1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
27
28 #include "gc_implementation/g1/heapRegionSets.hpp"
29 #include "utilities/taskqueue.hpp"
30
31 class G1CollectedHeap;
32 class CMTask;
33 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue;
34 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
35
36 // Closure used by CM during concurrent reference discovery
37 // and reference processing (during remarking) to determine
38 // if a particular object is alive. It is primarily used
39 // to determine if referents of discovered reference objects
40 // are alive. An instance is also embedded into the
41 // reference processor as the _is_alive_non_header field
42 class G1CMIsAliveClosure: public BoolObjectClosure {
43 G1CollectedHeap* _g1;
44 public:
45 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
46
47 void do_object(oop obj) {
48 ShouldNotCallThis();
49 }
50 bool do_object_b(oop obj);
51 };
52
53 // A generic CM bit map. This is essentially a wrapper around the BitMap
54 // class, with one bit per (1<<_shifter) HeapWords.
55
56 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
57 protected:
58 HeapWord* _bmStartWord; // base address of range covered by map
59 size_t _bmWordSize; // map size (in #HeapWords covered)
60 const int _shifter; // map to char or bit
61 VirtualSpace _virtual_space; // underlying the bit map
62 BitMap _bm; // the bit map itself
63
64 public:
65 // constructor
66 CMBitMapRO(int shifter);
67
68 enum { do_yield = true };
69
70 // inquiries
71 HeapWord* startWord() const { return _bmStartWord; }
72 size_t sizeInWords() const { return _bmWordSize; }
73 // the following is one past the last word in space
74 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
75
76 // read marks
77
78 bool isMarked(HeapWord* addr) const {
79 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
80 "outside underlying space?");
81 return _bm.at(heapWordToOffset(addr));
82 }
83
84 // iteration
85 inline bool iterate(BitMapClosure* cl, MemRegion mr);
86 inline bool iterate(BitMapClosure* cl);
87
88 // Return the address corresponding to the next marked bit at or after
89 // "addr", and before "limit", if "limit" is non-NULL. If there is no
90 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
91 HeapWord* getNextMarkedWordAddress(HeapWord* addr,
92 HeapWord* limit = NULL) const;
93 // Return the address corresponding to the next unmarked bit at or after
94 // "addr", and before "limit", if "limit" is non-NULL. If there is no
95 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
96 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr,
97 HeapWord* limit = NULL) const;
98
99 // conversion utilities
100 // XXX Fix these so that offsets are size_t's...
101 HeapWord* offsetToHeapWord(size_t offset) const {
102 return _bmStartWord + (offset << _shifter);
103 }
104 size_t heapWordToOffset(HeapWord* addr) const {
105 return pointer_delta(addr, _bmStartWord) >> _shifter;
106 }
107 int heapWordDiffToOffsetDiff(size_t diff) const;
108
109 HeapWord* nextObject(HeapWord* addr) {
110 oop obj = (oop) addr;
111 return addr + obj->size();
112 }
113
114 // debugging
115 NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
116 };
117
118 class CMBitMap : public CMBitMapRO {
119
120 public:
121 // constructor
122 CMBitMap(int shifter) :
123 CMBitMapRO(shifter) {}
124
125 // Allocates the back store for the marking bitmap
126 bool allocate(ReservedSpace heap_rs);
127
128 // write marks
129 void mark(HeapWord* addr) {
130 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
131 "outside underlying space?");
132 _bm.set_bit(heapWordToOffset(addr));
133 }
134 void clear(HeapWord* addr) {
135 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
136 "outside underlying space?");
137 _bm.clear_bit(heapWordToOffset(addr));
138 }
139 bool parMark(HeapWord* addr) {
140 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
141 "outside underlying space?");
142 return _bm.par_set_bit(heapWordToOffset(addr));
143 }
144 bool parClear(HeapWord* addr) {
145 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
146 "outside underlying space?");
147 return _bm.par_clear_bit(heapWordToOffset(addr));
148 }
149 void markRange(MemRegion mr);
150 void clearAll();
151 void clearRange(MemRegion mr);
152
153 // Starting at the bit corresponding to "addr" (inclusive), find the next
154 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
155 // the end of this run (stopping at "end_addr"). Return the MemRegion
156 // covering from the start of the region corresponding to the first bit
157 // of the run to the end of the region corresponding to the last bit of
158 // the run. If there is no "1" bit at or after "addr", return an empty
159 // MemRegion.
160 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
161 };
162
163 // Represents a marking stack used by ConcurrentMarking in the G1 collector.
164 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
165 VirtualSpace _virtual_space; // Underlying backing store for actual stack
166 ConcurrentMark* _cm;
167 oop* _base; // bottom of stack
168 jint _index; // one more than last occupied index
169 jint _capacity; // max #elements
170 jint _saved_index; // value of _index saved at start of GC
171 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
172
173 bool _overflow;
174 bool _should_expand;
175 DEBUG_ONLY(bool _drain_in_progress;)
176 DEBUG_ONLY(bool _drain_in_progress_yields;)
177
178 public:
179 CMMarkStack(ConcurrentMark* cm);
180 ~CMMarkStack();
181
182 #ifndef PRODUCT
183 jint max_depth() const {
184 return _max_depth;
185 }
186 #endif
187
188 bool allocate(size_t capacity);
189
190 oop pop() {
191 if (!isEmpty()) {
192 return _base[--_index] ;
193 }
194 return NULL;
195 }
196
197 // If overflow happens, don't do the push, and record the overflow.
198 // *Requires* that "ptr" is already marked.
199 void push(oop ptr) {
200 if (isFull()) {
201 // Record overflow.
202 _overflow = true;
203 return;
204 } else {
205 _base[_index++] = ptr;
206 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
207 }
208 }
209 // Non-block impl. Note: concurrency is allowed only with other
210 // "par_push" operations, not with "pop" or "drain". We would need
211 // parallel versions of them if such concurrency was desired.
212 void par_push(oop ptr);
213
214 // Pushes the first "n" elements of "ptr_arr" on the stack.
215 // Non-block impl. Note: concurrency is allowed only with other
216 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
217 void par_adjoin_arr(oop* ptr_arr, int n);
218
219 // Pushes the first "n" elements of "ptr_arr" on the stack.
220 // Locking impl: concurrency is allowed only with
221 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
222 // locking strategy.
223 void par_push_arr(oop* ptr_arr, int n);
224
225 // If returns false, the array was empty. Otherwise, removes up to "max"
226 // elements from the stack, and transfers them to "ptr_arr" in an
227 // unspecified order. The actual number transferred is given in "n" ("n
228 // == 0" is deliberately redundant with the return value.) Locking impl:
229 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
230 // operations, which use the same locking strategy.
231 bool par_pop_arr(oop* ptr_arr, int max, int* n);
232
233 // Drain the mark stack, applying the given closure to all fields of
234 // objects on the stack. (That is, continue until the stack is empty,
235 // even if closure applications add entries to the stack.) The "bm"
236 // argument, if non-null, may be used to verify that only marked objects
237 // are on the mark stack. If "yield_after" is "true", then the
238 // concurrent marker performing the drain offers to yield after
239 // processing each object. If a yield occurs, stops the drain operation
240 // and returns false. Otherwise, returns true.
241 template<class OopClosureClass>
242 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
243
244 bool isEmpty() { return _index == 0; }
245 bool isFull() { return _index == _capacity; }
246 int maxElems() { return _capacity; }
247
248 bool overflow() { return _overflow; }
249 void clear_overflow() { _overflow = false; }
250
251 bool should_expand() const { return _should_expand; }
252 void set_should_expand();
253
254 // Expand the stack, typically in response to an overflow condition
255 void expand();
256
257 int size() { return _index; }
258
259 void setEmpty() { _index = 0; clear_overflow(); }
260
261 // Record the current index.
262 void note_start_of_gc();
263
264 // Make sure that we have not added any entries to the stack during GC.
265 void note_end_of_gc();
266
267 // iterate over the oops in the mark stack, up to the bound recorded via
268 // the call above.
269 void oops_do(OopClosure* f);
270 };
271
272 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
273 private:
274 #ifndef PRODUCT
275 uintx _num_remaining;
276 bool _force;
277 #endif // !defined(PRODUCT)
278
279 public:
280 void init() PRODUCT_RETURN;
281 void update() PRODUCT_RETURN;
282 bool should_force() PRODUCT_RETURN_( return false; );
283 };
284
285 // this will enable a variety of different statistics per GC task
286 #define _MARKING_STATS_ 0
287 // this will enable the higher verbose levels
288 #define _MARKING_VERBOSE_ 0
289
290 #if _MARKING_STATS_
291 #define statsOnly(statement) \
292 do { \
293 statement ; \
294 } while (0)
295 #else // _MARKING_STATS_
296 #define statsOnly(statement) \
297 do { \
298 } while (0)
299 #endif // _MARKING_STATS_
300
301 typedef enum {
302 no_verbose = 0, // verbose turned off
303 stats_verbose, // only prints stats at the end of marking
304 low_verbose, // low verbose, mostly per region and per major event
305 medium_verbose, // a bit more detailed than low
306 high_verbose // per object verbose
307 } CMVerboseLevel;
308
309 class YoungList;
310
311 // Root Regions are regions that are not empty at the beginning of a
312 // marking cycle and which we might collect during an evacuation pause
313 // while the cycle is active. Given that, during evacuation pauses, we
314 // do not copy objects that are explicitly marked, what we have to do
315 // for the root regions is to scan them and mark all objects reachable
316 // from them. According to the SATB assumptions, we only need to visit
317 // each object once during marking. So, as long as we finish this scan
318 // before the next evacuation pause, we can copy the objects from the
319 // root regions without having to mark them or do anything else to them.
320 //
321 // Currently, we only support root region scanning once (at the start
322 // of the marking cycle) and the root regions are all the survivor
323 // regions populated during the initial-mark pause.
324 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
325 private:
326 YoungList* _young_list;
327 ConcurrentMark* _cm;
328
329 volatile bool _scan_in_progress;
330 volatile bool _should_abort;
331 HeapRegion* volatile _next_survivor;
332
333 public:
334 CMRootRegions();
335 // We actually do most of the initialization in this method.
336 void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
337
338 // Reset the claiming / scanning of the root regions.
339 void prepare_for_scan();
340
341 // Forces get_next() to return NULL so that the iteration aborts early.
342 void abort() { _should_abort = true; }
343
344 // Return true if the CM thread are actively scanning root regions,
345 // false otherwise.
346 bool scan_in_progress() { return _scan_in_progress; }
347
348 // Claim the next root region to scan atomically, or return NULL if
349 // all have been claimed.
350 HeapRegion* claim_next();
351
352 // Flag that we're done with root region scanning and notify anyone
353 // who's waiting on it. If aborted is false, assume that all regions
354 // have been claimed.
355 void scan_finished();
356
357 // If CM threads are still scanning root regions, wait until they
358 // are done. Return true if we had to wait, false otherwise.
359 bool wait_until_scan_finished();
360 };
361
362 class ConcurrentMarkThread;
363
364 class ConcurrentMark: public CHeapObj<mtGC> {
365 friend class CMMarkStack;
366 friend class ConcurrentMarkThread;
367 friend class CMTask;
368 friend class CMBitMapClosure;
369 friend class CMGlobalObjectClosure;
370 friend class CMRemarkTask;
371 friend class CMConcurrentMarkingTask;
372 friend class G1ParNoteEndTask;
373 friend class CalcLiveObjectsClosure;
374 friend class G1CMRefProcTaskProxy;
375 friend class G1CMRefProcTaskExecutor;
376 friend class G1CMKeepAliveAndDrainClosure;
377 friend class G1CMDrainMarkingStackClosure;
378
379 protected:
380 ConcurrentMarkThread* _cmThread; // the thread doing the work
381 G1CollectedHeap* _g1h; // the heap.
382 uint _parallel_marking_threads; // the number of marking
383 // threads we're use
384 uint _max_parallel_marking_threads; // max number of marking
385 // threads we'll ever use
386 double _sleep_factor; // how much we have to sleep, with
387 // respect to the work we just did, to
388 // meet the marking overhead goal
389 double _marking_task_overhead; // marking target overhead for
390 // a single task
391
392 // same as the two above, but for the cleanup task
393 double _cleanup_sleep_factor;
394 double _cleanup_task_overhead;
395
396 FreeRegionList _cleanup_list;
397
398 // Concurrent marking support structures
399 CMBitMap _markBitMap1;
400 CMBitMap _markBitMap2;
401 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
402 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
403
404 BitMap _region_bm;
405 BitMap _card_bm;
406
407 // Heap bounds
408 HeapWord* _heap_start;
409 HeapWord* _heap_end;
410
411 // Root region tracking and claiming.
412 CMRootRegions _root_regions;
413
414 // For gray objects
415 CMMarkStack _markStack; // Grey objects behind global finger.
416 HeapWord* volatile _finger; // the global finger, region aligned,
417 // always points to the end of the
418 // last claimed region
419
420 // marking tasks
421 uint _max_worker_id;// maximum worker id
422 uint _active_tasks; // task num currently active
423 CMTask** _tasks; // task queue array (max_worker_id len)
424 CMTaskQueueSet* _task_queues; // task queue set
425 ParallelTaskTerminator _terminator; // for termination
426
427 // Two sync barriers that are used to synchronise tasks when an
428 // overflow occurs. The algorithm is the following. All tasks enter
429 // the first one to ensure that they have all stopped manipulating
430 // the global data structures. After they exit it, they re-initialise
431 // their data structures and task 0 re-initialises the global data
432 // structures. Then, they enter the second sync barrier. This
433 // ensure, that no task starts doing work before all data
434 // structures (local and global) have been re-initialised. When they
435 // exit it, they are free to start working again.
436 WorkGangBarrierSync _first_overflow_barrier_sync;
437 WorkGangBarrierSync _second_overflow_barrier_sync;
438
439 // this is set by any task, when an overflow on the global data
440 // structures is detected.
441 volatile bool _has_overflown;
442 // true: marking is concurrent, false: we're in remark
443 volatile bool _concurrent;
444 // set at the end of a Full GC so that marking aborts
445 volatile bool _has_aborted;
446
447 // used when remark aborts due to an overflow to indicate that
448 // another concurrent marking phase should start
449 volatile bool _restart_for_overflow;
450
451 // This is true from the very start of concurrent marking until the
452 // point when all the tasks complete their work. It is really used
453 // to determine the points between the end of concurrent marking and
454 // time of remark.
455 volatile bool _concurrent_marking_in_progress;
456
457 // verbose level
458 CMVerboseLevel _verbose_level;
459
460 // All of these times are in ms.
461 NumberSeq _init_times;
462 NumberSeq _remark_times;
463 NumberSeq _remark_mark_times;
464 NumberSeq _remark_weak_ref_times;
465 NumberSeq _cleanup_times;
466 double _total_counting_time;
467 double _total_rs_scrub_time;
468
469 double* _accum_task_vtime; // accumulated task vtime
470
471 FlexibleWorkGang* _parallel_workers;
472
473 ForceOverflowSettings _force_overflow_conc;
474 ForceOverflowSettings _force_overflow_stw;
475
476 void weakRefsWork(bool clear_all_soft_refs);
477
478 void swapMarkBitMaps();
479
480 // It resets the global marking data structures, as well as the
481 // task local ones; should be called during initial mark.
482 void reset();
483
484 // Resets all the marking data structures. Called when we have to restart
485 // marking or when marking completes (via set_non_marking_state below).
486 void reset_marking_state(bool clear_overflow = true);
487
488 // We do this after we're done with marking so that the marking data
489 // structures are initialised to a sensible and predictable state.
490 void set_non_marking_state();
491
492 // It should be called to indicate which phase we're in (concurrent
493 // mark or remark) and how many threads are currently active.
494 void set_phase(uint active_tasks, bool concurrent);
495
496 // prints all gathered CM-related statistics
497 void print_stats();
498
499 bool cleanup_list_is_empty() {
500 return _cleanup_list.is_empty();
501 }
502
503 // accessor methods
504 uint parallel_marking_threads() const { return _parallel_marking_threads; }
505 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
506 double sleep_factor() { return _sleep_factor; }
507 double marking_task_overhead() { return _marking_task_overhead;}
508 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
509 double cleanup_task_overhead() { return _cleanup_task_overhead;}
510
511 bool use_parallel_marking_threads() const {
512 assert(parallel_marking_threads() <=
513 max_parallel_marking_threads(), "sanity");
514 assert((_parallel_workers == NULL && parallel_marking_threads() == 0) ||
515 parallel_marking_threads() > 0,
516 "parallel workers not set up correctly");
517 return _parallel_workers != NULL;
518 }
519
520 HeapWord* finger() { return _finger; }
521 bool concurrent() { return _concurrent; }
522 uint active_tasks() { return _active_tasks; }
523 ParallelTaskTerminator* terminator() { return &_terminator; }
524
525 // It claims the next available region to be scanned by a marking
526 // task/thread. It might return NULL if the next region is empty or
527 // we have run out of regions. In the latter case, out_of_regions()
528 // determines whether we've really run out of regions or the task
529 // should call claim_region() again. This might seem a bit
530 // awkward. Originally, the code was written so that claim_region()
531 // either successfully returned with a non-empty region or there
532 // were no more regions to be claimed. The problem with this was
533 // that, in certain circumstances, it iterated over large chunks of
534 // the heap finding only empty regions and, while it was working, it
535 // was preventing the calling task to call its regular clock
536 // method. So, this way, each task will spend very little time in
537 // claim_region() and is allowed to call the regular clock method
538 // frequently.
539 HeapRegion* claim_region(uint worker_id);
540
541 // It determines whether we've run out of regions to scan.
542 bool out_of_regions() { return _finger == _heap_end; }
543
544 // Returns the task with the given id
545 CMTask* task(int id) {
546 assert(0 <= id && id < (int) _active_tasks,
547 "task id not within active bounds");
548 return _tasks[id];
549 }
550
551 // Returns the task queue with the given id
552 CMTaskQueue* task_queue(int id) {
553 assert(0 <= id && id < (int) _active_tasks,
554 "task queue id not within active bounds");
555 return (CMTaskQueue*) _task_queues->queue(id);
556 }
557
558 // Returns the task queue set
559 CMTaskQueueSet* task_queues() { return _task_queues; }
560
561 // Access / manipulation of the overflow flag which is set to
562 // indicate that the global stack has overflown
563 bool has_overflown() { return _has_overflown; }
564 void set_has_overflown() { _has_overflown = true; }
565 void clear_has_overflown() { _has_overflown = false; }
566 bool restart_for_overflow() { return _restart_for_overflow; }
567
568 bool has_aborted() { return _has_aborted; }
569
570 // Methods to enter the two overflow sync barriers
571 void enter_first_sync_barrier(uint worker_id);
572 void enter_second_sync_barrier(uint worker_id);
573
574 ForceOverflowSettings* force_overflow_conc() {
575 return &_force_overflow_conc;
576 }
577
578 ForceOverflowSettings* force_overflow_stw() {
579 return &_force_overflow_stw;
580 }
581
582 ForceOverflowSettings* force_overflow() {
583 if (concurrent()) {
584 return force_overflow_conc();
585 } else {
586 return force_overflow_stw();
587 }
588 }
589
590 // Live Data Counting data structures...
591 // These data structures are initialized at the start of
592 // marking. They are written to while marking is active.
593 // They are aggregated during remark; the aggregated values
594 // are then used to populate the _region_bm, _card_bm, and
595 // the total live bytes, which are then subsequently updated
596 // during cleanup.
597
598 // An array of bitmaps (one bit map per task). Each bitmap
599 // is used to record the cards spanned by the live objects
600 // marked by that task/worker.
601 BitMap* _count_card_bitmaps;
602
603 // Used to record the number of marked live bytes
604 // (for each region, by worker thread).
605 size_t** _count_marked_bytes;
606
607 // Card index of the bottom of the G1 heap. Used for biasing indices into
608 // the card bitmaps.
609 intptr_t _heap_bottom_card_num;
610
611 // Set to true when initialization is complete
612 bool _completed_initialization;
613
614 public:
615 // Manipulation of the global mark stack.
616 // Notice that the first mark_stack_push is CAS-based, whereas the
617 // two below are Mutex-based. This is OK since the first one is only
618 // called during evacuation pauses and doesn't compete with the
619 // other two (which are called by the marking tasks during
620 // concurrent marking or remark).
621 bool mark_stack_push(oop p) {
622 _markStack.par_push(p);
623 if (_markStack.overflow()) {
624 set_has_overflown();
625 return false;
626 }
627 return true;
628 }
629 bool mark_stack_push(oop* arr, int n) {
630 _markStack.par_push_arr(arr, n);
631 if (_markStack.overflow()) {
632 set_has_overflown();
633 return false;
634 }
635 return true;
636 }
637 void mark_stack_pop(oop* arr, int max, int* n) {
638 _markStack.par_pop_arr(arr, max, n);
639 }
640 size_t mark_stack_size() { return _markStack.size(); }
641 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
642 bool mark_stack_overflow() { return _markStack.overflow(); }
643 bool mark_stack_empty() { return _markStack.isEmpty(); }
644
645 CMRootRegions* root_regions() { return &_root_regions; }
646
647 bool concurrent_marking_in_progress() {
648 return _concurrent_marking_in_progress;
649 }
650 void set_concurrent_marking_in_progress() {
651 _concurrent_marking_in_progress = true;
652 }
653 void clear_concurrent_marking_in_progress() {
654 _concurrent_marking_in_progress = false;
655 }
656
657 void update_accum_task_vtime(int i, double vtime) {
658 _accum_task_vtime[i] += vtime;
659 }
660
661 double all_task_accum_vtime() {
662 double ret = 0.0;
663 for (uint i = 0; i < _max_worker_id; ++i)
664 ret += _accum_task_vtime[i];
665 return ret;
666 }
667
668 // Attempts to steal an object from the task queues of other tasks
669 bool try_stealing(uint worker_id, int* hash_seed, oop& obj) {
670 return _task_queues->steal(worker_id, hash_seed, obj);
671 }
672
673 ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs);
674 ~ConcurrentMark();
675
676 ConcurrentMarkThread* cmThread() { return _cmThread; }
677
678 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
679 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
680
681 // Returns the number of GC threads to be used in a concurrent
682 // phase based on the number of GC threads being used in a STW
683 // phase.
684 uint scale_parallel_threads(uint n_par_threads);
685
686 // Calculates the number of GC threads to be used in a concurrent phase.
687 uint calc_parallel_marking_threads();
688
689 // The following three are interaction between CM and
690 // G1CollectedHeap
691
692 // This notifies CM that a root during initial-mark needs to be
693 // grayed. It is MT-safe. word_size is the size of the object in
694 // words. It is passed explicitly as sometimes we cannot calculate
695 // it from the given object because it might be in an inconsistent
696 // state (e.g., in to-space and being copied). So the caller is
697 // responsible for dealing with this issue (e.g., get the size from
698 // the from-space image when the to-space image might be
699 // inconsistent) and always passing the size. hr is the region that
700 // contains the object and it's passed optionally from callers who
701 // might already have it (no point in recalculating it).
702 inline void grayRoot(oop obj, size_t word_size,
703 uint worker_id, HeapRegion* hr = NULL);
704
705 // It iterates over the heap and for each object it comes across it
706 // will dump the contents of its reference fields, as well as
707 // liveness information for the object and its referents. The dump
708 // will be written to a file with the following name:
709 // G1PrintReachableBaseFile + "." + str.
710 // vo decides whether the prev (vo == UsePrevMarking), the next
711 // (vo == UseNextMarking) marking information, or the mark word
712 // (vo == UseMarkWord) will be used to determine the liveness of
713 // each object / referent.
714 // If all is true, all objects in the heap will be dumped, otherwise
715 // only the live ones. In the dump the following symbols / breviations
716 // are used:
717 // M : an explicitly live object (its bitmap bit is set)
718 // > : an implicitly live object (over tams)
719 // O : an object outside the G1 heap (typically: in the perm gen)
720 // NOT : a reference field whose referent is not live
721 // AND MARKED : indicates that an object is both explicitly and
722 // implicitly live (it should be one or the other, not both)
723 void print_reachable(const char* str,
724 VerifyOption vo, bool all) PRODUCT_RETURN;
725
726 // Clear the next marking bitmap (will be called concurrently).
727 void clearNextBitmap();
728
729 // These two do the work that needs to be done before and after the
730 // initial root checkpoint. Since this checkpoint can be done at two
731 // different points (i.e. an explicit pause or piggy-backed on a
732 // young collection), then it's nice to be able to easily share the
733 // pre/post code. It might be the case that we can put everything in
734 // the post method. TP
735 void checkpointRootsInitialPre();
736 void checkpointRootsInitialPost();
737
738 // Scan all the root regions and mark everything reachable from
739 // them.
740 void scanRootRegions();
741
742 // Scan a single root region and mark everything reachable from it.
743 void scanRootRegion(HeapRegion* hr, uint worker_id);
744
745 // Do concurrent phase of marking, to a tentative transitive closure.
746 void markFromRoots();
747
748 void checkpointRootsFinal(bool clear_all_soft_refs);
749 void checkpointRootsFinalWork();
750 void cleanup();
751 void completeCleanup();
752
753 // Mark in the previous bitmap. NB: this is usually read-only, so use
754 // this carefully!
755 inline void markPrev(oop p);
756
757 // Clears marks for all objects in the given range, for the prev,
758 // next, or both bitmaps. NB: the previous bitmap is usually
759 // read-only, so use this carefully!
760 void clearRangePrevBitmap(MemRegion mr);
761 void clearRangeNextBitmap(MemRegion mr);
762 void clearRangeBothBitmaps(MemRegion mr);
763
764 // Notify data structures that a GC has started.
765 void note_start_of_gc() {
766 _markStack.note_start_of_gc();
767 }
768
769 // Notify data structures that a GC is finished.
770 void note_end_of_gc() {
771 _markStack.note_end_of_gc();
772 }
773
774 // Verify that there are no CSet oops on the stacks (taskqueues /
775 // global mark stack), enqueued SATB buffers, per-thread SATB
776 // buffers, and fingers (global / per-task). The boolean parameters
777 // decide which of the above data structures to verify. If marking
778 // is not in progress, it's a no-op.
779 void verify_no_cset_oops(bool verify_stacks,
780 bool verify_enqueued_buffers,
781 bool verify_thread_buffers,
782 bool verify_fingers) PRODUCT_RETURN;
783
784 // It is called at the end of an evacuation pause during marking so
785 // that CM is notified of where the new end of the heap is. It
786 // doesn't do anything if concurrent_marking_in_progress() is false,
787 // unless the force parameter is true.
788 void update_g1_committed(bool force = false);
789
790 bool isMarked(oop p) const {
791 assert(p != NULL && p->is_oop(), "expected an oop");
792 HeapWord* addr = (HeapWord*)p;
793 assert(addr >= _nextMarkBitMap->startWord() ||
794 addr < _nextMarkBitMap->endWord(), "in a region");
795
796 return _nextMarkBitMap->isMarked(addr);
797 }
798
799 inline bool not_yet_marked(oop p) const;
800
801 // XXX Debug code
802 bool containing_card_is_marked(void* p);
803 bool containing_cards_are_marked(void* start, void* last);
804
805 bool isPrevMarked(oop p) const {
806 assert(p != NULL && p->is_oop(), "expected an oop");
807 HeapWord* addr = (HeapWord*)p;
808 assert(addr >= _prevMarkBitMap->startWord() ||
809 addr < _prevMarkBitMap->endWord(), "in a region");
810
811 return _prevMarkBitMap->isMarked(addr);
812 }
813
814 inline bool do_yield_check(uint worker_i = 0);
815 inline bool should_yield();
816
817 // Called to abort the marking cycle after a Full GC takes palce.
818 void abort();
819
820 // This prints the global/local fingers. It is used for debugging.
821 NOT_PRODUCT(void print_finger();)
822
823 void print_summary_info();
824
825 void print_worker_threads_on(outputStream* st) const;
826
827 // The following indicate whether a given verbose level has been
828 // set. Notice that anything above stats is conditional to
829 // _MARKING_VERBOSE_ having been set to 1
830 bool verbose_stats() {
831 return _verbose_level >= stats_verbose;
832 }
833 bool verbose_low() {
834 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
835 }
836 bool verbose_medium() {
837 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
838 }
839 bool verbose_high() {
840 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
841 }
842
843 // Liveness counting
844
845 // Utility routine to set an exclusive range of cards on the given
846 // card liveness bitmap
847 inline void set_card_bitmap_range(BitMap* card_bm,
848 BitMap::idx_t start_idx,
849 BitMap::idx_t end_idx,
850 bool is_par);
851
852 // Returns the card number of the bottom of the G1 heap.
853 // Used in biasing indices into accounting card bitmaps.
854 intptr_t heap_bottom_card_num() const {
855 return _heap_bottom_card_num;
856 }
857
858 // Returns the card bitmap for a given task or worker id.
859 BitMap* count_card_bitmap_for(uint worker_id) {
860 assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
861 assert(_count_card_bitmaps != NULL, "uninitialized");
862 BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
863 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
864 return task_card_bm;
865 }
866
867 // Returns the array containing the marked bytes for each region,
868 // for the given worker or task id.
869 size_t* count_marked_bytes_array_for(uint worker_id) {
870 assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
871 assert(_count_marked_bytes != NULL, "uninitialized");
872 size_t* marked_bytes_array = _count_marked_bytes[worker_id];
873 assert(marked_bytes_array != NULL, "uninitialized");
874 return marked_bytes_array;
875 }
876
877 // Returns the index in the liveness accounting card table bitmap
878 // for the given address
879 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
880
881 // Counts the size of the given memory region in the the given
882 // marked_bytes array slot for the given HeapRegion.
883 // Sets the bits in the given card bitmap that are associated with the
884 // cards that are spanned by the memory region.
885 inline void count_region(MemRegion mr, HeapRegion* hr,
886 size_t* marked_bytes_array,
887 BitMap* task_card_bm);
888
889 // Counts the given memory region in the task/worker counting
890 // data structures for the given worker id.
891 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
892
893 // Counts the given memory region in the task/worker counting
894 // data structures for the given worker id.
895 inline void count_region(MemRegion mr, uint worker_id);
896
897 // Counts the given object in the given task/worker counting
898 // data structures.
899 inline void count_object(oop obj, HeapRegion* hr,
900 size_t* marked_bytes_array,
901 BitMap* task_card_bm);
902
903 // Counts the given object in the task/worker counting data
904 // structures for the given worker id.
905 inline void count_object(oop obj, HeapRegion* hr, uint worker_id);
906
907 // Attempts to mark the given object and, if successful, counts
908 // the object in the given task/worker counting structures.
909 inline bool par_mark_and_count(oop obj, HeapRegion* hr,
910 size_t* marked_bytes_array,
911 BitMap* task_card_bm);
912
913 // Attempts to mark the given object and, if successful, counts
914 // the object in the task/worker counting structures for the
915 // given worker id.
916 inline bool par_mark_and_count(oop obj, size_t word_size,
917 HeapRegion* hr, uint worker_id);
918
919 // Attempts to mark the given object and, if successful, counts
920 // the object in the task/worker counting structures for the
921 // given worker id.
922 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id);
923
924 // Similar to the above routine but we don't know the heap region that
925 // contains the object to be marked/counted, which this routine looks up.
926 inline bool par_mark_and_count(oop obj, uint worker_id);
927
928 // Similar to the above routine but there are times when we cannot
929 // safely calculate the size of obj due to races and we, therefore,
930 // pass the size in as a parameter. It is the caller's reponsibility
931 // to ensure that the size passed in for obj is valid.
932 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id);
933
934 // Unconditionally mark the given object, and unconditinally count
935 // the object in the counting structures for worker id 0.
936 // Should *not* be called from parallel code.
937 inline bool mark_and_count(oop obj, HeapRegion* hr);
938
939 // Similar to the above routine but we don't know the heap region that
940 // contains the object to be marked/counted, which this routine looks up.
941 // Should *not* be called from parallel code.
942 inline bool mark_and_count(oop obj);
943
944 // Returns true if initialization was successfully completed.
945 bool completed_initialization() const {
946 return _completed_initialization;
947 }
948
949 protected:
950 // Clear all the per-task bitmaps and arrays used to store the
951 // counting data.
952 void clear_all_count_data();
953
954 // Aggregates the counting data for each worker/task
955 // that was constructed while marking. Also sets
956 // the amount of marked bytes for each region and
957 // the top at concurrent mark count.
958 void aggregate_count_data();
959
960 // Verification routine
961 void verify_count_data();
962 };
963
964 // A class representing a marking task.
965 class CMTask : public TerminatorTerminator {
966 private:
967 enum PrivateConstants {
968 // the regular clock call is called once the scanned words reaches
969 // this limit
970 words_scanned_period = 12*1024,
971 // the regular clock call is called once the number of visited
972 // references reaches this limit
973 refs_reached_period = 384,
974 // initial value for the hash seed, used in the work stealing code
975 init_hash_seed = 17,
976 // how many entries will be transferred between global stack and
977 // local queues
978 global_stack_transfer_size = 16
979 };
980
981 uint _worker_id;
982 G1CollectedHeap* _g1h;
983 ConcurrentMark* _cm;
984 CMBitMap* _nextMarkBitMap;
985 // the task queue of this task
986 CMTaskQueue* _task_queue;
987 private:
988 // the task queue set---needed for stealing
989 CMTaskQueueSet* _task_queues;
990 // indicates whether the task has been claimed---this is only for
991 // debugging purposes
992 bool _claimed;
993
994 // number of calls to this task
995 int _calls;
996
997 // when the virtual timer reaches this time, the marking step should
998 // exit
999 double _time_target_ms;
1000 // the start time of the current marking step
1001 double _start_time_ms;
1002
1003 // the oop closure used for iterations over oops
1004 G1CMOopClosure* _cm_oop_closure;
1005
1006 // the region this task is scanning, NULL if we're not scanning any
1007 HeapRegion* _curr_region;
1008 // the local finger of this task, NULL if we're not scanning a region
1009 HeapWord* _finger;
1010 // limit of the region this task is scanning, NULL if we're not scanning one
1011 HeapWord* _region_limit;
1012
1013 // the number of words this task has scanned
1014 size_t _words_scanned;
1015 // When _words_scanned reaches this limit, the regular clock is
1016 // called. Notice that this might be decreased under certain
1017 // circumstances (i.e. when we believe that we did an expensive
1018 // operation).
1019 size_t _words_scanned_limit;
1020 // the initial value of _words_scanned_limit (i.e. what it was
1021 // before it was decreased).
1022 size_t _real_words_scanned_limit;
1023
1024 // the number of references this task has visited
1025 size_t _refs_reached;
1026 // When _refs_reached reaches this limit, the regular clock is
1027 // called. Notice this this might be decreased under certain
1028 // circumstances (i.e. when we believe that we did an expensive
1029 // operation).
1030 size_t _refs_reached_limit;
1031 // the initial value of _refs_reached_limit (i.e. what it was before
1032 // it was decreased).
1033 size_t _real_refs_reached_limit;
1034
1035 // used by the work stealing stuff
1036 int _hash_seed;
1037 // if this is true, then the task has aborted for some reason
1038 bool _has_aborted;
1039 // set when the task aborts because it has met its time quota
1040 bool _has_timed_out;
1041 // true when we're draining SATB buffers; this avoids the task
1042 // aborting due to SATB buffers being available (as we're already
1043 // dealing with them)
1044 bool _draining_satb_buffers;
1045
1046 // number sequence of past step times
1047 NumberSeq _step_times_ms;
1048 // elapsed time of this task
1049 double _elapsed_time_ms;
1050 // termination time of this task
1051 double _termination_time_ms;
1052 // when this task got into the termination protocol
1053 double _termination_start_time_ms;
1054
1055 // true when the task is during a concurrent phase, false when it is
1056 // in the remark phase (so, in the latter case, we do not have to
1057 // check all the things that we have to check during the concurrent
1058 // phase, i.e. SATB buffer availability...)
1059 bool _concurrent;
1060
1061 TruncatedSeq _marking_step_diffs_ms;
1062
1063 // Counting data structures. Embedding the task's marked_bytes_array
1064 // and card bitmap into the actual task saves having to go through
1065 // the ConcurrentMark object.
1066 size_t* _marked_bytes_array;
1067 BitMap* _card_bm;
1068
1069 // LOTS of statistics related with this task
1070 #if _MARKING_STATS_
1071 NumberSeq _all_clock_intervals_ms;
1072 double _interval_start_time_ms;
1073
1074 int _aborted;
1075 int _aborted_overflow;
1076 int _aborted_cm_aborted;
1077 int _aborted_yield;
1078 int _aborted_timed_out;
1079 int _aborted_satb;
1080 int _aborted_termination;
1081
1082 int _steal_attempts;
1083 int _steals;
1084
1085 int _clock_due_to_marking;
1086 int _clock_due_to_scanning;
1087
1088 int _local_pushes;
1089 int _local_pops;
1090 int _local_max_size;
1091 int _objs_scanned;
1092
1093 int _global_pushes;
1094 int _global_pops;
1095 int _global_max_size;
1096
1097 int _global_transfers_to;
1098 int _global_transfers_from;
1099
1100 int _regions_claimed;
1101 int _objs_found_on_bitmap;
1102
1103 int _satb_buffers_processed;
1104 #endif // _MARKING_STATS_
1105
1106 // it updates the local fields after this task has claimed
1107 // a new region to scan
1108 void setup_for_region(HeapRegion* hr);
1109 // it brings up-to-date the limit of the region
1110 void update_region_limit();
1111
1112 // called when either the words scanned or the refs visited limit
1113 // has been reached
1114 void reached_limit();
1115 // recalculates the words scanned and refs visited limits
1116 void recalculate_limits();
1117 // decreases the words scanned and refs visited limits when we reach
1118 // an expensive operation
1119 void decrease_limits();
1120 // it checks whether the words scanned or refs visited reached their
1121 // respective limit and calls reached_limit() if they have
1122 void check_limits() {
1123 if (_words_scanned >= _words_scanned_limit ||
1124 _refs_reached >= _refs_reached_limit) {
1125 reached_limit();
1126 }
1127 }
1128 // this is supposed to be called regularly during a marking step as
1129 // it checks a bunch of conditions that might cause the marking step
1130 // to abort
1131 void regular_clock_call();
1132 bool concurrent() { return _concurrent; }
1133
1134 public:
1135 // It resets the task; it should be called right at the beginning of
1136 // a marking phase.
1137 void reset(CMBitMap* _nextMarkBitMap);
1138 // it clears all the fields that correspond to a claimed region.
1139 void clear_region_fields();
1140
1141 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
1142
1143 // The main method of this class which performs a marking step
1144 // trying not to exceed the given duration. However, it might exit
1145 // prematurely, according to some conditions (i.e. SATB buffers are
1146 // available for processing).
1147 void do_marking_step(double target_ms, bool do_stealing, bool do_termination);
1148
1149 // These two calls start and stop the timer
1150 void record_start_time() {
1151 _elapsed_time_ms = os::elapsedTime() * 1000.0;
1152 }
1153 void record_end_time() {
1154 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
1155 }
1156
1157 // returns the worker ID associated with this task.
1158 uint worker_id() { return _worker_id; }
1159
1160 // From TerminatorTerminator. It determines whether this task should
1161 // exit the termination protocol after it's entered it.
1162 virtual bool should_exit_termination();
1163
1164 // Resets the local region fields after a task has finished scanning a
1165 // region; or when they have become stale as a result of the region
1166 // being evacuated.
1167 void giveup_current_region();
1168
1169 HeapWord* finger() { return _finger; }
1170
1171 bool has_aborted() { return _has_aborted; }
1172 void set_has_aborted() { _has_aborted = true; }
1173 void clear_has_aborted() { _has_aborted = false; }
1174 bool has_timed_out() { return _has_timed_out; }
1175 bool claimed() { return _claimed; }
1176
1177 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
1178
1179 // It grays the object by marking it and, if necessary, pushing it
1180 // on the local queue
1181 inline void deal_with_reference(oop obj);
1182
1183 // It scans an object and visits its children.
1184 void scan_object(oop obj);
1185
1186 // It pushes an object on the local queue.
1187 inline void push(oop obj);
1188
1189 // These two move entries to/from the global stack.
1190 void move_entries_to_global_stack();
1191 void get_entries_from_global_stack();
1192
1193 // It pops and scans objects from the local queue. If partially is
1194 // true, then it stops when the queue size is of a given limit. If
1195 // partially is false, then it stops when the queue is empty.
1196 void drain_local_queue(bool partially);
1197 // It moves entries from the global stack to the local queue and
1198 // drains the local queue. If partially is true, then it stops when
1199 // both the global stack and the local queue reach a given size. If
1200 // partially if false, it tries to empty them totally.
1201 void drain_global_stack(bool partially);
1202 // It keeps picking SATB buffers and processing them until no SATB
1203 // buffers are available.
1204 void drain_satb_buffers();
1205
1206 // moves the local finger to a new location
1207 inline void move_finger_to(HeapWord* new_finger) {
1208 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
1209 _finger = new_finger;
1210 }
1211
1212 CMTask(uint worker_id, ConcurrentMark *cm,
1213 size_t* marked_bytes, BitMap* card_bm,
1214 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1215
1216 // it prints statistics associated with this task
1217 void print_stats();
1218
1219 #if _MARKING_STATS_
1220 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1221 #endif // _MARKING_STATS_
1222 };
1223
1224 // Class that's used to to print out per-region liveness
1225 // information. It's currently used at the end of marking and also
1226 // after we sort the old regions at the end of the cleanup operation.
1227 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
1228 private:
1229 outputStream* _out;
1230
1231 // Accumulators for these values.
1232 size_t _total_used_bytes;
1233 size_t _total_capacity_bytes;
1234 size_t _total_prev_live_bytes;
1235 size_t _total_next_live_bytes;
1236
1237 // These are set up when we come across a "stars humongous" region
1238 // (as this is where most of this information is stored, not in the
1239 // subsequent "continues humongous" regions). After that, for every
1240 // region in a given humongous region series we deduce the right
1241 // values for it by simply subtracting the appropriate amount from
1242 // these fields. All these values should reach 0 after we've visited
1243 // the last region in the series.
1244 size_t _hum_used_bytes;
1245 size_t _hum_capacity_bytes;
1246 size_t _hum_prev_live_bytes;
1247 size_t _hum_next_live_bytes;
1248
1249 static double perc(size_t val, size_t total) {
1250 if (total == 0) {
1251 return 0.0;
1252 } else {
1253 return 100.0 * ((double) val / (double) total);
1254 }
1255 }
1256
1257 static double bytes_to_mb(size_t val) {
1258 return (double) val / (double) M;
1259 }
1260
1261 // See the .cpp file.
1262 size_t get_hum_bytes(size_t* hum_bytes);
1263 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1264 size_t* prev_live_bytes, size_t* next_live_bytes);
1265
1266 public:
1267 // The header and footer are printed in the constructor and
1268 // destructor respectively.
1269 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
1270 virtual bool doHeapRegion(HeapRegion* r);
1271 ~G1PrintRegionLivenessInfoClosure();
1272 };
1273
1274 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP