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/heapRegionSet.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 bool do_object_b(oop obj);
48 };
49
50 // A generic CM bit map. This is essentially a wrapper around the BitMap
51 // class, with one bit per (1<<_shifter) HeapWords.
52
53 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
54 protected:
55 HeapWord* _bmStartWord; // base address of range covered by map
56 size_t _bmWordSize; // map size (in #HeapWords covered)
57 const int _shifter; // map to char or bit
58 VirtualSpace _virtual_space; // underlying the bit map
59 BitMap _bm; // the bit map itself
60
61 public:
62 // constructor
63 CMBitMapRO(int shifter);
64
65 enum { do_yield = true };
66
67 // inquiries
68 HeapWord* startWord() const { return _bmStartWord; }
69 size_t sizeInWords() const { return _bmWordSize; }
70 // the following is one past the last word in space
71 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
72
73 // read marks
74
75 bool isMarked(HeapWord* addr) const {
76 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
77 "outside underlying space?");
78 return _bm.at(heapWordToOffset(addr));
79 }
80
81 // iteration
82 inline bool iterate(BitMapClosure* cl, MemRegion mr);
83 inline bool iterate(BitMapClosure* cl);
84
85 // Return the address corresponding to the next marked bit at or after
86 // "addr", and before "limit", if "limit" is non-NULL. If there is no
87 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
88 HeapWord* getNextMarkedWordAddress(HeapWord* addr,
89 HeapWord* limit = NULL) const;
90 // Return the address corresponding to the next unmarked bit at or after
91 // "addr", and before "limit", if "limit" is non-NULL. If there is no
92 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
93 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr,
94 HeapWord* limit = NULL) const;
95
96 // conversion utilities
97 HeapWord* offsetToHeapWord(size_t offset) const {
98 return _bmStartWord + (offset << _shifter);
99 }
100 size_t heapWordToOffset(HeapWord* addr) const {
101 return pointer_delta(addr, _bmStartWord) >> _shifter;
102 }
103 int heapWordDiffToOffsetDiff(size_t diff) const;
104
105 // The argument addr should be the start address of a valid object
106 HeapWord* nextObject(HeapWord* addr) {
107 oop obj = (oop) addr;
108 HeapWord* res = addr + obj->size();
109 assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
110 return res;
111 }
112
113 void print_on_error(outputStream* st, const char* prefix) const;
114
115 // debugging
116 NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
117 };
118
119 class CMBitMap : public CMBitMapRO {
120
121 public:
122 // constructor
123 CMBitMap(int shifter) :
124 CMBitMapRO(shifter) {}
125
126 // Allocates the back store for the marking bitmap
127 bool allocate(ReservedSpace heap_rs);
128
129 // write marks
130 void mark(HeapWord* addr) {
131 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
132 "outside underlying space?");
133 _bm.set_bit(heapWordToOffset(addr));
134 }
135 void clear(HeapWord* addr) {
136 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
137 "outside underlying space?");
138 _bm.clear_bit(heapWordToOffset(addr));
139 }
140 bool parMark(HeapWord* addr) {
141 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
142 "outside underlying space?");
143 return _bm.par_set_bit(heapWordToOffset(addr));
144 }
145 bool parClear(HeapWord* addr) {
146 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
147 "outside underlying space?");
148 return _bm.par_clear_bit(heapWordToOffset(addr));
149 }
150 void markRange(MemRegion mr);
151 void clearAll();
152 void clearRange(MemRegion mr);
153
154 // Starting at the bit corresponding to "addr" (inclusive), find the next
155 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
156 // the end of this run (stopping at "end_addr"). Return the MemRegion
157 // covering from the start of the region corresponding to the first bit
158 // of the run to the end of the region corresponding to the last bit of
159 // the run. If there is no "1" bit at or after "addr", return an empty
160 // MemRegion.
161 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
162 };
163
164 // Represents a marking stack used by ConcurrentMarking in the G1 collector.
165 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
166 VirtualSpace _virtual_space; // Underlying backing store for actual stack
167 ConcurrentMark* _cm;
168 oop* _base; // bottom of stack
169 jint _index; // one more than last occupied index
170 jint _capacity; // max #elements
171 jint _saved_index; // value of _index saved at start of GC
172 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
173
174 bool _overflow;
175 bool _should_expand;
176 DEBUG_ONLY(bool _drain_in_progress;)
177 DEBUG_ONLY(bool _drain_in_progress_yields;)
178
179 public:
180 CMMarkStack(ConcurrentMark* cm);
181 ~CMMarkStack();
182
183 #ifndef PRODUCT
184 jint max_depth() const {
185 return _max_depth;
186 }
187 #endif
188
189 bool allocate(size_t capacity);
190
191 oop pop() {
192 if (!isEmpty()) {
193 return _base[--_index] ;
194 }
195 return NULL;
196 }
197
198 // If overflow happens, don't do the push, and record the overflow.
199 // *Requires* that "ptr" is already marked.
200 void push(oop ptr) {
201 if (isFull()) {
202 // Record overflow.
203 _overflow = true;
204 return;
205 } else {
206 _base[_index++] = ptr;
207 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
208 }
209 }
210 // Non-block impl. Note: concurrency is allowed only with other
211 // "par_push" operations, not with "pop" or "drain". We would need
212 // parallel versions of them if such concurrency was desired.
213 void par_push(oop ptr);
214
215 // Pushes the first "n" elements of "ptr_arr" on the stack.
216 // Non-block impl. Note: concurrency is allowed only with other
217 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
218 void par_adjoin_arr(oop* ptr_arr, int n);
219
220 // Pushes the first "n" elements of "ptr_arr" on the stack.
221 // Locking impl: concurrency is allowed only with
222 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
223 // locking strategy.
224 void par_push_arr(oop* ptr_arr, int n);
225
226 // If returns false, the array was empty. Otherwise, removes up to "max"
227 // elements from the stack, and transfers them to "ptr_arr" in an
228 // unspecified order. The actual number transferred is given in "n" ("n
229 // == 0" is deliberately redundant with the return value.) Locking impl:
230 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
231 // operations, which use the same locking strategy.
232 bool par_pop_arr(oop* ptr_arr, int max, int* n);
233
234 // Drain the mark stack, applying the given closure to all fields of
235 // objects on the stack. (That is, continue until the stack is empty,
236 // even if closure applications add entries to the stack.) The "bm"
237 // argument, if non-null, may be used to verify that only marked objects
238 // are on the mark stack. If "yield_after" is "true", then the
239 // concurrent marker performing the drain offers to yield after
240 // processing each object. If a yield occurs, stops the drain operation
241 // and returns false. Otherwise, returns true.
242 template<class OopClosureClass>
243 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
244
245 bool isEmpty() { return _index == 0; }
246 bool isFull() { return _index == _capacity; }
247 int maxElems() { return _capacity; }
248
249 bool overflow() { return _overflow; }
250 void clear_overflow() { _overflow = false; }
251
252 bool should_expand() const { return _should_expand; }
253 void set_should_expand();
254
255 // Expand the stack, typically in response to an overflow condition
256 void expand();
257
258 int size() { return _index; }
259
260 void setEmpty() { _index = 0; clear_overflow(); }
261
262 // Record the current index.
263 void note_start_of_gc();
264
265 // Make sure that we have not added any entries to the stack during GC.
266 void note_end_of_gc();
267
268 // iterate over the oops in the mark stack, up to the bound recorded via
269 // the call above.
270 void oops_do(OopClosure* f);
271 };
272
273 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
274 private:
275 #ifndef PRODUCT
276 uintx _num_remaining;
277 bool _force;
278 #endif // !defined(PRODUCT)
279
280 public:
281 void init() PRODUCT_RETURN;
282 void update() PRODUCT_RETURN;
283 bool should_force() PRODUCT_RETURN_( return false; );
284 };
285
286 // this will enable a variety of different statistics per GC task
287 #define _MARKING_STATS_ 0
288 // this will enable the higher verbose levels
289 #define _MARKING_VERBOSE_ 0
290
291 #if _MARKING_STATS_
292 #define statsOnly(statement) \
293 do { \
294 statement ; \
295 } while (0)
296 #else // _MARKING_STATS_
297 #define statsOnly(statement) \
298 do { \
299 } while (0)
300 #endif // _MARKING_STATS_
301
302 typedef enum {
303 no_verbose = 0, // verbose turned off
304 stats_verbose, // only prints stats at the end of marking
305 low_verbose, // low verbose, mostly per region and per major event
306 medium_verbose, // a bit more detailed than low
307 high_verbose // per object verbose
308 } CMVerboseLevel;
309
310 class YoungList;
311
312 // Root Regions are regions that are not empty at the beginning of a
313 // marking cycle and which we might collect during an evacuation pause
314 // while the cycle is active. Given that, during evacuation pauses, we
315 // do not copy objects that are explicitly marked, what we have to do
316 // for the root regions is to scan them and mark all objects reachable
317 // from them. According to the SATB assumptions, we only need to visit
318 // each object once during marking. So, as long as we finish this scan
319 // before the next evacuation pause, we can copy the objects from the
320 // root regions without having to mark them or do anything else to them.
321 //
322 // Currently, we only support root region scanning once (at the start
323 // of the marking cycle) and the root regions are all the survivor
324 // regions populated during the initial-mark pause.
325 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
326 private:
327 YoungList* _young_list;
328 ConcurrentMark* _cm;
329
330 volatile bool _scan_in_progress;
331 volatile bool _should_abort;
332 HeapRegion* volatile _next_survivor;
333
334 public:
335 CMRootRegions();
336 // We actually do most of the initialization in this method.
337 void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
338
339 // Reset the claiming / scanning of the root regions.
340 void prepare_for_scan();
341
342 // Forces get_next() to return NULL so that the iteration aborts early.
343 void abort() { _should_abort = true; }
344
345 // Return true if the CM thread are actively scanning root regions,
346 // false otherwise.
347 bool scan_in_progress() { return _scan_in_progress; }
348
349 // Claim the next root region to scan atomically, or return NULL if
350 // all have been claimed.
351 HeapRegion* claim_next();
352
353 // Flag that we're done with root region scanning and notify anyone
354 // who's waiting on it. If aborted is false, assume that all regions
355 // have been claimed.
356 void scan_finished();
357
358 // If CM threads are still scanning root regions, wait until they
359 // are done. Return true if we had to wait, false otherwise.
360 bool wait_until_scan_finished();
361 };
362
363 class ConcurrentMarkThread;
364
365 class ConcurrentMark: public CHeapObj<mtGC> {
366 friend class CMMarkStack;
367 friend class ConcurrentMarkThread;
368 friend class CMTask;
369 friend class CMBitMapClosure;
370 friend class CMGlobalObjectClosure;
371 friend class CMRemarkTask;
372 friend class CMConcurrentMarkingTask;
373 friend class G1ParNoteEndTask;
374 friend class CalcLiveObjectsClosure;
375 friend class G1CMRefProcTaskProxy;
376 friend class G1CMRefProcTaskExecutor;
377 friend class G1CMKeepAliveAndDrainClosure;
378 friend class G1CMDrainMarkingStackClosure;
379
380 protected:
381 ConcurrentMarkThread* _cmThread; // The thread doing the work
382 G1CollectedHeap* _g1h; // The heap
383 uint _parallel_marking_threads; // The number of marking
384 // threads we're using
385 uint _max_parallel_marking_threads; // Max number of marking
386 // threads we'll ever use
387 double _sleep_factor; // How much we have to sleep, with
388 // respect to the work we just did, to
389 // meet the marking overhead goal
390 double _marking_task_overhead; // Marking target overhead for
391 // a single task
392
393 // Same as the two above, but for the cleanup task
394 double _cleanup_sleep_factor;
395 double _cleanup_task_overhead;
396
397 FreeRegionList _cleanup_list;
398
399 // Concurrent marking support structures
400 CMBitMap _markBitMap1;
401 CMBitMap _markBitMap2;
402 CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap
403 CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
404
405 BitMap _region_bm;
406 BitMap _card_bm;
407
408 // Heap bounds
409 HeapWord* _heap_start;
410 HeapWord* _heap_end;
411
412 // Root region tracking and claiming
413 CMRootRegions _root_regions;
414
415 // For gray objects
416 CMMarkStack _markStack; // Grey objects behind global finger
417 HeapWord* volatile _finger; // The global finger, region aligned,
418 // always points to the end of the
419 // last claimed region
420
421 // Marking tasks
422 uint _max_worker_id;// Maximum worker id
423 uint _active_tasks; // Task num currently active
424 CMTask** _tasks; // Task queue array (max_worker_id len)
425 CMTaskQueueSet* _task_queues; // Task queue set
426 ParallelTaskTerminator _terminator; // For termination
427
428 // Two sync barriers that are used to synchronize tasks when an
429 // overflow occurs. The algorithm is the following. All tasks enter
430 // the first one to ensure that they have all stopped manipulating
431 // the global data structures. After they exit it, they re-initialize
432 // their data structures and task 0 re-initializes the global data
433 // structures. Then, they enter the second sync barrier. This
434 // ensure, that no task starts doing work before all data
435 // structures (local and global) have been re-initialized. When they
436 // exit it, they are free to start working again.
437 WorkGangBarrierSync _first_overflow_barrier_sync;
438 WorkGangBarrierSync _second_overflow_barrier_sync;
439
440 // This is set by any task, when an overflow on the global data
441 // structures is detected
442 volatile bool _has_overflown;
443 // True: marking is concurrent, false: we're in remark
444 volatile bool _concurrent;
445 // Set at the end of a Full GC so that marking aborts
446 volatile bool _has_aborted;
447
448 // Used when remark aborts due to an overflow to indicate that
449 // another concurrent marking phase should start
450 volatile bool _restart_for_overflow;
451
452 // This is true from the very start of concurrent marking until the
453 // point when all the tasks complete their work. It is really used
454 // to determine the points between the end of concurrent marking and
455 // time of remark.
456 volatile bool _concurrent_marking_in_progress;
457
458 // Verbose level
459 CMVerboseLevel _verbose_level;
460
461 // All of these times are in ms
462 NumberSeq _init_times;
463 NumberSeq _remark_times;
464 NumberSeq _remark_mark_times;
465 NumberSeq _remark_weak_ref_times;
466 NumberSeq _cleanup_times;
467 double _total_counting_time;
468 double _total_rs_scrub_time;
469
470 double* _accum_task_vtime; // Accumulated task vtime
471
472 FlexibleWorkGang* _parallel_workers;
473
474 ForceOverflowSettings _force_overflow_conc;
475 ForceOverflowSettings _force_overflow_stw;
476
477 void weakRefsWork(bool clear_all_soft_refs);
478
479 void swapMarkBitMaps();
480
481 // It resets the global marking data structures, as well as the
482 // task local ones; should be called during initial mark.
483 void reset();
484
485 // Resets all the marking data structures. Called when we have to restart
486 // marking or when marking completes (via set_non_marking_state below).
487 void reset_marking_state(bool clear_overflow = true);
488
489 // We do this after we're done with marking so that the marking data
490 // structures are initialized to a sensible and predictable state.
491 void set_non_marking_state();
492
493 // Called to indicate how many threads are currently active.
494 void set_concurrency(uint active_tasks);
495
496 // It should be called to indicate which phase we're in (concurrent
497 // mark or remark) and how many threads are currently active.
498 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
499
500 // Prints all gathered CM-related statistics
501 void print_stats();
502
503 bool cleanup_list_is_empty() {
504 return _cleanup_list.is_empty();
505 }
506
507 // Accessor methods
508 uint parallel_marking_threads() const { return _parallel_marking_threads; }
509 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
510 double sleep_factor() { return _sleep_factor; }
511 double marking_task_overhead() { return _marking_task_overhead;}
512 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
513 double cleanup_task_overhead() { return _cleanup_task_overhead;}
514
515 bool use_parallel_marking_threads() const {
516 assert(parallel_marking_threads() <=
517 max_parallel_marking_threads(), "sanity");
518 assert((_parallel_workers == NULL && parallel_marking_threads() == 0) ||
519 parallel_marking_threads() > 0,
520 "parallel workers not set up correctly");
521 return _parallel_workers != NULL;
522 }
523
524 HeapWord* finger() { return _finger; }
525 bool concurrent() { return _concurrent; }
526 uint active_tasks() { return _active_tasks; }
527 ParallelTaskTerminator* terminator() { return &_terminator; }
528
529 // It claims the next available region to be scanned by a marking
530 // task/thread. It might return NULL if the next region is empty or
531 // we have run out of regions. In the latter case, out_of_regions()
532 // determines whether we've really run out of regions or the task
533 // should call claim_region() again. This might seem a bit
534 // awkward. Originally, the code was written so that claim_region()
535 // either successfully returned with a non-empty region or there
536 // were no more regions to be claimed. The problem with this was
537 // that, in certain circumstances, it iterated over large chunks of
538 // the heap finding only empty regions and, while it was working, it
539 // was preventing the calling task to call its regular clock
540 // method. So, this way, each task will spend very little time in
541 // claim_region() and is allowed to call the regular clock method
542 // frequently.
543 HeapRegion* claim_region(uint worker_id);
544
545 // It determines whether we've run out of regions to scan. Note that
546 // the finger can point past the heap end in case the heap was expanded
547 // to satisfy an allocation without doing a GC. This is fine, because all
548 // objects in those regions will be considered live anyway because of
549 // SATB guarantees (i.e. their TAMS will be equal to bottom).
550 bool out_of_regions() { return _finger >= _heap_end; }
551
552 // Returns the task with the given id
553 CMTask* task(int id) {
554 assert(0 <= id && id < (int) _active_tasks,
555 "task id not within active bounds");
556 return _tasks[id];
557 }
558
559 // Returns the task queue with the given id
560 CMTaskQueue* task_queue(int id) {
561 assert(0 <= id && id < (int) _active_tasks,
562 "task queue id not within active bounds");
563 return (CMTaskQueue*) _task_queues->queue(id);
564 }
565
566 // Returns the task queue set
567 CMTaskQueueSet* task_queues() { return _task_queues; }
568
569 // Access / manipulation of the overflow flag which is set to
570 // indicate that the global stack has overflown
571 bool has_overflown() { return _has_overflown; }
572 void set_has_overflown() { _has_overflown = true; }
573 void clear_has_overflown() { _has_overflown = false; }
574 bool restart_for_overflow() { return _restart_for_overflow; }
575
576 // Methods to enter the two overflow sync barriers
577 void enter_first_sync_barrier(uint worker_id);
578 void enter_second_sync_barrier(uint worker_id);
579
580 ForceOverflowSettings* force_overflow_conc() {
581 return &_force_overflow_conc;
582 }
583
584 ForceOverflowSettings* force_overflow_stw() {
585 return &_force_overflow_stw;
586 }
587
588 ForceOverflowSettings* force_overflow() {
589 if (concurrent()) {
590 return force_overflow_conc();
591 } else {
592 return force_overflow_stw();
593 }
594 }
595
596 // Live Data Counting data structures...
597 // These data structures are initialized at the start of
598 // marking. They are written to while marking is active.
599 // They are aggregated during remark; the aggregated values
600 // are then used to populate the _region_bm, _card_bm, and
601 // the total live bytes, which are then subsequently updated
602 // during cleanup.
603
604 // An array of bitmaps (one bit map per task). Each bitmap
605 // is used to record the cards spanned by the live objects
606 // marked by that task/worker.
607 BitMap* _count_card_bitmaps;
608
609 // Used to record the number of marked live bytes
610 // (for each region, by worker thread).
611 size_t** _count_marked_bytes;
612
613 // Card index of the bottom of the G1 heap. Used for biasing indices into
614 // the card bitmaps.
615 intptr_t _heap_bottom_card_num;
616
617 // Set to true when initialization is complete
618 bool _completed_initialization;
619
620 public:
621 // Manipulation of the global mark stack.
622 // Notice that the first mark_stack_push is CAS-based, whereas the
623 // two below are Mutex-based. This is OK since the first one is only
624 // called during evacuation pauses and doesn't compete with the
625 // other two (which are called by the marking tasks during
626 // concurrent marking or remark).
627 bool mark_stack_push(oop p) {
628 _markStack.par_push(p);
629 if (_markStack.overflow()) {
630 set_has_overflown();
631 return false;
632 }
633 return true;
634 }
635 bool mark_stack_push(oop* arr, int n) {
636 _markStack.par_push_arr(arr, n);
637 if (_markStack.overflow()) {
638 set_has_overflown();
639 return false;
640 }
641 return true;
642 }
643 void mark_stack_pop(oop* arr, int max, int* n) {
644 _markStack.par_pop_arr(arr, max, n);
645 }
646 size_t mark_stack_size() { return _markStack.size(); }
647 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
648 bool mark_stack_overflow() { return _markStack.overflow(); }
649 bool mark_stack_empty() { return _markStack.isEmpty(); }
650
651 CMRootRegions* root_regions() { return &_root_regions; }
652
653 bool concurrent_marking_in_progress() {
654 return _concurrent_marking_in_progress;
655 }
656 void set_concurrent_marking_in_progress() {
657 _concurrent_marking_in_progress = true;
658 }
659 void clear_concurrent_marking_in_progress() {
660 _concurrent_marking_in_progress = false;
661 }
662
663 void update_accum_task_vtime(int i, double vtime) {
664 _accum_task_vtime[i] += vtime;
665 }
666
667 double all_task_accum_vtime() {
668 double ret = 0.0;
669 for (uint i = 0; i < _max_worker_id; ++i)
670 ret += _accum_task_vtime[i];
671 return ret;
672 }
673
674 // Attempts to steal an object from the task queues of other tasks
675 bool try_stealing(uint worker_id, int* hash_seed, oop& obj) {
676 return _task_queues->steal(worker_id, hash_seed, obj);
677 }
678
679 ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs);
680 ~ConcurrentMark();
681
682 ConcurrentMarkThread* cmThread() { return _cmThread; }
683
684 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
685 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
686
687 // Returns the number of GC threads to be used in a concurrent
688 // phase based on the number of GC threads being used in a STW
689 // phase.
690 uint scale_parallel_threads(uint n_par_threads);
691
692 // Calculates the number of GC threads to be used in a concurrent phase.
693 uint calc_parallel_marking_threads();
694
695 // The following three are interaction between CM and
696 // G1CollectedHeap
697
698 // This notifies CM that a root during initial-mark needs to be
699 // grayed. It is MT-safe. word_size is the size of the object in
700 // words. It is passed explicitly as sometimes we cannot calculate
701 // it from the given object because it might be in an inconsistent
702 // state (e.g., in to-space and being copied). So the caller is
703 // responsible for dealing with this issue (e.g., get the size from
704 // the from-space image when the to-space image might be
705 // inconsistent) and always passing the size. hr is the region that
706 // contains the object and it's passed optionally from callers who
707 // might already have it (no point in recalculating it).
708 inline void grayRoot(oop obj, size_t word_size,
709 uint worker_id, HeapRegion* hr = NULL);
710
711 // It iterates over the heap and for each object it comes across it
712 // will dump the contents of its reference fields, as well as
713 // liveness information for the object and its referents. The dump
714 // will be written to a file with the following name:
715 // G1PrintReachableBaseFile + "." + str.
716 // vo decides whether the prev (vo == UsePrevMarking), the next
717 // (vo == UseNextMarking) marking information, or the mark word
718 // (vo == UseMarkWord) will be used to determine the liveness of
719 // each object / referent.
720 // If all is true, all objects in the heap will be dumped, otherwise
721 // only the live ones. In the dump the following symbols / breviations
722 // are used:
723 // M : an explicitly live object (its bitmap bit is set)
724 // > : an implicitly live object (over tams)
725 // O : an object outside the G1 heap (typically: in the perm gen)
726 // NOT : a reference field whose referent is not live
727 // AND MARKED : indicates that an object is both explicitly and
728 // implicitly live (it should be one or the other, not both)
729 void print_reachable(const char* str,
730 VerifyOption vo, bool all) PRODUCT_RETURN;
731
732 // Clear the next marking bitmap (will be called concurrently).
733 void clearNextBitmap();
734
735 // These two do the work that needs to be done before and after the
736 // initial root checkpoint. Since this checkpoint can be done at two
737 // different points (i.e. an explicit pause or piggy-backed on a
738 // young collection), then it's nice to be able to easily share the
739 // pre/post code. It might be the case that we can put everything in
740 // the post method. TP
741 void checkpointRootsInitialPre();
742 void checkpointRootsInitialPost();
743
744 // Scan all the root regions and mark everything reachable from
745 // them.
746 void scanRootRegions();
747
748 // Scan a single root region and mark everything reachable from it.
749 void scanRootRegion(HeapRegion* hr, uint worker_id);
750
751 // Do concurrent phase of marking, to a tentative transitive closure.
752 void markFromRoots();
753
754 void checkpointRootsFinal(bool clear_all_soft_refs);
755 void checkpointRootsFinalWork();
756 void cleanup();
757 void completeCleanup();
758
759 // Mark in the previous bitmap. NB: this is usually read-only, so use
760 // this carefully!
761 inline void markPrev(oop p);
762
763 // Clears marks for all objects in the given range, for the prev,
764 // next, or both bitmaps. NB: the previous bitmap is usually
765 // read-only, so use this carefully!
766 void clearRangePrevBitmap(MemRegion mr);
767 void clearRangeNextBitmap(MemRegion mr);
768 void clearRangeBothBitmaps(MemRegion mr);
769
770 // Notify data structures that a GC has started.
771 void note_start_of_gc() {
772 _markStack.note_start_of_gc();
773 }
774
775 // Notify data structures that a GC is finished.
776 void note_end_of_gc() {
777 _markStack.note_end_of_gc();
778 }
779
780 // Verify that there are no CSet oops on the stacks (taskqueues /
781 // global mark stack), enqueued SATB buffers, per-thread SATB
782 // buffers, and fingers (global / per-task). The boolean parameters
783 // decide which of the above data structures to verify. If marking
784 // is not in progress, it's a no-op.
785 void verify_no_cset_oops(bool verify_stacks,
786 bool verify_enqueued_buffers,
787 bool verify_thread_buffers,
788 bool verify_fingers) PRODUCT_RETURN;
789
790 // It is called at the end of an evacuation pause during marking so
791 // that CM is notified of where the new end of the heap is. It
792 // doesn't do anything if concurrent_marking_in_progress() is false,
793 // unless the force parameter is true.
794 void update_g1_committed(bool force = false);
795
796 bool isMarked(oop p) const {
797 assert(p != NULL && p->is_oop(), "expected an oop");
798 HeapWord* addr = (HeapWord*)p;
799 assert(addr >= _nextMarkBitMap->startWord() ||
800 addr < _nextMarkBitMap->endWord(), "in a region");
801
802 return _nextMarkBitMap->isMarked(addr);
803 }
804
805 inline bool not_yet_marked(oop p) const;
806
807 // XXX Debug code
808 bool containing_card_is_marked(void* p);
809 bool containing_cards_are_marked(void* start, void* last);
810
811 bool isPrevMarked(oop p) const {
812 assert(p != NULL && p->is_oop(), "expected an oop");
813 HeapWord* addr = (HeapWord*)p;
814 assert(addr >= _prevMarkBitMap->startWord() ||
815 addr < _prevMarkBitMap->endWord(), "in a region");
816
817 return _prevMarkBitMap->isMarked(addr);
818 }
819
820 inline bool do_yield_check(uint worker_i = 0);
821
822 // Called to abort the marking cycle after a Full GC takes place.
823 void abort();
824
825 bool has_aborted() { return _has_aborted; }
826
827 // This prints the global/local fingers. It is used for debugging.
828 NOT_PRODUCT(void print_finger();)
829
830 void print_summary_info();
831
832 void print_worker_threads_on(outputStream* st) const;
833
834 void print_on_error(outputStream* st) const;
835
836 // The following indicate whether a given verbose level has been
837 // set. Notice that anything above stats is conditional to
838 // _MARKING_VERBOSE_ having been set to 1
839 bool verbose_stats() {
840 return _verbose_level >= stats_verbose;
841 }
842 bool verbose_low() {
843 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
844 }
845 bool verbose_medium() {
846 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
847 }
848 bool verbose_high() {
849 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
850 }
851
852 // Liveness counting
853
854 // Utility routine to set an exclusive range of cards on the given
855 // card liveness bitmap
856 inline void set_card_bitmap_range(BitMap* card_bm,
857 BitMap::idx_t start_idx,
858 BitMap::idx_t end_idx,
859 bool is_par);
860
861 // Returns the card number of the bottom of the G1 heap.
862 // Used in biasing indices into accounting card bitmaps.
863 intptr_t heap_bottom_card_num() const {
864 return _heap_bottom_card_num;
865 }
866
867 // Returns the card bitmap for a given task or worker id.
868 BitMap* count_card_bitmap_for(uint worker_id) {
869 assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
870 assert(_count_card_bitmaps != NULL, "uninitialized");
871 BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
872 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
873 return task_card_bm;
874 }
875
876 // Returns the array containing the marked bytes for each region,
877 // for the given worker or task id.
878 size_t* count_marked_bytes_array_for(uint worker_id) {
879 assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
880 assert(_count_marked_bytes != NULL, "uninitialized");
881 size_t* marked_bytes_array = _count_marked_bytes[worker_id];
882 assert(marked_bytes_array != NULL, "uninitialized");
883 return marked_bytes_array;
884 }
885
886 // Returns the index in the liveness accounting card table bitmap
887 // for the given address
888 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
889
890 // Counts the size of the given memory region in the the given
891 // marked_bytes array slot for the given HeapRegion.
892 // Sets the bits in the given card bitmap that are associated with the
893 // cards that are spanned by the memory region.
894 inline void count_region(MemRegion mr, HeapRegion* hr,
895 size_t* marked_bytes_array,
896 BitMap* task_card_bm);
897
898 // Counts the given memory region in the task/worker counting
899 // data structures for the given worker id.
900 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
901
902 // Counts the given memory region in the task/worker counting
903 // data structures for the given worker id.
904 inline void count_region(MemRegion mr, uint worker_id);
905
906 // Counts the given object in the given task/worker counting
907 // data structures.
908 inline void count_object(oop obj, HeapRegion* hr,
909 size_t* marked_bytes_array,
910 BitMap* task_card_bm);
911
912 // Counts the given object in the task/worker counting data
913 // structures for the given worker id.
914 inline void count_object(oop obj, HeapRegion* hr, uint worker_id);
915
916 // Attempts to mark the given object and, if successful, counts
917 // the object in the given task/worker counting structures.
918 inline bool par_mark_and_count(oop obj, HeapRegion* hr,
919 size_t* marked_bytes_array,
920 BitMap* task_card_bm);
921
922 // Attempts to mark the given object and, if successful, counts
923 // the object in the task/worker counting structures for the
924 // given worker id.
925 inline bool par_mark_and_count(oop obj, size_t word_size,
926 HeapRegion* hr, uint worker_id);
927
928 // Attempts to mark the given object and, if successful, counts
929 // the object in the task/worker counting structures for the
930 // given worker id.
931 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id);
932
933 // Similar to the above routine but we don't know the heap region that
934 // contains the object to be marked/counted, which this routine looks up.
935 inline bool par_mark_and_count(oop obj, uint worker_id);
936
937 // Similar to the above routine but there are times when we cannot
938 // safely calculate the size of obj due to races and we, therefore,
939 // pass the size in as a parameter. It is the caller's responsibility
940 // to ensure that the size passed in for obj is valid.
941 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id);
942
943 // Unconditionally mark the given object, and unconditionally count
944 // the object in the counting structures for worker id 0.
945 // Should *not* be called from parallel code.
946 inline bool mark_and_count(oop obj, HeapRegion* hr);
947
948 // Similar to the above routine but we don't know the heap region that
949 // contains the object to be marked/counted, which this routine looks up.
950 // Should *not* be called from parallel code.
951 inline bool mark_and_count(oop obj);
952
953 // Returns true if initialization was successfully completed.
954 bool completed_initialization() const {
955 return _completed_initialization;
956 }
957
958 protected:
959 // Clear all the per-task bitmaps and arrays used to store the
960 // counting data.
961 void clear_all_count_data();
962
963 // Aggregates the counting data for each worker/task
964 // that was constructed while marking. Also sets
965 // the amount of marked bytes for each region and
966 // the top at concurrent mark count.
967 void aggregate_count_data();
968
969 // Verification routine
970 void verify_count_data();
971 };
972
973 // A class representing a marking task.
974 class CMTask : public TerminatorTerminator {
975 private:
976 enum PrivateConstants {
977 // the regular clock call is called once the scanned words reaches
978 // this limit
979 words_scanned_period = 12*1024,
980 // the regular clock call is called once the number of visited
981 // references reaches this limit
982 refs_reached_period = 384,
983 // initial value for the hash seed, used in the work stealing code
984 init_hash_seed = 17,
985 // how many entries will be transferred between global stack and
986 // local queues
987 global_stack_transfer_size = 16
988 };
989
990 uint _worker_id;
991 G1CollectedHeap* _g1h;
992 ConcurrentMark* _cm;
993 CMBitMap* _nextMarkBitMap;
994 // the task queue of this task
995 CMTaskQueue* _task_queue;
996 private:
997 // the task queue set---needed for stealing
998 CMTaskQueueSet* _task_queues;
999 // indicates whether the task has been claimed---this is only for
1000 // debugging purposes
1001 bool _claimed;
1002
1003 // number of calls to this task
1004 int _calls;
1005
1006 // when the virtual timer reaches this time, the marking step should
1007 // exit
1008 double _time_target_ms;
1009 // the start time of the current marking step
1010 double _start_time_ms;
1011
1012 // the oop closure used for iterations over oops
1013 G1CMOopClosure* _cm_oop_closure;
1014
1015 // the region this task is scanning, NULL if we're not scanning any
1016 HeapRegion* _curr_region;
1017 // the local finger of this task, NULL if we're not scanning a region
1018 HeapWord* _finger;
1019 // limit of the region this task is scanning, NULL if we're not scanning one
1020 HeapWord* _region_limit;
1021
1022 // the number of words this task has scanned
1023 size_t _words_scanned;
1024 // When _words_scanned reaches this limit, the regular clock is
1025 // called. Notice that this might be decreased under certain
1026 // circumstances (i.e. when we believe that we did an expensive
1027 // operation).
1028 size_t _words_scanned_limit;
1029 // the initial value of _words_scanned_limit (i.e. what it was
1030 // before it was decreased).
1031 size_t _real_words_scanned_limit;
1032
1033 // the number of references this task has visited
1034 size_t _refs_reached;
1035 // When _refs_reached reaches this limit, the regular clock is
1036 // called. Notice this this might be decreased under certain
1037 // circumstances (i.e. when we believe that we did an expensive
1038 // operation).
1039 size_t _refs_reached_limit;
1040 // the initial value of _refs_reached_limit (i.e. what it was before
1041 // it was decreased).
1042 size_t _real_refs_reached_limit;
1043
1044 // used by the work stealing stuff
1045 int _hash_seed;
1046 // if this is true, then the task has aborted for some reason
1047 bool _has_aborted;
1048 // set when the task aborts because it has met its time quota
1049 bool _has_timed_out;
1050 // true when we're draining SATB buffers; this avoids the task
1051 // aborting due to SATB buffers being available (as we're already
1052 // dealing with them)
1053 bool _draining_satb_buffers;
1054
1055 // number sequence of past step times
1056 NumberSeq _step_times_ms;
1057 // elapsed time of this task
1058 double _elapsed_time_ms;
1059 // termination time of this task
1060 double _termination_time_ms;
1061 // when this task got into the termination protocol
1062 double _termination_start_time_ms;
1063
1064 // true when the task is during a concurrent phase, false when it is
1065 // in the remark phase (so, in the latter case, we do not have to
1066 // check all the things that we have to check during the concurrent
1067 // phase, i.e. SATB buffer availability...)
1068 bool _concurrent;
1069
1070 TruncatedSeq _marking_step_diffs_ms;
1071
1072 // Counting data structures. Embedding the task's marked_bytes_array
1073 // and card bitmap into the actual task saves having to go through
1074 // the ConcurrentMark object.
1075 size_t* _marked_bytes_array;
1076 BitMap* _card_bm;
1077
1078 // LOTS of statistics related with this task
1079 #if _MARKING_STATS_
1080 NumberSeq _all_clock_intervals_ms;
1081 double _interval_start_time_ms;
1082
1083 int _aborted;
1084 int _aborted_overflow;
1085 int _aborted_cm_aborted;
1086 int _aborted_yield;
1087 int _aborted_timed_out;
1088 int _aborted_satb;
1089 int _aborted_termination;
1090
1091 int _steal_attempts;
1092 int _steals;
1093
1094 int _clock_due_to_marking;
1095 int _clock_due_to_scanning;
1096
1097 int _local_pushes;
1098 int _local_pops;
1099 int _local_max_size;
1100 int _objs_scanned;
1101
1102 int _global_pushes;
1103 int _global_pops;
1104 int _global_max_size;
1105
1106 int _global_transfers_to;
1107 int _global_transfers_from;
1108
1109 int _regions_claimed;
1110 int _objs_found_on_bitmap;
1111
1112 int _satb_buffers_processed;
1113 #endif // _MARKING_STATS_
1114
1115 // it updates the local fields after this task has claimed
1116 // a new region to scan
1117 void setup_for_region(HeapRegion* hr);
1118 // it brings up-to-date the limit of the region
1119 void update_region_limit();
1120
1121 // called when either the words scanned or the refs visited limit
1122 // has been reached
1123 void reached_limit();
1124 // recalculates the words scanned and refs visited limits
1125 void recalculate_limits();
1126 // decreases the words scanned and refs visited limits when we reach
1127 // an expensive operation
1128 void decrease_limits();
1129 // it checks whether the words scanned or refs visited reached their
1130 // respective limit and calls reached_limit() if they have
1131 void check_limits() {
1132 if (_words_scanned >= _words_scanned_limit ||
1133 _refs_reached >= _refs_reached_limit) {
1134 reached_limit();
1135 }
1136 }
1137 // this is supposed to be called regularly during a marking step as
1138 // it checks a bunch of conditions that might cause the marking step
1139 // to abort
1140 void regular_clock_call();
1141 bool concurrent() { return _concurrent; }
1142
1143 public:
1144 // It resets the task; it should be called right at the beginning of
1145 // a marking phase.
1146 void reset(CMBitMap* _nextMarkBitMap);
1147 // it clears all the fields that correspond to a claimed region.
1148 void clear_region_fields();
1149
1150 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
1151
1152 // The main method of this class which performs a marking step
1153 // trying not to exceed the given duration. However, it might exit
1154 // prematurely, according to some conditions (i.e. SATB buffers are
1155 // available for processing).
1156 void do_marking_step(double target_ms,
1157 bool do_termination,
1158 bool is_serial);
1159
1160 // These two calls start and stop the timer
1161 void record_start_time() {
1162 _elapsed_time_ms = os::elapsedTime() * 1000.0;
1163 }
1164 void record_end_time() {
1165 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
1166 }
1167
1168 // returns the worker ID associated with this task.
1169 uint worker_id() { return _worker_id; }
1170
1171 // From TerminatorTerminator. It determines whether this task should
1172 // exit the termination protocol after it's entered it.
1173 virtual bool should_exit_termination();
1174
1175 // Resets the local region fields after a task has finished scanning a
1176 // region; or when they have become stale as a result of the region
1177 // being evacuated.
1178 void giveup_current_region();
1179
1180 HeapWord* finger() { return _finger; }
1181
1182 bool has_aborted() { return _has_aborted; }
1183 void set_has_aborted() { _has_aborted = true; }
1184 void clear_has_aborted() { _has_aborted = false; }
1185 bool has_timed_out() { return _has_timed_out; }
1186 bool claimed() { return _claimed; }
1187
1188 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
1189
1190 // It grays the object by marking it and, if necessary, pushing it
1191 // on the local queue
1192 inline void deal_with_reference(oop obj);
1193
1194 // It scans an object and visits its children.
1195 void scan_object(oop obj);
1196
1197 // It pushes an object on the local queue.
1198 inline void push(oop obj);
1199
1200 // These two move entries to/from the global stack.
1201 void move_entries_to_global_stack();
1202 void get_entries_from_global_stack();
1203
1204 // It pops and scans objects from the local queue. If partially is
1205 // true, then it stops when the queue size is of a given limit. If
1206 // partially is false, then it stops when the queue is empty.
1207 void drain_local_queue(bool partially);
1208 // It moves entries from the global stack to the local queue and
1209 // drains the local queue. If partially is true, then it stops when
1210 // both the global stack and the local queue reach a given size. If
1211 // partially if false, it tries to empty them totally.
1212 void drain_global_stack(bool partially);
1213 // It keeps picking SATB buffers and processing them until no SATB
1214 // buffers are available.
1215 void drain_satb_buffers();
1216
1217 // moves the local finger to a new location
1218 inline void move_finger_to(HeapWord* new_finger) {
1219 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
1220 _finger = new_finger;
1221 }
1222
1223 CMTask(uint worker_id, ConcurrentMark *cm,
1224 size_t* marked_bytes, BitMap* card_bm,
1225 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1226
1227 // it prints statistics associated with this task
1228 void print_stats();
1229
1230 #if _MARKING_STATS_
1231 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1232 #endif // _MARKING_STATS_
1233 };
1234
1235 // Class that's used to to print out per-region liveness
1236 // information. It's currently used at the end of marking and also
1237 // after we sort the old regions at the end of the cleanup operation.
1238 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
1239 private:
1240 outputStream* _out;
1241
1242 // Accumulators for these values.
1243 size_t _total_used_bytes;
1244 size_t _total_capacity_bytes;
1245 size_t _total_prev_live_bytes;
1246 size_t _total_next_live_bytes;
1247
1248 // These are set up when we come across a "stars humongous" region
1249 // (as this is where most of this information is stored, not in the
1250 // subsequent "continues humongous" regions). After that, for every
1251 // region in a given humongous region series we deduce the right
1252 // values for it by simply subtracting the appropriate amount from
1253 // these fields. All these values should reach 0 after we've visited
1254 // the last region in the series.
1255 size_t _hum_used_bytes;
1256 size_t _hum_capacity_bytes;
1257 size_t _hum_prev_live_bytes;
1258 size_t _hum_next_live_bytes;
1259
1260 // Accumulator for the remembered set size
1261 size_t _total_remset_bytes;
1262
1263 // Accumulator for strong code roots memory size
1264 size_t _total_strong_code_roots_bytes;
1265
1266 static double perc(size_t val, size_t total) {
1267 if (total == 0) {
1268 return 0.0;
1269 } else {
1270 return 100.0 * ((double) val / (double) total);
1271 }
1272 }
1273
1274 static double bytes_to_mb(size_t val) {
1275 return (double) val / (double) M;
1276 }
1277
1278 // See the .cpp file.
1279 size_t get_hum_bytes(size_t* hum_bytes);
1280 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1281 size_t* prev_live_bytes, size_t* next_live_bytes);
1282
1283 public:
1284 // The header and footer are printed in the constructor and
1285 // destructor respectively.
1286 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
1287 virtual bool doHeapRegion(HeapRegion* r);
1288 ~G1PrintRegionLivenessInfoClosure();
1289 };
1290
1291 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP