Tue, 23 Nov 2010 13:22:55 -0800
6989984: Use standard include model for Hospot
Summary: Replaced MakeDeps and the includeDB files with more standardized solutions.
Reviewed-by: coleenp, kvn, kamg
1 /*
2 * Copyright (c) 2001, 2010, 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 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "gc_implementation/g1/concurrentMark.hpp"
28 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
30 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
31 #include "gc_implementation/g1/g1RemSet.hpp"
32 #include "gc_implementation/g1/heapRegionRemSet.hpp"
33 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
34 #include "memory/genOopClosures.inline.hpp"
35 #include "memory/referencePolicy.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/handles.inline.hpp"
39 #include "runtime/java.hpp"
41 //
42 // CMS Bit Map Wrapper
44 CMBitMapRO::CMBitMapRO(ReservedSpace rs, int shifter):
45 _bm((uintptr_t*)NULL,0),
46 _shifter(shifter) {
47 _bmStartWord = (HeapWord*)(rs.base());
48 _bmWordSize = rs.size()/HeapWordSize; // rs.size() is in bytes
49 ReservedSpace brs(ReservedSpace::allocation_align_size_up(
50 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1));
52 guarantee(brs.is_reserved(), "couldn't allocate CMS bit map");
53 // For now we'll just commit all of the bit map up fromt.
54 // Later on we'll try to be more parsimonious with swap.
55 guarantee(_virtual_space.initialize(brs, brs.size()),
56 "couldn't reseve backing store for CMS bit map");
57 assert(_virtual_space.committed_size() == brs.size(),
58 "didn't reserve backing store for all of CMS bit map?");
59 _bm.set_map((uintptr_t*)_virtual_space.low());
60 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >=
61 _bmWordSize, "inconsistency in bit map sizing");
62 _bm.set_size(_bmWordSize >> _shifter);
63 }
65 HeapWord* CMBitMapRO::getNextMarkedWordAddress(HeapWord* addr,
66 HeapWord* limit) const {
67 // First we must round addr *up* to a possible object boundary.
68 addr = (HeapWord*)align_size_up((intptr_t)addr,
69 HeapWordSize << _shifter);
70 size_t addrOffset = heapWordToOffset(addr);
71 if (limit == NULL) limit = _bmStartWord + _bmWordSize;
72 size_t limitOffset = heapWordToOffset(limit);
73 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
74 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
75 assert(nextAddr >= addr, "get_next_one postcondition");
76 assert(nextAddr == limit || isMarked(nextAddr),
77 "get_next_one postcondition");
78 return nextAddr;
79 }
81 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(HeapWord* addr,
82 HeapWord* limit) const {
83 size_t addrOffset = heapWordToOffset(addr);
84 if (limit == NULL) limit = _bmStartWord + _bmWordSize;
85 size_t limitOffset = heapWordToOffset(limit);
86 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
87 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
88 assert(nextAddr >= addr, "get_next_one postcondition");
89 assert(nextAddr == limit || !isMarked(nextAddr),
90 "get_next_one postcondition");
91 return nextAddr;
92 }
94 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
95 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
96 return (int) (diff >> _shifter);
97 }
99 bool CMBitMapRO::iterate(BitMapClosure* cl, MemRegion mr) {
100 HeapWord* left = MAX2(_bmStartWord, mr.start());
101 HeapWord* right = MIN2(_bmStartWord + _bmWordSize, mr.end());
102 if (right > left) {
103 // Right-open interval [leftOffset, rightOffset).
104 return _bm.iterate(cl, heapWordToOffset(left), heapWordToOffset(right));
105 } else {
106 return true;
107 }
108 }
110 void CMBitMapRO::mostly_disjoint_range_union(BitMap* from_bitmap,
111 size_t from_start_index,
112 HeapWord* to_start_word,
113 size_t word_num) {
114 _bm.mostly_disjoint_range_union(from_bitmap,
115 from_start_index,
116 heapWordToOffset(to_start_word),
117 word_num);
118 }
120 #ifndef PRODUCT
121 bool CMBitMapRO::covers(ReservedSpace rs) const {
122 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
123 assert(((size_t)_bm.size() * (size_t)(1 << _shifter)) == _bmWordSize,
124 "size inconsistency");
125 return _bmStartWord == (HeapWord*)(rs.base()) &&
126 _bmWordSize == rs.size()>>LogHeapWordSize;
127 }
128 #endif
130 void CMBitMap::clearAll() {
131 _bm.clear();
132 return;
133 }
135 void CMBitMap::markRange(MemRegion mr) {
136 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
137 assert(!mr.is_empty(), "unexpected empty region");
138 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
139 ((HeapWord *) mr.end())),
140 "markRange memory region end is not card aligned");
141 // convert address range into offset range
142 _bm.at_put_range(heapWordToOffset(mr.start()),
143 heapWordToOffset(mr.end()), true);
144 }
146 void CMBitMap::clearRange(MemRegion mr) {
147 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
148 assert(!mr.is_empty(), "unexpected empty region");
149 // convert address range into offset range
150 _bm.at_put_range(heapWordToOffset(mr.start()),
151 heapWordToOffset(mr.end()), false);
152 }
154 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
155 HeapWord* end_addr) {
156 HeapWord* start = getNextMarkedWordAddress(addr);
157 start = MIN2(start, end_addr);
158 HeapWord* end = getNextUnmarkedWordAddress(start);
159 end = MIN2(end, end_addr);
160 assert(start <= end, "Consistency check");
161 MemRegion mr(start, end);
162 if (!mr.is_empty()) {
163 clearRange(mr);
164 }
165 return mr;
166 }
168 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
169 _base(NULL), _cm(cm)
170 #ifdef ASSERT
171 , _drain_in_progress(false)
172 , _drain_in_progress_yields(false)
173 #endif
174 {}
176 void CMMarkStack::allocate(size_t size) {
177 _base = NEW_C_HEAP_ARRAY(oop, size);
178 if (_base == NULL)
179 vm_exit_during_initialization("Failed to allocate "
180 "CM region mark stack");
181 _index = 0;
182 // QQQQ cast ...
183 _capacity = (jint) size;
184 _oops_do_bound = -1;
185 NOT_PRODUCT(_max_depth = 0);
186 }
188 CMMarkStack::~CMMarkStack() {
189 if (_base != NULL) FREE_C_HEAP_ARRAY(oop, _base);
190 }
192 void CMMarkStack::par_push(oop ptr) {
193 while (true) {
194 if (isFull()) {
195 _overflow = true;
196 return;
197 }
198 // Otherwise...
199 jint index = _index;
200 jint next_index = index+1;
201 jint res = Atomic::cmpxchg(next_index, &_index, index);
202 if (res == index) {
203 _base[index] = ptr;
204 // Note that we don't maintain this atomically. We could, but it
205 // doesn't seem necessary.
206 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
207 return;
208 }
209 // Otherwise, we need to try again.
210 }
211 }
213 void CMMarkStack::par_adjoin_arr(oop* ptr_arr, int n) {
214 while (true) {
215 if (isFull()) {
216 _overflow = true;
217 return;
218 }
219 // Otherwise...
220 jint index = _index;
221 jint next_index = index + n;
222 if (next_index > _capacity) {
223 _overflow = true;
224 return;
225 }
226 jint res = Atomic::cmpxchg(next_index, &_index, index);
227 if (res == index) {
228 for (int i = 0; i < n; i++) {
229 int ind = index + i;
230 assert(ind < _capacity, "By overflow test above.");
231 _base[ind] = ptr_arr[i];
232 }
233 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
234 return;
235 }
236 // Otherwise, we need to try again.
237 }
238 }
241 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
242 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
243 jint start = _index;
244 jint next_index = start + n;
245 if (next_index > _capacity) {
246 _overflow = true;
247 return;
248 }
249 // Otherwise.
250 _index = next_index;
251 for (int i = 0; i < n; i++) {
252 int ind = start + i;
253 assert(ind < _capacity, "By overflow test above.");
254 _base[ind] = ptr_arr[i];
255 }
256 }
259 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
260 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
261 jint index = _index;
262 if (index == 0) {
263 *n = 0;
264 return false;
265 } else {
266 int k = MIN2(max, index);
267 jint new_ind = index - k;
268 for (int j = 0; j < k; j++) {
269 ptr_arr[j] = _base[new_ind + j];
270 }
271 _index = new_ind;
272 *n = k;
273 return true;
274 }
275 }
278 CMRegionStack::CMRegionStack() : _base(NULL) {}
280 void CMRegionStack::allocate(size_t size) {
281 _base = NEW_C_HEAP_ARRAY(MemRegion, size);
282 if (_base == NULL)
283 vm_exit_during_initialization("Failed to allocate "
284 "CM region mark stack");
285 _index = 0;
286 // QQQQ cast ...
287 _capacity = (jint) size;
288 }
290 CMRegionStack::~CMRegionStack() {
291 if (_base != NULL) FREE_C_HEAP_ARRAY(oop, _base);
292 }
294 void CMRegionStack::push_lock_free(MemRegion mr) {
295 assert(mr.word_size() > 0, "Precondition");
296 while (true) {
297 jint index = _index;
299 if (index >= _capacity) {
300 _overflow = true;
301 return;
302 }
303 // Otherwise...
304 jint next_index = index+1;
305 jint res = Atomic::cmpxchg(next_index, &_index, index);
306 if (res == index) {
307 _base[index] = mr;
308 return;
309 }
310 // Otherwise, we need to try again.
311 }
312 }
314 // Lock-free pop of the region stack. Called during the concurrent
315 // marking / remark phases. Should only be called in tandem with
316 // other lock-free pops.
317 MemRegion CMRegionStack::pop_lock_free() {
318 while (true) {
319 jint index = _index;
321 if (index == 0) {
322 return MemRegion();
323 }
324 // Otherwise...
325 jint next_index = index-1;
326 jint res = Atomic::cmpxchg(next_index, &_index, index);
327 if (res == index) {
328 MemRegion mr = _base[next_index];
329 if (mr.start() != NULL) {
330 assert(mr.end() != NULL, "invariant");
331 assert(mr.word_size() > 0, "invariant");
332 return mr;
333 } else {
334 // that entry was invalidated... let's skip it
335 assert(mr.end() == NULL, "invariant");
336 }
337 }
338 // Otherwise, we need to try again.
339 }
340 }
342 #if 0
343 // The routines that manipulate the region stack with a lock are
344 // not currently used. They should be retained, however, as a
345 // diagnostic aid.
347 void CMRegionStack::push_with_lock(MemRegion mr) {
348 assert(mr.word_size() > 0, "Precondition");
349 MutexLockerEx x(CMRegionStack_lock, Mutex::_no_safepoint_check_flag);
351 if (isFull()) {
352 _overflow = true;
353 return;
354 }
356 _base[_index] = mr;
357 _index += 1;
358 }
360 MemRegion CMRegionStack::pop_with_lock() {
361 MutexLockerEx x(CMRegionStack_lock, Mutex::_no_safepoint_check_flag);
363 while (true) {
364 if (_index == 0) {
365 return MemRegion();
366 }
367 _index -= 1;
369 MemRegion mr = _base[_index];
370 if (mr.start() != NULL) {
371 assert(mr.end() != NULL, "invariant");
372 assert(mr.word_size() > 0, "invariant");
373 return mr;
374 } else {
375 // that entry was invalidated... let's skip it
376 assert(mr.end() == NULL, "invariant");
377 }
378 }
379 }
380 #endif
382 bool CMRegionStack::invalidate_entries_into_cset() {
383 bool result = false;
384 G1CollectedHeap* g1h = G1CollectedHeap::heap();
385 for (int i = 0; i < _oops_do_bound; ++i) {
386 MemRegion mr = _base[i];
387 if (mr.start() != NULL) {
388 assert(mr.end() != NULL, "invariant");
389 assert(mr.word_size() > 0, "invariant");
390 HeapRegion* hr = g1h->heap_region_containing(mr.start());
391 assert(hr != NULL, "invariant");
392 if (hr->in_collection_set()) {
393 // The region points into the collection set
394 _base[i] = MemRegion();
395 result = true;
396 }
397 } else {
398 // that entry was invalidated... let's skip it
399 assert(mr.end() == NULL, "invariant");
400 }
401 }
402 return result;
403 }
405 template<class OopClosureClass>
406 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
407 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
408 || SafepointSynchronize::is_at_safepoint(),
409 "Drain recursion must be yield-safe.");
410 bool res = true;
411 debug_only(_drain_in_progress = true);
412 debug_only(_drain_in_progress_yields = yield_after);
413 while (!isEmpty()) {
414 oop newOop = pop();
415 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
416 assert(newOop->is_oop(), "Expected an oop");
417 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
418 "only grey objects on this stack");
419 // iterate over the oops in this oop, marking and pushing
420 // the ones in CMS generation.
421 newOop->oop_iterate(cl);
422 if (yield_after && _cm->do_yield_check()) {
423 res = false; break;
424 }
425 }
426 debug_only(_drain_in_progress = false);
427 return res;
428 }
430 void CMMarkStack::oops_do(OopClosure* f) {
431 if (_index == 0) return;
432 assert(_oops_do_bound != -1 && _oops_do_bound <= _index,
433 "Bound must be set.");
434 for (int i = 0; i < _oops_do_bound; i++) {
435 f->do_oop(&_base[i]);
436 }
437 _oops_do_bound = -1;
438 }
440 bool ConcurrentMark::not_yet_marked(oop obj) const {
441 return (_g1h->is_obj_ill(obj)
442 || (_g1h->is_in_permanent(obj)
443 && !nextMarkBitMap()->isMarked((HeapWord*)obj)));
444 }
446 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
447 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
448 #endif // _MSC_VER
450 ConcurrentMark::ConcurrentMark(ReservedSpace rs,
451 int max_regions) :
452 _markBitMap1(rs, MinObjAlignment - 1),
453 _markBitMap2(rs, MinObjAlignment - 1),
455 _parallel_marking_threads(0),
456 _sleep_factor(0.0),
457 _marking_task_overhead(1.0),
458 _cleanup_sleep_factor(0.0),
459 _cleanup_task_overhead(1.0),
460 _region_bm(max_regions, false /* in_resource_area*/),
461 _card_bm((rs.size() + CardTableModRefBS::card_size - 1) >>
462 CardTableModRefBS::card_shift,
463 false /* in_resource_area*/),
464 _prevMarkBitMap(&_markBitMap1),
465 _nextMarkBitMap(&_markBitMap2),
466 _at_least_one_mark_complete(false),
468 _markStack(this),
469 _regionStack(),
470 // _finger set in set_non_marking_state
472 _max_task_num(MAX2(ParallelGCThreads, (size_t)1)),
473 // _active_tasks set in set_non_marking_state
474 // _tasks set inside the constructor
475 _task_queues(new CMTaskQueueSet((int) _max_task_num)),
476 _terminator(ParallelTaskTerminator((int) _max_task_num, _task_queues)),
478 _has_overflown(false),
479 _concurrent(false),
480 _has_aborted(false),
481 _restart_for_overflow(false),
482 _concurrent_marking_in_progress(false),
483 _should_gray_objects(false),
485 // _verbose_level set below
487 _init_times(),
488 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
489 _cleanup_times(),
490 _total_counting_time(0.0),
491 _total_rs_scrub_time(0.0),
493 _parallel_workers(NULL)
494 {
495 CMVerboseLevel verbose_level =
496 (CMVerboseLevel) G1MarkingVerboseLevel;
497 if (verbose_level < no_verbose)
498 verbose_level = no_verbose;
499 if (verbose_level > high_verbose)
500 verbose_level = high_verbose;
501 _verbose_level = verbose_level;
503 if (verbose_low())
504 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", "
505 "heap end = "PTR_FORMAT, _heap_start, _heap_end);
507 _markStack.allocate(MarkStackSize);
508 _regionStack.allocate(G1MarkRegionStackSize);
510 // Create & start a ConcurrentMark thread.
511 _cmThread = new ConcurrentMarkThread(this);
512 assert(cmThread() != NULL, "CM Thread should have been created");
513 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
515 _g1h = G1CollectedHeap::heap();
516 assert(CGC_lock != NULL, "Where's the CGC_lock?");
517 assert(_markBitMap1.covers(rs), "_markBitMap1 inconsistency");
518 assert(_markBitMap2.covers(rs), "_markBitMap2 inconsistency");
520 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
521 satb_qs.set_buffer_size(G1SATBBufferSize);
523 int size = (int) MAX2(ParallelGCThreads, (size_t)1);
524 _par_cleanup_thread_state = NEW_C_HEAP_ARRAY(ParCleanupThreadState*, size);
525 for (int i = 0 ; i < size; i++) {
526 _par_cleanup_thread_state[i] = new ParCleanupThreadState;
527 }
529 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_task_num);
530 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_task_num);
532 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
533 _active_tasks = _max_task_num;
534 for (int i = 0; i < (int) _max_task_num; ++i) {
535 CMTaskQueue* task_queue = new CMTaskQueue();
536 task_queue->initialize();
537 _task_queues->register_queue(i, task_queue);
539 _tasks[i] = new CMTask(i, this, task_queue, _task_queues);
540 _accum_task_vtime[i] = 0.0;
541 }
543 if (ConcGCThreads > ParallelGCThreads) {
544 vm_exit_during_initialization("Can't have more ConcGCThreads "
545 "than ParallelGCThreads.");
546 }
547 if (ParallelGCThreads == 0) {
548 // if we are not running with any parallel GC threads we will not
549 // spawn any marking threads either
550 _parallel_marking_threads = 0;
551 _sleep_factor = 0.0;
552 _marking_task_overhead = 1.0;
553 } else {
554 if (ConcGCThreads > 0) {
555 // notice that ConcGCThreads overwrites G1MarkingOverheadPercent
556 // if both are set
558 _parallel_marking_threads = ConcGCThreads;
559 _sleep_factor = 0.0;
560 _marking_task_overhead = 1.0;
561 } else if (G1MarkingOverheadPercent > 0) {
562 // we will calculate the number of parallel marking threads
563 // based on a target overhead with respect to the soft real-time
564 // goal
566 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
567 double overall_cm_overhead =
568 (double) MaxGCPauseMillis * marking_overhead /
569 (double) GCPauseIntervalMillis;
570 double cpu_ratio = 1.0 / (double) os::processor_count();
571 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
572 double marking_task_overhead =
573 overall_cm_overhead / marking_thread_num *
574 (double) os::processor_count();
575 double sleep_factor =
576 (1.0 - marking_task_overhead) / marking_task_overhead;
578 _parallel_marking_threads = (size_t) marking_thread_num;
579 _sleep_factor = sleep_factor;
580 _marking_task_overhead = marking_task_overhead;
581 } else {
582 _parallel_marking_threads = MAX2((ParallelGCThreads + 2) / 4, (size_t)1);
583 _sleep_factor = 0.0;
584 _marking_task_overhead = 1.0;
585 }
587 if (parallel_marking_threads() > 1)
588 _cleanup_task_overhead = 1.0;
589 else
590 _cleanup_task_overhead = marking_task_overhead();
591 _cleanup_sleep_factor =
592 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
594 #if 0
595 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
596 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
597 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
598 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
599 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
600 #endif
602 guarantee(parallel_marking_threads() > 0, "peace of mind");
603 _parallel_workers = new FlexibleWorkGang("G1 Parallel Marking Threads",
604 (int) _parallel_marking_threads, false, true);
605 if (_parallel_workers == NULL) {
606 vm_exit_during_initialization("Failed necessary allocation.");
607 } else {
608 _parallel_workers->initialize_workers();
609 }
610 }
612 // so that the call below can read a sensible value
613 _heap_start = (HeapWord*) rs.base();
614 set_non_marking_state();
615 }
617 void ConcurrentMark::update_g1_committed(bool force) {
618 // If concurrent marking is not in progress, then we do not need to
619 // update _heap_end. This has a subtle and important
620 // side-effect. Imagine that two evacuation pauses happen between
621 // marking completion and remark. The first one can grow the
622 // heap (hence now the finger is below the heap end). Then, the
623 // second one could unnecessarily push regions on the region
624 // stack. This causes the invariant that the region stack is empty
625 // at the beginning of remark to be false. By ensuring that we do
626 // not observe heap expansions after marking is complete, then we do
627 // not have this problem.
628 if (!concurrent_marking_in_progress() && !force)
629 return;
631 MemRegion committed = _g1h->g1_committed();
632 assert(committed.start() == _heap_start, "start shouldn't change");
633 HeapWord* new_end = committed.end();
634 if (new_end > _heap_end) {
635 // The heap has been expanded.
637 _heap_end = new_end;
638 }
639 // Notice that the heap can also shrink. However, this only happens
640 // during a Full GC (at least currently) and the entire marking
641 // phase will bail out and the task will not be restarted. So, let's
642 // do nothing.
643 }
645 void ConcurrentMark::reset() {
646 // Starting values for these two. This should be called in a STW
647 // phase. CM will be notified of any future g1_committed expansions
648 // will be at the end of evacuation pauses, when tasks are
649 // inactive.
650 MemRegion committed = _g1h->g1_committed();
651 _heap_start = committed.start();
652 _heap_end = committed.end();
654 // Separated the asserts so that we know which one fires.
655 assert(_heap_start != NULL, "heap bounds should look ok");
656 assert(_heap_end != NULL, "heap bounds should look ok");
657 assert(_heap_start < _heap_end, "heap bounds should look ok");
659 // reset all the marking data structures and any necessary flags
660 clear_marking_state();
662 if (verbose_low())
663 gclog_or_tty->print_cr("[global] resetting");
665 // We do reset all of them, since different phases will use
666 // different number of active threads. So, it's easiest to have all
667 // of them ready.
668 for (int i = 0; i < (int) _max_task_num; ++i) {
669 _tasks[i]->reset(_nextMarkBitMap);
670 }
672 // we need this to make sure that the flag is on during the evac
673 // pause with initial mark piggy-backed
674 set_concurrent_marking_in_progress();
675 }
677 void ConcurrentMark::set_phase(size_t active_tasks, bool concurrent) {
678 assert(active_tasks <= _max_task_num, "we should not have more");
680 _active_tasks = active_tasks;
681 // Need to update the three data structures below according to the
682 // number of active threads for this phase.
683 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
684 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
685 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
687 _concurrent = concurrent;
688 // We propagate this to all tasks, not just the active ones.
689 for (int i = 0; i < (int) _max_task_num; ++i)
690 _tasks[i]->set_concurrent(concurrent);
692 if (concurrent) {
693 set_concurrent_marking_in_progress();
694 } else {
695 // We currently assume that the concurrent flag has been set to
696 // false before we start remark. At this point we should also be
697 // in a STW phase.
698 assert(!concurrent_marking_in_progress(), "invariant");
699 assert(_finger == _heap_end, "only way to get here");
700 update_g1_committed(true);
701 }
702 }
704 void ConcurrentMark::set_non_marking_state() {
705 // We set the global marking state to some default values when we're
706 // not doing marking.
707 clear_marking_state();
708 _active_tasks = 0;
709 clear_concurrent_marking_in_progress();
710 }
712 ConcurrentMark::~ConcurrentMark() {
713 int size = (int) MAX2(ParallelGCThreads, (size_t)1);
714 for (int i = 0; i < size; i++) delete _par_cleanup_thread_state[i];
715 FREE_C_HEAP_ARRAY(ParCleanupThreadState*,
716 _par_cleanup_thread_state);
718 for (int i = 0; i < (int) _max_task_num; ++i) {
719 delete _task_queues->queue(i);
720 delete _tasks[i];
721 }
722 delete _task_queues;
723 FREE_C_HEAP_ARRAY(CMTask*, _max_task_num);
724 }
726 // This closure is used to mark refs into the g1 generation
727 // from external roots in the CMS bit map.
728 // Called at the first checkpoint.
729 //
731 void ConcurrentMark::clearNextBitmap() {
732 G1CollectedHeap* g1h = G1CollectedHeap::heap();
733 G1CollectorPolicy* g1p = g1h->g1_policy();
735 // Make sure that the concurrent mark thread looks to still be in
736 // the current cycle.
737 guarantee(cmThread()->during_cycle(), "invariant");
739 // We are finishing up the current cycle by clearing the next
740 // marking bitmap and getting it ready for the next cycle. During
741 // this time no other cycle can start. So, let's make sure that this
742 // is the case.
743 guarantee(!g1h->mark_in_progress(), "invariant");
745 // clear the mark bitmap (no grey objects to start with).
746 // We need to do this in chunks and offer to yield in between
747 // each chunk.
748 HeapWord* start = _nextMarkBitMap->startWord();
749 HeapWord* end = _nextMarkBitMap->endWord();
750 HeapWord* cur = start;
751 size_t chunkSize = M;
752 while (cur < end) {
753 HeapWord* next = cur + chunkSize;
754 if (next > end)
755 next = end;
756 MemRegion mr(cur,next);
757 _nextMarkBitMap->clearRange(mr);
758 cur = next;
759 do_yield_check();
761 // Repeat the asserts from above. We'll do them as asserts here to
762 // minimize their overhead on the product. However, we'll have
763 // them as guarantees at the beginning / end of the bitmap
764 // clearing to get some checking in the product.
765 assert(cmThread()->during_cycle(), "invariant");
766 assert(!g1h->mark_in_progress(), "invariant");
767 }
769 // Repeat the asserts from above.
770 guarantee(cmThread()->during_cycle(), "invariant");
771 guarantee(!g1h->mark_in_progress(), "invariant");
772 }
774 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
775 public:
776 bool doHeapRegion(HeapRegion* r) {
777 if (!r->continuesHumongous()) {
778 r->note_start_of_marking(true);
779 }
780 return false;
781 }
782 };
784 void ConcurrentMark::checkpointRootsInitialPre() {
785 G1CollectedHeap* g1h = G1CollectedHeap::heap();
786 G1CollectorPolicy* g1p = g1h->g1_policy();
788 _has_aborted = false;
790 #ifndef PRODUCT
791 if (G1PrintReachableAtInitialMark) {
792 print_reachable("at-cycle-start",
793 true /* use_prev_marking */, true /* all */);
794 }
795 #endif
797 // Initialise marking structures. This has to be done in a STW phase.
798 reset();
799 }
801 class CMMarkRootsClosure: public OopsInGenClosure {
802 private:
803 ConcurrentMark* _cm;
804 G1CollectedHeap* _g1h;
805 bool _do_barrier;
807 public:
808 CMMarkRootsClosure(ConcurrentMark* cm,
809 G1CollectedHeap* g1h,
810 bool do_barrier) : _cm(cm), _g1h(g1h),
811 _do_barrier(do_barrier) { }
813 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
814 virtual void do_oop( oop* p) { do_oop_work(p); }
816 template <class T> void do_oop_work(T* p) {
817 T heap_oop = oopDesc::load_heap_oop(p);
818 if (!oopDesc::is_null(heap_oop)) {
819 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
820 assert(obj->is_oop() || obj->mark() == NULL,
821 "expected an oop, possibly with mark word displaced");
822 HeapWord* addr = (HeapWord*)obj;
823 if (_g1h->is_in_g1_reserved(addr)) {
824 _cm->grayRoot(obj);
825 }
826 }
827 if (_do_barrier) {
828 assert(!_g1h->is_in_g1_reserved(p),
829 "Should be called on external roots");
830 do_barrier(p);
831 }
832 }
833 };
835 void ConcurrentMark::checkpointRootsInitialPost() {
836 G1CollectedHeap* g1h = G1CollectedHeap::heap();
838 // For each region note start of marking.
839 NoteStartOfMarkHRClosure startcl;
840 g1h->heap_region_iterate(&startcl);
842 // Start weak-reference discovery.
843 ReferenceProcessor* rp = g1h->ref_processor();
844 rp->verify_no_references_recorded();
845 rp->enable_discovery(); // enable ("weak") refs discovery
846 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
848 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
849 // This is the start of the marking cycle, we're expected all
850 // threads to have SATB queues with active set to false.
851 satb_mq_set.set_active_all_threads(true, /* new active value */
852 false /* expected_active */);
854 // update_g1_committed() will be called at the end of an evac pause
855 // when marking is on. So, it's also called at the end of the
856 // initial-mark pause to update the heap end, if the heap expands
857 // during it. No need to call it here.
858 }
860 // Checkpoint the roots into this generation from outside
861 // this generation. [Note this initial checkpoint need only
862 // be approximate -- we'll do a catch up phase subsequently.]
863 void ConcurrentMark::checkpointRootsInitial() {
864 assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped");
865 G1CollectedHeap* g1h = G1CollectedHeap::heap();
867 double start = os::elapsedTime();
869 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
870 g1p->record_concurrent_mark_init_start();
871 checkpointRootsInitialPre();
873 // YSR: when concurrent precleaning is in place, we'll
874 // need to clear the cached card table here
876 ResourceMark rm;
877 HandleMark hm;
879 g1h->ensure_parsability(false);
880 g1h->perm_gen()->save_marks();
882 CMMarkRootsClosure notOlder(this, g1h, false);
883 CMMarkRootsClosure older(this, g1h, true);
885 g1h->set_marking_started();
886 g1h->rem_set()->prepare_for_younger_refs_iterate(false);
888 g1h->process_strong_roots(true, // activate StrongRootsScope
889 false, // fake perm gen collection
890 SharedHeap::SO_AllClasses,
891 ¬Older, // Regular roots
892 NULL, // do not visit active blobs
893 &older // Perm Gen Roots
894 );
895 checkpointRootsInitialPost();
897 // Statistics.
898 double end = os::elapsedTime();
899 _init_times.add((end - start) * 1000.0);
901 g1p->record_concurrent_mark_init_end();
902 }
904 /*
905 Notice that in the next two methods, we actually leave the STS
906 during the barrier sync and join it immediately afterwards. If we
907 do not do this, this then the following deadlock can occur: one
908 thread could be in the barrier sync code, waiting for the other
909 thread to also sync up, whereas another one could be trying to
910 yield, while also waiting for the other threads to sync up too.
912 Because the thread that does the sync barrier has left the STS, it
913 is possible to be suspended for a Full GC or an evacuation pause
914 could occur. This is actually safe, since the entering the sync
915 barrier is one of the last things do_marking_step() does, and it
916 doesn't manipulate any data structures afterwards.
917 */
919 void ConcurrentMark::enter_first_sync_barrier(int task_num) {
920 if (verbose_low())
921 gclog_or_tty->print_cr("[%d] entering first barrier", task_num);
923 ConcurrentGCThread::stsLeave();
924 _first_overflow_barrier_sync.enter();
925 ConcurrentGCThread::stsJoin();
926 // at this point everyone should have synced up and not be doing any
927 // more work
929 if (verbose_low())
930 gclog_or_tty->print_cr("[%d] leaving first barrier", task_num);
932 // let task 0 do this
933 if (task_num == 0) {
934 // task 0 is responsible for clearing the global data structures
935 clear_marking_state();
937 if (PrintGC) {
938 gclog_or_tty->date_stamp(PrintGCDateStamps);
939 gclog_or_tty->stamp(PrintGCTimeStamps);
940 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
941 }
942 }
944 // after this, each task should reset its own data structures then
945 // then go into the second barrier
946 }
948 void ConcurrentMark::enter_second_sync_barrier(int task_num) {
949 if (verbose_low())
950 gclog_or_tty->print_cr("[%d] entering second barrier", task_num);
952 ConcurrentGCThread::stsLeave();
953 _second_overflow_barrier_sync.enter();
954 ConcurrentGCThread::stsJoin();
955 // at this point everything should be re-initialised and ready to go
957 if (verbose_low())
958 gclog_or_tty->print_cr("[%d] leaving second barrier", task_num);
959 }
961 void ConcurrentMark::grayRoot(oop p) {
962 HeapWord* addr = (HeapWord*) p;
963 // We can't really check against _heap_start and _heap_end, since it
964 // is possible during an evacuation pause with piggy-backed
965 // initial-mark that the committed space is expanded during the
966 // pause without CM observing this change. So the assertions below
967 // is a bit conservative; but better than nothing.
968 assert(_g1h->g1_committed().contains(addr),
969 "address should be within the heap bounds");
971 if (!_nextMarkBitMap->isMarked(addr))
972 _nextMarkBitMap->parMark(addr);
973 }
975 void ConcurrentMark::grayRegionIfNecessary(MemRegion mr) {
976 // The objects on the region have already been marked "in bulk" by
977 // the caller. We only need to decide whether to push the region on
978 // the region stack or not.
980 if (!concurrent_marking_in_progress() || !_should_gray_objects)
981 // We're done with marking and waiting for remark. We do not need to
982 // push anything else on the region stack.
983 return;
985 HeapWord* finger = _finger;
987 if (verbose_low())
988 gclog_or_tty->print_cr("[global] attempting to push "
989 "region ["PTR_FORMAT", "PTR_FORMAT"), finger is at "
990 PTR_FORMAT, mr.start(), mr.end(), finger);
992 if (mr.start() < finger) {
993 // The finger is always heap region aligned and it is not possible
994 // for mr to span heap regions.
995 assert(mr.end() <= finger, "invariant");
997 // Separated the asserts so that we know which one fires.
998 assert(mr.start() <= mr.end(),
999 "region boundaries should fall within the committed space");
1000 assert(_heap_start <= mr.start(),
1001 "region boundaries should fall within the committed space");
1002 assert(mr.end() <= _heap_end,
1003 "region boundaries should fall within the committed space");
1004 if (verbose_low())
1005 gclog_or_tty->print_cr("[global] region ["PTR_FORMAT", "PTR_FORMAT") "
1006 "below the finger, pushing it",
1007 mr.start(), mr.end());
1009 if (!region_stack_push_lock_free(mr)) {
1010 if (verbose_low())
1011 gclog_or_tty->print_cr("[global] region stack has overflown.");
1012 }
1013 }
1014 }
1016 void ConcurrentMark::markAndGrayObjectIfNecessary(oop p) {
1017 // The object is not marked by the caller. We need to at least mark
1018 // it and maybe push in on the stack.
1020 HeapWord* addr = (HeapWord*)p;
1021 if (!_nextMarkBitMap->isMarked(addr)) {
1022 // We definitely need to mark it, irrespective whether we bail out
1023 // because we're done with marking.
1024 if (_nextMarkBitMap->parMark(addr)) {
1025 if (!concurrent_marking_in_progress() || !_should_gray_objects)
1026 // If we're done with concurrent marking and we're waiting for
1027 // remark, then we're not pushing anything on the stack.
1028 return;
1030 // No OrderAccess:store_load() is needed. It is implicit in the
1031 // CAS done in parMark(addr) above
1032 HeapWord* finger = _finger;
1034 if (addr < finger) {
1035 if (!mark_stack_push(oop(addr))) {
1036 if (verbose_low())
1037 gclog_or_tty->print_cr("[global] global stack overflow "
1038 "during parMark");
1039 }
1040 }
1041 }
1042 }
1043 }
1045 class CMConcurrentMarkingTask: public AbstractGangTask {
1046 private:
1047 ConcurrentMark* _cm;
1048 ConcurrentMarkThread* _cmt;
1050 public:
1051 void work(int worker_i) {
1052 assert(Thread::current()->is_ConcurrentGC_thread(),
1053 "this should only be done by a conc GC thread");
1055 double start_vtime = os::elapsedVTime();
1057 ConcurrentGCThread::stsJoin();
1059 assert((size_t) worker_i < _cm->active_tasks(), "invariant");
1060 CMTask* the_task = _cm->task(worker_i);
1061 the_task->record_start_time();
1062 if (!_cm->has_aborted()) {
1063 do {
1064 double start_vtime_sec = os::elapsedVTime();
1065 double start_time_sec = os::elapsedTime();
1066 the_task->do_marking_step(10.0);
1067 double end_time_sec = os::elapsedTime();
1068 double end_vtime_sec = os::elapsedVTime();
1069 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1070 double elapsed_time_sec = end_time_sec - start_time_sec;
1071 _cm->clear_has_overflown();
1073 bool ret = _cm->do_yield_check(worker_i);
1075 jlong sleep_time_ms;
1076 if (!_cm->has_aborted() && the_task->has_aborted()) {
1077 sleep_time_ms =
1078 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1079 ConcurrentGCThread::stsLeave();
1080 os::sleep(Thread::current(), sleep_time_ms, false);
1081 ConcurrentGCThread::stsJoin();
1082 }
1083 double end_time2_sec = os::elapsedTime();
1084 double elapsed_time2_sec = end_time2_sec - start_time_sec;
1086 #if 0
1087 gclog_or_tty->print_cr("CM: elapsed %1.4lf ms, sleep %1.4lf ms, "
1088 "overhead %1.4lf",
1089 elapsed_vtime_sec * 1000.0, (double) sleep_time_ms,
1090 the_task->conc_overhead(os::elapsedTime()) * 8.0);
1091 gclog_or_tty->print_cr("elapsed time %1.4lf ms, time 2: %1.4lf ms",
1092 elapsed_time_sec * 1000.0, elapsed_time2_sec * 1000.0);
1093 #endif
1094 } while (!_cm->has_aborted() && the_task->has_aborted());
1095 }
1096 the_task->record_end_time();
1097 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1099 ConcurrentGCThread::stsLeave();
1101 double end_vtime = os::elapsedVTime();
1102 _cm->update_accum_task_vtime(worker_i, end_vtime - start_vtime);
1103 }
1105 CMConcurrentMarkingTask(ConcurrentMark* cm,
1106 ConcurrentMarkThread* cmt) :
1107 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1109 ~CMConcurrentMarkingTask() { }
1110 };
1112 void ConcurrentMark::markFromRoots() {
1113 // we might be tempted to assert that:
1114 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1115 // "inconsistent argument?");
1116 // However that wouldn't be right, because it's possible that
1117 // a safepoint is indeed in progress as a younger generation
1118 // stop-the-world GC happens even as we mark in this generation.
1120 _restart_for_overflow = false;
1122 set_phase(MAX2((size_t) 1, parallel_marking_threads()), true);
1124 CMConcurrentMarkingTask markingTask(this, cmThread());
1125 if (parallel_marking_threads() > 0)
1126 _parallel_workers->run_task(&markingTask);
1127 else
1128 markingTask.work(0);
1129 print_stats();
1130 }
1132 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1133 // world is stopped at this checkpoint
1134 assert(SafepointSynchronize::is_at_safepoint(),
1135 "world should be stopped");
1136 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1138 // If a full collection has happened, we shouldn't do this.
1139 if (has_aborted()) {
1140 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1141 return;
1142 }
1144 if (VerifyDuringGC) {
1145 HandleMark hm; // handle scope
1146 gclog_or_tty->print(" VerifyDuringGC:(before)");
1147 Universe::heap()->prepare_for_verify();
1148 Universe::verify(true, false, true);
1149 }
1151 G1CollectorPolicy* g1p = g1h->g1_policy();
1152 g1p->record_concurrent_mark_remark_start();
1154 double start = os::elapsedTime();
1156 checkpointRootsFinalWork();
1158 double mark_work_end = os::elapsedTime();
1160 weakRefsWork(clear_all_soft_refs);
1162 if (has_overflown()) {
1163 // Oops. We overflowed. Restart concurrent marking.
1164 _restart_for_overflow = true;
1165 // Clear the flag. We do not need it any more.
1166 clear_has_overflown();
1167 if (G1TraceMarkStackOverflow)
1168 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1169 } else {
1170 // We're done with marking.
1171 // This is the end of the marking cycle, we're expected all
1172 // threads to have SATB queues with active set to true.
1173 JavaThread::satb_mark_queue_set().set_active_all_threads(
1174 false, /* new active value */
1175 true /* expected_active */);
1177 if (VerifyDuringGC) {
1178 HandleMark hm; // handle scope
1179 gclog_or_tty->print(" VerifyDuringGC:(after)");
1180 Universe::heap()->prepare_for_verify();
1181 Universe::heap()->verify(/* allow_dirty */ true,
1182 /* silent */ false,
1183 /* use_prev_marking */ false);
1184 }
1185 }
1187 #if VERIFY_OBJS_PROCESSED
1188 _scan_obj_cl.objs_processed = 0;
1189 ThreadLocalObjQueue::objs_enqueued = 0;
1190 #endif
1192 // Statistics
1193 double now = os::elapsedTime();
1194 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1195 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1196 _remark_times.add((now - start) * 1000.0);
1198 g1p->record_concurrent_mark_remark_end();
1199 }
1202 #define CARD_BM_TEST_MODE 0
1204 class CalcLiveObjectsClosure: public HeapRegionClosure {
1206 CMBitMapRO* _bm;
1207 ConcurrentMark* _cm;
1208 bool _changed;
1209 bool _yield;
1210 size_t _words_done;
1211 size_t _tot_live;
1212 size_t _tot_used;
1213 size_t _regions_done;
1214 double _start_vtime_sec;
1216 BitMap* _region_bm;
1217 BitMap* _card_bm;
1218 intptr_t _bottom_card_num;
1219 bool _final;
1221 void mark_card_num_range(intptr_t start_card_num, intptr_t last_card_num) {
1222 for (intptr_t i = start_card_num; i <= last_card_num; i++) {
1223 #if CARD_BM_TEST_MODE
1224 guarantee(_card_bm->at(i - _bottom_card_num), "Should already be set.");
1225 #else
1226 _card_bm->par_at_put(i - _bottom_card_num, 1);
1227 #endif
1228 }
1229 }
1231 public:
1232 CalcLiveObjectsClosure(bool final,
1233 CMBitMapRO *bm, ConcurrentMark *cm,
1234 BitMap* region_bm, BitMap* card_bm) :
1235 _bm(bm), _cm(cm), _changed(false), _yield(true),
1236 _words_done(0), _tot_live(0), _tot_used(0),
1237 _region_bm(region_bm), _card_bm(card_bm),_final(final),
1238 _regions_done(0), _start_vtime_sec(0.0)
1239 {
1240 _bottom_card_num =
1241 intptr_t(uintptr_t(G1CollectedHeap::heap()->reserved_region().start()) >>
1242 CardTableModRefBS::card_shift);
1243 }
1245 // It takes a region that's not empty (i.e., it has at least one
1246 // live object in it and sets its corresponding bit on the region
1247 // bitmap to 1. If the region is "starts humongous" it will also set
1248 // to 1 the bits on the region bitmap that correspond to its
1249 // associated "continues humongous" regions.
1250 void set_bit_for_region(HeapRegion* hr) {
1251 assert(!hr->continuesHumongous(), "should have filtered those out");
1253 size_t index = hr->hrs_index();
1254 if (!hr->startsHumongous()) {
1255 // Normal (non-humongous) case: just set the bit.
1256 _region_bm->par_at_put((BitMap::idx_t) index, true);
1257 } else {
1258 // Starts humongous case: calculate how many regions are part of
1259 // this humongous region and then set the bit range. It might
1260 // have been a bit more efficient to look at the object that
1261 // spans these humongous regions to calculate their number from
1262 // the object's size. However, it's a good idea to calculate
1263 // this based on the metadata itself, and not the region
1264 // contents, so that this code is not aware of what goes into
1265 // the humongous regions (in case this changes in the future).
1266 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1267 size_t end_index = index + 1;
1268 while (end_index < g1h->n_regions()) {
1269 HeapRegion* chr = g1h->region_at(end_index);
1270 if (!chr->continuesHumongous()) {
1271 break;
1272 }
1273 end_index += 1;
1274 }
1275 _region_bm->par_at_put_range((BitMap::idx_t) index,
1276 (BitMap::idx_t) end_index, true);
1277 }
1278 }
1280 bool doHeapRegion(HeapRegion* hr) {
1281 if (!_final && _regions_done == 0)
1282 _start_vtime_sec = os::elapsedVTime();
1284 if (hr->continuesHumongous()) {
1285 // We will ignore these here and process them when their
1286 // associated "starts humongous" region is processed (see
1287 // set_bit_for_heap_region()). Note that we cannot rely on their
1288 // associated "starts humongous" region to have their bit set to
1289 // 1 since, due to the region chunking in the parallel region
1290 // iteration, a "continues humongous" region might be visited
1291 // before its associated "starts humongous".
1292 return false;
1293 }
1295 HeapWord* nextTop = hr->next_top_at_mark_start();
1296 HeapWord* start = hr->top_at_conc_mark_count();
1297 assert(hr->bottom() <= start && start <= hr->end() &&
1298 hr->bottom() <= nextTop && nextTop <= hr->end() &&
1299 start <= nextTop,
1300 "Preconditions.");
1301 // Otherwise, record the number of word's we'll examine.
1302 size_t words_done = (nextTop - start);
1303 // Find the first marked object at or after "start".
1304 start = _bm->getNextMarkedWordAddress(start, nextTop);
1305 size_t marked_bytes = 0;
1307 // Below, the term "card num" means the result of shifting an address
1308 // by the card shift -- address 0 corresponds to card number 0. One
1309 // must subtract the card num of the bottom of the heap to obtain a
1310 // card table index.
1311 // The first card num of the sequence of live cards currently being
1312 // constructed. -1 ==> no sequence.
1313 intptr_t start_card_num = -1;
1314 // The last card num of the sequence of live cards currently being
1315 // constructed. -1 ==> no sequence.
1316 intptr_t last_card_num = -1;
1318 while (start < nextTop) {
1319 if (_yield && _cm->do_yield_check()) {
1320 // We yielded. It might be for a full collection, in which case
1321 // all bets are off; terminate the traversal.
1322 if (_cm->has_aborted()) {
1323 _changed = false;
1324 return true;
1325 } else {
1326 // Otherwise, it might be a collection pause, and the region
1327 // we're looking at might be in the collection set. We'll
1328 // abandon this region.
1329 return false;
1330 }
1331 }
1332 oop obj = oop(start);
1333 int obj_sz = obj->size();
1334 // The card num of the start of the current object.
1335 intptr_t obj_card_num =
1336 intptr_t(uintptr_t(start) >> CardTableModRefBS::card_shift);
1338 HeapWord* obj_last = start + obj_sz - 1;
1339 intptr_t obj_last_card_num =
1340 intptr_t(uintptr_t(obj_last) >> CardTableModRefBS::card_shift);
1342 if (obj_card_num != last_card_num) {
1343 if (start_card_num == -1) {
1344 assert(last_card_num == -1, "Both or neither.");
1345 start_card_num = obj_card_num;
1346 } else {
1347 assert(last_card_num != -1, "Both or neither.");
1348 assert(obj_card_num >= last_card_num, "Inv");
1349 if ((obj_card_num - last_card_num) > 1) {
1350 // Mark the last run, and start a new one.
1351 mark_card_num_range(start_card_num, last_card_num);
1352 start_card_num = obj_card_num;
1353 }
1354 }
1355 #if CARD_BM_TEST_MODE
1356 /*
1357 gclog_or_tty->print_cr("Setting bits from %d/%d.",
1358 obj_card_num - _bottom_card_num,
1359 obj_last_card_num - _bottom_card_num);
1360 */
1361 for (intptr_t j = obj_card_num; j <= obj_last_card_num; j++) {
1362 _card_bm->par_at_put(j - _bottom_card_num, 1);
1363 }
1364 #endif
1365 }
1366 // In any case, we set the last card num.
1367 last_card_num = obj_last_card_num;
1369 marked_bytes += (size_t)obj_sz * HeapWordSize;
1370 // Find the next marked object after this one.
1371 start = _bm->getNextMarkedWordAddress(start + 1, nextTop);
1372 _changed = true;
1373 }
1374 // Handle the last range, if any.
1375 if (start_card_num != -1)
1376 mark_card_num_range(start_card_num, last_card_num);
1377 if (_final) {
1378 // Mark the allocated-since-marking portion...
1379 HeapWord* tp = hr->top();
1380 if (nextTop < tp) {
1381 start_card_num =
1382 intptr_t(uintptr_t(nextTop) >> CardTableModRefBS::card_shift);
1383 last_card_num =
1384 intptr_t(uintptr_t(tp) >> CardTableModRefBS::card_shift);
1385 mark_card_num_range(start_card_num, last_card_num);
1386 // This definitely means the region has live objects.
1387 set_bit_for_region(hr);
1388 }
1389 }
1391 hr->add_to_marked_bytes(marked_bytes);
1392 // Update the live region bitmap.
1393 if (marked_bytes > 0) {
1394 set_bit_for_region(hr);
1395 }
1396 hr->set_top_at_conc_mark_count(nextTop);
1397 _tot_live += hr->next_live_bytes();
1398 _tot_used += hr->used();
1399 _words_done = words_done;
1401 if (!_final) {
1402 ++_regions_done;
1403 if (_regions_done % 10 == 0) {
1404 double end_vtime_sec = os::elapsedVTime();
1405 double elapsed_vtime_sec = end_vtime_sec - _start_vtime_sec;
1406 if (elapsed_vtime_sec > (10.0 / 1000.0)) {
1407 jlong sleep_time_ms =
1408 (jlong) (elapsed_vtime_sec * _cm->cleanup_sleep_factor() * 1000.0);
1409 os::sleep(Thread::current(), sleep_time_ms, false);
1410 _start_vtime_sec = end_vtime_sec;
1411 }
1412 }
1413 }
1415 return false;
1416 }
1418 bool changed() { return _changed; }
1419 void reset() { _changed = false; _words_done = 0; }
1420 void no_yield() { _yield = false; }
1421 size_t words_done() { return _words_done; }
1422 size_t tot_live() { return _tot_live; }
1423 size_t tot_used() { return _tot_used; }
1424 };
1427 void ConcurrentMark::calcDesiredRegions() {
1428 _region_bm.clear();
1429 _card_bm.clear();
1430 CalcLiveObjectsClosure calccl(false /*final*/,
1431 nextMarkBitMap(), this,
1432 &_region_bm, &_card_bm);
1433 G1CollectedHeap *g1h = G1CollectedHeap::heap();
1434 g1h->heap_region_iterate(&calccl);
1436 do {
1437 calccl.reset();
1438 g1h->heap_region_iterate(&calccl);
1439 } while (calccl.changed());
1440 }
1442 class G1ParFinalCountTask: public AbstractGangTask {
1443 protected:
1444 G1CollectedHeap* _g1h;
1445 CMBitMap* _bm;
1446 size_t _n_workers;
1447 size_t *_live_bytes;
1448 size_t *_used_bytes;
1449 BitMap* _region_bm;
1450 BitMap* _card_bm;
1451 public:
1452 G1ParFinalCountTask(G1CollectedHeap* g1h, CMBitMap* bm,
1453 BitMap* region_bm, BitMap* card_bm) :
1454 AbstractGangTask("G1 final counting"), _g1h(g1h),
1455 _bm(bm), _region_bm(region_bm), _card_bm(card_bm)
1456 {
1457 if (ParallelGCThreads > 0)
1458 _n_workers = _g1h->workers()->total_workers();
1459 else
1460 _n_workers = 1;
1461 _live_bytes = NEW_C_HEAP_ARRAY(size_t, _n_workers);
1462 _used_bytes = NEW_C_HEAP_ARRAY(size_t, _n_workers);
1463 }
1465 ~G1ParFinalCountTask() {
1466 FREE_C_HEAP_ARRAY(size_t, _live_bytes);
1467 FREE_C_HEAP_ARRAY(size_t, _used_bytes);
1468 }
1470 void work(int i) {
1471 CalcLiveObjectsClosure calccl(true /*final*/,
1472 _bm, _g1h->concurrent_mark(),
1473 _region_bm, _card_bm);
1474 calccl.no_yield();
1475 if (G1CollectedHeap::use_parallel_gc_threads()) {
1476 _g1h->heap_region_par_iterate_chunked(&calccl, i,
1477 HeapRegion::FinalCountClaimValue);
1478 } else {
1479 _g1h->heap_region_iterate(&calccl);
1480 }
1481 assert(calccl.complete(), "Shouldn't have yielded!");
1483 assert((size_t) i < _n_workers, "invariant");
1484 _live_bytes[i] = calccl.tot_live();
1485 _used_bytes[i] = calccl.tot_used();
1486 }
1487 size_t live_bytes() {
1488 size_t live_bytes = 0;
1489 for (size_t i = 0; i < _n_workers; ++i)
1490 live_bytes += _live_bytes[i];
1491 return live_bytes;
1492 }
1493 size_t used_bytes() {
1494 size_t used_bytes = 0;
1495 for (size_t i = 0; i < _n_workers; ++i)
1496 used_bytes += _used_bytes[i];
1497 return used_bytes;
1498 }
1499 };
1501 class G1ParNoteEndTask;
1503 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1504 G1CollectedHeap* _g1;
1505 int _worker_num;
1506 size_t _max_live_bytes;
1507 size_t _regions_claimed;
1508 size_t _freed_bytes;
1509 size_t _cleared_h_regions;
1510 size_t _freed_regions;
1511 UncleanRegionList* _unclean_region_list;
1512 double _claimed_region_time;
1513 double _max_region_time;
1515 public:
1516 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1517 UncleanRegionList* list,
1518 int worker_num);
1519 size_t freed_bytes() { return _freed_bytes; }
1520 size_t cleared_h_regions() { return _cleared_h_regions; }
1521 size_t freed_regions() { return _freed_regions; }
1522 UncleanRegionList* unclean_region_list() {
1523 return _unclean_region_list;
1524 }
1526 bool doHeapRegion(HeapRegion *r);
1528 size_t max_live_bytes() { return _max_live_bytes; }
1529 size_t regions_claimed() { return _regions_claimed; }
1530 double claimed_region_time_sec() { return _claimed_region_time; }
1531 double max_region_time_sec() { return _max_region_time; }
1532 };
1534 class G1ParNoteEndTask: public AbstractGangTask {
1535 friend class G1NoteEndOfConcMarkClosure;
1536 protected:
1537 G1CollectedHeap* _g1h;
1538 size_t _max_live_bytes;
1539 size_t _freed_bytes;
1540 ConcurrentMark::ParCleanupThreadState** _par_cleanup_thread_state;
1541 public:
1542 G1ParNoteEndTask(G1CollectedHeap* g1h,
1543 ConcurrentMark::ParCleanupThreadState**
1544 par_cleanup_thread_state) :
1545 AbstractGangTask("G1 note end"), _g1h(g1h),
1546 _max_live_bytes(0), _freed_bytes(0),
1547 _par_cleanup_thread_state(par_cleanup_thread_state)
1548 {}
1550 void work(int i) {
1551 double start = os::elapsedTime();
1552 G1NoteEndOfConcMarkClosure g1_note_end(_g1h,
1553 &_par_cleanup_thread_state[i]->list,
1554 i);
1555 if (G1CollectedHeap::use_parallel_gc_threads()) {
1556 _g1h->heap_region_par_iterate_chunked(&g1_note_end, i,
1557 HeapRegion::NoteEndClaimValue);
1558 } else {
1559 _g1h->heap_region_iterate(&g1_note_end);
1560 }
1561 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1563 // Now finish up freeing the current thread's regions.
1564 _g1h->finish_free_region_work(g1_note_end.freed_bytes(),
1565 g1_note_end.cleared_h_regions(),
1566 0, NULL);
1567 {
1568 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1569 _max_live_bytes += g1_note_end.max_live_bytes();
1570 _freed_bytes += g1_note_end.freed_bytes();
1571 }
1572 double end = os::elapsedTime();
1573 if (G1PrintParCleanupStats) {
1574 gclog_or_tty->print(" Worker thread %d [%8.3f..%8.3f = %8.3f ms] "
1575 "claimed %d regions (tot = %8.3f ms, max = %8.3f ms).\n",
1576 i, start, end, (end-start)*1000.0,
1577 g1_note_end.regions_claimed(),
1578 g1_note_end.claimed_region_time_sec()*1000.0,
1579 g1_note_end.max_region_time_sec()*1000.0);
1580 }
1581 }
1582 size_t max_live_bytes() { return _max_live_bytes; }
1583 size_t freed_bytes() { return _freed_bytes; }
1584 };
1586 class G1ParScrubRemSetTask: public AbstractGangTask {
1587 protected:
1588 G1RemSet* _g1rs;
1589 BitMap* _region_bm;
1590 BitMap* _card_bm;
1591 public:
1592 G1ParScrubRemSetTask(G1CollectedHeap* g1h,
1593 BitMap* region_bm, BitMap* card_bm) :
1594 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()),
1595 _region_bm(region_bm), _card_bm(card_bm)
1596 {}
1598 void work(int i) {
1599 if (G1CollectedHeap::use_parallel_gc_threads()) {
1600 _g1rs->scrub_par(_region_bm, _card_bm, i,
1601 HeapRegion::ScrubRemSetClaimValue);
1602 } else {
1603 _g1rs->scrub(_region_bm, _card_bm);
1604 }
1605 }
1607 };
1609 G1NoteEndOfConcMarkClosure::
1610 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1611 UncleanRegionList* list,
1612 int worker_num)
1613 : _g1(g1), _worker_num(worker_num),
1614 _max_live_bytes(0), _regions_claimed(0),
1615 _freed_bytes(0), _cleared_h_regions(0), _freed_regions(0),
1616 _claimed_region_time(0.0), _max_region_time(0.0),
1617 _unclean_region_list(list)
1618 {}
1620 bool G1NoteEndOfConcMarkClosure::doHeapRegion(HeapRegion *r) {
1621 // We use a claim value of zero here because all regions
1622 // were claimed with value 1 in the FinalCount task.
1623 r->reset_gc_time_stamp();
1624 if (!r->continuesHumongous()) {
1625 double start = os::elapsedTime();
1626 _regions_claimed++;
1627 r->note_end_of_marking();
1628 _max_live_bytes += r->max_live_bytes();
1629 _g1->free_region_if_totally_empty_work(r,
1630 _freed_bytes,
1631 _cleared_h_regions,
1632 _freed_regions,
1633 _unclean_region_list,
1634 true /*par*/);
1635 double region_time = (os::elapsedTime() - start);
1636 _claimed_region_time += region_time;
1637 if (region_time > _max_region_time) _max_region_time = region_time;
1638 }
1639 return false;
1640 }
1642 void ConcurrentMark::cleanup() {
1643 // world is stopped at this checkpoint
1644 assert(SafepointSynchronize::is_at_safepoint(),
1645 "world should be stopped");
1646 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1648 // If a full collection has happened, we shouldn't do this.
1649 if (has_aborted()) {
1650 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1651 return;
1652 }
1654 if (VerifyDuringGC) {
1655 HandleMark hm; // handle scope
1656 gclog_or_tty->print(" VerifyDuringGC:(before)");
1657 Universe::heap()->prepare_for_verify();
1658 Universe::verify(/* allow dirty */ true,
1659 /* silent */ false,
1660 /* prev marking */ true);
1661 }
1663 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
1664 g1p->record_concurrent_mark_cleanup_start();
1666 double start = os::elapsedTime();
1668 // Do counting once more with the world stopped for good measure.
1669 G1ParFinalCountTask g1_par_count_task(g1h, nextMarkBitMap(),
1670 &_region_bm, &_card_bm);
1671 if (G1CollectedHeap::use_parallel_gc_threads()) {
1672 assert(g1h->check_heap_region_claim_values(
1673 HeapRegion::InitialClaimValue),
1674 "sanity check");
1676 int n_workers = g1h->workers()->total_workers();
1677 g1h->set_par_threads(n_workers);
1678 g1h->workers()->run_task(&g1_par_count_task);
1679 g1h->set_par_threads(0);
1681 assert(g1h->check_heap_region_claim_values(
1682 HeapRegion::FinalCountClaimValue),
1683 "sanity check");
1684 } else {
1685 g1_par_count_task.work(0);
1686 }
1688 size_t known_garbage_bytes =
1689 g1_par_count_task.used_bytes() - g1_par_count_task.live_bytes();
1690 #if 0
1691 gclog_or_tty->print_cr("used %1.2lf, live %1.2lf, garbage %1.2lf",
1692 (double) g1_par_count_task.used_bytes() / (double) (1024 * 1024),
1693 (double) g1_par_count_task.live_bytes() / (double) (1024 * 1024),
1694 (double) known_garbage_bytes / (double) (1024 * 1024));
1695 #endif // 0
1696 g1p->set_known_garbage_bytes(known_garbage_bytes);
1698 size_t start_used_bytes = g1h->used();
1699 _at_least_one_mark_complete = true;
1700 g1h->set_marking_complete();
1702 double count_end = os::elapsedTime();
1703 double this_final_counting_time = (count_end - start);
1704 if (G1PrintParCleanupStats) {
1705 gclog_or_tty->print_cr("Cleanup:");
1706 gclog_or_tty->print_cr(" Finalize counting: %8.3f ms",
1707 this_final_counting_time*1000.0);
1708 }
1709 _total_counting_time += this_final_counting_time;
1711 // Install newly created mark bitMap as "prev".
1712 swapMarkBitMaps();
1714 g1h->reset_gc_time_stamp();
1716 // Note end of marking in all heap regions.
1717 double note_end_start = os::elapsedTime();
1718 G1ParNoteEndTask g1_par_note_end_task(g1h, _par_cleanup_thread_state);
1719 if (G1CollectedHeap::use_parallel_gc_threads()) {
1720 int n_workers = g1h->workers()->total_workers();
1721 g1h->set_par_threads(n_workers);
1722 g1h->workers()->run_task(&g1_par_note_end_task);
1723 g1h->set_par_threads(0);
1725 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue),
1726 "sanity check");
1727 } else {
1728 g1_par_note_end_task.work(0);
1729 }
1730 g1h->set_unclean_regions_coming(true);
1731 double note_end_end = os::elapsedTime();
1732 // Tell the mutators that there might be unclean regions coming...
1733 if (G1PrintParCleanupStats) {
1734 gclog_or_tty->print_cr(" note end of marking: %8.3f ms.",
1735 (note_end_end - note_end_start)*1000.0);
1736 }
1739 // call below, since it affects the metric by which we sort the heap
1740 // regions.
1741 if (G1ScrubRemSets) {
1742 double rs_scrub_start = os::elapsedTime();
1743 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm);
1744 if (G1CollectedHeap::use_parallel_gc_threads()) {
1745 int n_workers = g1h->workers()->total_workers();
1746 g1h->set_par_threads(n_workers);
1747 g1h->workers()->run_task(&g1_par_scrub_rs_task);
1748 g1h->set_par_threads(0);
1750 assert(g1h->check_heap_region_claim_values(
1751 HeapRegion::ScrubRemSetClaimValue),
1752 "sanity check");
1753 } else {
1754 g1_par_scrub_rs_task.work(0);
1755 }
1757 double rs_scrub_end = os::elapsedTime();
1758 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
1759 _total_rs_scrub_time += this_rs_scrub_time;
1760 }
1762 // this will also free any regions totally full of garbage objects,
1763 // and sort the regions.
1764 g1h->g1_policy()->record_concurrent_mark_cleanup_end(
1765 g1_par_note_end_task.freed_bytes(),
1766 g1_par_note_end_task.max_live_bytes());
1768 // Statistics.
1769 double end = os::elapsedTime();
1770 _cleanup_times.add((end - start) * 1000.0);
1772 // G1CollectedHeap::heap()->print();
1773 // gclog_or_tty->print_cr("HEAP GC TIME STAMP : %d",
1774 // G1CollectedHeap::heap()->get_gc_time_stamp());
1776 if (PrintGC || PrintGCDetails) {
1777 g1h->print_size_transition(gclog_or_tty,
1778 start_used_bytes,
1779 g1h->used(),
1780 g1h->capacity());
1781 }
1783 size_t cleaned_up_bytes = start_used_bytes - g1h->used();
1784 g1p->decrease_known_garbage_bytes(cleaned_up_bytes);
1786 // We need to make this be a "collection" so any collection pause that
1787 // races with it goes around and waits for completeCleanup to finish.
1788 g1h->increment_total_collections();
1790 if (VerifyDuringGC) {
1791 HandleMark hm; // handle scope
1792 gclog_or_tty->print(" VerifyDuringGC:(after)");
1793 Universe::heap()->prepare_for_verify();
1794 Universe::verify(/* allow dirty */ true,
1795 /* silent */ false,
1796 /* prev marking */ true);
1797 }
1798 }
1800 void ConcurrentMark::completeCleanup() {
1801 // A full collection intervened.
1802 if (has_aborted()) return;
1804 int first = 0;
1805 int last = (int)MAX2(ParallelGCThreads, (size_t)1);
1806 for (int t = 0; t < last; t++) {
1807 UncleanRegionList* list = &_par_cleanup_thread_state[t]->list;
1808 assert(list->well_formed(), "Inv");
1809 HeapRegion* hd = list->hd();
1810 while (hd != NULL) {
1811 // Now finish up the other stuff.
1812 hd->rem_set()->clear();
1813 HeapRegion* next_hd = hd->next_from_unclean_list();
1814 (void)list->pop();
1815 assert(list->hd() == next_hd, "how not?");
1816 _g1h->put_region_on_unclean_list(hd);
1817 if (!hd->isHumongous()) {
1818 // Add this to the _free_regions count by 1.
1819 _g1h->finish_free_region_work(0, 0, 1, NULL);
1820 }
1821 hd = list->hd();
1822 assert(hd == next_hd, "how not?");
1823 }
1824 }
1825 }
1828 class G1CMIsAliveClosure: public BoolObjectClosure {
1829 G1CollectedHeap* _g1;
1830 public:
1831 G1CMIsAliveClosure(G1CollectedHeap* g1) :
1832 _g1(g1)
1833 {}
1835 void do_object(oop obj) {
1836 assert(false, "not to be invoked");
1837 }
1838 bool do_object_b(oop obj) {
1839 HeapWord* addr = (HeapWord*)obj;
1840 return addr != NULL &&
1841 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
1842 }
1843 };
1845 class G1CMKeepAliveClosure: public OopClosure {
1846 G1CollectedHeap* _g1;
1847 ConcurrentMark* _cm;
1848 CMBitMap* _bitMap;
1849 public:
1850 G1CMKeepAliveClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
1851 CMBitMap* bitMap) :
1852 _g1(g1), _cm(cm),
1853 _bitMap(bitMap) {}
1855 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1856 virtual void do_oop( oop* p) { do_oop_work(p); }
1858 template <class T> void do_oop_work(T* p) {
1859 oop thisOop = oopDesc::load_decode_heap_oop(p);
1860 HeapWord* addr = (HeapWord*)thisOop;
1861 if (_g1->is_in_g1_reserved(addr) && _g1->is_obj_ill(thisOop)) {
1862 _bitMap->mark(addr);
1863 _cm->mark_stack_push(thisOop);
1864 }
1865 }
1866 };
1868 class G1CMDrainMarkingStackClosure: public VoidClosure {
1869 CMMarkStack* _markStack;
1870 CMBitMap* _bitMap;
1871 G1CMKeepAliveClosure* _oopClosure;
1872 public:
1873 G1CMDrainMarkingStackClosure(CMBitMap* bitMap, CMMarkStack* markStack,
1874 G1CMKeepAliveClosure* oopClosure) :
1875 _bitMap(bitMap),
1876 _markStack(markStack),
1877 _oopClosure(oopClosure)
1878 {}
1880 void do_void() {
1881 _markStack->drain((OopClosure*)_oopClosure, _bitMap, false);
1882 }
1883 };
1885 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
1886 ResourceMark rm;
1887 HandleMark hm;
1888 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1889 ReferenceProcessor* rp = g1h->ref_processor();
1891 // Process weak references.
1892 rp->setup_policy(clear_all_soft_refs);
1893 assert(_markStack.isEmpty(), "mark stack should be empty");
1895 G1CMIsAliveClosure g1IsAliveClosure (g1h);
1896 G1CMKeepAliveClosure g1KeepAliveClosure(g1h, this, nextMarkBitMap());
1897 G1CMDrainMarkingStackClosure
1898 g1DrainMarkingStackClosure(nextMarkBitMap(), &_markStack,
1899 &g1KeepAliveClosure);
1901 // XXXYYY Also: copy the parallel ref processing code from CMS.
1902 rp->process_discovered_references(&g1IsAliveClosure,
1903 &g1KeepAliveClosure,
1904 &g1DrainMarkingStackClosure,
1905 NULL);
1906 assert(_markStack.overflow() || _markStack.isEmpty(),
1907 "mark stack should be empty (unless it overflowed)");
1908 if (_markStack.overflow()) {
1909 set_has_overflown();
1910 }
1912 rp->enqueue_discovered_references();
1913 rp->verify_no_references_recorded();
1914 assert(!rp->discovery_enabled(), "should have been disabled");
1916 // Now clean up stale oops in SymbolTable and StringTable
1917 SymbolTable::unlink(&g1IsAliveClosure);
1918 StringTable::unlink(&g1IsAliveClosure);
1919 }
1921 void ConcurrentMark::swapMarkBitMaps() {
1922 CMBitMapRO* temp = _prevMarkBitMap;
1923 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
1924 _nextMarkBitMap = (CMBitMap*) temp;
1925 }
1927 class CMRemarkTask: public AbstractGangTask {
1928 private:
1929 ConcurrentMark *_cm;
1931 public:
1932 void work(int worker_i) {
1933 // Since all available tasks are actually started, we should
1934 // only proceed if we're supposed to be actived.
1935 if ((size_t)worker_i < _cm->active_tasks()) {
1936 CMTask* task = _cm->task(worker_i);
1937 task->record_start_time();
1938 do {
1939 task->do_marking_step(1000000000.0 /* something very large */);
1940 } while (task->has_aborted() && !_cm->has_overflown());
1941 // If we overflow, then we do not want to restart. We instead
1942 // want to abort remark and do concurrent marking again.
1943 task->record_end_time();
1944 }
1945 }
1947 CMRemarkTask(ConcurrentMark* cm) :
1948 AbstractGangTask("Par Remark"), _cm(cm) { }
1949 };
1951 void ConcurrentMark::checkpointRootsFinalWork() {
1952 ResourceMark rm;
1953 HandleMark hm;
1954 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1956 g1h->ensure_parsability(false);
1958 if (G1CollectedHeap::use_parallel_gc_threads()) {
1959 G1CollectedHeap::StrongRootsScope srs(g1h);
1960 // this is remark, so we'll use up all available threads
1961 int active_workers = ParallelGCThreads;
1962 set_phase(active_workers, false);
1964 CMRemarkTask remarkTask(this);
1965 // We will start all available threads, even if we decide that the
1966 // active_workers will be fewer. The extra ones will just bail out
1967 // immediately.
1968 int n_workers = g1h->workers()->total_workers();
1969 g1h->set_par_threads(n_workers);
1970 g1h->workers()->run_task(&remarkTask);
1971 g1h->set_par_threads(0);
1972 } else {
1973 G1CollectedHeap::StrongRootsScope srs(g1h);
1974 // this is remark, so we'll use up all available threads
1975 int active_workers = 1;
1976 set_phase(active_workers, false);
1978 CMRemarkTask remarkTask(this);
1979 // We will start all available threads, even if we decide that the
1980 // active_workers will be fewer. The extra ones will just bail out
1981 // immediately.
1982 remarkTask.work(0);
1983 }
1984 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1985 guarantee(satb_mq_set.completed_buffers_num() == 0, "invariant");
1987 print_stats();
1989 if (!restart_for_overflow())
1990 set_non_marking_state();
1992 #if VERIFY_OBJS_PROCESSED
1993 if (_scan_obj_cl.objs_processed != ThreadLocalObjQueue::objs_enqueued) {
1994 gclog_or_tty->print_cr("Processed = %d, enqueued = %d.",
1995 _scan_obj_cl.objs_processed,
1996 ThreadLocalObjQueue::objs_enqueued);
1997 guarantee(_scan_obj_cl.objs_processed ==
1998 ThreadLocalObjQueue::objs_enqueued,
1999 "Different number of objs processed and enqueued.");
2000 }
2001 #endif
2002 }
2004 #ifndef PRODUCT
2006 class PrintReachableOopClosure: public OopClosure {
2007 private:
2008 G1CollectedHeap* _g1h;
2009 CMBitMapRO* _bitmap;
2010 outputStream* _out;
2011 bool _use_prev_marking;
2012 bool _all;
2014 public:
2015 PrintReachableOopClosure(CMBitMapRO* bitmap,
2016 outputStream* out,
2017 bool use_prev_marking,
2018 bool all) :
2019 _g1h(G1CollectedHeap::heap()),
2020 _bitmap(bitmap), _out(out), _use_prev_marking(use_prev_marking), _all(all) { }
2022 void do_oop(narrowOop* p) { do_oop_work(p); }
2023 void do_oop( oop* p) { do_oop_work(p); }
2025 template <class T> void do_oop_work(T* p) {
2026 oop obj = oopDesc::load_decode_heap_oop(p);
2027 const char* str = NULL;
2028 const char* str2 = "";
2030 if (obj == NULL) {
2031 str = "";
2032 } else if (!_g1h->is_in_g1_reserved(obj)) {
2033 str = " O";
2034 } else {
2035 HeapRegion* hr = _g1h->heap_region_containing(obj);
2036 guarantee(hr != NULL, "invariant");
2037 bool over_tams = false;
2038 if (_use_prev_marking) {
2039 over_tams = hr->obj_allocated_since_prev_marking(obj);
2040 } else {
2041 over_tams = hr->obj_allocated_since_next_marking(obj);
2042 }
2043 bool marked = _bitmap->isMarked((HeapWord*) obj);
2045 if (over_tams) {
2046 str = " >";
2047 if (marked) {
2048 str2 = " AND MARKED";
2049 }
2050 } else if (marked) {
2051 str = " M";
2052 } else {
2053 str = " NOT";
2054 }
2055 }
2057 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s",
2058 p, (void*) obj, str, str2);
2059 }
2060 };
2062 class PrintReachableObjectClosure : public ObjectClosure {
2063 private:
2064 CMBitMapRO* _bitmap;
2065 outputStream* _out;
2066 bool _use_prev_marking;
2067 bool _all;
2068 HeapRegion* _hr;
2070 public:
2071 PrintReachableObjectClosure(CMBitMapRO* bitmap,
2072 outputStream* out,
2073 bool use_prev_marking,
2074 bool all,
2075 HeapRegion* hr) :
2076 _bitmap(bitmap), _out(out),
2077 _use_prev_marking(use_prev_marking), _all(all), _hr(hr) { }
2079 void do_object(oop o) {
2080 bool over_tams;
2081 if (_use_prev_marking) {
2082 over_tams = _hr->obj_allocated_since_prev_marking(o);
2083 } else {
2084 over_tams = _hr->obj_allocated_since_next_marking(o);
2085 }
2086 bool marked = _bitmap->isMarked((HeapWord*) o);
2087 bool print_it = _all || over_tams || marked;
2089 if (print_it) {
2090 _out->print_cr(" "PTR_FORMAT"%s",
2091 o, (over_tams) ? " >" : (marked) ? " M" : "");
2092 PrintReachableOopClosure oopCl(_bitmap, _out, _use_prev_marking, _all);
2093 o->oop_iterate(&oopCl);
2094 }
2095 }
2096 };
2098 class PrintReachableRegionClosure : public HeapRegionClosure {
2099 private:
2100 CMBitMapRO* _bitmap;
2101 outputStream* _out;
2102 bool _use_prev_marking;
2103 bool _all;
2105 public:
2106 bool doHeapRegion(HeapRegion* hr) {
2107 HeapWord* b = hr->bottom();
2108 HeapWord* e = hr->end();
2109 HeapWord* t = hr->top();
2110 HeapWord* p = NULL;
2111 if (_use_prev_marking) {
2112 p = hr->prev_top_at_mark_start();
2113 } else {
2114 p = hr->next_top_at_mark_start();
2115 }
2116 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" "
2117 "TAMS: "PTR_FORMAT, b, e, t, p);
2118 _out->cr();
2120 HeapWord* from = b;
2121 HeapWord* to = t;
2123 if (to > from) {
2124 _out->print_cr("Objects in ["PTR_FORMAT", "PTR_FORMAT"]", from, to);
2125 _out->cr();
2126 PrintReachableObjectClosure ocl(_bitmap, _out,
2127 _use_prev_marking, _all, hr);
2128 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl);
2129 _out->cr();
2130 }
2132 return false;
2133 }
2135 PrintReachableRegionClosure(CMBitMapRO* bitmap,
2136 outputStream* out,
2137 bool use_prev_marking,
2138 bool all) :
2139 _bitmap(bitmap), _out(out), _use_prev_marking(use_prev_marking), _all(all) { }
2140 };
2142 void ConcurrentMark::print_reachable(const char* str,
2143 bool use_prev_marking,
2144 bool all) {
2145 gclog_or_tty->cr();
2146 gclog_or_tty->print_cr("== Doing heap dump... ");
2148 if (G1PrintReachableBaseFile == NULL) {
2149 gclog_or_tty->print_cr(" #### error: no base file defined");
2150 return;
2151 }
2153 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) >
2154 (JVM_MAXPATHLEN - 1)) {
2155 gclog_or_tty->print_cr(" #### error: file name too long");
2156 return;
2157 }
2159 char file_name[JVM_MAXPATHLEN];
2160 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str);
2161 gclog_or_tty->print_cr(" dumping to file %s", file_name);
2163 fileStream fout(file_name);
2164 if (!fout.is_open()) {
2165 gclog_or_tty->print_cr(" #### error: could not open file");
2166 return;
2167 }
2169 outputStream* out = &fout;
2171 CMBitMapRO* bitmap = NULL;
2172 if (use_prev_marking) {
2173 bitmap = _prevMarkBitMap;
2174 } else {
2175 bitmap = _nextMarkBitMap;
2176 }
2178 out->print_cr("-- USING %s", (use_prev_marking) ? "PTAMS" : "NTAMS");
2179 out->cr();
2181 out->print_cr("--- ITERATING OVER REGIONS");
2182 out->cr();
2183 PrintReachableRegionClosure rcl(bitmap, out, use_prev_marking, all);
2184 _g1h->heap_region_iterate(&rcl);
2185 out->cr();
2187 gclog_or_tty->print_cr(" done");
2188 gclog_or_tty->flush();
2189 }
2191 #endif // PRODUCT
2193 // This note is for drainAllSATBBuffers and the code in between.
2194 // In the future we could reuse a task to do this work during an
2195 // evacuation pause (since now tasks are not active and can be claimed
2196 // during an evacuation pause). This was a late change to the code and
2197 // is currently not being taken advantage of.
2199 class CMGlobalObjectClosure : public ObjectClosure {
2200 private:
2201 ConcurrentMark* _cm;
2203 public:
2204 void do_object(oop obj) {
2205 _cm->deal_with_reference(obj);
2206 }
2208 CMGlobalObjectClosure(ConcurrentMark* cm) : _cm(cm) { }
2209 };
2211 void ConcurrentMark::deal_with_reference(oop obj) {
2212 if (verbose_high())
2213 gclog_or_tty->print_cr("[global] we're dealing with reference "PTR_FORMAT,
2214 (void*) obj);
2217 HeapWord* objAddr = (HeapWord*) obj;
2218 assert(obj->is_oop_or_null(true /* ignore mark word */), "Error");
2219 if (_g1h->is_in_g1_reserved(objAddr)) {
2220 assert(obj != NULL, "is_in_g1_reserved should ensure this");
2221 HeapRegion* hr = _g1h->heap_region_containing(obj);
2222 if (_g1h->is_obj_ill(obj, hr)) {
2223 if (verbose_high())
2224 gclog_or_tty->print_cr("[global] "PTR_FORMAT" is not considered "
2225 "marked", (void*) obj);
2227 // we need to mark it first
2228 if (_nextMarkBitMap->parMark(objAddr)) {
2229 // No OrderAccess:store_load() is needed. It is implicit in the
2230 // CAS done in parMark(objAddr) above
2231 HeapWord* finger = _finger;
2232 if (objAddr < finger) {
2233 if (verbose_high())
2234 gclog_or_tty->print_cr("[global] below the global finger "
2235 "("PTR_FORMAT"), pushing it", finger);
2236 if (!mark_stack_push(obj)) {
2237 if (verbose_low())
2238 gclog_or_tty->print_cr("[global] global stack overflow during "
2239 "deal_with_reference");
2240 }
2241 }
2242 }
2243 }
2244 }
2245 }
2247 void ConcurrentMark::drainAllSATBBuffers() {
2248 CMGlobalObjectClosure oc(this);
2249 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2250 satb_mq_set.set_closure(&oc);
2252 while (satb_mq_set.apply_closure_to_completed_buffer()) {
2253 if (verbose_medium())
2254 gclog_or_tty->print_cr("[global] processed an SATB buffer");
2255 }
2257 // no need to check whether we should do this, as this is only
2258 // called during an evacuation pause
2259 satb_mq_set.iterate_closure_all_threads();
2261 satb_mq_set.set_closure(NULL);
2262 assert(satb_mq_set.completed_buffers_num() == 0, "invariant");
2263 }
2265 void ConcurrentMark::markPrev(oop p) {
2266 // Note we are overriding the read-only view of the prev map here, via
2267 // the cast.
2268 ((CMBitMap*)_prevMarkBitMap)->mark((HeapWord*)p);
2269 }
2271 void ConcurrentMark::clear(oop p) {
2272 assert(p != NULL && p->is_oop(), "expected an oop");
2273 HeapWord* addr = (HeapWord*)p;
2274 assert(addr >= _nextMarkBitMap->startWord() ||
2275 addr < _nextMarkBitMap->endWord(), "in a region");
2277 _nextMarkBitMap->clear(addr);
2278 }
2280 void ConcurrentMark::clearRangeBothMaps(MemRegion mr) {
2281 // Note we are overriding the read-only view of the prev map here, via
2282 // the cast.
2283 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2284 _nextMarkBitMap->clearRange(mr);
2285 }
2287 HeapRegion*
2288 ConcurrentMark::claim_region(int task_num) {
2289 // "checkpoint" the finger
2290 HeapWord* finger = _finger;
2292 // _heap_end will not change underneath our feet; it only changes at
2293 // yield points.
2294 while (finger < _heap_end) {
2295 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2297 // is the gap between reading the finger and doing the CAS too long?
2299 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
2300 HeapWord* bottom = curr_region->bottom();
2301 HeapWord* end = curr_region->end();
2302 HeapWord* limit = curr_region->next_top_at_mark_start();
2304 if (verbose_low())
2305 gclog_or_tty->print_cr("[%d] curr_region = "PTR_FORMAT" "
2306 "["PTR_FORMAT", "PTR_FORMAT"), "
2307 "limit = "PTR_FORMAT,
2308 task_num, curr_region, bottom, end, limit);
2310 HeapWord* res =
2311 (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2312 if (res == finger) {
2313 // we succeeded
2315 // notice that _finger == end cannot be guaranteed here since,
2316 // someone else might have moved the finger even further
2317 assert(_finger >= end, "the finger should have moved forward");
2319 if (verbose_low())
2320 gclog_or_tty->print_cr("[%d] we were successful with region = "
2321 PTR_FORMAT, task_num, curr_region);
2323 if (limit > bottom) {
2324 if (verbose_low())
2325 gclog_or_tty->print_cr("[%d] region "PTR_FORMAT" is not empty, "
2326 "returning it ", task_num, curr_region);
2327 return curr_region;
2328 } else {
2329 assert(limit == bottom,
2330 "the region limit should be at bottom");
2331 if (verbose_low())
2332 gclog_or_tty->print_cr("[%d] region "PTR_FORMAT" is empty, "
2333 "returning NULL", task_num, curr_region);
2334 // we return NULL and the caller should try calling
2335 // claim_region() again.
2336 return NULL;
2337 }
2338 } else {
2339 assert(_finger > finger, "the finger should have moved forward");
2340 if (verbose_low())
2341 gclog_or_tty->print_cr("[%d] somebody else moved the finger, "
2342 "global finger = "PTR_FORMAT", "
2343 "our finger = "PTR_FORMAT,
2344 task_num, _finger, finger);
2346 // read it again
2347 finger = _finger;
2348 }
2349 }
2351 return NULL;
2352 }
2354 bool ConcurrentMark::invalidate_aborted_regions_in_cset() {
2355 bool result = false;
2356 for (int i = 0; i < (int)_max_task_num; ++i) {
2357 CMTask* the_task = _tasks[i];
2358 MemRegion mr = the_task->aborted_region();
2359 if (mr.start() != NULL) {
2360 assert(mr.end() != NULL, "invariant");
2361 assert(mr.word_size() > 0, "invariant");
2362 HeapRegion* hr = _g1h->heap_region_containing(mr.start());
2363 assert(hr != NULL, "invariant");
2364 if (hr->in_collection_set()) {
2365 // The region points into the collection set
2366 the_task->set_aborted_region(MemRegion());
2367 result = true;
2368 }
2369 }
2370 }
2371 return result;
2372 }
2374 bool ConcurrentMark::has_aborted_regions() {
2375 for (int i = 0; i < (int)_max_task_num; ++i) {
2376 CMTask* the_task = _tasks[i];
2377 MemRegion mr = the_task->aborted_region();
2378 if (mr.start() != NULL) {
2379 assert(mr.end() != NULL, "invariant");
2380 assert(mr.word_size() > 0, "invariant");
2381 return true;
2382 }
2383 }
2384 return false;
2385 }
2387 void ConcurrentMark::oops_do(OopClosure* cl) {
2388 if (_markStack.size() > 0 && verbose_low())
2389 gclog_or_tty->print_cr("[global] scanning the global marking stack, "
2390 "size = %d", _markStack.size());
2391 // we first iterate over the contents of the mark stack...
2392 _markStack.oops_do(cl);
2394 for (int i = 0; i < (int)_max_task_num; ++i) {
2395 OopTaskQueue* queue = _task_queues->queue((int)i);
2397 if (queue->size() > 0 && verbose_low())
2398 gclog_or_tty->print_cr("[global] scanning task queue of task %d, "
2399 "size = %d", i, queue->size());
2401 // ...then over the contents of the all the task queues.
2402 queue->oops_do(cl);
2403 }
2405 // Invalidate any entries, that are in the region stack, that
2406 // point into the collection set
2407 if (_regionStack.invalidate_entries_into_cset()) {
2408 // otherwise, any gray objects copied during the evacuation pause
2409 // might not be visited.
2410 assert(_should_gray_objects, "invariant");
2411 }
2413 // Invalidate any aborted regions, recorded in the individual CM
2414 // tasks, that point into the collection set.
2415 if (invalidate_aborted_regions_in_cset()) {
2416 // otherwise, any gray objects copied during the evacuation pause
2417 // might not be visited.
2418 assert(_should_gray_objects, "invariant");
2419 }
2421 }
2423 void ConcurrentMark::clear_marking_state() {
2424 _markStack.setEmpty();
2425 _markStack.clear_overflow();
2426 _regionStack.setEmpty();
2427 _regionStack.clear_overflow();
2428 clear_has_overflown();
2429 _finger = _heap_start;
2431 for (int i = 0; i < (int)_max_task_num; ++i) {
2432 OopTaskQueue* queue = _task_queues->queue(i);
2433 queue->set_empty();
2434 // Clear any partial regions from the CMTasks
2435 _tasks[i]->clear_aborted_region();
2436 }
2437 }
2439 void ConcurrentMark::print_stats() {
2440 if (verbose_stats()) {
2441 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2442 for (size_t i = 0; i < _active_tasks; ++i) {
2443 _tasks[i]->print_stats();
2444 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2445 }
2446 }
2447 }
2449 class CSMarkOopClosure: public OopClosure {
2450 friend class CSMarkBitMapClosure;
2452 G1CollectedHeap* _g1h;
2453 CMBitMap* _bm;
2454 ConcurrentMark* _cm;
2455 oop* _ms;
2456 jint* _array_ind_stack;
2457 int _ms_size;
2458 int _ms_ind;
2459 int _array_increment;
2461 bool push(oop obj, int arr_ind = 0) {
2462 if (_ms_ind == _ms_size) {
2463 gclog_or_tty->print_cr("Mark stack is full.");
2464 return false;
2465 }
2466 _ms[_ms_ind] = obj;
2467 if (obj->is_objArray()) _array_ind_stack[_ms_ind] = arr_ind;
2468 _ms_ind++;
2469 return true;
2470 }
2472 oop pop() {
2473 if (_ms_ind == 0) return NULL;
2474 else {
2475 _ms_ind--;
2476 return _ms[_ms_ind];
2477 }
2478 }
2480 template <class T> bool drain() {
2481 while (_ms_ind > 0) {
2482 oop obj = pop();
2483 assert(obj != NULL, "Since index was non-zero.");
2484 if (obj->is_objArray()) {
2485 jint arr_ind = _array_ind_stack[_ms_ind];
2486 objArrayOop aobj = objArrayOop(obj);
2487 jint len = aobj->length();
2488 jint next_arr_ind = arr_ind + _array_increment;
2489 if (next_arr_ind < len) {
2490 push(obj, next_arr_ind);
2491 }
2492 // Now process this portion of this one.
2493 int lim = MIN2(next_arr_ind, len);
2494 for (int j = arr_ind; j < lim; j++) {
2495 do_oop(aobj->objArrayOopDesc::obj_at_addr<T>(j));
2496 }
2498 } else {
2499 obj->oop_iterate(this);
2500 }
2501 if (abort()) return false;
2502 }
2503 return true;
2504 }
2506 public:
2507 CSMarkOopClosure(ConcurrentMark* cm, int ms_size) :
2508 _g1h(G1CollectedHeap::heap()),
2509 _cm(cm),
2510 _bm(cm->nextMarkBitMap()),
2511 _ms_size(ms_size), _ms_ind(0),
2512 _ms(NEW_C_HEAP_ARRAY(oop, ms_size)),
2513 _array_ind_stack(NEW_C_HEAP_ARRAY(jint, ms_size)),
2514 _array_increment(MAX2(ms_size/8, 16))
2515 {}
2517 ~CSMarkOopClosure() {
2518 FREE_C_HEAP_ARRAY(oop, _ms);
2519 FREE_C_HEAP_ARRAY(jint, _array_ind_stack);
2520 }
2522 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2523 virtual void do_oop( oop* p) { do_oop_work(p); }
2525 template <class T> void do_oop_work(T* p) {
2526 T heap_oop = oopDesc::load_heap_oop(p);
2527 if (oopDesc::is_null(heap_oop)) return;
2528 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2529 if (obj->is_forwarded()) {
2530 // If the object has already been forwarded, we have to make sure
2531 // that it's marked. So follow the forwarding pointer. Note that
2532 // this does the right thing for self-forwarding pointers in the
2533 // evacuation failure case.
2534 obj = obj->forwardee();
2535 }
2536 HeapRegion* hr = _g1h->heap_region_containing(obj);
2537 if (hr != NULL) {
2538 if (hr->in_collection_set()) {
2539 if (_g1h->is_obj_ill(obj)) {
2540 _bm->mark((HeapWord*)obj);
2541 if (!push(obj)) {
2542 gclog_or_tty->print_cr("Setting abort in CSMarkOopClosure because push failed.");
2543 set_abort();
2544 }
2545 }
2546 } else {
2547 // Outside the collection set; we need to gray it
2548 _cm->deal_with_reference(obj);
2549 }
2550 }
2551 }
2552 };
2554 class CSMarkBitMapClosure: public BitMapClosure {
2555 G1CollectedHeap* _g1h;
2556 CMBitMap* _bitMap;
2557 ConcurrentMark* _cm;
2558 CSMarkOopClosure _oop_cl;
2559 public:
2560 CSMarkBitMapClosure(ConcurrentMark* cm, int ms_size) :
2561 _g1h(G1CollectedHeap::heap()),
2562 _bitMap(cm->nextMarkBitMap()),
2563 _oop_cl(cm, ms_size)
2564 {}
2566 ~CSMarkBitMapClosure() {}
2568 bool do_bit(size_t offset) {
2569 // convert offset into a HeapWord*
2570 HeapWord* addr = _bitMap->offsetToHeapWord(offset);
2571 assert(_bitMap->endWord() && addr < _bitMap->endWord(),
2572 "address out of range");
2573 assert(_bitMap->isMarked(addr), "tautology");
2574 oop obj = oop(addr);
2575 if (!obj->is_forwarded()) {
2576 if (!_oop_cl.push(obj)) return false;
2577 if (UseCompressedOops) {
2578 if (!_oop_cl.drain<narrowOop>()) return false;
2579 } else {
2580 if (!_oop_cl.drain<oop>()) return false;
2581 }
2582 }
2583 // Otherwise...
2584 return true;
2585 }
2586 };
2589 class CompleteMarkingInCSHRClosure: public HeapRegionClosure {
2590 CMBitMap* _bm;
2591 CSMarkBitMapClosure _bit_cl;
2592 enum SomePrivateConstants {
2593 MSSize = 1000
2594 };
2595 bool _completed;
2596 public:
2597 CompleteMarkingInCSHRClosure(ConcurrentMark* cm) :
2598 _bm(cm->nextMarkBitMap()),
2599 _bit_cl(cm, MSSize),
2600 _completed(true)
2601 {}
2603 ~CompleteMarkingInCSHRClosure() {}
2605 bool doHeapRegion(HeapRegion* r) {
2606 if (!r->evacuation_failed()) {
2607 MemRegion mr = MemRegion(r->bottom(), r->next_top_at_mark_start());
2608 if (!mr.is_empty()) {
2609 if (!_bm->iterate(&_bit_cl, mr)) {
2610 _completed = false;
2611 return true;
2612 }
2613 }
2614 }
2615 return false;
2616 }
2618 bool completed() { return _completed; }
2619 };
2621 class ClearMarksInHRClosure: public HeapRegionClosure {
2622 CMBitMap* _bm;
2623 public:
2624 ClearMarksInHRClosure(CMBitMap* bm): _bm(bm) { }
2626 bool doHeapRegion(HeapRegion* r) {
2627 if (!r->used_region().is_empty() && !r->evacuation_failed()) {
2628 MemRegion usedMR = r->used_region();
2629 _bm->clearRange(r->used_region());
2630 }
2631 return false;
2632 }
2633 };
2635 void ConcurrentMark::complete_marking_in_collection_set() {
2636 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2638 if (!g1h->mark_in_progress()) {
2639 g1h->g1_policy()->record_mark_closure_time(0.0);
2640 return;
2641 }
2643 int i = 1;
2644 double start = os::elapsedTime();
2645 while (true) {
2646 i++;
2647 CompleteMarkingInCSHRClosure cmplt(this);
2648 g1h->collection_set_iterate(&cmplt);
2649 if (cmplt.completed()) break;
2650 }
2651 double end_time = os::elapsedTime();
2652 double elapsed_time_ms = (end_time - start) * 1000.0;
2653 g1h->g1_policy()->record_mark_closure_time(elapsed_time_ms);
2655 ClearMarksInHRClosure clr(nextMarkBitMap());
2656 g1h->collection_set_iterate(&clr);
2657 }
2659 // The next two methods deal with the following optimisation. Some
2660 // objects are gray by being marked and located above the finger. If
2661 // they are copied, during an evacuation pause, below the finger then
2662 // the need to be pushed on the stack. The observation is that, if
2663 // there are no regions in the collection set located above the
2664 // finger, then the above cannot happen, hence we do not need to
2665 // explicitly gray any objects when copying them to below the
2666 // finger. The global stack will be scanned to ensure that, if it
2667 // points to objects being copied, it will update their
2668 // location. There is a tricky situation with the gray objects in
2669 // region stack that are being coped, however. See the comment in
2670 // newCSet().
2672 void ConcurrentMark::newCSet() {
2673 if (!concurrent_marking_in_progress())
2674 // nothing to do if marking is not in progress
2675 return;
2677 // find what the lowest finger is among the global and local fingers
2678 _min_finger = _finger;
2679 for (int i = 0; i < (int)_max_task_num; ++i) {
2680 CMTask* task = _tasks[i];
2681 HeapWord* task_finger = task->finger();
2682 if (task_finger != NULL && task_finger < _min_finger)
2683 _min_finger = task_finger;
2684 }
2686 _should_gray_objects = false;
2688 // This fixes a very subtle and fustrating bug. It might be the case
2689 // that, during en evacuation pause, heap regions that contain
2690 // objects that are gray (by being in regions contained in the
2691 // region stack) are included in the collection set. Since such gray
2692 // objects will be moved, and because it's not easy to redirect
2693 // region stack entries to point to a new location (because objects
2694 // in one region might be scattered to multiple regions after they
2695 // are copied), one option is to ensure that all marked objects
2696 // copied during a pause are pushed on the stack. Notice, however,
2697 // that this problem can only happen when the region stack is not
2698 // empty during an evacuation pause. So, we make the fix a bit less
2699 // conservative and ensure that regions are pushed on the stack,
2700 // irrespective whether all collection set regions are below the
2701 // finger, if the region stack is not empty. This is expected to be
2702 // a rare case, so I don't think it's necessary to be smarted about it.
2703 if (!region_stack_empty() || has_aborted_regions())
2704 _should_gray_objects = true;
2705 }
2707 void ConcurrentMark::registerCSetRegion(HeapRegion* hr) {
2708 if (!concurrent_marking_in_progress())
2709 return;
2711 HeapWord* region_end = hr->end();
2712 if (region_end > _min_finger)
2713 _should_gray_objects = true;
2714 }
2716 // abandon current marking iteration due to a Full GC
2717 void ConcurrentMark::abort() {
2718 // Clear all marks to force marking thread to do nothing
2719 _nextMarkBitMap->clearAll();
2720 // Empty mark stack
2721 clear_marking_state();
2722 for (int i = 0; i < (int)_max_task_num; ++i) {
2723 _tasks[i]->clear_region_fields();
2724 }
2725 _has_aborted = true;
2727 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2728 satb_mq_set.abandon_partial_marking();
2729 // This can be called either during or outside marking, we'll read
2730 // the expected_active value from the SATB queue set.
2731 satb_mq_set.set_active_all_threads(
2732 false, /* new active value */
2733 satb_mq_set.is_active() /* expected_active */);
2734 }
2736 static void print_ms_time_info(const char* prefix, const char* name,
2737 NumberSeq& ns) {
2738 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2739 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2740 if (ns.num() > 0) {
2741 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2742 prefix, ns.sd(), ns.maximum());
2743 }
2744 }
2746 void ConcurrentMark::print_summary_info() {
2747 gclog_or_tty->print_cr(" Concurrent marking:");
2748 print_ms_time_info(" ", "init marks", _init_times);
2749 print_ms_time_info(" ", "remarks", _remark_times);
2750 {
2751 print_ms_time_info(" ", "final marks", _remark_mark_times);
2752 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2754 }
2755 print_ms_time_info(" ", "cleanups", _cleanup_times);
2756 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
2757 _total_counting_time,
2758 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
2759 (double)_cleanup_times.num()
2760 : 0.0));
2761 if (G1ScrubRemSets) {
2762 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
2763 _total_rs_scrub_time,
2764 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
2765 (double)_cleanup_times.num()
2766 : 0.0));
2767 }
2768 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
2769 (_init_times.sum() + _remark_times.sum() +
2770 _cleanup_times.sum())/1000.0);
2771 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
2772 "(%8.2f s marking, %8.2f s counting).",
2773 cmThread()->vtime_accum(),
2774 cmThread()->vtime_mark_accum(),
2775 cmThread()->vtime_count_accum());
2776 }
2778 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2779 _parallel_workers->print_worker_threads_on(st);
2780 }
2782 // Closures
2783 // XXX: there seems to be a lot of code duplication here;
2784 // should refactor and consolidate the shared code.
2786 // This closure is used to mark refs into the CMS generation in
2787 // the CMS bit map. Called at the first checkpoint.
2789 // We take a break if someone is trying to stop the world.
2790 bool ConcurrentMark::do_yield_check(int worker_i) {
2791 if (should_yield()) {
2792 if (worker_i == 0)
2793 _g1h->g1_policy()->record_concurrent_pause();
2794 cmThread()->yield();
2795 if (worker_i == 0)
2796 _g1h->g1_policy()->record_concurrent_pause_end();
2797 return true;
2798 } else {
2799 return false;
2800 }
2801 }
2803 bool ConcurrentMark::should_yield() {
2804 return cmThread()->should_yield();
2805 }
2807 bool ConcurrentMark::containing_card_is_marked(void* p) {
2808 size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1);
2809 return _card_bm.at(offset >> CardTableModRefBS::card_shift);
2810 }
2812 bool ConcurrentMark::containing_cards_are_marked(void* start,
2813 void* last) {
2814 return
2815 containing_card_is_marked(start) &&
2816 containing_card_is_marked(last);
2817 }
2819 #ifndef PRODUCT
2820 // for debugging purposes
2821 void ConcurrentMark::print_finger() {
2822 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
2823 _heap_start, _heap_end, _finger);
2824 for (int i = 0; i < (int) _max_task_num; ++i) {
2825 gclog_or_tty->print(" %d: "PTR_FORMAT, i, _tasks[i]->finger());
2826 }
2827 gclog_or_tty->print_cr("");
2828 }
2829 #endif
2831 // Closure for iteration over bitmaps
2832 class CMBitMapClosure : public BitMapClosure {
2833 private:
2834 // the bitmap that is being iterated over
2835 CMBitMap* _nextMarkBitMap;
2836 ConcurrentMark* _cm;
2837 CMTask* _task;
2838 // true if we're scanning a heap region claimed by the task (so that
2839 // we move the finger along), false if we're not, i.e. currently when
2840 // scanning a heap region popped from the region stack (so that we
2841 // do not move the task finger along; it'd be a mistake if we did so).
2842 bool _scanning_heap_region;
2844 public:
2845 CMBitMapClosure(CMTask *task,
2846 ConcurrentMark* cm,
2847 CMBitMap* nextMarkBitMap)
2848 : _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
2850 void set_scanning_heap_region(bool scanning_heap_region) {
2851 _scanning_heap_region = scanning_heap_region;
2852 }
2854 bool do_bit(size_t offset) {
2855 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
2856 assert(_nextMarkBitMap->isMarked(addr), "invariant");
2857 assert( addr < _cm->finger(), "invariant");
2859 if (_scanning_heap_region) {
2860 statsOnly( _task->increase_objs_found_on_bitmap() );
2861 assert(addr >= _task->finger(), "invariant");
2862 // We move that task's local finger along.
2863 _task->move_finger_to(addr);
2864 } else {
2865 // We move the task's region finger along.
2866 _task->move_region_finger_to(addr);
2867 }
2869 _task->scan_object(oop(addr));
2870 // we only partially drain the local queue and global stack
2871 _task->drain_local_queue(true);
2872 _task->drain_global_stack(true);
2874 // if the has_aborted flag has been raised, we need to bail out of
2875 // the iteration
2876 return !_task->has_aborted();
2877 }
2878 };
2880 // Closure for iterating over objects, currently only used for
2881 // processing SATB buffers.
2882 class CMObjectClosure : public ObjectClosure {
2883 private:
2884 CMTask* _task;
2886 public:
2887 void do_object(oop obj) {
2888 _task->deal_with_reference(obj);
2889 }
2891 CMObjectClosure(CMTask* task) : _task(task) { }
2892 };
2894 // Closure for iterating over object fields
2895 class CMOopClosure : public OopClosure {
2896 private:
2897 G1CollectedHeap* _g1h;
2898 ConcurrentMark* _cm;
2899 CMTask* _task;
2901 public:
2902 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2903 virtual void do_oop( oop* p) { do_oop_work(p); }
2905 template <class T> void do_oop_work(T* p) {
2906 assert(_g1h->is_in_g1_reserved((HeapWord*) p), "invariant");
2907 assert(!_g1h->heap_region_containing((HeapWord*) p)->is_on_free_list(),
2908 "invariant");
2910 oop obj = oopDesc::load_decode_heap_oop(p);
2911 if (_cm->verbose_high())
2912 gclog_or_tty->print_cr("[%d] we're looking at location "
2913 "*"PTR_FORMAT" = "PTR_FORMAT,
2914 _task->task_id(), p, (void*) obj);
2915 _task->deal_with_reference(obj);
2916 }
2918 CMOopClosure(G1CollectedHeap* g1h,
2919 ConcurrentMark* cm,
2920 CMTask* task)
2921 : _g1h(g1h), _cm(cm), _task(task) { }
2922 };
2924 void CMTask::setup_for_region(HeapRegion* hr) {
2925 // Separated the asserts so that we know which one fires.
2926 assert(hr != NULL,
2927 "claim_region() should have filtered out continues humongous regions");
2928 assert(!hr->continuesHumongous(),
2929 "claim_region() should have filtered out continues humongous regions");
2931 if (_cm->verbose_low())
2932 gclog_or_tty->print_cr("[%d] setting up for region "PTR_FORMAT,
2933 _task_id, hr);
2935 _curr_region = hr;
2936 _finger = hr->bottom();
2937 update_region_limit();
2938 }
2940 void CMTask::update_region_limit() {
2941 HeapRegion* hr = _curr_region;
2942 HeapWord* bottom = hr->bottom();
2943 HeapWord* limit = hr->next_top_at_mark_start();
2945 if (limit == bottom) {
2946 if (_cm->verbose_low())
2947 gclog_or_tty->print_cr("[%d] found an empty region "
2948 "["PTR_FORMAT", "PTR_FORMAT")",
2949 _task_id, bottom, limit);
2950 // The region was collected underneath our feet.
2951 // We set the finger to bottom to ensure that the bitmap
2952 // iteration that will follow this will not do anything.
2953 // (this is not a condition that holds when we set the region up,
2954 // as the region is not supposed to be empty in the first place)
2955 _finger = bottom;
2956 } else if (limit >= _region_limit) {
2957 assert(limit >= _finger, "peace of mind");
2958 } else {
2959 assert(limit < _region_limit, "only way to get here");
2960 // This can happen under some pretty unusual circumstances. An
2961 // evacuation pause empties the region underneath our feet (NTAMS
2962 // at bottom). We then do some allocation in the region (NTAMS
2963 // stays at bottom), followed by the region being used as a GC
2964 // alloc region (NTAMS will move to top() and the objects
2965 // originally below it will be grayed). All objects now marked in
2966 // the region are explicitly grayed, if below the global finger,
2967 // and we do not need in fact to scan anything else. So, we simply
2968 // set _finger to be limit to ensure that the bitmap iteration
2969 // doesn't do anything.
2970 _finger = limit;
2971 }
2973 _region_limit = limit;
2974 }
2976 void CMTask::giveup_current_region() {
2977 assert(_curr_region != NULL, "invariant");
2978 if (_cm->verbose_low())
2979 gclog_or_tty->print_cr("[%d] giving up region "PTR_FORMAT,
2980 _task_id, _curr_region);
2981 clear_region_fields();
2982 }
2984 void CMTask::clear_region_fields() {
2985 // Values for these three fields that indicate that we're not
2986 // holding on to a region.
2987 _curr_region = NULL;
2988 _finger = NULL;
2989 _region_limit = NULL;
2991 _region_finger = NULL;
2992 }
2994 void CMTask::reset(CMBitMap* nextMarkBitMap) {
2995 guarantee(nextMarkBitMap != NULL, "invariant");
2997 if (_cm->verbose_low())
2998 gclog_or_tty->print_cr("[%d] resetting", _task_id);
3000 _nextMarkBitMap = nextMarkBitMap;
3001 clear_region_fields();
3002 assert(_aborted_region.is_empty(), "should have been cleared");
3004 _calls = 0;
3005 _elapsed_time_ms = 0.0;
3006 _termination_time_ms = 0.0;
3007 _termination_start_time_ms = 0.0;
3009 #if _MARKING_STATS_
3010 _local_pushes = 0;
3011 _local_pops = 0;
3012 _local_max_size = 0;
3013 _objs_scanned = 0;
3014 _global_pushes = 0;
3015 _global_pops = 0;
3016 _global_max_size = 0;
3017 _global_transfers_to = 0;
3018 _global_transfers_from = 0;
3019 _region_stack_pops = 0;
3020 _regions_claimed = 0;
3021 _objs_found_on_bitmap = 0;
3022 _satb_buffers_processed = 0;
3023 _steal_attempts = 0;
3024 _steals = 0;
3025 _aborted = 0;
3026 _aborted_overflow = 0;
3027 _aborted_cm_aborted = 0;
3028 _aborted_yield = 0;
3029 _aborted_timed_out = 0;
3030 _aborted_satb = 0;
3031 _aborted_termination = 0;
3032 #endif // _MARKING_STATS_
3033 }
3035 bool CMTask::should_exit_termination() {
3036 regular_clock_call();
3037 // This is called when we are in the termination protocol. We should
3038 // quit if, for some reason, this task wants to abort or the global
3039 // stack is not empty (this means that we can get work from it).
3040 return !_cm->mark_stack_empty() || has_aborted();
3041 }
3043 // This determines whether the method below will check both the local
3044 // and global fingers when determining whether to push on the stack a
3045 // gray object (value 1) or whether it will only check the global one
3046 // (value 0). The tradeoffs are that the former will be a bit more
3047 // accurate and possibly push less on the stack, but it might also be
3048 // a little bit slower.
3050 #define _CHECK_BOTH_FINGERS_ 1
3052 void CMTask::deal_with_reference(oop obj) {
3053 if (_cm->verbose_high())
3054 gclog_or_tty->print_cr("[%d] we're dealing with reference = "PTR_FORMAT,
3055 _task_id, (void*) obj);
3057 ++_refs_reached;
3059 HeapWord* objAddr = (HeapWord*) obj;
3060 assert(obj->is_oop_or_null(true /* ignore mark word */), "Error");
3061 if (_g1h->is_in_g1_reserved(objAddr)) {
3062 assert(obj != NULL, "is_in_g1_reserved should ensure this");
3063 HeapRegion* hr = _g1h->heap_region_containing(obj);
3064 if (_g1h->is_obj_ill(obj, hr)) {
3065 if (_cm->verbose_high())
3066 gclog_or_tty->print_cr("[%d] "PTR_FORMAT" is not considered marked",
3067 _task_id, (void*) obj);
3069 // we need to mark it first
3070 if (_nextMarkBitMap->parMark(objAddr)) {
3071 // No OrderAccess:store_load() is needed. It is implicit in the
3072 // CAS done in parMark(objAddr) above
3073 HeapWord* global_finger = _cm->finger();
3075 #if _CHECK_BOTH_FINGERS_
3076 // we will check both the local and global fingers
3078 if (_finger != NULL && objAddr < _finger) {
3079 if (_cm->verbose_high())
3080 gclog_or_tty->print_cr("[%d] below the local finger ("PTR_FORMAT"), "
3081 "pushing it", _task_id, _finger);
3082 push(obj);
3083 } else if (_curr_region != NULL && objAddr < _region_limit) {
3084 // do nothing
3085 } else if (objAddr < global_finger) {
3086 // Notice that the global finger might be moving forward
3087 // concurrently. This is not a problem. In the worst case, we
3088 // mark the object while it is above the global finger and, by
3089 // the time we read the global finger, it has moved forward
3090 // passed this object. In this case, the object will probably
3091 // be visited when a task is scanning the region and will also
3092 // be pushed on the stack. So, some duplicate work, but no
3093 // correctness problems.
3095 if (_cm->verbose_high())
3096 gclog_or_tty->print_cr("[%d] below the global finger "
3097 "("PTR_FORMAT"), pushing it",
3098 _task_id, global_finger);
3099 push(obj);
3100 } else {
3101 // do nothing
3102 }
3103 #else // _CHECK_BOTH_FINGERS_
3104 // we will only check the global finger
3106 if (objAddr < global_finger) {
3107 // see long comment above
3109 if (_cm->verbose_high())
3110 gclog_or_tty->print_cr("[%d] below the global finger "
3111 "("PTR_FORMAT"), pushing it",
3112 _task_id, global_finger);
3113 push(obj);
3114 }
3115 #endif // _CHECK_BOTH_FINGERS_
3116 }
3117 }
3118 }
3119 }
3121 void CMTask::push(oop obj) {
3122 HeapWord* objAddr = (HeapWord*) obj;
3123 assert(_g1h->is_in_g1_reserved(objAddr), "invariant");
3124 assert(!_g1h->heap_region_containing(objAddr)->is_on_free_list(),
3125 "invariant");
3126 assert(!_g1h->is_obj_ill(obj), "invariant");
3127 assert(_nextMarkBitMap->isMarked(objAddr), "invariant");
3129 if (_cm->verbose_high())
3130 gclog_or_tty->print_cr("[%d] pushing "PTR_FORMAT, _task_id, (void*) obj);
3132 if (!_task_queue->push(obj)) {
3133 // The local task queue looks full. We need to push some entries
3134 // to the global stack.
3136 if (_cm->verbose_medium())
3137 gclog_or_tty->print_cr("[%d] task queue overflow, "
3138 "moving entries to the global stack",
3139 _task_id);
3140 move_entries_to_global_stack();
3142 // this should succeed since, even if we overflow the global
3143 // stack, we should have definitely removed some entries from the
3144 // local queue. So, there must be space on it.
3145 bool success = _task_queue->push(obj);
3146 assert(success, "invariant");
3147 }
3149 statsOnly( int tmp_size = _task_queue->size();
3150 if (tmp_size > _local_max_size)
3151 _local_max_size = tmp_size;
3152 ++_local_pushes );
3153 }
3155 void CMTask::reached_limit() {
3156 assert(_words_scanned >= _words_scanned_limit ||
3157 _refs_reached >= _refs_reached_limit ,
3158 "shouldn't have been called otherwise");
3159 regular_clock_call();
3160 }
3162 void CMTask::regular_clock_call() {
3163 if (has_aborted())
3164 return;
3166 // First, we need to recalculate the words scanned and refs reached
3167 // limits for the next clock call.
3168 recalculate_limits();
3170 // During the regular clock call we do the following
3172 // (1) If an overflow has been flagged, then we abort.
3173 if (_cm->has_overflown()) {
3174 set_has_aborted();
3175 return;
3176 }
3178 // If we are not concurrent (i.e. we're doing remark) we don't need
3179 // to check anything else. The other steps are only needed during
3180 // the concurrent marking phase.
3181 if (!concurrent())
3182 return;
3184 // (2) If marking has been aborted for Full GC, then we also abort.
3185 if (_cm->has_aborted()) {
3186 set_has_aborted();
3187 statsOnly( ++_aborted_cm_aborted );
3188 return;
3189 }
3191 double curr_time_ms = os::elapsedVTime() * 1000.0;
3193 // (3) If marking stats are enabled, then we update the step history.
3194 #if _MARKING_STATS_
3195 if (_words_scanned >= _words_scanned_limit)
3196 ++_clock_due_to_scanning;
3197 if (_refs_reached >= _refs_reached_limit)
3198 ++_clock_due_to_marking;
3200 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3201 _interval_start_time_ms = curr_time_ms;
3202 _all_clock_intervals_ms.add(last_interval_ms);
3204 if (_cm->verbose_medium()) {
3205 gclog_or_tty->print_cr("[%d] regular clock, interval = %1.2lfms, "
3206 "scanned = %d%s, refs reached = %d%s",
3207 _task_id, last_interval_ms,
3208 _words_scanned,
3209 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3210 _refs_reached,
3211 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3212 }
3213 #endif // _MARKING_STATS_
3215 // (4) We check whether we should yield. If we have to, then we abort.
3216 if (_cm->should_yield()) {
3217 // We should yield. To do this we abort the task. The caller is
3218 // responsible for yielding.
3219 set_has_aborted();
3220 statsOnly( ++_aborted_yield );
3221 return;
3222 }
3224 // (5) We check whether we've reached our time quota. If we have,
3225 // then we abort.
3226 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3227 if (elapsed_time_ms > _time_target_ms) {
3228 set_has_aborted();
3229 _has_aborted_timed_out = true;
3230 statsOnly( ++_aborted_timed_out );
3231 return;
3232 }
3234 // (6) Finally, we check whether there are enough completed STAB
3235 // buffers available for processing. If there are, we abort.
3236 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3237 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3238 if (_cm->verbose_low())
3239 gclog_or_tty->print_cr("[%d] aborting to deal with pending SATB buffers",
3240 _task_id);
3241 // we do need to process SATB buffers, we'll abort and restart
3242 // the marking task to do so
3243 set_has_aborted();
3244 statsOnly( ++_aborted_satb );
3245 return;
3246 }
3247 }
3249 void CMTask::recalculate_limits() {
3250 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3251 _words_scanned_limit = _real_words_scanned_limit;
3253 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3254 _refs_reached_limit = _real_refs_reached_limit;
3255 }
3257 void CMTask::decrease_limits() {
3258 // This is called when we believe that we're going to do an infrequent
3259 // operation which will increase the per byte scanned cost (i.e. move
3260 // entries to/from the global stack). It basically tries to decrease the
3261 // scanning limit so that the clock is called earlier.
3263 if (_cm->verbose_medium())
3264 gclog_or_tty->print_cr("[%d] decreasing limits", _task_id);
3266 _words_scanned_limit = _real_words_scanned_limit -
3267 3 * words_scanned_period / 4;
3268 _refs_reached_limit = _real_refs_reached_limit -
3269 3 * refs_reached_period / 4;
3270 }
3272 void CMTask::move_entries_to_global_stack() {
3273 // local array where we'll store the entries that will be popped
3274 // from the local queue
3275 oop buffer[global_stack_transfer_size];
3277 int n = 0;
3278 oop obj;
3279 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3280 buffer[n] = obj;
3281 ++n;
3282 }
3284 if (n > 0) {
3285 // we popped at least one entry from the local queue
3287 statsOnly( ++_global_transfers_to; _local_pops += n );
3289 if (!_cm->mark_stack_push(buffer, n)) {
3290 if (_cm->verbose_low())
3291 gclog_or_tty->print_cr("[%d] aborting due to global stack overflow", _task_id);
3292 set_has_aborted();
3293 } else {
3294 // the transfer was successful
3296 if (_cm->verbose_medium())
3297 gclog_or_tty->print_cr("[%d] pushed %d entries to the global stack",
3298 _task_id, n);
3299 statsOnly( int tmp_size = _cm->mark_stack_size();
3300 if (tmp_size > _global_max_size)
3301 _global_max_size = tmp_size;
3302 _global_pushes += n );
3303 }
3304 }
3306 // this operation was quite expensive, so decrease the limits
3307 decrease_limits();
3308 }
3310 void CMTask::get_entries_from_global_stack() {
3311 // local array where we'll store the entries that will be popped
3312 // from the global stack.
3313 oop buffer[global_stack_transfer_size];
3314 int n;
3315 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3316 assert(n <= global_stack_transfer_size,
3317 "we should not pop more than the given limit");
3318 if (n > 0) {
3319 // yes, we did actually pop at least one entry
3321 statsOnly( ++_global_transfers_from; _global_pops += n );
3322 if (_cm->verbose_medium())
3323 gclog_or_tty->print_cr("[%d] popped %d entries from the global stack",
3324 _task_id, n);
3325 for (int i = 0; i < n; ++i) {
3326 bool success = _task_queue->push(buffer[i]);
3327 // We only call this when the local queue is empty or under a
3328 // given target limit. So, we do not expect this push to fail.
3329 assert(success, "invariant");
3330 }
3332 statsOnly( int tmp_size = _task_queue->size();
3333 if (tmp_size > _local_max_size)
3334 _local_max_size = tmp_size;
3335 _local_pushes += n );
3336 }
3338 // this operation was quite expensive, so decrease the limits
3339 decrease_limits();
3340 }
3342 void CMTask::drain_local_queue(bool partially) {
3343 if (has_aborted())
3344 return;
3346 // Decide what the target size is, depending whether we're going to
3347 // drain it partially (so that other tasks can steal if they run out
3348 // of things to do) or totally (at the very end).
3349 size_t target_size;
3350 if (partially)
3351 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3352 else
3353 target_size = 0;
3355 if (_task_queue->size() > target_size) {
3356 if (_cm->verbose_high())
3357 gclog_or_tty->print_cr("[%d] draining local queue, target size = %d",
3358 _task_id, target_size);
3360 oop obj;
3361 bool ret = _task_queue->pop_local(obj);
3362 while (ret) {
3363 statsOnly( ++_local_pops );
3365 if (_cm->verbose_high())
3366 gclog_or_tty->print_cr("[%d] popped "PTR_FORMAT, _task_id,
3367 (void*) obj);
3369 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3370 assert(!_g1h->heap_region_containing(obj)->is_on_free_list(),
3371 "invariant");
3373 scan_object(obj);
3375 if (_task_queue->size() <= target_size || has_aborted())
3376 ret = false;
3377 else
3378 ret = _task_queue->pop_local(obj);
3379 }
3381 if (_cm->verbose_high())
3382 gclog_or_tty->print_cr("[%d] drained local queue, size = %d",
3383 _task_id, _task_queue->size());
3384 }
3385 }
3387 void CMTask::drain_global_stack(bool partially) {
3388 if (has_aborted())
3389 return;
3391 // We have a policy to drain the local queue before we attempt to
3392 // drain the global stack.
3393 assert(partially || _task_queue->size() == 0, "invariant");
3395 // Decide what the target size is, depending whether we're going to
3396 // drain it partially (so that other tasks can steal if they run out
3397 // of things to do) or totally (at the very end). Notice that,
3398 // because we move entries from the global stack in chunks or
3399 // because another task might be doing the same, we might in fact
3400 // drop below the target. But, this is not a problem.
3401 size_t target_size;
3402 if (partially)
3403 target_size = _cm->partial_mark_stack_size_target();
3404 else
3405 target_size = 0;
3407 if (_cm->mark_stack_size() > target_size) {
3408 if (_cm->verbose_low())
3409 gclog_or_tty->print_cr("[%d] draining global_stack, target size %d",
3410 _task_id, target_size);
3412 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3413 get_entries_from_global_stack();
3414 drain_local_queue(partially);
3415 }
3417 if (_cm->verbose_low())
3418 gclog_or_tty->print_cr("[%d] drained global stack, size = %d",
3419 _task_id, _cm->mark_stack_size());
3420 }
3421 }
3423 // SATB Queue has several assumptions on whether to call the par or
3424 // non-par versions of the methods. this is why some of the code is
3425 // replicated. We should really get rid of the single-threaded version
3426 // of the code to simplify things.
3427 void CMTask::drain_satb_buffers() {
3428 if (has_aborted())
3429 return;
3431 // We set this so that the regular clock knows that we're in the
3432 // middle of draining buffers and doesn't set the abort flag when it
3433 // notices that SATB buffers are available for draining. It'd be
3434 // very counter productive if it did that. :-)
3435 _draining_satb_buffers = true;
3437 CMObjectClosure oc(this);
3438 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3439 if (G1CollectedHeap::use_parallel_gc_threads())
3440 satb_mq_set.set_par_closure(_task_id, &oc);
3441 else
3442 satb_mq_set.set_closure(&oc);
3444 // This keeps claiming and applying the closure to completed buffers
3445 // until we run out of buffers or we need to abort.
3446 if (G1CollectedHeap::use_parallel_gc_threads()) {
3447 while (!has_aborted() &&
3448 satb_mq_set.par_apply_closure_to_completed_buffer(_task_id)) {
3449 if (_cm->verbose_medium())
3450 gclog_or_tty->print_cr("[%d] processed an SATB buffer", _task_id);
3451 statsOnly( ++_satb_buffers_processed );
3452 regular_clock_call();
3453 }
3454 } else {
3455 while (!has_aborted() &&
3456 satb_mq_set.apply_closure_to_completed_buffer()) {
3457 if (_cm->verbose_medium())
3458 gclog_or_tty->print_cr("[%d] processed an SATB buffer", _task_id);
3459 statsOnly( ++_satb_buffers_processed );
3460 regular_clock_call();
3461 }
3462 }
3464 if (!concurrent() && !has_aborted()) {
3465 // We should only do this during remark.
3466 if (G1CollectedHeap::use_parallel_gc_threads())
3467 satb_mq_set.par_iterate_closure_all_threads(_task_id);
3468 else
3469 satb_mq_set.iterate_closure_all_threads();
3470 }
3472 _draining_satb_buffers = false;
3474 assert(has_aborted() ||
3475 concurrent() ||
3476 satb_mq_set.completed_buffers_num() == 0, "invariant");
3478 if (G1CollectedHeap::use_parallel_gc_threads())
3479 satb_mq_set.set_par_closure(_task_id, NULL);
3480 else
3481 satb_mq_set.set_closure(NULL);
3483 // again, this was a potentially expensive operation, decrease the
3484 // limits to get the regular clock call early
3485 decrease_limits();
3486 }
3488 void CMTask::drain_region_stack(BitMapClosure* bc) {
3489 if (has_aborted())
3490 return;
3492 assert(_region_finger == NULL,
3493 "it should be NULL when we're not scanning a region");
3495 if (!_cm->region_stack_empty() || !_aborted_region.is_empty()) {
3496 if (_cm->verbose_low())
3497 gclog_or_tty->print_cr("[%d] draining region stack, size = %d",
3498 _task_id, _cm->region_stack_size());
3500 MemRegion mr;
3502 if (!_aborted_region.is_empty()) {
3503 mr = _aborted_region;
3504 _aborted_region = MemRegion();
3506 if (_cm->verbose_low())
3507 gclog_or_tty->print_cr("[%d] scanning aborted region [ " PTR_FORMAT ", " PTR_FORMAT " )",
3508 _task_id, mr.start(), mr.end());
3509 } else {
3510 mr = _cm->region_stack_pop_lock_free();
3511 // it returns MemRegion() if the pop fails
3512 statsOnly(if (mr.start() != NULL) ++_region_stack_pops );
3513 }
3515 while (mr.start() != NULL) {
3516 if (_cm->verbose_medium())
3517 gclog_or_tty->print_cr("[%d] we are scanning region "
3518 "["PTR_FORMAT", "PTR_FORMAT")",
3519 _task_id, mr.start(), mr.end());
3521 assert(mr.end() <= _cm->finger(),
3522 "otherwise the region shouldn't be on the stack");
3523 assert(!mr.is_empty(), "Only non-empty regions live on the region stack");
3524 if (_nextMarkBitMap->iterate(bc, mr)) {
3525 assert(!has_aborted(),
3526 "cannot abort the task without aborting the bitmap iteration");
3528 // We finished iterating over the region without aborting.
3529 regular_clock_call();
3530 if (has_aborted())
3531 mr = MemRegion();
3532 else {
3533 mr = _cm->region_stack_pop_lock_free();
3534 // it returns MemRegion() if the pop fails
3535 statsOnly(if (mr.start() != NULL) ++_region_stack_pops );
3536 }
3537 } else {
3538 assert(has_aborted(), "currently the only way to do so");
3540 // The only way to abort the bitmap iteration is to return
3541 // false from the do_bit() method. However, inside the
3542 // do_bit() method we move the _region_finger to point to the
3543 // object currently being looked at. So, if we bail out, we
3544 // have definitely set _region_finger to something non-null.
3545 assert(_region_finger != NULL, "invariant");
3547 // Make sure that any previously aborted region has been
3548 // cleared.
3549 assert(_aborted_region.is_empty(), "aborted region not cleared");
3551 // The iteration was actually aborted. So now _region_finger
3552 // points to the address of the object we last scanned. If we
3553 // leave it there, when we restart this task, we will rescan
3554 // the object. It is easy to avoid this. We move the finger by
3555 // enough to point to the next possible object header (the
3556 // bitmap knows by how much we need to move it as it knows its
3557 // granularity).
3558 MemRegion newRegion =
3559 MemRegion(_nextMarkBitMap->nextWord(_region_finger), mr.end());
3561 if (!newRegion.is_empty()) {
3562 if (_cm->verbose_low()) {
3563 gclog_or_tty->print_cr("[%d] recording unscanned region"
3564 "[" PTR_FORMAT "," PTR_FORMAT ") in CMTask",
3565 _task_id,
3566 newRegion.start(), newRegion.end());
3567 }
3568 // Now record the part of the region we didn't scan to
3569 // make sure this task scans it later.
3570 _aborted_region = newRegion;
3571 }
3572 // break from while
3573 mr = MemRegion();
3574 }
3575 _region_finger = NULL;
3576 }
3578 if (_cm->verbose_low())
3579 gclog_or_tty->print_cr("[%d] drained region stack, size = %d",
3580 _task_id, _cm->region_stack_size());
3581 }
3582 }
3584 void CMTask::print_stats() {
3585 gclog_or_tty->print_cr("Marking Stats, task = %d, calls = %d",
3586 _task_id, _calls);
3587 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3588 _elapsed_time_ms, _termination_time_ms);
3589 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3590 _step_times_ms.num(), _step_times_ms.avg(),
3591 _step_times_ms.sd());
3592 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3593 _step_times_ms.maximum(), _step_times_ms.sum());
3595 #if _MARKING_STATS_
3596 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3597 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3598 _all_clock_intervals_ms.sd());
3599 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3600 _all_clock_intervals_ms.maximum(),
3601 _all_clock_intervals_ms.sum());
3602 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d",
3603 _clock_due_to_scanning, _clock_due_to_marking);
3604 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d",
3605 _objs_scanned, _objs_found_on_bitmap);
3606 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d",
3607 _local_pushes, _local_pops, _local_max_size);
3608 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d",
3609 _global_pushes, _global_pops, _global_max_size);
3610 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d",
3611 _global_transfers_to,_global_transfers_from);
3612 gclog_or_tty->print_cr(" Regions: claimed = %d, Region Stack: pops = %d",
3613 _regions_claimed, _region_stack_pops);
3614 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed);
3615 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d",
3616 _steal_attempts, _steals);
3617 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted);
3618 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d",
3619 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3620 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d",
3621 _aborted_timed_out, _aborted_satb, _aborted_termination);
3622 #endif // _MARKING_STATS_
3623 }
3625 /*****************************************************************************
3627 The do_marking_step(time_target_ms) method is the building block
3628 of the parallel marking framework. It can be called in parallel
3629 with other invocations of do_marking_step() on different tasks
3630 (but only one per task, obviously) and concurrently with the
3631 mutator threads, or during remark, hence it eliminates the need
3632 for two versions of the code. When called during remark, it will
3633 pick up from where the task left off during the concurrent marking
3634 phase. Interestingly, tasks are also claimable during evacuation
3635 pauses too, since do_marking_step() ensures that it aborts before
3636 it needs to yield.
3638 The data structures that is uses to do marking work are the
3639 following:
3641 (1) Marking Bitmap. If there are gray objects that appear only
3642 on the bitmap (this happens either when dealing with an overflow
3643 or when the initial marking phase has simply marked the roots
3644 and didn't push them on the stack), then tasks claim heap
3645 regions whose bitmap they then scan to find gray objects. A
3646 global finger indicates where the end of the last claimed region
3647 is. A local finger indicates how far into the region a task has
3648 scanned. The two fingers are used to determine how to gray an
3649 object (i.e. whether simply marking it is OK, as it will be
3650 visited by a task in the future, or whether it needs to be also
3651 pushed on a stack).
3653 (2) Local Queue. The local queue of the task which is accessed
3654 reasonably efficiently by the task. Other tasks can steal from
3655 it when they run out of work. Throughout the marking phase, a
3656 task attempts to keep its local queue short but not totally
3657 empty, so that entries are available for stealing by other
3658 tasks. Only when there is no more work, a task will totally
3659 drain its local queue.
3661 (3) Global Mark Stack. This handles local queue overflow. During
3662 marking only sets of entries are moved between it and the local
3663 queues, as access to it requires a mutex and more fine-grain
3664 interaction with it which might cause contention. If it
3665 overflows, then the marking phase should restart and iterate
3666 over the bitmap to identify gray objects. Throughout the marking
3667 phase, tasks attempt to keep the global mark stack at a small
3668 length but not totally empty, so that entries are available for
3669 popping by other tasks. Only when there is no more work, tasks
3670 will totally drain the global mark stack.
3672 (4) Global Region Stack. Entries on it correspond to areas of
3673 the bitmap that need to be scanned since they contain gray
3674 objects. Pushes on the region stack only happen during
3675 evacuation pauses and typically correspond to areas covered by
3676 GC LABS. If it overflows, then the marking phase should restart
3677 and iterate over the bitmap to identify gray objects. Tasks will
3678 try to totally drain the region stack as soon as possible.
3680 (5) SATB Buffer Queue. This is where completed SATB buffers are
3681 made available. Buffers are regularly removed from this queue
3682 and scanned for roots, so that the queue doesn't get too
3683 long. During remark, all completed buffers are processed, as
3684 well as the filled in parts of any uncompleted buffers.
3686 The do_marking_step() method tries to abort when the time target
3687 has been reached. There are a few other cases when the
3688 do_marking_step() method also aborts:
3690 (1) When the marking phase has been aborted (after a Full GC).
3692 (2) When a global overflow (either on the global stack or the
3693 region stack) has been triggered. Before the task aborts, it
3694 will actually sync up with the other tasks to ensure that all
3695 the marking data structures (local queues, stacks, fingers etc.)
3696 are re-initialised so that when do_marking_step() completes,
3697 the marking phase can immediately restart.
3699 (3) When enough completed SATB buffers are available. The
3700 do_marking_step() method only tries to drain SATB buffers right
3701 at the beginning. So, if enough buffers are available, the
3702 marking step aborts and the SATB buffers are processed at
3703 the beginning of the next invocation.
3705 (4) To yield. when we have to yield then we abort and yield
3706 right at the end of do_marking_step(). This saves us from a lot
3707 of hassle as, by yielding we might allow a Full GC. If this
3708 happens then objects will be compacted underneath our feet, the
3709 heap might shrink, etc. We save checking for this by just
3710 aborting and doing the yield right at the end.
3712 From the above it follows that the do_marking_step() method should
3713 be called in a loop (or, otherwise, regularly) until it completes.
3715 If a marking step completes without its has_aborted() flag being
3716 true, it means it has completed the current marking phase (and
3717 also all other marking tasks have done so and have all synced up).
3719 A method called regular_clock_call() is invoked "regularly" (in
3720 sub ms intervals) throughout marking. It is this clock method that
3721 checks all the abort conditions which were mentioned above and
3722 decides when the task should abort. A work-based scheme is used to
3723 trigger this clock method: when the number of object words the
3724 marking phase has scanned or the number of references the marking
3725 phase has visited reach a given limit. Additional invocations to
3726 the method clock have been planted in a few other strategic places
3727 too. The initial reason for the clock method was to avoid calling
3728 vtime too regularly, as it is quite expensive. So, once it was in
3729 place, it was natural to piggy-back all the other conditions on it
3730 too and not constantly check them throughout the code.
3732 *****************************************************************************/
3734 void CMTask::do_marking_step(double time_target_ms) {
3735 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3736 assert(concurrent() == _cm->concurrent(), "they should be the same");
3738 assert(concurrent() || _cm->region_stack_empty(),
3739 "the region stack should have been cleared before remark");
3740 assert(concurrent() || !_cm->has_aborted_regions(),
3741 "aborted regions should have been cleared before remark");
3742 assert(_region_finger == NULL,
3743 "this should be non-null only when a region is being scanned");
3745 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3746 assert(_task_queues != NULL, "invariant");
3747 assert(_task_queue != NULL, "invariant");
3748 assert(_task_queues->queue(_task_id) == _task_queue, "invariant");
3750 assert(!_claimed,
3751 "only one thread should claim this task at any one time");
3753 // OK, this doesn't safeguard again all possible scenarios, as it is
3754 // possible for two threads to set the _claimed flag at the same
3755 // time. But it is only for debugging purposes anyway and it will
3756 // catch most problems.
3757 _claimed = true;
3759 _start_time_ms = os::elapsedVTime() * 1000.0;
3760 statsOnly( _interval_start_time_ms = _start_time_ms );
3762 double diff_prediction_ms =
3763 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
3764 _time_target_ms = time_target_ms - diff_prediction_ms;
3766 // set up the variables that are used in the work-based scheme to
3767 // call the regular clock method
3768 _words_scanned = 0;
3769 _refs_reached = 0;
3770 recalculate_limits();
3772 // clear all flags
3773 clear_has_aborted();
3774 _has_aborted_timed_out = false;
3775 _draining_satb_buffers = false;
3777 ++_calls;
3779 if (_cm->verbose_low())
3780 gclog_or_tty->print_cr("[%d] >>>>>>>>>> START, call = %d, "
3781 "target = %1.2lfms >>>>>>>>>>",
3782 _task_id, _calls, _time_target_ms);
3784 // Set up the bitmap and oop closures. Anything that uses them is
3785 // eventually called from this method, so it is OK to allocate these
3786 // statically.
3787 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
3788 CMOopClosure oop_closure(_g1h, _cm, this);
3789 set_oop_closure(&oop_closure);
3791 if (_cm->has_overflown()) {
3792 // This can happen if the region stack or the mark stack overflows
3793 // during a GC pause and this task, after a yield point,
3794 // restarts. We have to abort as we need to get into the overflow
3795 // protocol which happens right at the end of this task.
3796 set_has_aborted();
3797 }
3799 // First drain any available SATB buffers. After this, we will not
3800 // look at SATB buffers before the next invocation of this method.
3801 // If enough completed SATB buffers are queued up, the regular clock
3802 // will abort this task so that it restarts.
3803 drain_satb_buffers();
3804 // ...then partially drain the local queue and the global stack
3805 drain_local_queue(true);
3806 drain_global_stack(true);
3808 // Then totally drain the region stack. We will not look at
3809 // it again before the next invocation of this method. Entries on
3810 // the region stack are only added during evacuation pauses, for
3811 // which we have to yield. When we do, we abort the task anyway so
3812 // it will look at the region stack again when it restarts.
3813 bitmap_closure.set_scanning_heap_region(false);
3814 drain_region_stack(&bitmap_closure);
3815 // ...then partially drain the local queue and the global stack
3816 drain_local_queue(true);
3817 drain_global_stack(true);
3819 do {
3820 if (!has_aborted() && _curr_region != NULL) {
3821 // This means that we're already holding on to a region.
3822 assert(_finger != NULL, "if region is not NULL, then the finger "
3823 "should not be NULL either");
3825 // We might have restarted this task after an evacuation pause
3826 // which might have evacuated the region we're holding on to
3827 // underneath our feet. Let's read its limit again to make sure
3828 // that we do not iterate over a region of the heap that
3829 // contains garbage (update_region_limit() will also move
3830 // _finger to the start of the region if it is found empty).
3831 update_region_limit();
3832 // We will start from _finger not from the start of the region,
3833 // as we might be restarting this task after aborting half-way
3834 // through scanning this region. In this case, _finger points to
3835 // the address where we last found a marked object. If this is a
3836 // fresh region, _finger points to start().
3837 MemRegion mr = MemRegion(_finger, _region_limit);
3839 if (_cm->verbose_low())
3840 gclog_or_tty->print_cr("[%d] we're scanning part "
3841 "["PTR_FORMAT", "PTR_FORMAT") "
3842 "of region "PTR_FORMAT,
3843 _task_id, _finger, _region_limit, _curr_region);
3845 // Let's iterate over the bitmap of the part of the
3846 // region that is left.
3847 bitmap_closure.set_scanning_heap_region(true);
3848 if (mr.is_empty() ||
3849 _nextMarkBitMap->iterate(&bitmap_closure, mr)) {
3850 // We successfully completed iterating over the region. Now,
3851 // let's give up the region.
3852 giveup_current_region();
3853 regular_clock_call();
3854 } else {
3855 assert(has_aborted(), "currently the only way to do so");
3856 // The only way to abort the bitmap iteration is to return
3857 // false from the do_bit() method. However, inside the
3858 // do_bit() method we move the _finger to point to the
3859 // object currently being looked at. So, if we bail out, we
3860 // have definitely set _finger to something non-null.
3861 assert(_finger != NULL, "invariant");
3863 // Region iteration was actually aborted. So now _finger
3864 // points to the address of the object we last scanned. If we
3865 // leave it there, when we restart this task, we will rescan
3866 // the object. It is easy to avoid this. We move the finger by
3867 // enough to point to the next possible object header (the
3868 // bitmap knows by how much we need to move it as it knows its
3869 // granularity).
3870 assert(_finger < _region_limit, "invariant");
3871 HeapWord* new_finger = _nextMarkBitMap->nextWord(_finger);
3872 // Check if bitmap iteration was aborted while scanning the last object
3873 if (new_finger >= _region_limit) {
3874 giveup_current_region();
3875 } else {
3876 move_finger_to(new_finger);
3877 }
3878 }
3879 }
3880 // At this point we have either completed iterating over the
3881 // region we were holding on to, or we have aborted.
3883 // We then partially drain the local queue and the global stack.
3884 // (Do we really need this?)
3885 drain_local_queue(true);
3886 drain_global_stack(true);
3888 // Read the note on the claim_region() method on why it might
3889 // return NULL with potentially more regions available for
3890 // claiming and why we have to check out_of_regions() to determine
3891 // whether we're done or not.
3892 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
3893 // We are going to try to claim a new region. We should have
3894 // given up on the previous one.
3895 // Separated the asserts so that we know which one fires.
3896 assert(_curr_region == NULL, "invariant");
3897 assert(_finger == NULL, "invariant");
3898 assert(_region_limit == NULL, "invariant");
3899 if (_cm->verbose_low())
3900 gclog_or_tty->print_cr("[%d] trying to claim a new region", _task_id);
3901 HeapRegion* claimed_region = _cm->claim_region(_task_id);
3902 if (claimed_region != NULL) {
3903 // Yes, we managed to claim one
3904 statsOnly( ++_regions_claimed );
3906 if (_cm->verbose_low())
3907 gclog_or_tty->print_cr("[%d] we successfully claimed "
3908 "region "PTR_FORMAT,
3909 _task_id, claimed_region);
3911 setup_for_region(claimed_region);
3912 assert(_curr_region == claimed_region, "invariant");
3913 }
3914 // It is important to call the regular clock here. It might take
3915 // a while to claim a region if, for example, we hit a large
3916 // block of empty regions. So we need to call the regular clock
3917 // method once round the loop to make sure it's called
3918 // frequently enough.
3919 regular_clock_call();
3920 }
3922 if (!has_aborted() && _curr_region == NULL) {
3923 assert(_cm->out_of_regions(),
3924 "at this point we should be out of regions");
3925 }
3926 } while ( _curr_region != NULL && !has_aborted());
3928 if (!has_aborted()) {
3929 // We cannot check whether the global stack is empty, since other
3930 // tasks might be pushing objects to it concurrently. We also cannot
3931 // check if the region stack is empty because if a thread is aborting
3932 // it can push a partially done region back.
3933 assert(_cm->out_of_regions(),
3934 "at this point we should be out of regions");
3936 if (_cm->verbose_low())
3937 gclog_or_tty->print_cr("[%d] all regions claimed", _task_id);
3939 // Try to reduce the number of available SATB buffers so that
3940 // remark has less work to do.
3941 drain_satb_buffers();
3942 }
3944 // Since we've done everything else, we can now totally drain the
3945 // local queue and global stack.
3946 drain_local_queue(false);
3947 drain_global_stack(false);
3949 // Attempt at work stealing from other task's queues.
3950 if (!has_aborted()) {
3951 // We have not aborted. This means that we have finished all that
3952 // we could. Let's try to do some stealing...
3954 // We cannot check whether the global stack is empty, since other
3955 // tasks might be pushing objects to it concurrently. We also cannot
3956 // check if the region stack is empty because if a thread is aborting
3957 // it can push a partially done region back.
3958 assert(_cm->out_of_regions() && _task_queue->size() == 0,
3959 "only way to reach here");
3961 if (_cm->verbose_low())
3962 gclog_or_tty->print_cr("[%d] starting to steal", _task_id);
3964 while (!has_aborted()) {
3965 oop obj;
3966 statsOnly( ++_steal_attempts );
3968 if (_cm->try_stealing(_task_id, &_hash_seed, obj)) {
3969 if (_cm->verbose_medium())
3970 gclog_or_tty->print_cr("[%d] stolen "PTR_FORMAT" successfully",
3971 _task_id, (void*) obj);
3973 statsOnly( ++_steals );
3975 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
3976 "any stolen object should be marked");
3977 scan_object(obj);
3979 // And since we're towards the end, let's totally drain the
3980 // local queue and global stack.
3981 drain_local_queue(false);
3982 drain_global_stack(false);
3983 } else {
3984 break;
3985 }
3986 }
3987 }
3989 // We still haven't aborted. Now, let's try to get into the
3990 // termination protocol.
3991 if (!has_aborted()) {
3992 // We cannot check whether the global stack is empty, since other
3993 // tasks might be concurrently pushing objects on it. We also cannot
3994 // check if the region stack is empty because if a thread is aborting
3995 // it can push a partially done region back.
3996 // Separated the asserts so that we know which one fires.
3997 assert(_cm->out_of_regions(), "only way to reach here");
3998 assert(_task_queue->size() == 0, "only way to reach here");
4000 if (_cm->verbose_low())
4001 gclog_or_tty->print_cr("[%d] starting termination protocol", _task_id);
4003 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4004 // The CMTask class also extends the TerminatorTerminator class,
4005 // hence its should_exit_termination() method will also decide
4006 // whether to exit the termination protocol or not.
4007 bool finished = _cm->terminator()->offer_termination(this);
4008 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4009 _termination_time_ms +=
4010 termination_end_time_ms - _termination_start_time_ms;
4012 if (finished) {
4013 // We're all done.
4015 if (_task_id == 0) {
4016 // let's allow task 0 to do this
4017 if (concurrent()) {
4018 assert(_cm->concurrent_marking_in_progress(), "invariant");
4019 // we need to set this to false before the next
4020 // safepoint. This way we ensure that the marking phase
4021 // doesn't observe any more heap expansions.
4022 _cm->clear_concurrent_marking_in_progress();
4023 }
4024 }
4026 // We can now guarantee that the global stack is empty, since
4027 // all other tasks have finished. We separated the guarantees so
4028 // that, if a condition is false, we can immediately find out
4029 // which one.
4030 guarantee(_cm->out_of_regions(), "only way to reach here");
4031 guarantee(_aborted_region.is_empty(), "only way to reach here");
4032 guarantee(_cm->region_stack_empty(), "only way to reach here");
4033 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4034 guarantee(_task_queue->size() == 0, "only way to reach here");
4035 guarantee(!_cm->has_overflown(), "only way to reach here");
4036 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4037 guarantee(!_cm->region_stack_overflow(), "only way to reach here");
4039 if (_cm->verbose_low())
4040 gclog_or_tty->print_cr("[%d] all tasks terminated", _task_id);
4041 } else {
4042 // Apparently there's more work to do. Let's abort this task. It
4043 // will restart it and we can hopefully find more things to do.
4045 if (_cm->verbose_low())
4046 gclog_or_tty->print_cr("[%d] apparently there is more work to do", _task_id);
4048 set_has_aborted();
4049 statsOnly( ++_aborted_termination );
4050 }
4051 }
4053 // Mainly for debugging purposes to make sure that a pointer to the
4054 // closure which was statically allocated in this frame doesn't
4055 // escape it by accident.
4056 set_oop_closure(NULL);
4057 double end_time_ms = os::elapsedVTime() * 1000.0;
4058 double elapsed_time_ms = end_time_ms - _start_time_ms;
4059 // Update the step history.
4060 _step_times_ms.add(elapsed_time_ms);
4062 if (has_aborted()) {
4063 // The task was aborted for some reason.
4065 statsOnly( ++_aborted );
4067 if (_has_aborted_timed_out) {
4068 double diff_ms = elapsed_time_ms - _time_target_ms;
4069 // Keep statistics of how well we did with respect to hitting
4070 // our target only if we actually timed out (if we aborted for
4071 // other reasons, then the results might get skewed).
4072 _marking_step_diffs_ms.add(diff_ms);
4073 }
4075 if (_cm->has_overflown()) {
4076 // This is the interesting one. We aborted because a global
4077 // overflow was raised. This means we have to restart the
4078 // marking phase and start iterating over regions. However, in
4079 // order to do this we have to make sure that all tasks stop
4080 // what they are doing and re-initialise in a safe manner. We
4081 // will achieve this with the use of two barrier sync points.
4083 if (_cm->verbose_low())
4084 gclog_or_tty->print_cr("[%d] detected overflow", _task_id);
4086 _cm->enter_first_sync_barrier(_task_id);
4087 // When we exit this sync barrier we know that all tasks have
4088 // stopped doing marking work. So, it's now safe to
4089 // re-initialise our data structures. At the end of this method,
4090 // task 0 will clear the global data structures.
4092 statsOnly( ++_aborted_overflow );
4094 // We clear the local state of this task...
4095 clear_region_fields();
4097 // ...and enter the second barrier.
4098 _cm->enter_second_sync_barrier(_task_id);
4099 // At this point everything has bee re-initialised and we're
4100 // ready to restart.
4101 }
4103 if (_cm->verbose_low()) {
4104 gclog_or_tty->print_cr("[%d] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4105 "elapsed = %1.2lfms <<<<<<<<<<",
4106 _task_id, _time_target_ms, elapsed_time_ms);
4107 if (_cm->has_aborted())
4108 gclog_or_tty->print_cr("[%d] ========== MARKING ABORTED ==========",
4109 _task_id);
4110 }
4111 } else {
4112 if (_cm->verbose_low())
4113 gclog_or_tty->print_cr("[%d] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4114 "elapsed = %1.2lfms <<<<<<<<<<",
4115 _task_id, _time_target_ms, elapsed_time_ms);
4116 }
4118 _claimed = false;
4119 }
4121 CMTask::CMTask(int task_id,
4122 ConcurrentMark* cm,
4123 CMTaskQueue* task_queue,
4124 CMTaskQueueSet* task_queues)
4125 : _g1h(G1CollectedHeap::heap()),
4126 _task_id(task_id), _cm(cm),
4127 _claimed(false),
4128 _nextMarkBitMap(NULL), _hash_seed(17),
4129 _task_queue(task_queue),
4130 _task_queues(task_queues),
4131 _oop_closure(NULL),
4132 _aborted_region(MemRegion()) {
4133 guarantee(task_queue != NULL, "invariant");
4134 guarantee(task_queues != NULL, "invariant");
4136 statsOnly( _clock_due_to_scanning = 0;
4137 _clock_due_to_marking = 0 );
4139 _marking_step_diffs_ms.add(0.5);
4140 }