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/taskTerminator.hpp" 34 #include "gc/shared/taskqueue.hpp" 35 #include "gc/shared/verifyOption.hpp" 36 #include "gc/shared/workgroup.hpp" 37 #include "memory/allocation.hpp" 38 #include "utilities/compilerWarnings.hpp" 39 40 class ConcurrentGCTimer; 41 class G1ConcurrentMarkThread; 42 class G1CollectedHeap; 43 class G1CMOopClosure; 44 class G1CMTask; 45 class G1ConcurrentMark; 46 class G1OldTracer; 47 class G1RegionToSpaceMapper; 48 class G1SurvivorRegions; 49 class ThreadClosure; 50 51 PRAGMA_DIAG_PUSH 52 // warning C4522: multiple assignment operators specified 53 PRAGMA_DISABLE_MSVC_WARNING(4522) 54 55 // This is a container class for either an oop or a continuation address for 56 // mark stack entries. Both are pushed onto the mark stack. 57 class G1TaskQueueEntry { 58 private: 59 void* _holder; 60 61 static const uintptr_t ArraySliceBit = 1; 62 63 G1TaskQueueEntry(oop obj) : _holder(obj) { 64 assert(_holder != NULL, "Not allowed to set NULL task queue element"); 65 } 66 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { } 67 public: 68 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; } 69 G1TaskQueueEntry() : _holder(NULL) { } 70 71 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); } 72 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); } 73 74 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) { 75 _holder = t._holder; 76 return *this; 77 } 78 79 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile { 80 _holder = t._holder; 81 return *this; 82 } 83 84 oop obj() const { 85 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder)); 86 return (oop)_holder; 87 } 88 89 HeapWord* slice() const { 90 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder)); 91 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit); 92 } 93 94 bool is_oop() const { return !is_array_slice(); } 95 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; } 96 bool is_null() const { return _holder == NULL; } 97 }; 98 99 PRAGMA_DIAG_POP 100 101 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue; 102 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet; 103 104 // Closure used by CM during concurrent reference discovery 105 // and reference processing (during remarking) to determine 106 // if a particular object is alive. It is primarily used 107 // to determine if referents of discovered reference objects 108 // are alive. An instance is also embedded into the 109 // reference processor as the _is_alive_non_header field 110 class G1CMIsAliveClosure : public BoolObjectClosure { 111 G1CollectedHeap* _g1h; 112 public: 113 G1CMIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 114 bool do_object_b(oop obj); 115 }; 116 117 class G1CMSubjectToDiscoveryClosure : public BoolObjectClosure { 118 G1CollectedHeap* _g1h; 119 public: 120 G1CMSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 121 bool do_object_b(oop obj); 122 }; 123 124 // Represents the overflow mark stack used by concurrent marking. 125 // 126 // Stores oops in a huge buffer in virtual memory that is always fully committed. 127 // Resizing may only happen during a STW pause when the stack is empty. 128 // 129 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark 130 // stack memory is split into evenly sized chunks of oops. Users can only 131 // add or remove entries on that basis. 132 // Chunks are filled in increasing address order. Not completely filled chunks 133 // have a NULL element as a terminating element. 134 // 135 // Every chunk has a header containing a single pointer element used for memory 136 // management. This wastes some space, but is negligible (< .1% with current sizing). 137 // 138 // Memory management is done using a mix of tracking a high water-mark indicating 139 // that all chunks at a lower address are valid chunks, and a singly linked free 140 // list connecting all empty chunks. 141 class G1CMMarkStack { 142 public: 143 // Number of TaskQueueEntries that can fit in a single chunk. 144 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */; 145 private: 146 struct TaskQueueEntryChunk { 147 TaskQueueEntryChunk* next; 148 G1TaskQueueEntry data[EntriesPerChunk]; 149 }; 150 151 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack. 152 153 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area. 154 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements. 155 156 char _pad0[DEFAULT_CACHE_LINE_SIZE]; 157 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users. 158 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)]; 159 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data. 160 volatile size_t _chunks_in_chunk_list; 161 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)]; 162 163 volatile size_t _hwm; // High water mark within the reserved space. 164 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)]; 165 166 // Allocate a new chunk from the reserved memory, using the high water mark. Returns 167 // NULL if out of memory. 168 TaskQueueEntryChunk* allocate_new_chunk(); 169 170 // Atomically add the given chunk to the list. 171 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem); 172 // Atomically remove and return a chunk from the given list. Returns NULL if the 173 // list is empty. 174 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list); 175 176 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem); 177 void add_chunk_to_free_list(TaskQueueEntryChunk* elem); 178 179 TaskQueueEntryChunk* remove_chunk_from_chunk_list(); 180 TaskQueueEntryChunk* remove_chunk_from_free_list(); 181 182 // Resizes the mark stack to the given new capacity. Releases any previous 183 // memory if successful. 184 bool resize(size_t new_capacity); 185 186 public: 187 G1CMMarkStack(); 188 ~G1CMMarkStack(); 189 190 // Alignment and minimum capacity of this mark stack in number of oops. 191 static size_t capacity_alignment(); 192 193 // Allocate and initialize the mark stack with the given number of oops. 194 bool initialize(size_t initial_capacity, size_t max_capacity); 195 196 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark 197 // stack. If less than EntriesPerChunk elements are to be pushed, the array must 198 // be terminated with a NULL. 199 // Returns whether the buffer contents were successfully pushed to the global mark 200 // stack. 201 bool par_push_chunk(G1TaskQueueEntry* buffer); 202 203 // Pops a chunk from this mark stack, copying them into the given buffer. This 204 // chunk may contain up to EntriesPerChunk elements. If there are less, the last 205 // element in the array is a NULL pointer. 206 bool par_pop_chunk(G1TaskQueueEntry* buffer); 207 208 // Return whether the chunk list is empty. Racy due to unsynchronized access to 209 // _chunk_list. 210 bool is_empty() const { return _chunk_list == NULL; } 211 212 size_t capacity() const { return _chunk_capacity; } 213 214 // Expand the stack, typically in response to an overflow condition 215 void expand(); 216 217 // Return the approximate number of oops on this mark stack. Racy due to 218 // unsynchronized access to _chunks_in_chunk_list. 219 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; } 220 221 void set_empty(); 222 223 // Apply Fn to every oop on the mark stack. The mark stack must not 224 // be modified while iterating. 225 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN; 226 }; 227 228 // Root MemRegions are memory areas that contain objects which references are 229 // roots wrt to the marking. They must be scanned before marking to maintain the 230 // SATB invariant. 231 // Typically they contain the areas from nTAMS to top of the regions. 232 // We could scan and mark through these objects during the initial-mark pause, but for 233 // pause time reasons we move this work to the concurrent phase. 234 // We need to complete this procedure before the next GC because it might determine 235 // that some of these "root objects" are dead, potentially dropping some required 236 // references. 237 // Root MemRegions comprise of the contents of survivor regions at the end 238 // of the GC, and any objects copied into the old gen during GC. 239 class G1CMRootMemRegions { 240 // The set of root MemRegions. 241 MemRegion* _root_regions; 242 size_t const _max_regions; 243 244 volatile size_t _num_root_regions; // Actual number of root regions. 245 246 volatile size_t _claimed_root_regions; // Number of root regions currently claimed. 247 248 volatile bool _scan_in_progress; 249 volatile bool _should_abort; 250 251 void notify_scan_done(); 252 253 public: 254 G1CMRootMemRegions(uint const max_regions); 255 ~G1CMRootMemRegions(); 256 257 // Reset the data structure to allow addition of new root regions. 258 void reset(); 259 260 void add(HeapWord* start, HeapWord* end); 261 262 // Reset the claiming / scanning of the root regions. 263 void prepare_for_scan(); 264 265 // Forces get_next() to return NULL so that the iteration aborts early. 266 void abort() { _should_abort = true; } 267 268 // Return true if the CM thread are actively scanning root regions, 269 // false otherwise. 270 bool scan_in_progress() { return _scan_in_progress; } 271 272 // Claim the next root MemRegion to scan atomically, or return NULL if 273 // all have been claimed. 274 const MemRegion* claim_next(); 275 276 // The number of root regions to scan. 277 uint num_root_regions() const; 278 279 void cancel_scan(); 280 281 // Flag that we're done with root region scanning and notify anyone 282 // who's waiting on it. If aborted is false, assume that all regions 283 // have been claimed. 284 void scan_finished(); 285 286 // If CM threads are still scanning root regions, wait until they 287 // are done. Return true if we had to wait, false otherwise. 288 bool wait_until_scan_finished(); 289 }; 290 291 // This class manages data structures and methods for doing liveness analysis in 292 // G1's concurrent cycle. 293 class G1ConcurrentMark : public CHeapObj<mtGC> { 294 friend class G1ConcurrentMarkThread; 295 friend class G1CMRefProcTaskProxy; 296 friend class G1CMRefProcTaskExecutor; 297 friend class G1CMKeepAliveAndDrainClosure; 298 friend class G1CMDrainMarkingStackClosure; 299 friend class G1CMBitMapClosure; 300 friend class G1CMConcurrentMarkingTask; 301 friend class G1CMRemarkTask; 302 friend class G1CMTask; 303 304 G1ConcurrentMarkThread* _cm_thread; // The thread doing the work 305 G1CollectedHeap* _g1h; // The heap 306 307 // Concurrent marking support structures 308 G1CMBitMap _mark_bitmap_1; 309 G1CMBitMap _mark_bitmap_2; 310 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap 311 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap 312 313 // Heap bounds 314 MemRegion const _heap; 315 316 // Root region tracking and claiming 317 G1CMRootMemRegions _root_regions; 318 319 // For grey objects 320 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger 321 HeapWord* volatile _finger; // The global finger, region aligned, 322 // always pointing to the end of the 323 // last claimed region 324 325 uint _worker_id_offset; 326 uint _max_num_tasks; // Maximum number of marking tasks 327 uint _num_active_tasks; // Number of tasks currently active 328 G1CMTask** _tasks; // Task queue array (max_worker_id length) 329 330 G1CMTaskQueueSet* _task_queues; // Task queue set 331 TaskTerminator _terminator; // For termination 332 333 // Two sync barriers that are used to synchronize tasks when an 334 // overflow occurs. The algorithm is the following. All tasks enter 335 // the first one to ensure that they have all stopped manipulating 336 // the global data structures. After they exit it, they re-initialize 337 // their data structures and task 0 re-initializes the global data 338 // structures. Then, they enter the second sync barrier. This 339 // ensure, that no task starts doing work before all data 340 // structures (local and global) have been re-initialized. When they 341 // exit it, they are free to start working again. 342 WorkGangBarrierSync _first_overflow_barrier_sync; 343 WorkGangBarrierSync _second_overflow_barrier_sync; 344 345 // This is set by any task, when an overflow on the global data 346 // structures is detected 347 volatile bool _has_overflown; 348 // True: marking is concurrent, false: we're in remark 349 volatile bool _concurrent; 350 // Set at the end of a Full GC so that marking aborts 351 volatile bool _aborted_by_fullgc; 352 // Set at the end of a inital mark young GC if doesn't need to do concurrent mark 353 // so that marking aborts 354 volatile bool _aborted_by_initial_mark; 355 356 // Used when remark aborts due to an overflow to indicate that 357 // another concurrent marking phase should start 358 volatile bool _restart_for_overflow; 359 360 ConcurrentGCTimer* _gc_timer_cm; 361 362 G1OldTracer* _gc_tracer_cm; 363 364 // Timing statistics. All of them are in ms 365 NumberSeq _init_times; 366 NumberSeq _remark_times; 367 NumberSeq _remark_mark_times; 368 NumberSeq _remark_weak_ref_times; 369 NumberSeq _cleanup_times; 370 double _total_cleanup_time; 371 372 double* _accum_task_vtime; // Accumulated task vtime 373 374 WorkGang* _concurrent_workers; 375 uint _num_concurrent_workers; // The number of marking worker threads we're using 376 uint _max_concurrent_workers; // Maximum number of marking worker threads 377 378 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller); 379 380 void finalize_marking(); 381 382 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes); 383 void weak_refs_work(bool clear_all_soft_refs); 384 385 void report_object_count(bool mark_completed); 386 387 void swap_mark_bitmaps(); 388 389 void reclaim_empty_regions(); 390 391 // After reclaiming empty regions, update heap sizes. 392 void compute_new_sizes(); 393 394 // Clear statistics gathered during the concurrent cycle for the given region after 395 // it has been reclaimed. 396 void clear_statistics(HeapRegion* r); 397 398 // Resets the global marking data structures, as well as the 399 // task local ones; should be called during initial mark. 400 void reset(); 401 402 // Resets all the marking data structures. Called when we have to restart 403 // marking or when marking completes (via set_non_marking_state below). 404 void reset_marking_for_restart(); 405 406 // We do this after we're done with marking so that the marking data 407 // structures are initialized to a sensible and predictable state. 408 void reset_at_marking_complete(); 409 410 // Called to indicate how many threads are currently active. 411 void set_concurrency(uint active_tasks); 412 413 // Should be called to indicate which phase we're in (concurrent 414 // mark or remark) and how many threads are currently active. 415 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 416 417 // Prints all gathered CM-related statistics 418 void print_stats(); 419 420 HeapWord* finger() { return _finger; } 421 bool concurrent() { return _concurrent; } 422 uint active_tasks() { return _num_active_tasks; } 423 TaskTerminator* terminator() { return &_terminator; } 424 425 // Claims the next available region to be scanned by a marking 426 // task/thread. It might return NULL if the next region is empty or 427 // we have run out of regions. In the latter case, out_of_regions() 428 // determines whether we've really run out of regions or the task 429 // should call claim_region() again. This might seem a bit 430 // awkward. Originally, the code was written so that claim_region() 431 // either successfully returned with a non-empty region or there 432 // were no more regions to be claimed. The problem with this was 433 // that, in certain circumstances, it iterated over large chunks of 434 // the heap finding only empty regions and, while it was working, it 435 // was preventing the calling task to call its regular clock 436 // method. So, this way, each task will spend very little time in 437 // claim_region() and is allowed to call the regular clock method 438 // frequently. 439 HeapRegion* claim_region(uint worker_id); 440 441 // Determines whether we've run out of regions to scan. Note that 442 // the finger can point past the heap end in case the heap was expanded 443 // to satisfy an allocation without doing a GC. This is fine, because all 444 // objects in those regions will be considered live anyway because of 445 // SATB guarantees (i.e. their TAMS will be equal to bottom). 446 bool out_of_regions() { return _finger >= _heap.end(); } 447 448 // Returns the task with the given id 449 G1CMTask* task(uint id) { 450 // During initial mark we use the parallel gc threads to do some work, so 451 // we can only compare against _max_num_tasks. 452 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks); 453 return _tasks[id]; 454 } 455 456 // Access / manipulation of the overflow flag which is set to 457 // indicate that the global stack has overflown 458 bool has_overflown() { return _has_overflown; } 459 void set_has_overflown() { _has_overflown = true; } 460 void clear_has_overflown() { _has_overflown = false; } 461 bool restart_for_overflow() { return _restart_for_overflow; } 462 463 // Methods to enter the two overflow sync barriers 464 void enter_first_sync_barrier(uint worker_id); 465 void enter_second_sync_barrier(uint worker_id); 466 467 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is 468 // true, periodically insert checks to see if this method should exit prematurely. 469 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield); 470 471 // Region statistics gathered during marking. 472 G1RegionMarkStats* _region_mark_stats; 473 // Top pointer for each region at the start of the rebuild remembered set process 474 // for regions which remembered sets need to be rebuilt. A NULL for a given region 475 // means that this region does not be scanned during the rebuilding remembered 476 // set phase at all. 477 HeapWord* volatile* _top_at_rebuild_starts; 478 public: 479 void add_to_liveness(uint worker_id, oop const obj, size_t size); 480 // Liveness of the given region as determined by concurrent marking, i.e. the amount of 481 // live words between bottom and nTAMS. 482 size_t liveness(uint region) const { return _region_mark_stats[region]._live_words; } 483 484 // Sets the internal top_at_region_start for the given region to current top of the region. 485 inline void update_top_at_rebuild_start(HeapRegion* r); 486 // TARS for the given region during remembered set rebuilding. 487 inline HeapWord* top_at_rebuild_start(uint region) const; 488 489 // Clear statistics gathered during the concurrent cycle for the given region after 490 // it has been reclaimed. 491 void clear_statistics_in_region(uint region_idx); 492 // Notification for eagerly reclaimed regions to clean up. 493 void humongous_object_eagerly_reclaimed(HeapRegion* r); 494 // Manipulation of the global mark stack. 495 // The push and pop operations are used by tasks for transfers 496 // between task-local queues and the global mark stack. 497 bool mark_stack_push(G1TaskQueueEntry* arr) { 498 if (!_global_mark_stack.par_push_chunk(arr)) { 499 set_has_overflown(); 500 return false; 501 } 502 return true; 503 } 504 bool mark_stack_pop(G1TaskQueueEntry* arr) { 505 return _global_mark_stack.par_pop_chunk(arr); 506 } 507 size_t mark_stack_size() const { return _global_mark_stack.size(); } 508 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; } 509 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); } 510 511 G1CMRootMemRegions* root_regions() { return &_root_regions; } 512 513 void concurrent_cycle_start(); 514 // Abandon current marking iteration due to a Full GC. 515 void concurrent_cycle_abort_by_fullgc(); 516 void concurrent_cycle_end(); 517 518 void concurrent_cycle_abort_by_initial_mark(); 519 520 void update_accum_task_vtime(int i, double vtime) { 521 _accum_task_vtime[i] += vtime; 522 } 523 524 double all_task_accum_vtime() { 525 double ret = 0.0; 526 for (uint i = 0; i < _max_num_tasks; ++i) 527 ret += _accum_task_vtime[i]; 528 return ret; 529 } 530 531 // Attempts to steal an object from the task queues of other tasks 532 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry); 533 534 G1ConcurrentMark(G1CollectedHeap* g1h, 535 G1RegionToSpaceMapper* prev_bitmap_storage, 536 G1RegionToSpaceMapper* next_bitmap_storage); 537 ~G1ConcurrentMark(); 538 539 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; } 540 541 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; } 542 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; } 543 544 // Calculates the number of concurrent GC threads to be used in the marking phase. 545 uint calc_active_marking_workers(); 546 547 // Moves all per-task cached data into global state. 548 void flush_all_task_caches(); 549 // Prepare internal data structures for the next mark cycle. This includes clearing 550 // the next mark bitmap and some internal data structures. This method is intended 551 // to be called concurrently to the mutator. It will yield to safepoint requests. 552 void cleanup_for_next_mark(); 553 554 // Clear the previous marking bitmap during safepoint. 555 void clear_prev_bitmap(WorkGang* workers); 556 557 // These two methods do the work that needs to be done at the start and end of the 558 // initial mark pause. 559 void pre_initial_mark(); 560 void post_initial_mark(); 561 562 // Scan all the root regions and mark everything reachable from 563 // them. 564 void scan_root_regions(); 565 566 // Scan a single root MemRegion to mark everything reachable from it. 567 void scan_root_region(const MemRegion* region, uint worker_id); 568 569 // Do concurrent phase of marking, to a tentative transitive closure. 570 void mark_from_roots(); 571 572 // Do concurrent preclean work. 573 void preclean(); 574 575 void remark(); 576 577 void cleanup(); 578 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use 579 // this carefully. 580 inline void mark_in_prev_bitmap(oop p); 581 582 // Clears marks for all objects in the given range, for the prev or 583 // next bitmaps. Caution: the previous bitmap is usually 584 // read-only, so use this carefully! 585 void clear_range_in_prev_bitmap(MemRegion mr); 586 587 inline bool is_marked_in_prev_bitmap(oop p) const; 588 589 // Verify that there are no collection set oops on the stacks (taskqueues / 590 // global mark stack) and fingers (global / per-task). 591 // If marking is not in progress, it's a no-op. 592 void verify_no_collection_set_oops() PRODUCT_RETURN; 593 594 inline bool do_yield_check(); 595 596 bool aborted_by_fullgc() { return _aborted_by_fullgc; } 597 bool aborted_by_initial_mark() { return _aborted_by_initial_mark; } 598 bool has_aborted() { return aborted_by_fullgc() || aborted_by_initial_mark(); } 599 600 void print_summary_info(); 601 602 void print_worker_threads_on(outputStream* st) const; 603 void threads_do(ThreadClosure* tc) const; 604 605 void print_on_error(outputStream* st) const; 606 607 // Mark the given object on the next bitmap if it is below nTAMS. 608 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj); 609 inline bool mark_in_next_bitmap(uint worker_id, oop const obj); 610 611 inline bool is_marked_in_next_bitmap(oop p) const; 612 613 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 614 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 615 616 private: 617 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application. 618 void rebuild_rem_set_concurrently(); 619 }; 620 621 // A class representing a marking task. 622 class G1CMTask : public TerminatorTerminator { 623 private: 624 enum PrivateConstants { 625 // The regular clock call is called once the scanned words reaches 626 // this limit 627 words_scanned_period = 12*1024, 628 // The regular clock call is called once the number of visited 629 // references reaches this limit 630 refs_reached_period = 1024, 631 // Initial value for the hash seed, used in the work stealing code 632 init_hash_seed = 17 633 }; 634 635 // Number of entries in the per-task stats entry. This seems enough to have a very 636 // low cache miss rate. 637 static const uint RegionMarkStatsCacheSize = 1024; 638 639 G1CMObjArrayProcessor _objArray_processor; 640 641 uint _worker_id; 642 G1CollectedHeap* _g1h; 643 G1ConcurrentMark* _cm; 644 G1CMBitMap* _next_mark_bitmap; 645 // the task queue of this task 646 G1CMTaskQueue* _task_queue; 647 648 G1RegionMarkStatsCache _mark_stats_cache; 649 // Number of calls to this task 650 uint _calls; 651 652 // When the virtual timer reaches this time, the marking step should exit 653 double _time_target_ms; 654 // Start time of the current marking step 655 double _start_time_ms; 656 657 // Oop closure used for iterations over oops 658 G1CMOopClosure* _cm_oop_closure; 659 660 // Region this task is scanning, NULL if we're not scanning any 661 HeapRegion* _curr_region; 662 // Local finger of this task, NULL if we're not scanning a region 663 HeapWord* _finger; 664 // Limit of the region this task is scanning, NULL if we're not scanning one 665 HeapWord* _region_limit; 666 667 // Number of words this task has scanned 668 size_t _words_scanned; 669 // When _words_scanned reaches this limit, the regular clock is 670 // called. Notice that this might be decreased under certain 671 // circumstances (i.e. when we believe that we did an expensive 672 // operation). 673 size_t _words_scanned_limit; 674 // Initial value of _words_scanned_limit (i.e. what it was 675 // before it was decreased). 676 size_t _real_words_scanned_limit; 677 678 // Number of references this task has visited 679 size_t _refs_reached; 680 // When _refs_reached reaches this limit, the regular clock is 681 // called. Notice this this might be decreased under certain 682 // circumstances (i.e. when we believe that we did an expensive 683 // operation). 684 size_t _refs_reached_limit; 685 // Initial value of _refs_reached_limit (i.e. what it was before 686 // it was decreased). 687 size_t _real_refs_reached_limit; 688 689 // If true, then the task has aborted for some reason 690 bool _has_aborted; 691 // Set when the task aborts because it has met its time quota 692 bool _has_timed_out; 693 // True when we're draining SATB buffers; this avoids the task 694 // aborting due to SATB buffers being available (as we're already 695 // dealing with them) 696 bool _draining_satb_buffers; 697 698 // Number sequence of past step times 699 NumberSeq _step_times_ms; 700 // Elapsed time of this task 701 double _elapsed_time_ms; 702 // Termination time of this task 703 double _termination_time_ms; 704 // When this task got into the termination protocol 705 double _termination_start_time_ms; 706 707 TruncatedSeq _marking_step_diff_ms; 708 709 // Updates the local fields after this task has claimed 710 // a new region to scan 711 void setup_for_region(HeapRegion* hr); 712 // Makes the limit of the region up-to-date 713 void update_region_limit(); 714 715 // Called when either the words scanned or the refs visited limit 716 // has been reached 717 void reached_limit(); 718 // Recalculates the words scanned and refs visited limits 719 void recalculate_limits(); 720 // Decreases the words scanned and refs visited limits when we reach 721 // an expensive operation 722 void decrease_limits(); 723 // Checks whether the words scanned or refs visited reached their 724 // respective limit and calls reached_limit() if they have 725 void check_limits() { 726 if (_words_scanned >= _words_scanned_limit || 727 _refs_reached >= _refs_reached_limit) { 728 reached_limit(); 729 } 730 } 731 // Supposed to be called regularly during a marking step as 732 // it checks a bunch of conditions that might cause the marking step 733 // to abort 734 // Return true if the marking step should continue. Otherwise, return false to abort 735 bool regular_clock_call(); 736 737 // Set abort flag if regular_clock_call() check fails 738 inline void abort_marking_if_regular_check_fail(); 739 740 // Test whether obj might have already been passed over by the 741 // mark bitmap scan, and so needs to be pushed onto the mark stack. 742 bool is_below_finger(oop obj, HeapWord* global_finger) const; 743 744 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry); 745 public: 746 // Apply the closure on the given area of the objArray. Return the number of words 747 // scanned. 748 inline size_t scan_objArray(objArrayOop obj, MemRegion mr); 749 // Resets the task; should be called right at the beginning of a marking phase. 750 void reset(G1CMBitMap* next_mark_bitmap); 751 // Clears all the fields that correspond to a claimed region. 752 void clear_region_fields(); 753 754 // The main method of this class which performs a marking step 755 // trying not to exceed the given duration. However, it might exit 756 // prematurely, according to some conditions (i.e. SATB buffers are 757 // available for processing). 758 void do_marking_step(double target_ms, 759 bool do_termination, 760 bool is_serial); 761 762 // These two calls start and stop the timer 763 void record_start_time() { 764 _elapsed_time_ms = os::elapsedTime() * 1000.0; 765 } 766 void record_end_time() { 767 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 768 } 769 770 // Returns the worker ID associated with this task. 771 uint worker_id() { return _worker_id; } 772 773 // From TerminatorTerminator. It determines whether this task should 774 // exit the termination protocol after it's entered it. 775 virtual bool should_exit_termination(); 776 777 // Resets the local region fields after a task has finished scanning a 778 // region; or when they have become stale as a result of the region 779 // being evacuated. 780 void giveup_current_region(); 781 782 HeapWord* finger() { return _finger; } 783 784 bool has_aborted() { return _has_aborted; } 785 void set_has_aborted() { _has_aborted = true; } 786 void clear_has_aborted() { _has_aborted = false; } 787 788 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 789 790 // Increment the number of references this task has visited. 791 void increment_refs_reached() { ++_refs_reached; } 792 793 // Grey the object by marking it. If not already marked, push it on 794 // the local queue if below the finger. obj is required to be below its region's NTAMS. 795 // Returns whether there has been a mark to the bitmap. 796 inline bool make_reference_grey(oop obj); 797 798 // Grey the object (by calling make_grey_reference) if required, 799 // e.g. obj is below its containing region's NTAMS. 800 // Precondition: obj is a valid heap object. 801 // Returns true if the reference caused a mark to be set in the next bitmap. 802 template <class T> 803 inline bool deal_with_reference(T* p); 804 805 // Scans an object and visits its children. 806 inline void scan_task_entry(G1TaskQueueEntry task_entry); 807 808 // Pushes an object on the local queue. 809 inline void push(G1TaskQueueEntry task_entry); 810 811 // Move entries to the global stack. 812 void move_entries_to_global_stack(); 813 // Move entries from the global stack, return true if we were successful to do so. 814 bool get_entries_from_global_stack(); 815 816 // Pops and scans objects from the local queue. If partially is 817 // true, then it stops when the queue size is of a given limit. If 818 // partially is false, then it stops when the queue is empty. 819 void drain_local_queue(bool partially); 820 // Moves entries from the global stack to the local queue and 821 // drains the local queue. If partially is true, then it stops when 822 // both the global stack and the local queue reach a given size. If 823 // partially if false, it tries to empty them totally. 824 void drain_global_stack(bool partially); 825 // Keeps picking SATB buffers and processing them until no SATB 826 // buffers are available. 827 void drain_satb_buffers(); 828 829 // Moves the local finger to a new location 830 inline void move_finger_to(HeapWord* new_finger) { 831 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 832 _finger = new_finger; 833 } 834 835 G1CMTask(uint worker_id, 836 G1ConcurrentMark *cm, 837 G1CMTaskQueue* task_queue, 838 G1RegionMarkStats* mark_stats, 839 uint max_regions); 840 841 inline void update_liveness(oop const obj, size_t const obj_size); 842 843 // Clear (without flushing) the mark cache entry for the given region. 844 void clear_mark_stats_cache(uint region_idx); 845 // Evict the whole statistics cache into the global statistics. Returns the 846 // number of cache hits and misses so far. 847 Pair<size_t, size_t> flush_mark_stats_cache(); 848 // Prints statistics associated with this task 849 void print_stats(); 850 }; 851 852 // Class that's used to to print out per-region liveness 853 // information. It's currently used at the end of marking and also 854 // after we sort the old regions at the end of the cleanup operation. 855 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure { 856 // Accumulators for these values. 857 size_t _total_used_bytes; 858 size_t _total_capacity_bytes; 859 size_t _total_prev_live_bytes; 860 size_t _total_next_live_bytes; 861 862 // Accumulator for the remembered set size 863 size_t _total_remset_bytes; 864 865 // Accumulator for strong code roots memory size 866 size_t _total_strong_code_roots_bytes; 867 868 static double bytes_to_mb(size_t val) { 869 return (double) val / (double) M; 870 } 871 872 public: 873 // The header and footer are printed in the constructor and 874 // destructor respectively. 875 G1PrintRegionLivenessInfoClosure(const char* phase_name); 876 virtual bool do_heap_region(HeapRegion* r); 877 ~G1PrintRegionLivenessInfoClosure(); 878 }; 879 880 #endif // SHARE_GC_G1_G1CONCURRENTMARK_HPP