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 ConcurrentMarkThread; 38 class G1CollectedHeap; 39 class G1CMTask; 40 class G1ConcurrentMark; 41 class G1OldTracer; 42 class G1RegionToSpaceMapper; 43 class G1SurvivorRegions; 44 45 #ifdef _MSC_VER 46 #pragma warning(push) 47 // warning C4522: multiple assignment operators specified 48 #pragma warning(disable:4522) 49 #endif 50 51 // This is a container class for either an oop or a continuation address for 52 // mark stack entries. Both are pushed onto the mark stack. 53 class G1TaskQueueEntry { 54 private: 55 void* _holder; 56 57 static const uintptr_t ArraySliceBit = 1; 58 59 G1TaskQueueEntry(oop obj) : _holder(obj) { 60 assert(_holder != NULL, "Not allowed to set NULL task queue element"); 61 } 62 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { } 63 public: 64 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; } 65 G1TaskQueueEntry() : _holder(NULL) { } 66 67 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); } 68 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); } 69 70 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) { 71 _holder = t._holder; 72 return *this; 73 } 74 75 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile { 76 _holder = t._holder; 77 return *this; 78 } 79 80 oop obj() const { 81 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder)); 82 return (oop)_holder; 83 } 84 85 HeapWord* slice() const { 86 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder)); 87 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit); 88 } 89 90 bool is_oop() const { return !is_array_slice(); } 91 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; } 92 bool is_null() const { return _holder == NULL; } 93 }; 94 95 #ifdef _MSC_VER 96 #pragma warning(pop) 97 #endif 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* g1) : _g1h(g1) { } 112 113 bool do_object_b(oop obj); 114 }; 115 116 // Represents the overflow mark stack used by concurrent marking. 117 // 118 // Stores oops in a huge buffer in virtual memory that is always fully committed. 119 // Resizing may only happen during a STW pause when the stack is empty. 120 // 121 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark 122 // stack memory is split into evenly sized chunks of oops. Users can only 123 // add or remove entries on that basis. 124 // Chunks are filled in increasing address order. Not completely filled chunks 125 // have a NULL element as a terminating element. 126 // 127 // Every chunk has a header containing a single pointer element used for memory 128 // management. This wastes some space, but is negligible (< .1% with current sizing). 129 // 130 // Memory management is done using a mix of tracking a high water-mark indicating 131 // that all chunks at a lower address are valid chunks, and a singly linked free 132 // list connecting all empty chunks. 133 class G1CMMarkStack { 134 public: 135 // Number of TaskQueueEntries that can fit in a single chunk. 136 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */; 137 private: 138 struct TaskQueueEntryChunk { 139 TaskQueueEntryChunk* next; 140 G1TaskQueueEntry data[EntriesPerChunk]; 141 }; 142 143 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack. 144 145 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area. 146 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements. 147 148 char _pad0[DEFAULT_CACHE_LINE_SIZE]; 149 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users. 150 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)]; 151 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data. 152 volatile size_t _chunks_in_chunk_list; 153 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)]; 154 155 volatile size_t _hwm; // High water mark within the reserved space. 156 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)]; 157 158 // Allocate a new chunk from the reserved memory, using the high water mark. Returns 159 // NULL if out of memory. 160 TaskQueueEntryChunk* allocate_new_chunk(); 161 162 // Atomically add the given chunk to the list. 163 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem); 164 // Atomically remove and return a chunk from the given list. Returns NULL if the 165 // list is empty. 166 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list); 167 168 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem); 169 void add_chunk_to_free_list(TaskQueueEntryChunk* elem); 170 171 TaskQueueEntryChunk* remove_chunk_from_chunk_list(); 172 TaskQueueEntryChunk* remove_chunk_from_free_list(); 173 174 // Resizes the mark stack to the given new capacity. Releases any previous 175 // memory if successful. 176 bool resize(size_t new_capacity); 177 178 public: 179 G1CMMarkStack(); 180 ~G1CMMarkStack(); 181 182 // Alignment and minimum capacity of this mark stack in number of oops. 183 static size_t capacity_alignment(); 184 185 // Allocate and initialize the mark stack with the given number of oops. 186 bool initialize(size_t initial_capacity, size_t max_capacity); 187 188 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark 189 // stack. If less than EntriesPerChunk elements are to be pushed, the array must 190 // be terminated with a NULL. 191 // Returns whether the buffer contents were successfully pushed to the global mark 192 // stack. 193 bool par_push_chunk(G1TaskQueueEntry* buffer); 194 195 // Pops a chunk from this mark stack, copying them into the given buffer. This 196 // chunk may contain up to EntriesPerChunk elements. If there are less, the last 197 // element in the array is a NULL pointer. 198 bool par_pop_chunk(G1TaskQueueEntry* buffer); 199 200 // Return whether the chunk list is empty. Racy due to unsynchronized access to 201 // _chunk_list. 202 bool is_empty() const { return _chunk_list == NULL; } 203 204 size_t capacity() const { return _chunk_capacity; } 205 206 // Expand the stack, typically in response to an overflow condition 207 void expand(); 208 209 // Return the approximate number of oops on this mark stack. Racy due to 210 // unsynchronized access to _chunks_in_chunk_list. 211 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; } 212 213 void set_empty(); 214 215 // Apply Fn to every oop on the mark stack. The mark stack must not 216 // be modified while iterating. 217 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN; 218 }; 219 220 // Root Regions are regions that are not empty at the beginning of a 221 // marking cycle and which we might collect during an evacuation pause 222 // while the cycle is active. Given that, during evacuation pauses, we 223 // do not copy objects that are explicitly marked, what we have to do 224 // for the root regions is to scan them and mark all objects reachable 225 // from them. According to the SATB assumptions, we only need to visit 226 // each object once during marking. So, as long as we finish this scan 227 // before the next evacuation pause, we can copy the objects from the 228 // root regions without having to mark them or do anything else to them. 229 // 230 // Currently, we only support root region scanning once (at the start 231 // of the marking cycle) and the root regions are all the survivor 232 // regions populated during the initial-mark pause. 233 class G1CMRootRegions { 234 private: 235 const G1SurvivorRegions* _survivors; 236 G1ConcurrentMark* _cm; 237 238 volatile bool _scan_in_progress; 239 volatile bool _should_abort; 240 volatile int _claimed_survivor_index; 241 242 void notify_scan_done(); 243 244 public: 245 G1CMRootRegions(); 246 // We actually do most of the initialization in this method. 247 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm); 248 249 // Reset the claiming / scanning of the root regions. 250 void prepare_for_scan(); 251 252 // Forces get_next() to return NULL so that the iteration aborts early. 253 void abort() { _should_abort = true; } 254 255 // Return true if the CM thread are actively scanning root regions, 256 // false otherwise. 257 bool scan_in_progress() { return _scan_in_progress; } 258 259 // Claim the next root region to scan atomically, or return NULL if 260 // all have been claimed. 261 HeapRegion* claim_next(); 262 263 // The number of root regions to scan. 264 uint num_root_regions() const; 265 266 void cancel_scan(); 267 268 // Flag that we're done with root region scanning and notify anyone 269 // who's waiting on it. If aborted is false, assume that all regions 270 // have been claimed. 271 void scan_finished(); 272 273 // If CM threads are still scanning root regions, wait until they 274 // are done. Return true if we had to wait, false otherwise. 275 bool wait_until_scan_finished(); 276 }; 277 278 // This class manages data structures and methods for doing liveness analysis in 279 // G1's concurrent cycle. 280 class G1ConcurrentMark : public CHeapObj<mtGC> { 281 friend class ConcurrentMarkThread; 282 friend class G1CMRefProcTaskProxy; 283 friend class G1CMRefProcTaskExecutor; 284 friend class G1CMKeepAliveAndDrainClosure; 285 friend class G1CMDrainMarkingStackClosure; 286 friend class G1CMBitMapClosure; 287 friend class G1CMConcurrentMarkingTask; 288 friend class G1CMRemarkTask; 289 friend class G1CMTask; 290 291 ConcurrentMarkThread* _cm_thread; // The thread doing the work 292 G1CollectedHeap* _g1h; // The heap 293 bool _completed_initialization; // Set to true when initialization is complete 294 295 // Concurrent marking support structures 296 G1CMBitMap _mark_bitmap_1; 297 G1CMBitMap _mark_bitmap_2; 298 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap 299 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap 300 301 // Heap bounds 302 MemRegion const _heap; 303 304 // Root region tracking and claiming 305 G1CMRootRegions _root_regions; 306 307 // For grey objects 308 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger 309 HeapWord* volatile _finger; // The global finger, region aligned, 310 // always pointing to the end of the 311 // last claimed region 312 313 uint _worker_id_offset; 314 uint _max_num_tasks; // Maximum number of marking tasks 315 uint _num_active_tasks; // Number of tasks currently active 316 G1CMTask** _tasks; // Task queue array (max_worker_id length) 317 318 G1CMTaskQueueSet* _task_queues; // Task queue set 319 ParallelTaskTerminator _terminator; // For termination 320 321 // Two sync barriers that are used to synchronize tasks when an 322 // overflow occurs. The algorithm is the following. All tasks enter 323 // the first one to ensure that they have all stopped manipulating 324 // the global data structures. After they exit it, they re-initialize 325 // their data structures and task 0 re-initializes the global data 326 // structures. Then, they enter the second sync barrier. This 327 // ensure, that no task starts doing work before all data 328 // structures (local and global) have been re-initialized. When they 329 // exit it, they are free to start working again. 330 WorkGangBarrierSync _first_overflow_barrier_sync; 331 WorkGangBarrierSync _second_overflow_barrier_sync; 332 333 // This is set by any task, when an overflow on the global data 334 // structures is detected 335 volatile bool _has_overflown; 336 // True: marking is concurrent, false: we're in remark 337 volatile bool _concurrent; 338 // Set at the end of a Full GC so that marking aborts 339 volatile bool _has_aborted; 340 341 // Used when remark aborts due to an overflow to indicate that 342 // another concurrent marking phase should start 343 volatile bool _restart_for_overflow; 344 345 // This is true from the very start of concurrent marking until the 346 // point when all the tasks complete their work. It is really used 347 // to determine the points between the end of concurrent marking and 348 // time of remark. 349 volatile bool _concurrent_marking_in_progress; 350 351 ConcurrentGCTimer* _gc_timer_cm; 352 353 G1OldTracer* _gc_tracer_cm; 354 355 // Timing statistics. All of them are in ms 356 NumberSeq _init_times; 357 NumberSeq _remark_times; 358 NumberSeq _remark_mark_times; 359 NumberSeq _remark_weak_ref_times; 360 NumberSeq _cleanup_times; 361 double _total_cleanup_time; 362 363 double* _accum_task_vtime; // Accumulated task vtime 364 365 WorkGang* _concurrent_workers; 366 uint _num_concurrent_workers; // The number of marking worker threads we're using 367 uint _max_concurrent_workers; // Maximum number of marking worker threads 368 369 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller); 370 371 void finalize_marking(); 372 373 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes); 374 void weak_refs_work(bool clear_all_soft_refs); 375 376 void report_object_count(); 377 378 void swap_mark_bitmaps(); 379 380 void reclaim_empty_regions(); 381 382 // Clear statistics gathered during the concurrent cycle for the given region after 383 // it has been reclaimed. 384 void clear_statistics(HeapRegion* r); 385 386 // Resets the global marking data structures, as well as the 387 // task local ones; should be called during initial mark. 388 void reset(); 389 390 // Resets all the marking data structures. Called when we have to restart 391 // marking or when marking completes (via set_non_marking_state below). 392 void reset_marking_for_restart(); 393 394 // We do this after we're done with marking so that the marking data 395 // structures are initialized to a sensible and predictable state. 396 void reset_at_marking_complete(); 397 398 // Called to indicate how many threads are currently active. 399 void set_concurrency(uint active_tasks); 400 401 // Should be called to indicate which phase we're in (concurrent 402 // mark or remark) and how many threads are currently active. 403 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 404 405 // Prints all gathered CM-related statistics 406 void print_stats(); 407 408 HeapWord* finger() { return _finger; } 409 bool concurrent() { return _concurrent; } 410 uint active_tasks() { return _num_active_tasks; } 411 ParallelTaskTerminator* terminator() { return &_terminator; } 412 413 // Claims the next available region to be scanned by a marking 414 // task/thread. It might return NULL if the next region is empty or 415 // we have run out of regions. In the latter case, out_of_regions() 416 // determines whether we've really run out of regions or the task 417 // should call claim_region() again. This might seem a bit 418 // awkward. Originally, the code was written so that claim_region() 419 // either successfully returned with a non-empty region or there 420 // were no more regions to be claimed. The problem with this was 421 // that, in certain circumstances, it iterated over large chunks of 422 // the heap finding only empty regions and, while it was working, it 423 // was preventing the calling task to call its regular clock 424 // method. So, this way, each task will spend very little time in 425 // claim_region() and is allowed to call the regular clock method 426 // frequently. 427 HeapRegion* claim_region(uint worker_id); 428 429 // Determines whether we've run out of regions to scan. Note that 430 // the finger can point past the heap end in case the heap was expanded 431 // to satisfy an allocation without doing a GC. This is fine, because all 432 // objects in those regions will be considered live anyway because of 433 // SATB guarantees (i.e. their TAMS will be equal to bottom). 434 bool out_of_regions() { return _finger >= _heap.end(); } 435 436 // Returns the task with the given id 437 G1CMTask* task(uint id) { 438 // During initial mark we use the parallel gc threads to do some work, so 439 // we can only compare against _max_num_tasks. 440 assert(id < _max_num_tasks, "Task id %u not within bounds up to %u", id, _max_num_tasks); 441 return _tasks[id]; 442 } 443 444 // Access / manipulation of the overflow flag which is set to 445 // indicate that the global stack has overflown 446 bool has_overflown() { return _has_overflown; } 447 void set_has_overflown() { _has_overflown = true; } 448 void clear_has_overflown() { _has_overflown = false; } 449 bool restart_for_overflow() { return _restart_for_overflow; } 450 451 // Methods to enter the two overflow sync barriers 452 void enter_first_sync_barrier(uint worker_id); 453 void enter_second_sync_barrier(uint worker_id); 454 455 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is 456 // true, periodically insert checks to see if this method should exit prematurely. 457 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield); 458 459 // Region statistics gathered during marking. 460 G1RegionMarkStats* _region_mark_stats; 461 // Top pointer for each region at the start of the rebuild remembered set process 462 // for regions which remembered sets need to be rebuilt. A NULL for a given region 463 // means that this region does not be scanned during the rebuilding remembered 464 // set phase at all. 465 HeapWord* volatile* _top_at_rebuild_starts; 466 public: 467 void add_to_liveness(uint worker_id, oop const obj, size_t size); 468 // Liveness of the given region as determined by concurrent marking, i.e. the amount of 469 // live words between bottom and nTAMS. 470 size_t liveness(uint region) { return _region_mark_stats[region]._live_words; } 471 472 // Sets the internal top_at_region_start for the given region to current top of the region. 473 inline void update_top_at_rebuild_start(HeapRegion* r); 474 // TARS for the given region during remembered set rebuilding. 475 inline HeapWord* top_at_rebuild_start(uint region) const; 476 477 // Clear statistics gathered during the concurrent cycle for the given region after 478 // it has been reclaimed. 479 void clear_statistics_in_region(uint region_idx); 480 // Notification for eagerly reclaimed regions to clean up. 481 void humongous_object_eagerly_reclaimed(HeapRegion* r); 482 // Manipulation of the global mark stack. 483 // The push and pop operations are used by tasks for transfers 484 // between task-local queues and the global mark stack. 485 bool mark_stack_push(G1TaskQueueEntry* arr) { 486 if (!_global_mark_stack.par_push_chunk(arr)) { 487 set_has_overflown(); 488 return false; 489 } 490 return true; 491 } 492 bool mark_stack_pop(G1TaskQueueEntry* arr) { 493 return _global_mark_stack.par_pop_chunk(arr); 494 } 495 size_t mark_stack_size() const { return _global_mark_stack.size(); } 496 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; } 497 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); } 498 499 G1CMRootRegions* root_regions() { return &_root_regions; } 500 501 bool concurrent_marking_in_progress() const { 502 return _concurrent_marking_in_progress; 503 } 504 void set_concurrent_marking_in_progress() { 505 _concurrent_marking_in_progress = true; 506 } 507 void clear_concurrent_marking_in_progress() { 508 _concurrent_marking_in_progress = false; 509 } 510 511 void concurrent_cycle_start(); 512 // Abandon current marking iteration due to a Full GC. 513 void concurrent_cycle_abort(); 514 void concurrent_cycle_end(); 515 516 void update_accum_task_vtime(int i, double vtime) { 517 _accum_task_vtime[i] += vtime; 518 } 519 520 double all_task_accum_vtime() { 521 double ret = 0.0; 522 for (uint i = 0; i < _max_num_tasks; ++i) 523 ret += _accum_task_vtime[i]; 524 return ret; 525 } 526 527 // Attempts to steal an object from the task queues of other tasks 528 bool try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry); 529 530 G1ConcurrentMark(G1CollectedHeap* g1h, 531 G1RegionToSpaceMapper* prev_bitmap_storage, 532 G1RegionToSpaceMapper* next_bitmap_storage); 533 ~G1ConcurrentMark(); 534 535 ConcurrentMarkThread* cm_thread() { return _cm_thread; } 536 537 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; } 538 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; } 539 540 // Calculates the number of concurrent GC threads to be used in the marking phase. 541 uint calc_active_marking_workers(); 542 543 // Moves all per-task cached data into global state. 544 void flush_all_task_caches(); 545 // Prepare internal data structures for the next mark cycle. This includes clearing 546 // the next mark bitmap and some internal data structures. This method is intended 547 // to be called concurrently to the mutator. It will yield to safepoint requests. 548 void cleanup_for_next_mark(); 549 550 // Clear the previous marking bitmap during safepoint. 551 void clear_prev_bitmap(WorkGang* workers); 552 553 // Return whether the next mark bitmap has no marks set. To be used for assertions 554 // only. Will not yield to pause requests. 555 bool next_mark_bitmap_is_clear(); 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 region and mark everything reachable from it. 567 void scan_root_region(HeapRegion* hr, uint worker_id); 568 569 // Do concurrent phase of marking, to a tentative transitive closure. 570 void mark_from_roots(); 571 572 void remark(); 573 574 void cleanup(); 575 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use 576 // this carefully. 577 inline void mark_in_prev_bitmap(oop p); 578 579 // Clears marks for all objects in the given range, for the prev or 580 // next bitmaps. Caution: the previous bitmap is usually 581 // read-only, so use this carefully! 582 void clear_range_in_prev_bitmap(MemRegion mr); 583 584 inline bool is_marked_in_prev_bitmap(oop p) const; 585 586 // Verify that there are no collection set oops on the stacks (taskqueues / 587 // global mark stack) and fingers (global / per-task). 588 // If marking is not in progress, it's a no-op. 589 void verify_no_cset_oops() PRODUCT_RETURN; 590 591 inline bool do_yield_check(); 592 593 bool has_aborted() { return _has_aborted; } 594 595 void print_summary_info(); 596 597 void print_worker_threads_on(outputStream* st) const; 598 void threads_do(ThreadClosure* tc) const; 599 600 void print_on_error(outputStream* st) const; 601 602 // Mark the given object on the next bitmap if it is below nTAMS. 603 // If the passed obj_size is zero, it is recalculated from the given object if 604 // needed. This is to be as lazy as possible with accessing the object's size. 605 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj, size_t const obj_size = 0); 606 inline bool mark_in_next_bitmap(uint worker_id, oop const obj, size_t const obj_size = 0); 607 608 // Returns true if initialization was successfully completed. 609 bool completed_initialization() const { 610 return _completed_initialization; 611 } 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 // Used by the work stealing 690 int _hash_seed; 691 // If true, then the task has aborted for some reason 692 bool _has_aborted; 693 // Set when the task aborts because it has met its time quota 694 bool _has_timed_out; 695 // True when we're draining SATB buffers; this avoids the task 696 // aborting due to SATB buffers being available (as we're already 697 // dealing with them) 698 bool _draining_satb_buffers; 699 700 // Number sequence of past step times 701 NumberSeq _step_times_ms; 702 // Elapsed time of this task 703 double _elapsed_time_ms; 704 // Termination time of this task 705 double _termination_time_ms; 706 // When this task got into the termination protocol 707 double _termination_start_time_ms; 708 709 // True when the task is during a concurrent phase, false when it is 710 // in the remark phase (so, in the latter case, we do not have to 711 // check all the things that we have to check during the concurrent 712 // phase, i.e. SATB buffer availability...) 713 bool _concurrent; 714 715 TruncatedSeq _marking_step_diffs_ms; 716 717 // Updates the local fields after this task has claimed 718 // a new region to scan 719 void setup_for_region(HeapRegion* hr); 720 // Makes the limit of the region up-to-date 721 void update_region_limit(); 722 723 // Called when either the words scanned or the refs visited limit 724 // has been reached 725 void reached_limit(); 726 // Recalculates the words scanned and refs visited limits 727 void recalculate_limits(); 728 // Decreases the words scanned and refs visited limits when we reach 729 // an expensive operation 730 void decrease_limits(); 731 // Checks whether the words scanned or refs visited reached their 732 // respective limit and calls reached_limit() if they have 733 void check_limits() { 734 if (_words_scanned >= _words_scanned_limit || 735 _refs_reached >= _refs_reached_limit) { 736 reached_limit(); 737 } 738 } 739 // Supposed to be called regularly during a marking step as 740 // it checks a bunch of conditions that might cause the marking step 741 // to abort 742 void regular_clock_call(); 743 744 // Test whether obj might have already been passed over by the 745 // mark bitmap scan, and so needs to be pushed onto the mark stack. 746 bool is_below_finger(oop obj, HeapWord* global_finger) const; 747 748 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry); 749 public: 750 // Apply the closure on the given area of the objArray. Return the number of words 751 // scanned. 752 inline size_t scan_objArray(objArrayOop obj, MemRegion mr); 753 // Resets the task; should be called right at the beginning of a marking phase. 754 void reset(G1CMBitMap* next_mark_bitmap); 755 // Clears all the fields that correspond to a claimed region. 756 void clear_region_fields(); 757 758 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 759 760 // The main method of this class which performs a marking step 761 // trying not to exceed the given duration. However, it might exit 762 // prematurely, according to some conditions (i.e. SATB buffers are 763 // available for processing). 764 void do_marking_step(double target_ms, 765 bool do_termination, 766 bool is_serial); 767 768 // These two calls start and stop the timer 769 void record_start_time() { 770 _elapsed_time_ms = os::elapsedTime() * 1000.0; 771 } 772 void record_end_time() { 773 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 774 } 775 776 // Returns the worker ID associated with this task. 777 uint worker_id() { return _worker_id; } 778 779 // From TerminatorTerminator. It determines whether this task should 780 // exit the termination protocol after it's entered it. 781 virtual bool should_exit_termination(); 782 783 // Resets the local region fields after a task has finished scanning a 784 // region; or when they have become stale as a result of the region 785 // being evacuated. 786 void giveup_current_region(); 787 788 HeapWord* finger() { return _finger; } 789 790 bool has_aborted() { return _has_aborted; } 791 void set_has_aborted() { _has_aborted = true; } 792 void clear_has_aborted() { _has_aborted = false; } 793 794 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 795 796 // Increment the number of references this task has visited. 797 void increment_refs_reached() { ++_refs_reached; } 798 799 // Grey the object by marking it. If not already marked, push it on 800 // the local queue if below the finger. 801 // obj is below its region's NTAMS. 802 inline void make_reference_grey(oop obj); 803 804 // Grey the object (by calling make_grey_reference) if required, 805 // e.g. obj is below its containing region's NTAMS. 806 // Precondition: obj is a valid heap object. 807 template <class T> 808 inline void deal_with_reference(T* p); 809 810 // Scans an object and visits its children. 811 inline void scan_task_entry(G1TaskQueueEntry task_entry); 812 813 // Pushes an object on the local queue. 814 inline void push(G1TaskQueueEntry task_entry); 815 816 // Move entries to the global stack. 817 void move_entries_to_global_stack(); 818 // Move entries from the global stack, return true if we were successful to do so. 819 bool get_entries_from_global_stack(); 820 821 // Pops and scans objects from the local queue. If partially is 822 // true, then it stops when the queue size is of a given limit. If 823 // partially is false, then it stops when the queue is empty. 824 void drain_local_queue(bool partially); 825 // Moves entries from the global stack to the local queue and 826 // drains the local queue. If partially is true, then it stops when 827 // both the global stack and the local queue reach a given size. If 828 // partially if false, it tries to empty them totally. 829 void drain_global_stack(bool partially); 830 // Keeps picking SATB buffers and processing them until no SATB 831 // buffers are available. 832 void drain_satb_buffers(); 833 834 // Moves the local finger to a new location 835 inline void move_finger_to(HeapWord* new_finger) { 836 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 837 _finger = new_finger; 838 } 839 840 G1CMTask(uint worker_id, 841 G1ConcurrentMark *cm, 842 G1CMTaskQueue* task_queue, 843 G1RegionMarkStats* mark_stats, 844 uint max_regions); 845 846 inline void update_liveness(oop const obj, size_t const obj_size); 847 848 // Clear (without flushing) the mark cache entry for the given region. 849 void clear_mark_stats_cache(uint region_idx); 850 // Evict the whole statistics cache into the global statistics. Returns the 851 // number of cache hits and misses so far. 852 Pair<size_t, size_t> flush_mark_stats_cache(); 853 // Prints statistics associated with this task 854 void print_stats(); 855 }; 856 857 // Class that's used to to print out per-region liveness 858 // information. It's currently used at the end of marking and also 859 // after we sort the old regions at the end of the cleanup operation. 860 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure { 861 private: 862 // Accumulators for these values. 863 size_t _total_used_bytes; 864 size_t _total_capacity_bytes; 865 size_t _total_prev_live_bytes; 866 size_t _total_next_live_bytes; 867 868 // Accumulator for the remembered set size 869 size_t _total_remset_bytes; 870 871 // Accumulator for strong code roots memory size 872 size_t _total_strong_code_roots_bytes; 873 874 static double bytes_to_mb(size_t val) { 875 return (double) val / (double) M; 876 } 877 878 public: 879 // The header and footer are printed in the constructor and 880 // destructor respectively. 881 G1PrintRegionLivenessInfoClosure(const char* phase_name); 882 virtual bool do_heap_region(HeapRegion* r); 883 ~G1PrintRegionLivenessInfoClosure(); 884 }; 885 886 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP