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/g1SATBCardTableModRefBS.hpp" 40 #include "gc/g1/g1YCTypes.hpp" 41 #include "gc/g1/hSpaceCounters.hpp" 42 #include "gc/g1/heapRegionManager.hpp" 43 #include "gc/g1/heapRegionSet.hpp" 44 #include "gc/g1/youngList.hpp" 45 #include "gc/shared/barrierSet.hpp" 46 #include "gc/shared/collectedHeap.hpp" 47 #include "gc/shared/plab.hpp" 48 #include "memory/memRegion.hpp" 49 #include "utilities/stack.hpp" 50 51 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 52 // It uses the "Garbage First" heap organization and algorithm, which 53 // may combine concurrent marking with parallel, incremental compaction of 54 // heap subsets that will yield large amounts of garbage. 55 56 // Forward declarations 57 class HeapRegion; 58 class HRRSCleanupTask; 59 class GenerationSpec; 60 class OopsInHeapRegionClosure; 61 class G1ParScanThreadState; 62 class G1ParScanThreadStateSet; 63 class G1KlassScanClosure; 64 class G1ParScanThreadState; 65 class ObjectClosure; 66 class SpaceClosure; 67 class CompactibleSpaceClosure; 68 class Space; 69 class G1CollectionSet; 70 class G1CollectorPolicy; 71 class G1RemSet; 72 class HeapRegionRemSetIterator; 73 class G1ConcurrentMark; 74 class ConcurrentMarkThread; 75 class ConcurrentG1Refine; 76 class ConcurrentGCTimer; 77 class GenerationCounters; 78 class STWGCTimer; 79 class G1NewTracer; 80 class G1OldTracer; 81 class EvacuationFailedInfo; 82 class nmethod; 83 class Ticks; 84 class WorkGang; 85 class G1Allocator; 86 class G1ArchiveAllocator; 87 class G1HeapVerifier; 88 89 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 90 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 91 92 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 93 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 94 95 // The G1 STW is alive closure. 96 // An instance is embedded into the G1CH and used as the 97 // (optional) _is_alive_non_header closure in the STW 98 // reference processor. It is also extensively used during 99 // reference processing during STW evacuation pauses. 100 class G1STWIsAliveClosure: public BoolObjectClosure { 101 G1CollectedHeap* _g1; 102 public: 103 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 104 bool do_object_b(oop p); 105 }; 106 107 class RefineCardTableEntryClosure; 108 109 class G1RegionMappingChangedListener : public G1MappingChangedListener { 110 private: 111 void reset_from_card_cache(uint start_idx, size_t num_regions); 112 public: 113 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 114 }; 115 116 class G1CollectedHeap : public CollectedHeap { 117 friend class VM_CollectForMetadataAllocation; 118 friend class VM_G1CollectForAllocation; 119 friend class VM_G1CollectFull; 120 friend class VM_G1IncCollectionPause; 121 friend class VMStructs; 122 friend class MutatorAllocRegion; 123 friend class G1GCAllocRegion; 124 friend class G1HeapVerifier; 125 126 // Closures used in implementation. 127 friend class G1ParScanThreadState; 128 friend class G1ParScanThreadStateSet; 129 friend class G1ParTask; 130 friend class G1PLABAllocator; 131 friend class G1PrepareCompactClosure; 132 133 // Other related classes. 134 friend class HeapRegionClaimer; 135 136 // Testing classes. 137 friend class G1CheckCSetFastTableClosure; 138 139 private: 140 WorkGang* _workers; 141 142 static size_t _humongous_object_threshold_in_words; 143 144 // The secondary free list which contains regions that have been 145 // freed up during the cleanup process. This will be appended to 146 // the master free list when appropriate. 147 FreeRegionList _secondary_free_list; 148 149 // It keeps track of the old regions. 150 HeapRegionSet _old_set; 151 152 // It keeps track of the humongous regions. 153 HeapRegionSet _humongous_set; 154 155 void eagerly_reclaim_humongous_regions(); 156 157 // The number of regions we could create by expansion. 158 uint _expansion_regions; 159 160 // The block offset table for the G1 heap. 161 G1BlockOffsetTable* _bot; 162 163 // Tears down the region sets / lists so that they are empty and the 164 // regions on the heap do not belong to a region set / list. The 165 // only exception is the humongous set which we leave unaltered. If 166 // free_list_only is true, it will only tear down the master free 167 // list. It is called before a Full GC (free_list_only == false) or 168 // before heap shrinking (free_list_only == true). 169 void tear_down_region_sets(bool free_list_only); 170 171 // Rebuilds the region sets / lists so that they are repopulated to 172 // reflect the contents of the heap. The only exception is the 173 // humongous set which was not torn down in the first place. If 174 // free_list_only is true, it will only rebuild the master free 175 // list. It is called after a Full GC (free_list_only == false) or 176 // after heap shrinking (free_list_only == true). 177 void rebuild_region_sets(bool free_list_only); 178 179 // Callback for region mapping changed events. 180 G1RegionMappingChangedListener _listener; 181 182 // The sequence of all heap regions in the heap. 183 HeapRegionManager _hrm; 184 185 // Manages all allocations with regions except humongous object allocations. 186 G1Allocator* _allocator; 187 188 // Manages all heap verification. 189 G1HeapVerifier* _verifier; 190 191 // Outside of GC pauses, the number of bytes used in all regions other 192 // than the current allocation region(s). 193 size_t _summary_bytes_used; 194 195 void increase_used(size_t bytes); 196 void decrease_used(size_t bytes); 197 198 void set_used(size_t bytes); 199 200 // Class that handles archive allocation ranges. 201 G1ArchiveAllocator* _archive_allocator; 202 203 // Statistics for each allocation context 204 AllocationContextStats _allocation_context_stats; 205 206 // GC allocation statistics policy for survivors. 207 G1EvacStats _survivor_evac_stats; 208 209 // GC allocation statistics policy for tenured objects. 210 G1EvacStats _old_evac_stats; 211 212 // It specifies whether we should attempt to expand the heap after a 213 // region allocation failure. If heap expansion fails we set this to 214 // false so that we don't re-attempt the heap expansion (it's likely 215 // that subsequent expansion attempts will also fail if one fails). 216 // Currently, it is only consulted during GC and it's reset at the 217 // start of each GC. 218 bool _expand_heap_after_alloc_failure; 219 220 // Helper for monitoring and management support. 221 G1MonitoringSupport* _g1mm; 222 223 // Records whether the region at the given index is (still) a 224 // candidate for eager reclaim. Only valid for humongous start 225 // regions; other regions have unspecified values. Humongous start 226 // regions are initialized at start of collection pause, with 227 // candidates removed from the set as they are found reachable from 228 // roots or the young generation. 229 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 230 protected: 231 bool default_value() const { return false; } 232 public: 233 void clear() { G1BiasedMappedArray<bool>::clear(); } 234 void set_candidate(uint region, bool value) { 235 set_by_index(region, value); 236 } 237 bool is_candidate(uint region) { 238 return get_by_index(region); 239 } 240 }; 241 242 HumongousReclaimCandidates _humongous_reclaim_candidates; 243 // Stores whether during humongous object registration we found candidate regions. 244 // If not, we can skip a few steps. 245 bool _has_humongous_reclaim_candidates; 246 247 volatile unsigned _gc_time_stamp; 248 249 G1HRPrinter _hr_printer; 250 251 // It decides whether an explicit GC should start a concurrent cycle 252 // instead of doing a STW GC. Currently, a concurrent cycle is 253 // explicitly started if: 254 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 255 // (b) cause == _g1_humongous_allocation 256 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 257 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 258 // (e) cause == _update_allocation_context_stats_inc 259 // (f) cause == _wb_conc_mark 260 bool should_do_concurrent_full_gc(GCCause::Cause cause); 261 262 // indicates whether we are in young or mixed GC mode 263 G1CollectorState _collector_state; 264 265 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 266 // concurrent cycles) we have started. 267 volatile uint _old_marking_cycles_started; 268 269 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 270 // concurrent cycles) we have completed. 271 volatile uint _old_marking_cycles_completed; 272 273 bool _heap_summary_sent; 274 275 // This is a non-product method that is helpful for testing. It is 276 // called at the end of a GC and artificially expands the heap by 277 // allocating a number of dead regions. This way we can induce very 278 // frequent marking cycles and stress the cleanup / concurrent 279 // cleanup code more (as all the regions that will be allocated by 280 // this method will be found dead by the marking cycle). 281 void allocate_dummy_regions() PRODUCT_RETURN; 282 283 // Clear RSets after a compaction. It also resets the GC time stamps. 284 void clear_rsets_post_compaction(); 285 286 // If the HR printer is active, dump the state of the regions in the 287 // heap after a compaction. 288 void print_hrm_post_compaction(); 289 290 // Create a memory mapper for auxiliary data structures of the given size and 291 // translation factor. 292 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 293 size_t size, 294 size_t translation_factor); 295 296 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 297 298 void process_weak_jni_handles(); 299 300 // These are macros so that, if the assert fires, we get the correct 301 // line number, file, etc. 302 303 #define heap_locking_asserts_params(_extra_message_) \ 304 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 305 (_extra_message_), \ 306 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 307 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 308 BOOL_TO_STR(Thread::current()->is_VM_thread()) 309 310 #define assert_heap_locked() \ 311 do { \ 312 assert(Heap_lock->owned_by_self(), \ 313 heap_locking_asserts_params("should be holding the Heap_lock")); \ 314 } while (0) 315 316 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 317 do { \ 318 assert(Heap_lock->owned_by_self() || \ 319 (SafepointSynchronize::is_at_safepoint() && \ 320 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 321 heap_locking_asserts_params("should be holding the Heap_lock or " \ 322 "should be at a safepoint")); \ 323 } while (0) 324 325 #define assert_heap_locked_and_not_at_safepoint() \ 326 do { \ 327 assert(Heap_lock->owned_by_self() && \ 328 !SafepointSynchronize::is_at_safepoint(), \ 329 heap_locking_asserts_params("should be holding the Heap_lock and " \ 330 "should not be at a safepoint")); \ 331 } while (0) 332 333 #define assert_heap_not_locked() \ 334 do { \ 335 assert(!Heap_lock->owned_by_self(), \ 336 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 337 } while (0) 338 339 #define assert_heap_not_locked_and_not_at_safepoint() \ 340 do { \ 341 assert(!Heap_lock->owned_by_self() && \ 342 !SafepointSynchronize::is_at_safepoint(), \ 343 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 344 "should not be at a safepoint")); \ 345 } while (0) 346 347 #define assert_at_safepoint(_should_be_vm_thread_) \ 348 do { \ 349 assert(SafepointSynchronize::is_at_safepoint() && \ 350 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 351 heap_locking_asserts_params("should be at a safepoint")); \ 352 } while (0) 353 354 #define assert_not_at_safepoint() \ 355 do { \ 356 assert(!SafepointSynchronize::is_at_safepoint(), \ 357 heap_locking_asserts_params("should not be at a safepoint")); \ 358 } while (0) 359 360 protected: 361 362 // The young region list. 363 YoungList* _young_list; 364 365 // The current policy object for the collector. 366 G1CollectorPolicy* _g1_policy; 367 368 G1CollectionSet _collection_set; 369 370 // This is the second level of trying to allocate a new region. If 371 // new_region() didn't find a region on the free_list, this call will 372 // check whether there's anything available on the 373 // secondary_free_list and/or wait for more regions to appear on 374 // that list, if _free_regions_coming is set. 375 HeapRegion* new_region_try_secondary_free_list(bool is_old); 376 377 // Try to allocate a single non-humongous HeapRegion sufficient for 378 // an allocation of the given word_size. If do_expand is true, 379 // attempt to expand the heap if necessary to satisfy the allocation 380 // request. If the region is to be used as an old region or for a 381 // humongous object, set is_old to true. If not, to false. 382 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 383 384 // Initialize a contiguous set of free regions of length num_regions 385 // and starting at index first so that they appear as a single 386 // humongous region. 387 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 388 uint num_regions, 389 size_t word_size, 390 AllocationContext_t context); 391 392 // Attempt to allocate a humongous object of the given size. Return 393 // NULL if unsuccessful. 394 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 395 396 // The following two methods, allocate_new_tlab() and 397 // mem_allocate(), are the two main entry points from the runtime 398 // into the G1's allocation routines. They have the following 399 // assumptions: 400 // 401 // * They should both be called outside safepoints. 402 // 403 // * They should both be called without holding the Heap_lock. 404 // 405 // * All allocation requests for new TLABs should go to 406 // allocate_new_tlab(). 407 // 408 // * All non-TLAB allocation requests should go to mem_allocate(). 409 // 410 // * If either call cannot satisfy the allocation request using the 411 // current allocating region, they will try to get a new one. If 412 // this fails, they will attempt to do an evacuation pause and 413 // retry the allocation. 414 // 415 // * If all allocation attempts fail, even after trying to schedule 416 // an evacuation pause, allocate_new_tlab() will return NULL, 417 // whereas mem_allocate() will attempt a heap expansion and/or 418 // schedule a Full GC. 419 // 420 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 421 // should never be called with word_size being humongous. All 422 // humongous allocation requests should go to mem_allocate() which 423 // will satisfy them with a special path. 424 425 virtual HeapWord* allocate_new_tlab(size_t word_size); 426 427 virtual HeapWord* mem_allocate(size_t word_size, 428 bool* gc_overhead_limit_was_exceeded); 429 430 // The following three methods take a gc_count_before_ret 431 // parameter which is used to return the GC count if the method 432 // returns NULL. Given that we are required to read the GC count 433 // while holding the Heap_lock, and these paths will take the 434 // Heap_lock at some point, it's easier to get them to read the GC 435 // count while holding the Heap_lock before they return NULL instead 436 // of the caller (namely: mem_allocate()) having to also take the 437 // Heap_lock just to read the GC count. 438 439 // First-level mutator allocation attempt: try to allocate out of 440 // the mutator alloc region without taking the Heap_lock. This 441 // should only be used for non-humongous allocations. 442 inline HeapWord* attempt_allocation(size_t word_size, 443 uint* gc_count_before_ret, 444 uint* gclocker_retry_count_ret); 445 446 // Second-level mutator allocation attempt: take the Heap_lock and 447 // retry the allocation attempt, potentially scheduling a GC 448 // pause. This should only be used for non-humongous allocations. 449 HeapWord* attempt_allocation_slow(size_t word_size, 450 AllocationContext_t context, 451 uint* gc_count_before_ret, 452 uint* gclocker_retry_count_ret); 453 454 // Takes the Heap_lock and attempts a humongous allocation. It can 455 // potentially schedule a GC pause. 456 HeapWord* attempt_allocation_humongous(size_t word_size, 457 uint* gc_count_before_ret, 458 uint* gclocker_retry_count_ret); 459 460 // Allocation attempt that should be called during safepoints (e.g., 461 // at the end of a successful GC). expect_null_mutator_alloc_region 462 // specifies whether the mutator alloc region is expected to be NULL 463 // or not. 464 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 465 AllocationContext_t context, 466 bool expect_null_mutator_alloc_region); 467 468 // These methods are the "callbacks" from the G1AllocRegion class. 469 470 // For mutator alloc regions. 471 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 472 void retire_mutator_alloc_region(HeapRegion* alloc_region, 473 size_t allocated_bytes); 474 475 // For GC alloc regions. 476 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 477 InCSetState dest); 478 void retire_gc_alloc_region(HeapRegion* alloc_region, 479 size_t allocated_bytes, InCSetState dest); 480 481 // - if explicit_gc is true, the GC is for a System.gc() etc, 482 // otherwise it's for a failed allocation. 483 // - if clear_all_soft_refs is true, all soft references should be 484 // cleared during the GC. 485 // - it returns false if it is unable to do the collection due to the 486 // GC locker being active, true otherwise. 487 bool do_full_collection(bool explicit_gc, 488 bool clear_all_soft_refs); 489 490 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 491 virtual void do_full_collection(bool clear_all_soft_refs); 492 493 // Resize the heap if necessary after a full collection. 494 void resize_if_necessary_after_full_collection(); 495 496 // Callback from VM_G1CollectForAllocation operation. 497 // This function does everything necessary/possible to satisfy a 498 // failed allocation request (including collection, expansion, etc.) 499 HeapWord* satisfy_failed_allocation(size_t word_size, 500 AllocationContext_t context, 501 bool* succeeded); 502 private: 503 // Helper method for satisfy_failed_allocation() 504 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 505 AllocationContext_t context, 506 bool do_gc, 507 bool clear_all_soft_refs, 508 bool expect_null_mutator_alloc_region, 509 bool* gc_succeeded); 510 511 protected: 512 // Attempting to expand the heap sufficiently 513 // to support an allocation of the given "word_size". If 514 // successful, perform the allocation and return the address of the 515 // allocated block, or else "NULL". 516 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 517 518 // Preserve any referents discovered by concurrent marking that have not yet been 519 // copied by the STW pause. 520 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states); 521 // Process any reference objects discovered during 522 // an incremental evacuation pause. 523 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 524 525 // Enqueue any remaining discovered references 526 // after processing. 527 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 528 529 // Merges the information gathered on a per-thread basis for all worker threads 530 // during GC into global variables. 531 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states); 532 public: 533 WorkGang* workers() const { return _workers; } 534 535 G1Allocator* allocator() { 536 return _allocator; 537 } 538 539 G1HeapVerifier* verifier() { 540 return _verifier; 541 } 542 543 G1MonitoringSupport* g1mm() { 544 assert(_g1mm != NULL, "should have been initialized"); 545 return _g1mm; 546 } 547 548 // Expand the garbage-first heap by at least the given size (in bytes!). 549 // Returns true if the heap was expanded by the requested amount; 550 // false otherwise. 551 // (Rounds up to a HeapRegion boundary.) 552 bool expand(size_t expand_bytes, double* expand_time_ms = NULL); 553 554 // Returns the PLAB statistics for a given destination. 555 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 556 557 // Determines PLAB size for a given destination. 558 inline size_t desired_plab_sz(InCSetState dest); 559 560 inline AllocationContextStats& allocation_context_stats(); 561 562 // Do anything common to GC's. 563 void gc_prologue(bool full); 564 void gc_epilogue(bool full); 565 566 // Modify the reclaim candidate set and test for presence. 567 // These are only valid for starts_humongous regions. 568 inline void set_humongous_reclaim_candidate(uint region, bool value); 569 inline bool is_humongous_reclaim_candidate(uint region); 570 571 // Remove from the reclaim candidate set. Also remove from the 572 // collection set so that later encounters avoid the slow path. 573 inline void set_humongous_is_live(oop obj); 574 575 // Register the given region to be part of the collection set. 576 inline void register_humongous_region_with_cset(uint index); 577 // Register regions with humongous objects (actually on the start region) in 578 // the in_cset_fast_test table. 579 void register_humongous_regions_with_cset(); 580 // We register a region with the fast "in collection set" test. We 581 // simply set to true the array slot corresponding to this region. 582 void register_young_region_with_cset(HeapRegion* r) { 583 _in_cset_fast_test.set_in_young(r->hrm_index()); 584 } 585 void register_old_region_with_cset(HeapRegion* r) { 586 _in_cset_fast_test.set_in_old(r->hrm_index()); 587 } 588 inline void register_ext_region_with_cset(HeapRegion* r) { 589 _in_cset_fast_test.set_ext(r->hrm_index()); 590 } 591 void clear_in_cset(const HeapRegion* hr) { 592 _in_cset_fast_test.clear(hr); 593 } 594 595 void clear_cset_fast_test() { 596 _in_cset_fast_test.clear(); 597 } 598 599 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 600 601 // This is called at the start of either a concurrent cycle or a Full 602 // GC to update the number of old marking cycles started. 603 void increment_old_marking_cycles_started(); 604 605 // This is called at the end of either a concurrent cycle or a Full 606 // GC to update the number of old marking cycles completed. Those two 607 // can happen in a nested fashion, i.e., we start a concurrent 608 // cycle, a Full GC happens half-way through it which ends first, 609 // and then the cycle notices that a Full GC happened and ends 610 // too. The concurrent parameter is a boolean to help us do a bit 611 // tighter consistency checking in the method. If concurrent is 612 // false, the caller is the inner caller in the nesting (i.e., the 613 // Full GC). If concurrent is true, the caller is the outer caller 614 // in this nesting (i.e., the concurrent cycle). Further nesting is 615 // not currently supported. The end of this call also notifies 616 // the FullGCCount_lock in case a Java thread is waiting for a full 617 // GC to happen (e.g., it called System.gc() with 618 // +ExplicitGCInvokesConcurrent). 619 void increment_old_marking_cycles_completed(bool concurrent); 620 621 uint old_marking_cycles_completed() { 622 return _old_marking_cycles_completed; 623 } 624 625 void register_concurrent_cycle_start(const Ticks& start_time); 626 void register_concurrent_cycle_end(); 627 void trace_heap_after_concurrent_cycle(); 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 preserved mark words for objects with self-forwarding pointers. 803 void restore_preserved_marks(); 804 805 // Restore the objects in the regions in the collection set after an 806 // evacuation failure. 807 void restore_after_evac_failure(); 808 809 // Stores marks with the corresponding oop that we need to preserve during evacuation 810 // failure. 811 OopAndMarkOopStack* _preserved_objs; 812 813 // Preserve the mark of "obj", if necessary, in preparation for its mark 814 // word being overwritten with a self-forwarding-pointer. 815 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 816 817 #ifndef PRODUCT 818 // Support for forcing evacuation failures. Analogous to 819 // PromotionFailureALot for the other collectors. 820 821 // Records whether G1EvacuationFailureALot should be in effect 822 // for the current GC 823 bool _evacuation_failure_alot_for_current_gc; 824 825 // Used to record the GC number for interval checking when 826 // determining whether G1EvaucationFailureALot is in effect 827 // for the current GC. 828 size_t _evacuation_failure_alot_gc_number; 829 830 // Count of the number of evacuations between failures. 831 volatile size_t _evacuation_failure_alot_count; 832 833 // Set whether G1EvacuationFailureALot should be in effect 834 // for the current GC (based upon the type of GC and which 835 // command line flags are set); 836 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 837 bool during_initial_mark, 838 bool during_marking); 839 840 inline void set_evacuation_failure_alot_for_current_gc(); 841 842 // Return true if it's time to cause an evacuation failure. 843 inline bool evacuation_should_fail(); 844 845 // Reset the G1EvacuationFailureALot counters. Should be called at 846 // the end of an evacuation pause in which an evacuation failure occurred. 847 inline void reset_evacuation_should_fail(); 848 #endif // !PRODUCT 849 850 // ("Weak") Reference processing support. 851 // 852 // G1 has 2 instances of the reference processor class. One 853 // (_ref_processor_cm) handles reference object discovery 854 // and subsequent processing during concurrent marking cycles. 855 // 856 // The other (_ref_processor_stw) handles reference object 857 // discovery and processing during full GCs and incremental 858 // evacuation pauses. 859 // 860 // During an incremental pause, reference discovery will be 861 // temporarily disabled for _ref_processor_cm and will be 862 // enabled for _ref_processor_stw. At the end of the evacuation 863 // pause references discovered by _ref_processor_stw will be 864 // processed and discovery will be disabled. The previous 865 // setting for reference object discovery for _ref_processor_cm 866 // will be re-instated. 867 // 868 // At the start of marking: 869 // * Discovery by the CM ref processor is verified to be inactive 870 // and it's discovered lists are empty. 871 // * Discovery by the CM ref processor is then enabled. 872 // 873 // At the end of marking: 874 // * Any references on the CM ref processor's discovered 875 // lists are processed (possibly MT). 876 // 877 // At the start of full GC we: 878 // * Disable discovery by the CM ref processor and 879 // empty CM ref processor's discovered lists 880 // (without processing any entries). 881 // * Verify that the STW ref processor is inactive and it's 882 // discovered lists are empty. 883 // * Temporarily set STW ref processor discovery as single threaded. 884 // * Temporarily clear the STW ref processor's _is_alive_non_header 885 // field. 886 // * Finally enable discovery by the STW ref processor. 887 // 888 // The STW ref processor is used to record any discovered 889 // references during the full GC. 890 // 891 // At the end of a full GC we: 892 // * Enqueue any reference objects discovered by the STW ref processor 893 // that have non-live referents. This has the side-effect of 894 // making the STW ref processor inactive by disabling discovery. 895 // * Verify that the CM ref processor is still inactive 896 // and no references have been placed on it's discovered 897 // lists (also checked as a precondition during initial marking). 898 899 // The (stw) reference processor... 900 ReferenceProcessor* _ref_processor_stw; 901 902 STWGCTimer* _gc_timer_stw; 903 ConcurrentGCTimer* _gc_timer_cm; 904 905 G1OldTracer* _gc_tracer_cm; 906 G1NewTracer* _gc_tracer_stw; 907 908 // During reference object discovery, the _is_alive_non_header 909 // closure (if non-null) is applied to the referent object to 910 // determine whether the referent is live. If so then the 911 // reference object does not need to be 'discovered' and can 912 // be treated as a regular oop. This has the benefit of reducing 913 // the number of 'discovered' reference objects that need to 914 // be processed. 915 // 916 // Instance of the is_alive closure for embedding into the 917 // STW reference processor as the _is_alive_non_header field. 918 // Supplying a value for the _is_alive_non_header field is 919 // optional but doing so prevents unnecessary additions to 920 // the discovered lists during reference discovery. 921 G1STWIsAliveClosure _is_alive_closure_stw; 922 923 // The (concurrent marking) reference processor... 924 ReferenceProcessor* _ref_processor_cm; 925 926 // Instance of the concurrent mark is_alive closure for embedding 927 // into the Concurrent Marking reference processor as the 928 // _is_alive_non_header field. Supplying a value for the 929 // _is_alive_non_header field is optional but doing so prevents 930 // unnecessary additions to the discovered lists during reference 931 // discovery. 932 G1CMIsAliveClosure _is_alive_closure_cm; 933 934 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 935 HeapRegion** _worker_cset_start_region; 936 937 // Time stamp to validate the regions recorded in the cache 938 // used by G1CollectedHeap::start_cset_region_for_worker(). 939 // The heap region entry for a given worker is valid iff 940 // the associated time stamp value matches the current value 941 // of G1CollectedHeap::_gc_time_stamp. 942 uint* _worker_cset_start_region_time_stamp; 943 944 volatile bool _free_regions_coming; 945 946 public: 947 948 void set_refine_cte_cl_concurrency(bool concurrent); 949 950 RefToScanQueue *task_queue(uint i) const; 951 952 uint num_task_queues() const; 953 954 // A set of cards where updates happened during the GC 955 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 956 957 // Create a G1CollectedHeap with the specified policy. 958 // Must call the initialize method afterwards. 959 // May not return if something goes wrong. 960 G1CollectedHeap(G1CollectorPolicy* policy); 961 962 // Initialize the G1CollectedHeap to have the initial and 963 // maximum sizes and remembered and barrier sets 964 // specified by the policy object. 965 jint initialize(); 966 967 virtual void stop(); 968 969 // Return the (conservative) maximum heap alignment for any G1 heap 970 static size_t conservative_max_heap_alignment(); 971 972 // Does operations required after initialization has been done. 973 void post_initialize(); 974 975 // Initialize weak reference processing. 976 void ref_processing_init(); 977 978 virtual Name kind() const { 979 return CollectedHeap::G1CollectedHeap; 980 } 981 982 virtual const char* name() const { 983 return "G1"; 984 } 985 986 const G1CollectorState* collector_state() const { return &_collector_state; } 987 G1CollectorState* collector_state() { return &_collector_state; } 988 989 // The current policy object for the collector. 990 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 991 992 const G1CollectionSet* collection_set() const { return &_collection_set; } 993 G1CollectionSet* collection_set() { return &_collection_set; } 994 995 virtual CollectorPolicy* collector_policy() const; 996 997 // Adaptive size policy. No such thing for g1. 998 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 999 1000 // The rem set and barrier set. 1001 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1002 1003 void scrub_rem_set(BitMap* region_bm, BitMap* card_bm); 1004 1005 unsigned get_gc_time_stamp() { 1006 return _gc_time_stamp; 1007 } 1008 1009 inline void reset_gc_time_stamp(); 1010 1011 void check_gc_time_stamps() PRODUCT_RETURN; 1012 1013 inline void increment_gc_time_stamp(); 1014 1015 // Reset the given region's GC timestamp. If it's starts humongous, 1016 // also reset the GC timestamp of its corresponding 1017 // continues humongous regions too. 1018 void reset_gc_time_stamps(HeapRegion* hr); 1019 1020 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1021 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1022 1023 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1024 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1025 1026 // The shared block offset table array. 1027 G1BlockOffsetTable* bot() const { return _bot; } 1028 1029 // Reference Processing accessors 1030 1031 // The STW reference processor.... 1032 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1033 1034 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1035 1036 // The Concurrent Marking reference processor... 1037 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1038 1039 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1040 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1041 1042 virtual size_t capacity() const; 1043 virtual size_t used() const; 1044 // This should be called when we're not holding the heap lock. The 1045 // result might be a bit inaccurate. 1046 size_t used_unlocked() const; 1047 size_t recalculate_used() const; 1048 1049 // These virtual functions do the actual allocation. 1050 // Some heaps may offer a contiguous region for shared non-blocking 1051 // allocation, via inlined code (by exporting the address of the top and 1052 // end fields defining the extent of the contiguous allocation region.) 1053 // But G1CollectedHeap doesn't yet support this. 1054 1055 virtual bool is_maximal_no_gc() const { 1056 return _hrm.available() == 0; 1057 } 1058 1059 // The current number of regions in the heap. 1060 uint num_regions() const { return _hrm.length(); } 1061 1062 // The max number of regions in the heap. 1063 uint max_regions() const { return _hrm.max_length(); } 1064 1065 // The number of regions that are completely free. 1066 uint num_free_regions() const { return _hrm.num_free_regions(); } 1067 1068 MemoryUsage get_auxiliary_data_memory_usage() const { 1069 return _hrm.get_auxiliary_data_memory_usage(); 1070 } 1071 1072 // The number of regions that are not completely free. 1073 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1074 1075 #ifdef ASSERT 1076 bool is_on_master_free_list(HeapRegion* hr) { 1077 return _hrm.is_free(hr); 1078 } 1079 #endif // ASSERT 1080 1081 // Wrapper for the region list operations that can be called from 1082 // methods outside this class. 1083 1084 void secondary_free_list_add(FreeRegionList* list) { 1085 _secondary_free_list.add_ordered(list); 1086 } 1087 1088 void append_secondary_free_list() { 1089 _hrm.insert_list_into_free_list(&_secondary_free_list); 1090 } 1091 1092 void append_secondary_free_list_if_not_empty_with_lock() { 1093 // If the secondary free list looks empty there's no reason to 1094 // take the lock and then try to append it. 1095 if (!_secondary_free_list.is_empty()) { 1096 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1097 append_secondary_free_list(); 1098 } 1099 } 1100 1101 inline void old_set_add(HeapRegion* hr); 1102 inline void old_set_remove(HeapRegion* hr); 1103 1104 size_t non_young_capacity_bytes() { 1105 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes; 1106 } 1107 1108 void set_free_regions_coming(); 1109 void reset_free_regions_coming(); 1110 bool free_regions_coming() { return _free_regions_coming; } 1111 void wait_while_free_regions_coming(); 1112 1113 // Determine whether the given region is one that we are using as an 1114 // old GC alloc region. 1115 bool is_old_gc_alloc_region(HeapRegion* hr); 1116 1117 // Perform a collection of the heap; intended for use in implementing 1118 // "System.gc". This probably implies as full a collection as the 1119 // "CollectedHeap" supports. 1120 virtual void collect(GCCause::Cause cause); 1121 1122 virtual bool copy_allocation_context_stats(const jint* contexts, 1123 jlong* totals, 1124 jbyte* accuracy, 1125 jint len); 1126 1127 // True iff an evacuation has failed in the most-recent collection. 1128 bool evacuation_failed() { return _evacuation_failed; } 1129 1130 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed); 1131 void prepend_to_freelist(FreeRegionList* list); 1132 void decrement_summary_bytes(size_t bytes); 1133 1134 virtual bool is_in(const void* p) const; 1135 #ifdef ASSERT 1136 // Returns whether p is in one of the available areas of the heap. Slow but 1137 // extensive version. 1138 bool is_in_exact(const void* p) const; 1139 #endif 1140 1141 // Return "TRUE" iff the given object address is within the collection 1142 // set. Slow implementation. 1143 bool obj_in_cs(oop obj); 1144 1145 inline bool is_in_cset(const HeapRegion *hr); 1146 inline bool is_in_cset(oop obj); 1147 1148 inline bool is_in_cset_or_humongous(const oop obj); 1149 1150 private: 1151 // This array is used for a quick test on whether a reference points into 1152 // the collection set or not. Each of the array's elements denotes whether the 1153 // corresponding region is in the collection set or not. 1154 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1155 1156 public: 1157 1158 inline InCSetState in_cset_state(const oop obj); 1159 1160 // Return "TRUE" iff the given object address is in the reserved 1161 // region of g1. 1162 bool is_in_g1_reserved(const void* p) const { 1163 return _hrm.reserved().contains(p); 1164 } 1165 1166 // Returns a MemRegion that corresponds to the space that has been 1167 // reserved for the heap 1168 MemRegion g1_reserved() const { 1169 return _hrm.reserved(); 1170 } 1171 1172 virtual bool is_in_closed_subset(const void* p) const; 1173 1174 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1175 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1176 } 1177 1178 // This resets the card table to all zeros. It is used after 1179 // a collection pause which used the card table to claim cards. 1180 void cleanUpCardTable(); 1181 1182 // Iteration functions. 1183 1184 // Iterate over all objects, calling "cl.do_object" on each. 1185 virtual void object_iterate(ObjectClosure* cl); 1186 1187 virtual void safe_object_iterate(ObjectClosure* cl) { 1188 object_iterate(cl); 1189 } 1190 1191 // Iterate over heap regions, in address order, terminating the 1192 // iteration early if the "doHeapRegion" method returns "true". 1193 void heap_region_iterate(HeapRegionClosure* blk) const; 1194 1195 // Return the region with the given index. It assumes the index is valid. 1196 inline HeapRegion* region_at(uint index) const; 1197 1198 // Return the next region (by index) that is part of the same 1199 // humongous object that hr is part of. 1200 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1201 1202 // Calculate the region index of the given address. Given address must be 1203 // within the heap. 1204 inline uint addr_to_region(HeapWord* addr) const; 1205 1206 inline HeapWord* bottom_addr_for_region(uint index) const; 1207 1208 // Iterate over the heap regions in parallel. Assumes that this will be called 1209 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1210 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1211 // to each of the regions, by attempting to claim the region using the 1212 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1213 // region. The concurrent argument should be set to true if iteration is 1214 // performed concurrently, during which no assumptions are made for consistent 1215 // attributes of the heap regions (as they might be modified while iterating). 1216 void heap_region_par_iterate(HeapRegionClosure* cl, 1217 uint worker_id, 1218 HeapRegionClaimer* hrclaimer, 1219 bool concurrent = false) const; 1220 1221 // Clear the cached cset start regions and (more importantly) 1222 // the time stamps. Called when we reset the GC time stamp. 1223 void clear_cset_start_regions(); 1224 1225 // Given the id of a worker, obtain or calculate a suitable 1226 // starting region for iterating over the current collection set. 1227 HeapRegion* start_cset_region_for_worker(uint worker_i); 1228 1229 // Iterate over the regions (if any) in the current collection set. 1230 void collection_set_iterate(HeapRegionClosure* blk); 1231 1232 // As above but starting from region r 1233 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1234 1235 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1236 1237 // Returns the HeapRegion that contains addr. addr must not be NULL. 1238 template <class T> 1239 inline HeapRegion* heap_region_containing(const T addr) const; 1240 1241 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1242 // each address in the (reserved) heap is a member of exactly 1243 // one block. The defining characteristic of a block is that it is 1244 // possible to find its size, and thus to progress forward to the next 1245 // block. (Blocks may be of different sizes.) Thus, blocks may 1246 // represent Java objects, or they might be free blocks in a 1247 // free-list-based heap (or subheap), as long as the two kinds are 1248 // distinguishable and the size of each is determinable. 1249 1250 // Returns the address of the start of the "block" that contains the 1251 // address "addr". We say "blocks" instead of "object" since some heaps 1252 // may not pack objects densely; a chunk may either be an object or a 1253 // non-object. 1254 virtual HeapWord* block_start(const void* addr) const; 1255 1256 // Requires "addr" to be the start of a chunk, and returns its size. 1257 // "addr + size" is required to be the start of a new chunk, or the end 1258 // of the active area of the heap. 1259 virtual size_t block_size(const HeapWord* addr) const; 1260 1261 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1262 // the block is an object. 1263 virtual bool block_is_obj(const HeapWord* addr) const; 1264 1265 // Section on thread-local allocation buffers (TLABs) 1266 // See CollectedHeap for semantics. 1267 1268 bool supports_tlab_allocation() const; 1269 size_t tlab_capacity(Thread* ignored) const; 1270 size_t tlab_used(Thread* ignored) const; 1271 size_t max_tlab_size() const; 1272 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1273 1274 // Can a compiler initialize a new object without store barriers? 1275 // This permission only extends from the creation of a new object 1276 // via a TLAB up to the first subsequent safepoint. If such permission 1277 // is granted for this heap type, the compiler promises to call 1278 // defer_store_barrier() below on any slow path allocation of 1279 // a new object for which such initializing store barriers will 1280 // have been elided. G1, like CMS, allows this, but should be 1281 // ready to provide a compensating write barrier as necessary 1282 // if that storage came out of a non-young region. The efficiency 1283 // of this implementation depends crucially on being able to 1284 // answer very efficiently in constant time whether a piece of 1285 // storage in the heap comes from a young region or not. 1286 // See ReduceInitialCardMarks. 1287 virtual bool can_elide_tlab_store_barriers() const { 1288 return true; 1289 } 1290 1291 virtual bool card_mark_must_follow_store() const { 1292 return true; 1293 } 1294 1295 // The reference pending list lock is acquired from from the 1296 // ConcurrentMarkThread. 1297 virtual bool needs_reference_pending_list_locker_thread() const { 1298 return true; 1299 } 1300 1301 inline bool is_in_young(const oop obj); 1302 1303 virtual bool is_scavengable(const void* addr); 1304 1305 // We don't need barriers for initializing stores to objects 1306 // in the young gen: for the SATB pre-barrier, there is no 1307 // pre-value that needs to be remembered; for the remembered-set 1308 // update logging post-barrier, we don't maintain remembered set 1309 // information for young gen objects. 1310 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1311 1312 // Returns "true" iff the given word_size is "very large". 1313 static bool is_humongous(size_t word_size) { 1314 // Note this has to be strictly greater-than as the TLABs 1315 // are capped at the humongous threshold and we want to 1316 // ensure that we don't try to allocate a TLAB as 1317 // humongous and that we don't allocate a humongous 1318 // object in a TLAB. 1319 return word_size > _humongous_object_threshold_in_words; 1320 } 1321 1322 // Returns the humongous threshold for a specific region size 1323 static size_t humongous_threshold_for(size_t region_size) { 1324 return (region_size / 2); 1325 } 1326 1327 // Returns the number of regions the humongous object of the given word size 1328 // requires. 1329 static size_t humongous_obj_size_in_regions(size_t word_size); 1330 1331 // Print the maximum heap capacity. 1332 virtual size_t max_capacity() const; 1333 1334 virtual jlong millis_since_last_gc(); 1335 1336 1337 // Convenience function to be used in situations where the heap type can be 1338 // asserted to be this type. 1339 static G1CollectedHeap* heap(); 1340 1341 void set_region_short_lived_locked(HeapRegion* hr); 1342 // add appropriate methods for any other surv rate groups 1343 1344 YoungList* young_list() const { return _young_list; } 1345 1346 uint old_regions_count() const { return _old_set.length(); } 1347 1348 uint humongous_regions_count() const { return _humongous_set.length(); } 1349 1350 // debugging 1351 bool check_young_list_well_formed() { 1352 return _young_list->check_list_well_formed(); 1353 } 1354 1355 bool check_young_list_empty(bool check_heap); 1356 1357 // *** Stuff related to concurrent marking. It's not clear to me that so 1358 // many of these need to be public. 1359 1360 // The functions below are helper functions that a subclass of 1361 // "CollectedHeap" can use in the implementation of its virtual 1362 // functions. 1363 // This performs a concurrent marking of the live objects in a 1364 // bitmap off to the side. 1365 void doConcurrentMark(); 1366 1367 bool isMarkedPrev(oop obj) const; 1368 bool isMarkedNext(oop obj) const; 1369 1370 // Determine if an object is dead, given the object and also 1371 // the region to which the object belongs. An object is dead 1372 // iff a) it was not allocated since the last mark, b) it 1373 // is not marked, and c) it is not in an archive region. 1374 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1375 return 1376 !hr->obj_allocated_since_prev_marking(obj) && 1377 !isMarkedPrev(obj) && 1378 !hr->is_archive(); 1379 } 1380 1381 // This function returns true when an object has been 1382 // around since the previous marking and hasn't yet 1383 // been marked during this marking, and is not in an archive region. 1384 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1385 return 1386 !hr->obj_allocated_since_next_marking(obj) && 1387 !isMarkedNext(obj) && 1388 !hr->is_archive(); 1389 } 1390 1391 // Determine if an object is dead, given only the object itself. 1392 // This will find the region to which the object belongs and 1393 // then call the region version of the same function. 1394 1395 // Added if it is NULL it isn't dead. 1396 1397 inline bool is_obj_dead(const oop obj) const; 1398 1399 inline bool is_obj_ill(const oop obj) const; 1400 1401 G1ConcurrentMark* concurrent_mark() const { return _cm; } 1402 1403 // Refinement 1404 1405 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1406 1407 // The dirty cards region list is used to record a subset of regions 1408 // whose cards need clearing. The list if populated during the 1409 // remembered set scanning and drained during the card table 1410 // cleanup. Although the methods are reentrant, population/draining 1411 // phases must not overlap. For synchronization purposes the last 1412 // element on the list points to itself. 1413 HeapRegion* _dirty_cards_region_list; 1414 void push_dirty_cards_region(HeapRegion* hr); 1415 HeapRegion* pop_dirty_cards_region(); 1416 1417 // Optimized nmethod scanning support routines 1418 1419 // Register the given nmethod with the G1 heap. 1420 virtual void register_nmethod(nmethod* nm); 1421 1422 // Unregister the given nmethod from the G1 heap. 1423 virtual void unregister_nmethod(nmethod* nm); 1424 1425 // Free up superfluous code root memory. 1426 void purge_code_root_memory(); 1427 1428 // Rebuild the strong code root lists for each region 1429 // after a full GC. 1430 void rebuild_strong_code_roots(); 1431 1432 // Delete entries for dead interned string and clean up unreferenced symbols 1433 // in symbol table, possibly in parallel. 1434 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1435 1436 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1437 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1438 1439 // Redirty logged cards in the refinement queue. 1440 void redirty_logged_cards(); 1441 // Verification 1442 1443 // Perform any cleanup actions necessary before allowing a verification. 1444 virtual void prepare_for_verify(); 1445 1446 // Perform verification. 1447 1448 // vo == UsePrevMarking -> use "prev" marking information, 1449 // vo == UseNextMarking -> use "next" marking information 1450 // vo == UseMarkWord -> use the mark word in the object header 1451 // 1452 // NOTE: Only the "prev" marking information is guaranteed to be 1453 // consistent most of the time, so most calls to this should use 1454 // vo == UsePrevMarking. 1455 // Currently, there is only one case where this is called with 1456 // vo == UseNextMarking, which is to verify the "next" marking 1457 // information at the end of remark. 1458 // Currently there is only one place where this is called with 1459 // vo == UseMarkWord, which is to verify the marking during a 1460 // full GC. 1461 void verify(VerifyOption vo); 1462 1463 // The methods below are here for convenience and dispatch the 1464 // appropriate method depending on value of the given VerifyOption 1465 // parameter. The values for that parameter, and their meanings, 1466 // are the same as those above. 1467 1468 bool is_obj_dead_cond(const oop obj, 1469 const HeapRegion* hr, 1470 const VerifyOption vo) const; 1471 1472 bool is_obj_dead_cond(const oop obj, 1473 const VerifyOption vo) const; 1474 1475 G1HeapSummary create_g1_heap_summary(); 1476 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1477 1478 // Printing 1479 1480 virtual void print_on(outputStream* st) const; 1481 virtual void print_extended_on(outputStream* st) const; 1482 virtual void print_on_error(outputStream* st) const; 1483 1484 virtual void print_gc_threads_on(outputStream* st) const; 1485 virtual void gc_threads_do(ThreadClosure* tc) const; 1486 1487 // Override 1488 void print_tracing_info() const; 1489 1490 // The following two methods are helpful for debugging RSet issues. 1491 void print_cset_rsets() PRODUCT_RETURN; 1492 void print_all_rsets() PRODUCT_RETURN; 1493 1494 public: 1495 size_t pending_card_num(); 1496 1497 protected: 1498 size_t _max_heap_capacity; 1499 }; 1500 1501 class G1ParEvacuateFollowersClosure : public VoidClosure { 1502 private: 1503 double _start_term; 1504 double _term_time; 1505 size_t _term_attempts; 1506 1507 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1508 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1509 protected: 1510 G1CollectedHeap* _g1h; 1511 G1ParScanThreadState* _par_scan_state; 1512 RefToScanQueueSet* _queues; 1513 ParallelTaskTerminator* _terminator; 1514 1515 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1516 RefToScanQueueSet* queues() { return _queues; } 1517 ParallelTaskTerminator* terminator() { return _terminator; } 1518 1519 public: 1520 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1521 G1ParScanThreadState* par_scan_state, 1522 RefToScanQueueSet* queues, 1523 ParallelTaskTerminator* terminator) 1524 : _g1h(g1h), _par_scan_state(par_scan_state), 1525 _queues(queues), _terminator(terminator), 1526 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1527 1528 void do_void(); 1529 1530 double term_time() const { return _term_time; } 1531 size_t term_attempts() const { return _term_attempts; } 1532 1533 private: 1534 inline bool offer_termination(); 1535 }; 1536 1537 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP