Tue, 14 Jul 2009 15:40:39 -0700
6700789: G1: Enable use of compressed oops with G1 heaps
Summary: Modifications to G1 so as to allow the use of compressed oops.
Reviewed-by: apetrusenko, coleenp, jmasa, kvn, never, phh, tonyp
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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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 // Some extra guarantees that I like to also enable in optimised mode
299 // when debugging. If you want to enable them, comment out the assert
300 // macro and uncomment out the guaratee macro
301 // #define tmp_guarantee_CM(expr, str) guarantee(expr, str)
302 #define tmp_guarantee_CM(expr, str) assert(expr, str)
304 typedef enum {
305 no_verbose = 0, // verbose turned off
306 stats_verbose, // only prints stats at the end of marking
307 low_verbose, // low verbose, mostly per region and per major event
308 medium_verbose, // a bit more detailed than low
309 high_verbose // per object verbose
310 } CMVerboseLevel;
313 class ConcurrentMarkThread;
315 class ConcurrentMark: public CHeapObj {
316 friend class ConcurrentMarkThread;
317 friend class CMTask;
318 friend class CMBitMapClosure;
319 friend class CSMarkOopClosure;
320 friend class CMGlobalObjectClosure;
321 friend class CMRemarkTask;
322 friend class CMConcurrentMarkingTask;
323 friend class G1ParNoteEndTask;
324 friend class CalcLiveObjectsClosure;
326 protected:
327 ConcurrentMarkThread* _cmThread; // the thread doing the work
328 G1CollectedHeap* _g1h; // the heap.
329 size_t _parallel_marking_threads; // the number of marking
330 // threads we'll use
331 double _sleep_factor; // how much we have to sleep, with
332 // respect to the work we just did, to
333 // meet the marking overhead goal
334 double _marking_task_overhead; // marking target overhead for
335 // a single task
337 // same as the two above, but for the cleanup task
338 double _cleanup_sleep_factor;
339 double _cleanup_task_overhead;
341 // Stuff related to age cohort processing.
342 struct ParCleanupThreadState {
343 char _pre[64];
344 UncleanRegionList list;
345 char _post[64];
346 };
347 ParCleanupThreadState** _par_cleanup_thread_state;
349 // CMS marking support structures
350 CMBitMap _markBitMap1;
351 CMBitMap _markBitMap2;
352 CMBitMapRO* _prevMarkBitMap; // completed mark bitmap
353 CMBitMap* _nextMarkBitMap; // under-construction mark bitmap
354 bool _at_least_one_mark_complete;
356 BitMap _region_bm;
357 BitMap _card_bm;
359 // Heap bounds
360 HeapWord* _heap_start;
361 HeapWord* _heap_end;
363 // For gray objects
364 CMMarkStack _markStack; // Grey objects behind global finger.
365 CMRegionStack _regionStack; // Grey regions behind global finger.
366 HeapWord* volatile _finger; // the global finger, region aligned,
367 // always points to the end of the
368 // last claimed region
370 // marking tasks
371 size_t _max_task_num; // maximum task number
372 size_t _active_tasks; // task num currently active
373 CMTask** _tasks; // task queue array (max_task_num len)
374 CMTaskQueueSet* _task_queues; // task queue set
375 ParallelTaskTerminator _terminator; // for termination
377 // Two sync barriers that are used to synchronise tasks when an
378 // overflow occurs. The algorithm is the following. All tasks enter
379 // the first one to ensure that they have all stopped manipulating
380 // the global data structures. After they exit it, they re-initialise
381 // their data structures and task 0 re-initialises the global data
382 // structures. Then, they enter the second sync barrier. This
383 // ensure, that no task starts doing work before all data
384 // structures (local and global) have been re-initialised. When they
385 // exit it, they are free to start working again.
386 WorkGangBarrierSync _first_overflow_barrier_sync;
387 WorkGangBarrierSync _second_overflow_barrier_sync;
390 // this is set by any task, when an overflow on the global data
391 // structures is detected.
392 volatile bool _has_overflown;
393 // true: marking is concurrent, false: we're in remark
394 volatile bool _concurrent;
395 // set at the end of a Full GC so that marking aborts
396 volatile bool _has_aborted;
397 // used when remark aborts due to an overflow to indicate that
398 // another concurrent marking phase should start
399 volatile bool _restart_for_overflow;
401 // This is true from the very start of concurrent marking until the
402 // point when all the tasks complete their work. It is really used
403 // to determine the points between the end of concurrent marking and
404 // time of remark.
405 volatile bool _concurrent_marking_in_progress;
407 // verbose level
408 CMVerboseLevel _verbose_level;
410 COTracker _cleanup_co_tracker;
412 // These two fields are used to implement the optimisation that
413 // avoids pushing objects on the global/region stack if there are
414 // no collection set regions above the lowest finger.
416 // This is the lowest finger (among the global and local fingers),
417 // which is calculated before a new collection set is chosen.
418 HeapWord* _min_finger;
419 // If this flag is true, objects/regions that are marked below the
420 // finger should be pushed on the stack(s). If this is flag is
421 // false, it is safe not to push them on the stack(s).
422 bool _should_gray_objects;
424 // All of these times are in ms.
425 NumberSeq _init_times;
426 NumberSeq _remark_times;
427 NumberSeq _remark_mark_times;
428 NumberSeq _remark_weak_ref_times;
429 NumberSeq _cleanup_times;
430 double _total_counting_time;
431 double _total_rs_scrub_time;
433 double* _accum_task_vtime; // accumulated task vtime
435 WorkGang* _parallel_workers;
437 void weakRefsWork(bool clear_all_soft_refs);
439 void swapMarkBitMaps();
441 // It resets the global marking data structures, as well as the
442 // task local ones; should be called during initial mark.
443 void reset();
444 // It resets all the marking data structures.
445 void clear_marking_state();
447 // It should be called to indicate which phase we're in (concurrent
448 // mark or remark) and how many threads are currently active.
449 void set_phase(size_t active_tasks, bool concurrent);
450 // We do this after we're done with marking so that the marking data
451 // structures are initialised to a sensible and predictable state.
452 void set_non_marking_state();
454 // prints all gathered CM-related statistics
455 void print_stats();
457 // accessor methods
458 size_t parallel_marking_threads() { return _parallel_marking_threads; }
459 double sleep_factor() { return _sleep_factor; }
460 double marking_task_overhead() { return _marking_task_overhead;}
461 double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
462 double cleanup_task_overhead() { return _cleanup_task_overhead;}
464 HeapWord* finger() { return _finger; }
465 bool concurrent() { return _concurrent; }
466 size_t active_tasks() { return _active_tasks; }
467 ParallelTaskTerminator* terminator() { return &_terminator; }
469 // It claims the next available region to be scanned by a marking
470 // task. It might return NULL if the next region is empty or we have
471 // run out of regions. In the latter case, out_of_regions()
472 // determines whether we've really run out of regions or the task
473 // should call claim_region() again. This might seem a bit
474 // awkward. Originally, the code was written so that claim_region()
475 // either successfully returned with a non-empty region or there
476 // were no more regions to be claimed. The problem with this was
477 // that, in certain circumstances, it iterated over large chunks of
478 // the heap finding only empty regions and, while it was working, it
479 // was preventing the calling task to call its regular clock
480 // method. So, this way, each task will spend very little time in
481 // claim_region() and is allowed to call the regular clock method
482 // frequently.
483 HeapRegion* claim_region(int task);
485 // It determines whether we've run out of regions to scan.
486 bool out_of_regions() { return _finger == _heap_end; }
488 // Returns the task with the given id
489 CMTask* task(int id) {
490 guarantee( 0 <= id && id < (int) _active_tasks, "task id not within "
491 "active bounds" );
492 return _tasks[id];
493 }
495 // Returns the task queue with the given id
496 CMTaskQueue* task_queue(int id) {
497 guarantee( 0 <= id && id < (int) _active_tasks, "task queue id not within "
498 "active bounds" );
499 return (CMTaskQueue*) _task_queues->queue(id);
500 }
502 // Returns the task queue set
503 CMTaskQueueSet* task_queues() { return _task_queues; }
505 // Access / manipulation of the overflow flag which is set to
506 // indicate that the global stack or region stack has overflown
507 bool has_overflown() { return _has_overflown; }
508 void set_has_overflown() { _has_overflown = true; }
509 void clear_has_overflown() { _has_overflown = false; }
511 bool has_aborted() { return _has_aborted; }
512 bool restart_for_overflow() { return _restart_for_overflow; }
514 // Methods to enter the two overflow sync barriers
515 void enter_first_sync_barrier(int task_num);
516 void enter_second_sync_barrier(int task_num);
518 public:
519 // Manipulation of the global mark stack.
520 // Notice that the first mark_stack_push is CAS-based, whereas the
521 // two below are Mutex-based. This is OK since the first one is only
522 // called during evacuation pauses and doesn't compete with the
523 // other two (which are called by the marking tasks during
524 // concurrent marking or remark).
525 bool mark_stack_push(oop p) {
526 _markStack.par_push(p);
527 if (_markStack.overflow()) {
528 set_has_overflown();
529 return false;
530 }
531 return true;
532 }
533 bool mark_stack_push(oop* arr, int n) {
534 _markStack.par_push_arr(arr, n);
535 if (_markStack.overflow()) {
536 set_has_overflown();
537 return false;
538 }
539 return true;
540 }
541 void mark_stack_pop(oop* arr, int max, int* n) {
542 _markStack.par_pop_arr(arr, max, n);
543 }
544 size_t mark_stack_size() { return _markStack.size(); }
545 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
546 bool mark_stack_overflow() { return _markStack.overflow(); }
547 bool mark_stack_empty() { return _markStack.isEmpty(); }
549 // Manipulation of the region stack
550 bool region_stack_push(MemRegion mr) {
551 _regionStack.push(mr);
552 if (_regionStack.overflow()) {
553 set_has_overflown();
554 return false;
555 }
556 return true;
557 }
558 MemRegion region_stack_pop() { return _regionStack.pop(); }
559 int region_stack_size() { return _regionStack.size(); }
560 bool region_stack_overflow() { return _regionStack.overflow(); }
561 bool region_stack_empty() { return _regionStack.isEmpty(); }
563 bool concurrent_marking_in_progress() {
564 return _concurrent_marking_in_progress;
565 }
566 void set_concurrent_marking_in_progress() {
567 _concurrent_marking_in_progress = true;
568 }
569 void clear_concurrent_marking_in_progress() {
570 _concurrent_marking_in_progress = false;
571 }
573 void update_accum_task_vtime(int i, double vtime) {
574 _accum_task_vtime[i] += vtime;
575 }
577 double all_task_accum_vtime() {
578 double ret = 0.0;
579 for (int i = 0; i < (int)_max_task_num; ++i)
580 ret += _accum_task_vtime[i];
581 return ret;
582 }
584 // Attempts to steal an object from the task queues of other tasks
585 bool try_stealing(int task_num, int* hash_seed, oop& obj) {
586 return _task_queues->steal(task_num, hash_seed, obj);
587 }
589 // It grays an object by first marking it. Then, if it's behind the
590 // global finger, it also pushes it on the global stack.
591 void deal_with_reference(oop obj);
593 ConcurrentMark(ReservedSpace rs, int max_regions);
594 ~ConcurrentMark();
595 ConcurrentMarkThread* cmThread() { return _cmThread; }
597 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
598 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
600 // The following three are interaction between CM and
601 // G1CollectedHeap
603 // This notifies CM that a root during initial-mark needs to be
604 // grayed and it's MT-safe. Currently, we just mark it. But, in the
605 // future, we can experiment with pushing it on the stack and we can
606 // do this without changing G1CollectedHeap.
607 void grayRoot(oop p);
608 // It's used during evacuation pauses to gray a region, if
609 // necessary, and it's MT-safe. It assumes that the caller has
610 // marked any objects on that region. If _should_gray_objects is
611 // true and we're still doing concurrent marking, the region is
612 // pushed on the region stack, if it is located below the global
613 // finger, otherwise we do nothing.
614 void grayRegionIfNecessary(MemRegion mr);
615 // It's used during evacuation pauses to mark and, if necessary,
616 // gray a single object and it's MT-safe. It assumes the caller did
617 // not mark the object. If _should_gray_objects is true and we're
618 // still doing concurrent marking, the objects is pushed on the
619 // global stack, if it is located below the global finger, otherwise
620 // we do nothing.
621 void markAndGrayObjectIfNecessary(oop p);
623 // This iterates over the bitmap of the previous marking and prints
624 // out all objects that are marked on the bitmap and indicates
625 // whether what they point to is also marked or not.
626 void print_prev_bitmap_reachable();
628 // Clear the next marking bitmap (will be called concurrently).
629 void clearNextBitmap();
631 // main CMS steps and related support
632 void checkpointRootsInitial();
634 // These two do the work that needs to be done before and after the
635 // initial root checkpoint. Since this checkpoint can be done at two
636 // different points (i.e. an explicit pause or piggy-backed on a
637 // young collection), then it's nice to be able to easily share the
638 // pre/post code. It might be the case that we can put everything in
639 // the post method. TP
640 void checkpointRootsInitialPre();
641 void checkpointRootsInitialPost();
643 // Do concurrent phase of marking, to a tentative transitive closure.
644 void markFromRoots();
646 // Process all unprocessed SATB buffers. It is called at the
647 // beginning of an evacuation pause.
648 void drainAllSATBBuffers();
650 void checkpointRootsFinal(bool clear_all_soft_refs);
651 void checkpointRootsFinalWork();
652 void calcDesiredRegions();
653 void cleanup();
654 void completeCleanup();
656 // Mark in the previous bitmap. NB: this is usually read-only, so use
657 // this carefully!
658 void markPrev(oop p);
659 void clear(oop p);
660 // Clears marks for all objects in the given range, for both prev and
661 // next bitmaps. NB: the previous bitmap is usually read-only, so use
662 // this carefully!
663 void clearRangeBothMaps(MemRegion mr);
665 // Record the current top of the mark and region stacks; a
666 // subsequent oops_do() on the mark stack and
667 // invalidate_entries_into_cset() on the region stack will iterate
668 // only over indices valid at the time of this call.
669 void set_oops_do_bound() {
670 _markStack.set_oops_do_bound();
671 _regionStack.set_oops_do_bound();
672 }
673 // Iterate over the oops in the mark stack and all local queues. It
674 // also calls invalidate_entries_into_cset() on the region stack.
675 void oops_do(OopClosure* f);
676 // It is called at the end of an evacuation pause during marking so
677 // that CM is notified of where the new end of the heap is. It
678 // doesn't do anything if concurrent_marking_in_progress() is false,
679 // unless the force parameter is true.
680 void update_g1_committed(bool force = false);
682 void complete_marking_in_collection_set();
684 // It indicates that a new collection set is being chosen.
685 void newCSet();
686 // It registers a collection set heap region with CM. This is used
687 // to determine whether any heap regions are located above the finger.
688 void registerCSetRegion(HeapRegion* hr);
690 // Returns "true" if at least one mark has been completed.
691 bool at_least_one_mark_complete() { return _at_least_one_mark_complete; }
693 bool isMarked(oop p) const {
694 assert(p != NULL && p->is_oop(), "expected an oop");
695 HeapWord* addr = (HeapWord*)p;
696 assert(addr >= _nextMarkBitMap->startWord() ||
697 addr < _nextMarkBitMap->endWord(), "in a region");
699 return _nextMarkBitMap->isMarked(addr);
700 }
702 inline bool not_yet_marked(oop p) const;
704 // XXX Debug code
705 bool containing_card_is_marked(void* p);
706 bool containing_cards_are_marked(void* start, void* last);
708 bool isPrevMarked(oop p) const {
709 assert(p != NULL && p->is_oop(), "expected an oop");
710 HeapWord* addr = (HeapWord*)p;
711 assert(addr >= _prevMarkBitMap->startWord() ||
712 addr < _prevMarkBitMap->endWord(), "in a region");
714 return _prevMarkBitMap->isMarked(addr);
715 }
717 inline bool do_yield_check(int worker_i = 0);
718 inline bool should_yield();
720 // Called to abort the marking cycle after a Full GC takes palce.
721 void abort();
723 void disable_co_trackers();
725 // This prints the global/local fingers. It is used for debugging.
726 NOT_PRODUCT(void print_finger();)
728 void print_summary_info();
730 // The following indicate whether a given verbose level has been
731 // set. Notice that anything above stats is conditional to
732 // _MARKING_VERBOSE_ having been set to 1
733 bool verbose_stats()
734 { return _verbose_level >= stats_verbose; }
735 bool verbose_low()
736 { return _MARKING_VERBOSE_ && _verbose_level >= low_verbose; }
737 bool verbose_medium()
738 { return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose; }
739 bool verbose_high()
740 { return _MARKING_VERBOSE_ && _verbose_level >= high_verbose; }
741 };
743 // A class representing a marking task.
744 class CMTask : public TerminatorTerminator {
745 private:
746 enum PrivateConstants {
747 // the regular clock call is called once the scanned words reaches
748 // this limit
749 words_scanned_period = 12*1024,
750 // the regular clock call is called once the number of visited
751 // references reaches this limit
752 refs_reached_period = 384,
753 // initial value for the hash seed, used in the work stealing code
754 init_hash_seed = 17,
755 // how many entries will be transferred between global stack and
756 // local queues
757 global_stack_transfer_size = 16
758 };
760 int _task_id;
761 G1CollectedHeap* _g1h;
762 ConcurrentMark* _cm;
763 CMBitMap* _nextMarkBitMap;
764 // the task queue of this task
765 CMTaskQueue* _task_queue;
766 private:
767 // the task queue set---needed for stealing
768 CMTaskQueueSet* _task_queues;
769 // indicates whether the task has been claimed---this is only for
770 // debugging purposes
771 bool _claimed;
773 // number of calls to this task
774 int _calls;
776 // concurrent overhead over a single CPU for this task
777 COTracker _co_tracker;
779 // when the virtual timer reaches this time, the marking step should
780 // exit
781 double _time_target_ms;
782 // the start time of the current marking step
783 double _start_time_ms;
785 // the oop closure used for iterations over oops
786 OopClosure* _oop_closure;
788 // the region this task is scanning, NULL if we're not scanning any
789 HeapRegion* _curr_region;
790 // the local finger of this task, NULL if we're not scanning a region
791 HeapWord* _finger;
792 // limit of the region this task is scanning, NULL if we're not scanning one
793 HeapWord* _region_limit;
795 // This is used only when we scan regions popped from the region
796 // stack. It records what the last object on such a region we
797 // scanned was. It is used to ensure that, if we abort region
798 // iteration, we do not rescan the first part of the region. This
799 // should be NULL when we're not scanning a region from the region
800 // stack.
801 HeapWord* _region_finger;
803 // the number of words this task has scanned
804 size_t _words_scanned;
805 // When _words_scanned reaches this limit, the regular clock is
806 // called. Notice that this might be decreased under certain
807 // circumstances (i.e. when we believe that we did an expensive
808 // operation).
809 size_t _words_scanned_limit;
810 // the initial value of _words_scanned_limit (i.e. what it was
811 // before it was decreased).
812 size_t _real_words_scanned_limit;
814 // the number of references this task has visited
815 size_t _refs_reached;
816 // When _refs_reached reaches this limit, the regular clock is
817 // called. Notice this this might be decreased under certain
818 // circumstances (i.e. when we believe that we did an expensive
819 // operation).
820 size_t _refs_reached_limit;
821 // the initial value of _refs_reached_limit (i.e. what it was before
822 // it was decreased).
823 size_t _real_refs_reached_limit;
825 // used by the work stealing stuff
826 int _hash_seed;
827 // if this is true, then the task has aborted for some reason
828 bool _has_aborted;
829 // set when the task aborts because it has met its time quota
830 bool _has_aborted_timed_out;
831 // true when we're draining SATB buffers; this avoids the task
832 // aborting due to SATB buffers being available (as we're already
833 // dealing with them)
834 bool _draining_satb_buffers;
836 // number sequence of past step times
837 NumberSeq _step_times_ms;
838 // elapsed time of this task
839 double _elapsed_time_ms;
840 // termination time of this task
841 double _termination_time_ms;
842 // when this task got into the termination protocol
843 double _termination_start_time_ms;
845 // true when the task is during a concurrent phase, false when it is
846 // in the remark phase (so, in the latter case, we do not have to
847 // check all the things that we have to check during the concurrent
848 // phase, i.e. SATB buffer availability...)
849 bool _concurrent;
851 TruncatedSeq _marking_step_diffs_ms;
853 // LOTS of statistics related with this task
854 #if _MARKING_STATS_
855 NumberSeq _all_clock_intervals_ms;
856 double _interval_start_time_ms;
858 int _aborted;
859 int _aborted_overflow;
860 int _aborted_cm_aborted;
861 int _aborted_yield;
862 int _aborted_timed_out;
863 int _aborted_satb;
864 int _aborted_termination;
866 int _steal_attempts;
867 int _steals;
869 int _clock_due_to_marking;
870 int _clock_due_to_scanning;
872 int _local_pushes;
873 int _local_pops;
874 int _local_max_size;
875 int _objs_scanned;
877 int _global_pushes;
878 int _global_pops;
879 int _global_max_size;
881 int _global_transfers_to;
882 int _global_transfers_from;
884 int _region_stack_pops;
886 int _regions_claimed;
887 int _objs_found_on_bitmap;
889 int _satb_buffers_processed;
890 #endif // _MARKING_STATS_
892 // it updates the local fields after this task has claimed
893 // a new region to scan
894 void setup_for_region(HeapRegion* hr);
895 // it brings up-to-date the limit of the region
896 void update_region_limit();
897 // it resets the local fields after a task has finished scanning a
898 // region
899 void giveup_current_region();
901 // called when either the words scanned or the refs visited limit
902 // has been reached
903 void reached_limit();
904 // recalculates the words scanned and refs visited limits
905 void recalculate_limits();
906 // decreases the words scanned and refs visited limits when we reach
907 // an expensive operation
908 void decrease_limits();
909 // it checks whether the words scanned or refs visited reached their
910 // respective limit and calls reached_limit() if they have
911 void check_limits() {
912 if (_words_scanned >= _words_scanned_limit ||
913 _refs_reached >= _refs_reached_limit)
914 reached_limit();
915 }
916 // this is supposed to be called regularly during a marking step as
917 // it checks a bunch of conditions that might cause the marking step
918 // to abort
919 void regular_clock_call();
920 bool concurrent() { return _concurrent; }
922 public:
923 // It resets the task; it should be called right at the beginning of
924 // a marking phase.
925 void reset(CMBitMap* _nextMarkBitMap);
926 // it clears all the fields that correspond to a claimed region.
927 void clear_region_fields();
929 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
931 void enable_co_tracker() {
932 guarantee( !_co_tracker.enabled(), "invariant" );
933 _co_tracker.enable();
934 }
935 void disable_co_tracker() {
936 guarantee( _co_tracker.enabled(), "invariant" );
937 _co_tracker.disable();
938 }
939 bool co_tracker_enabled() {
940 return _co_tracker.enabled();
941 }
942 void reset_co_tracker(double starting_conc_overhead = 0.0) {
943 _co_tracker.reset(starting_conc_overhead);
944 }
945 void start_co_tracker() {
946 _co_tracker.start();
947 }
948 void update_co_tracker(bool force_end = false) {
949 _co_tracker.update(force_end);
950 }
952 // The main method of this class which performs a marking step
953 // trying not to exceed the given duration. However, it might exit
954 // prematurely, according to some conditions (i.e. SATB buffers are
955 // available for processing).
956 void do_marking_step(double target_ms);
958 // These two calls start and stop the timer
959 void record_start_time() {
960 _elapsed_time_ms = os::elapsedTime() * 1000.0;
961 }
962 void record_end_time() {
963 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
964 }
966 // returns the task ID
967 int task_id() { return _task_id; }
969 // From TerminatorTerminator. It determines whether this task should
970 // exit the termination protocol after it's entered it.
971 virtual bool should_exit_termination();
973 HeapWord* finger() { return _finger; }
975 bool has_aborted() { return _has_aborted; }
976 void set_has_aborted() { _has_aborted = true; }
977 void clear_has_aborted() { _has_aborted = false; }
978 bool claimed() { return _claimed; }
980 void set_oop_closure(OopClosure* oop_closure) {
981 _oop_closure = oop_closure;
982 }
984 // It grays the object by marking it and, if necessary, pushing it
985 // on the local queue
986 void deal_with_reference(oop obj);
988 // It scans an object and visits its children.
989 void scan_object(oop obj) {
990 tmp_guarantee_CM( _nextMarkBitMap->isMarked((HeapWord*) obj),
991 "invariant" );
993 if (_cm->verbose_high())
994 gclog_or_tty->print_cr("[%d] we're scanning object "PTR_FORMAT,
995 _task_id, (void*) obj);
997 size_t obj_size = obj->size();
998 _words_scanned += obj_size;
1000 obj->oop_iterate(_oop_closure);
1001 statsOnly( ++_objs_scanned );
1002 check_limits();
1003 }
1005 // It pushes an object on the local queue.
1006 void push(oop obj);
1008 // These two move entries to/from the global stack.
1009 void move_entries_to_global_stack();
1010 void get_entries_from_global_stack();
1012 // It pops and scans objects from the local queue. If partially is
1013 // true, then it stops when the queue size is of a given limit. If
1014 // partially is false, then it stops when the queue is empty.
1015 void drain_local_queue(bool partially);
1016 // It moves entries from the global stack to the local queue and
1017 // drains the local queue. If partially is true, then it stops when
1018 // both the global stack and the local queue reach a given size. If
1019 // partially if false, it tries to empty them totally.
1020 void drain_global_stack(bool partially);
1021 // It keeps picking SATB buffers and processing them until no SATB
1022 // buffers are available.
1023 void drain_satb_buffers();
1024 // It keeps popping regions from the region stack and processing
1025 // them until the region stack is empty.
1026 void drain_region_stack(BitMapClosure* closure);
1028 // moves the local finger to a new location
1029 inline void move_finger_to(HeapWord* new_finger) {
1030 tmp_guarantee_CM( new_finger >= _finger && new_finger < _region_limit,
1031 "invariant" );
1032 _finger = new_finger;
1033 }
1035 // moves the region finger to a new location
1036 inline void move_region_finger_to(HeapWord* new_finger) {
1037 tmp_guarantee_CM( new_finger < _cm->finger(), "invariant" );
1038 _region_finger = new_finger;
1039 }
1041 CMTask(int task_num, ConcurrentMark *cm,
1042 CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
1044 // it prints statistics associated with this task
1045 void print_stats();
1047 #if _MARKING_STATS_
1048 void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1049 #endif // _MARKING_STATS_
1050 };