 929 930 // Time stamp to validate the regions recorded in the cache 931 // used by G1CollectedHeap::start_cset_region_for_worker(). 932 // The heap region entry for a given worker is valid iff 933 // the associated time stamp value matches the current value 934 // of G1CollectedHeap::_gc_time_stamp. 935 uint* _worker_cset_start_region_time_stamp; 936 937 volatile bool _free_regions_coming; 938 939 public: 940 941 void set_refine_cte_cl_concurrency(bool concurrent); 942 943 RefToScanQueue *task_queue(uint i) const; 944 945 uint num_task_queues() const; 946 947 // A set of cards where updates happened during the GC 948 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 949 950 // Create a G1CollectedHeap with the specified policy. 951 // Must call the initialize method afterwards. 952 // May not return if something goes wrong. 953 G1CollectedHeap(G1CollectorPolicy* policy); 954 955 // Initialize the G1CollectedHeap to have the initial and 956 // maximum sizes and remembered and barrier sets 957 // specified by the policy object. 958 jint initialize(); 959 960 virtual void stop(); 961 962 // Return the (conservative) maximum heap alignment for any G1 heap 963 static size_t conservative_max_heap_alignment(); 964 965 // Does operations required after initialization has been done. 966 void post_initialize(); 967 968 // Initialize weak reference processing. 969 void ref_processing_init(); 970 971 virtual Name kind() const { 972 return CollectedHeap::G1CollectedHeap; 973 } 974 975 virtual const char* name() const { 976 return "G1"; 977 } 978 979 const G1CollectorState* collector_state() const { return &_collector_state; } 980 G1CollectorState* collector_state() { return &_collector_state; } 981 982 // The current policy object for the collector. 983 G1Policy* g1_policy() const { return _g1_policy; } 984 985 const G1CollectionSet* collection_set() const { return &_collection_set; } 986 G1CollectionSet* collection_set() { return &_collection_set; } 987 988 virtual CollectorPolicy* collector_policy() const; 989 990 // Adaptive size policy. No such thing for g1. 991 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 992 993 // The rem set and barrier set. 994 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 995 996 // Try to minimize the remembered set. 997 void scrub_rem_set(); 998 999 uint get_gc_time_stamp() { 1000 return _gc_time_stamp; 1001 } 1002 1003 inline void reset_gc_time_stamp(); 1004 1005 void check_gc_time_stamps() PRODUCT_RETURN; 1006 1007 inline void increment_gc_time_stamp(); 1008 1009 // Reset the given region's GC timestamp. If it's starts humongous, 1010 // also reset the GC timestamp of its corresponding 1011 // continues humongous regions too. 1012 void reset_gc_time_stamps(HeapRegion* hr); 1013 1014 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1015 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1016 1017 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1018 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1019 1020 // The shared block offset table array. 1021 G1BlockOffsetTable* bot() const { return _bot; } 1022 1023 // Reference Processing accessors 1024 1025 // The STW reference processor.... 1026 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1027 1028 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1029 1030 // The Concurrent Marking reference processor... 1031 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1032 1033 virtual size_t capacity() const; 1034 virtual size_t used() const; 1035 // This should be called when we're not holding the heap lock. The 1036 // result might be a bit inaccurate. 1037 size_t used_unlocked() const; 1038 size_t recalculate_used() const; 1039 1040 // These virtual functions do the actual allocation. 1041 // Some heaps may offer a contiguous region for shared non-blocking 1042 // allocation, via inlined code (by exporting the address of the top and 1043 // end fields defining the extent of the contiguous allocation region.) 1044 // But G1CollectedHeap doesn't yet support this. 1045 1046 virtual bool is_maximal_no_gc() const { 1047 return _hrm.available() == 0; 1048 } 1049 1050 // The current number of regions in the heap. 1051 uint num_regions() const { return _hrm.length(); } 1052 1053 // The max number of regions in the heap. 1054 uint max_regions() const { return _hrm.max_length(); } 1055 1056 // The number of regions that are completely free. 1057 uint num_free_regions() const { return _hrm.num_free_regions(); } 1058 1059 MemoryUsage get_auxiliary_data_memory_usage() const { 1060 return _hrm.get_auxiliary_data_memory_usage(); 1061 } 1062 1063 // The number of regions that are not completely free. 1064 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1065 1066 #ifdef ASSERT 1067 bool is_on_master_free_list(HeapRegion* hr) { 1068 return _hrm.is_free(hr); 1069 } 1070 #endif // ASSERT 1071 1072 // Wrapper for the region list operations that can be called from 1073 // methods outside this class. 1074 1075 void secondary_free_list_add(FreeRegionList* list) { 1076 _secondary_free_list.add_ordered(list); 1077 } 1078 1079 void append_secondary_free_list() { 1080 _hrm.insert_list_into_free_list(&_secondary_free_list); 1081 } 1082 1083 void append_secondary_free_list_if_not_empty_with_lock() { 1084 // If the secondary free list looks empty there's no reason to 1085 // take the lock and then try to append it. 1086 if (!_secondary_free_list.is_empty()) { 1087 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1088 append_secondary_free_list(); 1089 } 1090 } 1091 1092 inline void old_set_add(HeapRegion* hr); 1093 inline void old_set_remove(HeapRegion* hr); 1094 1095 size_t non_young_capacity_bytes() { 1096 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes; 1097 } 1098 1099 void set_free_regions_coming(); 1100 void reset_free_regions_coming(); 1101 bool free_regions_coming() { return _free_regions_coming; } 1102 void wait_while_free_regions_coming(); 1103 1104 // Determine whether the given region is one that we are using as an 1105 // old GC alloc region. 1106 bool is_old_gc_alloc_region(HeapRegion* hr); 1107 1108 // Perform a collection of the heap; intended for use in implementing 1109 // "System.gc". This probably implies as full a collection as the 1110 // "CollectedHeap" supports. 1111 virtual void collect(GCCause::Cause cause); 1112 1113 virtual bool copy_allocation_context_stats(const jint* contexts, 1114 jlong* totals, 1115 jbyte* accuracy, 1116 jint len); 1117 1118 // True iff an evacuation has failed in the most-recent collection. 1119 bool evacuation_failed() { return _evacuation_failed; } 1120 1121 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed); 1122 void prepend_to_freelist(FreeRegionList* list); 1123 void decrement_summary_bytes(size_t bytes); 1124 1125 virtual bool is_in(const void* p) const; 1126 #ifdef ASSERT 1127 // Returns whether p is in one of the available areas of the heap. Slow but 1128 // extensive version. 1129 bool is_in_exact(const void* p) const; 1130 #endif 1131 1132 // Return "TRUE" iff the given object address is within the collection 1133 // set. Slow implementation. 1134 bool obj_in_cs(oop obj); 1135 1136 inline bool is_in_cset(const HeapRegion *hr); 1137 inline bool is_in_cset(oop obj); 1138 1139 inline bool is_in_cset_or_humongous(const oop obj); 1140 1141 private: 1142 // This array is used for a quick test on whether a reference points into 1143 // the collection set or not. Each of the array's elements denotes whether the 1144 // corresponding region is in the collection set or not. 1145 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1146 1147 public: 1148 1149 inline InCSetState in_cset_state(const oop obj); 1150 1151 // Return "TRUE" iff the given object address is in the reserved 1152 // region of g1. 1153 bool is_in_g1_reserved(const void* p) const { 1154 return _hrm.reserved().contains(p); 1155 } 1156 1157 // Returns a MemRegion that corresponds to the space that has been 1158 // reserved for the heap 1159 MemRegion g1_reserved() const { 1160 return _hrm.reserved(); 1161 } 1162 1163 virtual bool is_in_closed_subset(const void* p) const; 1164 1165 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1166 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1167 } 1168 1169 // Iteration functions. 1170 1171 // Iterate over all objects, calling "cl.do_object" on each. 1172 virtual void object_iterate(ObjectClosure* cl); 1173 1174 virtual void safe_object_iterate(ObjectClosure* cl) { 1175 object_iterate(cl); 1176 } 1177 1178 // Iterate over heap regions, in address order, terminating the 1179 // iteration early if the "doHeapRegion" method returns "true". 1180 void heap_region_iterate(HeapRegionClosure* blk) const; 1181 1182 // Return the region with the given index. It assumes the index is valid. 1183 inline HeapRegion* region_at(uint index) const; 1184 1185 // Return the next region (by index) that is part of the same 1186 // humongous object that hr is part of. 1187 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1188 1189 // Calculate the region index of the given address. Given address must be 1190 // within the heap. 1191 inline uint addr_to_region(HeapWord* addr) const; 1192 1193 inline HeapWord* bottom_addr_for_region(uint index) const; 1194 1195 // Iterate over the heap regions in parallel. Assumes that this will be called 1196 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1197 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1198 // to each of the regions, by attempting to claim the region using the 1199 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1200 // region. The concurrent argument should be set to true if iteration is 1201 // performed concurrently, during which no assumptions are made for consistent 1202 // attributes of the heap regions (as they might be modified while iterating). 1203 void heap_region_par_iterate(HeapRegionClosure* cl, 1204 uint worker_id, 1205 HeapRegionClaimer* hrclaimer, 1206 bool concurrent = false) const; 1207 1208 // Clear the cached cset start regions and (more importantly) 1209 // the time stamps. Called when we reset the GC time stamp. 1210 void clear_cset_start_regions(); 1211 1212 // Given the id of a worker, obtain or calculate a suitable 1213 // starting region for iterating over the current collection set. 1214 HeapRegion* start_cset_region_for_worker(uint worker_i); 1215 1216 // Iterate over the regions (if any) in the current collection set. 1217 void collection_set_iterate(HeapRegionClosure* blk); 1218 1219 // As above but starting from region r 1220 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1221 1222 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1223 1224 // Returns the HeapRegion that contains addr. addr must not be NULL. 1225 template <class T> 1226 inline HeapRegion* heap_region_containing(const T addr) const; 1227 1228 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1229 // each address in the (reserved) heap is a member of exactly 1230 // one block. The defining characteristic of a block is that it is 1231 // possible to find its size, and thus to progress forward to the next 1232 // block. (Blocks may be of different sizes.) Thus, blocks may 1233 // represent Java objects, or they might be free blocks in a 1234 // free-list-based heap (or subheap), as long as the two kinds are 1235 // distinguishable and the size of each is determinable. 1236 1237 // Returns the address of the start of the "block" that contains the 1238 // address "addr". We say "blocks" instead of "object" since some heaps 1239 // may not pack objects densely; a chunk may either be an object or a 1240 // non-object. 1241 virtual HeapWord* block_start(const void* addr) const; 1242 1243 // Requires "addr" to be the start of a chunk, and returns its size. 1244 // "addr + size" is required to be the start of a new chunk, or the end 1245 // of the active area of the heap. 1246 virtual size_t block_size(const HeapWord* addr) const; 1247 1248 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1249 // the block is an object. 1250 virtual bool block_is_obj(const HeapWord* addr) const; 1251 1252 // Section on thread-local allocation buffers (TLABs) 1253 // See CollectedHeap for semantics. 1254 1255 bool supports_tlab_allocation() const; 1256 size_t tlab_capacity(Thread* ignored) const; 1257 size_t tlab_used(Thread* ignored) const; 1258 size_t max_tlab_size() const; 1259 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1260 1261 // Can a compiler initialize a new object without store barriers? 1262 // This permission only extends from the creation of a new object 1263 // via a TLAB up to the first subsequent safepoint. If such permission 1264 // is granted for this heap type, the compiler promises to call 1265 // defer_store_barrier() below on any slow path allocation of 1266 // a new object for which such initializing store barriers will 1267 // have been elided. G1, like CMS, allows this, but should be 1268 // ready to provide a compensating write barrier as necessary 1269 // if that storage came out of a non-young region. The efficiency 1270 // of this implementation depends crucially on being able to 1271 // answer very efficiently in constant time whether a piece of 1272 // storage in the heap comes from a young region or not. 1273 // See ReduceInitialCardMarks. 1274 virtual bool can_elide_tlab_store_barriers() const { 1275 return true; 1276 } 1277 1278 virtual bool card_mark_must_follow_store() const { 1279 return true; 1280 } 1281 1282 // The reference pending list lock is acquired from from the 1283 // ConcurrentMarkThread. 1284 virtual bool needs_reference_pending_list_locker_thread() const { 1285 return true; 1286 } 1287 1288 inline bool is_in_young(const oop obj); 1289 1290 virtual bool is_scavengable(const void* addr); 1291 1292 // We don't need barriers for initializing stores to objects 1293 // in the young gen: for the SATB pre-barrier, there is no 1294 // pre-value that needs to be remembered; for the remembered-set 1295 // update logging post-barrier, we don't maintain remembered set 1296 // information for young gen objects. 1297 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1298 1299 // Returns "true" iff the given word_size is "very large". 1300 static bool is_humongous(size_t word_size) { 1301 // Note this has to be strictly greater-than as the TLABs 1302 // are capped at the humongous threshold and we want to 1303 // ensure that we don't try to allocate a TLAB as 1304 // humongous and that we don't allocate a humongous 1305 // object in a TLAB. 1306 return word_size > _humongous_object_threshold_in_words; 1307 } 1308 1309 // Returns the humongous threshold for a specific region size 1310 static size_t humongous_threshold_for(size_t region_size) { 1311 return (region_size / 2); 1312 } 1313 1314 // Returns the number of regions the humongous object of the given word size 1315 // requires. 1316 static size_t humongous_obj_size_in_regions(size_t word_size); 1317 1318 // Print the maximum heap capacity. 1319 virtual size_t max_capacity() const; 1320 1321 virtual jlong millis_since_last_gc(); 1322 1323 1324 // Convenience function to be used in situations where the heap type can be 1325 // asserted to be this type. 1326 static G1CollectedHeap* heap(); 1327 1328 void set_region_short_lived_locked(HeapRegion* hr); 1329 // add appropriate methods for any other surv rate groups 1330 1331 YoungList* young_list() const { return _young_list; } 1332 1333 uint old_regions_count() const { return _old_set.length(); } 1334 1335 uint humongous_regions_count() const { return _humongous_set.length(); } 1336 1337 // debugging 1338 bool check_young_list_well_formed() { 1339 return _young_list->check_list_well_formed(); 1340 } 1341 1342 bool check_young_list_empty(bool check_heap); 1343 1344 // *** Stuff related to concurrent marking. It's not clear to me that so 1345 // many of these need to be public. 1346 1347 // The functions below are helper functions that a subclass of 1348 // "CollectedHeap" can use in the implementation of its virtual 1349 // functions. 1350 // This performs a concurrent marking of the live objects in a 1351 // bitmap off to the side. 1352 void doConcurrentMark(); 1353 1354 bool isMarkedPrev(oop obj) const; 1355 bool isMarkedNext(oop obj) const; 1356 1357 // Determine if an object is dead, given the object and also 1358 // the region to which the object belongs. An object is dead 1359 // iff a) it was not allocated since the last mark, b) it 1360 // is not marked, and c) it is not in an archive region. 1361 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1362 return 1363 !hr->obj_allocated_since_prev_marking(obj) && 1364 !isMarkedPrev(obj) && 1365 !hr->is_archive(); 1366 } 1367 1368 // This function returns true when an object has been 1369 // around since the previous marking and hasn't yet 1370 // been marked during this marking, and is not in an archive region. 1371 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1372 return 1373 !hr->obj_allocated_since_next_marking(obj) && 1374 !isMarkedNext(obj) && 1375 !hr->is_archive(); 1376 } 1377 1378 // Determine if an object is dead, given only the object itself. 1379 // This will find the region to which the object belongs and 1380 // then call the region version of the same function. 1381 1382 // Added if it is NULL it isn't dead. 1383 1384 inline bool is_obj_dead(const oop obj) const; 1385 1386 inline bool is_obj_ill(const oop obj) const; 1387 1388 G1ConcurrentMark* concurrent_mark() const { return _cm; } 1389 1390 // Refinement 1391 1392 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1393 1394 // Optimized nmethod scanning support routines 1395 1396 // Register the given nmethod with the G1 heap. 1397 virtual void register_nmethod(nmethod* nm); 1398 1399 // Unregister the given nmethod from the G1 heap. 1400 virtual void unregister_nmethod(nmethod* nm); 1401 1402 // Free up superfluous code root memory. 1403 void purge_code_root_memory(); 1404 1405 // Rebuild the strong code root lists for each region 1406 // after a full GC. 1407 void rebuild_strong_code_roots(); 1408 1409 // Delete entries for dead interned string and clean up unreferenced symbols 1410 // in symbol table, possibly in parallel. 1411 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1412 1413 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1414 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1415 1416 // Redirty logged cards in the refinement queue. 1417 void redirty_logged_cards(); 1418 // Verification 1419 1420 // Perform any cleanup actions necessary before allowing a verification. 1421 virtual void prepare_for_verify(); 1422 1423 // Perform verification. 1424 1425 // vo == UsePrevMarking -> use "prev" marking information, 1426 // vo == UseNextMarking -> use "next" marking information 1427 // vo == UseMarkWord -> use the mark word in the object header 1428 // 1429 // NOTE: Only the "prev" marking information is guaranteed to be 1430 // consistent most of the time, so most calls to this should use 1431 // vo == UsePrevMarking. 1432 // Currently, there is only one case where this is called with 1433 // vo == UseNextMarking, which is to verify the "next" marking 1434 // information at the end of remark. 1435 // Currently there is only one place where this is called with 1436 // vo == UseMarkWord, which is to verify the marking during a 1437 // full GC. 1438 void verify(VerifyOption vo); 1439 1440 // The methods below are here for convenience and dispatch the 1441 // appropriate method depending on value of the given VerifyOption 1442 // parameter. The values for that parameter, and their meanings, 1443 // are the same as those above. 1444 1445 bool is_obj_dead_cond(const oop obj, 1446 const HeapRegion* hr, 1447 const VerifyOption vo) const; 1448 1449 bool is_obj_dead_cond(const oop obj, 1450 const VerifyOption vo) const; 1451 1452 G1HeapSummary create_g1_heap_summary(); 1453 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1454 1455 // Printing 1456 private: 1457 void print_heap_regions() const; 1458 void print_regions_on(outputStream* st) const; 1459 1460 public: 1461 virtual void print_on(outputStream* st) const; 1462 virtual void print_extended_on(outputStream* st) const; 1463 virtual void print_on_error(outputStream* st) const; 1464 1465 virtual void print_gc_threads_on(outputStream* st) const; 1466 virtual void gc_threads_do(ThreadClosure* tc) const; 1467 1468 // Override 1469 void print_tracing_info() const; 1470 1471 // The following two methods are helpful for debugging RSet issues. 1472 void print_cset_rsets() PRODUCT_RETURN; 1473 void print_all_rsets() PRODUCT_RETURN; 1474 1475 public: 1476 size_t pending_card_num(); 1477 1478 protected: 1479 size_t _max_heap_capacity; 1480 }; 1481 1482 class G1ParEvacuateFollowersClosure : public VoidClosure { 1483 private: 1484 double _start_term; 1485 double _term_time; 1486 size_t _term_attempts; 1487 1488 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1489 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1490 protected: 1491 G1CollectedHeap* _g1h; 1492 G1ParScanThreadState* _par_scan_state; 1493 RefToScanQueueSet* _queues; 1494 ParallelTaskTerminator* _terminator; 1495 1496 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1497 RefToScanQueueSet* queues() { return _queues; } 1498 ParallelTaskTerminator* terminator() { return _terminator; } 1499 1500 public: 1501 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1502 G1ParScanThreadState* par_scan_state, 1503 RefToScanQueueSet* queues, 1504 ParallelTaskTerminator* terminator) 1505 : _g1h(g1h), _par_scan_state(par_scan_state), 1506 _queues(queues), _terminator(terminator), 1507 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1508 1509 void do_void(); 1510 1511 double term_time() const { return _term_time; } 1512 size_t term_attempts() const { return _term_attempts; } 1513 1514 private: 1515 inline bool offer_termination(); 1516 }; 1517 1518 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP