1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_G1_CONCURRENTMARK_HPP 26 #define SHARE_VM_GC_G1_CONCURRENTMARK_HPP 27 28 #include "classfile/javaClasses.hpp" 29 #include "gc/g1/g1RegionToSpaceMapper.hpp" 30 #include "gc/g1/heapRegionSet.hpp" 31 #include "gc/shared/taskqueue.hpp" 32 33 class G1CollectedHeap; 34 class CMBitMap; 35 class CMTask; 36 class ConcurrentMark; 37 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue; 38 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet; 39 40 // Closure used by CM during concurrent reference discovery 41 // and reference processing (during remarking) to determine 42 // if a particular object is alive. It is primarily used 43 // to determine if referents of discovered reference objects 44 // are alive. An instance is also embedded into the 45 // reference processor as the _is_alive_non_header field 46 class G1CMIsAliveClosure: public BoolObjectClosure { 47 G1CollectedHeap* _g1; 48 public: 49 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { } 50 51 bool do_object_b(oop obj); 52 }; 53 54 // A generic CM bit map. This is essentially a wrapper around the BitMap 55 // class, with one bit per (1<<_shifter) HeapWords. 56 57 class CMBitMapRO VALUE_OBJ_CLASS_SPEC { 58 protected: 59 HeapWord* _bmStartWord; // base address of range covered by map 60 size_t _bmWordSize; // map size (in #HeapWords covered) 61 const int _shifter; // map to char or bit 62 BitMap _bm; // the bit map itself 63 64 public: 65 // constructor 66 CMBitMapRO(int shifter); 67 68 enum { do_yield = true }; 69 70 // inquiries 71 HeapWord* startWord() const { return _bmStartWord; } 72 size_t sizeInWords() const { return _bmWordSize; } 73 // the following is one past the last word in space 74 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; } 75 76 // read marks 77 78 bool isMarked(HeapWord* addr) const { 79 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize), 80 "outside underlying space?"); 81 return _bm.at(heapWordToOffset(addr)); 82 } 83 84 // iteration 85 inline bool iterate(BitMapClosure* cl, MemRegion mr); 86 inline bool iterate(BitMapClosure* cl); 87 88 // Return the address corresponding to the next marked bit at or after 89 // "addr", and before "limit", if "limit" is non-NULL. If there is no 90 // such bit, returns "limit" if that is non-NULL, or else "endWord()". 91 HeapWord* getNextMarkedWordAddress(const HeapWord* addr, 92 const HeapWord* limit = NULL) const; 93 // Return the address corresponding to the next unmarked bit at or after 94 // "addr", and before "limit", if "limit" is non-NULL. If there is no 95 // such bit, returns "limit" if that is non-NULL, or else "endWord()". 96 HeapWord* getNextUnmarkedWordAddress(const HeapWord* addr, 97 const HeapWord* limit = NULL) const; 98 99 // conversion utilities 100 HeapWord* offsetToHeapWord(size_t offset) const { 101 return _bmStartWord + (offset << _shifter); 102 } 103 size_t heapWordToOffset(const HeapWord* addr) const { 104 return pointer_delta(addr, _bmStartWord) >> _shifter; 105 } 106 int heapWordDiffToOffsetDiff(size_t diff) const; 107 108 // The argument addr should be the start address of a valid object 109 HeapWord* nextObject(HeapWord* addr) { 110 oop obj = (oop) addr; 111 HeapWord* res = addr + obj->size(); 112 assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity"); 113 return res; 114 } 115 116 void print_on_error(outputStream* st, const char* prefix) const; 117 118 // debugging 119 NOT_PRODUCT(bool covers(MemRegion rs) const;) 120 }; 121 122 class CMBitMapMappingChangedListener : public G1MappingChangedListener { 123 private: 124 CMBitMap* _bm; 125 public: 126 CMBitMapMappingChangedListener() : _bm(NULL) {} 127 128 void set_bitmap(CMBitMap* bm) { _bm = bm; } 129 130 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled); 131 }; 132 133 class CMBitMap : public CMBitMapRO { 134 private: 135 CMBitMapMappingChangedListener _listener; 136 137 public: 138 static size_t compute_size(size_t heap_size); 139 // Returns the amount of bytes on the heap between two marks in the bitmap. 140 static size_t mark_distance(); 141 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the 142 // mark bitmap corresponds to. This is the same as the mark distance above. 143 static size_t heap_map_factor() { 144 return mark_distance(); 145 } 146 147 CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); } 148 149 // Initializes the underlying BitMap to cover the given area. 150 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage); 151 152 // Write marks. 153 inline void mark(HeapWord* addr); 154 inline void clear(HeapWord* addr); 155 inline bool parMark(HeapWord* addr); 156 inline bool parClear(HeapWord* addr); 157 158 void markRange(MemRegion mr); 159 void clearRange(MemRegion mr); 160 161 // Starting at the bit corresponding to "addr" (inclusive), find the next 162 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find 163 // the end of this run (stopping at "end_addr"). Return the MemRegion 164 // covering from the start of the region corresponding to the first bit 165 // of the run to the end of the region corresponding to the last bit of 166 // the run. If there is no "1" bit at or after "addr", return an empty 167 // MemRegion. 168 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr); 169 170 // Clear the whole mark bitmap. 171 void clearAll(); 172 }; 173 174 // Represents a marking stack used by ConcurrentMarking in the G1 collector. 175 class CMMarkStack VALUE_OBJ_CLASS_SPEC { 176 VirtualSpace _virtual_space; // Underlying backing store for actual stack 177 ConcurrentMark* _cm; 178 oop* _base; // bottom of stack 179 jint _index; // one more than last occupied index 180 jint _capacity; // max #elements 181 jint _saved_index; // value of _index saved at start of GC 182 183 bool _overflow; 184 bool _should_expand; 185 186 public: 187 CMMarkStack(ConcurrentMark* cm); 188 ~CMMarkStack(); 189 190 bool allocate(size_t capacity); 191 192 // Pushes the first "n" elements of "ptr_arr" on the stack. 193 // Locking impl: concurrency is allowed only with 194 // "par_push_arr" and/or "par_pop_arr" operations, which use the same 195 // locking strategy. 196 void par_push_arr(oop* ptr_arr, int n); 197 198 // If returns false, the array was empty. Otherwise, removes up to "max" 199 // elements from the stack, and transfers them to "ptr_arr" in an 200 // unspecified order. The actual number transferred is given in "n" ("n 201 // == 0" is deliberately redundant with the return value.) Locking impl: 202 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr" 203 // operations, which use the same locking strategy. 204 bool par_pop_arr(oop* ptr_arr, int max, int* n); 205 206 bool isEmpty() { return _index == 0; } 207 int maxElems() { return _capacity; } 208 209 bool overflow() { return _overflow; } 210 void clear_overflow() { _overflow = false; } 211 212 bool should_expand() const { return _should_expand; } 213 void set_should_expand(); 214 215 // Expand the stack, typically in response to an overflow condition 216 void expand(); 217 218 int size() { return _index; } 219 220 void setEmpty() { _index = 0; clear_overflow(); } 221 222 // Record the current index. 223 void note_start_of_gc(); 224 225 // Make sure that we have not added any entries to the stack during GC. 226 void note_end_of_gc(); 227 228 // Apply fn to each oop in the mark stack, up to the bound recorded 229 // via one of the above "note" functions. The mark stack must not 230 // be modified while iterating. 231 template<typename Fn> void iterate(Fn fn); 232 }; 233 234 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC { 235 private: 236 #ifndef PRODUCT 237 uintx _num_remaining; 238 bool _force; 239 #endif // !defined(PRODUCT) 240 241 public: 242 void init() PRODUCT_RETURN; 243 void update() PRODUCT_RETURN; 244 bool should_force() PRODUCT_RETURN_( return false; ); 245 }; 246 247 class YoungList; 248 249 // Root Regions are regions that are not empty at the beginning of a 250 // marking cycle and which we might collect during an evacuation pause 251 // while the cycle is active. Given that, during evacuation pauses, we 252 // do not copy objects that are explicitly marked, what we have to do 253 // for the root regions is to scan them and mark all objects reachable 254 // from them. According to the SATB assumptions, we only need to visit 255 // each object once during marking. So, as long as we finish this scan 256 // before the next evacuation pause, we can copy the objects from the 257 // root regions without having to mark them or do anything else to them. 258 // 259 // Currently, we only support root region scanning once (at the start 260 // of the marking cycle) and the root regions are all the survivor 261 // regions populated during the initial-mark pause. 262 class CMRootRegions VALUE_OBJ_CLASS_SPEC { 263 private: 264 YoungList* _young_list; 265 ConcurrentMark* _cm; 266 267 volatile bool _scan_in_progress; 268 volatile bool _should_abort; 269 HeapRegion* volatile _next_survivor; 270 271 public: 272 CMRootRegions(); 273 // We actually do most of the initialization in this method. 274 void init(G1CollectedHeap* g1h, ConcurrentMark* cm); 275 276 // Reset the claiming / scanning of the root regions. 277 void prepare_for_scan(); 278 279 // Forces get_next() to return NULL so that the iteration aborts early. 280 void abort() { _should_abort = true; } 281 282 // Return true if the CM thread are actively scanning root regions, 283 // false otherwise. 284 bool scan_in_progress() { return _scan_in_progress; } 285 286 // Claim the next root region to scan atomically, or return NULL if 287 // all have been claimed. 288 HeapRegion* claim_next(); 289 290 // Flag that we're done with root region scanning and notify anyone 291 // who's waiting on it. If aborted is false, assume that all regions 292 // have been claimed. 293 void scan_finished(); 294 295 // If CM threads are still scanning root regions, wait until they 296 // are done. Return true if we had to wait, false otherwise. 297 bool wait_until_scan_finished(); 298 }; 299 300 class ConcurrentMarkThread; 301 302 class ConcurrentMark: public CHeapObj<mtGC> { 303 friend class CMMarkStack; 304 friend class ConcurrentMarkThread; 305 friend class CMTask; 306 friend class CMBitMapClosure; 307 friend class CMRemarkTask; 308 friend class CMConcurrentMarkingTask; 309 friend class G1ParNoteEndTask; 310 friend class CalcLiveObjectsClosure; 311 friend class G1CMRefProcTaskProxy; 312 friend class G1CMRefProcTaskExecutor; 313 friend class G1CMKeepAliveAndDrainClosure; 314 friend class G1CMDrainMarkingStackClosure; 315 316 protected: 317 ConcurrentMarkThread* _cmThread; // The thread doing the work 318 G1CollectedHeap* _g1h; // The heap 319 uint _parallel_marking_threads; // The number of marking 320 // threads we're using 321 uint _max_parallel_marking_threads; // Max number of marking 322 // threads we'll ever use 323 double _sleep_factor; // How much we have to sleep, with 324 // respect to the work we just did, to 325 // meet the marking overhead goal 326 double _marking_task_overhead; // Marking target overhead for 327 // a single task 328 329 // Same as the two above, but for the cleanup task 330 double _cleanup_sleep_factor; 331 double _cleanup_task_overhead; 332 333 FreeRegionList _cleanup_list; 334 335 // Concurrent marking support structures 336 CMBitMap _markBitMap1; 337 CMBitMap _markBitMap2; 338 CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap 339 CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap 340 341 BitMap _region_bm; 342 BitMap _card_bm; 343 344 // Heap bounds 345 HeapWord* _heap_start; 346 HeapWord* _heap_end; 347 348 // Root region tracking and claiming 349 CMRootRegions _root_regions; 350 351 // For gray objects 352 CMMarkStack _markStack; // Grey objects behind global finger 353 HeapWord* volatile _finger; // The global finger, region aligned, 354 // always points to the end of the 355 // last claimed region 356 357 // Marking tasks 358 uint _max_worker_id;// Maximum worker id 359 uint _active_tasks; // Task num currently active 360 CMTask** _tasks; // Task queue array (max_worker_id len) 361 CMTaskQueueSet* _task_queues; // Task queue set 362 ParallelTaskTerminator _terminator; // For termination 363 364 // Two sync barriers that are used to synchronize tasks when an 365 // overflow occurs. The algorithm is the following. All tasks enter 366 // the first one to ensure that they have all stopped manipulating 367 // the global data structures. After they exit it, they re-initialize 368 // their data structures and task 0 re-initializes the global data 369 // structures. Then, they enter the second sync barrier. This 370 // ensure, that no task starts doing work before all data 371 // structures (local and global) have been re-initialized. When they 372 // exit it, they are free to start working again. 373 WorkGangBarrierSync _first_overflow_barrier_sync; 374 WorkGangBarrierSync _second_overflow_barrier_sync; 375 376 // This is set by any task, when an overflow on the global data 377 // structures is detected 378 volatile bool _has_overflown; 379 // True: marking is concurrent, false: we're in remark 380 volatile bool _concurrent; 381 // Set at the end of a Full GC so that marking aborts 382 volatile bool _has_aborted; 383 384 // Used when remark aborts due to an overflow to indicate that 385 // another concurrent marking phase should start 386 volatile bool _restart_for_overflow; 387 388 // This is true from the very start of concurrent marking until the 389 // point when all the tasks complete their work. It is really used 390 // to determine the points between the end of concurrent marking and 391 // time of remark. 392 volatile bool _concurrent_marking_in_progress; 393 394 // All of these times are in ms 395 NumberSeq _init_times; 396 NumberSeq _remark_times; 397 NumberSeq _remark_mark_times; 398 NumberSeq _remark_weak_ref_times; 399 NumberSeq _cleanup_times; 400 double _total_counting_time; 401 double _total_rs_scrub_time; 402 403 double* _accum_task_vtime; // Accumulated task vtime 404 405 WorkGang* _parallel_workers; 406 407 ForceOverflowSettings _force_overflow_conc; 408 ForceOverflowSettings _force_overflow_stw; 409 410 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes); 411 void weakRefsWork(bool clear_all_soft_refs); 412 413 void swapMarkBitMaps(); 414 415 // It resets the global marking data structures, as well as the 416 // task local ones; should be called during initial mark. 417 void reset(); 418 419 // Resets all the marking data structures. Called when we have to restart 420 // marking or when marking completes (via set_non_marking_state below). 421 void reset_marking_state(bool clear_overflow = true); 422 423 // We do this after we're done with marking so that the marking data 424 // structures are initialized to a sensible and predictable state. 425 void set_non_marking_state(); 426 427 // Called to indicate how many threads are currently active. 428 void set_concurrency(uint active_tasks); 429 430 // It should be called to indicate which phase we're in (concurrent 431 // mark or remark) and how many threads are currently active. 432 void set_concurrency_and_phase(uint active_tasks, bool concurrent); 433 434 // Prints all gathered CM-related statistics 435 void print_stats(); 436 437 bool cleanup_list_is_empty() { 438 return _cleanup_list.is_empty(); 439 } 440 441 // Accessor methods 442 uint parallel_marking_threads() const { return _parallel_marking_threads; } 443 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;} 444 double sleep_factor() { return _sleep_factor; } 445 double marking_task_overhead() { return _marking_task_overhead;} 446 double cleanup_sleep_factor() { return _cleanup_sleep_factor; } 447 double cleanup_task_overhead() { return _cleanup_task_overhead;} 448 449 HeapWord* finger() { return _finger; } 450 bool concurrent() { return _concurrent; } 451 uint active_tasks() { return _active_tasks; } 452 ParallelTaskTerminator* terminator() { return &_terminator; } 453 454 // It claims the next available region to be scanned by a marking 455 // task/thread. It might return NULL if the next region is empty or 456 // we have run out of regions. In the latter case, out_of_regions() 457 // determines whether we've really run out of regions or the task 458 // should call claim_region() again. This might seem a bit 459 // awkward. Originally, the code was written so that claim_region() 460 // either successfully returned with a non-empty region or there 461 // were no more regions to be claimed. The problem with this was 462 // that, in certain circumstances, it iterated over large chunks of 463 // the heap finding only empty regions and, while it was working, it 464 // was preventing the calling task to call its regular clock 465 // method. So, this way, each task will spend very little time in 466 // claim_region() and is allowed to call the regular clock method 467 // frequently. 468 HeapRegion* claim_region(uint worker_id); 469 470 // It determines whether we've run out of regions to scan. Note that 471 // the finger can point past the heap end in case the heap was expanded 472 // to satisfy an allocation without doing a GC. This is fine, because all 473 // objects in those regions will be considered live anyway because of 474 // SATB guarantees (i.e. their TAMS will be equal to bottom). 475 bool out_of_regions() { return _finger >= _heap_end; } 476 477 // Returns the task with the given id 478 CMTask* task(int id) { 479 assert(0 <= id && id < (int) _active_tasks, 480 "task id not within active bounds"); 481 return _tasks[id]; 482 } 483 484 // Returns the task queue with the given id 485 CMTaskQueue* task_queue(int id) { 486 assert(0 <= id && id < (int) _active_tasks, 487 "task queue id not within active bounds"); 488 return (CMTaskQueue*) _task_queues->queue(id); 489 } 490 491 // Returns the task queue set 492 CMTaskQueueSet* task_queues() { return _task_queues; } 493 494 // Access / manipulation of the overflow flag which is set to 495 // indicate that the global stack has overflown 496 bool has_overflown() { return _has_overflown; } 497 void set_has_overflown() { _has_overflown = true; } 498 void clear_has_overflown() { _has_overflown = false; } 499 bool restart_for_overflow() { return _restart_for_overflow; } 500 501 // Methods to enter the two overflow sync barriers 502 void enter_first_sync_barrier(uint worker_id); 503 void enter_second_sync_barrier(uint worker_id); 504 505 ForceOverflowSettings* force_overflow_conc() { 506 return &_force_overflow_conc; 507 } 508 509 ForceOverflowSettings* force_overflow_stw() { 510 return &_force_overflow_stw; 511 } 512 513 ForceOverflowSettings* force_overflow() { 514 if (concurrent()) { 515 return force_overflow_conc(); 516 } else { 517 return force_overflow_stw(); 518 } 519 } 520 521 // Live Data Counting data structures... 522 // These data structures are initialized at the start of 523 // marking. They are written to while marking is active. 524 // They are aggregated during remark; the aggregated values 525 // are then used to populate the _region_bm, _card_bm, and 526 // the total live bytes, which are then subsequently updated 527 // during cleanup. 528 529 // An array of bitmaps (one bit map per task). Each bitmap 530 // is used to record the cards spanned by the live objects 531 // marked by that task/worker. 532 BitMap* _count_card_bitmaps; 533 534 // Used to record the number of marked live bytes 535 // (for each region, by worker thread). 536 size_t** _count_marked_bytes; 537 538 // Card index of the bottom of the G1 heap. Used for biasing indices into 539 // the card bitmaps. 540 intptr_t _heap_bottom_card_num; 541 542 // Set to true when initialization is complete 543 bool _completed_initialization; 544 545 public: 546 // Manipulation of the global mark stack. 547 // The push and pop operations are used by tasks for transfers 548 // between task-local queues and the global mark stack, and use 549 // locking for concurrency safety. 550 bool mark_stack_push(oop* arr, int n) { 551 _markStack.par_push_arr(arr, n); 552 if (_markStack.overflow()) { 553 set_has_overflown(); 554 return false; 555 } 556 return true; 557 } 558 void mark_stack_pop(oop* arr, int max, int* n) { 559 _markStack.par_pop_arr(arr, max, n); 560 } 561 size_t mark_stack_size() { return _markStack.size(); } 562 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; } 563 bool mark_stack_overflow() { return _markStack.overflow(); } 564 bool mark_stack_empty() { return _markStack.isEmpty(); } 565 566 CMRootRegions* root_regions() { return &_root_regions; } 567 568 bool concurrent_marking_in_progress() { 569 return _concurrent_marking_in_progress; 570 } 571 void set_concurrent_marking_in_progress() { 572 _concurrent_marking_in_progress = true; 573 } 574 void clear_concurrent_marking_in_progress() { 575 _concurrent_marking_in_progress = false; 576 } 577 578 void update_accum_task_vtime(int i, double vtime) { 579 _accum_task_vtime[i] += vtime; 580 } 581 582 double all_task_accum_vtime() { 583 double ret = 0.0; 584 for (uint i = 0; i < _max_worker_id; ++i) 585 ret += _accum_task_vtime[i]; 586 return ret; 587 } 588 589 // Attempts to steal an object from the task queues of other tasks 590 bool try_stealing(uint worker_id, int* hash_seed, oop& obj); 591 592 ConcurrentMark(G1CollectedHeap* g1h, 593 G1RegionToSpaceMapper* prev_bitmap_storage, 594 G1RegionToSpaceMapper* next_bitmap_storage); 595 ~ConcurrentMark(); 596 597 ConcurrentMarkThread* cmThread() { return _cmThread; } 598 599 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; } 600 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; } 601 602 // Returns the number of GC threads to be used in a concurrent 603 // phase based on the number of GC threads being used in a STW 604 // phase. 605 uint scale_parallel_threads(uint n_par_threads); 606 607 // Calculates the number of GC threads to be used in a concurrent phase. 608 uint calc_parallel_marking_threads(); 609 610 // The following three are interaction between CM and 611 // G1CollectedHeap 612 613 // This notifies CM that a root during initial-mark needs to be 614 // grayed. It is MT-safe. word_size is the size of the object in 615 // words. It is passed explicitly as sometimes we cannot calculate 616 // it from the given object because it might be in an inconsistent 617 // state (e.g., in to-space and being copied). So the caller is 618 // responsible for dealing with this issue (e.g., get the size from 619 // the from-space image when the to-space image might be 620 // inconsistent) and always passing the size. hr is the region that 621 // contains the object and it's passed optionally from callers who 622 // might already have it (no point in recalculating it). 623 inline void grayRoot(oop obj, 624 size_t word_size, 625 uint worker_id, 626 HeapRegion* hr = NULL); 627 628 // It iterates over the heap and for each object it comes across it 629 // will dump the contents of its reference fields, as well as 630 // liveness information for the object and its referents. The dump 631 // will be written to a file with the following name: 632 // G1PrintReachableBaseFile + "." + str. 633 // vo decides whether the prev (vo == UsePrevMarking), the next 634 // (vo == UseNextMarking) marking information, or the mark word 635 // (vo == UseMarkWord) will be used to determine the liveness of 636 // each object / referent. 637 // If all is true, all objects in the heap will be dumped, otherwise 638 // only the live ones. In the dump the following symbols / breviations 639 // are used: 640 // M : an explicitly live object (its bitmap bit is set) 641 // > : an implicitly live object (over tams) 642 // O : an object outside the G1 heap (typically: in the perm gen) 643 // NOT : a reference field whose referent is not live 644 // AND MARKED : indicates that an object is both explicitly and 645 // implicitly live (it should be one or the other, not both) 646 void print_reachable(const char* str, 647 VerifyOption vo, 648 bool all) PRODUCT_RETURN; 649 650 // Clear the next marking bitmap (will be called concurrently). 651 void clearNextBitmap(); 652 653 // Return whether the next mark bitmap has no marks set. To be used for assertions 654 // only. Will not yield to pause requests. 655 bool nextMarkBitmapIsClear(); 656 657 // These two do the work that needs to be done before and after the 658 // initial root checkpoint. Since this checkpoint can be done at two 659 // different points (i.e. an explicit pause or piggy-backed on a 660 // young collection), then it's nice to be able to easily share the 661 // pre/post code. It might be the case that we can put everything in 662 // the post method. TP 663 void checkpointRootsInitialPre(); 664 void checkpointRootsInitialPost(); 665 666 // Scan all the root regions and mark everything reachable from 667 // them. 668 void scanRootRegions(); 669 670 // Scan a single root region and mark everything reachable from it. 671 void scanRootRegion(HeapRegion* hr, uint worker_id); 672 673 // Do concurrent phase of marking, to a tentative transitive closure. 674 void markFromRoots(); 675 676 void checkpointRootsFinal(bool clear_all_soft_refs); 677 void checkpointRootsFinalWork(); 678 void cleanup(); 679 void completeCleanup(); 680 681 // Mark in the previous bitmap. NB: this is usually read-only, so use 682 // this carefully! 683 inline void markPrev(oop p); 684 685 // Clears marks for all objects in the given range, for the prev or 686 // next bitmaps. NB: the previous bitmap is usually 687 // read-only, so use this carefully! 688 void clearRangePrevBitmap(MemRegion mr); 689 void clearRangeNextBitmap(MemRegion mr); 690 691 // Notify data structures that a GC has started. 692 void note_start_of_gc() { 693 _markStack.note_start_of_gc(); 694 } 695 696 // Notify data structures that a GC is finished. 697 void note_end_of_gc() { 698 _markStack.note_end_of_gc(); 699 } 700 701 // Verify that there are no CSet oops on the stacks (taskqueues / 702 // global mark stack) and fingers (global / per-task). 703 // If marking is not in progress, it's a no-op. 704 void verify_no_cset_oops() PRODUCT_RETURN; 705 706 bool isPrevMarked(oop p) const { 707 assert(p != NULL && p->is_oop(), "expected an oop"); 708 HeapWord* addr = (HeapWord*)p; 709 assert(addr >= _prevMarkBitMap->startWord() || 710 addr < _prevMarkBitMap->endWord(), "in a region"); 711 712 return _prevMarkBitMap->isMarked(addr); 713 } 714 715 inline bool do_yield_check(uint worker_i = 0); 716 717 // Called to abort the marking cycle after a Full GC takes place. 718 void abort(); 719 720 bool has_aborted() { return _has_aborted; } 721 722 void print_summary_info(); 723 724 void print_worker_threads_on(outputStream* st) const; 725 726 void print_on_error(outputStream* st) const; 727 728 // Liveness counting 729 730 // Utility routine to set an exclusive range of cards on the given 731 // card liveness bitmap 732 inline void set_card_bitmap_range(BitMap* card_bm, 733 BitMap::idx_t start_idx, 734 BitMap::idx_t end_idx, 735 bool is_par); 736 737 // Returns the card number of the bottom of the G1 heap. 738 // Used in biasing indices into accounting card bitmaps. 739 intptr_t heap_bottom_card_num() const { 740 return _heap_bottom_card_num; 741 } 742 743 // Returns the card bitmap for a given task or worker id. 744 BitMap* count_card_bitmap_for(uint worker_id) { 745 assert(worker_id < _max_worker_id, "oob"); 746 assert(_count_card_bitmaps != NULL, "uninitialized"); 747 BitMap* task_card_bm = &_count_card_bitmaps[worker_id]; 748 assert(task_card_bm->size() == _card_bm.size(), "size mismatch"); 749 return task_card_bm; 750 } 751 752 // Returns the array containing the marked bytes for each region, 753 // for the given worker or task id. 754 size_t* count_marked_bytes_array_for(uint worker_id) { 755 assert(worker_id < _max_worker_id, "oob"); 756 assert(_count_marked_bytes != NULL, "uninitialized"); 757 size_t* marked_bytes_array = _count_marked_bytes[worker_id]; 758 assert(marked_bytes_array != NULL, "uninitialized"); 759 return marked_bytes_array; 760 } 761 762 // Returns the index in the liveness accounting card table bitmap 763 // for the given address 764 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr); 765 766 // Counts the size of the given memory region in the the given 767 // marked_bytes array slot for the given HeapRegion. 768 // Sets the bits in the given card bitmap that are associated with the 769 // cards that are spanned by the memory region. 770 inline void count_region(MemRegion mr, 771 HeapRegion* hr, 772 size_t* marked_bytes_array, 773 BitMap* task_card_bm); 774 775 // Counts the given object in the given task/worker counting 776 // data structures. 777 inline void count_object(oop obj, 778 HeapRegion* hr, 779 size_t* marked_bytes_array, 780 BitMap* task_card_bm, 781 size_t word_size); 782 783 // Attempts to mark the given object and, if successful, counts 784 // the object in the given task/worker counting structures. 785 inline bool par_mark_and_count(oop obj, 786 HeapRegion* hr, 787 size_t* marked_bytes_array, 788 BitMap* task_card_bm); 789 790 // Attempts to mark the given object and, if successful, counts 791 // the object in the task/worker counting structures for the 792 // given worker id. 793 inline bool par_mark_and_count(oop obj, 794 size_t word_size, 795 HeapRegion* hr, 796 uint worker_id); 797 798 // Returns true if initialization was successfully completed. 799 bool completed_initialization() const { 800 return _completed_initialization; 801 } 802 803 protected: 804 // Clear all the per-task bitmaps and arrays used to store the 805 // counting data. 806 void clear_all_count_data(); 807 808 // Aggregates the counting data for each worker/task 809 // that was constructed while marking. Also sets 810 // the amount of marked bytes for each region and 811 // the top at concurrent mark count. 812 void aggregate_count_data(); 813 814 // Verification routine 815 void verify_count_data(); 816 }; 817 818 // A class representing a marking task. 819 class CMTask : public TerminatorTerminator { 820 private: 821 enum PrivateConstants { 822 // the regular clock call is called once the scanned words reaches 823 // this limit 824 words_scanned_period = 12*1024, 825 // the regular clock call is called once the number of visited 826 // references reaches this limit 827 refs_reached_period = 384, 828 // initial value for the hash seed, used in the work stealing code 829 init_hash_seed = 17, 830 // how many entries will be transferred between global stack and 831 // local queues 832 global_stack_transfer_size = 16 833 }; 834 835 uint _worker_id; 836 G1CollectedHeap* _g1h; 837 ConcurrentMark* _cm; 838 CMBitMap* _nextMarkBitMap; 839 // the task queue of this task 840 CMTaskQueue* _task_queue; 841 private: 842 // the task queue set---needed for stealing 843 CMTaskQueueSet* _task_queues; 844 // indicates whether the task has been claimed---this is only for 845 // debugging purposes 846 bool _claimed; 847 848 // number of calls to this task 849 int _calls; 850 851 // when the virtual timer reaches this time, the marking step should 852 // exit 853 double _time_target_ms; 854 // the start time of the current marking step 855 double _start_time_ms; 856 857 // the oop closure used for iterations over oops 858 G1CMOopClosure* _cm_oop_closure; 859 860 // the region this task is scanning, NULL if we're not scanning any 861 HeapRegion* _curr_region; 862 // the local finger of this task, NULL if we're not scanning a region 863 HeapWord* _finger; 864 // limit of the region this task is scanning, NULL if we're not scanning one 865 HeapWord* _region_limit; 866 867 // the number of words this task has scanned 868 size_t _words_scanned; 869 // When _words_scanned reaches this limit, the regular clock is 870 // called. Notice that this might be decreased under certain 871 // circumstances (i.e. when we believe that we did an expensive 872 // operation). 873 size_t _words_scanned_limit; 874 // the initial value of _words_scanned_limit (i.e. what it was 875 // before it was decreased). 876 size_t _real_words_scanned_limit; 877 878 // the number of references this task has visited 879 size_t _refs_reached; 880 // When _refs_reached reaches this limit, the regular clock is 881 // called. Notice this this might be decreased under certain 882 // circumstances (i.e. when we believe that we did an expensive 883 // operation). 884 size_t _refs_reached_limit; 885 // the initial value of _refs_reached_limit (i.e. what it was before 886 // it was decreased). 887 size_t _real_refs_reached_limit; 888 889 // used by the work stealing stuff 890 int _hash_seed; 891 // if this is true, then the task has aborted for some reason 892 bool _has_aborted; 893 // set when the task aborts because it has met its time quota 894 bool _has_timed_out; 895 // true when we're draining SATB buffers; this avoids the task 896 // aborting due to SATB buffers being available (as we're already 897 // dealing with them) 898 bool _draining_satb_buffers; 899 900 // number sequence of past step times 901 NumberSeq _step_times_ms; 902 // elapsed time of this task 903 double _elapsed_time_ms; 904 // termination time of this task 905 double _termination_time_ms; 906 // when this task got into the termination protocol 907 double _termination_start_time_ms; 908 909 // true when the task is during a concurrent phase, false when it is 910 // in the remark phase (so, in the latter case, we do not have to 911 // check all the things that we have to check during the concurrent 912 // phase, i.e. SATB buffer availability...) 913 bool _concurrent; 914 915 TruncatedSeq _marking_step_diffs_ms; 916 917 // Counting data structures. Embedding the task's marked_bytes_array 918 // and card bitmap into the actual task saves having to go through 919 // the ConcurrentMark object. 920 size_t* _marked_bytes_array; 921 BitMap* _card_bm; 922 923 // it updates the local fields after this task has claimed 924 // a new region to scan 925 void setup_for_region(HeapRegion* hr); 926 // it brings up-to-date the limit of the region 927 void update_region_limit(); 928 929 // called when either the words scanned or the refs visited limit 930 // has been reached 931 void reached_limit(); 932 // recalculates the words scanned and refs visited limits 933 void recalculate_limits(); 934 // decreases the words scanned and refs visited limits when we reach 935 // an expensive operation 936 void decrease_limits(); 937 // it checks whether the words scanned or refs visited reached their 938 // respective limit and calls reached_limit() if they have 939 void check_limits() { 940 if (_words_scanned >= _words_scanned_limit || 941 _refs_reached >= _refs_reached_limit) { 942 reached_limit(); 943 } 944 } 945 // this is supposed to be called regularly during a marking step as 946 // it checks a bunch of conditions that might cause the marking step 947 // to abort 948 void regular_clock_call(); 949 bool concurrent() { return _concurrent; } 950 951 // Test whether obj might have already been passed over by the 952 // mark bitmap scan, and so needs to be pushed onto the mark stack. 953 bool is_below_finger(oop obj, HeapWord* global_finger) const; 954 955 template<bool scan> void process_grey_object(oop obj); 956 957 public: 958 // It resets the task; it should be called right at the beginning of 959 // a marking phase. 960 void reset(CMBitMap* _nextMarkBitMap); 961 // it clears all the fields that correspond to a claimed region. 962 void clear_region_fields(); 963 964 void set_concurrent(bool concurrent) { _concurrent = concurrent; } 965 966 // The main method of this class which performs a marking step 967 // trying not to exceed the given duration. However, it might exit 968 // prematurely, according to some conditions (i.e. SATB buffers are 969 // available for processing). 970 void do_marking_step(double target_ms, 971 bool do_termination, 972 bool is_serial); 973 974 // These two calls start and stop the timer 975 void record_start_time() { 976 _elapsed_time_ms = os::elapsedTime() * 1000.0; 977 } 978 void record_end_time() { 979 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms; 980 } 981 982 // returns the worker ID associated with this task. 983 uint worker_id() { return _worker_id; } 984 985 // From TerminatorTerminator. It determines whether this task should 986 // exit the termination protocol after it's entered it. 987 virtual bool should_exit_termination(); 988 989 // Resets the local region fields after a task has finished scanning a 990 // region; or when they have become stale as a result of the region 991 // being evacuated. 992 void giveup_current_region(); 993 994 HeapWord* finger() { return _finger; } 995 996 bool has_aborted() { return _has_aborted; } 997 void set_has_aborted() { _has_aborted = true; } 998 void clear_has_aborted() { _has_aborted = false; } 999 bool has_timed_out() { return _has_timed_out; } 1000 bool claimed() { return _claimed; } 1001 1002 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure); 1003 1004 // Increment the number of references this task has visited. 1005 void increment_refs_reached() { ++_refs_reached; } 1006 1007 // Grey the object by marking it. If not already marked, push it on 1008 // the local queue if below the finger. 1009 // Precondition: obj is in region. 1010 // Precondition: obj is below region's NTAMS. 1011 inline void make_reference_grey(oop obj, HeapRegion* region); 1012 1013 // Grey the object (by calling make_grey_reference) if required, 1014 // e.g. obj is below its containing region's NTAMS. 1015 // Precondition: obj is a valid heap object. 1016 inline void deal_with_reference(oop obj); 1017 1018 // It scans an object and visits its children. 1019 inline void scan_object(oop obj); 1020 1021 // It pushes an object on the local queue. 1022 inline void push(oop obj); 1023 1024 // These two move entries to/from the global stack. 1025 void move_entries_to_global_stack(); 1026 void get_entries_from_global_stack(); 1027 1028 // It pops and scans objects from the local queue. If partially is 1029 // true, then it stops when the queue size is of a given limit. If 1030 // partially is false, then it stops when the queue is empty. 1031 void drain_local_queue(bool partially); 1032 // It moves entries from the global stack to the local queue and 1033 // drains the local queue. If partially is true, then it stops when 1034 // both the global stack and the local queue reach a given size. If 1035 // partially if false, it tries to empty them totally. 1036 void drain_global_stack(bool partially); 1037 // It keeps picking SATB buffers and processing them until no SATB 1038 // buffers are available. 1039 void drain_satb_buffers(); 1040 1041 // moves the local finger to a new location 1042 inline void move_finger_to(HeapWord* new_finger) { 1043 assert(new_finger >= _finger && new_finger < _region_limit, "invariant"); 1044 _finger = new_finger; 1045 } 1046 1047 CMTask(uint worker_id, 1048 ConcurrentMark *cm, 1049 size_t* marked_bytes, 1050 BitMap* card_bm, 1051 CMTaskQueue* task_queue, 1052 CMTaskQueueSet* task_queues); 1053 1054 // it prints statistics associated with this task 1055 void print_stats(); 1056 }; 1057 1058 // Class that's used to to print out per-region liveness 1059 // information. It's currently used at the end of marking and also 1060 // after we sort the old regions at the end of the cleanup operation. 1061 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure { 1062 private: 1063 // Accumulators for these values. 1064 size_t _total_used_bytes; 1065 size_t _total_capacity_bytes; 1066 size_t _total_prev_live_bytes; 1067 size_t _total_next_live_bytes; 1068 1069 // These are set up when we come across a "stars humongous" region 1070 // (as this is where most of this information is stored, not in the 1071 // subsequent "continues humongous" regions). After that, for every 1072 // region in a given humongous region series we deduce the right 1073 // values for it by simply subtracting the appropriate amount from 1074 // these fields. All these values should reach 0 after we've visited 1075 // the last region in the series. 1076 size_t _hum_used_bytes; 1077 size_t _hum_capacity_bytes; 1078 size_t _hum_prev_live_bytes; 1079 size_t _hum_next_live_bytes; 1080 1081 // Accumulator for the remembered set size 1082 size_t _total_remset_bytes; 1083 1084 // Accumulator for strong code roots memory size 1085 size_t _total_strong_code_roots_bytes; 1086 1087 static double perc(size_t val, size_t total) { 1088 if (total == 0) { 1089 return 0.0; 1090 } else { 1091 return 100.0 * ((double) val / (double) total); 1092 } 1093 } 1094 1095 static double bytes_to_mb(size_t val) { 1096 return (double) val / (double) M; 1097 } 1098 1099 // See the .cpp file. 1100 size_t get_hum_bytes(size_t* hum_bytes); 1101 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes, 1102 size_t* prev_live_bytes, size_t* next_live_bytes); 1103 1104 public: 1105 // The header and footer are printed in the constructor and 1106 // destructor respectively. 1107 G1PrintRegionLivenessInfoClosure(const char* phase_name); 1108 virtual bool doHeapRegion(HeapRegion* r); 1109 ~G1PrintRegionLivenessInfoClosure(); 1110 }; 1111 1112 #endif // SHARE_VM_GC_G1_CONCURRENTMARK_HPP