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