1 /* 2 * Copyright (c) 2001, 2017, 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/heapRegionSet.hpp" 31 #include "gc/shared/taskqueue.hpp" 32 33 class ConcurrentGCTimer; 34 class ConcurrentMarkThread; 35 class G1CollectedHeap; 36 class G1CMTask; 37 class G1ConcurrentMark; 38 class G1OldTracer; 39 class G1RegionToSpaceMapper; 40 class G1SurvivorRegions; 41 42 #ifdef _MSC_VER 43 #pragma warning(push) 44 // warning C4522: multiple assignment operators specified 45 #pragma warning(disable:4522) 46 #endif 47 48 // This is a container class for either an oop or a continuation address for 49 // mark stack entries. Both are pushed onto the mark stack. 50 class G1TaskQueueEntry VALUE_OBJ_CLASS_SPEC { 51 private: 52 void* _holder; 53 54 static const uintptr_t ArraySliceBit = 1; 55 56 G1TaskQueueEntry(oop obj) : _holder(obj) { 57 assert(_holder != NULL, "Not allowed to set NULL task queue element"); 58 } 59 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { } 60 public: 61 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; } 62 G1TaskQueueEntry() : _holder(NULL) { } 63 64 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); } 65 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); } 66 67 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) { 68 _holder = t._holder; 69 return *this; 70 } 71 72 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile { 73 _holder = t._holder; 74 return *this; 75 } 76 77 oop obj() const { 78 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder)); 79 return (oop)_holder; 80 } 81 82 HeapWord* slice() const { 83 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder)); 84 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit); 85 } 86 87 bool is_oop() const { return !is_array_slice(); } 88 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; } 89 bool is_null() const { return _holder == NULL; } 90 }; 91 92 #ifdef _MSC_VER 93 #pragma warning(pop) 94 #endif 95 96 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue; 97 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet; 98 99 // Closure used by CM during concurrent reference discovery 100 // and reference processing (during remarking) to determine 101 // if a particular object is alive. It is primarily used 102 // to determine if referents of discovered reference objects 103 // are alive. An instance is also embedded into the 104 // reference processor as the _is_alive_non_header field 105 class G1CMIsAliveClosure: public BoolObjectClosure { 106 G1CollectedHeap* _g1; 107 public: 108 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { } 109 110 bool do_object_b(oop obj); 111 }; 112 113 // Represents the overflow mark stack used by concurrent marking. 114 // 115 // Stores oops in a huge buffer in virtual memory that is always fully committed. 116 // Resizing may only happen during a STW pause when the stack is empty. 117 // 118 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark 119 // stack memory is split into evenly sized chunks of oops. Users can only 120 // add or remove entries on that basis. 121 // Chunks are filled in increasing address order. Not completely filled chunks 122 // have a NULL element as a terminating element. 123 // 124 // Every chunk has a header containing a single pointer element used for memory 125 // management. This wastes some space, but is negligible (< .1% with current sizing). 126 // 127 // Memory management is done using a mix of tracking a high water-mark indicating 128 // that all chunks at a lower address are valid chunks, and a singly linked free 129 // list connecting all empty chunks. 130 class G1CMMarkStack VALUE_OBJ_CLASS_SPEC { 131 public: 132 // Number of TaskQueueEntries that can fit in a single chunk. 133 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */; 134 private: 135 struct TaskQueueEntryChunk { 136 TaskQueueEntryChunk* next; 137 G1TaskQueueEntry data[EntriesPerChunk]; 138 }; 139 140 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack. 141 142 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area. 143 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements. 144 145 char _pad0[DEFAULT_CACHE_LINE_SIZE]; 146 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users. 147 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)]; 148 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data. 149 volatile size_t _chunks_in_chunk_list; 150 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)]; 151 152 volatile size_t _hwm; // High water mark within the reserved space. 153 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)]; 154 155 // Allocate a new chunk from the reserved memory, using the high water mark. Returns 156 // NULL if out of memory. 157 TaskQueueEntryChunk* allocate_new_chunk(); 158 159 // Atomically add the given chunk to the list. 160 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem); 161 // Atomically remove and return a chunk from the given list. Returns NULL if the 162 // list is empty. 163 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list); 164 165 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem); 166 void add_chunk_to_free_list(TaskQueueEntryChunk* elem); 167 168 TaskQueueEntryChunk* remove_chunk_from_chunk_list(); 169 TaskQueueEntryChunk* remove_chunk_from_free_list(); 170 171 // Resizes the mark stack to the given new capacity. Releases any previous 172 // memory if successful. 173 bool resize(size_t new_capacity); 174 175 public: 176 G1CMMarkStack(); 177 ~G1CMMarkStack(); 178 179 // Alignment and minimum capacity of this mark stack in number of oops. 180 static size_t capacity_alignment(); 181 182 // Allocate and initialize the mark stack with the given number of oops. 183 bool initialize(size_t initial_capacity, size_t max_capacity); 184 185 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark 186 // stack. If less than EntriesPerChunk elements are to be pushed, the array must 187 // be terminated with a NULL. 188 // Returns whether the buffer contents were successfully pushed to the global mark 189 // stack. 190 bool par_push_chunk(G1TaskQueueEntry* buffer); 191 192 // Pops a chunk from this mark stack, copying them into the given buffer. This 193 // chunk may contain up to EntriesPerChunk elements. If there are less, the last 194 // element in the array is a NULL pointer. 195 bool par_pop_chunk(G1TaskQueueEntry* buffer); 196 197 // Return whether the chunk list is empty. Racy due to unsynchronized access to 198 // _chunk_list. 199 bool is_empty() const { return _chunk_list == NULL; } 200 201 size_t capacity() const { return _chunk_capacity; } 202 203 // Expand the stack, typically in response to an overflow condition 204 void expand(); 205 206 // Return the approximate number of oops on this mark stack. Racy due to 207 // unsynchronized access to _chunks_in_chunk_list. 208 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; } 209 210 void set_empty(); 211 212 // Apply Fn to every oop on the mark stack. The mark stack must not 213 // be modified while iterating. 214 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN; 215 }; 216 217 // Root Regions are regions that are not empty at the beginning of a 218 // marking cycle and which we might collect during an evacuation pause 219 // while the cycle is active. Given that, during evacuation pauses, we 220 // do not copy objects that are explicitly marked, what we have to do 221 // for the root regions is to scan them and mark all objects reachable 222 // from them. According to the SATB assumptions, we only need to visit 223 // each object once during marking. So, as long as we finish this scan 224 // before the next evacuation pause, we can copy the objects from the 225 // root regions without having to mark them or do anything else to them. 226 // 227 // Currently, we only support root region scanning once (at the start 228 // of the marking cycle) and the root regions are all the survivor 229 // regions populated during the initial-mark pause. 230 class G1CMRootRegions VALUE_OBJ_CLASS_SPEC { 231 private: 232 const G1SurvivorRegions* _survivors; 233 G1ConcurrentMark* _cm; 234 235 volatile bool _scan_in_progress; 236 volatile bool _should_abort; 237 volatile int _claimed_survivor_index; 238 239 void notify_scan_done(); 240 241 public: 242 G1CMRootRegions(); 243 // We actually do most of the initialization in this method. 244 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm); 245 246 // Reset the claiming / scanning of the root regions. 247 void prepare_for_scan(); 248 249 // Forces get_next() to return NULL so that the iteration aborts early. 250 void abort() { _should_abort = true; } 251 252 // Return true if the CM thread are actively scanning root regions, 253 // false otherwise. 254 bool scan_in_progress() { return _scan_in_progress; } 255 256 // Claim the next root region to scan atomically, or return NULL if 257 // all have been claimed. 258 HeapRegion* claim_next(); 259 260 // The number of root regions to scan. 261 uint num_root_regions() const; 262 263 void cancel_scan(); 264 265 // Flag that we're done with root region scanning and notify anyone 266 // who's waiting on it. If aborted is false, assume that all regions 267 // have been claimed. 268 void scan_finished(); 269 270 // If CM threads are still scanning root regions, wait until they 271 // are done. Return true if we had to wait, false otherwise. 272 bool wait_until_scan_finished(); 273 }; 274 275 // This class manages data structures and methods for doing liveness analysis in 276 // G1's concurrent cycle. 277 class G1ConcurrentMark: public CHeapObj<mtGC> { 278 friend class ConcurrentMarkThread; 279 friend class G1CMRefProcTaskProxy; 280 friend class G1CMRefProcTaskExecutor; 281 friend class G1CMKeepAliveAndDrainClosure; 282 friend class G1CMDrainMarkingStackClosure; 283 friend class G1CMBitMapClosure; 284 friend class G1CMConcurrentMarkingTask; 285 friend class G1CMRemarkTask; 286 friend class G1CMTask; 287 288 ConcurrentMarkThread* _cm_thread; // The thread doing the work 289 G1CollectedHeap* _g1h; // The heap 290 bool _completed_initialization; // Set to true when initialization is complete 291 292 FreeRegionList _cleanup_list; 293 294 // Concurrent marking support structures 295 G1CMBitMap _mark_bitmap_1; 296 G1CMBitMap _mark_bitmap_2; 297 G1CMBitMap* _prev_mark_bitmap; // Completed mark bitmap 298 G1CMBitMap* _next_mark_bitmap; // Under-construction mark bitmap 299 300 // Heap bounds 301 HeapWord* _heap_start; 302 HeapWord* _heap_end; 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 _max_num_tasks; // Maximum number of marking tasks 314 uint _num_active_tasks; // Number of tasks currently active 315 G1CMTask** _tasks; // Task queue array (max_worker_id length) 316 317 G1CMTaskQueueSet* _task_queues; // Task queue set 318 ParallelTaskTerminator _terminator; // For termination 319 320 // Two sync barriers that are used to synchronize tasks when an 321 // overflow occurs. The algorithm is the following. All tasks enter 322 // the first one to ensure that they have all stopped manipulating 323 // the global data structures. After they exit it, they re-initialize 324 // their data structures and task 0 re-initializes the global data 325 // structures. Then, they enter the second sync barrier. This 326 // ensure, that no task starts doing work before all data 327 // structures (local and global) have been re-initialized. When they 328 // exit it, they are free to start working again. 329 WorkGangBarrierSync _first_overflow_barrier_sync; 330 WorkGangBarrierSync _second_overflow_barrier_sync; 331 332 // This is set by any task, when an overflow on the global data 333 // structures is detected 334 volatile bool _has_overflown; 335 // True: marking is concurrent, false: we're in remark 336 volatile bool _concurrent; 337 // Set at the end of a Full GC so that marking aborts 338 volatile bool _has_aborted; 339 340 // Used when remark aborts due to an overflow to indicate that 341 // another concurrent marking phase should start 342 volatile bool _restart_for_overflow; 343 344 // This is true from the very start of concurrent marking until the 345 // point when all the tasks complete their work. It is really used 346 // to determine the points between the end of concurrent marking and 347 // time of remark. 348 volatile bool _concurrent_marking_in_progress; 349 350 ConcurrentGCTimer* _gc_timer_cm; 351 352 G1OldTracer* _gc_tracer_cm; 353 354 // Timing statistics. All of them are in ms 355 NumberSeq _init_times; 356 NumberSeq _remark_times; 357 NumberSeq _remark_mark_times; 358 NumberSeq _remark_weak_ref_times; 359 NumberSeq _cleanup_times; 360 double _total_counting_time; 361 double _total_rs_scrub_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 weak_refs_work_parallel_part(BoolObjectClosure* is_alive, bool purged_classes); 370 void weak_refs_work(bool clear_all_soft_refs); 371 372 void swap_mark_bitmaps(); 373 374 // Resets the global marking data structures, as well as the 375 // task local ones; should be called during initial mark. 376 void reset(); 377 378 // Resets all the marking data structures. Called when we have to restart 379 // marking or when marking completes (via set_non_marking_state below). 380 void reset_marking_state(); 381 382 // We do this after we're done with marking so that the marking data 383 // structures are initialized to a sensible and predictable state. 384 void set_non_marking_state(); 385 386 // Called to indicate how many threads are currently active. 387 void set_concurrency(uint active_tasks); 388 389 // Should be called to indicate which phase we're in (concurrent 390 // mark or remark) and how many threads are currently active. 391 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 392 393 // Prints all gathered CM-related statistics 394 void print_stats(); 395 396 bool cleanup_list_is_empty() { 397 return _cleanup_list.is_empty(); 398 } 399 400 HeapWord* finger() { return _finger; } 401 bool concurrent() { return _concurrent; } 402 uint active_tasks() { return _num_active_tasks; } 403 ParallelTaskTerminator* terminator() { return &_terminator; } 404 405 // Claims the next available region to be scanned by a marking 406 // task/thread. It might return NULL if the next region is empty or 407 // we have run out of regions. In the latter case, out_of_regions() 408 // determines whether we've really run out of regions or the task 409 // should call claim_region() again. This might seem a bit 410 // awkward. Originally, the code was written so that claim_region() 411 // either successfully returned with a non-empty region or there 412 // were no more regions to be claimed. The problem with this was 413 // that, in certain circumstances, it iterated over large chunks of 414 // the heap finding only empty regions and, while it was working, it 415 // was preventing the calling task to call its regular clock 416 // method. So, this way, each task will spend very little time in 417 // claim_region() and is allowed to call the regular clock method 418 // frequently. 419 HeapRegion* claim_region(uint worker_id); 420 421 // Determines whether we've run out of regions to scan. Note that 422 // the finger can point past the heap end in case the heap was expanded 423 // to satisfy an allocation without doing a GC. This is fine, because all 424 // objects in those regions will be considered live anyway because of 425 // SATB guarantees (i.e. their TAMS will be equal to bottom). 426 bool out_of_regions() { return _finger >= _heap_end; } 427 428 // Returns the task with the given id 429 G1CMTask* task(uint id) { 430 assert(id < _num_active_tasks, "Task id %u not within active bounds up to %u", id, _num_active_tasks); 431 return _tasks[id]; 432 } 433 434 // Access / manipulation of the overflow flag which is set to 435 // indicate that the global stack has overflown 436 bool has_overflown() { return _has_overflown; } 437 void set_has_overflown() { _has_overflown = true; } 438 void clear_has_overflown() { _has_overflown = false; } 439 bool restart_for_overflow() { return _restart_for_overflow; } 440 441 // Methods to enter the two overflow sync barriers 442 void enter_first_sync_barrier(uint worker_id); 443 void enter_second_sync_barrier(uint worker_id); 444 445 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is 446 // true, periodically insert checks to see if this method should exit prematurely. 447 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield); 448 public: 449 // Manipulation of the global mark stack. 450 // The push and pop operations are used by tasks for transfers 451 // between task-local queues and the global mark stack. 452 bool mark_stack_push(G1TaskQueueEntry* arr) { 453 if (!_global_mark_stack.par_push_chunk(arr)) { 454 set_has_overflown(); 455 return false; 456 } 457 return true; 458 } 459 bool mark_stack_pop(G1TaskQueueEntry* arr) { 460 return _global_mark_stack.par_pop_chunk(arr); 461 } 462 size_t mark_stack_size() const { return _global_mark_stack.size(); } 463 size_t partial_mark_stack_size_target() const { return _global_mark_stack.capacity() / 3; } 464 bool mark_stack_empty() const { return _global_mark_stack.is_empty(); } 465 466 G1CMRootRegions* root_regions() { return &_root_regions; } 467 468 bool concurrent_marking_in_progress() const { 469 return _concurrent_marking_in_progress; 470 } 471 void set_concurrent_marking_in_progress() { 472 _concurrent_marking_in_progress = true; 473 } 474 void clear_concurrent_marking_in_progress() { 475 _concurrent_marking_in_progress = false; 476 } 477 478 void concurrent_cycle_start(); 479 void concurrent_cycle_end(); 480 481 void update_accum_task_vtime(int i, double vtime) { 482 _accum_task_vtime[i] += vtime; 483 } 484 485 double all_task_accum_vtime() { 486 double ret = 0.0; 487 for (uint i = 0; i < _max_num_tasks; ++i) 488 ret += _accum_task_vtime[i]; 489 return ret; 490 } 491 492 // Attempts to steal an object from the task queues of other tasks 493 bool try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry); 494 495 G1ConcurrentMark(G1CollectedHeap* g1h, 496 G1RegionToSpaceMapper* prev_bitmap_storage, 497 G1RegionToSpaceMapper* next_bitmap_storage); 498 ~G1ConcurrentMark(); 499 500 ConcurrentMarkThread* cm_thread() { return _cm_thread; } 501 502 const G1CMBitMap* const prev_mark_bitmap() const { return _prev_mark_bitmap; } 503 G1CMBitMap* next_mark_bitmap() const { return _next_mark_bitmap; } 504 505 // Calculates the number of concurrent GC threads to be used in the marking phase. 506 uint calc_active_marking_workers(); 507 508 // Prepare internal data structures for the next mark cycle. This includes clearing 509 // the next mark bitmap and some internal data structures. This method is intended 510 // to be called concurrently to the mutator. It will yield to safepoint requests. 511 void cleanup_for_next_mark(); 512 513 // Clear the previous marking bitmap during safepoint. 514 void clear_prev_bitmap(WorkGang* workers); 515 516 // Return whether the next mark bitmap has no marks set. To be used for assertions 517 // only. Will not yield to pause requests. 518 bool next_mark_bitmap_is_clear(); 519 520 // These two do the work that needs to be done before and after the 521 // initial root checkpoint. Since this checkpoint can be done at two 522 // different points (i.e. an explicit pause or piggy-backed on a 523 // young collection), then it's nice to be able to easily share the 524 // pre/post code. It might be the case that we can put everything in 525 // the post method. 526 void checkpoint_roots_initial_pre(); 527 void checkpoint_roots_initial_post(); 528 529 // Scan all the root regions and mark everything reachable from 530 // them. 531 void scan_root_regions(); 532 533 // Scan a single root region and mark everything reachable from it. 534 void scan_root_region(HeapRegion* hr); 535 536 // Do concurrent phase of marking, to a tentative transitive closure. 537 void mark_from_roots(); 538 539 void checkpoint_roots_final(bool clear_all_soft_refs); 540 void checkpoint_roots_final_work(); 541 542 void cleanup(); 543 void complete_cleanup(); 544 545 // Mark in the previous bitmap. Caution: the prev bitmap is usually read-only, so use 546 // this carefully. 547 inline void mark_in_prev_bitmap(oop p); 548 549 // Clears marks for all objects in the given range, for the prev or 550 // next bitmaps. Caution: the previous bitmap is usually 551 // read-only, so use this carefully! 552 void clear_range_in_prev_bitmap(MemRegion mr); 553 554 inline bool is_marked_in_prev_bitmap(oop p) const; 555 556 // Verify that there are no CSet oops on the stacks (taskqueues / 557 // global mark stack) and fingers (global / per-task). 558 // If marking is not in progress, it's a no-op. 559 void verify_no_cset_oops() PRODUCT_RETURN; 560 561 inline bool do_yield_check(); 562 563 // Abandon current marking iteration due to a Full GC. 564 void abort(); 565 566 bool has_aborted() { return _has_aborted; } 567 568 void print_summary_info(); 569 570 void print_worker_threads_on(outputStream* st) const; 571 void threads_do(ThreadClosure* tc) const; 572 573 void print_on_error(outputStream* st) const; 574 575 // Mark the given object on the next bitmap if it is below nTAMS. 576 inline bool mark_in_next_bitmap(HeapRegion* const hr, oop const obj); 577 inline bool mark_in_next_bitmap(oop const obj); 578 579 // Returns true if initialization was successfully completed. 580 bool completed_initialization() const { 581 return _completed_initialization; 582 } 583 584 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; } 585 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; } 586 587 private: 588 // Clear (Reset) all liveness count data. 589 void clear_live_data(WorkGang* workers); 590 591 #ifdef ASSERT 592 // Verify all of the above data structures that they are in initial state. 593 void verify_live_data_clear(); 594 #endif 595 596 // Aggregates the per-card liveness data based on the current marking. Also sets 597 // the amount of marked bytes for each region. 598 void create_live_data(); 599 600 void finalize_live_data(); 601 602 void verify_live_data(); 603 }; 604 605 // A class representing a marking task. 606 class G1CMTask : public TerminatorTerminator { 607 private: 608 enum PrivateConstants { 609 // The regular clock call is called once the scanned words reaches 610 // this limit 611 words_scanned_period = 12*1024, 612 // The regular clock call is called once the number of visited 613 // references reaches this limit 614 refs_reached_period = 1024, 615 // Initial value for the hash seed, used in the work stealing code 616 init_hash_seed = 17 617 }; 618 619 G1CMObjArrayProcessor _objArray_processor; 620 621 uint _worker_id; 622 G1CollectedHeap* _g1h; 623 G1ConcurrentMark* _cm; 624 G1CMBitMap* _next_mark_bitmap; 625 // the task queue of this task 626 G1CMTaskQueue* _task_queue; 627 628 // Number of calls to this task 629 uint _calls; 630 631 // When the virtual timer reaches this time, the marking step should exit 632 double _time_target_ms; 633 // Start time of the current marking step 634 double _start_time_ms; 635 636 // Oop closure used for iterations over oops 637 G1CMOopClosure* _cm_oop_closure; 638 639 // Region this task is scanning, NULL if we're not scanning any 640 HeapRegion* _curr_region; 641 // Local finger of this task, NULL if we're not scanning a region 642 HeapWord* _finger; 643 // Limit of the region this task is scanning, NULL if we're not scanning one 644 HeapWord* _region_limit; 645 646 // Number of words this task has scanned 647 size_t _words_scanned; 648 // When _words_scanned reaches this limit, the regular clock is 649 // called. Notice that this might be decreased under certain 650 // circumstances (i.e. when we believe that we did an expensive 651 // operation). 652 size_t _words_scanned_limit; 653 // Initial value of _words_scanned_limit (i.e. what it was 654 // before it was decreased). 655 size_t _real_words_scanned_limit; 656 657 // Number of references this task has visited 658 size_t _refs_reached; 659 // When _refs_reached reaches this limit, the regular clock is 660 // called. Notice this this might be decreased under certain 661 // circumstances (i.e. when we believe that we did an expensive 662 // operation). 663 size_t _refs_reached_limit; 664 // Initial value of _refs_reached_limit (i.e. what it was before 665 // it was decreased). 666 size_t _real_refs_reached_limit; 667 668 // Used by the work stealing 669 int _hash_seed; 670 // If true, then the task has aborted for some reason 671 bool _has_aborted; 672 // Set when the task aborts because it has met its time quota 673 bool _has_timed_out; 674 // True when we're draining SATB buffers; this avoids the task 675 // aborting due to SATB buffers being available (as we're already 676 // dealing with them) 677 bool _draining_satb_buffers; 678 679 // Number sequence of past step times 680 NumberSeq _step_times_ms; 681 // Elapsed time of this task 682 double _elapsed_time_ms; 683 // Termination time of this task 684 double _termination_time_ms; 685 // When this task got into the termination protocol 686 double _termination_start_time_ms; 687 688 // True when the task is during a concurrent phase, false when it is 689 // in the remark phase (so, in the latter case, we do not have to 690 // check all the things that we have to check during the concurrent 691 // phase, i.e. SATB buffer availability...) 692 bool _concurrent; 693 694 TruncatedSeq _marking_step_diffs_ms; 695 696 // Updates the local fields after this task has claimed 697 // a new region to scan 698 void setup_for_region(HeapRegion* hr); 699 // Makes the limit of the region up-to-date 700 void update_region_limit(); 701 702 // Called when either the words scanned or the refs visited limit 703 // has been reached 704 void reached_limit(); 705 // Recalculates the words scanned and refs visited limits 706 void recalculate_limits(); 707 // Decreases the words scanned and refs visited limits when we reach 708 // an expensive operation 709 void decrease_limits(); 710 // Checks whether the words scanned or refs visited reached their 711 // respective limit and calls reached_limit() if they have 712 void check_limits() { 713 if (_words_scanned >= _words_scanned_limit || 714 _refs_reached >= _refs_reached_limit) { 715 reached_limit(); 716 } 717 } 718 // Supposed to be called regularly during a marking step as 719 // it checks a bunch of conditions that might cause the marking step 720 // to abort 721 void regular_clock_call(); 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 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 738 739 // The main method of this class which performs a marking step 740 // trying not to exceed the given duration. However, it might exit 741 // prematurely, according to some conditions (i.e. SATB buffers are 742 // available for processing). 743 void do_marking_step(double target_ms, 744 bool do_termination, 745 bool is_serial); 746 747 // These two calls start and stop the timer 748 void record_start_time() { 749 _elapsed_time_ms = os::elapsedTime() * 1000.0; 750 } 751 void record_end_time() { 752 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 753 } 754 755 // Returns the worker ID associated with this task. 756 uint worker_id() { return _worker_id; } 757 758 // From TerminatorTerminator. It determines whether this task should 759 // exit the termination protocol after it's entered it. 760 virtual bool should_exit_termination(); 761 762 // Resets the local region fields after a task has finished scanning a 763 // region; or when they have become stale as a result of the region 764 // being evacuated. 765 void giveup_current_region(); 766 767 HeapWord* finger() { return _finger; } 768 769 bool has_aborted() { return _has_aborted; } 770 void set_has_aborted() { _has_aborted = true; } 771 void clear_has_aborted() { _has_aborted = false; } 772 773 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 774 775 // Increment the number of references this task has visited. 776 void increment_refs_reached() { ++_refs_reached; } 777 778 // Grey the object by marking it. If not already marked, push it on 779 // the local queue if below the finger. 780 // obj is below its region's NTAMS. 781 inline void make_reference_grey(oop obj); 782 783 // Grey the object (by calling make_grey_reference) if required, 784 // e.g. obj is below its containing region's NTAMS. 785 // Precondition: obj is a valid heap object. 786 inline void deal_with_reference(oop obj); 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 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); 821 822 // Prints statistics associated with this task 823 void print_stats(); 824 }; 825 826 // Class that's used to to print out per-region liveness 827 // information. It's currently used at the end of marking and also 828 // after we sort the old regions at the end of the cleanup operation. 829 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 830 private: 831 // Accumulators for these values. 832 size_t _total_used_bytes; 833 size_t _total_capacity_bytes; 834 size_t _total_prev_live_bytes; 835 size_t _total_next_live_bytes; 836 837 // Accumulator for the remembered set size 838 size_t _total_remset_bytes; 839 840 // Accumulator for strong code roots memory size 841 size_t _total_strong_code_roots_bytes; 842 843 static double bytes_to_mb(size_t val) { 844 return (double) val / (double) M; 845 } 846 847 public: 848 // The header and footer are printed in the constructor and 849 // destructor respectively. 850 G1PrintRegionLivenessInfoClosure(const char* phase_name); 851 virtual bool doHeapRegion(HeapRegion* r); 852 ~G1PrintRegionLivenessInfoClosure(); 853 }; 854 855 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP