Tue, 05 Feb 2013 09:13:05 -0800
8005032: G1: Cleanup serial reference processing closures in concurrent marking
Summary: Reuse the parallel reference processing oop closures during serial reference processing.
Reviewed-by: brutisso
1 /*
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
28 #include "gc_implementation/g1/heapRegionSets.hpp"
29 #include "utilities/taskqueue.hpp"
31 class G1CollectedHeap;
32 class CMTask;
33 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue;
34 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
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) { }
47 void do_object(oop obj) {
48 ShouldNotCallThis();
49 }
50 bool do_object_b(oop obj);
51 };
53 // A generic CM bit map. This is essentially a wrapper around the BitMap
54 // class, with one bit per (1<<_shifter) HeapWords.
56 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
57 protected:
58 HeapWord* _bmStartWord; // base address of range covered by map
59 size_t _bmWordSize; // map size (in #HeapWords covered)
60 const int _shifter; // map to char or bit
61 VirtualSpace _virtual_space; // underlying the bit map
62 BitMap _bm; // the bit map itself
64 public:
65 // constructor
66 CMBitMapRO(int shifter);
68 enum { do_yield = true };
70 // inquiries
71 HeapWord* startWord() const { return _bmStartWord; }
72 size_t sizeInWords() const { return _bmWordSize; }
73 // the following is one past the last word in space
74 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
76 // read marks
78 bool isMarked(HeapWord* addr) const {
79 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
80 "outside underlying space?");
81 return _bm.at(heapWordToOffset(addr));
82 }
84 // iteration
85 inline bool iterate(BitMapClosure* cl, MemRegion mr);
86 inline bool iterate(BitMapClosure* cl);
88 // Return the address corresponding to the next marked bit at or after
89 // "addr", and before "limit", if "limit" is non-NULL. If there is no
90 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
91 HeapWord* getNextMarkedWordAddress(HeapWord* addr,
92 HeapWord* limit = NULL) const;
93 // Return the address corresponding to the next unmarked bit at or after
94 // "addr", and before "limit", if "limit" is non-NULL. If there is no
95 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
96 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr,
97 HeapWord* limit = NULL) const;
99 // conversion utilities
100 // XXX Fix these so that offsets are size_t's...
101 HeapWord* offsetToHeapWord(size_t offset) const {
102 return _bmStartWord + (offset << _shifter);
103 }
104 size_t heapWordToOffset(HeapWord* addr) const {
105 return pointer_delta(addr, _bmStartWord) >> _shifter;
106 }
107 int heapWordDiffToOffsetDiff(size_t diff) const;
108 HeapWord* nextWord(HeapWord* addr) {
109 return offsetToHeapWord(heapWordToOffset(addr) + 1);
110 }
112 // debugging
113 NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
114 };
116 class CMBitMap : public CMBitMapRO {
118 public:
119 // constructor
120 CMBitMap(int shifter) :
121 CMBitMapRO(shifter) {}
123 // Allocates the back store for the marking bitmap
124 bool allocate(ReservedSpace heap_rs);
126 // write marks
127 void mark(HeapWord* addr) {
128 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
129 "outside underlying space?");
130 _bm.set_bit(heapWordToOffset(addr));
131 }
132 void clear(HeapWord* addr) {
133 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
134 "outside underlying space?");
135 _bm.clear_bit(heapWordToOffset(addr));
136 }
137 bool parMark(HeapWord* addr) {
138 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
139 "outside underlying space?");
140 return _bm.par_set_bit(heapWordToOffset(addr));
141 }
142 bool parClear(HeapWord* addr) {
143 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
144 "outside underlying space?");
145 return _bm.par_clear_bit(heapWordToOffset(addr));
146 }
147 void markRange(MemRegion mr);
148 void clearAll();
149 void clearRange(MemRegion mr);
151 // Starting at the bit corresponding to "addr" (inclusive), find the next
152 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
153 // the end of this run (stopping at "end_addr"). Return the MemRegion
154 // covering from the start of the region corresponding to the first bit
155 // of the run to the end of the region corresponding to the last bit of
156 // the run. If there is no "1" bit at or after "addr", return an empty
157 // MemRegion.
158 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
159 };
161 // Represents a marking stack used by ConcurrentMarking in the G1 collector.
162 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
163 VirtualSpace _virtual_space; // Underlying backing store for actual stack
164 ConcurrentMark* _cm;
165 oop* _base; // bottom of stack
166 jint _index; // one more than last occupied index
167 jint _capacity; // max #elements
168 jint _saved_index; // value of _index saved at start of GC
169 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
171 bool _overflow;
172 bool _should_expand;
173 DEBUG_ONLY(bool _drain_in_progress;)
174 DEBUG_ONLY(bool _drain_in_progress_yields;)
176 public:
177 CMMarkStack(ConcurrentMark* cm);
178 ~CMMarkStack();
180 #ifndef PRODUCT
181 jint max_depth() const {
182 return _max_depth;
183 }
184 #endif
186 bool allocate(size_t capacity);
188 oop pop() {
189 if (!isEmpty()) {
190 return _base[--_index] ;
191 }
192 return NULL;
193 }
195 // If overflow happens, don't do the push, and record the overflow.
196 // *Requires* that "ptr" is already marked.
197 void push(oop ptr) {
198 if (isFull()) {
199 // Record overflow.
200 _overflow = true;
201 return;
202 } else {
203 _base[_index++] = ptr;
204 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
205 }
206 }
207 // Non-block impl. Note: concurrency is allowed only with other
208 // "par_push" operations, not with "pop" or "drain". We would need
209 // parallel versions of them if such concurrency was desired.
210 void par_push(oop ptr);
212 // Pushes the first "n" elements of "ptr_arr" on the stack.
213 // Non-block impl. Note: concurrency is allowed only with other
214 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
215 void par_adjoin_arr(oop* ptr_arr, int n);
217 // Pushes the first "n" elements of "ptr_arr" on the stack.
218 // Locking impl: concurrency is allowed only with
219 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
220 // locking strategy.
221 void par_push_arr(oop* ptr_arr, int n);
223 // If returns false, the array was empty. Otherwise, removes up to "max"
224 // elements from the stack, and transfers them to "ptr_arr" in an
225 // unspecified order. The actual number transferred is given in "n" ("n
226 // == 0" is deliberately redundant with the return value.) Locking impl:
227 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
228 // operations, which use the same locking strategy.
229 bool par_pop_arr(oop* ptr_arr, int max, int* n);
231 // Drain the mark stack, applying the given closure to all fields of
232 // objects on the stack. (That is, continue until the stack is empty,
233 // even if closure applications add entries to the stack.) The "bm"
234 // argument, if non-null, may be used to verify that only marked objects
235 // are on the mark stack. If "yield_after" is "true", then the
236 // concurrent marker performing the drain offers to yield after
237 // processing each object. If a yield occurs, stops the drain operation
238 // and returns false. Otherwise, returns true.
239 template<class OopClosureClass>
240 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
242 bool isEmpty() { return _index == 0; }
243 bool isFull() { return _index == _capacity; }
244 int maxElems() { return _capacity; }
246 bool overflow() { return _overflow; }
247 void clear_overflow() { _overflow = false; }
249 bool should_expand() const { return _should_expand; }
250 void set_should_expand();
252 // Expand the stack, typically in response to an overflow condition
253 void expand();
255 int size() { return _index; }
257 void setEmpty() { _index = 0; clear_overflow(); }
259 // Record the current index.
260 void note_start_of_gc();
262 // Make sure that we have not added any entries to the stack during GC.
263 void note_end_of_gc();
265 // iterate over the oops in the mark stack, up to the bound recorded via
266 // the call above.
267 void oops_do(OopClosure* f);
268 };
270 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
271 private:
272 #ifndef PRODUCT
273 uintx _num_remaining;
274 bool _force;
275 #endif // !defined(PRODUCT)
277 public:
278 void init() PRODUCT_RETURN;
279 void update() PRODUCT_RETURN;
280 bool should_force() PRODUCT_RETURN_( return false; );
281 };
283 // this will enable a variety of different statistics per GC task
284 #define _MARKING_STATS_ 0
285 // this will enable the higher verbose levels
286 #define _MARKING_VERBOSE_ 0
288 #if _MARKING_STATS_
289 #define statsOnly(statement) \
290 do { \
291 statement ; \
292 } while (0)
293 #else // _MARKING_STATS_
294 #define statsOnly(statement) \
295 do { \
296 } while (0)
297 #endif // _MARKING_STATS_
299 typedef enum {
300 no_verbose = 0, // verbose turned off
301 stats_verbose, // only prints stats at the end of marking
302 low_verbose, // low verbose, mostly per region and per major event
303 medium_verbose, // a bit more detailed than low
304 high_verbose // per object verbose
305 } CMVerboseLevel;
307 class YoungList;
309 // Root Regions are regions that are not empty at the beginning of a
310 // marking cycle and which we might collect during an evacuation pause
311 // while the cycle is active. Given that, during evacuation pauses, we
312 // do not copy objects that are explicitly marked, what we have to do
313 // for the root regions is to scan them and mark all objects reachable
314 // from them. According to the SATB assumptions, we only need to visit
315 // each object once during marking. So, as long as we finish this scan
316 // before the next evacuation pause, we can copy the objects from the
317 // root regions without having to mark them or do anything else to them.
318 //
319 // Currently, we only support root region scanning once (at the start
320 // of the marking cycle) and the root regions are all the survivor
321 // regions populated during the initial-mark pause.
322 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
323 private:
324 YoungList* _young_list;
325 ConcurrentMark* _cm;
327 volatile bool _scan_in_progress;
328 volatile bool _should_abort;
329 HeapRegion* volatile _next_survivor;
331 public:
332 CMRootRegions();
333 // We actually do most of the initialization in this method.
334 void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
336 // Reset the claiming / scanning of the root regions.
337 void prepare_for_scan();
339 // Forces get_next() to return NULL so that the iteration aborts early.
340 void abort() { _should_abort = true; }
342 // Return true if the CM thread are actively scanning root regions,
343 // false otherwise.
344 bool scan_in_progress() { return _scan_in_progress; }
346 // Claim the next root region to scan atomically, or return NULL if
347 // all have been claimed.
348 HeapRegion* claim_next();
350 // Flag that we're done with root region scanning and notify anyone
351 // who's waiting on it. If aborted is false, assume that all regions
352 // have been claimed.
353 void scan_finished();
355 // If CM threads are still scanning root regions, wait until they
356 // are done. Return true if we had to wait, false otherwise.
357 bool wait_until_scan_finished();
358 };
360 class ConcurrentMarkThread;
362 class ConcurrentMark: public CHeapObj<mtGC> {
363 friend class CMMarkStack;
364 friend class ConcurrentMarkThread;
365 friend class CMTask;
366 friend class CMBitMapClosure;
367 friend class CMGlobalObjectClosure;
368 friend class CMRemarkTask;
369 friend class CMConcurrentMarkingTask;
370 friend class G1ParNoteEndTask;
371 friend class CalcLiveObjectsClosure;
372 friend class G1CMRefProcTaskProxy;
373 friend class G1CMRefProcTaskExecutor;
374 friend class G1CMKeepAliveAndDrainClosure;
375 friend class G1CMDrainMarkingStackClosure;
377 protected:
378 ConcurrentMarkThread* _cmThread; // the thread doing the work
379 G1CollectedHeap* _g1h; // the heap.
380 uint _parallel_marking_threads; // the number of marking
381 // threads we're use
382 uint _max_parallel_marking_threads; // max number of marking
383 // threads we'll ever use
384 double _sleep_factor; // how much we have to sleep, with
385 // respect to the work we just did, to
386 // meet the marking overhead goal
387 double _marking_task_overhead; // marking target overhead for
388 // a single task
390 // same as the two above, but for the cleanup task
391 double _cleanup_sleep_factor;
392 double _cleanup_task_overhead;
394 FreeRegionList _cleanup_list;
396 // Concurrent marking support structures
397 CMBitMap _markBitMap1;
398 CMBitMap _markBitMap2;
399 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
400 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
402 BitMap _region_bm;
403 BitMap _card_bm;
405 // Heap bounds
406 HeapWord* _heap_start;
407 HeapWord* _heap_end;
409 // Root region tracking and claiming.
410 CMRootRegions _root_regions;
412 // For gray objects
413 CMMarkStack _markStack; // Grey objects behind global finger.
414 HeapWord* volatile _finger; // the global finger, region aligned,
415 // always points to the end of the
416 // last claimed region
418 // marking tasks
419 uint _max_worker_id;// maximum worker id
420 uint _active_tasks; // task num currently active
421 CMTask** _tasks; // task queue array (max_worker_id len)
422 CMTaskQueueSet* _task_queues; // task queue set
423 ParallelTaskTerminator _terminator; // for termination
425 // Two sync barriers that are used to synchronise tasks when an
426 // overflow occurs. The algorithm is the following. All tasks enter
427 // the first one to ensure that they have all stopped manipulating
428 // the global data structures. After they exit it, they re-initialise
429 // their data structures and task 0 re-initialises the global data
430 // structures. Then, they enter the second sync barrier. This
431 // ensure, that no task starts doing work before all data
432 // structures (local and global) have been re-initialised. When they
433 // exit it, they are free to start working again.
434 WorkGangBarrierSync _first_overflow_barrier_sync;
435 WorkGangBarrierSync _second_overflow_barrier_sync;
437 // this is set by any task, when an overflow on the global data
438 // structures is detected.
439 volatile bool _has_overflown;
440 // true: marking is concurrent, false: we're in remark
441 volatile bool _concurrent;
442 // set at the end of a Full GC so that marking aborts
443 volatile bool _has_aborted;
445 // used when remark aborts due to an overflow to indicate that
446 // another concurrent marking phase should start
447 volatile bool _restart_for_overflow;
449 // This is true from the very start of concurrent marking until the
450 // point when all the tasks complete their work. It is really used
451 // to determine the points between the end of concurrent marking and
452 // time of remark.
453 volatile bool _concurrent_marking_in_progress;
455 // verbose level
456 CMVerboseLevel _verbose_level;
458 // All of these times are in ms.
459 NumberSeq _init_times;
460 NumberSeq _remark_times;
461 NumberSeq _remark_mark_times;
462 NumberSeq _remark_weak_ref_times;
463 NumberSeq _cleanup_times;
464 double _total_counting_time;
465 double _total_rs_scrub_time;
467 double* _accum_task_vtime; // accumulated task vtime
469 FlexibleWorkGang* _parallel_workers;
471 ForceOverflowSettings _force_overflow_conc;
472 ForceOverflowSettings _force_overflow_stw;
474 void weakRefsWork(bool clear_all_soft_refs);
476 void swapMarkBitMaps();
478 // It resets the global marking data structures, as well as the
479 // task local ones; should be called during initial mark.
480 void reset();
482 // Resets all the marking data structures. Called when we have to restart
483 // marking or when marking completes (via set_non_marking_state below).
484 void reset_marking_state(bool clear_overflow = true);
486 // We do this after we're done with marking so that the marking data
487 // structures are initialised to a sensible and predictable state.
488 void set_non_marking_state();
490 // It should be called to indicate which phase we're in (concurrent
491 // mark or remark) and how many threads are currently active.
492 void set_phase(uint active_tasks, bool concurrent);
494 // prints all gathered CM-related statistics
495 void print_stats();
497 bool cleanup_list_is_empty() {
498 return _cleanup_list.is_empty();
499 }
501 // accessor methods
502 uint parallel_marking_threads() const { return _parallel_marking_threads; }
503 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
504 double sleep_factor() { return _sleep_factor; }
505 double marking_task_overhead() { return _marking_task_overhead;}
506 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
507 double cleanup_task_overhead() { return _cleanup_task_overhead;}
509 bool use_parallel_marking_threads() const {
510 assert(parallel_marking_threads() <=
511 max_parallel_marking_threads(), "sanity");
512 assert((_parallel_workers == NULL && parallel_marking_threads() == 0) ||
513 parallel_marking_threads() > 0,
514 "parallel workers not set up correctly");
515 return _parallel_workers != NULL;
516 }
518 HeapWord* finger() { return _finger; }
519 bool concurrent() { return _concurrent; }
520 uint active_tasks() { return _active_tasks; }
521 ParallelTaskTerminator* terminator() { return &_terminator; }
523 // It claims the next available region to be scanned by a marking
524 // task/thread. It might return NULL if the next region is empty or
525 // we have run out of regions. In the latter case, out_of_regions()
526 // determines whether we've really run out of regions or the task
527 // should call claim_region() again. This might seem a bit
528 // awkward. Originally, the code was written so that claim_region()
529 // either successfully returned with a non-empty region or there
530 // were no more regions to be claimed. The problem with this was
531 // that, in certain circumstances, it iterated over large chunks of
532 // the heap finding only empty regions and, while it was working, it
533 // was preventing the calling task to call its regular clock
534 // method. So, this way, each task will spend very little time in
535 // claim_region() and is allowed to call the regular clock method
536 // frequently.
537 HeapRegion* claim_region(uint worker_id);
539 // It determines whether we've run out of regions to scan.
540 bool out_of_regions() { return _finger == _heap_end; }
542 // Returns the task with the given id
543 CMTask* task(int id) {
544 assert(0 <= id && id < (int) _active_tasks,
545 "task id not within active bounds");
546 return _tasks[id];
547 }
549 // Returns the task queue with the given id
550 CMTaskQueue* task_queue(int id) {
551 assert(0 <= id && id < (int) _active_tasks,
552 "task queue id not within active bounds");
553 return (CMTaskQueue*) _task_queues->queue(id);
554 }
556 // Returns the task queue set
557 CMTaskQueueSet* task_queues() { return _task_queues; }
559 // Access / manipulation of the overflow flag which is set to
560 // indicate that the global stack has overflown
561 bool has_overflown() { return _has_overflown; }
562 void set_has_overflown() { _has_overflown = true; }
563 void clear_has_overflown() { _has_overflown = false; }
564 bool restart_for_overflow() { return _restart_for_overflow; }
566 bool has_aborted() { return _has_aborted; }
568 // Methods to enter the two overflow sync barriers
569 void enter_first_sync_barrier(uint worker_id);
570 void enter_second_sync_barrier(uint worker_id);
572 ForceOverflowSettings* force_overflow_conc() {
573 return &_force_overflow_conc;
574 }
576 ForceOverflowSettings* force_overflow_stw() {
577 return &_force_overflow_stw;
578 }
580 ForceOverflowSettings* force_overflow() {
581 if (concurrent()) {
582 return force_overflow_conc();
583 } else {
584 return force_overflow_stw();
585 }
586 }
588 // Live Data Counting data structures...
589 // These data structures are initialized at the start of
590 // marking. They are written to while marking is active.
591 // They are aggregated during remark; the aggregated values
592 // are then used to populate the _region_bm, _card_bm, and
593 // the total live bytes, which are then subsequently updated
594 // during cleanup.
596 // An array of bitmaps (one bit map per task). Each bitmap
597 // is used to record the cards spanned by the live objects
598 // marked by that task/worker.
599 BitMap* _count_card_bitmaps;
601 // Used to record the number of marked live bytes
602 // (for each region, by worker thread).
603 size_t** _count_marked_bytes;
605 // Card index of the bottom of the G1 heap. Used for biasing indices into
606 // the card bitmaps.
607 intptr_t _heap_bottom_card_num;
609 // Set to true when initialization is complete
610 bool _completed_initialization;
612 public:
613 // Manipulation of the global mark stack.
614 // Notice that the first mark_stack_push is CAS-based, whereas the
615 // two below are Mutex-based. This is OK since the first one is only
616 // called during evacuation pauses and doesn't compete with the
617 // other two (which are called by the marking tasks during
618 // concurrent marking or remark).
619 bool mark_stack_push(oop p) {
620 _markStack.par_push(p);
621 if (_markStack.overflow()) {
622 set_has_overflown();
623 return false;
624 }
625 return true;
626 }
627 bool mark_stack_push(oop* arr, int n) {
628 _markStack.par_push_arr(arr, n);
629 if (_markStack.overflow()) {
630 set_has_overflown();
631 return false;
632 }
633 return true;
634 }
635 void mark_stack_pop(oop* arr, int max, int* n) {
636 _markStack.par_pop_arr(arr, max, n);
637 }
638 size_t mark_stack_size() { return _markStack.size(); }
639 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
640 bool mark_stack_overflow() { return _markStack.overflow(); }
641 bool mark_stack_empty() { return _markStack.isEmpty(); }
643 CMRootRegions* root_regions() { return &_root_regions; }
645 bool concurrent_marking_in_progress() {
646 return _concurrent_marking_in_progress;
647 }
648 void set_concurrent_marking_in_progress() {
649 _concurrent_marking_in_progress = true;
650 }
651 void clear_concurrent_marking_in_progress() {
652 _concurrent_marking_in_progress = false;
653 }
655 void update_accum_task_vtime(int i, double vtime) {
656 _accum_task_vtime[i] += vtime;
657 }
659 double all_task_accum_vtime() {
660 double ret = 0.0;
661 for (uint i = 0; i < _max_worker_id; ++i)
662 ret += _accum_task_vtime[i];
663 return ret;
664 }
666 // Attempts to steal an object from the task queues of other tasks
667 bool try_stealing(uint worker_id, int* hash_seed, oop& obj) {
668 return _task_queues->steal(worker_id, hash_seed, obj);
669 }
671 ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs);
672 ~ConcurrentMark();
674 ConcurrentMarkThread* cmThread() { return _cmThread; }
676 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
677 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
679 // Returns the number of GC threads to be used in a concurrent
680 // phase based on the number of GC threads being used in a STW
681 // phase.
682 uint scale_parallel_threads(uint n_par_threads);
684 // Calculates the number of GC threads to be used in a concurrent phase.
685 uint calc_parallel_marking_threads();
687 // The following three are interaction between CM and
688 // G1CollectedHeap
690 // This notifies CM that a root during initial-mark needs to be
691 // grayed. It is MT-safe. word_size is the size of the object in
692 // words. It is passed explicitly as sometimes we cannot calculate
693 // it from the given object because it might be in an inconsistent
694 // state (e.g., in to-space and being copied). So the caller is
695 // responsible for dealing with this issue (e.g., get the size from
696 // the from-space image when the to-space image might be
697 // inconsistent) and always passing the size. hr is the region that
698 // contains the object and it's passed optionally from callers who
699 // might already have it (no point in recalculating it).
700 inline void grayRoot(oop obj, size_t word_size,
701 uint worker_id, HeapRegion* hr = NULL);
703 // It iterates over the heap and for each object it comes across it
704 // will dump the contents of its reference fields, as well as
705 // liveness information for the object and its referents. The dump
706 // will be written to a file with the following name:
707 // G1PrintReachableBaseFile + "." + str.
708 // vo decides whether the prev (vo == UsePrevMarking), the next
709 // (vo == UseNextMarking) marking information, or the mark word
710 // (vo == UseMarkWord) will be used to determine the liveness of
711 // each object / referent.
712 // If all is true, all objects in the heap will be dumped, otherwise
713 // only the live ones. In the dump the following symbols / breviations
714 // are used:
715 // M : an explicitly live object (its bitmap bit is set)
716 // > : an implicitly live object (over tams)
717 // O : an object outside the G1 heap (typically: in the perm gen)
718 // NOT : a reference field whose referent is not live
719 // AND MARKED : indicates that an object is both explicitly and
720 // implicitly live (it should be one or the other, not both)
721 void print_reachable(const char* str,
722 VerifyOption vo, bool all) PRODUCT_RETURN;
724 // Clear the next marking bitmap (will be called concurrently).
725 void clearNextBitmap();
727 // These two do the work that needs to be done before and after the
728 // initial root checkpoint. Since this checkpoint can be done at two
729 // different points (i.e. an explicit pause or piggy-backed on a
730 // young collection), then it's nice to be able to easily share the
731 // pre/post code. It might be the case that we can put everything in
732 // the post method. TP
733 void checkpointRootsInitialPre();
734 void checkpointRootsInitialPost();
736 // Scan all the root regions and mark everything reachable from
737 // them.
738 void scanRootRegions();
740 // Scan a single root region and mark everything reachable from it.
741 void scanRootRegion(HeapRegion* hr, uint worker_id);
743 // Do concurrent phase of marking, to a tentative transitive closure.
744 void markFromRoots();
746 void checkpointRootsFinal(bool clear_all_soft_refs);
747 void checkpointRootsFinalWork();
748 void cleanup();
749 void completeCleanup();
751 // Mark in the previous bitmap. NB: this is usually read-only, so use
752 // this carefully!
753 inline void markPrev(oop p);
755 // Clears marks for all objects in the given range, for the prev,
756 // next, or both bitmaps. NB: the previous bitmap is usually
757 // read-only, so use this carefully!
758 void clearRangePrevBitmap(MemRegion mr);
759 void clearRangeNextBitmap(MemRegion mr);
760 void clearRangeBothBitmaps(MemRegion mr);
762 // Notify data structures that a GC has started.
763 void note_start_of_gc() {
764 _markStack.note_start_of_gc();
765 }
767 // Notify data structures that a GC is finished.
768 void note_end_of_gc() {
769 _markStack.note_end_of_gc();
770 }
772 // Verify that there are no CSet oops on the stacks (taskqueues /
773 // global mark stack), enqueued SATB buffers, per-thread SATB
774 // buffers, and fingers (global / per-task). The boolean parameters
775 // decide which of the above data structures to verify. If marking
776 // is not in progress, it's a no-op.
777 void verify_no_cset_oops(bool verify_stacks,
778 bool verify_enqueued_buffers,
779 bool verify_thread_buffers,
780 bool verify_fingers) PRODUCT_RETURN;
782 // It is called at the end of an evacuation pause during marking so
783 // that CM is notified of where the new end of the heap is. It
784 // doesn't do anything if concurrent_marking_in_progress() is false,
785 // unless the force parameter is true.
786 void update_g1_committed(bool force = false);
788 bool isMarked(oop p) const {
789 assert(p != NULL && p->is_oop(), "expected an oop");
790 HeapWord* addr = (HeapWord*)p;
791 assert(addr >= _nextMarkBitMap->startWord() ||
792 addr < _nextMarkBitMap->endWord(), "in a region");
794 return _nextMarkBitMap->isMarked(addr);
795 }
797 inline bool not_yet_marked(oop p) const;
799 // XXX Debug code
800 bool containing_card_is_marked(void* p);
801 bool containing_cards_are_marked(void* start, void* last);
803 bool isPrevMarked(oop p) const {
804 assert(p != NULL && p->is_oop(), "expected an oop");
805 HeapWord* addr = (HeapWord*)p;
806 assert(addr >= _prevMarkBitMap->startWord() ||
807 addr < _prevMarkBitMap->endWord(), "in a region");
809 return _prevMarkBitMap->isMarked(addr);
810 }
812 inline bool do_yield_check(uint worker_i = 0);
813 inline bool should_yield();
815 // Called to abort the marking cycle after a Full GC takes palce.
816 void abort();
818 // This prints the global/local fingers. It is used for debugging.
819 NOT_PRODUCT(void print_finger();)
821 void print_summary_info();
823 void print_worker_threads_on(outputStream* st) const;
825 // The following indicate whether a given verbose level has been
826 // set. Notice that anything above stats is conditional to
827 // _MARKING_VERBOSE_ having been set to 1
828 bool verbose_stats() {
829 return _verbose_level >= stats_verbose;
830 }
831 bool verbose_low() {
832 return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
833 }
834 bool verbose_medium() {
835 return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
836 }
837 bool verbose_high() {
838 return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
839 }
841 // Liveness counting
843 // Utility routine to set an exclusive range of cards on the given
844 // card liveness bitmap
845 inline void set_card_bitmap_range(BitMap* card_bm,
846 BitMap::idx_t start_idx,
847 BitMap::idx_t end_idx,
848 bool is_par);
850 // Returns the card number of the bottom of the G1 heap.
851 // Used in biasing indices into accounting card bitmaps.
852 intptr_t heap_bottom_card_num() const {
853 return _heap_bottom_card_num;
854 }
856 // Returns the card bitmap for a given task or worker id.
857 BitMap* count_card_bitmap_for(uint worker_id) {
858 assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
859 assert(_count_card_bitmaps != NULL, "uninitialized");
860 BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
861 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
862 return task_card_bm;
863 }
865 // Returns the array containing the marked bytes for each region,
866 // for the given worker or task id.
867 size_t* count_marked_bytes_array_for(uint worker_id) {
868 assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
869 assert(_count_marked_bytes != NULL, "uninitialized");
870 size_t* marked_bytes_array = _count_marked_bytes[worker_id];
871 assert(marked_bytes_array != NULL, "uninitialized");
872 return marked_bytes_array;
873 }
875 // Returns the index in the liveness accounting card table bitmap
876 // for the given address
877 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
879 // Counts the size of the given memory region in the the given
880 // marked_bytes array slot for the given HeapRegion.
881 // Sets the bits in the given card bitmap that are associated with the
882 // cards that are spanned by the memory region.
883 inline void count_region(MemRegion mr, HeapRegion* hr,
884 size_t* marked_bytes_array,
885 BitMap* task_card_bm);
887 // Counts the given memory region in the task/worker counting
888 // data structures for the given worker id.
889 inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
891 // Counts the given memory region in the task/worker counting
892 // data structures for the given worker id.
893 inline void count_region(MemRegion mr, uint worker_id);
895 // Counts the given object in the given task/worker counting
896 // data structures.
897 inline void count_object(oop obj, HeapRegion* hr,
898 size_t* marked_bytes_array,
899 BitMap* task_card_bm);
901 // Counts the given object in the task/worker counting data
902 // structures for the given worker id.
903 inline void count_object(oop obj, HeapRegion* hr, uint worker_id);
905 // Attempts to mark the given object and, if successful, counts
906 // the object in the given task/worker counting structures.
907 inline bool par_mark_and_count(oop obj, HeapRegion* hr,
908 size_t* marked_bytes_array,
909 BitMap* task_card_bm);
911 // Attempts to mark the given object and, if successful, counts
912 // the object in the task/worker counting structures for the
913 // given worker id.
914 inline bool par_mark_and_count(oop obj, size_t word_size,
915 HeapRegion* hr, uint worker_id);
917 // Attempts to mark the given object and, if successful, counts
918 // the object in the task/worker counting structures for the
919 // given worker id.
920 inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id);
922 // Similar to the above routine but we don't know the heap region that
923 // contains the object to be marked/counted, which this routine looks up.
924 inline bool par_mark_and_count(oop obj, uint worker_id);
926 // Similar to the above routine but there are times when we cannot
927 // safely calculate the size of obj due to races and we, therefore,
928 // pass the size in as a parameter. It is the caller's reponsibility
929 // to ensure that the size passed in for obj is valid.
930 inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id);
932 // Unconditionally mark the given object, and unconditinally count
933 // the object in the counting structures for worker id 0.
934 // Should *not* be called from parallel code.
935 inline bool mark_and_count(oop obj, HeapRegion* hr);
937 // Similar to the above routine but we don't know the heap region that
938 // contains the object to be marked/counted, which this routine looks up.
939 // Should *not* be called from parallel code.
940 inline bool mark_and_count(oop obj);
942 // Returns true if initialization was successfully completed.
943 bool completed_initialization() const {
944 return _completed_initialization;
945 }
947 protected:
948 // Clear all the per-task bitmaps and arrays used to store the
949 // counting data.
950 void clear_all_count_data();
952 // Aggregates the counting data for each worker/task
953 // that was constructed while marking. Also sets
954 // the amount of marked bytes for each region and
955 // the top at concurrent mark count.
956 void aggregate_count_data();
958 // Verification routine
959 void verify_count_data();
960 };
962 // A class representing a marking task.
963 class CMTask : public TerminatorTerminator {
964 private:
965 enum PrivateConstants {
966 // the regular clock call is called once the scanned words reaches
967 // this limit
968 words_scanned_period = 12*1024,
969 // the regular clock call is called once the number of visited
970 // references reaches this limit
971 refs_reached_period = 384,
972 // initial value for the hash seed, used in the work stealing code
973 init_hash_seed = 17,
974 // how many entries will be transferred between global stack and
975 // local queues
976 global_stack_transfer_size = 16
977 };
979 uint _worker_id;
980 G1CollectedHeap* _g1h;
981 ConcurrentMark* _cm;
982 CMBitMap* _nextMarkBitMap;
983 // the task queue of this task
984 CMTaskQueue* _task_queue;
985 private:
986 // the task queue set---needed for stealing
987 CMTaskQueueSet* _task_queues;
988 // indicates whether the task has been claimed---this is only for
989 // debugging purposes
990 bool _claimed;
992 // number of calls to this task
993 int _calls;
995 // when the virtual timer reaches this time, the marking step should
996 // exit
997 double _time_target_ms;
998 // the start time of the current marking step
999 double _start_time_ms;
1001 // the oop closure used for iterations over oops
1002 G1CMOopClosure* _cm_oop_closure;
1004 // the region this task is scanning, NULL if we're not scanning any
1005 HeapRegion* _curr_region;
1006 // the local finger of this task, NULL if we're not scanning a region
1007 HeapWord* _finger;
1008 // limit of the region this task is scanning, NULL if we're not scanning one
1009 HeapWord* _region_limit;
1011 // the number of words this task has scanned
1012 size_t _words_scanned;
1013 // When _words_scanned reaches this limit, the regular clock is
1014 // called. Notice that this might be decreased under certain
1015 // circumstances (i.e. when we believe that we did an expensive
1016 // operation).
1017 size_t _words_scanned_limit;
1018 // the initial value of _words_scanned_limit (i.e. what it was
1019 // before it was decreased).
1020 size_t _real_words_scanned_limit;
1022 // the number of references this task has visited
1023 size_t _refs_reached;
1024 // When _refs_reached reaches this limit, the regular clock is
1025 // called. Notice this this might be decreased under certain
1026 // circumstances (i.e. when we believe that we did an expensive
1027 // operation).
1028 size_t _refs_reached_limit;
1029 // the initial value of _refs_reached_limit (i.e. what it was before
1030 // it was decreased).
1031 size_t _real_refs_reached_limit;
1033 // used by the work stealing stuff
1034 int _hash_seed;
1035 // if this is true, then the task has aborted for some reason
1036 bool _has_aborted;
1037 // set when the task aborts because it has met its time quota
1038 bool _has_timed_out;
1039 // true when we're draining SATB buffers; this avoids the task
1040 // aborting due to SATB buffers being available (as we're already
1041 // dealing with them)
1042 bool _draining_satb_buffers;
1044 // number sequence of past step times
1045 NumberSeq _step_times_ms;
1046 // elapsed time of this task
1047 double _elapsed_time_ms;
1048 // termination time of this task
1049 double _termination_time_ms;
1050 // when this task got into the termination protocol
1051 double _termination_start_time_ms;
1053 // true when the task is during a concurrent phase, false when it is
1054 // in the remark phase (so, in the latter case, we do not have to
1055 // check all the things that we have to check during the concurrent
1056 // phase, i.e. SATB buffer availability...)
1057 bool _concurrent;
1059 TruncatedSeq _marking_step_diffs_ms;
1061 // Counting data structures. Embedding the task's marked_bytes_array
1062 // and card bitmap into the actual task saves having to go through
1063 // the ConcurrentMark object.
1064 size_t* _marked_bytes_array;
1065 BitMap* _card_bm;
1067 // LOTS of statistics related with this task
1068 #if _MARKING_STATS_
1069 NumberSeq _all_clock_intervals_ms;
1070 double _interval_start_time_ms;
1072 int _aborted;
1073 int _aborted_overflow;
1074 int _aborted_cm_aborted;
1075 int _aborted_yield;
1076 int _aborted_timed_out;
1077 int _aborted_satb;
1078 int _aborted_termination;
1080 int _steal_attempts;
1081 int _steals;
1083 int _clock_due_to_marking;
1084 int _clock_due_to_scanning;
1086 int _local_pushes;
1087 int _local_pops;
1088 int _local_max_size;
1089 int _objs_scanned;
1091 int _global_pushes;
1092 int _global_pops;
1093 int _global_max_size;
1095 int _global_transfers_to;
1096 int _global_transfers_from;
1098 int _regions_claimed;
1099 int _objs_found_on_bitmap;
1101 int _satb_buffers_processed;
1102 #endif // _MARKING_STATS_
1104 // it updates the local fields after this task has claimed
1105 // a new region to scan
1106 void setup_for_region(HeapRegion* hr);
1107 // it brings up-to-date the limit of the region
1108 void update_region_limit();
1110 // called when either the words scanned or the refs visited limit
1111 // has been reached
1112 void reached_limit();
1113 // recalculates the words scanned and refs visited limits
1114 void recalculate_limits();
1115 // decreases the words scanned and refs visited limits when we reach
1116 // an expensive operation
1117 void decrease_limits();
1118 // it checks whether the words scanned or refs visited reached their
1119 // respective limit and calls reached_limit() if they have
1120 void check_limits() {
1121 if (_words_scanned >= _words_scanned_limit ||
1122 _refs_reached >= _refs_reached_limit) {
1123 reached_limit();
1124 }
1125 }
1126 // this is supposed to be called regularly during a marking step as
1127 // it checks a bunch of conditions that might cause the marking step
1128 // to abort
1129 void regular_clock_call();
1130 bool concurrent() { return _concurrent; }
1132 public:
1133 // It resets the task; it should be called right at the beginning of
1134 // a marking phase.
1135 void reset(CMBitMap* _nextMarkBitMap);
1136 // it clears all the fields that correspond to a claimed region.
1137 void clear_region_fields();
1139 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
1141 // The main method of this class which performs a marking step
1142 // trying not to exceed the given duration. However, it might exit
1143 // prematurely, according to some conditions (i.e. SATB buffers are
1144 // available for processing).
1145 void do_marking_step(double target_ms, bool do_stealing, bool do_termination);
1147 // These two calls start and stop the timer
1148 void record_start_time() {
1149 _elapsed_time_ms = os::elapsedTime() * 1000.0;
1150 }
1151 void record_end_time() {
1152 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
1153 }
1155 // returns the worker ID associated with this task.
1156 uint worker_id() { return _worker_id; }
1158 // From TerminatorTerminator. It determines whether this task should
1159 // exit the termination protocol after it's entered it.
1160 virtual bool should_exit_termination();
1162 // Resets the local region fields after a task has finished scanning a
1163 // region; or when they have become stale as a result of the region
1164 // being evacuated.
1165 void giveup_current_region();
1167 HeapWord* finger() { return _finger; }
1169 bool has_aborted() { return _has_aborted; }
1170 void set_has_aborted() { _has_aborted = true; }
1171 void clear_has_aborted() { _has_aborted = false; }
1172 bool has_timed_out() { return _has_timed_out; }
1173 bool claimed() { return _claimed; }
1175 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
1177 // It grays the object by marking it and, if necessary, pushing it
1178 // on the local queue
1179 inline void deal_with_reference(oop obj);
1181 // It scans an object and visits its children.
1182 void scan_object(oop obj);
1184 // It pushes an object on the local queue.
1185 inline void push(oop obj);
1187 // These two move entries to/from the global stack.
1188 void move_entries_to_global_stack();
1189 void get_entries_from_global_stack();
1191 // It pops and scans objects from the local queue. If partially is
1192 // true, then it stops when the queue size is of a given limit. If
1193 // partially is false, then it stops when the queue is empty.
1194 void drain_local_queue(bool partially);
1195 // It moves entries from the global stack to the local queue and
1196 // drains the local queue. If partially is true, then it stops when
1197 // both the global stack and the local queue reach a given size. If
1198 // partially if false, it tries to empty them totally.
1199 void drain_global_stack(bool partially);
1200 // It keeps picking SATB buffers and processing them until no SATB
1201 // buffers are available.
1202 void drain_satb_buffers();
1204 // moves the local finger to a new location
1205 inline void move_finger_to(HeapWord* new_finger) {
1206 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
1207 _finger = new_finger;
1208 }
1210 CMTask(uint worker_id, ConcurrentMark *cm,
1211 size_t* marked_bytes, BitMap* card_bm,
1212 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1214 // it prints statistics associated with this task
1215 void print_stats();
1217 #if _MARKING_STATS_
1218 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1219 #endif // _MARKING_STATS_
1220 };
1222 // Class that's used to to print out per-region liveness
1223 // information. It's currently used at the end of marking and also
1224 // after we sort the old regions at the end of the cleanup operation.
1225 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
1226 private:
1227 outputStream* _out;
1229 // Accumulators for these values.
1230 size_t _total_used_bytes;
1231 size_t _total_capacity_bytes;
1232 size_t _total_prev_live_bytes;
1233 size_t _total_next_live_bytes;
1235 // These are set up when we come across a "stars humongous" region
1236 // (as this is where most of this information is stored, not in the
1237 // subsequent "continues humongous" regions). After that, for every
1238 // region in a given humongous region series we deduce the right
1239 // values for it by simply subtracting the appropriate amount from
1240 // these fields. All these values should reach 0 after we've visited
1241 // the last region in the series.
1242 size_t _hum_used_bytes;
1243 size_t _hum_capacity_bytes;
1244 size_t _hum_prev_live_bytes;
1245 size_t _hum_next_live_bytes;
1247 static double perc(size_t val, size_t total) {
1248 if (total == 0) {
1249 return 0.0;
1250 } else {
1251 return 100.0 * ((double) val / (double) total);
1252 }
1253 }
1255 static double bytes_to_mb(size_t val) {
1256 return (double) val / (double) M;
1257 }
1259 // See the .cpp file.
1260 size_t get_hum_bytes(size_t* hum_bytes);
1261 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1262 size_t* prev_live_bytes, size_t* next_live_bytes);
1264 public:
1265 // The header and footer are printed in the constructor and
1266 // destructor respectively.
1267 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
1268 virtual bool doHeapRegion(HeapRegion* r);
1269 ~G1PrintRegionLivenessInfoClosure();
1270 };
1272 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP