1 /* 2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP 26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP 27 28 #include "gc/g1/evacuationInfo.hpp" 29 #include "gc/g1/g1AllocationContext.hpp" 30 #include "gc/g1/g1BiasedArray.hpp" 31 #include "gc/g1/g1CollectionSet.hpp" 32 #include "gc/g1/g1CollectorState.hpp" 33 #include "gc/g1/g1ConcurrentMark.hpp" 34 #include "gc/g1/g1HRPrinter.hpp" 35 #include "gc/g1/g1InCSetState.hpp" 36 #include "gc/g1/g1MonitoringSupport.hpp" 37 #include "gc/g1/g1EvacFailure.hpp" 38 #include "gc/g1/g1EvacStats.hpp" 39 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 40 #include "gc/g1/g1YCTypes.hpp" 41 #include "gc/g1/hSpaceCounters.hpp" 42 #include "gc/g1/heapRegionManager.hpp" 43 #include "gc/g1/heapRegionSet.hpp" 44 #include "gc/g1/youngList.hpp" 45 #include "gc/shared/barrierSet.hpp" 46 #include "gc/shared/collectedHeap.hpp" 47 #include "gc/shared/plab.hpp" 48 #include "memory/memRegion.hpp" 49 #include "utilities/stack.hpp" 50 51 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 52 // It uses the "Garbage First" heap organization and algorithm, which 53 // may combine concurrent marking with parallel, incremental compaction of 54 // heap subsets that will yield large amounts of garbage. 55 56 // Forward declarations 57 class HeapRegion; 58 class HRRSCleanupTask; 59 class GenerationSpec; 60 class OopsInHeapRegionClosure; 61 class G1ParScanThreadState; 62 class G1ParScanThreadStateSet; 63 class G1KlassScanClosure; 64 class G1ParScanThreadState; 65 class ObjectClosure; 66 class SpaceClosure; 67 class CompactibleSpaceClosure; 68 class Space; 69 class G1CollectionSet; 70 class G1CollectorPolicy; 71 class G1RemSet; 72 class HeapRegionRemSetIterator; 73 class G1ConcurrentMark; 74 class ConcurrentMarkThread; 75 class ConcurrentG1Refine; 76 class ConcurrentGCTimer; 77 class GenerationCounters; 78 class STWGCTimer; 79 class G1NewTracer; 80 class G1OldTracer; 81 class EvacuationFailedInfo; 82 class nmethod; 83 class Ticks; 84 class WorkGang; 85 class G1Allocator; 86 class G1ArchiveAllocator; 87 class G1HeapVerifier; 88 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; 142 143 static size_t _humongous_object_threshold_in_words; 144 145 // The secondary free list which contains regions that have been 146 // freed up during the cleanup process. This will be appended to 147 // the master free list when appropriate. 148 FreeRegionList _secondary_free_list; 149 150 // It keeps track of the old regions. 151 HeapRegionSet _old_set; 152 153 // It keeps track of the humongous regions. 154 HeapRegionSet _humongous_set; 155 156 void eagerly_reclaim_humongous_regions(); 157 158 // The number of regions we could create by expansion. 159 uint _expansion_regions; 160 161 // The block offset table for the G1 heap. 162 G1BlockOffsetTable* _bot; 163 164 // Tears down the region sets / lists so that they are empty and the 165 // regions on the heap do not belong to a region set / list. The 166 // only exception is the humongous set which we leave unaltered. If 167 // free_list_only is true, it will only tear down the master free 168 // list. It is called before a Full GC (free_list_only == false) or 169 // before heap shrinking (free_list_only == true). 170 void tear_down_region_sets(bool free_list_only); 171 172 // Rebuilds the region sets / lists so that they are repopulated to 173 // reflect the contents of the heap. The only exception is the 174 // humongous set which was not torn down in the first place. If 175 // free_list_only is true, it will only rebuild the master free 176 // list. It is called after a Full GC (free_list_only == false) or 177 // after heap shrinking (free_list_only == true). 178 void rebuild_region_sets(bool free_list_only); 179 180 // Callback for region mapping changed events. 181 G1RegionMappingChangedListener _listener; 182 183 // The sequence of all heap regions in the heap. 184 HeapRegionManager _hrm; 185 186 // Manages all allocations with regions except humongous object allocations. 187 G1Allocator* _allocator; 188 189 // Manages all heap verification. 190 G1HeapVerifier* _verifier; 191 192 // Outside of GC pauses, the number of bytes used in all regions other 193 // than the current allocation region(s). 194 size_t _summary_bytes_used; 195 196 void increase_used(size_t bytes); 197 void decrease_used(size_t bytes); 198 199 void set_used(size_t bytes); 200 201 // Class that handles archive allocation ranges. 202 G1ArchiveAllocator* _archive_allocator; 203 204 // Statistics for each allocation context 205 AllocationContextStats _allocation_context_stats; 206 207 // GC allocation statistics policy for survivors. 208 G1EvacStats _survivor_evac_stats; 209 210 // GC allocation statistics policy for tenured objects. 211 G1EvacStats _old_evac_stats; 212 213 // It specifies whether we should attempt to expand the heap after a 214 // region allocation failure. If heap expansion fails we set this to 215 // false so that we don't re-attempt the heap expansion (it's likely 216 // that subsequent expansion attempts will also fail if one fails). 217 // Currently, it is only consulted during GC and it's reset at the 218 // start of each GC. 219 bool _expand_heap_after_alloc_failure; 220 221 // Helper for monitoring and management support. 222 G1MonitoringSupport* _g1mm; 223 224 // Records whether the region at the given index is (still) a 225 // candidate for eager reclaim. Only valid for humongous start 226 // regions; other regions have unspecified values. Humongous start 227 // regions are initialized at start of collection pause, with 228 // candidates removed from the set as they are found reachable from 229 // roots or the young generation. 230 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 231 protected: 232 bool default_value() const { return false; } 233 public: 234 void clear() { G1BiasedMappedArray<bool>::clear(); } 235 void set_candidate(uint region, bool value) { 236 set_by_index(region, value); 237 } 238 bool is_candidate(uint region) { 239 return get_by_index(region); 240 } 241 }; 242 243 HumongousReclaimCandidates _humongous_reclaim_candidates; 244 // Stores whether during humongous object registration we found candidate regions. 245 // If not, we can skip a few steps. 246 bool _has_humongous_reclaim_candidates; 247 248 volatile unsigned _gc_time_stamp; 249 250 G1HRPrinter _hr_printer; 251 252 // It decides whether an explicit GC should start a concurrent cycle 253 // instead of doing a STW GC. Currently, a concurrent cycle is 254 // explicitly started if: 255 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 256 // (b) cause == _g1_humongous_allocation 257 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 258 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 259 // (e) cause == _update_allocation_context_stats_inc 260 // (f) cause == _wb_conc_mark 261 bool should_do_concurrent_full_gc(GCCause::Cause cause); 262 263 // indicates whether we are in young or mixed GC mode 264 G1CollectorState _collector_state; 265 266 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 267 // concurrent cycles) we have started. 268 volatile uint _old_marking_cycles_started; 269 270 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 271 // concurrent cycles) we have completed. 272 volatile uint _old_marking_cycles_completed; 273 274 bool _heap_summary_sent; 275 276 // This is a non-product method that is helpful for testing. It is 277 // called at the end of a GC and artificially expands the heap by 278 // allocating a number of dead regions. This way we can induce very 279 // frequent marking cycles and stress the cleanup / concurrent 280 // cleanup code more (as all the regions that will be allocated by 281 // this method will be found dead by the marking cycle). 282 void allocate_dummy_regions() PRODUCT_RETURN; 283 284 // Clear RSets after a compaction. It also resets the GC time stamps. 285 void clear_rsets_post_compaction(); 286 287 // If the HR printer is active, dump the state of the regions in the 288 // heap after a compaction. 289 void print_hrm_post_compaction(); 290 291 // Create a memory mapper for auxiliary data structures of the given size and 292 // translation factor. 293 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 294 size_t size, 295 size_t translation_factor); 296 297 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 298 299 void process_weak_jni_handles(); 300 301 // These are macros so that, if the assert fires, we get the correct 302 // line number, file, etc. 303 304 #define heap_locking_asserts_params(_extra_message_) \ 305 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 306 (_extra_message_), \ 307 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 308 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 309 BOOL_TO_STR(Thread::current()->is_VM_thread()) 310 311 #define assert_heap_locked() \ 312 do { \ 313 assert(Heap_lock->owned_by_self(), \ 314 heap_locking_asserts_params("should be holding the Heap_lock")); \ 315 } while (0) 316 317 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 318 do { \ 319 assert(Heap_lock->owned_by_self() || \ 320 (SafepointSynchronize::is_at_safepoint() && \ 321 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 322 heap_locking_asserts_params("should be holding the Heap_lock or " \ 323 "should be at a safepoint")); \ 324 } while (0) 325 326 #define assert_heap_locked_and_not_at_safepoint() \ 327 do { \ 328 assert(Heap_lock->owned_by_self() && \ 329 !SafepointSynchronize::is_at_safepoint(), \ 330 heap_locking_asserts_params("should be holding the Heap_lock and " \ 331 "should not be at a safepoint")); \ 332 } while (0) 333 334 #define assert_heap_not_locked() \ 335 do { \ 336 assert(!Heap_lock->owned_by_self(), \ 337 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 338 } while (0) 339 340 #define assert_heap_not_locked_and_not_at_safepoint() \ 341 do { \ 342 assert(!Heap_lock->owned_by_self() && \ 343 !SafepointSynchronize::is_at_safepoint(), \ 344 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 345 "should not be at a safepoint")); \ 346 } while (0) 347 348 #define assert_at_safepoint(_should_be_vm_thread_) \ 349 do { \ 350 assert(SafepointSynchronize::is_at_safepoint() && \ 351 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 352 heap_locking_asserts_params("should be at a safepoint")); \ 353 } while (0) 354 355 #define assert_not_at_safepoint() \ 356 do { \ 357 assert(!SafepointSynchronize::is_at_safepoint(), \ 358 heap_locking_asserts_params("should not be at a safepoint")); \ 359 } while (0) 360 361 protected: 362 363 // The young region list. 364 YoungList* _young_list; 365 366 // The current policy object for the collector. 367 G1CollectorPolicy* _g1_policy; 368 G1HeapSizingPolicy* _heap_sizing_policy; 369 370 G1CollectionSet _collection_set; 371 372 // This is the second level of trying to allocate a new region. If 373 // new_region() didn't find a region on the free_list, this call will 374 // check whether there's anything available on the 375 // secondary_free_list and/or wait for more regions to appear on 376 // that list, if _free_regions_coming is set. 377 HeapRegion* new_region_try_secondary_free_list(bool is_old); 378 379 // Try to allocate a single non-humongous HeapRegion sufficient for 380 // an allocation of the given word_size. If do_expand is true, 381 // attempt to expand the heap if necessary to satisfy the allocation 382 // request. If the region is to be used as an old region or for a 383 // humongous object, set is_old to true. If not, to false. 384 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 385 386 // Initialize a contiguous set of free regions of length num_regions 387 // and starting at index first so that they appear as a single 388 // humongous region. 389 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 390 uint num_regions, 391 size_t word_size, 392 AllocationContext_t context); 393 394 // Attempt to allocate a humongous object of the given size. Return 395 // NULL if unsuccessful. 396 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 397 398 // The following two methods, allocate_new_tlab() and 399 // mem_allocate(), are the two main entry points from the runtime 400 // into the G1's allocation routines. They have the following 401 // assumptions: 402 // 403 // * They should both be called outside safepoints. 404 // 405 // * They should both be called without holding the Heap_lock. 406 // 407 // * All allocation requests for new TLABs should go to 408 // allocate_new_tlab(). 409 // 410 // * All non-TLAB allocation requests should go to mem_allocate(). 411 // 412 // * If either call cannot satisfy the allocation request using the 413 // current allocating region, they will try to get a new one. If 414 // this fails, they will attempt to do an evacuation pause and 415 // retry the allocation. 416 // 417 // * If all allocation attempts fail, even after trying to schedule 418 // an evacuation pause, allocate_new_tlab() will return NULL, 419 // whereas mem_allocate() will attempt a heap expansion and/or 420 // schedule a Full GC. 421 // 422 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 423 // should never be called with word_size being humongous. All 424 // humongous allocation requests should go to mem_allocate() which 425 // will satisfy them with a special path. 426 427 virtual HeapWord* allocate_new_tlab(size_t word_size); 428 429 virtual HeapWord* mem_allocate(size_t word_size, 430 bool* gc_overhead_limit_was_exceeded); 431 432 // The following three methods take a gc_count_before_ret 433 // parameter which is used to return the GC count if the method 434 // returns NULL. Given that we are required to read the GC count 435 // while holding the Heap_lock, and these paths will take the 436 // Heap_lock at some point, it's easier to get them to read the GC 437 // count while holding the Heap_lock before they return NULL instead 438 // of the caller (namely: mem_allocate()) having to also take the 439 // Heap_lock just to read the GC count. 440 441 // First-level mutator allocation attempt: try to allocate out of 442 // the mutator alloc region without taking the Heap_lock. This 443 // should only be used for non-humongous allocations. 444 inline HeapWord* attempt_allocation(size_t word_size, 445 uint* gc_count_before_ret, 446 uint* gclocker_retry_count_ret); 447 448 // Second-level mutator allocation attempt: take the Heap_lock and 449 // retry the allocation attempt, potentially scheduling a GC 450 // pause. This should only be used for non-humongous allocations. 451 HeapWord* attempt_allocation_slow(size_t word_size, 452 AllocationContext_t context, 453 uint* gc_count_before_ret, 454 uint* gclocker_retry_count_ret); 455 456 // Takes the Heap_lock and attempts a humongous allocation. It can 457 // potentially schedule a GC pause. 458 HeapWord* attempt_allocation_humongous(size_t word_size, 459 uint* gc_count_before_ret, 460 uint* gclocker_retry_count_ret); 461 462 // Allocation attempt that should be called during safepoints (e.g., 463 // at the end of a successful GC). expect_null_mutator_alloc_region 464 // specifies whether the mutator alloc region is expected to be NULL 465 // or not. 466 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 467 AllocationContext_t context, 468 bool expect_null_mutator_alloc_region); 469 470 // These methods are the "callbacks" from the G1AllocRegion class. 471 472 // For mutator alloc regions. 473 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 474 void retire_mutator_alloc_region(HeapRegion* alloc_region, 475 size_t allocated_bytes); 476 477 // For GC alloc regions. 478 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 479 InCSetState dest); 480 void retire_gc_alloc_region(HeapRegion* alloc_region, 481 size_t allocated_bytes, InCSetState dest); 482 483 // - if explicit_gc is true, the GC is for a System.gc() etc, 484 // otherwise it's for a failed allocation. 485 // - if clear_all_soft_refs is true, all soft references should be 486 // cleared during the GC. 487 // - it returns false if it is unable to do the collection due to the 488 // GC locker being active, true otherwise. 489 bool do_full_collection(bool explicit_gc, 490 bool clear_all_soft_refs); 491 492 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 493 virtual void do_full_collection(bool clear_all_soft_refs); 494 495 // Resize the heap if necessary after a full collection. 496 void resize_if_necessary_after_full_collection(); 497 498 // Callback from VM_G1CollectForAllocation operation. 499 // This function does everything necessary/possible to satisfy a 500 // failed allocation request (including collection, expansion, etc.) 501 HeapWord* satisfy_failed_allocation(size_t word_size, 502 AllocationContext_t context, 503 bool* succeeded); 504 private: 505 // Helper method for satisfy_failed_allocation() 506 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 507 AllocationContext_t context, 508 bool do_gc, 509 bool clear_all_soft_refs, 510 bool expect_null_mutator_alloc_region, 511 bool* gc_succeeded); 512 513 protected: 514 // Attempting to expand the heap sufficiently 515 // to support an allocation of the given "word_size". If 516 // successful, perform the allocation and return the address of the 517 // allocated block, or else "NULL". 518 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 519 520 // Preserve any referents discovered by concurrent marking that have not yet been 521 // copied by the STW pause. 522 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states); 523 // Process any reference objects discovered during 524 // an incremental evacuation pause. 525 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 526 527 // Enqueue any remaining discovered references 528 // after processing. 529 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 530 531 // Merges the information gathered on a per-thread basis for all worker threads 532 // during GC into global variables. 533 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states); 534 public: 535 WorkGang* workers() const { return _workers; } 536 537 G1Allocator* allocator() { 538 return _allocator; 539 } 540 541 G1HeapVerifier* verifier() { 542 return _verifier; 543 } 544 545 G1MonitoringSupport* g1mm() { 546 assert(_g1mm != NULL, "should have been initialized"); 547 return _g1mm; 548 } 549 550 // Expand the garbage-first heap by at least the given size (in bytes!). 551 // Returns true if the heap was expanded by the requested amount; 552 // false otherwise. 553 // (Rounds up to a HeapRegion boundary.) 554 bool expand(size_t expand_bytes, double* expand_time_ms = NULL); 555 556 // Returns the PLAB statistics for a given destination. 557 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 558 559 // Determines PLAB size for a given destination. 560 inline size_t desired_plab_sz(InCSetState dest); 561 562 inline AllocationContextStats& allocation_context_stats(); 563 564 // Do anything common to GC's. 565 void gc_prologue(bool full); 566 void gc_epilogue(bool full); 567 568 // Modify the reclaim candidate set and test for presence. 569 // These are only valid for starts_humongous regions. 570 inline void set_humongous_reclaim_candidate(uint region, bool value); 571 inline bool is_humongous_reclaim_candidate(uint region); 572 573 // Remove from the reclaim candidate set. Also remove from the 574 // collection set so that later encounters avoid the slow path. 575 inline void set_humongous_is_live(oop obj); 576 577 // Register the given region to be part of the collection set. 578 inline void register_humongous_region_with_cset(uint index); 579 // Register regions with humongous objects (actually on the start region) in 580 // the in_cset_fast_test table. 581 void register_humongous_regions_with_cset(); 582 // We register a region with the fast "in collection set" test. We 583 // simply set to true the array slot corresponding to this region. 584 void register_young_region_with_cset(HeapRegion* r) { 585 _in_cset_fast_test.set_in_young(r->hrm_index()); 586 } 587 void register_old_region_with_cset(HeapRegion* r) { 588 _in_cset_fast_test.set_in_old(r->hrm_index()); 589 } 590 inline void register_ext_region_with_cset(HeapRegion* r) { 591 _in_cset_fast_test.set_ext(r->hrm_index()); 592 } 593 void clear_in_cset(const HeapRegion* hr) { 594 _in_cset_fast_test.clear(hr); 595 } 596 597 void clear_cset_fast_test() { 598 _in_cset_fast_test.clear(); 599 } 600 601 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 602 603 // This is called at the start of either a concurrent cycle or a Full 604 // GC to update the number of old marking cycles started. 605 void increment_old_marking_cycles_started(); 606 607 // This is called at the end of either a concurrent cycle or a Full 608 // GC to update the number of old marking cycles completed. Those two 609 // can happen in a nested fashion, i.e., we start a concurrent 610 // cycle, a Full GC happens half-way through it which ends first, 611 // and then the cycle notices that a Full GC happened and ends 612 // too. The concurrent parameter is a boolean to help us do a bit 613 // tighter consistency checking in the method. If concurrent is 614 // false, the caller is the inner caller in the nesting (i.e., the 615 // Full GC). If concurrent is true, the caller is the outer caller 616 // in this nesting (i.e., the concurrent cycle). Further nesting is 617 // not currently supported. The end of this call also notifies 618 // the FullGCCount_lock in case a Java thread is waiting for a full 619 // GC to happen (e.g., it called System.gc() with 620 // +ExplicitGCInvokesConcurrent). 621 void increment_old_marking_cycles_completed(bool concurrent); 622 623 uint old_marking_cycles_completed() { 624 return _old_marking_cycles_completed; 625 } 626 627 void register_concurrent_cycle_start(const Ticks& start_time); 628 void register_concurrent_cycle_end(); 629 void trace_heap_after_concurrent_cycle(); 630 631 G1HRPrinter* hr_printer() { return &_hr_printer; } 632 633 // Allocates a new heap region instance. 634 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 635 636 // Allocate the highest free region in the reserved heap. This will commit 637 // regions as necessary. 638 HeapRegion* alloc_highest_free_region(); 639 640 // Frees a non-humongous region by initializing its contents and 641 // adding it to the free list that's passed as a parameter (this is 642 // usually a local list which will be appended to the master free 643 // list later). The used bytes of freed regions are accumulated in 644 // pre_used. If par is true, the region's RSet will not be freed 645 // up. The assumption is that this will be done later. 646 // The locked parameter indicates if the caller has already taken 647 // care of proper synchronization. This may allow some optimizations. 648 void free_region(HeapRegion* hr, 649 FreeRegionList* free_list, 650 bool par, 651 bool locked = false); 652 653 // It dirties the cards that cover the block so that the post 654 // write barrier never queues anything when updating objects on this 655 // block. It is assumed (and in fact we assert) that the block 656 // belongs to a young region. 657 inline void dirty_young_block(HeapWord* start, size_t word_size); 658 659 // Frees a humongous region by collapsing it into individual regions 660 // and calling free_region() for each of them. The freed regions 661 // will be added to the free list that's passed as a parameter (this 662 // is usually a local list which will be appended to the master free 663 // list later). The used bytes of freed regions are accumulated in 664 // pre_used. If par is true, the region's RSet will not be freed 665 // up. The assumption is that this will be done later. 666 void free_humongous_region(HeapRegion* hr, 667 FreeRegionList* free_list, 668 bool par); 669 670 // Facility for allocating in 'archive' regions in high heap memory and 671 // recording the allocated ranges. These should all be called from the 672 // VM thread at safepoints, without the heap lock held. They can be used 673 // to create and archive a set of heap regions which can be mapped at the 674 // same fixed addresses in a subsequent JVM invocation. 675 void begin_archive_alloc_range(); 676 677 // Check if the requested size would be too large for an archive allocation. 678 bool is_archive_alloc_too_large(size_t word_size); 679 680 // Allocate memory of the requested size from the archive region. This will 681 // return NULL if the size is too large or if no memory is available. It 682 // does not trigger a garbage collection. 683 HeapWord* archive_mem_allocate(size_t word_size); 684 685 // Optionally aligns the end address and returns the allocated ranges in 686 // an array of MemRegions in order of ascending addresses. 687 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 688 size_t end_alignment_in_bytes = 0); 689 690 // Facility for allocating a fixed range within the heap and marking 691 // the containing regions as 'archive'. For use at JVM init time, when the 692 // caller may mmap archived heap data at the specified range(s). 693 // Verify that the MemRegions specified in the argument array are within the 694 // reserved heap. 695 bool check_archive_addresses(MemRegion* range, size_t count); 696 697 // Commit the appropriate G1 regions containing the specified MemRegions 698 // and mark them as 'archive' regions. The regions in the array must be 699 // non-overlapping and in order of ascending address. 700 bool alloc_archive_regions(MemRegion* range, size_t count); 701 702 // Insert any required filler objects in the G1 regions around the specified 703 // ranges to make the regions parseable. This must be called after 704 // alloc_archive_regions, and after class loading has occurred. 705 void fill_archive_regions(MemRegion* range, size_t count); 706 707 // For each of the specified MemRegions, uncommit the containing G1 regions 708 // which had been allocated by alloc_archive_regions. This should be called 709 // rather than fill_archive_regions at JVM init time if the archive file 710 // mapping failed, with the same non-overlapping and sorted MemRegion array. 711 void dealloc_archive_regions(MemRegion* range, size_t count); 712 713 protected: 714 715 // Shrink the garbage-first heap by at most the given size (in bytes!). 716 // (Rounds down to a HeapRegion boundary.) 717 virtual void shrink(size_t expand_bytes); 718 void shrink_helper(size_t expand_bytes); 719 720 #if TASKQUEUE_STATS 721 static void print_taskqueue_stats_hdr(outputStream* const st); 722 void print_taskqueue_stats() const; 723 void reset_taskqueue_stats(); 724 #endif // TASKQUEUE_STATS 725 726 // Schedule the VM operation that will do an evacuation pause to 727 // satisfy an allocation request of word_size. *succeeded will 728 // return whether the VM operation was successful (it did do an 729 // evacuation pause) or not (another thread beat us to it or the GC 730 // locker was active). Given that we should not be holding the 731 // Heap_lock when we enter this method, we will pass the 732 // gc_count_before (i.e., total_collections()) as a parameter since 733 // it has to be read while holding the Heap_lock. Currently, both 734 // methods that call do_collection_pause() release the Heap_lock 735 // before the call, so it's easy to read gc_count_before just before. 736 HeapWord* do_collection_pause(size_t word_size, 737 uint gc_count_before, 738 bool* succeeded, 739 GCCause::Cause gc_cause); 740 741 void wait_for_root_region_scanning(); 742 743 // The guts of the incremental collection pause, executed by the vm 744 // thread. It returns false if it is unable to do the collection due 745 // to the GC locker being active, true otherwise 746 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 747 748 // Actually do the work of evacuating the collection set. 749 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 750 751 void pre_evacuate_collection_set(); 752 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 753 754 // Print the header for the per-thread termination statistics. 755 static void print_termination_stats_hdr(); 756 // Print actual per-thread termination statistics. 757 void print_termination_stats(uint worker_id, 758 double elapsed_ms, 759 double strong_roots_ms, 760 double term_ms, 761 size_t term_attempts, 762 size_t alloc_buffer_waste, 763 size_t undo_waste) const; 764 // Update object copying statistics. 765 void record_obj_copy_mem_stats(); 766 767 // The g1 remembered set of the heap. 768 G1RemSet* _g1_rem_set; 769 770 // A set of cards that cover the objects for which the Rsets should be updated 771 // concurrently after the collection. 772 DirtyCardQueueSet _dirty_card_queue_set; 773 774 // The closure used to refine a single card. 775 RefineCardTableEntryClosure* _refine_cte_cl; 776 777 // After a collection pause, make the regions in the CS into free 778 // regions. 779 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 780 781 // Abandon the current collection set without recording policy 782 // statistics or updating free lists. 783 void abandon_collection_set(HeapRegion* cs_head); 784 785 // The concurrent marker (and the thread it runs in.) 786 G1ConcurrentMark* _cm; 787 ConcurrentMarkThread* _cmThread; 788 789 // The concurrent refiner. 790 ConcurrentG1Refine* _cg1r; 791 792 // The parallel task queues 793 RefToScanQueueSet *_task_queues; 794 795 // True iff a evacuation has failed in the current collection. 796 bool _evacuation_failed; 797 798 EvacuationFailedInfo* _evacuation_failed_info_array; 799 800 // Failed evacuations cause some logical from-space objects to have 801 // forwarding pointers to themselves. Reset them. 802 void remove_self_forwarding_pointers(); 803 804 // Restore the preserved mark words for objects with self-forwarding pointers. 805 void restore_preserved_marks(); 806 807 // Restore the objects in the regions in the collection set after an 808 // evacuation failure. 809 void restore_after_evac_failure(); 810 811 // Stores marks with the corresponding oop that we need to preserve during evacuation 812 // failure. 813 OopAndMarkOopStack* _preserved_objs; 814 815 // Preserve the mark of "obj", if necessary, in preparation for its mark 816 // word being overwritten with a self-forwarding-pointer. 817 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 818 819 #ifndef PRODUCT 820 // Support for forcing evacuation failures. Analogous to 821 // PromotionFailureALot for the other collectors. 822 823 // Records whether G1EvacuationFailureALot should be in effect 824 // for the current GC 825 bool _evacuation_failure_alot_for_current_gc; 826 827 // Used to record the GC number for interval checking when 828 // determining whether G1EvaucationFailureALot is in effect 829 // for the current GC. 830 size_t _evacuation_failure_alot_gc_number; 831 832 // Count of the number of evacuations between failures. 833 volatile size_t _evacuation_failure_alot_count; 834 835 // Set whether G1EvacuationFailureALot should be in effect 836 // for the current GC (based upon the type of GC and which 837 // command line flags are set); 838 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 839 bool during_initial_mark, 840 bool during_marking); 841 842 inline void set_evacuation_failure_alot_for_current_gc(); 843 844 // Return true if it's time to cause an evacuation failure. 845 inline bool evacuation_should_fail(); 846 847 // Reset the G1EvacuationFailureALot counters. Should be called at 848 // the end of an evacuation pause in which an evacuation failure occurred. 849 inline void reset_evacuation_should_fail(); 850 #endif // !PRODUCT 851 852 // ("Weak") Reference processing support. 853 // 854 // G1 has 2 instances of the reference processor class. One 855 // (_ref_processor_cm) handles reference object discovery 856 // and subsequent processing during concurrent marking cycles. 857 // 858 // The other (_ref_processor_stw) handles reference object 859 // discovery and processing during full GCs and incremental 860 // evacuation pauses. 861 // 862 // During an incremental pause, reference discovery will be 863 // temporarily disabled for _ref_processor_cm and will be 864 // enabled for _ref_processor_stw. At the end of the evacuation 865 // pause references discovered by _ref_processor_stw will be 866 // processed and discovery will be disabled. The previous 867 // setting for reference object discovery for _ref_processor_cm 868 // will be re-instated. 869 // 870 // At the start of marking: 871 // * Discovery by the CM ref processor is verified to be inactive 872 // and it's discovered lists are empty. 873 // * Discovery by the CM ref processor is then enabled. 874 // 875 // At the end of marking: 876 // * Any references on the CM ref processor's discovered 877 // lists are processed (possibly MT). 878 // 879 // At the start of full GC we: 880 // * Disable discovery by the CM ref processor and 881 // empty CM ref processor's discovered lists 882 // (without processing any entries). 883 // * Verify that the STW ref processor is inactive and it's 884 // discovered lists are empty. 885 // * Temporarily set STW ref processor discovery as single threaded. 886 // * Temporarily clear the STW ref processor's _is_alive_non_header 887 // field. 888 // * Finally enable discovery by the STW ref processor. 889 // 890 // The STW ref processor is used to record any discovered 891 // references during the full GC. 892 // 893 // At the end of a full GC we: 894 // * Enqueue any reference objects discovered by the STW ref processor 895 // that have non-live referents. This has the side-effect of 896 // making the STW ref processor inactive by disabling discovery. 897 // * Verify that the CM ref processor is still inactive 898 // and no references have been placed on it's discovered 899 // lists (also checked as a precondition during initial marking). 900 901 // The (stw) reference processor... 902 ReferenceProcessor* _ref_processor_stw; 903 904 STWGCTimer* _gc_timer_stw; 905 ConcurrentGCTimer* _gc_timer_cm; 906 907 G1OldTracer* _gc_tracer_cm; 908 G1NewTracer* _gc_tracer_stw; 909 910 // During reference object discovery, the _is_alive_non_header 911 // closure (if non-null) is applied to the referent object to 912 // determine whether the referent is live. If so then the 913 // reference object does not need to be 'discovered' and can 914 // be treated as a regular oop. This has the benefit of reducing 915 // the number of 'discovered' reference objects that need to 916 // be processed. 917 // 918 // Instance of the is_alive closure for embedding into the 919 // STW reference processor as the _is_alive_non_header field. 920 // Supplying a value for the _is_alive_non_header field is 921 // optional but doing so prevents unnecessary additions to 922 // the discovered lists during reference discovery. 923 G1STWIsAliveClosure _is_alive_closure_stw; 924 925 // The (concurrent marking) reference processor... 926 ReferenceProcessor* _ref_processor_cm; 927 928 // Instance of the concurrent mark is_alive closure for embedding 929 // into the Concurrent Marking reference processor as the 930 // _is_alive_non_header field. Supplying a value for the 931 // _is_alive_non_header field is optional but doing so prevents 932 // unnecessary additions to the discovered lists during reference 933 // discovery. 934 G1CMIsAliveClosure _is_alive_closure_cm; 935 936 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 937 HeapRegion** _worker_cset_start_region; 938 939 // Time stamp to validate the regions recorded in the cache 940 // used by G1CollectedHeap::start_cset_region_for_worker(). 941 // The heap region entry for a given worker is valid iff 942 // the associated time stamp value matches the current value 943 // of G1CollectedHeap::_gc_time_stamp. 944 uint* _worker_cset_start_region_time_stamp; 945 946 volatile bool _free_regions_coming; 947 948 public: 949 950 void set_refine_cte_cl_concurrency(bool concurrent); 951 952 RefToScanQueue *task_queue(uint i) const; 953 954 uint num_task_queues() const; 955 956 // A set of cards where updates happened during the GC 957 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 958 959 // Create a G1CollectedHeap with the specified policy. 960 // Must call the initialize method afterwards. 961 // May not return if something goes wrong. 962 G1CollectedHeap(G1CollectorPolicy* policy); 963 964 // Initialize the G1CollectedHeap to have the initial and 965 // maximum sizes and remembered and barrier sets 966 // specified by the policy object. 967 jint initialize(); 968 969 virtual void stop(); 970 971 // Return the (conservative) maximum heap alignment for any G1 heap 972 static size_t conservative_max_heap_alignment(); 973 974 // Does operations required after initialization has been done. 975 void post_initialize(); 976 977 // Initialize weak reference processing. 978 void ref_processing_init(); 979 980 virtual Name kind() const { 981 return CollectedHeap::G1CollectedHeap; 982 } 983 984 virtual const char* name() const { 985 return "G1"; 986 } 987 988 const G1CollectorState* collector_state() const { return &_collector_state; } 989 G1CollectorState* collector_state() { return &_collector_state; } 990 991 // The current policy object for the collector. 992 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 993 994 const G1CollectionSet* collection_set() const { return &_collection_set; } 995 G1CollectionSet* collection_set() { return &_collection_set; } 996 997 virtual CollectorPolicy* collector_policy() const; 998 999 // Adaptive size policy. No such thing for g1. 1000 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 1001 1002 // The rem set and barrier set. 1003 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 1004 1005 void scrub_rem_set(BitMap* region_bm, BitMap* card_bm); 1006 1007 unsigned get_gc_time_stamp() { 1008 return _gc_time_stamp; 1009 } 1010 1011 inline void reset_gc_time_stamp(); 1012 1013 void check_gc_time_stamps() PRODUCT_RETURN; 1014 1015 inline void increment_gc_time_stamp(); 1016 1017 // Reset the given region's GC timestamp. If it's starts humongous, 1018 // also reset the GC timestamp of its corresponding 1019 // continues humongous regions too. 1020 void reset_gc_time_stamps(HeapRegion* hr); 1021 1022 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1023 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1024 1025 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1026 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1027 1028 // The shared block offset table array. 1029 G1BlockOffsetTable* bot() const { return _bot; } 1030 1031 // Reference Processing accessors 1032 1033 // The STW reference processor.... 1034 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1035 1036 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1037 1038 // The Concurrent Marking reference processor... 1039 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1040 1041 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1042 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1043 1044 virtual size_t capacity() const; 1045 virtual size_t used() const; 1046 // This should be called when we're not holding the heap lock. The 1047 // result might be a bit inaccurate. 1048 size_t used_unlocked() const; 1049 size_t recalculate_used() const; 1050 1051 // These virtual functions do the actual allocation. 1052 // Some heaps may offer a contiguous region for shared non-blocking 1053 // allocation, via inlined code (by exporting the address of the top and 1054 // end fields defining the extent of the contiguous allocation region.) 1055 // But G1CollectedHeap doesn't yet support this. 1056 1057 virtual bool is_maximal_no_gc() const { 1058 return _hrm.available() == 0; 1059 } 1060 1061 // The current number of regions in the heap. 1062 uint num_regions() const { return _hrm.length(); } 1063 1064 // The max number of regions in the heap. 1065 uint max_regions() const { return _hrm.max_length(); } 1066 1067 // The number of regions that are completely free. 1068 uint num_free_regions() const { return _hrm.num_free_regions(); } 1069 1070 MemoryUsage get_auxiliary_data_memory_usage() const { 1071 return _hrm.get_auxiliary_data_memory_usage(); 1072 } 1073 1074 // The number of regions that are not completely free. 1075 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1076 1077 #ifdef ASSERT 1078 bool is_on_master_free_list(HeapRegion* hr) { 1079 return _hrm.is_free(hr); 1080 } 1081 #endif // ASSERT 1082 1083 // Wrapper for the region list operations that can be called from 1084 // methods outside this class. 1085 1086 void secondary_free_list_add(FreeRegionList* list) { 1087 _secondary_free_list.add_ordered(list); 1088 } 1089 1090 void append_secondary_free_list() { 1091 _hrm.insert_list_into_free_list(&_secondary_free_list); 1092 } 1093 1094 void append_secondary_free_list_if_not_empty_with_lock() { 1095 // If the secondary free list looks empty there's no reason to 1096 // take the lock and then try to append it. 1097 if (!_secondary_free_list.is_empty()) { 1098 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1099 append_secondary_free_list(); 1100 } 1101 } 1102 1103 inline void old_set_add(HeapRegion* hr); 1104 inline void old_set_remove(HeapRegion* hr); 1105 1106 size_t non_young_capacity_bytes() { 1107 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes; 1108 } 1109 1110 void set_free_regions_coming(); 1111 void reset_free_regions_coming(); 1112 bool free_regions_coming() { return _free_regions_coming; } 1113 void wait_while_free_regions_coming(); 1114 1115 // Determine whether the given region is one that we are using as an 1116 // old GC alloc region. 1117 bool is_old_gc_alloc_region(HeapRegion* hr); 1118 1119 // Perform a collection of the heap; intended for use in implementing 1120 // "System.gc". This probably implies as full a collection as the 1121 // "CollectedHeap" supports. 1122 virtual void collect(GCCause::Cause cause); 1123 1124 virtual bool copy_allocation_context_stats(const jint* contexts, 1125 jlong* totals, 1126 jbyte* accuracy, 1127 jint len); 1128 1129 // True iff an evacuation has failed in the most-recent collection. 1130 bool evacuation_failed() { return _evacuation_failed; } 1131 1132 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed); 1133 void prepend_to_freelist(FreeRegionList* list); 1134 void decrement_summary_bytes(size_t bytes); 1135 1136 virtual bool is_in(const void* p) const; 1137 #ifdef ASSERT 1138 // Returns whether p is in one of the available areas of the heap. Slow but 1139 // extensive version. 1140 bool is_in_exact(const void* p) const; 1141 #endif 1142 1143 // Return "TRUE" iff the given object address is within the collection 1144 // set. Slow implementation. 1145 bool obj_in_cs(oop obj); 1146 1147 inline bool is_in_cset(const HeapRegion *hr); 1148 inline bool is_in_cset(oop obj); 1149 1150 inline bool is_in_cset_or_humongous(const oop obj); 1151 1152 private: 1153 // This array is used for a quick test on whether a reference points into 1154 // the collection set or not. Each of the array's elements denotes whether the 1155 // corresponding region is in the collection set or not. 1156 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1157 1158 public: 1159 1160 inline InCSetState in_cset_state(const oop obj); 1161 1162 // Return "TRUE" iff the given object address is in the reserved 1163 // region of g1. 1164 bool is_in_g1_reserved(const void* p) const { 1165 return _hrm.reserved().contains(p); 1166 } 1167 1168 // Returns a MemRegion that corresponds to the space that has been 1169 // reserved for the heap 1170 MemRegion g1_reserved() const { 1171 return _hrm.reserved(); 1172 } 1173 1174 virtual bool is_in_closed_subset(const void* p) const; 1175 1176 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1177 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1178 } 1179 1180 // This resets the card table to all zeros. It is used after 1181 // a collection pause which used the card table to claim cards. 1182 void cleanUpCardTable(); 1183 1184 // Iteration functions. 1185 1186 // Iterate over all objects, calling "cl.do_object" on each. 1187 virtual void object_iterate(ObjectClosure* cl); 1188 1189 virtual void safe_object_iterate(ObjectClosure* cl) { 1190 object_iterate(cl); 1191 } 1192 1193 // Iterate over heap regions, in address order, terminating the 1194 // iteration early if the "doHeapRegion" method returns "true". 1195 void heap_region_iterate(HeapRegionClosure* blk) const; 1196 1197 // Return the region with the given index. It assumes the index is valid. 1198 inline HeapRegion* region_at(uint index) const; 1199 1200 // Return the next region (by index) that is part of the same 1201 // humongous object that hr is part of. 1202 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1203 1204 // Calculate the region index of the given address. Given address must be 1205 // within the heap. 1206 inline uint addr_to_region(HeapWord* addr) const; 1207 1208 inline HeapWord* bottom_addr_for_region(uint index) const; 1209 1210 // Iterate over the heap regions in parallel. Assumes that this will be called 1211 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1212 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1213 // to each of the regions, by attempting to claim the region using the 1214 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1215 // region. The concurrent argument should be set to true if iteration is 1216 // performed concurrently, during which no assumptions are made for consistent 1217 // attributes of the heap regions (as they might be modified while iterating). 1218 void heap_region_par_iterate(HeapRegionClosure* cl, 1219 uint worker_id, 1220 HeapRegionClaimer* hrclaimer, 1221 bool concurrent = false) const; 1222 1223 // Clear the cached cset start regions and (more importantly) 1224 // the time stamps. Called when we reset the GC time stamp. 1225 void clear_cset_start_regions(); 1226 1227 // Given the id of a worker, obtain or calculate a suitable 1228 // starting region for iterating over the current collection set. 1229 HeapRegion* start_cset_region_for_worker(uint worker_i); 1230 1231 // Iterate over the regions (if any) in the current collection set. 1232 void collection_set_iterate(HeapRegionClosure* blk); 1233 1234 // As above but starting from region r 1235 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1236 1237 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1238 1239 // Returns the HeapRegion that contains addr. addr must not be NULL. 1240 template <class T> 1241 inline HeapRegion* heap_region_containing(const T addr) const; 1242 1243 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1244 // each address in the (reserved) heap is a member of exactly 1245 // one block. The defining characteristic of a block is that it is 1246 // possible to find its size, and thus to progress forward to the next 1247 // block. (Blocks may be of different sizes.) Thus, blocks may 1248 // represent Java objects, or they might be free blocks in a 1249 // free-list-based heap (or subheap), as long as the two kinds are 1250 // distinguishable and the size of each is determinable. 1251 1252 // Returns the address of the start of the "block" that contains the 1253 // address "addr". We say "blocks" instead of "object" since some heaps 1254 // may not pack objects densely; a chunk may either be an object or a 1255 // non-object. 1256 virtual HeapWord* block_start(const void* addr) const; 1257 1258 // Requires "addr" to be the start of a chunk, and returns its size. 1259 // "addr + size" is required to be the start of a new chunk, or the end 1260 // of the active area of the heap. 1261 virtual size_t block_size(const HeapWord* addr) const; 1262 1263 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1264 // the block is an object. 1265 virtual bool block_is_obj(const HeapWord* addr) const; 1266 1267 // Section on thread-local allocation buffers (TLABs) 1268 // See CollectedHeap for semantics. 1269 1270 bool supports_tlab_allocation() const; 1271 size_t tlab_capacity(Thread* ignored) const; 1272 size_t tlab_used(Thread* ignored) const; 1273 size_t max_tlab_size() const; 1274 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1275 1276 // Can a compiler initialize a new object without store barriers? 1277 // This permission only extends from the creation of a new object 1278 // via a TLAB up to the first subsequent safepoint. If such permission 1279 // is granted for this heap type, the compiler promises to call 1280 // defer_store_barrier() below on any slow path allocation of 1281 // a new object for which such initializing store barriers will 1282 // have been elided. G1, like CMS, allows this, but should be 1283 // ready to provide a compensating write barrier as necessary 1284 // if that storage came out of a non-young region. The efficiency 1285 // of this implementation depends crucially on being able to 1286 // answer very efficiently in constant time whether a piece of 1287 // storage in the heap comes from a young region or not. 1288 // See ReduceInitialCardMarks. 1289 virtual bool can_elide_tlab_store_barriers() const { 1290 return true; 1291 } 1292 1293 virtual bool card_mark_must_follow_store() const { 1294 return true; 1295 } 1296 1297 inline bool is_in_young(const oop obj); 1298 1299 virtual bool is_scavengable(const void* addr); 1300 1301 // We don't need barriers for initializing stores to objects 1302 // in the young gen: for the SATB pre-barrier, there is no 1303 // pre-value that needs to be remembered; for the remembered-set 1304 // update logging post-barrier, we don't maintain remembered set 1305 // information for young gen objects. 1306 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1307 1308 // Returns "true" iff the given word_size is "very large". 1309 static bool is_humongous(size_t word_size) { 1310 // Note this has to be strictly greater-than as the TLABs 1311 // are capped at the humongous threshold and we want to 1312 // ensure that we don't try to allocate a TLAB as 1313 // humongous and that we don't allocate a humongous 1314 // object in a TLAB. 1315 return word_size > _humongous_object_threshold_in_words; 1316 } 1317 1318 // Returns the humongous threshold for a specific region size 1319 static size_t humongous_threshold_for(size_t region_size) { 1320 return (region_size / 2); 1321 } 1322 1323 // Returns the number of regions the humongous object of the given word size 1324 // requires. 1325 static size_t humongous_obj_size_in_regions(size_t word_size); 1326 1327 // Print the maximum heap capacity. 1328 virtual size_t max_capacity() const; 1329 1330 virtual jlong millis_since_last_gc(); 1331 1332 1333 // Convenience function to be used in situations where the heap type can be 1334 // asserted to be this type. 1335 static G1CollectedHeap* heap(); 1336 1337 void set_region_short_lived_locked(HeapRegion* hr); 1338 // add appropriate methods for any other surv rate groups 1339 1340 YoungList* young_list() const { return _young_list; } 1341 1342 uint old_regions_count() const { return _old_set.length(); } 1343 1344 uint humongous_regions_count() const { return _humongous_set.length(); } 1345 1346 // debugging 1347 bool check_young_list_well_formed() { 1348 return _young_list->check_list_well_formed(); 1349 } 1350 1351 bool check_young_list_empty(bool check_heap); 1352 1353 // *** Stuff related to concurrent marking. It's not clear to me that so 1354 // many of these need to be public. 1355 1356 // The functions below are helper functions that a subclass of 1357 // "CollectedHeap" can use in the implementation of its virtual 1358 // functions. 1359 // This performs a concurrent marking of the live objects in a 1360 // bitmap off to the side. 1361 void doConcurrentMark(); 1362 1363 bool isMarkedPrev(oop obj) const; 1364 bool isMarkedNext(oop obj) const; 1365 1366 // Determine if an object is dead, given the object and also 1367 // the region to which the object belongs. An object is dead 1368 // iff a) it was not allocated since the last mark, b) it 1369 // is not marked, and c) it is not in an archive region. 1370 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1371 return 1372 !hr->obj_allocated_since_prev_marking(obj) && 1373 !isMarkedPrev(obj) && 1374 !hr->is_archive(); 1375 } 1376 1377 // This function returns true when an object has been 1378 // around since the previous marking and hasn't yet 1379 // been marked during this marking, and is not in an archive region. 1380 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1381 return 1382 !hr->obj_allocated_since_next_marking(obj) && 1383 !isMarkedNext(obj) && 1384 !hr->is_archive(); 1385 } 1386 1387 // Determine if an object is dead, given only the object itself. 1388 // This will find the region to which the object belongs and 1389 // then call the region version of the same function. 1390 1391 // Added if it is NULL it isn't dead. 1392 1393 inline bool is_obj_dead(const oop obj) const; 1394 1395 inline bool is_obj_ill(const oop obj) const; 1396 1397 G1ConcurrentMark* concurrent_mark() const { return _cm; } 1398 1399 // Refinement 1400 1401 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1402 1403 // The dirty cards region list is used to record a subset of regions 1404 // whose cards need clearing. The list if populated during the 1405 // remembered set scanning and drained during the card table 1406 // cleanup. Although the methods are reentrant, population/draining 1407 // phases must not overlap. For synchronization purposes the last 1408 // element on the list points to itself. 1409 HeapRegion* _dirty_cards_region_list; 1410 void push_dirty_cards_region(HeapRegion* hr); 1411 HeapRegion* pop_dirty_cards_region(); 1412 1413 // Optimized nmethod scanning support routines 1414 1415 // Register the given nmethod with the G1 heap. 1416 virtual void register_nmethod(nmethod* nm); 1417 1418 // Unregister the given nmethod from the G1 heap. 1419 virtual void unregister_nmethod(nmethod* nm); 1420 1421 // Free up superfluous code root memory. 1422 void purge_code_root_memory(); 1423 1424 // Rebuild the strong code root lists for each region 1425 // after a full GC. 1426 void rebuild_strong_code_roots(); 1427 1428 // Delete entries for dead interned string and clean up unreferenced symbols 1429 // in symbol table, possibly in parallel. 1430 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1431 1432 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1433 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1434 1435 // Redirty logged cards in the refinement queue. 1436 void redirty_logged_cards(); 1437 // Verification 1438 1439 // Perform any cleanup actions necessary before allowing a verification. 1440 virtual void prepare_for_verify(); 1441 1442 // Perform verification. 1443 1444 // vo == UsePrevMarking -> use "prev" marking information, 1445 // vo == UseNextMarking -> use "next" marking information 1446 // vo == UseMarkWord -> use the mark word in the object header 1447 // 1448 // NOTE: Only the "prev" marking information is guaranteed to be 1449 // consistent most of the time, so most calls to this should use 1450 // vo == UsePrevMarking. 1451 // Currently, there is only one case where this is called with 1452 // vo == UseNextMarking, which is to verify the "next" marking 1453 // information at the end of remark. 1454 // Currently there is only one place where this is called with 1455 // vo == UseMarkWord, which is to verify the marking during a 1456 // full GC. 1457 void verify(VerifyOption vo); 1458 1459 // The methods below are here for convenience and dispatch the 1460 // appropriate method depending on value of the given VerifyOption 1461 // parameter. The values for that parameter, and their meanings, 1462 // are the same as those above. 1463 1464 bool is_obj_dead_cond(const oop obj, 1465 const HeapRegion* hr, 1466 const VerifyOption vo) const; 1467 1468 bool is_obj_dead_cond(const oop obj, 1469 const VerifyOption vo) const; 1470 1471 G1HeapSummary create_g1_heap_summary(); 1472 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1473 1474 // Printing 1475 1476 virtual void print_on(outputStream* st) const; 1477 virtual void print_extended_on(outputStream* st) const; 1478 virtual void print_on_error(outputStream* st) const; 1479 1480 virtual void print_gc_threads_on(outputStream* st) const; 1481 virtual void gc_threads_do(ThreadClosure* tc) const; 1482 1483 // Override 1484 void print_tracing_info() const; 1485 1486 // The following two methods are helpful for debugging RSet issues. 1487 void print_cset_rsets() PRODUCT_RETURN; 1488 void print_all_rsets() PRODUCT_RETURN; 1489 1490 public: 1491 size_t pending_card_num(); 1492 1493 protected: 1494 size_t _max_heap_capacity; 1495 }; 1496 1497 class G1ParEvacuateFollowersClosure : public VoidClosure { 1498 private: 1499 double _start_term; 1500 double _term_time; 1501 size_t _term_attempts; 1502 1503 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1504 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1505 protected: 1506 G1CollectedHeap* _g1h; 1507 G1ParScanThreadState* _par_scan_state; 1508 RefToScanQueueSet* _queues; 1509 ParallelTaskTerminator* _terminator; 1510 1511 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1512 RefToScanQueueSet* queues() { return _queues; } 1513 ParallelTaskTerminator* terminator() { return _terminator; } 1514 1515 public: 1516 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1517 G1ParScanThreadState* par_scan_state, 1518 RefToScanQueueSet* queues, 1519 ParallelTaskTerminator* terminator) 1520 : _g1h(g1h), _par_scan_state(par_scan_state), 1521 _queues(queues), _terminator(terminator), 1522 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1523 1524 void do_void(); 1525 1526 double term_time() const { return _term_time; } 1527 size_t term_attempts() const { return _term_attempts; } 1528 1529 private: 1530 inline bool offer_termination(); 1531 }; 1532 1533 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP