1 /* 2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP 26 #define SHARE_VM_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 "memory/allocation.hpp" 35 36 class ConcurrentGCTimer; 37 class G1ConcurrentMarkThread; 38 class G1CollectedHeap; 39 class G1CMOopClosure; 40 class G1CMTask; 41 class G1ConcurrentMark; 42 class G1OldTracer; 43 class G1RegionToSpaceMapper; 44 class G1SurvivorRegions; 45 46 #ifdef _MSC_VER 47 #pragma warning(push) 48 // warning C4522: multiple assignment operators specified 49 #pragma warning(disable:4522) 50 #endif 51 52 // This is a container class for either an oop or a continuation address for 53 // mark stack entries. Both are pushed onto the mark stack. 54 class G1TaskQueueEntry { 55 private: 56 void* _holder; 57 58 static const uintptr_t ArraySliceBit = 1; 59 60 G1TaskQueueEntry(oop obj) : _holder(obj) { 61 assert(_holder != NULL, "Not allowed to set NULL task queue element"); 62 } 63 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { } 64 public: 65 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; } 66 G1TaskQueueEntry() : _holder(NULL) { } 67 68 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); } 69 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); } 70 71 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) { 72 _holder = t._holder; 73 return *this; 74 } 75 76 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile { 77 _holder = t._holder; 78 return *this; 79 } 80 81 oop obj() const { 82 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder)); 83 return (oop)_holder; 84 } 85 86 HeapWord* slice() const { 87 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder)); 88 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit); 89 } 90 91 bool is_oop() const { return !is_array_slice(); } 92 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; } 93 bool is_null() const { return _holder == NULL; } 94 }; 95 96 #ifdef _MSC_VER 97 #pragma warning(pop) 98 #endif 99 100 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue; 101 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet; 102 103 // Closure used by CM during concurrent reference discovery 104 // and reference processing (during remarking) to determine 105 // if a particular object is alive. It is primarily used 106 // to determine if referents of discovered reference objects 107 // are alive. An instance is also embedded into the 108 // reference processor as the _is_alive_non_header field 109 class G1CMIsAliveClosure : public BoolObjectClosure { 110 G1CollectedHeap* _g1h; 111 public: 112 G1CMIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 113 bool do_object_b(oop obj); 114 }; 115 116 class G1CMSubjectToDiscoveryClosure : public BoolObjectClosure { 117 G1CollectedHeap* _g1h; 118 public: 119 G1CMSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 120 bool do_object_b(oop obj); 121 }; 122 123 // Represents the overflow mark stack used by concurrent marking. 124 // 125 // Stores oops in a huge buffer in virtual memory that is always fully committed. 126 // Resizing may only happen during a STW pause when the stack is empty. 127 // 128 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark 129 // stack memory is split into evenly sized chunks of oops. Users can only 130 // add or remove entries on that basis. 131 // Chunks are filled in increasing address order. Not completely filled chunks 132 // have a NULL element as a terminating element. 133 // 134 // Every chunk has a header containing a single pointer element used for memory 135 // management. This wastes some space, but is negligible (< .1% with current sizing). 136 // 137 // Memory management is done using a mix of tracking a high water-mark indicating 138 // that all chunks at a lower address are valid chunks, and a singly linked free 139 // list connecting all empty chunks. 140 class G1CMMarkStack { 141 public: 142 // Number of TaskQueueEntries that can fit in a single chunk. 143 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */; 144 private: 145 struct TaskQueueEntryChunk { 146 TaskQueueEntryChunk* next; 147 G1TaskQueueEntry data[EntriesPerChunk]; 148 }; 149 150 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack. 151 152 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area. 153 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements. 154 155 char _pad0[DEFAULT_CACHE_LINE_SIZE]; 156 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users. 157 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)]; 158 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data. 159 volatile size_t _chunks_in_chunk_list; 160 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)]; 161 162 volatile size_t _hwm; // High water mark within the reserved space. 163 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)]; 164 165 // Allocate a new chunk from the reserved memory, using the high water mark. Returns 166 // NULL if out of memory. 167 TaskQueueEntryChunk* allocate_new_chunk(); 168 169 // Atomically add the given chunk to the list. 170 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem); 171 // Atomically remove and return a chunk from the given list. Returns NULL if the 172 // list is empty. 173 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list); 174 175 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem); 176 void add_chunk_to_free_list(TaskQueueEntryChunk* elem); 177 178 TaskQueueEntryChunk* remove_chunk_from_chunk_list(); 179 TaskQueueEntryChunk* remove_chunk_from_free_list(); 180 181 // Resizes the mark stack to the given new capacity. Releases any previous 182 // memory if successful. 183 bool resize(size_t new_capacity); 184 185 public: 186 G1CMMarkStack(); 187 ~G1CMMarkStack(); 188 189 // Alignment and minimum capacity of this mark stack in number of oops. 190 static size_t capacity_alignment(); 191 192 // Allocate and initialize the mark stack with the given number of oops. 193 bool initialize(size_t initial_capacity, size_t max_capacity); 194 195 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark 196 // stack. If less than EntriesPerChunk elements are to be pushed, the array must 197 // be terminated with a NULL. 198 // Returns whether the buffer contents were successfully pushed to the global mark 199 // stack. 200 bool par_push_chunk(G1TaskQueueEntry* buffer); 201 202 // Pops a chunk from this mark stack, copying them into the given buffer. This 203 // chunk may contain up to EntriesPerChunk elements. If there are less, the last 204 // element in the array is a NULL pointer. 205 bool par_pop_chunk(G1TaskQueueEntry* buffer); 206 207 // Return whether the chunk list is empty. Racy due to unsynchronized access to 208 // _chunk_list. 209 bool is_empty() const { return _chunk_list == NULL; } 210 211 size_t capacity() const { return _chunk_capacity; } 212 213 // Expand the stack, typically in response to an overflow condition 214 void expand(); 215 216 // Return the approximate number of oops on this mark stack. Racy due to 217 // unsynchronized access to _chunks_in_chunk_list. 218 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; } 219 220 void set_empty(); 221 222 // Apply Fn to every oop on the mark stack. The mark stack must not 223 // be modified while iterating. 224 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN; 225 }; 226 227 // Root Regions are regions that are not empty at the beginning of a 228 // marking cycle and which we might collect during an evacuation pause 229 // while the cycle is active. Given that, during evacuation pauses, we 230 // do not copy objects that are explicitly marked, what we have to do 231 // for the root regions is to scan them and mark all objects reachable 232 // from them. According to the SATB assumptions, we only need to visit 233 // each object once during marking. So, as long as we finish this scan 234 // before the next evacuation pause, we can copy the objects from the 235 // root regions without having to mark them or do anything else to them. 236 // 237 // Currently, we only support root region scanning once (at the start 238 // of the marking cycle) and the root regions are all the survivor 239 // regions populated during the initial-mark pause. 240 class G1CMRootRegions { 241 private: 242 const G1SurvivorRegions* _survivors; 243 G1ConcurrentMark* _cm; 244 245 volatile bool _scan_in_progress; 246 volatile bool _should_abort; 247 volatile int _claimed_survivor_index; 248 249 void notify_scan_done(); 250 251 public: 252 G1CMRootRegions(); 253 // We actually do most of the initialization in this method. 254 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm); 255 256 // Reset the claiming / scanning of the root regions. 257 void prepare_for_scan(); 258 259 // Forces get_next() to return NULL so that the iteration aborts early. 260 void abort() { _should_abort = true; } 261 262 // Return true if the CM thread are actively scanning root regions, 263 // false otherwise. 264 bool scan_in_progress() { return _scan_in_progress; } 265 266 // Claim the next root region to scan atomically, or return NULL if 267 // all have been claimed. 268 HeapRegion* claim_next(); 269 270 // The number of root regions to scan. 271 uint num_root_regions() const; 272 273 void cancel_scan(); 274 275 // Flag that we're done with root region scanning and notify anyone 276 // who's waiting on it. If aborted is false, assume that all regions 277 // have been claimed. 278 void scan_finished(); 279 280 // If CM threads are still scanning root regions, wait until they 281 // are done. Return true if we had to wait, false otherwise. 282 bool wait_until_scan_finished(); 283 }; 284 285 // This class manages data structures and methods for doing liveness analysis in 286 // G1's concurrent cycle. 287 class G1ConcurrentMark : public CHeapObj<mtGC> { 288 friend class G1ConcurrentMarkThread; 289 friend class G1CMRefProcTaskProxy; 290 friend class G1CMRefProcTaskExecutor; 291 friend class G1CMKeepAliveAndDrainClosure; 292 friend class G1CMDrainMarkingStackClosure; 293 friend class G1CMBitMapClosure; 294 friend class G1CMConcurrentMarkingTask; 295 friend class G1CMRemarkTask; 296 friend class G1CMTask; 297 298 G1ConcurrentMarkThread* _cm_thread; // The thread doing the work 299 G1CollectedHeap* _g1h; // The heap 300 bool _completed_initialization; // Set to true when initialization is complete 301 302 // Concurrent marking support structures 303 G1CMBitMap _mark_bitmap_1; 304 G1CMBitMap _mark_bitmap_2; 305 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap 306 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap 307 308 // Heap bounds 309 MemRegion const _heap; 310 311 // Root region tracking and claiming 312 G1CMRootRegions _root_regions; 313 314 // For grey objects 315 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger 316 HeapWord* volatile _finger; // The global finger, region aligned, 317 // always pointing to the end of the 318 // last claimed region 319 320 uint _worker_id_offset; 321 uint _max_num_tasks; // Maximum number of marking tasks 322 uint _num_active_tasks; // Number of tasks currently active 323 G1CMTask** _tasks; // Task queue array (max_worker_id length) 324 325 G1CMTaskQueueSet* _task_queues; // Task queue set 326 TaskTerminator _terminator; // For termination 327 328 // Two sync barriers that are used to synchronize tasks when an 329 // overflow occurs. The algorithm is the following. All tasks enter 330 // the first one to ensure that they have all stopped manipulating 331 // the global data structures. After they exit it, they re-initialize 332 // their data structures and task 0 re-initializes the global data 333 // structures. Then, they enter the second sync barrier. This 334 // ensure, that no task starts doing work before all data 335 // structures (local and global) have been re-initialized. When they 336 // exit it, they are free to start working again. 337 WorkGangBarrierSync _first_overflow_barrier_sync; 338 WorkGangBarrierSync _second_overflow_barrier_sync; 339 340 // This is set by any task, when an overflow on the global data 341 // structures is detected 342 volatile bool _has_overflown; 343 // True: marking is concurrent, false: we're in remark 344 volatile bool _concurrent; 345 // Set at the end of a Full GC so that marking aborts 346 volatile bool _has_aborted; 347 348 // Used when remark aborts due to an overflow to indicate that 349 // another concurrent marking phase should start 350 volatile bool _restart_for_overflow; 351 352 ConcurrentGCTimer* _gc_timer_cm; 353 354 G1OldTracer* _gc_tracer_cm; 355 356 // Timing statistics. All of them are in ms 357 NumberSeq _init_times; 358 NumberSeq _remark_times; 359 NumberSeq _remark_mark_times; 360 NumberSeq _remark_weak_ref_times; 361 NumberSeq _cleanup_times; 362 double _total_cleanup_time; 363 364 double* _accum_task_vtime; // Accumulated task vtime 365 366 WorkGang* _concurrent_workers; 367 uint _num_concurrent_workers; // The number of marking worker threads we're using 368 uint _max_concurrent_workers; // Maximum number of marking worker threads 369 370 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller); 371 372 void finalize_marking(); 373 374 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes); 375 void weak_refs_work(bool clear_all_soft_refs); 376 377 void report_object_count(bool mark_completed); 378 379 void swap_mark_bitmaps(); 380 381 void reclaim_empty_regions(); 382 383 // After reclaiming empty regions, update heap sizes. 384 void compute_new_sizes(); 385 386 // Clear statistics gathered during the concurrent cycle for the given region after 387 // it has been reclaimed. 388 void clear_statistics(HeapRegion* r); 389 390 // Resets the global marking data structures, as well as the 391 // task local ones; should be called during initial mark. 392 void reset(); 393 394 // Resets all the marking data structures. Called when we have to restart 395 // marking or when marking completes (via set_non_marking_state below). 396 void reset_marking_for_restart(); 397 398 // We do this after we're done with marking so that the marking data 399 // structures are initialized to a sensible and predictable state. 400 void reset_at_marking_complete(); 401 402 // Called to indicate how many threads are currently active. 403 void set_concurrency(uint active_tasks); 404 405 // Should be called to indicate which phase we're in (concurrent 406 // mark or remark) and how many threads are currently active. 407 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 408 409 // Prints all gathered CM-related statistics 410 void print_stats(); 411 412 HeapWord* finger() { return _finger; } 413 bool concurrent() { return _concurrent; } 414 uint active_tasks() { return _num_active_tasks; } 415 ParallelTaskTerminator* terminator() const { return _terminator.terminator(); } 416 417 // Claims the next available region to be scanned by a marking 418 // task/thread. It might return NULL if the next region is empty or 419 // we have run out of regions. In the latter case, out_of_regions() 420 // determines whether we've really run out of regions or the task 421 // should call claim_region() again. This might seem a bit 422 // awkward. Originally, the code was written so that claim_region() 423 // either successfully returned with a non-empty region or there 424 // were no more regions to be claimed. The problem with this was 425 // that, in certain circumstances, it iterated over large chunks of 426 // the heap finding only empty regions and, while it was working, it 427 // was preventing the calling task to call its regular clock 428 // method. So, this way, each task will spend very little time in 429 // claim_region() and is allowed to call the regular clock method 430 // frequently. 431 HeapRegion* claim_region(uint worker_id); 432 433 // Determines whether we've run out of regions to scan. Note that 434 // the finger can point past the heap end in case the heap was expanded 435 // to satisfy an allocation without doing a GC. This is fine, because all 436 // objects in those regions will be considered live anyway because of 437 // SATB guarantees (i.e. their TAMS will be equal to bottom). 438 bool out_of_regions() { return _finger >= _heap.end(); } 439 440 // Returns the task with the given id 441 G1CMTask* task(uint id) { 442 // During initial mark we use the parallel gc threads to do some work, so 443 // we can only compare against _max_num_tasks. 444 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks); 445 return _tasks[id]; 446 } 447 448 // Access / manipulation of the overflow flag which is set to 449 // indicate that the global stack has overflown 450 bool has_overflown() { return _has_overflown; } 451 void set_has_overflown() { _has_overflown = true; } 452 void clear_has_overflown() { _has_overflown = false; } 453 bool restart_for_overflow() { return _restart_for_overflow; } 454 455 // Methods to enter the two overflow sync barriers 456 void enter_first_sync_barrier(uint worker_id); 457 void enter_second_sync_barrier(uint worker_id); 458 459 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is 460 // true, periodically insert checks to see if this method should exit prematurely. 461 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield); 462 463 // Region statistics gathered during marking. 464 G1RegionMarkStats* _region_mark_stats; 465 // Top pointer for each region at the start of the rebuild remembered set process 466 // for regions which remembered sets need to be rebuilt. A NULL for a given region 467 // means that this region does not be scanned during the rebuilding remembered 468 // set phase at all. 469 HeapWord* volatile* _top_at_rebuild_starts; 470 public: 471 void add_to_liveness(uint worker_id, oop const obj, size_t size); 472 // Liveness of the given region as determined by concurrent marking, i.e. the amount of 473 // live words between bottom and nTAMS. 474 size_t liveness(uint region) const { return _region_mark_stats[region]._live_words; } 475 476 // Sets the internal top_at_region_start for the given region to current top of the region. 477 inline void update_top_at_rebuild_start(HeapRegion* r); 478 // TARS for the given region during remembered set rebuilding. 479 inline HeapWord* top_at_rebuild_start(uint region) const; 480 481 // Clear statistics gathered during the concurrent cycle for the given region after 482 // it has been reclaimed. 483 void clear_statistics_in_region(uint region_idx); 484 // Notification for eagerly reclaimed regions to clean up. 485 void humongous_object_eagerly_reclaimed(HeapRegion* r); 486 // Manipulation of the global mark stack. 487 // The push and pop operations are used by tasks for transfers 488 // between task-local queues and the global mark stack. 489 bool mark_stack_push(G1TaskQueueEntry* arr) { 490 if (!_global_mark_stack.par_push_chunk(arr)) { 491 set_has_overflown(); 492 return false; 493 } 494 return true; 495 } 496 bool mark_stack_pop(G1TaskQueueEntry* arr) { 497 return _global_mark_stack.par_pop_chunk(arr); 498 } 499 size_t mark_stack_size() const { return _global_mark_stack.size(); } 500 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; } 501 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); } 502 503 G1CMRootRegions* root_regions() { return &_root_regions; } 504 505 void concurrent_cycle_start(); 506 // Abandon current marking iteration due to a Full GC. 507 void concurrent_cycle_abort(); 508 void concurrent_cycle_end(); 509 510 void update_accum_task_vtime(int i, double vtime) { 511 _accum_task_vtime[i] += vtime; 512 } 513 514 double all_task_accum_vtime() { 515 double ret = 0.0; 516 for (uint i = 0; i < _max_num_tasks; ++i) 517 ret += _accum_task_vtime[i]; 518 return ret; 519 } 520 521 // Attempts to steal an object from the task queues of other tasks 522 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry); 523 524 G1ConcurrentMark(G1CollectedHeap* g1h, 525 G1RegionToSpaceMapper* prev_bitmap_storage, 526 G1RegionToSpaceMapper* next_bitmap_storage); 527 ~G1ConcurrentMark(); 528 529 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; } 530 531 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; } 532 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; } 533 534 // Calculates the number of concurrent GC threads to be used in the marking phase. 535 uint calc_active_marking_workers(); 536 537 // Moves all per-task cached data into global state. 538 void flush_all_task_caches(); 539 // Prepare internal data structures for the next mark cycle. This includes clearing 540 // the next mark bitmap and some internal data structures. This method is intended 541 // to be called concurrently to the mutator. It will yield to safepoint requests. 542 void cleanup_for_next_mark(); 543 544 // Clear the previous marking bitmap during safepoint. 545 void clear_prev_bitmap(WorkGang* workers); 546 547 // These two methods do the work that needs to be done at the start and end of the 548 // initial mark pause. 549 void pre_initial_mark(); 550 void post_initial_mark(); 551 552 // Scan all the root regions and mark everything reachable from 553 // them. 554 void scan_root_regions(); 555 556 // Scan a single root region and mark everything reachable from it. 557 void scan_root_region(HeapRegion* hr, uint worker_id); 558 559 // Do concurrent phase of marking, to a tentative transitive closure. 560 void mark_from_roots(); 561 562 // Do concurrent preclean work. 563 void preclean(); 564 565 void remark(); 566 567 void cleanup(); 568 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use 569 // this carefully. 570 inline void mark_in_prev_bitmap(oop p); 571 572 // Clears marks for all objects in the given range, for the prev or 573 // next bitmaps. Caution: the previous bitmap is usually 574 // read-only, so use this carefully! 575 void clear_range_in_prev_bitmap(MemRegion mr); 576 577 inline bool is_marked_in_prev_bitmap(oop p) const; 578 579 // Verify that there are no collection set oops on the stacks (taskqueues / 580 // global mark stack) and fingers (global / per-task). 581 // If marking is not in progress, it's a no-op. 582 void verify_no_cset_oops() PRODUCT_RETURN; 583 584 inline bool do_yield_check(); 585 586 bool has_aborted() { return _has_aborted; } 587 588 void print_summary_info(); 589 590 void print_worker_threads_on(outputStream* st) const; 591 void threads_do(ThreadClosure* tc) const; 592 593 void print_on_error(outputStream* st) const; 594 595 // Mark the given object on the next bitmap if it is below nTAMS. 596 // If the passed obj_size is zero, it is recalculated from the given object if 597 // needed. This is to be as lazy as possible with accessing the object's size. 598 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj, size_t const obj_size = 0); 599 inline bool mark_in_next_bitmap(uint worker_id, oop const obj, size_t const obj_size = 0); 600 601 inline bool is_marked_in_next_bitmap(oop p) const; 602 603 // Returns true if initialization was successfully completed. 604 bool completed_initialization() const { 605 return _completed_initialization; 606 } 607 608 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 609 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 610 611 private: 612 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application. 613 void rebuild_rem_set_concurrently(); 614 }; 615 616 // A class representing a marking task. 617 class G1CMTask : public TerminatorTerminator { 618 private: 619 enum PrivateConstants { 620 // The regular clock call is called once the scanned words reaches 621 // this limit 622 words_scanned_period = 12*1024, 623 // The regular clock call is called once the number of visited 624 // references reaches this limit 625 refs_reached_period = 1024, 626 // Initial value for the hash seed, used in the work stealing code 627 init_hash_seed = 17 628 }; 629 630 // Number of entries in the per-task stats entry. This seems enough to have a very 631 // low cache miss rate. 632 static const uint RegionMarkStatsCacheSize = 1024; 633 634 G1CMObjArrayProcessor _objArray_processor; 635 636 uint _worker_id; 637 G1CollectedHeap* _g1h; 638 G1ConcurrentMark* _cm; 639 G1CMBitMap* _next_mark_bitmap; 640 // the task queue of this task 641 G1CMTaskQueue* _task_queue; 642 643 G1RegionMarkStatsCache _mark_stats_cache; 644 // Number of calls to this task 645 uint _calls; 646 647 // When the virtual timer reaches this time, the marking step should exit 648 double _time_target_ms; 649 // Start time of the current marking step 650 double _start_time_ms; 651 652 // Oop closure used for iterations over oops 653 G1CMOopClosure* _cm_oop_closure; 654 655 // Region this task is scanning, NULL if we're not scanning any 656 HeapRegion* _curr_region; 657 // Local finger of this task, NULL if we're not scanning a region 658 HeapWord* _finger; 659 // Limit of the region this task is scanning, NULL if we're not scanning one 660 HeapWord* _region_limit; 661 662 // Number of words this task has scanned 663 size_t _words_scanned; 664 // When _words_scanned reaches this limit, the regular clock is 665 // called. Notice that this might be decreased under certain 666 // circumstances (i.e. when we believe that we did an expensive 667 // operation). 668 size_t _words_scanned_limit; 669 // Initial value of _words_scanned_limit (i.e. what it was 670 // before it was decreased). 671 size_t _real_words_scanned_limit; 672 673 // Number of references this task has visited 674 size_t _refs_reached; 675 // When _refs_reached reaches this limit, the regular clock is 676 // called. Notice this this might be decreased under certain 677 // circumstances (i.e. when we believe that we did an expensive 678 // operation). 679 size_t _refs_reached_limit; 680 // Initial value of _refs_reached_limit (i.e. what it was before 681 // it was decreased). 682 size_t _real_refs_reached_limit; 683 684 // If true, then the task has aborted for some reason 685 bool _has_aborted; 686 // Set when the task aborts because it has met its time quota 687 bool _has_timed_out; 688 // True when we're draining SATB buffers; this avoids the task 689 // aborting due to SATB buffers being available (as we're already 690 // dealing with them) 691 bool _draining_satb_buffers; 692 693 // Number sequence of past step times 694 NumberSeq _step_times_ms; 695 // Elapsed time of this task 696 double _elapsed_time_ms; 697 // Termination time of this task 698 double _termination_time_ms; 699 // When this task got into the termination protocol 700 double _termination_start_time_ms; 701 702 TruncatedSeq _marking_step_diffs_ms; 703 704 // Updates the local fields after this task has claimed 705 // a new region to scan 706 void setup_for_region(HeapRegion* hr); 707 // Makes the limit of the region up-to-date 708 void update_region_limit(); 709 710 // Called when either the words scanned or the refs visited limit 711 // has been reached 712 void reached_limit(); 713 // Recalculates the words scanned and refs visited limits 714 void recalculate_limits(); 715 // Decreases the words scanned and refs visited limits when we reach 716 // an expensive operation 717 void decrease_limits(); 718 // Checks whether the words scanned or refs visited reached their 719 // respective limit and calls reached_limit() if they have 720 void check_limits() { 721 if (_words_scanned >= _words_scanned_limit || 722 _refs_reached >= _refs_reached_limit) { 723 reached_limit(); 724 } 725 } 726 // Supposed to be called regularly during a marking step as 727 // it checks a bunch of conditions that might cause the marking step 728 // to abort 729 void regular_clock_call(); 730 731 // Test whether obj might have already been passed over by the 732 // mark bitmap scan, and so needs to be pushed onto the mark stack. 733 bool is_below_finger(oop obj, HeapWord* global_finger) const; 734 735 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry); 736 public: 737 // Apply the closure on the given area of the objArray. Return the number of words 738 // scanned. 739 inline size_t scan_objArray(objArrayOop obj, MemRegion mr); 740 // Resets the task; should be called right at the beginning of a marking phase. 741 void reset(G1CMBitMap* next_mark_bitmap); 742 // Clears all the fields that correspond to a claimed region. 743 void clear_region_fields(); 744 745 // The main method of this class which performs a marking step 746 // trying not to exceed the given duration. However, it might exit 747 // prematurely, according to some conditions (i.e. SATB buffers are 748 // available for processing). 749 void do_marking_step(double target_ms, 750 bool do_termination, 751 bool is_serial); 752 753 // These two calls start and stop the timer 754 void record_start_time() { 755 _elapsed_time_ms = os::elapsedTime() * 1000.0; 756 } 757 void record_end_time() { 758 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 759 } 760 761 // Returns the worker ID associated with this task. 762 uint worker_id() { return _worker_id; } 763 764 // From TerminatorTerminator. It determines whether this task should 765 // exit the termination protocol after it's entered it. 766 virtual bool should_exit_termination(); 767 768 // Resets the local region fields after a task has finished scanning a 769 // region; or when they have become stale as a result of the region 770 // being evacuated. 771 void giveup_current_region(); 772 773 HeapWord* finger() { return _finger; } 774 775 bool has_aborted() { return _has_aborted; } 776 void set_has_aborted() { _has_aborted = true; } 777 void clear_has_aborted() { _has_aborted = false; } 778 779 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 780 781 // Increment the number of references this task has visited. 782 void increment_refs_reached() { ++_refs_reached; } 783 784 // Grey the object by marking it. If not already marked, push it on 785 // the local queue if below the finger. obj is required to be below its region's NTAMS. 786 // Returns whether there has been a mark to the bitmap. 787 inline bool make_reference_grey(oop obj); 788 789 // Grey the object (by calling make_grey_reference) if required, 790 // e.g. obj is below its containing region's NTAMS. 791 // Precondition: obj is a valid heap object. 792 // Returns true if the reference caused a mark to be set in the next bitmap. 793 template <class T> 794 inline bool deal_with_reference(T* p); 795 796 // Scans an object and visits its children. 797 inline void scan_task_entry(G1TaskQueueEntry task_entry); 798 799 // Pushes an object on the local queue. 800 inline void push(G1TaskQueueEntry task_entry); 801 802 // Move entries to the global stack. 803 void move_entries_to_global_stack(); 804 // Move entries from the global stack, return true if we were successful to do so. 805 bool get_entries_from_global_stack(); 806 807 // Pops and scans objects from the local queue. If partially is 808 // true, then it stops when the queue size is of a given limit. If 809 // partially is false, then it stops when the queue is empty. 810 void drain_local_queue(bool partially); 811 // Moves entries from the global stack to the local queue and 812 // drains the local queue. If partially is true, then it stops when 813 // both the global stack and the local queue reach a given size. If 814 // partially if false, it tries to empty them totally. 815 void drain_global_stack(bool partially); 816 // Keeps picking SATB buffers and processing them until no SATB 817 // buffers are available. 818 void drain_satb_buffers(); 819 820 // Moves the local finger to a new location 821 inline void move_finger_to(HeapWord* new_finger) { 822 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 823 _finger = new_finger; 824 } 825 826 G1CMTask(uint worker_id, 827 G1ConcurrentMark *cm, 828 G1CMTaskQueue* task_queue, 829 G1RegionMarkStats* mark_stats, 830 uint max_regions); 831 832 inline void update_liveness(oop const obj, size_t const obj_size); 833 834 // Clear (without flushing) the mark cache entry for the given region. 835 void clear_mark_stats_cache(uint region_idx); 836 // Evict the whole statistics cache into the global statistics. Returns the 837 // number of cache hits and misses so far. 838 Pair<size_t, size_t> flush_mark_stats_cache(); 839 // Prints statistics associated with this task 840 void print_stats(); 841 }; 842 843 // Class that's used to to print out per-region liveness 844 // information. It's currently used at the end of marking and also 845 // after we sort the old regions at the end of the cleanup operation. 846 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure { 847 // Accumulators for these values. 848 size_t _total_used_bytes; 849 size_t _total_capacity_bytes; 850 size_t _total_prev_live_bytes; 851 size_t _total_next_live_bytes; 852 853 // Accumulator for the remembered set size 854 size_t _total_remset_bytes; 855 856 // Accumulator for strong code roots memory size 857 size_t _total_strong_code_roots_bytes; 858 859 static double bytes_to_mb(size_t val) { 860 return (double) val / (double) M; 861 } 862 863 public: 864 // The header and footer are printed in the constructor and 865 // destructor respectively. 866 G1PrintRegionLivenessInfoClosure(const char* phase_name); 867 virtual bool do_heap_region(HeapRegion* r); 868 ~G1PrintRegionLivenessInfoClosure(); 869 }; 870 871 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP