1 /* 2 * Copyright (c) 2001, 2015, 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/concurrentMark.hpp" 29 #include "gc/g1/evacuationInfo.hpp" 30 #include "gc/g1/g1AllocationContext.hpp" 31 #include "gc/g1/g1BiasedArray.hpp" 32 #include "gc/g1/g1CollectorState.hpp" 33 #include "gc/g1/g1HRPrinter.hpp" 34 #include "gc/g1/g1InCSetState.hpp" 35 #include "gc/g1/g1MonitoringSupport.hpp" 36 #include "gc/g1/g1EvacFailure.hpp" 37 #include "gc/g1/g1EvacStats.hpp" 38 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 39 #include "gc/g1/g1YCTypes.hpp" 40 #include "gc/g1/hSpaceCounters.hpp" 41 #include "gc/g1/heapRegionManager.hpp" 42 #include "gc/g1/heapRegionSet.hpp" 43 #include "gc/g1/youngList.hpp" 44 #include "gc/shared/barrierSet.hpp" 45 #include "gc/shared/collectedHeap.hpp" 46 #include "gc/shared/plab.hpp" 47 #include "memory/memRegion.hpp" 48 #include "utilities/stack.hpp" 49 50 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 51 // It uses the "Garbage First" heap organization and algorithm, which 52 // may combine concurrent marking with parallel, incremental compaction of 53 // heap subsets that will yield large amounts of garbage. 54 55 // Forward declarations 56 class HeapRegion; 57 class HRRSCleanupTask; 58 class GenerationSpec; 59 class OopsInHeapRegionClosure; 60 class G1ParScanThreadState; 61 class G1ParScanThreadStateSet; 62 class G1KlassScanClosure; 63 class G1ParScanThreadState; 64 class ObjectClosure; 65 class SpaceClosure; 66 class CompactibleSpaceClosure; 67 class Space; 68 class G1CollectorPolicy; 69 class G1RemSet; 70 class HeapRegionRemSetIterator; 71 class ConcurrentMark; 72 class ConcurrentMarkThread; 73 class ConcurrentG1Refine; 74 class ConcurrentGCTimer; 75 class GenerationCounters; 76 class STWGCTimer; 77 class G1NewTracer; 78 class G1OldTracer; 79 class EvacuationFailedInfo; 80 class nmethod; 81 class Ticks; 82 class WorkGang; 83 class G1Allocator; 84 class G1ArchiveAllocator; 85 class G1HeapVerifier; 86 87 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 88 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 89 90 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 91 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 92 93 // The G1 STW is alive closure. 94 // An instance is embedded into the G1CH and used as the 95 // (optional) _is_alive_non_header closure in the STW 96 // reference processor. It is also extensively used during 97 // reference processing during STW evacuation pauses. 98 class G1STWIsAliveClosure: public BoolObjectClosure { 99 G1CollectedHeap* _g1; 100 public: 101 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 102 bool do_object_b(oop p); 103 }; 104 105 class RefineCardTableEntryClosure; 106 107 class G1RegionMappingChangedListener : public G1MappingChangedListener { 108 private: 109 void reset_from_card_cache(uint start_idx, size_t num_regions); 110 public: 111 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 112 }; 113 114 class G1CollectedHeap : public CollectedHeap { 115 friend class VM_CollectForMetadataAllocation; 116 friend class VM_G1CollectForAllocation; 117 friend class VM_G1CollectFull; 118 friend class VM_G1IncCollectionPause; 119 friend class VMStructs; 120 friend class MutatorAllocRegion; 121 friend class G1GCAllocRegion; 122 friend class G1HeapVerifier; 123 124 // Closures used in implementation. 125 friend class G1ParScanThreadState; 126 friend class G1ParScanThreadStateSet; 127 friend class G1ParTask; 128 friend class G1PLABAllocator; 129 friend class G1PrepareCompactClosure; 130 131 // Other related classes. 132 friend class HeapRegionClaimer; 133 134 // Testing classes. 135 friend class G1CheckCSetFastTableClosure; 136 137 private: 138 WorkGang* _workers; 139 140 static size_t _humongous_object_threshold_in_words; 141 142 // The secondary free list which contains regions that have been 143 // freed up during the cleanup process. This will be appended to 144 // the master free list when appropriate. 145 FreeRegionList _secondary_free_list; 146 147 // It keeps track of the old regions. 148 HeapRegionSet _old_set; 149 150 // It keeps track of the humongous regions. 151 HeapRegionSet _humongous_set; 152 153 void eagerly_reclaim_humongous_regions(); 154 155 // The number of regions we could create by expansion. 156 uint _expansion_regions; 157 158 // The block offset table for the G1 heap. 159 G1BlockOffsetTable* _bot; 160 161 // Tears down the region sets / lists so that they are empty and the 162 // regions on the heap do not belong to a region set / list. The 163 // only exception is the humongous set which we leave unaltered. If 164 // free_list_only is true, it will only tear down the master free 165 // list. It is called before a Full GC (free_list_only == false) or 166 // before heap shrinking (free_list_only == true). 167 void tear_down_region_sets(bool free_list_only); 168 169 // Rebuilds the region sets / lists so that they are repopulated to 170 // reflect the contents of the heap. The only exception is the 171 // humongous set which was not torn down in the first place. If 172 // free_list_only is true, it will only rebuild the master free 173 // list. It is called after a Full GC (free_list_only == false) or 174 // after heap shrinking (free_list_only == true). 175 void rebuild_region_sets(bool free_list_only); 176 177 // Callback for region mapping changed events. 178 G1RegionMappingChangedListener _listener; 179 180 // The sequence of all heap regions in the heap. 181 HeapRegionManager _hrm; 182 183 // Manages all allocations with regions except humongous object allocations. 184 G1Allocator* _allocator; 185 186 // Manages all heap verification. 187 G1HeapVerifier* _verifier; 188 189 // Outside of GC pauses, the number of bytes used in all regions other 190 // than the current allocation region(s). 191 size_t _summary_bytes_used; 192 193 void increase_used(size_t bytes); 194 void decrease_used(size_t bytes); 195 196 void set_used(size_t bytes); 197 198 // Class that handles archive allocation ranges. 199 G1ArchiveAllocator* _archive_allocator; 200 201 // Statistics for each allocation context 202 AllocationContextStats _allocation_context_stats; 203 204 // GC allocation statistics policy for survivors. 205 G1EvacStats _survivor_evac_stats; 206 207 // GC allocation statistics policy for tenured objects. 208 G1EvacStats _old_evac_stats; 209 210 // It specifies whether we should attempt to expand the heap after a 211 // region allocation failure. If heap expansion fails we set this to 212 // false so that we don't re-attempt the heap expansion (it's likely 213 // that subsequent expansion attempts will also fail if one fails). 214 // Currently, it is only consulted during GC and it's reset at the 215 // start of each GC. 216 bool _expand_heap_after_alloc_failure; 217 218 // Helper for monitoring and management support. 219 G1MonitoringSupport* _g1mm; 220 221 // Records whether the region at the given index is (still) a 222 // candidate for eager reclaim. Only valid for humongous start 223 // regions; other regions have unspecified values. Humongous start 224 // regions are initialized at start of collection pause, with 225 // candidates removed from the set as they are found reachable from 226 // roots or the young generation. 227 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 228 protected: 229 bool default_value() const { return false; } 230 public: 231 void clear() { G1BiasedMappedArray<bool>::clear(); } 232 void set_candidate(uint region, bool value) { 233 set_by_index(region, value); 234 } 235 bool is_candidate(uint region) { 236 return get_by_index(region); 237 } 238 }; 239 240 HumongousReclaimCandidates _humongous_reclaim_candidates; 241 // Stores whether during humongous object registration we found candidate regions. 242 // If not, we can skip a few steps. 243 bool _has_humongous_reclaim_candidates; 244 245 volatile unsigned _gc_time_stamp; 246 247 G1HRPrinter _hr_printer; 248 249 // It decides whether an explicit GC should start a concurrent cycle 250 // instead of doing a STW GC. Currently, a concurrent cycle is 251 // explicitly started if: 252 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 253 // (b) cause == _g1_humongous_allocation 254 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 255 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 256 // (e) cause == _update_allocation_context_stats_inc 257 // (f) cause == _wb_conc_mark 258 bool should_do_concurrent_full_gc(GCCause::Cause cause); 259 260 // indicates whether we are in young or mixed GC mode 261 G1CollectorState _collector_state; 262 263 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 264 // concurrent cycles) we have started. 265 volatile uint _old_marking_cycles_started; 266 267 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 268 // concurrent cycles) we have completed. 269 volatile uint _old_marking_cycles_completed; 270 271 bool _heap_summary_sent; 272 273 // This is a non-product method that is helpful for testing. It is 274 // called at the end of a GC and artificially expands the heap by 275 // allocating a number of dead regions. This way we can induce very 276 // frequent marking cycles and stress the cleanup / concurrent 277 // cleanup code more (as all the regions that will be allocated by 278 // this method will be found dead by the marking cycle). 279 void allocate_dummy_regions() PRODUCT_RETURN; 280 281 // Clear RSets after a compaction. It also resets the GC time stamps. 282 void clear_rsets_post_compaction(); 283 284 // If the HR printer is active, dump the state of the regions in the 285 // heap after a compaction. 286 void print_hrm_post_compaction(); 287 288 // Create a memory mapper for auxiliary data structures of the given size and 289 // translation factor. 290 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 291 size_t size, 292 size_t translation_factor); 293 294 void log_gc_footer(); 295 296 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 297 298 void process_weak_jni_handles(); 299 300 // These are macros so that, if the assert fires, we get the correct 301 // line number, file, etc. 302 303 #define heap_locking_asserts_params(_extra_message_) \ 304 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 305 (_extra_message_), \ 306 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 307 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 308 BOOL_TO_STR(Thread::current()->is_VM_thread()) 309 310 #define assert_heap_locked() \ 311 do { \ 312 assert(Heap_lock->owned_by_self(), \ 313 heap_locking_asserts_params("should be holding the Heap_lock")); \ 314 } while (0) 315 316 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 317 do { \ 318 assert(Heap_lock->owned_by_self() || \ 319 (SafepointSynchronize::is_at_safepoint() && \ 320 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 321 heap_locking_asserts_params("should be holding the Heap_lock or " \ 322 "should be at a safepoint")); \ 323 } while (0) 324 325 #define assert_heap_locked_and_not_at_safepoint() \ 326 do { \ 327 assert(Heap_lock->owned_by_self() && \ 328 !SafepointSynchronize::is_at_safepoint(), \ 329 heap_locking_asserts_params("should be holding the Heap_lock and " \ 330 "should not be at a safepoint")); \ 331 } while (0) 332 333 #define assert_heap_not_locked() \ 334 do { \ 335 assert(!Heap_lock->owned_by_self(), \ 336 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 337 } while (0) 338 339 #define assert_heap_not_locked_and_not_at_safepoint() \ 340 do { \ 341 assert(!Heap_lock->owned_by_self() && \ 342 !SafepointSynchronize::is_at_safepoint(), \ 343 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 344 "should not be at a safepoint")); \ 345 } while (0) 346 347 #define assert_at_safepoint(_should_be_vm_thread_) \ 348 do { \ 349 assert(SafepointSynchronize::is_at_safepoint() && \ 350 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 351 heap_locking_asserts_params("should be at a safepoint")); \ 352 } while (0) 353 354 #define assert_not_at_safepoint() \ 355 do { \ 356 assert(!SafepointSynchronize::is_at_safepoint(), \ 357 heap_locking_asserts_params("should not be at a safepoint")); \ 358 } while (0) 359 360 protected: 361 362 // The young region list. 363 YoungList* _young_list; 364 365 // The current policy object for the collector. 366 G1CollectorPolicy* _g1_policy; 367 368 // This is the second level of trying to allocate a new region. If 369 // new_region() didn't find a region on the free_list, this call will 370 // check whether there's anything available on the 371 // secondary_free_list and/or wait for more regions to appear on 372 // that list, if _free_regions_coming is set. 373 HeapRegion* new_region_try_secondary_free_list(bool is_old); 374 375 // Try to allocate a single non-humongous HeapRegion sufficient for 376 // an allocation of the given word_size. If do_expand is true, 377 // attempt to expand the heap if necessary to satisfy the allocation 378 // request. If the region is to be used as an old region or for a 379 // humongous object, set is_old to true. If not, to false. 380 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 381 382 // Initialize a contiguous set of free regions of length num_regions 383 // and starting at index first so that they appear as a single 384 // humongous region. 385 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 386 uint num_regions, 387 size_t word_size, 388 AllocationContext_t context); 389 390 // Attempt to allocate a humongous object of the given size. Return 391 // NULL if unsuccessful. 392 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 393 394 // The following two methods, allocate_new_tlab() and 395 // mem_allocate(), are the two main entry points from the runtime 396 // into the G1's allocation routines. They have the following 397 // assumptions: 398 // 399 // * They should both be called outside safepoints. 400 // 401 // * They should both be called without holding the Heap_lock. 402 // 403 // * All allocation requests for new TLABs should go to 404 // allocate_new_tlab(). 405 // 406 // * All non-TLAB allocation requests should go to mem_allocate(). 407 // 408 // * If either call cannot satisfy the allocation request using the 409 // current allocating region, they will try to get a new one. If 410 // this fails, they will attempt to do an evacuation pause and 411 // retry the allocation. 412 // 413 // * If all allocation attempts fail, even after trying to schedule 414 // an evacuation pause, allocate_new_tlab() will return NULL, 415 // whereas mem_allocate() will attempt a heap expansion and/or 416 // schedule a Full GC. 417 // 418 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 419 // should never be called with word_size being humongous. All 420 // humongous allocation requests should go to mem_allocate() which 421 // will satisfy them with a special path. 422 423 virtual HeapWord* allocate_new_tlab(size_t word_size); 424 425 virtual HeapWord* mem_allocate(size_t word_size, 426 bool* gc_overhead_limit_was_exceeded); 427 428 // The following three methods take a gc_count_before_ret 429 // parameter which is used to return the GC count if the method 430 // returns NULL. Given that we are required to read the GC count 431 // while holding the Heap_lock, and these paths will take the 432 // Heap_lock at some point, it's easier to get them to read the GC 433 // count while holding the Heap_lock before they return NULL instead 434 // of the caller (namely: mem_allocate()) having to also take the 435 // Heap_lock just to read the GC count. 436 437 // First-level mutator allocation attempt: try to allocate out of 438 // the mutator alloc region without taking the Heap_lock. This 439 // should only be used for non-humongous allocations. 440 inline HeapWord* attempt_allocation(size_t word_size, 441 uint* gc_count_before_ret, 442 uint* gclocker_retry_count_ret); 443 444 // Second-level mutator allocation attempt: take the Heap_lock and 445 // retry the allocation attempt, potentially scheduling a GC 446 // pause. This should only be used for non-humongous allocations. 447 HeapWord* attempt_allocation_slow(size_t word_size, 448 AllocationContext_t context, 449 uint* gc_count_before_ret, 450 uint* gclocker_retry_count_ret); 451 452 // Takes the Heap_lock and attempts a humongous allocation. It can 453 // potentially schedule a GC pause. 454 HeapWord* attempt_allocation_humongous(size_t word_size, 455 uint* gc_count_before_ret, 456 uint* gclocker_retry_count_ret); 457 458 // Allocation attempt that should be called during safepoints (e.g., 459 // at the end of a successful GC). expect_null_mutator_alloc_region 460 // specifies whether the mutator alloc region is expected to be NULL 461 // or not. 462 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 463 AllocationContext_t context, 464 bool expect_null_mutator_alloc_region); 465 466 // These methods are the "callbacks" from the G1AllocRegion class. 467 468 // For mutator alloc regions. 469 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 470 void retire_mutator_alloc_region(HeapRegion* alloc_region, 471 size_t allocated_bytes); 472 473 // For GC alloc regions. 474 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 475 InCSetState dest); 476 void retire_gc_alloc_region(HeapRegion* alloc_region, 477 size_t allocated_bytes, InCSetState dest); 478 479 // - if explicit_gc is true, the GC is for a System.gc() etc, 480 // otherwise it's for a failed allocation. 481 // - if clear_all_soft_refs is true, all soft references should be 482 // cleared during the GC. 483 // - it returns false if it is unable to do the collection due to the 484 // GC locker being active, true otherwise. 485 bool do_full_collection(bool explicit_gc, 486 bool clear_all_soft_refs); 487 488 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 489 virtual void do_full_collection(bool clear_all_soft_refs); 490 491 // Resize the heap if necessary after a full collection. 492 void resize_if_necessary_after_full_collection(); 493 494 // Callback from VM_G1CollectForAllocation operation. 495 // This function does everything necessary/possible to satisfy a 496 // failed allocation request (including collection, expansion, etc.) 497 HeapWord* satisfy_failed_allocation(size_t word_size, 498 AllocationContext_t context, 499 bool* succeeded); 500 private: 501 // Helper method for satisfy_failed_allocation() 502 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 503 AllocationContext_t context, 504 bool do_gc, 505 bool clear_all_soft_refs, 506 bool expect_null_mutator_alloc_region, 507 bool* gc_succeeded); 508 509 protected: 510 // Attempting to expand the heap sufficiently 511 // to support an allocation of the given "word_size". If 512 // successful, perform the allocation and return the address of the 513 // allocated block, or else "NULL". 514 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 515 516 // Process any reference objects discovered during 517 // an incremental evacuation pause. 518 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 519 520 // Enqueue any remaining discovered references 521 // after processing. 522 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 523 524 public: 525 WorkGang* workers() const { return _workers; } 526 527 G1Allocator* allocator() { 528 return _allocator; 529 } 530 531 G1HeapVerifier* verifier() { 532 return _verifier; 533 } 534 535 G1MonitoringSupport* g1mm() { 536 assert(_g1mm != NULL, "should have been initialized"); 537 return _g1mm; 538 } 539 540 // Expand the garbage-first heap by at least the given size (in bytes!). 541 // Returns true if the heap was expanded by the requested amount; 542 // false otherwise. 543 // (Rounds up to a HeapRegion boundary.) 544 bool expand(size_t expand_bytes, double* expand_time_ms = NULL); 545 546 // Returns the PLAB statistics for a given destination. 547 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 548 549 // Determines PLAB size for a given destination. 550 inline size_t desired_plab_sz(InCSetState dest); 551 552 inline AllocationContextStats& allocation_context_stats(); 553 554 // Do anything common to GC's. 555 void gc_prologue(bool full); 556 void gc_epilogue(bool full); 557 558 // Modify the reclaim candidate set and test for presence. 559 // These are only valid for starts_humongous regions. 560 inline void set_humongous_reclaim_candidate(uint region, bool value); 561 inline bool is_humongous_reclaim_candidate(uint region); 562 563 // Remove from the reclaim candidate set. Also remove from the 564 // collection set so that later encounters avoid the slow path. 565 inline void set_humongous_is_live(oop obj); 566 567 // Register the given region to be part of the collection set. 568 inline void register_humongous_region_with_cset(uint index); 569 // Register regions with humongous objects (actually on the start region) in 570 // the in_cset_fast_test table. 571 void register_humongous_regions_with_cset(); 572 // We register a region with the fast "in collection set" test. We 573 // simply set to true the array slot corresponding to this region. 574 void register_young_region_with_cset(HeapRegion* r) { 575 _in_cset_fast_test.set_in_young(r->hrm_index()); 576 } 577 void register_old_region_with_cset(HeapRegion* r) { 578 _in_cset_fast_test.set_in_old(r->hrm_index()); 579 } 580 inline void register_ext_region_with_cset(HeapRegion* r) { 581 _in_cset_fast_test.set_ext(r->hrm_index()); 582 } 583 void clear_in_cset(const HeapRegion* hr) { 584 _in_cset_fast_test.clear(hr); 585 } 586 587 void clear_cset_fast_test() { 588 _in_cset_fast_test.clear(); 589 } 590 591 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 592 593 // This is called at the start of either a concurrent cycle or a Full 594 // GC to update the number of old marking cycles started. 595 void increment_old_marking_cycles_started(); 596 597 // This is called at the end of either a concurrent cycle or a Full 598 // GC to update the number of old marking cycles completed. Those two 599 // can happen in a nested fashion, i.e., we start a concurrent 600 // cycle, a Full GC happens half-way through it which ends first, 601 // and then the cycle notices that a Full GC happened and ends 602 // too. The concurrent parameter is a boolean to help us do a bit 603 // tighter consistency checking in the method. If concurrent is 604 // false, the caller is the inner caller in the nesting (i.e., the 605 // Full GC). If concurrent is true, the caller is the outer caller 606 // in this nesting (i.e., the concurrent cycle). Further nesting is 607 // not currently supported. The end of this call also notifies 608 // the FullGCCount_lock in case a Java thread is waiting for a full 609 // GC to happen (e.g., it called System.gc() with 610 // +ExplicitGCInvokesConcurrent). 611 void increment_old_marking_cycles_completed(bool concurrent); 612 613 uint old_marking_cycles_completed() { 614 return _old_marking_cycles_completed; 615 } 616 617 void register_concurrent_cycle_start(const Ticks& start_time); 618 void register_concurrent_cycle_end(); 619 void trace_heap_after_concurrent_cycle(); 620 621 G1HRPrinter* hr_printer() { return &_hr_printer; } 622 623 // Allocates a new heap region instance. 624 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 625 626 // Allocate the highest free region in the reserved heap. This will commit 627 // regions as necessary. 628 HeapRegion* alloc_highest_free_region(); 629 630 // Frees a non-humongous region by initializing its contents and 631 // adding it to the free list that's passed as a parameter (this is 632 // usually a local list which will be appended to the master free 633 // list later). The used bytes of freed regions are accumulated in 634 // pre_used. If par is true, the region's RSet will not be freed 635 // up. The assumption is that this will be done later. 636 // The locked parameter indicates if the caller has already taken 637 // care of proper synchronization. This may allow some optimizations. 638 void free_region(HeapRegion* hr, 639 FreeRegionList* free_list, 640 bool par, 641 bool locked = false); 642 643 // It dirties the cards that cover the block so that the post 644 // write barrier never queues anything when updating objects on this 645 // block. It is assumed (and in fact we assert) that the block 646 // belongs to a young region. 647 inline void dirty_young_block(HeapWord* start, size_t word_size); 648 649 // Frees a humongous region by collapsing it into individual regions 650 // and calling free_region() for each of them. The freed regions 651 // will be added to the free list that's passed as a parameter (this 652 // is usually a local list which will be appended to the master free 653 // list later). The used bytes of freed regions are accumulated in 654 // pre_used. If par is true, the region's RSet will not be freed 655 // up. The assumption is that this will be done later. 656 void free_humongous_region(HeapRegion* hr, 657 FreeRegionList* free_list, 658 bool par); 659 660 // Facility for allocating in 'archive' regions in high heap memory and 661 // recording the allocated ranges. These should all be called from the 662 // VM thread at safepoints, without the heap lock held. They can be used 663 // to create and archive a set of heap regions which can be mapped at the 664 // same fixed addresses in a subsequent JVM invocation. 665 void begin_archive_alloc_range(); 666 667 // Check if the requested size would be too large for an archive allocation. 668 bool is_archive_alloc_too_large(size_t word_size); 669 670 // Allocate memory of the requested size from the archive region. This will 671 // return NULL if the size is too large or if no memory is available. It 672 // does not trigger a garbage collection. 673 HeapWord* archive_mem_allocate(size_t word_size); 674 675 // Optionally aligns the end address and returns the allocated ranges in 676 // an array of MemRegions in order of ascending addresses. 677 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 678 size_t end_alignment_in_bytes = 0); 679 680 // Facility for allocating a fixed range within the heap and marking 681 // the containing regions as 'archive'. For use at JVM init time, when the 682 // caller may mmap archived heap data at the specified range(s). 683 // Verify that the MemRegions specified in the argument array are within the 684 // reserved heap. 685 bool check_archive_addresses(MemRegion* range, size_t count); 686 687 // Commit the appropriate G1 regions containing the specified MemRegions 688 // and mark them as 'archive' regions. The regions in the array must be 689 // non-overlapping and in order of ascending address. 690 bool alloc_archive_regions(MemRegion* range, size_t count); 691 692 // Insert any required filler objects in the G1 regions around the specified 693 // ranges to make the regions parseable. This must be called after 694 // alloc_archive_regions, and after class loading has occurred. 695 void fill_archive_regions(MemRegion* range, size_t count); 696 697 // For each of the specified MemRegions, uncommit the containing G1 regions 698 // which had been allocated by alloc_archive_regions. This should be called 699 // rather than fill_archive_regions at JVM init time if the archive file 700 // mapping failed, with the same non-overlapping and sorted MemRegion array. 701 void dealloc_archive_regions(MemRegion* range, size_t count); 702 703 protected: 704 705 // Shrink the garbage-first heap by at most the given size (in bytes!). 706 // (Rounds down to a HeapRegion boundary.) 707 virtual void shrink(size_t expand_bytes); 708 void shrink_helper(size_t expand_bytes); 709 710 #if TASKQUEUE_STATS 711 static void print_taskqueue_stats_hdr(outputStream* const st); 712 void print_taskqueue_stats() const; 713 void reset_taskqueue_stats(); 714 #endif // TASKQUEUE_STATS 715 716 // Schedule the VM operation that will do an evacuation pause to 717 // satisfy an allocation request of word_size. *succeeded will 718 // return whether the VM operation was successful (it did do an 719 // evacuation pause) or not (another thread beat us to it or the GC 720 // locker was active). Given that we should not be holding the 721 // Heap_lock when we enter this method, we will pass the 722 // gc_count_before (i.e., total_collections()) as a parameter since 723 // it has to be read while holding the Heap_lock. Currently, both 724 // methods that call do_collection_pause() release the Heap_lock 725 // before the call, so it's easy to read gc_count_before just before. 726 HeapWord* do_collection_pause(size_t word_size, 727 uint gc_count_before, 728 bool* succeeded, 729 GCCause::Cause gc_cause); 730 731 void wait_for_root_region_scanning(); 732 733 // The guts of the incremental collection pause, executed by the vm 734 // thread. It returns false if it is unable to do the collection due 735 // to the GC locker being active, true otherwise 736 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 737 738 // Actually do the work of evacuating the collection set. 739 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 740 741 void pre_evacuate_collection_set(); 742 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 743 744 // Print the header for the per-thread termination statistics. 745 static void print_termination_stats_hdr(); 746 // Print actual per-thread termination statistics. 747 void print_termination_stats(uint worker_id, 748 double elapsed_ms, 749 double strong_roots_ms, 750 double term_ms, 751 size_t term_attempts, 752 size_t alloc_buffer_waste, 753 size_t undo_waste) const; 754 // Update object copying statistics. 755 void record_obj_copy_mem_stats(); 756 757 // The g1 remembered set of the heap. 758 G1RemSet* _g1_rem_set; 759 760 // A set of cards that cover the objects for which the Rsets should be updated 761 // concurrently after the collection. 762 DirtyCardQueueSet _dirty_card_queue_set; 763 764 // The closure used to refine a single card. 765 RefineCardTableEntryClosure* _refine_cte_cl; 766 767 // After a collection pause, make the regions in the CS into free 768 // regions. 769 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 770 771 // Abandon the current collection set without recording policy 772 // statistics or updating free lists. 773 void abandon_collection_set(HeapRegion* cs_head); 774 775 // The concurrent marker (and the thread it runs in.) 776 ConcurrentMark* _cm; 777 ConcurrentMarkThread* _cmThread; 778 779 // The concurrent refiner. 780 ConcurrentG1Refine* _cg1r; 781 782 // The parallel task queues 783 RefToScanQueueSet *_task_queues; 784 785 // True iff a evacuation has failed in the current collection. 786 bool _evacuation_failed; 787 788 EvacuationFailedInfo* _evacuation_failed_info_array; 789 790 // Failed evacuations cause some logical from-space objects to have 791 // forwarding pointers to themselves. Reset them. 792 void remove_self_forwarding_pointers(); 793 794 // Restore the preserved mark words for objects with self-forwarding pointers. 795 void restore_preserved_marks(); 796 797 // Restore the objects in the regions in the collection set after an 798 // evacuation failure. 799 void restore_after_evac_failure(); 800 801 // Stores marks with the corresponding oop that we need to preserve during evacuation 802 // failure. 803 OopAndMarkOopStack* _preserved_objs; 804 805 // Preserve the mark of "obj", if necessary, in preparation for its mark 806 // word being overwritten with a self-forwarding-pointer. 807 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 808 809 #ifndef PRODUCT 810 // Support for forcing evacuation failures. Analogous to 811 // PromotionFailureALot for the other collectors. 812 813 // Records whether G1EvacuationFailureALot should be in effect 814 // for the current GC 815 bool _evacuation_failure_alot_for_current_gc; 816 817 // Used to record the GC number for interval checking when 818 // determining whether G1EvaucationFailureALot is in effect 819 // for the current GC. 820 size_t _evacuation_failure_alot_gc_number; 821 822 // Count of the number of evacuations between failures. 823 volatile size_t _evacuation_failure_alot_count; 824 825 // Set whether G1EvacuationFailureALot should be in effect 826 // for the current GC (based upon the type of GC and which 827 // command line flags are set); 828 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 829 bool during_initial_mark, 830 bool during_marking); 831 832 inline void set_evacuation_failure_alot_for_current_gc(); 833 834 // Return true if it's time to cause an evacuation failure. 835 inline bool evacuation_should_fail(); 836 837 // Reset the G1EvacuationFailureALot counters. Should be called at 838 // the end of an evacuation pause in which an evacuation failure occurred. 839 inline void reset_evacuation_should_fail(); 840 #endif // !PRODUCT 841 842 // ("Weak") Reference processing support. 843 // 844 // G1 has 2 instances of the reference processor class. One 845 // (_ref_processor_cm) handles reference object discovery 846 // and subsequent processing during concurrent marking cycles. 847 // 848 // The other (_ref_processor_stw) handles reference object 849 // discovery and processing during full GCs and incremental 850 // evacuation pauses. 851 // 852 // During an incremental pause, reference discovery will be 853 // temporarily disabled for _ref_processor_cm and will be 854 // enabled for _ref_processor_stw. At the end of the evacuation 855 // pause references discovered by _ref_processor_stw will be 856 // processed and discovery will be disabled. The previous 857 // setting for reference object discovery for _ref_processor_cm 858 // will be re-instated. 859 // 860 // At the start of marking: 861 // * Discovery by the CM ref processor is verified to be inactive 862 // and it's discovered lists are empty. 863 // * Discovery by the CM ref processor is then enabled. 864 // 865 // At the end of marking: 866 // * Any references on the CM ref processor's discovered 867 // lists are processed (possibly MT). 868 // 869 // At the start of full GC we: 870 // * Disable discovery by the CM ref processor and 871 // empty CM ref processor's discovered lists 872 // (without processing any entries). 873 // * Verify that the STW ref processor is inactive and it's 874 // discovered lists are empty. 875 // * Temporarily set STW ref processor discovery as single threaded. 876 // * Temporarily clear the STW ref processor's _is_alive_non_header 877 // field. 878 // * Finally enable discovery by the STW ref processor. 879 // 880 // The STW ref processor is used to record any discovered 881 // references during the full GC. 882 // 883 // At the end of a full GC we: 884 // * Enqueue any reference objects discovered by the STW ref processor 885 // that have non-live referents. This has the side-effect of 886 // making the STW ref processor inactive by disabling discovery. 887 // * Verify that the CM ref processor is still inactive 888 // and no references have been placed on it's discovered 889 // lists (also checked as a precondition during initial marking). 890 891 // The (stw) reference processor... 892 ReferenceProcessor* _ref_processor_stw; 893 894 STWGCTimer* _gc_timer_stw; 895 ConcurrentGCTimer* _gc_timer_cm; 896 897 G1OldTracer* _gc_tracer_cm; 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 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 983 984 virtual CollectorPolicy* collector_policy() const; 985 986 // Adaptive size policy. No such thing for g1. 987 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 988 989 // The rem set and barrier set. 990 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 991 992 void scrub_rem_set(BitMap* region_bm, BitMap* card_bm); 993 994 unsigned get_gc_time_stamp() { 995 return _gc_time_stamp; 996 } 997 998 inline void reset_gc_time_stamp(); 999 1000 void check_gc_time_stamps() PRODUCT_RETURN; 1001 1002 inline void increment_gc_time_stamp(); 1003 1004 // Reset the given region's GC timestamp. If it's starts humongous, 1005 // also reset the GC timestamp of its corresponding 1006 // continues humongous regions too. 1007 void reset_gc_time_stamps(HeapRegion* hr); 1008 1009 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1010 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1011 1012 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1013 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1014 1015 // The shared block offset table array. 1016 G1BlockOffsetTable* bot() const { return _bot; } 1017 1018 // Reference Processing accessors 1019 1020 // The STW reference processor.... 1021 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1022 1023 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1024 1025 // The Concurrent Marking reference processor... 1026 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1027 1028 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1029 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1030 1031 virtual size_t capacity() const; 1032 virtual size_t used() const; 1033 // This should be called when we're not holding the heap lock. The 1034 // result might be a bit inaccurate. 1035 size_t used_unlocked() const; 1036 size_t recalculate_used() const; 1037 1038 // These virtual functions do the actual allocation. 1039 // Some heaps may offer a contiguous region for shared non-blocking 1040 // allocation, via inlined code (by exporting the address of the top and 1041 // end fields defining the extent of the contiguous allocation region.) 1042 // But G1CollectedHeap doesn't yet support this. 1043 1044 virtual bool is_maximal_no_gc() const { 1045 return _hrm.available() == 0; 1046 } 1047 1048 // The current number of regions in the heap. 1049 uint num_regions() const { return _hrm.length(); } 1050 1051 // The max number of regions in the heap. 1052 uint max_regions() const { return _hrm.max_length(); } 1053 1054 // The number of regions that are completely free. 1055 uint num_free_regions() const { return _hrm.num_free_regions(); } 1056 1057 MemoryUsage get_auxiliary_data_memory_usage() const { 1058 return _hrm.get_auxiliary_data_memory_usage(); 1059 } 1060 1061 // The number of regions that are not completely free. 1062 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1063 1064 #ifdef ASSERT 1065 bool is_on_master_free_list(HeapRegion* hr) { 1066 return _hrm.is_free(hr); 1067 } 1068 #endif // ASSERT 1069 1070 // Wrapper for the region list operations that can be called from 1071 // methods outside this class. 1072 1073 void secondary_free_list_add(FreeRegionList* list) { 1074 _secondary_free_list.add_ordered(list); 1075 } 1076 1077 void append_secondary_free_list() { 1078 _hrm.insert_list_into_free_list(&_secondary_free_list); 1079 } 1080 1081 void append_secondary_free_list_if_not_empty_with_lock() { 1082 // If the secondary free list looks empty there's no reason to 1083 // take the lock and then try to append it. 1084 if (!_secondary_free_list.is_empty()) { 1085 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1086 append_secondary_free_list(); 1087 } 1088 } 1089 1090 inline void old_set_add(HeapRegion* hr); 1091 inline void old_set_remove(HeapRegion* hr); 1092 1093 size_t non_young_capacity_bytes() { 1094 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes; 1095 } 1096 1097 void set_free_regions_coming(); 1098 void reset_free_regions_coming(); 1099 bool free_regions_coming() { return _free_regions_coming; } 1100 void wait_while_free_regions_coming(); 1101 1102 // Determine whether the given region is one that we are using as an 1103 // old GC alloc region. 1104 bool is_old_gc_alloc_region(HeapRegion* hr); 1105 1106 // Perform a collection of the heap; intended for use in implementing 1107 // "System.gc". This probably implies as full a collection as the 1108 // "CollectedHeap" supports. 1109 virtual void collect(GCCause::Cause cause); 1110 1111 virtual bool copy_allocation_context_stats(const jint* contexts, 1112 jlong* totals, 1113 jbyte* accuracy, 1114 jint len); 1115 1116 // True iff an evacuation has failed in the most-recent collection. 1117 bool evacuation_failed() { return _evacuation_failed; } 1118 1119 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed); 1120 void prepend_to_freelist(FreeRegionList* list); 1121 void decrement_summary_bytes(size_t bytes); 1122 1123 virtual bool is_in(const void* p) const; 1124 #ifdef ASSERT 1125 // Returns whether p is in one of the available areas of the heap. Slow but 1126 // extensive version. 1127 bool is_in_exact(const void* p) const; 1128 #endif 1129 1130 // Return "TRUE" iff the given object address is within the collection 1131 // set. Slow implementation. 1132 bool obj_in_cs(oop obj); 1133 1134 inline bool is_in_cset(const HeapRegion *hr); 1135 inline bool is_in_cset(oop obj); 1136 1137 inline bool is_in_cset_or_humongous(const oop obj); 1138 1139 private: 1140 // This array is used for a quick test on whether a reference points into 1141 // the collection set or not. Each of the array's elements denotes whether the 1142 // corresponding region is in the collection set or not. 1143 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1144 1145 public: 1146 1147 inline InCSetState in_cset_state(const oop obj); 1148 1149 // Return "TRUE" iff the given object address is in the reserved 1150 // region of g1. 1151 bool is_in_g1_reserved(const void* p) const { 1152 return _hrm.reserved().contains(p); 1153 } 1154 1155 // Returns a MemRegion that corresponds to the space that has been 1156 // reserved for the heap 1157 MemRegion g1_reserved() const { 1158 return _hrm.reserved(); 1159 } 1160 1161 virtual bool is_in_closed_subset(const void* p) const; 1162 1163 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1164 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1165 } 1166 1167 // This resets the card table to all zeros. It is used after 1168 // a collection pause which used the card table to claim cards. 1169 void cleanUpCardTable(); 1170 1171 // Iteration functions. 1172 1173 // Iterate over all objects, calling "cl.do_object" on each. 1174 virtual void object_iterate(ObjectClosure* cl); 1175 1176 virtual void safe_object_iterate(ObjectClosure* cl) { 1177 object_iterate(cl); 1178 } 1179 1180 // Iterate over heap regions, in address order, terminating the 1181 // iteration early if the "doHeapRegion" method returns "true". 1182 void heap_region_iterate(HeapRegionClosure* blk) const; 1183 1184 // Return the region with the given index. It assumes the index is valid. 1185 inline HeapRegion* region_at(uint index) const; 1186 1187 // Return the next region (by index) that is part of the same 1188 // humongous object that hr is part of. 1189 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1190 1191 // Calculate the region index of the given address. Given address must be 1192 // within the heap. 1193 inline uint addr_to_region(HeapWord* addr) const; 1194 1195 inline HeapWord* bottom_addr_for_region(uint index) const; 1196 1197 // Iterate over the heap regions in parallel. Assumes that this will be called 1198 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1199 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1200 // to each of the regions, by attempting to claim the region using the 1201 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1202 // region. The concurrent argument should be set to true if iteration is 1203 // performed concurrently, during which no assumptions are made for consistent 1204 // attributes of the heap regions (as they might be modified while iterating). 1205 void heap_region_par_iterate(HeapRegionClosure* cl, 1206 uint worker_id, 1207 HeapRegionClaimer* hrclaimer, 1208 bool concurrent = false) const; 1209 1210 // Clear the cached cset start regions and (more importantly) 1211 // the time stamps. Called when we reset the GC time stamp. 1212 void clear_cset_start_regions(); 1213 1214 // Given the id of a worker, obtain or calculate a suitable 1215 // starting region for iterating over the current collection set. 1216 HeapRegion* start_cset_region_for_worker(uint worker_i); 1217 1218 // Iterate over the regions (if any) in the current collection set. 1219 void collection_set_iterate(HeapRegionClosure* blk); 1220 1221 // As above but starting from region r 1222 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1223 1224 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1225 1226 // Returns the HeapRegion that contains addr. addr must not be NULL. 1227 template <class T> 1228 inline HeapRegion* heap_region_containing(const T addr) const; 1229 1230 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1231 // each address in the (reserved) heap is a member of exactly 1232 // one block. The defining characteristic of a block is that it is 1233 // possible to find its size, and thus to progress forward to the next 1234 // block. (Blocks may be of different sizes.) Thus, blocks may 1235 // represent Java objects, or they might be free blocks in a 1236 // free-list-based heap (or subheap), as long as the two kinds are 1237 // distinguishable and the size of each is determinable. 1238 1239 // Returns the address of the start of the "block" that contains the 1240 // address "addr". We say "blocks" instead of "object" since some heaps 1241 // may not pack objects densely; a chunk may either be an object or a 1242 // non-object. 1243 virtual HeapWord* block_start(const void* addr) const; 1244 1245 // Requires "addr" to be the start of a chunk, and returns its size. 1246 // "addr + size" is required to be the start of a new chunk, or the end 1247 // of the active area of the heap. 1248 virtual size_t block_size(const HeapWord* addr) const; 1249 1250 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1251 // the block is an object. 1252 virtual bool block_is_obj(const HeapWord* addr) const; 1253 1254 // Section on thread-local allocation buffers (TLABs) 1255 // See CollectedHeap for semantics. 1256 1257 bool supports_tlab_allocation() const; 1258 size_t tlab_capacity(Thread* ignored) const; 1259 size_t tlab_used(Thread* ignored) const; 1260 size_t max_tlab_size() const; 1261 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1262 1263 // Can a compiler initialize a new object without store barriers? 1264 // This permission only extends from the creation of a new object 1265 // via a TLAB up to the first subsequent safepoint. If such permission 1266 // is granted for this heap type, the compiler promises to call 1267 // defer_store_barrier() below on any slow path allocation of 1268 // a new object for which such initializing store barriers will 1269 // have been elided. G1, like CMS, allows this, but should be 1270 // ready to provide a compensating write barrier as necessary 1271 // if that storage came out of a non-young region. The efficiency 1272 // of this implementation depends crucially on being able to 1273 // answer very efficiently in constant time whether a piece of 1274 // storage in the heap comes from a young region or not. 1275 // See ReduceInitialCardMarks. 1276 virtual bool can_elide_tlab_store_barriers() const { 1277 return true; 1278 } 1279 1280 virtual bool card_mark_must_follow_store() const { 1281 return true; 1282 } 1283 1284 inline bool is_in_young(const oop obj); 1285 1286 virtual bool is_scavengable(const void* addr); 1287 1288 // We don't need barriers for initializing stores to objects 1289 // in the young gen: for the SATB pre-barrier, there is no 1290 // pre-value that needs to be remembered; for the remembered-set 1291 // update logging post-barrier, we don't maintain remembered set 1292 // information for young gen objects. 1293 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1294 1295 // Returns "true" iff the given word_size is "very large". 1296 static bool is_humongous(size_t word_size) { 1297 // Note this has to be strictly greater-than as the TLABs 1298 // are capped at the humongous threshold and we want to 1299 // ensure that we don't try to allocate a TLAB as 1300 // humongous and that we don't allocate a humongous 1301 // object in a TLAB. 1302 return word_size > _humongous_object_threshold_in_words; 1303 } 1304 1305 // Returns the humongous threshold for a specific region size 1306 static size_t humongous_threshold_for(size_t region_size) { 1307 return (region_size / 2); 1308 } 1309 1310 // Returns the number of regions the humongous object of the given word size 1311 // requires. 1312 static size_t humongous_obj_size_in_regions(size_t word_size); 1313 1314 // Print the maximum heap capacity. 1315 virtual size_t max_capacity() const; 1316 1317 virtual jlong millis_since_last_gc(); 1318 1319 1320 // Convenience function to be used in situations where the heap type can be 1321 // asserted to be this type. 1322 static G1CollectedHeap* heap(); 1323 1324 void set_region_short_lived_locked(HeapRegion* hr); 1325 // add appropriate methods for any other surv rate groups 1326 1327 YoungList* young_list() const { return _young_list; } 1328 1329 uint old_regions_count() const { return _old_set.length(); } 1330 1331 uint humongous_regions_count() const { return _humongous_set.length(); } 1332 1333 // debugging 1334 bool check_young_list_well_formed() { 1335 return _young_list->check_list_well_formed(); 1336 } 1337 1338 bool check_young_list_empty(bool check_heap, 1339 bool check_sample = true); 1340 1341 // *** Stuff related to concurrent marking. It's not clear to me that so 1342 // many of these need to be public. 1343 1344 // The functions below are helper functions that a subclass of 1345 // "CollectedHeap" can use in the implementation of its virtual 1346 // functions. 1347 // This performs a concurrent marking of the live objects in a 1348 // bitmap off to the side. 1349 void doConcurrentMark(); 1350 1351 bool isMarkedPrev(oop obj) const; 1352 bool isMarkedNext(oop obj) const; 1353 1354 // Determine if an object is dead, given the object and also 1355 // the region to which the object belongs. An object is dead 1356 // iff a) it was not allocated since the last mark, b) it 1357 // is not marked, and c) it is not in an archive region. 1358 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1359 return 1360 !hr->obj_allocated_since_prev_marking(obj) && 1361 !isMarkedPrev(obj) && 1362 !hr->is_archive(); 1363 } 1364 1365 // This function returns true when an object has been 1366 // around since the previous marking and hasn't yet 1367 // been marked during this marking, and is not in an archive region. 1368 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1369 return 1370 !hr->obj_allocated_since_next_marking(obj) && 1371 !isMarkedNext(obj) && 1372 !hr->is_archive(); 1373 } 1374 1375 // Determine if an object is dead, given only the object itself. 1376 // This will find the region to which the object belongs and 1377 // then call the region version of the same function. 1378 1379 // Added if it is NULL it isn't dead. 1380 1381 inline bool is_obj_dead(const oop obj) const; 1382 1383 inline bool is_obj_ill(const oop obj) const; 1384 1385 ConcurrentMark* concurrent_mark() const { return _cm; } 1386 1387 // Refinement 1388 1389 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1390 1391 // The dirty cards region list is used to record a subset of regions 1392 // whose cards need clearing. The list if populated during the 1393 // remembered set scanning and drained during the card table 1394 // cleanup. Although the methods are reentrant, population/draining 1395 // phases must not overlap. For synchronization purposes the last 1396 // element on the list points to itself. 1397 HeapRegion* _dirty_cards_region_list; 1398 void push_dirty_cards_region(HeapRegion* hr); 1399 HeapRegion* pop_dirty_cards_region(); 1400 1401 // Optimized nmethod scanning support routines 1402 1403 // Register the given nmethod with the G1 heap. 1404 virtual void register_nmethod(nmethod* nm); 1405 1406 // Unregister the given nmethod from the G1 heap. 1407 virtual void unregister_nmethod(nmethod* nm); 1408 1409 // Free up superfluous code root memory. 1410 void purge_code_root_memory(); 1411 1412 // Rebuild the strong code root lists for each region 1413 // after a full GC. 1414 void rebuild_strong_code_roots(); 1415 1416 // Delete entries for dead interned string and clean up unreferenced symbols 1417 // in symbol table, possibly in parallel. 1418 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1419 1420 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1421 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1422 1423 // Redirty logged cards in the refinement queue. 1424 void redirty_logged_cards(); 1425 // Verification 1426 1427 // Perform any cleanup actions necessary before allowing a verification. 1428 virtual void prepare_for_verify(); 1429 1430 // Perform verification. 1431 1432 // vo == UsePrevMarking -> use "prev" marking information, 1433 // vo == UseNextMarking -> use "next" marking information 1434 // vo == UseMarkWord -> use the mark word in the object header 1435 // 1436 // NOTE: Only the "prev" marking information is guaranteed to be 1437 // consistent most of the time, so most calls to this should use 1438 // vo == UsePrevMarking. 1439 // Currently, there is only one case where this is called with 1440 // vo == UseNextMarking, which is to verify the "next" marking 1441 // information at the end of remark. 1442 // Currently there is only one place where this is called with 1443 // vo == UseMarkWord, which is to verify the marking during a 1444 // full GC. 1445 void verify(VerifyOption vo); 1446 1447 // The methods below are here for convenience and dispatch the 1448 // appropriate method depending on value of the given VerifyOption 1449 // parameter. The values for that parameter, and their meanings, 1450 // are the same as those above. 1451 1452 bool is_obj_dead_cond(const oop obj, 1453 const HeapRegion* hr, 1454 const VerifyOption vo) const; 1455 1456 bool is_obj_dead_cond(const oop obj, 1457 const VerifyOption vo) const; 1458 1459 G1HeapSummary create_g1_heap_summary(); 1460 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1461 1462 // Printing 1463 1464 virtual void print_on(outputStream* st) const; 1465 virtual void print_extended_on(outputStream* st) const; 1466 virtual void print_on_error(outputStream* st) const; 1467 1468 virtual void print_gc_threads_on(outputStream* st) const; 1469 virtual void gc_threads_do(ThreadClosure* tc) const; 1470 1471 // Override 1472 void print_tracing_info() const; 1473 1474 // The following two methods are helpful for debugging RSet issues. 1475 void print_cset_rsets() PRODUCT_RETURN; 1476 void print_all_rsets() PRODUCT_RETURN; 1477 1478 public: 1479 size_t pending_card_num(); 1480 1481 protected: 1482 size_t _max_heap_capacity; 1483 }; 1484 1485 class G1ParEvacuateFollowersClosure : public VoidClosure { 1486 private: 1487 double _start_term; 1488 double _term_time; 1489 size_t _term_attempts; 1490 1491 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); } 1492 void end_term_time() { _term_time += os::elapsedTime() - _start_term; } 1493 protected: 1494 G1CollectedHeap* _g1h; 1495 G1ParScanThreadState* _par_scan_state; 1496 RefToScanQueueSet* _queues; 1497 ParallelTaskTerminator* _terminator; 1498 1499 G1ParScanThreadState* par_scan_state() { return _par_scan_state; } 1500 RefToScanQueueSet* queues() { return _queues; } 1501 ParallelTaskTerminator* terminator() { return _terminator; } 1502 1503 public: 1504 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h, 1505 G1ParScanThreadState* par_scan_state, 1506 RefToScanQueueSet* queues, 1507 ParallelTaskTerminator* terminator) 1508 : _g1h(g1h), _par_scan_state(par_scan_state), 1509 _queues(queues), _terminator(terminator), 1510 _start_term(0.0), _term_time(0.0), _term_attempts(0) {} 1511 1512 void do_void(); 1513 1514 double term_time() const { return _term_time; } 1515 size_t term_attempts() const { return _term_attempts; } 1516 1517 private: 1518 inline bool offer_termination(); 1519 }; 1520 1521 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP