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 "gc/shared/preservedMarks.hpp" 49 #include "memory/memRegion.hpp" 50 #include "utilities/stack.hpp" 51 52 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 53 // It uses the "Garbage First" heap organization and algorithm, which 54 // may combine concurrent marking with parallel, incremental compaction of 55 // heap subsets that will yield large amounts of garbage. 56 57 // Forward declarations 58 class HeapRegion; 59 class HRRSCleanupTask; 60 class GenerationSpec; 61 class OopsInHeapRegionClosure; 62 class G1ParScanThreadState; 63 class G1ParScanThreadStateSet; 64 class G1KlassScanClosure; 65 class G1ParScanThreadState; 66 class ObjectClosure; 67 class SpaceClosure; 68 class CompactibleSpaceClosure; 69 class Space; 70 class G1CollectionSet; 71 class G1CollectorPolicy; 72 class G1Policy; 73 class G1RemSet; 74 class HeapRegionRemSetIterator; 75 class G1ConcurrentMark; 76 class ConcurrentMarkThread; 77 class ConcurrentG1Refine; 78 class GenerationCounters; 79 class STWGCTimer; 80 class G1NewTracer; 81 class EvacuationFailedInfo; 82 class nmethod; 83 class Ticks; 84 class WorkGang; 85 class G1Allocator; 86 class G1ArchiveAllocator; 87 class G1HeapVerifier; 88 class G1HeapSizingPolicy; 89 90 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 91 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 92 93 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 94 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 95 96 // The G1 STW is alive closure. 97 // An instance is embedded into the G1CH and used as the 98 // (optional) _is_alive_non_header closure in the STW 99 // reference processor. It is also extensively used during 100 // reference processing during STW evacuation pauses. 101 class G1STWIsAliveClosure: public BoolObjectClosure { 102 G1CollectedHeap* _g1; 103 public: 104 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 105 bool do_object_b(oop p); 106 }; 107 108 class RefineCardTableEntryClosure; 109 110 class G1RegionMappingChangedListener : public G1MappingChangedListener { 111 private: 112 void reset_from_card_cache(uint start_idx, size_t num_regions); 113 public: 114 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 115 }; 116 117 class G1CollectedHeap : public CollectedHeap { 118 friend class VM_CollectForMetadataAllocation; 119 friend class VM_G1CollectForAllocation; 120 friend class VM_G1CollectFull; 121 friend class VM_G1IncCollectionPause; 122 friend class VMStructs; 123 friend class MutatorAllocRegion; 124 friend class G1GCAllocRegion; 125 friend class G1HeapVerifier; 126 127 // Closures used in implementation. 128 friend class G1ParScanThreadState; 129 friend class G1ParScanThreadStateSet; 130 friend class G1ParTask; 131 friend class G1PLABAllocator; 132 friend class G1PrepareCompactClosure; 133 134 // Other related classes. 135 friend class HeapRegionClaimer; 136 137 // Testing classes. 138 friend class G1CheckCSetFastTableClosure; 139 140 private: 141 WorkGang* _workers; 142 G1CollectorPolicy* _collector_policy; 143 144 static size_t _humongous_object_threshold_in_words; 145 146 // The secondary free list which contains regions that have been 147 // freed up during the cleanup process. This will be appended to 148 // the master free list when appropriate. 149 FreeRegionList _secondary_free_list; 150 151 // It keeps track of the old regions. 152 HeapRegionSet _old_set; 153 154 // It keeps track of the humongous regions. 155 HeapRegionSet _humongous_set; 156 157 void eagerly_reclaim_humongous_regions(); 158 159 // The number of regions we could create by expansion. 160 uint _expansion_regions; 161 162 // The block offset table for the G1 heap. 163 G1BlockOffsetTable* _bot; 164 165 // Tears down the region sets / lists so that they are empty and the 166 // regions on the heap do not belong to a region set / list. The 167 // only exception is the humongous set which we leave unaltered. If 168 // free_list_only is true, it will only tear down the master free 169 // list. It is called before a Full GC (free_list_only == false) or 170 // before heap shrinking (free_list_only == true). 171 void tear_down_region_sets(bool free_list_only); 172 173 // Rebuilds the region sets / lists so that they are repopulated to 174 // reflect the contents of the heap. The only exception is the 175 // humongous set which was not torn down in the first place. If 176 // free_list_only is true, it will only rebuild the master free 177 // list. It is called after a Full GC (free_list_only == false) or 178 // after heap shrinking (free_list_only == true). 179 void rebuild_region_sets(bool free_list_only); 180 181 // Callback for region mapping changed events. 182 G1RegionMappingChangedListener _listener; 183 184 // The sequence of all heap regions in the heap. 185 HeapRegionManager _hrm; 186 187 // Manages all allocations with regions except humongous object allocations. 188 G1Allocator* _allocator; 189 190 // Manages all heap verification. 191 G1HeapVerifier* _verifier; 192 193 // Outside of GC pauses, the number of bytes used in all regions other 194 // than the current allocation region(s). 195 size_t _summary_bytes_used; 196 197 void increase_used(size_t bytes); 198 void decrease_used(size_t bytes); 199 200 void set_used(size_t bytes); 201 202 // Class that handles archive allocation ranges. 203 G1ArchiveAllocator* _archive_allocator; 204 205 // Statistics for each allocation context 206 AllocationContextStats _allocation_context_stats; 207 208 // GC allocation statistics policy for survivors. 209 G1EvacStats _survivor_evac_stats; 210 211 // GC allocation statistics policy for tenured objects. 212 G1EvacStats _old_evac_stats; 213 214 // It specifies whether we should attempt to expand the heap after a 215 // region allocation failure. If heap expansion fails we set this to 216 // false so that we don't re-attempt the heap expansion (it's likely 217 // that subsequent expansion attempts will also fail if one fails). 218 // Currently, it is only consulted during GC and it's reset at the 219 // start of each GC. 220 bool _expand_heap_after_alloc_failure; 221 222 // Helper for monitoring and management support. 223 G1MonitoringSupport* _g1mm; 224 225 // Records whether the region at the given index is (still) a 226 // candidate for eager reclaim. Only valid for humongous start 227 // regions; other regions have unspecified values. Humongous start 228 // regions are initialized at start of collection pause, with 229 // candidates removed from the set as they are found reachable from 230 // roots or the young generation. 231 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 232 protected: 233 bool default_value() const { return false; } 234 public: 235 void clear() { G1BiasedMappedArray<bool>::clear(); } 236 void set_candidate(uint region, bool value) { 237 set_by_index(region, value); 238 } 239 bool is_candidate(uint region) { 240 return get_by_index(region); 241 } 242 }; 243 244 HumongousReclaimCandidates _humongous_reclaim_candidates; 245 // Stores whether during humongous object registration we found candidate regions. 246 // If not, we can skip a few steps. 247 bool _has_humongous_reclaim_candidates; 248 249 volatile uint _gc_time_stamp; 250 251 G1HRPrinter _hr_printer; 252 253 // It decides whether an explicit GC should start a concurrent cycle 254 // instead of doing a STW GC. Currently, a concurrent cycle is 255 // explicitly started if: 256 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 257 // (b) cause == _g1_humongous_allocation 258 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 259 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 260 // (e) cause == _update_allocation_context_stats_inc 261 // (f) cause == _wb_conc_mark 262 bool should_do_concurrent_full_gc(GCCause::Cause cause); 263 264 // indicates whether we are in young or mixed GC mode 265 G1CollectorState _collector_state; 266 267 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 268 // concurrent cycles) we have started. 269 volatile uint _old_marking_cycles_started; 270 271 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 272 // concurrent cycles) we have completed. 273 volatile uint _old_marking_cycles_completed; 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 static G1Policy* create_g1_policy(); 297 298 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 299 300 void process_weak_jni_handles(); 301 302 // These are macros so that, if the assert fires, we get the correct 303 // line number, file, etc. 304 305 #define heap_locking_asserts_params(_extra_message_) \ 306 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 307 (_extra_message_), \ 308 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 309 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 310 BOOL_TO_STR(Thread::current()->is_VM_thread()) 311 312 #define assert_heap_locked() \ 313 do { \ 314 assert(Heap_lock->owned_by_self(), \ 315 heap_locking_asserts_params("should be holding the Heap_lock")); \ 316 } while (0) 317 318 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 319 do { \ 320 assert(Heap_lock->owned_by_self() || \ 321 (SafepointSynchronize::is_at_safepoint() && \ 322 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 323 heap_locking_asserts_params("should be holding the Heap_lock or " \ 324 "should be at a safepoint")); \ 325 } while (0) 326 327 #define assert_heap_locked_and_not_at_safepoint() \ 328 do { \ 329 assert(Heap_lock->owned_by_self() && \ 330 !SafepointSynchronize::is_at_safepoint(), \ 331 heap_locking_asserts_params("should be holding the Heap_lock and " \ 332 "should not be at a safepoint")); \ 333 } while (0) 334 335 #define assert_heap_not_locked() \ 336 do { \ 337 assert(!Heap_lock->owned_by_self(), \ 338 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 339 } while (0) 340 341 #define assert_heap_not_locked_and_not_at_safepoint() \ 342 do { \ 343 assert(!Heap_lock->owned_by_self() && \ 344 !SafepointSynchronize::is_at_safepoint(), \ 345 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 346 "should not be at a safepoint")); \ 347 } while (0) 348 349 #define assert_at_safepoint(_should_be_vm_thread_) \ 350 do { \ 351 assert(SafepointSynchronize::is_at_safepoint() && \ 352 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 353 heap_locking_asserts_params("should be at a safepoint")); \ 354 } while (0) 355 356 #define assert_not_at_safepoint() \ 357 do { \ 358 assert(!SafepointSynchronize::is_at_safepoint(), \ 359 heap_locking_asserts_params("should not be at a safepoint")); \ 360 } while (0) 361 362 protected: 363 364 // The young region list. 365 YoungList* _young_list; 366 367 // The current policy object for the collector. 368 G1Policy* _g1_policy; 369 G1HeapSizingPolicy* _heap_sizing_policy; 370 371 G1CollectionSet _collection_set; 372 373 // This is the second level of trying to allocate a new region. If 374 // new_region() didn't find a region on the free_list, this call will 375 // check whether there's anything available on the 376 // secondary_free_list and/or wait for more regions to appear on 377 // that list, if _free_regions_coming is set. 378 HeapRegion* new_region_try_secondary_free_list(bool is_old); 379 380 // Try to allocate a single non-humongous HeapRegion sufficient for 381 // an allocation of the given word_size. If do_expand is true, 382 // attempt to expand the heap if necessary to satisfy the allocation 383 // request. If the region is to be used as an old region or for a 384 // humongous object, set is_old to true. If not, to false. 385 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 386 387 // Initialize a contiguous set of free regions of length num_regions 388 // and starting at index first so that they appear as a single 389 // humongous region. 390 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 391 uint num_regions, 392 size_t word_size, 393 AllocationContext_t context); 394 395 // Attempt to allocate a humongous object of the given size. Return 396 // NULL if unsuccessful. 397 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 398 399 // The following two methods, allocate_new_tlab() and 400 // mem_allocate(), are the two main entry points from the runtime 401 // into the G1's allocation routines. They have the following 402 // assumptions: 403 // 404 // * They should both be called outside safepoints. 405 // 406 // * They should both be called without holding the Heap_lock. 407 // 408 // * All allocation requests for new TLABs should go to 409 // allocate_new_tlab(). 410 // 411 // * All non-TLAB allocation requests should go to mem_allocate(). 412 // 413 // * If either call cannot satisfy the allocation request using the 414 // current allocating region, they will try to get a new one. If 415 // this fails, they will attempt to do an evacuation pause and 416 // retry the allocation. 417 // 418 // * If all allocation attempts fail, even after trying to schedule 419 // an evacuation pause, allocate_new_tlab() will return NULL, 420 // whereas mem_allocate() will attempt a heap expansion and/or 421 // schedule a Full GC. 422 // 423 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 424 // should never be called with word_size being humongous. All 425 // humongous allocation requests should go to mem_allocate() which 426 // will satisfy them with a special path. 427 428 virtual HeapWord* allocate_new_tlab(size_t word_size); 429 430 virtual HeapWord* mem_allocate(size_t word_size, 431 bool* gc_overhead_limit_was_exceeded); 432 433 // The following three methods take a gc_count_before_ret 434 // parameter which is used to return the GC count if the method 435 // returns NULL. Given that we are required to read the GC count 436 // while holding the Heap_lock, and these paths will take the 437 // Heap_lock at some point, it's easier to get them to read the GC 438 // count while holding the Heap_lock before they return NULL instead 439 // of the caller (namely: mem_allocate()) having to also take the 440 // Heap_lock just to read the GC count. 441 442 // First-level mutator allocation attempt: try to allocate out of 443 // the mutator alloc region without taking the Heap_lock. This 444 // should only be used for non-humongous allocations. 445 inline HeapWord* attempt_allocation(size_t word_size, 446 uint* gc_count_before_ret, 447 uint* gclocker_retry_count_ret); 448 449 // Second-level mutator allocation attempt: take the Heap_lock and 450 // retry the allocation attempt, potentially scheduling a GC 451 // pause. This should only be used for non-humongous allocations. 452 HeapWord* attempt_allocation_slow(size_t word_size, 453 AllocationContext_t context, 454 uint* gc_count_before_ret, 455 uint* gclocker_retry_count_ret); 456 457 // Takes the Heap_lock and attempts a humongous allocation. It can 458 // potentially schedule a GC pause. 459 HeapWord* attempt_allocation_humongous(size_t word_size, 460 uint* gc_count_before_ret, 461 uint* gclocker_retry_count_ret); 462 463 // Allocation attempt that should be called during safepoints (e.g., 464 // at the end of a successful GC). expect_null_mutator_alloc_region 465 // specifies whether the mutator alloc region is expected to be NULL 466 // or not. 467 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 468 AllocationContext_t context, 469 bool expect_null_mutator_alloc_region); 470 471 // These methods are the "callbacks" from the G1AllocRegion class. 472 473 // For mutator alloc regions. 474 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 475 void retire_mutator_alloc_region(HeapRegion* alloc_region, 476 size_t allocated_bytes); 477 478 // For GC alloc regions. 479 bool has_more_regions(InCSetState dest); 480 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest); 481 void retire_gc_alloc_region(HeapRegion* alloc_region, 482 size_t allocated_bytes, InCSetState dest); 483 484 // - if explicit_gc is true, the GC is for a System.gc() etc, 485 // otherwise it's for a failed allocation. 486 // - if clear_all_soft_refs is true, all soft references should be 487 // cleared during the GC. 488 // - it returns false if it is unable to do the collection due to the 489 // GC locker being active, true otherwise. 490 bool do_full_collection(bool explicit_gc, 491 bool clear_all_soft_refs); 492 493 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 494 virtual void do_full_collection(bool clear_all_soft_refs); 495 496 // Resize the heap if necessary after a full collection. 497 void resize_if_necessary_after_full_collection(); 498 499 // Callback from VM_G1CollectForAllocation operation. 500 // This function does everything necessary/possible to satisfy a 501 // failed allocation request (including collection, expansion, etc.) 502 HeapWord* satisfy_failed_allocation(size_t word_size, 503 AllocationContext_t context, 504 bool* succeeded); 505 private: 506 // Helper method for satisfy_failed_allocation() 507 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 508 AllocationContext_t context, 509 bool do_gc, 510 bool clear_all_soft_refs, 511 bool expect_null_mutator_alloc_region, 512 bool* gc_succeeded); 513 514 protected: 515 // Attempting to expand the heap sufficiently 516 // to support an allocation of the given "word_size". If 517 // successful, perform the allocation and return the address of the 518 // allocated block, or else "NULL". 519 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 520 521 // Preserve any referents discovered by concurrent marking that have not yet been 522 // copied by the STW pause. 523 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states); 524 // Process any reference objects discovered during 525 // an incremental evacuation pause. 526 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 527 528 // Enqueue any remaining discovered references 529 // after processing. 530 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 531 532 // Merges the information gathered on a per-thread basis for all worker threads 533 // during GC into global variables. 534 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states); 535 public: 536 WorkGang* workers() const { return _workers; } 537 538 G1Allocator* allocator() { 539 return _allocator; 540 } 541 542 G1HeapVerifier* verifier() { 543 return _verifier; 544 } 545 546 G1MonitoringSupport* g1mm() { 547 assert(_g1mm != NULL, "should have been initialized"); 548 return _g1mm; 549 } 550 551 // Expand the garbage-first heap by at least the given size (in bytes!). 552 // Returns true if the heap was expanded by the requested amount; 553 // false otherwise. 554 // (Rounds up to a HeapRegion boundary.) 555 bool expand(size_t expand_bytes, double* expand_time_ms = NULL); 556 557 // Returns the PLAB statistics for a given destination. 558 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 559 560 // Determines PLAB size for a given destination. 561 inline size_t desired_plab_sz(InCSetState dest); 562 563 inline AllocationContextStats& allocation_context_stats(); 564 565 // Do anything common to GC's. 566 void gc_prologue(bool full); 567 void gc_epilogue(bool full); 568 569 // Modify the reclaim candidate set and test for presence. 570 // These are only valid for starts_humongous regions. 571 inline void set_humongous_reclaim_candidate(uint region, bool value); 572 inline bool is_humongous_reclaim_candidate(uint region); 573 574 // Remove from the reclaim candidate set. Also remove from the 575 // collection set so that later encounters avoid the slow path. 576 inline void set_humongous_is_live(oop obj); 577 578 // Register the given region to be part of the collection set. 579 inline void register_humongous_region_with_cset(uint index); 580 // Register regions with humongous objects (actually on the start region) in 581 // the in_cset_fast_test table. 582 void register_humongous_regions_with_cset(); 583 // We register a region with the fast "in collection set" test. We 584 // simply set to true the array slot corresponding to this region. 585 void register_young_region_with_cset(HeapRegion* r) { 586 _in_cset_fast_test.set_in_young(r->hrm_index()); 587 } 588 void register_old_region_with_cset(HeapRegion* r) { 589 _in_cset_fast_test.set_in_old(r->hrm_index()); 590 } 591 inline void register_ext_region_with_cset(HeapRegion* r) { 592 _in_cset_fast_test.set_ext(r->hrm_index()); 593 } 594 void clear_in_cset(const HeapRegion* hr) { 595 _in_cset_fast_test.clear(hr); 596 } 597 598 void clear_cset_fast_test() { 599 _in_cset_fast_test.clear(); 600 } 601 602 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 603 604 // This is called at the start of either a concurrent cycle or a Full 605 // GC to update the number of old marking cycles started. 606 void increment_old_marking_cycles_started(); 607 608 // This is called at the end of either a concurrent cycle or a Full 609 // GC to update the number of old marking cycles completed. Those two 610 // can happen in a nested fashion, i.e., we start a concurrent 611 // cycle, a Full GC happens half-way through it which ends first, 612 // and then the cycle notices that a Full GC happened and ends 613 // too. The concurrent parameter is a boolean to help us do a bit 614 // tighter consistency checking in the method. If concurrent is 615 // false, the caller is the inner caller in the nesting (i.e., the 616 // Full GC). If concurrent is true, the caller is the outer caller 617 // in this nesting (i.e., the concurrent cycle). Further nesting is 618 // not currently supported. The end of this call also notifies 619 // the FullGCCount_lock in case a Java thread is waiting for a full 620 // GC to happen (e.g., it called System.gc() with 621 // +ExplicitGCInvokesConcurrent). 622 void increment_old_marking_cycles_completed(bool concurrent); 623 624 uint old_marking_cycles_completed() { 625 return _old_marking_cycles_completed; 626 } 627 628 G1HRPrinter* hr_printer() { return &_hr_printer; } 629 630 // Allocates a new heap region instance. 631 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 632 633 // Allocate the highest free region in the reserved heap. This will commit 634 // regions as necessary. 635 HeapRegion* alloc_highest_free_region(); 636 637 // Frees a non-humongous region by initializing its contents and 638 // adding it to the free list that's passed as a parameter (this is 639 // usually a local list which will be appended to the master free 640 // list later). The used bytes of freed regions are accumulated in 641 // pre_used. If par is true, the region's RSet will not be freed 642 // up. The assumption is that this will be done later. 643 // The locked parameter indicates if the caller has already taken 644 // care of proper synchronization. This may allow some optimizations. 645 void free_region(HeapRegion* hr, 646 FreeRegionList* free_list, 647 bool par, 648 bool locked = false); 649 650 // It dirties the cards that cover the block so that the post 651 // write barrier never queues anything when updating objects on this 652 // block. It is assumed (and in fact we assert) that the block 653 // belongs to a young region. 654 inline void dirty_young_block(HeapWord* start, size_t word_size); 655 656 // Frees a humongous region by collapsing it into individual regions 657 // and calling free_region() for each of them. The freed regions 658 // will be added to the free list that's passed as a parameter (this 659 // is usually a local list which will be appended to the master free 660 // list later). The used bytes of freed regions are accumulated in 661 // pre_used. If par is true, the region's RSet will not be freed 662 // up. The assumption is that this will be done later. 663 void free_humongous_region(HeapRegion* hr, 664 FreeRegionList* free_list, 665 bool par); 666 667 // Facility for allocating in 'archive' regions in high heap memory and 668 // recording the allocated ranges. These should all be called from the 669 // VM thread at safepoints, without the heap lock held. They can be used 670 // to create and archive a set of heap regions which can be mapped at the 671 // same fixed addresses in a subsequent JVM invocation. 672 void begin_archive_alloc_range(); 673 674 // Check if the requested size would be too large for an archive allocation. 675 bool is_archive_alloc_too_large(size_t word_size); 676 677 // Allocate memory of the requested size from the archive region. This will 678 // return NULL if the size is too large or if no memory is available. It 679 // does not trigger a garbage collection. 680 HeapWord* archive_mem_allocate(size_t word_size); 681 682 // Optionally aligns the end address and returns the allocated ranges in 683 // an array of MemRegions in order of ascending addresses. 684 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 685 size_t end_alignment_in_bytes = 0); 686 687 // Facility for allocating a fixed range within the heap and marking 688 // the containing regions as 'archive'. For use at JVM init time, when the 689 // caller may mmap archived heap data at the specified range(s). 690 // Verify that the MemRegions specified in the argument array are within the 691 // reserved heap. 692 bool check_archive_addresses(MemRegion* range, size_t count); 693 694 // Commit the appropriate G1 regions containing the specified MemRegions 695 // and mark them as 'archive' regions. The regions in the array must be 696 // non-overlapping and in order of ascending address. 697 bool alloc_archive_regions(MemRegion* range, size_t count); 698 699 // Insert any required filler objects in the G1 regions around the specified 700 // ranges to make the regions parseable. This must be called after 701 // alloc_archive_regions, and after class loading has occurred. 702 void fill_archive_regions(MemRegion* range, size_t count); 703 704 // For each of the specified MemRegions, uncommit the containing G1 regions 705 // which had been allocated by alloc_archive_regions. This should be called 706 // rather than fill_archive_regions at JVM init time if the archive file 707 // mapping failed, with the same non-overlapping and sorted MemRegion array. 708 void dealloc_archive_regions(MemRegion* range, size_t count); 709 710 protected: 711 712 // Shrink the garbage-first heap by at most the given size (in bytes!). 713 // (Rounds down to a HeapRegion boundary.) 714 virtual void shrink(size_t expand_bytes); 715 void shrink_helper(size_t expand_bytes); 716 717 #if TASKQUEUE_STATS 718 static void print_taskqueue_stats_hdr(outputStream* const st); 719 void print_taskqueue_stats() const; 720 void reset_taskqueue_stats(); 721 #endif // TASKQUEUE_STATS 722 723 // Schedule the VM operation that will do an evacuation pause to 724 // satisfy an allocation request of word_size. *succeeded will 725 // return whether the VM operation was successful (it did do an 726 // evacuation pause) or not (another thread beat us to it or the GC 727 // locker was active). Given that we should not be holding the 728 // Heap_lock when we enter this method, we will pass the 729 // gc_count_before (i.e., total_collections()) as a parameter since 730 // it has to be read while holding the Heap_lock. Currently, both 731 // methods that call do_collection_pause() release the Heap_lock 732 // before the call, so it's easy to read gc_count_before just before. 733 HeapWord* do_collection_pause(size_t word_size, 734 uint gc_count_before, 735 bool* succeeded, 736 GCCause::Cause gc_cause); 737 738 void wait_for_root_region_scanning(); 739 740 // The guts of the incremental collection pause, executed by the vm 741 // thread. It returns false if it is unable to do the collection due 742 // to the GC locker being active, true otherwise 743 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 744 745 // Actually do the work of evacuating the collection set. 746 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 747 748 void pre_evacuate_collection_set(); 749 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 750 751 // Print the header for the per-thread termination statistics. 752 static void print_termination_stats_hdr(); 753 // Print actual per-thread termination statistics. 754 void print_termination_stats(uint worker_id, 755 double elapsed_ms, 756 double strong_roots_ms, 757 double term_ms, 758 size_t term_attempts, 759 size_t alloc_buffer_waste, 760 size_t undo_waste) const; 761 // Update object copying statistics. 762 void record_obj_copy_mem_stats(); 763 764 // The g1 remembered set of the heap. 765 G1RemSet* _g1_rem_set; 766 767 // A set of cards that cover the objects for which the Rsets should be updated 768 // concurrently after the collection. 769 DirtyCardQueueSet _dirty_card_queue_set; 770 771 // The closure used to refine a single card. 772 RefineCardTableEntryClosure* _refine_cte_cl; 773 774 // After a collection pause, make the regions in the CS into free 775 // regions. 776 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 777 778 // Abandon the current collection set without recording policy 779 // statistics or updating free lists. 780 void abandon_collection_set(HeapRegion* cs_head); 781 782 // The concurrent marker (and the thread it runs in.) 783 G1ConcurrentMark* _cm; 784 ConcurrentMarkThread* _cmThread; 785 786 // The concurrent refiner. 787 ConcurrentG1Refine* _cg1r; 788 789 // The parallel task queues 790 RefToScanQueueSet *_task_queues; 791 792 // True iff a evacuation has failed in the current collection. 793 bool _evacuation_failed; 794 795 EvacuationFailedInfo* _evacuation_failed_info_array; 796 797 // Failed evacuations cause some logical from-space objects to have 798 // forwarding pointers to themselves. Reset them. 799 void remove_self_forwarding_pointers(); 800 801 // Restore the objects in the regions in the collection set after an 802 // evacuation failure. 803 void restore_after_evac_failure(); 804 805 PreservedMarksSet _preserved_marks_set; 806 807 // Preserve the mark of "obj", if necessary, in preparation for its mark 808 // word being overwritten with a self-forwarding-pointer. 809 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 810 811 #ifndef PRODUCT 812 // Support for forcing evacuation failures. Analogous to 813 // PromotionFailureALot for the other collectors. 814 815 // Records whether G1EvacuationFailureALot should be in effect 816 // for the current GC 817 bool _evacuation_failure_alot_for_current_gc; 818 819 // Used to record the GC number for interval checking when 820 // determining whether G1EvaucationFailureALot is in effect 821 // for the current GC. 822 size_t _evacuation_failure_alot_gc_number; 823 824 // Count of the number of evacuations between failures. 825 volatile size_t _evacuation_failure_alot_count; 826 827 // Set whether G1EvacuationFailureALot should be in effect 828 // for the current GC (based upon the type of GC and which 829 // command line flags are set); 830 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 831 bool during_initial_mark, 832 bool during_marking); 833 834 inline void set_evacuation_failure_alot_for_current_gc(); 835 836 // Return true if it's time to cause an evacuation failure. 837 inline bool evacuation_should_fail(); 838 839 // Reset the G1EvacuationFailureALot counters. Should be called at 840 // the end of an evacuation pause in which an evacuation failure occurred. 841 inline void reset_evacuation_should_fail(); 842 #endif // !PRODUCT 843 844 // ("Weak") Reference processing support. 845 // 846 // G1 has 2 instances of the reference processor class. One 847 // (_ref_processor_cm) handles reference object discovery 848 // and subsequent processing during concurrent marking cycles. 849 // 850 // The other (_ref_processor_stw) handles reference object 851 // discovery and processing during full GCs and incremental 852 // evacuation pauses. 853 // 854 // During an incremental pause, reference discovery will be 855 // temporarily disabled for _ref_processor_cm and will be 856 // enabled for _ref_processor_stw. At the end of the evacuation 857 // pause references discovered by _ref_processor_stw will be 858 // processed and discovery will be disabled. The previous 859 // setting for reference object discovery for _ref_processor_cm 860 // will be re-instated. 861 // 862 // At the start of marking: 863 // * Discovery by the CM ref processor is verified to be inactive 864 // and it's discovered lists are empty. 865 // * Discovery by the CM ref processor is then enabled. 866 // 867 // At the end of marking: 868 // * Any references on the CM ref processor's discovered 869 // lists are processed (possibly MT). 870 // 871 // At the start of full GC we: 872 // * Disable discovery by the CM ref processor and 873 // empty CM ref processor's discovered lists 874 // (without processing any entries). 875 // * Verify that the STW ref processor is inactive and it's 876 // discovered lists are empty. 877 // * Temporarily set STW ref processor discovery as single threaded. 878 // * Temporarily clear the STW ref processor's _is_alive_non_header 879 // field. 880 // * Finally enable discovery by the STW ref processor. 881 // 882 // The STW ref processor is used to record any discovered 883 // references during the full GC. 884 // 885 // At the end of a full GC we: 886 // * Enqueue any reference objects discovered by the STW ref processor 887 // that have non-live referents. This has the side-effect of 888 // making the STW ref processor inactive by disabling discovery. 889 // * Verify that the CM ref processor is still inactive 890 // and no references have been placed on it's discovered 891 // lists (also checked as a precondition during initial marking). 892 893 // The (stw) reference processor... 894 ReferenceProcessor* _ref_processor_stw; 895 896 STWGCTimer* _gc_timer_stw; 897 898 G1NewTracer* _gc_tracer_stw; 899 900 // During reference object discovery, the _is_alive_non_header 901 // closure (if non-null) is applied to the referent object to 902 // determine whether the referent is live. If so then the 903 // reference object does not need to be 'discovered' and can 904 // be treated as a regular oop. This has the benefit of reducing 905 // the number of 'discovered' reference objects that need to 906 // be processed. 907 // 908 // Instance of the is_alive closure for embedding into the 909 // STW reference processor as the _is_alive_non_header field. 910 // Supplying a value for the _is_alive_non_header field is 911 // optional but doing so prevents unnecessary additions to 912 // the discovered lists during reference discovery. 913 G1STWIsAliveClosure _is_alive_closure_stw; 914 915 // The (concurrent marking) reference processor... 916 ReferenceProcessor* _ref_processor_cm; 917 918 // Instance of the concurrent mark is_alive closure for embedding 919 // into the Concurrent Marking reference processor as the 920 // _is_alive_non_header field. Supplying a value for the 921 // _is_alive_non_header field is optional but doing so prevents 922 // unnecessary additions to the discovered lists during reference 923 // discovery. 924 G1CMIsAliveClosure _is_alive_closure_cm; 925 926 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 927 HeapRegion** _worker_cset_start_region; 928 929 // Time stamp to validate the regions recorded in the cache 930 // used by G1CollectedHeap::start_cset_region_for_worker(). 931 // The heap region entry for a given worker is valid iff 932 // the associated time stamp value matches the current value 933 // of G1CollectedHeap::_gc_time_stamp. 934 uint* _worker_cset_start_region_time_stamp; 935 936 volatile bool _free_regions_coming; 937 938 public: 939 940 void set_refine_cte_cl_concurrency(bool concurrent); 941 942 RefToScanQueue *task_queue(uint i) const; 943 944 uint num_task_queues() const; 945 946 // A set of cards where updates happened during the GC 947 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 948 949 // Create a G1CollectedHeap with the specified policy. 950 // Must call the initialize method afterwards. 951 // May not return if something goes wrong. 952 G1CollectedHeap(G1CollectorPolicy* policy); 953 954 // Initialize the G1CollectedHeap to have the initial and 955 // maximum sizes and remembered and barrier sets 956 // specified by the policy object. 957 jint initialize(); 958 959 virtual void stop(); 960 961 // Return the (conservative) maximum heap alignment for any G1 heap 962 static size_t conservative_max_heap_alignment(); 963 964 // Does operations required after initialization has been done. 965 void post_initialize(); 966 967 // Initialize weak reference processing. 968 void ref_processing_init(); 969 970 virtual Name kind() const { 971 return CollectedHeap::G1CollectedHeap; 972 } 973 974 virtual const char* name() const { 975 return "G1"; 976 } 977 978 const G1CollectorState* collector_state() const { return &_collector_state; } 979 G1CollectorState* collector_state() { return &_collector_state; } 980 981 // The current policy object for the collector. 982 G1Policy* g1_policy() const { return _g1_policy; } 983 984 const G1CollectionSet* collection_set() const { return &_collection_set; } 985 G1CollectionSet* collection_set() { return &_collection_set; } 986 987 virtual CollectorPolicy* collector_policy() const; 988 989 // Adaptive size policy. No such thing for g1. 990 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 991 992 // The rem set and barrier set. 993 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 994 995 // Try to minimize the remembered set. 996 void scrub_rem_set(); 997 998 uint get_gc_time_stamp() { 999 return _gc_time_stamp; 1000 } 1001 1002 inline void reset_gc_time_stamp(); 1003 1004 void check_gc_time_stamps() PRODUCT_RETURN; 1005 1006 inline void increment_gc_time_stamp(); 1007 1008 // Reset the given region's GC timestamp. If it's starts humongous, 1009 // also reset the GC timestamp of its corresponding 1010 // continues humongous regions too. 1011 void reset_gc_time_stamps(HeapRegion* hr); 1012 1013 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1014 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1015 1016 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1017 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1018 1019 // The shared block offset table array. 1020 G1BlockOffsetTable* bot() const { return _bot; } 1021 1022 // Reference Processing accessors 1023 1024 // The STW reference processor.... 1025 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1026 1027 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1028 1029 // The Concurrent Marking reference processor... 1030 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1031 1032 virtual size_t capacity() const; 1033 virtual size_t used() const; 1034 // This should be called when we're not holding the heap lock. The 1035 // result might be a bit inaccurate. 1036 size_t used_unlocked() const; 1037 size_t recalculate_used() const; 1038 1039 // These virtual functions do the actual allocation. 1040 // Some heaps may offer a contiguous region for shared non-blocking 1041 // allocation, via inlined code (by exporting the address of the top and 1042 // end fields defining the extent of the contiguous allocation region.) 1043 // But G1CollectedHeap doesn't yet support this. 1044 1045 virtual bool is_maximal_no_gc() const { 1046 return _hrm.available() == 0; 1047 } 1048 1049 // The current number of regions in the heap. 1050 uint num_regions() const { return _hrm.length(); } 1051 1052 // The max number of regions in the heap. 1053 uint max_regions() const { return _hrm.max_length(); } 1054 1055 // The number of regions that are completely free. 1056 uint num_free_regions() const { return _hrm.num_free_regions(); } 1057 1058 MemoryUsage get_auxiliary_data_memory_usage() const { 1059 return _hrm.get_auxiliary_data_memory_usage(); 1060 } 1061 1062 // The number of regions that are not completely free. 1063 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1064 1065 #ifdef ASSERT 1066 bool is_on_master_free_list(HeapRegion* hr) { 1067 return _hrm.is_free(hr); 1068 } 1069 #endif // ASSERT 1070 1071 // Wrapper for the region list operations that can be called from 1072 // methods outside this class. 1073 1074 void secondary_free_list_add(FreeRegionList* list) { 1075 _secondary_free_list.add_ordered(list); 1076 } 1077 1078 void append_secondary_free_list() { 1079 _hrm.insert_list_into_free_list(&_secondary_free_list); 1080 } 1081 1082 void append_secondary_free_list_if_not_empty_with_lock() { 1083 // If the secondary free list looks empty there's no reason to 1084 // take the lock and then try to append it. 1085 if (!_secondary_free_list.is_empty()) { 1086 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1087 append_secondary_free_list(); 1088 } 1089 } 1090 1091 inline void old_set_add(HeapRegion* hr); 1092 inline void old_set_remove(HeapRegion* hr); 1093 1094 size_t non_young_capacity_bytes() { 1095 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes; 1096 } 1097 1098 void set_free_regions_coming(); 1099 void reset_free_regions_coming(); 1100 bool free_regions_coming() { return _free_regions_coming; } 1101 void wait_while_free_regions_coming(); 1102 1103 // Determine whether the given region is one that we are using as an 1104 // old GC alloc region. 1105 bool is_old_gc_alloc_region(HeapRegion* hr); 1106 1107 // Perform a collection of the heap; intended for use in implementing 1108 // "System.gc". This probably implies as full a collection as the 1109 // "CollectedHeap" supports. 1110 virtual void collect(GCCause::Cause cause); 1111 1112 virtual bool copy_allocation_context_stats(const jint* contexts, 1113 jlong* totals, 1114 jbyte* accuracy, 1115 jint len); 1116 1117 // True iff an evacuation has failed in the most-recent collection. 1118 bool evacuation_failed() { return _evacuation_failed; } 1119 1120 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed); 1121 void prepend_to_freelist(FreeRegionList* list); 1122 void decrement_summary_bytes(size_t bytes); 1123 1124 virtual bool is_in(const void* p) const; 1125 #ifdef ASSERT 1126 // Returns whether p is in one of the available areas of the heap. Slow but 1127 // extensive version. 1128 bool is_in_exact(const void* p) const; 1129 #endif 1130 1131 // Return "TRUE" iff the given object address is within the collection 1132 // set. Slow implementation. 1133 bool obj_in_cs(oop obj); 1134 1135 inline bool is_in_cset(const HeapRegion *hr); 1136 inline bool is_in_cset(oop obj); 1137 1138 inline bool is_in_cset_or_humongous(const oop obj); 1139 1140 private: 1141 // This array is used for a quick test on whether a reference points into 1142 // the collection set or not. Each of the array's elements denotes whether the 1143 // corresponding region is in the collection set or not. 1144 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1145 1146 public: 1147 1148 inline InCSetState in_cset_state(const oop obj); 1149 1150 // Return "TRUE" iff the given object address is in the reserved 1151 // region of g1. 1152 bool is_in_g1_reserved(const void* p) const { 1153 return _hrm.reserved().contains(p); 1154 } 1155 1156 // Returns a MemRegion that corresponds to the space that has been 1157 // reserved for the heap 1158 MemRegion g1_reserved() const { 1159 return _hrm.reserved(); 1160 } 1161 1162 virtual bool is_in_closed_subset(const void* p) const; 1163 1164 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1165 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1166 } 1167 1168 // This resets the card table to all zeros. It is used after 1169 // a collection pause which used the card table to claim cards. 1170 void cleanUpCardTable(); 1171 1172 // Iteration functions. 1173 1174 // Iterate over all objects, calling "cl.do_object" on each. 1175 virtual void object_iterate(ObjectClosure* cl); 1176 1177 virtual void safe_object_iterate(ObjectClosure* cl) { 1178 object_iterate(cl); 1179 } 1180 1181 // Iterate over heap regions, in address order, terminating the 1182 // iteration early if the "doHeapRegion" method returns "true". 1183 void heap_region_iterate(HeapRegionClosure* blk) const; 1184 1185 // Return the region with the given index. It assumes the index is valid. 1186 inline HeapRegion* region_at(uint index) const; 1187 1188 // Return the next region (by index) that is part of the same 1189 // humongous object that hr is part of. 1190 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1191 1192 // Calculate the region index of the given address. Given address must be 1193 // within the heap. 1194 inline uint addr_to_region(HeapWord* addr) const; 1195 1196 inline HeapWord* bottom_addr_for_region(uint index) const; 1197 1198 // Iterate over the heap regions in parallel. Assumes that this will be called 1199 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1200 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1201 // to each of the regions, by attempting to claim the region using the 1202 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1203 // region. The concurrent argument should be set to true if iteration is 1204 // performed concurrently, during which no assumptions are made for consistent 1205 // attributes of the heap regions (as they might be modified while iterating). 1206 void heap_region_par_iterate(HeapRegionClosure* cl, 1207 uint worker_id, 1208 HeapRegionClaimer* hrclaimer, 1209 bool concurrent = false) const; 1210 1211 // Clear the cached cset start regions and (more importantly) 1212 // the time stamps. Called when we reset the GC time stamp. 1213 void clear_cset_start_regions(); 1214 1215 // Given the id of a worker, obtain or calculate a suitable 1216 // starting region for iterating over the current collection set. 1217 HeapRegion* start_cset_region_for_worker(uint worker_i); 1218 1219 // Iterate over the regions (if any) in the current collection set. 1220 void collection_set_iterate(HeapRegionClosure* blk); 1221 1222 // As above but starting from region r 1223 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1224 1225 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1226 1227 // Returns the HeapRegion that contains addr. addr must not be NULL. 1228 template <class T> 1229 inline HeapRegion* heap_region_containing(const T addr) const; 1230 1231 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1232 // each address in the (reserved) heap is a member of exactly 1233 // one block. The defining characteristic of a block is that it is 1234 // possible to find its size, and thus to progress forward to the next 1235 // block. (Blocks may be of different sizes.) Thus, blocks may 1236 // represent Java objects, or they might be free blocks in a 1237 // free-list-based heap (or subheap), as long as the two kinds are 1238 // distinguishable and the size of each is determinable. 1239 1240 // Returns the address of the start of the "block" that contains the 1241 // address "addr". We say "blocks" instead of "object" since some heaps 1242 // may not pack objects densely; a chunk may either be an object or a 1243 // non-object. 1244 virtual HeapWord* block_start(const void* addr) const; 1245 1246 // Requires "addr" to be the start of a chunk, and returns its size. 1247 // "addr + size" is required to be the start of a new chunk, or the end 1248 // of the active area of the heap. 1249 virtual size_t block_size(const HeapWord* addr) const; 1250 1251 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1252 // the block is an object. 1253 virtual bool block_is_obj(const HeapWord* addr) const; 1254 1255 // Section on thread-local allocation buffers (TLABs) 1256 // See CollectedHeap for semantics. 1257 1258 bool supports_tlab_allocation() const; 1259 size_t tlab_capacity(Thread* ignored) const; 1260 size_t tlab_used(Thread* ignored) const; 1261 size_t max_tlab_size() const; 1262 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1263 1264 // Can a compiler initialize a new object without store barriers? 1265 // This permission only extends from the creation of a new object 1266 // via a TLAB up to the first subsequent safepoint. If such permission 1267 // is granted for this heap type, the compiler promises to call 1268 // defer_store_barrier() below on any slow path allocation of 1269 // a new object for which such initializing store barriers will 1270 // have been elided. G1, like CMS, allows this, but should be 1271 // ready to provide a compensating write barrier as necessary 1272 // if that storage came out of a non-young region. The efficiency 1273 // of this implementation depends crucially on being able to 1274 // answer very efficiently in constant time whether a piece of 1275 // storage in the heap comes from a young region or not. 1276 // See ReduceInitialCardMarks. 1277 virtual bool can_elide_tlab_store_barriers() const { 1278 return true; 1279 } 1280 1281 virtual bool card_mark_must_follow_store() const { 1282 return true; 1283 } 1284 1285 // The reference pending list lock is acquired from from the 1286 // ConcurrentMarkThread. 1287 virtual bool needs_reference_pending_list_locker_thread() const { 1288 return true; 1289 } 1290 1291 inline bool is_in_young(const oop obj); 1292 1293 virtual bool is_scavengable(const void* addr); 1294 1295 // We don't need barriers for initializing stores to objects 1296 // in the young gen: for the SATB pre-barrier, there is no 1297 // pre-value that needs to be remembered; for the remembered-set 1298 // update logging post-barrier, we don't maintain remembered set 1299 // information for young gen objects. 1300 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1301 1302 // Returns "true" iff the given word_size is "very large". 1303 static bool is_humongous(size_t word_size) { 1304 // Note this has to be strictly greater-than as the TLABs 1305 // are capped at the humongous threshold and we want to 1306 // ensure that we don't try to allocate a TLAB as 1307 // humongous and that we don't allocate a humongous 1308 // object in a TLAB. 1309 return word_size > _humongous_object_threshold_in_words; 1310 } 1311 1312 // Returns the humongous threshold for a specific region size 1313 static size_t humongous_threshold_for(size_t region_size) { 1314 return (region_size / 2); 1315 } 1316 1317 // Returns the number of regions the humongous object of the given word size 1318 // requires. 1319 static size_t humongous_obj_size_in_regions(size_t word_size); 1320 1321 // Print the maximum heap capacity. 1322 virtual size_t max_capacity() const; 1323 1324 virtual jlong millis_since_last_gc(); 1325 1326 1327 // Convenience function to be used in situations where the heap type can be 1328 // asserted to be this type. 1329 static G1CollectedHeap* heap(); 1330 1331 void set_region_short_lived_locked(HeapRegion* hr); 1332 // add appropriate methods for any other surv rate groups 1333 1334 YoungList* young_list() const { return _young_list; } 1335 1336 uint old_regions_count() const { return _old_set.length(); } 1337 1338 uint humongous_regions_count() const { return _humongous_set.length(); } 1339 1340 // debugging 1341 bool check_young_list_well_formed() { 1342 return _young_list->check_list_well_formed(); 1343 } 1344 1345 bool check_young_list_empty(bool check_heap); 1346 1347 // *** Stuff related to concurrent marking. It's not clear to me that so 1348 // many of these need to be public. 1349 1350 // The functions below are helper functions that a subclass of 1351 // "CollectedHeap" can use in the implementation of its virtual 1352 // functions. 1353 // This performs a concurrent marking of the live objects in a 1354 // bitmap off to the side. 1355 void doConcurrentMark(); 1356 1357 bool isMarkedPrev(oop obj) const; 1358 bool isMarkedNext(oop obj) const; 1359 1360 // Determine if an object is dead, given the object and also 1361 // the region to which the object belongs. An object is dead 1362 // iff a) it was not allocated since the last mark, b) it 1363 // is not marked, and c) it is not in an archive region. 1364 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1365 return 1366 !hr->obj_allocated_since_prev_marking(obj) && 1367 !isMarkedPrev(obj) && 1368 !hr->is_archive(); 1369 } 1370 1371 // This function returns true when an object has been 1372 // around since the previous marking and hasn't yet 1373 // been marked during this marking, and is not in an archive region. 1374 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1375 return 1376 !hr->obj_allocated_since_next_marking(obj) && 1377 !isMarkedNext(obj) && 1378 !hr->is_archive(); 1379 } 1380 1381 // Determine if an object is dead, given only the object itself. 1382 // This will find the region to which the object belongs and 1383 // then call the region version of the same function. 1384 1385 // Added if it is NULL it isn't dead. 1386 1387 inline bool is_obj_dead(const oop obj) const; 1388 1389 inline bool is_obj_ill(const oop obj) const; 1390 1391 G1ConcurrentMark* concurrent_mark() const { return _cm; } 1392 1393 // Refinement 1394 1395 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1396 1397 // The dirty cards region list is used to record a subset of regions 1398 // whose cards need clearing. The list if populated during the 1399 // remembered set scanning and drained during the card table 1400 // cleanup. Although the methods are reentrant, population/draining 1401 // phases must not overlap. For synchronization purposes the last 1402 // element on the list points to itself. 1403 HeapRegion* _dirty_cards_region_list; 1404 void push_dirty_cards_region(HeapRegion* hr); 1405 HeapRegion* pop_dirty_cards_region(); 1406 1407 // Optimized nmethod scanning support routines 1408 1409 // Register the given nmethod with the G1 heap. 1410 virtual void register_nmethod(nmethod* nm); 1411 1412 // Unregister the given nmethod from the G1 heap. 1413 virtual void unregister_nmethod(nmethod* nm); 1414 1415 // Free up superfluous code root memory. 1416 void purge_code_root_memory(); 1417 1418 // Rebuild the strong code root lists for each region 1419 // after a full GC. 1420 void rebuild_strong_code_roots(); 1421 1422 // Delete entries for dead interned string and clean up unreferenced symbols 1423 // in symbol table, possibly in parallel. 1424 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1425 1426 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1427 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1428 1429 // Redirty logged cards in the refinement queue. 1430 void redirty_logged_cards(); 1431 // Verification 1432 1433 // Perform any cleanup actions necessary before allowing a verification. 1434 virtual void prepare_for_verify(); 1435 1436 // Perform verification. 1437 1438 // vo == UsePrevMarking -> use "prev" marking information, 1439 // vo == UseNextMarking -> use "next" marking information 1440 // vo == UseMarkWord -> use the mark word in the object header 1441 // 1442 // NOTE: Only the "prev" marking information is guaranteed to be 1443 // consistent most of the time, so most calls to this should use 1444 // vo == UsePrevMarking. 1445 // Currently, there is only one case where this is called with 1446 // vo == UseNextMarking, which is to verify the "next" marking 1447 // information at the end of remark. 1448 // Currently there is only one place where this is called with 1449 // vo == UseMarkWord, which is to verify the marking during a 1450 // full GC. 1451 void verify(VerifyOption vo); 1452 1453 // The methods below are here for convenience and dispatch the 1454 // appropriate method depending on value of the given VerifyOption 1455 // parameter. The values for that parameter, and their meanings, 1456 // are the same as those above. 1457 1458 bool is_obj_dead_cond(const oop obj, 1459 const HeapRegion* hr, 1460 const VerifyOption vo) const; 1461 1462 bool is_obj_dead_cond(const oop obj, 1463 const VerifyOption vo) const; 1464 1465 G1HeapSummary create_g1_heap_summary(); 1466 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1467 1468 // Printing 1469 private: 1470 void print_heap_regions() const; 1471 void print_regions_on(outputStream* st) const; 1472 1473 public: 1474 virtual void print_on(outputStream* st) const; 1475 virtual void print_extended_on(outputStream* st) const; 1476 virtual void print_on_error(outputStream* st) const; 1477 1478 virtual void print_gc_threads_on(outputStream* st) const; 1479 virtual void gc_threads_do(ThreadClosure* tc) const; 1480 1481 // Override 1482 void print_tracing_info() const; 1483 1484 // The following two methods are helpful for debugging RSet issues. 1485 void print_cset_rsets() PRODUCT_RETURN; 1486 void print_all_rsets() PRODUCT_RETURN; 1487 1488 public: 1489 size_t pending_card_num(); 1490 1491 protected: 1492 size_t _max_heap_capacity; 1493 }; 1494 1495 class G1ParEvacuateFollowersClosure : public VoidClosure { 1496 private: 1497 double _start_term; 1498 double _term_time; 1499 size_t _term_attempts; 1500 1501 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1502 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1503 protected: 1504 G1CollectedHeap* _g1h; 1505 G1ParScanThreadState* _par_scan_state; 1506 RefToScanQueueSet* _queues; 1507 ParallelTaskTerminator* _terminator; 1508 1509 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1510 RefToScanQueueSet* queues() { return _queues; } 1511 ParallelTaskTerminator* terminator() { return _terminator; } 1512 1513 public: 1514 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1515 G1ParScanThreadState* par_scan_state, 1516 RefToScanQueueSet* queues, 1517 ParallelTaskTerminator* terminator) 1518 : _g1h(g1h), _par_scan_state(par_scan_state), 1519 _queues(queues), _terminator(terminator), 1520 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1521 1522 void do_void(); 1523 1524 double term_time() const { return _term_time; } 1525 size_t term_attempts() const { return _term_attempts; } 1526 1527 private: 1528 inline bool offer_termination(); 1529 }; 1530 1531 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP