1 /* 2 * Copyright (c) 2001, 2015, 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 enum { do_yield = true }; 69 70 // inquiries 71 HeapWord* startWord() const { return _bmStartWord; } 72 size_t sizeInWords() const { return _bmWordSize; } 73 // the following is one past the last word in space 74 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 75 76 // read marks 77 78 bool isMarked(HeapWord* addr) const { 79 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 80 "outside underlying space?"); 81 return _bm.at(heapWordToOffset(addr)); 82 } 83 84 // iteration 85 inline bool iterate(BitMapClosure* cl, MemRegion mr); 86 inline bool iterate(BitMapClosure* cl); 87 88 // Return the address corresponding to the next marked bit at or after 89 // "addr", and before "limit", if "limit" is non-NULL. If there is no 90 // such bit, returns "limit" if that is non-NULL, or else "endWord()". 91 HeapWord* getNextMarkedWordAddress(const HeapWord* addr, 92 const HeapWord* limit = NULL) const; 93 // Return the address corresponding to the next unmarked bit at or after 94 // "addr", and before "limit", if "limit" is non-NULL. If there is no 95 // such bit, returns "limit" if that is non-NULL, or else "endWord()". 96 HeapWord* getNextUnmarkedWordAddress(const HeapWord* addr, 97 const HeapWord* limit = NULL) const; 98 99 // conversion utilities 100 HeapWord* offsetToHeapWord(size_t offset) const { 101 return _bmStartWord + (offset << _shifter); 102 } 103 size_t heapWordToOffset(const HeapWord* addr) const { 104 return pointer_delta(addr, _bmStartWord) >> _shifter; 105 } 106 int heapWordDiffToOffsetDiff(size_t diff) const; 107 108 // The argument addr should be the start address of a valid object 109 HeapWord* nextObject(HeapWord* addr) { 110 oop obj = (oop) addr; 111 HeapWord* res = addr + obj->size(); 112 assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity"); 113 return res; 114 } 115 116 void print_on_error(outputStream* st, const char* prefix) const; 117 118 // debugging 119 NOT_PRODUCT(bool covers(MemRegion rs) const;) 120 }; 121 122 class CMBitMapMappingChangedListener : public G1MappingChangedListener { 123 private: 124 CMBitMap* _bm; 125 public: 126 CMBitMapMappingChangedListener() : _bm(NULL) {} 127 128 void set_bitmap(CMBitMap* bm) { _bm = bm; } 129 130 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 131 }; 132 133 class CMBitMap : public CMBitMapRO { 134 private: 135 CMBitMapMappingChangedListener _listener; 136 137 public: 138 static size_t compute_size(size_t heap_size); 139 // Returns the amount of bytes on the heap between two marks in the bitmap. 140 static size_t mark_distance(); 141 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the 142 // mark bitmap corresponds to. This is the same as the mark distance above. 143 static size_t heap_map_factor() { 144 return mark_distance(); 145 } 146 147 CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); } 148 149 // Initializes the underlying BitMap to cover the given area. 150 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage); 151 152 // Write marks. 153 inline void mark(HeapWord* addr); 154 inline void clear(HeapWord* addr); 155 inline bool parMark(HeapWord* addr); 156 inline bool parClear(HeapWord* addr); 157 158 void markRange(MemRegion mr); 159 void clearRange(MemRegion mr); 160 161 // Starting at the bit corresponding to "addr" (inclusive), find the next 162 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find 163 // the end of this run (stopping at "end_addr"). Return the MemRegion 164 // covering from the start of the region corresponding to the first bit 165 // of the run to the end of the region corresponding to the last bit of 166 // the run. If there is no "1" bit at or after "addr", return an empty 167 // MemRegion. 168 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr); 169 170 // Clear the whole mark bitmap. 171 void clearAll(); 172 }; 173 174 // Represents a marking stack used by ConcurrentMarking in the G1 collector. 175 class CMMarkStack VALUE_OBJ_CLASS_SPEC { 176 VirtualSpace _virtual_space; // Underlying backing store for actual stack 177 ConcurrentMark* _cm; 178 oop* _base; // bottom of stack 179 jint _index; // one more than last occupied index 180 jint _capacity; // max #elements 181 jint _saved_index; // value of _index saved at start of GC 182 183 bool _overflow; 184 bool _should_expand; 185 186 public: 187 CMMarkStack(ConcurrentMark* cm); 188 ~CMMarkStack(); 189 190 bool allocate(size_t capacity); 191 192 // Pushes the first "n" elements of "ptr_arr" on the stack. 193 // Locking impl: concurrency is allowed only with 194 // "par_push_arr" and/or "par_pop_arr" operations, which use the same 195 // locking strategy. 196 void par_push_arr(oop* ptr_arr, int n); 197 198 // If returns false, the array was empty. Otherwise, removes up to "max" 199 // elements from the stack, and transfers them to "ptr_arr" in an 200 // unspecified order. The actual number transferred is given in "n" ("n 201 // == 0" is deliberately redundant with the return value.) Locking impl: 202 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" 203 // operations, which use the same locking strategy. 204 bool par_pop_arr(oop* ptr_arr, int max, int* n); 205 206 bool isEmpty() { return _index == 0; } 207 int maxElems() { return _capacity; } 208 209 bool overflow() { return _overflow; } 210 void clear_overflow() { _overflow = false; } 211 212 bool should_expand() const { return _should_expand; } 213 void set_should_expand(); 214 215 // Expand the stack, typically in response to an overflow condition 216 void expand(); 217 218 int size() { return _index; } 219 220 void setEmpty() { _index = 0; clear_overflow(); } 221 222 // Record the current index. 223 void note_start_of_gc(); 224 225 // Make sure that we have not added any entries to the stack during GC. 226 void note_end_of_gc(); 227 228 // Apply fn to each oop in the mark stack, up to the bound recorded 229 // via one of the above "note" functions. The mark stack must not 230 // be modified while iterating. 231 template<typename Fn> void iterate(Fn fn); 232 }; 233 234 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC { 235 private: 236 #ifndef PRODUCT 237 uintx _num_remaining; 238 bool _force; 239 #endif // !defined(PRODUCT) 240 241 public: 242 void init() PRODUCT_RETURN; 243 void update() PRODUCT_RETURN; 244 bool should_force() PRODUCT_RETURN_( return false; ); 245 }; 246 247 // this will enable a variety of different statistics per GC task 248 #define _MARKING_STATS_ 0 249 // this will enable the higher verbose levels 250 #define _MARKING_VERBOSE_ 0 251 252 #if _MARKING_STATS_ 253 #define statsOnly(statement) \ 254 do { \ 255 statement ; \ 256 } while (0) 257 #else // _MARKING_STATS_ 258 #define statsOnly(statement) \ 259 do { \ 260 } while (0) 261 #endif // _MARKING_STATS_ 262 263 typedef enum { 264 no_verbose = 0, // verbose turned off 265 stats_verbose, // only prints stats at the end of marking 266 low_verbose, // low verbose, mostly per region and per major event 267 medium_verbose, // a bit more detailed than low 268 high_verbose // per object verbose 269 } CMVerboseLevel; 270 271 class YoungList; 272 273 // Root Regions are regions that are not empty at the beginning of a 274 // marking cycle and which we might collect during an evacuation pause 275 // while the cycle is active. Given that, during evacuation pauses, we 276 // do not copy objects that are explicitly marked, what we have to do 277 // for the root regions is to scan them and mark all objects reachable 278 // from them. According to the SATB assumptions, we only need to visit 279 // each object once during marking. So, as long as we finish this scan 280 // before the next evacuation pause, we can copy the objects from the 281 // root regions without having to mark them or do anything else to them. 282 // 283 // Currently, we only support root region scanning once (at the start 284 // of the marking cycle) and the root regions are all the survivor 285 // regions populated during the initial-mark pause. 286 class CMRootRegions VALUE_OBJ_CLASS_SPEC { 287 private: 288 YoungList* _young_list; 289 ConcurrentMark* _cm; 290 291 volatile bool _scan_in_progress; 292 volatile bool _should_abort; 293 HeapRegion* volatile _next_survivor; 294 295 public: 296 CMRootRegions(); 297 // We actually do most of the initialization in this method. 298 void init(G1CollectedHeap* g1h, ConcurrentMark* cm); 299 300 // Reset the claiming / scanning of the root regions. 301 void prepare_for_scan(); 302 303 // Forces get_next() to return NULL so that the iteration aborts early. 304 void abort() { _should_abort = true; } 305 306 // Return true if the CM thread are actively scanning root regions, 307 // false otherwise. 308 bool scan_in_progress() { return _scan_in_progress; } 309 310 // Claim the next root region to scan atomically, or return NULL if 311 // all have been claimed. 312 HeapRegion* claim_next(); 313 314 // Flag that we're done with root region scanning and notify anyone 315 // who's waiting on it. If aborted is false, assume that all regions 316 // have been claimed. 317 void scan_finished(); 318 319 // If CM threads are still scanning root regions, wait until they 320 // are done. Return true if we had to wait, false otherwise. 321 bool wait_until_scan_finished(); 322 }; 323 324 class ConcurrentMarkThread; 325 326 class ConcurrentMark: public CHeapObj<mtGC> { 327 friend class CMMarkStack; 328 friend class ConcurrentMarkThread; 329 friend class CMTask; 330 friend class CMBitMapClosure; 331 friend class CMRemarkTask; 332 friend class CMConcurrentMarkingTask; 333 friend class G1ParNoteEndTask; 334 friend class CalcLiveObjectsClosure; 335 friend class G1CMRefProcTaskProxy; 336 friend class G1CMRefProcTaskExecutor; 337 friend class G1CMKeepAliveAndDrainClosure; 338 friend class G1CMDrainMarkingStackClosure; 339 340 protected: 341 ConcurrentMarkThread* _cmThread; // The thread doing the work 342 G1CollectedHeap* _g1h; // The heap 343 uint _parallel_marking_threads; // The number of marking 344 // threads we're using 345 uint _max_parallel_marking_threads; // Max number of marking 346 // threads we'll ever use 347 double _sleep_factor; // How much we have to sleep, with 348 // respect to the work we just did, to 349 // meet the marking overhead goal 350 double _marking_task_overhead; // Marking target overhead for 351 // a single task 352 353 // Same as the two above, but for the cleanup task 354 double _cleanup_sleep_factor; 355 double _cleanup_task_overhead; 356 357 FreeRegionList _cleanup_list; 358 359 // Concurrent marking support structures 360 CMBitMap _markBitMap1; 361 CMBitMap _markBitMap2; 362 CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap 363 CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap 364 365 BitMap _region_bm; 366 BitMap _card_bm; 367 368 // Heap bounds 369 HeapWord* _heap_start; 370 HeapWord* _heap_end; 371 372 // Root region tracking and claiming 373 CMRootRegions _root_regions; 374 375 // For gray objects 376 CMMarkStack _markStack; // Grey objects behind global finger 377 HeapWord* volatile _finger; // The global finger, region aligned, 378 // always points to the end of the 379 // last claimed region 380 381 // Marking tasks 382 uint _max_worker_id;// Maximum worker id 383 uint _active_tasks; // Task num currently active 384 CMTask** _tasks; // Task queue array (max_worker_id len) 385 CMTaskQueueSet* _task_queues; // Task queue set 386 ParallelTaskTerminator _terminator; // For termination 387 388 // Two sync barriers that are used to synchronize tasks when an 389 // overflow occurs. The algorithm is the following. All tasks enter 390 // the first one to ensure that they have all stopped manipulating 391 // the global data structures. After they exit it, they re-initialize 392 // their data structures and task 0 re-initializes the global data 393 // structures. Then, they enter the second sync barrier. This 394 // ensure, that no task starts doing work before all data 395 // structures (local and global) have been re-initialized. When they 396 // exit it, they are free to start working again. 397 WorkGangBarrierSync _first_overflow_barrier_sync; 398 WorkGangBarrierSync _second_overflow_barrier_sync; 399 400 // This is set by any task, when an overflow on the global data 401 // structures is detected 402 volatile bool _has_overflown; 403 // True: marking is concurrent, false: we're in remark 404 volatile bool _concurrent; 405 // Set at the end of a Full GC so that marking aborts 406 volatile bool _has_aborted; 407 408 // Used when remark aborts due to an overflow to indicate that 409 // another concurrent marking phase should start 410 volatile bool _restart_for_overflow; 411 412 // This is true from the very start of concurrent marking until the 413 // point when all the tasks complete their work. It is really used 414 // to determine the points between the end of concurrent marking and 415 // time of remark. 416 volatile bool _concurrent_marking_in_progress; 417 418 // Verbose level 419 CMVerboseLevel _verbose_level; 420 421 // All of these times are in ms 422 NumberSeq _init_times; 423 NumberSeq _remark_times; 424 NumberSeq _remark_mark_times; 425 NumberSeq _remark_weak_ref_times; 426 NumberSeq _cleanup_times; 427 double _total_counting_time; 428 double _total_rs_scrub_time; 429 430 double* _accum_task_vtime; // Accumulated task vtime 431 432 WorkGang* _parallel_workers; 433 434 ForceOverflowSettings _force_overflow_conc; 435 ForceOverflowSettings _force_overflow_stw; 436 437 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes); 438 void weakRefsWork(bool clear_all_soft_refs); 439 440 void swapMarkBitMaps(); 441 442 // It resets the global marking data structures, as well as the 443 // task local ones; should be called during initial mark. 444 void reset(); 445 446 // Resets all the marking data structures. Called when we have to restart 447 // marking or when marking completes (via set_non_marking_state below). 448 void reset_marking_state(bool clear_overflow = true); 449 450 // We do this after we're done with marking so that the marking data 451 // structures are initialized to a sensible and predictable state. 452 void set_non_marking_state(); 453 454 // Called to indicate how many threads are currently active. 455 void set_concurrency(uint active_tasks); 456 457 // It should be called to indicate which phase we're in (concurrent 458 // mark or remark) and how many threads are currently active. 459 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 460 461 // Prints all gathered CM-related statistics 462 void print_stats(); 463 464 bool cleanup_list_is_empty() { 465 return _cleanup_list.is_empty(); 466 } 467 468 // Accessor methods 469 uint parallel_marking_threads() const { return _parallel_marking_threads; } 470 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} 471 double sleep_factor() { return _sleep_factor; } 472 double marking_task_overhead() { return _marking_task_overhead;} 473 double cleanup_sleep_factor() { return _cleanup_sleep_factor; } 474 double cleanup_task_overhead() { return _cleanup_task_overhead;} 475 476 HeapWord* finger() { return _finger; } 477 bool concurrent() { return _concurrent; } 478 uint active_tasks() { return _active_tasks; } 479 ParallelTaskTerminator* terminator() { return &_terminator; } 480 481 // It claims the next available region to be scanned by a marking 482 // task/thread. It might return NULL if the next region is empty or 483 // we have run out of regions. In the latter case, out_of_regions() 484 // determines whether we've really run out of regions or the task 485 // should call claim_region() again. This might seem a bit 486 // awkward. Originally, the code was written so that claim_region() 487 // either successfully returned with a non-empty region or there 488 // were no more regions to be claimed. The problem with this was 489 // that, in certain circumstances, it iterated over large chunks of 490 // the heap finding only empty regions and, while it was working, it 491 // was preventing the calling task to call its regular clock 492 // method. So, this way, each task will spend very little time in 493 // claim_region() and is allowed to call the regular clock method 494 // frequently. 495 HeapRegion* claim_region(uint worker_id); 496 497 // It determines whether we've run out of regions to scan. Note that 498 // the finger can point past the heap end in case the heap was expanded 499 // to satisfy an allocation without doing a GC. This is fine, because all 500 // objects in those regions will be considered live anyway because of 501 // SATB guarantees (i.e. their TAMS will be equal to bottom). 502 bool out_of_regions() { return _finger >= _heap_end; } 503 504 // Returns the task with the given id 505 CMTask* task(int id) { 506 assert(0 <= id && id < (int) _active_tasks, 507 "task id not within active bounds"); 508 return _tasks[id]; 509 } 510 511 // Returns the task queue with the given id 512 CMTaskQueue* task_queue(int id) { 513 assert(0 <= id && id < (int) _active_tasks, 514 "task queue id not within active bounds"); 515 return (CMTaskQueue*) _task_queues->queue(id); 516 } 517 518 // Returns the task queue set 519 CMTaskQueueSet* task_queues() { return _task_queues; } 520 521 // Access / manipulation of the overflow flag which is set to 522 // indicate that the global stack has overflown 523 bool has_overflown() { return _has_overflown; } 524 void set_has_overflown() { _has_overflown = true; } 525 void clear_has_overflown() { _has_overflown = false; } 526 bool restart_for_overflow() { return _restart_for_overflow; } 527 528 // Methods to enter the two overflow sync barriers 529 void enter_first_sync_barrier(uint worker_id); 530 void enter_second_sync_barrier(uint worker_id); 531 532 ForceOverflowSettings* force_overflow_conc() { 533 return &_force_overflow_conc; 534 } 535 536 ForceOverflowSettings* force_overflow_stw() { 537 return &_force_overflow_stw; 538 } 539 540 ForceOverflowSettings* force_overflow() { 541 if (concurrent()) { 542 return force_overflow_conc(); 543 } else { 544 return force_overflow_stw(); 545 } 546 } 547 548 // Live Data Counting data structures... 549 // These data structures are initialized at the start of 550 // marking. They are written to while marking is active. 551 // They are aggregated during remark; the aggregated values 552 // are then used to populate the _region_bm, _card_bm, and 553 // the total live bytes, which are then subsequently updated 554 // during cleanup. 555 556 // An array of bitmaps (one bit map per task). Each bitmap 557 // is used to record the cards spanned by the live objects 558 // marked by that task/worker. 559 BitMap* _count_card_bitmaps; 560 561 // Used to record the number of marked live bytes 562 // (for each region, by worker thread). 563 size_t** _count_marked_bytes; 564 565 // Card index of the bottom of the G1 heap. Used for biasing indices into 566 // the card bitmaps. 567 intptr_t _heap_bottom_card_num; 568 569 // Set to true when initialization is complete 570 bool _completed_initialization; 571 572 public: 573 // Manipulation of the global mark stack. 574 // The push and pop operations are used by tasks for transfers 575 // between task-local queues and the global mark stack, and use 576 // locking for concurrency safety. 577 bool mark_stack_push(oop* arr, int n) { 578 _markStack.par_push_arr(arr, n); 579 if (_markStack.overflow()) { 580 set_has_overflown(); 581 return false; 582 } 583 return true; 584 } 585 void mark_stack_pop(oop* arr, int max, int* n) { 586 _markStack.par_pop_arr(arr, max, n); 587 } 588 size_t mark_stack_size() { return _markStack.size(); } 589 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 590 bool mark_stack_overflow() { return _markStack.overflow(); } 591 bool mark_stack_empty() { return _markStack.isEmpty(); } 592 593 CMRootRegions* root_regions() { return &_root_regions; } 594 595 bool concurrent_marking_in_progress() { 596 return _concurrent_marking_in_progress; 597 } 598 void set_concurrent_marking_in_progress() { 599 _concurrent_marking_in_progress = true; 600 } 601 void clear_concurrent_marking_in_progress() { 602 _concurrent_marking_in_progress = false; 603 } 604 605 void update_accum_task_vtime(int i, double vtime) { 606 _accum_task_vtime[i] += vtime; 607 } 608 609 double all_task_accum_vtime() { 610 double ret = 0.0; 611 for (uint i = 0; i < _max_worker_id; ++i) 612 ret += _accum_task_vtime[i]; 613 return ret; 614 } 615 616 // Attempts to steal an object from the task queues of other tasks 617 bool try_stealing(uint worker_id, int* hash_seed, oop& obj); 618 619 ConcurrentMark(G1CollectedHeap* g1h, 620 G1RegionToSpaceMapper* prev_bitmap_storage, 621 G1RegionToSpaceMapper* next_bitmap_storage); 622 ~ConcurrentMark(); 623 624 ConcurrentMarkThread* cmThread() { return _cmThread; } 625 626 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 627 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 628 629 // Returns the number of GC threads to be used in a concurrent 630 // phase based on the number of GC threads being used in a STW 631 // phase. 632 uint scale_parallel_threads(uint n_par_threads); 633 634 // Calculates the number of GC threads to be used in a concurrent phase. 635 uint calc_parallel_marking_threads(); 636 637 // The following three are interaction between CM and 638 // G1CollectedHeap 639 640 // This notifies CM that a root during initial-mark needs to be 641 // grayed. It is MT-safe. word_size is the size of the object in 642 // words. It is passed explicitly as sometimes we cannot calculate 643 // it from the given object because it might be in an inconsistent 644 // state (e.g., in to-space and being copied). So the caller is 645 // responsible for dealing with this issue (e.g., get the size from 646 // the from-space image when the to-space image might be 647 // inconsistent) and always passing the size. hr is the region that 648 // contains the object and it's passed optionally from callers who 649 // might already have it (no point in recalculating it). 650 inline void grayRoot(oop obj, 651 size_t word_size, 652 uint worker_id, 653 HeapRegion* hr = NULL); 654 655 // It iterates over the heap and for each object it comes across it 656 // will dump the contents of its reference fields, as well as 657 // liveness information for the object and its referents. The dump 658 // will be written to a file with the following name: 659 // G1PrintReachableBaseFile + "." + str. 660 // vo decides whether the prev (vo == UsePrevMarking), the next 661 // (vo == UseNextMarking) marking information, or the mark word 662 // (vo == UseMarkWord) will be used to determine the liveness of 663 // each object / referent. 664 // If all is true, all objects in the heap will be dumped, otherwise 665 // only the live ones. In the dump the following symbols / breviations 666 // are used: 667 // M : an explicitly live object (its bitmap bit is set) 668 // > : an implicitly live object (over tams) 669 // O : an object outside the G1 heap (typically: in the perm gen) 670 // NOT : a reference field whose referent is not live 671 // AND MARKED : indicates that an object is both explicitly and 672 // implicitly live (it should be one or the other, not both) 673 void print_reachable(const char* str, 674 VerifyOption vo, 675 bool all) PRODUCT_RETURN; 676 677 // Clear the next marking bitmap (will be called concurrently). 678 void clearNextBitmap(); 679 680 // Return whether the next mark bitmap has no marks set. To be used for assertions 681 // only. Will not yield to pause requests. 682 bool nextMarkBitmapIsClear(); 683 684 // These two do the work that needs to be done before and after the 685 // initial root checkpoint. Since this checkpoint can be done at two 686 // different points (i.e. an explicit pause or piggy-backed on a 687 // young collection), then it's nice to be able to easily share the 688 // pre/post code. It might be the case that we can put everything in 689 // the post method. TP 690 void checkpointRootsInitialPre(); 691 void checkpointRootsInitialPost(); 692 693 // Scan all the root regions and mark everything reachable from 694 // them. 695 void scanRootRegions(); 696 697 // Scan a single root region and mark everything reachable from it. 698 void scanRootRegion(HeapRegion* hr, uint worker_id); 699 700 // Do concurrent phase of marking, to a tentative transitive closure. 701 void markFromRoots(); 702 703 void checkpointRootsFinal(bool clear_all_soft_refs); 704 void checkpointRootsFinalWork(); 705 void cleanup(); 706 void completeCleanup(); 707 708 // Mark in the previous bitmap. NB: this is usually read-only, so use 709 // this carefully! 710 inline void markPrev(oop p); 711 712 // Clears marks for all objects in the given range, for the prev or 713 // next bitmaps. NB: the previous bitmap is usually 714 // read-only, so use this carefully! 715 void clearRangePrevBitmap(MemRegion mr); 716 void clearRangeNextBitmap(MemRegion mr); 717 718 // Notify data structures that a GC has started. 719 void note_start_of_gc() { 720 _markStack.note_start_of_gc(); 721 } 722 723 // Notify data structures that a GC is finished. 724 void note_end_of_gc() { 725 _markStack.note_end_of_gc(); 726 } 727 728 // Verify that there are no CSet oops on the stacks (taskqueues / 729 // global mark stack) and fingers (global / per-task). 730 // If marking is not in progress, it's a no-op. 731 void verify_no_cset_oops() PRODUCT_RETURN; 732 733 bool isPrevMarked(oop p) const { 734 assert(p != NULL && p->is_oop(), "expected an oop"); 735 HeapWord* addr = (HeapWord*)p; 736 assert(addr >= _prevMarkBitMap->startWord() || 737 addr < _prevMarkBitMap->endWord(), "in a region"); 738 739 return _prevMarkBitMap->isMarked(addr); 740 } 741 742 inline bool do_yield_check(uint worker_i = 0); 743 744 // Called to abort the marking cycle after a Full GC takes place. 745 void abort(); 746 747 bool has_aborted() { return _has_aborted; } 748 749 // This prints the global/local fingers. It is used for debugging. 750 NOT_PRODUCT(void print_finger();) 751 752 void print_summary_info(); 753 754 void print_worker_threads_on(outputStream* st) const; 755 756 void print_on_error(outputStream* st) const; 757 758 // The following indicate whether a given verbose level has been 759 // set. Notice that anything above stats is conditional to 760 // _MARKING_VERBOSE_ having been set to 1 761 bool verbose_stats() { 762 return _verbose_level >= stats_verbose; 763 } 764 bool verbose_low() { 765 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; 766 } 767 bool verbose_medium() { 768 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; 769 } 770 bool verbose_high() { 771 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; 772 } 773 774 // Liveness counting 775 776 // Utility routine to set an exclusive range of cards on the given 777 // card liveness bitmap 778 inline void set_card_bitmap_range(BitMap* card_bm, 779 BitMap::idx_t start_idx, 780 BitMap::idx_t end_idx, 781 bool is_par); 782 783 // Returns the card number of the bottom of the G1 heap. 784 // Used in biasing indices into accounting card bitmaps. 785 intptr_t heap_bottom_card_num() const { 786 return _heap_bottom_card_num; 787 } 788 789 // Returns the card bitmap for a given task or worker id. 790 BitMap* count_card_bitmap_for(uint worker_id) { 791 assert(worker_id < _max_worker_id, "oob"); 792 assert(_count_card_bitmaps != NULL, "uninitialized"); 793 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 794 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 795 return task_card_bm; 796 } 797 798 // Returns the array containing the marked bytes for each region, 799 // for the given worker or task id. 800 size_t* count_marked_bytes_array_for(uint worker_id) { 801 assert(worker_id < _max_worker_id, "oob"); 802 assert(_count_marked_bytes != NULL, "uninitialized"); 803 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 804 assert(marked_bytes_array != NULL, "uninitialized"); 805 return marked_bytes_array; 806 } 807 808 // Returns the index in the liveness accounting card table bitmap 809 // for the given address 810 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 811 812 // Counts the size of the given memory region in the the given 813 // marked_bytes array slot for the given HeapRegion. 814 // Sets the bits in the given card bitmap that are associated with the 815 // cards that are spanned by the memory region. 816 inline void count_region(MemRegion mr, 817 HeapRegion* hr, 818 size_t* marked_bytes_array, 819 BitMap* task_card_bm); 820 821 // Counts the given object in the given task/worker counting 822 // data structures. 823 inline void count_object(oop obj, 824 HeapRegion* hr, 825 size_t* marked_bytes_array, 826 BitMap* task_card_bm, 827 size_t word_size); 828 829 // Attempts to mark the given object and, if successful, counts 830 // the object in the given task/worker counting structures. 831 inline bool par_mark_and_count(oop obj, 832 HeapRegion* hr, 833 size_t* marked_bytes_array, 834 BitMap* task_card_bm); 835 836 // Attempts to mark the given object and, if successful, counts 837 // the object in the task/worker counting structures for the 838 // given worker id. 839 inline bool par_mark_and_count(oop obj, 840 size_t word_size, 841 HeapRegion* hr, 842 uint worker_id); 843 844 // Returns true if initialization was successfully completed. 845 bool completed_initialization() const { 846 return _completed_initialization; 847 } 848 849 protected: 850 // Clear all the per-task bitmaps and arrays used to store the 851 // counting data. 852 void clear_all_count_data(); 853 854 // Aggregates the counting data for each worker/task 855 // that was constructed while marking. Also sets 856 // the amount of marked bytes for each region and 857 // the top at concurrent mark count. 858 void aggregate_count_data(); 859 860 // Verification routine 861 void verify_count_data(); 862 }; 863 864 // A class representing a marking task. 865 class CMTask : public TerminatorTerminator { 866 private: 867 enum PrivateConstants { 868 // the regular clock call is called once the scanned words reaches 869 // this limit 870 words_scanned_period = 12*1024, 871 // the regular clock call is called once the number of visited 872 // references reaches this limit 873 refs_reached_period = 384, 874 // initial value for the hash seed, used in the work stealing code 875 init_hash_seed = 17, 876 // how many entries will be transferred between global stack and 877 // local queues 878 global_stack_transfer_size = 16 879 }; 880 881 uint _worker_id; 882 G1CollectedHeap* _g1h; 883 ConcurrentMark* _cm; 884 CMBitMap* _nextMarkBitMap; 885 // the task queue of this task 886 CMTaskQueue* _task_queue; 887 private: 888 // the task queue set---needed for stealing 889 CMTaskQueueSet* _task_queues; 890 // indicates whether the task has been claimed---this is only for 891 // debugging purposes 892 bool _claimed; 893 894 // number of calls to this task 895 int _calls; 896 897 // when the virtual timer reaches this time, the marking step should 898 // exit 899 double _time_target_ms; 900 // the start time of the current marking step 901 double _start_time_ms; 902 903 // the oop closure used for iterations over oops 904 G1CMOopClosure* _cm_oop_closure; 905 906 // the region this task is scanning, NULL if we're not scanning any 907 HeapRegion* _curr_region; 908 // the local finger of this task, NULL if we're not scanning a region 909 HeapWord* _finger; 910 // limit of the region this task is scanning, NULL if we're not scanning one 911 HeapWord* _region_limit; 912 913 // the number of words this task has scanned 914 size_t _words_scanned; 915 // When _words_scanned reaches this limit, the regular clock is 916 // called. Notice that this might be decreased under certain 917 // circumstances (i.e. when we believe that we did an expensive 918 // operation). 919 size_t _words_scanned_limit; 920 // the initial value of _words_scanned_limit (i.e. what it was 921 // before it was decreased). 922 size_t _real_words_scanned_limit; 923 924 // the number of references this task has visited 925 size_t _refs_reached; 926 // When _refs_reached reaches this limit, the regular clock is 927 // called. Notice this this might be decreased under certain 928 // circumstances (i.e. when we believe that we did an expensive 929 // operation). 930 size_t _refs_reached_limit; 931 // the initial value of _refs_reached_limit (i.e. what it was before 932 // it was decreased). 933 size_t _real_refs_reached_limit; 934 935 // used by the work stealing stuff 936 int _hash_seed; 937 // if this is true, then the task has aborted for some reason 938 bool _has_aborted; 939 // set when the task aborts because it has met its time quota 940 bool _has_timed_out; 941 // true when we're draining SATB buffers; this avoids the task 942 // aborting due to SATB buffers being available (as we're already 943 // dealing with them) 944 bool _draining_satb_buffers; 945 946 // number sequence of past step times 947 NumberSeq _step_times_ms; 948 // elapsed time of this task 949 double _elapsed_time_ms; 950 // termination time of this task 951 double _termination_time_ms; 952 // when this task got into the termination protocol 953 double _termination_start_time_ms; 954 955 // true when the task is during a concurrent phase, false when it is 956 // in the remark phase (so, in the latter case, we do not have to 957 // check all the things that we have to check during the concurrent 958 // phase, i.e. SATB buffer availability...) 959 bool _concurrent; 960 961 TruncatedSeq _marking_step_diffs_ms; 962 963 // Counting data structures. Embedding the task's marked_bytes_array 964 // and card bitmap into the actual task saves having to go through 965 // the ConcurrentMark object. 966 size_t* _marked_bytes_array; 967 BitMap* _card_bm; 968 969 // LOTS of statistics related with this task 970 #if _MARKING_STATS_ 971 NumberSeq _all_clock_intervals_ms; 972 double _interval_start_time_ms; 973 974 size_t _aborted; 975 size_t _aborted_overflow; 976 size_t _aborted_cm_aborted; 977 size_t _aborted_yield; 978 size_t _aborted_timed_out; 979 size_t _aborted_satb; 980 size_t _aborted_termination; 981 982 size_t _steal_attempts; 983 size_t _steals; 984 985 size_t _clock_due_to_marking; 986 size_t _clock_due_to_scanning; 987 988 size_t _local_pushes; 989 size_t _local_pops; 990 size_t _local_max_size; 991 size_t _objs_scanned; 992 993 size_t _global_pushes; 994 size_t _global_pops; 995 size_t _global_max_size; 996 997 size_t _global_transfers_to; 998 size_t _global_transfers_from; 999 1000 size_t _regions_claimed; 1001 size_t _objs_found_on_bitmap; 1002 1003 size_t _satb_buffers_processed; 1004 #endif // _MARKING_STATS_ 1005 1006 // it updates the local fields after this task has claimed 1007 // a new region to scan 1008 void setup_for_region(HeapRegion* hr); 1009 // it brings up-to-date the limit of the region 1010 void update_region_limit(); 1011 1012 // called when either the words scanned or the refs visited limit 1013 // has been reached 1014 void reached_limit(); 1015 // recalculates the words scanned and refs visited limits 1016 void recalculate_limits(); 1017 // decreases the words scanned and refs visited limits when we reach 1018 // an expensive operation 1019 void decrease_limits(); 1020 // it checks whether the words scanned or refs visited reached their 1021 // respective limit and calls reached_limit() if they have 1022 void check_limits() { 1023 if (_words_scanned >= _words_scanned_limit || 1024 _refs_reached >= _refs_reached_limit) { 1025 reached_limit(); 1026 } 1027 } 1028 // this is supposed to be called regularly during a marking step as 1029 // it checks a bunch of conditions that might cause the marking step 1030 // to abort 1031 void regular_clock_call(); 1032 bool concurrent() { return _concurrent; } 1033 1034 // Test whether obj might have already been passed over by the 1035 // mark bitmap scan, and so needs to be pushed onto the mark stack. 1036 bool is_below_finger(oop obj, HeapWord* global_finger) const; 1037 1038 template<bool scan> void process_grey_object(oop obj); 1039 1040 public: 1041 // It resets the task; it should be called right at the beginning of 1042 // a marking phase. 1043 void reset(CMBitMap* _nextMarkBitMap); 1044 // it clears all the fields that correspond to a claimed region. 1045 void clear_region_fields(); 1046 1047 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 1048 1049 // The main method of this class which performs a marking step 1050 // trying not to exceed the given duration. However, it might exit 1051 // prematurely, according to some conditions (i.e. SATB buffers are 1052 // available for processing). 1053 void do_marking_step(double target_ms, 1054 bool do_termination, 1055 bool is_serial); 1056 1057 // These two calls start and stop the timer 1058 void record_start_time() { 1059 _elapsed_time_ms = os::elapsedTime() * 1000.0; 1060 } 1061 void record_end_time() { 1062 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 1063 } 1064 1065 // returns the worker ID associated with this task. 1066 uint worker_id() { return _worker_id; } 1067 1068 // From TerminatorTerminator. It determines whether this task should 1069 // exit the termination protocol after it's entered it. 1070 virtual bool should_exit_termination(); 1071 1072 // Resets the local region fields after a task has finished scanning a 1073 // region; or when they have become stale as a result of the region 1074 // being evacuated. 1075 void giveup_current_region(); 1076 1077 HeapWord* finger() { return _finger; } 1078 1079 bool has_aborted() { return _has_aborted; } 1080 void set_has_aborted() { _has_aborted = true; } 1081 void clear_has_aborted() { _has_aborted = false; } 1082 bool has_timed_out() { return _has_timed_out; } 1083 bool claimed() { return _claimed; } 1084 1085 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 1086 1087 // Increment the number of references this task has visited. 1088 void increment_refs_reached() { ++_refs_reached; } 1089 1090 // Grey the object by marking it. If not already marked, push it on 1091 // the local queue if below the finger. 1092 // Precondition: obj is in region. 1093 // Precondition: obj is below region's NTAMS. 1094 inline void make_reference_grey(oop obj, HeapRegion* region); 1095 1096 // Grey the object (by calling make_grey_reference) if required, 1097 // e.g. obj is below its containing region's NTAMS. 1098 // Precondition: obj is a valid heap object. 1099 inline void deal_with_reference(oop obj); 1100 1101 // It scans an object and visits its children. 1102 inline void scan_object(oop obj); 1103 1104 // It pushes an object on the local queue. 1105 inline void push(oop obj); 1106 1107 // These two move entries to/from the global stack. 1108 void move_entries_to_global_stack(); 1109 void get_entries_from_global_stack(); 1110 1111 // It pops and scans objects from the local queue. If partially is 1112 // true, then it stops when the queue size is of a given limit. If 1113 // partially is false, then it stops when the queue is empty. 1114 void drain_local_queue(bool partially); 1115 // It moves entries from the global stack to the local queue and 1116 // drains the local queue. If partially is true, then it stops when 1117 // both the global stack and the local queue reach a given size. If 1118 // partially if false, it tries to empty them totally. 1119 void drain_global_stack(bool partially); 1120 // It keeps picking SATB buffers and processing them until no SATB 1121 // buffers are available. 1122 void drain_satb_buffers(); 1123 1124 // moves the local finger to a new location 1125 inline void move_finger_to(HeapWord* new_finger) { 1126 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 1127 _finger = new_finger; 1128 } 1129 1130 CMTask(uint worker_id, 1131 ConcurrentMark *cm, 1132 size_t* marked_bytes, 1133 BitMap* card_bm, 1134 CMTaskQueue* task_queue, 1135 CMTaskQueueSet* task_queues); 1136 1137 // it prints statistics associated with this task 1138 void print_stats(); 1139 1140 #if _MARKING_STATS_ 1141 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; } 1142 #endif // _MARKING_STATS_ 1143 }; 1144 1145 // Class that's used to to print out per-region liveness 1146 // information. It's currently used at the end of marking and also 1147 // after we sort the old regions at the end of the cleanup operation. 1148 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 1149 private: 1150 outputStream* _out; 1151 1152 // Accumulators for these values. 1153 size_t _total_used_bytes; 1154 size_t _total_capacity_bytes; 1155 size_t _total_prev_live_bytes; 1156 size_t _total_next_live_bytes; 1157 1158 // These are set up when we come across a "stars humongous" region 1159 // (as this is where most of this information is stored, not in the 1160 // subsequent "continues humongous" regions). After that, for every 1161 // region in a given humongous region series we deduce the right 1162 // values for it by simply subtracting the appropriate amount from 1163 // these fields. All these values should reach 0 after we've visited 1164 // the last region in the series. 1165 size_t _hum_used_bytes; 1166 size_t _hum_capacity_bytes; 1167 size_t _hum_prev_live_bytes; 1168 size_t _hum_next_live_bytes; 1169 1170 // Accumulator for the remembered set size 1171 size_t _total_remset_bytes; 1172 1173 // Accumulator for strong code roots memory size 1174 size_t _total_strong_code_roots_bytes; 1175 1176 static double perc(size_t val, size_t total) { 1177 if (total == 0) { 1178 return 0.0; 1179 } else { 1180 return 100.0 * ((double) val / (double) total); 1181 } 1182 } 1183 1184 static double bytes_to_mb(size_t val) { 1185 return (double) val / (double) M; 1186 } 1187 1188 // See the .cpp file. 1189 size_t get_hum_bytes(size_t* hum_bytes); 1190 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1191 size_t* prev_live_bytes, size_t* next_live_bytes); 1192 1193 public: 1194 // The header and footer are printed in the constructor and 1195 // destructor respectively. 1196 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name); 1197 virtual bool doHeapRegion(HeapRegion* r); 1198 ~G1PrintRegionLivenessInfoClosure(); 1199 }; 1200 1201 #endif // SHARE_VM_GC_G1_CONCURRENTMARK_HPP