1 /* 2 * Copyright (c) 2001, 2012, 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_IMPLEMENTATION_G1_CONCURRENTMARK_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP 27 28 #include "gc_implementation/g1/heapRegionSets.hpp" 29 #include "utilities/taskqueue.hpp" 30 31 class G1CollectedHeap; 32 class CMTask; 33 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue; 34 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet; 35 36 // Closure used by CM during concurrent reference discovery 37 // and reference processing (during remarking) to determine 38 // if a particular object is alive. It is primarily used 39 // to determine if referents of discovered reference objects 40 // are alive. An instance is also embedded into the 41 // reference processor as the _is_alive_non_header field 42 class G1CMIsAliveClosure: public BoolObjectClosure { 43 G1CollectedHeap* _g1; 44 public: 45 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { } 46 47 void do_object(oop obj) { 48 ShouldNotCallThis(); 49 } 50 bool do_object_b(oop obj); 51 }; 52 53 // A generic CM bit map. This is essentially a wrapper around the BitMap 54 // class, with one bit per (1<<_shifter) HeapWords. 55 56 class CMBitMapRO VALUE_OBJ_CLASS_SPEC { 57 protected: 58 HeapWord* _bmStartWord; // base address of range covered by map 59 size_t _bmWordSize; // map size (in #HeapWords covered) 60 const int _shifter; // map to char or bit 61 VirtualSpace _virtual_space; // underlying the bit map 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(HeapWord* addr, 92 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(HeapWord* addr, 97 HeapWord* limit = NULL) const; 98 99 // conversion utilities 100 // XXX Fix these so that offsets are size_t's... 101 HeapWord* offsetToHeapWord(size_t offset) const { 102 return _bmStartWord + (offset << _shifter); 103 } 104 size_t heapWordToOffset(HeapWord* addr) const { 105 return pointer_delta(addr, _bmStartWord) >> _shifter; 106 } 107 int heapWordDiffToOffsetDiff(size_t diff) const; 108 HeapWord* nextWord(HeapWord* addr) { 109 return offsetToHeapWord(heapWordToOffset(addr) + 1); 110 } 111 112 // debugging 113 NOT_PRODUCT(bool covers(ReservedSpace rs) const;) 114 }; 115 116 class CMBitMap : public CMBitMapRO { 117 118 public: 119 // constructor 120 CMBitMap(int shifter) : 121 CMBitMapRO(shifter) {} 122 123 // Allocates the back store for the marking bitmap 124 bool allocate(ReservedSpace heap_rs); 125 126 // write marks 127 void mark(HeapWord* addr) { 128 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 129 "outside underlying space?"); 130 _bm.set_bit(heapWordToOffset(addr)); 131 } 132 void clear(HeapWord* addr) { 133 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 134 "outside underlying space?"); 135 _bm.clear_bit(heapWordToOffset(addr)); 136 } 137 bool parMark(HeapWord* addr) { 138 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 139 "outside underlying space?"); 140 return _bm.par_set_bit(heapWordToOffset(addr)); 141 } 142 bool parClear(HeapWord* addr) { 143 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 144 "outside underlying space?"); 145 return _bm.par_clear_bit(heapWordToOffset(addr)); 146 } 147 void markRange(MemRegion mr); 148 void clearAll(); 149 void clearRange(MemRegion mr); 150 151 // Starting at the bit corresponding to "addr" (inclusive), find the next 152 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find 153 // the end of this run (stopping at "end_addr"). Return the MemRegion 154 // covering from the start of the region corresponding to the first bit 155 // of the run to the end of the region corresponding to the last bit of 156 // the run. If there is no "1" bit at or after "addr", return an empty 157 // MemRegion. 158 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr); 159 }; 160 161 // Represents a marking stack used by ConcurrentMarking in the G1 collector. 162 class CMMarkStack VALUE_OBJ_CLASS_SPEC { 163 VirtualSpace _virtual_space; // Underlying backing store for actual stack 164 ConcurrentMark* _cm; 165 oop* _base; // bottom of stack 166 jint _index; // one more than last occupied index 167 jint _capacity; // max #elements 168 jint _saved_index; // value of _index saved at start of GC 169 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run 170 171 bool _overflow; 172 bool _should_expand; 173 DEBUG_ONLY(bool _drain_in_progress;) 174 DEBUG_ONLY(bool _drain_in_progress_yields;) 175 176 public: 177 CMMarkStack(ConcurrentMark* cm); 178 ~CMMarkStack(); 179 180 #ifndef PRODUCT 181 jint max_depth() const { 182 return _max_depth; 183 } 184 #endif 185 186 bool allocate(size_t capacity); 187 188 oop pop() { 189 if (!isEmpty()) { 190 return _base[--_index] ; 191 } 192 return NULL; 193 } 194 195 // If overflow happens, don't do the push, and record the overflow. 196 // *Requires* that "ptr" is already marked. 197 void push(oop ptr) { 198 if (isFull()) { 199 // Record overflow. 200 _overflow = true; 201 return; 202 } else { 203 _base[_index++] = ptr; 204 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 205 } 206 } 207 // Non-block impl. Note: concurrency is allowed only with other 208 // "par_push" operations, not with "pop" or "drain". We would need 209 // parallel versions of them if such concurrency was desired. 210 void par_push(oop ptr); 211 212 // Pushes the first "n" elements of "ptr_arr" on the stack. 213 // Non-block impl. Note: concurrency is allowed only with other 214 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain". 215 void par_adjoin_arr(oop* ptr_arr, int n); 216 217 // Pushes the first "n" elements of "ptr_arr" on the stack. 218 // Locking impl: concurrency is allowed only with 219 // "par_push_arr" and/or "par_pop_arr" operations, which use the same 220 // locking strategy. 221 void par_push_arr(oop* ptr_arr, int n); 222 223 // If returns false, the array was empty. Otherwise, removes up to "max" 224 // elements from the stack, and transfers them to "ptr_arr" in an 225 // unspecified order. The actual number transferred is given in "n" ("n 226 // == 0" is deliberately redundant with the return value.) Locking impl: 227 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" 228 // operations, which use the same locking strategy. 229 bool par_pop_arr(oop* ptr_arr, int max, int* n); 230 231 // Drain the mark stack, applying the given closure to all fields of 232 // objects on the stack. (That is, continue until the stack is empty, 233 // even if closure applications add entries to the stack.) The "bm" 234 // argument, if non-null, may be used to verify that only marked objects 235 // are on the mark stack. If "yield_after" is "true", then the 236 // concurrent marker performing the drain offers to yield after 237 // processing each object. If a yield occurs, stops the drain operation 238 // and returns false. Otherwise, returns true. 239 template<class OopClosureClass> 240 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false); 241 242 bool isEmpty() { return _index == 0; } 243 bool isFull() { return _index == _capacity; } 244 int maxElems() { return _capacity; } 245 246 bool overflow() { return _overflow; } 247 void clear_overflow() { _overflow = false; } 248 249 bool should_expand() const { return _should_expand; } 250 void set_should_expand(); 251 252 // Expand the stack, typically in response to an overflow condition 253 void expand(); 254 255 int size() { return _index; } 256 257 void setEmpty() { _index = 0; clear_overflow(); } 258 259 // Record the current index. 260 void note_start_of_gc(); 261 262 // Make sure that we have not added any entries to the stack during GC. 263 void note_end_of_gc(); 264 265 // iterate over the oops in the mark stack, up to the bound recorded via 266 // the call above. 267 void oops_do(OopClosure* f); 268 }; 269 270 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC { 271 private: 272 #ifndef PRODUCT 273 uintx _num_remaining; 274 bool _force; 275 #endif // !defined(PRODUCT) 276 277 public: 278 void init() PRODUCT_RETURN; 279 void update() PRODUCT_RETURN; 280 bool should_force() PRODUCT_RETURN_( return false; ); 281 }; 282 283 // this will enable a variety of different statistics per GC task 284 #define _MARKING_STATS_ 0 285 // this will enable the higher verbose levels 286 #define _MARKING_VERBOSE_ 0 287 288 #if _MARKING_STATS_ 289 #define statsOnly(statement) \ 290 do { \ 291 statement ; \ 292 } while (0) 293 #else // _MARKING_STATS_ 294 #define statsOnly(statement) \ 295 do { \ 296 } while (0) 297 #endif // _MARKING_STATS_ 298 299 typedef enum { 300 no_verbose = 0, // verbose turned off 301 stats_verbose, // only prints stats at the end of marking 302 low_verbose, // low verbose, mostly per region and per major event 303 medium_verbose, // a bit more detailed than low 304 high_verbose // per object verbose 305 } CMVerboseLevel; 306 307 class YoungList; 308 309 // Root Regions are regions that are not empty at the beginning of a 310 // marking cycle and which we might collect during an evacuation pause 311 // while the cycle is active. Given that, during evacuation pauses, we 312 // do not copy objects that are explicitly marked, what we have to do 313 // for the root regions is to scan them and mark all objects reachable 314 // from them. According to the SATB assumptions, we only need to visit 315 // each object once during marking. So, as long as we finish this scan 316 // before the next evacuation pause, we can copy the objects from the 317 // root regions without having to mark them or do anything else to them. 318 // 319 // Currently, we only support root region scanning once (at the start 320 // of the marking cycle) and the root regions are all the survivor 321 // regions populated during the initial-mark pause. 322 class CMRootRegions VALUE_OBJ_CLASS_SPEC { 323 private: 324 YoungList* _young_list; 325 ConcurrentMark* _cm; 326 327 volatile bool _scan_in_progress; 328 volatile bool _should_abort; 329 HeapRegion* volatile _next_survivor; 330 331 public: 332 CMRootRegions(); 333 // We actually do most of the initialization in this method. 334 void init(G1CollectedHeap* g1h, ConcurrentMark* cm); 335 336 // Reset the claiming / scanning of the root regions. 337 void prepare_for_scan(); 338 339 // Forces get_next() to return NULL so that the iteration aborts early. 340 void abort() { _should_abort = true; } 341 342 // Return true if the CM thread are actively scanning root regions, 343 // false otherwise. 344 bool scan_in_progress() { return _scan_in_progress; } 345 346 // Claim the next root region to scan atomically, or return NULL if 347 // all have been claimed. 348 HeapRegion* claim_next(); 349 350 // Flag that we're done with root region scanning and notify anyone 351 // who's waiting on it. If aborted is false, assume that all regions 352 // have been claimed. 353 void scan_finished(); 354 355 // If CM threads are still scanning root regions, wait until they 356 // are done. Return true if we had to wait, false otherwise. 357 bool wait_until_scan_finished(); 358 }; 359 360 class ConcurrentMarkThread; 361 362 class ConcurrentMark: public CHeapObj<mtGC> { 363 friend class CMMarkStack; 364 friend class ConcurrentMarkThread; 365 friend class CMTask; 366 friend class CMBitMapClosure; 367 friend class CMGlobalObjectClosure; 368 friend class CMRemarkTask; 369 friend class CMConcurrentMarkingTask; 370 friend class G1ParNoteEndTask; 371 friend class CalcLiveObjectsClosure; 372 friend class G1CMRefProcTaskProxy; 373 friend class G1CMRefProcTaskExecutor; 374 friend class G1CMParKeepAliveAndDrainClosure; 375 friend class G1CMParDrainMarkingStackClosure; 376 377 protected: 378 ConcurrentMarkThread* _cmThread; // the thread doing the work 379 G1CollectedHeap* _g1h; // the heap. 380 uint _parallel_marking_threads; // the number of marking 381 // threads we're use 382 uint _max_parallel_marking_threads; // max number of marking 383 // threads we'll ever use 384 double _sleep_factor; // how much we have to sleep, with 385 // respect to the work we just did, to 386 // meet the marking overhead goal 387 double _marking_task_overhead; // marking target overhead for 388 // a single task 389 390 // same as the two above, but for the cleanup task 391 double _cleanup_sleep_factor; 392 double _cleanup_task_overhead; 393 394 FreeRegionList _cleanup_list; 395 396 // Concurrent marking support structures 397 CMBitMap _markBitMap1; 398 CMBitMap _markBitMap2; 399 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap 400 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap 401 402 BitMap _region_bm; 403 BitMap _card_bm; 404 405 // Heap bounds 406 HeapWord* _heap_start; 407 HeapWord* _heap_end; 408 409 // Root region tracking and claiming. 410 CMRootRegions _root_regions; 411 412 // For gray objects 413 CMMarkStack _markStack; // Grey objects behind global finger. 414 HeapWord* volatile _finger; // the global finger, region aligned, 415 // always points to the end of the 416 // last claimed region 417 418 // marking tasks 419 uint _max_worker_id;// maximum worker id 420 uint _active_tasks; // task num currently active 421 CMTask** _tasks; // task queue array (max_worker_id len) 422 CMTaskQueueSet* _task_queues; // task queue set 423 ParallelTaskTerminator _terminator; // for termination 424 425 // Two sync barriers that are used to synchronise tasks when an 426 // overflow occurs. The algorithm is the following. All tasks enter 427 // the first one to ensure that they have all stopped manipulating 428 // the global data structures. After they exit it, they re-initialise 429 // their data structures and task 0 re-initialises the global data 430 // structures. Then, they enter the second sync barrier. This 431 // ensure, that no task starts doing work before all data 432 // structures (local and global) have been re-initialised. When they 433 // exit it, they are free to start working again. 434 WorkGangBarrierSync _first_overflow_barrier_sync; 435 WorkGangBarrierSync _second_overflow_barrier_sync; 436 437 // this is set by any task, when an overflow on the global data 438 // structures is detected. 439 volatile bool _has_overflown; 440 // true: marking is concurrent, false: we're in remark 441 volatile bool _concurrent; 442 // set at the end of a Full GC so that marking aborts 443 volatile bool _has_aborted; 444 445 // used when remark aborts due to an overflow to indicate that 446 // another concurrent marking phase should start 447 volatile bool _restart_for_overflow; 448 449 // This is true from the very start of concurrent marking until the 450 // point when all the tasks complete their work. It is really used 451 // to determine the points between the end of concurrent marking and 452 // time of remark. 453 volatile bool _concurrent_marking_in_progress; 454 455 // verbose level 456 CMVerboseLevel _verbose_level; 457 458 // All of these times are in ms. 459 NumberSeq _init_times; 460 NumberSeq _remark_times; 461 NumberSeq _remark_mark_times; 462 NumberSeq _remark_weak_ref_times; 463 NumberSeq _cleanup_times; 464 double _total_counting_time; 465 double _total_rs_scrub_time; 466 467 double* _accum_task_vtime; // accumulated task vtime 468 469 FlexibleWorkGang* _parallel_workers; 470 471 ForceOverflowSettings _force_overflow_conc; 472 ForceOverflowSettings _force_overflow_stw; 473 474 void weakRefsWork(bool clear_all_soft_refs); 475 476 void swapMarkBitMaps(); 477 478 // It resets the global marking data structures, as well as the 479 // task local ones; should be called during initial mark. 480 void reset(); 481 // It resets all the marking data structures. 482 void clear_marking_state(bool clear_overflow = true); 483 484 // It should be called to indicate which phase we're in (concurrent 485 // mark or remark) and how many threads are currently active. 486 void set_phase(uint active_tasks, bool concurrent); 487 // We do this after we're done with marking so that the marking data 488 // structures are initialised to a sensible and predictable state. 489 void set_non_marking_state(); 490 491 // prints all gathered CM-related statistics 492 void print_stats(); 493 494 bool cleanup_list_is_empty() { 495 return _cleanup_list.is_empty(); 496 } 497 498 // accessor methods 499 uint parallel_marking_threads() { return _parallel_marking_threads; } 500 uint max_parallel_marking_threads() { return _max_parallel_marking_threads;} 501 double sleep_factor() { return _sleep_factor; } 502 double marking_task_overhead() { return _marking_task_overhead;} 503 double cleanup_sleep_factor() { return _cleanup_sleep_factor; } 504 double cleanup_task_overhead() { return _cleanup_task_overhead;} 505 506 HeapWord* finger() { return _finger; } 507 bool concurrent() { return _concurrent; } 508 uint active_tasks() { return _active_tasks; } 509 ParallelTaskTerminator* terminator() { return &_terminator; } 510 511 // It claims the next available region to be scanned by a marking 512 // task/thread. It might return NULL if the next region is empty or 513 // we have run out of regions. In the latter case, out_of_regions() 514 // determines whether we've really run out of regions or the task 515 // should call claim_region() again. This might seem a bit 516 // awkward. Originally, the code was written so that claim_region() 517 // either successfully returned with a non-empty region or there 518 // were no more regions to be claimed. The problem with this was 519 // that, in certain circumstances, it iterated over large chunks of 520 // the heap finding only empty regions and, while it was working, it 521 // was preventing the calling task to call its regular clock 522 // method. So, this way, each task will spend very little time in 523 // claim_region() and is allowed to call the regular clock method 524 // frequently. 525 HeapRegion* claim_region(uint worker_id); 526 527 // It determines whether we've run out of regions to scan. 528 bool out_of_regions() { return _finger == _heap_end; } 529 530 // Returns the task with the given id 531 CMTask* task(int id) { 532 assert(0 <= id && id < (int) _active_tasks, 533 "task id not within active bounds"); 534 return _tasks[id]; 535 } 536 537 // Returns the task queue with the given id 538 CMTaskQueue* task_queue(int id) { 539 assert(0 <= id && id < (int) _active_tasks, 540 "task queue id not within active bounds"); 541 return (CMTaskQueue*) _task_queues->queue(id); 542 } 543 544 // Returns the task queue set 545 CMTaskQueueSet* task_queues() { return _task_queues; } 546 547 // Access / manipulation of the overflow flag which is set to 548 // indicate that the global stack has overflown 549 bool has_overflown() { return _has_overflown; } 550 void set_has_overflown() { _has_overflown = true; } 551 void clear_has_overflown() { _has_overflown = false; } 552 bool restart_for_overflow() { return _restart_for_overflow; } 553 554 bool has_aborted() { return _has_aborted; } 555 556 // Methods to enter the two overflow sync barriers 557 void enter_first_sync_barrier(uint worker_id); 558 void enter_second_sync_barrier(uint worker_id); 559 560 ForceOverflowSettings* force_overflow_conc() { 561 return &_force_overflow_conc; 562 } 563 564 ForceOverflowSettings* force_overflow_stw() { 565 return &_force_overflow_stw; 566 } 567 568 ForceOverflowSettings* force_overflow() { 569 if (concurrent()) { 570 return force_overflow_conc(); 571 } else { 572 return force_overflow_stw(); 573 } 574 } 575 576 // Live Data Counting data structures... 577 // These data structures are initialized at the start of 578 // marking. They are written to while marking is active. 579 // They are aggregated during remark; the aggregated values 580 // are then used to populate the _region_bm, _card_bm, and 581 // the total live bytes, which are then subsequently updated 582 // during cleanup. 583 584 // An array of bitmaps (one bit map per task). Each bitmap 585 // is used to record the cards spanned by the live objects 586 // marked by that task/worker. 587 BitMap* _count_card_bitmaps; 588 589 // Used to record the number of marked live bytes 590 // (for each region, by worker thread). 591 size_t** _count_marked_bytes; 592 593 // Card index of the bottom of the G1 heap. Used for biasing indices into 594 // the card bitmaps. 595 intptr_t _heap_bottom_card_num; 596 597 // Set to true when initialization is complete 598 bool _completed_initialization; 599 600 public: 601 // Manipulation of the global mark stack. 602 // Notice that the first mark_stack_push is CAS-based, whereas the 603 // two below are Mutex-based. This is OK since the first one is only 604 // called during evacuation pauses and doesn't compete with the 605 // other two (which are called by the marking tasks during 606 // concurrent marking or remark). 607 bool mark_stack_push(oop p) { 608 _markStack.par_push(p); 609 if (_markStack.overflow()) { 610 set_has_overflown(); 611 return false; 612 } 613 return true; 614 } 615 bool mark_stack_push(oop* arr, int n) { 616 _markStack.par_push_arr(arr, n); 617 if (_markStack.overflow()) { 618 set_has_overflown(); 619 return false; 620 } 621 return true; 622 } 623 void mark_stack_pop(oop* arr, int max, int* n) { 624 _markStack.par_pop_arr(arr, max, n); 625 } 626 size_t mark_stack_size() { return _markStack.size(); } 627 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 628 bool mark_stack_overflow() { return _markStack.overflow(); } 629 bool mark_stack_empty() { return _markStack.isEmpty(); } 630 631 CMRootRegions* root_regions() { return &_root_regions; } 632 633 bool concurrent_marking_in_progress() { 634 return _concurrent_marking_in_progress; 635 } 636 void set_concurrent_marking_in_progress() { 637 _concurrent_marking_in_progress = true; 638 } 639 void clear_concurrent_marking_in_progress() { 640 _concurrent_marking_in_progress = false; 641 } 642 643 void update_accum_task_vtime(int i, double vtime) { 644 _accum_task_vtime[i] += vtime; 645 } 646 647 double all_task_accum_vtime() { 648 double ret = 0.0; 649 for (uint i = 0; i < _max_worker_id; ++i) 650 ret += _accum_task_vtime[i]; 651 return ret; 652 } 653 654 // Attempts to steal an object from the task queues of other tasks 655 bool try_stealing(uint worker_id, int* hash_seed, oop& obj) { 656 return _task_queues->steal(worker_id, hash_seed, obj); 657 } 658 659 ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs); 660 ~ConcurrentMark(); 661 662 ConcurrentMarkThread* cmThread() { return _cmThread; } 663 664 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 665 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 666 667 // Returns the number of GC threads to be used in a concurrent 668 // phase based on the number of GC threads being used in a STW 669 // phase. 670 uint scale_parallel_threads(uint n_par_threads); 671 672 // Calculates the number of GC threads to be used in a concurrent phase. 673 uint calc_parallel_marking_threads(); 674 675 // The following three are interaction between CM and 676 // G1CollectedHeap 677 678 // This notifies CM that a root during initial-mark needs to be 679 // grayed. It is MT-safe. word_size is the size of the object in 680 // words. It is passed explicitly as sometimes we cannot calculate 681 // it from the given object because it might be in an inconsistent 682 // state (e.g., in to-space and being copied). So the caller is 683 // responsible for dealing with this issue (e.g., get the size from 684 // the from-space image when the to-space image might be 685 // inconsistent) and always passing the size. hr is the region that 686 // contains the object and it's passed optionally from callers who 687 // might already have it (no point in recalculating it). 688 inline void grayRoot(oop obj, size_t word_size, 689 uint worker_id, HeapRegion* hr = NULL); 690 691 // It iterates over the heap and for each object it comes across it 692 // will dump the contents of its reference fields, as well as 693 // liveness information for the object and its referents. The dump 694 // will be written to a file with the following name: 695 // G1PrintReachableBaseFile + "." + str. 696 // vo decides whether the prev (vo == UsePrevMarking), the next 697 // (vo == UseNextMarking) marking information, or the mark word 698 // (vo == UseMarkWord) will be used to determine the liveness of 699 // each object / referent. 700 // If all is true, all objects in the heap will be dumped, otherwise 701 // only the live ones. In the dump the following symbols / breviations 702 // are used: 703 // M : an explicitly live object (its bitmap bit is set) 704 // > : an implicitly live object (over tams) 705 // O : an object outside the G1 heap (typically: in the perm gen) 706 // NOT : a reference field whose referent is not live 707 // AND MARKED : indicates that an object is both explicitly and 708 // implicitly live (it should be one or the other, not both) 709 void print_reachable(const char* str, 710 VerifyOption vo, bool all) PRODUCT_RETURN; 711 712 // Clear the next marking bitmap (will be called concurrently). 713 void clearNextBitmap(); 714 715 // These two do the work that needs to be done before and after the 716 // initial root checkpoint. Since this checkpoint can be done at two 717 // different points (i.e. an explicit pause or piggy-backed on a 718 // young collection), then it's nice to be able to easily share the 719 // pre/post code. It might be the case that we can put everything in 720 // the post method. TP 721 void checkpointRootsInitialPre(); 722 void checkpointRootsInitialPost(); 723 724 // Scan all the root regions and mark everything reachable from 725 // them. 726 void scanRootRegions(); 727 728 // Scan a single root region and mark everything reachable from it. 729 void scanRootRegion(HeapRegion* hr, uint worker_id); 730 731 // Do concurrent phase of marking, to a tentative transitive closure. 732 void markFromRoots(); 733 734 void checkpointRootsFinal(bool clear_all_soft_refs); 735 void checkpointRootsFinalWork(); 736 void cleanup(); 737 void completeCleanup(); 738 739 // Mark in the previous bitmap. NB: this is usually read-only, so use 740 // this carefully! 741 inline void markPrev(oop p); 742 743 // Clears marks for all objects in the given range, for the prev, 744 // next, or both bitmaps. NB: the previous bitmap is usually 745 // read-only, so use this carefully! 746 void clearRangePrevBitmap(MemRegion mr); 747 void clearRangeNextBitmap(MemRegion mr); 748 void clearRangeBothBitmaps(MemRegion mr); 749 750 // Notify data structures that a GC has started. 751 void note_start_of_gc() { 752 _markStack.note_start_of_gc(); 753 } 754 755 // Notify data structures that a GC is finished. 756 void note_end_of_gc() { 757 _markStack.note_end_of_gc(); 758 } 759 760 // Verify that there are no CSet oops on the stacks (taskqueues / 761 // global mark stack), enqueued SATB buffers, per-thread SATB 762 // buffers, and fingers (global / per-task). The boolean parameters 763 // decide which of the above data structures to verify. If marking 764 // is not in progress, it's a no-op. 765 void verify_no_cset_oops(bool verify_stacks, 766 bool verify_enqueued_buffers, 767 bool verify_thread_buffers, 768 bool verify_fingers) PRODUCT_RETURN; 769 770 // It is called at the end of an evacuation pause during marking so 771 // that CM is notified of where the new end of the heap is. It 772 // doesn't do anything if concurrent_marking_in_progress() is false, 773 // unless the force parameter is true. 774 void update_g1_committed(bool force = false); 775 776 bool isMarked(oop p) const { 777 assert(p != NULL && p->is_oop(), "expected an oop"); 778 HeapWord* addr = (HeapWord*)p; 779 assert(addr >= _nextMarkBitMap->startWord() || 780 addr < _nextMarkBitMap->endWord(), "in a region"); 781 782 return _nextMarkBitMap->isMarked(addr); 783 } 784 785 inline bool not_yet_marked(oop p) const; 786 787 // XXX Debug code 788 bool containing_card_is_marked(void* p); 789 bool containing_cards_are_marked(void* start, void* last); 790 791 bool isPrevMarked(oop p) const { 792 assert(p != NULL && p->is_oop(), "expected an oop"); 793 HeapWord* addr = (HeapWord*)p; 794 assert(addr >= _prevMarkBitMap->startWord() || 795 addr < _prevMarkBitMap->endWord(), "in a region"); 796 797 return _prevMarkBitMap->isMarked(addr); 798 } 799 800 inline bool do_yield_check(uint worker_i = 0); 801 inline bool should_yield(); 802 803 // Called to abort the marking cycle after a Full GC takes palce. 804 void abort(); 805 806 // This prints the global/local fingers. It is used for debugging. 807 NOT_PRODUCT(void print_finger();) 808 809 void print_summary_info(); 810 811 void print_worker_threads_on(outputStream* st) const; 812 813 // The following indicate whether a given verbose level has been 814 // set. Notice that anything above stats is conditional to 815 // _MARKING_VERBOSE_ having been set to 1 816 bool verbose_stats() { 817 return _verbose_level >= stats_verbose; 818 } 819 bool verbose_low() { 820 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; 821 } 822 bool verbose_medium() { 823 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; 824 } 825 bool verbose_high() { 826 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; 827 } 828 829 // Liveness counting 830 831 // Utility routine to set an exclusive range of cards on the given 832 // card liveness bitmap 833 inline void set_card_bitmap_range(BitMap* card_bm, 834 BitMap::idx_t start_idx, 835 BitMap::idx_t end_idx, 836 bool is_par); 837 838 // Returns the card number of the bottom of the G1 heap. 839 // Used in biasing indices into accounting card bitmaps. 840 intptr_t heap_bottom_card_num() const { 841 return _heap_bottom_card_num; 842 } 843 844 // Returns the card bitmap for a given task or worker id. 845 BitMap* count_card_bitmap_for(uint worker_id) { 846 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 847 assert(_count_card_bitmaps != NULL, "uninitialized"); 848 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 849 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 850 return task_card_bm; 851 } 852 853 // Returns the array containing the marked bytes for each region, 854 // for the given worker or task id. 855 size_t* count_marked_bytes_array_for(uint worker_id) { 856 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 857 assert(_count_marked_bytes != NULL, "uninitialized"); 858 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 859 assert(marked_bytes_array != NULL, "uninitialized"); 860 return marked_bytes_array; 861 } 862 863 // Returns the index in the liveness accounting card table bitmap 864 // for the given address 865 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 866 867 // Counts the size of the given memory region in the the given 868 // marked_bytes array slot for the given HeapRegion. 869 // Sets the bits in the given card bitmap that are associated with the 870 // cards that are spanned by the memory region. 871 inline void count_region(MemRegion mr, HeapRegion* hr, 872 size_t* marked_bytes_array, 873 BitMap* task_card_bm); 874 875 // Counts the given memory region in the task/worker counting 876 // data structures for the given worker id. 877 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id); 878 879 // Counts the given memory region in the task/worker counting 880 // data structures for the given worker id. 881 inline void count_region(MemRegion mr, uint worker_id); 882 883 // Counts the given object in the given task/worker counting 884 // data structures. 885 inline void count_object(oop obj, HeapRegion* hr, 886 size_t* marked_bytes_array, 887 BitMap* task_card_bm); 888 889 // Counts the given object in the task/worker counting data 890 // structures for the given worker id. 891 inline void count_object(oop obj, HeapRegion* hr, uint worker_id); 892 893 // Attempts to mark the given object and, if successful, counts 894 // the object in the given task/worker counting structures. 895 inline bool par_mark_and_count(oop obj, HeapRegion* hr, 896 size_t* marked_bytes_array, 897 BitMap* task_card_bm); 898 899 // Attempts to mark the given object and, if successful, counts 900 // the object in the task/worker counting structures for the 901 // given worker id. 902 inline bool par_mark_and_count(oop obj, size_t word_size, 903 HeapRegion* hr, uint worker_id); 904 905 // Attempts to mark the given object and, if successful, counts 906 // the object in the task/worker counting structures for the 907 // given worker id. 908 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id); 909 910 // Similar to the above routine but we don't know the heap region that 911 // contains the object to be marked/counted, which this routine looks up. 912 inline bool par_mark_and_count(oop obj, uint worker_id); 913 914 // Similar to the above routine but there are times when we cannot 915 // safely calculate the size of obj due to races and we, therefore, 916 // pass the size in as a parameter. It is the caller's reponsibility 917 // to ensure that the size passed in for obj is valid. 918 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id); 919 920 // Unconditionally mark the given object, and unconditinally count 921 // the object in the counting structures for worker id 0. 922 // Should *not* be called from parallel code. 923 inline bool mark_and_count(oop obj, HeapRegion* hr); 924 925 // Similar to the above routine but we don't know the heap region that 926 // contains the object to be marked/counted, which this routine looks up. 927 // Should *not* be called from parallel code. 928 inline bool mark_and_count(oop obj); 929 930 // Returns true if initialization was successfully completed. 931 bool completed_initialization() const { 932 return _completed_initialization; 933 } 934 935 protected: 936 // Clear all the per-task bitmaps and arrays used to store the 937 // counting data. 938 void clear_all_count_data(); 939 940 // Aggregates the counting data for each worker/task 941 // that was constructed while marking. Also sets 942 // the amount of marked bytes for each region and 943 // the top at concurrent mark count. 944 void aggregate_count_data(); 945 946 // Verification routine 947 void verify_count_data(); 948 }; 949 950 // A class representing a marking task. 951 class CMTask : public TerminatorTerminator { 952 private: 953 enum PrivateConstants { 954 // the regular clock call is called once the scanned words reaches 955 // this limit 956 words_scanned_period = 12*1024, 957 // the regular clock call is called once the number of visited 958 // references reaches this limit 959 refs_reached_period = 384, 960 // initial value for the hash seed, used in the work stealing code 961 init_hash_seed = 17, 962 // how many entries will be transferred between global stack and 963 // local queues 964 global_stack_transfer_size = 16 965 }; 966 967 uint _worker_id; 968 G1CollectedHeap* _g1h; 969 ConcurrentMark* _cm; 970 CMBitMap* _nextMarkBitMap; 971 // the task queue of this task 972 CMTaskQueue* _task_queue; 973 private: 974 // the task queue set---needed for stealing 975 CMTaskQueueSet* _task_queues; 976 // indicates whether the task has been claimed---this is only for 977 // debugging purposes 978 bool _claimed; 979 980 // number of calls to this task 981 int _calls; 982 983 // when the virtual timer reaches this time, the marking step should 984 // exit 985 double _time_target_ms; 986 // the start time of the current marking step 987 double _start_time_ms; 988 989 // the oop closure used for iterations over oops 990 G1CMOopClosure* _cm_oop_closure; 991 992 // the region this task is scanning, NULL if we're not scanning any 993 HeapRegion* _curr_region; 994 // the local finger of this task, NULL if we're not scanning a region 995 HeapWord* _finger; 996 // limit of the region this task is scanning, NULL if we're not scanning one 997 HeapWord* _region_limit; 998 999 // the number of words this task has scanned 1000 size_t _words_scanned; 1001 // When _words_scanned reaches this limit, the regular clock is 1002 // called. Notice that this might be decreased under certain 1003 // circumstances (i.e. when we believe that we did an expensive 1004 // operation). 1005 size_t _words_scanned_limit; 1006 // the initial value of _words_scanned_limit (i.e. what it was 1007 // before it was decreased). 1008 size_t _real_words_scanned_limit; 1009 1010 // the number of references this task has visited 1011 size_t _refs_reached; 1012 // When _refs_reached reaches this limit, the regular clock is 1013 // called. Notice this this might be decreased under certain 1014 // circumstances (i.e. when we believe that we did an expensive 1015 // operation). 1016 size_t _refs_reached_limit; 1017 // the initial value of _refs_reached_limit (i.e. what it was before 1018 // it was decreased). 1019 size_t _real_refs_reached_limit; 1020 1021 // used by the work stealing stuff 1022 int _hash_seed; 1023 // if this is true, then the task has aborted for some reason 1024 bool _has_aborted; 1025 // set when the task aborts because it has met its time quota 1026 bool _has_timed_out; 1027 // true when we're draining SATB buffers; this avoids the task 1028 // aborting due to SATB buffers being available (as we're already 1029 // dealing with them) 1030 bool _draining_satb_buffers; 1031 1032 // number sequence of past step times 1033 NumberSeq _step_times_ms; 1034 // elapsed time of this task 1035 double _elapsed_time_ms; 1036 // termination time of this task 1037 double _termination_time_ms; 1038 // when this task got into the termination protocol 1039 double _termination_start_time_ms; 1040 1041 // true when the task is during a concurrent phase, false when it is 1042 // in the remark phase (so, in the latter case, we do not have to 1043 // check all the things that we have to check during the concurrent 1044 // phase, i.e. SATB buffer availability...) 1045 bool _concurrent; 1046 1047 TruncatedSeq _marking_step_diffs_ms; 1048 1049 // Counting data structures. Embedding the task's marked_bytes_array 1050 // and card bitmap into the actual task saves having to go through 1051 // the ConcurrentMark object. 1052 size_t* _marked_bytes_array; 1053 BitMap* _card_bm; 1054 1055 // LOTS of statistics related with this task 1056 #if _MARKING_STATS_ 1057 NumberSeq _all_clock_intervals_ms; 1058 double _interval_start_time_ms; 1059 1060 int _aborted; 1061 int _aborted_overflow; 1062 int _aborted_cm_aborted; 1063 int _aborted_yield; 1064 int _aborted_timed_out; 1065 int _aborted_satb; 1066 int _aborted_termination; 1067 1068 int _steal_attempts; 1069 int _steals; 1070 1071 int _clock_due_to_marking; 1072 int _clock_due_to_scanning; 1073 1074 int _local_pushes; 1075 int _local_pops; 1076 int _local_max_size; 1077 int _objs_scanned; 1078 1079 int _global_pushes; 1080 int _global_pops; 1081 int _global_max_size; 1082 1083 int _global_transfers_to; 1084 int _global_transfers_from; 1085 1086 int _regions_claimed; 1087 int _objs_found_on_bitmap; 1088 1089 int _satb_buffers_processed; 1090 #endif // _MARKING_STATS_ 1091 1092 // it updates the local fields after this task has claimed 1093 // a new region to scan 1094 void setup_for_region(HeapRegion* hr); 1095 // it brings up-to-date the limit of the region 1096 void update_region_limit(); 1097 1098 // called when either the words scanned or the refs visited limit 1099 // has been reached 1100 void reached_limit(); 1101 // recalculates the words scanned and refs visited limits 1102 void recalculate_limits(); 1103 // decreases the words scanned and refs visited limits when we reach 1104 // an expensive operation 1105 void decrease_limits(); 1106 // it checks whether the words scanned or refs visited reached their 1107 // respective limit and calls reached_limit() if they have 1108 void check_limits() { 1109 if (_words_scanned >= _words_scanned_limit || 1110 _refs_reached >= _refs_reached_limit) { 1111 reached_limit(); 1112 } 1113 } 1114 // this is supposed to be called regularly during a marking step as 1115 // it checks a bunch of conditions that might cause the marking step 1116 // to abort 1117 void regular_clock_call(); 1118 bool concurrent() { return _concurrent; } 1119 1120 public: 1121 // It resets the task; it should be called right at the beginning of 1122 // a marking phase. 1123 void reset(CMBitMap* _nextMarkBitMap); 1124 // it clears all the fields that correspond to a claimed region. 1125 void clear_region_fields(); 1126 1127 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 1128 1129 // The main method of this class which performs a marking step 1130 // trying not to exceed the given duration. However, it might exit 1131 // prematurely, according to some conditions (i.e. SATB buffers are 1132 // available for processing). 1133 void do_marking_step(double target_ms, bool do_stealing, bool do_termination); 1134 1135 // These two calls start and stop the timer 1136 void record_start_time() { 1137 _elapsed_time_ms = os::elapsedTime() * 1000.0; 1138 } 1139 void record_end_time() { 1140 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 1141 } 1142 1143 // returns the worker ID associated with this task. 1144 uint worker_id() { return _worker_id; } 1145 1146 // From TerminatorTerminator. It determines whether this task should 1147 // exit the termination protocol after it's entered it. 1148 virtual bool should_exit_termination(); 1149 1150 // Resets the local region fields after a task has finished scanning a 1151 // region; or when they have become stale as a result of the region 1152 // being evacuated. 1153 void giveup_current_region(); 1154 1155 HeapWord* finger() { return _finger; } 1156 1157 bool has_aborted() { return _has_aborted; } 1158 void set_has_aborted() { _has_aborted = true; } 1159 void clear_has_aborted() { _has_aborted = false; } 1160 bool has_timed_out() { return _has_timed_out; } 1161 bool claimed() { return _claimed; } 1162 1163 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 1164 1165 // It grays the object by marking it and, if necessary, pushing it 1166 // on the local queue 1167 inline void deal_with_reference(oop obj); 1168 1169 // It scans an object and visits its children. 1170 void scan_object(oop obj); 1171 1172 // It pushes an object on the local queue. 1173 inline void push(oop obj); 1174 1175 // These two move entries to/from the global stack. 1176 void move_entries_to_global_stack(); 1177 void get_entries_from_global_stack(); 1178 1179 // It pops and scans objects from the local queue. If partially is 1180 // true, then it stops when the queue size is of a given limit. If 1181 // partially is false, then it stops when the queue is empty. 1182 void drain_local_queue(bool partially); 1183 // It moves entries from the global stack to the local queue and 1184 // drains the local queue. If partially is true, then it stops when 1185 // both the global stack and the local queue reach a given size. If 1186 // partially if false, it tries to empty them totally. 1187 void drain_global_stack(bool partially); 1188 // It keeps picking SATB buffers and processing them until no SATB 1189 // buffers are available. 1190 void drain_satb_buffers(); 1191 1192 // moves the local finger to a new location 1193 inline void move_finger_to(HeapWord* new_finger) { 1194 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 1195 _finger = new_finger; 1196 } 1197 1198 CMTask(uint worker_id, ConcurrentMark *cm, 1199 size_t* marked_bytes, BitMap* card_bm, 1200 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues); 1201 1202 // it prints statistics associated with this task 1203 void print_stats(); 1204 1205 #if _MARKING_STATS_ 1206 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; } 1207 #endif // _MARKING_STATS_ 1208 }; 1209 1210 // Class that's used to to print out per-region liveness 1211 // information. It's currently used at the end of marking and also 1212 // after we sort the old regions at the end of the cleanup operation. 1213 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 1214 private: 1215 outputStream* _out; 1216 1217 // Accumulators for these values. 1218 size_t _total_used_bytes; 1219 size_t _total_capacity_bytes; 1220 size_t _total_prev_live_bytes; 1221 size_t _total_next_live_bytes; 1222 1223 // These are set up when we come across a "stars humongous" region 1224 // (as this is where most of this information is stored, not in the 1225 // subsequent "continues humongous" regions). After that, for every 1226 // region in a given humongous region series we deduce the right 1227 // values for it by simply subtracting the appropriate amount from 1228 // these fields. All these values should reach 0 after we've visited 1229 // the last region in the series. 1230 size_t _hum_used_bytes; 1231 size_t _hum_capacity_bytes; 1232 size_t _hum_prev_live_bytes; 1233 size_t _hum_next_live_bytes; 1234 1235 static double perc(size_t val, size_t total) { 1236 if (total == 0) { 1237 return 0.0; 1238 } else { 1239 return 100.0 * ((double) val / (double) total); 1240 } 1241 } 1242 1243 static double bytes_to_mb(size_t val) { 1244 return (double) val / (double) M; 1245 } 1246 1247 // See the .cpp file. 1248 size_t get_hum_bytes(size_t* hum_bytes); 1249 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1250 size_t* prev_live_bytes, size_t* next_live_bytes); 1251 1252 public: 1253 // The header and footer are printed in the constructor and 1254 // destructor respectively. 1255 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name); 1256 virtual bool doHeapRegion(HeapRegion* r); 1257 ~G1PrintRegionLivenessInfoClosure(); 1258 }; 1259 1260 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP