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/g1EvacStats.hpp" 37 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 38 #include "gc/g1/g1YCTypes.hpp" 39 #include "gc/g1/hSpaceCounters.hpp" 40 #include "gc/g1/heapRegionManager.hpp" 41 #include "gc/g1/heapRegionSet.hpp" 42 #include "gc/g1/youngList.hpp" 43 #include "gc/shared/barrierSet.hpp" 44 #include "gc/shared/collectedHeap.hpp" 45 #include "gc/shared/plab.hpp" 46 #include "memory/memRegion.hpp" 47 #include "utilities/stack.hpp" 48 49 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot. 50 // It uses the "Garbage First" heap organization and algorithm, which 51 // may combine concurrent marking with parallel, incremental compaction of 52 // heap subsets that will yield large amounts of garbage. 53 54 // Forward declarations 55 class HeapRegion; 56 class HRRSCleanupTask; 57 class GenerationSpec; 58 class OopsInHeapRegionClosure; 59 class G1ParScanThreadState; 60 class G1ParScanThreadStateSet; 61 class G1KlassScanClosure; 62 class G1ParScanThreadState; 63 class ObjectClosure; 64 class SpaceClosure; 65 class CompactibleSpaceClosure; 66 class Space; 67 class G1CollectorPolicy; 68 class G1RemSet; 69 class HeapRegionRemSetIterator; 70 class ConcurrentMark; 71 class ConcurrentMarkThread; 72 class ConcurrentG1Refine; 73 class ConcurrentGCTimer; 74 class GenerationCounters; 75 class STWGCTimer; 76 class G1NewTracer; 77 class G1OldTracer; 78 class EvacuationFailedInfo; 79 class nmethod; 80 class Ticks; 81 class WorkGang; 82 class G1Allocator; 83 class G1ArchiveAllocator; 84 85 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue; 86 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet; 87 88 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() ) 89 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion ) 90 91 // The G1 STW is alive closure. 92 // An instance is embedded into the G1CH and used as the 93 // (optional) _is_alive_non_header closure in the STW 94 // reference processor. It is also extensively used during 95 // reference processing during STW evacuation pauses. 96 class G1STWIsAliveClosure: public BoolObjectClosure { 97 G1CollectedHeap* _g1; 98 public: 99 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {} 100 bool do_object_b(oop p); 101 }; 102 103 class RefineCardTableEntryClosure; 104 105 class G1RegionMappingChangedListener : public G1MappingChangedListener { 106 private: 107 void reset_from_card_cache(uint start_idx, size_t num_regions); 108 public: 109 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 110 }; 111 112 class G1CollectedHeap : public CollectedHeap { 113 friend class VM_CollectForMetadataAllocation; 114 friend class VM_G1CollectForAllocation; 115 friend class VM_G1CollectFull; 116 friend class VM_G1IncCollectionPause; 117 friend class VMStructs; 118 friend class MutatorAllocRegion; 119 friend class G1GCAllocRegion; 120 121 // Closures used in implementation. 122 friend class G1ParScanThreadState; 123 friend class G1ParScanThreadStateSet; 124 friend class G1ParTask; 125 friend class G1PLABAllocator; 126 friend class G1PrepareCompactClosure; 127 128 // Other related classes. 129 friend class HeapRegionClaimer; 130 131 // Testing classes. 132 friend class G1CheckCSetFastTableClosure; 133 134 private: 135 WorkGang* _workers; 136 137 static size_t _humongous_object_threshold_in_words; 138 139 // The secondary free list which contains regions that have been 140 // freed up during the cleanup process. This will be appended to 141 // the master free list when appropriate. 142 FreeRegionList _secondary_free_list; 143 144 // It keeps track of the old regions. 145 HeapRegionSet _old_set; 146 147 // It keeps track of the humongous regions. 148 HeapRegionSet _humongous_set; 149 150 void eagerly_reclaim_humongous_regions(); 151 152 // The number of regions we could create by expansion. 153 uint _expansion_regions; 154 155 // The block offset table for the G1 heap. 156 G1BlockOffsetSharedArray* _bot_shared; 157 158 // Tears down the region sets / lists so that they are empty and the 159 // regions on the heap do not belong to a region set / list. The 160 // only exception is the humongous set which we leave unaltered. If 161 // free_list_only is true, it will only tear down the master free 162 // list. It is called before a Full GC (free_list_only == false) or 163 // before heap shrinking (free_list_only == true). 164 void tear_down_region_sets(bool free_list_only); 165 166 // Rebuilds the region sets / lists so that they are repopulated to 167 // reflect the contents of the heap. The only exception is the 168 // humongous set which was not torn down in the first place. If 169 // free_list_only is true, it will only rebuild the master free 170 // list. It is called after a Full GC (free_list_only == false) or 171 // after heap shrinking (free_list_only == true). 172 void rebuild_region_sets(bool free_list_only); 173 174 // Callback for region mapping changed events. 175 G1RegionMappingChangedListener _listener; 176 177 // The sequence of all heap regions in the heap. 178 HeapRegionManager _hrm; 179 180 // Manages all allocations with regions except humongous object allocations. 181 G1Allocator* _allocator; 182 183 // Outside of GC pauses, the number of bytes used in all regions other 184 // than the current allocation region(s). 185 size_t _summary_bytes_used; 186 187 void increase_used(size_t bytes); 188 void decrease_used(size_t bytes); 189 190 void set_used(size_t bytes); 191 192 // Class that handles archive allocation ranges. 193 G1ArchiveAllocator* _archive_allocator; 194 195 // Statistics for each allocation context 196 AllocationContextStats _allocation_context_stats; 197 198 // GC allocation statistics policy for survivors. 199 G1EvacStats _survivor_evac_stats; 200 201 // GC allocation statistics policy for tenured objects. 202 G1EvacStats _old_evac_stats; 203 204 // It specifies whether we should attempt to expand the heap after a 205 // region allocation failure. If heap expansion fails we set this to 206 // false so that we don't re-attempt the heap expansion (it's likely 207 // that subsequent expansion attempts will also fail if one fails). 208 // Currently, it is only consulted during GC and it's reset at the 209 // start of each GC. 210 bool _expand_heap_after_alloc_failure; 211 212 // Helper for monitoring and management support. 213 G1MonitoringSupport* _g1mm; 214 215 // Records whether the region at the given index is (still) a 216 // candidate for eager reclaim. Only valid for humongous start 217 // regions; other regions have unspecified values. Humongous start 218 // regions are initialized at start of collection pause, with 219 // candidates removed from the set as they are found reachable from 220 // roots or the young generation. 221 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> { 222 protected: 223 bool default_value() const { return false; } 224 public: 225 void clear() { G1BiasedMappedArray<bool>::clear(); } 226 void set_candidate(uint region, bool value) { 227 set_by_index(region, value); 228 } 229 bool is_candidate(uint region) { 230 return get_by_index(region); 231 } 232 }; 233 234 HumongousReclaimCandidates _humongous_reclaim_candidates; 235 // Stores whether during humongous object registration we found candidate regions. 236 // If not, we can skip a few steps. 237 bool _has_humongous_reclaim_candidates; 238 239 volatile unsigned _gc_time_stamp; 240 241 G1HRPrinter _hr_printer; 242 243 // It decides whether an explicit GC should start a concurrent cycle 244 // instead of doing a STW GC. Currently, a concurrent cycle is 245 // explicitly started if: 246 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or 247 // (b) cause == _g1_humongous_allocation 248 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 249 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 250 // (e) cause == _update_allocation_context_stats_inc 251 // (f) cause == _wb_conc_mark 252 bool should_do_concurrent_full_gc(GCCause::Cause cause); 253 254 // indicates whether we are in young or mixed GC mode 255 G1CollectorState _collector_state; 256 257 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 258 // concurrent cycles) we have started. 259 volatile uint _old_marking_cycles_started; 260 261 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 262 // concurrent cycles) we have completed. 263 volatile uint _old_marking_cycles_completed; 264 265 bool _heap_summary_sent; 266 267 // This is a non-product method that is helpful for testing. It is 268 // called at the end of a GC and artificially expands the heap by 269 // allocating a number of dead regions. This way we can induce very 270 // frequent marking cycles and stress the cleanup / concurrent 271 // cleanup code more (as all the regions that will be allocated by 272 // this method will be found dead by the marking cycle). 273 void allocate_dummy_regions() PRODUCT_RETURN; 274 275 // Clear RSets after a compaction. It also resets the GC time stamps. 276 void clear_rsets_post_compaction(); 277 278 // If the HR printer is active, dump the state of the regions in the 279 // heap after a compaction. 280 void print_hrm_post_compaction(); 281 282 // Create a memory mapper for auxiliary data structures of the given size and 283 // translation factor. 284 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 285 size_t size, 286 size_t translation_factor); 287 288 double verify(bool guard, const char* msg); 289 void verify_before_gc(); 290 void verify_after_gc(); 291 292 void log_gc_header(); 293 void log_gc_footer(double pause_time_sec); 294 295 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 296 297 // These are macros so that, if the assert fires, we get the correct 298 // line number, file, etc. 299 300 #define heap_locking_asserts_params(_extra_message_) \ 301 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 302 (_extra_message_), \ 303 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 304 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 305 BOOL_TO_STR(Thread::current()->is_VM_thread()) 306 307 #define assert_heap_locked() \ 308 do { \ 309 assert(Heap_lock->owned_by_self(), \ 310 heap_locking_asserts_params("should be holding the Heap_lock")); \ 311 } while (0) 312 313 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 314 do { \ 315 assert(Heap_lock->owned_by_self() || \ 316 (SafepointSynchronize::is_at_safepoint() && \ 317 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 318 heap_locking_asserts_params("should be holding the Heap_lock or " \ 319 "should be at a safepoint")); \ 320 } while (0) 321 322 #define assert_heap_locked_and_not_at_safepoint() \ 323 do { \ 324 assert(Heap_lock->owned_by_self() && \ 325 !SafepointSynchronize::is_at_safepoint(), \ 326 heap_locking_asserts_params("should be holding the Heap_lock and " \ 327 "should not be at a safepoint")); \ 328 } while (0) 329 330 #define assert_heap_not_locked() \ 331 do { \ 332 assert(!Heap_lock->owned_by_self(), \ 333 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 334 } while (0) 335 336 #define assert_heap_not_locked_and_not_at_safepoint() \ 337 do { \ 338 assert(!Heap_lock->owned_by_self() && \ 339 !SafepointSynchronize::is_at_safepoint(), \ 340 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 341 "should not be at a safepoint")); \ 342 } while (0) 343 344 #define assert_at_safepoint(_should_be_vm_thread_) \ 345 do { \ 346 assert(SafepointSynchronize::is_at_safepoint() && \ 347 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 348 heap_locking_asserts_params("should be at a safepoint")); \ 349 } while (0) 350 351 #define assert_not_at_safepoint() \ 352 do { \ 353 assert(!SafepointSynchronize::is_at_safepoint(), \ 354 heap_locking_asserts_params("should not be at a safepoint")); \ 355 } while (0) 356 357 protected: 358 359 // The young region list. 360 YoungList* _young_list; 361 362 // The current policy object for the collector. 363 G1CollectorPolicy* _g1_policy; 364 365 // This is the second level of trying to allocate a new region. If 366 // new_region() didn't find a region on the free_list, this call will 367 // check whether there's anything available on the 368 // secondary_free_list and/or wait for more regions to appear on 369 // that list, if _free_regions_coming is set. 370 HeapRegion* new_region_try_secondary_free_list(bool is_old); 371 372 // Try to allocate a single non-humongous HeapRegion sufficient for 373 // an allocation of the given word_size. If do_expand is true, 374 // attempt to expand the heap if necessary to satisfy the allocation 375 // request. If the region is to be used as an old region or for a 376 // humongous object, set is_old to true. If not, to false. 377 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 378 379 // Initialize a contiguous set of free regions of length num_regions 380 // and starting at index first so that they appear as a single 381 // humongous region. 382 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 383 uint num_regions, 384 size_t word_size, 385 AllocationContext_t context); 386 387 // Attempt to allocate a humongous object of the given size. Return 388 // NULL if unsuccessful. 389 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 390 391 // The following two methods, allocate_new_tlab() and 392 // mem_allocate(), are the two main entry points from the runtime 393 // into the G1's allocation routines. They have the following 394 // assumptions: 395 // 396 // * They should both be called outside safepoints. 397 // 398 // * They should both be called without holding the Heap_lock. 399 // 400 // * All allocation requests for new TLABs should go to 401 // allocate_new_tlab(). 402 // 403 // * All non-TLAB allocation requests should go to mem_allocate(). 404 // 405 // * If either call cannot satisfy the allocation request using the 406 // current allocating region, they will try to get a new one. If 407 // this fails, they will attempt to do an evacuation pause and 408 // retry the allocation. 409 // 410 // * If all allocation attempts fail, even after trying to schedule 411 // an evacuation pause, allocate_new_tlab() will return NULL, 412 // whereas mem_allocate() will attempt a heap expansion and/or 413 // schedule a Full GC. 414 // 415 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 416 // should never be called with word_size being humongous. All 417 // humongous allocation requests should go to mem_allocate() which 418 // will satisfy them with a special path. 419 420 virtual HeapWord* allocate_new_tlab(size_t word_size); 421 422 virtual HeapWord* mem_allocate(size_t word_size, 423 bool* gc_overhead_limit_was_exceeded); 424 425 // The following three methods take a gc_count_before_ret 426 // parameter which is used to return the GC count if the method 427 // returns NULL. Given that we are required to read the GC count 428 // while holding the Heap_lock, and these paths will take the 429 // Heap_lock at some point, it's easier to get them to read the GC 430 // count while holding the Heap_lock before they return NULL instead 431 // of the caller (namely: mem_allocate()) having to also take the 432 // Heap_lock just to read the GC count. 433 434 // First-level mutator allocation attempt: try to allocate out of 435 // the mutator alloc region without taking the Heap_lock. This 436 // should only be used for non-humongous allocations. 437 inline HeapWord* attempt_allocation(size_t word_size, 438 uint* gc_count_before_ret, 439 uint* gclocker_retry_count_ret); 440 441 // Second-level mutator allocation attempt: take the Heap_lock and 442 // retry the allocation attempt, potentially scheduling a GC 443 // pause. This should only be used for non-humongous allocations. 444 HeapWord* attempt_allocation_slow(size_t word_size, 445 AllocationContext_t context, 446 uint* gc_count_before_ret, 447 uint* gclocker_retry_count_ret); 448 449 // Takes the Heap_lock and attempts a humongous allocation. It can 450 // potentially schedule a GC pause. 451 HeapWord* attempt_allocation_humongous(size_t word_size, 452 uint* gc_count_before_ret, 453 uint* gclocker_retry_count_ret); 454 455 // Allocation attempt that should be called during safepoints (e.g., 456 // at the end of a successful GC). expect_null_mutator_alloc_region 457 // specifies whether the mutator alloc region is expected to be NULL 458 // or not. 459 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 460 AllocationContext_t context, 461 bool expect_null_mutator_alloc_region); 462 463 // These methods are the "callbacks" from the G1AllocRegion class. 464 465 // For mutator alloc regions. 466 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 467 void retire_mutator_alloc_region(HeapRegion* alloc_region, 468 size_t allocated_bytes); 469 470 // For GC alloc regions. 471 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 472 InCSetState dest); 473 void retire_gc_alloc_region(HeapRegion* alloc_region, 474 size_t allocated_bytes, InCSetState dest); 475 476 // - if explicit_gc is true, the GC is for a System.gc() etc, 477 // otherwise it's for a failed allocation. 478 // - if clear_all_soft_refs is true, all soft references should be 479 // cleared during the GC. 480 // - it returns false if it is unable to do the collection due to the 481 // GC locker being active, true otherwise. 482 bool do_full_collection(bool explicit_gc, 483 bool clear_all_soft_refs); 484 485 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 486 virtual void do_full_collection(bool clear_all_soft_refs); 487 488 // Resize the heap if necessary after a full collection. 489 void resize_if_necessary_after_full_collection(); 490 491 // Callback from VM_G1CollectForAllocation operation. 492 // This function does everything necessary/possible to satisfy a 493 // failed allocation request (including collection, expansion, etc.) 494 HeapWord* satisfy_failed_allocation(size_t word_size, 495 AllocationContext_t context, 496 bool* succeeded); 497 private: 498 // Helper method for satisfy_failed_allocation() 499 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 500 AllocationContext_t context, 501 bool do_gc, 502 bool clear_all_soft_refs, 503 bool expect_null_mutator_alloc_region, 504 bool* gc_succeeded); 505 506 protected: 507 // Attempting to expand the heap sufficiently 508 // to support an allocation of the given "word_size". If 509 // successful, perform the allocation and return the address of the 510 // allocated block, or else "NULL". 511 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 512 513 // Process any reference objects discovered during 514 // an incremental evacuation pause. 515 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 516 517 // Enqueue any remaining discovered references 518 // after processing. 519 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 520 521 public: 522 WorkGang* workers() const { return _workers; } 523 524 G1Allocator* allocator() { 525 return _allocator; 526 } 527 528 G1MonitoringSupport* g1mm() { 529 assert(_g1mm != NULL, "should have been initialized"); 530 return _g1mm; 531 } 532 533 // Expand the garbage-first heap by at least the given size (in bytes!). 534 // Returns true if the heap was expanded by the requested amount; 535 // false otherwise. 536 // (Rounds up to a HeapRegion boundary.) 537 bool expand(size_t expand_bytes, double* expand_time_ms = NULL); 538 539 // Returns the PLAB statistics for a given destination. 540 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 541 542 // Determines PLAB size for a given destination. 543 inline size_t desired_plab_sz(InCSetState dest); 544 545 inline AllocationContextStats& allocation_context_stats(); 546 547 // Do anything common to GC's. 548 void gc_prologue(bool full); 549 void gc_epilogue(bool full); 550 551 // Modify the reclaim candidate set and test for presence. 552 // These are only valid for starts_humongous regions. 553 inline void set_humongous_reclaim_candidate(uint region, bool value); 554 inline bool is_humongous_reclaim_candidate(uint region); 555 556 // Remove from the reclaim candidate set. Also remove from the 557 // collection set so that later encounters avoid the slow path. 558 inline void set_humongous_is_live(oop obj); 559 560 // Register the given region to be part of the collection set. 561 inline void register_humongous_region_with_cset(uint index); 562 // Register regions with humongous objects (actually on the start region) in 563 // the in_cset_fast_test table. 564 void register_humongous_regions_with_cset(); 565 // We register a region with the fast "in collection set" test. We 566 // simply set to true the array slot corresponding to this region. 567 void register_young_region_with_cset(HeapRegion* r) { 568 _in_cset_fast_test.set_in_young(r->hrm_index()); 569 } 570 void register_old_region_with_cset(HeapRegion* r) { 571 _in_cset_fast_test.set_in_old(r->hrm_index()); 572 } 573 void clear_in_cset(const HeapRegion* hr) { 574 _in_cset_fast_test.clear(hr); 575 } 576 577 void clear_cset_fast_test() { 578 _in_cset_fast_test.clear(); 579 } 580 581 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause); 582 583 // This is called at the start of either a concurrent cycle or a Full 584 // GC to update the number of old marking cycles started. 585 void increment_old_marking_cycles_started(); 586 587 // This is called at the end of either a concurrent cycle or a Full 588 // GC to update the number of old marking cycles completed. Those two 589 // can happen in a nested fashion, i.e., we start a concurrent 590 // cycle, a Full GC happens half-way through it which ends first, 591 // and then the cycle notices that a Full GC happened and ends 592 // too. The concurrent parameter is a boolean to help us do a bit 593 // tighter consistency checking in the method. If concurrent is 594 // false, the caller is the inner caller in the nesting (i.e., the 595 // Full GC). If concurrent is true, the caller is the outer caller 596 // in this nesting (i.e., the concurrent cycle). Further nesting is 597 // not currently supported. The end of this call also notifies 598 // the FullGCCount_lock in case a Java thread is waiting for a full 599 // GC to happen (e.g., it called System.gc() with 600 // +ExplicitGCInvokesConcurrent). 601 void increment_old_marking_cycles_completed(bool concurrent); 602 603 uint old_marking_cycles_completed() { 604 return _old_marking_cycles_completed; 605 } 606 607 void register_concurrent_cycle_start(const Ticks& start_time); 608 void register_concurrent_cycle_end(); 609 void trace_heap_after_concurrent_cycle(); 610 611 G1HRPrinter* hr_printer() { return &_hr_printer; } 612 613 // Allocates a new heap region instance. 614 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 615 616 // Allocate the highest free region in the reserved heap. This will commit 617 // regions as necessary. 618 HeapRegion* alloc_highest_free_region(); 619 620 // Frees a non-humongous region by initializing its contents and 621 // adding it to the free list that's passed as a parameter (this is 622 // usually a local list which will be appended to the master free 623 // list later). The used bytes of freed regions are accumulated in 624 // pre_used. If par is true, the region's RSet will not be freed 625 // up. The assumption is that this will be done later. 626 // The locked parameter indicates if the caller has already taken 627 // care of proper synchronization. This may allow some optimizations. 628 void free_region(HeapRegion* hr, 629 FreeRegionList* free_list, 630 bool par, 631 bool locked = false); 632 633 // It dirties the cards that cover the block so that the post 634 // write barrier never queues anything when updating objects on this 635 // block. It is assumed (and in fact we assert) that the block 636 // belongs to a young region. 637 inline void dirty_young_block(HeapWord* start, size_t word_size); 638 639 // Frees a humongous region by collapsing it into individual regions 640 // and calling free_region() for each of them. The freed regions 641 // will be added to the free list that's passed as a parameter (this 642 // is 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 void free_humongous_region(HeapRegion* hr, 647 FreeRegionList* free_list, 648 bool par); 649 650 // Facility for allocating in 'archive' regions in high heap memory and 651 // recording the allocated ranges. These should all be called from the 652 // VM thread at safepoints, without the heap lock held. They can be used 653 // to create and archive a set of heap regions which can be mapped at the 654 // same fixed addresses in a subsequent JVM invocation. 655 void begin_archive_alloc_range(); 656 657 // Check if the requested size would be too large for an archive allocation. 658 bool is_archive_alloc_too_large(size_t word_size); 659 660 // Allocate memory of the requested size from the archive region. This will 661 // return NULL if the size is too large or if no memory is available. It 662 // does not trigger a garbage collection. 663 HeapWord* archive_mem_allocate(size_t word_size); 664 665 // Optionally aligns the end address and returns the allocated ranges in 666 // an array of MemRegions in order of ascending addresses. 667 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 668 size_t end_alignment_in_bytes = 0); 669 670 // Facility for allocating a fixed range within the heap and marking 671 // the containing regions as 'archive'. For use at JVM init time, when the 672 // caller may mmap archived heap data at the specified range(s). 673 // Verify that the MemRegions specified in the argument array are within the 674 // reserved heap. 675 bool check_archive_addresses(MemRegion* range, size_t count); 676 677 // Commit the appropriate G1 regions containing the specified MemRegions 678 // and mark them as 'archive' regions. The regions in the array must be 679 // non-overlapping and in order of ascending address. 680 bool alloc_archive_regions(MemRegion* range, size_t count); 681 682 // Insert any required filler objects in the G1 regions around the specified 683 // ranges to make the regions parseable. This must be called after 684 // alloc_archive_regions, and after class loading has occurred. 685 void fill_archive_regions(MemRegion* range, size_t count); 686 687 // For each of the specified MemRegions, uncommit the containing G1 regions 688 // which had been allocated by alloc_archive_regions. This should be called 689 // rather than fill_archive_regions at JVM init time if the archive file 690 // mapping failed, with the same non-overlapping and sorted MemRegion array. 691 void dealloc_archive_regions(MemRegion* range, size_t count); 692 693 protected: 694 695 // Shrink the garbage-first heap by at most the given size (in bytes!). 696 // (Rounds down to a HeapRegion boundary.) 697 virtual void shrink(size_t expand_bytes); 698 void shrink_helper(size_t expand_bytes); 699 700 #if TASKQUEUE_STATS 701 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 702 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 703 void reset_taskqueue_stats(); 704 #endif // TASKQUEUE_STATS 705 706 // Schedule the VM operation that will do an evacuation pause to 707 // satisfy an allocation request of word_size. *succeeded will 708 // return whether the VM operation was successful (it did do an 709 // evacuation pause) or not (another thread beat us to it or the GC 710 // locker was active). Given that we should not be holding the 711 // Heap_lock when we enter this method, we will pass the 712 // gc_count_before (i.e., total_collections()) as a parameter since 713 // it has to be read while holding the Heap_lock. Currently, both 714 // methods that call do_collection_pause() release the Heap_lock 715 // before the call, so it's easy to read gc_count_before just before. 716 HeapWord* do_collection_pause(size_t word_size, 717 uint gc_count_before, 718 bool* succeeded, 719 GCCause::Cause gc_cause); 720 721 void wait_for_root_region_scanning(); 722 723 // The guts of the incremental collection pause, executed by the vm 724 // thread. It returns false if it is unable to do the collection due 725 // to the GC locker being active, true otherwise 726 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 727 728 // Actually do the work of evacuating the collection set. 729 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 730 731 void pre_evacuate_collection_set(); 732 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 733 734 // Print the header for the per-thread termination statistics. 735 static void print_termination_stats_hdr(outputStream* const st); 736 // Print actual per-thread termination statistics. 737 void print_termination_stats(outputStream* const st, 738 uint worker_id, 739 double elapsed_ms, 740 double strong_roots_ms, 741 double term_ms, 742 size_t term_attempts, 743 size_t alloc_buffer_waste, 744 size_t undo_waste) const; 745 // Update object copying statistics. 746 void record_obj_copy_mem_stats(); 747 748 // The g1 remembered set of the heap. 749 G1RemSet* _g1_rem_set; 750 751 // A set of cards that cover the objects for which the Rsets should be updated 752 // concurrently after the collection. 753 DirtyCardQueueSet _dirty_card_queue_set; 754 755 // The closure used to refine a single card. 756 RefineCardTableEntryClosure* _refine_cte_cl; 757 758 // After a collection pause, make the regions in the CS into free 759 // regions. 760 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 761 762 // Abandon the current collection set without recording policy 763 // statistics or updating free lists. 764 void abandon_collection_set(HeapRegion* cs_head); 765 766 // The concurrent marker (and the thread it runs in.) 767 ConcurrentMark* _cm; 768 ConcurrentMarkThread* _cmThread; 769 770 // The concurrent refiner. 771 ConcurrentG1Refine* _cg1r; 772 773 // The parallel task queues 774 RefToScanQueueSet *_task_queues; 775 776 // True iff a evacuation has failed in the current collection. 777 bool _evacuation_failed; 778 779 EvacuationFailedInfo* _evacuation_failed_info_array; 780 781 // Failed evacuations cause some logical from-space objects to have 782 // forwarding pointers to themselves. Reset them. 783 void remove_self_forwarding_pointers(); 784 785 struct OopAndMarkOop { 786 private: 787 oop _o; 788 markOop _m; 789 public: 790 OopAndMarkOop(oop obj, markOop m) : _o(obj), _m(m) { 791 } 792 793 void set_mark() { 794 _o->set_mark(_m); 795 } 796 }; 797 798 typedef Stack<OopAndMarkOop,mtGC> OopAndMarkOopStack; 799 // Stores marks with the corresponding oop that we need to preserve during evacuation 800 // failure. 801 OopAndMarkOopStack* _preserved_objs; 802 803 // Preserve the mark of "obj", if necessary, in preparation for its mark 804 // word being overwritten with a self-forwarding-pointer. 805 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 806 807 #ifndef PRODUCT 808 // Support for forcing evacuation failures. Analogous to 809 // PromotionFailureALot for the other collectors. 810 811 // Records whether G1EvacuationFailureALot should be in effect 812 // for the current GC 813 bool _evacuation_failure_alot_for_current_gc; 814 815 // Used to record the GC number for interval checking when 816 // determining whether G1EvaucationFailureALot is in effect 817 // for the current GC. 818 size_t _evacuation_failure_alot_gc_number; 819 820 // Count of the number of evacuations between failures. 821 volatile size_t _evacuation_failure_alot_count; 822 823 // Set whether G1EvacuationFailureALot should be in effect 824 // for the current GC (based upon the type of GC and which 825 // command line flags are set); 826 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 827 bool during_initial_mark, 828 bool during_marking); 829 830 inline void set_evacuation_failure_alot_for_current_gc(); 831 832 // Return true if it's time to cause an evacuation failure. 833 inline bool evacuation_should_fail(); 834 835 // Reset the G1EvacuationFailureALot counters. Should be called at 836 // the end of an evacuation pause in which an evacuation failure occurred. 837 inline void reset_evacuation_should_fail(); 838 #endif // !PRODUCT 839 840 // ("Weak") Reference processing support. 841 // 842 // G1 has 2 instances of the reference processor class. One 843 // (_ref_processor_cm) handles reference object discovery 844 // and subsequent processing during concurrent marking cycles. 845 // 846 // The other (_ref_processor_stw) handles reference object 847 // discovery and processing during full GCs and incremental 848 // evacuation pauses. 849 // 850 // During an incremental pause, reference discovery will be 851 // temporarily disabled for _ref_processor_cm and will be 852 // enabled for _ref_processor_stw. At the end of the evacuation 853 // pause references discovered by _ref_processor_stw will be 854 // processed and discovery will be disabled. The previous 855 // setting for reference object discovery for _ref_processor_cm 856 // will be re-instated. 857 // 858 // At the start of marking: 859 // * Discovery by the CM ref processor is verified to be inactive 860 // and it's discovered lists are empty. 861 // * Discovery by the CM ref processor is then enabled. 862 // 863 // At the end of marking: 864 // * Any references on the CM ref processor's discovered 865 // lists are processed (possibly MT). 866 // 867 // At the start of full GC we: 868 // * Disable discovery by the CM ref processor and 869 // empty CM ref processor's discovered lists 870 // (without processing any entries). 871 // * Verify that the STW ref processor is inactive and it's 872 // discovered lists are empty. 873 // * Temporarily set STW ref processor discovery as single threaded. 874 // * Temporarily clear the STW ref processor's _is_alive_non_header 875 // field. 876 // * Finally enable discovery by the STW ref processor. 877 // 878 // The STW ref processor is used to record any discovered 879 // references during the full GC. 880 // 881 // At the end of a full GC we: 882 // * Enqueue any reference objects discovered by the STW ref processor 883 // that have non-live referents. This has the side-effect of 884 // making the STW ref processor inactive by disabling discovery. 885 // * Verify that the CM ref processor is still inactive 886 // and no references have been placed on it's discovered 887 // lists (also checked as a precondition during initial marking). 888 889 // The (stw) reference processor... 890 ReferenceProcessor* _ref_processor_stw; 891 892 STWGCTimer* _gc_timer_stw; 893 ConcurrentGCTimer* _gc_timer_cm; 894 895 G1OldTracer* _gc_tracer_cm; 896 G1NewTracer* _gc_tracer_stw; 897 898 // During reference object discovery, the _is_alive_non_header 899 // closure (if non-null) is applied to the referent object to 900 // determine whether the referent is live. If so then the 901 // reference object does not need to be 'discovered' and can 902 // be treated as a regular oop. This has the benefit of reducing 903 // the number of 'discovered' reference objects that need to 904 // be processed. 905 // 906 // Instance of the is_alive closure for embedding into the 907 // STW reference processor as the _is_alive_non_header field. 908 // Supplying a value for the _is_alive_non_header field is 909 // optional but doing so prevents unnecessary additions to 910 // the discovered lists during reference discovery. 911 G1STWIsAliveClosure _is_alive_closure_stw; 912 913 // The (concurrent marking) reference processor... 914 ReferenceProcessor* _ref_processor_cm; 915 916 // Instance of the concurrent mark is_alive closure for embedding 917 // into the Concurrent Marking reference processor as the 918 // _is_alive_non_header field. Supplying a value for the 919 // _is_alive_non_header field is optional but doing so prevents 920 // unnecessary additions to the discovered lists during reference 921 // discovery. 922 G1CMIsAliveClosure _is_alive_closure_cm; 923 924 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 925 HeapRegion** _worker_cset_start_region; 926 927 // Time stamp to validate the regions recorded in the cache 928 // used by G1CollectedHeap::start_cset_region_for_worker(). 929 // The heap region entry for a given worker is valid iff 930 // the associated time stamp value matches the current value 931 // of G1CollectedHeap::_gc_time_stamp. 932 uint* _worker_cset_start_region_time_stamp; 933 934 volatile bool _free_regions_coming; 935 936 public: 937 938 void set_refine_cte_cl_concurrency(bool concurrent); 939 940 RefToScanQueue *task_queue(uint i) const; 941 942 uint num_task_queues() const; 943 944 // A set of cards where updates happened during the GC 945 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 946 947 // Create a G1CollectedHeap with the specified policy. 948 // Must call the initialize method afterwards. 949 // May not return if something goes wrong. 950 G1CollectedHeap(G1CollectorPolicy* policy); 951 952 // Initialize the G1CollectedHeap to have the initial and 953 // maximum sizes and remembered and barrier sets 954 // specified by the policy object. 955 jint initialize(); 956 957 virtual void stop(); 958 959 // Return the (conservative) maximum heap alignment for any G1 heap 960 static size_t conservative_max_heap_alignment(); 961 962 // Does operations required after initialization has been done. 963 void post_initialize(); 964 965 // Initialize weak reference processing. 966 void ref_processing_init(); 967 968 virtual Name kind() const { 969 return CollectedHeap::G1CollectedHeap; 970 } 971 972 const G1CollectorState* collector_state() const { return &_collector_state; } 973 G1CollectorState* collector_state() { return &_collector_state; } 974 975 // The current policy object for the collector. 976 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 977 978 virtual CollectorPolicy* collector_policy() const; 979 980 // Adaptive size policy. No such thing for g1. 981 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 982 983 // The rem set and barrier set. 984 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 985 986 unsigned get_gc_time_stamp() { 987 return _gc_time_stamp; 988 } 989 990 inline void reset_gc_time_stamp(); 991 992 void check_gc_time_stamps() PRODUCT_RETURN; 993 994 inline void increment_gc_time_stamp(); 995 996 // Reset the given region's GC timestamp. If it's starts humongous, 997 // also reset the GC timestamp of its corresponding 998 // continues humongous regions too. 999 void reset_gc_time_stamps(HeapRegion* hr); 1000 1001 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 1002 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 1003 1004 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1005 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1006 1007 // The shared block offset table array. 1008 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1009 1010 // Reference Processing accessors 1011 1012 // The STW reference processor.... 1013 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1014 1015 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1016 1017 // The Concurrent Marking reference processor... 1018 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1019 1020 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1021 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1022 1023 virtual size_t capacity() const; 1024 virtual size_t used() const; 1025 // This should be called when we're not holding the heap lock. The 1026 // result might be a bit inaccurate. 1027 size_t used_unlocked() const; 1028 size_t recalculate_used() const; 1029 1030 // These virtual functions do the actual allocation. 1031 // Some heaps may offer a contiguous region for shared non-blocking 1032 // allocation, via inlined code (by exporting the address of the top and 1033 // end fields defining the extent of the contiguous allocation region.) 1034 // But G1CollectedHeap doesn't yet support this. 1035 1036 virtual bool is_maximal_no_gc() const { 1037 return _hrm.available() == 0; 1038 } 1039 1040 // The current number of regions in the heap. 1041 uint num_regions() const { return _hrm.length(); } 1042 1043 // The max number of regions in the heap. 1044 uint max_regions() const { return _hrm.max_length(); } 1045 1046 // The number of regions that are completely free. 1047 uint num_free_regions() const { return _hrm.num_free_regions(); } 1048 1049 MemoryUsage get_auxiliary_data_memory_usage() const { 1050 return _hrm.get_auxiliary_data_memory_usage(); 1051 } 1052 1053 // The number of regions that are not completely free. 1054 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1055 1056 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1057 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1058 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1059 void verify_dirty_young_regions() PRODUCT_RETURN; 1060 1061 #ifndef PRODUCT 1062 // Make sure that the given bitmap has no marked objects in the 1063 // range [from,limit). If it does, print an error message and return 1064 // false. Otherwise, just return true. bitmap_name should be "prev" 1065 // or "next". 1066 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1067 HeapWord* from, HeapWord* limit); 1068 1069 // Verify that the prev / next bitmap range [tams,end) for the given 1070 // region has no marks. Return true if all is well, false if errors 1071 // are detected. 1072 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1073 #endif // PRODUCT 1074 1075 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1076 // the given region do not have any spurious marks. If errors are 1077 // detected, print appropriate error messages and crash. 1078 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1079 1080 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1081 // have any spurious marks. If errors are detected, print 1082 // appropriate error messages and crash. 1083 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1084 1085 // Do sanity check on the contents of the in-cset fast test table. 1086 bool check_cset_fast_test() PRODUCT_RETURN_( return true; ); 1087 1088 // verify_region_sets() performs verification over the region 1089 // lists. It will be compiled in the product code to be used when 1090 // necessary (i.e., during heap verification). 1091 void verify_region_sets(); 1092 1093 // verify_region_sets_optional() is planted in the code for 1094 // list verification in non-product builds (and it can be enabled in 1095 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1096 #if HEAP_REGION_SET_FORCE_VERIFY 1097 void verify_region_sets_optional() { 1098 verify_region_sets(); 1099 } 1100 #else // HEAP_REGION_SET_FORCE_VERIFY 1101 void verify_region_sets_optional() { } 1102 #endif // HEAP_REGION_SET_FORCE_VERIFY 1103 1104 #ifdef ASSERT 1105 bool is_on_master_free_list(HeapRegion* hr) { 1106 return _hrm.is_free(hr); 1107 } 1108 #endif // ASSERT 1109 1110 // Wrapper for the region list operations that can be called from 1111 // methods outside this class. 1112 1113 void secondary_free_list_add(FreeRegionList* list) { 1114 _secondary_free_list.add_ordered(list); 1115 } 1116 1117 void append_secondary_free_list() { 1118 _hrm.insert_list_into_free_list(&_secondary_free_list); 1119 } 1120 1121 void append_secondary_free_list_if_not_empty_with_lock() { 1122 // If the secondary free list looks empty there's no reason to 1123 // take the lock and then try to append it. 1124 if (!_secondary_free_list.is_empty()) { 1125 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1126 append_secondary_free_list(); 1127 } 1128 } 1129 1130 inline void old_set_add(HeapRegion* hr); 1131 inline void old_set_remove(HeapRegion* hr); 1132 1133 size_t non_young_capacity_bytes() { 1134 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1135 } 1136 1137 void set_free_regions_coming(); 1138 void reset_free_regions_coming(); 1139 bool free_regions_coming() { return _free_regions_coming; } 1140 void wait_while_free_regions_coming(); 1141 1142 // Determine whether the given region is one that we are using as an 1143 // old GC alloc region. 1144 bool is_old_gc_alloc_region(HeapRegion* hr); 1145 1146 // Perform a collection of the heap; intended for use in implementing 1147 // "System.gc". This probably implies as full a collection as the 1148 // "CollectedHeap" supports. 1149 virtual void collect(GCCause::Cause cause); 1150 1151 virtual bool copy_allocation_context_stats(const jint* contexts, 1152 jlong* totals, 1153 jbyte* accuracy, 1154 jint len); 1155 1156 // True iff an evacuation has failed in the most-recent collection. 1157 bool evacuation_failed() { return _evacuation_failed; } 1158 1159 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1160 void prepend_to_freelist(FreeRegionList* list); 1161 void decrement_summary_bytes(size_t bytes); 1162 1163 virtual bool is_in(const void* p) const; 1164 #ifdef ASSERT 1165 // Returns whether p is in one of the available areas of the heap. Slow but 1166 // extensive version. 1167 bool is_in_exact(const void* p) const; 1168 #endif 1169 1170 // Return "TRUE" iff the given object address is within the collection 1171 // set. Slow implementation. 1172 bool obj_in_cs(oop obj); 1173 1174 inline bool is_in_cset(const HeapRegion *hr); 1175 inline bool is_in_cset(oop obj); 1176 1177 inline bool is_in_cset_or_humongous(const oop obj); 1178 1179 private: 1180 // This array is used for a quick test on whether a reference points into 1181 // the collection set or not. Each of the array's elements denotes whether the 1182 // corresponding region is in the collection set or not. 1183 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1184 1185 public: 1186 1187 inline InCSetState in_cset_state(const oop obj); 1188 1189 // Return "TRUE" iff the given object address is in the reserved 1190 // region of g1. 1191 bool is_in_g1_reserved(const void* p) const { 1192 return _hrm.reserved().contains(p); 1193 } 1194 1195 // Returns a MemRegion that corresponds to the space that has been 1196 // reserved for the heap 1197 MemRegion g1_reserved() const { 1198 return _hrm.reserved(); 1199 } 1200 1201 virtual bool is_in_closed_subset(const void* p) const; 1202 1203 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1204 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1205 } 1206 1207 // This resets the card table to all zeros. It is used after 1208 // a collection pause which used the card table to claim cards. 1209 void cleanUpCardTable(); 1210 1211 // Iteration functions. 1212 1213 // Iterate over all objects, calling "cl.do_object" on each. 1214 virtual void object_iterate(ObjectClosure* cl); 1215 1216 virtual void safe_object_iterate(ObjectClosure* cl) { 1217 object_iterate(cl); 1218 } 1219 1220 // Iterate over heap regions, in address order, terminating the 1221 // iteration early if the "doHeapRegion" method returns "true". 1222 void heap_region_iterate(HeapRegionClosure* blk) const; 1223 1224 // Return the region with the given index. It assumes the index is valid. 1225 inline HeapRegion* region_at(uint index) const; 1226 1227 // Return the next region (by index) that is part of the same 1228 // humongous object that hr is part of. 1229 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1230 1231 // Calculate the region index of the given address. Given address must be 1232 // within the heap. 1233 inline uint addr_to_region(HeapWord* addr) const; 1234 1235 inline HeapWord* bottom_addr_for_region(uint index) const; 1236 1237 // Iterate over the heap regions in parallel. Assumes that this will be called 1238 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1239 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1240 // to each of the regions, by attempting to claim the region using the 1241 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1242 // region. The concurrent argument should be set to true if iteration is 1243 // performed concurrently, during which no assumptions are made for consistent 1244 // attributes of the heap regions (as they might be modified while iterating). 1245 void heap_region_par_iterate(HeapRegionClosure* cl, 1246 uint worker_id, 1247 HeapRegionClaimer* hrclaimer, 1248 bool concurrent = false) const; 1249 1250 // Clear the cached cset start regions and (more importantly) 1251 // the time stamps. Called when we reset the GC time stamp. 1252 void clear_cset_start_regions(); 1253 1254 // Given the id of a worker, obtain or calculate a suitable 1255 // starting region for iterating over the current collection set. 1256 HeapRegion* start_cset_region_for_worker(uint worker_i); 1257 1258 // Iterate over the regions (if any) in the current collection set. 1259 void collection_set_iterate(HeapRegionClosure* blk); 1260 1261 // As above but starting from region r 1262 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1263 1264 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1265 1266 // Returns the HeapRegion that contains addr. addr must not be NULL. 1267 template <class T> 1268 inline HeapRegion* heap_region_containing(const T addr) const; 1269 1270 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1271 // each address in the (reserved) heap is a member of exactly 1272 // one block. The defining characteristic of a block is that it is 1273 // possible to find its size, and thus to progress forward to the next 1274 // block. (Blocks may be of different sizes.) Thus, blocks may 1275 // represent Java objects, or they might be free blocks in a 1276 // free-list-based heap (or subheap), as long as the two kinds are 1277 // distinguishable and the size of each is determinable. 1278 1279 // Returns the address of the start of the "block" that contains the 1280 // address "addr". We say "blocks" instead of "object" since some heaps 1281 // may not pack objects densely; a chunk may either be an object or a 1282 // non-object. 1283 virtual HeapWord* block_start(const void* addr) const; 1284 1285 // Requires "addr" to be the start of a chunk, and returns its size. 1286 // "addr + size" is required to be the start of a new chunk, or the end 1287 // of the active area of the heap. 1288 virtual size_t block_size(const HeapWord* addr) const; 1289 1290 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1291 // the block is an object. 1292 virtual bool block_is_obj(const HeapWord* addr) const; 1293 1294 // Section on thread-local allocation buffers (TLABs) 1295 // See CollectedHeap for semantics. 1296 1297 bool supports_tlab_allocation() const; 1298 size_t tlab_capacity(Thread* ignored) const; 1299 size_t tlab_used(Thread* ignored) const; 1300 size_t max_tlab_size() const; 1301 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1302 1303 // Can a compiler initialize a new object without store barriers? 1304 // This permission only extends from the creation of a new object 1305 // via a TLAB up to the first subsequent safepoint. If such permission 1306 // is granted for this heap type, the compiler promises to call 1307 // defer_store_barrier() below on any slow path allocation of 1308 // a new object for which such initializing store barriers will 1309 // have been elided. G1, like CMS, allows this, but should be 1310 // ready to provide a compensating write barrier as necessary 1311 // if that storage came out of a non-young region. The efficiency 1312 // of this implementation depends crucially on being able to 1313 // answer very efficiently in constant time whether a piece of 1314 // storage in the heap comes from a young region or not. 1315 // See ReduceInitialCardMarks. 1316 virtual bool can_elide_tlab_store_barriers() const { 1317 return true; 1318 } 1319 1320 virtual bool card_mark_must_follow_store() const { 1321 return true; 1322 } 1323 1324 inline bool is_in_young(const oop obj); 1325 1326 virtual bool is_scavengable(const void* addr); 1327 1328 // We don't need barriers for initializing stores to objects 1329 // in the young gen: for the SATB pre-barrier, there is no 1330 // pre-value that needs to be remembered; for the remembered-set 1331 // update logging post-barrier, we don't maintain remembered set 1332 // information for young gen objects. 1333 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1334 1335 // Returns "true" iff the given word_size is "very large". 1336 static bool is_humongous(size_t word_size) { 1337 // Note this has to be strictly greater-than as the TLABs 1338 // are capped at the humongous threshold and we want to 1339 // ensure that we don't try to allocate a TLAB as 1340 // humongous and that we don't allocate a humongous 1341 // object in a TLAB. 1342 return word_size > _humongous_object_threshold_in_words; 1343 } 1344 1345 // Returns the humongous threshold for a specific region size 1346 static size_t humongous_threshold_for(size_t region_size) { 1347 return (region_size / 2); 1348 } 1349 1350 // Print the maximum heap capacity. 1351 virtual size_t max_capacity() const; 1352 1353 virtual jlong millis_since_last_gc(); 1354 1355 1356 // Convenience function to be used in situations where the heap type can be 1357 // asserted to be this type. 1358 static G1CollectedHeap* heap(); 1359 1360 void set_region_short_lived_locked(HeapRegion* hr); 1361 // add appropriate methods for any other surv rate groups 1362 1363 YoungList* young_list() const { return _young_list; } 1364 1365 // debugging 1366 bool check_young_list_well_formed() { 1367 return _young_list->check_list_well_formed(); 1368 } 1369 1370 bool check_young_list_empty(bool check_heap, 1371 bool check_sample = true); 1372 1373 // *** Stuff related to concurrent marking. It's not clear to me that so 1374 // many of these need to be public. 1375 1376 // The functions below are helper functions that a subclass of 1377 // "CollectedHeap" can use in the implementation of its virtual 1378 // functions. 1379 // This performs a concurrent marking of the live objects in a 1380 // bitmap off to the side. 1381 void doConcurrentMark(); 1382 1383 bool isMarkedPrev(oop obj) const; 1384 bool isMarkedNext(oop obj) const; 1385 1386 // Determine if an object is dead, given the object and also 1387 // the region to which the object belongs. An object is dead 1388 // iff a) it was not allocated since the last mark, b) it 1389 // is not marked, and c) it is not in an archive region. 1390 bool is_obj_dead(const oop obj, const HeapRegion* hr) const { 1391 return 1392 !hr->obj_allocated_since_prev_marking(obj) && 1393 !isMarkedPrev(obj) && 1394 !hr->is_archive(); 1395 } 1396 1397 // This function returns true when an object has been 1398 // around since the previous marking and hasn't yet 1399 // been marked during this marking, and is not in an archive region. 1400 bool is_obj_ill(const oop obj, const HeapRegion* hr) const { 1401 return 1402 !hr->obj_allocated_since_next_marking(obj) && 1403 !isMarkedNext(obj) && 1404 !hr->is_archive(); 1405 } 1406 1407 // Determine if an object is dead, given only the object itself. 1408 // This will find the region to which the object belongs and 1409 // then call the region version of the same function. 1410 1411 // Added if it is NULL it isn't dead. 1412 1413 inline bool is_obj_dead(const oop obj) const; 1414 1415 inline bool is_obj_ill(const oop obj) const; 1416 1417 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo); 1418 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo); 1419 bool is_marked(oop obj, VerifyOption vo); 1420 const char* top_at_mark_start_str(VerifyOption vo); 1421 1422 ConcurrentMark* concurrent_mark() const { return _cm; } 1423 1424 // Refinement 1425 1426 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; } 1427 1428 // The dirty cards region list is used to record a subset of regions 1429 // whose cards need clearing. The list if populated during the 1430 // remembered set scanning and drained during the card table 1431 // cleanup. Although the methods are reentrant, population/draining 1432 // phases must not overlap. For synchronization purposes the last 1433 // element on the list points to itself. 1434 HeapRegion* _dirty_cards_region_list; 1435 void push_dirty_cards_region(HeapRegion* hr); 1436 HeapRegion* pop_dirty_cards_region(); 1437 1438 // Optimized nmethod scanning support routines 1439 1440 // Register the given nmethod with the G1 heap. 1441 virtual void register_nmethod(nmethod* nm); 1442 1443 // Unregister the given nmethod from the G1 heap. 1444 virtual void unregister_nmethod(nmethod* nm); 1445 1446 // Free up superfluous code root memory. 1447 void purge_code_root_memory(); 1448 1449 // Rebuild the strong code root lists for each region 1450 // after a full GC. 1451 void rebuild_strong_code_roots(); 1452 1453 // Delete entries for dead interned string and clean up unreferenced symbols 1454 // in symbol table, possibly in parallel. 1455 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true); 1456 1457 // Parallel phase of unloading/cleaning after G1 concurrent mark. 1458 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred); 1459 1460 // Redirty logged cards in the refinement queue. 1461 void redirty_logged_cards(); 1462 // Verification 1463 1464 // Perform any cleanup actions necessary before allowing a verification. 1465 virtual void prepare_for_verify(); 1466 1467 // Perform verification. 1468 1469 // vo == UsePrevMarking -> use "prev" marking information, 1470 // vo == UseNextMarking -> use "next" marking information 1471 // vo == UseMarkWord -> use the mark word in the object header 1472 // 1473 // NOTE: Only the "prev" marking information is guaranteed to be 1474 // consistent most of the time, so most calls to this should use 1475 // vo == UsePrevMarking. 1476 // Currently, there is only one case where this is called with 1477 // vo == UseNextMarking, which is to verify the "next" marking 1478 // information at the end of remark. 1479 // Currently there is only one place where this is called with 1480 // vo == UseMarkWord, which is to verify the marking during a 1481 // full GC. 1482 void verify(bool silent, VerifyOption vo); 1483 1484 // Override; it uses the "prev" marking information 1485 virtual void verify(bool silent); 1486 1487 // The methods below are here for convenience and dispatch the 1488 // appropriate method depending on value of the given VerifyOption 1489 // parameter. The values for that parameter, and their meanings, 1490 // are the same as those above. 1491 1492 bool is_obj_dead_cond(const oop obj, 1493 const HeapRegion* hr, 1494 const VerifyOption vo) const; 1495 1496 bool is_obj_dead_cond(const oop obj, 1497 const VerifyOption vo) const; 1498 1499 G1HeapSummary create_g1_heap_summary(); 1500 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats); 1501 1502 // Printing 1503 1504 virtual void print_on(outputStream* st) const; 1505 virtual void print_extended_on(outputStream* st) const; 1506 virtual void print_on_error(outputStream* st) const; 1507 1508 virtual void print_gc_threads_on(outputStream* st) const; 1509 virtual void gc_threads_do(ThreadClosure* tc) const; 1510 1511 // Override 1512 void print_tracing_info() const; 1513 1514 // The following two methods are helpful for debugging RSet issues. 1515 void print_cset_rsets() PRODUCT_RETURN; 1516 void print_all_rsets() PRODUCT_RETURN; 1517 1518 public: 1519 size_t pending_card_num(); 1520 1521 protected: 1522 size_t _max_heap_capacity; 1523 }; 1524 1525 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP