Wed, 07 Oct 2009 10:09:57 -0400
6888619: G1: too many guarantees in concurrent marking
Summary: change more guarantees in concurrent marking into asserts.
Reviewed-by: apetrusenko, iveresov
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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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 typedef enum {
299 no_verbose = 0, // verbose turned off
300 stats_verbose, // only prints stats at the end of marking
301 low_verbose, // low verbose, mostly per region and per major event
302 medium_verbose, // a bit more detailed than low
303 high_verbose // per object verbose
304 } CMVerboseLevel;
307 class ConcurrentMarkThread;
309 class ConcurrentMark: public CHeapObj {
310 friend class ConcurrentMarkThread;
311 friend class CMTask;
312 friend class CMBitMapClosure;
313 friend class CSMarkOopClosure;
314 friend class CMGlobalObjectClosure;
315 friend class CMRemarkTask;
316 friend class CMConcurrentMarkingTask;
317 friend class G1ParNoteEndTask;
318 friend class CalcLiveObjectsClosure;
320 protected:
321 ConcurrentMarkThread* _cmThread; // the thread doing the work
322 G1CollectedHeap* _g1h; // the heap.
323 size_t _parallel_marking_threads; // the number of marking
324 // threads we'll use
325 double _sleep_factor; // how much we have to sleep, with
326 // respect to the work we just did, to
327 // meet the marking overhead goal
328 double _marking_task_overhead; // marking target overhead for
329 // a single task
331 // same as the two above, but for the cleanup task
332 double _cleanup_sleep_factor;
333 double _cleanup_task_overhead;
335 // Stuff related to age cohort processing.
336 struct ParCleanupThreadState {
337 char _pre[64];
338 UncleanRegionList list;
339 char _post[64];
340 };
341 ParCleanupThreadState** _par_cleanup_thread_state;
343 // CMS marking support structures
344 CMBitMap _markBitMap1;
345 CMBitMap _markBitMap2;
346 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
347 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
348 bool _at_least_one_mark_complete;
350 BitMap _region_bm;
351 BitMap _card_bm;
353 // Heap bounds
354 HeapWord* _heap_start;
355 HeapWord* _heap_end;
357 // For gray objects
358 CMMarkStack _markStack; // Grey objects behind global finger.
359 CMRegionStack _regionStack; // Grey regions behind global finger.
360 HeapWord* volatile _finger; // the global finger, region aligned,
361 // always points to the end of the
362 // last claimed region
364 // marking tasks
365 size_t _max_task_num; // maximum task number
366 size_t _active_tasks; // task num currently active
367 CMTask** _tasks; // task queue array (max_task_num len)
368 CMTaskQueueSet* _task_queues; // task queue set
369 ParallelTaskTerminator _terminator; // for termination
371 // Two sync barriers that are used to synchronise tasks when an
372 // overflow occurs. The algorithm is the following. All tasks enter
373 // the first one to ensure that they have all stopped manipulating
374 // the global data structures. After they exit it, they re-initialise
375 // their data structures and task 0 re-initialises the global data
376 // structures. Then, they enter the second sync barrier. This
377 // ensure, that no task starts doing work before all data
378 // structures (local and global) have been re-initialised. When they
379 // exit it, they are free to start working again.
380 WorkGangBarrierSync _first_overflow_barrier_sync;
381 WorkGangBarrierSync _second_overflow_barrier_sync;
384 // this is set by any task, when an overflow on the global data
385 // structures is detected.
386 volatile bool _has_overflown;
387 // true: marking is concurrent, false: we're in remark
388 volatile bool _concurrent;
389 // set at the end of a Full GC so that marking aborts
390 volatile bool _has_aborted;
391 // used when remark aborts due to an overflow to indicate that
392 // another concurrent marking phase should start
393 volatile bool _restart_for_overflow;
395 // This is true from the very start of concurrent marking until the
396 // point when all the tasks complete their work. It is really used
397 // to determine the points between the end of concurrent marking and
398 // time of remark.
399 volatile bool _concurrent_marking_in_progress;
401 // verbose level
402 CMVerboseLevel _verbose_level;
404 // These two fields are used to implement the optimisation that
405 // avoids pushing objects on the global/region stack if there are
406 // no collection set regions above the lowest finger.
408 // This is the lowest finger (among the global and local fingers),
409 // which is calculated before a new collection set is chosen.
410 HeapWord* _min_finger;
411 // If this flag is true, objects/regions that are marked below the
412 // finger should be pushed on the stack(s). If this is flag is
413 // false, it is safe not to push them on the stack(s).
414 bool _should_gray_objects;
416 // All of these times are in ms.
417 NumberSeq _init_times;
418 NumberSeq _remark_times;
419 NumberSeq _remark_mark_times;
420 NumberSeq _remark_weak_ref_times;
421 NumberSeq _cleanup_times;
422 double _total_counting_time;
423 double _total_rs_scrub_time;
425 double* _accum_task_vtime; // accumulated task vtime
427 WorkGang* _parallel_workers;
429 void weakRefsWork(bool clear_all_soft_refs);
431 void swapMarkBitMaps();
433 // It resets the global marking data structures, as well as the
434 // task local ones; should be called during initial mark.
435 void reset();
436 // It resets all the marking data structures.
437 void clear_marking_state();
439 // It should be called to indicate which phase we're in (concurrent
440 // mark or remark) and how many threads are currently active.
441 void set_phase(size_t active_tasks, bool concurrent);
442 // We do this after we're done with marking so that the marking data
443 // structures are initialised to a sensible and predictable state.
444 void set_non_marking_state();
446 // prints all gathered CM-related statistics
447 void print_stats();
449 // accessor methods
450 size_t parallel_marking_threads() { return _parallel_marking_threads; }
451 double sleep_factor() { return _sleep_factor; }
452 double marking_task_overhead() { return _marking_task_overhead;}
453 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
454 double cleanup_task_overhead() { return _cleanup_task_overhead;}
456 HeapWord* finger() { return _finger; }
457 bool concurrent() { return _concurrent; }
458 size_t active_tasks() { return _active_tasks; }
459 ParallelTaskTerminator* terminator() { return &_terminator; }
461 // It claims the next available region to be scanned by a marking
462 // task. It might return NULL if the next region is empty or we have
463 // run out of regions. In the latter case, out_of_regions()
464 // determines whether we've really run out of regions or the task
465 // should call claim_region() again. This might seem a bit
466 // awkward. Originally, the code was written so that claim_region()
467 // either successfully returned with a non-empty region or there
468 // were no more regions to be claimed. The problem with this was
469 // that, in certain circumstances, it iterated over large chunks of
470 // the heap finding only empty regions and, while it was working, it
471 // was preventing the calling task to call its regular clock
472 // method. So, this way, each task will spend very little time in
473 // claim_region() and is allowed to call the regular clock method
474 // frequently.
475 HeapRegion* claim_region(int task);
477 // It determines whether we've run out of regions to scan.
478 bool out_of_regions() { return _finger == _heap_end; }
480 // Returns the task with the given id
481 CMTask* task(int id) {
482 assert(0 <= id && id < (int) _active_tasks,
483 "task id not within active bounds");
484 return _tasks[id];
485 }
487 // Returns the task queue with the given id
488 CMTaskQueue* task_queue(int id) {
489 assert(0 <= id && id < (int) _active_tasks,
490 "task queue id not within active bounds");
491 return (CMTaskQueue*) _task_queues->queue(id);
492 }
494 // Returns the task queue set
495 CMTaskQueueSet* task_queues() { return _task_queues; }
497 // Access / manipulation of the overflow flag which is set to
498 // indicate that the global stack or region stack has overflown
499 bool has_overflown() { return _has_overflown; }
500 void set_has_overflown() { _has_overflown = true; }
501 void clear_has_overflown() { _has_overflown = false; }
503 bool has_aborted() { return _has_aborted; }
504 bool restart_for_overflow() { return _restart_for_overflow; }
506 // Methods to enter the two overflow sync barriers
507 void enter_first_sync_barrier(int task_num);
508 void enter_second_sync_barrier(int task_num);
510 public:
511 // Manipulation of the global mark stack.
512 // Notice that the first mark_stack_push is CAS-based, whereas the
513 // two below are Mutex-based. This is OK since the first one is only
514 // called during evacuation pauses and doesn't compete with the
515 // other two (which are called by the marking tasks during
516 // concurrent marking or remark).
517 bool mark_stack_push(oop p) {
518 _markStack.par_push(p);
519 if (_markStack.overflow()) {
520 set_has_overflown();
521 return false;
522 }
523 return true;
524 }
525 bool mark_stack_push(oop* arr, int n) {
526 _markStack.par_push_arr(arr, n);
527 if (_markStack.overflow()) {
528 set_has_overflown();
529 return false;
530 }
531 return true;
532 }
533 void mark_stack_pop(oop* arr, int max, int* n) {
534 _markStack.par_pop_arr(arr, max, n);
535 }
536 size_t mark_stack_size() { return _markStack.size(); }
537 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
538 bool mark_stack_overflow() { return _markStack.overflow(); }
539 bool mark_stack_empty() { return _markStack.isEmpty(); }
541 // Manipulation of the region stack
542 bool region_stack_push(MemRegion mr) {
543 _regionStack.push(mr);
544 if (_regionStack.overflow()) {
545 set_has_overflown();
546 return false;
547 }
548 return true;
549 }
550 MemRegion region_stack_pop() { return _regionStack.pop(); }
551 int region_stack_size() { return _regionStack.size(); }
552 bool region_stack_overflow() { return _regionStack.overflow(); }
553 bool region_stack_empty() { return _regionStack.isEmpty(); }
555 bool concurrent_marking_in_progress() {
556 return _concurrent_marking_in_progress;
557 }
558 void set_concurrent_marking_in_progress() {
559 _concurrent_marking_in_progress = true;
560 }
561 void clear_concurrent_marking_in_progress() {
562 _concurrent_marking_in_progress = false;
563 }
565 void update_accum_task_vtime(int i, double vtime) {
566 _accum_task_vtime[i] += vtime;
567 }
569 double all_task_accum_vtime() {
570 double ret = 0.0;
571 for (int i = 0; i < (int)_max_task_num; ++i)
572 ret += _accum_task_vtime[i];
573 return ret;
574 }
576 // Attempts to steal an object from the task queues of other tasks
577 bool try_stealing(int task_num, int* hash_seed, oop& obj) {
578 return _task_queues->steal(task_num, hash_seed, obj);
579 }
581 // It grays an object by first marking it. Then, if it's behind the
582 // global finger, it also pushes it on the global stack.
583 void deal_with_reference(oop obj);
585 ConcurrentMark(ReservedSpace rs, int max_regions);
586 ~ConcurrentMark();
587 ConcurrentMarkThread* cmThread() { return _cmThread; }
589 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
590 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
592 // The following three are interaction between CM and
593 // G1CollectedHeap
595 // This notifies CM that a root during initial-mark needs to be
596 // grayed and it's MT-safe. Currently, we just mark it. But, in the
597 // future, we can experiment with pushing it on the stack and we can
598 // do this without changing G1CollectedHeap.
599 void grayRoot(oop p);
600 // It's used during evacuation pauses to gray a region, if
601 // necessary, and it's MT-safe. It assumes that the caller has
602 // marked any objects on that region. If _should_gray_objects is
603 // true and we're still doing concurrent marking, the region is
604 // pushed on the region stack, if it is located below the global
605 // finger, otherwise we do nothing.
606 void grayRegionIfNecessary(MemRegion mr);
607 // It's used during evacuation pauses to mark and, if necessary,
608 // gray a single object and it's MT-safe. It assumes the caller did
609 // not mark the object. If _should_gray_objects is true and we're
610 // still doing concurrent marking, the objects is pushed on the
611 // global stack, if it is located below the global finger, otherwise
612 // we do nothing.
613 void markAndGrayObjectIfNecessary(oop p);
615 // This iterates over the bitmap of the previous marking and prints
616 // out all objects that are marked on the bitmap and indicates
617 // whether what they point to is also marked or not.
618 void print_prev_bitmap_reachable();
620 // Clear the next marking bitmap (will be called concurrently).
621 void clearNextBitmap();
623 // main CMS steps and related support
624 void checkpointRootsInitial();
626 // These two do the work that needs to be done before and after the
627 // initial root checkpoint. Since this checkpoint can be done at two
628 // different points (i.e. an explicit pause or piggy-backed on a
629 // young collection), then it's nice to be able to easily share the
630 // pre/post code. It might be the case that we can put everything in
631 // the post method. TP
632 void checkpointRootsInitialPre();
633 void checkpointRootsInitialPost();
635 // Do concurrent phase of marking, to a tentative transitive closure.
636 void markFromRoots();
638 // Process all unprocessed SATB buffers. It is called at the
639 // beginning of an evacuation pause.
640 void drainAllSATBBuffers();
642 void checkpointRootsFinal(bool clear_all_soft_refs);
643 void checkpointRootsFinalWork();
644 void calcDesiredRegions();
645 void cleanup();
646 void completeCleanup();
648 // Mark in the previous bitmap. NB: this is usually read-only, so use
649 // this carefully!
650 void markPrev(oop p);
651 void clear(oop p);
652 // Clears marks for all objects in the given range, for both prev and
653 // next bitmaps. NB: the previous bitmap is usually read-only, so use
654 // this carefully!
655 void clearRangeBothMaps(MemRegion mr);
657 // Record the current top of the mark and region stacks; a
658 // subsequent oops_do() on the mark stack and
659 // invalidate_entries_into_cset() on the region stack will iterate
660 // only over indices valid at the time of this call.
661 void set_oops_do_bound() {
662 _markStack.set_oops_do_bound();
663 _regionStack.set_oops_do_bound();
664 }
665 // Iterate over the oops in the mark stack and all local queues. It
666 // also calls invalidate_entries_into_cset() on the region stack.
667 void oops_do(OopClosure* f);
668 // It is called at the end of an evacuation pause during marking so
669 // that CM is notified of where the new end of the heap is. It
670 // doesn't do anything if concurrent_marking_in_progress() is false,
671 // unless the force parameter is true.
672 void update_g1_committed(bool force = false);
674 void complete_marking_in_collection_set();
676 // It indicates that a new collection set is being chosen.
677 void newCSet();
678 // It registers a collection set heap region with CM. This is used
679 // to determine whether any heap regions are located above the finger.
680 void registerCSetRegion(HeapRegion* hr);
682 // Returns "true" if at least one mark has been completed.
683 bool at_least_one_mark_complete() { return _at_least_one_mark_complete; }
685 bool isMarked(oop p) const {
686 assert(p != NULL && p->is_oop(), "expected an oop");
687 HeapWord* addr = (HeapWord*)p;
688 assert(addr >= _nextMarkBitMap->startWord() ||
689 addr < _nextMarkBitMap->endWord(), "in a region");
691 return _nextMarkBitMap->isMarked(addr);
692 }
694 inline bool not_yet_marked(oop p) const;
696 // XXX Debug code
697 bool containing_card_is_marked(void* p);
698 bool containing_cards_are_marked(void* start, void* last);
700 bool isPrevMarked(oop p) const {
701 assert(p != NULL && p->is_oop(), "expected an oop");
702 HeapWord* addr = (HeapWord*)p;
703 assert(addr >= _prevMarkBitMap->startWord() ||
704 addr < _prevMarkBitMap->endWord(), "in a region");
706 return _prevMarkBitMap->isMarked(addr);
707 }
709 inline bool do_yield_check(int worker_i = 0);
710 inline bool should_yield();
712 // Called to abort the marking cycle after a Full GC takes palce.
713 void abort();
715 // This prints the global/local fingers. It is used for debugging.
716 NOT_PRODUCT(void print_finger();)
718 void print_summary_info();
720 void print_worker_threads_on(outputStream* st) const;
722 // The following indicate whether a given verbose level has been
723 // set. Notice that anything above stats is conditional to
724 // _MARKING_VERBOSE_ having been set to 1
725 bool verbose_stats()
726 { return _verbose_level >= stats_verbose; }
727 bool verbose_low()
728 { return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; }
729 bool verbose_medium()
730 { return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; }
731 bool verbose_high()
732 { return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; }
733 };
735 // A class representing a marking task.
736 class CMTask : public TerminatorTerminator {
737 private:
738 enum PrivateConstants {
739 // the regular clock call is called once the scanned words reaches
740 // this limit
741 words_scanned_period = 12*1024,
742 // the regular clock call is called once the number of visited
743 // references reaches this limit
744 refs_reached_period = 384,
745 // initial value for the hash seed, used in the work stealing code
746 init_hash_seed = 17,
747 // how many entries will be transferred between global stack and
748 // local queues
749 global_stack_transfer_size = 16
750 };
752 int _task_id;
753 G1CollectedHeap* _g1h;
754 ConcurrentMark* _cm;
755 CMBitMap* _nextMarkBitMap;
756 // the task queue of this task
757 CMTaskQueue* _task_queue;
758 private:
759 // the task queue set---needed for stealing
760 CMTaskQueueSet* _task_queues;
761 // indicates whether the task has been claimed---this is only for
762 // debugging purposes
763 bool _claimed;
765 // number of calls to this task
766 int _calls;
768 // when the virtual timer reaches this time, the marking step should
769 // exit
770 double _time_target_ms;
771 // the start time of the current marking step
772 double _start_time_ms;
774 // the oop closure used for iterations over oops
775 OopClosure* _oop_closure;
777 // the region this task is scanning, NULL if we're not scanning any
778 HeapRegion* _curr_region;
779 // the local finger of this task, NULL if we're not scanning a region
780 HeapWord* _finger;
781 // limit of the region this task is scanning, NULL if we're not scanning one
782 HeapWord* _region_limit;
784 // This is used only when we scan regions popped from the region
785 // stack. It records what the last object on such a region we
786 // scanned was. It is used to ensure that, if we abort region
787 // iteration, we do not rescan the first part of the region. This
788 // should be NULL when we're not scanning a region from the region
789 // stack.
790 HeapWord* _region_finger;
792 // the number of words this task has scanned
793 size_t _words_scanned;
794 // When _words_scanned reaches this limit, the regular clock is
795 // called. Notice that this might be decreased under certain
796 // circumstances (i.e. when we believe that we did an expensive
797 // operation).
798 size_t _words_scanned_limit;
799 // the initial value of _words_scanned_limit (i.e. what it was
800 // before it was decreased).
801 size_t _real_words_scanned_limit;
803 // the number of references this task has visited
804 size_t _refs_reached;
805 // When _refs_reached reaches this limit, the regular clock is
806 // called. Notice this this might be decreased under certain
807 // circumstances (i.e. when we believe that we did an expensive
808 // operation).
809 size_t _refs_reached_limit;
810 // the initial value of _refs_reached_limit (i.e. what it was before
811 // it was decreased).
812 size_t _real_refs_reached_limit;
814 // used by the work stealing stuff
815 int _hash_seed;
816 // if this is true, then the task has aborted for some reason
817 bool _has_aborted;
818 // set when the task aborts because it has met its time quota
819 bool _has_aborted_timed_out;
820 // true when we're draining SATB buffers; this avoids the task
821 // aborting due to SATB buffers being available (as we're already
822 // dealing with them)
823 bool _draining_satb_buffers;
825 // number sequence of past step times
826 NumberSeq _step_times_ms;
827 // elapsed time of this task
828 double _elapsed_time_ms;
829 // termination time of this task
830 double _termination_time_ms;
831 // when this task got into the termination protocol
832 double _termination_start_time_ms;
834 // true when the task is during a concurrent phase, false when it is
835 // in the remark phase (so, in the latter case, we do not have to
836 // check all the things that we have to check during the concurrent
837 // phase, i.e. SATB buffer availability...)
838 bool _concurrent;
840 TruncatedSeq _marking_step_diffs_ms;
842 // LOTS of statistics related with this task
843 #if _MARKING_STATS_
844 NumberSeq _all_clock_intervals_ms;
845 double _interval_start_time_ms;
847 int _aborted;
848 int _aborted_overflow;
849 int _aborted_cm_aborted;
850 int _aborted_yield;
851 int _aborted_timed_out;
852 int _aborted_satb;
853 int _aborted_termination;
855 int _steal_attempts;
856 int _steals;
858 int _clock_due_to_marking;
859 int _clock_due_to_scanning;
861 int _local_pushes;
862 int _local_pops;
863 int _local_max_size;
864 int _objs_scanned;
866 int _global_pushes;
867 int _global_pops;
868 int _global_max_size;
870 int _global_transfers_to;
871 int _global_transfers_from;
873 int _region_stack_pops;
875 int _regions_claimed;
876 int _objs_found_on_bitmap;
878 int _satb_buffers_processed;
879 #endif // _MARKING_STATS_
881 // it updates the local fields after this task has claimed
882 // a new region to scan
883 void setup_for_region(HeapRegion* hr);
884 // it brings up-to-date the limit of the region
885 void update_region_limit();
886 // it resets the local fields after a task has finished scanning a
887 // region
888 void giveup_current_region();
890 // called when either the words scanned or the refs visited limit
891 // has been reached
892 void reached_limit();
893 // recalculates the words scanned and refs visited limits
894 void recalculate_limits();
895 // decreases the words scanned and refs visited limits when we reach
896 // an expensive operation
897 void decrease_limits();
898 // it checks whether the words scanned or refs visited reached their
899 // respective limit and calls reached_limit() if they have
900 void check_limits() {
901 if (_words_scanned >= _words_scanned_limit ||
902 _refs_reached >= _refs_reached_limit)
903 reached_limit();
904 }
905 // this is supposed to be called regularly during a marking step as
906 // it checks a bunch of conditions that might cause the marking step
907 // to abort
908 void regular_clock_call();
909 bool concurrent() { return _concurrent; }
911 public:
912 // It resets the task; it should be called right at the beginning of
913 // a marking phase.
914 void reset(CMBitMap* _nextMarkBitMap);
915 // it clears all the fields that correspond to a claimed region.
916 void clear_region_fields();
918 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
920 // The main method of this class which performs a marking step
921 // trying not to exceed the given duration. However, it might exit
922 // prematurely, according to some conditions (i.e. SATB buffers are
923 // available for processing).
924 void do_marking_step(double target_ms);
926 // These two calls start and stop the timer
927 void record_start_time() {
928 _elapsed_time_ms = os::elapsedTime() * 1000.0;
929 }
930 void record_end_time() {
931 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
932 }
934 // returns the task ID
935 int task_id() { return _task_id; }
937 // From TerminatorTerminator. It determines whether this task should
938 // exit the termination protocol after it's entered it.
939 virtual bool should_exit_termination();
941 HeapWord* finger() { return _finger; }
943 bool has_aborted() { return _has_aborted; }
944 void set_has_aborted() { _has_aborted = true; }
945 void clear_has_aborted() { _has_aborted = false; }
946 bool claimed() { return _claimed; }
948 void set_oop_closure(OopClosure* oop_closure) {
949 _oop_closure = oop_closure;
950 }
952 // It grays the object by marking it and, if necessary, pushing it
953 // on the local queue
954 void deal_with_reference(oop obj);
956 // It scans an object and visits its children.
957 void scan_object(oop obj) {
958 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
960 if (_cm->verbose_high())
961 gclog_or_tty->print_cr("[%d] we're scanning object "PTR_FORMAT,
962 _task_id, (void*) obj);
964 size_t obj_size = obj->size();
965 _words_scanned += obj_size;
967 obj->oop_iterate(_oop_closure);
968 statsOnly( ++_objs_scanned );
969 check_limits();
970 }
972 // It pushes an object on the local queue.
973 void push(oop obj);
975 // These two move entries to/from the global stack.
976 void move_entries_to_global_stack();
977 void get_entries_from_global_stack();
979 // It pops and scans objects from the local queue. If partially is
980 // true, then it stops when the queue size is of a given limit. If
981 // partially is false, then it stops when the queue is empty.
982 void drain_local_queue(bool partially);
983 // It moves entries from the global stack to the local queue and
984 // drains the local queue. If partially is true, then it stops when
985 // both the global stack and the local queue reach a given size. If
986 // partially if false, it tries to empty them totally.
987 void drain_global_stack(bool partially);
988 // It keeps picking SATB buffers and processing them until no SATB
989 // buffers are available.
990 void drain_satb_buffers();
991 // It keeps popping regions from the region stack and processing
992 // them until the region stack is empty.
993 void drain_region_stack(BitMapClosure* closure);
995 // moves the local finger to a new location
996 inline void move_finger_to(HeapWord* new_finger) {
997 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
998 _finger = new_finger;
999 }
1001 // moves the region finger to a new location
1002 inline void move_region_finger_to(HeapWord* new_finger) {
1003 assert(new_finger < _cm->finger(), "invariant");
1004 _region_finger = new_finger;
1005 }
1007 CMTask(int task_num, ConcurrentMark *cm,
1008 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1010 // it prints statistics associated with this task
1011 void print_stats();
1013 #if _MARKING_STATS_
1014 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1015 #endif // _MARKING_STATS_
1016 };