1 /*
2 * Copyright (c) 2001, 2017, 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_G1CONCURRENTMARK_HPP
26 #define SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP
27
28 #include "classfile/javaClasses.hpp"
29 #include "gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp"
30 #include "gc/g1/g1RegionToSpaceMapper.hpp"
31 #include "gc/g1/heapRegionSet.hpp"
32 #include "gc/shared/taskqueue.hpp"
33
34 class G1CollectedHeap;
35 class G1CMBitMap;
36 class G1CMTask;
37 class G1ConcurrentMark;
38 class ConcurrentGCTimer;
39 class G1OldTracer;
40 class G1SurvivorRegions;
41
42 #ifdef _MSC_VER
43 #pragma warning(push)
44 // warning C4522: multiple assignment operators specified
45 #pragma warning(disable:4522)
46 #endif
47
48 // This is a container class for either an oop or a continuation address for
49 // mark stack entries. Both are pushed onto the mark stack.
50 class G1TaskQueueEntry VALUE_OBJ_CLASS_SPEC {
51 private:
52 void* _holder;
53
54 static const uintptr_t ArraySliceBit = 1;
55
56 G1TaskQueueEntry(oop obj) : _holder(obj) {
57 assert(_holder != NULL, "Not allowed to set NULL task queue element");
58 }
59 G1TaskQueueEntry(HeapWord* addr) : _holder((void*)((uintptr_t)addr | ArraySliceBit)) { }
60 public:
61 G1TaskQueueEntry(const G1TaskQueueEntry& other) { _holder = other._holder; }
62 G1TaskQueueEntry() : _holder(NULL) { }
63
64 static G1TaskQueueEntry from_slice(HeapWord* what) { return G1TaskQueueEntry(what); }
65 static G1TaskQueueEntry from_oop(oop obj) { return G1TaskQueueEntry(obj); }
66
67 G1TaskQueueEntry& operator=(const G1TaskQueueEntry& t) {
68 _holder = t._holder;
69 return *this;
70 }
71
72 volatile G1TaskQueueEntry& operator=(const volatile G1TaskQueueEntry& t) volatile {
73 _holder = t._holder;
74 return *this;
75 }
76
77 oop obj() const {
78 assert(!is_array_slice(), "Trying to read array slice " PTR_FORMAT " as oop", p2i(_holder));
79 return (oop)_holder;
80 }
81
82 HeapWord* slice() const {
83 assert(is_array_slice(), "Trying to read oop " PTR_FORMAT " as array slice", p2i(_holder));
84 return (HeapWord*)((uintptr_t)_holder & ~ArraySliceBit);
85 }
86
87 bool is_oop() const { return !is_array_slice(); }
88 bool is_array_slice() const { return ((uintptr_t)_holder & ArraySliceBit) != 0; }
89 bool is_null() const { return _holder == NULL; }
90 };
91
92 #ifdef _MSC_VER
93 #pragma warning(pop)
94 #endif
95
96 typedef GenericTaskQueue<G1TaskQueueEntry, mtGC> G1CMTaskQueue;
97 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
98
99 // Closure used by CM during concurrent reference discovery
100 // and reference processing (during remarking) to determine
101 // if a particular object is alive. It is primarily used
102 // to determine if referents of discovered reference objects
103 // are alive. An instance is also embedded into the
104 // reference processor as the _is_alive_non_header field
105 class G1CMIsAliveClosure: public BoolObjectClosure {
106 G1CollectedHeap* _g1;
107 public:
108 G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
109
110 bool do_object_b(oop obj);
111 };
112
113 // Closure for iteration over bitmaps
114 class G1CMBitMapClosure VALUE_OBJ_CLASS_SPEC {
115 private:
116 G1ConcurrentMark* const _cm;
117 G1CMTask* const _task;
118 public:
119 G1CMBitMapClosure(G1CMTask *task, G1ConcurrentMark* cm) : _task(task), _cm(cm) { }
120
121 bool do_addr(HeapWord* const addr);
122 };
123
124 class G1CMBitMapMappingChangedListener : public G1MappingChangedListener {
125 private:
126 G1CMBitMap* _bm;
127 public:
128 G1CMBitMapMappingChangedListener() : _bm(NULL) {}
129
130 void set_bitmap(G1CMBitMap* bm) { _bm = bm; }
131
132 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
133 };
134
135 // A generic mark bitmap for concurrent marking. This is essentially a wrapper
136 // around the BitMap class that is based on HeapWords, with one bit per (1 << _shifter) HeapWords.
137 class G1CMBitMap VALUE_OBJ_CLASS_SPEC {
138 private:
139 MemRegion _covered; // The heap area covered by this bitmap.
140
141 const int _shifter; // Shift amount from heap index to bit index in the bitmap.
142
143 BitMapView _bm; // The actual bitmap.
144
145 G1CMBitMapMappingChangedListener _listener;
146
147 inline void check_mark(HeapWord* addr) NOT_DEBUG_RETURN;
148
149 // Convert from bit offset to address.
150 HeapWord* offset_to_addr(size_t offset) const {
151 return _covered.start() + (offset << _shifter);
152 }
153 // Convert from address to bit offset.
154 size_t addr_to_offset(const HeapWord* addr) const {
155 return pointer_delta(addr, _covered.start()) >> _shifter;
156 }
157 public:
158 static size_t compute_size(size_t heap_size);
159 // Returns the amount of bytes on the heap between two marks in the bitmap.
160 static size_t mark_distance();
161 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
162 // mark bitmap corresponds to. This is the same as the mark distance above.
163 static size_t heap_map_factor() {
164 return mark_distance();
165 }
166
167 G1CMBitMap() : _covered(), _bm(), _shifter(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
168
169 // Initializes the underlying BitMap to cover the given area.
170 void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
171
172 // read marks
173 bool is_marked(HeapWord* addr) const {
174 assert(_covered.contains(addr),
175 "Address " PTR_FORMAT " is outside underlying space from " PTR_FORMAT " to " PTR_FORMAT,
176 p2i(addr), p2i(_covered.start()), p2i(_covered.end()));
177 return _bm.at(addr_to_offset(addr));
178 }
179
180 // Apply the closure to the addresses that correspond to marked bits in the bitmap.
181 inline bool iterate(G1CMBitMapClosure* cl, MemRegion mr);
182
183 // Return the address corresponding to the next marked bit at or after
184 // "addr", and before "limit", if "limit" is non-NULL. If there is no
185 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
186 inline HeapWord* get_next_marked_addr(const HeapWord* addr,
187 const HeapWord* limit) const;
188
189 // The argument addr should be the start address of a valid object
190 inline HeapWord* addr_after_obj(HeapWord* addr);
191
192 void print_on_error(outputStream* st, const char* prefix) const;
193
194 // Write marks.
195 inline void mark(HeapWord* addr);
196 inline void clear(HeapWord* addr);
197 inline bool par_mark(HeapWord* addr);
198
199 void clear_range(MemRegion mr);
200 };
201
202 // Represents the overflow mark stack used by concurrent marking.
203 //
204 // Stores oops in a huge buffer in virtual memory that is always fully committed.
205 // Resizing may only happen during a STW pause when the stack is empty.
206 //
207 // Memory is allocated on a "chunk" basis, i.e. a set of oops. For this, the mark
208 // stack memory is split into evenly sized chunks of oops. Users can only
209 // add or remove entries on that basis.
210 // Chunks are filled in increasing address order. Not completely filled chunks
211 // have a NULL element as a terminating element.
212 //
213 // Every chunk has a header containing a single pointer element used for memory
214 // management. This wastes some space, but is negligible (< .1% with current sizing).
215 //
216 // Memory management is done using a mix of tracking a high water-mark indicating
217 // that all chunks at a lower address are valid chunks, and a singly linked free
218 // list connecting all empty chunks.
219 class G1CMMarkStack VALUE_OBJ_CLASS_SPEC {
220 public:
221 // Number of TaskQueueEntries that can fit in a single chunk.
222 static const size_t EntriesPerChunk = 1024 - 1 /* One reference for the next pointer */;
223 private:
224 struct TaskQueueEntryChunk {
225 TaskQueueEntryChunk* next;
226 G1TaskQueueEntry data[EntriesPerChunk];
227 };
228
229 size_t _max_chunk_capacity; // Maximum number of TaskQueueEntryChunk elements on the stack.
230
231 TaskQueueEntryChunk* _base; // Bottom address of allocated memory area.
232 size_t _chunk_capacity; // Current maximum number of TaskQueueEntryChunk elements.
233
234 char _pad0[DEFAULT_CACHE_LINE_SIZE];
235 TaskQueueEntryChunk* volatile _free_list; // Linked list of free chunks that can be allocated by users.
236 char _pad1[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*)];
237 TaskQueueEntryChunk* volatile _chunk_list; // List of chunks currently containing data.
238 volatile size_t _chunks_in_chunk_list;
239 char _pad2[DEFAULT_CACHE_LINE_SIZE - sizeof(TaskQueueEntryChunk*) - sizeof(size_t)];
240
241 volatile size_t _hwm; // High water mark within the reserved space.
242 char _pad4[DEFAULT_CACHE_LINE_SIZE - sizeof(size_t)];
243
244 // Allocate a new chunk from the reserved memory, using the high water mark. Returns
245 // NULL if out of memory.
246 TaskQueueEntryChunk* allocate_new_chunk();
247
248 // Atomically add the given chunk to the list.
249 void add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem);
250 // Atomically remove and return a chunk from the given list. Returns NULL if the
251 // list is empty.
252 TaskQueueEntryChunk* remove_chunk_from_list(TaskQueueEntryChunk* volatile* list);
253
254 void add_chunk_to_chunk_list(TaskQueueEntryChunk* elem);
255 void add_chunk_to_free_list(TaskQueueEntryChunk* elem);
256
257 TaskQueueEntryChunk* remove_chunk_from_chunk_list();
258 TaskQueueEntryChunk* remove_chunk_from_free_list();
259
260 // Resizes the mark stack to the given new capacity. Releases any previous
261 // memory if successful.
262 bool resize(size_t new_capacity);
263
264 public:
265 G1CMMarkStack();
266 ~G1CMMarkStack();
267
268 // Alignment and minimum capacity of this mark stack in number of oops.
269 static size_t capacity_alignment();
270
271 // Allocate and initialize the mark stack with the given number of oops.
272 bool initialize(size_t initial_capacity, size_t max_capacity);
273
274 // Pushes the given buffer containing at most EntriesPerChunk elements on the mark
275 // stack. If less than EntriesPerChunk elements are to be pushed, the array must
276 // be terminated with a NULL.
277 // Returns whether the buffer contents were successfully pushed to the global mark
278 // stack.
279 bool par_push_chunk(G1TaskQueueEntry* buffer);
280
281 // Pops a chunk from this mark stack, copying them into the given buffer. This
282 // chunk may contain up to EntriesPerChunk elements. If there are less, the last
283 // element in the array is a NULL pointer.
284 bool par_pop_chunk(G1TaskQueueEntry* buffer);
285
286 // Return whether the chunk list is empty. Racy due to unsynchronized access to
287 // _chunk_list.
288 bool is_empty() const { return _chunk_list == NULL; }
289
290 size_t capacity() const { return _chunk_capacity; }
291
292 // Expand the stack, typically in response to an overflow condition
293 void expand();
294
295 // Return the approximate number of oops on this mark stack. Racy due to
296 // unsynchronized access to _chunks_in_chunk_list.
297 size_t size() const { return _chunks_in_chunk_list * EntriesPerChunk; }
298
299 void set_empty();
300
301 // Apply Fn to every oop on the mark stack. The mark stack must not
302 // be modified while iterating.
303 template<typename Fn> void iterate(Fn fn) const PRODUCT_RETURN;
304 };
305
306 // Root Regions are regions that are not empty at the beginning of a
307 // marking cycle and which we might collect during an evacuation pause
308 // while the cycle is active. Given that, during evacuation pauses, we
309 // do not copy objects that are explicitly marked, what we have to do
310 // for the root regions is to scan them and mark all objects reachable
311 // from them. According to the SATB assumptions, we only need to visit
312 // each object once during marking. So, as long as we finish this scan
313 // before the next evacuation pause, we can copy the objects from the
314 // root regions without having to mark them or do anything else to them.
315 //
316 // Currently, we only support root region scanning once (at the start
317 // of the marking cycle) and the root regions are all the survivor
318 // regions populated during the initial-mark pause.
319 class G1CMRootRegions VALUE_OBJ_CLASS_SPEC {
320 private:
321 const G1SurvivorRegions* _survivors;
322 G1ConcurrentMark* _cm;
323
324 volatile bool _scan_in_progress;
325 volatile bool _should_abort;
326 volatile int _claimed_survivor_index;
327
328 void notify_scan_done();
329
330 public:
331 G1CMRootRegions();
332 // We actually do most of the initialization in this method.
333 void init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm);
334
335 // Reset the claiming / scanning of the root regions.
336 void prepare_for_scan();
337
338 // Forces get_next() to return NULL so that the iteration aborts early.
339 void abort() { _should_abort = true; }
340
341 // Return true if the CM thread are actively scanning root regions,
342 // false otherwise.
343 bool scan_in_progress() { return _scan_in_progress; }
344
345 // Claim the next root region to scan atomically, or return NULL if
346 // all have been claimed.
347 HeapRegion* claim_next();
348
349 // The number of root regions to scan.
350 uint num_root_regions() const;
351
352 void cancel_scan();
353
354 // Flag that we're done with root region scanning and notify anyone
355 // who's waiting on it. If aborted is false, assume that all regions
356 // have been claimed.
357 void scan_finished();
358
359 // If CM threads are still scanning root regions, wait until they
360 // are done. Return true if we had to wait, false otherwise.
361 bool wait_until_scan_finished();
362 };
363
364 class ConcurrentMarkThread;
365
366 class G1ConcurrentMark: public CHeapObj<mtGC> {
367 friend class ConcurrentMarkThread;
368 friend class G1ParNoteEndTask;
369 friend class G1VerifyLiveDataClosure;
370 friend class G1CMRefProcTaskProxy;
371 friend class G1CMRefProcTaskExecutor;
372 friend class G1CMKeepAliveAndDrainClosure;
373 friend class G1CMDrainMarkingStackClosure;
374 friend class G1CMBitMapClosure;
375 friend class G1CMConcurrentMarkingTask;
376 friend class G1CMRemarkTask;
377 friend class G1CMTask;
378
379 protected:
380 ConcurrentMarkThread* _cmThread; // The thread doing the work
381 G1CollectedHeap* _g1h; // The heap
382 uint _parallel_marking_threads; // The number of marking
383 // threads we're using
384 uint _max_parallel_marking_threads; // Max number of marking
385 // threads we'll ever use
386 double _sleep_factor; // How much we have to sleep, with
387 // respect to the work we just did, to
388 // meet the marking overhead goal
389 double _marking_task_overhead; // Marking target overhead for
390 // a single task
391
392 FreeRegionList _cleanup_list;
393
394 // Concurrent marking support structures
395 G1CMBitMap _markBitMap1;
396 G1CMBitMap _markBitMap2;
397 G1CMBitMap* _prevMarkBitMap; // Completed mark bitmap
398 G1CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
399
400 // Heap bounds
401 HeapWord* _heap_start;
402 HeapWord* _heap_end;
403
404 // Root region tracking and claiming
405 G1CMRootRegions _root_regions;
406
407 // For gray objects
408 G1CMMarkStack _global_mark_stack; // Grey objects behind global finger
409 HeapWord* volatile _finger; // The global finger, region aligned,
410 // always points to the end of the
411 // last claimed region
412
413 // Marking tasks
414 uint _max_worker_id;// Maximum worker id
415 uint _active_tasks; // Task num currently active
416 G1CMTask** _tasks; // Task queue array (max_worker_id len)
417 G1CMTaskQueueSet* _task_queues; // Task queue set
418 ParallelTaskTerminator _terminator; // For termination
419
420 // Two sync barriers that are used to synchronize tasks when an
421 // overflow occurs. The algorithm is the following. All tasks enter
422 // the first one to ensure that they have all stopped manipulating
423 // the global data structures. After they exit it, they re-initialize
424 // their data structures and task 0 re-initializes the global data
425 // structures. Then, they enter the second sync barrier. This
426 // ensure, that no task starts doing work before all data
427 // structures (local and global) have been re-initialized. When they
428 // exit it, they are free to start working again.
429 WorkGangBarrierSync _first_overflow_barrier_sync;
430 WorkGangBarrierSync _second_overflow_barrier_sync;
431
432 // This is set by any task, when an overflow on the global data
433 // structures is detected
434 volatile bool _has_overflown;
435 // True: marking is concurrent, false: we're in remark
436 volatile bool _concurrent;
437 // Set at the end of a Full GC so that marking aborts
438 volatile bool _has_aborted;
439
440 // Used when remark aborts due to an overflow to indicate that
441 // another concurrent marking phase should start
442 volatile bool _restart_for_overflow;
443
444 // This is true from the very start of concurrent marking until the
445 // point when all the tasks complete their work. It is really used
446 // to determine the points between the end of concurrent marking and
447 // time of remark.
448 volatile bool _concurrent_marking_in_progress;
449
450 ConcurrentGCTimer* _gc_timer_cm;
451
452 G1OldTracer* _gc_tracer_cm;
453
454 // All of these times are in ms
455 NumberSeq _init_times;
456 NumberSeq _remark_times;
457 NumberSeq _remark_mark_times;
458 NumberSeq _remark_weak_ref_times;
459 NumberSeq _cleanup_times;
460 double _total_counting_time;
461 double _total_rs_scrub_time;
462
463 double* _accum_task_vtime; // Accumulated task vtime
464
465 WorkGang* _parallel_workers;
466
467 void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
468 void weakRefsWork(bool clear_all_soft_refs);
469
470 void swapMarkBitMaps();
471
472 // It resets the global marking data structures, as well as the
473 // task local ones; should be called during initial mark.
474 void reset();
475
476 // Resets all the marking data structures. Called when we have to restart
477 // marking or when marking completes (via set_non_marking_state below).
478 void reset_marking_state();
479
480 // We do this after we're done with marking so that the marking data
481 // structures are initialized to a sensible and predictable state.
482 void set_non_marking_state();
483
484 // Called to indicate how many threads are currently active.
485 void set_concurrency(uint active_tasks);
486
487 // It should be called to indicate which phase we're in (concurrent
488 // mark or remark) and how many threads are currently active.
489 void set_concurrency_and_phase(uint active_tasks, bool concurrent);
490
491 // Prints all gathered CM-related statistics
492 void print_stats();
493
494 bool cleanup_list_is_empty() {
495 return _cleanup_list.is_empty();
496 }
497
498 // Accessor methods
499 uint parallel_marking_threads() const { return _parallel_marking_threads; }
500 uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
501 double sleep_factor() { return _sleep_factor; }
502 double marking_task_overhead() { return _marking_task_overhead;}
503
504 HeapWord* finger() { return _finger; }
505 bool concurrent() { return _concurrent; }
506 uint active_tasks() { return _active_tasks; }
507 ParallelTaskTerminator* terminator() { return &_terminator; }
508
509 // It claims the next available region to be scanned by a marking
510 // task/thread. It might return NULL if the next region is empty or
511 // we have run out of regions. In the latter case, out_of_regions()
512 // determines whether we've really run out of regions or the task
513 // should call claim_region() again. This might seem a bit
514 // awkward. Originally, the code was written so that claim_region()
515 // either successfully returned with a non-empty region or there
516 // were no more regions to be claimed. The problem with this was
517 // that, in certain circumstances, it iterated over large chunks of
518 // the heap finding only empty regions and, while it was working, it
519 // was preventing the calling task to call its regular clock
520 // method. So, this way, each task will spend very little time in
521 // claim_region() and is allowed to call the regular clock method
522 // frequently.
523 HeapRegion* claim_region(uint worker_id);
524
525 // It determines whether we've run out of regions to scan. Note that
526 // the finger can point past the heap end in case the heap was expanded
527 // to satisfy an allocation without doing a GC. This is fine, because all
528 // objects in those regions will be considered live anyway because of
529 // SATB guarantees (i.e. their TAMS will be equal to bottom).
530 bool out_of_regions() { return _finger >= _heap_end; }
531
532 // Returns the task with the given id
533 G1CMTask* task(int id) {
534 assert(0 <= id && id < (int) _active_tasks,
535 "task id not within active bounds");
536 return _tasks[id];
537 }
538
539 // Returns the task queue with the given id
540 G1CMTaskQueue* task_queue(int id) {
541 assert(0 <= id && id < (int) _active_tasks,
542 "task queue id not within active bounds");
543 return (G1CMTaskQueue*) _task_queues->queue(id);
544 }
545
546 // Returns the task queue set
547 G1CMTaskQueueSet* task_queues() { return _task_queues; }
548
549 // Access / manipulation of the overflow flag which is set to
550 // indicate that the global stack has overflown
551 bool has_overflown() { return _has_overflown; }
552 void set_has_overflown() { _has_overflown = true; }
553 void clear_has_overflown() { _has_overflown = false; }
554 bool restart_for_overflow() { return _restart_for_overflow; }
555
556 // Methods to enter the two overflow sync barriers
557 void enter_first_sync_barrier(uint worker_id);
558 void enter_second_sync_barrier(uint worker_id);
559
560 // Card index of the bottom of the G1 heap. Used for biasing indices into
561 // the card bitmaps.
562 intptr_t _heap_bottom_card_num;
563
564 // Set to true when initialization is complete
565 bool _completed_initialization;
566
567 // end_timer, true to end gc timer after ending concurrent phase.
568 void register_concurrent_phase_end_common(bool end_timer);
569
570 // Clear the given bitmap in parallel using the given WorkGang. If may_yield is
571 // true, periodically insert checks to see if this method should exit prematurely.
572 void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
573 public:
574 // Manipulation of the global mark stack.
575 // The push and pop operations are used by tasks for transfers
576 // between task-local queues and the global mark stack.
577 bool mark_stack_push(G1TaskQueueEntry* arr) {
578 if (!_global_mark_stack.par_push_chunk(arr)) {
579 set_has_overflown();
580 return false;
581 }
582 return true;
583 }
584 bool mark_stack_pop(G1TaskQueueEntry* arr) {
585 return _global_mark_stack.par_pop_chunk(arr);
586 }
587 size_t mark_stack_size() { return _global_mark_stack.size(); }
588 size_t partial_mark_stack_size_target() { return _global_mark_stack.capacity()/3; }
589 bool mark_stack_empty() { return _global_mark_stack.is_empty(); }
590
591 G1CMRootRegions* root_regions() { return &_root_regions; }
592
593 bool concurrent_marking_in_progress() {
594 return _concurrent_marking_in_progress;
595 }
596 void set_concurrent_marking_in_progress() {
597 _concurrent_marking_in_progress = true;
598 }
599 void clear_concurrent_marking_in_progress() {
600 _concurrent_marking_in_progress = false;
601 }
602
603 void concurrent_cycle_start();
604 void concurrent_cycle_end();
605
606 void update_accum_task_vtime(int i, double vtime) {
607 _accum_task_vtime[i] += vtime;
608 }
609
610 double all_task_accum_vtime() {
611 double ret = 0.0;
612 for (uint i = 0; i < _max_worker_id; ++i)
613 ret += _accum_task_vtime[i];
614 return ret;
615 }
616
617 // Attempts to steal an object from the task queues of other tasks
618 bool try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry);
619
620 G1ConcurrentMark(G1CollectedHeap* g1h,
621 G1RegionToSpaceMapper* prev_bitmap_storage,
622 G1RegionToSpaceMapper* next_bitmap_storage);
623 ~G1ConcurrentMark();
624
625 ConcurrentMarkThread* cmThread() { return _cmThread; }
626
627 const G1CMBitMap* const prevMarkBitMap() const { return _prevMarkBitMap; }
628 G1CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
629
630 // Returns the number of GC threads to be used in a concurrent
631 // phase based on the number of GC threads being used in a STW
632 // phase.
633 uint scale_parallel_threads(uint n_par_threads);
634
635 // Calculates the number of GC threads to be used in a concurrent phase.
636 uint calc_parallel_marking_threads();
637
638 // The following three are interaction between CM and
639 // G1CollectedHeap
640
641 // This notifies CM that a root during initial-mark needs to be
642 // grayed. It is MT-safe. hr is the region that
643 // contains the object and it's passed optionally from callers who
644 // might already have it (no point in recalculating it).
645 inline void grayRoot(oop obj,
646 HeapRegion* hr = NULL);
647
648 // Prepare internal data structures for the next mark cycle. This includes clearing
649 // the next mark bitmap and some internal data structures. This method is intended
650 // to be called concurrently to the mutator. It will yield to safepoint requests.
651 void cleanup_for_next_mark();
652
653 // Clear the previous marking bitmap during safepoint.
654 void clear_prev_bitmap(WorkGang* workers);
655
656 // Return whether the next mark bitmap has no marks set. To be used for assertions
657 // only. Will not yield to pause requests.
658 bool nextMarkBitmapIsClear();
659
660 // These two do the work that needs to be done before and after the
661 // initial root checkpoint. Since this checkpoint can be done at two
662 // different points (i.e. an explicit pause or piggy-backed on a
663 // young collection), then it's nice to be able to easily share the
664 // pre/post code. It might be the case that we can put everything in
665 // the post method. TP
666 void checkpointRootsInitialPre();
667 void checkpointRootsInitialPost();
668
669 // Scan all the root regions and mark everything reachable from
670 // them.
671 void scan_root_regions();
672
673 // Scan a single root region and mark everything reachable from it.
674 void scanRootRegion(HeapRegion* hr);
675
676 // Do concurrent phase of marking, to a tentative transitive closure.
677 void mark_from_roots();
678
679 void checkpointRootsFinal(bool clear_all_soft_refs);
680 void checkpointRootsFinalWork();
681 void cleanup();
682 void complete_cleanup();
683
684 // Mark in the previous bitmap. NB: this is usually read-only, so use
685 // this carefully!
686 inline void markPrev(oop p);
687
688 // Clears marks for all objects in the given range, for the prev or
689 // next bitmaps. NB: the previous bitmap is usually
690 // read-only, so use this carefully!
691 void clearRangePrevBitmap(MemRegion mr);
692
693 // Verify that there are no CSet oops on the stacks (taskqueues /
694 // global mark stack) and fingers (global / per-task).
695 // If marking is not in progress, it's a no-op.
696 void verify_no_cset_oops() PRODUCT_RETURN;
697
698 inline bool isPrevMarked(oop p) const;
699
700 inline bool do_yield_check();
701
702 // Abandon current marking iteration due to a Full GC.
703 void abort();
704
705 bool has_aborted() { return _has_aborted; }
706
707 void print_summary_info();
708
709 void print_worker_threads_on(outputStream* st) const;
710 void threads_do(ThreadClosure* tc) const;
711
712 void print_on_error(outputStream* st) const;
713
714 // Attempts to mark the given object on the next mark bitmap.
715 inline bool par_mark(oop obj);
716
717 // Returns true if initialization was successfully completed.
718 bool completed_initialization() const {
719 return _completed_initialization;
720 }
721
722 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
723 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
724
725 private:
726 // Clear (Reset) all liveness count data.
727 void clear_live_data(WorkGang* workers);
728
729 #ifdef ASSERT
730 // Verify all of the above data structures that they are in initial state.
731 void verify_live_data_clear();
732 #endif
733
734 // Aggregates the per-card liveness data based on the current marking. Also sets
735 // the amount of marked bytes for each region.
736 void create_live_data();
737
738 void finalize_live_data();
739
740 void verify_live_data();
741 };
742
743 // A class representing a marking task.
744 class G1CMTask : 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 = 1024,
753 // Initial value for the hash seed, used in the work stealing code
754 init_hash_seed = 17
755 };
756
757 G1CMObjArrayProcessor _objArray_processor;
758
759 uint _worker_id;
760 G1CollectedHeap* _g1h;
761 G1ConcurrentMark* _cm;
762 G1CMBitMap* _nextMarkBitMap;
763 // the task queue of this task
764 G1CMTaskQueue* _task_queue;
765 private:
766 // the task queue set---needed for stealing
767 G1CMTaskQueueSet* _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 // it updates the local fields after this task has claimed
842 // a new region to scan
843 void setup_for_region(HeapRegion* hr);
844 // it brings up-to-date the limit of the region
845 void update_region_limit();
846
847 // called when either the words scanned or the refs visited limit
848 // has been reached
849 void reached_limit();
850 // recalculates the words scanned and refs visited limits
851 void recalculate_limits();
852 // decreases the words scanned and refs visited limits when we reach
853 // an expensive operation
854 void decrease_limits();
855 // it checks whether the words scanned or refs visited reached their
856 // respective limit and calls reached_limit() if they have
857 void check_limits() {
858 if (_words_scanned >= _words_scanned_limit ||
859 _refs_reached >= _refs_reached_limit) {
860 reached_limit();
861 }
862 }
863 // this is supposed to be called regularly during a marking step as
864 // it checks a bunch of conditions that might cause the marking step
865 // to abort
866 void regular_clock_call();
867 bool concurrent() { return _concurrent; }
868
869 // Test whether obj might have already been passed over by the
870 // mark bitmap scan, and so needs to be pushed onto the mark stack.
871 bool is_below_finger(oop obj, HeapWord* global_finger) const;
872
873 template<bool scan> void process_grey_task_entry(G1TaskQueueEntry task_entry);
874 public:
875 // Apply the closure on the given area of the objArray. Return the number of words
876 // scanned.
877 inline size_t scan_objArray(objArrayOop obj, MemRegion mr);
878 // It resets the task; it should be called right at the beginning of
879 // a marking phase.
880 void reset(G1CMBitMap* _nextMarkBitMap);
881 // it clears all the fields that correspond to a claimed region.
882 void clear_region_fields();
883
884 void set_concurrent(bool concurrent) { _concurrent = concurrent; }
885
886 // The main method of this class which performs a marking step
887 // trying not to exceed the given duration. However, it might exit
888 // prematurely, according to some conditions (i.e. SATB buffers are
889 // available for processing).
890 void do_marking_step(double target_ms,
891 bool do_termination,
892 bool is_serial);
893
894 // These two calls start and stop the timer
895 void record_start_time() {
896 _elapsed_time_ms = os::elapsedTime() * 1000.0;
897 }
898 void record_end_time() {
899 _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
900 }
901
902 // returns the worker ID associated with this task.
903 uint worker_id() { return _worker_id; }
904
905 // From TerminatorTerminator. It determines whether this task should
906 // exit the termination protocol after it's entered it.
907 virtual bool should_exit_termination();
908
909 // Resets the local region fields after a task has finished scanning a
910 // region; or when they have become stale as a result of the region
911 // being evacuated.
912 void giveup_current_region();
913
914 HeapWord* finger() { return _finger; }
915
916 bool has_aborted() { return _has_aborted; }
917 void set_has_aborted() { _has_aborted = true; }
918 void clear_has_aborted() { _has_aborted = false; }
919 bool has_timed_out() { return _has_timed_out; }
920 bool claimed() { return _claimed; }
921
922 void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
923
924 // Increment the number of references this task has visited.
925 void increment_refs_reached() { ++_refs_reached; }
926
927 // Grey the object by marking it. If not already marked, push it on
928 // the local queue if below the finger.
929 // obj is below its region's NTAMS.
930 inline void make_reference_grey(oop obj);
931
932 // Grey the object (by calling make_grey_reference) if required,
933 // e.g. obj is below its containing region's NTAMS.
934 // Precondition: obj is a valid heap object.
935 inline void deal_with_reference(oop obj);
936
937 // It scans an object and visits its children.
938 inline void scan_task_entry(G1TaskQueueEntry task_entry);
939
940 // It pushes an object on the local queue.
941 inline void push(G1TaskQueueEntry task_entry);
942
943 // Move entries to the global stack.
944 void move_entries_to_global_stack();
945 // Move entries from the global stack, return true if we were successful to do so.
946 bool get_entries_from_global_stack();
947
948 // It pops and scans objects from the local queue. If partially is
949 // true, then it stops when the queue size is of a given limit. If
950 // partially is false, then it stops when the queue is empty.
951 void drain_local_queue(bool partially);
952 // It moves entries from the global stack to the local queue and
953 // drains the local queue. If partially is true, then it stops when
954 // both the global stack and the local queue reach a given size. If
955 // partially if false, it tries to empty them totally.
956 void drain_global_stack(bool partially);
957 // It keeps picking SATB buffers and processing them until no SATB
958 // buffers are available.
959 void drain_satb_buffers();
960
961 // moves the local finger to a new location
962 inline void move_finger_to(HeapWord* new_finger) {
963 assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
964 _finger = new_finger;
965 }
966
967 G1CMTask(uint worker_id,
968 G1ConcurrentMark *cm,
969 G1CMTaskQueue* task_queue,
970 G1CMTaskQueueSet* task_queues);
971
972 // it prints statistics associated with this task
973 void print_stats();
974 };
975
976 // Class that's used to to print out per-region liveness
977 // information. It's currently used at the end of marking and also
978 // after we sort the old regions at the end of the cleanup operation.
979 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
980 private:
981 // Accumulators for these values.
982 size_t _total_used_bytes;
983 size_t _total_capacity_bytes;
984 size_t _total_prev_live_bytes;
985 size_t _total_next_live_bytes;
986
987 // Accumulator for the remembered set size
988 size_t _total_remset_bytes;
989
990 // Accumulator for strong code roots memory size
991 size_t _total_strong_code_roots_bytes;
992
993 static double perc(size_t val, size_t total) {
994 if (total == 0) {
995 return 0.0;
996 } else {
997 return 100.0 * ((double) val / (double) total);
998 }
999 }
1000
1001 static double bytes_to_mb(size_t val) {
1002 return (double) val / (double) M;
1003 }
1004
1005 public:
1006 // The header and footer are printed in the constructor and
1007 // destructor respectively.
1008 G1PrintRegionLivenessInfoClosure(const char* phase_name);
1009 virtual bool doHeapRegion(HeapRegion* r);
1010 ~G1PrintRegionLivenessInfoClosure();
1011 };
1012
1013 #endif // SHARE_VM_GC_G1_G1CONCURRENTMARK_HPP