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 G1TaskQueueEntry(oop obj)63 G1TaskQueueEntry(oop obj) : _holder(obj) { 64 assert(_holder != NULL, "Not allowed to set NULL task queue element"); 65 } G1TaskQueueEntry(HeapWord * addr)66 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { } 67 public: 68 G1TaskQueueEntry()69 G1TaskQueueEntry() : _holder(NULL) { } 70 // Trivially copyable, for use in GenericTaskQueue. 71 from_slice(HeapWord * what)72 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); } from_oop(oop obj)73 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); } 74 obj() const75 oop obj() const { 76 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder)); 77 return (oop)_holder; 78 } 79 slice() const80 HeapWord* slice() const { 81 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder)); 82 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit); 83 } 84 is_oop() const85 bool is_oop() const { return !is_array_slice(); } is_array_slice() const86 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; } is_null() const87 bool is_null() const { return _holder == NULL; } 88 }; 89 90 PRAGMA_DIAG_POP 91 92 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue; 93 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet; 94 95 // Closure used by CM during concurrent reference discovery 96 // and reference processing (during remarking) to determine 97 // if a particular object is alive. It is primarily used 98 // to determine if referents of discovered reference objects 99 // are alive. An instance is also embedded into the 100 // reference processor as the _is_alive_non_header field 101 class G1CMIsAliveClosure : public BoolObjectClosure { 102 G1CollectedHeap* _g1h; 103 public: G1CMIsAliveClosure(G1CollectedHeap * g1h)104 G1CMIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 105 bool do_object_b(oop obj); 106 }; 107 108 class G1CMSubjectToDiscoveryClosure : public BoolObjectClosure { 109 G1CollectedHeap* _g1h; 110 public: G1CMSubjectToDiscoveryClosure(G1CollectedHeap * g1h)111 G1CMSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 112 bool do_object_b(oop obj); 113 }; 114 115 // Represents the overflow mark stack used by concurrent marking. 116 // 117 // Stores oops in a huge buffer in virtual memory that is always fully committed. 118 // Resizing may only happen during a STW pause when the stack is empty. 119 // 120 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark 121 // stack memory is split into evenly sized chunks of oops. Users can only 122 // add or remove entries on that basis. 123 // Chunks are filled in increasing address order. Not completely filled chunks 124 // have a NULL element as a terminating element. 125 // 126 // Every chunk has a header containing a single pointer element used for memory 127 // management. This wastes some space, but is negligible (< .1% with current sizing). 128 // 129 // Memory management is done using a mix of tracking a high water-mark indicating 130 // that all chunks at a lower address are valid chunks, and a singly linked free 131 // list connecting all empty chunks. 132 class G1CMMarkStack { 133 public: 134 // Number of TaskQueueEntries that can fit in a single chunk. 135 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */; 136 private: 137 struct TaskQueueEntryChunk { 138 TaskQueueEntryChunk* next; 139 G1TaskQueueEntry data[EntriesPerChunk]; 140 }; 141 142 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack. 143 144 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area. 145 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements. 146 147 char _pad0[DEFAULT_CACHE_LINE_SIZE]; 148 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users. 149 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)]; 150 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data. 151 volatile size_t _chunks_in_chunk_list; 152 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)]; 153 154 volatile size_t _hwm; // High water mark within the reserved space. 155 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)]; 156 157 // Allocate a new chunk from the reserved memory, using the high water mark. Returns 158 // NULL if out of memory. 159 TaskQueueEntryChunk* allocate_new_chunk(); 160 161 // Atomically add the given chunk to the list. 162 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem); 163 // Atomically remove and return a chunk from the given list. Returns NULL if the 164 // list is empty. 165 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list); 166 167 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem); 168 void add_chunk_to_free_list(TaskQueueEntryChunk* elem); 169 170 TaskQueueEntryChunk* remove_chunk_from_chunk_list(); 171 TaskQueueEntryChunk* remove_chunk_from_free_list(); 172 173 // Resizes the mark stack to the given new capacity. Releases any previous 174 // memory if successful. 175 bool resize(size_t new_capacity); 176 177 public: 178 G1CMMarkStack(); 179 ~G1CMMarkStack(); 180 181 // Alignment and minimum capacity of this mark stack in number of oops. 182 static size_t capacity_alignment(); 183 184 // Allocate and initialize the mark stack with the given number of oops. 185 bool initialize(size_t initial_capacity, size_t max_capacity); 186 187 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark 188 // stack. If less than EntriesPerChunk elements are to be pushed, the array must 189 // be terminated with a NULL. 190 // Returns whether the buffer contents were successfully pushed to the global mark 191 // stack. 192 bool par_push_chunk(G1TaskQueueEntry* buffer); 193 194 // Pops a chunk from this mark stack, copying them into the given buffer. This 195 // chunk may contain up to EntriesPerChunk elements. If there are less, the last 196 // element in the array is a NULL pointer. 197 bool par_pop_chunk(G1TaskQueueEntry* buffer); 198 199 // Return whether the chunk list is empty. Racy due to unsynchronized access to 200 // _chunk_list. is_empty() const201 bool is_empty() const { return _chunk_list == NULL; } 202 capacity() const203 size_t capacity() const { return _chunk_capacity; } 204 205 // Expand the stack, typically in response to an overflow condition 206 void expand(); 207 208 // Return the approximate number of oops on this mark stack. Racy due to 209 // unsynchronized access to _chunks_in_chunk_list. size() const210 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; } 211 212 void set_empty(); 213 214 // Apply Fn to every oop on the mark stack. The mark stack must not 215 // be modified while iterating. 216 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN; 217 }; 218 219 // Root MemRegions are memory areas that contain objects which references are 220 // roots wrt to the marking. They must be scanned before marking to maintain the 221 // SATB invariant. 222 // Typically they contain the areas from nTAMS to top of the regions. 223 // We could scan and mark through these objects during the initial-mark pause, but for 224 // pause time reasons we move this work to the concurrent phase. 225 // We need to complete this procedure before the next GC because it might determine 226 // that some of these "root objects" are dead, potentially dropping some required 227 // references. 228 // Root MemRegions comprise of the contents of survivor regions at the end 229 // of the GC, and any objects copied into the old gen during GC. 230 class G1CMRootMemRegions { 231 // The set of root MemRegions. 232 MemRegion* _root_regions; 233 size_t const _max_regions; 234 235 volatile size_t _num_root_regions; // Actual number of root regions. 236 237 volatile size_t _claimed_root_regions; // Number of root regions currently claimed. 238 239 volatile bool _scan_in_progress; 240 volatile bool _should_abort; 241 242 void notify_scan_done(); 243 244 public: 245 G1CMRootMemRegions(uint const max_regions); 246 ~G1CMRootMemRegions(); 247 248 // Reset the data structure to allow addition of new root regions. 249 void reset(); 250 251 void add(HeapWord* start, HeapWord* end); 252 253 // Reset the claiming / scanning of the root regions. 254 void prepare_for_scan(); 255 256 // Forces get_next() to return NULL so that the iteration aborts early. abort()257 void abort() { _should_abort = true; } 258 259 // Return true if the CM thread are actively scanning root regions, 260 // false otherwise. scan_in_progress()261 bool scan_in_progress() { return _scan_in_progress; } 262 263 // Claim the next root MemRegion to scan atomically, or return NULL if 264 // all have been claimed. 265 const MemRegion* claim_next(); 266 267 // The number of root regions to scan. 268 uint num_root_regions() const; 269 270 void cancel_scan(); 271 272 // Flag that we're done with root region scanning and notify anyone 273 // who's waiting on it. If aborted is false, assume that all regions 274 // have been claimed. 275 void scan_finished(); 276 277 // If CM threads are still scanning root regions, wait until they 278 // are done. Return true if we had to wait, false otherwise. 279 bool wait_until_scan_finished(); 280 }; 281 282 // This class manages data structures and methods for doing liveness analysis in 283 // G1's concurrent cycle. 284 class G1ConcurrentMark : public CHeapObj<mtGC> { 285 friend class G1ConcurrentMarkThread; 286 friend class G1CMRefProcTaskProxy; 287 friend class G1CMRefProcTaskExecutor; 288 friend class G1CMKeepAliveAndDrainClosure; 289 friend class G1CMDrainMarkingStackClosure; 290 friend class G1CMBitMapClosure; 291 friend class G1CMConcurrentMarkingTask; 292 friend class G1CMRemarkTask; 293 friend class G1CMTask; 294 295 G1ConcurrentMarkThread* _cm_thread; // The thread doing the work 296 G1CollectedHeap* _g1h; // The heap 297 298 // Concurrent marking support structures 299 G1CMBitMap _mark_bitmap_1; 300 G1CMBitMap _mark_bitmap_2; 301 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap 302 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap 303 304 // Heap bounds 305 MemRegion const _heap; 306 307 // Root region tracking and claiming 308 G1CMRootMemRegions _root_regions; 309 310 // For grey objects 311 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger 312 HeapWord* volatile _finger; // The global finger, region aligned, 313 // always pointing to the end of the 314 // last claimed region 315 316 uint _worker_id_offset; 317 uint _max_num_tasks; // Maximum number of marking tasks 318 uint _num_active_tasks; // Number of tasks currently active 319 G1CMTask** _tasks; // Task queue array (max_worker_id length) 320 321 G1CMTaskQueueSet* _task_queues; // Task queue set 322 TaskTerminator _terminator; // For termination 323 324 // Two sync barriers that are used to synchronize tasks when an 325 // overflow occurs. The algorithm is the following. All tasks enter 326 // the first one to ensure that they have all stopped manipulating 327 // the global data structures. After they exit it, they re-initialize 328 // their data structures and task 0 re-initializes the global data 329 // structures. Then, they enter the second sync barrier. This 330 // ensure, that no task starts doing work before all data 331 // structures (local and global) have been re-initialized. When they 332 // exit it, they are free to start working again. 333 WorkGangBarrierSync _first_overflow_barrier_sync; 334 WorkGangBarrierSync _second_overflow_barrier_sync; 335 336 // This is set by any task, when an overflow on the global data 337 // structures is detected 338 volatile bool _has_overflown; 339 // True: marking is concurrent, false: we're in remark 340 volatile bool _concurrent; 341 // Set at the end of a Full GC so that marking aborts 342 volatile bool _has_aborted; 343 344 // Used when remark aborts due to an overflow to indicate that 345 // another concurrent marking phase should start 346 volatile bool _restart_for_overflow; 347 348 ConcurrentGCTimer* _gc_timer_cm; 349 350 G1OldTracer* _gc_tracer_cm; 351 352 // Timing statistics. All of them are in ms 353 NumberSeq _init_times; 354 NumberSeq _remark_times; 355 NumberSeq _remark_mark_times; 356 NumberSeq _remark_weak_ref_times; 357 NumberSeq _cleanup_times; 358 double _total_cleanup_time; 359 360 double* _accum_task_vtime; // Accumulated task vtime 361 362 WorkGang* _concurrent_workers; 363 uint _num_concurrent_workers; // The number of marking worker threads we're using 364 uint _max_concurrent_workers; // Maximum number of marking worker threads 365 366 void verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller); 367 368 void finalize_marking(); 369 370 void weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes); 371 void weak_refs_work(bool clear_all_soft_refs); 372 373 void report_object_count(bool mark_completed); 374 375 void swap_mark_bitmaps(); 376 377 void reclaim_empty_regions(); 378 379 // After reclaiming empty regions, update heap sizes. 380 void compute_new_sizes(); 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 finger()408 HeapWord* finger() { return _finger; } concurrent()409 bool concurrent() { return _concurrent; } active_tasks()410 uint active_tasks() { return _num_active_tasks; } terminator()411 TaskTerminator* 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). out_of_regions()434 bool out_of_regions() { return _finger >= _heap.end(); } 435 436 // Returns the task with the given id task(uint 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 has_overflown()446 bool has_overflown() { return _has_overflown; } set_has_overflown()447 void set_has_overflown() { _has_overflown = true; } clear_has_overflown()448 void clear_has_overflown() { _has_overflown = false; } restart_for_overflow()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. liveness(uint region) const470 size_t liveness(uint region) const { 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. mark_stack_push(G1TaskQueueEntry * arr)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 } mark_stack_pop(G1TaskQueueEntry * arr)492 bool mark_stack_pop(G1TaskQueueEntry* arr) { 493 return _global_mark_stack.par_pop_chunk(arr); 494 } mark_stack_size() const495 size_t mark_stack_size() const { return _global_mark_stack.size(); } partial_mark_stack_size_target() const496 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; } mark_stack_empty() const497 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); } 498 root_regions()499 G1CMRootMemRegions* root_regions() { return &_root_regions; } 500 501 void concurrent_cycle_start(); 502 // Abandon current marking iteration due to a Full GC. 503 void concurrent_cycle_abort(); 504 void concurrent_cycle_end(); 505 update_accum_task_vtime(int i,double vtime)506 void update_accum_task_vtime(int i, double vtime) { 507 _accum_task_vtime[i] += vtime; 508 } 509 all_task_accum_vtime()510 double all_task_accum_vtime() { 511 double ret = 0.0; 512 for (uint i = 0; i < _max_num_tasks; ++i) 513 ret += _accum_task_vtime[i]; 514 return ret; 515 } 516 517 // Attempts to steal an object from the task queues of other tasks 518 bool try_stealing(uint worker_id, G1TaskQueueEntry& task_entry); 519 520 G1ConcurrentMark(G1CollectedHeap* g1h, 521 G1RegionToSpaceMapper* prev_bitmap_storage, 522 G1RegionToSpaceMapper* next_bitmap_storage); 523 ~G1ConcurrentMark(); 524 cm_thread()525 G1ConcurrentMarkThread* cm_thread() { return _cm_thread; } 526 prev_mark_bitmap() const527 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; } next_mark_bitmap() const528 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; } 529 530 // Calculates the number of concurrent GC threads to be used in the marking phase. 531 uint calc_active_marking_workers(); 532 533 // Moves all per-task cached data into global state. 534 void flush_all_task_caches(); 535 // Prepare internal data structures for the next mark cycle. This includes clearing 536 // the next mark bitmap and some internal data structures. This method is intended 537 // to be called concurrently to the mutator. It will yield to safepoint requests. 538 void cleanup_for_next_mark(); 539 540 // Clear the previous marking bitmap during safepoint. 541 void clear_prev_bitmap(WorkGang* workers); 542 543 // These two methods do the work that needs to be done at the start and end of the 544 // initial mark pause. 545 void pre_initial_mark(); 546 void post_initial_mark(); 547 548 // Scan all the root regions and mark everything reachable from 549 // them. 550 void scan_root_regions(); 551 552 // Scan a single root MemRegion to mark everything reachable from it. 553 void scan_root_region(const MemRegion* region, uint worker_id); 554 555 // Do concurrent phase of marking, to a tentative transitive closure. 556 void mark_from_roots(); 557 558 // Do concurrent preclean work. 559 void preclean(); 560 561 void remark(); 562 563 void cleanup(); 564 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use 565 // this carefully. 566 inline void mark_in_prev_bitmap(oop p); 567 568 // Clears marks for all objects in the given range, for the prev or 569 // next bitmaps. Caution: the previous bitmap is usually 570 // read-only, so use this carefully! 571 void clear_range_in_prev_bitmap(MemRegion mr); 572 573 inline bool is_marked_in_prev_bitmap(oop p) const; 574 575 // Verify that there are no collection set oops on the stacks (taskqueues / 576 // global mark stack) and fingers (global / per-task). 577 // If marking is not in progress, it's a no-op. 578 void verify_no_collection_set_oops() PRODUCT_RETURN; 579 580 inline bool do_yield_check(); 581 has_aborted()582 bool has_aborted() { return _has_aborted; } 583 584 void print_summary_info(); 585 586 void threads_do(ThreadClosure* tc) const; 587 588 void print_on_error(outputStream* st) const; 589 590 // Mark the given object on the next bitmap if it is below nTAMS. 591 inline bool mark_in_next_bitmap(uint worker_id, HeapRegion* const hr, oop const obj); 592 inline bool mark_in_next_bitmap(uint worker_id, oop const obj); 593 594 inline bool is_marked_in_next_bitmap(oop p) const; 595 gc_timer_cm() const596 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } gc_tracer_cm() const597 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 598 599 private: 600 // Rebuilds the remembered sets for chosen regions in parallel and concurrently to the application. 601 void rebuild_rem_set_concurrently(); 602 }; 603 604 // A class representing a marking task. 605 class G1CMTask : public TerminatorTerminator { 606 private: 607 enum PrivateConstants { 608 // The regular clock call is called once the scanned words reaches 609 // this limit 610 words_scanned_period = 12*1024, 611 // The regular clock call is called once the number of visited 612 // references reaches this limit 613 refs_reached_period = 1024, 614 // Initial value for the hash seed, used in the work stealing code 615 init_hash_seed = 17 616 }; 617 618 // Number of entries in the per-task stats entry. This seems enough to have a very 619 // low cache miss rate. 620 static const uint RegionMarkStatsCacheSize = 1024; 621 622 G1CMObjArrayProcessor _objArray_processor; 623 624 uint _worker_id; 625 G1CollectedHeap* _g1h; 626 G1ConcurrentMark* _cm; 627 G1CMBitMap* _next_mark_bitmap; 628 // the task queue of this task 629 G1CMTaskQueue* _task_queue; 630 631 G1RegionMarkStatsCache _mark_stats_cache; 632 // Number of calls to this task 633 uint _calls; 634 635 // When the virtual timer reaches this time, the marking step should exit 636 double _time_target_ms; 637 // Start time of the current marking step 638 double _start_time_ms; 639 640 // Oop closure used for iterations over oops 641 G1CMOopClosure* _cm_oop_closure; 642 643 // Region this task is scanning, NULL if we're not scanning any 644 HeapRegion* _curr_region; 645 // Local finger of this task, NULL if we're not scanning a region 646 HeapWord* _finger; 647 // Limit of the region this task is scanning, NULL if we're not scanning one 648 HeapWord* _region_limit; 649 650 // Number of words this task has scanned 651 size_t _words_scanned; 652 // When _words_scanned reaches this limit, the regular clock is 653 // called. Notice that this might be decreased under certain 654 // circumstances (i.e. when we believe that we did an expensive 655 // operation). 656 size_t _words_scanned_limit; 657 // Initial value of _words_scanned_limit (i.e. what it was 658 // before it was decreased). 659 size_t _real_words_scanned_limit; 660 661 // Number of references this task has visited 662 size_t _refs_reached; 663 // When _refs_reached reaches this limit, the regular clock is 664 // called. Notice this this might be decreased under certain 665 // circumstances (i.e. when we believe that we did an expensive 666 // operation). 667 size_t _refs_reached_limit; 668 // Initial value of _refs_reached_limit (i.e. what it was before 669 // it was decreased). 670 size_t _real_refs_reached_limit; 671 672 // If true, then the task has aborted for some reason 673 bool _has_aborted; 674 // Set when the task aborts because it has met its time quota 675 bool _has_timed_out; 676 // True when we're draining SATB buffers; this avoids the task 677 // aborting due to SATB buffers being available (as we're already 678 // dealing with them) 679 bool _draining_satb_buffers; 680 681 // Number sequence of past step times 682 NumberSeq _step_times_ms; 683 // Elapsed time of this task 684 double _elapsed_time_ms; 685 // Termination time of this task 686 double _termination_time_ms; 687 // When this task got into the termination protocol 688 double _termination_start_time_ms; 689 690 TruncatedSeq _marking_step_diff_ms; 691 692 // Updates the local fields after this task has claimed 693 // a new region to scan 694 void setup_for_region(HeapRegion* hr); 695 // Makes the limit of the region up-to-date 696 void update_region_limit(); 697 698 // Called when either the words scanned or the refs visited limit 699 // has been reached 700 void reached_limit(); 701 // Recalculates the words scanned and refs visited limits 702 void recalculate_limits(); 703 // Decreases the words scanned and refs visited limits when we reach 704 // an expensive operation 705 void decrease_limits(); 706 // Checks whether the words scanned or refs visited reached their 707 // respective limit and calls reached_limit() if they have check_limits()708 void check_limits() { 709 if (_words_scanned >= _words_scanned_limit || 710 _refs_reached >= _refs_reached_limit) { 711 reached_limit(); 712 } 713 } 714 // Supposed to be called regularly during a marking step as 715 // it checks a bunch of conditions that might cause the marking step 716 // to abort 717 // Return true if the marking step should continue. Otherwise, return false to abort 718 bool regular_clock_call(); 719 720 // Set abort flag if regular_clock_call() check fails 721 inline void abort_marking_if_regular_check_fail(); 722 723 // Test whether obj might have already been passed over by the 724 // mark bitmap scan, and so needs to be pushed onto the mark stack. 725 bool is_below_finger(oop obj, HeapWord* global_finger) const; 726 727 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry); 728 public: 729 // Apply the closure on the given area of the objArray. Return the number of words 730 // scanned. 731 inline size_t scan_objArray(objArrayOop obj, MemRegion mr); 732 // Resets the task; should be called right at the beginning of a marking phase. 733 void reset(G1CMBitMap* next_mark_bitmap); 734 // Clears all the fields that correspond to a claimed region. 735 void clear_region_fields(); 736 737 // The main method of this class which performs a marking step 738 // trying not to exceed the given duration. However, it might exit 739 // prematurely, according to some conditions (i.e. SATB buffers are 740 // available for processing). 741 void do_marking_step(double target_ms, 742 bool do_termination, 743 bool is_serial); 744 745 // These two calls start and stop the timer record_start_time()746 void record_start_time() { 747 _elapsed_time_ms = os::elapsedTime() * 1000.0; 748 } record_end_time()749 void record_end_time() { 750 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 751 } 752 753 // Returns the worker ID associated with this task. worker_id()754 uint worker_id() { return _worker_id; } 755 756 // From TerminatorTerminator. It determines whether this task should 757 // exit the termination protocol after it's entered it. 758 virtual bool should_exit_termination(); 759 760 // Resets the local region fields after a task has finished scanning a 761 // region; or when they have become stale as a result of the region 762 // being evacuated. 763 void giveup_current_region(); 764 finger()765 HeapWord* finger() { return _finger; } 766 has_aborted()767 bool has_aborted() { return _has_aborted; } set_has_aborted()768 void set_has_aborted() { _has_aborted = true; } clear_has_aborted()769 void clear_has_aborted() { _has_aborted = false; } 770 771 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 772 773 // Increment the number of references this task has visited. increment_refs_reached()774 void increment_refs_reached() { ++_refs_reached; } 775 776 // Grey the object by marking it. If not already marked, push it on 777 // the local queue if below the finger. obj is required to be below its region's NTAMS. 778 // Returns whether there has been a mark to the bitmap. 779 inline bool make_reference_grey(oop obj); 780 781 // Grey the object (by calling make_grey_reference) if required, 782 // e.g. obj is below its containing region's NTAMS. 783 // Precondition: obj is a valid heap object. 784 // Returns true if the reference caused a mark to be set in the next bitmap. 785 template <class T> 786 inline bool deal_with_reference(T* p); 787 788 // Scans an object and visits its children. 789 inline void scan_task_entry(G1TaskQueueEntry task_entry); 790 791 // Pushes an object on the local queue. 792 inline void push(G1TaskQueueEntry task_entry); 793 794 // Move entries to the global stack. 795 void move_entries_to_global_stack(); 796 // Move entries from the global stack, return true if we were successful to do so. 797 bool get_entries_from_global_stack(); 798 799 // Pops and scans objects from the local queue. If partially is 800 // true, then it stops when the queue size is of a given limit. If 801 // partially is false, then it stops when the queue is empty. 802 void drain_local_queue(bool partially); 803 // Moves entries from the global stack to the local queue and 804 // drains the local queue. If partially is true, then it stops when 805 // both the global stack and the local queue reach a given size. If 806 // partially if false, it tries to empty them totally. 807 void drain_global_stack(bool partially); 808 // Keeps picking SATB buffers and processing them until no SATB 809 // buffers are available. 810 void drain_satb_buffers(); 811 812 // Moves the local finger to a new location move_finger_to(HeapWord * new_finger)813 inline void move_finger_to(HeapWord* new_finger) { 814 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 815 _finger = new_finger; 816 } 817 818 G1CMTask(uint worker_id, 819 G1ConcurrentMark *cm, 820 G1CMTaskQueue* task_queue, 821 G1RegionMarkStats* mark_stats, 822 uint max_regions); 823 824 inline void update_liveness(oop const obj, size_t const obj_size); 825 826 // Clear (without flushing) the mark cache entry for the given region. 827 void clear_mark_stats_cache(uint region_idx); 828 // Evict the whole statistics cache into the global statistics. Returns the 829 // number of cache hits and misses so far. 830 Pair<size_t, size_t> flush_mark_stats_cache(); 831 // Prints statistics associated with this task 832 void print_stats(); 833 }; 834 835 // Class that's used to to print out per-region liveness 836 // information. It's currently used at the end of marking and also 837 // after we sort the old regions at the end of the cleanup operation. 838 class G1PrintRegionLivenessInfoClosure : public HeapRegionClosure { 839 // Accumulators for these values. 840 size_t _total_used_bytes; 841 size_t _total_capacity_bytes; 842 size_t _total_prev_live_bytes; 843 size_t _total_next_live_bytes; 844 845 // Accumulator for the remembered set size 846 size_t _total_remset_bytes; 847 848 // Accumulator for strong code roots memory size 849 size_t _total_strong_code_roots_bytes; 850 bytes_to_mb(size_t val)851 static double bytes_to_mb(size_t val) { 852 return (double) val / (double) M; 853 } 854 855 public: 856 // The header and footer are printed in the constructor and 857 // destructor respectively. 858 G1PrintRegionLivenessInfoClosure(const char* phase_name); 859 virtual bool do_heap_region(HeapRegion* r); 860 ~G1PrintRegionLivenessInfoClosure(); 861 }; 862 863 #endif // SHARE_GC_G1_G1CONCURRENTMARK_HPP 864