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 HeapWord* offsetToHeapWord(size_t offset) const { 101 return _bmStartWord + (offset << _shifter); 102 } 103 size_t heapWordToOffset(HeapWord* addr) const { 104 return pointer_delta(addr, _bmStartWord) >> _shifter; 105 } 106 int heapWordDiffToOffsetDiff(size_t diff) const; 107 108 // The argument addr should be the start address of a valid object 109 HeapWord* nextObject(HeapWord* addr) { 110 oop obj = (oop) addr; 111 HeapWord* res = addr + obj->size(); 112 assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity"); 113 return res; 114 } 115 116 // debugging 117 NOT_PRODUCT(bool covers(ReservedSpace rs) const;) 118 }; 119 120 class CMBitMap : public CMBitMapRO { 121 122 public: 123 // constructor 124 CMBitMap(int shifter) : 125 CMBitMapRO(shifter) {} 126 127 // Allocates the back store for the marking bitmap 128 bool allocate(ReservedSpace heap_rs); 129 130 // write marks 131 void mark(HeapWord* addr) { 132 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 133 "outside underlying space?"); 134 _bm.set_bit(heapWordToOffset(addr)); 135 } 136 void clear(HeapWord* addr) { 137 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 138 "outside underlying space?"); 139 _bm.clear_bit(heapWordToOffset(addr)); 140 } 141 bool parMark(HeapWord* addr) { 142 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 143 "outside underlying space?"); 144 return _bm.par_set_bit(heapWordToOffset(addr)); 145 } 146 bool parClear(HeapWord* addr) { 147 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 148 "outside underlying space?"); 149 return _bm.par_clear_bit(heapWordToOffset(addr)); 150 } 151 void markRange(MemRegion mr); 152 void clearAll(); 153 void clearRange(MemRegion mr); 154 155 // Starting at the bit corresponding to "addr" (inclusive), find the next 156 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find 157 // the end of this run (stopping at "end_addr"). Return the MemRegion 158 // covering from the start of the region corresponding to the first bit 159 // of the run to the end of the region corresponding to the last bit of 160 // the run. If there is no "1" bit at or after "addr", return an empty 161 // MemRegion. 162 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr); 163 }; 164 165 // Represents a marking stack used by ConcurrentMarking in the G1 collector. 166 class CMMarkStack VALUE_OBJ_CLASS_SPEC { 167 VirtualSpace _virtual_space; // Underlying backing store for actual stack 168 ConcurrentMark* _cm; 169 oop* _base; // bottom of stack 170 jint _index; // one more than last occupied index 171 jint _capacity; // max #elements 172 jint _saved_index; // value of _index saved at start of GC 173 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run 174 175 bool _overflow; 176 bool _should_expand; 177 DEBUG_ONLY(bool _drain_in_progress;) 178 DEBUG_ONLY(bool _drain_in_progress_yields;) 179 180 public: 181 CMMarkStack(ConcurrentMark* cm); 182 ~CMMarkStack(); 183 184 #ifndef PRODUCT 185 jint max_depth() const { 186 return _max_depth; 187 } 188 #endif 189 190 bool allocate(size_t capacity); 191 192 oop pop() { 193 if (!isEmpty()) { 194 return _base[--_index] ; 195 } 196 return NULL; 197 } 198 199 // If overflow happens, don't do the push, and record the overflow. 200 // *Requires* that "ptr" is already marked. 201 void push(oop ptr) { 202 if (isFull()) { 203 // Record overflow. 204 _overflow = true; 205 return; 206 } else { 207 _base[_index++] = ptr; 208 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index)); 209 } 210 } 211 // Non-block impl. Note: concurrency is allowed only with other 212 // "par_push" operations, not with "pop" or "drain". We would need 213 // parallel versions of them if such concurrency was desired. 214 void par_push(oop ptr); 215 216 // Pushes the first "n" elements of "ptr_arr" on the stack. 217 // Non-block impl. Note: concurrency is allowed only with other 218 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain". 219 void par_adjoin_arr(oop* ptr_arr, int n); 220 221 // Pushes the first "n" elements of "ptr_arr" on the stack. 222 // Locking impl: concurrency is allowed only with 223 // "par_push_arr" and/or "par_pop_arr" operations, which use the same 224 // locking strategy. 225 void par_push_arr(oop* ptr_arr, int n); 226 227 // If returns false, the array was empty. Otherwise, removes up to "max" 228 // elements from the stack, and transfers them to "ptr_arr" in an 229 // unspecified order. The actual number transferred is given in "n" ("n 230 // == 0" is deliberately redundant with the return value.) Locking impl: 231 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" 232 // operations, which use the same locking strategy. 233 bool par_pop_arr(oop* ptr_arr, int max, int* n); 234 235 // Drain the mark stack, applying the given closure to all fields of 236 // objects on the stack. (That is, continue until the stack is empty, 237 // even if closure applications add entries to the stack.) The "bm" 238 // argument, if non-null, may be used to verify that only marked objects 239 // are on the mark stack. If "yield_after" is "true", then the 240 // concurrent marker performing the drain offers to yield after 241 // processing each object. If a yield occurs, stops the drain operation 242 // and returns false. Otherwise, returns true. 243 template<class OopClosureClass> 244 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false); 245 246 bool isEmpty() { return _index == 0; } 247 bool isFull() { return _index == _capacity; } 248 int maxElems() { return _capacity; } 249 250 bool overflow() { return _overflow; } 251 void clear_overflow() { _overflow = false; } 252 253 bool should_expand() const { return _should_expand; } 254 void set_should_expand(); 255 256 // Expand the stack, typically in response to an overflow condition 257 void expand(); 258 259 int size() { return _index; } 260 261 void setEmpty() { _index = 0; clear_overflow(); } 262 263 // Record the current index. 264 void note_start_of_gc(); 265 266 // Make sure that we have not added any entries to the stack during GC. 267 void note_end_of_gc(); 268 269 // iterate over the oops in the mark stack, up to the bound recorded via 270 // the call above. 271 void oops_do(OopClosure* f); 272 }; 273 274 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC { 275 private: 276 #ifndef PRODUCT 277 uintx _num_remaining; 278 bool _force; 279 #endif // !defined(PRODUCT) 280 281 public: 282 void init() PRODUCT_RETURN; 283 void update() PRODUCT_RETURN; 284 bool should_force() PRODUCT_RETURN_( return false; ); 285 }; 286 287 // this will enable a variety of different statistics per GC task 288 #define _MARKING_STATS_ 0 289 // this will enable the higher verbose levels 290 #define _MARKING_VERBOSE_ 0 291 292 #if _MARKING_STATS_ 293 #define statsOnly(statement) \ 294 do { \ 295 statement ; \ 296 } while (0) 297 #else // _MARKING_STATS_ 298 #define statsOnly(statement) \ 299 do { \ 300 } while (0) 301 #endif // _MARKING_STATS_ 302 303 typedef enum { 304 no_verbose = 0, // verbose turned off 305 stats_verbose, // only prints stats at the end of marking 306 low_verbose, // low verbose, mostly per region and per major event 307 medium_verbose, // a bit more detailed than low 308 high_verbose // per object verbose 309 } CMVerboseLevel; 310 311 class YoungList; 312 313 // Root Regions are regions that are not empty at the beginning of a 314 // marking cycle and which we might collect during an evacuation pause 315 // while the cycle is active. Given that, during evacuation pauses, we 316 // do not copy objects that are explicitly marked, what we have to do 317 // for the root regions is to scan them and mark all objects reachable 318 // from them. According to the SATB assumptions, we only need to visit 319 // each object once during marking. So, as long as we finish this scan 320 // before the next evacuation pause, we can copy the objects from the 321 // root regions without having to mark them or do anything else to them. 322 // 323 // Currently, we only support root region scanning once (at the start 324 // of the marking cycle) and the root regions are all the survivor 325 // regions populated during the initial-mark pause. 326 class CMRootRegions VALUE_OBJ_CLASS_SPEC { 327 private: 328 YoungList* _young_list; 329 ConcurrentMark* _cm; 330 331 volatile bool _scan_in_progress; 332 volatile bool _should_abort; 333 HeapRegion* volatile _next_survivor; 334 335 public: 336 CMRootRegions(); 337 // We actually do most of the initialization in this method. 338 void init(G1CollectedHeap* g1h, ConcurrentMark* cm); 339 340 // Reset the claiming / scanning of the root regions. 341 void prepare_for_scan(); 342 343 // Forces get_next() to return NULL so that the iteration aborts early. 344 void abort() { _should_abort = true; } 345 346 // Return true if the CM thread are actively scanning root regions, 347 // false otherwise. 348 bool scan_in_progress() { return _scan_in_progress; } 349 350 // Claim the next root region to scan atomically, or return NULL if 351 // all have been claimed. 352 HeapRegion* claim_next(); 353 354 // Flag that we're done with root region scanning and notify anyone 355 // who's waiting on it. If aborted is false, assume that all regions 356 // have been claimed. 357 void scan_finished(); 358 359 // If CM threads are still scanning root regions, wait until they 360 // are done. Return true if we had to wait, false otherwise. 361 bool wait_until_scan_finished(); 362 }; 363 364 class ConcurrentMarkThread; 365 366 class ConcurrentMark: public CHeapObj<mtGC> { 367 friend class CMMarkStack; 368 friend class ConcurrentMarkThread; 369 friend class CMTask; 370 friend class CMBitMapClosure; 371 friend class CMGlobalObjectClosure; 372 friend class CMRemarkTask; 373 friend class CMConcurrentMarkingTask; 374 friend class G1ParNoteEndTask; 375 friend class CalcLiveObjectsClosure; 376 friend class G1CMRefProcTaskProxy; 377 friend class G1CMRefProcTaskExecutor; 378 friend class G1CMKeepAliveAndDrainClosure; 379 friend class G1CMDrainMarkingStackClosure; 380 381 protected: 382 ConcurrentMarkThread* _cmThread; // the thread doing the work 383 G1CollectedHeap* _g1h; // the heap. 384 uint _parallel_marking_threads; // the number of marking 385 // threads we're use 386 uint _max_parallel_marking_threads; // max number of marking 387 // threads we'll ever use 388 double _sleep_factor; // how much we have to sleep, with 389 // respect to the work we just did, to 390 // meet the marking overhead goal 391 double _marking_task_overhead; // marking target overhead for 392 // a single task 393 394 // same as the two above, but for the cleanup task 395 double _cleanup_sleep_factor; 396 double _cleanup_task_overhead; 397 398 FreeRegionList _cleanup_list; 399 400 // Concurrent marking support structures 401 CMBitMap _markBitMap1; 402 CMBitMap _markBitMap2; 403 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap 404 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap 405 406 BitMap _region_bm; 407 BitMap _card_bm; 408 409 // Heap bounds 410 HeapWord* _heap_start; 411 HeapWord* _heap_end; 412 413 // Root region tracking and claiming. 414 CMRootRegions _root_regions; 415 416 // For gray objects 417 CMMarkStack _markStack; // Grey objects behind global finger. 418 HeapWord* volatile _finger; // the global finger, region aligned, 419 // always points to the end of the 420 // last claimed region 421 422 // marking tasks 423 uint _max_worker_id;// maximum worker id 424 uint _active_tasks; // task num currently active 425 CMTask** _tasks; // task queue array (max_worker_id len) 426 CMTaskQueueSet* _task_queues; // task queue set 427 ParallelTaskTerminator _terminator; // for termination 428 429 // Two sync barriers that are used to synchronise tasks when an 430 // overflow occurs. The algorithm is the following. All tasks enter 431 // the first one to ensure that they have all stopped manipulating 432 // the global data structures. After they exit it, they re-initialise 433 // their data structures and task 0 re-initialises the global data 434 // structures. Then, they enter the second sync barrier. This 435 // ensure, that no task starts doing work before all data 436 // structures (local and global) have been re-initialised. When they 437 // exit it, they are free to start working again. 438 WorkGangBarrierSync _first_overflow_barrier_sync; 439 WorkGangBarrierSync _second_overflow_barrier_sync; 440 441 // this is set by any task, when an overflow on the global data 442 // structures is detected. 443 volatile bool _has_overflown; 444 // true: marking is concurrent, false: we're in remark 445 volatile bool _concurrent; 446 // set at the end of a Full GC so that marking aborts 447 volatile bool _has_aborted; 448 449 // used when remark aborts due to an overflow to indicate that 450 // another concurrent marking phase should start 451 volatile bool _restart_for_overflow; 452 453 // This is true from the very start of concurrent marking until the 454 // point when all the tasks complete their work. It is really used 455 // to determine the points between the end of concurrent marking and 456 // time of remark. 457 volatile bool _concurrent_marking_in_progress; 458 459 // verbose level 460 CMVerboseLevel _verbose_level; 461 462 // All of these times are in ms. 463 NumberSeq _init_times; 464 NumberSeq _remark_times; 465 NumberSeq _remark_mark_times; 466 NumberSeq _remark_weak_ref_times; 467 NumberSeq _cleanup_times; 468 double _total_counting_time; 469 double _total_rs_scrub_time; 470 471 double* _accum_task_vtime; // accumulated task vtime 472 473 FlexibleWorkGang* _parallel_workers; 474 475 ForceOverflowSettings _force_overflow_conc; 476 ForceOverflowSettings _force_overflow_stw; 477 478 void weakRefsWork(bool clear_all_soft_refs); 479 480 void swapMarkBitMaps(); 481 482 // It resets the global marking data structures, as well as the 483 // task local ones; should be called during initial mark. 484 void reset(); 485 486 // Resets all the marking data structures. Called when we have to restart 487 // marking or when marking completes (via set_non_marking_state below). 488 void reset_marking_state(bool clear_overflow = true); 489 490 // We do this after we're done with marking so that the marking data 491 // structures are initialised to a sensible and predictable state. 492 void set_non_marking_state(); 493 494 // It should be called to indicate which phase we're in (concurrent 495 // mark or remark) and how many threads are currently active. 496 void set_phase(uint active_tasks, bool concurrent); 497 498 // prints all gathered CM-related statistics 499 void print_stats(); 500 501 bool cleanup_list_is_empty() { 502 return _cleanup_list.is_empty(); 503 } 504 505 // accessor methods 506 uint parallel_marking_threads() const { return _parallel_marking_threads; } 507 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} 508 double sleep_factor() { return _sleep_factor; } 509 double marking_task_overhead() { return _marking_task_overhead;} 510 double cleanup_sleep_factor() { return _cleanup_sleep_factor; } 511 double cleanup_task_overhead() { return _cleanup_task_overhead;} 512 513 bool use_parallel_marking_threads() const { 514 assert(parallel_marking_threads() <= 515 max_parallel_marking_threads(), "sanity"); 516 assert((_parallel_workers == NULL && parallel_marking_threads() == 0) || 517 parallel_marking_threads() > 0, 518 "parallel workers not set up correctly"); 519 return _parallel_workers != NULL; 520 } 521 522 HeapWord* finger() { return _finger; } 523 bool concurrent() { return _concurrent; } 524 uint active_tasks() { return _active_tasks; } 525 ParallelTaskTerminator* terminator() { return &_terminator; } 526 527 // It claims the next available region to be scanned by a marking 528 // task/thread. It might return NULL if the next region is empty or 529 // we have run out of regions. In the latter case, out_of_regions() 530 // determines whether we've really run out of regions or the task 531 // should call claim_region() again. This might seem a bit 532 // awkward. Originally, the code was written so that claim_region() 533 // either successfully returned with a non-empty region or there 534 // were no more regions to be claimed. The problem with this was 535 // that, in certain circumstances, it iterated over large chunks of 536 // the heap finding only empty regions and, while it was working, it 537 // was preventing the calling task to call its regular clock 538 // method. So, this way, each task will spend very little time in 539 // claim_region() and is allowed to call the regular clock method 540 // frequently. 541 HeapRegion* claim_region(uint worker_id); 542 543 // It determines whether we've run out of regions to scan. 544 bool out_of_regions() { return _finger == _heap_end; } 545 546 // Returns the task with the given id 547 CMTask* task(int id) { 548 assert(0 <= id && id < (int) _active_tasks, 549 "task id not within active bounds"); 550 return _tasks[id]; 551 } 552 553 // Returns the task queue with the given id 554 CMTaskQueue* task_queue(int id) { 555 assert(0 <= id && id < (int) _active_tasks, 556 "task queue id not within active bounds"); 557 return (CMTaskQueue*) _task_queues->queue(id); 558 } 559 560 // Returns the task queue set 561 CMTaskQueueSet* task_queues() { return _task_queues; } 562 563 // Access / manipulation of the overflow flag which is set to 564 // indicate that the global stack has overflown 565 bool has_overflown() { return _has_overflown; } 566 void set_has_overflown() { _has_overflown = true; } 567 void clear_has_overflown() { _has_overflown = false; } 568 bool restart_for_overflow() { return _restart_for_overflow; } 569 570 bool has_aborted() { return _has_aborted; } 571 572 // Methods to enter the two overflow sync barriers 573 void enter_first_sync_barrier(uint worker_id); 574 void enter_second_sync_barrier(uint worker_id); 575 576 ForceOverflowSettings* force_overflow_conc() { 577 return &_force_overflow_conc; 578 } 579 580 ForceOverflowSettings* force_overflow_stw() { 581 return &_force_overflow_stw; 582 } 583 584 ForceOverflowSettings* force_overflow() { 585 if (concurrent()) { 586 return force_overflow_conc(); 587 } else { 588 return force_overflow_stw(); 589 } 590 } 591 592 // Live Data Counting data structures... 593 // These data structures are initialized at the start of 594 // marking. They are written to while marking is active. 595 // They are aggregated during remark; the aggregated values 596 // are then used to populate the _region_bm, _card_bm, and 597 // the total live bytes, which are then subsequently updated 598 // during cleanup. 599 600 // An array of bitmaps (one bit map per task). Each bitmap 601 // is used to record the cards spanned by the live objects 602 // marked by that task/worker. 603 BitMap* _count_card_bitmaps; 604 605 // Used to record the number of marked live bytes 606 // (for each region, by worker thread). 607 size_t** _count_marked_bytes; 608 609 // Card index of the bottom of the G1 heap. Used for biasing indices into 610 // the card bitmaps. 611 intptr_t _heap_bottom_card_num; 612 613 // Set to true when initialization is complete 614 bool _completed_initialization; 615 616 public: 617 // Manipulation of the global mark stack. 618 // Notice that the first mark_stack_push is CAS-based, whereas the 619 // two below are Mutex-based. This is OK since the first one is only 620 // called during evacuation pauses and doesn't compete with the 621 // other two (which are called by the marking tasks during 622 // concurrent marking or remark). 623 bool mark_stack_push(oop p) { 624 _markStack.par_push(p); 625 if (_markStack.overflow()) { 626 set_has_overflown(); 627 return false; 628 } 629 return true; 630 } 631 bool mark_stack_push(oop* arr, int n) { 632 _markStack.par_push_arr(arr, n); 633 if (_markStack.overflow()) { 634 set_has_overflown(); 635 return false; 636 } 637 return true; 638 } 639 void mark_stack_pop(oop* arr, int max, int* n) { 640 _markStack.par_pop_arr(arr, max, n); 641 } 642 size_t mark_stack_size() { return _markStack.size(); } 643 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 644 bool mark_stack_overflow() { return _markStack.overflow(); } 645 bool mark_stack_empty() { return _markStack.isEmpty(); } 646 647 CMRootRegions* root_regions() { return &_root_regions; } 648 649 bool concurrent_marking_in_progress() { 650 return _concurrent_marking_in_progress; 651 } 652 void set_concurrent_marking_in_progress() { 653 _concurrent_marking_in_progress = true; 654 } 655 void clear_concurrent_marking_in_progress() { 656 _concurrent_marking_in_progress = false; 657 } 658 659 void update_accum_task_vtime(int i, double vtime) { 660 _accum_task_vtime[i] += vtime; 661 } 662 663 double all_task_accum_vtime() { 664 double ret = 0.0; 665 for (uint i = 0; i < _max_worker_id; ++i) 666 ret += _accum_task_vtime[i]; 667 return ret; 668 } 669 670 // Attempts to steal an object from the task queues of other tasks 671 bool try_stealing(uint worker_id, int* hash_seed, oop& obj) { 672 return _task_queues->steal(worker_id, hash_seed, obj); 673 } 674 675 ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs); 676 ~ConcurrentMark(); 677 678 ConcurrentMarkThread* cmThread() { return _cmThread; } 679 680 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 681 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 682 683 // Returns the number of GC threads to be used in a concurrent 684 // phase based on the number of GC threads being used in a STW 685 // phase. 686 uint scale_parallel_threads(uint n_par_threads); 687 688 // Calculates the number of GC threads to be used in a concurrent phase. 689 uint calc_parallel_marking_threads(); 690 691 // The following three are interaction between CM and 692 // G1CollectedHeap 693 694 // This notifies CM that a root during initial-mark needs to be 695 // grayed. It is MT-safe. word_size is the size of the object in 696 // words. It is passed explicitly as sometimes we cannot calculate 697 // it from the given object because it might be in an inconsistent 698 // state (e.g., in to-space and being copied). So the caller is 699 // responsible for dealing with this issue (e.g., get the size from 700 // the from-space image when the to-space image might be 701 // inconsistent) and always passing the size. hr is the region that 702 // contains the object and it's passed optionally from callers who 703 // might already have it (no point in recalculating it). 704 inline void grayRoot(oop obj, size_t word_size, 705 uint worker_id, HeapRegion* hr = NULL); 706 707 // It iterates over the heap and for each object it comes across it 708 // will dump the contents of its reference fields, as well as 709 // liveness information for the object and its referents. The dump 710 // will be written to a file with the following name: 711 // G1PrintReachableBaseFile + "." + str. 712 // vo decides whether the prev (vo == UsePrevMarking), the next 713 // (vo == UseNextMarking) marking information, or the mark word 714 // (vo == UseMarkWord) will be used to determine the liveness of 715 // each object / referent. 716 // If all is true, all objects in the heap will be dumped, otherwise 717 // only the live ones. In the dump the following symbols / breviations 718 // are used: 719 // M : an explicitly live object (its bitmap bit is set) 720 // > : an implicitly live object (over tams) 721 // O : an object outside the G1 heap (typically: in the perm gen) 722 // NOT : a reference field whose referent is not live 723 // AND MARKED : indicates that an object is both explicitly and 724 // implicitly live (it should be one or the other, not both) 725 void print_reachable(const char* str, 726 VerifyOption vo, bool all) PRODUCT_RETURN; 727 728 // Clear the next marking bitmap (will be called concurrently). 729 void clearNextBitmap(); 730 731 // These two do the work that needs to be done before and after the 732 // initial root checkpoint. Since this checkpoint can be done at two 733 // different points (i.e. an explicit pause or piggy-backed on a 734 // young collection), then it's nice to be able to easily share the 735 // pre/post code. It might be the case that we can put everything in 736 // the post method. TP 737 void checkpointRootsInitialPre(); 738 void checkpointRootsInitialPost(); 739 740 // Scan all the root regions and mark everything reachable from 741 // them. 742 void scanRootRegions(); 743 744 // Scan a single root region and mark everything reachable from it. 745 void scanRootRegion(HeapRegion* hr, uint worker_id); 746 747 // Do concurrent phase of marking, to a tentative transitive closure. 748 void markFromRoots(); 749 750 void checkpointRootsFinal(bool clear_all_soft_refs); 751 void checkpointRootsFinalWork(); 752 void cleanup(); 753 void completeCleanup(); 754 755 // Mark in the previous bitmap. NB: this is usually read-only, so use 756 // this carefully! 757 inline void markPrev(oop p); 758 759 // Clears marks for all objects in the given range, for the prev, 760 // next, or both bitmaps. NB: the previous bitmap is usually 761 // read-only, so use this carefully! 762 void clearRangePrevBitmap(MemRegion mr); 763 void clearRangeNextBitmap(MemRegion mr); 764 void clearRangeBothBitmaps(MemRegion mr); 765 766 // Notify data structures that a GC has started. 767 void note_start_of_gc() { 768 _markStack.note_start_of_gc(); 769 } 770 771 // Notify data structures that a GC is finished. 772 void note_end_of_gc() { 773 _markStack.note_end_of_gc(); 774 } 775 776 // Verify that there are no CSet oops on the stacks (taskqueues / 777 // global mark stack), enqueued SATB buffers, per-thread SATB 778 // buffers, and fingers (global / per-task). The boolean parameters 779 // decide which of the above data structures to verify. If marking 780 // is not in progress, it's a no-op. 781 void verify_no_cset_oops(bool verify_stacks, 782 bool verify_enqueued_buffers, 783 bool verify_thread_buffers, 784 bool verify_fingers) PRODUCT_RETURN; 785 786 // It is called at the end of an evacuation pause during marking so 787 // that CM is notified of where the new end of the heap is. It 788 // doesn't do anything if concurrent_marking_in_progress() is false, 789 // unless the force parameter is true. 790 void update_g1_committed(bool force = false); 791 792 bool isMarked(oop p) const { 793 assert(p != NULL && p->is_oop(), "expected an oop"); 794 HeapWord* addr = (HeapWord*)p; 795 assert(addr >= _nextMarkBitMap->startWord() || 796 addr < _nextMarkBitMap->endWord(), "in a region"); 797 798 return _nextMarkBitMap->isMarked(addr); 799 } 800 801 inline bool not_yet_marked(oop p) const; 802 803 // XXX Debug code 804 bool containing_card_is_marked(void* p); 805 bool containing_cards_are_marked(void* start, void* last); 806 807 bool isPrevMarked(oop p) const { 808 assert(p != NULL && p->is_oop(), "expected an oop"); 809 HeapWord* addr = (HeapWord*)p; 810 assert(addr >= _prevMarkBitMap->startWord() || 811 addr < _prevMarkBitMap->endWord(), "in a region"); 812 813 return _prevMarkBitMap->isMarked(addr); 814 } 815 816 inline bool do_yield_check(uint worker_i = 0); 817 inline bool should_yield(); 818 819 // Called to abort the marking cycle after a Full GC takes palce. 820 void abort(); 821 822 // This prints the global/local fingers. It is used for debugging. 823 NOT_PRODUCT(void print_finger();) 824 825 void print_summary_info(); 826 827 void print_worker_threads_on(outputStream* st) const; 828 829 // The following indicate whether a given verbose level has been 830 // set. Notice that anything above stats is conditional to 831 // _MARKING_VERBOSE_ having been set to 1 832 bool verbose_stats() { 833 return _verbose_level >= stats_verbose; 834 } 835 bool verbose_low() { 836 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; 837 } 838 bool verbose_medium() { 839 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; 840 } 841 bool verbose_high() { 842 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; 843 } 844 845 // Liveness counting 846 847 // Utility routine to set an exclusive range of cards on the given 848 // card liveness bitmap 849 inline void set_card_bitmap_range(BitMap* card_bm, 850 BitMap::idx_t start_idx, 851 BitMap::idx_t end_idx, 852 bool is_par); 853 854 // Returns the card number of the bottom of the G1 heap. 855 // Used in biasing indices into accounting card bitmaps. 856 intptr_t heap_bottom_card_num() const { 857 return _heap_bottom_card_num; 858 } 859 860 // Returns the card bitmap for a given task or worker id. 861 BitMap* count_card_bitmap_for(uint worker_id) { 862 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 863 assert(_count_card_bitmaps != NULL, "uninitialized"); 864 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 865 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 866 return task_card_bm; 867 } 868 869 // Returns the array containing the marked bytes for each region, 870 // for the given worker or task id. 871 size_t* count_marked_bytes_array_for(uint worker_id) { 872 assert(0 <= worker_id && worker_id < _max_worker_id, "oob"); 873 assert(_count_marked_bytes != NULL, "uninitialized"); 874 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 875 assert(marked_bytes_array != NULL, "uninitialized"); 876 return marked_bytes_array; 877 } 878 879 // Returns the index in the liveness accounting card table bitmap 880 // for the given address 881 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 882 883 // Counts the size of the given memory region in the the given 884 // marked_bytes array slot for the given HeapRegion. 885 // Sets the bits in the given card bitmap that are associated with the 886 // cards that are spanned by the memory region. 887 inline void count_region(MemRegion mr, HeapRegion* hr, 888 size_t* marked_bytes_array, 889 BitMap* task_card_bm); 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, HeapRegion* hr, uint worker_id); 894 895 // Counts the given memory region in the task/worker counting 896 // data structures for the given worker id. 897 inline void count_region(MemRegion mr, uint worker_id); 898 899 // Counts the given object in the given task/worker counting 900 // data structures. 901 inline void count_object(oop obj, HeapRegion* hr, 902 size_t* marked_bytes_array, 903 BitMap* task_card_bm); 904 905 // Counts the given object in the task/worker counting data 906 // structures for the given worker id. 907 inline void count_object(oop obj, HeapRegion* hr, uint worker_id); 908 909 // Attempts to mark the given object and, if successful, counts 910 // the object in the given task/worker counting structures. 911 inline bool par_mark_and_count(oop obj, HeapRegion* hr, 912 size_t* marked_bytes_array, 913 BitMap* task_card_bm); 914 915 // Attempts to mark the given object and, if successful, counts 916 // the object in the task/worker counting structures for the 917 // given worker id. 918 inline bool par_mark_and_count(oop obj, size_t word_size, 919 HeapRegion* hr, uint worker_id); 920 921 // Attempts to mark the given object and, if successful, counts 922 // the object in the task/worker counting structures for the 923 // given worker id. 924 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id); 925 926 // Similar to the above routine but we don't know the heap region that 927 // contains the object to be marked/counted, which this routine looks up. 928 inline bool par_mark_and_count(oop obj, uint worker_id); 929 930 // Similar to the above routine but there are times when we cannot 931 // safely calculate the size of obj due to races and we, therefore, 932 // pass the size in as a parameter. It is the caller's reponsibility 933 // to ensure that the size passed in for obj is valid. 934 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id); 935 936 // Unconditionally mark the given object, and unconditinally count 937 // the object in the counting structures for worker id 0. 938 // Should *not* be called from parallel code. 939 inline bool mark_and_count(oop obj, HeapRegion* hr); 940 941 // Similar to the above routine but we don't know the heap region that 942 // contains the object to be marked/counted, which this routine looks up. 943 // Should *not* be called from parallel code. 944 inline bool mark_and_count(oop obj); 945 946 // Returns true if initialization was successfully completed. 947 bool completed_initialization() const { 948 return _completed_initialization; 949 } 950 951 protected: 952 // Clear all the per-task bitmaps and arrays used to store the 953 // counting data. 954 void clear_all_count_data(); 955 956 // Aggregates the counting data for each worker/task 957 // that was constructed while marking. Also sets 958 // the amount of marked bytes for each region and 959 // the top at concurrent mark count. 960 void aggregate_count_data(); 961 962 // Verification routine 963 void verify_count_data(); 964 }; 965 966 // A class representing a marking task. 967 class CMTask : public TerminatorTerminator { 968 private: 969 enum PrivateConstants { 970 // the regular clock call is called once the scanned words reaches 971 // this limit 972 words_scanned_period = 12*1024, 973 // the regular clock call is called once the number of visited 974 // references reaches this limit 975 refs_reached_period = 384, 976 // initial value for the hash seed, used in the work stealing code 977 init_hash_seed = 17, 978 // how many entries will be transferred between global stack and 979 // local queues 980 global_stack_transfer_size = 16 981 }; 982 983 uint _worker_id; 984 G1CollectedHeap* _g1h; 985 ConcurrentMark* _cm; 986 CMBitMap* _nextMarkBitMap; 987 // the task queue of this task 988 CMTaskQueue* _task_queue; 989 private: 990 // the task queue set---needed for stealing 991 CMTaskQueueSet* _task_queues; 992 // indicates whether the task has been claimed---this is only for 993 // debugging purposes 994 bool _claimed; 995 996 // number of calls to this task 997 int _calls; 998 999 // when the virtual timer reaches this time, the marking step should 1000 // exit 1001 double _time_target_ms; 1002 // the start time of the current marking step 1003 double _start_time_ms; 1004 1005 // the oop closure used for iterations over oops 1006 G1CMOopClosure* _cm_oop_closure; 1007 1008 // the region this task is scanning, NULL if we're not scanning any 1009 HeapRegion* _curr_region; 1010 // the local finger of this task, NULL if we're not scanning a region 1011 HeapWord* _finger; 1012 // limit of the region this task is scanning, NULL if we're not scanning one 1013 HeapWord* _region_limit; 1014 1015 // the number of words this task has scanned 1016 size_t _words_scanned; 1017 // When _words_scanned reaches this limit, the regular clock is 1018 // called. Notice that this might be decreased under certain 1019 // circumstances (i.e. when we believe that we did an expensive 1020 // operation). 1021 size_t _words_scanned_limit; 1022 // the initial value of _words_scanned_limit (i.e. what it was 1023 // before it was decreased). 1024 size_t _real_words_scanned_limit; 1025 1026 // the number of references this task has visited 1027 size_t _refs_reached; 1028 // When _refs_reached reaches this limit, the regular clock is 1029 // called. Notice this this might be decreased under certain 1030 // circumstances (i.e. when we believe that we did an expensive 1031 // operation). 1032 size_t _refs_reached_limit; 1033 // the initial value of _refs_reached_limit (i.e. what it was before 1034 // it was decreased). 1035 size_t _real_refs_reached_limit; 1036 1037 // used by the work stealing stuff 1038 int _hash_seed; 1039 // if this is true, then the task has aborted for some reason 1040 bool _has_aborted; 1041 // set when the task aborts because it has met its time quota 1042 bool _has_timed_out; 1043 // true when we're draining SATB buffers; this avoids the task 1044 // aborting due to SATB buffers being available (as we're already 1045 // dealing with them) 1046 bool _draining_satb_buffers; 1047 1048 // number sequence of past step times 1049 NumberSeq _step_times_ms; 1050 // elapsed time of this task 1051 double _elapsed_time_ms; 1052 // termination time of this task 1053 double _termination_time_ms; 1054 // when this task got into the termination protocol 1055 double _termination_start_time_ms; 1056 1057 // true when the task is during a concurrent phase, false when it is 1058 // in the remark phase (so, in the latter case, we do not have to 1059 // check all the things that we have to check during the concurrent 1060 // phase, i.e. SATB buffer availability...) 1061 bool _concurrent; 1062 1063 TruncatedSeq _marking_step_diffs_ms; 1064 1065 // Counting data structures. Embedding the task's marked_bytes_array 1066 // and card bitmap into the actual task saves having to go through 1067 // the ConcurrentMark object. 1068 size_t* _marked_bytes_array; 1069 BitMap* _card_bm; 1070 1071 // LOTS of statistics related with this task 1072 #if _MARKING_STATS_ 1073 NumberSeq _all_clock_intervals_ms; 1074 double _interval_start_time_ms; 1075 1076 int _aborted; 1077 int _aborted_overflow; 1078 int _aborted_cm_aborted; 1079 int _aborted_yield; 1080 int _aborted_timed_out; 1081 int _aborted_satb; 1082 int _aborted_termination; 1083 1084 int _steal_attempts; 1085 int _steals; 1086 1087 int _clock_due_to_marking; 1088 int _clock_due_to_scanning; 1089 1090 int _local_pushes; 1091 int _local_pops; 1092 int _local_max_size; 1093 int _objs_scanned; 1094 1095 int _global_pushes; 1096 int _global_pops; 1097 int _global_max_size; 1098 1099 int _global_transfers_to; 1100 int _global_transfers_from; 1101 1102 int _regions_claimed; 1103 int _objs_found_on_bitmap; 1104 1105 int _satb_buffers_processed; 1106 #endif // _MARKING_STATS_ 1107 1108 // it updates the local fields after this task has claimed 1109 // a new region to scan 1110 void setup_for_region(HeapRegion* hr); 1111 // it brings up-to-date the limit of the region 1112 void update_region_limit(); 1113 1114 // called when either the words scanned or the refs visited limit 1115 // has been reached 1116 void reached_limit(); 1117 // recalculates the words scanned and refs visited limits 1118 void recalculate_limits(); 1119 // decreases the words scanned and refs visited limits when we reach 1120 // an expensive operation 1121 void decrease_limits(); 1122 // it checks whether the words scanned or refs visited reached their 1123 // respective limit and calls reached_limit() if they have 1124 void check_limits() { 1125 if (_words_scanned >= _words_scanned_limit || 1126 _refs_reached >= _refs_reached_limit) { 1127 reached_limit(); 1128 } 1129 } 1130 // this is supposed to be called regularly during a marking step as 1131 // it checks a bunch of conditions that might cause the marking step 1132 // to abort 1133 void regular_clock_call(); 1134 bool concurrent() { return _concurrent; } 1135 1136 public: 1137 // It resets the task; it should be called right at the beginning of 1138 // a marking phase. 1139 void reset(CMBitMap* _nextMarkBitMap); 1140 // it clears all the fields that correspond to a claimed region. 1141 void clear_region_fields(); 1142 1143 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 1144 1145 // The main method of this class which performs a marking step 1146 // trying not to exceed the given duration. However, it might exit 1147 // prematurely, according to some conditions (i.e. SATB buffers are 1148 // available for processing). 1149 void do_marking_step(double target_ms, 1150 bool do_stealing, 1151 bool do_termination, 1152 bool is_serial); 1153 1154 // These two calls start and stop the timer 1155 void record_start_time() { 1156 _elapsed_time_ms = os::elapsedTime() * 1000.0; 1157 } 1158 void record_end_time() { 1159 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 1160 } 1161 1162 // returns the worker ID associated with this task. 1163 uint worker_id() { return _worker_id; } 1164 1165 // From TerminatorTerminator. It determines whether this task should 1166 // exit the termination protocol after it's entered it. 1167 virtual bool should_exit_termination(); 1168 1169 // Resets the local region fields after a task has finished scanning a 1170 // region; or when they have become stale as a result of the region 1171 // being evacuated. 1172 void giveup_current_region(); 1173 1174 HeapWord* finger() { return _finger; } 1175 1176 bool has_aborted() { return _has_aborted; } 1177 void set_has_aborted() { _has_aborted = true; } 1178 void clear_has_aborted() { _has_aborted = false; } 1179 bool has_timed_out() { return _has_timed_out; } 1180 bool claimed() { return _claimed; } 1181 1182 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 1183 1184 // It grays the object by marking it and, if necessary, pushing it 1185 // on the local queue 1186 inline void deal_with_reference(oop obj); 1187 1188 // It scans an object and visits its children. 1189 void scan_object(oop obj); 1190 1191 // It pushes an object on the local queue. 1192 inline void push(oop obj); 1193 1194 // These two move entries to/from the global stack. 1195 void move_entries_to_global_stack(); 1196 void get_entries_from_global_stack(); 1197 1198 // It pops and scans objects from the local queue. If partially is 1199 // true, then it stops when the queue size is of a given limit. If 1200 // partially is false, then it stops when the queue is empty. 1201 void drain_local_queue(bool partially); 1202 // It moves entries from the global stack to the local queue and 1203 // drains the local queue. If partially is true, then it stops when 1204 // both the global stack and the local queue reach a given size. If 1205 // partially if false, it tries to empty them totally. 1206 void drain_global_stack(bool partially); 1207 // It keeps picking SATB buffers and processing them until no SATB 1208 // buffers are available. 1209 void drain_satb_buffers(); 1210 1211 // moves the local finger to a new location 1212 inline void move_finger_to(HeapWord* new_finger) { 1213 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 1214 _finger = new_finger; 1215 } 1216 1217 CMTask(uint worker_id, ConcurrentMark *cm, 1218 size_t* marked_bytes, BitMap* card_bm, 1219 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues); 1220 1221 // it prints statistics associated with this task 1222 void print_stats(); 1223 1224 #if _MARKING_STATS_ 1225 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; } 1226 #endif // _MARKING_STATS_ 1227 }; 1228 1229 // Class that's used to to print out per-region liveness 1230 // information. It's currently used at the end of marking and also 1231 // after we sort the old regions at the end of the cleanup operation. 1232 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 1233 private: 1234 outputStream* _out; 1235 1236 // Accumulators for these values. 1237 size_t _total_used_bytes; 1238 size_t _total_capacity_bytes; 1239 size_t _total_prev_live_bytes; 1240 size_t _total_next_live_bytes; 1241 1242 // These are set up when we come across a "stars humongous" region 1243 // (as this is where most of this information is stored, not in the 1244 // subsequent "continues humongous" regions). After that, for every 1245 // region in a given humongous region series we deduce the right 1246 // values for it by simply subtracting the appropriate amount from 1247 // these fields. All these values should reach 0 after we've visited 1248 // the last region in the series. 1249 size_t _hum_used_bytes; 1250 size_t _hum_capacity_bytes; 1251 size_t _hum_prev_live_bytes; 1252 size_t _hum_next_live_bytes; 1253 1254 static double perc(size_t val, size_t total) { 1255 if (total == 0) { 1256 return 0.0; 1257 } else { 1258 return 100.0 * ((double) val / (double) total); 1259 } 1260 } 1261 1262 static double bytes_to_mb(size_t val) { 1263 return (double) val / (double) M; 1264 } 1265 1266 // See the .cpp file. 1267 size_t get_hum_bytes(size_t* hum_bytes); 1268 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1269 size_t* prev_live_bytes, size_t* next_live_bytes); 1270 1271 public: 1272 // The header and footer are printed in the constructor and 1273 // destructor respectively. 1274 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name); 1275 virtual bool doHeapRegion(HeapRegion* r); 1276 ~G1PrintRegionLivenessInfoClosure(); 1277 }; 1278 1279 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP