1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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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(ReservedSpace rs, 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(ReservedSpace rs, int shifter) :
121 CMBitMapRO(rs, shifter) {}
122
123 // write marks
124 void mark(HeapWord* addr) {
125 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
126 "outside underlying space?");
127 _bm.set_bit(heapWordToOffset(addr));
128 }
129 void clear(HeapWord* addr) {
130 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
131 "outside underlying space?");
132 _bm.clear_bit(heapWordToOffset(addr));
133 }
134 bool parMark(HeapWord* addr) {
135 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
136 "outside underlying space?");
137 return _bm.par_set_bit(heapWordToOffset(addr));
138 }
139 bool parClear(HeapWord* addr) {
140 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
141 "outside underlying space?");
142 return _bm.par_clear_bit(heapWordToOffset(addr));
143 }
144 void markRange(MemRegion mr);
145 void clearAll();
146 void clearRange(MemRegion mr);
147
148 // Starting at the bit corresponding to "addr" (inclusive), find the next
149 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
150 // the end of this run (stopping at "end_addr"). Return the MemRegion
151 // covering from the start of the region corresponding to the first bit
152 // of the run to the end of the region corresponding to the last bit of
153 // the run. If there is no "1" bit at or after "addr", return an empty
154 // MemRegion.
155 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
156 };
157
158 // Represents a marking stack used by the CM collector.
159 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
160 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
161 ConcurrentMark* _cm;
162 oop* _base; // bottom of stack
163 jint _index; // one more than last occupied index
164 jint _capacity; // max #elements
165 jint _saved_index; // value of _index saved at start of GC
166 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
167 VirtualSpace _virtual_space; // Underlying backing store for actual stack
168
169 bool _overflow;
170 DEBUG_ONLY(bool _drain_in_progress;)
171 DEBUG_ONLY(bool _drain_in_progress_yields;)
172
173 public:
174 CMMarkStack(ConcurrentMark* cm);
175 ~CMMarkStack();
176
177 void allocate(size_t size);
178
179 oop pop() {
180 if (!isEmpty()) {
181 return _base[--_index] ;
182 }
183 return NULL;
184 }
185
186 // If overflow happens, don't do the push, and record the overflow.
187 // *Requires* that "ptr" is already marked.
188 void push(oop ptr) {
189 if (isFull()) {
190 // Record overflow.
191 _overflow = true;
192 return;
193 } else {
194 _base[_index++] = ptr;
195 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
196 }
197 }
198 // Non-block impl. Note: concurrency is allowed only with other
199 // "par_push" operations, not with "pop" or "drain". We would need
200 // parallel versions of them if such concurrency was desired.
201 void par_push(oop ptr);
202
203 // Pushes the first "n" elements of "ptr_arr" on the stack.
204 // Non-block impl. Note: concurrency is allowed only with other
205 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
206 void par_adjoin_arr(oop* ptr_arr, int n);
207
208 // Pushes the first "n" elements of "ptr_arr" on the stack.
209 // Locking impl: concurrency is allowed only with
210 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
211 // locking strategy.
212 void par_push_arr(oop* ptr_arr, int n);
213
214 // If returns false, the array was empty. Otherwise, removes up to "max"
215 // elements from the stack, and transfers them to "ptr_arr" in an
216 // unspecified order. The actual number transferred is given in "n" ("n
217 // == 0" is deliberately redundant with the return value.) Locking impl:
218 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
219 // operations, which use the same locking strategy.
220 bool par_pop_arr(oop* ptr_arr, int max, int* n);
221
222 // Drain the mark stack, applying the given closure to all fields of
223 // objects on the stack. (That is, continue until the stack is empty,
224 // even if closure applications add entries to the stack.) The "bm"
225 // argument, if non-null, may be used to verify that only marked objects
226 // are on the mark stack. If "yield_after" is "true", then the
227 // concurrent marker performing the drain offers to yield after
228 // processing each object. If a yield occurs, stops the drain operation
229 // and returns false. Otherwise, returns true.
230 template<class OopClosureClass>
231 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
232
233 bool isEmpty() { return _index == 0; }
234 bool isFull() { return _index == _capacity; }
235 int maxElems() { return _capacity; }
236
237 bool overflow() { return _overflow; }
238 void clear_overflow() { _overflow = false; }
239
240 int size() { return _index; }
241
242 void setEmpty() { _index = 0; clear_overflow(); }
243
244 // Record the current index.
245 void note_start_of_gc();
246
247 // Make sure that we have not added any entries to the stack during GC.
248 void note_end_of_gc();
249
250 // iterate over the oops in the mark stack, up to the bound recorded via
251 // the call above.
252 void oops_do(OopClosure* f);
253 };
254
255 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
256 private:
257 #ifndef PRODUCT
258 uintx _num_remaining;
259 bool _force;
260 #endif // !defined(PRODUCT)
261
262 public:
263 void init() PRODUCT_RETURN;
264 void update() PRODUCT_RETURN;
265 bool should_force() PRODUCT_RETURN_( return false; );
266 };
267
268 // this will enable a variety of different statistics per GC task
269 #define _MARKING_STATS_ 0
270 // this will enable the higher verbose levels
271 #define _MARKING_VERBOSE_ 0
272
273 #if _MARKING_STATS_
274 #define statsOnly(statement) \
275 do { \
276 statement ; \
277 } while (0)
278 #else // _MARKING_STATS_
279 #define statsOnly(statement) \
280 do { \
281 } while (0)
282 #endif // _MARKING_STATS_
283
284 typedef enum {
285 no_verbose = 0, // verbose turned off
286 stats_verbose, // only prints stats at the end of marking
287 low_verbose, // low verbose, mostly per region and per major event
288 medium_verbose, // a bit more detailed than low
289 high_verbose // per object verbose
290 } CMVerboseLevel;
291
292 class YoungList;
293
294 // Root Regions are regions that are not empty at the beginning of a
295 // marking cycle and which we might collect during an evacuation pause
296 // while the cycle is active. Given that, during evacuation pauses, we
297 // do not copy objects that are explicitly marked, what we have to do
298 // for the root regions is to scan them and mark all objects reachable
299 // from them. According to the SATB assumptions, we only need to visit
300 // each object once during marking. So, as long as we finish this scan
301 // before the next evacuation pause, we can copy the objects from the
302 // root regions without having to mark them or do anything else to them.
303 //
304 // Currently, we only support root region scanning once (at the start
305 // of the marking cycle) and the root regions are all the survivor
306 // regions populated during the initial-mark pause.
307 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
308 private:
309 YoungList* _young_list;
310 ConcurrentMark* _cm;
311
312 volatile bool _scan_in_progress;
313 volatile bool _should_abort;
314 HeapRegion* volatile _next_survivor;
315
316 public:
317 CMRootRegions();
318 // We actually do most of the initialization in this method.
319 void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
320
321 // Reset the claiming / scanning of the root regions.
322 void prepare_for_scan();
323
324 // Forces get_next() to return NULL so that the iteration aborts early.
325 void abort() { _should_abort = true; }
326
327 // Return true if the CM thread are actively scanning root regions,
328 // false otherwise.
329 bool scan_in_progress() { return _scan_in_progress; }
330
331 // Claim the next root region to scan atomically, or return NULL if
332 // all have been claimed.
333 HeapRegion* claim_next();
334
335 // Flag that we're done with root region scanning and notify anyone
336 // who's waiting on it. If aborted is false, assume that all regions
337 // have been claimed.
338 void scan_finished();
339
340 // If CM threads are still scanning root regions, wait until they
341 // are done. Return true if we had to wait, false otherwise.
342 bool wait_until_scan_finished();
343 };
344
345 class ConcurrentMarkThread;
346
347 class ConcurrentMark: public CHeapObj<mtGC> {
348 friend class ConcurrentMarkThread;
349 friend class CMTask;
350 friend class CMBitMapClosure;
351 friend class CMGlobalObjectClosure;
352 friend class CMRemarkTask;
353 friend class CMConcurrentMarkingTask;
354 friend class G1ParNoteEndTask;
355 friend class CalcLiveObjectsClosure;
356 friend class G1CMRefProcTaskProxy;
357 friend class G1CMRefProcTaskExecutor;
358 friend class G1CMParKeepAliveAndDrainClosure;
359 friend class G1CMParDrainMarkingStackClosure;
360
361 protected:
362 ConcurrentMarkThread* _cmThread; // the thread doing the work
363 G1CollectedHeap* _g1h; // the heap.
364 uint _parallel_marking_threads; // the number of marking
365 // threads we're use
366 uint _max_parallel_marking_threads; // max number of marking
367 // threads we'll ever use
368 double _sleep_factor; // how much we have to sleep, with
369 // respect to the work we just did, to
370 // meet the marking overhead goal
371 double _marking_task_overhead; // marking target overhead for
372 // a single task
373
374 // same as the two above, but for the cleanup task
375 double _cleanup_sleep_factor;
376 double _cleanup_task_overhead;
377
378 FreeRegionList _cleanup_list;
379
380 // Concurrent marking support structures
381 CMBitMap _markBitMap1;
382 CMBitMap _markBitMap2;
383 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
384 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
385
386 BitMap _region_bm;
387 BitMap _card_bm;
388
389 VirtualSpace _virtual_space; // Backing store for worker liveness
390 // counting structures
391
392 // Heap bounds
393 HeapWord* _heap_start;
394 HeapWord* _heap_end;
395
396 // Root region tracking and claiming.
397 CMRootRegions _root_regions;
398
399 // For gray objects
400 CMMarkStack _markStack; // Grey objects behind global finger.
401 HeapWord* volatile _finger; // the global finger, region aligned,
402 // always points to the end of the
403 // last claimed region
404
405 // marking tasks
406 uint _max_task_num; // maximum task number
407 uint _active_tasks; // task num currently active
408 CMTask** _tasks; // task queue array (max_task_num len)
409 CMTaskQueueSet* _task_queues; // task queue set
410 ParallelTaskTerminator _terminator; // for termination
411
412 // Two sync barriers that are used to synchronise tasks when an
413 // overflow occurs. The algorithm is the following. All tasks enter
414 // the first one to ensure that they have all stopped manipulating
415 // the global data structures. After they exit it, they re-initialise
416 // their data structures and task 0 re-initialises the global data
417 // structures. Then, they enter the second sync barrier. This
418 // ensure, that no task starts doing work before all data
419 // structures (local and global) have been re-initialised. When they
420 // exit it, they are free to start working again.
421 WorkGangBarrierSync _first_overflow_barrier_sync;
422 WorkGangBarrierSync _second_overflow_barrier_sync;
423
424 // this is set by any task, when an overflow on the global data
425 // structures is detected.
426 volatile bool _has_overflown;
427 // true: marking is concurrent, false: we're in remark
428 volatile bool _concurrent;
429 // set at the end of a Full GC so that marking aborts
430 volatile bool _has_aborted;
431
432 // used when remark aborts due to an overflow to indicate that
433 // another concurrent marking phase should start
434 volatile bool _restart_for_overflow;
435
436 // This is true from the very start of concurrent marking until the
437 // point when all the tasks complete their work. It is really used
438 // to determine the points between the end of concurrent marking and
439 // time of remark.
440 volatile bool _concurrent_marking_in_progress;
441
442 // verbose level
443 CMVerboseLevel _verbose_level;
444
445 // All of these times are in ms.
446 NumberSeq _init_times;
447 NumberSeq _remark_times;
448 NumberSeq _remark_mark_times;
449 NumberSeq _remark_weak_ref_times;
450 NumberSeq _cleanup_times;
451 double _total_counting_time;
452 double _total_rs_scrub_time;
453
454 double* _accum_task_vtime; // accumulated task vtime
455
456 FlexibleWorkGang* _parallel_workers;
457
458 ForceOverflowSettings _force_overflow_conc;
459 ForceOverflowSettings _force_overflow_stw;
460
461 void weakRefsWork(bool clear_all_soft_refs);
462
463 void swapMarkBitMaps();
464
465 // It resets the global marking data structures, as well as the
466 // task local ones; should be called during initial mark.
467 void reset();
468 // It resets all the marking data structures.
469 void clear_marking_state(bool clear_overflow = true);
470
471 // It should be called to indicate which phase we're in (concurrent
472 // mark or remark) and how many threads are currently active.
473 void set_phase(uint active_tasks, bool concurrent);
474 // We do this after we're done with marking so that the marking data
475 // structures are initialised to a sensible and predictable state.
476 void set_non_marking_state();
477
478 // prints all gathered CM-related statistics
479 void print_stats();
480
481 bool cleanup_list_is_empty() {
482 return _cleanup_list.is_empty();
483 }
484
485 // accessor methods
486 uint parallel_marking_threads() { return _parallel_marking_threads; }
487 uint max_parallel_marking_threads() { return _max_parallel_marking_threads;}
488 double sleep_factor() { return _sleep_factor; }
489 double marking_task_overhead() { return _marking_task_overhead;}
490 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
491 double cleanup_task_overhead() { return _cleanup_task_overhead;}
492
493 HeapWord* finger() { return _finger; }
494 bool concurrent() { return _concurrent; }
495 uint active_tasks() { return _active_tasks; }
496 ParallelTaskTerminator* terminator() { return &_terminator; }
497
498 // It claims the next available region to be scanned by a marking
499 // task. It might return NULL if the next region is empty or we have
500 // run out of regions. In the latter case, out_of_regions()
501 // determines whether we've really run out of regions or the task
502 // should call claim_region() again. This might seem a bit
503 // awkward. Originally, the code was written so that claim_region()
504 // either successfully returned with a non-empty region or there
505 // were no more regions to be claimed. The problem with this was
506 // that, in certain circumstances, it iterated over large chunks of
507 // the heap finding only empty regions and, while it was working, it
508 // was preventing the calling task to call its regular clock
509 // method. So, this way, each task will spend very little time in
510 // claim_region() and is allowed to call the regular clock method
511 // frequently.
512 HeapRegion* claim_region(int task);
513
514 // It determines whether we've run out of regions to scan.
515 bool out_of_regions() { return _finger == _heap_end; }
516
517 // Returns the task with the given id
518 CMTask* task(int id) {
519 assert(0 <= id && id < (int) _active_tasks,
520 "task id not within active bounds");
521 return _tasks[id];
522 }
523
524 // Returns the task queue with the given id
525 CMTaskQueue* task_queue(int id) {
526 assert(0 <= id && id < (int) _active_tasks,
527 "task queue id not within active bounds");
528 return (CMTaskQueue*) _task_queues->queue(id);
529 }
530
531 // Returns the task queue set
532 CMTaskQueueSet* task_queues() { return _task_queues; }
533
534 // Access / manipulation of the overflow flag which is set to
535 // indicate that the global stack has overflown
536 bool has_overflown() { return _has_overflown; }
537 void set_has_overflown() { _has_overflown = true; }
538 void clear_has_overflown() { _has_overflown = false; }
539 bool restart_for_overflow() { return _restart_for_overflow; }
540
541 bool has_aborted() { return _has_aborted; }
542
543 // Methods to enter the two overflow sync barriers
544 void enter_first_sync_barrier(int task_num);
545 void enter_second_sync_barrier(int task_num);
546
547 ForceOverflowSettings* force_overflow_conc() {
548 return &_force_overflow_conc;
549 }
550
551 ForceOverflowSettings* force_overflow_stw() {
552 return &_force_overflow_stw;
553 }
554
555 ForceOverflowSettings* force_overflow() {
556 if (concurrent()) {
557 return force_overflow_conc();
558 } else {
559 return force_overflow_stw();
560 }
561 }
562
563 // Live Data Counting data structures...
564 // These data structures are initialized at the start of
565 // marking. They are written to while marking is active.
566 // They are aggregated during remark; the aggregated values
567 // are then used to populate the _region_bm, _card_bm, and
568 // the total live bytes, which are then subsequently updated
569 // during cleanup.
570
571 // An array of bitmaps (one bit map per task). Each bitmap
572 // is used to record the cards spanned by the live objects
573 // marked by that task/worker.
574 BitMap* _count_card_bitmaps;
575
576 // Used to record the number of marked live bytes
577 // (for each region, by worker thread).
578 size_t** _count_marked_bytes;
579
580 // Card index of the bottom of the G1 heap. Used for biasing indices into
581 // the card bitmaps.
582 intptr_t _heap_bottom_card_num;
583
584 public:
585 // Manipulation of the global mark stack.
586 // Notice that the first mark_stack_push is CAS-based, whereas the
587 // two below are Mutex-based. This is OK since the first one is only
588 // called during evacuation pauses and doesn't compete with the
589 // other two (which are called by the marking tasks during
590 // concurrent marking or remark).
591 bool mark_stack_push(oop p) {
592 _markStack.par_push(p);
593 if (_markStack.overflow()) {
594 set_has_overflown();
595 return false;
596 }
597 return true;
598 }
599 bool mark_stack_push(oop* arr, int n) {
600 _markStack.par_push_arr(arr, n);
601 if (_markStack.overflow()) {
602 set_has_overflown();
603 return false;
604 }
605 return true;
606 }
607 void mark_stack_pop(oop* arr, int max, int* n) {
608 _markStack.par_pop_arr(arr, max, n);
609 }
610 size_t mark_stack_size() { return _markStack.size(); }
611 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
612 bool mark_stack_overflow() { return _markStack.overflow(); }
613 bool mark_stack_empty() { return _markStack.isEmpty(); }
614
615 CMRootRegions* root_regions() { return &_root_regions; }
616
617 bool concurrent_marking_in_progress() {
618 return _concurrent_marking_in_progress;
619 }
620 void set_concurrent_marking_in_progress() {
621 _concurrent_marking_in_progress = true;
622 }
623 void clear_concurrent_marking_in_progress() {
624 _concurrent_marking_in_progress = false;
625 }
626
627 void update_accum_task_vtime(int i, double vtime) {
628 _accum_task_vtime[i] += vtime;
629 }
630
631 double all_task_accum_vtime() {
632 double ret = 0.0;
633 for (int i = 0; i < (int)_max_task_num; ++i)
634 ret += _accum_task_vtime[i];
635 return ret;
636 }
637
638 // Attempts to steal an object from the task queues of other tasks
639 bool try_stealing(int task_num, int* hash_seed, oop& obj) {
640 return _task_queues->steal(task_num, hash_seed, obj);
641 }
642
643 ConcurrentMark(ReservedSpace heap_rs, uint max_regions);
644 ~ConcurrentMark();
645
646 ConcurrentMarkThread* cmThread() { return _cmThread; }
647
648 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
649 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
650
651 // Returns the number of GC threads to be used in a concurrent
652 // phase based on the number of GC threads being used in a STW
653 // phase.
654 uint scale_parallel_threads(uint n_par_threads);
655
656 // Calculates the number of GC threads to be used in a concurrent phase.
657 uint calc_parallel_marking_threads();
658
659 // The following three are interaction between CM and
660 // G1CollectedHeap
661
662 // This notifies CM that a root during initial-mark needs to be
663 // grayed. It is MT-safe. word_size is the size of the object in
664 // words. It is passed explicitly as sometimes we cannot calculate
665 // it from the given object because it might be in an inconsistent
666 // state (e.g., in to-space and being copied). So the caller is
667 // responsible for dealing with this issue (e.g., get the size from
668 // the from-space image when the to-space image might be
669 // inconsistent) and always passing the size. hr is the region that
670 // contains the object and it's passed optionally from callers who
671 // might already have it (no point in recalculating it).
672 inline void grayRoot(oop obj, size_t word_size,
673 uint worker_id, HeapRegion* hr = NULL);
674
675 // It iterates over the heap and for each object it comes across it
676 // will dump the contents of its reference fields, as well as
677 // liveness information for the object and its referents. The dump
678 // will be written to a file with the following name:
679 // G1PrintReachableBaseFile + "." + str.
680 // vo decides whether the prev (vo == UsePrevMarking), the next
681 // (vo == UseNextMarking) marking information, or the mark word
682 // (vo == UseMarkWord) will be used to determine the liveness of
683 // each object / referent.
684 // If all is true, all objects in the heap will be dumped, otherwise
685 // only the live ones. In the dump the following symbols / breviations
686 // are used:
687 // M : an explicitly live object (its bitmap bit is set)
688 // > : an implicitly live object (over tams)
689 // O : an object outside the G1 heap (typically: in the perm gen)
690 // NOT : a reference field whose referent is not live
691 // AND MARKED : indicates that an object is both explicitly and
692 // implicitly live (it should be one or the other, not both)
693 void print_reachable(const char* str,
694 VerifyOption vo, bool all) PRODUCT_RETURN;
695
696 // Clear the next marking bitmap (will be called concurrently).
697 void clearNextBitmap();
698
699 // These two do the work that needs to be done before and after the
700 // initial root checkpoint. Since this checkpoint can be done at two
701 // different points (i.e. an explicit pause or piggy-backed on a
702 // young collection), then it's nice to be able to easily share the
703 // pre/post code. It might be the case that we can put everything in
704 // the post method. TP
705 void checkpointRootsInitialPre();
706 void checkpointRootsInitialPost();
707
708 // Scan all the root regions and mark everything reachable from
709 // them.
710 void scanRootRegions();
711
712 // Scan a single root region and mark everything reachable from it.
713 void scanRootRegion(HeapRegion* hr, uint worker_id);
714
715 // Do concurrent phase of marking, to a tentative transitive closure.
716 void markFromRoots();
717
718 void checkpointRootsFinal(bool clear_all_soft_refs);
719 void checkpointRootsFinalWork();
720 void cleanup();
721 void completeCleanup();
722
723 // Mark in the previous bitmap. NB: this is usually read-only, so use
724 // this carefully!
725 inline void markPrev(oop p);
726
727 // Clears marks for all objects in the given range, for the prev,
728 // next, or both bitmaps. NB: the previous bitmap is usually
729 // read-only, so use this carefully!
730 void clearRangePrevBitmap(MemRegion mr);
731 void clearRangeNextBitmap(MemRegion mr);
732 void clearRangeBothBitmaps(MemRegion mr);
733
734 // Notify data structures that a GC has started.
735 void note_start_of_gc() {
736 _markStack.note_start_of_gc();
737 }
738
739 // Notify data structures that a GC is finished.
740 void note_end_of_gc() {
741 _markStack.note_end_of_gc();
742 }
743
744 // Verify that there are no CSet oops on the stacks (taskqueues /
745 // global mark stack), enqueued SATB buffers, per-thread SATB
746 // buffers, and fingers (global / per-task). The boolean parameters
747 // decide which of the above data structures to verify. If marking
748 // is not in progress, it's a no-op.
749 void verify_no_cset_oops(bool verify_stacks,
750 bool verify_enqueued_buffers,
751 bool verify_thread_buffers,
752 bool verify_fingers) PRODUCT_RETURN;
753
754 // It is called at the end of an evacuation pause during marking so
755 // that CM is notified of where the new end of the heap is. It
756 // doesn't do anything if concurrent_marking_in_progress() is false,
757 // unless the force parameter is true.
758 void update_g1_committed(bool force = false);
759
760 bool isMarked(oop p) const {
761 assert(p != NULL && p->is_oop(), "expected an oop");
762 HeapWord* addr = (HeapWord*)p;
763 assert(addr >= _nextMarkBitMap->startWord() ||
764 addr < _nextMarkBitMap->endWord(), "in a region");
765
766 return _nextMarkBitMap->isMarked(addr);
767 }
768
769 inline bool not_yet_marked(oop p) const;
770
771 // XXX Debug code
772 bool containing_card_is_marked(void* p);
773 bool containing_cards_are_marked(void* start, void* last);
774
775 bool isPrevMarked(oop p) const {
776 assert(p != NULL && p->is_oop(), "expected an oop");
777 HeapWord* addr = (HeapWord*)p;
778 assert(addr >= _prevMarkBitMap->startWord() ||
779 addr < _prevMarkBitMap->endWord(), "in a region");
780
781 return _prevMarkBitMap->isMarked(addr);
782 }
783
784 inline bool do_yield_check(uint worker_i = 0);
785 inline bool should_yield();
786
787 // Called to abort the marking cycle after a Full GC takes palce.
788 void abort();
789
790 // This prints the global/local fingers. It is used for debugging.
791 NOT_PRODUCT(void print_finger();)
792
793 void print_summary_info();
794
795 void print_worker_threads_on(outputStream* st) const;
796
797 // The following indicate whether a given verbose level has been
798 // set. Notice that anything above stats is conditional to
799 // _MARKING_VERBOSE_ having been set to 1
800 bool verbose_stats() {
801 return _verbose_level >= stats_verbose;
802 }
803 bool verbose_low() {
804 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
805 }
806 bool verbose_medium() {
807 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
808 }
809 bool verbose_high() {
810 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
811 }
812
813 // Counting data structure accessors
814
815 // Returns the card number of the bottom of the G1 heap.
816 // Used in biasing indices into accounting card bitmaps.
817 intptr_t heap_bottom_card_num() const {
818 return _heap_bottom_card_num;
819 }
820
821 // Returns the card bitmap for a given task or worker id.
822 BitMap* count_card_bitmap_for(uint worker_id) {
823 assert(0 <= worker_id && worker_id < _max_task_num, "oob");
824 assert(_count_card_bitmaps != NULL, "uninitialized");
825 BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
826 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
827 return task_card_bm;
828 }
829
830 // Returns the array containing the marked bytes for each region,
831 // for the given worker or task id.
832 size_t* count_marked_bytes_array_for(uint worker_id) {
833 assert(0 <= worker_id && worker_id < _max_task_num, "oob");
834 assert(_count_marked_bytes != NULL, "uninitialized");
835 size_t* marked_bytes_array = _count_marked_bytes[worker_id];
836 assert(marked_bytes_array != NULL, "uninitialized");
837 return marked_bytes_array;
838 }
839
840 // Returns the index in the liveness accounting card table bitmap
841 // for the given address
842 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
843
844 // Counts the size of the given memory region in the the given
845 // marked_bytes array slot for the given HeapRegion.
846 // Sets the bits in the given card bitmap that are associated with the
847 // cards that are spanned by the memory region.
848 inline void count_region(MemRegion mr, HeapRegion* hr,
849 size_t* marked_bytes_array,
850 BitMap* task_card_bm);
851
852 // Counts the given memory region in the task/worker counting
853 // data structures for the given worker id.
854 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
855
856 // Counts the given memory region in the task/worker counting
857 // data structures for the given worker id.
858 inline void count_region(MemRegion mr, uint worker_id);
859
860 // Counts the given object in the given task/worker counting
861 // data structures.
862 inline void count_object(oop obj, HeapRegion* hr,
863 size_t* marked_bytes_array,
864 BitMap* task_card_bm);
865
866 // Counts the given object in the task/worker counting data
867 // structures for the given worker id.
868 inline void count_object(oop obj, HeapRegion* hr, uint worker_id);
869
870 // Attempts to mark the given object and, if successful, counts
871 // the object in the given task/worker counting structures.
872 inline bool par_mark_and_count(oop obj, HeapRegion* hr,
873 size_t* marked_bytes_array,
874 BitMap* task_card_bm);
875
876 // Attempts to mark the given object and, if successful, counts
877 // the object in the task/worker counting structures for the
878 // given worker id.
879 inline bool par_mark_and_count(oop obj, size_t word_size,
880 HeapRegion* hr, uint worker_id);
881
882 // Attempts to mark the given object and, if successful, counts
883 // the object in the task/worker counting structures for the
884 // given worker id.
885 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id);
886
887 // Similar to the above routine but we don't know the heap region that
888 // contains the object to be marked/counted, which this routine looks up.
889 inline bool par_mark_and_count(oop obj, uint worker_id);
890
891 // Similar to the above routine but there are times when we cannot
892 // safely calculate the size of obj due to races and we, therefore,
893 // pass the size in as a parameter. It is the caller's reponsibility
894 // to ensure that the size passed in for obj is valid.
895 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id);
896
897 // Unconditionally mark the given object, and unconditinally count
898 // the object in the counting structures for worker id 0.
899 // Should *not* be called from parallel code.
900 inline bool mark_and_count(oop obj, HeapRegion* hr);
901
902 // Similar to the above routine but we don't know the heap region that
903 // contains the object to be marked/counted, which this routine looks up.
904 // Should *not* be called from parallel code.
905 inline bool mark_and_count(oop obj);
906
907 protected:
908 // Clear all the per-task bitmaps and arrays used to store the
909 // counting data.
910 void clear_all_count_data();
911
912 // Aggregates the counting data for each worker/task
913 // that was constructed while marking. Also sets
914 // the amount of marked bytes for each region and
915 // the top at concurrent mark count.
916 void aggregate_count_data();
917
918 // Verification routine
919 void verify_count_data();
920 };
921
922 // A class representing a marking task.
923 class CMTask : public TerminatorTerminator {
924 private:
925 enum PrivateConstants {
926 // the regular clock call is called once the scanned words reaches
927 // this limit
928 words_scanned_period = 12*1024,
929 // the regular clock call is called once the number of visited
930 // references reaches this limit
931 refs_reached_period = 384,
932 // initial value for the hash seed, used in the work stealing code
933 init_hash_seed = 17,
934 // how many entries will be transferred between global stack and
935 // local queues
936 global_stack_transfer_size = 16
937 };
938
939 int _task_id;
940 G1CollectedHeap* _g1h;
941 ConcurrentMark* _cm;
942 CMBitMap* _nextMarkBitMap;
943 // the task queue of this task
944 CMTaskQueue* _task_queue;
945 private:
946 // the task queue set---needed for stealing
947 CMTaskQueueSet* _task_queues;
948 // indicates whether the task has been claimed---this is only for
949 // debugging purposes
950 bool _claimed;
951
952 // number of calls to this task
953 int _calls;
954
955 // when the virtual timer reaches this time, the marking step should
956 // exit
957 double _time_target_ms;
958 // the start time of the current marking step
959 double _start_time_ms;
960
961 // the oop closure used for iterations over oops
962 G1CMOopClosure* _cm_oop_closure;
963
964 // the region this task is scanning, NULL if we're not scanning any
965 HeapRegion* _curr_region;
966 // the local finger of this task, NULL if we're not scanning a region
967 HeapWord* _finger;
968 // limit of the region this task is scanning, NULL if we're not scanning one
969 HeapWord* _region_limit;
970
971 // the number of words this task has scanned
972 size_t _words_scanned;
973 // When _words_scanned reaches this limit, the regular clock is
974 // called. Notice that this might be decreased under certain
975 // circumstances (i.e. when we believe that we did an expensive
976 // operation).
977 size_t _words_scanned_limit;
978 // the initial value of _words_scanned_limit (i.e. what it was
979 // before it was decreased).
980 size_t _real_words_scanned_limit;
981
982 // the number of references this task has visited
983 size_t _refs_reached;
984 // When _refs_reached reaches this limit, the regular clock is
985 // called. Notice this this might be decreased under certain
986 // circumstances (i.e. when we believe that we did an expensive
987 // operation).
988 size_t _refs_reached_limit;
989 // the initial value of _refs_reached_limit (i.e. what it was before
990 // it was decreased).
991 size_t _real_refs_reached_limit;
992
993 // used by the work stealing stuff
994 int _hash_seed;
995 // if this is true, then the task has aborted for some reason
996 bool _has_aborted;
997 // set when the task aborts because it has met its time quota
998 bool _has_timed_out;
999 // true when we're draining SATB buffers; this avoids the task
1000 // aborting due to SATB buffers being available (as we're already
1001 // dealing with them)
1002 bool _draining_satb_buffers;
1003
1004 // number sequence of past step times
1005 NumberSeq _step_times_ms;
1006 // elapsed time of this task
1007 double _elapsed_time_ms;
1008 // termination time of this task
1009 double _termination_time_ms;
1010 // when this task got into the termination protocol
1011 double _termination_start_time_ms;
1012
1013 // true when the task is during a concurrent phase, false when it is
1014 // in the remark phase (so, in the latter case, we do not have to
1015 // check all the things that we have to check during the concurrent
1016 // phase, i.e. SATB buffer availability...)
1017 bool _concurrent;
1018
1019 TruncatedSeq _marking_step_diffs_ms;
1020
1021 // Counting data structures. Embedding the task's marked_bytes_array
1022 // and card bitmap into the actual task saves having to go through
1023 // the ConcurrentMark object.
1024 size_t* _marked_bytes_array;
1025 BitMap* _card_bm;
1026
1027 // LOTS of statistics related with this task
1028 #if _MARKING_STATS_
1029 NumberSeq _all_clock_intervals_ms;
1030 double _interval_start_time_ms;
1031
1032 int _aborted;
1033 int _aborted_overflow;
1034 int _aborted_cm_aborted;
1035 int _aborted_yield;
1036 int _aborted_timed_out;
1037 int _aborted_satb;
1038 int _aborted_termination;
1039
1040 int _steal_attempts;
1041 int _steals;
1042
1043 int _clock_due_to_marking;
1044 int _clock_due_to_scanning;
1045
1046 int _local_pushes;
1047 int _local_pops;
1048 int _local_max_size;
1049 int _objs_scanned;
1050
1051 int _global_pushes;
1052 int _global_pops;
1053 int _global_max_size;
1054
1055 int _global_transfers_to;
1056 int _global_transfers_from;
1057
1058 int _regions_claimed;
1059 int _objs_found_on_bitmap;
1060
1061 int _satb_buffers_processed;
1062 #endif // _MARKING_STATS_
1063
1064 // it updates the local fields after this task has claimed
1065 // a new region to scan
1066 void setup_for_region(HeapRegion* hr);
1067 // it brings up-to-date the limit of the region
1068 void update_region_limit();
1069
1070 // called when either the words scanned or the refs visited limit
1071 // has been reached
1072 void reached_limit();
1073 // recalculates the words scanned and refs visited limits
1074 void recalculate_limits();
1075 // decreases the words scanned and refs visited limits when we reach
1076 // an expensive operation
1077 void decrease_limits();
1078 // it checks whether the words scanned or refs visited reached their
1079 // respective limit and calls reached_limit() if they have
1080 void check_limits() {
1081 if (_words_scanned >= _words_scanned_limit ||
1082 _refs_reached >= _refs_reached_limit) {
1083 reached_limit();
1084 }
1085 }
1086 // this is supposed to be called regularly during a marking step as
1087 // it checks a bunch of conditions that might cause the marking step
1088 // to abort
1089 void regular_clock_call();
1090 bool concurrent() { return _concurrent; }
1091
1092 public:
1093 // It resets the task; it should be called right at the beginning of
1094 // a marking phase.
1095 void reset(CMBitMap* _nextMarkBitMap);
1096 // it clears all the fields that correspond to a claimed region.
1097 void clear_region_fields();
1098
1099 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
1100
1101 // The main method of this class which performs a marking step
1102 // trying not to exceed the given duration. However, it might exit
1103 // prematurely, according to some conditions (i.e. SATB buffers are
1104 // available for processing).
1105 void do_marking_step(double target_ms, bool do_stealing, bool do_termination);
1106
1107 // These two calls start and stop the timer
1108 void record_start_time() {
1109 _elapsed_time_ms = os::elapsedTime() * 1000.0;
1110 }
1111 void record_end_time() {
1112 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
1113 }
1114
1115 // returns the task ID
1116 int task_id() { return _task_id; }
1117
1118 // From TerminatorTerminator. It determines whether this task should
1119 // exit the termination protocol after it's entered it.
1120 virtual bool should_exit_termination();
1121
1122 // Resets the local region fields after a task has finished scanning a
1123 // region; or when they have become stale as a result of the region
1124 // being evacuated.
1125 void giveup_current_region();
1126
1127 HeapWord* finger() { return _finger; }
1128
1129 bool has_aborted() { return _has_aborted; }
1130 void set_has_aborted() { _has_aborted = true; }
1131 void clear_has_aborted() { _has_aborted = false; }
1132 bool has_timed_out() { return _has_timed_out; }
1133 bool claimed() { return _claimed; }
1134
1135 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
1136
1137 // It grays the object by marking it and, if necessary, pushing it
1138 // on the local queue
1139 inline void deal_with_reference(oop obj);
1140
1141 // It scans an object and visits its children.
1142 void scan_object(oop obj);
1143
1144 // It pushes an object on the local queue.
1145 inline void push(oop obj);
1146
1147 // These two move entries to/from the global stack.
1148 void move_entries_to_global_stack();
1149 void get_entries_from_global_stack();
1150
1151 // It pops and scans objects from the local queue. If partially is
1152 // true, then it stops when the queue size is of a given limit. If
1153 // partially is false, then it stops when the queue is empty.
1154 void drain_local_queue(bool partially);
1155 // It moves entries from the global stack to the local queue and
1156 // drains the local queue. If partially is true, then it stops when
1157 // both the global stack and the local queue reach a given size. If
1158 // partially if false, it tries to empty them totally.
1159 void drain_global_stack(bool partially);
1160 // It keeps picking SATB buffers and processing them until no SATB
1161 // buffers are available.
1162 void drain_satb_buffers();
1163
1164 // moves the local finger to a new location
1165 inline void move_finger_to(HeapWord* new_finger) {
1166 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
1167 _finger = new_finger;
1168 }
1169
1170 CMTask(int task_num, ConcurrentMark *cm,
1171 size_t* marked_bytes, BitMap* card_bm,
1172 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1173
1174 // it prints statistics associated with this task
1175 void print_stats();
1176
1177 #if _MARKING_STATS_
1178 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1179 #endif // _MARKING_STATS_
1180 };
1181
1182 // Class that's used to to print out per-region liveness
1183 // information. It's currently used at the end of marking and also
1184 // after we sort the old regions at the end of the cleanup operation.
1185 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
1186 private:
1187 outputStream* _out;
1188
1189 // Accumulators for these values.
1190 size_t _total_used_bytes;
1191 size_t _total_capacity_bytes;
1192 size_t _total_prev_live_bytes;
1193 size_t _total_next_live_bytes;
1194
1195 // These are set up when we come across a "stars humongous" region
1196 // (as this is where most of this information is stored, not in the
1197 // subsequent "continues humongous" regions). After that, for every
1198 // region in a given humongous region series we deduce the right
1199 // values for it by simply subtracting the appropriate amount from
1200 // these fields. All these values should reach 0 after we've visited
1201 // the last region in the series.
1202 size_t _hum_used_bytes;
1203 size_t _hum_capacity_bytes;
1204 size_t _hum_prev_live_bytes;
1205 size_t _hum_next_live_bytes;
1206
1207 static double perc(size_t val, size_t total) {
1208 if (total == 0) {
1209 return 0.0;
1210 } else {
1211 return 100.0 * ((double) val / (double) total);
1212 }
1213 }
1214
1215 static double bytes_to_mb(size_t val) {
1216 return (double) val / (double) M;
1217 }
1218
1219 // See the .cpp file.
1220 size_t get_hum_bytes(size_t* hum_bytes);
1221 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1222 size_t* prev_live_bytes, size_t* next_live_bytes);
1223
1224 public:
1225 // The header and footer are printed in the constructor and
1226 // destructor respectively.
1227 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
1228 virtual bool doHeapRegion(HeapRegion* r);
1229 ~G1PrintRegionLivenessInfoClosure();
1230 };
1231
1232 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP