1 /* 2 * Copyright (c) 2001, 2020, 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_GC_G1_G1CONCURRENTMARK_HPP 26 #define SHARE_GC_G1_G1CONCURRENTMARK_HPP 27 28 #include "gc/g1/g1ConcurrentMarkBitMap.hpp" 29 #include "gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp" 30 #include "gc/g1/g1HeapVerifier.hpp" 31 #include "gc/g1/g1RegionMarkStatsCache.hpp" 32 #include "gc/g1/heapRegionSet.hpp" 33 #include "gc/shared/gcCause.hpp" 34 #include "gc/shared/taskTerminator.hpp" 35 #include "gc/shared/taskqueue.hpp" 36 #include "gc/shared/verifyOption.hpp" 37 #include "gc/shared/workgroup.hpp" 38 #include "memory/allocation.hpp" 39 #include "utilities/compilerWarnings.hpp" 40 #include "utilities/numberSeq.hpp" 41 42 class ConcurrentGCTimer; 43 class G1ConcurrentMarkThread; 44 class G1CollectedHeap; 45 class G1CMOopClosure; 46 class G1CMTask; 47 class G1ConcurrentMark; 48 class G1OldTracer; 49 class G1RegionToSpaceMapper; 50 class G1SurvivorRegions; 51 class ThreadClosure; 52 53 PRAGMA_DIAG_PUSH 54 // warning C4522: multiple assignment operators specified 55 PRAGMA_DISABLE_MSVC_WARNING(4522) 56 57 // This is a container class for either an oop or a continuation address for 58 // mark stack entries. Both are pushed onto the mark stack. 59 class G1TaskQueueEntry { 60 private: 61 void* _holder; 62 63 static const uintptr_t ArraySliceBit = 1; 64 65 G1TaskQueueEntry(oop obj) : _holder(obj) { 66 assert(_holder != NULL, "Not allowed to set NULL task queue element"); 67 } 68 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { } 69 public: 70 71 G1TaskQueueEntry() : _holder(NULL) { } 72 // Trivially copyable, for use in GenericTaskQueue. 73 74 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); } 75 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); } 76 77 oop obj() const { 78 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder)); 79 return (oop)_holder; 80 } 81 82 HeapWord* slice() const { 83 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder)); 84 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit); 85 } 86 87 bool is_oop() const { return !is_array_slice(); } 88 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; } 89 bool is_null() const { return _holder == NULL; } 90 }; 91 92 PRAGMA_DIAG_POP 93 94 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue; 95 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet; 96 97 // Closure used by CM during concurrent reference discovery 98 // and reference processing (during remarking) to determine 99 // if a particular object is alive. It is primarily used 100 // to determine if referents of discovered reference objects 101 // are alive. An instance is also embedded into the 102 // reference processor as the _is_alive_non_header field 103 class G1CMIsAliveClosure : public BoolObjectClosure { 104 G1CollectedHeap* _g1h; 105 public: 106 G1CMIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 107 bool do_object_b(oop obj); 108 }; 109 110 class G1CMSubjectToDiscoveryClosure : public BoolObjectClosure { 111 G1CollectedHeap* _g1h; 112 public: 113 G1CMSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 114 bool do_object_b(oop obj); 115 }; 116 117 // Represents the overflow mark stack used by concurrent marking. 118 // 119 // Stores oops in a huge buffer in virtual memory that is always fully committed. 120 // Resizing may only happen during a STW pause when the stack is empty. 121 // 122 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark 123 // stack memory is split into evenly sized chunks of oops. Users can only 124 // add or remove entries on that basis. 125 // Chunks are filled in increasing address order. Not completely filled chunks 126 // have a NULL element as a terminating element. 127 // 128 // Every chunk has a header containing a single pointer element used for memory 129 // management. This wastes some space, but is negligible (< .1% with current sizing). 130 // 131 // Memory management is done using a mix of tracking a high water-mark indicating 132 // that all chunks at a lower address are valid chunks, and a singly linked free 133 // list connecting all empty chunks. 134 class G1CMMarkStack { 135 public: 136 // Number of TaskQueueEntries that can fit in a single chunk. 137 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */; 138 private: 139 struct TaskQueueEntryChunk { 140 TaskQueueEntryChunk* next; 141 G1TaskQueueEntry data[EntriesPerChunk]; 142 }; 143 144 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack. 145 146 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area. 147 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements. 148 149 char _pad0[DEFAULT_CACHE_LINE_SIZE]; 150 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users. 151 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)]; 152 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data. 153 volatile size_t _chunks_in_chunk_list; 154 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)]; 155 156 volatile size_t _hwm; // High water mark within the reserved space. 157 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)]; 158 159 // Allocate a new chunk from the reserved memory, using the high water mark. Returns 160 // NULL if out of memory. 161 TaskQueueEntryChunk* allocate_new_chunk(); 162 163 // Atomically add the given chunk to the list. 164 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem); 165 // Atomically remove and return a chunk from the given list. Returns NULL if the 166 // list is empty. 167 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list); 168 169 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem); 170 void add_chunk_to_free_list(TaskQueueEntryChunk* elem); 171 172 TaskQueueEntryChunk* remove_chunk_from_chunk_list(); 173 TaskQueueEntryChunk* remove_chunk_from_free_list(); 174 175 // Resizes the mark stack to the given new capacity. Releases any previous 176 // memory if successful. 177 bool resize(size_t new_capacity); 178 179 public: 180 G1CMMarkStack(); 181 ~G1CMMarkStack(); 182 183 // Alignment and minimum capacity of this mark stack in number of oops. 184 static size_t capacity_alignment(); 185 186 // Allocate and initialize the mark stack with the given number of oops. 187 bool initialize(size_t initial_capacity, size_t max_capacity); 188 189 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark 190 // stack. If less than EntriesPerChunk elements are to be pushed, the array must 191 // be terminated with a NULL. 192 // Returns whether the buffer contents were successfully pushed to the global mark 193 // stack. 194 bool par_push_chunk(G1TaskQueueEntry* buffer); 195 196 // Pops a chunk from this mark stack, copying them into the given buffer. This 197 // chunk may contain up to EntriesPerChunk elements. If there are less, the last 198 // element in the array is a NULL pointer. 199 bool par_pop_chunk(G1TaskQueueEntry* buffer); 200 201 // Return whether the chunk list is empty. Racy due to unsynchronized access to 202 // _chunk_list. 203 bool is_empty() const { return _chunk_list == NULL; } 204 205 size_t capacity() const { return _chunk_capacity; } 206 207 // Expand the stack, typically in response to an overflow condition 208 void expand(); 209 210 // Return the approximate number of oops on this mark stack. Racy due to 211 // unsynchronized access to _chunks_in_chunk_list. 212 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; } 213 214 void set_empty(); 215 216 // Apply Fn to every oop on the mark stack. The mark stack must not 217 // be modified while iterating. 218 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN; 219 }; 220 221 // Root MemRegions are memory areas that contain objects which references are 222 // roots wrt to the marking. They must be scanned before marking to maintain the 223 // SATB invariant. 224 // Typically they contain the areas from nTAMS to top of the regions. 225 // We could scan and mark through these objects during the concurrent start pause, 226 // but for pause time reasons we move this work to the concurrent phase. 227 // We need to complete this procedure before the next GC because it might determine 228 // that some of these "root objects" are dead, potentially dropping some required 229 // references. 230 // Root MemRegions comprise of the contents of survivor regions at the end 231 // of the GC, and any objects copied into the old gen during GC. 232 class G1CMRootMemRegions { 233 // The set of root MemRegions. 234 MemRegion* _root_regions; 235 size_t const _max_regions; 236 237 volatile size_t _num_root_regions; // Actual number of root regions. 238 239 volatile size_t _claimed_root_regions; // Number of root regions currently claimed. 240 241 volatile bool _scan_in_progress; 242 volatile bool _should_abort; 243 244 void notify_scan_done(); 245 246 public: 247 G1CMRootMemRegions(uint const max_regions); 248 ~G1CMRootMemRegions(); 249 250 // Reset the data structure to allow addition of new root regions. 251 void reset(); 252 253 void add(HeapWord* start, HeapWord* end); 254 255 // Reset the claiming / scanning of the root regions. 256 void prepare_for_scan(); 257 258 // Forces get_next() to return NULL so that the iteration aborts early. 259 void abort() { _should_abort = true; } 260 261 // Return true if the CM thread are actively scanning root regions, 262 // false otherwise. 263 bool scan_in_progress() { return _scan_in_progress; } 264 265 // Claim the next root MemRegion to scan atomically, or return NULL if 266 // all have been claimed. 267 const MemRegion* claim_next(); 268 269 // The number of root regions to scan. 270 uint num_root_regions() const; 271 272 void cancel_scan(); 273 274 // Flag that we're done with root region scanning and notify anyone 275 // who's waiting on it. If aborted is false, assume that all regions 276 // have been claimed. 277 void scan_finished(); 278 279 // If CM threads are still scanning root regions, wait until they 280 // are done. Return true if we had to wait, false otherwise. 281 bool wait_until_scan_finished(); 282 }; 283 284 // This class manages data structures and methods for doing liveness analysis in 285 // G1's concurrent cycle. 286 class G1ConcurrentMark : public CHeapObj<mtGC> { 287 friend class G1ConcurrentMarkThread; 288 friend class G1CMRefProcTaskProxy; 289 friend class G1CMRefProcTaskExecutor; 290 friend class G1CMKeepAliveAndDrainClosure; 291 friend class G1CMDrainMarkingStackClosure; 292 friend class G1CMBitMapClosure; 293 friend class G1CMConcurrentMarkingTask; 294 friend class G1CMRemarkTask; 295 friend class G1CMTask; 296 297 G1ConcurrentMarkThread* _cm_thread; // The thread doing the work 298 G1CollectedHeap* _g1h; // The heap 299 300 // Concurrent marking support structures 301 G1CMBitMap _mark_bitmap_1; 302 G1CMBitMap _mark_bitmap_2; 303 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap 304 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap 305 306 // Heap bounds 307 MemRegion const _heap; 308 309 // Root region tracking and claiming 310 G1CMRootMemRegions _root_regions; 311 312 // For grey objects 313 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger 314 HeapWord* volatile _finger; // The global finger, region aligned, 315 // always pointing to the end of the 316 // last claimed region 317 318 uint _worker_id_offset; 319 uint _max_num_tasks; // Maximum number of marking tasks 320 uint _num_active_tasks; // Number of tasks currently active 321 G1CMTask** _tasks; // Task queue array (max_worker_id length) 322 323 G1CMTaskQueueSet* _task_queues; // Task queue set 324 TaskTerminator _terminator; // For termination 325 326 // Two sync barriers that are used to synchronize tasks when an 327 // overflow occurs. The algorithm is the following. All tasks enter 328 // the first one to ensure that they have all stopped manipulating 329 // the global data structures. After they exit it, they re-initialize 330 // their data structures and task 0 re-initializes the global data 331 // structures. Then, they enter the second sync barrier. This 332 // ensure, that no task starts doing work before all data 333 // structures (local and global) have been re-initialized. When they 334 // exit it, they are free to start working again. 335 WorkGangBarrierSync _first_overflow_barrier_sync; 336 WorkGangBarrierSync _second_overflow_barrier_sync; 337 338 // This is set by any task, when an overflow on the global data 339 // structures is detected 340 volatile bool _has_overflown; 341 // True: marking is concurrent, false: we're in remark 342 volatile bool _concurrent; 343 // Set at the end of a Full GC so that marking aborts 344 volatile bool _has_aborted; 345 346 // Used when remark aborts due to an overflow to indicate that 347 // another concurrent marking phase should start 348 volatile bool _restart_for_overflow; 349 350 ConcurrentGCTimer* _gc_timer_cm; 351 352 G1OldTracer* _gc_tracer_cm; 353 354 // Timing statistics. All of them are in ms 355 NumberSeq _init_times; 356 NumberSeq _remark_times; 357 NumberSeq _remark_mark_times; 358 NumberSeq _remark_weak_ref_times; 359 NumberSeq _cleanup_times; 360 double _total_cleanup_time; 361 362 double* _accum_task_vtime; // Accumulated task vtime 363 364 WorkGang* _concurrent_workers; 365 uint _num_concurrent_workers; // The number of marking worker threads we're using 366 uint _max_concurrent_workers; // Maximum number of marking worker threads 367 368 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller); 369 370 void finalize_marking(); 371 372 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes); 373 void weak_refs_work(bool clear_all_soft_refs); 374 375 void report_object_count(bool mark_completed); 376 377 void swap_mark_bitmaps(); 378 379 void reclaim_empty_regions(); 380 381 // After reclaiming empty regions, update heap sizes. 382 void compute_new_sizes(); 383 384 // Clear statistics gathered during the concurrent cycle for the given region after 385 // it has been reclaimed. 386 void clear_statistics(HeapRegion* r); 387 388 // Resets the global marking data structures, as well as the 389 // task local ones; should be called during concurrent start. 390 void reset(); 391 392 // Resets all the marking data structures. Called when we have to restart 393 // marking or when marking completes (via set_non_marking_state below). 394 void reset_marking_for_restart(); 395 396 // We do this after we're done with marking so that the marking data 397 // structures are initialized to a sensible and predictable state. 398 void reset_at_marking_complete(); 399 400 // Called to indicate how many threads are currently active. 401 void set_concurrency(uint active_tasks); 402 403 // Should be called to indicate which phase we're in (concurrent 404 // mark or remark) and how many threads are currently active. 405 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 406 407 // Prints all gathered CM-related statistics 408 void print_stats(); 409 410 HeapWord* finger() { return _finger; } 411 bool concurrent() { return _concurrent; } 412 uint active_tasks() { return _num_active_tasks; } 413 TaskTerminator* terminator() { return &_terminator; } 414 415 // Claims the next available region to be scanned by a marking 416 // task/thread. It might return NULL if the next region is empty or 417 // we have run out of regions. In the latter case, out_of_regions() 418 // determines whether we've really run out of regions or the task 419 // should call claim_region() again. This might seem a bit 420 // awkward. Originally, the code was written so that claim_region() 421 // either successfully returned with a non-empty region or there 422 // were no more regions to be claimed. The problem with this was 423 // that, in certain circumstances, it iterated over large chunks of 424 // the heap finding only empty regions and, while it was working, it 425 // was preventing the calling task to call its regular clock 426 // method. So, this way, each task will spend very little time in 427 // claim_region() and is allowed to call the regular clock method 428 // frequently. 429 HeapRegion* claim_region(uint worker_id); 430 431 // Determines whether we've run out of regions to scan. Note that 432 // the finger can point past the heap end in case the heap was expanded 433 // to satisfy an allocation without doing a GC. This is fine, because all 434 // objects in those regions will be considered live anyway because of 435 // SATB guarantees (i.e. their TAMS will be equal to bottom). 436 bool out_of_regions() { return _finger >= _heap.end(); } 437 438 // Returns the task with the given id 439 G1CMTask* task(uint id) { 440 // During concurrent start we use the parallel gc threads to do some work, so 441 // we can only compare against _max_num_tasks. 442 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks); 443 return _tasks[id]; 444 } 445 446 // Access / manipulation of the overflow flag which is set to 447 // indicate that the global stack has overflown 448 bool has_overflown() { return _has_overflown; } 449 void set_has_overflown() { _has_overflown = true; } 450 void clear_has_overflown() { _has_overflown = false; } 451 bool restart_for_overflow() { return _restart_for_overflow; } 452 453 // Methods to enter the two overflow sync barriers 454 void enter_first_sync_barrier(uint worker_id); 455 void enter_second_sync_barrier(uint worker_id); 456 457 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is 458 // true, periodically insert checks to see if this method should exit prematurely. 459 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield); 460 461 // Region statistics gathered during marking. 462 G1RegionMarkStats* _region_mark_stats; 463 // Top pointer for each region at the start of the rebuild remembered set process 464 // for regions which remembered sets need to be rebuilt. A NULL for a given region 465 // means that this region does not be scanned during the rebuilding remembered 466 // set phase at all. 467 HeapWord* volatile* _top_at_rebuild_starts; 468 public: 469 void add_to_liveness(uint worker_id, oop const obj, size_t size); 470 // Liveness of the given region as determined by concurrent marking, i.e. the amount of 471 // live words between bottom and nTAMS. 472 size_t liveness(uint region) const { return _region_mark_stats[region]._live_words; } 473 474 // Sets the internal top_at_region_start for the given region to current top of the region. 475 inline void update_top_at_rebuild_start(HeapRegion* r); 476 // TARS for the given region during remembered set rebuilding. 477 inline HeapWord* top_at_rebuild_start(uint region) const; 478 479 // Clear statistics gathered during the concurrent cycle for the given region after 480 // it has been reclaimed. 481 void clear_statistics_in_region(uint region_idx); 482 // Notification for eagerly reclaimed regions to clean up. 483 void humongous_object_eagerly_reclaimed(HeapRegion* r); 484 // Manipulation of the global mark stack. 485 // The push and pop operations are used by tasks for transfers 486 // between task-local queues and the global mark stack. 487 bool mark_stack_push(G1TaskQueueEntry* arr) { 488 if (!_global_mark_stack.par_push_chunk(arr)) { 489 set_has_overflown(); 490 return false; 491 } 492 return true; 493 } 494 bool mark_stack_pop(G1TaskQueueEntry* arr) { 495 return _global_mark_stack.par_pop_chunk(arr); 496 } 497 size_t mark_stack_size() const { return _global_mark_stack.size(); } 498 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; } 499 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); } 500 501 G1CMRootMemRegions* root_regions() { return &_root_regions; } 502 503 void concurrent_cycle_start(); 504 // Abandon current marking iteration due to a Full GC. 505 void concurrent_cycle_abort(); 506 void concurrent_cycle_end(); 507 508 void update_accum_task_vtime(int i, double vtime) { 509 _accum_task_vtime[i] += vtime; 510 } 511 512 double all_task_accum_vtime() { 513 double ret = 0.0; 514 for (uint i = 0; i < _max_num_tasks; ++i) 515 ret += _accum_task_vtime[i]; 516 return ret; 517 } 518 519 // Attempts to steal an object from the task queues of other tasks 520 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry); 521 522 G1ConcurrentMark(G1CollectedHeap* g1h, 523 G1RegionToSpaceMapper* prev_bitmap_storage, 524 G1RegionToSpaceMapper* next_bitmap_storage); 525 ~G1ConcurrentMark(); 526 527 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; } 528 529 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; } 530 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; } 531 532 // Calculates the number of concurrent GC threads to be used in the marking phase. 533 uint calc_active_marking_workers(); 534 535 // Moves all per-task cached data into global state. 536 void flush_all_task_caches(); 537 // Prepare internal data structures for the next mark cycle. This includes clearing 538 // the next mark bitmap and some internal data structures. This method is intended 539 // to be called concurrently to the mutator. It will yield to safepoint requests. 540 void cleanup_for_next_mark(); 541 542 // Clear the previous marking bitmap during safepoint. 543 void clear_prev_bitmap(WorkGang* workers); 544 545 // These two methods do the work that needs to be done at the start and end of the 546 // concurrent start pause. 547 void pre_concurrent_start(GCCause::Cause cause); 548 void post_concurrent_start(bool is_mark_cycle); 549 550 // Scan all the root regions and mark everything reachable from 551 // them. 552 void scan_root_regions(); 553 554 // Scan a single root MemRegion to mark everything reachable from it. 555 void scan_root_region(const MemRegion* region, uint worker_id); 556 557 // Do concurrent phase of marking, to a tentative transitive closure. 558 void mark_from_roots(); 559 560 // Do concurrent preclean work. 561 void preclean(); 562 563 void remark(); 564 565 void cleanup(); 566 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use 567 // this carefully. 568 inline void mark_in_prev_bitmap(oop p); 569 570 // Clears marks for all objects in the given range, for the prev or 571 // next bitmaps. Caution: the previous bitmap is usually 572 // read-only, so use this carefully! 573 void clear_range_in_prev_bitmap(MemRegion mr); 574 575 inline bool is_marked_in_prev_bitmap(oop p) const; 576 577 // Verify that there are no collection set oops on the stacks (taskqueues / 578 // global mark stack) and fingers (global / per-task). 579 // If marking is not in progress, it's a no-op. 580 void verify_no_collection_set_oops() PRODUCT_RETURN; 581 582 inline bool do_yield_check(); 583 584 bool has_aborted() { return _has_aborted; } 585 586 void print_summary_info(); 587 588 void threads_do(ThreadClosure* tc) const; 589 590 void print_on_error(outputStream* st) const; 591 592 // Mark the given object on the next bitmap if it is below nTAMS. 593 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj); 594 inline bool mark_in_next_bitmap(uint worker_id, oop const obj); 595 596 inline bool is_marked_in_next_bitmap(oop p) const; 597 598 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 599 600 private: 601 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application. 602 void rebuild_rem_set_concurrently(); 603 }; 604 605 // A class representing a marking task. 606 class G1CMTask : public TerminatorTerminator { 607 private: 608 enum PrivateConstants { 609 // The regular clock call is called once the scanned words reaches 610 // this limit 611 words_scanned_period = 12*1024, 612 // The regular clock call is called once the number of visited 613 // references reaches this limit 614 refs_reached_period = 1024, 615 // Initial value for the hash seed, used in the work stealing code 616 init_hash_seed = 17 617 }; 618 619 // Number of entries in the per-task stats entry. This seems enough to have a very 620 // low cache miss rate. 621 static const uint RegionMarkStatsCacheSize = 1024; 622 623 G1CMObjArrayProcessor _objArray_processor; 624 625 uint _worker_id; 626 G1CollectedHeap* _g1h; 627 G1ConcurrentMark* _cm; 628 G1CMBitMap* _next_mark_bitmap; 629 // the task queue of this task 630 G1CMTaskQueue* _task_queue; 631 632 G1RegionMarkStatsCache _mark_stats_cache; 633 // Number of calls to this task 634 uint _calls; 635 636 // When the virtual timer reaches this time, the marking step should exit 637 double _time_target_ms; 638 // Start time of the current marking step 639 double _start_time_ms; 640 641 // Oop closure used for iterations over oops 642 G1CMOopClosure* _cm_oop_closure; 643 644 // Region this task is scanning, NULL if we're not scanning any 645 HeapRegion* _curr_region; 646 // Local finger of this task, NULL if we're not scanning a region 647 HeapWord* _finger; 648 // Limit of the region this task is scanning, NULL if we're not scanning one 649 HeapWord* _region_limit; 650 651 // Number of words this task has scanned 652 size_t _words_scanned; 653 // When _words_scanned reaches this limit, the regular clock is 654 // called. Notice that this might be decreased under certain 655 // circumstances (i.e. when we believe that we did an expensive 656 // operation). 657 size_t _words_scanned_limit; 658 // Initial value of _words_scanned_limit (i.e. what it was 659 // before it was decreased). 660 size_t _real_words_scanned_limit; 661 662 // Number of references this task has visited 663 size_t _refs_reached; 664 // When _refs_reached reaches this limit, the regular clock is 665 // called. Notice this this might be decreased under certain 666 // circumstances (i.e. when we believe that we did an expensive 667 // operation). 668 size_t _refs_reached_limit; 669 // Initial value of _refs_reached_limit (i.e. what it was before 670 // it was decreased). 671 size_t _real_refs_reached_limit; 672 673 // If true, then the task has aborted for some reason 674 bool _has_aborted; 675 // Set when the task aborts because it has met its time quota 676 bool _has_timed_out; 677 // True when we're draining SATB buffers; this avoids the task 678 // aborting due to SATB buffers being available (as we're already 679 // dealing with them) 680 bool _draining_satb_buffers; 681 682 // Number sequence of past step times 683 NumberSeq _step_times_ms; 684 // Elapsed time of this task 685 double _elapsed_time_ms; 686 // Termination time of this task 687 double _termination_time_ms; 688 // When this task got into the termination protocol 689 double _termination_start_time_ms; 690 691 TruncatedSeq _marking_step_diff_ms; 692 693 // Updates the local fields after this task has claimed 694 // a new region to scan 695 void setup_for_region(HeapRegion* hr); 696 // Makes the limit of the region up-to-date 697 void update_region_limit(); 698 699 // Called when either the words scanned or the refs visited limit 700 // has been reached 701 void reached_limit(); 702 // Recalculates the words scanned and refs visited limits 703 void recalculate_limits(); 704 // Decreases the words scanned and refs visited limits when we reach 705 // an expensive operation 706 void decrease_limits(); 707 // Checks whether the words scanned or refs visited reached their 708 // respective limit and calls reached_limit() if they have 709 void check_limits() { 710 if (_words_scanned >= _words_scanned_limit || 711 _refs_reached >= _refs_reached_limit) { 712 reached_limit(); 713 } 714 } 715 // Supposed to be called regularly during a marking step as 716 // it checks a bunch of conditions that might cause the marking step 717 // to abort 718 // Return true if the marking step should continue. Otherwise, return false to abort 719 bool regular_clock_call(); 720 721 // Set abort flag if regular_clock_call() check fails 722 inline void abort_marking_if_regular_check_fail(); 723 724 // Test whether obj might have already been passed over by the 725 // mark bitmap scan, and so needs to be pushed onto the mark stack. 726 bool is_below_finger(oop obj, HeapWord* global_finger) const; 727 728 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry); 729 public: 730 // Apply the closure on the given area of the objArray. Return the number of words 731 // scanned. 732 inline size_t scan_objArray(objArrayOop obj, MemRegion mr); 733 // Resets the task; should be called right at the beginning of a marking phase. 734 void reset(G1CMBitMap* next_mark_bitmap); 735 // Clears all the fields that correspond to a claimed region. 736 void clear_region_fields(); 737 738 // The main method of this class which performs a marking step 739 // trying not to exceed the given duration. However, it might exit 740 // prematurely, according to some conditions (i.e. SATB buffers are 741 // available for processing). 742 void do_marking_step(double target_ms, 743 bool do_termination, 744 bool is_serial); 745 746 // These two calls start and stop the timer 747 void record_start_time() { 748 _elapsed_time_ms = os::elapsedTime() * 1000.0; 749 } 750 void record_end_time() { 751 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 752 } 753 754 // Returns the worker ID associated with this task. 755 uint worker_id() { return _worker_id; } 756 757 // From TerminatorTerminator. It determines whether this task should 758 // exit the termination protocol after it's entered it. 759 virtual bool should_exit_termination(); 760 761 // Resets the local region fields after a task has finished scanning a 762 // region; or when they have become stale as a result of the region 763 // being evacuated. 764 void giveup_current_region(); 765 766 HeapWord* finger() { return _finger; } 767 768 bool has_aborted() { return _has_aborted; } 769 void set_has_aborted() { _has_aborted = true; } 770 void clear_has_aborted() { _has_aborted = false; } 771 772 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 773 774 // Increment the number of references this task has visited. 775 void increment_refs_reached() { ++_refs_reached; } 776 777 // Grey the object by marking it. If not already marked, push it on 778 // the local queue if below the finger. obj is required to be below its region's NTAMS. 779 // Returns whether there has been a mark to the bitmap. 780 inline bool make_reference_grey(oop obj); 781 782 // Grey the object (by calling make_grey_reference) if required, 783 // e.g. obj is below its containing region's NTAMS. 784 // Precondition: obj is a valid heap object. 785 // Returns true if the reference caused a mark to be set in the next bitmap. 786 template <class T> 787 inline bool deal_with_reference(T* p); 788 789 // Scans an object and visits its children. 790 inline void scan_task_entry(G1TaskQueueEntry task_entry); 791 792 // Pushes an object on the local queue. 793 inline void push(G1TaskQueueEntry task_entry); 794 795 // Move entries to the global stack. 796 void move_entries_to_global_stack(); 797 // Move entries from the global stack, return true if we were successful to do so. 798 bool get_entries_from_global_stack(); 799 800 // Pops and scans objects from the local queue. If partially is 801 // true, then it stops when the queue size is of a given limit. If 802 // partially is false, then it stops when the queue is empty. 803 void drain_local_queue(bool partially); 804 // Moves entries from the global stack to the local queue and 805 // drains the local queue. If partially is true, then it stops when 806 // both the global stack and the local queue reach a given size. If 807 // partially if false, it tries to empty them totally. 808 void drain_global_stack(bool partially); 809 // Keeps picking SATB buffers and processing them until no SATB 810 // buffers are available. 811 void drain_satb_buffers(); 812 813 // Moves the local finger to a new location 814 inline void move_finger_to(HeapWord* new_finger) { 815 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 816 _finger = new_finger; 817 } 818 819 G1CMTask(uint worker_id, 820 G1ConcurrentMark *cm, 821 G1CMTaskQueue* task_queue, 822 G1RegionMarkStats* mark_stats, 823 uint max_regions); 824 825 inline void update_liveness(oop const obj, size_t const obj_size); 826 827 // Clear (without flushing) the mark cache entry for the given region. 828 void clear_mark_stats_cache(uint region_idx); 829 // Evict the whole statistics cache into the global statistics. Returns the 830 // number of cache hits and misses so far. 831 Pair<size_t, size_t> flush_mark_stats_cache(); 832 // Prints statistics associated with this task 833 void print_stats(); 834 }; 835 836 // Class that's used to to print out per-region liveness 837 // information. It's currently used at the end of marking and also 838 // after we sort the old regions at the end of the cleanup operation. 839 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure { 840 // Accumulators for these values. 841 size_t _total_used_bytes; 842 size_t _total_capacity_bytes; 843 size_t _total_prev_live_bytes; 844 size_t _total_next_live_bytes; 845 846 // Accumulator for the remembered set size 847 size_t _total_remset_bytes; 848 849 // Accumulator for strong code roots memory size 850 size_t _total_strong_code_roots_bytes; 851 852 static double bytes_to_mb(size_t val) { 853 return (double) val / (double) M; 854 } 855 856 public: 857 // The header and footer are printed in the constructor and 858 // destructor respectively. 859 G1PrintRegionLivenessInfoClosure(const char* phase_name); 860 virtual bool do_heap_region(HeapRegion* r); 861 ~G1PrintRegionLivenessInfoClosure(); 862 }; 863 864 #endif // SHARE_GC_G1_G1CONCURRENTMARK_HPP