Fri, 18 Feb 2011 10:07:34 -0800
7020042: G1: Partially remove fix for 6994628
Summary: Disable reference discovery and processing during concurrent marking by disabling fix for 6994628.
Reviewed-by: tonyp, ysr
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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> CMTaskQueue;
34 typedef GenericTaskQueueSet<CMTaskQueue> 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) :
46 _g1(g1)
47 {}
49 void do_object(oop obj) {
50 ShouldNotCallThis();
51 }
52 bool do_object_b(oop obj);
53 };
55 // A generic CM bit map. This is essentially a wrapper around the BitMap
56 // class, with one bit per (1<<_shifter) HeapWords.
58 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
59 protected:
60 HeapWord* _bmStartWord; // base address of range covered by map
61 size_t _bmWordSize; // map size (in #HeapWords covered)
62 const int _shifter; // map to char or bit
63 VirtualSpace _virtual_space; // underlying the bit map
64 BitMap _bm; // the bit map itself
66 public:
67 // constructor
68 CMBitMapRO(ReservedSpace rs, int shifter);
70 enum { do_yield = true };
72 // inquiries
73 HeapWord* startWord() const { return _bmStartWord; }
74 size_t sizeInWords() const { return _bmWordSize; }
75 // the following is one past the last word in space
76 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
78 // read marks
80 bool isMarked(HeapWord* addr) const {
81 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
82 "outside underlying space?");
83 return _bm.at(heapWordToOffset(addr));
84 }
86 // iteration
87 bool iterate(BitMapClosure* cl) { return _bm.iterate(cl); }
88 bool iterate(BitMapClosure* cl, MemRegion mr);
90 // Return the address corresponding to the next marked bit at or after
91 // "addr", and before "limit", if "limit" is non-NULL. If there is no
92 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
93 HeapWord* getNextMarkedWordAddress(HeapWord* addr,
94 HeapWord* limit = NULL) const;
95 // Return the address corresponding to the next unmarked bit at or after
96 // "addr", and before "limit", if "limit" is non-NULL. If there is no
97 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
98 HeapWord* getNextUnmarkedWordAddress(HeapWord* addr,
99 HeapWord* limit = NULL) const;
101 // conversion utilities
102 // XXX Fix these so that offsets are size_t's...
103 HeapWord* offsetToHeapWord(size_t offset) const {
104 return _bmStartWord + (offset << _shifter);
105 }
106 size_t heapWordToOffset(HeapWord* addr) const {
107 return pointer_delta(addr, _bmStartWord) >> _shifter;
108 }
109 int heapWordDiffToOffsetDiff(size_t diff) const;
110 HeapWord* nextWord(HeapWord* addr) {
111 return offsetToHeapWord(heapWordToOffset(addr) + 1);
112 }
114 void mostly_disjoint_range_union(BitMap* from_bitmap,
115 size_t from_start_index,
116 HeapWord* to_start_word,
117 size_t word_num);
119 // debugging
120 NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
121 };
123 class CMBitMap : public CMBitMapRO {
125 public:
126 // constructor
127 CMBitMap(ReservedSpace rs, int shifter) :
128 CMBitMapRO(rs, shifter) {}
130 // write marks
131 void mark(HeapWord* addr) {
132 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
133 "outside underlying space?");
134 _bm.at_put(heapWordToOffset(addr), true);
135 }
136 void clear(HeapWord* addr) {
137 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
138 "outside underlying space?");
139 _bm.at_put(heapWordToOffset(addr), false);
140 }
141 bool parMark(HeapWord* addr) {
142 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
143 "outside underlying space?");
144 return _bm.par_at_put(heapWordToOffset(addr), true);
145 }
146 bool parClear(HeapWord* addr) {
147 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
148 "outside underlying space?");
149 return _bm.par_at_put(heapWordToOffset(addr), false);
150 }
151 void markRange(MemRegion mr);
152 void clearAll();
153 void clearRange(MemRegion mr);
155 // Starting at the bit corresponding to "addr" (inclusive), find the next
156 // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
157 // the end of this run (stopping at "end_addr"). Return the MemRegion
158 // covering from the start of the region corresponding to the first bit
159 // of the run to the end of the region corresponding to the last bit of
160 // the run. If there is no "1" bit at or after "addr", return an empty
161 // MemRegion.
162 MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
163 };
165 // Represents a marking stack used by the CM collector.
166 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
167 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
168 ConcurrentMark* _cm;
169 oop* _base; // bottom of stack
170 jint _index; // one more than last occupied index
171 jint _capacity; // max #elements
172 jint _oops_do_bound; // Number of elements to include in next iteration.
173 NOT_PRODUCT(jint _max_depth;) // max depth plumbed during run
175 bool _overflow;
176 DEBUG_ONLY(bool _drain_in_progress;)
177 DEBUG_ONLY(bool _drain_in_progress_yields;)
179 public:
180 CMMarkStack(ConcurrentMark* cm);
181 ~CMMarkStack();
183 void allocate(size_t size);
185 oop pop() {
186 if (!isEmpty()) {
187 return _base[--_index] ;
188 }
189 return NULL;
190 }
192 // If overflow happens, don't do the push, and record the overflow.
193 // *Requires* that "ptr" is already marked.
194 void push(oop ptr) {
195 if (isFull()) {
196 // Record overflow.
197 _overflow = true;
198 return;
199 } else {
200 _base[_index++] = ptr;
201 NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
202 }
203 }
204 // Non-block impl. Note: concurrency is allowed only with other
205 // "par_push" operations, not with "pop" or "drain". We would need
206 // parallel versions of them if such concurrency was desired.
207 void par_push(oop ptr);
209 // Pushes the first "n" elements of "ptr_arr" on the stack.
210 // Non-block impl. Note: concurrency is allowed only with other
211 // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
212 void par_adjoin_arr(oop* ptr_arr, int n);
214 // Pushes the first "n" elements of "ptr_arr" on the stack.
215 // Locking impl: concurrency is allowed only with
216 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
217 // locking strategy.
218 void par_push_arr(oop* ptr_arr, int n);
220 // If returns false, the array was empty. Otherwise, removes up to "max"
221 // elements from the stack, and transfers them to "ptr_arr" in an
222 // unspecified order. The actual number transferred is given in "n" ("n
223 // == 0" is deliberately redundant with the return value.) Locking impl:
224 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
225 // operations, which use the same locking strategy.
226 bool par_pop_arr(oop* ptr_arr, int max, int* n);
228 // Drain the mark stack, applying the given closure to all fields of
229 // objects on the stack. (That is, continue until the stack is empty,
230 // even if closure applications add entries to the stack.) The "bm"
231 // argument, if non-null, may be used to verify that only marked objects
232 // are on the mark stack. If "yield_after" is "true", then the
233 // concurrent marker performing the drain offers to yield after
234 // processing each object. If a yield occurs, stops the drain operation
235 // and returns false. Otherwise, returns true.
236 template<class OopClosureClass>
237 bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
239 bool isEmpty() { return _index == 0; }
240 bool isFull() { return _index == _capacity; }
241 int maxElems() { return _capacity; }
243 bool overflow() { return _overflow; }
244 void clear_overflow() { _overflow = false; }
246 int size() { return _index; }
248 void setEmpty() { _index = 0; clear_overflow(); }
250 // Record the current size; a subsequent "oops_do" will iterate only over
251 // indices valid at the time of this call.
252 void set_oops_do_bound(jint bound = -1) {
253 if (bound == -1) {
254 _oops_do_bound = _index;
255 } else {
256 _oops_do_bound = bound;
257 }
258 }
259 jint oops_do_bound() { return _oops_do_bound; }
260 // iterate over the oops in the mark stack, up to the bound recorded via
261 // the call above.
262 void oops_do(OopClosure* f);
263 };
265 class CMRegionStack VALUE_OBJ_CLASS_SPEC {
266 MemRegion* _base;
267 jint _capacity;
268 jint _index;
269 jint _oops_do_bound;
270 bool _overflow;
271 public:
272 CMRegionStack();
273 ~CMRegionStack();
274 void allocate(size_t size);
276 // This is lock-free; assumes that it will only be called in parallel
277 // with other "push" operations (no pops).
278 void push_lock_free(MemRegion mr);
280 // Lock-free; assumes that it will only be called in parallel
281 // with other "pop" operations (no pushes).
282 MemRegion pop_lock_free();
284 #if 0
285 // The routines that manipulate the region stack with a lock are
286 // not currently used. They should be retained, however, as a
287 // diagnostic aid.
289 // These two are the implementations that use a lock. They can be
290 // called concurrently with each other but they should not be called
291 // concurrently with the lock-free versions (push() / pop()).
292 void push_with_lock(MemRegion mr);
293 MemRegion pop_with_lock();
294 #endif
296 bool isEmpty() { return _index == 0; }
297 bool isFull() { return _index == _capacity; }
299 bool overflow() { return _overflow; }
300 void clear_overflow() { _overflow = false; }
302 int size() { return _index; }
304 // It iterates over the entries in the region stack and it
305 // invalidates (i.e. assigns MemRegion()) the ones that point to
306 // regions in the collection set.
307 bool invalidate_entries_into_cset();
309 // This gives an upper bound up to which the iteration in
310 // invalidate_entries_into_cset() will reach. This prevents
311 // newly-added entries to be unnecessarily scanned.
312 void set_oops_do_bound() {
313 _oops_do_bound = _index;
314 }
316 void setEmpty() { _index = 0; clear_overflow(); }
317 };
319 // this will enable a variety of different statistics per GC task
320 #define _MARKING_STATS_ 0
321 // this will enable the higher verbose levels
322 #define _MARKING_VERBOSE_ 0
324 #if _MARKING_STATS_
325 #define statsOnly(statement) \
326 do { \
327 statement ; \
328 } while (0)
329 #else // _MARKING_STATS_
330 #define statsOnly(statement) \
331 do { \
332 } while (0)
333 #endif // _MARKING_STATS_
335 typedef enum {
336 no_verbose = 0, // verbose turned off
337 stats_verbose, // only prints stats at the end of marking
338 low_verbose, // low verbose, mostly per region and per major event
339 medium_verbose, // a bit more detailed than low
340 high_verbose // per object verbose
341 } CMVerboseLevel;
344 class ConcurrentMarkThread;
346 class ConcurrentMark: public CHeapObj {
347 friend class ConcurrentMarkThread;
348 friend class CMTask;
349 friend class CMBitMapClosure;
350 friend class CSMarkOopClosure;
351 friend class CMGlobalObjectClosure;
352 friend class CMRemarkTask;
353 friend class CMConcurrentMarkingTask;
354 friend class G1ParNoteEndTask;
355 friend class CalcLiveObjectsClosure;
356 friend class G1RefProcTaskProxy;
357 friend class G1RefProcTaskExecutor;
358 friend class G1CMParKeepAliveAndDrainClosure;
359 friend class G1CMParDrainMarkingStackClosure;
361 protected:
362 ConcurrentMarkThread* _cmThread; // the thread doing the work
363 G1CollectedHeap* _g1h; // the heap.
364 size_t _parallel_marking_threads; // the number of marking
365 // threads we'll use
366 double _sleep_factor; // how much we have to sleep, with
367 // respect to the work we just did, to
368 // meet the marking overhead goal
369 double _marking_task_overhead; // marking target overhead for
370 // a single task
372 // same as the two above, but for the cleanup task
373 double _cleanup_sleep_factor;
374 double _cleanup_task_overhead;
376 FreeRegionList _cleanup_list;
378 // CMS marking support structures
379 CMBitMap _markBitMap1;
380 CMBitMap _markBitMap2;
381 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
382 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
383 bool _at_least_one_mark_complete;
385 BitMap _region_bm;
386 BitMap _card_bm;
388 // Heap bounds
389 HeapWord* _heap_start;
390 HeapWord* _heap_end;
392 // For gray objects
393 CMMarkStack _markStack; // Grey objects behind global finger.
394 CMRegionStack _regionStack; // Grey regions behind global finger.
395 HeapWord* volatile _finger; // the global finger, region aligned,
396 // always points to the end of the
397 // last claimed region
399 // marking tasks
400 size_t _max_task_num; // maximum task number
401 size_t _active_tasks; // task num currently active
402 CMTask** _tasks; // task queue array (max_task_num len)
403 CMTaskQueueSet* _task_queues; // task queue set
404 ParallelTaskTerminator _terminator; // for termination
406 // Two sync barriers that are used to synchronise tasks when an
407 // overflow occurs. The algorithm is the following. All tasks enter
408 // the first one to ensure that they have all stopped manipulating
409 // the global data structures. After they exit it, they re-initialise
410 // their data structures and task 0 re-initialises the global data
411 // structures. Then, they enter the second sync barrier. This
412 // ensure, that no task starts doing work before all data
413 // structures (local and global) have been re-initialised. When they
414 // exit it, they are free to start working again.
415 WorkGangBarrierSync _first_overflow_barrier_sync;
416 WorkGangBarrierSync _second_overflow_barrier_sync;
419 // this is set by any task, when an overflow on the global data
420 // structures is detected.
421 volatile bool _has_overflown;
422 // true: marking is concurrent, false: we're in remark
423 volatile bool _concurrent;
424 // set at the end of a Full GC so that marking aborts
425 volatile bool _has_aborted;
427 // used when remark aborts due to an overflow to indicate that
428 // another concurrent marking phase should start
429 volatile bool _restart_for_overflow;
431 // This is true from the very start of concurrent marking until the
432 // point when all the tasks complete their work. It is really used
433 // to determine the points between the end of concurrent marking and
434 // time of remark.
435 volatile bool _concurrent_marking_in_progress;
437 // verbose level
438 CMVerboseLevel _verbose_level;
440 // These two fields are used to implement the optimisation that
441 // avoids pushing objects on the global/region stack if there are
442 // no collection set regions above the lowest finger.
444 // This is the lowest finger (among the global and local fingers),
445 // which is calculated before a new collection set is chosen.
446 HeapWord* _min_finger;
447 // If this flag is true, objects/regions that are marked below the
448 // finger should be pushed on the stack(s). If this is flag is
449 // false, it is safe not to push them on the stack(s).
450 bool _should_gray_objects;
452 // All of these times are in ms.
453 NumberSeq _init_times;
454 NumberSeq _remark_times;
455 NumberSeq _remark_mark_times;
456 NumberSeq _remark_weak_ref_times;
457 NumberSeq _cleanup_times;
458 double _total_counting_time;
459 double _total_rs_scrub_time;
461 double* _accum_task_vtime; // accumulated task vtime
463 WorkGang* _parallel_workers;
465 void weakRefsWork(bool clear_all_soft_refs);
467 void swapMarkBitMaps();
469 // It resets the global marking data structures, as well as the
470 // task local ones; should be called during initial mark.
471 void reset();
472 // It resets all the marking data structures.
473 void clear_marking_state();
475 // It should be called to indicate which phase we're in (concurrent
476 // mark or remark) and how many threads are currently active.
477 void set_phase(size_t active_tasks, bool concurrent);
478 // We do this after we're done with marking so that the marking data
479 // structures are initialised to a sensible and predictable state.
480 void set_non_marking_state();
482 // prints all gathered CM-related statistics
483 void print_stats();
485 bool cleanup_list_is_empty() {
486 return _cleanup_list.is_empty();
487 }
489 // accessor methods
490 size_t parallel_marking_threads() { return _parallel_marking_threads; }
491 double sleep_factor() { return _sleep_factor; }
492 double marking_task_overhead() { return _marking_task_overhead;}
493 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
494 double cleanup_task_overhead() { return _cleanup_task_overhead;}
496 HeapWord* finger() { return _finger; }
497 bool concurrent() { return _concurrent; }
498 size_t active_tasks() { return _active_tasks; }
499 ParallelTaskTerminator* terminator() { return &_terminator; }
501 // It claims the next available region to be scanned by a marking
502 // task. It might return NULL if the next region is empty or we have
503 // run out of regions. In the latter case, out_of_regions()
504 // determines whether we've really run out of regions or the task
505 // should call claim_region() again. This might seem a bit
506 // awkward. Originally, the code was written so that claim_region()
507 // either successfully returned with a non-empty region or there
508 // were no more regions to be claimed. The problem with this was
509 // that, in certain circumstances, it iterated over large chunks of
510 // the heap finding only empty regions and, while it was working, it
511 // was preventing the calling task to call its regular clock
512 // method. So, this way, each task will spend very little time in
513 // claim_region() and is allowed to call the regular clock method
514 // frequently.
515 HeapRegion* claim_region(int task);
517 // It determines whether we've run out of regions to scan.
518 bool out_of_regions() { return _finger == _heap_end; }
520 // Returns the task with the given id
521 CMTask* task(int id) {
522 assert(0 <= id && id < (int) _active_tasks,
523 "task id not within active bounds");
524 return _tasks[id];
525 }
527 // Returns the task queue with the given id
528 CMTaskQueue* task_queue(int id) {
529 assert(0 <= id && id < (int) _active_tasks,
530 "task queue id not within active bounds");
531 return (CMTaskQueue*) _task_queues->queue(id);
532 }
534 // Returns the task queue set
535 CMTaskQueueSet* task_queues() { return _task_queues; }
537 // Access / manipulation of the overflow flag which is set to
538 // indicate that the global stack or region stack has overflown
539 bool has_overflown() { return _has_overflown; }
540 void set_has_overflown() { _has_overflown = true; }
541 void clear_has_overflown() { _has_overflown = false; }
543 bool has_aborted() { return _has_aborted; }
544 bool restart_for_overflow() { return _restart_for_overflow; }
546 // Methods to enter the two overflow sync barriers
547 void enter_first_sync_barrier(int task_num);
548 void enter_second_sync_barrier(int task_num);
550 public:
551 // Manipulation of the global mark stack.
552 // Notice that the first mark_stack_push is CAS-based, whereas the
553 // two below are Mutex-based. This is OK since the first one is only
554 // called during evacuation pauses and doesn't compete with the
555 // other two (which are called by the marking tasks during
556 // concurrent marking or remark).
557 bool mark_stack_push(oop p) {
558 _markStack.par_push(p);
559 if (_markStack.overflow()) {
560 set_has_overflown();
561 return false;
562 }
563 return true;
564 }
565 bool mark_stack_push(oop* arr, int n) {
566 _markStack.par_push_arr(arr, n);
567 if (_markStack.overflow()) {
568 set_has_overflown();
569 return false;
570 }
571 return true;
572 }
573 void mark_stack_pop(oop* arr, int max, int* n) {
574 _markStack.par_pop_arr(arr, max, n);
575 }
576 size_t mark_stack_size() { return _markStack.size(); }
577 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
578 bool mark_stack_overflow() { return _markStack.overflow(); }
579 bool mark_stack_empty() { return _markStack.isEmpty(); }
581 // (Lock-free) Manipulation of the region stack
582 bool region_stack_push_lock_free(MemRegion mr) {
583 // Currently we only call the lock-free version during evacuation
584 // pauses.
585 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped");
587 _regionStack.push_lock_free(mr);
588 if (_regionStack.overflow()) {
589 set_has_overflown();
590 return false;
591 }
592 return true;
593 }
595 // Lock-free version of region-stack pop. Should only be
596 // called in tandem with other lock-free pops.
597 MemRegion region_stack_pop_lock_free() {
598 return _regionStack.pop_lock_free();
599 }
601 #if 0
602 // The routines that manipulate the region stack with a lock are
603 // not currently used. They should be retained, however, as a
604 // diagnostic aid.
606 bool region_stack_push_with_lock(MemRegion mr) {
607 // Currently we only call the lock-based version during either
608 // concurrent marking or remark.
609 assert(!SafepointSynchronize::is_at_safepoint() || !concurrent(),
610 "if we are at a safepoint it should be the remark safepoint");
612 _regionStack.push_with_lock(mr);
613 if (_regionStack.overflow()) {
614 set_has_overflown();
615 return false;
616 }
617 return true;
618 }
620 MemRegion region_stack_pop_with_lock() {
621 // Currently we only call the lock-based version during either
622 // concurrent marking or remark.
623 assert(!SafepointSynchronize::is_at_safepoint() || !concurrent(),
624 "if we are at a safepoint it should be the remark safepoint");
626 return _regionStack.pop_with_lock();
627 }
628 #endif
630 int region_stack_size() { return _regionStack.size(); }
631 bool region_stack_overflow() { return _regionStack.overflow(); }
632 bool region_stack_empty() { return _regionStack.isEmpty(); }
634 // Iterate over any regions that were aborted while draining the
635 // region stack (any such regions are saved in the corresponding
636 // CMTask) and invalidate (i.e. assign to the empty MemRegion())
637 // any regions that point into the collection set.
638 bool invalidate_aborted_regions_in_cset();
640 // Returns true if there are any aborted memory regions.
641 bool has_aborted_regions();
643 bool concurrent_marking_in_progress() {
644 return _concurrent_marking_in_progress;
645 }
646 void set_concurrent_marking_in_progress() {
647 _concurrent_marking_in_progress = true;
648 }
649 void clear_concurrent_marking_in_progress() {
650 _concurrent_marking_in_progress = false;
651 }
653 void update_accum_task_vtime(int i, double vtime) {
654 _accum_task_vtime[i] += vtime;
655 }
657 double all_task_accum_vtime() {
658 double ret = 0.0;
659 for (int i = 0; i < (int)_max_task_num; ++i)
660 ret += _accum_task_vtime[i];
661 return ret;
662 }
664 // Attempts to steal an object from the task queues of other tasks
665 bool try_stealing(int task_num, int* hash_seed, oop& obj) {
666 return _task_queues->steal(task_num, hash_seed, obj);
667 }
669 // It grays an object by first marking it. Then, if it's behind the
670 // global finger, it also pushes it on the global stack.
671 void deal_with_reference(oop obj);
673 ConcurrentMark(ReservedSpace rs, int max_regions);
674 ~ConcurrentMark();
675 ConcurrentMarkThread* cmThread() { return _cmThread; }
677 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
678 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
680 // The following three are interaction between CM and
681 // G1CollectedHeap
683 // This notifies CM that a root during initial-mark needs to be
684 // grayed and it's MT-safe. Currently, we just mark it. But, in the
685 // future, we can experiment with pushing it on the stack and we can
686 // do this without changing G1CollectedHeap.
687 void grayRoot(oop p);
688 // It's used during evacuation pauses to gray a region, if
689 // necessary, and it's MT-safe. It assumes that the caller has
690 // marked any objects on that region. If _should_gray_objects is
691 // true and we're still doing concurrent marking, the region is
692 // pushed on the region stack, if it is located below the global
693 // finger, otherwise we do nothing.
694 void grayRegionIfNecessary(MemRegion mr);
695 // It's used during evacuation pauses to mark and, if necessary,
696 // gray a single object and it's MT-safe. It assumes the caller did
697 // not mark the object. If _should_gray_objects is true and we're
698 // still doing concurrent marking, the objects is pushed on the
699 // global stack, if it is located below the global finger, otherwise
700 // we do nothing.
701 void markAndGrayObjectIfNecessary(oop p);
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. use_prev_marking decides
708 // whether the prev (use_prev_marking == true) or next
709 // (use_prev_marking == false) marking information will be used to
710 // determine the liveness of each object / referent. If all is true,
711 // all objects in the heap will be dumped, otherwise only the live
712 // ones. In the dump the following symbols / abbreviations are used:
713 // M : an explicitly live object (its bitmap bit is set)
714 // > : an implicitly live object (over tams)
715 // O : an object outside the G1 heap (typically: in the perm gen)
716 // NOT : a reference field whose referent is not live
717 // AND MARKED : indicates that an object is both explicitly and
718 // implicitly live (it should be one or the other, not both)
719 void print_reachable(const char* str,
720 bool use_prev_marking, bool all) PRODUCT_RETURN;
722 // Clear the next marking bitmap (will be called concurrently).
723 void clearNextBitmap();
725 // main CMS steps and related support
726 void checkpointRootsInitial();
728 // These two do the work that needs to be done before and after the
729 // initial root checkpoint. Since this checkpoint can be done at two
730 // different points (i.e. an explicit pause or piggy-backed on a
731 // young collection), then it's nice to be able to easily share the
732 // pre/post code. It might be the case that we can put everything in
733 // the post method. TP
734 void checkpointRootsInitialPre();
735 void checkpointRootsInitialPost();
737 // Do concurrent phase of marking, to a tentative transitive closure.
738 void markFromRoots();
740 // Process all unprocessed SATB buffers. It is called at the
741 // beginning of an evacuation pause.
742 void drainAllSATBBuffers();
744 void checkpointRootsFinal(bool clear_all_soft_refs);
745 void checkpointRootsFinalWork();
746 void calcDesiredRegions();
747 void cleanup();
748 void completeCleanup();
750 // Mark in the previous bitmap. NB: this is usually read-only, so use
751 // this carefully!
752 void markPrev(oop p);
753 void clear(oop p);
754 // Clears marks for all objects in the given range, for both prev and
755 // next bitmaps. NB: the previous bitmap is usually read-only, so use
756 // this carefully!
757 void clearRangeBothMaps(MemRegion mr);
759 // Record the current top of the mark and region stacks; a
760 // subsequent oops_do() on the mark stack and
761 // invalidate_entries_into_cset() on the region stack will iterate
762 // only over indices valid at the time of this call.
763 void set_oops_do_bound() {
764 _markStack.set_oops_do_bound();
765 _regionStack.set_oops_do_bound();
766 }
767 // Iterate over the oops in the mark stack and all local queues. It
768 // also calls invalidate_entries_into_cset() on the region stack.
769 void oops_do(OopClosure* f);
770 // It is called at the end of an evacuation pause during marking so
771 // that CM is notified of where the new end of the heap is. It
772 // doesn't do anything if concurrent_marking_in_progress() is false,
773 // unless the force parameter is true.
774 void update_g1_committed(bool force = false);
776 void complete_marking_in_collection_set();
778 // It indicates that a new collection set is being chosen.
779 void newCSet();
780 // It registers a collection set heap region with CM. This is used
781 // to determine whether any heap regions are located above the finger.
782 void registerCSetRegion(HeapRegion* hr);
784 // Registers the maximum region-end associated with a set of
785 // regions with CM. Again this is used to determine whether any
786 // heap regions are located above the finger.
787 void register_collection_set_finger(HeapWord* max_finger) {
788 // max_finger is the highest heap region end of the regions currently
789 // contained in the collection set. If this value is larger than
790 // _min_finger then we need to gray objects.
791 // This routine is like registerCSetRegion but for an entire
792 // collection of regions.
793 if (max_finger > _min_finger)
794 _should_gray_objects = true;
795 }
797 // Returns "true" if at least one mark has been completed.
798 bool at_least_one_mark_complete() { return _at_least_one_mark_complete; }
800 bool isMarked(oop p) const {
801 assert(p != NULL && p->is_oop(), "expected an oop");
802 HeapWord* addr = (HeapWord*)p;
803 assert(addr >= _nextMarkBitMap->startWord() ||
804 addr < _nextMarkBitMap->endWord(), "in a region");
806 return _nextMarkBitMap->isMarked(addr);
807 }
809 inline bool not_yet_marked(oop p) const;
811 // XXX Debug code
812 bool containing_card_is_marked(void* p);
813 bool containing_cards_are_marked(void* start, void* last);
815 bool isPrevMarked(oop p) const {
816 assert(p != NULL && p->is_oop(), "expected an oop");
817 HeapWord* addr = (HeapWord*)p;
818 assert(addr >= _prevMarkBitMap->startWord() ||
819 addr < _prevMarkBitMap->endWord(), "in a region");
821 return _prevMarkBitMap->isMarked(addr);
822 }
824 inline bool do_yield_check(int worker_i = 0);
825 inline bool should_yield();
827 // Called to abort the marking cycle after a Full GC takes palce.
828 void abort();
830 // This prints the global/local fingers. It is used for debugging.
831 NOT_PRODUCT(void print_finger();)
833 void print_summary_info();
835 void print_worker_threads_on(outputStream* st) const;
837 // The following indicate whether a given verbose level has been
838 // set. Notice that anything above stats is conditional to
839 // _MARKING_VERBOSE_ having been set to 1
840 bool verbose_stats()
841 { return _verbose_level >= stats_verbose; }
842 bool verbose_low()
843 { return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; }
844 bool verbose_medium()
845 { return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; }
846 bool verbose_high()
847 { return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; }
848 };
850 // A class representing a marking task.
851 class CMTask : public TerminatorTerminator {
852 private:
853 enum PrivateConstants {
854 // the regular clock call is called once the scanned words reaches
855 // this limit
856 words_scanned_period = 12*1024,
857 // the regular clock call is called once the number of visited
858 // references reaches this limit
859 refs_reached_period = 384,
860 // initial value for the hash seed, used in the work stealing code
861 init_hash_seed = 17,
862 // how many entries will be transferred between global stack and
863 // local queues
864 global_stack_transfer_size = 16
865 };
867 int _task_id;
868 G1CollectedHeap* _g1h;
869 ConcurrentMark* _cm;
870 CMBitMap* _nextMarkBitMap;
871 // the task queue of this task
872 CMTaskQueue* _task_queue;
873 private:
874 // the task queue set---needed for stealing
875 CMTaskQueueSet* _task_queues;
876 // indicates whether the task has been claimed---this is only for
877 // debugging purposes
878 bool _claimed;
880 // number of calls to this task
881 int _calls;
883 // when the virtual timer reaches this time, the marking step should
884 // exit
885 double _time_target_ms;
886 // the start time of the current marking step
887 double _start_time_ms;
889 // the oop closure used for iterations over oops
890 OopClosure* _oop_closure;
892 // the region this task is scanning, NULL if we're not scanning any
893 HeapRegion* _curr_region;
894 // the local finger of this task, NULL if we're not scanning a region
895 HeapWord* _finger;
896 // limit of the region this task is scanning, NULL if we're not scanning one
897 HeapWord* _region_limit;
899 // This is used only when we scan regions popped from the region
900 // stack. It records what the last object on such a region we
901 // scanned was. It is used to ensure that, if we abort region
902 // iteration, we do not rescan the first part of the region. This
903 // should be NULL when we're not scanning a region from the region
904 // stack.
905 HeapWord* _region_finger;
907 // If we abort while scanning a region we record the remaining
908 // unscanned portion and check this field when marking restarts.
909 // This avoids having to push on the region stack while other
910 // marking threads may still be popping regions.
911 // If we were to push the unscanned portion directly to the
912 // region stack then we would need to using locking versions
913 // of the push and pop operations.
914 MemRegion _aborted_region;
916 // the number of words this task has scanned
917 size_t _words_scanned;
918 // When _words_scanned reaches this limit, the regular clock is
919 // called. Notice that this might be decreased under certain
920 // circumstances (i.e. when we believe that we did an expensive
921 // operation).
922 size_t _words_scanned_limit;
923 // the initial value of _words_scanned_limit (i.e. what it was
924 // before it was decreased).
925 size_t _real_words_scanned_limit;
927 // the number of references this task has visited
928 size_t _refs_reached;
929 // When _refs_reached reaches this limit, the regular clock is
930 // called. Notice this this might be decreased under certain
931 // circumstances (i.e. when we believe that we did an expensive
932 // operation).
933 size_t _refs_reached_limit;
934 // the initial value of _refs_reached_limit (i.e. what it was before
935 // it was decreased).
936 size_t _real_refs_reached_limit;
938 // used by the work stealing stuff
939 int _hash_seed;
940 // if this is true, then the task has aborted for some reason
941 bool _has_aborted;
942 // set when the task aborts because it has met its time quota
943 bool _has_timed_out;
944 // true when we're draining SATB buffers; this avoids the task
945 // aborting due to SATB buffers being available (as we're already
946 // dealing with them)
947 bool _draining_satb_buffers;
949 // number sequence of past step times
950 NumberSeq _step_times_ms;
951 // elapsed time of this task
952 double _elapsed_time_ms;
953 // termination time of this task
954 double _termination_time_ms;
955 // when this task got into the termination protocol
956 double _termination_start_time_ms;
958 // true when the task is during a concurrent phase, false when it is
959 // in the remark phase (so, in the latter case, we do not have to
960 // check all the things that we have to check during the concurrent
961 // phase, i.e. SATB buffer availability...)
962 bool _concurrent;
964 TruncatedSeq _marking_step_diffs_ms;
966 // LOTS of statistics related with this task
967 #if _MARKING_STATS_
968 NumberSeq _all_clock_intervals_ms;
969 double _interval_start_time_ms;
971 int _aborted;
972 int _aborted_overflow;
973 int _aborted_cm_aborted;
974 int _aborted_yield;
975 int _aborted_timed_out;
976 int _aborted_satb;
977 int _aborted_termination;
979 int _steal_attempts;
980 int _steals;
982 int _clock_due_to_marking;
983 int _clock_due_to_scanning;
985 int _local_pushes;
986 int _local_pops;
987 int _local_max_size;
988 int _objs_scanned;
990 int _global_pushes;
991 int _global_pops;
992 int _global_max_size;
994 int _global_transfers_to;
995 int _global_transfers_from;
997 int _region_stack_pops;
999 int _regions_claimed;
1000 int _objs_found_on_bitmap;
1002 int _satb_buffers_processed;
1003 #endif // _MARKING_STATS_
1005 // it updates the local fields after this task has claimed
1006 // a new region to scan
1007 void setup_for_region(HeapRegion* hr);
1008 // it brings up-to-date the limit of the region
1009 void update_region_limit();
1010 // it resets the local fields after a task has finished scanning a
1011 // region
1012 void giveup_current_region();
1014 // called when either the words scanned or the refs visited limit
1015 // has been reached
1016 void reached_limit();
1017 // recalculates the words scanned and refs visited limits
1018 void recalculate_limits();
1019 // decreases the words scanned and refs visited limits when we reach
1020 // an expensive operation
1021 void decrease_limits();
1022 // it checks whether the words scanned or refs visited reached their
1023 // respective limit and calls reached_limit() if they have
1024 void check_limits() {
1025 if (_words_scanned >= _words_scanned_limit ||
1026 _refs_reached >= _refs_reached_limit)
1027 reached_limit();
1028 }
1029 // this is supposed to be called regularly during a marking step as
1030 // it checks a bunch of conditions that might cause the marking step
1031 // to abort
1032 void regular_clock_call();
1033 bool concurrent() { return _concurrent; }
1035 public:
1036 // It resets the task; it should be called right at the beginning of
1037 // a marking phase.
1038 void reset(CMBitMap* _nextMarkBitMap);
1039 // it clears all the fields that correspond to a claimed region.
1040 void clear_region_fields();
1042 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
1044 // The main method of this class which performs a marking step
1045 // trying not to exceed the given duration. However, it might exit
1046 // prematurely, according to some conditions (i.e. SATB buffers are
1047 // available for processing).
1048 void do_marking_step(double target_ms, bool do_stealing, bool do_termination);
1050 // These two calls start and stop the timer
1051 void record_start_time() {
1052 _elapsed_time_ms = os::elapsedTime() * 1000.0;
1053 }
1054 void record_end_time() {
1055 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
1056 }
1058 // returns the task ID
1059 int task_id() { return _task_id; }
1061 // From TerminatorTerminator. It determines whether this task should
1062 // exit the termination protocol after it's entered it.
1063 virtual bool should_exit_termination();
1065 HeapWord* finger() { return _finger; }
1067 bool has_aborted() { return _has_aborted; }
1068 void set_has_aborted() { _has_aborted = true; }
1069 void clear_has_aborted() { _has_aborted = false; }
1070 bool has_timed_out() { return _has_timed_out; }
1071 bool claimed() { return _claimed; }
1073 // Support routines for the partially scanned region that may be
1074 // recorded as a result of aborting while draining the CMRegionStack
1075 MemRegion aborted_region() { return _aborted_region; }
1076 void set_aborted_region(MemRegion mr)
1077 { _aborted_region = mr; }
1079 // Clears any recorded partially scanned region
1080 void clear_aborted_region() { set_aborted_region(MemRegion()); }
1082 void set_oop_closure(OopClosure* oop_closure) {
1083 _oop_closure = oop_closure;
1084 }
1086 // It grays the object by marking it and, if necessary, pushing it
1087 // on the local queue
1088 void deal_with_reference(oop obj);
1090 // It scans an object and visits its children.
1091 void scan_object(oop obj) {
1092 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
1094 if (_cm->verbose_high())
1095 gclog_or_tty->print_cr("[%d] we're scanning object "PTR_FORMAT,
1096 _task_id, (void*) obj);
1098 size_t obj_size = obj->size();
1099 _words_scanned += obj_size;
1101 obj->oop_iterate(_oop_closure);
1102 statsOnly( ++_objs_scanned );
1103 check_limits();
1104 }
1106 // It pushes an object on the local queue.
1107 void push(oop obj);
1109 // These two move entries to/from the global stack.
1110 void move_entries_to_global_stack();
1111 void get_entries_from_global_stack();
1113 // It pops and scans objects from the local queue. If partially is
1114 // true, then it stops when the queue size is of a given limit. If
1115 // partially is false, then it stops when the queue is empty.
1116 void drain_local_queue(bool partially);
1117 // It moves entries from the global stack to the local queue and
1118 // drains the local queue. If partially is true, then it stops when
1119 // both the global stack and the local queue reach a given size. If
1120 // partially if false, it tries to empty them totally.
1121 void drain_global_stack(bool partially);
1122 // It keeps picking SATB buffers and processing them until no SATB
1123 // buffers are available.
1124 void drain_satb_buffers();
1125 // It keeps popping regions from the region stack and processing
1126 // them until the region stack is empty.
1127 void drain_region_stack(BitMapClosure* closure);
1129 // moves the local finger to a new location
1130 inline void move_finger_to(HeapWord* new_finger) {
1131 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
1132 _finger = new_finger;
1133 }
1135 // moves the region finger to a new location
1136 inline void move_region_finger_to(HeapWord* new_finger) {
1137 assert(new_finger < _cm->finger(), "invariant");
1138 _region_finger = new_finger;
1139 }
1141 CMTask(int task_num, ConcurrentMark *cm,
1142 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1144 // it prints statistics associated with this task
1145 void print_stats();
1147 #if _MARKING_STATS_
1148 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1149 #endif // _MARKING_STATS_
1150 };
1152 // Class that's used to to print out per-region liveness
1153 // information. It's currently used at the end of marking and also
1154 // after we sort the old regions at the end of the cleanup operation.
1155 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
1156 private:
1157 outputStream* _out;
1159 // Accumulators for these values.
1160 size_t _total_used_bytes;
1161 size_t _total_capacity_bytes;
1162 size_t _total_prev_live_bytes;
1163 size_t _total_next_live_bytes;
1165 // These are set up when we come across a "stars humongous" region
1166 // (as this is where most of this information is stored, not in the
1167 // subsequent "continues humongous" regions). After that, for every
1168 // region in a given humongous region series we deduce the right
1169 // values for it by simply subtracting the appropriate amount from
1170 // these fields. All these values should reach 0 after we've visited
1171 // the last region in the series.
1172 size_t _hum_used_bytes;
1173 size_t _hum_capacity_bytes;
1174 size_t _hum_prev_live_bytes;
1175 size_t _hum_next_live_bytes;
1177 static double perc(size_t val, size_t total) {
1178 if (total == 0) {
1179 return 0.0;
1180 } else {
1181 return 100.0 * ((double) val / (double) total);
1182 }
1183 }
1185 static double bytes_to_mb(size_t val) {
1186 return (double) val / (double) M;
1187 }
1189 // See the .cpp file.
1190 size_t get_hum_bytes(size_t* hum_bytes);
1191 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1192 size_t* prev_live_bytes, size_t* next_live_bytes);
1194 public:
1195 // The header and footer are printed in the constructor and
1196 // destructor respectively.
1197 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
1198 virtual bool doHeapRegion(HeapRegion* r);
1199 ~G1PrintRegionLivenessInfoClosure();
1200 };
1202 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP