1 /* 2 * Copyright (c) 2001, 2019, 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/taskqueue.hpp" 34 #include "gc/shared/verifyOption.hpp" 35 #include "gc/shared/workgroup.hpp" 36 #include "memory/allocation.hpp" 37 #include "utilities/compilerWarnings.hpp" 38 39 class ConcurrentGCTimer; 40 class G1ConcurrentMarkThread; 41 class G1CollectedHeap; 42 class G1CMOopClosure; 43 class G1CMTask; 44 class G1ConcurrentMark; 45 class G1OldTracer; 46 class G1RegionToSpaceMapper; 47 class G1SurvivorRegions; 48 49 PRAGMA_DIAG_PUSH 50 // warning C4522: multiple assignment operators specified 51 PRAGMA_DISABLE_MSVC_WARNING(4522) 52 53 // This is a container class for either an oop or a continuation address for 54 // mark stack entries. Both are pushed onto the mark stack. 55 class G1TaskQueueEntry { 56 private: 57 void* _holder; 58 59 static const uintptr_t ArraySliceBit = 1; 60 61 G1TaskQueueEntry(oop obj) : _holder(obj) { 62 assert(_holder != NULL, "Not allowed to set NULL task queue element"); 63 } 64 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { } 65 public: 66 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; } 67 G1TaskQueueEntry() : _holder(NULL) { } 68 69 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); } 70 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); } 71 72 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) { 73 _holder = t._holder; 74 return *this; 75 } 76 77 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile { 78 _holder = t._holder; 79 return *this; 80 } 81 82 oop obj() const { 83 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder)); 84 return (oop)_holder; 85 } 86 87 HeapWord* slice() const { 88 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder)); 89 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit); 90 } 91 92 bool is_oop() const { return !is_array_slice(); } 93 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; } 94 bool is_null() const { return _holder == NULL; } 95 }; 96 97 PRAGMA_DIAG_POP 98 99 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue; 100 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet; 101 102 // Closure used by CM during concurrent reference discovery 103 // and reference processing (during remarking) to determine 104 // if a particular object is alive. It is primarily used 105 // to determine if referents of discovered reference objects 106 // are alive. An instance is also embedded into the 107 // reference processor as the _is_alive_non_header field 108 class G1CMIsAliveClosure : public BoolObjectClosure { 109 G1CollectedHeap* _g1h; 110 public: 111 G1CMIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 112 bool do_object_b(oop obj); 113 }; 114 115 class G1CMSubjectToDiscoveryClosure : public BoolObjectClosure { 116 G1CollectedHeap* _g1h; 117 public: 118 G1CMSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 119 bool do_object_b(oop obj); 120 }; 121 122 // Represents the overflow mark stack used by concurrent marking. 123 // 124 // Stores oops in a huge buffer in virtual memory that is always fully committed. 125 // Resizing may only happen during a STW pause when the stack is empty. 126 // 127 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark 128 // stack memory is split into evenly sized chunks of oops. Users can only 129 // add or remove entries on that basis. 130 // Chunks are filled in increasing address order. Not completely filled chunks 131 // have a NULL element as a terminating element. 132 // 133 // Every chunk has a header containing a single pointer element used for memory 134 // management. This wastes some space, but is negligible (< .1% with current sizing). 135 // 136 // Memory management is done using a mix of tracking a high water-mark indicating 137 // that all chunks at a lower address are valid chunks, and a singly linked free 138 // list connecting all empty chunks. 139 class G1CMMarkStack { 140 public: 141 // Number of TaskQueueEntries that can fit in a single chunk. 142 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */; 143 private: 144 struct TaskQueueEntryChunk { 145 TaskQueueEntryChunk* next; 146 G1TaskQueueEntry data[EntriesPerChunk]; 147 }; 148 149 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack. 150 151 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area. 152 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements. 153 154 char _pad0[DEFAULT_CACHE_LINE_SIZE]; 155 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users. 156 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)]; 157 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data. 158 volatile size_t _chunks_in_chunk_list; 159 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)]; 160 161 volatile size_t _hwm; // High water mark within the reserved space. 162 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)]; 163 164 // Allocate a new chunk from the reserved memory, using the high water mark. Returns 165 // NULL if out of memory. 166 TaskQueueEntryChunk* allocate_new_chunk(); 167 168 // Atomically add the given chunk to the list. 169 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem); 170 // Atomically remove and return a chunk from the given list. Returns NULL if the 171 // list is empty. 172 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list); 173 174 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem); 175 void add_chunk_to_free_list(TaskQueueEntryChunk* elem); 176 177 TaskQueueEntryChunk* remove_chunk_from_chunk_list(); 178 TaskQueueEntryChunk* remove_chunk_from_free_list(); 179 180 // Resizes the mark stack to the given new capacity. Releases any previous 181 // memory if successful. 182 bool resize(size_t new_capacity); 183 184 public: 185 G1CMMarkStack(); 186 ~G1CMMarkStack(); 187 188 // Alignment and minimum capacity of this mark stack in number of oops. 189 static size_t capacity_alignment(); 190 191 // Allocate and initialize the mark stack with the given number of oops. 192 bool initialize(size_t initial_capacity, size_t max_capacity); 193 194 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark 195 // stack. If less than EntriesPerChunk elements are to be pushed, the array must 196 // be terminated with a NULL. 197 // Returns whether the buffer contents were successfully pushed to the global mark 198 // stack. 199 bool par_push_chunk(G1TaskQueueEntry* buffer); 200 201 // Pops a chunk from this mark stack, copying them into the given buffer. This 202 // chunk may contain up to EntriesPerChunk elements. If there are less, the last 203 // element in the array is a NULL pointer. 204 bool par_pop_chunk(G1TaskQueueEntry* buffer); 205 206 // Return whether the chunk list is empty. Racy due to unsynchronized access to 207 // _chunk_list. 208 bool is_empty() const { return _chunk_list == NULL; } 209 210 size_t capacity() const { return _chunk_capacity; } 211 212 // Expand the stack, typically in response to an overflow condition 213 void expand(); 214 215 // Return the approximate number of oops on this mark stack. Racy due to 216 // unsynchronized access to _chunks_in_chunk_list. 217 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; } 218 219 void set_empty(); 220 221 // Apply Fn to every oop on the mark stack. The mark stack must not 222 // be modified while iterating. 223 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN; 224 }; 225 226 // Root MemRegions are memory areas that contain objects which references are 227 // roots wrt to the marking. They must be scanned before marking to maintain the 228 // SATB invariant. 229 // Typically they contain the areas from nTAMS to top of the regions. 230 // We could scan and mark through these objects during the initial-mark pause, but for 231 // pause time reasons we move this work to the concurrent phase. 232 // We need to complete this procedure before the next GC because it might determine 233 // that some of these "root objects" are dead, potentially dropping some required 234 // references. 235 // Root MemRegions comprise of the contents of survivor regions at the end 236 // of the GC, and any objects copied into the old gen during GC. 237 class G1CMRootMemRegions { 238 // The set of root MemRegions. 239 MemRegion* _root_regions; 240 size_t const _max_regions; 241 242 volatile size_t _num_root_regions; // Actual number of root regions. 243 244 volatile size_t _claimed_root_regions; // Number of root regions currently claimed. 245 246 volatile bool _scan_in_progress; 247 volatile bool _should_abort; 248 249 void notify_scan_done(); 250 251 public: 252 G1CMRootMemRegions(uint const max_regions); 253 ~G1CMRootMemRegions(); 254 255 // Reset the data structure to allow addition of new root regions. 256 void reset(); 257 258 void add(HeapWord* start, HeapWord* end); 259 260 // Reset the claiming / scanning of the root regions. 261 void prepare_for_scan(); 262 263 // Forces get_next() to return NULL so that the iteration aborts early. 264 void abort() { _should_abort = true; } 265 266 // Return true if the CM thread are actively scanning root regions, 267 // false otherwise. 268 bool scan_in_progress() { return _scan_in_progress; } 269 270 // Claim the next root MemRegion to scan atomically, or return NULL if 271 // all have been claimed. 272 const MemRegion* claim_next(); 273 274 // The number of root regions to scan. 275 uint num_root_regions() const; 276 277 void cancel_scan(); 278 279 // Flag that we're done with root region scanning and notify anyone 280 // who's waiting on it. If aborted is false, assume that all regions 281 // have been claimed. 282 void scan_finished(); 283 284 // If CM threads are still scanning root regions, wait until they 285 // are done. Return true if we had to wait, false otherwise. 286 bool wait_until_scan_finished(); 287 }; 288 289 // This class manages data structures and methods for doing liveness analysis in 290 // G1's concurrent cycle. 291 class G1ConcurrentMark : public CHeapObj<mtGC> { 292 friend class G1ConcurrentMarkThread; 293 friend class G1CMRefProcTaskProxy; 294 friend class G1CMRefProcTaskExecutor; 295 friend class G1CMKeepAliveAndDrainClosure; 296 friend class G1CMDrainMarkingStackClosure; 297 friend class G1CMBitMapClosure; 298 friend class G1CMConcurrentMarkingTask; 299 friend class G1CMRemarkTask; 300 friend class G1CMTask; 301 302 G1ConcurrentMarkThread* _cm_thread; // The thread doing the work 303 G1CollectedHeap* _g1h; // The heap 304 bool _completed_initialization; // Set to true when initialization is complete 305 306 // Concurrent marking support structures 307 G1CMBitMap _mark_bitmap_1; 308 G1CMBitMap _mark_bitmap_2; 309 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap 310 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap 311 312 // Heap bounds 313 MemRegion const _heap; 314 315 // Root region tracking and claiming 316 G1CMRootMemRegions _root_regions; 317 318 // For grey objects 319 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger 320 HeapWord* volatile _finger; // The global finger, region aligned, 321 // always pointing to the end of the 322 // last claimed region 323 324 uint _worker_id_offset; 325 uint _max_num_tasks; // Maximum number of marking tasks 326 uint _num_active_tasks; // Number of tasks currently active 327 G1CMTask** _tasks; // Task queue array (max_worker_id length) 328 329 G1CMTaskQueueSet* _task_queues; // Task queue set 330 TaskTerminator _terminator; // For termination 331 332 // Two sync barriers that are used to synchronize tasks when an 333 // overflow occurs. The algorithm is the following. All tasks enter 334 // the first one to ensure that they have all stopped manipulating 335 // the global data structures. After they exit it, they re-initialize 336 // their data structures and task 0 re-initializes the global data 337 // structures. Then, they enter the second sync barrier. This 338 // ensure, that no task starts doing work before all data 339 // structures (local and global) have been re-initialized. When they 340 // exit it, they are free to start working again. 341 WorkGangBarrierSync _first_overflow_barrier_sync; 342 WorkGangBarrierSync _second_overflow_barrier_sync; 343 344 // This is set by any task, when an overflow on the global data 345 // structures is detected 346 volatile bool _has_overflown; 347 // True: marking is concurrent, false: we're in remark 348 volatile bool _concurrent; 349 // Set at the end of a Full GC so that marking aborts 350 volatile bool _has_aborted; 351 352 // Used when remark aborts due to an overflow to indicate that 353 // another concurrent marking phase should start 354 volatile bool _restart_for_overflow; 355 356 ConcurrentGCTimer* _gc_timer_cm; 357 358 G1OldTracer* _gc_tracer_cm; 359 360 // Timing statistics. All of them are in ms 361 NumberSeq _init_times; 362 NumberSeq _remark_times; 363 NumberSeq _remark_mark_times; 364 NumberSeq _remark_weak_ref_times; 365 NumberSeq _cleanup_times; 366 double _total_cleanup_time; 367 368 double* _accum_task_vtime; // Accumulated task vtime 369 370 WorkGang* _concurrent_workers; 371 uint _num_concurrent_workers; // The number of marking worker threads we're using 372 uint _max_concurrent_workers; // Maximum number of marking worker threads 373 374 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller); 375 376 void finalize_marking(); 377 378 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes); 379 void weak_refs_work(bool clear_all_soft_refs); 380 381 void report_object_count(bool mark_completed); 382 383 void swap_mark_bitmaps(); 384 385 void reclaim_empty_regions(); 386 387 // After reclaiming empty regions, update heap sizes. 388 void compute_new_sizes(); 389 390 // Clear statistics gathered during the concurrent cycle for the given region after 391 // it has been reclaimed. 392 void clear_statistics(HeapRegion* r); 393 394 // Resets the global marking data structures, as well as the 395 // task local ones; should be called during initial mark. 396 void reset(); 397 398 // Resets all the marking data structures. Called when we have to restart 399 // marking or when marking completes (via set_non_marking_state below). 400 void reset_marking_for_restart(); 401 402 // We do this after we're done with marking so that the marking data 403 // structures are initialized to a sensible and predictable state. 404 void reset_at_marking_complete(); 405 406 // Called to indicate how many threads are currently active. 407 void set_concurrency(uint active_tasks); 408 409 // Should be called to indicate which phase we're in (concurrent 410 // mark or remark) and how many threads are currently active. 411 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 412 413 // Prints all gathered CM-related statistics 414 void print_stats(); 415 416 HeapWord* finger() { return _finger; } 417 bool concurrent() { return _concurrent; } 418 uint active_tasks() { return _num_active_tasks; } 419 ParallelTaskTerminator* terminator() const { return _terminator.terminator(); } 420 421 // Claims the next available region to be scanned by a marking 422 // task/thread. It might return NULL if the next region is empty or 423 // we have run out of regions. In the latter case, out_of_regions() 424 // determines whether we've really run out of regions or the task 425 // should call claim_region() again. This might seem a bit 426 // awkward. Originally, the code was written so that claim_region() 427 // either successfully returned with a non-empty region or there 428 // were no more regions to be claimed. The problem with this was 429 // that, in certain circumstances, it iterated over large chunks of 430 // the heap finding only empty regions and, while it was working, it 431 // was preventing the calling task to call its regular clock 432 // method. So, this way, each task will spend very little time in 433 // claim_region() and is allowed to call the regular clock method 434 // frequently. 435 HeapRegion* claim_region(uint worker_id); 436 437 // Determines whether we've run out of regions to scan. Note that 438 // the finger can point past the heap end in case the heap was expanded 439 // to satisfy an allocation without doing a GC. This is fine, because all 440 // objects in those regions will be considered live anyway because of 441 // SATB guarantees (i.e. their TAMS will be equal to bottom). 442 bool out_of_regions() { return _finger >= _heap.end(); } 443 444 // Returns the task with the given id 445 G1CMTask* task(uint id) { 446 // During initial mark we use the parallel gc threads to do some work, so 447 // we can only compare against _max_num_tasks. 448 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks); 449 return _tasks[id]; 450 } 451 452 // Access / manipulation of the overflow flag which is set to 453 // indicate that the global stack has overflown 454 bool has_overflown() { return _has_overflown; } 455 void set_has_overflown() { _has_overflown = true; } 456 void clear_has_overflown() { _has_overflown = false; } 457 bool restart_for_overflow() { return _restart_for_overflow; } 458 459 // Methods to enter the two overflow sync barriers 460 void enter_first_sync_barrier(uint worker_id); 461 void enter_second_sync_barrier(uint worker_id); 462 463 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is 464 // true, periodically insert checks to see if this method should exit prematurely. 465 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield); 466 467 // Region statistics gathered during marking. 468 G1RegionMarkStats* _region_mark_stats; 469 // Top pointer for each region at the start of the rebuild remembered set process 470 // for regions which remembered sets need to be rebuilt. A NULL for a given region 471 // means that this region does not be scanned during the rebuilding remembered 472 // set phase at all. 473 HeapWord* volatile* _top_at_rebuild_starts; 474 public: 475 void add_to_liveness(uint worker_id, oop const obj, size_t size); 476 // Liveness of the given region as determined by concurrent marking, i.e. the amount of 477 // live words between bottom and nTAMS. 478 size_t liveness(uint region) const { return _region_mark_stats[region]._live_words; } 479 480 // Sets the internal top_at_region_start for the given region to current top of the region. 481 inline void update_top_at_rebuild_start(HeapRegion* r); 482 // TARS for the given region during remembered set rebuilding. 483 inline HeapWord* top_at_rebuild_start(uint region) const; 484 485 // Clear statistics gathered during the concurrent cycle for the given region after 486 // it has been reclaimed. 487 void clear_statistics_in_region(uint region_idx); 488 // Notification for eagerly reclaimed regions to clean up. 489 void humongous_object_eagerly_reclaimed(HeapRegion* r); 490 // Manipulation of the global mark stack. 491 // The push and pop operations are used by tasks for transfers 492 // between task-local queues and the global mark stack. 493 bool mark_stack_push(G1TaskQueueEntry* arr) { 494 if (!_global_mark_stack.par_push_chunk(arr)) { 495 set_has_overflown(); 496 return false; 497 } 498 return true; 499 } 500 bool mark_stack_pop(G1TaskQueueEntry* arr) { 501 return _global_mark_stack.par_pop_chunk(arr); 502 } 503 size_t mark_stack_size() const { return _global_mark_stack.size(); } 504 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; } 505 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); } 506 507 G1CMRootMemRegions* root_regions() { return &_root_regions; } 508 509 void concurrent_cycle_start(); 510 // Abandon current marking iteration due to a Full GC. 511 void concurrent_cycle_abort(); 512 void concurrent_cycle_end(); 513 514 void update_accum_task_vtime(int i, double vtime) { 515 _accum_task_vtime[i] += vtime; 516 } 517 518 double all_task_accum_vtime() { 519 double ret = 0.0; 520 for (uint i = 0; i < _max_num_tasks; ++i) 521 ret += _accum_task_vtime[i]; 522 return ret; 523 } 524 525 // Attempts to steal an object from the task queues of other tasks 526 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry); 527 528 G1ConcurrentMark(G1CollectedHeap* g1h, 529 G1RegionToSpaceMapper* prev_bitmap_storage, 530 G1RegionToSpaceMapper* next_bitmap_storage); 531 ~G1ConcurrentMark(); 532 533 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; } 534 535 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; } 536 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; } 537 538 // Calculates the number of concurrent GC threads to be used in the marking phase. 539 uint calc_active_marking_workers(); 540 541 // Moves all per-task cached data into global state. 542 void flush_all_task_caches(); 543 // Prepare internal data structures for the next mark cycle. This includes clearing 544 // the next mark bitmap and some internal data structures. This method is intended 545 // to be called concurrently to the mutator. It will yield to safepoint requests. 546 void cleanup_for_next_mark(); 547 548 // Clear the previous marking bitmap during safepoint. 549 void clear_prev_bitmap(WorkGang* workers); 550 551 // These two methods do the work that needs to be done at the start and end of the 552 // initial mark pause. 553 void pre_initial_mark(); 554 void post_initial_mark(); 555 556 // Scan all the root regions and mark everything reachable from 557 // them. 558 void scan_root_regions(); 559 560 // Scan a single root MemRegion to mark everything reachable from it. 561 void scan_root_region(const MemRegion* region, uint worker_id); 562 563 // Do concurrent phase of marking, to a tentative transitive closure. 564 void mark_from_roots(); 565 566 // Do concurrent preclean work. 567 void preclean(); 568 569 void remark(); 570 571 void cleanup(); 572 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use 573 // this carefully. 574 inline void mark_in_prev_bitmap(oop p); 575 576 // Clears marks for all objects in the given range, for the prev or 577 // next bitmaps. Caution: the previous bitmap is usually 578 // read-only, so use this carefully! 579 void clear_range_in_prev_bitmap(MemRegion mr); 580 581 inline bool is_marked_in_prev_bitmap(oop p) const; 582 583 // Verify that there are no collection set oops on the stacks (taskqueues / 584 // global mark stack) and fingers (global / per-task). 585 // If marking is not in progress, it's a no-op. 586 void verify_no_collection_set_oops() PRODUCT_RETURN; 587 588 inline bool do_yield_check(); 589 590 bool has_aborted() { return _has_aborted; } 591 592 void print_summary_info(); 593 594 void print_worker_threads_on(outputStream* st) const; 595 void threads_do(ThreadClosure* tc) const; 596 597 void print_on_error(outputStream* st) const; 598 599 // Mark the given object on the next bitmap if it is below nTAMS. 600 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj); 601 inline bool mark_in_next_bitmap(uint worker_id, oop const obj); 602 603 inline bool is_marked_in_next_bitmap(oop p) const; 604 605 // Returns true if initialization was successfully completed. 606 bool completed_initialization() const { 607 return _completed_initialization; 608 } 609 610 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 611 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 612 613 private: 614 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application. 615 void rebuild_rem_set_concurrently(); 616 }; 617 618 // A class representing a marking task. 619 class G1CMTask : public TerminatorTerminator { 620 private: 621 enum PrivateConstants { 622 // The regular clock call is called once the scanned words reaches 623 // this limit 624 words_scanned_period = 12*1024, 625 // The regular clock call is called once the number of visited 626 // references reaches this limit 627 refs_reached_period = 1024, 628 // Initial value for the hash seed, used in the work stealing code 629 init_hash_seed = 17 630 }; 631 632 // Number of entries in the per-task stats entry. This seems enough to have a very 633 // low cache miss rate. 634 static const uint RegionMarkStatsCacheSize = 1024; 635 636 G1CMObjArrayProcessor _objArray_processor; 637 638 uint _worker_id; 639 G1CollectedHeap* _g1h; 640 G1ConcurrentMark* _cm; 641 G1CMBitMap* _next_mark_bitmap; 642 // the task queue of this task 643 G1CMTaskQueue* _task_queue; 644 645 G1RegionMarkStatsCache _mark_stats_cache; 646 // Number of calls to this task 647 uint _calls; 648 649 // When the virtual timer reaches this time, the marking step should exit 650 double _time_target_ms; 651 // Start time of the current marking step 652 double _start_time_ms; 653 654 // Oop closure used for iterations over oops 655 G1CMOopClosure* _cm_oop_closure; 656 657 // Region this task is scanning, NULL if we're not scanning any 658 HeapRegion* _curr_region; 659 // Local finger of this task, NULL if we're not scanning a region 660 HeapWord* _finger; 661 // Limit of the region this task is scanning, NULL if we're not scanning one 662 HeapWord* _region_limit; 663 664 // Number of words this task has scanned 665 size_t _words_scanned; 666 // When _words_scanned reaches this limit, the regular clock is 667 // called. Notice that this might be decreased under certain 668 // circumstances (i.e. when we believe that we did an expensive 669 // operation). 670 size_t _words_scanned_limit; 671 // Initial value of _words_scanned_limit (i.e. what it was 672 // before it was decreased). 673 size_t _real_words_scanned_limit; 674 675 // Number of references this task has visited 676 size_t _refs_reached; 677 // When _refs_reached reaches this limit, the regular clock is 678 // called. Notice this this might be decreased under certain 679 // circumstances (i.e. when we believe that we did an expensive 680 // operation). 681 size_t _refs_reached_limit; 682 // Initial value of _refs_reached_limit (i.e. what it was before 683 // it was decreased). 684 size_t _real_refs_reached_limit; 685 686 // If true, then the task has aborted for some reason 687 bool _has_aborted; 688 // Set when the task aborts because it has met its time quota 689 bool _has_timed_out; 690 // True when we're draining SATB buffers; this avoids the task 691 // aborting due to SATB buffers being available (as we're already 692 // dealing with them) 693 bool _draining_satb_buffers; 694 695 // Number sequence of past step times 696 NumberSeq _step_times_ms; 697 // Elapsed time of this task 698 double _elapsed_time_ms; 699 // Termination time of this task 700 double _termination_time_ms; 701 // When this task got into the termination protocol 702 double _termination_start_time_ms; 703 704 TruncatedSeq _marking_step_diff_ms; 705 706 // Updates the local fields after this task has claimed 707 // a new region to scan 708 void setup_for_region(HeapRegion* hr); 709 // Makes the limit of the region up-to-date 710 void update_region_limit(); 711 712 // Called when either the words scanned or the refs visited limit 713 // has been reached 714 void reached_limit(); 715 // Recalculates the words scanned and refs visited limits 716 void recalculate_limits(); 717 // Decreases the words scanned and refs visited limits when we reach 718 // an expensive operation 719 void decrease_limits(); 720 // Checks whether the words scanned or refs visited reached their 721 // respective limit and calls reached_limit() if they have 722 void check_limits() { 723 if (_words_scanned >= _words_scanned_limit || 724 _refs_reached >= _refs_reached_limit) { 725 reached_limit(); 726 } 727 } 728 // Supposed to be called regularly during a marking step as 729 // it checks a bunch of conditions that might cause the marking step 730 // to abort 731 // Return true if the marking step should continue. Otherwise, return false to abort 732 bool regular_clock_call(); 733 734 // Set abort flag if regular_clock_call() check fails 735 inline void abort_marking_if_regular_check_fail(); 736 737 // Test whether obj might have already been passed over by the 738 // mark bitmap scan, and so needs to be pushed onto the mark stack. 739 bool is_below_finger(oop obj, HeapWord* global_finger) const; 740 741 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry); 742 public: 743 // Apply the closure on the given area of the objArray. Return the number of words 744 // scanned. 745 inline size_t scan_objArray(objArrayOop obj, MemRegion mr); 746 // Resets the task; should be called right at the beginning of a marking phase. 747 void reset(G1CMBitMap* next_mark_bitmap); 748 // Clears all the fields that correspond to a claimed region. 749 void clear_region_fields(); 750 751 // The main method of this class which performs a marking step 752 // trying not to exceed the given duration. However, it might exit 753 // prematurely, according to some conditions (i.e. SATB buffers are 754 // available for processing). 755 void do_marking_step(double target_ms, 756 bool do_termination, 757 bool is_serial); 758 759 // These two calls start and stop the timer 760 void record_start_time() { 761 _elapsed_time_ms = os::elapsedTime() * 1000.0; 762 } 763 void record_end_time() { 764 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 765 } 766 767 // Returns the worker ID associated with this task. 768 uint worker_id() { return _worker_id; } 769 770 // From TerminatorTerminator. It determines whether this task should 771 // exit the termination protocol after it's entered it. 772 virtual bool should_exit_termination(); 773 774 // Resets the local region fields after a task has finished scanning a 775 // region; or when they have become stale as a result of the region 776 // being evacuated. 777 void giveup_current_region(); 778 779 HeapWord* finger() { return _finger; } 780 781 bool has_aborted() { return _has_aborted; } 782 void set_has_aborted() { _has_aborted = true; } 783 void clear_has_aborted() { _has_aborted = false; } 784 785 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 786 787 // Increment the number of references this task has visited. 788 void increment_refs_reached() { ++_refs_reached; } 789 790 // Grey the object by marking it. If not already marked, push it on 791 // the local queue if below the finger. obj is required to be below its region's NTAMS. 792 // Returns whether there has been a mark to the bitmap. 793 inline bool make_reference_grey(oop obj); 794 795 // Grey the object (by calling make_grey_reference) if required, 796 // e.g. obj is below its containing region's NTAMS. 797 // Precondition: obj is a valid heap object. 798 // Returns true if the reference caused a mark to be set in the next bitmap. 799 template <class T> 800 inline bool deal_with_reference(T* p); 801 802 // Scans an object and visits its children. 803 inline void scan_task_entry(G1TaskQueueEntry task_entry); 804 805 // Pushes an object on the local queue. 806 inline void push(G1TaskQueueEntry task_entry); 807 808 // Move entries to the global stack. 809 void move_entries_to_global_stack(); 810 // Move entries from the global stack, return true if we were successful to do so. 811 bool get_entries_from_global_stack(); 812 813 // Pops and scans objects from the local queue. If partially is 814 // true, then it stops when the queue size is of a given limit. If 815 // partially is false, then it stops when the queue is empty. 816 void drain_local_queue(bool partially); 817 // Moves entries from the global stack to the local queue and 818 // drains the local queue. If partially is true, then it stops when 819 // both the global stack and the local queue reach a given size. If 820 // partially if false, it tries to empty them totally. 821 void drain_global_stack(bool partially); 822 // Keeps picking SATB buffers and processing them until no SATB 823 // buffers are available. 824 void drain_satb_buffers(); 825 826 // Moves the local finger to a new location 827 inline void move_finger_to(HeapWord* new_finger) { 828 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 829 _finger = new_finger; 830 } 831 832 G1CMTask(uint worker_id, 833 G1ConcurrentMark *cm, 834 G1CMTaskQueue* task_queue, 835 G1RegionMarkStats* mark_stats, 836 uint max_regions); 837 838 inline void update_liveness(oop const obj, size_t const obj_size); 839 840 // Clear (without flushing) the mark cache entry for the given region. 841 void clear_mark_stats_cache(uint region_idx); 842 // Evict the whole statistics cache into the global statistics. Returns the 843 // number of cache hits and misses so far. 844 Pair<size_t, size_t> flush_mark_stats_cache(); 845 // Prints statistics associated with this task 846 void print_stats(); 847 }; 848 849 // Class that's used to to print out per-region liveness 850 // information. It's currently used at the end of marking and also 851 // after we sort the old regions at the end of the cleanup operation. 852 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure { 853 // Accumulators for these values. 854 size_t _total_used_bytes; 855 size_t _total_capacity_bytes; 856 size_t _total_prev_live_bytes; 857 size_t _total_next_live_bytes; 858 859 // Accumulator for the remembered set size 860 size_t _total_remset_bytes; 861 862 // Accumulator for strong code roots memory size 863 size_t _total_strong_code_roots_bytes; 864 865 static double bytes_to_mb(size_t val) { 866 return (double) val / (double) M; 867 } 868 869 public: 870 // The header and footer are printed in the constructor and 871 // destructor respectively. 872 G1PrintRegionLivenessInfoClosure(const char* phase_name); 873 virtual bool do_heap_region(HeapRegion* r); 874 ~G1PrintRegionLivenessInfoClosure(); 875 }; 876 877 #endif // SHARE_GC_G1_G1CONCURRENTMARK_HPP