1 /* 2 * Copyright (c) 2001, 2013, 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 G1CMKeepAliveAndDrainClosure; 375 friend class G1CMDrainMarkingStackClosure; 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(); 481 482 // Resets all the marking data structures. Called when we have to restart 483 // marking or when marking completes (via set_non_marking_state below). 484 void reset_marking_state(bool clear_overflow = true); 485 486 // We do this after we're done with marking so that the marking data 487 // structures are initialised to a sensible and predictable state. 488 void set_non_marking_state(); 489 490 // It should be called to indicate which phase we're in (concurrent 491 // mark or remark) and how many threads are currently active. 492 void set_phase(uint active_tasks, bool concurrent); 493 494 // prints all gathered CM-related statistics 495 void print_stats(); 496 497 bool cleanup_list_is_empty() { 498 return _cleanup_list.is_empty(); 499 } 500 501 // accessor methods 502 uint parallel_marking_threads() const { return _parallel_marking_threads; } 503 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} 504 double sleep_factor() { return _sleep_factor; } 505 double marking_task_overhead() { return _marking_task_overhead;} 506 double cleanup_sleep_factor() { return _cleanup_sleep_factor; } 507 double cleanup_task_overhead() { return _cleanup_task_overhead;} 508 509 bool use_parallel_marking_threads() const { 510 assert(parallel_marking_threads() <= 511 max_parallel_marking_threads(), "sanity"); 512 assert((_parallel_workers == NULL && parallel_marking_threads() == 0) || 513 parallel_marking_threads() > 0, 514 "parallel workers not set up correctly"); 515 return _parallel_workers != NULL; 516 } 517 518 HeapWord* finger() { return _finger; } 519 bool concurrent() { return _concurrent; } 520 uint active_tasks() { return _active_tasks; } 521 ParallelTaskTerminator* terminator() { return &_terminator; } 522 523 // It claims the next available region to be scanned by a marking 524 // task/thread. It might return NULL if the next region is empty or 525 // we have run out of regions. In the latter case, out_of_regions() 526 // determines whether we've really run out of regions or the task 527 // should call claim_region() again. This might seem a bit 528 // awkward. Originally, the code was written so that claim_region() 529 // either successfully returned with a non-empty region or there 530 // were no more regions to be claimed. The problem with this was 531 // that, in certain circumstances, it iterated over large chunks of 532 // the heap finding only empty regions and, while it was working, it 533 // was preventing the calling task to call its regular clock 534 // method. So, this way, each task will spend very little time in 535 // claim_region() and is allowed to call the regular clock method 536 // frequently. 537 HeapRegion* claim_region(uint worker_id); 538 539 // It determines whether we've run out of regions to scan. 540 bool out_of_regions() { return _finger == _heap_end; } 541 542 // Returns the task with the given id 543 CMTask* task(int id) { 544 assert(0 <= id && id < (int) _active_tasks, 545 "task id not within active bounds"); 546 return _tasks[id]; 547 } 548 549 // Returns the task queue with the given id 550 CMTaskQueue* task_queue(int id) { 551 assert(0 <= id && id < (int) _active_tasks, 552 "task queue id not within active bounds"); 553 return (CMTaskQueue*) _task_queues->queue(id); 554 } 555 556 // Returns the task queue set 557 CMTaskQueueSet* task_queues() { return _task_queues; } 558 559 // Access / manipulation of the overflow flag which is set to 560 // indicate that the global stack has overflown 561 bool has_overflown() { return _has_overflown; } 562 void set_has_overflown() { _has_overflown = true; } 563 void clear_has_overflown() { _has_overflown = false; } 564 bool restart_for_overflow() { return _restart_for_overflow; } 565 566 bool has_aborted() { return _has_aborted; } 567 568 // Methods to enter the two overflow sync barriers 569 void enter_first_sync_barrier(uint worker_id); 570 void enter_second_sync_barrier(uint worker_id); 571 572 ForceOverflowSettings* force_overflow_conc() { 573 return &_force_overflow_conc; 574 } 575 576 ForceOverflowSettings* force_overflow_stw() { 577 return &_force_overflow_stw; 578 } 579 580 ForceOverflowSettings* force_overflow() { 581 if (concurrent()) { 582 return force_overflow_conc(); 583 } else { 584 return force_overflow_stw(); 585 } 586 } 587 588 // Live Data Counting data structures... 589 // These data structures are initialized at the start of 590 // marking. They are written to while marking is active. 591 // They are aggregated during remark; the aggregated values 592 // are then used to populate the _region_bm, _card_bm, and 593 // the total live bytes, which are then subsequently updated 594 // during cleanup. 595 596 // An array of bitmaps (one bit map per task). Each bitmap 597 // is used to record the cards spanned by the live objects 598 // marked by that task/worker. 599 BitMap* _count_card_bitmaps; 600 601 // Used to record the number of marked live bytes 602 // (for each region, by worker thread). 603 size_t** _count_marked_bytes; 604 605 // Card index of the bottom of the G1 heap. Used for biasing indices into 606 // the card bitmaps. 607 intptr_t _heap_bottom_card_num; 608 609 // Set to true when initialization is complete 610 bool _completed_initialization; 611 612 public: 613 // Manipulation of the global mark stack. 614 // Notice that the first mark_stack_push is CAS-based, whereas the 615 // two below are Mutex-based. This is OK since the first one is only 616 // called during evacuation pauses and doesn't compete with the 617 // other two (which are called by the marking tasks during 618 // concurrent marking or remark). 619 bool mark_stack_push(oop p) { 620 _markStack.par_push(p); 621 if (_markStack.overflow()) { 622 set_has_overflown(); 623 return false; 624 } 625 return true; 626 } 627 bool mark_stack_push(oop* arr, int n) { 628 _markStack.par_push_arr(arr, n); 629 if (_markStack.overflow()) { 630 set_has_overflown(); 631 return false; 632 } 633 return true; 634 } 635 void mark_stack_pop(oop* arr, int max, int* n) { 636 _markStack.par_pop_arr(arr, max, n); 637 } 638 size_t mark_stack_size() { return _markStack.size(); } 639 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 640 bool mark_stack_overflow() { return _markStack.overflow(); } 641 bool mark_stack_empty() { return _markStack.isEmpty(); } 642 643 CMRootRegions* root_regions() { return &_root_regions; } 644 645 bool concurrent_marking_in_progress() { 646 return _concurrent_marking_in_progress; 647 } 648 void set_concurrent_marking_in_progress() { 649 _concurrent_marking_in_progress = true; 650 } 651 void clear_concurrent_marking_in_progress() { 652 _concurrent_marking_in_progress = false; 653 } 654 655 void update_accum_task_vtime(int i, double vtime) { 656 _accum_task_vtime[i] += vtime; 657 } 658 659 double all_task_accum_vtime() { 660 double ret = 0.0; 661 for (uint i = 0; i < _max_worker_id; ++i) 662 ret += _accum_task_vtime[i]; 663 return ret; 664 } 665 666 // Attempts to steal an object from the task queues of other tasks 667 bool try_stealing(uint worker_id, int* hash_seed, oop& obj) { 668 return _task_queues->steal(worker_id, hash_seed, obj); 669 } 670 671 ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs); 672 ~ConcurrentMark(); 673 674 ConcurrentMarkThread* cmThread() { return _cmThread; } 675 676 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 677 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 678 679 // Returns the number of GC threads to be used in a concurrent 680 // phase based on the number of GC threads being used in a STW 681 // phase. 682 uint scale_parallel_threads(uint n_par_threads); 683 684 // Calculates the number of GC threads to be used in a concurrent phase. 685 uint calc_parallel_marking_threads(); 686 687 // The following three are interaction between CM and 688 // G1CollectedHeap 689 690 // This notifies CM that a root during initial-mark needs to be 691 // grayed. It is MT-safe. word_size is the size of the object in 692 // words. It is passed explicitly as sometimes we cannot calculate 693 // it from the given object because it might be in an inconsistent 694 // state (e.g., in to-space and being copied). So the caller is 695 // responsible for dealing with this issue (e.g., get the size from 696 // the from-space image when the to-space image might be 697 // inconsistent) and always passing the size. hr is the region that 698 // contains the object and it's passed optionally from callers who 699 // might already have it (no point in recalculating it). 700 inline void grayRoot(oop obj, size_t word_size, 701 uint worker_id, HeapRegion* hr = NULL); 702 703 // It iterates over the heap and for each object it comes across it 704 // will dump the contents of its reference fields, as well as 705 // liveness information for the object and its referents. The dump 706 // will be written to a file with the following name: 707 // G1PrintReachableBaseFile + "." + str. 708 // vo decides whether the prev (vo == UsePrevMarking), the next 709 // (vo == UseNextMarking) marking information, or the mark word 710 // (vo == UseMarkWord) will be used to determine the liveness of 711 // each object / referent. 712 // If all is true, all objects in the heap will be dumped, otherwise 713 // only the live ones. In the dump the following symbols / breviations 714 // are used: 715 // M : an explicitly live object (its bitmap bit is set) 716 // > : an implicitly live object (over tams) 717 // O : an object outside the G1 heap (typically: in the perm gen) 718 // NOT : a reference field whose referent is not live 719 // AND MARKED : indicates that an object is both explicitly and 720 // implicitly live (it should be one or the other, not both) 721 void print_reachable(const char* str, 722 VerifyOption vo, bool all) PRODUCT_RETURN; 723 724 // Clear the next marking bitmap (will be called concurrently). 725 void clearNextBitmap(); 726 727 // These two do the work that needs to be done before and after the 728 // initial root checkpoint. Since this checkpoint can be done at two 729 // different points (i.e. an explicit pause or piggy-backed on a 730 // young collection), then it's nice to be able to easily share the 731 // pre/post code. It might be the case that we can put everything in 732 // the post method. TP 733 void checkpointRootsInitialPre(); 734 void checkpointRootsInitialPost(); 735 736 // Scan all the root regions and mark everything reachable from 737 // them. 738 void scanRootRegions(); 739 740 // Scan a single root region and mark everything reachable from it. 741 void scanRootRegion(HeapRegion* hr, uint worker_id); 742 743 // Do concurrent phase of marking, to a tentative transitive closure. 744 void markFromRoots(); 745 746 void checkpointRootsFinal(bool clear_all_soft_refs); 747 void checkpointRootsFinalWork(); 748 void cleanup(); 749 void completeCleanup(); 750 751 // Mark in the previous bitmap. NB: this is usually read-only, so use 752 // this carefully! 753 inline void markPrev(oop p); 754 755 // Clears marks for all objects in the given range, for the prev, 756 // next, or both bitmaps. NB: the previous bitmap is usually 757 // read-only, so use this carefully! 758 void clearRangePrevBitmap(MemRegion mr); 759 void clearRangeNextBitmap(MemRegion mr); 760 void clearRangeBothBitmaps(MemRegion mr); 761 762 // Notify data structures that a GC has started. 763 void note_start_of_gc() { 764 _markStack.note_start_of_gc(); 765 } 766 767 // Notify data structures that a GC is finished. 768 void note_end_of_gc() { 769 _markStack.note_end_of_gc(); 770 } 771 772 // Verify that there are no CSet oops on the stacks (taskqueues / 773 // global mark stack), enqueued SATB buffers, per-thread SATB 774 // buffers, and fingers (global / per-task). The boolean parameters 775 // decide which of the above data structures to verify. If marking 776 // is not in progress, it's a no-op. 777 void verify_no_cset_oops(bool verify_stacks, 778 bool verify_enqueued_buffers, 779 bool verify_thread_buffers, 780 bool verify_fingers) PRODUCT_RETURN; 781 782 // It is called at the end of an evacuation pause during marking so 783 // that CM is notified of where the new end of the heap is. It 784 // doesn't do anything if concurrent_marking_in_progress() is false, 785 // unless the force parameter is true. 786 void update_g1_committed(bool force = false); 787 788 bool isMarked(oop p) const { 789 assert(p != NULL && p->is_oop(), "expected an oop"); 790 HeapWord* addr = (HeapWord*)p; 791 assert(addr >= _nextMarkBitMap->startWord() || 792 addr < _nextMarkBitMap->endWord(), "in a region"); 793 794 return _nextMarkBitMap->isMarked(addr); 795 } 796 797 inline bool not_yet_marked(oop p) const; 798 799 // XXX Debug code 800 bool containing_card_is_marked(void* p); 801 bool containing_cards_are_marked(void* start, void* last); 802 803 bool isPrevMarked(oop p) const { 804 assert(p != NULL && p->is_oop(), "expected an oop"); 805 HeapWord* addr = (HeapWord*)p; 806 assert(addr >= _prevMarkBitMap->startWord() || 807 addr < _prevMarkBitMap->endWord(), "in a region"); 808 809 return _prevMarkBitMap->isMarked(addr); 810 } 811 812 inline bool do_yield_check(uint worker_i = 0); 813 inline bool should_yield(); 814 815 // Called to abort the marking cycle after a Full GC takes palce. 816 void abort(); 817 818 // This prints the global/local fingers. It is used for debugging. 819 NOT_PRODUCT(void print_finger();) 820 821 void print_summary_info(); 822 823 void print_worker_threads_on(outputStream* st) const; 824 825 // The following indicate whether a given verbose level has been 826 // set. Notice that anything above stats is conditional to 827 // _MARKING_VERBOSE_ having been set to 1 828 bool verbose_stats() { 829 return _verbose_level >= stats_verbose; 830 } 831 bool verbose_low() { 832 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; 833 } 834 bool verbose_medium() { 835 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; 836 } 837 bool verbose_high() { 838 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; 839 } 840 841 // Liveness counting 842 843 // Utility routine to set an exclusive range of cards on the given 844 // card liveness bitmap 845 inline void set_card_bitmap_range(BitMap* card_bm, 846 BitMap::idx_t start_idx, 847 BitMap::idx_t end_idx, 848 bool is_par); 849 850 // Returns the card number of the bottom of the G1 heap. 851 // Used in biasing indices into accounting card bitmaps. 852 intptr_t heap_bottom_card_num() const { 853 return _heap_bottom_card_num; 854 } 855 856 // Returns the card bitmap for a given task or worker id. 857 BitMap* count_card_bitmap_for(uint worker_id) { 858 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 859 assert(_count_card_bitmaps != NULL, "uninitialized"); 860 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 861 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 862 return task_card_bm; 863 } 864 865 // Returns the array containing the marked bytes for each region, 866 // for the given worker or task id. 867 size_t* count_marked_bytes_array_for(uint worker_id) { 868 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 869 assert(_count_marked_bytes != NULL, "uninitialized"); 870 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 871 assert(marked_bytes_array != NULL, "uninitialized"); 872 return marked_bytes_array; 873 } 874 875 // Returns the index in the liveness accounting card table bitmap 876 // for the given address 877 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 878 879 // Counts the size of the given memory region in the the given 880 // marked_bytes array slot for the given HeapRegion. 881 // Sets the bits in the given card bitmap that are associated with the 882 // cards that are spanned by the memory region. 883 inline void count_region(MemRegion mr, HeapRegion* hr, 884 size_t* marked_bytes_array, 885 BitMap* task_card_bm); 886 887 // Counts the given memory region in the task/worker counting 888 // data structures for the given worker id. 889 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id); 890 891 // Counts the given memory region in the task/worker counting 892 // data structures for the given worker id. 893 inline void count_region(MemRegion mr, uint worker_id); 894 895 // Counts the given object in the given task/worker counting 896 // data structures. 897 inline void count_object(oop obj, HeapRegion* hr, 898 size_t* marked_bytes_array, 899 BitMap* task_card_bm); 900 901 // Counts the given object in the task/worker counting data 902 // structures for the given worker id. 903 inline void count_object(oop obj, HeapRegion* hr, uint worker_id); 904 905 // Attempts to mark the given object and, if successful, counts 906 // the object in the given task/worker counting structures. 907 inline bool par_mark_and_count(oop obj, HeapRegion* hr, 908 size_t* marked_bytes_array, 909 BitMap* task_card_bm); 910 911 // Attempts to mark the given object and, if successful, counts 912 // the object in the task/worker counting structures for the 913 // given worker id. 914 inline bool par_mark_and_count(oop obj, size_t word_size, 915 HeapRegion* hr, uint worker_id); 916 917 // Attempts to mark the given object and, if successful, counts 918 // the object in the task/worker counting structures for the 919 // given worker id. 920 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id); 921 922 // Similar to the above routine but we don't know the heap region that 923 // contains the object to be marked/counted, which this routine looks up. 924 inline bool par_mark_and_count(oop obj, uint worker_id); 925 926 // Similar to the above routine but there are times when we cannot 927 // safely calculate the size of obj due to races and we, therefore, 928 // pass the size in as a parameter. It is the caller's reponsibility 929 // to ensure that the size passed in for obj is valid. 930 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id); 931 932 // Unconditionally mark the given object, and unconditinally count 933 // the object in the counting structures for worker id 0. 934 // Should *not* be called from parallel code. 935 inline bool mark_and_count(oop obj, HeapRegion* hr); 936 937 // Similar to the above routine but we don't know the heap region that 938 // contains the object to be marked/counted, which this routine looks up. 939 // Should *not* be called from parallel code. 940 inline bool mark_and_count(oop obj); 941 942 // Returns true if initialization was successfully completed. 943 bool completed_initialization() const { 944 return _completed_initialization; 945 } 946 947 protected: 948 // Clear all the per-task bitmaps and arrays used to store the 949 // counting data. 950 void clear_all_count_data(); 951 952 // Aggregates the counting data for each worker/task 953 // that was constructed while marking. Also sets 954 // the amount of marked bytes for each region and 955 // the top at concurrent mark count. 956 void aggregate_count_data(); 957 958 // Verification routine 959 void verify_count_data(); 960 }; 961 962 // A class representing a marking task. 963 class CMTask : public TerminatorTerminator { 964 private: 965 enum PrivateConstants { 966 // the regular clock call is called once the scanned words reaches 967 // this limit 968 words_scanned_period = 12*1024, 969 // the regular clock call is called once the number of visited 970 // references reaches this limit 971 refs_reached_period = 384, 972 // initial value for the hash seed, used in the work stealing code 973 init_hash_seed = 17, 974 // how many entries will be transferred between global stack and 975 // local queues 976 global_stack_transfer_size = 16 977 }; 978 979 uint _worker_id; 980 G1CollectedHeap* _g1h; 981 ConcurrentMark* _cm; 982 CMBitMap* _nextMarkBitMap; 983 // the task queue of this task 984 CMTaskQueue* _task_queue; 985 private: 986 // the task queue set---needed for stealing 987 CMTaskQueueSet* _task_queues; 988 // indicates whether the task has been claimed---this is only for 989 // debugging purposes 990 bool _claimed; 991 992 // number of calls to this task 993 int _calls; 994 995 // when the virtual timer reaches this time, the marking step should 996 // exit 997 double _time_target_ms; 998 // the start time of the current marking step 999 double _start_time_ms; 1000 1001 // the oop closure used for iterations over oops 1002 G1CMOopClosure* _cm_oop_closure; 1003 1004 // the region this task is scanning, NULL if we're not scanning any 1005 HeapRegion* _curr_region; 1006 // the local finger of this task, NULL if we're not scanning a region 1007 HeapWord* _finger; 1008 // limit of the region this task is scanning, NULL if we're not scanning one 1009 HeapWord* _region_limit; 1010 1011 // the number of words this task has scanned 1012 size_t _words_scanned; 1013 // When _words_scanned reaches this limit, the regular clock is 1014 // called. Notice that this might be decreased under certain 1015 // circumstances (i.e. when we believe that we did an expensive 1016 // operation). 1017 size_t _words_scanned_limit; 1018 // the initial value of _words_scanned_limit (i.e. what it was 1019 // before it was decreased). 1020 size_t _real_words_scanned_limit; 1021 1022 // the number of references this task has visited 1023 size_t _refs_reached; 1024 // When _refs_reached reaches this limit, the regular clock is 1025 // called. Notice this this might be decreased under certain 1026 // circumstances (i.e. when we believe that we did an expensive 1027 // operation). 1028 size_t _refs_reached_limit; 1029 // the initial value of _refs_reached_limit (i.e. what it was before 1030 // it was decreased). 1031 size_t _real_refs_reached_limit; 1032 1033 // used by the work stealing stuff 1034 int _hash_seed; 1035 // if this is true, then the task has aborted for some reason 1036 bool _has_aborted; 1037 // set when the task aborts because it has met its time quota 1038 bool _has_timed_out; 1039 // true when we're draining SATB buffers; this avoids the task 1040 // aborting due to SATB buffers being available (as we're already 1041 // dealing with them) 1042 bool _draining_satb_buffers; 1043 1044 // number sequence of past step times 1045 NumberSeq _step_times_ms; 1046 // elapsed time of this task 1047 double _elapsed_time_ms; 1048 // termination time of this task 1049 double _termination_time_ms; 1050 // when this task got into the termination protocol 1051 double _termination_start_time_ms; 1052 1053 // true when the task is during a concurrent phase, false when it is 1054 // in the remark phase (so, in the latter case, we do not have to 1055 // check all the things that we have to check during the concurrent 1056 // phase, i.e. SATB buffer availability...) 1057 bool _concurrent; 1058 1059 TruncatedSeq _marking_step_diffs_ms; 1060 1061 // Counting data structures. Embedding the task's marked_bytes_array 1062 // and card bitmap into the actual task saves having to go through 1063 // the ConcurrentMark object. 1064 size_t* _marked_bytes_array; 1065 BitMap* _card_bm; 1066 1067 // LOTS of statistics related with this task 1068 #if _MARKING_STATS_ 1069 NumberSeq _all_clock_intervals_ms; 1070 double _interval_start_time_ms; 1071 1072 int _aborted; 1073 int _aborted_overflow; 1074 int _aborted_cm_aborted; 1075 int _aborted_yield; 1076 int _aborted_timed_out; 1077 int _aborted_satb; 1078 int _aborted_termination; 1079 1080 int _steal_attempts; 1081 int _steals; 1082 1083 int _clock_due_to_marking; 1084 int _clock_due_to_scanning; 1085 1086 int _local_pushes; 1087 int _local_pops; 1088 int _local_max_size; 1089 int _objs_scanned; 1090 1091 int _global_pushes; 1092 int _global_pops; 1093 int _global_max_size; 1094 1095 int _global_transfers_to; 1096 int _global_transfers_from; 1097 1098 int _regions_claimed; 1099 int _objs_found_on_bitmap; 1100 1101 int _satb_buffers_processed; 1102 #endif // _MARKING_STATS_ 1103 1104 // it updates the local fields after this task has claimed 1105 // a new region to scan 1106 void setup_for_region(HeapRegion* hr); 1107 // it brings up-to-date the limit of the region 1108 void update_region_limit(); 1109 1110 // called when either the words scanned or the refs visited limit 1111 // has been reached 1112 void reached_limit(); 1113 // recalculates the words scanned and refs visited limits 1114 void recalculate_limits(); 1115 // decreases the words scanned and refs visited limits when we reach 1116 // an expensive operation 1117 void decrease_limits(); 1118 // it checks whether the words scanned or refs visited reached their 1119 // respective limit and calls reached_limit() if they have 1120 void check_limits() { 1121 if (_words_scanned >= _words_scanned_limit || 1122 _refs_reached >= _refs_reached_limit) { 1123 reached_limit(); 1124 } 1125 } 1126 // this is supposed to be called regularly during a marking step as 1127 // it checks a bunch of conditions that might cause the marking step 1128 // to abort 1129 void regular_clock_call(); 1130 bool concurrent() { return _concurrent; } 1131 1132 public: 1133 // It resets the task; it should be called right at the beginning of 1134 // a marking phase. 1135 void reset(CMBitMap* _nextMarkBitMap); 1136 // it clears all the fields that correspond to a claimed region. 1137 void clear_region_fields(); 1138 1139 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 1140 1141 // The main method of this class which performs a marking step 1142 // trying not to exceed the given duration. However, it might exit 1143 // prematurely, according to some conditions (i.e. SATB buffers are 1144 // available for processing). 1145 void do_marking_step(double target_ms, bool do_stealing, bool do_termination); 1146 1147 // These two calls start and stop the timer 1148 void record_start_time() { 1149 _elapsed_time_ms = os::elapsedTime() * 1000.0; 1150 } 1151 void record_end_time() { 1152 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 1153 } 1154 1155 // returns the worker ID associated with this task. 1156 uint worker_id() { return _worker_id; } 1157 1158 // From TerminatorTerminator. It determines whether this task should 1159 // exit the termination protocol after it's entered it. 1160 virtual bool should_exit_termination(); 1161 1162 // Resets the local region fields after a task has finished scanning a 1163 // region; or when they have become stale as a result of the region 1164 // being evacuated. 1165 void giveup_current_region(); 1166 1167 HeapWord* finger() { return _finger; } 1168 1169 bool has_aborted() { return _has_aborted; } 1170 void set_has_aborted() { _has_aborted = true; } 1171 void clear_has_aborted() { _has_aborted = false; } 1172 bool has_timed_out() { return _has_timed_out; } 1173 bool claimed() { return _claimed; } 1174 1175 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 1176 1177 // It grays the object by marking it and, if necessary, pushing it 1178 // on the local queue 1179 inline void deal_with_reference(oop obj); 1180 1181 // It scans an object and visits its children. 1182 void scan_object(oop obj); 1183 1184 // It pushes an object on the local queue. 1185 inline void push(oop obj); 1186 1187 // These two move entries to/from the global stack. 1188 void move_entries_to_global_stack(); 1189 void get_entries_from_global_stack(); 1190 1191 // It pops and scans objects from the local queue. If partially is 1192 // true, then it stops when the queue size is of a given limit. If 1193 // partially is false, then it stops when the queue is empty. 1194 void drain_local_queue(bool partially); 1195 // It moves entries from the global stack to the local queue and 1196 // drains the local queue. If partially is true, then it stops when 1197 // both the global stack and the local queue reach a given size. If 1198 // partially if false, it tries to empty them totally. 1199 void drain_global_stack(bool partially); 1200 // It keeps picking SATB buffers and processing them until no SATB 1201 // buffers are available. 1202 void drain_satb_buffers(); 1203 1204 // moves the local finger to a new location 1205 inline void move_finger_to(HeapWord* new_finger) { 1206 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 1207 _finger = new_finger; 1208 } 1209 1210 CMTask(uint worker_id, ConcurrentMark *cm, 1211 size_t* marked_bytes, BitMap* card_bm, 1212 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues); 1213 1214 // it prints statistics associated with this task 1215 void print_stats(); 1216 1217 #if _MARKING_STATS_ 1218 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; } 1219 #endif // _MARKING_STATS_ 1220 }; 1221 1222 // Class that's used to to print out per-region liveness 1223 // information. It's currently used at the end of marking and also 1224 // after we sort the old regions at the end of the cleanup operation. 1225 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 1226 private: 1227 outputStream* _out; 1228 1229 // Accumulators for these values. 1230 size_t _total_used_bytes; 1231 size_t _total_capacity_bytes; 1232 size_t _total_prev_live_bytes; 1233 size_t _total_next_live_bytes; 1234 1235 // These are set up when we come across a "stars humongous" region 1236 // (as this is where most of this information is stored, not in the 1237 // subsequent "continues humongous" regions). After that, for every 1238 // region in a given humongous region series we deduce the right 1239 // values for it by simply subtracting the appropriate amount from 1240 // these fields. All these values should reach 0 after we've visited 1241 // the last region in the series. 1242 size_t _hum_used_bytes; 1243 size_t _hum_capacity_bytes; 1244 size_t _hum_prev_live_bytes; 1245 size_t _hum_next_live_bytes; 1246 1247 static double perc(size_t val, size_t total) { 1248 if (total == 0) { 1249 return 0.0; 1250 } else { 1251 return 100.0 * ((double) val / (double) total); 1252 } 1253 } 1254 1255 static double bytes_to_mb(size_t val) { 1256 return (double) val / (double) M; 1257 } 1258 1259 // See the .cpp file. 1260 size_t get_hum_bytes(size_t* hum_bytes); 1261 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1262 size_t* prev_live_bytes, size_t* next_live_bytes); 1263 1264 public: 1265 // The header and footer are printed in the constructor and 1266 // destructor respectively. 1267 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name); 1268 virtual bool doHeapRegion(HeapRegion* r); 1269 ~G1PrintRegionLivenessInfoClosure(); 1270 }; 1271 1272 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP