1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_G1_CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_G1_CONCURRENTMARK_HPP
27
28 #include "classfile/javaClasses.hpp"
29 #include "gc/g1/g1RegionToSpaceMapper.hpp"
30 #include "gc/g1/heapRegionSet.hpp"
31 #include "gc/shared/taskqueue.hpp"
32
33 class G1CollectedHeap;
34 class CMBitMap;
35 class CMTask;
36 class ConcurrentMark;
37 typedef GenericTaskQueue<oop, mtGC> CMTaskQueue;
38 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
39
40 // Closure used by CM during concurrent reference discovery
41 // and reference processing (during remarking) to determine
42 // if a particular object is alive. It is primarily used
43 // to determine if referents of discovered reference objects
44 // are alive. An instance is also embedded into the
45 // reference processor as the _is_alive_non_header field
46 class G1CMIsAliveClosure: public BoolObjectClosure {
47 G1CollectedHeap* _g1;
48 public:
49 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
50
51 bool do_object_b(oop obj);
52 };
53
54 // A generic CM bit map. This is essentially a wrapper around the BitMap
55 // class, with one bit per (1<<_shifter) HeapWords.
56
57 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
58 protected:
59 HeapWord* _bmStartWord; // base address of range covered by map
60 size_t _bmWordSize; // map size (in #HeapWords covered)
61 const int _shifter; // map to char or bit
62 BitMap _bm; // the bit map itself
63
64 public:
65 // constructor
66 CMBitMapRO(int shifter);
67
68 // inquiries
69 HeapWord* startWord() const { return _bmStartWord; }
70 // the following is one past the last word in space
71 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
72
73 // read marks
74
75 bool isMarked(HeapWord* addr) const {
76 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
77 "outside underlying space?");
78 return _bm.at(heapWordToOffset(addr));
79 }
80
81 // iteration
82 inline bool iterate(BitMapClosure* cl, MemRegion mr);
83
84 // Return the address corresponding to the next marked bit at or after
85 // "addr", and before "limit", if "limit" is non-NULL. If there is no
86 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
87 HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
88 const HeapWord* limit = NULL) const;
89
90 // conversion utilities
91 HeapWord* offsetToHeapWord(size_t offset) const {
92 return _bmStartWord + (offset << _shifter);
93 }
94 size_t heapWordToOffset(const HeapWord* addr) const {
95 return pointer_delta(addr, _bmStartWord) >> _shifter;
96 }
97
98 // The argument addr should be the start address of a valid object
99 HeapWord* nextObject(HeapWord* addr) {
100 oop obj = (oop) addr;
101 HeapWord* res = addr + obj->size();
102 assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
103 return res;
104 }
105
106 void print_on_error(outputStream* st, const char* prefix) const;
107
108 // debugging
109 NOT_PRODUCT(bool covers(MemRegion rs) const;)
110 };
111
112 class CMBitMapMappingChangedListener : public G1MappingChangedListener {
113 private:
114 CMBitMap* _bm;
115 public:
116 CMBitMapMappingChangedListener() : _bm(NULL) {}
117
118 void set_bitmap(CMBitMap* bm) { _bm = bm; }
119
120 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
121 };
122
123 class CMBitMap : public CMBitMapRO {
124 private:
125 CMBitMapMappingChangedListener _listener;
126
127 public:
128 static size_t compute_size(size_t heap_size);
129 // Returns the amount of bytes on the heap between two marks in the bitmap.
130 static size_t mark_distance();
131 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
132 // mark bitmap corresponds to. This is the same as the mark distance above.
133 static size_t heap_map_factor() {
134 return mark_distance();
135 }
136
137 CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
138
139 // Initializes the underlying BitMap to cover the given area.
140 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
141
142 // Write marks.
143 inline void mark(HeapWord* addr);
144 inline void clear(HeapWord* addr);
145 inline bool parMark(HeapWord* addr);
146
147 void clearRange(MemRegion mr);
148
149 // Clear the whole mark bitmap.
150 void clearAll();
151 };
152
153 // Represents a marking stack used by ConcurrentMarking in the G1 collector.
154 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
155 VirtualSpace _virtual_space; // Underlying backing store for actual stack
156 ConcurrentMark* _cm;
157 oop* _base; // bottom of stack
158 jint _index; // one more than last occupied index
159 jint _capacity; // max #elements
160 jint _saved_index; // value of _index saved at start of GC
161
162 bool _overflow;
163 bool _should_expand;
164
165 public:
166 CMMarkStack(ConcurrentMark* cm);
167 ~CMMarkStack();
168
169 bool allocate(size_t capacity);
170
171 // Pushes the first "n" elements of "ptr_arr" on the stack.
172 // Locking impl: concurrency is allowed only with
173 // "par_push_arr" and/or "par_pop_arr" operations, which use the same
174 // locking strategy.
175 void par_push_arr(oop* ptr_arr, int n);
176
177 // If returns false, the array was empty. Otherwise, removes up to "max"
178 // elements from the stack, and transfers them to "ptr_arr" in an
179 // unspecified order. The actual number transferred is given in "n" ("n
180 // == 0" is deliberately redundant with the return value.) Locking impl:
181 // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
182 // operations, which use the same locking strategy.
183 bool par_pop_arr(oop* ptr_arr, int max, int* n);
184
185 bool isEmpty() { return _index == 0; }
186 int maxElems() { return _capacity; }
187
188 bool overflow() { return _overflow; }
189 void clear_overflow() { _overflow = false; }
190
191 bool should_expand() const { return _should_expand; }
192 void set_should_expand();
193
194 // Expand the stack, typically in response to an overflow condition
195 void expand();
196
197 int size() { return _index; }
198
199 void setEmpty() { _index = 0; clear_overflow(); }
200
201 // Record the current index.
202 void note_start_of_gc();
203
204 // Make sure that we have not added any entries to the stack during GC.
205 void note_end_of_gc();
206
207 // Apply fn to each oop in the mark stack, up to the bound recorded
208 // via one of the above "note" functions. The mark stack must not
209 // be modified while iterating.
210 template<typename Fn> void iterate(Fn fn);
211 };
212
213 class YoungList;
214
215 // Root Regions are regions that are not empty at the beginning of a
216 // marking cycle and which we might collect during an evacuation pause
217 // while the cycle is active. Given that, during evacuation pauses, we
218 // do not copy objects that are explicitly marked, what we have to do
219 // for the root regions is to scan them and mark all objects reachable
220 // from them. According to the SATB assumptions, we only need to visit
221 // each object once during marking. So, as long as we finish this scan
222 // before the next evacuation pause, we can copy the objects from the
223 // root regions without having to mark them or do anything else to them.
224 //
225 // Currently, we only support root region scanning once (at the start
226 // of the marking cycle) and the root regions are all the survivor
227 // regions populated during the initial-mark pause.
228 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
229 private:
230 YoungList* _young_list;
231 ConcurrentMark* _cm;
232
233 volatile bool _scan_in_progress;
234 volatile bool _should_abort;
235 HeapRegion* volatile _next_survivor;
236
237 public:
238 CMRootRegions();
239 // We actually do most of the initialization in this method.
240 void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
241
242 // Reset the claiming / scanning of the root regions.
243 void prepare_for_scan();
244
245 // Forces get_next() to return NULL so that the iteration aborts early.
246 void abort() { _should_abort = true; }
247
248 // Return true if the CM thread are actively scanning root regions,
249 // false otherwise.
250 bool scan_in_progress() { return _scan_in_progress; }
251
252 // Claim the next root region to scan atomically, or return NULL if
253 // all have been claimed.
254 HeapRegion* claim_next();
255
256 // Flag that we're done with root region scanning and notify anyone
257 // who's waiting on it. If aborted is false, assume that all regions
258 // have been claimed.
259 void scan_finished();
260
261 // If CM threads are still scanning root regions, wait until they
262 // are done. Return true if we had to wait, false otherwise.
263 bool wait_until_scan_finished();
264 };
265
266 class ConcurrentMarkThread;
267
268 class ConcurrentMark: public CHeapObj<mtGC> {
269 friend class CMMarkStack;
270 friend class ConcurrentMarkThread;
271 friend class CMTask;
272 friend class CMBitMapClosure;
273 friend class CMRemarkTask;
274 friend class CMConcurrentMarkingTask;
275 friend class G1ParNoteEndTask;
276 friend class CalcLiveObjectsClosure;
277 friend class G1CMRefProcTaskProxy;
278 friend class G1CMRefProcTaskExecutor;
279 friend class G1CMKeepAliveAndDrainClosure;
280 friend class G1CMDrainMarkingStackClosure;
281
282 protected:
283 ConcurrentMarkThread* _cmThread; // The thread doing the work
284 G1CollectedHeap* _g1h; // The heap
285 uint _parallel_marking_threads; // The number of marking
286 // threads we're using
287 uint _max_parallel_marking_threads; // Max number of marking
288 // threads we'll ever use
289 double _sleep_factor; // How much we have to sleep, with
290 // respect to the work we just did, to
291 // meet the marking overhead goal
292 double _marking_task_overhead; // Marking target overhead for
293 // a single task
294
295 FreeRegionList _cleanup_list;
296
297 // Concurrent marking support structures
298 CMBitMap _markBitMap1;
299 CMBitMap _markBitMap2;
300 CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap
301 CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
302
303 BitMap _region_bm;
304 BitMap _card_bm;
305
306 // Heap bounds
307 HeapWord* _heap_start;
308 HeapWord* _heap_end;
309
310 // Root region tracking and claiming
311 CMRootRegions _root_regions;
312
313 // For gray objects
314 CMMarkStack _markStack; // Grey objects behind global finger
315 HeapWord* volatile _finger; // The global finger, region aligned,
316 // always points to the end of the
317 // last claimed region
318
319 // Marking tasks
320 uint _max_worker_id;// Maximum worker id
321 uint _active_tasks; // Task num currently active
322 CMTask** _tasks; // Task queue array (max_worker_id len)
323 CMTaskQueueSet* _task_queues; // Task queue set
324 ParallelTaskTerminator _terminator; // For termination
325
326 // Two sync barriers that are used to synchronize tasks when an
327 // overflow occurs. The algorithm is the following. All tasks enter
328 // the first one to ensure that they have all stopped manipulating
329 // the global data structures. After they exit it, they re-initialize
330 // their data structures and task 0 re-initializes the global data
331 // structures. Then, they enter the second sync barrier. This
332 // ensure, that no task starts doing work before all data
333 // structures (local and global) have been re-initialized. When they
334 // exit it, they are free to start working again.
335 WorkGangBarrierSync _first_overflow_barrier_sync;
336 WorkGangBarrierSync _second_overflow_barrier_sync;
337
338 // This is set by any task, when an overflow on the global data
339 // structures is detected
340 volatile bool _has_overflown;
341 // True: marking is concurrent, false: we're in remark
342 volatile bool _concurrent;
343 // Set at the end of a Full GC so that marking aborts
344 volatile bool _has_aborted;
345
346 // Used when remark aborts due to an overflow to indicate that
347 // another concurrent marking phase should start
348 volatile bool _restart_for_overflow;
349
350 // This is true from the very start of concurrent marking until the
351 // point when all the tasks complete their work. It is really used
352 // to determine the points between the end of concurrent marking and
353 // time of remark.
354 volatile bool _concurrent_marking_in_progress;
355
356 // Keep track of whether we have started concurrent phase or not.
357 bool _concurrent_phase_started;
358
359 // All of these times are in ms
360 NumberSeq _init_times;
361 NumberSeq _remark_times;
362 NumberSeq _remark_mark_times;
363 NumberSeq _remark_weak_ref_times;
364 NumberSeq _cleanup_times;
365 double _total_counting_time;
366 double _total_rs_scrub_time;
367
368 double* _accum_task_vtime; // Accumulated task vtime
369
370 WorkGang* _parallel_workers;
371
372 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
373 void weakRefsWork(bool clear_all_soft_refs);
374
375 void swapMarkBitMaps();
376
377 // It resets the global marking data structures, as well as the
378 // task local ones; should be called during initial mark.
379 void reset();
380
381 // Resets all the marking data structures. Called when we have to restart
382 // marking or when marking completes (via set_non_marking_state below).
383 void reset_marking_state(bool clear_overflow = true);
384
385 // We do this after we're done with marking so that the marking data
386 // structures are initialized to a sensible and predictable state.
387 void set_non_marking_state();
388
389 // Called to indicate how many threads are currently active.
390 void set_concurrency(uint active_tasks);
391
392 // It should be called to indicate which phase we're in (concurrent
393 // mark or remark) and how many threads are currently active.
394 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
395
396 // Prints all gathered CM-related statistics
397 void print_stats();
398
399 bool cleanup_list_is_empty() {
400 return _cleanup_list.is_empty();
401 }
402
403 // Accessor methods
404 uint parallel_marking_threads() const { return _parallel_marking_threads; }
405 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
406 double sleep_factor() { return _sleep_factor; }
407 double marking_task_overhead() { return _marking_task_overhead;}
408
409 HeapWord* finger() { return _finger; }
410 bool concurrent() { return _concurrent; }
411 uint active_tasks() { return _active_tasks; }
412 ParallelTaskTerminator* terminator() { return &_terminator; }
413
414 // It claims the next available region to be scanned by a marking
415 // task/thread. It might return NULL if the next region is empty or
416 // we have run out of regions. In the latter case, out_of_regions()
417 // determines whether we've really run out of regions or the task
418 // should call claim_region() again. This might seem a bit
419 // awkward. Originally, the code was written so that claim_region()
420 // either successfully returned with a non-empty region or there
421 // were no more regions to be claimed. The problem with this was
422 // that, in certain circumstances, it iterated over large chunks of
423 // the heap finding only empty regions and, while it was working, it
424 // was preventing the calling task to call its regular clock
425 // method. So, this way, each task will spend very little time in
426 // claim_region() and is allowed to call the regular clock method
427 // frequently.
428 HeapRegion* claim_region(uint worker_id);
429
430 // It determines whether we've run out of regions to scan. Note that
431 // the finger can point past the heap end in case the heap was expanded
432 // to satisfy an allocation without doing a GC. This is fine, because all
433 // objects in those regions will be considered live anyway because of
434 // SATB guarantees (i.e. their TAMS will be equal to bottom).
435 bool out_of_regions() { return _finger >= _heap_end; }
436
437 // Returns the task with the given id
438 CMTask* task(int id) {
439 assert(0 <= id && id < (int) _active_tasks,
440 "task id not within active bounds");
441 return _tasks[id];
442 }
443
444 // Returns the task queue with the given id
445 CMTaskQueue* task_queue(int id) {
446 assert(0 <= id && id < (int) _active_tasks,
447 "task queue id not within active bounds");
448 return (CMTaskQueue*) _task_queues->queue(id);
449 }
450
451 // Returns the task queue set
452 CMTaskQueueSet* task_queues() { return _task_queues; }
453
454 // Access / manipulation of the overflow flag which is set to
455 // indicate that the global stack has overflown
456 bool has_overflown() { return _has_overflown; }
457 void set_has_overflown() { _has_overflown = true; }
458 void clear_has_overflown() { _has_overflown = false; }
459 bool restart_for_overflow() { return _restart_for_overflow; }
460
461 // Methods to enter the two overflow sync barriers
462 void enter_first_sync_barrier(uint worker_id);
463 void enter_second_sync_barrier(uint worker_id);
464
465 // Live Data Counting data structures...
466 // These data structures are initialized at the start of
467 // marking. They are written to while marking is active.
468 // They are aggregated during remark; the aggregated values
469 // are then used to populate the _region_bm, _card_bm, and
470 // the total live bytes, which are then subsequently updated
471 // during cleanup.
472
473 // An array of bitmaps (one bit map per task). Each bitmap
474 // is used to record the cards spanned by the live objects
475 // marked by that task/worker.
476 BitMap* _count_card_bitmaps;
477
478 // Used to record the number of marked live bytes
479 // (for each region, by worker thread).
480 size_t** _count_marked_bytes;
481
482 // Card index of the bottom of the G1 heap. Used for biasing indices into
483 // the card bitmaps.
484 intptr_t _heap_bottom_card_num;
485
486 // Set to true when initialization is complete
487 bool _completed_initialization;
488
489 public:
490 // Manipulation of the global mark stack.
491 // The push and pop operations are used by tasks for transfers
492 // between task-local queues and the global mark stack, and use
493 // locking for concurrency safety.
494 bool mark_stack_push(oop* arr, int n) {
495 _markStack.par_push_arr(arr, n);
496 if (_markStack.overflow()) {
497 set_has_overflown();
498 return false;
499 }
500 return true;
501 }
502 void mark_stack_pop(oop* arr, int max, int* n) {
503 _markStack.par_pop_arr(arr, max, n);
504 }
505 size_t mark_stack_size() { return _markStack.size(); }
506 size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
507 bool mark_stack_overflow() { return _markStack.overflow(); }
508 bool mark_stack_empty() { return _markStack.isEmpty(); }
509
510 CMRootRegions* root_regions() { return &_root_regions; }
511
512 bool concurrent_marking_in_progress() {
513 return _concurrent_marking_in_progress;
514 }
515 void set_concurrent_marking_in_progress() {
516 _concurrent_marking_in_progress = true;
517 }
518 void clear_concurrent_marking_in_progress() {
519 _concurrent_marking_in_progress = false;
520 }
521
522 void register_concurrent_phase_start(const char* title);
523 void register_concurrent_phase_end();
524
525 void update_accum_task_vtime(int i, double vtime) {
526 _accum_task_vtime[i] += vtime;
527 }
528
529 double all_task_accum_vtime() {
530 double ret = 0.0;
531 for (uint i = 0; i < _max_worker_id; ++i)
532 ret += _accum_task_vtime[i];
533 return ret;
534 }
535
536 // Attempts to steal an object from the task queues of other tasks
537 bool try_stealing(uint worker_id, int* hash_seed, oop& obj);
538
539 ConcurrentMark(G1CollectedHeap* g1h,
540 G1RegionToSpaceMapper* prev_bitmap_storage,
541 G1RegionToSpaceMapper* next_bitmap_storage);
542 ~ConcurrentMark();
543
544 ConcurrentMarkThread* cmThread() { return _cmThread; }
545
546 CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
547 CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
548
549 // Returns the number of GC threads to be used in a concurrent
550 // phase based on the number of GC threads being used in a STW
551 // phase.
552 uint scale_parallel_threads(uint n_par_threads);
553
554 // Calculates the number of GC threads to be used in a concurrent phase.
555 uint calc_parallel_marking_threads();
556
557 // The following three are interaction between CM and
558 // G1CollectedHeap
559
560 // This notifies CM that a root during initial-mark needs to be
561 // grayed. It is MT-safe. word_size is the size of the object in
562 // words. It is passed explicitly as sometimes we cannot calculate
563 // it from the given object because it might be in an inconsistent
564 // state (e.g., in to-space and being copied). So the caller is
565 // responsible for dealing with this issue (e.g., get the size from
566 // the from-space image when the to-space image might be
567 // inconsistent) and always passing the size. hr is the region that
568 // contains the object and it's passed optionally from callers who
569 // might already have it (no point in recalculating it).
570 inline void grayRoot(oop obj,
571 size_t word_size,
572 uint worker_id,
573 HeapRegion* hr = NULL);
574
575 // Clear the next marking bitmap (will be called concurrently).
576 void clearNextBitmap();
577
578 // Return whether the next mark bitmap has no marks set. To be used for assertions
579 // only. Will not yield to pause requests.
580 bool nextMarkBitmapIsClear();
581
582 // These two do the work that needs to be done before and after the
583 // initial root checkpoint. Since this checkpoint can be done at two
584 // different points (i.e. an explicit pause or piggy-backed on a
585 // young collection), then it's nice to be able to easily share the
586 // pre/post code. It might be the case that we can put everything in
587 // the post method. TP
588 void checkpointRootsInitialPre();
589 void checkpointRootsInitialPost();
590
591 // Scan all the root regions and mark everything reachable from
592 // them.
593 void scanRootRegions();
594
595 // Scan a single root region and mark everything reachable from it.
596 void scanRootRegion(HeapRegion* hr, uint worker_id);
597
598 // Do concurrent phase of marking, to a tentative transitive closure.
599 void markFromRoots();
600
601 void checkpointRootsFinal(bool clear_all_soft_refs);
602 void checkpointRootsFinalWork();
603 void cleanup();
604 void completeCleanup();
605
606 // Mark in the previous bitmap. NB: this is usually read-only, so use
607 // this carefully!
608 inline void markPrev(oop p);
609
610 // Clears marks for all objects in the given range, for the prev or
611 // next bitmaps. NB: the previous bitmap is usually
612 // read-only, so use this carefully!
613 void clearRangePrevBitmap(MemRegion mr);
614
615 // Notify data structures that a GC has started.
616 void note_start_of_gc() {
617 _markStack.note_start_of_gc();
618 }
619
620 // Notify data structures that a GC is finished.
621 void note_end_of_gc() {
622 _markStack.note_end_of_gc();
623 }
624
625 // Verify that there are no CSet oops on the stacks (taskqueues /
626 // global mark stack) and fingers (global / per-task).
627 // If marking is not in progress, it's a no-op.
628 void verify_no_cset_oops() PRODUCT_RETURN;
629
630 bool isPrevMarked(oop p) const {
631 assert(p != NULL && p->is_oop(), "expected an oop");
632 HeapWord* addr = (HeapWord*)p;
633 assert(addr >= _prevMarkBitMap->startWord() ||
634 addr < _prevMarkBitMap->endWord(), "in a region");
635
636 return _prevMarkBitMap->isMarked(addr);
637 }
638
639 inline bool do_yield_check(uint worker_i = 0);
640
641 // Called to abort the marking cycle after a Full GC takes place.
642 void abort();
643
644 bool has_aborted() { return _has_aborted; }
645
646 void print_summary_info();
647
648 void print_worker_threads_on(outputStream* st) const;
649
650 void print_on_error(outputStream* st) const;
651
652 // Liveness counting
653
654 // Utility routine to set an exclusive range of cards on the given
655 // card liveness bitmap
656 inline void set_card_bitmap_range(BitMap* card_bm,
657 BitMap::idx_t start_idx,
658 BitMap::idx_t end_idx,
659 bool is_par);
660
661 // Returns the card number of the bottom of the G1 heap.
662 // Used in biasing indices into accounting card bitmaps.
663 intptr_t heap_bottom_card_num() const {
664 return _heap_bottom_card_num;
665 }
666
667 // Returns the card bitmap for a given task or worker id.
668 BitMap* count_card_bitmap_for(uint worker_id) {
669 assert(worker_id < _max_worker_id, "oob");
670 assert(_count_card_bitmaps != NULL, "uninitialized");
671 BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
672 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
673 return task_card_bm;
674 }
675
676 // Returns the array containing the marked bytes for each region,
677 // for the given worker or task id.
678 size_t* count_marked_bytes_array_for(uint worker_id) {
679 assert(worker_id < _max_worker_id, "oob");
680 assert(_count_marked_bytes != NULL, "uninitialized");
681 size_t* marked_bytes_array = _count_marked_bytes[worker_id];
682 assert(marked_bytes_array != NULL, "uninitialized");
683 return marked_bytes_array;
684 }
685
686 // Returns the index in the liveness accounting card table bitmap
687 // for the given address
688 inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
689
690 // Counts the size of the given memory region in the the given
691 // marked_bytes array slot for the given HeapRegion.
692 // Sets the bits in the given card bitmap that are associated with the
693 // cards that are spanned by the memory region.
694 inline void count_region(MemRegion mr,
695 HeapRegion* hr,
696 size_t* marked_bytes_array,
697 BitMap* task_card_bm);
698
699 // Counts the given object in the given task/worker counting
700 // data structures.
701 inline void count_object(oop obj,
702 HeapRegion* hr,
703 size_t* marked_bytes_array,
704 BitMap* task_card_bm,
705 size_t word_size);
706
707 // Attempts to mark the given object and, if successful, counts
708 // the object in the given task/worker counting structures.
709 inline bool par_mark_and_count(oop obj,
710 HeapRegion* hr,
711 size_t* marked_bytes_array,
712 BitMap* task_card_bm);
713
714 // Attempts to mark the given object and, if successful, counts
715 // the object in the task/worker counting structures for the
716 // given worker id.
717 inline bool par_mark_and_count(oop obj,
718 size_t word_size,
719 HeapRegion* hr,
720 uint worker_id);
721
722 // Returns true if initialization was successfully completed.
723 bool completed_initialization() const {
724 return _completed_initialization;
725 }
726
727 protected:
728 // Clear all the per-task bitmaps and arrays used to store the
729 // counting data.
730 void clear_all_count_data();
731
732 // Aggregates the counting data for each worker/task
733 // that was constructed while marking. Also sets
734 // the amount of marked bytes for each region and
735 // the top at concurrent mark count.
736 void aggregate_count_data();
737
738 // Verification routine
739 void verify_count_data();
740 };
741
742 // A class representing a marking task.
743 class CMTask : public TerminatorTerminator {
744 private:
745 enum PrivateConstants {
746 // the regular clock call is called once the scanned words reaches
747 // this limit
748 words_scanned_period = 12*1024,
749 // the regular clock call is called once the number of visited
750 // references reaches this limit
751 refs_reached_period = 384,
752 // initial value for the hash seed, used in the work stealing code
753 init_hash_seed = 17,
754 // how many entries will be transferred between global stack and
755 // local queues
756 global_stack_transfer_size = 16
757 };
758
759 uint _worker_id;
760 G1CollectedHeap* _g1h;
761 ConcurrentMark* _cm;
762 CMBitMap* _nextMarkBitMap;
763 // the task queue of this task
764 CMTaskQueue* _task_queue;
765 private:
766 // the task queue set---needed for stealing
767 CMTaskQueueSet* _task_queues;
768 // indicates whether the task has been claimed---this is only for
769 // debugging purposes
770 bool _claimed;
771
772 // number of calls to this task
773 int _calls;
774
775 // when the virtual timer reaches this time, the marking step should
776 // exit
777 double _time_target_ms;
778 // the start time of the current marking step
779 double _start_time_ms;
780
781 // the oop closure used for iterations over oops
782 G1CMOopClosure* _cm_oop_closure;
783
784 // the region this task is scanning, NULL if we're not scanning any
785 HeapRegion* _curr_region;
786 // the local finger of this task, NULL if we're not scanning a region
787 HeapWord* _finger;
788 // limit of the region this task is scanning, NULL if we're not scanning one
789 HeapWord* _region_limit;
790
791 // the number of words this task has scanned
792 size_t _words_scanned;
793 // When _words_scanned reaches this limit, the regular clock is
794 // called. Notice that this might be decreased under certain
795 // circumstances (i.e. when we believe that we did an expensive
796 // operation).
797 size_t _words_scanned_limit;
798 // the initial value of _words_scanned_limit (i.e. what it was
799 // before it was decreased).
800 size_t _real_words_scanned_limit;
801
802 // the number of references this task has visited
803 size_t _refs_reached;
804 // When _refs_reached reaches this limit, the regular clock is
805 // called. Notice this this might be decreased under certain
806 // circumstances (i.e. when we believe that we did an expensive
807 // operation).
808 size_t _refs_reached_limit;
809 // the initial value of _refs_reached_limit (i.e. what it was before
810 // it was decreased).
811 size_t _real_refs_reached_limit;
812
813 // used by the work stealing stuff
814 int _hash_seed;
815 // if this is true, then the task has aborted for some reason
816 bool _has_aborted;
817 // set when the task aborts because it has met its time quota
818 bool _has_timed_out;
819 // true when we're draining SATB buffers; this avoids the task
820 // aborting due to SATB buffers being available (as we're already
821 // dealing with them)
822 bool _draining_satb_buffers;
823
824 // number sequence of past step times
825 NumberSeq _step_times_ms;
826 // elapsed time of this task
827 double _elapsed_time_ms;
828 // termination time of this task
829 double _termination_time_ms;
830 // when this task got into the termination protocol
831 double _termination_start_time_ms;
832
833 // true when the task is during a concurrent phase, false when it is
834 // in the remark phase (so, in the latter case, we do not have to
835 // check all the things that we have to check during the concurrent
836 // phase, i.e. SATB buffer availability...)
837 bool _concurrent;
838
839 TruncatedSeq _marking_step_diffs_ms;
840
841 // Counting data structures. Embedding the task's marked_bytes_array
842 // and card bitmap into the actual task saves having to go through
843 // the ConcurrentMark object.
844 size_t* _marked_bytes_array;
845 BitMap* _card_bm;
846
847 // it updates the local fields after this task has claimed
848 // a new region to scan
849 void setup_for_region(HeapRegion* hr);
850 // it brings up-to-date the limit of the region
851 void update_region_limit();
852
853 // called when either the words scanned or the refs visited limit
854 // has been reached
855 void reached_limit();
856 // recalculates the words scanned and refs visited limits
857 void recalculate_limits();
858 // decreases the words scanned and refs visited limits when we reach
859 // an expensive operation
860 void decrease_limits();
861 // it checks whether the words scanned or refs visited reached their
862 // respective limit and calls reached_limit() if they have
863 void check_limits() {
864 if (_words_scanned >= _words_scanned_limit ||
865 _refs_reached >= _refs_reached_limit) {
866 reached_limit();
867 }
868 }
869 // this is supposed to be called regularly during a marking step as
870 // it checks a bunch of conditions that might cause the marking step
871 // to abort
872 void regular_clock_call();
873 bool concurrent() { return _concurrent; }
874
875 // Test whether obj might have already been passed over by the
876 // mark bitmap scan, and so needs to be pushed onto the mark stack.
877 bool is_below_finger(oop obj, HeapWord* global_finger) const;
878
879 template<bool scan> void process_grey_object(oop obj);
880
881 public:
882 // It resets the task; it should be called right at the beginning of
883 // a marking phase.
884 void reset(CMBitMap* _nextMarkBitMap);
885 // it clears all the fields that correspond to a claimed region.
886 void clear_region_fields();
887
888 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
889
890 // The main method of this class which performs a marking step
891 // trying not to exceed the given duration. However, it might exit
892 // prematurely, according to some conditions (i.e. SATB buffers are
893 // available for processing).
894 void do_marking_step(double target_ms,
895 bool do_termination,
896 bool is_serial);
897
898 // These two calls start and stop the timer
899 void record_start_time() {
900 _elapsed_time_ms = os::elapsedTime() * 1000.0;
901 }
902 void record_end_time() {
903 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
904 }
905
906 // returns the worker ID associated with this task.
907 uint worker_id() { return _worker_id; }
908
909 // From TerminatorTerminator. It determines whether this task should
910 // exit the termination protocol after it's entered it.
911 virtual bool should_exit_termination();
912
913 // Resets the local region fields after a task has finished scanning a
914 // region; or when they have become stale as a result of the region
915 // being evacuated.
916 void giveup_current_region();
917
918 HeapWord* finger() { return _finger; }
919
920 bool has_aborted() { return _has_aborted; }
921 void set_has_aborted() { _has_aborted = true; }
922 void clear_has_aborted() { _has_aborted = false; }
923 bool has_timed_out() { return _has_timed_out; }
924 bool claimed() { return _claimed; }
925
926 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
927
928 // Increment the number of references this task has visited.
929 void increment_refs_reached() { ++_refs_reached; }
930
931 // Grey the object by marking it. If not already marked, push it on
932 // the local queue if below the finger.
933 // Precondition: obj is in region.
934 // Precondition: obj is below region's NTAMS.
935 inline void make_reference_grey(oop obj, HeapRegion* region);
936
937 // Grey the object (by calling make_grey_reference) if required,
938 // e.g. obj is below its containing region's NTAMS.
939 // Precondition: obj is a valid heap object.
940 inline void deal_with_reference(oop obj);
941
942 // It scans an object and visits its children.
943 inline void scan_object(oop obj);
944
945 // It pushes an object on the local queue.
946 inline void push(oop obj);
947
948 // These two move entries to/from the global stack.
949 void move_entries_to_global_stack();
950 void get_entries_from_global_stack();
951
952 // It pops and scans objects from the local queue. If partially is
953 // true, then it stops when the queue size is of a given limit. If
954 // partially is false, then it stops when the queue is empty.
955 void drain_local_queue(bool partially);
956 // It moves entries from the global stack to the local queue and
957 // drains the local queue. If partially is true, then it stops when
958 // both the global stack and the local queue reach a given size. If
959 // partially if false, it tries to empty them totally.
960 void drain_global_stack(bool partially);
961 // It keeps picking SATB buffers and processing them until no SATB
962 // buffers are available.
963 void drain_satb_buffers();
964
965 // moves the local finger to a new location
966 inline void move_finger_to(HeapWord* new_finger) {
967 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
968 _finger = new_finger;
969 }
970
971 CMTask(uint worker_id,
972 ConcurrentMark *cm,
973 size_t* marked_bytes,
974 BitMap* card_bm,
975 CMTaskQueue* task_queue,
976 CMTaskQueueSet* task_queues);
977
978 // it prints statistics associated with this task
979 void print_stats();
980 };
981
982 // Class that's used to to print out per-region liveness
983 // information. It's currently used at the end of marking and also
984 // after we sort the old regions at the end of the cleanup operation.
985 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
986 private:
987 // Accumulators for these values.
988 size_t _total_used_bytes;
989 size_t _total_capacity_bytes;
990 size_t _total_prev_live_bytes;
991 size_t _total_next_live_bytes;
992
993 // These are set up when we come across a "stars humongous" region
994 // (as this is where most of this information is stored, not in the
995 // subsequent "continues humongous" regions). After that, for every
996 // region in a given humongous region series we deduce the right
997 // values for it by simply subtracting the appropriate amount from
998 // these fields. All these values should reach 0 after we've visited
999 // the last region in the series.
1000 size_t _hum_used_bytes;
1001 size_t _hum_capacity_bytes;
1002 size_t _hum_prev_live_bytes;
1003 size_t _hum_next_live_bytes;
1004
1005 // Accumulator for the remembered set size
1006 size_t _total_remset_bytes;
1007
1008 // Accumulator for strong code roots memory size
1009 size_t _total_strong_code_roots_bytes;
1010
1011 static double perc(size_t val, size_t total) {
1012 if (total == 0) {
1013 return 0.0;
1014 } else {
1015 return 100.0 * ((double) val / (double) total);
1016 }
1017 }
1018
1019 static double bytes_to_mb(size_t val) {
1020 return (double) val / (double) M;
1021 }
1022
1023 // See the .cpp file.
1024 size_t get_hum_bytes(size_t* hum_bytes);
1025 void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1026 size_t* prev_live_bytes, size_t* next_live_bytes);
1027
1028 public:
1029 // The header and footer are printed in the constructor and
1030 // destructor respectively.
1031 G1PrintRegionLivenessInfoClosure(const char* phase_name);
1032 virtual bool doHeapRegion(HeapRegion* r);
1033 ~G1PrintRegionLivenessInfoClosure();
1034 };
1035
1036 #endif // SHARE_VM_GC_G1_CONCURRENTMARK_HPP