1 /* 2 * Copyright (c) 2001, 2016, 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_CONCURRENTMARK_HPP 26 #define SHARE_VM_GC_G1_CONCURRENTMARK_HPP 27 28 #include "classfile/javaClasses.hpp" 29 #include "gc/g1/g1RegionToSpaceMapper.hpp" 30 #include "gc/g1/heapRegionSet.hpp" 31 #include "gc/shared/taskqueue.hpp" 32 33 class G1CollectedHeap; 34 class CMBitMap; 35 class CMTask; 36 class ConcurrentMark; 37 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue; 38 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet; 39 40 // Closure used by CM during concurrent reference discovery 41 // and reference processing (during remarking) to determine 42 // if a particular object is alive. It is primarily used 43 // to determine if referents of discovered reference objects 44 // are alive. An instance is also embedded into the 45 // reference processor as the _is_alive_non_header field 46 class G1CMIsAliveClosure: public BoolObjectClosure { 47 G1CollectedHeap* _g1; 48 public: 49 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { } 50 51 bool do_object_b(oop obj); 52 }; 53 54 // A generic CM bit map. This is essentially a wrapper around the BitMap 55 // class, with one bit per (1<<_shifter) HeapWords. 56 57 class CMBitMapRO VALUE_OBJ_CLASS_SPEC { 58 protected: 59 HeapWord* _bmStartWord; // base address of range covered by map 60 size_t _bmWordSize; // map size (in #HeapWords covered) 61 const int _shifter; // map to char or bit 62 BitMap _bm; // the bit map itself 63 64 public: 65 // constructor 66 CMBitMapRO(int shifter); 67 68 // inquiries 69 HeapWord* startWord() const { return _bmStartWord; } 70 // the following is one past the last word in space 71 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 72 73 // read marks 74 75 bool isMarked(HeapWord* addr) const { 76 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 77 "outside underlying space?"); 78 return _bm.at(heapWordToOffset(addr)); 79 } 80 81 // iteration 82 inline bool iterate(BitMapClosure* cl, MemRegion mr); 83 84 // Return the address corresponding to the next marked bit at or after 85 // "addr", and before "limit", if "limit" is non-NULL. If there is no 86 // such bit, returns "limit" if that is non-NULL, or else "endWord()". 87 HeapWord* getNextMarkedWordAddress(const HeapWord* addr, 88 const HeapWord* limit = NULL) const; 89 90 // conversion utilities 91 HeapWord* offsetToHeapWord(size_t offset) const { 92 return _bmStartWord + (offset << _shifter); 93 } 94 size_t heapWordToOffset(const HeapWord* addr) const { 95 return pointer_delta(addr, _bmStartWord) >> _shifter; 96 } 97 98 // The argument addr should be the start address of a valid object 99 inline HeapWord* nextObject(HeapWord* addr); 100 101 void print_on_error(outputStream* st, const char* prefix) const; 102 103 // debugging 104 NOT_PRODUCT(bool covers(MemRegion rs) const;) 105 }; 106 107 class CMBitMapMappingChangedListener : public G1MappingChangedListener { 108 private: 109 CMBitMap* _bm; 110 public: 111 CMBitMapMappingChangedListener() : _bm(NULL) {} 112 113 void set_bitmap(CMBitMap* bm) { _bm = bm; } 114 115 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 116 }; 117 118 class CMBitMap : public CMBitMapRO { 119 private: 120 CMBitMapMappingChangedListener _listener; 121 122 public: 123 static size_t compute_size(size_t heap_size); 124 // Returns the amount of bytes on the heap between two marks in the bitmap. 125 static size_t mark_distance(); 126 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the 127 // mark bitmap corresponds to. This is the same as the mark distance above. 128 static size_t heap_map_factor() { 129 return mark_distance(); 130 } 131 132 CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); } 133 134 // Initializes the underlying BitMap to cover the given area. 135 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage); 136 137 // Write marks. 138 inline void mark(HeapWord* addr); 139 inline void clear(HeapWord* addr); 140 inline bool parMark(HeapWord* addr); 141 142 void clearRange(MemRegion mr); 143 144 // Clear the whole mark bitmap. 145 void clearAll(); 146 }; 147 148 // Represents a marking stack used by ConcurrentMarking in the G1 collector. 149 class CMMarkStack VALUE_OBJ_CLASS_SPEC { 150 VirtualSpace _virtual_space; // Underlying backing store for actual stack 151 ConcurrentMark* _cm; 152 oop* _base; // bottom of stack 153 jint _index; // one more than last occupied index 154 jint _capacity; // max #elements 155 jint _saved_index; // value of _index saved at start of GC 156 157 bool _overflow; 158 bool _should_expand; 159 160 public: 161 CMMarkStack(ConcurrentMark* cm); 162 ~CMMarkStack(); 163 164 bool allocate(size_t capacity); 165 166 // Pushes the first "n" elements of "ptr_arr" on the stack. 167 // Locking impl: concurrency is allowed only with 168 // "par_push_arr" and/or "par_pop_arr" operations, which use the same 169 // locking strategy. 170 void par_push_arr(oop* ptr_arr, int n); 171 172 // If returns false, the array was empty. Otherwise, removes up to "max" 173 // elements from the stack, and transfers them to "ptr_arr" in an 174 // unspecified order. The actual number transferred is given in "n" ("n 175 // == 0" is deliberately redundant with the return value.) Locking impl: 176 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" 177 // operations, which use the same locking strategy. 178 bool par_pop_arr(oop* ptr_arr, int max, int* n); 179 180 bool isEmpty() { return _index == 0; } 181 int maxElems() { return _capacity; } 182 183 bool overflow() { return _overflow; } 184 void clear_overflow() { _overflow = false; } 185 186 bool should_expand() const { return _should_expand; } 187 void set_should_expand(); 188 189 // Expand the stack, typically in response to an overflow condition 190 void expand(); 191 192 int size() { return _index; } 193 194 void setEmpty() { _index = 0; clear_overflow(); } 195 196 // Record the current index. 197 void note_start_of_gc(); 198 199 // Make sure that we have not added any entries to the stack during GC. 200 void note_end_of_gc(); 201 202 // Apply fn to each oop in the mark stack, up to the bound recorded 203 // via one of the above "note" functions. The mark stack must not 204 // be modified while iterating. 205 template<typename Fn> void iterate(Fn fn); 206 }; 207 208 class YoungList; 209 210 // Root Regions are regions that are not empty at the beginning of a 211 // marking cycle and which we might collect during an evacuation pause 212 // while the cycle is active. Given that, during evacuation pauses, we 213 // do not copy objects that are explicitly marked, what we have to do 214 // for the root regions is to scan them and mark all objects reachable 215 // from them. According to the SATB assumptions, we only need to visit 216 // each object once during marking. So, as long as we finish this scan 217 // before the next evacuation pause, we can copy the objects from the 218 // root regions without having to mark them or do anything else to them. 219 // 220 // Currently, we only support root region scanning once (at the start 221 // of the marking cycle) and the root regions are all the survivor 222 // regions populated during the initial-mark pause. 223 class CMRootRegions VALUE_OBJ_CLASS_SPEC { 224 private: 225 YoungList* _young_list; 226 ConcurrentMark* _cm; 227 228 volatile bool _scan_in_progress; 229 volatile bool _should_abort; 230 HeapRegion* volatile _next_survivor; 231 232 public: 233 CMRootRegions(); 234 // We actually do most of the initialization in this method. 235 void init(G1CollectedHeap* g1h, ConcurrentMark* cm); 236 237 // Reset the claiming / scanning of the root regions. 238 void prepare_for_scan(); 239 240 // Forces get_next() to return NULL so that the iteration aborts early. 241 void abort() { _should_abort = true; } 242 243 // Return true if the CM thread are actively scanning root regions, 244 // false otherwise. 245 bool scan_in_progress() { return _scan_in_progress; } 246 247 // Claim the next root region to scan atomically, or return NULL if 248 // all have been claimed. 249 HeapRegion* claim_next(); 250 251 // Flag that we're done with root region scanning and notify anyone 252 // who's waiting on it. If aborted is false, assume that all regions 253 // have been claimed. 254 void scan_finished(); 255 256 // If CM threads are still scanning root regions, wait until they 257 // are done. Return true if we had to wait, false otherwise. 258 bool wait_until_scan_finished(); 259 }; 260 261 class ConcurrentMarkThread; 262 263 class ConcurrentMark: public CHeapObj<mtGC> { 264 friend class CMMarkStack; 265 friend class ConcurrentMarkThread; 266 friend class CMTask; 267 friend class CMBitMapClosure; 268 friend class CMRemarkTask; 269 friend class CMConcurrentMarkingTask; 270 friend class G1ParNoteEndTask; 271 friend class CalcLiveObjectsClosure; 272 friend class G1CMRefProcTaskProxy; 273 friend class G1CMRefProcTaskExecutor; 274 friend class G1CMKeepAliveAndDrainClosure; 275 friend class G1CMDrainMarkingStackClosure; 276 277 protected: 278 ConcurrentMarkThread* _cmThread; // The thread doing the work 279 G1CollectedHeap* _g1h; // The heap 280 uint _parallel_marking_threads; // The number of marking 281 // threads we're using 282 uint _max_parallel_marking_threads; // Max number of marking 283 // threads we'll ever use 284 double _sleep_factor; // How much we have to sleep, with 285 // respect to the work we just did, to 286 // meet the marking overhead goal 287 double _marking_task_overhead; // Marking target overhead for 288 // a single task 289 290 FreeRegionList _cleanup_list; 291 292 // Concurrent marking support structures 293 CMBitMap _markBitMap1; 294 CMBitMap _markBitMap2; 295 CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap 296 CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap 297 298 BitMap _region_bm; 299 BitMap _card_bm; 300 301 // Heap bounds 302 HeapWord* _heap_start; 303 HeapWord* _heap_end; 304 305 // Root region tracking and claiming 306 CMRootRegions _root_regions; 307 308 // For gray objects 309 CMMarkStack _markStack; // Grey objects behind global finger 310 HeapWord* volatile _finger; // The global finger, region aligned, 311 // always points to the end of the 312 // last claimed region 313 314 // Marking tasks 315 uint _max_worker_id;// Maximum worker id 316 uint _active_tasks; // Task num currently active 317 CMTask** _tasks; // Task queue array (max_worker_id len) 318 CMTaskQueueSet* _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 // Keep track of whether we have started concurrent phase or not. 352 bool _concurrent_phase_started; 353 354 // All of these times 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* _parallel_workers; 366 367 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes); 368 void weakRefsWork(bool clear_all_soft_refs); 369 370 void swapMarkBitMaps(); 371 372 // It resets the global marking data structures, as well as the 373 // task local ones; should be called during initial mark. 374 void reset(); 375 376 // Resets all the marking data structures. Called when we have to restart 377 // marking or when marking completes (via set_non_marking_state below). 378 void reset_marking_state(bool clear_overflow = true); 379 380 // We do this after we're done with marking so that the marking data 381 // structures are initialized to a sensible and predictable state. 382 void set_non_marking_state(); 383 384 // Called to indicate how many threads are currently active. 385 void set_concurrency(uint active_tasks); 386 387 // It should be called to indicate which phase we're in (concurrent 388 // mark or remark) and how many threads are currently active. 389 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 390 391 // Prints all gathered CM-related statistics 392 void print_stats(); 393 394 bool cleanup_list_is_empty() { 395 return _cleanup_list.is_empty(); 396 } 397 398 // Accessor methods 399 uint parallel_marking_threads() const { return _parallel_marking_threads; } 400 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} 401 double sleep_factor() { return _sleep_factor; } 402 double marking_task_overhead() { return _marking_task_overhead;} 403 404 HeapWord* finger() { return _finger; } 405 bool concurrent() { return _concurrent; } 406 uint active_tasks() { return _active_tasks; } 407 ParallelTaskTerminator* terminator() { return &_terminator; } 408 409 // It claims the next available region to be scanned by a marking 410 // task/thread. It might return NULL if the next region is empty or 411 // we have run out of regions. In the latter case, out_of_regions() 412 // determines whether we've really run out of regions or the task 413 // should call claim_region() again. This might seem a bit 414 // awkward. Originally, the code was written so that claim_region() 415 // either successfully returned with a non-empty region or there 416 // were no more regions to be claimed. The problem with this was 417 // that, in certain circumstances, it iterated over large chunks of 418 // the heap finding only empty regions and, while it was working, it 419 // was preventing the calling task to call its regular clock 420 // method. So, this way, each task will spend very little time in 421 // claim_region() and is allowed to call the regular clock method 422 // frequently. 423 HeapRegion* claim_region(uint worker_id); 424 425 // It determines whether we've run out of regions to scan. Note that 426 // the finger can point past the heap end in case the heap was expanded 427 // to satisfy an allocation without doing a GC. This is fine, because all 428 // objects in those regions will be considered live anyway because of 429 // SATB guarantees (i.e. their TAMS will be equal to bottom). 430 bool out_of_regions() { return _finger >= _heap_end; } 431 432 // Returns the task with the given id 433 CMTask* task(int id) { 434 assert(0 <= id && id < (int) _active_tasks, 435 "task id not within active bounds"); 436 return _tasks[id]; 437 } 438 439 // Returns the task queue with the given id 440 CMTaskQueue* task_queue(int id) { 441 assert(0 <= id && id < (int) _active_tasks, 442 "task queue id not within active bounds"); 443 return (CMTaskQueue*) _task_queues->queue(id); 444 } 445 446 // Returns the task queue set 447 CMTaskQueueSet* task_queues() { return _task_queues; } 448 449 // Access / manipulation of the overflow flag which is set to 450 // indicate that the global stack has overflown 451 bool has_overflown() { return _has_overflown; } 452 void set_has_overflown() { _has_overflown = true; } 453 void clear_has_overflown() { _has_overflown = false; } 454 bool restart_for_overflow() { return _restart_for_overflow; } 455 456 // Methods to enter the two overflow sync barriers 457 void enter_first_sync_barrier(uint worker_id); 458 void enter_second_sync_barrier(uint worker_id); 459 460 // Live Data Counting data structures... 461 // These data structures are initialized at the start of 462 // marking. They are written to while marking is active. 463 // They are aggregated during remark; the aggregated values 464 // are then used to populate the _region_bm, _card_bm, and 465 // the total live bytes, which are then subsequently updated 466 // during cleanup. 467 468 // An array of bitmaps (one bit map per task). Each bitmap 469 // is used to record the cards spanned by the live objects 470 // marked by that task/worker. 471 BitMap* _count_card_bitmaps; 472 473 // Used to record the number of marked live bytes 474 // (for each region, by worker thread). 475 size_t** _count_marked_bytes; 476 477 // Card index of the bottom of the G1 heap. Used for biasing indices into 478 // the card bitmaps. 479 intptr_t _heap_bottom_card_num; 480 481 // Set to true when initialization is complete 482 bool _completed_initialization; 483 484 public: 485 // Manipulation of the global mark stack. 486 // The push and pop operations are used by tasks for transfers 487 // between task-local queues and the global mark stack, and use 488 // locking for concurrency safety. 489 bool mark_stack_push(oop* arr, int n) { 490 _markStack.par_push_arr(arr, n); 491 if (_markStack.overflow()) { 492 set_has_overflown(); 493 return false; 494 } 495 return true; 496 } 497 void mark_stack_pop(oop* arr, int max, int* n) { 498 _markStack.par_pop_arr(arr, max, n); 499 } 500 size_t mark_stack_size() { return _markStack.size(); } 501 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 502 bool mark_stack_overflow() { return _markStack.overflow(); } 503 bool mark_stack_empty() { return _markStack.isEmpty(); } 504 505 CMRootRegions* root_regions() { return &_root_regions; } 506 507 bool concurrent_marking_in_progress() { 508 return _concurrent_marking_in_progress; 509 } 510 void set_concurrent_marking_in_progress() { 511 _concurrent_marking_in_progress = true; 512 } 513 void clear_concurrent_marking_in_progress() { 514 _concurrent_marking_in_progress = false; 515 } 516 517 void register_concurrent_phase_start(const char* title); 518 void register_concurrent_phase_end(); 519 520 void update_accum_task_vtime(int i, double vtime) { 521 _accum_task_vtime[i] += vtime; 522 } 523 524 double all_task_accum_vtime() { 525 double ret = 0.0; 526 for (uint i = 0; i < _max_worker_id; ++i) 527 ret += _accum_task_vtime[i]; 528 return ret; 529 } 530 531 // Attempts to steal an object from the task queues of other tasks 532 bool try_stealing(uint worker_id, int* hash_seed, oop& obj); 533 534 ConcurrentMark(G1CollectedHeap* g1h, 535 G1RegionToSpaceMapper* prev_bitmap_storage, 536 G1RegionToSpaceMapper* next_bitmap_storage); 537 ~ConcurrentMark(); 538 539 ConcurrentMarkThread* cmThread() { return _cmThread; } 540 541 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 542 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 543 544 // Returns the number of GC threads to be used in a concurrent 545 // phase based on the number of GC threads being used in a STW 546 // phase. 547 uint scale_parallel_threads(uint n_par_threads); 548 549 // Calculates the number of GC threads to be used in a concurrent phase. 550 uint calc_parallel_marking_threads(); 551 552 // The following three are interaction between CM and 553 // G1CollectedHeap 554 555 // This notifies CM that a root during initial-mark needs to be 556 // grayed. It is MT-safe. word_size is the size of the object in 557 // words. It is passed explicitly as sometimes we cannot calculate 558 // it from the given object because it might be in an inconsistent 559 // state (e.g., in to-space and being copied). So the caller is 560 // responsible for dealing with this issue (e.g., get the size from 561 // the from-space image when the to-space image might be 562 // inconsistent) and always passing the size. hr is the region that 563 // contains the object and it's passed optionally from callers who 564 // might already have it (no point in recalculating it). 565 inline void grayRoot(oop obj, 566 size_t word_size, 567 uint worker_id, 568 HeapRegion* hr = NULL); 569 570 // Clear the next marking bitmap (will be called concurrently). 571 void clearNextBitmap(); 572 573 // Return whether the next mark bitmap has no marks set. To be used for assertions 574 // only. Will not yield to pause requests. 575 bool nextMarkBitmapIsClear(); 576 577 // These two do the work that needs to be done before and after the 578 // initial root checkpoint. Since this checkpoint can be done at two 579 // different points (i.e. an explicit pause or piggy-backed on a 580 // young collection), then it's nice to be able to easily share the 581 // pre/post code. It might be the case that we can put everything in 582 // the post method. TP 583 void checkpointRootsInitialPre(); 584 void checkpointRootsInitialPost(); 585 586 // Scan all the root regions and mark everything reachable from 587 // them. 588 void scanRootRegions(); 589 590 // Scan a single root region and mark everything reachable from it. 591 void scanRootRegion(HeapRegion* hr, uint worker_id); 592 593 // Do concurrent phase of marking, to a tentative transitive closure. 594 void markFromRoots(); 595 596 void checkpointRootsFinal(bool clear_all_soft_refs); 597 void checkpointRootsFinalWork(); 598 void cleanup(); 599 void completeCleanup(); 600 601 // Mark in the previous bitmap. NB: this is usually read-only, so use 602 // this carefully! 603 inline void markPrev(oop p); 604 605 // Clears marks for all objects in the given range, for the prev or 606 // next bitmaps. NB: the previous bitmap is usually 607 // read-only, so use this carefully! 608 void clearRangePrevBitmap(MemRegion mr); 609 610 // Notify data structures that a GC has started. 611 void note_start_of_gc() { 612 _markStack.note_start_of_gc(); 613 } 614 615 // Notify data structures that a GC is finished. 616 void note_end_of_gc() { 617 _markStack.note_end_of_gc(); 618 } 619 620 // Verify that there are no CSet oops on the stacks (taskqueues / 621 // global mark stack) and fingers (global / per-task). 622 // If marking is not in progress, it's a no-op. 623 void verify_no_cset_oops() PRODUCT_RETURN; 624 625 inline bool isPrevMarked(oop p) const; 626 627 inline bool do_yield_check(uint worker_i = 0); 628 629 // Called to abort the marking cycle after a Full GC takes place. 630 void abort(); 631 632 bool has_aborted() { return _has_aborted; } 633 634 void print_summary_info(); 635 636 void print_worker_threads_on(outputStream* st) const; 637 638 void print_on_error(outputStream* st) const; 639 640 // Liveness counting 641 642 // Utility routine to set an exclusive range of cards on the given 643 // card liveness bitmap 644 inline void set_card_bitmap_range(BitMap* card_bm, 645 BitMap::idx_t start_idx, 646 BitMap::idx_t end_idx, 647 bool is_par); 648 649 // Returns the card number of the bottom of the G1 heap. 650 // Used in biasing indices into accounting card bitmaps. 651 intptr_t heap_bottom_card_num() const { 652 return _heap_bottom_card_num; 653 } 654 655 // Returns the card bitmap for a given task or worker id. 656 BitMap* count_card_bitmap_for(uint worker_id) { 657 assert(worker_id < _max_worker_id, "oob"); 658 assert(_count_card_bitmaps != NULL, "uninitialized"); 659 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 660 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 661 return task_card_bm; 662 } 663 664 // Returns the array containing the marked bytes for each region, 665 // for the given worker or task id. 666 size_t* count_marked_bytes_array_for(uint worker_id) { 667 assert(worker_id < _max_worker_id, "oob"); 668 assert(_count_marked_bytes != NULL, "uninitialized"); 669 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 670 assert(marked_bytes_array != NULL, "uninitialized"); 671 return marked_bytes_array; 672 } 673 674 // Returns the index in the liveness accounting card table bitmap 675 // for the given address 676 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 677 678 // Counts the size of the given memory region in the the given 679 // marked_bytes array slot for the given HeapRegion. 680 // Sets the bits in the given card bitmap that are associated with the 681 // cards that are spanned by the memory region. 682 inline void count_region(MemRegion mr, 683 HeapRegion* hr, 684 size_t* marked_bytes_array, 685 BitMap* task_card_bm); 686 687 // Counts the given object in the given task/worker counting 688 // data structures. 689 inline void count_object(oop obj, 690 HeapRegion* hr, 691 size_t* marked_bytes_array, 692 BitMap* task_card_bm, 693 size_t word_size); 694 695 // Attempts to mark the given object and, if successful, counts 696 // the object in the given task/worker counting structures. 697 inline bool par_mark_and_count(oop obj, 698 HeapRegion* hr, 699 size_t* marked_bytes_array, 700 BitMap* task_card_bm); 701 702 // Attempts to mark the given object and, if successful, counts 703 // the object in the task/worker counting structures for the 704 // given worker id. 705 inline bool par_mark_and_count(oop obj, 706 size_t word_size, 707 HeapRegion* hr, 708 uint worker_id); 709 710 // Returns true if initialization was successfully completed. 711 bool completed_initialization() const { 712 return _completed_initialization; 713 } 714 715 protected: 716 // Clear all the per-task bitmaps and arrays used to store the 717 // counting data. 718 void clear_all_count_data(); 719 720 // Aggregates the counting data for each worker/task 721 // that was constructed while marking. Also sets 722 // the amount of marked bytes for each region and 723 // the top at concurrent mark count. 724 void aggregate_count_data(); 725 726 // Verification routine 727 void verify_count_data(); 728 }; 729 730 // A class representing a marking task. 731 class CMTask : public TerminatorTerminator { 732 private: 733 enum PrivateConstants { 734 // the regular clock call is called once the scanned words reaches 735 // this limit 736 words_scanned_period = 12*1024, 737 // the regular clock call is called once the number of visited 738 // references reaches this limit 739 refs_reached_period = 384, 740 // initial value for the hash seed, used in the work stealing code 741 init_hash_seed = 17, 742 // how many entries will be transferred between global stack and 743 // local queues 744 global_stack_transfer_size = 16 745 }; 746 747 uint _worker_id; 748 G1CollectedHeap* _g1h; 749 ConcurrentMark* _cm; 750 CMBitMap* _nextMarkBitMap; 751 // the task queue of this task 752 CMTaskQueue* _task_queue; 753 private: 754 // the task queue set---needed for stealing 755 CMTaskQueueSet* _task_queues; 756 // indicates whether the task has been claimed---this is only for 757 // debugging purposes 758 bool _claimed; 759 760 // number of calls to this task 761 int _calls; 762 763 // when the virtual timer reaches this time, the marking step should 764 // exit 765 double _time_target_ms; 766 // the start time of the current marking step 767 double _start_time_ms; 768 769 // the oop closure used for iterations over oops 770 G1CMOopClosure* _cm_oop_closure; 771 772 // the region this task is scanning, NULL if we're not scanning any 773 HeapRegion* _curr_region; 774 // the local finger of this task, NULL if we're not scanning a region 775 HeapWord* _finger; 776 // limit of the region this task is scanning, NULL if we're not scanning one 777 HeapWord* _region_limit; 778 779 // the number of words this task has scanned 780 size_t _words_scanned; 781 // When _words_scanned reaches this limit, the regular clock is 782 // called. Notice that this might be decreased under certain 783 // circumstances (i.e. when we believe that we did an expensive 784 // operation). 785 size_t _words_scanned_limit; 786 // the initial value of _words_scanned_limit (i.e. what it was 787 // before it was decreased). 788 size_t _real_words_scanned_limit; 789 790 // the number of references this task has visited 791 size_t _refs_reached; 792 // When _refs_reached reaches this limit, the regular clock is 793 // called. Notice this this might be decreased under certain 794 // circumstances (i.e. when we believe that we did an expensive 795 // operation). 796 size_t _refs_reached_limit; 797 // the initial value of _refs_reached_limit (i.e. what it was before 798 // it was decreased). 799 size_t _real_refs_reached_limit; 800 801 // used by the work stealing stuff 802 int _hash_seed; 803 // if this is true, then the task has aborted for some reason 804 bool _has_aborted; 805 // set when the task aborts because it has met its time quota 806 bool _has_timed_out; 807 // true when we're draining SATB buffers; this avoids the task 808 // aborting due to SATB buffers being available (as we're already 809 // dealing with them) 810 bool _draining_satb_buffers; 811 812 // number sequence of past step times 813 NumberSeq _step_times_ms; 814 // elapsed time of this task 815 double _elapsed_time_ms; 816 // termination time of this task 817 double _termination_time_ms; 818 // when this task got into the termination protocol 819 double _termination_start_time_ms; 820 821 // true when the task is during a concurrent phase, false when it is 822 // in the remark phase (so, in the latter case, we do not have to 823 // check all the things that we have to check during the concurrent 824 // phase, i.e. SATB buffer availability...) 825 bool _concurrent; 826 827 TruncatedSeq _marking_step_diffs_ms; 828 829 // Counting data structures. Embedding the task's marked_bytes_array 830 // and card bitmap into the actual task saves having to go through 831 // the ConcurrentMark object. 832 size_t* _marked_bytes_array; 833 BitMap* _card_bm; 834 835 // it updates the local fields after this task has claimed 836 // a new region to scan 837 void setup_for_region(HeapRegion* hr); 838 // it brings up-to-date the limit of the region 839 void update_region_limit(); 840 841 // called when either the words scanned or the refs visited limit 842 // has been reached 843 void reached_limit(); 844 // recalculates the words scanned and refs visited limits 845 void recalculate_limits(); 846 // decreases the words scanned and refs visited limits when we reach 847 // an expensive operation 848 void decrease_limits(); 849 // it checks whether the words scanned or refs visited reached their 850 // respective limit and calls reached_limit() if they have 851 void check_limits() { 852 if (_words_scanned >= _words_scanned_limit || 853 _refs_reached >= _refs_reached_limit) { 854 reached_limit(); 855 } 856 } 857 // this is supposed to be called regularly during a marking step as 858 // it checks a bunch of conditions that might cause the marking step 859 // to abort 860 void regular_clock_call(); 861 bool concurrent() { return _concurrent; } 862 863 // Test whether obj might have already been passed over by the 864 // mark bitmap scan, and so needs to be pushed onto the mark stack. 865 bool is_below_finger(oop obj, HeapWord* global_finger) const; 866 867 template<bool scan> void process_grey_object(oop obj); 868 869 public: 870 // It resets the task; it should be called right at the beginning of 871 // a marking phase. 872 void reset(CMBitMap* _nextMarkBitMap); 873 // it clears all the fields that correspond to a claimed region. 874 void clear_region_fields(); 875 876 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 877 878 // The main method of this class which performs a marking step 879 // trying not to exceed the given duration. However, it might exit 880 // prematurely, according to some conditions (i.e. SATB buffers are 881 // available for processing). 882 void do_marking_step(double target_ms, 883 bool do_termination, 884 bool is_serial); 885 886 // These two calls start and stop the timer 887 void record_start_time() { 888 _elapsed_time_ms = os::elapsedTime() * 1000.0; 889 } 890 void record_end_time() { 891 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 892 } 893 894 // returns the worker ID associated with this task. 895 uint worker_id() { return _worker_id; } 896 897 // From TerminatorTerminator. It determines whether this task should 898 // exit the termination protocol after it's entered it. 899 virtual bool should_exit_termination(); 900 901 // Resets the local region fields after a task has finished scanning a 902 // region; or when they have become stale as a result of the region 903 // being evacuated. 904 void giveup_current_region(); 905 906 HeapWord* finger() { return _finger; } 907 908 bool has_aborted() { return _has_aborted; } 909 void set_has_aborted() { _has_aborted = true; } 910 void clear_has_aborted() { _has_aborted = false; } 911 bool has_timed_out() { return _has_timed_out; } 912 bool claimed() { return _claimed; } 913 914 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 915 916 // Increment the number of references this task has visited. 917 void increment_refs_reached() { ++_refs_reached; } 918 919 // Grey the object by marking it. If not already marked, push it on 920 // the local queue if below the finger. 921 // Precondition: obj is in region. 922 // Precondition: obj is below region's NTAMS. 923 inline void make_reference_grey(oop obj, HeapRegion* region); 924 925 // Grey the object (by calling make_grey_reference) if required, 926 // e.g. obj is below its containing region's NTAMS. 927 // Precondition: obj is a valid heap object. 928 inline void deal_with_reference(oop obj); 929 930 // It scans an object and visits its children. 931 inline void scan_object(oop obj); 932 933 // It pushes an object on the local queue. 934 inline void push(oop obj); 935 936 // These two move entries to/from the global stack. 937 void move_entries_to_global_stack(); 938 void get_entries_from_global_stack(); 939 940 // It pops and scans objects from the local queue. If partially is 941 // true, then it stops when the queue size is of a given limit. If 942 // partially is false, then it stops when the queue is empty. 943 void drain_local_queue(bool partially); 944 // It moves entries from the global stack to the local queue and 945 // drains the local queue. If partially is true, then it stops when 946 // both the global stack and the local queue reach a given size. If 947 // partially if false, it tries to empty them totally. 948 void drain_global_stack(bool partially); 949 // It keeps picking SATB buffers and processing them until no SATB 950 // buffers are available. 951 void drain_satb_buffers(); 952 953 // moves the local finger to a new location 954 inline void move_finger_to(HeapWord* new_finger) { 955 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 956 _finger = new_finger; 957 } 958 959 CMTask(uint worker_id, 960 ConcurrentMark *cm, 961 size_t* marked_bytes, 962 BitMap* card_bm, 963 CMTaskQueue* task_queue, 964 CMTaskQueueSet* task_queues); 965 966 // it prints statistics associated with this task 967 void print_stats(); 968 }; 969 970 // Class that's used to to print out per-region liveness 971 // information. It's currently used at the end of marking and also 972 // after we sort the old regions at the end of the cleanup operation. 973 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 974 private: 975 // Accumulators for these values. 976 size_t _total_used_bytes; 977 size_t _total_capacity_bytes; 978 size_t _total_prev_live_bytes; 979 size_t _total_next_live_bytes; 980 981 // These are set up when we come across a "stars humongous" region 982 // (as this is where most of this information is stored, not in the 983 // subsequent "continues humongous" regions). After that, for every 984 // region in a given humongous region series we deduce the right 985 // values for it by simply subtracting the appropriate amount from 986 // these fields. All these values should reach 0 after we've visited 987 // the last region in the series. 988 size_t _hum_used_bytes; 989 size_t _hum_capacity_bytes; 990 size_t _hum_prev_live_bytes; 991 size_t _hum_next_live_bytes; 992 993 // Accumulator for the remembered set size 994 size_t _total_remset_bytes; 995 996 // Accumulator for strong code roots memory size 997 size_t _total_strong_code_roots_bytes; 998 999 static double perc(size_t val, size_t total) { 1000 if (total == 0) { 1001 return 0.0; 1002 } else { 1003 return 100.0 * ((double) val / (double) total); 1004 } 1005 } 1006 1007 static double bytes_to_mb(size_t val) { 1008 return (double) val / (double) M; 1009 } 1010 1011 // See the .cpp file. 1012 size_t get_hum_bytes(size_t* hum_bytes); 1013 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1014 size_t* prev_live_bytes, size_t* next_live_bytes); 1015 1016 public: 1017 // The header and footer are printed in the constructor and 1018 // destructor respectively. 1019 G1PrintRegionLivenessInfoClosure(const char* phase_name); 1020 virtual bool doHeapRegion(HeapRegion* r); 1021 ~G1PrintRegionLivenessInfoClosure(); 1022 }; 1023 1024 #endif // SHARE_VM_GC_G1_CONCURRENTMARK_HPP