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 == _java_lang_system_gc and +ExplicitGCInvokesConcurrent. 248 // (c) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent. 249 // (d) cause == _g1_humongous_allocation 250 bool should_do_concurrent_full_gc(GCCause::Cause cause); 251 252 // indicates whether we are in young or mixed GC mode 253 G1CollectorState _collector_state; 254 255 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 256 // concurrent cycles) we have started. 257 volatile uint _old_marking_cycles_started; 258 259 // Keeps track of how many "old marking cycles" (i.e., Full GCs or 260 // concurrent cycles) we have completed. 261 volatile uint _old_marking_cycles_completed; 262 263 bool _heap_summary_sent; 264 265 // This is a non-product method that is helpful for testing. It is 266 // called at the end of a GC and artificially expands the heap by 267 // allocating a number of dead regions. This way we can induce very 268 // frequent marking cycles and stress the cleanup / concurrent 269 // cleanup code more (as all the regions that will be allocated by 270 // this method will be found dead by the marking cycle). 271 void allocate_dummy_regions() PRODUCT_RETURN; 272 273 // Clear RSets after a compaction. It also resets the GC time stamps. 274 void clear_rsets_post_compaction(); 275 276 // If the HR printer is active, dump the state of the regions in the 277 // heap after a compaction. 278 void print_hrm_post_compaction(); 279 280 // Create a memory mapper for auxiliary data structures of the given size and 281 // translation factor. 282 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description, 283 size_t size, 284 size_t translation_factor); 285 286 double verify(bool guard, const char* msg); 287 void verify_before_gc(); 288 void verify_after_gc(); 289 290 void log_gc_header(); 291 void log_gc_footer(double pause_time_sec); 292 293 void trace_heap(GCWhen::Type when, const GCTracer* tracer); 294 295 // These are macros so that, if the assert fires, we get the correct 296 // line number, file, etc. 297 298 #define heap_locking_asserts_params(_extra_message_) \ 299 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \ 300 (_extra_message_), \ 301 BOOL_TO_STR(Heap_lock->owned_by_self()), \ 302 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \ 303 BOOL_TO_STR(Thread::current()->is_VM_thread()) 304 305 #define assert_heap_locked() \ 306 do { \ 307 assert(Heap_lock->owned_by_self(), \ 308 heap_locking_asserts_params("should be holding the Heap_lock")); \ 309 } while (0) 310 311 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \ 312 do { \ 313 assert(Heap_lock->owned_by_self() || \ 314 (SafepointSynchronize::is_at_safepoint() && \ 315 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \ 316 heap_locking_asserts_params("should be holding the Heap_lock or " \ 317 "should be at a safepoint")); \ 318 } while (0) 319 320 #define assert_heap_locked_and_not_at_safepoint() \ 321 do { \ 322 assert(Heap_lock->owned_by_self() && \ 323 !SafepointSynchronize::is_at_safepoint(), \ 324 heap_locking_asserts_params("should be holding the Heap_lock and " \ 325 "should not be at a safepoint")); \ 326 } while (0) 327 328 #define assert_heap_not_locked() \ 329 do { \ 330 assert(!Heap_lock->owned_by_self(), \ 331 heap_locking_asserts_params("should not be holding the Heap_lock")); \ 332 } while (0) 333 334 #define assert_heap_not_locked_and_not_at_safepoint() \ 335 do { \ 336 assert(!Heap_lock->owned_by_self() && \ 337 !SafepointSynchronize::is_at_safepoint(), \ 338 heap_locking_asserts_params("should not be holding the Heap_lock and " \ 339 "should not be at a safepoint")); \ 340 } while (0) 341 342 #define assert_at_safepoint(_should_be_vm_thread_) \ 343 do { \ 344 assert(SafepointSynchronize::is_at_safepoint() && \ 345 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \ 346 heap_locking_asserts_params("should be at a safepoint")); \ 347 } while (0) 348 349 #define assert_not_at_safepoint() \ 350 do { \ 351 assert(!SafepointSynchronize::is_at_safepoint(), \ 352 heap_locking_asserts_params("should not be at a safepoint")); \ 353 } while (0) 354 355 protected: 356 357 // The young region list. 358 YoungList* _young_list; 359 360 // The current policy object for the collector. 361 G1CollectorPolicy* _g1_policy; 362 363 // This is the second level of trying to allocate a new region. If 364 // new_region() didn't find a region on the free_list, this call will 365 // check whether there's anything available on the 366 // secondary_free_list and/or wait for more regions to appear on 367 // that list, if _free_regions_coming is set. 368 HeapRegion* new_region_try_secondary_free_list(bool is_old); 369 370 // Try to allocate a single non-humongous HeapRegion sufficient for 371 // an allocation of the given word_size. If do_expand is true, 372 // attempt to expand the heap if necessary to satisfy the allocation 373 // request. If the region is to be used as an old region or for a 374 // humongous object, set is_old to true. If not, to false. 375 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand); 376 377 // Initialize a contiguous set of free regions of length num_regions 378 // and starting at index first so that they appear as a single 379 // humongous region. 380 HeapWord* humongous_obj_allocate_initialize_regions(uint first, 381 uint num_regions, 382 size_t word_size, 383 AllocationContext_t context); 384 385 // Attempt to allocate a humongous object of the given size. Return 386 // NULL if unsuccessful. 387 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context); 388 389 // The following two methods, allocate_new_tlab() and 390 // mem_allocate(), are the two main entry points from the runtime 391 // into the G1's allocation routines. They have the following 392 // assumptions: 393 // 394 // * They should both be called outside safepoints. 395 // 396 // * They should both be called without holding the Heap_lock. 397 // 398 // * All allocation requests for new TLABs should go to 399 // allocate_new_tlab(). 400 // 401 // * All non-TLAB allocation requests should go to mem_allocate(). 402 // 403 // * If either call cannot satisfy the allocation request using the 404 // current allocating region, they will try to get a new one. If 405 // this fails, they will attempt to do an evacuation pause and 406 // retry the allocation. 407 // 408 // * If all allocation attempts fail, even after trying to schedule 409 // an evacuation pause, allocate_new_tlab() will return NULL, 410 // whereas mem_allocate() will attempt a heap expansion and/or 411 // schedule a Full GC. 412 // 413 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab 414 // should never be called with word_size being humongous. All 415 // humongous allocation requests should go to mem_allocate() which 416 // will satisfy them with a special path. 417 418 virtual HeapWord* allocate_new_tlab(size_t word_size); 419 420 virtual HeapWord* mem_allocate(size_t word_size, 421 bool* gc_overhead_limit_was_exceeded); 422 423 // The following three methods take a gc_count_before_ret 424 // parameter which is used to return the GC count if the method 425 // returns NULL. Given that we are required to read the GC count 426 // while holding the Heap_lock, and these paths will take the 427 // Heap_lock at some point, it's easier to get them to read the GC 428 // count while holding the Heap_lock before they return NULL instead 429 // of the caller (namely: mem_allocate()) having to also take the 430 // Heap_lock just to read the GC count. 431 432 // First-level mutator allocation attempt: try to allocate out of 433 // the mutator alloc region without taking the Heap_lock. This 434 // should only be used for non-humongous allocations. 435 inline HeapWord* attempt_allocation(size_t word_size, 436 uint* gc_count_before_ret, 437 uint* gclocker_retry_count_ret); 438 439 // Second-level mutator allocation attempt: take the Heap_lock and 440 // retry the allocation attempt, potentially scheduling a GC 441 // pause. This should only be used for non-humongous allocations. 442 HeapWord* attempt_allocation_slow(size_t word_size, 443 AllocationContext_t context, 444 uint* gc_count_before_ret, 445 uint* gclocker_retry_count_ret); 446 447 // Takes the Heap_lock and attempts a humongous allocation. It can 448 // potentially schedule a GC pause. 449 HeapWord* attempt_allocation_humongous(size_t word_size, 450 uint* gc_count_before_ret, 451 uint* gclocker_retry_count_ret); 452 453 // Allocation attempt that should be called during safepoints (e.g., 454 // at the end of a successful GC). expect_null_mutator_alloc_region 455 // specifies whether the mutator alloc region is expected to be NULL 456 // or not. 457 HeapWord* attempt_allocation_at_safepoint(size_t word_size, 458 AllocationContext_t context, 459 bool expect_null_mutator_alloc_region); 460 461 // These methods are the "callbacks" from the G1AllocRegion class. 462 463 // For mutator alloc regions. 464 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force); 465 void retire_mutator_alloc_region(HeapRegion* alloc_region, 466 size_t allocated_bytes); 467 468 // For GC alloc regions. 469 HeapRegion* new_gc_alloc_region(size_t word_size, uint count, 470 InCSetState dest); 471 void retire_gc_alloc_region(HeapRegion* alloc_region, 472 size_t allocated_bytes, InCSetState dest); 473 474 // - if explicit_gc is true, the GC is for a System.gc() etc, 475 // otherwise it's for a failed allocation. 476 // - if clear_all_soft_refs is true, all soft references should be 477 // cleared during the GC. 478 // - it returns false if it is unable to do the collection due to the 479 // GC locker being active, true otherwise. 480 bool do_full_collection(bool explicit_gc, 481 bool clear_all_soft_refs); 482 483 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread. 484 virtual void do_full_collection(bool clear_all_soft_refs); 485 486 // Resize the heap if necessary after a full collection. 487 void resize_if_necessary_after_full_collection(); 488 489 // Callback from VM_G1CollectForAllocation operation. 490 // This function does everything necessary/possible to satisfy a 491 // failed allocation request (including collection, expansion, etc.) 492 HeapWord* satisfy_failed_allocation(size_t word_size, 493 AllocationContext_t context, 494 bool* succeeded); 495 private: 496 // Helper method for satisfy_failed_allocation() 497 HeapWord* satisfy_failed_allocation_helper(size_t word_size, 498 AllocationContext_t context, 499 bool do_gc, 500 bool clear_all_soft_refs, 501 bool expect_null_mutator_alloc_region, 502 bool* gc_succeeded); 503 504 protected: 505 // Attempting to expand the heap sufficiently 506 // to support an allocation of the given "word_size". If 507 // successful, perform the allocation and return the address of the 508 // allocated block, or else "NULL". 509 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context); 510 511 // Process any reference objects discovered during 512 // an incremental evacuation pause. 513 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states); 514 515 // Enqueue any remaining discovered references 516 // after processing. 517 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states); 518 519 public: 520 WorkGang* workers() const { return _workers; } 521 522 G1Allocator* allocator() { 523 return _allocator; 524 } 525 526 G1MonitoringSupport* g1mm() { 527 assert(_g1mm != NULL, "should have been initialized"); 528 return _g1mm; 529 } 530 531 // Expand the garbage-first heap by at least the given size (in bytes!). 532 // Returns true if the heap was expanded by the requested amount; 533 // false otherwise. 534 // (Rounds up to a HeapRegion boundary.) 535 bool expand(size_t expand_bytes, double* expand_time_ms = NULL); 536 537 // Returns the PLAB statistics for a given destination. 538 inline G1EvacStats* alloc_buffer_stats(InCSetState dest); 539 540 // Determines PLAB size for a given destination. 541 inline size_t desired_plab_sz(InCSetState dest); 542 543 inline AllocationContextStats& allocation_context_stats(); 544 545 // Do anything common to GC's. 546 void gc_prologue(bool full); 547 void gc_epilogue(bool full); 548 549 // Modify the reclaim candidate set and test for presence. 550 // These are only valid for starts_humongous regions. 551 inline void set_humongous_reclaim_candidate(uint region, bool value); 552 inline bool is_humongous_reclaim_candidate(uint region); 553 554 // Remove from the reclaim candidate set. Also remove from the 555 // collection set so that later encounters avoid the slow path. 556 inline void set_humongous_is_live(oop obj); 557 558 // Register the given region to be part of the collection set. 559 inline void register_humongous_region_with_cset(uint index); 560 // Register regions with humongous objects (actually on the start region) in 561 // the in_cset_fast_test table. 562 void register_humongous_regions_with_cset(); 563 // We register a region with the fast "in collection set" test. We 564 // simply set to true the array slot corresponding to this region. 565 void register_young_region_with_cset(HeapRegion* r) { 566 _in_cset_fast_test.set_in_young(r->hrm_index()); 567 } 568 void register_old_region_with_cset(HeapRegion* r) { 569 _in_cset_fast_test.set_in_old(r->hrm_index()); 570 } 571 void clear_in_cset(const HeapRegion* hr) { 572 _in_cset_fast_test.clear(hr); 573 } 574 575 void clear_cset_fast_test() { 576 _in_cset_fast_test.clear(); 577 } 578 579 // This is called at the start of either a concurrent cycle or a Full 580 // GC to update the number of old marking cycles started. 581 void increment_old_marking_cycles_started(); 582 583 // This is called at the end of either a concurrent cycle or a Full 584 // GC to update the number of old marking cycles completed. Those two 585 // can happen in a nested fashion, i.e., we start a concurrent 586 // cycle, a Full GC happens half-way through it which ends first, 587 // and then the cycle notices that a Full GC happened and ends 588 // too. The concurrent parameter is a boolean to help us do a bit 589 // tighter consistency checking in the method. If concurrent is 590 // false, the caller is the inner caller in the nesting (i.e., the 591 // Full GC). If concurrent is true, the caller is the outer caller 592 // in this nesting (i.e., the concurrent cycle). Further nesting is 593 // not currently supported. The end of this call also notifies 594 // the FullGCCount_lock in case a Java thread is waiting for a full 595 // GC to happen (e.g., it called System.gc() with 596 // +ExplicitGCInvokesConcurrent). 597 void increment_old_marking_cycles_completed(bool concurrent); 598 599 uint old_marking_cycles_completed() { 600 return _old_marking_cycles_completed; 601 } 602 603 void register_concurrent_cycle_start(const Ticks& start_time); 604 void register_concurrent_cycle_end(); 605 void trace_heap_after_concurrent_cycle(); 606 607 G1HRPrinter* hr_printer() { return &_hr_printer; } 608 609 // Allocates a new heap region instance. 610 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr); 611 612 // Allocate the highest free region in the reserved heap. This will commit 613 // regions as necessary. 614 HeapRegion* alloc_highest_free_region(); 615 616 // Frees a non-humongous region by initializing its contents and 617 // adding it to the free list that's passed as a parameter (this is 618 // usually a local list which will be appended to the master free 619 // list later). The used bytes of freed regions are accumulated in 620 // pre_used. If par is true, the region's RSet will not be freed 621 // up. The assumption is that this will be done later. 622 // The locked parameter indicates if the caller has already taken 623 // care of proper synchronization. This may allow some optimizations. 624 void free_region(HeapRegion* hr, 625 FreeRegionList* free_list, 626 bool par, 627 bool locked = false); 628 629 // It dirties the cards that cover the block so that the post 630 // write barrier never queues anything when updating objects on this 631 // block. It is assumed (and in fact we assert) that the block 632 // belongs to a young region. 633 inline void dirty_young_block(HeapWord* start, size_t word_size); 634 635 // Frees a humongous region by collapsing it into individual regions 636 // and calling free_region() for each of them. The freed regions 637 // will be added to the free list that's passed as a parameter (this 638 // is usually a local list which will be appended to the master free 639 // list later). The used bytes of freed regions are accumulated in 640 // pre_used. If par is true, the region's RSet will not be freed 641 // up. The assumption is that this will be done later. 642 void free_humongous_region(HeapRegion* hr, 643 FreeRegionList* free_list, 644 bool par); 645 646 // Facility for allocating in 'archive' regions in high heap memory and 647 // recording the allocated ranges. These should all be called from the 648 // VM thread at safepoints, without the heap lock held. They can be used 649 // to create and archive a set of heap regions which can be mapped at the 650 // same fixed addresses in a subsequent JVM invocation. 651 void begin_archive_alloc_range(); 652 653 // Check if the requested size would be too large for an archive allocation. 654 bool is_archive_alloc_too_large(size_t word_size); 655 656 // Allocate memory of the requested size from the archive region. This will 657 // return NULL if the size is too large or if no memory is available. It 658 // does not trigger a garbage collection. 659 HeapWord* archive_mem_allocate(size_t word_size); 660 661 // Optionally aligns the end address and returns the allocated ranges in 662 // an array of MemRegions in order of ascending addresses. 663 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges, 664 size_t end_alignment_in_bytes = 0); 665 666 // Facility for allocating a fixed range within the heap and marking 667 // the containing regions as 'archive'. For use at JVM init time, when the 668 // caller may mmap archived heap data at the specified range(s). 669 // Verify that the MemRegions specified in the argument array are within the 670 // reserved heap. 671 bool check_archive_addresses(MemRegion* range, size_t count); 672 673 // Commit the appropriate G1 regions containing the specified MemRegions 674 // and mark them as 'archive' regions. The regions in the array must be 675 // non-overlapping and in order of ascending address. 676 bool alloc_archive_regions(MemRegion* range, size_t count); 677 678 // Insert any required filler objects in the G1 regions around the specified 679 // ranges to make the regions parseable. This must be called after 680 // alloc_archive_regions, and after class loading has occurred. 681 void fill_archive_regions(MemRegion* range, size_t count); 682 683 // For each of the specified MemRegions, uncommit the containing G1 regions 684 // which had been allocated by alloc_archive_regions. This should be called 685 // rather than fill_archive_regions at JVM init time if the archive file 686 // mapping failed, with the same non-overlapping and sorted MemRegion array. 687 void dealloc_archive_regions(MemRegion* range, size_t count); 688 689 protected: 690 691 // Shrink the garbage-first heap by at most the given size (in bytes!). 692 // (Rounds down to a HeapRegion boundary.) 693 virtual void shrink(size_t expand_bytes); 694 void shrink_helper(size_t expand_bytes); 695 696 #if TASKQUEUE_STATS 697 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); 698 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const; 699 void reset_taskqueue_stats(); 700 #endif // TASKQUEUE_STATS 701 702 // Schedule the VM operation that will do an evacuation pause to 703 // satisfy an allocation request of word_size. *succeeded will 704 // return whether the VM operation was successful (it did do an 705 // evacuation pause) or not (another thread beat us to it or the GC 706 // locker was active). Given that we should not be holding the 707 // Heap_lock when we enter this method, we will pass the 708 // gc_count_before (i.e., total_collections()) as a parameter since 709 // it has to be read while holding the Heap_lock. Currently, both 710 // methods that call do_collection_pause() release the Heap_lock 711 // before the call, so it's easy to read gc_count_before just before. 712 HeapWord* do_collection_pause(size_t word_size, 713 uint gc_count_before, 714 bool* succeeded, 715 GCCause::Cause gc_cause); 716 717 void wait_for_root_region_scanning(); 718 719 // The guts of the incremental collection pause, executed by the vm 720 // thread. It returns false if it is unable to do the collection due 721 // to the GC locker being active, true otherwise 722 bool do_collection_pause_at_safepoint(double target_pause_time_ms); 723 724 // Actually do the work of evacuating the collection set. 725 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states); 726 727 void pre_evacuate_collection_set(); 728 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss); 729 730 // Print the header for the per-thread termination statistics. 731 static void print_termination_stats_hdr(outputStream* const st); 732 // Print actual per-thread termination statistics. 733 void print_termination_stats(outputStream* const st, 734 uint worker_id, 735 double elapsed_ms, 736 double strong_roots_ms, 737 double term_ms, 738 size_t term_attempts, 739 size_t alloc_buffer_waste, 740 size_t undo_waste) const; 741 // Update object copying statistics. 742 void record_obj_copy_mem_stats(); 743 744 // The g1 remembered set of the heap. 745 G1RemSet* _g1_rem_set; 746 747 // A set of cards that cover the objects for which the Rsets should be updated 748 // concurrently after the collection. 749 DirtyCardQueueSet _dirty_card_queue_set; 750 751 // The closure used to refine a single card. 752 RefineCardTableEntryClosure* _refine_cte_cl; 753 754 // After a collection pause, make the regions in the CS into free 755 // regions. 756 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words); 757 758 // Abandon the current collection set without recording policy 759 // statistics or updating free lists. 760 void abandon_collection_set(HeapRegion* cs_head); 761 762 // The concurrent marker (and the thread it runs in.) 763 ConcurrentMark* _cm; 764 ConcurrentMarkThread* _cmThread; 765 766 // The concurrent refiner. 767 ConcurrentG1Refine* _cg1r; 768 769 // The parallel task queues 770 RefToScanQueueSet *_task_queues; 771 772 // True iff a evacuation has failed in the current collection. 773 bool _evacuation_failed; 774 775 EvacuationFailedInfo* _evacuation_failed_info_array; 776 777 // Failed evacuations cause some logical from-space objects to have 778 // forwarding pointers to themselves. Reset them. 779 void remove_self_forwarding_pointers(); 780 781 struct OopAndMarkOop { 782 private: 783 oop _o; 784 markOop _m; 785 public: 786 OopAndMarkOop(oop obj, markOop m) : _o(obj), _m(m) { 787 } 788 789 void set_mark() { 790 _o->set_mark(_m); 791 } 792 }; 793 794 typedef Stack<OopAndMarkOop,mtGC> OopAndMarkOopStack; 795 // Stores marks with the corresponding oop that we need to preserve during evacuation 796 // failure. 797 OopAndMarkOopStack* _preserved_objs; 798 799 // Preserve the mark of "obj", if necessary, in preparation for its mark 800 // word being overwritten with a self-forwarding-pointer. 801 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m); 802 803 #ifndef PRODUCT 804 // Support for forcing evacuation failures. Analogous to 805 // PromotionFailureALot for the other collectors. 806 807 // Records whether G1EvacuationFailureALot should be in effect 808 // for the current GC 809 bool _evacuation_failure_alot_for_current_gc; 810 811 // Used to record the GC number for interval checking when 812 // determining whether G1EvaucationFailureALot is in effect 813 // for the current GC. 814 size_t _evacuation_failure_alot_gc_number; 815 816 // Count of the number of evacuations between failures. 817 volatile size_t _evacuation_failure_alot_count; 818 819 // Set whether G1EvacuationFailureALot should be in effect 820 // for the current GC (based upon the type of GC and which 821 // command line flags are set); 822 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young, 823 bool during_initial_mark, 824 bool during_marking); 825 826 inline void set_evacuation_failure_alot_for_current_gc(); 827 828 // Return true if it's time to cause an evacuation failure. 829 inline bool evacuation_should_fail(); 830 831 // Reset the G1EvacuationFailureALot counters. Should be called at 832 // the end of an evacuation pause in which an evacuation failure occurred. 833 inline void reset_evacuation_should_fail(); 834 #endif // !PRODUCT 835 836 // ("Weak") Reference processing support. 837 // 838 // G1 has 2 instances of the reference processor class. One 839 // (_ref_processor_cm) handles reference object discovery 840 // and subsequent processing during concurrent marking cycles. 841 // 842 // The other (_ref_processor_stw) handles reference object 843 // discovery and processing during full GCs and incremental 844 // evacuation pauses. 845 // 846 // During an incremental pause, reference discovery will be 847 // temporarily disabled for _ref_processor_cm and will be 848 // enabled for _ref_processor_stw. At the end of the evacuation 849 // pause references discovered by _ref_processor_stw will be 850 // processed and discovery will be disabled. The previous 851 // setting for reference object discovery for _ref_processor_cm 852 // will be re-instated. 853 // 854 // At the start of marking: 855 // * Discovery by the CM ref processor is verified to be inactive 856 // and it's discovered lists are empty. 857 // * Discovery by the CM ref processor is then enabled. 858 // 859 // At the end of marking: 860 // * Any references on the CM ref processor's discovered 861 // lists are processed (possibly MT). 862 // 863 // At the start of full GC we: 864 // * Disable discovery by the CM ref processor and 865 // empty CM ref processor's discovered lists 866 // (without processing any entries). 867 // * Verify that the STW ref processor is inactive and it's 868 // discovered lists are empty. 869 // * Temporarily set STW ref processor discovery as single threaded. 870 // * Temporarily clear the STW ref processor's _is_alive_non_header 871 // field. 872 // * Finally enable discovery by the STW ref processor. 873 // 874 // The STW ref processor is used to record any discovered 875 // references during the full GC. 876 // 877 // At the end of a full GC we: 878 // * Enqueue any reference objects discovered by the STW ref processor 879 // that have non-live referents. This has the side-effect of 880 // making the STW ref processor inactive by disabling discovery. 881 // * Verify that the CM ref processor is still inactive 882 // and no references have been placed on it's discovered 883 // lists (also checked as a precondition during initial marking). 884 885 // The (stw) reference processor... 886 ReferenceProcessor* _ref_processor_stw; 887 888 STWGCTimer* _gc_timer_stw; 889 ConcurrentGCTimer* _gc_timer_cm; 890 891 G1OldTracer* _gc_tracer_cm; 892 G1NewTracer* _gc_tracer_stw; 893 894 // During reference object discovery, the _is_alive_non_header 895 // closure (if non-null) is applied to the referent object to 896 // determine whether the referent is live. If so then the 897 // reference object does not need to be 'discovered' and can 898 // be treated as a regular oop. This has the benefit of reducing 899 // the number of 'discovered' reference objects that need to 900 // be processed. 901 // 902 // Instance of the is_alive closure for embedding into the 903 // STW reference processor as the _is_alive_non_header field. 904 // Supplying a value for the _is_alive_non_header field is 905 // optional but doing so prevents unnecessary additions to 906 // the discovered lists during reference discovery. 907 G1STWIsAliveClosure _is_alive_closure_stw; 908 909 // The (concurrent marking) reference processor... 910 ReferenceProcessor* _ref_processor_cm; 911 912 // Instance of the concurrent mark is_alive closure for embedding 913 // into the Concurrent Marking reference processor as the 914 // _is_alive_non_header field. Supplying a value for the 915 // _is_alive_non_header field is optional but doing so prevents 916 // unnecessary additions to the discovered lists during reference 917 // discovery. 918 G1CMIsAliveClosure _is_alive_closure_cm; 919 920 // Cache used by G1CollectedHeap::start_cset_region_for_worker(). 921 HeapRegion** _worker_cset_start_region; 922 923 // Time stamp to validate the regions recorded in the cache 924 // used by G1CollectedHeap::start_cset_region_for_worker(). 925 // The heap region entry for a given worker is valid iff 926 // the associated time stamp value matches the current value 927 // of G1CollectedHeap::_gc_time_stamp. 928 uint* _worker_cset_start_region_time_stamp; 929 930 volatile bool _free_regions_coming; 931 932 public: 933 934 void set_refine_cte_cl_concurrency(bool concurrent); 935 936 RefToScanQueue *task_queue(uint i) const; 937 938 uint num_task_queues() const; 939 940 // A set of cards where updates happened during the GC 941 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; } 942 943 // Create a G1CollectedHeap with the specified policy. 944 // Must call the initialize method afterwards. 945 // May not return if something goes wrong. 946 G1CollectedHeap(G1CollectorPolicy* policy); 947 948 // Initialize the G1CollectedHeap to have the initial and 949 // maximum sizes and remembered and barrier sets 950 // specified by the policy object. 951 jint initialize(); 952 953 virtual void stop(); 954 955 // Return the (conservative) maximum heap alignment for any G1 heap 956 static size_t conservative_max_heap_alignment(); 957 958 // Does operations required after initialization has been done. 959 void post_initialize(); 960 961 // Initialize weak reference processing. 962 void ref_processing_init(); 963 964 virtual Name kind() const { 965 return CollectedHeap::G1CollectedHeap; 966 } 967 968 const G1CollectorState* collector_state() const { return &_collector_state; } 969 G1CollectorState* collector_state() { return &_collector_state; } 970 971 // The current policy object for the collector. 972 G1CollectorPolicy* g1_policy() const { return _g1_policy; } 973 974 virtual CollectorPolicy* collector_policy() const; 975 976 // Adaptive size policy. No such thing for g1. 977 virtual AdaptiveSizePolicy* size_policy() { return NULL; } 978 979 // The rem set and barrier set. 980 G1RemSet* g1_rem_set() const { return _g1_rem_set; } 981 982 unsigned get_gc_time_stamp() { 983 return _gc_time_stamp; 984 } 985 986 inline void reset_gc_time_stamp(); 987 988 void check_gc_time_stamps() PRODUCT_RETURN; 989 990 inline void increment_gc_time_stamp(); 991 992 // Reset the given region's GC timestamp. If it's starts humongous, 993 // also reset the GC timestamp of its corresponding 994 // continues humongous regions too. 995 void reset_gc_time_stamps(HeapRegion* hr); 996 997 // Apply the given closure on all cards in the Hot Card Cache, emptying it. 998 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i); 999 1000 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it. 1001 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i); 1002 1003 // The shared block offset table array. 1004 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; } 1005 1006 // Reference Processing accessors 1007 1008 // The STW reference processor.... 1009 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; } 1010 1011 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; } 1012 1013 // The Concurrent Marking reference processor... 1014 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; } 1015 1016 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 1017 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 1018 1019 virtual size_t capacity() const; 1020 virtual size_t used() const; 1021 // This should be called when we're not holding the heap lock. The 1022 // result might be a bit inaccurate. 1023 size_t used_unlocked() const; 1024 size_t recalculate_used() const; 1025 1026 // These virtual functions do the actual allocation. 1027 // Some heaps may offer a contiguous region for shared non-blocking 1028 // allocation, via inlined code (by exporting the address of the top and 1029 // end fields defining the extent of the contiguous allocation region.) 1030 // But G1CollectedHeap doesn't yet support this. 1031 1032 virtual bool is_maximal_no_gc() const { 1033 return _hrm.available() == 0; 1034 } 1035 1036 // The current number of regions in the heap. 1037 uint num_regions() const { return _hrm.length(); } 1038 1039 // The max number of regions in the heap. 1040 uint max_regions() const { return _hrm.max_length(); } 1041 1042 // The number of regions that are completely free. 1043 uint num_free_regions() const { return _hrm.num_free_regions(); } 1044 1045 MemoryUsage get_auxiliary_data_memory_usage() const { 1046 return _hrm.get_auxiliary_data_memory_usage(); 1047 } 1048 1049 // The number of regions that are not completely free. 1050 uint num_used_regions() const { return num_regions() - num_free_regions(); } 1051 1052 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1053 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN; 1054 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN; 1055 void verify_dirty_young_regions() PRODUCT_RETURN; 1056 1057 #ifndef PRODUCT 1058 // Make sure that the given bitmap has no marked objects in the 1059 // range [from,limit). If it does, print an error message and return 1060 // false. Otherwise, just return true. bitmap_name should be "prev" 1061 // or "next". 1062 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap, 1063 HeapWord* from, HeapWord* limit); 1064 1065 // Verify that the prev / next bitmap range [tams,end) for the given 1066 // region has no marks. Return true if all is well, false if errors 1067 // are detected. 1068 bool verify_bitmaps(const char* caller, HeapRegion* hr); 1069 #endif // PRODUCT 1070 1071 // If G1VerifyBitmaps is set, verify that the marking bitmaps for 1072 // the given region do not have any spurious marks. If errors are 1073 // detected, print appropriate error messages and crash. 1074 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN; 1075 1076 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not 1077 // have any spurious marks. If errors are detected, print 1078 // appropriate error messages and crash. 1079 void check_bitmaps(const char* caller) PRODUCT_RETURN; 1080 1081 // Do sanity check on the contents of the in-cset fast test table. 1082 bool check_cset_fast_test() PRODUCT_RETURN_( return true; ); 1083 1084 // verify_region_sets() performs verification over the region 1085 // lists. It will be compiled in the product code to be used when 1086 // necessary (i.e., during heap verification). 1087 void verify_region_sets(); 1088 1089 // verify_region_sets_optional() is planted in the code for 1090 // list verification in non-product builds (and it can be enabled in 1091 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1). 1092 #if HEAP_REGION_SET_FORCE_VERIFY 1093 void verify_region_sets_optional() { 1094 verify_region_sets(); 1095 } 1096 #else // HEAP_REGION_SET_FORCE_VERIFY 1097 void verify_region_sets_optional() { } 1098 #endif // HEAP_REGION_SET_FORCE_VERIFY 1099 1100 #ifdef ASSERT 1101 bool is_on_master_free_list(HeapRegion* hr) { 1102 return _hrm.is_free(hr); 1103 } 1104 #endif // ASSERT 1105 1106 // Wrapper for the region list operations that can be called from 1107 // methods outside this class. 1108 1109 void secondary_free_list_add(FreeRegionList* list) { 1110 _secondary_free_list.add_ordered(list); 1111 } 1112 1113 void append_secondary_free_list() { 1114 _hrm.insert_list_into_free_list(&_secondary_free_list); 1115 } 1116 1117 void append_secondary_free_list_if_not_empty_with_lock() { 1118 // If the secondary free list looks empty there's no reason to 1119 // take the lock and then try to append it. 1120 if (!_secondary_free_list.is_empty()) { 1121 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1122 append_secondary_free_list(); 1123 } 1124 } 1125 1126 inline void old_set_add(HeapRegion* hr); 1127 inline void old_set_remove(HeapRegion* hr); 1128 1129 size_t non_young_capacity_bytes() { 1130 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes(); 1131 } 1132 1133 void set_free_regions_coming(); 1134 void reset_free_regions_coming(); 1135 bool free_regions_coming() { return _free_regions_coming; } 1136 void wait_while_free_regions_coming(); 1137 1138 // Determine whether the given region is one that we are using as an 1139 // old GC alloc region. 1140 bool is_old_gc_alloc_region(HeapRegion* hr); 1141 1142 // Perform a collection of the heap; intended for use in implementing 1143 // "System.gc". This probably implies as full a collection as the 1144 // "CollectedHeap" supports. 1145 virtual void collect(GCCause::Cause cause); 1146 1147 virtual bool copy_allocation_context_stats(const jint* contexts, 1148 jlong* totals, 1149 jbyte* accuracy, 1150 jint len); 1151 1152 // True iff an evacuation has failed in the most-recent collection. 1153 bool evacuation_failed() { return _evacuation_failed; } 1154 1155 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed); 1156 void prepend_to_freelist(FreeRegionList* list); 1157 void decrement_summary_bytes(size_t bytes); 1158 1159 virtual bool is_in(const void* p) const; 1160 #ifdef ASSERT 1161 // Returns whether p is in one of the available areas of the heap. Slow but 1162 // extensive version. 1163 bool is_in_exact(const void* p) const; 1164 #endif 1165 1166 // Return "TRUE" iff the given object address is within the collection 1167 // set. Slow implementation. 1168 bool obj_in_cs(oop obj); 1169 1170 inline bool is_in_cset(const HeapRegion *hr); 1171 inline bool is_in_cset(oop obj); 1172 1173 inline bool is_in_cset_or_humongous(const oop obj); 1174 1175 private: 1176 // This array is used for a quick test on whether a reference points into 1177 // the collection set or not. Each of the array's elements denotes whether the 1178 // corresponding region is in the collection set or not. 1179 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test; 1180 1181 public: 1182 1183 inline InCSetState in_cset_state(const oop obj); 1184 1185 // Return "TRUE" iff the given object address is in the reserved 1186 // region of g1. 1187 bool is_in_g1_reserved(const void* p) const { 1188 return _hrm.reserved().contains(p); 1189 } 1190 1191 // Returns a MemRegion that corresponds to the space that has been 1192 // reserved for the heap 1193 MemRegion g1_reserved() const { 1194 return _hrm.reserved(); 1195 } 1196 1197 virtual bool is_in_closed_subset(const void* p) const; 1198 1199 G1SATBCardTableLoggingModRefBS* g1_barrier_set() { 1200 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set()); 1201 } 1202 1203 // This resets the card table to all zeros. It is used after 1204 // a collection pause which used the card table to claim cards. 1205 void cleanUpCardTable(); 1206 1207 // Iteration functions. 1208 1209 // Iterate over all objects, calling "cl.do_object" on each. 1210 virtual void object_iterate(ObjectClosure* cl); 1211 1212 virtual void safe_object_iterate(ObjectClosure* cl) { 1213 object_iterate(cl); 1214 } 1215 1216 // Iterate over heap regions, in address order, terminating the 1217 // iteration early if the "doHeapRegion" method returns "true". 1218 void heap_region_iterate(HeapRegionClosure* blk) const; 1219 1220 // Return the region with the given index. It assumes the index is valid. 1221 inline HeapRegion* region_at(uint index) const; 1222 1223 // Return the next region (by index) that is part of the same 1224 // humongous object that hr is part of. 1225 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const; 1226 1227 // Calculate the region index of the given address. Given address must be 1228 // within the heap. 1229 inline uint addr_to_region(HeapWord* addr) const; 1230 1231 inline HeapWord* bottom_addr_for_region(uint index) const; 1232 1233 // Iterate over the heap regions in parallel. Assumes that this will be called 1234 // in parallel by ParallelGCThreads worker threads with distinct worker ids 1235 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion" 1236 // to each of the regions, by attempting to claim the region using the 1237 // HeapRegionClaimer and, if successful, applying the closure to the claimed 1238 // region. The concurrent argument should be set to true if iteration is 1239 // performed concurrently, during which no assumptions are made for consistent 1240 // attributes of the heap regions (as they might be modified while iterating). 1241 void heap_region_par_iterate(HeapRegionClosure* cl, 1242 uint worker_id, 1243 HeapRegionClaimer* hrclaimer, 1244 bool concurrent = false) const; 1245 1246 // Clear the cached cset start regions and (more importantly) 1247 // the time stamps. Called when we reset the GC time stamp. 1248 void clear_cset_start_regions(); 1249 1250 // Given the id of a worker, obtain or calculate a suitable 1251 // starting region for iterating over the current collection set. 1252 HeapRegion* start_cset_region_for_worker(uint worker_i); 1253 1254 // Iterate over the regions (if any) in the current collection set. 1255 void collection_set_iterate(HeapRegionClosure* blk); 1256 1257 // As above but starting from region r 1258 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk); 1259 1260 HeapRegion* next_compaction_region(const HeapRegion* from) const; 1261 1262 // Returns the HeapRegion that contains addr. addr must not be NULL. 1263 template <class T> 1264 inline HeapRegion* heap_region_containing(const T addr) const; 1265 1266 // A CollectedHeap is divided into a dense sequence of "blocks"; that is, 1267 // each address in the (reserved) heap is a member of exactly 1268 // one block. The defining characteristic of a block is that it is 1269 // possible to find its size, and thus to progress forward to the next 1270 // block. (Blocks may be of different sizes.) Thus, blocks may 1271 // represent Java objects, or they might be free blocks in a 1272 // free-list-based heap (or subheap), as long as the two kinds are 1273 // distinguishable and the size of each is determinable. 1274 1275 // Returns the address of the start of the "block" that contains the 1276 // address "addr". We say "blocks" instead of "object" since some heaps 1277 // may not pack objects densely; a chunk may either be an object or a 1278 // non-object. 1279 virtual HeapWord* block_start(const void* addr) const; 1280 1281 // Requires "addr" to be the start of a chunk, and returns its size. 1282 // "addr + size" is required to be the start of a new chunk, or the end 1283 // of the active area of the heap. 1284 virtual size_t block_size(const HeapWord* addr) const; 1285 1286 // Requires "addr" to be the start of a block, and returns "TRUE" iff 1287 // the block is an object. 1288 virtual bool block_is_obj(const HeapWord* addr) const; 1289 1290 // Section on thread-local allocation buffers (TLABs) 1291 // See CollectedHeap for semantics. 1292 1293 bool supports_tlab_allocation() const; 1294 size_t tlab_capacity(Thread* ignored) const; 1295 size_t tlab_used(Thread* ignored) const; 1296 size_t max_tlab_size() const; 1297 size_t unsafe_max_tlab_alloc(Thread* ignored) const; 1298 1299 // Can a compiler initialize a new object without store barriers? 1300 // This permission only extends from the creation of a new object 1301 // via a TLAB up to the first subsequent safepoint. If such permission 1302 // is granted for this heap type, the compiler promises to call 1303 // defer_store_barrier() below on any slow path allocation of 1304 // a new object for which such initializing store barriers will 1305 // have been elided. G1, like CMS, allows this, but should be 1306 // ready to provide a compensating write barrier as necessary 1307 // if that storage came out of a non-young region. The efficiency 1308 // of this implementation depends crucially on being able to 1309 // answer very efficiently in constant time whether a piece of 1310 // storage in the heap comes from a young region or not. 1311 // See ReduceInitialCardMarks. 1312 virtual bool can_elide_tlab_store_barriers() const { 1313 return true; 1314 } 1315 1316 virtual bool card_mark_must_follow_store() const { 1317 return true; 1318 } 1319 1320 inline bool is_in_young(const oop obj); 1321 1322 virtual bool is_scavengable(const void* addr); 1323 1324 // We don't need barriers for initializing stores to objects 1325 // in the young gen: for the SATB pre-barrier, there is no 1326 // pre-value that needs to be remembered; for the remembered-set 1327 // update logging post-barrier, we don't maintain remembered set 1328 // information for young gen objects. 1329 virtual inline bool can_elide_initializing_store_barrier(oop new_obj); 1330 1331 // Returns "true" iff the given word_size is "very large". 1332 static bool is_humongous(size_t word_size) { 1333 // Note this has to be strictly greater-than as the TLABs 1334 // are capped at the humongous threshold and we want to 1335 // ensure that we don't try to allocate a TLAB as 1336 // humongous and that we don't allocate a humongous 1337 // object in a TLAB. 1338 return word_size > _humongous_object_threshold_in_words; 1339 } 1340 1341 // Returns the humongous threshold for a specific region size 1342 static size_t humongous_threshold_for(size_t region_size) { 1343 return (region_size / 2); 1344 } 1345 1346 // Returns the number of regions the humongous object of the given word size 1347 // requires. 1348 static size_t humongous_obj_size_in_regions(size_t word_size); 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