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_G1CONCURRENTMARK_HPP 26 #define SHARE_VM_GC_G1_G1CONCURRENTMARK_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 G1CMBitMap; 35 class G1CMTask; 36 class G1ConcurrentMark; 37 typedef GenericTaskQueue<oop, mtGC> G1CMTaskQueue; 38 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet; 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 G1CMBitMapRO 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 G1CMBitMapRO(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 G1CMBitMapMappingChangedListener : public G1MappingChangedListener { 108 private: 109 G1CMBitMap* _bm; 110 public: 111 G1CMBitMapMappingChangedListener() : _bm(NULL) {} 112 113 void set_bitmap(G1CMBitMap* bm) { _bm = bm; } 114 115 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 116 }; 117 118 class G1CMBitMap : public G1CMBitMapRO { 119 private: 120 G1CMBitMapMappingChangedListener _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 G1CMBitMap() : G1CMBitMapRO(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 clear_range(MemRegion mr); 143 }; 144 145 // Represents a marking stack used by ConcurrentMarking in the G1 collector. 146 class G1CMMarkStack VALUE_OBJ_CLASS_SPEC { 147 VirtualSpace _virtual_space; // Underlying backing store for actual stack 148 G1ConcurrentMark* _cm; 149 oop* _base; // bottom of stack 150 jint _index; // one more than last occupied index 151 jint _capacity; // max #elements 152 jint _saved_index; // value of _index saved at start of GC 153 154 bool _overflow; 155 bool _should_expand; 156 157 public: 158 G1CMMarkStack(G1ConcurrentMark* cm); 159 ~G1CMMarkStack(); 160 161 bool allocate(size_t capacity); 162 163 // Pushes the first "n" elements of "ptr_arr" on the stack. 164 // Locking impl: concurrency is allowed only with 165 // "par_push_arr" and/or "par_pop_arr" operations, which use the same 166 // locking strategy. 167 void par_push_arr(oop* ptr_arr, int n); 168 169 // If returns false, the array was empty. Otherwise, removes up to "max" 170 // elements from the stack, and transfers them to "ptr_arr" in an 171 // unspecified order. The actual number transferred is given in "n" ("n 172 // == 0" is deliberately redundant with the return value.) Locking impl: 173 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" 174 // operations, which use the same locking strategy. 175 bool par_pop_arr(oop* ptr_arr, int max, int* n); 176 177 bool isEmpty() { return _index == 0; } 178 int maxElems() { return _capacity; } 179 180 bool overflow() { return _overflow; } 181 void clear_overflow() { _overflow = false; } 182 183 bool should_expand() const { return _should_expand; } 184 void set_should_expand(); 185 186 // Expand the stack, typically in response to an overflow condition 187 void expand(); 188 189 int size() { return _index; } 190 191 void setEmpty() { _index = 0; clear_overflow(); } 192 193 // Record the current index. 194 void note_start_of_gc(); 195 196 // Make sure that we have not added any entries to the stack during GC. 197 void note_end_of_gc(); 198 199 // Apply fn to each oop in the mark stack, up to the bound recorded 200 // via one of the above "note" functions. The mark stack must not 201 // be modified while iterating. 202 template<typename Fn> void iterate(Fn fn); 203 }; 204 205 class YoungList; 206 207 // Root Regions are regions that are not empty at the beginning of a 208 // marking cycle and which we might collect during an evacuation pause 209 // while the cycle is active. Given that, during evacuation pauses, we 210 // do not copy objects that are explicitly marked, what we have to do 211 // for the root regions is to scan them and mark all objects reachable 212 // from them. According to the SATB assumptions, we only need to visit 213 // each object once during marking. So, as long as we finish this scan 214 // before the next evacuation pause, we can copy the objects from the 215 // root regions without having to mark them or do anything else to them. 216 // 217 // Currently, we only support root region scanning once (at the start 218 // of the marking cycle) and the root regions are all the survivor 219 // regions populated during the initial-mark pause. 220 class G1CMRootRegions VALUE_OBJ_CLASS_SPEC { 221 private: 222 YoungList* _young_list; 223 G1ConcurrentMark* _cm; 224 225 volatile bool _scan_in_progress; 226 volatile bool _should_abort; 227 HeapRegion* volatile _next_survivor; 228 229 void notify_scan_done(); 230 231 public: 232 G1CMRootRegions(); 233 // We actually do most of the initialization in this method. 234 void init(G1CollectedHeap* g1h, G1ConcurrentMark* cm); 235 236 // Reset the claiming / scanning of the root regions. 237 void prepare_for_scan(); 238 239 // Forces get_next() to return NULL so that the iteration aborts early. 240 void abort() { _should_abort = true; } 241 242 // Return true if the CM thread are actively scanning root regions, 243 // false otherwise. 244 bool scan_in_progress() { return _scan_in_progress; } 245 246 // Claim the next root region to scan atomically, or return NULL if 247 // all have been claimed. 248 HeapRegion* claim_next(); 249 250 void cancel_scan(); 251 252 // Flag that we're done with root region scanning and notify anyone 253 // who's waiting on it. If aborted is false, assume that all regions 254 // have been claimed. 255 void scan_finished(); 256 257 // If CM threads are still scanning root regions, wait until they 258 // are done. Return true if we had to wait, false otherwise. 259 bool wait_until_scan_finished(); 260 }; 261 262 class ConcurrentMarkThread; 263 264 class G1ConcurrentMark: public CHeapObj<mtGC> { 265 friend class ConcurrentMarkThread; 266 friend class G1ParNoteEndTask; 267 friend class CalcLiveObjectsClosure; 268 friend class G1CMRefProcTaskProxy; 269 friend class G1CMRefProcTaskExecutor; 270 friend class G1CMKeepAliveAndDrainClosure; 271 friend class G1CMDrainMarkingStackClosure; 272 friend class G1CMBitMapClosure; 273 friend class G1CMConcurrentMarkingTask; 274 friend class G1CMMarkStack; 275 friend class G1CMRemarkTask; 276 friend class G1CMTask; 277 278 protected: 279 ConcurrentMarkThread* _cmThread; // The thread doing the work 280 G1CollectedHeap* _g1h; // The heap 281 uint _parallel_marking_threads; // The number of marking 282 // threads we're using 283 uint _max_parallel_marking_threads; // Max number of marking 284 // threads we'll ever use 285 double _sleep_factor; // How much we have to sleep, with 286 // respect to the work we just did, to 287 // meet the marking overhead goal 288 double _marking_task_overhead; // Marking target overhead for 289 // a single task 290 291 FreeRegionList _cleanup_list; 292 293 // Concurrent marking support structures 294 G1CMBitMap _markBitMap1; 295 G1CMBitMap _markBitMap2; 296 G1CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap 297 G1CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap 298 299 BitMap _region_bm; 300 BitMap _card_bm; 301 302 // Heap bounds 303 HeapWord* _heap_start; 304 HeapWord* _heap_end; 305 306 // Root region tracking and claiming 307 G1CMRootRegions _root_regions; 308 309 // For gray objects 310 G1CMMarkStack _markStack; // Grey objects behind global finger 311 HeapWord* volatile _finger; // The global finger, region aligned, 312 // always points to the end of the 313 // last claimed region 314 315 // Marking tasks 316 uint _max_worker_id;// Maximum worker id 317 uint _active_tasks; // Task num currently active 318 G1CMTask** _tasks; // Task queue array (max_worker_id len) 319 G1CMTaskQueueSet* _task_queues; // Task queue set 320 ParallelTaskTerminator _terminator; // For termination 321 322 // Two sync barriers that are used to synchronize tasks when an 323 // overflow occurs. The algorithm is the following. All tasks enter 324 // the first one to ensure that they have all stopped manipulating 325 // the global data structures. After they exit it, they re-initialize 326 // their data structures and task 0 re-initializes the global data 327 // structures. Then, they enter the second sync barrier. This 328 // ensure, that no task starts doing work before all data 329 // structures (local and global) have been re-initialized. When they 330 // exit it, they are free to start working again. 331 WorkGangBarrierSync _first_overflow_barrier_sync; 332 WorkGangBarrierSync _second_overflow_barrier_sync; 333 334 // This is set by any task, when an overflow on the global data 335 // structures is detected 336 volatile bool _has_overflown; 337 // True: marking is concurrent, false: we're in remark 338 volatile bool _concurrent; 339 // Set at the end of a Full GC so that marking aborts 340 volatile bool _has_aborted; 341 342 // Used when remark aborts due to an overflow to indicate that 343 // another concurrent marking phase should start 344 volatile bool _restart_for_overflow; 345 346 // This is true from the very start of concurrent marking until the 347 // point when all the tasks complete their work. It is really used 348 // to determine the points between the end of concurrent marking and 349 // time of remark. 350 volatile bool _concurrent_marking_in_progress; 351 352 // There would be a race between ConcurrentMarkThread and VMThread(ConcurrentMark::abort()) 353 // to call ConcurrentGCTimer::register_gc_concurrent_end(). 354 // And this variable is used to keep track of concurrent phase. 355 volatile uint _concurrent_phase_status; 356 // Concurrent phase is not yet started. 357 static const uint ConcPhaseNotStarted = 0; 358 // Concurrent phase is started. 359 static const uint ConcPhaseStarted = 1; 360 // Caller thread of ConcurrentGCTimer::register_gc_concurrent_end() is ending concurrent phase. 361 // So other thread should wait until the status to be changed to ConcPhaseNotStarted. 362 static const uint ConcPhaseStopping = 2; 363 364 // All of these times are in ms 365 NumberSeq _init_times; 366 NumberSeq _remark_times; 367 NumberSeq _remark_mark_times; 368 NumberSeq _remark_weak_ref_times; 369 NumberSeq _cleanup_times; 370 double _total_counting_time; 371 double _total_rs_scrub_time; 372 373 double* _accum_task_vtime; // Accumulated task vtime 374 375 WorkGang* _parallel_workers; 376 377 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes); 378 void weakRefsWork(bool clear_all_soft_refs); 379 380 void swapMarkBitMaps(); 381 382 // It resets the global marking data structures, as well as the 383 // task local ones; should be called during initial mark. 384 void reset(); 385 386 // Resets all the marking data structures. Called when we have to restart 387 // marking or when marking completes (via set_non_marking_state below). 388 void reset_marking_state(bool clear_overflow = true); 389 390 // We do this after we're done with marking so that the marking data 391 // structures are initialized to a sensible and predictable state. 392 void set_non_marking_state(); 393 394 // Called to indicate how many threads are currently active. 395 void set_concurrency(uint active_tasks); 396 397 // It should be called to indicate which phase we're in (concurrent 398 // mark or remark) and how many threads are currently active. 399 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 400 401 // Prints all gathered CM-related statistics 402 void print_stats(); 403 404 bool cleanup_list_is_empty() { 405 return _cleanup_list.is_empty(); 406 } 407 408 // Accessor methods 409 uint parallel_marking_threads() const { return _parallel_marking_threads; } 410 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} 411 double sleep_factor() { return _sleep_factor; } 412 double marking_task_overhead() { return _marking_task_overhead;} 413 414 HeapWord* finger() { return _finger; } 415 bool concurrent() { return _concurrent; } 416 uint active_tasks() { return _active_tasks; } 417 ParallelTaskTerminator* terminator() { return &_terminator; } 418 419 // It claims the next available region to be scanned by a marking 420 // task/thread. It might return NULL if the next region is empty or 421 // we have run out of regions. In the latter case, out_of_regions() 422 // determines whether we've really run out of regions or the task 423 // should call claim_region() again. This might seem a bit 424 // awkward. Originally, the code was written so that claim_region() 425 // either successfully returned with a non-empty region or there 426 // were no more regions to be claimed. The problem with this was 427 // that, in certain circumstances, it iterated over large chunks of 428 // the heap finding only empty regions and, while it was working, it 429 // was preventing the calling task to call its regular clock 430 // method. So, this way, each task will spend very little time in 431 // claim_region() and is allowed to call the regular clock method 432 // frequently. 433 HeapRegion* claim_region(uint worker_id); 434 435 // It determines whether we've run out of regions to scan. Note that 436 // the finger can point past the heap end in case the heap was expanded 437 // to satisfy an allocation without doing a GC. This is fine, because all 438 // objects in those regions will be considered live anyway because of 439 // SATB guarantees (i.e. their TAMS will be equal to bottom). 440 bool out_of_regions() { return _finger >= _heap_end; } 441 442 // Returns the task with the given id 443 G1CMTask* task(int id) { 444 assert(0 <= id && id < (int) _active_tasks, 445 "task id not within active bounds"); 446 return _tasks[id]; 447 } 448 449 // Returns the task queue with the given id 450 G1CMTaskQueue* task_queue(int id) { 451 assert(0 <= id && id < (int) _active_tasks, 452 "task queue id not within active bounds"); 453 return (G1CMTaskQueue*) _task_queues->queue(id); 454 } 455 456 // Returns the task queue set 457 G1CMTaskQueueSet* task_queues() { return _task_queues; } 458 459 // Access / manipulation of the overflow flag which is set to 460 // indicate that the global stack has overflown 461 bool has_overflown() { return _has_overflown; } 462 void set_has_overflown() { _has_overflown = true; } 463 void clear_has_overflown() { _has_overflown = false; } 464 bool restart_for_overflow() { return _restart_for_overflow; } 465 466 // Methods to enter the two overflow sync barriers 467 void enter_first_sync_barrier(uint worker_id); 468 void enter_second_sync_barrier(uint worker_id); 469 470 // Live Data Counting data structures... 471 // These data structures are initialized at the start of 472 // marking. They are written to while marking is active. 473 // They are aggregated during remark; the aggregated values 474 // are then used to populate the _region_bm, _card_bm, and 475 // the total live bytes, which are then subsequently updated 476 // during cleanup. 477 478 // An array of bitmaps (one bit map per task). Each bitmap 479 // is used to record the cards spanned by the live objects 480 // marked by that task/worker. 481 BitMap* _count_card_bitmaps; 482 483 // Used to record the number of marked live bytes 484 // (for each region, by worker thread). 485 size_t** _count_marked_bytes; 486 487 // Card index of the bottom of the G1 heap. Used for biasing indices into 488 // the card bitmaps. 489 intptr_t _heap_bottom_card_num; 490 491 // Set to true when initialization is complete 492 bool _completed_initialization; 493 494 // end_timer, true to end gc timer after ending concurrent phase. 495 void register_concurrent_phase_end_common(bool end_timer); 496 497 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is 498 // true, periodically insert checks to see if this method should exit prematurely. 499 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield); 500 public: 501 // Manipulation of the global mark stack. 502 // The push and pop operations are used by tasks for transfers 503 // between task-local queues and the global mark stack, and use 504 // locking for concurrency safety. 505 bool mark_stack_push(oop* arr, int n) { 506 _markStack.par_push_arr(arr, n); 507 if (_markStack.overflow()) { 508 set_has_overflown(); 509 return false; 510 } 511 return true; 512 } 513 void mark_stack_pop(oop* arr, int max, int* n) { 514 _markStack.par_pop_arr(arr, max, n); 515 } 516 size_t mark_stack_size() { return _markStack.size(); } 517 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 518 bool mark_stack_overflow() { return _markStack.overflow(); } 519 bool mark_stack_empty() { return _markStack.isEmpty(); } 520 521 G1CMRootRegions* root_regions() { return &_root_regions; } 522 523 bool concurrent_marking_in_progress() { 524 return _concurrent_marking_in_progress; 525 } 526 void set_concurrent_marking_in_progress() { 527 _concurrent_marking_in_progress = true; 528 } 529 void clear_concurrent_marking_in_progress() { 530 _concurrent_marking_in_progress = false; 531 } 532 533 void register_concurrent_phase_start(const char* title); 534 void register_concurrent_phase_end(); 535 // Ends both concurrent phase and timer. 536 void register_concurrent_gc_end_and_stop_timer(); 537 538 void update_accum_task_vtime(int i, double vtime) { 539 _accum_task_vtime[i] += vtime; 540 } 541 542 double all_task_accum_vtime() { 543 double ret = 0.0; 544 for (uint i = 0; i < _max_worker_id; ++i) 545 ret += _accum_task_vtime[i]; 546 return ret; 547 } 548 549 // Attempts to steal an object from the task queues of other tasks 550 bool try_stealing(uint worker_id, int* hash_seed, oop& obj); 551 552 G1ConcurrentMark(G1CollectedHeap* g1h, 553 G1RegionToSpaceMapper* prev_bitmap_storage, 554 G1RegionToSpaceMapper* next_bitmap_storage); 555 ~G1ConcurrentMark(); 556 557 ConcurrentMarkThread* cmThread() { return _cmThread; } 558 559 G1CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 560 G1CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 561 562 // Returns the number of GC threads to be used in a concurrent 563 // phase based on the number of GC threads being used in a STW 564 // phase. 565 uint scale_parallel_threads(uint n_par_threads); 566 567 // Calculates the number of GC threads to be used in a concurrent phase. 568 uint calc_parallel_marking_threads(); 569 570 // The following three are interaction between CM and 571 // G1CollectedHeap 572 573 // This notifies CM that a root during initial-mark needs to be 574 // grayed. It is MT-safe. word_size is the size of the object in 575 // words. It is passed explicitly as sometimes we cannot calculate 576 // it from the given object because it might be in an inconsistent 577 // state (e.g., in to-space and being copied). So the caller is 578 // responsible for dealing with this issue (e.g., get the size from 579 // the from-space image when the to-space image might be 580 // inconsistent) and always passing the size. hr is the region that 581 // contains the object and it's passed optionally from callers who 582 // might already have it (no point in recalculating it). 583 inline void grayRoot(oop obj, 584 size_t word_size, 585 uint worker_id, 586 HeapRegion* hr = NULL); 587 588 // Prepare internal data structures for the next mark cycle. This includes clearing 589 // the next mark bitmap and some internal data structures. This method is intended 590 // to be called concurrently to the mutator. It will yield to safepoint requests. 591 void cleanup_for_next_mark(); 592 593 // Clear the previous marking bitmap during safepoint. 594 void clear_prev_bitmap(WorkGang* workers); 595 596 // Return whether the next mark bitmap has no marks set. To be used for assertions 597 // only. Will not yield to pause requests. 598 bool nextMarkBitmapIsClear(); 599 600 // These two do the work that needs to be done before and after the 601 // initial root checkpoint. Since this checkpoint can be done at two 602 // different points (i.e. an explicit pause or piggy-backed on a 603 // young collection), then it's nice to be able to easily share the 604 // pre/post code. It might be the case that we can put everything in 605 // the post method. TP 606 void checkpointRootsInitialPre(); 607 void checkpointRootsInitialPost(); 608 609 // Scan all the root regions and mark everything reachable from 610 // them. 611 void scanRootRegions(); 612 613 // Scan a single root region and mark everything reachable from it. 614 void scanRootRegion(HeapRegion* hr, uint worker_id); 615 616 // Do concurrent phase of marking, to a tentative transitive closure. 617 void markFromRoots(); 618 619 void checkpointRootsFinal(bool clear_all_soft_refs); 620 void checkpointRootsFinalWork(); 621 void cleanup(); 622 void completeCleanup(); 623 624 // Mark in the previous bitmap. NB: this is usually read-only, so use 625 // this carefully! 626 inline void markPrev(oop p); 627 628 // Clears marks for all objects in the given range, for the prev or 629 // next bitmaps. NB: the previous bitmap is usually 630 // read-only, so use this carefully! 631 void clearRangePrevBitmap(MemRegion mr); 632 633 // Notify data structures that a GC has started. 634 void note_start_of_gc() { 635 _markStack.note_start_of_gc(); 636 } 637 638 // Notify data structures that a GC is finished. 639 void note_end_of_gc() { 640 _markStack.note_end_of_gc(); 641 } 642 643 // Verify that there are no CSet oops on the stacks (taskqueues / 644 // global mark stack) and fingers (global / per-task). 645 // If marking is not in progress, it's a no-op. 646 void verify_no_cset_oops() PRODUCT_RETURN; 647 648 inline bool isPrevMarked(oop p) const; 649 650 inline bool do_yield_check(uint worker_i = 0); 651 652 // Called to abort the marking cycle after a Full GC takes place. 653 void abort(); 654 655 bool has_aborted() { return _has_aborted; } 656 657 void print_summary_info(); 658 659 void print_worker_threads_on(outputStream* st) const; 660 661 void print_on_error(outputStream* st) const; 662 663 // Liveness counting 664 665 // Utility routine to set an exclusive range of cards on the given 666 // card liveness bitmap 667 inline void set_card_bitmap_range(BitMap* card_bm, 668 BitMap::idx_t start_idx, 669 BitMap::idx_t end_idx, 670 bool is_par); 671 672 // Returns the card number of the bottom of the G1 heap. 673 // Used in biasing indices into accounting card bitmaps. 674 intptr_t heap_bottom_card_num() const { 675 return _heap_bottom_card_num; 676 } 677 678 // Returns the card bitmap for a given task or worker id. 679 BitMap* count_card_bitmap_for(uint worker_id) { 680 assert(worker_id < _max_worker_id, "oob"); 681 assert(_count_card_bitmaps != NULL, "uninitialized"); 682 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 683 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 684 return task_card_bm; 685 } 686 687 // Returns the array containing the marked bytes for each region, 688 // for the given worker or task id. 689 size_t* count_marked_bytes_array_for(uint worker_id) { 690 assert(worker_id < _max_worker_id, "oob"); 691 assert(_count_marked_bytes != NULL, "uninitialized"); 692 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 693 assert(marked_bytes_array != NULL, "uninitialized"); 694 return marked_bytes_array; 695 } 696 697 // Returns the index in the liveness accounting card table bitmap 698 // for the given address 699 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 700 701 // Counts the size of the given memory region in the the given 702 // marked_bytes array slot for the given HeapRegion. 703 // Sets the bits in the given card bitmap that are associated with the 704 // cards that are spanned by the memory region. 705 inline void count_region(MemRegion mr, 706 HeapRegion* hr, 707 size_t* marked_bytes_array, 708 BitMap* task_card_bm); 709 710 // Counts the given object in the given task/worker counting 711 // data structures. 712 inline void count_object(oop obj, 713 HeapRegion* hr, 714 size_t* marked_bytes_array, 715 BitMap* task_card_bm, 716 size_t word_size); 717 718 // Attempts to mark the given object and, if successful, counts 719 // the object in the given task/worker counting structures. 720 inline bool par_mark_and_count(oop obj, 721 HeapRegion* hr, 722 size_t* marked_bytes_array, 723 BitMap* task_card_bm); 724 725 // Attempts to mark the given object and, if successful, counts 726 // the object in the task/worker counting structures for the 727 // given worker id. 728 inline bool par_mark_and_count(oop obj, 729 size_t word_size, 730 HeapRegion* hr, 731 uint worker_id); 732 733 // Returns true if initialization was successfully completed. 734 bool completed_initialization() const { 735 return _completed_initialization; 736 } 737 738 protected: 739 // Clear all the per-task bitmaps and arrays used to store the 740 // counting data. 741 void clear_all_count_data(); 742 743 // Aggregates the counting data for each worker/task 744 // that was constructed while marking. Also sets 745 // the amount of marked bytes for each region and 746 // the top at concurrent mark count. 747 void aggregate_count_data(); 748 749 // Verification routine 750 void verify_count_data(); 751 }; 752 753 // A class representing a marking task. 754 class G1CMTask : public TerminatorTerminator { 755 private: 756 enum PrivateConstants { 757 // the regular clock call is called once the scanned words reaches 758 // this limit 759 words_scanned_period = 12*1024, 760 // the regular clock call is called once the number of visited 761 // references reaches this limit 762 refs_reached_period = 384, 763 // initial value for the hash seed, used in the work stealing code 764 init_hash_seed = 17, 765 // how many entries will be transferred between global stack and 766 // local queues 767 global_stack_transfer_size = 16 768 }; 769 770 uint _worker_id; 771 G1CollectedHeap* _g1h; 772 G1ConcurrentMark* _cm; 773 G1CMBitMap* _nextMarkBitMap; 774 // the task queue of this task 775 G1CMTaskQueue* _task_queue; 776 private: 777 // the task queue set---needed for stealing 778 G1CMTaskQueueSet* _task_queues; 779 // indicates whether the task has been claimed---this is only for 780 // debugging purposes 781 bool _claimed; 782 783 // number of calls to this task 784 int _calls; 785 786 // when the virtual timer reaches this time, the marking step should 787 // exit 788 double _time_target_ms; 789 // the start time of the current marking step 790 double _start_time_ms; 791 792 // the oop closure used for iterations over oops 793 G1CMOopClosure* _cm_oop_closure; 794 795 // the region this task is scanning, NULL if we're not scanning any 796 HeapRegion* _curr_region; 797 // the local finger of this task, NULL if we're not scanning a region 798 HeapWord* _finger; 799 // limit of the region this task is scanning, NULL if we're not scanning one 800 HeapWord* _region_limit; 801 802 // the number of words this task has scanned 803 size_t _words_scanned; 804 // When _words_scanned reaches this limit, the regular clock is 805 // called. Notice that this might be decreased under certain 806 // circumstances (i.e. when we believe that we did an expensive 807 // operation). 808 size_t _words_scanned_limit; 809 // the initial value of _words_scanned_limit (i.e. what it was 810 // before it was decreased). 811 size_t _real_words_scanned_limit; 812 813 // the number of references this task has visited 814 size_t _refs_reached; 815 // When _refs_reached reaches this limit, the regular clock is 816 // called. Notice this this might be decreased under certain 817 // circumstances (i.e. when we believe that we did an expensive 818 // operation). 819 size_t _refs_reached_limit; 820 // the initial value of _refs_reached_limit (i.e. what it was before 821 // it was decreased). 822 size_t _real_refs_reached_limit; 823 824 // used by the work stealing stuff 825 int _hash_seed; 826 // if this is true, then the task has aborted for some reason 827 bool _has_aborted; 828 // set when the task aborts because it has met its time quota 829 bool _has_timed_out; 830 // true when we're draining SATB buffers; this avoids the task 831 // aborting due to SATB buffers being available (as we're already 832 // dealing with them) 833 bool _draining_satb_buffers; 834 835 // number sequence of past step times 836 NumberSeq _step_times_ms; 837 // elapsed time of this task 838 double _elapsed_time_ms; 839 // termination time of this task 840 double _termination_time_ms; 841 // when this task got into the termination protocol 842 double _termination_start_time_ms; 843 844 // true when the task is during a concurrent phase, false when it is 845 // in the remark phase (so, in the latter case, we do not have to 846 // check all the things that we have to check during the concurrent 847 // phase, i.e. SATB buffer availability...) 848 bool _concurrent; 849 850 TruncatedSeq _marking_step_diffs_ms; 851 852 // Counting data structures. Embedding the task's marked_bytes_array 853 // and card bitmap into the actual task saves having to go through 854 // the ConcurrentMark object. 855 size_t* _marked_bytes_array; 856 BitMap* _card_bm; 857 858 // it updates the local fields after this task has claimed 859 // a new region to scan 860 void setup_for_region(HeapRegion* hr); 861 // it brings up-to-date the limit of the region 862 void update_region_limit(); 863 864 // called when either the words scanned or the refs visited limit 865 // has been reached 866 void reached_limit(); 867 // recalculates the words scanned and refs visited limits 868 void recalculate_limits(); 869 // decreases the words scanned and refs visited limits when we reach 870 // an expensive operation 871 void decrease_limits(); 872 // it checks whether the words scanned or refs visited reached their 873 // respective limit and calls reached_limit() if they have 874 void check_limits() { 875 if (_words_scanned >= _words_scanned_limit || 876 _refs_reached >= _refs_reached_limit) { 877 reached_limit(); 878 } 879 } 880 // this is supposed to be called regularly during a marking step as 881 // it checks a bunch of conditions that might cause the marking step 882 // to abort 883 void regular_clock_call(); 884 bool concurrent() { return _concurrent; } 885 886 // Test whether obj might have already been passed over by the 887 // mark bitmap scan, and so needs to be pushed onto the mark stack. 888 bool is_below_finger(oop obj, HeapWord* global_finger) const; 889 890 template<bool scan> void process_grey_object(oop obj); 891 892 public: 893 // It resets the task; it should be called right at the beginning of 894 // a marking phase. 895 void reset(G1CMBitMap* _nextMarkBitMap); 896 // it clears all the fields that correspond to a claimed region. 897 void clear_region_fields(); 898 899 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 900 901 // The main method of this class which performs a marking step 902 // trying not to exceed the given duration. However, it might exit 903 // prematurely, according to some conditions (i.e. SATB buffers are 904 // available for processing). 905 void do_marking_step(double target_ms, 906 bool do_termination, 907 bool is_serial); 908 909 // These two calls start and stop the timer 910 void record_start_time() { 911 _elapsed_time_ms = os::elapsedTime() * 1000.0; 912 } 913 void record_end_time() { 914 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 915 } 916 917 // returns the worker ID associated with this task. 918 uint worker_id() { return _worker_id; } 919 920 // From TerminatorTerminator. It determines whether this task should 921 // exit the termination protocol after it's entered it. 922 virtual bool should_exit_termination(); 923 924 // Resets the local region fields after a task has finished scanning a 925 // region; or when they have become stale as a result of the region 926 // being evacuated. 927 void giveup_current_region(); 928 929 HeapWord* finger() { return _finger; } 930 931 bool has_aborted() { return _has_aborted; } 932 void set_has_aborted() { _has_aborted = true; } 933 void clear_has_aborted() { _has_aborted = false; } 934 bool has_timed_out() { return _has_timed_out; } 935 bool claimed() { return _claimed; } 936 937 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 938 939 // Increment the number of references this task has visited. 940 void increment_refs_reached() { ++_refs_reached; } 941 942 // Grey the object by marking it. If not already marked, push it on 943 // the local queue if below the finger. 944 // Precondition: obj is in region. 945 // Precondition: obj is below region's NTAMS. 946 inline void make_reference_grey(oop obj, HeapRegion* region); 947 948 // Grey the object (by calling make_grey_reference) if required, 949 // e.g. obj is below its containing region's NTAMS. 950 // Precondition: obj is a valid heap object. 951 inline void deal_with_reference(oop obj); 952 953 // It scans an object and visits its children. 954 inline void scan_object(oop obj); 955 956 // It pushes an object on the local queue. 957 inline void push(oop obj); 958 959 // These two move entries to/from the global stack. 960 void move_entries_to_global_stack(); 961 void get_entries_from_global_stack(); 962 963 // It pops and scans objects from the local queue. If partially is 964 // true, then it stops when the queue size is of a given limit. If 965 // partially is false, then it stops when the queue is empty. 966 void drain_local_queue(bool partially); 967 // It moves entries from the global stack to the local queue and 968 // drains the local queue. If partially is true, then it stops when 969 // both the global stack and the local queue reach a given size. If 970 // partially if false, it tries to empty them totally. 971 void drain_global_stack(bool partially); 972 // It keeps picking SATB buffers and processing them until no SATB 973 // buffers are available. 974 void drain_satb_buffers(); 975 976 // moves the local finger to a new location 977 inline void move_finger_to(HeapWord* new_finger) { 978 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 979 _finger = new_finger; 980 } 981 982 G1CMTask(uint worker_id, 983 G1ConcurrentMark *cm, 984 size_t* marked_bytes, 985 BitMap* card_bm, 986 G1CMTaskQueue* task_queue, 987 G1CMTaskQueueSet* task_queues); 988 989 // it prints statistics associated with this task 990 void print_stats(); 991 }; 992 993 // Class that's used to to print out per-region liveness 994 // information. It's currently used at the end of marking and also 995 // after we sort the old regions at the end of the cleanup operation. 996 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 997 private: 998 // Accumulators for these values. 999 size_t _total_used_bytes; 1000 size_t _total_capacity_bytes; 1001 size_t _total_prev_live_bytes; 1002 size_t _total_next_live_bytes; 1003 1004 // These are set up when we come across a "stars humongous" region 1005 // (as this is where most of this information is stored, not in the 1006 // subsequent "continues humongous" regions). After that, for every 1007 // region in a given humongous region series we deduce the right 1008 // values for it by simply subtracting the appropriate amount from 1009 // these fields. All these values should reach 0 after we've visited 1010 // the last region in the series. 1011 size_t _hum_used_bytes; 1012 size_t _hum_capacity_bytes; 1013 size_t _hum_prev_live_bytes; 1014 size_t _hum_next_live_bytes; 1015 1016 // Accumulator for the remembered set size 1017 size_t _total_remset_bytes; 1018 1019 // Accumulator for strong code roots memory size 1020 size_t _total_strong_code_roots_bytes; 1021 1022 static double perc(size_t val, size_t total) { 1023 if (total == 0) { 1024 return 0.0; 1025 } else { 1026 return 100.0 * ((double) val / (double) total); 1027 } 1028 } 1029 1030 static double bytes_to_mb(size_t val) { 1031 return (double) val / (double) M; 1032 } 1033 1034 // See the .cpp file. 1035 size_t get_hum_bytes(size_t* hum_bytes); 1036 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1037 size_t* prev_live_bytes, size_t* next_live_bytes); 1038 1039 public: 1040 // The header and footer are printed in the constructor and 1041 // destructor respectively. 1042 G1PrintRegionLivenessInfoClosure(const char* phase_name); 1043 virtual bool doHeapRegion(HeapRegion* r); 1044 ~G1PrintRegionLivenessInfoClosure(); 1045 }; 1046 1047 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP