Mon, 03 Aug 2009 12:59:30 -0700
6865703: G1: Parallelize hot card cache cleanup
Summary: Have the GC worker threads clear the hot card cache in parallel by having each worker thread claim a chunk of the card cache and process the cards in that chunk. The size of the chunks that each thread will claim is determined at VM initialization from the size of the card cache and the number of worker threads.
Reviewed-by: jmasa, tonyp
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 class G1CollectedHeap;
26 class CMTask;
27 typedef GenericTaskQueue<oop> CMTaskQueue;
28 typedef GenericTaskQueueSet<oop> CMTaskQueueSet;
30 // A generic CM bit map. This is essentially a wrapper around the BitMap
31 // class, with one bit per (1<<_shifter) HeapWords.
33 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
34 protected:
35 HeapWord* _bmStartWord; // base address of range covered by map
36 size_t _bmWordSize; // map size (in #HeapWords covered)
37 const int _shifter; // map to char or bit
38 VirtualSpace _virtual_space; // underlying the bit map
39 BitMap _bm; // the bit map itself
41 public:
42 // constructor
43 CMBitMapRO(ReservedSpace rs, int shifter);
45 enum { do_yield = true };
47 // inquiries
48 HeapWord* startWord() const { return _bmStartWord; }
49 size_t sizeInWords() const { return _bmWordSize; }
50 // the following is one past the last word in space
51 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
53 // read marks
55 bool isMarked(HeapWord* addr) const {
56 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
57 "outside underlying space?");
58 return _bm.at(heapWordToOffset(addr));
59 }
61 // iteration
62 bool iterate(BitMapClosure* cl) { return _bm.iterate(cl); }
63 bool iterate(BitMapClosure* cl, MemRegion mr);
65 // Return the address corresponding to the next marked bit at or after
66 // "addr", and before "limit", if "limit" is non-NULL. If there is no
67 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
68 HeapWord* getNextMarkedWordAddress(HeapWord* addr,
69 HeapWord* limit = NULL) const;
70 // Return the address corresponding to the next unmarked bit at or after
71 // "addr", and before "limit", if "limit" is non-NULL. If there is no
72 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
73 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr,
74 HeapWord* limit = NULL) const;
76 // conversion utilities
77 // XXX Fix these so that offsets are size_t's...
78 HeapWord* offsetToHeapWord(size_t offset) const {
79 return _bmStartWord + (offset << _shifter);
80 }
81 size_t heapWordToOffset(HeapWord* addr) const {
82 return pointer_delta(addr, _bmStartWord) >> _shifter;
83 }
84 int heapWordDiffToOffsetDiff(size_t diff) const;
85 HeapWord* nextWord(HeapWord* addr) {
86 return offsetToHeapWord(heapWordToOffset(addr) + 1);
87 }
89 void mostly_disjoint_range_union(BitMap* from_bitmap,
90 size_t from_start_index,
91 HeapWord* to_start_word,
92 size_t word_num);
94 // debugging
95 NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
96 };
98 class CMBitMap : public CMBitMapRO {
100 public:
101 // constructor
102 CMBitMap(ReservedSpace rs, int shifter) :
103 CMBitMapRO(rs, shifter) {}
105 // write marks
106 void mark(HeapWord* addr) {
107 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
108 "outside underlying space?");
109 _bm.at_put(heapWordToOffset(addr), true);
110 }
111 void clear(HeapWord* addr) {
112 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
113 "outside underlying space?");
114 _bm.at_put(heapWordToOffset(addr), false);
115 }
116 bool parMark(HeapWord* addr) {
117 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
118 "outside underlying space?");
119 return _bm.par_at_put(heapWordToOffset(addr), true);
120 }
121 bool parClear(HeapWord* addr) {
122 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
123 "outside underlying space?");
124 return _bm.par_at_put(heapWordToOffset(addr), false);
125 }
126 void markRange(MemRegion mr);
127 void clearAll();
128 void clearRange(MemRegion mr);
130 // Starting at the bit corresponding to "addr" (inclusive), find the next
131 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
132 // the end of this run (stopping at "end_addr"). Return the MemRegion
133 // covering from the start of the region corresponding to the first bit
134 // of the run to the end of the region corresponding to the last bit of
135 // the run. If there is no "1" bit at or after "addr", return an empty
136 // MemRegion.
137 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
138 };
140 // Represents a marking stack used by the CM collector.
141 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
142 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
143 ConcurrentMark* _cm;
144 oop* _base; // bottom of stack
145 jint _index; // one more than last occupied index
146 jint _capacity; // max #elements
147 jint _oops_do_bound; // Number of elements to include in next iteration.
148 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
150 bool _overflow;
151 DEBUG_ONLY(bool _drain_in_progress;)
152 DEBUG_ONLY(bool _drain_in_progress_yields;)
154 public:
155 CMMarkStack(ConcurrentMark* cm);
156 ~CMMarkStack();
158 void allocate(size_t size);
160 oop pop() {
161 if (!isEmpty()) {
162 return _base[--_index] ;
163 }
164 return NULL;
165 }
167 // If overflow happens, don't do the push, and record the overflow.
168 // *Requires* that "ptr" is already marked.
169 void push(oop ptr) {
170 if (isFull()) {
171 // Record overflow.
172 _overflow = true;
173 return;
174 } else {
175 _base[_index++] = ptr;
176 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
177 }
178 }
179 // Non-block impl. Note: concurrency is allowed only with other
180 // "par_push" operations, not with "pop" or "drain". We would need
181 // parallel versions of them if such concurrency was desired.
182 void par_push(oop ptr);
184 // Pushes the first "n" elements of "ptr_arr" on the stack.
185 // Non-block impl. Note: concurrency is allowed only with other
186 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
187 void par_adjoin_arr(oop* ptr_arr, int n);
189 // Pushes the first "n" elements of "ptr_arr" on the stack.
190 // Locking impl: concurrency is allowed only with
191 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
192 // locking strategy.
193 void par_push_arr(oop* ptr_arr, int n);
195 // If returns false, the array was empty. Otherwise, removes up to "max"
196 // elements from the stack, and transfers them to "ptr_arr" in an
197 // unspecified order. The actual number transferred is given in "n" ("n
198 // == 0" is deliberately redundant with the return value.) Locking impl:
199 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
200 // operations, which use the same locking strategy.
201 bool par_pop_arr(oop* ptr_arr, int max, int* n);
203 // Drain the mark stack, applying the given closure to all fields of
204 // objects on the stack. (That is, continue until the stack is empty,
205 // even if closure applications add entries to the stack.) The "bm"
206 // argument, if non-null, may be used to verify that only marked objects
207 // are on the mark stack. If "yield_after" is "true", then the
208 // concurrent marker performing the drain offers to yield after
209 // processing each object. If a yield occurs, stops the drain operation
210 // and returns false. Otherwise, returns true.
211 template<class OopClosureClass>
212 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
214 bool isEmpty() { return _index == 0; }
215 bool isFull() { return _index == _capacity; }
216 int maxElems() { return _capacity; }
218 bool overflow() { return _overflow; }
219 void clear_overflow() { _overflow = false; }
221 int size() { return _index; }
223 void setEmpty() { _index = 0; clear_overflow(); }
225 // Record the current size; a subsequent "oops_do" will iterate only over
226 // indices valid at the time of this call.
227 void set_oops_do_bound(jint bound = -1) {
228 if (bound == -1) {
229 _oops_do_bound = _index;
230 } else {
231 _oops_do_bound = bound;
232 }
233 }
234 jint oops_do_bound() { return _oops_do_bound; }
235 // iterate over the oops in the mark stack, up to the bound recorded via
236 // the call above.
237 void oops_do(OopClosure* f);
238 };
240 class CMRegionStack VALUE_OBJ_CLASS_SPEC {
241 MemRegion* _base;
242 jint _capacity;
243 jint _index;
244 jint _oops_do_bound;
245 bool _overflow;
246 public:
247 CMRegionStack();
248 ~CMRegionStack();
249 void allocate(size_t size);
251 // This is lock-free; assumes that it will only be called in parallel
252 // with other "push" operations (no pops).
253 void push(MemRegion mr);
255 // Lock-free; assumes that it will only be called in parallel
256 // with other "pop" operations (no pushes).
257 MemRegion pop();
259 bool isEmpty() { return _index == 0; }
260 bool isFull() { return _index == _capacity; }
262 bool overflow() { return _overflow; }
263 void clear_overflow() { _overflow = false; }
265 int size() { return _index; }
267 // It iterates over the entries in the region stack and it
268 // invalidates (i.e. assigns MemRegion()) the ones that point to
269 // regions in the collection set.
270 bool invalidate_entries_into_cset();
272 // This gives an upper bound up to which the iteration in
273 // invalidate_entries_into_cset() will reach. This prevents
274 // newly-added entries to be unnecessarily scanned.
275 void set_oops_do_bound() {
276 _oops_do_bound = _index;
277 }
279 void setEmpty() { _index = 0; clear_overflow(); }
280 };
282 // this will enable a variety of different statistics per GC task
283 #define _MARKING_STATS_ 0
284 // this will enable the higher verbose levels
285 #define _MARKING_VERBOSE_ 0
287 #if _MARKING_STATS_
288 #define statsOnly(statement) \
289 do { \
290 statement ; \
291 } while (0)
292 #else // _MARKING_STATS_
293 #define statsOnly(statement) \
294 do { \
295 } while (0)
296 #endif // _MARKING_STATS_
298 // Some extra guarantees that I like to also enable in optimised mode
299 // when debugging. If you want to enable them, comment out the assert
300 // macro and uncomment out the guaratee macro
301 // #define tmp_guarantee_CM(expr, str) guarantee(expr, str)
302 #define tmp_guarantee_CM(expr, str) assert(expr, str)
304 typedef enum {
305 no_verbose = 0, // verbose turned off
306 stats_verbose, // only prints stats at the end of marking
307 low_verbose, // low verbose, mostly per region and per major event
308 medium_verbose, // a bit more detailed than low
309 high_verbose // per object verbose
310 } CMVerboseLevel;
313 class ConcurrentMarkThread;
315 class ConcurrentMark: public CHeapObj {
316 friend class ConcurrentMarkThread;
317 friend class CMTask;
318 friend class CMBitMapClosure;
319 friend class CSMarkOopClosure;
320 friend class CMGlobalObjectClosure;
321 friend class CMRemarkTask;
322 friend class CMConcurrentMarkingTask;
323 friend class G1ParNoteEndTask;
324 friend class CalcLiveObjectsClosure;
326 protected:
327 ConcurrentMarkThread* _cmThread; // the thread doing the work
328 G1CollectedHeap* _g1h; // the heap.
329 size_t _parallel_marking_threads; // the number of marking
330 // threads we'll use
331 double _sleep_factor; // how much we have to sleep, with
332 // respect to the work we just did, to
333 // meet the marking overhead goal
334 double _marking_task_overhead; // marking target overhead for
335 // a single task
337 // same as the two above, but for the cleanup task
338 double _cleanup_sleep_factor;
339 double _cleanup_task_overhead;
341 // Stuff related to age cohort processing.
342 struct ParCleanupThreadState {
343 char _pre[64];
344 UncleanRegionList list;
345 char _post[64];
346 };
347 ParCleanupThreadState** _par_cleanup_thread_state;
349 // CMS marking support structures
350 CMBitMap _markBitMap1;
351 CMBitMap _markBitMap2;
352 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
353 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
354 bool _at_least_one_mark_complete;
356 BitMap _region_bm;
357 BitMap _card_bm;
359 // Heap bounds
360 HeapWord* _heap_start;
361 HeapWord* _heap_end;
363 // For gray objects
364 CMMarkStack _markStack; // Grey objects behind global finger.
365 CMRegionStack _regionStack; // Grey regions behind global finger.
366 HeapWord* volatile _finger; // the global finger, region aligned,
367 // always points to the end of the
368 // last claimed region
370 // marking tasks
371 size_t _max_task_num; // maximum task number
372 size_t _active_tasks; // task num currently active
373 CMTask** _tasks; // task queue array (max_task_num len)
374 CMTaskQueueSet* _task_queues; // task queue set
375 ParallelTaskTerminator _terminator; // for termination
377 // Two sync barriers that are used to synchronise tasks when an
378 // overflow occurs. The algorithm is the following. All tasks enter
379 // the first one to ensure that they have all stopped manipulating
380 // the global data structures. After they exit it, they re-initialise
381 // their data structures and task 0 re-initialises the global data
382 // structures. Then, they enter the second sync barrier. This
383 // ensure, that no task starts doing work before all data
384 // structures (local and global) have been re-initialised. When they
385 // exit it, they are free to start working again.
386 WorkGangBarrierSync _first_overflow_barrier_sync;
387 WorkGangBarrierSync _second_overflow_barrier_sync;
390 // this is set by any task, when an overflow on the global data
391 // structures is detected.
392 volatile bool _has_overflown;
393 // true: marking is concurrent, false: we're in remark
394 volatile bool _concurrent;
395 // set at the end of a Full GC so that marking aborts
396 volatile bool _has_aborted;
397 // used when remark aborts due to an overflow to indicate that
398 // another concurrent marking phase should start
399 volatile bool _restart_for_overflow;
401 // This is true from the very start of concurrent marking until the
402 // point when all the tasks complete their work. It is really used
403 // to determine the points between the end of concurrent marking and
404 // time of remark.
405 volatile bool _concurrent_marking_in_progress;
407 // verbose level
408 CMVerboseLevel _verbose_level;
410 COTracker _cleanup_co_tracker;
412 // These two fields are used to implement the optimisation that
413 // avoids pushing objects on the global/region stack if there are
414 // no collection set regions above the lowest finger.
416 // This is the lowest finger (among the global and local fingers),
417 // which is calculated before a new collection set is chosen.
418 HeapWord* _min_finger;
419 // If this flag is true, objects/regions that are marked below the
420 // finger should be pushed on the stack(s). If this is flag is
421 // false, it is safe not to push them on the stack(s).
422 bool _should_gray_objects;
424 // All of these times are in ms.
425 NumberSeq _init_times;
426 NumberSeq _remark_times;
427 NumberSeq _remark_mark_times;
428 NumberSeq _remark_weak_ref_times;
429 NumberSeq _cleanup_times;
430 double _total_counting_time;
431 double _total_rs_scrub_time;
433 double* _accum_task_vtime; // accumulated task vtime
435 WorkGang* _parallel_workers;
437 void weakRefsWork(bool clear_all_soft_refs);
439 void swapMarkBitMaps();
441 // It resets the global marking data structures, as well as the
442 // task local ones; should be called during initial mark.
443 void reset();
444 // It resets all the marking data structures.
445 void clear_marking_state();
447 // It should be called to indicate which phase we're in (concurrent
448 // mark or remark) and how many threads are currently active.
449 void set_phase(size_t active_tasks, bool concurrent);
450 // We do this after we're done with marking so that the marking data
451 // structures are initialised to a sensible and predictable state.
452 void set_non_marking_state();
454 // prints all gathered CM-related statistics
455 void print_stats();
457 // accessor methods
458 size_t parallel_marking_threads() { return _parallel_marking_threads; }
459 double sleep_factor() { return _sleep_factor; }
460 double marking_task_overhead() { return _marking_task_overhead;}
461 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
462 double cleanup_task_overhead() { return _cleanup_task_overhead;}
464 HeapWord* finger() { return _finger; }
465 bool concurrent() { return _concurrent; }
466 size_t active_tasks() { return _active_tasks; }
467 ParallelTaskTerminator* terminator() { return &_terminator; }
469 // It claims the next available region to be scanned by a marking
470 // task. It might return NULL if the next region is empty or we have
471 // run out of regions. In the latter case, out_of_regions()
472 // determines whether we've really run out of regions or the task
473 // should call claim_region() again. This might seem a bit
474 // awkward. Originally, the code was written so that claim_region()
475 // either successfully returned with a non-empty region or there
476 // were no more regions to be claimed. The problem with this was
477 // that, in certain circumstances, it iterated over large chunks of
478 // the heap finding only empty regions and, while it was working, it
479 // was preventing the calling task to call its regular clock
480 // method. So, this way, each task will spend very little time in
481 // claim_region() and is allowed to call the regular clock method
482 // frequently.
483 HeapRegion* claim_region(int task);
485 // It determines whether we've run out of regions to scan.
486 bool out_of_regions() { return _finger == _heap_end; }
488 // Returns the task with the given id
489 CMTask* task(int id) {
490 guarantee( 0 <= id && id < (int) _active_tasks, "task id not within "
491 "active bounds" );
492 return _tasks[id];
493 }
495 // Returns the task queue with the given id
496 CMTaskQueue* task_queue(int id) {
497 guarantee( 0 <= id && id < (int) _active_tasks, "task queue id not within "
498 "active bounds" );
499 return (CMTaskQueue*) _task_queues->queue(id);
500 }
502 // Returns the task queue set
503 CMTaskQueueSet* task_queues() { return _task_queues; }
505 // Access / manipulation of the overflow flag which is set to
506 // indicate that the global stack or region stack has overflown
507 bool has_overflown() { return _has_overflown; }
508 void set_has_overflown() { _has_overflown = true; }
509 void clear_has_overflown() { _has_overflown = false; }
511 bool has_aborted() { return _has_aborted; }
512 bool restart_for_overflow() { return _restart_for_overflow; }
514 // Methods to enter the two overflow sync barriers
515 void enter_first_sync_barrier(int task_num);
516 void enter_second_sync_barrier(int task_num);
518 public:
519 // Manipulation of the global mark stack.
520 // Notice that the first mark_stack_push is CAS-based, whereas the
521 // two below are Mutex-based. This is OK since the first one is only
522 // called during evacuation pauses and doesn't compete with the
523 // other two (which are called by the marking tasks during
524 // concurrent marking or remark).
525 bool mark_stack_push(oop p) {
526 _markStack.par_push(p);
527 if (_markStack.overflow()) {
528 set_has_overflown();
529 return false;
530 }
531 return true;
532 }
533 bool mark_stack_push(oop* arr, int n) {
534 _markStack.par_push_arr(arr, n);
535 if (_markStack.overflow()) {
536 set_has_overflown();
537 return false;
538 }
539 return true;
540 }
541 void mark_stack_pop(oop* arr, int max, int* n) {
542 _markStack.par_pop_arr(arr, max, n);
543 }
544 size_t mark_stack_size() { return _markStack.size(); }
545 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
546 bool mark_stack_overflow() { return _markStack.overflow(); }
547 bool mark_stack_empty() { return _markStack.isEmpty(); }
549 // Manipulation of the region stack
550 bool region_stack_push(MemRegion mr) {
551 _regionStack.push(mr);
552 if (_regionStack.overflow()) {
553 set_has_overflown();
554 return false;
555 }
556 return true;
557 }
558 MemRegion region_stack_pop() { return _regionStack.pop(); }
559 int region_stack_size() { return _regionStack.size(); }
560 bool region_stack_overflow() { return _regionStack.overflow(); }
561 bool region_stack_empty() { return _regionStack.isEmpty(); }
563 bool concurrent_marking_in_progress() {
564 return _concurrent_marking_in_progress;
565 }
566 void set_concurrent_marking_in_progress() {
567 _concurrent_marking_in_progress = true;
568 }
569 void clear_concurrent_marking_in_progress() {
570 _concurrent_marking_in_progress = false;
571 }
573 void update_accum_task_vtime(int i, double vtime) {
574 _accum_task_vtime[i] += vtime;
575 }
577 double all_task_accum_vtime() {
578 double ret = 0.0;
579 for (int i = 0; i < (int)_max_task_num; ++i)
580 ret += _accum_task_vtime[i];
581 return ret;
582 }
584 // Attempts to steal an object from the task queues of other tasks
585 bool try_stealing(int task_num, int* hash_seed, oop& obj) {
586 return _task_queues->steal(task_num, hash_seed, obj);
587 }
589 // It grays an object by first marking it. Then, if it's behind the
590 // global finger, it also pushes it on the global stack.
591 void deal_with_reference(oop obj);
593 ConcurrentMark(ReservedSpace rs, int max_regions);
594 ~ConcurrentMark();
595 ConcurrentMarkThread* cmThread() { return _cmThread; }
597 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
598 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
600 // The following three are interaction between CM and
601 // G1CollectedHeap
603 // This notifies CM that a root during initial-mark needs to be
604 // grayed and it's MT-safe. Currently, we just mark it. But, in the
605 // future, we can experiment with pushing it on the stack and we can
606 // do this without changing G1CollectedHeap.
607 void grayRoot(oop p);
608 // It's used during evacuation pauses to gray a region, if
609 // necessary, and it's MT-safe. It assumes that the caller has
610 // marked any objects on that region. If _should_gray_objects is
611 // true and we're still doing concurrent marking, the region is
612 // pushed on the region stack, if it is located below the global
613 // finger, otherwise we do nothing.
614 void grayRegionIfNecessary(MemRegion mr);
615 // It's used during evacuation pauses to mark and, if necessary,
616 // gray a single object and it's MT-safe. It assumes the caller did
617 // not mark the object. If _should_gray_objects is true and we're
618 // still doing concurrent marking, the objects is pushed on the
619 // global stack, if it is located below the global finger, otherwise
620 // we do nothing.
621 void markAndGrayObjectIfNecessary(oop p);
623 // This iterates over the bitmap of the previous marking and prints
624 // out all objects that are marked on the bitmap and indicates
625 // whether what they point to is also marked or not.
626 void print_prev_bitmap_reachable();
628 // Clear the next marking bitmap (will be called concurrently).
629 void clearNextBitmap();
631 // main CMS steps and related support
632 void checkpointRootsInitial();
634 // These two do the work that needs to be done before and after the
635 // initial root checkpoint. Since this checkpoint can be done at two
636 // different points (i.e. an explicit pause or piggy-backed on a
637 // young collection), then it's nice to be able to easily share the
638 // pre/post code. It might be the case that we can put everything in
639 // the post method. TP
640 void checkpointRootsInitialPre();
641 void checkpointRootsInitialPost();
643 // Do concurrent phase of marking, to a tentative transitive closure.
644 void markFromRoots();
646 // Process all unprocessed SATB buffers. It is called at the
647 // beginning of an evacuation pause.
648 void drainAllSATBBuffers();
650 void checkpointRootsFinal(bool clear_all_soft_refs);
651 void checkpointRootsFinalWork();
652 void calcDesiredRegions();
653 void cleanup();
654 void completeCleanup();
656 // Mark in the previous bitmap. NB: this is usually read-only, so use
657 // this carefully!
658 void markPrev(oop p);
659 void clear(oop p);
660 // Clears marks for all objects in the given range, for both prev and
661 // next bitmaps. NB: the previous bitmap is usually read-only, so use
662 // this carefully!
663 void clearRangeBothMaps(MemRegion mr);
665 // Record the current top of the mark and region stacks; a
666 // subsequent oops_do() on the mark stack and
667 // invalidate_entries_into_cset() on the region stack will iterate
668 // only over indices valid at the time of this call.
669 void set_oops_do_bound() {
670 _markStack.set_oops_do_bound();
671 _regionStack.set_oops_do_bound();
672 }
673 // Iterate over the oops in the mark stack and all local queues. It
674 // also calls invalidate_entries_into_cset() on the region stack.
675 void oops_do(OopClosure* f);
676 // It is called at the end of an evacuation pause during marking so
677 // that CM is notified of where the new end of the heap is. It
678 // doesn't do anything if concurrent_marking_in_progress() is false,
679 // unless the force parameter is true.
680 void update_g1_committed(bool force = false);
682 void complete_marking_in_collection_set();
684 // It indicates that a new collection set is being chosen.
685 void newCSet();
686 // It registers a collection set heap region with CM. This is used
687 // to determine whether any heap regions are located above the finger.
688 void registerCSetRegion(HeapRegion* hr);
690 // Returns "true" if at least one mark has been completed.
691 bool at_least_one_mark_complete() { return _at_least_one_mark_complete; }
693 bool isMarked(oop p) const {
694 assert(p != NULL && p->is_oop(), "expected an oop");
695 HeapWord* addr = (HeapWord*)p;
696 assert(addr >= _nextMarkBitMap->startWord() ||
697 addr < _nextMarkBitMap->endWord(), "in a region");
699 return _nextMarkBitMap->isMarked(addr);
700 }
702 inline bool not_yet_marked(oop p) const;
704 // XXX Debug code
705 bool containing_card_is_marked(void* p);
706 bool containing_cards_are_marked(void* start, void* last);
708 bool isPrevMarked(oop p) const {
709 assert(p != NULL && p->is_oop(), "expected an oop");
710 HeapWord* addr = (HeapWord*)p;
711 assert(addr >= _prevMarkBitMap->startWord() ||
712 addr < _prevMarkBitMap->endWord(), "in a region");
714 return _prevMarkBitMap->isMarked(addr);
715 }
717 inline bool do_yield_check(int worker_i = 0);
718 inline bool should_yield();
720 // Called to abort the marking cycle after a Full GC takes palce.
721 void abort();
723 void disable_co_trackers();
725 // This prints the global/local fingers. It is used for debugging.
726 NOT_PRODUCT(void print_finger();)
728 void print_summary_info();
730 // The following indicate whether a given verbose level has been
731 // set. Notice that anything above stats is conditional to
732 // _MARKING_VERBOSE_ having been set to 1
733 bool verbose_stats()
734 { return _verbose_level >= stats_verbose; }
735 bool verbose_low()
736 { return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; }
737 bool verbose_medium()
738 { return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; }
739 bool verbose_high()
740 { return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; }
741 };
743 // A class representing a marking task.
744 class CMTask : public TerminatorTerminator {
745 private:
746 enum PrivateConstants {
747 // the regular clock call is called once the scanned words reaches
748 // this limit
749 words_scanned_period = 12*1024,
750 // the regular clock call is called once the number of visited
751 // references reaches this limit
752 refs_reached_period = 384,
753 // initial value for the hash seed, used in the work stealing code
754 init_hash_seed = 17,
755 // how many entries will be transferred between global stack and
756 // local queues
757 global_stack_transfer_size = 16
758 };
760 int _task_id;
761 G1CollectedHeap* _g1h;
762 ConcurrentMark* _cm;
763 CMBitMap* _nextMarkBitMap;
764 // the task queue of this task
765 CMTaskQueue* _task_queue;
766 private:
767 // the task queue set---needed for stealing
768 CMTaskQueueSet* _task_queues;
769 // indicates whether the task has been claimed---this is only for
770 // debugging purposes
771 bool _claimed;
773 // number of calls to this task
774 int _calls;
776 // concurrent overhead over a single CPU for this task
777 COTracker _co_tracker;
779 // when the virtual timer reaches this time, the marking step should
780 // exit
781 double _time_target_ms;
782 // the start time of the current marking step
783 double _start_time_ms;
785 // the oop closure used for iterations over oops
786 OopClosure* _oop_closure;
788 // the region this task is scanning, NULL if we're not scanning any
789 HeapRegion* _curr_region;
790 // the local finger of this task, NULL if we're not scanning a region
791 HeapWord* _finger;
792 // limit of the region this task is scanning, NULL if we're not scanning one
793 HeapWord* _region_limit;
795 // This is used only when we scan regions popped from the region
796 // stack. It records what the last object on such a region we
797 // scanned was. It is used to ensure that, if we abort region
798 // iteration, we do not rescan the first part of the region. This
799 // should be NULL when we're not scanning a region from the region
800 // stack.
801 HeapWord* _region_finger;
803 // the number of words this task has scanned
804 size_t _words_scanned;
805 // When _words_scanned reaches this limit, the regular clock is
806 // called. Notice that this might be decreased under certain
807 // circumstances (i.e. when we believe that we did an expensive
808 // operation).
809 size_t _words_scanned_limit;
810 // the initial value of _words_scanned_limit (i.e. what it was
811 // before it was decreased).
812 size_t _real_words_scanned_limit;
814 // the number of references this task has visited
815 size_t _refs_reached;
816 // When _refs_reached reaches this limit, the regular clock is
817 // called. Notice this this might be decreased under certain
818 // circumstances (i.e. when we believe that we did an expensive
819 // operation).
820 size_t _refs_reached_limit;
821 // the initial value of _refs_reached_limit (i.e. what it was before
822 // it was decreased).
823 size_t _real_refs_reached_limit;
825 // used by the work stealing stuff
826 int _hash_seed;
827 // if this is true, then the task has aborted for some reason
828 bool _has_aborted;
829 // set when the task aborts because it has met its time quota
830 bool _has_aborted_timed_out;
831 // true when we're draining SATB buffers; this avoids the task
832 // aborting due to SATB buffers being available (as we're already
833 // dealing with them)
834 bool _draining_satb_buffers;
836 // number sequence of past step times
837 NumberSeq _step_times_ms;
838 // elapsed time of this task
839 double _elapsed_time_ms;
840 // termination time of this task
841 double _termination_time_ms;
842 // when this task got into the termination protocol
843 double _termination_start_time_ms;
845 // true when the task is during a concurrent phase, false when it is
846 // in the remark phase (so, in the latter case, we do not have to
847 // check all the things that we have to check during the concurrent
848 // phase, i.e. SATB buffer availability...)
849 bool _concurrent;
851 TruncatedSeq _marking_step_diffs_ms;
853 // LOTS of statistics related with this task
854 #if _MARKING_STATS_
855 NumberSeq _all_clock_intervals_ms;
856 double _interval_start_time_ms;
858 int _aborted;
859 int _aborted_overflow;
860 int _aborted_cm_aborted;
861 int _aborted_yield;
862 int _aborted_timed_out;
863 int _aborted_satb;
864 int _aborted_termination;
866 int _steal_attempts;
867 int _steals;
869 int _clock_due_to_marking;
870 int _clock_due_to_scanning;
872 int _local_pushes;
873 int _local_pops;
874 int _local_max_size;
875 int _objs_scanned;
877 int _global_pushes;
878 int _global_pops;
879 int _global_max_size;
881 int _global_transfers_to;
882 int _global_transfers_from;
884 int _region_stack_pops;
886 int _regions_claimed;
887 int _objs_found_on_bitmap;
889 int _satb_buffers_processed;
890 #endif // _MARKING_STATS_
892 // it updates the local fields after this task has claimed
893 // a new region to scan
894 void setup_for_region(HeapRegion* hr);
895 // it brings up-to-date the limit of the region
896 void update_region_limit();
897 // it resets the local fields after a task has finished scanning a
898 // region
899 void giveup_current_region();
901 // called when either the words scanned or the refs visited limit
902 // has been reached
903 void reached_limit();
904 // recalculates the words scanned and refs visited limits
905 void recalculate_limits();
906 // decreases the words scanned and refs visited limits when we reach
907 // an expensive operation
908 void decrease_limits();
909 // it checks whether the words scanned or refs visited reached their
910 // respective limit and calls reached_limit() if they have
911 void check_limits() {
912 if (_words_scanned >= _words_scanned_limit ||
913 _refs_reached >= _refs_reached_limit)
914 reached_limit();
915 }
916 // this is supposed to be called regularly during a marking step as
917 // it checks a bunch of conditions that might cause the marking step
918 // to abort
919 void regular_clock_call();
920 bool concurrent() { return _concurrent; }
922 public:
923 // It resets the task; it should be called right at the beginning of
924 // a marking phase.
925 void reset(CMBitMap* _nextMarkBitMap);
926 // it clears all the fields that correspond to a claimed region.
927 void clear_region_fields();
929 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
931 void enable_co_tracker() {
932 guarantee( !_co_tracker.enabled(), "invariant" );
933 _co_tracker.enable();
934 }
935 void disable_co_tracker() {
936 guarantee( _co_tracker.enabled(), "invariant" );
937 _co_tracker.disable();
938 }
939 bool co_tracker_enabled() {
940 return _co_tracker.enabled();
941 }
942 void reset_co_tracker(double starting_conc_overhead = 0.0) {
943 _co_tracker.reset(starting_conc_overhead);
944 }
945 void start_co_tracker() {
946 _co_tracker.start();
947 }
948 void update_co_tracker(bool force_end = false) {
949 _co_tracker.update(force_end);
950 }
952 // The main method of this class which performs a marking step
953 // trying not to exceed the given duration. However, it might exit
954 // prematurely, according to some conditions (i.e. SATB buffers are
955 // available for processing).
956 void do_marking_step(double target_ms);
958 // These two calls start and stop the timer
959 void record_start_time() {
960 _elapsed_time_ms = os::elapsedTime() * 1000.0;
961 }
962 void record_end_time() {
963 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
964 }
966 // returns the task ID
967 int task_id() { return _task_id; }
969 // From TerminatorTerminator. It determines whether this task should
970 // exit the termination protocol after it's entered it.
971 virtual bool should_exit_termination();
973 HeapWord* finger() { return _finger; }
975 bool has_aborted() { return _has_aborted; }
976 void set_has_aborted() { _has_aborted = true; }
977 void clear_has_aborted() { _has_aborted = false; }
978 bool claimed() { return _claimed; }
980 void set_oop_closure(OopClosure* oop_closure) {
981 _oop_closure = oop_closure;
982 }
984 // It grays the object by marking it and, if necessary, pushing it
985 // on the local queue
986 void deal_with_reference(oop obj);
988 // It scans an object and visits its children.
989 void scan_object(oop obj) {
990 tmp_guarantee_CM( _nextMarkBitMap->isMarked((HeapWord*) obj),
991 "invariant" );
993 if (_cm->verbose_high())
994 gclog_or_tty->print_cr("[%d] we're scanning object "PTR_FORMAT,
995 _task_id, (void*) obj);
997 size_t obj_size = obj->size();
998 _words_scanned += obj_size;
1000 obj->oop_iterate(_oop_closure);
1001 statsOnly( ++_objs_scanned );
1002 check_limits();
1003 }
1005 // It pushes an object on the local queue.
1006 void push(oop obj);
1008 // These two move entries to/from the global stack.
1009 void move_entries_to_global_stack();
1010 void get_entries_from_global_stack();
1012 // It pops and scans objects from the local queue. If partially is
1013 // true, then it stops when the queue size is of a given limit. If
1014 // partially is false, then it stops when the queue is empty.
1015 void drain_local_queue(bool partially);
1016 // It moves entries from the global stack to the local queue and
1017 // drains the local queue. If partially is true, then it stops when
1018 // both the global stack and the local queue reach a given size. If
1019 // partially if false, it tries to empty them totally.
1020 void drain_global_stack(bool partially);
1021 // It keeps picking SATB buffers and processing them until no SATB
1022 // buffers are available.
1023 void drain_satb_buffers();
1024 // It keeps popping regions from the region stack and processing
1025 // them until the region stack is empty.
1026 void drain_region_stack(BitMapClosure* closure);
1028 // moves the local finger to a new location
1029 inline void move_finger_to(HeapWord* new_finger) {
1030 tmp_guarantee_CM( new_finger >= _finger && new_finger < _region_limit,
1031 "invariant" );
1032 _finger = new_finger;
1033 }
1035 // moves the region finger to a new location
1036 inline void move_region_finger_to(HeapWord* new_finger) {
1037 tmp_guarantee_CM( new_finger < _cm->finger(), "invariant" );
1038 _region_finger = new_finger;
1039 }
1041 CMTask(int task_num, ConcurrentMark *cm,
1042 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1044 // it prints statistics associated with this task
1045 void print_stats();
1047 #if _MARKING_STATS_
1048 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1049 #endif // _MARKING_STATS_
1050 };