Tue, 19 Aug 2014 02:05:49 -0700
8044406: JVM crash with JDK8 (build 1.8.0-b132) with G1 GC
Summary: Fill the last card that has been allocated into with a dummy object
Reviewed-by: tschatzl, mgerdin
1 /*
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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
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7 * published by the Free Software Foundation.
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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).
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23 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "gc_implementation/g1/concurrentMark.inline.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/g1ErgoVerbose.hpp"
32 #include "gc_implementation/g1/g1Log.hpp"
33 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
34 #include "gc_implementation/g1/g1RemSet.hpp"
35 #include "gc_implementation/g1/heapRegion.inline.hpp"
36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
37 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
38 #include "gc_implementation/shared/vmGCOperations.hpp"
39 #include "gc_implementation/shared/gcTimer.hpp"
40 #include "gc_implementation/shared/gcTrace.hpp"
41 #include "gc_implementation/shared/gcTraceTime.hpp"
42 #include "memory/genOopClosures.inline.hpp"
43 #include "memory/referencePolicy.hpp"
44 #include "memory/resourceArea.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "runtime/handles.inline.hpp"
47 #include "runtime/java.hpp"
48 #include "services/memTracker.hpp"
50 // Concurrent marking bit map wrapper
52 CMBitMapRO::CMBitMapRO(int shifter) :
53 _bm(),
54 _shifter(shifter) {
55 _bmStartWord = 0;
56 _bmWordSize = 0;
57 }
59 HeapWord* CMBitMapRO::getNextMarkedWordAddress(HeapWord* addr,
60 HeapWord* limit) const {
61 // First we must round addr *up* to a possible object boundary.
62 addr = (HeapWord*)align_size_up((intptr_t)addr,
63 HeapWordSize << _shifter);
64 size_t addrOffset = heapWordToOffset(addr);
65 if (limit == NULL) {
66 limit = _bmStartWord + _bmWordSize;
67 }
68 size_t limitOffset = heapWordToOffset(limit);
69 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
70 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
71 assert(nextAddr >= addr, "get_next_one postcondition");
72 assert(nextAddr == limit || isMarked(nextAddr),
73 "get_next_one postcondition");
74 return nextAddr;
75 }
77 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(HeapWord* addr,
78 HeapWord* limit) const {
79 size_t addrOffset = heapWordToOffset(addr);
80 if (limit == NULL) {
81 limit = _bmStartWord + _bmWordSize;
82 }
83 size_t limitOffset = heapWordToOffset(limit);
84 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
85 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
86 assert(nextAddr >= addr, "get_next_one postcondition");
87 assert(nextAddr == limit || !isMarked(nextAddr),
88 "get_next_one postcondition");
89 return nextAddr;
90 }
92 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
93 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
94 return (int) (diff >> _shifter);
95 }
97 #ifndef PRODUCT
98 bool CMBitMapRO::covers(ReservedSpace heap_rs) const {
99 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
100 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
101 "size inconsistency");
102 return _bmStartWord == (HeapWord*)(heap_rs.base()) &&
103 _bmWordSize == heap_rs.size()>>LogHeapWordSize;
104 }
105 #endif
107 void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
108 _bm.print_on_error(st, prefix);
109 }
111 bool CMBitMap::allocate(ReservedSpace heap_rs) {
112 _bmStartWord = (HeapWord*)(heap_rs.base());
113 _bmWordSize = heap_rs.size()/HeapWordSize; // heap_rs.size() is in bytes
114 ReservedSpace brs(ReservedSpace::allocation_align_size_up(
115 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1));
116 if (!brs.is_reserved()) {
117 warning("ConcurrentMark marking bit map allocation failure");
118 return false;
119 }
120 MemTracker::record_virtual_memory_type((address)brs.base(), mtGC);
121 // For now we'll just commit all of the bit map up front.
122 // Later on we'll try to be more parsimonious with swap.
123 if (!_virtual_space.initialize(brs, brs.size())) {
124 warning("ConcurrentMark marking bit map backing store failure");
125 return false;
126 }
127 assert(_virtual_space.committed_size() == brs.size(),
128 "didn't reserve backing store for all of concurrent marking bit map?");
129 _bm.set_map((uintptr_t*)_virtual_space.low());
130 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >=
131 _bmWordSize, "inconsistency in bit map sizing");
132 _bm.set_size(_bmWordSize >> _shifter);
133 return true;
134 }
136 void CMBitMap::clearAll() {
137 _bm.clear();
138 return;
139 }
141 void CMBitMap::markRange(MemRegion mr) {
142 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
143 assert(!mr.is_empty(), "unexpected empty region");
144 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
145 ((HeapWord *) mr.end())),
146 "markRange memory region end is not card aligned");
147 // convert address range into offset range
148 _bm.at_put_range(heapWordToOffset(mr.start()),
149 heapWordToOffset(mr.end()), true);
150 }
152 void CMBitMap::clearRange(MemRegion mr) {
153 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
154 assert(!mr.is_empty(), "unexpected empty region");
155 // convert address range into offset range
156 _bm.at_put_range(heapWordToOffset(mr.start()),
157 heapWordToOffset(mr.end()), false);
158 }
160 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
161 HeapWord* end_addr) {
162 HeapWord* start = getNextMarkedWordAddress(addr);
163 start = MIN2(start, end_addr);
164 HeapWord* end = getNextUnmarkedWordAddress(start);
165 end = MIN2(end, end_addr);
166 assert(start <= end, "Consistency check");
167 MemRegion mr(start, end);
168 if (!mr.is_empty()) {
169 clearRange(mr);
170 }
171 return mr;
172 }
174 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
175 _base(NULL), _cm(cm)
176 #ifdef ASSERT
177 , _drain_in_progress(false)
178 , _drain_in_progress_yields(false)
179 #endif
180 {}
182 bool CMMarkStack::allocate(size_t capacity) {
183 // allocate a stack of the requisite depth
184 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop)));
185 if (!rs.is_reserved()) {
186 warning("ConcurrentMark MarkStack allocation failure");
187 return false;
188 }
189 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
190 if (!_virtual_space.initialize(rs, rs.size())) {
191 warning("ConcurrentMark MarkStack backing store failure");
192 // Release the virtual memory reserved for the marking stack
193 rs.release();
194 return false;
195 }
196 assert(_virtual_space.committed_size() == rs.size(),
197 "Didn't reserve backing store for all of ConcurrentMark stack?");
198 _base = (oop*) _virtual_space.low();
199 setEmpty();
200 _capacity = (jint) capacity;
201 _saved_index = -1;
202 _should_expand = false;
203 NOT_PRODUCT(_max_depth = 0);
204 return true;
205 }
207 void CMMarkStack::expand() {
208 // Called, during remark, if we've overflown the marking stack during marking.
209 assert(isEmpty(), "stack should been emptied while handling overflow");
210 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted");
211 // Clear expansion flag
212 _should_expand = false;
213 if (_capacity == (jint) MarkStackSizeMax) {
214 if (PrintGCDetails && Verbose) {
215 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit");
216 }
217 return;
218 }
219 // Double capacity if possible
220 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax);
221 // Do not give up existing stack until we have managed to
222 // get the double capacity that we desired.
223 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity *
224 sizeof(oop)));
225 if (rs.is_reserved()) {
226 // Release the backing store associated with old stack
227 _virtual_space.release();
228 // Reinitialize virtual space for new stack
229 if (!_virtual_space.initialize(rs, rs.size())) {
230 fatal("Not enough swap for expanded marking stack capacity");
231 }
232 _base = (oop*)(_virtual_space.low());
233 _index = 0;
234 _capacity = new_capacity;
235 } else {
236 if (PrintGCDetails && Verbose) {
237 // Failed to double capacity, continue;
238 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from "
239 SIZE_FORMAT"K to " SIZE_FORMAT"K",
240 _capacity / K, new_capacity / K);
241 }
242 }
243 }
245 void CMMarkStack::set_should_expand() {
246 // If we're resetting the marking state because of an
247 // marking stack overflow, record that we should, if
248 // possible, expand the stack.
249 _should_expand = _cm->has_overflown();
250 }
252 CMMarkStack::~CMMarkStack() {
253 if (_base != NULL) {
254 _base = NULL;
255 _virtual_space.release();
256 }
257 }
259 void CMMarkStack::par_push(oop ptr) {
260 while (true) {
261 if (isFull()) {
262 _overflow = true;
263 return;
264 }
265 // Otherwise...
266 jint index = _index;
267 jint next_index = index+1;
268 jint res = Atomic::cmpxchg(next_index, &_index, index);
269 if (res == index) {
270 _base[index] = ptr;
271 // Note that we don't maintain this atomically. We could, but it
272 // doesn't seem necessary.
273 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
274 return;
275 }
276 // Otherwise, we need to try again.
277 }
278 }
280 void CMMarkStack::par_adjoin_arr(oop* ptr_arr, int n) {
281 while (true) {
282 if (isFull()) {
283 _overflow = true;
284 return;
285 }
286 // Otherwise...
287 jint index = _index;
288 jint next_index = index + n;
289 if (next_index > _capacity) {
290 _overflow = true;
291 return;
292 }
293 jint res = Atomic::cmpxchg(next_index, &_index, index);
294 if (res == index) {
295 for (int i = 0; i < n; i++) {
296 int ind = index + i;
297 assert(ind < _capacity, "By overflow test above.");
298 _base[ind] = ptr_arr[i];
299 }
300 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
301 return;
302 }
303 // Otherwise, we need to try again.
304 }
305 }
307 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
308 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
309 jint start = _index;
310 jint next_index = start + n;
311 if (next_index > _capacity) {
312 _overflow = true;
313 return;
314 }
315 // Otherwise.
316 _index = next_index;
317 for (int i = 0; i < n; i++) {
318 int ind = start + i;
319 assert(ind < _capacity, "By overflow test above.");
320 _base[ind] = ptr_arr[i];
321 }
322 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
323 }
325 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
326 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
327 jint index = _index;
328 if (index == 0) {
329 *n = 0;
330 return false;
331 } else {
332 int k = MIN2(max, index);
333 jint new_ind = index - k;
334 for (int j = 0; j < k; j++) {
335 ptr_arr[j] = _base[new_ind + j];
336 }
337 _index = new_ind;
338 *n = k;
339 return true;
340 }
341 }
343 template<class OopClosureClass>
344 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
345 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
346 || SafepointSynchronize::is_at_safepoint(),
347 "Drain recursion must be yield-safe.");
348 bool res = true;
349 debug_only(_drain_in_progress = true);
350 debug_only(_drain_in_progress_yields = yield_after);
351 while (!isEmpty()) {
352 oop newOop = pop();
353 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
354 assert(newOop->is_oop(), "Expected an oop");
355 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
356 "only grey objects on this stack");
357 newOop->oop_iterate(cl);
358 if (yield_after && _cm->do_yield_check()) {
359 res = false;
360 break;
361 }
362 }
363 debug_only(_drain_in_progress = false);
364 return res;
365 }
367 void CMMarkStack::note_start_of_gc() {
368 assert(_saved_index == -1,
369 "note_start_of_gc()/end_of_gc() bracketed incorrectly");
370 _saved_index = _index;
371 }
373 void CMMarkStack::note_end_of_gc() {
374 // This is intentionally a guarantee, instead of an assert. If we
375 // accidentally add something to the mark stack during GC, it
376 // will be a correctness issue so it's better if we crash. we'll
377 // only check this once per GC anyway, so it won't be a performance
378 // issue in any way.
379 guarantee(_saved_index == _index,
380 err_msg("saved index: %d index: %d", _saved_index, _index));
381 _saved_index = -1;
382 }
384 void CMMarkStack::oops_do(OopClosure* f) {
385 assert(_saved_index == _index,
386 err_msg("saved index: %d index: %d", _saved_index, _index));
387 for (int i = 0; i < _index; i += 1) {
388 f->do_oop(&_base[i]);
389 }
390 }
392 bool ConcurrentMark::not_yet_marked(oop obj) const {
393 return _g1h->is_obj_ill(obj);
394 }
396 CMRootRegions::CMRootRegions() :
397 _young_list(NULL), _cm(NULL), _scan_in_progress(false),
398 _should_abort(false), _next_survivor(NULL) { }
400 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) {
401 _young_list = g1h->young_list();
402 _cm = cm;
403 }
405 void CMRootRegions::prepare_for_scan() {
406 assert(!scan_in_progress(), "pre-condition");
408 // Currently, only survivors can be root regions.
409 assert(_next_survivor == NULL, "pre-condition");
410 _next_survivor = _young_list->first_survivor_region();
411 _scan_in_progress = (_next_survivor != NULL);
412 _should_abort = false;
413 }
415 HeapRegion* CMRootRegions::claim_next() {
416 if (_should_abort) {
417 // If someone has set the should_abort flag, we return NULL to
418 // force the caller to bail out of their loop.
419 return NULL;
420 }
422 // Currently, only survivors can be root regions.
423 HeapRegion* res = _next_survivor;
424 if (res != NULL) {
425 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
426 // Read it again in case it changed while we were waiting for the lock.
427 res = _next_survivor;
428 if (res != NULL) {
429 if (res == _young_list->last_survivor_region()) {
430 // We just claimed the last survivor so store NULL to indicate
431 // that we're done.
432 _next_survivor = NULL;
433 } else {
434 _next_survivor = res->get_next_young_region();
435 }
436 } else {
437 // Someone else claimed the last survivor while we were trying
438 // to take the lock so nothing else to do.
439 }
440 }
441 assert(res == NULL || res->is_survivor(), "post-condition");
443 return res;
444 }
446 void CMRootRegions::scan_finished() {
447 assert(scan_in_progress(), "pre-condition");
449 // Currently, only survivors can be root regions.
450 if (!_should_abort) {
451 assert(_next_survivor == NULL, "we should have claimed all survivors");
452 }
453 _next_survivor = NULL;
455 {
456 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
457 _scan_in_progress = false;
458 RootRegionScan_lock->notify_all();
459 }
460 }
462 bool CMRootRegions::wait_until_scan_finished() {
463 if (!scan_in_progress()) return false;
465 {
466 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
467 while (scan_in_progress()) {
468 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
469 }
470 }
471 return true;
472 }
474 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
475 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
476 #endif // _MSC_VER
478 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
479 return MAX2((n_par_threads + 2) / 4, 1U);
480 }
482 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs) :
483 _g1h(g1h),
484 _markBitMap1(log2_intptr(MinObjAlignment)),
485 _markBitMap2(log2_intptr(MinObjAlignment)),
486 _parallel_marking_threads(0),
487 _max_parallel_marking_threads(0),
488 _sleep_factor(0.0),
489 _marking_task_overhead(1.0),
490 _cleanup_sleep_factor(0.0),
491 _cleanup_task_overhead(1.0),
492 _cleanup_list("Cleanup List"),
493 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/),
494 _card_bm((heap_rs.size() + CardTableModRefBS::card_size - 1) >>
495 CardTableModRefBS::card_shift,
496 false /* in_resource_area*/),
498 _prevMarkBitMap(&_markBitMap1),
499 _nextMarkBitMap(&_markBitMap2),
501 _markStack(this),
502 // _finger set in set_non_marking_state
504 _max_worker_id(MAX2((uint)ParallelGCThreads, 1U)),
505 // _active_tasks set in set_non_marking_state
506 // _tasks set inside the constructor
507 _task_queues(new CMTaskQueueSet((int) _max_worker_id)),
508 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
510 _has_overflown(false),
511 _concurrent(false),
512 _has_aborted(false),
513 _restart_for_overflow(false),
514 _concurrent_marking_in_progress(false),
516 // _verbose_level set below
518 _init_times(),
519 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
520 _cleanup_times(),
521 _total_counting_time(0.0),
522 _total_rs_scrub_time(0.0),
524 _parallel_workers(NULL),
526 _count_card_bitmaps(NULL),
527 _count_marked_bytes(NULL),
528 _completed_initialization(false) {
529 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel;
530 if (verbose_level < no_verbose) {
531 verbose_level = no_verbose;
532 }
533 if (verbose_level > high_verbose) {
534 verbose_level = high_verbose;
535 }
536 _verbose_level = verbose_level;
538 if (verbose_low()) {
539 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", "
540 "heap end = " INTPTR_FORMAT, p2i(_heap_start), p2i(_heap_end));
541 }
543 if (!_markBitMap1.allocate(heap_rs)) {
544 warning("Failed to allocate first CM bit map");
545 return;
546 }
547 if (!_markBitMap2.allocate(heap_rs)) {
548 warning("Failed to allocate second CM bit map");
549 return;
550 }
552 // Create & start a ConcurrentMark thread.
553 _cmThread = new ConcurrentMarkThread(this);
554 assert(cmThread() != NULL, "CM Thread should have been created");
555 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
556 if (_cmThread->osthread() == NULL) {
557 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
558 }
560 assert(CGC_lock != NULL, "Where's the CGC_lock?");
561 assert(_markBitMap1.covers(heap_rs), "_markBitMap1 inconsistency");
562 assert(_markBitMap2.covers(heap_rs), "_markBitMap2 inconsistency");
564 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
565 satb_qs.set_buffer_size(G1SATBBufferSize);
567 _root_regions.init(_g1h, this);
569 if (ConcGCThreads > ParallelGCThreads) {
570 warning("Can't have more ConcGCThreads (" UINTX_FORMAT ") "
571 "than ParallelGCThreads (" UINTX_FORMAT ").",
572 ConcGCThreads, ParallelGCThreads);
573 return;
574 }
575 if (ParallelGCThreads == 0) {
576 // if we are not running with any parallel GC threads we will not
577 // spawn any marking threads either
578 _parallel_marking_threads = 0;
579 _max_parallel_marking_threads = 0;
580 _sleep_factor = 0.0;
581 _marking_task_overhead = 1.0;
582 } else {
583 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
584 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
585 // if both are set
586 _sleep_factor = 0.0;
587 _marking_task_overhead = 1.0;
588 } else if (G1MarkingOverheadPercent > 0) {
589 // We will calculate the number of parallel marking threads based
590 // on a target overhead with respect to the soft real-time goal
591 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
592 double overall_cm_overhead =
593 (double) MaxGCPauseMillis * marking_overhead /
594 (double) GCPauseIntervalMillis;
595 double cpu_ratio = 1.0 / (double) os::processor_count();
596 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
597 double marking_task_overhead =
598 overall_cm_overhead / marking_thread_num *
599 (double) os::processor_count();
600 double sleep_factor =
601 (1.0 - marking_task_overhead) / marking_task_overhead;
603 FLAG_SET_ERGO(uintx, ConcGCThreads, (uint) marking_thread_num);
604 _sleep_factor = sleep_factor;
605 _marking_task_overhead = marking_task_overhead;
606 } else {
607 // Calculate the number of parallel marking threads by scaling
608 // the number of parallel GC threads.
609 uint marking_thread_num = scale_parallel_threads((uint) ParallelGCThreads);
610 FLAG_SET_ERGO(uintx, ConcGCThreads, marking_thread_num);
611 _sleep_factor = 0.0;
612 _marking_task_overhead = 1.0;
613 }
615 assert(ConcGCThreads > 0, "Should have been set");
616 _parallel_marking_threads = (uint) ConcGCThreads;
617 _max_parallel_marking_threads = _parallel_marking_threads;
619 if (parallel_marking_threads() > 1) {
620 _cleanup_task_overhead = 1.0;
621 } else {
622 _cleanup_task_overhead = marking_task_overhead();
623 }
624 _cleanup_sleep_factor =
625 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
627 #if 0
628 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
629 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
630 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
631 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
632 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
633 #endif
635 guarantee(parallel_marking_threads() > 0, "peace of mind");
636 _parallel_workers = new FlexibleWorkGang("G1 Parallel Marking Threads",
637 _max_parallel_marking_threads, false, true);
638 if (_parallel_workers == NULL) {
639 vm_exit_during_initialization("Failed necessary allocation.");
640 } else {
641 _parallel_workers->initialize_workers();
642 }
643 }
645 if (FLAG_IS_DEFAULT(MarkStackSize)) {
646 uintx mark_stack_size =
647 MIN2(MarkStackSizeMax,
648 MAX2(MarkStackSize, (uintx) (parallel_marking_threads() * TASKQUEUE_SIZE)));
649 // Verify that the calculated value for MarkStackSize is in range.
650 // It would be nice to use the private utility routine from Arguments.
651 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
652 warning("Invalid value calculated for MarkStackSize (" UINTX_FORMAT "): "
653 "must be between " UINTX_FORMAT " and " UINTX_FORMAT,
654 mark_stack_size, (uintx) 1, MarkStackSizeMax);
655 return;
656 }
657 FLAG_SET_ERGO(uintx, MarkStackSize, mark_stack_size);
658 } else {
659 // Verify MarkStackSize is in range.
660 if (FLAG_IS_CMDLINE(MarkStackSize)) {
661 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
662 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
663 warning("Invalid value specified for MarkStackSize (" UINTX_FORMAT "): "
664 "must be between " UINTX_FORMAT " and " UINTX_FORMAT,
665 MarkStackSize, (uintx) 1, MarkStackSizeMax);
666 return;
667 }
668 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
669 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
670 warning("Invalid value specified for MarkStackSize (" UINTX_FORMAT ")"
671 " or for MarkStackSizeMax (" UINTX_FORMAT ")",
672 MarkStackSize, MarkStackSizeMax);
673 return;
674 }
675 }
676 }
677 }
679 if (!_markStack.allocate(MarkStackSize)) {
680 warning("Failed to allocate CM marking stack");
681 return;
682 }
684 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC);
685 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
687 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC);
688 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC);
690 BitMap::idx_t card_bm_size = _card_bm.size();
692 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
693 _active_tasks = _max_worker_id;
695 size_t max_regions = (size_t) _g1h->max_regions();
696 for (uint i = 0; i < _max_worker_id; ++i) {
697 CMTaskQueue* task_queue = new CMTaskQueue();
698 task_queue->initialize();
699 _task_queues->register_queue(i, task_queue);
701 _count_card_bitmaps[i] = BitMap(card_bm_size, false);
702 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
704 _tasks[i] = new CMTask(i, this,
705 _count_marked_bytes[i],
706 &_count_card_bitmaps[i],
707 task_queue, _task_queues);
709 _accum_task_vtime[i] = 0.0;
710 }
712 // Calculate the card number for the bottom of the heap. Used
713 // in biasing indexes into the accounting card bitmaps.
714 _heap_bottom_card_num =
715 intptr_t(uintptr_t(_g1h->reserved_region().start()) >>
716 CardTableModRefBS::card_shift);
718 // Clear all the liveness counting data
719 clear_all_count_data();
721 // so that the call below can read a sensible value
722 _heap_start = (HeapWord*) heap_rs.base();
723 set_non_marking_state();
724 _completed_initialization = true;
725 }
727 void ConcurrentMark::update_g1_committed(bool force) {
728 // If concurrent marking is not in progress, then we do not need to
729 // update _heap_end.
730 if (!concurrent_marking_in_progress() && !force) return;
732 MemRegion committed = _g1h->g1_committed();
733 assert(committed.start() == _heap_start, "start shouldn't change");
734 HeapWord* new_end = committed.end();
735 if (new_end > _heap_end) {
736 // The heap has been expanded.
738 _heap_end = new_end;
739 }
740 // Notice that the heap can also shrink. However, this only happens
741 // during a Full GC (at least currently) and the entire marking
742 // phase will bail out and the task will not be restarted. So, let's
743 // do nothing.
744 }
746 void ConcurrentMark::reset() {
747 // Starting values for these two. This should be called in a STW
748 // phase. CM will be notified of any future g1_committed expansions
749 // will be at the end of evacuation pauses, when tasks are
750 // inactive.
751 MemRegion committed = _g1h->g1_committed();
752 _heap_start = committed.start();
753 _heap_end = committed.end();
755 // Separated the asserts so that we know which one fires.
756 assert(_heap_start != NULL, "heap bounds should look ok");
757 assert(_heap_end != NULL, "heap bounds should look ok");
758 assert(_heap_start < _heap_end, "heap bounds should look ok");
760 // Reset all the marking data structures and any necessary flags
761 reset_marking_state();
763 if (verbose_low()) {
764 gclog_or_tty->print_cr("[global] resetting");
765 }
767 // We do reset all of them, since different phases will use
768 // different number of active threads. So, it's easiest to have all
769 // of them ready.
770 for (uint i = 0; i < _max_worker_id; ++i) {
771 _tasks[i]->reset(_nextMarkBitMap);
772 }
774 // we need this to make sure that the flag is on during the evac
775 // pause with initial mark piggy-backed
776 set_concurrent_marking_in_progress();
777 }
780 void ConcurrentMark::reset_marking_state(bool clear_overflow) {
781 _markStack.set_should_expand();
782 _markStack.setEmpty(); // Also clears the _markStack overflow flag
783 if (clear_overflow) {
784 clear_has_overflown();
785 } else {
786 assert(has_overflown(), "pre-condition");
787 }
788 _finger = _heap_start;
790 for (uint i = 0; i < _max_worker_id; ++i) {
791 CMTaskQueue* queue = _task_queues->queue(i);
792 queue->set_empty();
793 }
794 }
796 void ConcurrentMark::set_concurrency(uint active_tasks) {
797 assert(active_tasks <= _max_worker_id, "we should not have more");
799 _active_tasks = active_tasks;
800 // Need to update the three data structures below according to the
801 // number of active threads for this phase.
802 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
803 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
804 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
805 }
807 void ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
808 set_concurrency(active_tasks);
810 _concurrent = concurrent;
811 // We propagate this to all tasks, not just the active ones.
812 for (uint i = 0; i < _max_worker_id; ++i)
813 _tasks[i]->set_concurrent(concurrent);
815 if (concurrent) {
816 set_concurrent_marking_in_progress();
817 } else {
818 // We currently assume that the concurrent flag has been set to
819 // false before we start remark. At this point we should also be
820 // in a STW phase.
821 assert(!concurrent_marking_in_progress(), "invariant");
822 assert(out_of_regions(),
823 err_msg("only way to get here: _finger: "PTR_FORMAT", _heap_end: "PTR_FORMAT,
824 p2i(_finger), p2i(_heap_end)));
825 update_g1_committed(true);
826 }
827 }
829 void ConcurrentMark::set_non_marking_state() {
830 // We set the global marking state to some default values when we're
831 // not doing marking.
832 reset_marking_state();
833 _active_tasks = 0;
834 clear_concurrent_marking_in_progress();
835 }
837 ConcurrentMark::~ConcurrentMark() {
838 // The ConcurrentMark instance is never freed.
839 ShouldNotReachHere();
840 }
842 void ConcurrentMark::clearNextBitmap() {
843 G1CollectedHeap* g1h = G1CollectedHeap::heap();
844 G1CollectorPolicy* g1p = g1h->g1_policy();
846 // Make sure that the concurrent mark thread looks to still be in
847 // the current cycle.
848 guarantee(cmThread()->during_cycle(), "invariant");
850 // We are finishing up the current cycle by clearing the next
851 // marking bitmap and getting it ready for the next cycle. During
852 // this time no other cycle can start. So, let's make sure that this
853 // is the case.
854 guarantee(!g1h->mark_in_progress(), "invariant");
856 // clear the mark bitmap (no grey objects to start with).
857 // We need to do this in chunks and offer to yield in between
858 // each chunk.
859 HeapWord* start = _nextMarkBitMap->startWord();
860 HeapWord* end = _nextMarkBitMap->endWord();
861 HeapWord* cur = start;
862 size_t chunkSize = M;
863 while (cur < end) {
864 HeapWord* next = cur + chunkSize;
865 if (next > end) {
866 next = end;
867 }
868 MemRegion mr(cur,next);
869 _nextMarkBitMap->clearRange(mr);
870 cur = next;
871 do_yield_check();
873 // Repeat the asserts from above. We'll do them as asserts here to
874 // minimize their overhead on the product. However, we'll have
875 // them as guarantees at the beginning / end of the bitmap
876 // clearing to get some checking in the product.
877 assert(cmThread()->during_cycle(), "invariant");
878 assert(!g1h->mark_in_progress(), "invariant");
879 }
881 // Clear the liveness counting data
882 clear_all_count_data();
884 // Repeat the asserts from above.
885 guarantee(cmThread()->during_cycle(), "invariant");
886 guarantee(!g1h->mark_in_progress(), "invariant");
887 }
889 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
890 public:
891 bool doHeapRegion(HeapRegion* r) {
892 if (!r->continuesHumongous()) {
893 r->note_start_of_marking();
894 }
895 return false;
896 }
897 };
899 void ConcurrentMark::checkpointRootsInitialPre() {
900 G1CollectedHeap* g1h = G1CollectedHeap::heap();
901 G1CollectorPolicy* g1p = g1h->g1_policy();
903 _has_aborted = false;
905 #ifndef PRODUCT
906 if (G1PrintReachableAtInitialMark) {
907 print_reachable("at-cycle-start",
908 VerifyOption_G1UsePrevMarking, true /* all */);
909 }
910 #endif
912 // Initialise marking structures. This has to be done in a STW phase.
913 reset();
915 // For each region note start of marking.
916 NoteStartOfMarkHRClosure startcl;
917 g1h->heap_region_iterate(&startcl);
918 }
921 void ConcurrentMark::checkpointRootsInitialPost() {
922 G1CollectedHeap* g1h = G1CollectedHeap::heap();
924 // If we force an overflow during remark, the remark operation will
925 // actually abort and we'll restart concurrent marking. If we always
926 // force an oveflow during remark we'll never actually complete the
927 // marking phase. So, we initilize this here, at the start of the
928 // cycle, so that at the remaining overflow number will decrease at
929 // every remark and we'll eventually not need to cause one.
930 force_overflow_stw()->init();
932 // Start Concurrent Marking weak-reference discovery.
933 ReferenceProcessor* rp = g1h->ref_processor_cm();
934 // enable ("weak") refs discovery
935 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
936 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
938 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
939 // This is the start of the marking cycle, we're expected all
940 // threads to have SATB queues with active set to false.
941 satb_mq_set.set_active_all_threads(true, /* new active value */
942 false /* expected_active */);
944 _root_regions.prepare_for_scan();
946 // update_g1_committed() will be called at the end of an evac pause
947 // when marking is on. So, it's also called at the end of the
948 // initial-mark pause to update the heap end, if the heap expands
949 // during it. No need to call it here.
950 }
952 /*
953 * Notice that in the next two methods, we actually leave the STS
954 * during the barrier sync and join it immediately afterwards. If we
955 * do not do this, the following deadlock can occur: one thread could
956 * be in the barrier sync code, waiting for the other thread to also
957 * sync up, whereas another one could be trying to yield, while also
958 * waiting for the other threads to sync up too.
959 *
960 * Note, however, that this code is also used during remark and in
961 * this case we should not attempt to leave / enter the STS, otherwise
962 * we'll either hit an asseert (debug / fastdebug) or deadlock
963 * (product). So we should only leave / enter the STS if we are
964 * operating concurrently.
965 *
966 * Because the thread that does the sync barrier has left the STS, it
967 * is possible to be suspended for a Full GC or an evacuation pause
968 * could occur. This is actually safe, since the entering the sync
969 * barrier is one of the last things do_marking_step() does, and it
970 * doesn't manipulate any data structures afterwards.
971 */
973 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
974 if (verbose_low()) {
975 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id);
976 }
978 if (concurrent()) {
979 ConcurrentGCThread::stsLeave();
980 }
982 bool barrier_aborted = !_first_overflow_barrier_sync.enter();
984 if (concurrent()) {
985 ConcurrentGCThread::stsJoin();
986 }
987 // at this point everyone should have synced up and not be doing any
988 // more work
990 if (verbose_low()) {
991 if (barrier_aborted) {
992 gclog_or_tty->print_cr("[%u] aborted first barrier", worker_id);
993 } else {
994 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id);
995 }
996 }
998 if (barrier_aborted) {
999 // If the barrier aborted we ignore the overflow condition and
1000 // just abort the whole marking phase as quickly as possible.
1001 return;
1002 }
1004 // If we're executing the concurrent phase of marking, reset the marking
1005 // state; otherwise the marking state is reset after reference processing,
1006 // during the remark pause.
1007 // If we reset here as a result of an overflow during the remark we will
1008 // see assertion failures from any subsequent set_concurrency_and_phase()
1009 // calls.
1010 if (concurrent()) {
1011 // let the task associated with with worker 0 do this
1012 if (worker_id == 0) {
1013 // task 0 is responsible for clearing the global data structures
1014 // We should be here because of an overflow. During STW we should
1015 // not clear the overflow flag since we rely on it being true when
1016 // we exit this method to abort the pause and restart concurent
1017 // marking.
1018 reset_marking_state(true /* clear_overflow */);
1019 force_overflow()->update();
1021 if (G1Log::fine()) {
1022 gclog_or_tty->date_stamp(PrintGCDateStamps);
1023 gclog_or_tty->stamp(PrintGCTimeStamps);
1024 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
1025 }
1026 }
1027 }
1029 // after this, each task should reset its own data structures then
1030 // then go into the second barrier
1031 }
1033 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
1034 if (verbose_low()) {
1035 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id);
1036 }
1038 if (concurrent()) {
1039 ConcurrentGCThread::stsLeave();
1040 }
1042 bool barrier_aborted = !_second_overflow_barrier_sync.enter();
1044 if (concurrent()) {
1045 ConcurrentGCThread::stsJoin();
1046 }
1047 // at this point everything should be re-initialized and ready to go
1049 if (verbose_low()) {
1050 if (barrier_aborted) {
1051 gclog_or_tty->print_cr("[%u] aborted second barrier", worker_id);
1052 } else {
1053 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id);
1054 }
1055 }
1056 }
1058 #ifndef PRODUCT
1059 void ForceOverflowSettings::init() {
1060 _num_remaining = G1ConcMarkForceOverflow;
1061 _force = false;
1062 update();
1063 }
1065 void ForceOverflowSettings::update() {
1066 if (_num_remaining > 0) {
1067 _num_remaining -= 1;
1068 _force = true;
1069 } else {
1070 _force = false;
1071 }
1072 }
1074 bool ForceOverflowSettings::should_force() {
1075 if (_force) {
1076 _force = false;
1077 return true;
1078 } else {
1079 return false;
1080 }
1081 }
1082 #endif // !PRODUCT
1084 class CMConcurrentMarkingTask: public AbstractGangTask {
1085 private:
1086 ConcurrentMark* _cm;
1087 ConcurrentMarkThread* _cmt;
1089 public:
1090 void work(uint worker_id) {
1091 assert(Thread::current()->is_ConcurrentGC_thread(),
1092 "this should only be done by a conc GC thread");
1093 ResourceMark rm;
1095 double start_vtime = os::elapsedVTime();
1097 ConcurrentGCThread::stsJoin();
1099 assert(worker_id < _cm->active_tasks(), "invariant");
1100 CMTask* the_task = _cm->task(worker_id);
1101 the_task->record_start_time();
1102 if (!_cm->has_aborted()) {
1103 do {
1104 double start_vtime_sec = os::elapsedVTime();
1105 double start_time_sec = os::elapsedTime();
1106 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1108 the_task->do_marking_step(mark_step_duration_ms,
1109 true /* do_termination */,
1110 false /* is_serial*/);
1112 double end_time_sec = os::elapsedTime();
1113 double end_vtime_sec = os::elapsedVTime();
1114 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1115 double elapsed_time_sec = end_time_sec - start_time_sec;
1116 _cm->clear_has_overflown();
1118 bool ret = _cm->do_yield_check(worker_id);
1120 jlong sleep_time_ms;
1121 if (!_cm->has_aborted() && the_task->has_aborted()) {
1122 sleep_time_ms =
1123 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1124 ConcurrentGCThread::stsLeave();
1125 os::sleep(Thread::current(), sleep_time_ms, false);
1126 ConcurrentGCThread::stsJoin();
1127 }
1128 double end_time2_sec = os::elapsedTime();
1129 double elapsed_time2_sec = end_time2_sec - start_time_sec;
1131 #if 0
1132 gclog_or_tty->print_cr("CM: elapsed %1.4lf ms, sleep %1.4lf ms, "
1133 "overhead %1.4lf",
1134 elapsed_vtime_sec * 1000.0, (double) sleep_time_ms,
1135 the_task->conc_overhead(os::elapsedTime()) * 8.0);
1136 gclog_or_tty->print_cr("elapsed time %1.4lf ms, time 2: %1.4lf ms",
1137 elapsed_time_sec * 1000.0, elapsed_time2_sec * 1000.0);
1138 #endif
1139 } while (!_cm->has_aborted() && the_task->has_aborted());
1140 }
1141 the_task->record_end_time();
1142 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1144 ConcurrentGCThread::stsLeave();
1146 double end_vtime = os::elapsedVTime();
1147 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
1148 }
1150 CMConcurrentMarkingTask(ConcurrentMark* cm,
1151 ConcurrentMarkThread* cmt) :
1152 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1154 ~CMConcurrentMarkingTask() { }
1155 };
1157 // Calculates the number of active workers for a concurrent
1158 // phase.
1159 uint ConcurrentMark::calc_parallel_marking_threads() {
1160 if (G1CollectedHeap::use_parallel_gc_threads()) {
1161 uint n_conc_workers = 0;
1162 if (!UseDynamicNumberOfGCThreads ||
1163 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
1164 !ForceDynamicNumberOfGCThreads)) {
1165 n_conc_workers = max_parallel_marking_threads();
1166 } else {
1167 n_conc_workers =
1168 AdaptiveSizePolicy::calc_default_active_workers(
1169 max_parallel_marking_threads(),
1170 1, /* Minimum workers */
1171 parallel_marking_threads(),
1172 Threads::number_of_non_daemon_threads());
1173 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
1174 // that scaling has already gone into "_max_parallel_marking_threads".
1175 }
1176 assert(n_conc_workers > 0, "Always need at least 1");
1177 return n_conc_workers;
1178 }
1179 // If we are not running with any parallel GC threads we will not
1180 // have spawned any marking threads either. Hence the number of
1181 // concurrent workers should be 0.
1182 return 0;
1183 }
1185 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
1186 // Currently, only survivors can be root regions.
1187 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
1188 G1RootRegionScanClosure cl(_g1h, this, worker_id);
1190 const uintx interval = PrefetchScanIntervalInBytes;
1191 HeapWord* curr = hr->bottom();
1192 const HeapWord* end = hr->top();
1193 while (curr < end) {
1194 Prefetch::read(curr, interval);
1195 oop obj = oop(curr);
1196 int size = obj->oop_iterate(&cl);
1197 assert(size == obj->size(), "sanity");
1198 curr += size;
1199 }
1200 }
1202 class CMRootRegionScanTask : public AbstractGangTask {
1203 private:
1204 ConcurrentMark* _cm;
1206 public:
1207 CMRootRegionScanTask(ConcurrentMark* cm) :
1208 AbstractGangTask("Root Region Scan"), _cm(cm) { }
1210 void work(uint worker_id) {
1211 assert(Thread::current()->is_ConcurrentGC_thread(),
1212 "this should only be done by a conc GC thread");
1214 CMRootRegions* root_regions = _cm->root_regions();
1215 HeapRegion* hr = root_regions->claim_next();
1216 while (hr != NULL) {
1217 _cm->scanRootRegion(hr, worker_id);
1218 hr = root_regions->claim_next();
1219 }
1220 }
1221 };
1223 void ConcurrentMark::scanRootRegions() {
1224 // scan_in_progress() will have been set to true only if there was
1225 // at least one root region to scan. So, if it's false, we
1226 // should not attempt to do any further work.
1227 if (root_regions()->scan_in_progress()) {
1228 _parallel_marking_threads = calc_parallel_marking_threads();
1229 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1230 "Maximum number of marking threads exceeded");
1231 uint active_workers = MAX2(1U, parallel_marking_threads());
1233 CMRootRegionScanTask task(this);
1234 if (use_parallel_marking_threads()) {
1235 _parallel_workers->set_active_workers((int) active_workers);
1236 _parallel_workers->run_task(&task);
1237 } else {
1238 task.work(0);
1239 }
1241 // It's possible that has_aborted() is true here without actually
1242 // aborting the survivor scan earlier. This is OK as it's
1243 // mainly used for sanity checking.
1244 root_regions()->scan_finished();
1245 }
1246 }
1248 void ConcurrentMark::markFromRoots() {
1249 // we might be tempted to assert that:
1250 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1251 // "inconsistent argument?");
1252 // However that wouldn't be right, because it's possible that
1253 // a safepoint is indeed in progress as a younger generation
1254 // stop-the-world GC happens even as we mark in this generation.
1256 _restart_for_overflow = false;
1257 force_overflow_conc()->init();
1259 // _g1h has _n_par_threads
1260 _parallel_marking_threads = calc_parallel_marking_threads();
1261 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1262 "Maximum number of marking threads exceeded");
1264 uint active_workers = MAX2(1U, parallel_marking_threads());
1266 // Parallel task terminator is set in "set_concurrency_and_phase()"
1267 set_concurrency_and_phase(active_workers, true /* concurrent */);
1269 CMConcurrentMarkingTask markingTask(this, cmThread());
1270 if (use_parallel_marking_threads()) {
1271 _parallel_workers->set_active_workers((int)active_workers);
1272 // Don't set _n_par_threads because it affects MT in proceess_strong_roots()
1273 // and the decisions on that MT processing is made elsewhere.
1274 assert(_parallel_workers->active_workers() > 0, "Should have been set");
1275 _parallel_workers->run_task(&markingTask);
1276 } else {
1277 markingTask.work(0);
1278 }
1279 print_stats();
1280 }
1282 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1283 // world is stopped at this checkpoint
1284 assert(SafepointSynchronize::is_at_safepoint(),
1285 "world should be stopped");
1287 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1289 // If a full collection has happened, we shouldn't do this.
1290 if (has_aborted()) {
1291 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1292 return;
1293 }
1295 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1297 if (VerifyDuringGC) {
1298 HandleMark hm; // handle scope
1299 Universe::heap()->prepare_for_verify();
1300 Universe::verify(VerifyOption_G1UsePrevMarking,
1301 " VerifyDuringGC:(before)");
1302 }
1304 G1CollectorPolicy* g1p = g1h->g1_policy();
1305 g1p->record_concurrent_mark_remark_start();
1307 double start = os::elapsedTime();
1309 checkpointRootsFinalWork();
1311 double mark_work_end = os::elapsedTime();
1313 weakRefsWork(clear_all_soft_refs);
1315 if (has_overflown()) {
1316 // Oops. We overflowed. Restart concurrent marking.
1317 _restart_for_overflow = true;
1318 if (G1TraceMarkStackOverflow) {
1319 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1320 }
1322 // Verify the heap w.r.t. the previous marking bitmap.
1323 if (VerifyDuringGC) {
1324 HandleMark hm; // handle scope
1325 Universe::heap()->prepare_for_verify();
1326 Universe::verify(VerifyOption_G1UsePrevMarking,
1327 " VerifyDuringGC:(overflow)");
1328 }
1330 // Clear the marking state because we will be restarting
1331 // marking due to overflowing the global mark stack.
1332 reset_marking_state();
1333 } else {
1334 // Aggregate the per-task counting data that we have accumulated
1335 // while marking.
1336 aggregate_count_data();
1338 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1339 // We're done with marking.
1340 // This is the end of the marking cycle, we're expected all
1341 // threads to have SATB queues with active set to true.
1342 satb_mq_set.set_active_all_threads(false, /* new active value */
1343 true /* expected_active */);
1345 if (VerifyDuringGC) {
1346 HandleMark hm; // handle scope
1347 Universe::heap()->prepare_for_verify();
1348 Universe::verify(VerifyOption_G1UseNextMarking,
1349 " VerifyDuringGC:(after)");
1350 }
1351 assert(!restart_for_overflow(), "sanity");
1352 // Completely reset the marking state since marking completed
1353 set_non_marking_state();
1354 }
1356 // Expand the marking stack, if we have to and if we can.
1357 if (_markStack.should_expand()) {
1358 _markStack.expand();
1359 }
1361 // Statistics
1362 double now = os::elapsedTime();
1363 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1364 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1365 _remark_times.add((now - start) * 1000.0);
1367 g1p->record_concurrent_mark_remark_end();
1369 G1CMIsAliveClosure is_alive(g1h);
1370 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
1371 }
1373 // Base class of the closures that finalize and verify the
1374 // liveness counting data.
1375 class CMCountDataClosureBase: public HeapRegionClosure {
1376 protected:
1377 G1CollectedHeap* _g1h;
1378 ConcurrentMark* _cm;
1379 CardTableModRefBS* _ct_bs;
1381 BitMap* _region_bm;
1382 BitMap* _card_bm;
1384 // Takes a region that's not empty (i.e., it has at least one
1385 // live object in it and sets its corresponding bit on the region
1386 // bitmap to 1. If the region is "starts humongous" it will also set
1387 // to 1 the bits on the region bitmap that correspond to its
1388 // associated "continues humongous" regions.
1389 void set_bit_for_region(HeapRegion* hr) {
1390 assert(!hr->continuesHumongous(), "should have filtered those out");
1392 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1393 if (!hr->startsHumongous()) {
1394 // Normal (non-humongous) case: just set the bit.
1395 _region_bm->par_at_put(index, true);
1396 } else {
1397 // Starts humongous case: calculate how many regions are part of
1398 // this humongous region and then set the bit range.
1399 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1400 _region_bm->par_at_put_range(index, end_index, true);
1401 }
1402 }
1404 public:
1405 CMCountDataClosureBase(G1CollectedHeap* g1h,
1406 BitMap* region_bm, BitMap* card_bm):
1407 _g1h(g1h), _cm(g1h->concurrent_mark()),
1408 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
1409 _region_bm(region_bm), _card_bm(card_bm) { }
1410 };
1412 // Closure that calculates the # live objects per region. Used
1413 // for verification purposes during the cleanup pause.
1414 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1415 CMBitMapRO* _bm;
1416 size_t _region_marked_bytes;
1418 public:
1419 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1420 BitMap* region_bm, BitMap* card_bm) :
1421 CMCountDataClosureBase(g1h, region_bm, card_bm),
1422 _bm(bm), _region_marked_bytes(0) { }
1424 bool doHeapRegion(HeapRegion* hr) {
1426 if (hr->continuesHumongous()) {
1427 // We will ignore these here and process them when their
1428 // associated "starts humongous" region is processed (see
1429 // set_bit_for_heap_region()). Note that we cannot rely on their
1430 // associated "starts humongous" region to have their bit set to
1431 // 1 since, due to the region chunking in the parallel region
1432 // iteration, a "continues humongous" region might be visited
1433 // before its associated "starts humongous".
1434 return false;
1435 }
1437 HeapWord* ntams = hr->next_top_at_mark_start();
1438 HeapWord* start = hr->bottom();
1440 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1441 err_msg("Preconditions not met - "
1442 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT,
1443 p2i(start), p2i(ntams), p2i(hr->end())));
1445 // Find the first marked object at or after "start".
1446 start = _bm->getNextMarkedWordAddress(start, ntams);
1448 size_t marked_bytes = 0;
1450 while (start < ntams) {
1451 oop obj = oop(start);
1452 int obj_sz = obj->size();
1453 HeapWord* obj_end = start + obj_sz;
1455 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1456 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1458 // Note: if we're looking at the last region in heap - obj_end
1459 // could be actually just beyond the end of the heap; end_idx
1460 // will then correspond to a (non-existent) card that is also
1461 // just beyond the heap.
1462 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1463 // end of object is not card aligned - increment to cover
1464 // all the cards spanned by the object
1465 end_idx += 1;
1466 }
1468 // Set the bits in the card BM for the cards spanned by this object.
1469 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1471 // Add the size of this object to the number of marked bytes.
1472 marked_bytes += (size_t)obj_sz * HeapWordSize;
1474 // Find the next marked object after this one.
1475 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1476 }
1478 // Mark the allocated-since-marking portion...
1479 HeapWord* top = hr->top();
1480 if (ntams < top) {
1481 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1482 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1484 // Note: if we're looking at the last region in heap - top
1485 // could be actually just beyond the end of the heap; end_idx
1486 // will then correspond to a (non-existent) card that is also
1487 // just beyond the heap.
1488 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1489 // end of object is not card aligned - increment to cover
1490 // all the cards spanned by the object
1491 end_idx += 1;
1492 }
1493 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1495 // This definitely means the region has live objects.
1496 set_bit_for_region(hr);
1497 }
1499 // Update the live region bitmap.
1500 if (marked_bytes > 0) {
1501 set_bit_for_region(hr);
1502 }
1504 // Set the marked bytes for the current region so that
1505 // it can be queried by a calling verificiation routine
1506 _region_marked_bytes = marked_bytes;
1508 return false;
1509 }
1511 size_t region_marked_bytes() const { return _region_marked_bytes; }
1512 };
1514 // Heap region closure used for verifying the counting data
1515 // that was accumulated concurrently and aggregated during
1516 // the remark pause. This closure is applied to the heap
1517 // regions during the STW cleanup pause.
1519 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1520 G1CollectedHeap* _g1h;
1521 ConcurrentMark* _cm;
1522 CalcLiveObjectsClosure _calc_cl;
1523 BitMap* _region_bm; // Region BM to be verified
1524 BitMap* _card_bm; // Card BM to be verified
1525 bool _verbose; // verbose output?
1527 BitMap* _exp_region_bm; // Expected Region BM values
1528 BitMap* _exp_card_bm; // Expected card BM values
1530 int _failures;
1532 public:
1533 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1534 BitMap* region_bm,
1535 BitMap* card_bm,
1536 BitMap* exp_region_bm,
1537 BitMap* exp_card_bm,
1538 bool verbose) :
1539 _g1h(g1h), _cm(g1h->concurrent_mark()),
1540 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1541 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1542 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1543 _failures(0) { }
1545 int failures() const { return _failures; }
1547 bool doHeapRegion(HeapRegion* hr) {
1548 if (hr->continuesHumongous()) {
1549 // We will ignore these here and process them when their
1550 // associated "starts humongous" region is processed (see
1551 // set_bit_for_heap_region()). Note that we cannot rely on their
1552 // associated "starts humongous" region to have their bit set to
1553 // 1 since, due to the region chunking in the parallel region
1554 // iteration, a "continues humongous" region might be visited
1555 // before its associated "starts humongous".
1556 return false;
1557 }
1559 int failures = 0;
1561 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1562 // this region and set the corresponding bits in the expected region
1563 // and card bitmaps.
1564 bool res = _calc_cl.doHeapRegion(hr);
1565 assert(res == false, "should be continuing");
1567 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1568 Mutex::_no_safepoint_check_flag);
1570 // Verify the marked bytes for this region.
1571 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1572 size_t act_marked_bytes = hr->next_marked_bytes();
1574 // We're not OK if expected marked bytes > actual marked bytes. It means
1575 // we have missed accounting some objects during the actual marking.
1576 if (exp_marked_bytes > act_marked_bytes) {
1577 if (_verbose) {
1578 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1579 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1580 hr->hrs_index(), exp_marked_bytes, act_marked_bytes);
1581 }
1582 failures += 1;
1583 }
1585 // Verify the bit, for this region, in the actual and expected
1586 // (which was just calculated) region bit maps.
1587 // We're not OK if the bit in the calculated expected region
1588 // bitmap is set and the bit in the actual region bitmap is not.
1589 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1591 bool expected = _exp_region_bm->at(index);
1592 bool actual = _region_bm->at(index);
1593 if (expected && !actual) {
1594 if (_verbose) {
1595 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1596 "expected: %s, actual: %s",
1597 hr->hrs_index(),
1598 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1599 }
1600 failures += 1;
1601 }
1603 // Verify that the card bit maps for the cards spanned by the current
1604 // region match. We have an error if we have a set bit in the expected
1605 // bit map and the corresponding bit in the actual bitmap is not set.
1607 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1608 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1610 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1611 expected = _exp_card_bm->at(i);
1612 actual = _card_bm->at(i);
1614 if (expected && !actual) {
1615 if (_verbose) {
1616 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1617 "expected: %s, actual: %s",
1618 hr->hrs_index(), i,
1619 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1620 }
1621 failures += 1;
1622 }
1623 }
1625 if (failures > 0 && _verbose) {
1626 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1627 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1628 HR_FORMAT_PARAMS(hr), p2i(hr->next_top_at_mark_start()),
1629 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1630 }
1632 _failures += failures;
1634 // We could stop iteration over the heap when we
1635 // find the first violating region by returning true.
1636 return false;
1637 }
1638 };
1640 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1641 protected:
1642 G1CollectedHeap* _g1h;
1643 ConcurrentMark* _cm;
1644 BitMap* _actual_region_bm;
1645 BitMap* _actual_card_bm;
1647 uint _n_workers;
1649 BitMap* _expected_region_bm;
1650 BitMap* _expected_card_bm;
1652 int _failures;
1653 bool _verbose;
1655 public:
1656 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1657 BitMap* region_bm, BitMap* card_bm,
1658 BitMap* expected_region_bm, BitMap* expected_card_bm)
1659 : AbstractGangTask("G1 verify final counting"),
1660 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1661 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1662 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1663 _failures(0), _verbose(false),
1664 _n_workers(0) {
1665 assert(VerifyDuringGC, "don't call this otherwise");
1667 // Use the value already set as the number of active threads
1668 // in the call to run_task().
1669 if (G1CollectedHeap::use_parallel_gc_threads()) {
1670 assert( _g1h->workers()->active_workers() > 0,
1671 "Should have been previously set");
1672 _n_workers = _g1h->workers()->active_workers();
1673 } else {
1674 _n_workers = 1;
1675 }
1677 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1678 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1680 _verbose = _cm->verbose_medium();
1681 }
1683 void work(uint worker_id) {
1684 assert(worker_id < _n_workers, "invariant");
1686 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1687 _actual_region_bm, _actual_card_bm,
1688 _expected_region_bm,
1689 _expected_card_bm,
1690 _verbose);
1692 if (G1CollectedHeap::use_parallel_gc_threads()) {
1693 _g1h->heap_region_par_iterate_chunked(&verify_cl,
1694 worker_id,
1695 _n_workers,
1696 HeapRegion::VerifyCountClaimValue);
1697 } else {
1698 _g1h->heap_region_iterate(&verify_cl);
1699 }
1701 Atomic::add(verify_cl.failures(), &_failures);
1702 }
1704 int failures() const { return _failures; }
1705 };
1707 // Closure that finalizes the liveness counting data.
1708 // Used during the cleanup pause.
1709 // Sets the bits corresponding to the interval [NTAMS, top]
1710 // (which contains the implicitly live objects) in the
1711 // card liveness bitmap. Also sets the bit for each region,
1712 // containing live data, in the region liveness bitmap.
1714 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1715 public:
1716 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1717 BitMap* region_bm,
1718 BitMap* card_bm) :
1719 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1721 bool doHeapRegion(HeapRegion* hr) {
1723 if (hr->continuesHumongous()) {
1724 // We will ignore these here and process them when their
1725 // associated "starts humongous" region is processed (see
1726 // set_bit_for_heap_region()). Note that we cannot rely on their
1727 // associated "starts humongous" region to have their bit set to
1728 // 1 since, due to the region chunking in the parallel region
1729 // iteration, a "continues humongous" region might be visited
1730 // before its associated "starts humongous".
1731 return false;
1732 }
1734 HeapWord* ntams = hr->next_top_at_mark_start();
1735 HeapWord* top = hr->top();
1737 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1739 // Mark the allocated-since-marking portion...
1740 if (ntams < top) {
1741 // This definitely means the region has live objects.
1742 set_bit_for_region(hr);
1744 // Now set the bits in the card bitmap for [ntams, top)
1745 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1746 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1748 // Note: if we're looking at the last region in heap - top
1749 // could be actually just beyond the end of the heap; end_idx
1750 // will then correspond to a (non-existent) card that is also
1751 // just beyond the heap.
1752 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1753 // end of object is not card aligned - increment to cover
1754 // all the cards spanned by the object
1755 end_idx += 1;
1756 }
1758 assert(end_idx <= _card_bm->size(),
1759 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1760 end_idx, _card_bm->size()));
1761 assert(start_idx < _card_bm->size(),
1762 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1763 start_idx, _card_bm->size()));
1765 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1766 }
1768 // Set the bit for the region if it contains live data
1769 if (hr->next_marked_bytes() > 0) {
1770 set_bit_for_region(hr);
1771 }
1773 return false;
1774 }
1775 };
1777 class G1ParFinalCountTask: public AbstractGangTask {
1778 protected:
1779 G1CollectedHeap* _g1h;
1780 ConcurrentMark* _cm;
1781 BitMap* _actual_region_bm;
1782 BitMap* _actual_card_bm;
1784 uint _n_workers;
1786 public:
1787 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1788 : AbstractGangTask("G1 final counting"),
1789 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1790 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1791 _n_workers(0) {
1792 // Use the value already set as the number of active threads
1793 // in the call to run_task().
1794 if (G1CollectedHeap::use_parallel_gc_threads()) {
1795 assert( _g1h->workers()->active_workers() > 0,
1796 "Should have been previously set");
1797 _n_workers = _g1h->workers()->active_workers();
1798 } else {
1799 _n_workers = 1;
1800 }
1801 }
1803 void work(uint worker_id) {
1804 assert(worker_id < _n_workers, "invariant");
1806 FinalCountDataUpdateClosure final_update_cl(_g1h,
1807 _actual_region_bm,
1808 _actual_card_bm);
1810 if (G1CollectedHeap::use_parallel_gc_threads()) {
1811 _g1h->heap_region_par_iterate_chunked(&final_update_cl,
1812 worker_id,
1813 _n_workers,
1814 HeapRegion::FinalCountClaimValue);
1815 } else {
1816 _g1h->heap_region_iterate(&final_update_cl);
1817 }
1818 }
1819 };
1821 class G1ParNoteEndTask;
1823 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1824 G1CollectedHeap* _g1;
1825 size_t _max_live_bytes;
1826 uint _regions_claimed;
1827 size_t _freed_bytes;
1828 FreeRegionList* _local_cleanup_list;
1829 HeapRegionSetCount _old_regions_removed;
1830 HeapRegionSetCount _humongous_regions_removed;
1831 HRRSCleanupTask* _hrrs_cleanup_task;
1832 double _claimed_region_time;
1833 double _max_region_time;
1835 public:
1836 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1837 FreeRegionList* local_cleanup_list,
1838 HRRSCleanupTask* hrrs_cleanup_task) :
1839 _g1(g1),
1840 _max_live_bytes(0), _regions_claimed(0),
1841 _freed_bytes(0),
1842 _claimed_region_time(0.0), _max_region_time(0.0),
1843 _local_cleanup_list(local_cleanup_list),
1844 _old_regions_removed(),
1845 _humongous_regions_removed(),
1846 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1848 size_t freed_bytes() { return _freed_bytes; }
1849 const HeapRegionSetCount& old_regions_removed() { return _old_regions_removed; }
1850 const HeapRegionSetCount& humongous_regions_removed() { return _humongous_regions_removed; }
1852 bool doHeapRegion(HeapRegion *hr) {
1853 if (hr->continuesHumongous()) {
1854 return false;
1855 }
1856 // We use a claim value of zero here because all regions
1857 // were claimed with value 1 in the FinalCount task.
1858 _g1->reset_gc_time_stamps(hr);
1859 double start = os::elapsedTime();
1860 _regions_claimed++;
1861 hr->note_end_of_marking();
1862 _max_live_bytes += hr->max_live_bytes();
1864 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1865 _freed_bytes += hr->used();
1866 hr->set_containing_set(NULL);
1867 if (hr->isHumongous()) {
1868 assert(hr->startsHumongous(), "we should only see starts humongous");
1869 _humongous_regions_removed.increment(1u, hr->capacity());
1870 _g1->free_humongous_region(hr, _local_cleanup_list, true);
1871 } else {
1872 _old_regions_removed.increment(1u, hr->capacity());
1873 _g1->free_region(hr, _local_cleanup_list, true);
1874 }
1875 } else {
1876 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1877 }
1879 double region_time = (os::elapsedTime() - start);
1880 _claimed_region_time += region_time;
1881 if (region_time > _max_region_time) {
1882 _max_region_time = region_time;
1883 }
1884 return false;
1885 }
1887 size_t max_live_bytes() { return _max_live_bytes; }
1888 uint regions_claimed() { return _regions_claimed; }
1889 double claimed_region_time_sec() { return _claimed_region_time; }
1890 double max_region_time_sec() { return _max_region_time; }
1891 };
1893 class G1ParNoteEndTask: public AbstractGangTask {
1894 friend class G1NoteEndOfConcMarkClosure;
1896 protected:
1897 G1CollectedHeap* _g1h;
1898 size_t _max_live_bytes;
1899 size_t _freed_bytes;
1900 FreeRegionList* _cleanup_list;
1902 public:
1903 G1ParNoteEndTask(G1CollectedHeap* g1h,
1904 FreeRegionList* cleanup_list) :
1905 AbstractGangTask("G1 note end"), _g1h(g1h),
1906 _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list) { }
1908 void work(uint worker_id) {
1909 double start = os::elapsedTime();
1910 FreeRegionList local_cleanup_list("Local Cleanup List");
1911 HRRSCleanupTask hrrs_cleanup_task;
1912 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1913 &hrrs_cleanup_task);
1914 if (G1CollectedHeap::use_parallel_gc_threads()) {
1915 _g1h->heap_region_par_iterate_chunked(&g1_note_end, worker_id,
1916 _g1h->workers()->active_workers(),
1917 HeapRegion::NoteEndClaimValue);
1918 } else {
1919 _g1h->heap_region_iterate(&g1_note_end);
1920 }
1921 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1923 // Now update the lists
1924 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1925 {
1926 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1927 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1928 _max_live_bytes += g1_note_end.max_live_bytes();
1929 _freed_bytes += g1_note_end.freed_bytes();
1931 // If we iterate over the global cleanup list at the end of
1932 // cleanup to do this printing we will not guarantee to only
1933 // generate output for the newly-reclaimed regions (the list
1934 // might not be empty at the beginning of cleanup; we might
1935 // still be working on its previous contents). So we do the
1936 // printing here, before we append the new regions to the global
1937 // cleanup list.
1939 G1HRPrinter* hr_printer = _g1h->hr_printer();
1940 if (hr_printer->is_active()) {
1941 FreeRegionListIterator iter(&local_cleanup_list);
1942 while (iter.more_available()) {
1943 HeapRegion* hr = iter.get_next();
1944 hr_printer->cleanup(hr);
1945 }
1946 }
1948 _cleanup_list->add_ordered(&local_cleanup_list);
1949 assert(local_cleanup_list.is_empty(), "post-condition");
1951 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1952 }
1953 }
1954 size_t max_live_bytes() { return _max_live_bytes; }
1955 size_t freed_bytes() { return _freed_bytes; }
1956 };
1958 class G1ParScrubRemSetTask: public AbstractGangTask {
1959 protected:
1960 G1RemSet* _g1rs;
1961 BitMap* _region_bm;
1962 BitMap* _card_bm;
1963 public:
1964 G1ParScrubRemSetTask(G1CollectedHeap* g1h,
1965 BitMap* region_bm, BitMap* card_bm) :
1966 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()),
1967 _region_bm(region_bm), _card_bm(card_bm) { }
1969 void work(uint worker_id) {
1970 if (G1CollectedHeap::use_parallel_gc_threads()) {
1971 _g1rs->scrub_par(_region_bm, _card_bm, worker_id,
1972 HeapRegion::ScrubRemSetClaimValue);
1973 } else {
1974 _g1rs->scrub(_region_bm, _card_bm);
1975 }
1976 }
1978 };
1980 void ConcurrentMark::cleanup() {
1981 // world is stopped at this checkpoint
1982 assert(SafepointSynchronize::is_at_safepoint(),
1983 "world should be stopped");
1984 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1986 // If a full collection has happened, we shouldn't do this.
1987 if (has_aborted()) {
1988 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1989 return;
1990 }
1992 g1h->verify_region_sets_optional();
1994 if (VerifyDuringGC) {
1995 HandleMark hm; // handle scope
1996 Universe::heap()->prepare_for_verify();
1997 Universe::verify(VerifyOption_G1UsePrevMarking,
1998 " VerifyDuringGC:(before)");
1999 }
2001 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
2002 g1p->record_concurrent_mark_cleanup_start();
2004 double start = os::elapsedTime();
2006 HeapRegionRemSet::reset_for_cleanup_tasks();
2008 uint n_workers;
2010 // Do counting once more with the world stopped for good measure.
2011 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
2013 if (G1CollectedHeap::use_parallel_gc_threads()) {
2014 assert(g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
2015 "sanity check");
2017 g1h->set_par_threads();
2018 n_workers = g1h->n_par_threads();
2019 assert(g1h->n_par_threads() == n_workers,
2020 "Should not have been reset");
2021 g1h->workers()->run_task(&g1_par_count_task);
2022 // Done with the parallel phase so reset to 0.
2023 g1h->set_par_threads(0);
2025 assert(g1h->check_heap_region_claim_values(HeapRegion::FinalCountClaimValue),
2026 "sanity check");
2027 } else {
2028 n_workers = 1;
2029 g1_par_count_task.work(0);
2030 }
2032 if (VerifyDuringGC) {
2033 // Verify that the counting data accumulated during marking matches
2034 // that calculated by walking the marking bitmap.
2036 // Bitmaps to hold expected values
2037 BitMap expected_region_bm(_region_bm.size(), false);
2038 BitMap expected_card_bm(_card_bm.size(), false);
2040 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
2041 &_region_bm,
2042 &_card_bm,
2043 &expected_region_bm,
2044 &expected_card_bm);
2046 if (G1CollectedHeap::use_parallel_gc_threads()) {
2047 g1h->set_par_threads((int)n_workers);
2048 g1h->workers()->run_task(&g1_par_verify_task);
2049 // Done with the parallel phase so reset to 0.
2050 g1h->set_par_threads(0);
2052 assert(g1h->check_heap_region_claim_values(HeapRegion::VerifyCountClaimValue),
2053 "sanity check");
2054 } else {
2055 g1_par_verify_task.work(0);
2056 }
2058 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
2059 }
2061 size_t start_used_bytes = g1h->used();
2062 g1h->set_marking_complete();
2064 double count_end = os::elapsedTime();
2065 double this_final_counting_time = (count_end - start);
2066 _total_counting_time += this_final_counting_time;
2068 if (G1PrintRegionLivenessInfo) {
2069 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
2070 _g1h->heap_region_iterate(&cl);
2071 }
2073 // Install newly created mark bitMap as "prev".
2074 swapMarkBitMaps();
2076 g1h->reset_gc_time_stamp();
2078 // Note end of marking in all heap regions.
2079 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list);
2080 if (G1CollectedHeap::use_parallel_gc_threads()) {
2081 g1h->set_par_threads((int)n_workers);
2082 g1h->workers()->run_task(&g1_par_note_end_task);
2083 g1h->set_par_threads(0);
2085 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue),
2086 "sanity check");
2087 } else {
2088 g1_par_note_end_task.work(0);
2089 }
2090 g1h->check_gc_time_stamps();
2092 if (!cleanup_list_is_empty()) {
2093 // The cleanup list is not empty, so we'll have to process it
2094 // concurrently. Notify anyone else that might be wanting free
2095 // regions that there will be more free regions coming soon.
2096 g1h->set_free_regions_coming();
2097 }
2099 // call below, since it affects the metric by which we sort the heap
2100 // regions.
2101 if (G1ScrubRemSets) {
2102 double rs_scrub_start = os::elapsedTime();
2103 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm);
2104 if (G1CollectedHeap::use_parallel_gc_threads()) {
2105 g1h->set_par_threads((int)n_workers);
2106 g1h->workers()->run_task(&g1_par_scrub_rs_task);
2107 g1h->set_par_threads(0);
2109 assert(g1h->check_heap_region_claim_values(
2110 HeapRegion::ScrubRemSetClaimValue),
2111 "sanity check");
2112 } else {
2113 g1_par_scrub_rs_task.work(0);
2114 }
2116 double rs_scrub_end = os::elapsedTime();
2117 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
2118 _total_rs_scrub_time += this_rs_scrub_time;
2119 }
2121 // this will also free any regions totally full of garbage objects,
2122 // and sort the regions.
2123 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers);
2125 // Statistics.
2126 double end = os::elapsedTime();
2127 _cleanup_times.add((end - start) * 1000.0);
2129 if (G1Log::fine()) {
2130 g1h->print_size_transition(gclog_or_tty,
2131 start_used_bytes,
2132 g1h->used(),
2133 g1h->capacity());
2134 }
2136 // Clean up will have freed any regions completely full of garbage.
2137 // Update the soft reference policy with the new heap occupancy.
2138 Universe::update_heap_info_at_gc();
2140 // We need to make this be a "collection" so any collection pause that
2141 // races with it goes around and waits for completeCleanup to finish.
2142 g1h->increment_total_collections();
2144 // We reclaimed old regions so we should calculate the sizes to make
2145 // sure we update the old gen/space data.
2146 g1h->g1mm()->update_sizes();
2148 if (VerifyDuringGC) {
2149 HandleMark hm; // handle scope
2150 Universe::heap()->prepare_for_verify();
2151 Universe::verify(VerifyOption_G1UsePrevMarking,
2152 " VerifyDuringGC:(after)");
2153 }
2155 g1h->verify_region_sets_optional();
2156 g1h->trace_heap_after_concurrent_cycle();
2157 }
2159 void ConcurrentMark::completeCleanup() {
2160 if (has_aborted()) return;
2162 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2164 _cleanup_list.verify_optional();
2165 FreeRegionList tmp_free_list("Tmp Free List");
2167 if (G1ConcRegionFreeingVerbose) {
2168 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2169 "cleanup list has %u entries",
2170 _cleanup_list.length());
2171 }
2173 // Noone else should be accessing the _cleanup_list at this point,
2174 // so it's not necessary to take any locks
2175 while (!_cleanup_list.is_empty()) {
2176 HeapRegion* hr = _cleanup_list.remove_head();
2177 assert(hr != NULL, "Got NULL from a non-empty list");
2178 hr->par_clear();
2179 tmp_free_list.add_ordered(hr);
2181 // Instead of adding one region at a time to the secondary_free_list,
2182 // we accumulate them in the local list and move them a few at a
2183 // time. This also cuts down on the number of notify_all() calls
2184 // we do during this process. We'll also append the local list when
2185 // _cleanup_list is empty (which means we just removed the last
2186 // region from the _cleanup_list).
2187 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2188 _cleanup_list.is_empty()) {
2189 if (G1ConcRegionFreeingVerbose) {
2190 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2191 "appending %u entries to the secondary_free_list, "
2192 "cleanup list still has %u entries",
2193 tmp_free_list.length(),
2194 _cleanup_list.length());
2195 }
2197 {
2198 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2199 g1h->secondary_free_list_add(&tmp_free_list);
2200 SecondaryFreeList_lock->notify_all();
2201 }
2203 if (G1StressConcRegionFreeing) {
2204 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2205 os::sleep(Thread::current(), (jlong) 1, false);
2206 }
2207 }
2208 }
2209 }
2210 assert(tmp_free_list.is_empty(), "post-condition");
2211 }
2213 // Supporting Object and Oop closures for reference discovery
2214 // and processing in during marking
2216 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2217 HeapWord* addr = (HeapWord*)obj;
2218 return addr != NULL &&
2219 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2220 }
2222 // 'Keep Alive' oop closure used by both serial parallel reference processing.
2223 // Uses the CMTask associated with a worker thread (for serial reference
2224 // processing the CMTask for worker 0 is used) to preserve (mark) and
2225 // trace referent objects.
2226 //
2227 // Using the CMTask and embedded local queues avoids having the worker
2228 // threads operating on the global mark stack. This reduces the risk
2229 // of overflowing the stack - which we would rather avoid at this late
2230 // state. Also using the tasks' local queues removes the potential
2231 // of the workers interfering with each other that could occur if
2232 // operating on the global stack.
2234 class G1CMKeepAliveAndDrainClosure: public OopClosure {
2235 ConcurrentMark* _cm;
2236 CMTask* _task;
2237 int _ref_counter_limit;
2238 int _ref_counter;
2239 bool _is_serial;
2240 public:
2241 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2242 _cm(cm), _task(task), _is_serial(is_serial),
2243 _ref_counter_limit(G1RefProcDrainInterval) {
2244 assert(_ref_counter_limit > 0, "sanity");
2245 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2246 _ref_counter = _ref_counter_limit;
2247 }
2249 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2250 virtual void do_oop( oop* p) { do_oop_work(p); }
2252 template <class T> void do_oop_work(T* p) {
2253 if (!_cm->has_overflown()) {
2254 oop obj = oopDesc::load_decode_heap_oop(p);
2255 if (_cm->verbose_high()) {
2256 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2257 "*"PTR_FORMAT" = "PTR_FORMAT,
2258 _task->worker_id(), p2i(p), p2i((void*) obj));
2259 }
2261 _task->deal_with_reference(obj);
2262 _ref_counter--;
2264 if (_ref_counter == 0) {
2265 // We have dealt with _ref_counter_limit references, pushing them
2266 // and objects reachable from them on to the local stack (and
2267 // possibly the global stack). Call CMTask::do_marking_step() to
2268 // process these entries.
2269 //
2270 // We call CMTask::do_marking_step() in a loop, which we'll exit if
2271 // there's nothing more to do (i.e. we're done with the entries that
2272 // were pushed as a result of the CMTask::deal_with_reference() calls
2273 // above) or we overflow.
2274 //
2275 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2276 // flag while there may still be some work to do. (See the comment at
2277 // the beginning of CMTask::do_marking_step() for those conditions -
2278 // one of which is reaching the specified time target.) It is only
2279 // when CMTask::do_marking_step() returns without setting the
2280 // has_aborted() flag that the marking step has completed.
2281 do {
2282 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2283 _task->do_marking_step(mark_step_duration_ms,
2284 false /* do_termination */,
2285 _is_serial);
2286 } while (_task->has_aborted() && !_cm->has_overflown());
2287 _ref_counter = _ref_counter_limit;
2288 }
2289 } else {
2290 if (_cm->verbose_high()) {
2291 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2292 }
2293 }
2294 }
2295 };
2297 // 'Drain' oop closure used by both serial and parallel reference processing.
2298 // Uses the CMTask associated with a given worker thread (for serial
2299 // reference processing the CMtask for worker 0 is used). Calls the
2300 // do_marking_step routine, with an unbelievably large timeout value,
2301 // to drain the marking data structures of the remaining entries
2302 // added by the 'keep alive' oop closure above.
2304 class G1CMDrainMarkingStackClosure: public VoidClosure {
2305 ConcurrentMark* _cm;
2306 CMTask* _task;
2307 bool _is_serial;
2308 public:
2309 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2310 _cm(cm), _task(task), _is_serial(is_serial) {
2311 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2312 }
2314 void do_void() {
2315 do {
2316 if (_cm->verbose_high()) {
2317 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s",
2318 _task->worker_id(), BOOL_TO_STR(_is_serial));
2319 }
2321 // We call CMTask::do_marking_step() to completely drain the local
2322 // and global marking stacks of entries pushed by the 'keep alive'
2323 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
2324 //
2325 // CMTask::do_marking_step() is called in a loop, which we'll exit
2326 // if there's nothing more to do (i.e. we'completely drained the
2327 // entries that were pushed as a a result of applying the 'keep alive'
2328 // closure to the entries on the discovered ref lists) or we overflow
2329 // the global marking stack.
2330 //
2331 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2332 // flag while there may still be some work to do. (See the comment at
2333 // the beginning of CMTask::do_marking_step() for those conditions -
2334 // one of which is reaching the specified time target.) It is only
2335 // when CMTask::do_marking_step() returns without setting the
2336 // has_aborted() flag that the marking step has completed.
2338 _task->do_marking_step(1000000000.0 /* something very large */,
2339 true /* do_termination */,
2340 _is_serial);
2341 } while (_task->has_aborted() && !_cm->has_overflown());
2342 }
2343 };
2345 // Implementation of AbstractRefProcTaskExecutor for parallel
2346 // reference processing at the end of G1 concurrent marking
2348 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2349 private:
2350 G1CollectedHeap* _g1h;
2351 ConcurrentMark* _cm;
2352 WorkGang* _workers;
2353 int _active_workers;
2355 public:
2356 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2357 ConcurrentMark* cm,
2358 WorkGang* workers,
2359 int n_workers) :
2360 _g1h(g1h), _cm(cm),
2361 _workers(workers), _active_workers(n_workers) { }
2363 // Executes the given task using concurrent marking worker threads.
2364 virtual void execute(ProcessTask& task);
2365 virtual void execute(EnqueueTask& task);
2366 };
2368 class G1CMRefProcTaskProxy: public AbstractGangTask {
2369 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2370 ProcessTask& _proc_task;
2371 G1CollectedHeap* _g1h;
2372 ConcurrentMark* _cm;
2374 public:
2375 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2376 G1CollectedHeap* g1h,
2377 ConcurrentMark* cm) :
2378 AbstractGangTask("Process reference objects in parallel"),
2379 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
2380 ReferenceProcessor* rp = _g1h->ref_processor_cm();
2381 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
2382 }
2384 virtual void work(uint worker_id) {
2385 CMTask* task = _cm->task(worker_id);
2386 G1CMIsAliveClosure g1_is_alive(_g1h);
2387 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
2388 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
2390 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2391 }
2392 };
2394 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2395 assert(_workers != NULL, "Need parallel worker threads.");
2396 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2398 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2400 // We need to reset the concurrency level before each
2401 // proxy task execution, so that the termination protocol
2402 // and overflow handling in CMTask::do_marking_step() knows
2403 // how many workers to wait for.
2404 _cm->set_concurrency(_active_workers);
2405 _g1h->set_par_threads(_active_workers);
2406 _workers->run_task(&proc_task_proxy);
2407 _g1h->set_par_threads(0);
2408 }
2410 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2411 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2412 EnqueueTask& _enq_task;
2414 public:
2415 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2416 AbstractGangTask("Enqueue reference objects in parallel"),
2417 _enq_task(enq_task) { }
2419 virtual void work(uint worker_id) {
2420 _enq_task.work(worker_id);
2421 }
2422 };
2424 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2425 assert(_workers != NULL, "Need parallel worker threads.");
2426 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2428 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2430 // Not strictly necessary but...
2431 //
2432 // We need to reset the concurrency level before each
2433 // proxy task execution, so that the termination protocol
2434 // and overflow handling in CMTask::do_marking_step() knows
2435 // how many workers to wait for.
2436 _cm->set_concurrency(_active_workers);
2437 _g1h->set_par_threads(_active_workers);
2438 _workers->run_task(&enq_task_proxy);
2439 _g1h->set_par_threads(0);
2440 }
2442 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2443 if (has_overflown()) {
2444 // Skip processing the discovered references if we have
2445 // overflown the global marking stack. Reference objects
2446 // only get discovered once so it is OK to not
2447 // de-populate the discovered reference lists. We could have,
2448 // but the only benefit would be that, when marking restarts,
2449 // less reference objects are discovered.
2450 return;
2451 }
2453 ResourceMark rm;
2454 HandleMark hm;
2456 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2458 // Is alive closure.
2459 G1CMIsAliveClosure g1_is_alive(g1h);
2461 // Inner scope to exclude the cleaning of the string and symbol
2462 // tables from the displayed time.
2463 {
2464 if (G1Log::finer()) {
2465 gclog_or_tty->put(' ');
2466 }
2467 GCTraceTime t("GC ref-proc", G1Log::finer(), false, g1h->gc_timer_cm());
2469 ReferenceProcessor* rp = g1h->ref_processor_cm();
2471 // See the comment in G1CollectedHeap::ref_processing_init()
2472 // about how reference processing currently works in G1.
2474 // Set the soft reference policy
2475 rp->setup_policy(clear_all_soft_refs);
2476 assert(_markStack.isEmpty(), "mark stack should be empty");
2478 // Instances of the 'Keep Alive' and 'Complete GC' closures used
2479 // in serial reference processing. Note these closures are also
2480 // used for serially processing (by the the current thread) the
2481 // JNI references during parallel reference processing.
2482 //
2483 // These closures do not need to synchronize with the worker
2484 // threads involved in parallel reference processing as these
2485 // instances are executed serially by the current thread (e.g.
2486 // reference processing is not multi-threaded and is thus
2487 // performed by the current thread instead of a gang worker).
2488 //
2489 // The gang tasks involved in parallel reference procssing create
2490 // their own instances of these closures, which do their own
2491 // synchronization among themselves.
2492 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
2493 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
2495 // We need at least one active thread. If reference processing
2496 // is not multi-threaded we use the current (VMThread) thread,
2497 // otherwise we use the work gang from the G1CollectedHeap and
2498 // we utilize all the worker threads we can.
2499 bool processing_is_mt = rp->processing_is_mt() && g1h->workers() != NULL;
2500 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
2501 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2503 // Parallel processing task executor.
2504 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2505 g1h->workers(), active_workers);
2506 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
2508 // Set the concurrency level. The phase was already set prior to
2509 // executing the remark task.
2510 set_concurrency(active_workers);
2512 // Set the degree of MT processing here. If the discovery was done MT,
2513 // the number of threads involved during discovery could differ from
2514 // the number of active workers. This is OK as long as the discovered
2515 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2516 rp->set_active_mt_degree(active_workers);
2518 // Process the weak references.
2519 const ReferenceProcessorStats& stats =
2520 rp->process_discovered_references(&g1_is_alive,
2521 &g1_keep_alive,
2522 &g1_drain_mark_stack,
2523 executor,
2524 g1h->gc_timer_cm());
2525 g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
2527 // The do_oop work routines of the keep_alive and drain_marking_stack
2528 // oop closures will set the has_overflown flag if we overflow the
2529 // global marking stack.
2531 assert(_markStack.overflow() || _markStack.isEmpty(),
2532 "mark stack should be empty (unless it overflowed)");
2534 if (_markStack.overflow()) {
2535 // This should have been done already when we tried to push an
2536 // entry on to the global mark stack. But let's do it again.
2537 set_has_overflown();
2538 }
2540 assert(rp->num_q() == active_workers, "why not");
2542 rp->enqueue_discovered_references(executor);
2544 rp->verify_no_references_recorded();
2545 assert(!rp->discovery_enabled(), "Post condition");
2546 }
2548 if (has_overflown()) {
2549 // We can not trust g1_is_alive if the marking stack overflowed
2550 return;
2551 }
2553 g1h->unlink_string_and_symbol_table(&g1_is_alive,
2554 /* process_strings */ false, // currently strings are always roots
2555 /* process_symbols */ true);
2556 }
2558 void ConcurrentMark::swapMarkBitMaps() {
2559 CMBitMapRO* temp = _prevMarkBitMap;
2560 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2561 _nextMarkBitMap = (CMBitMap*) temp;
2562 }
2564 class CMRemarkTask: public AbstractGangTask {
2565 private:
2566 ConcurrentMark* _cm;
2567 bool _is_serial;
2568 public:
2569 void work(uint worker_id) {
2570 // Since all available tasks are actually started, we should
2571 // only proceed if we're supposed to be actived.
2572 if (worker_id < _cm->active_tasks()) {
2573 CMTask* task = _cm->task(worker_id);
2574 task->record_start_time();
2575 do {
2576 task->do_marking_step(1000000000.0 /* something very large */,
2577 true /* do_termination */,
2578 _is_serial);
2579 } while (task->has_aborted() && !_cm->has_overflown());
2580 // If we overflow, then we do not want to restart. We instead
2581 // want to abort remark and do concurrent marking again.
2582 task->record_end_time();
2583 }
2584 }
2586 CMRemarkTask(ConcurrentMark* cm, int active_workers, bool is_serial) :
2587 AbstractGangTask("Par Remark"), _cm(cm), _is_serial(is_serial) {
2588 _cm->terminator()->reset_for_reuse(active_workers);
2589 }
2590 };
2592 void ConcurrentMark::checkpointRootsFinalWork() {
2593 ResourceMark rm;
2594 HandleMark hm;
2595 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2597 g1h->ensure_parsability(false);
2599 if (G1CollectedHeap::use_parallel_gc_threads()) {
2600 G1CollectedHeap::StrongRootsScope srs(g1h);
2601 // this is remark, so we'll use up all active threads
2602 uint active_workers = g1h->workers()->active_workers();
2603 if (active_workers == 0) {
2604 assert(active_workers > 0, "Should have been set earlier");
2605 active_workers = (uint) ParallelGCThreads;
2606 g1h->workers()->set_active_workers(active_workers);
2607 }
2608 set_concurrency_and_phase(active_workers, false /* concurrent */);
2609 // Leave _parallel_marking_threads at it's
2610 // value originally calculated in the ConcurrentMark
2611 // constructor and pass values of the active workers
2612 // through the gang in the task.
2614 CMRemarkTask remarkTask(this, active_workers, false /* is_serial */);
2615 // We will start all available threads, even if we decide that the
2616 // active_workers will be fewer. The extra ones will just bail out
2617 // immediately.
2618 g1h->set_par_threads(active_workers);
2619 g1h->workers()->run_task(&remarkTask);
2620 g1h->set_par_threads(0);
2621 } else {
2622 G1CollectedHeap::StrongRootsScope srs(g1h);
2623 uint active_workers = 1;
2624 set_concurrency_and_phase(active_workers, false /* concurrent */);
2626 // Note - if there's no work gang then the VMThread will be
2627 // the thread to execute the remark - serially. We have
2628 // to pass true for the is_serial parameter so that
2629 // CMTask::do_marking_step() doesn't enter the sync
2630 // barriers in the event of an overflow. Doing so will
2631 // cause an assert that the current thread is not a
2632 // concurrent GC thread.
2633 CMRemarkTask remarkTask(this, active_workers, true /* is_serial*/);
2634 remarkTask.work(0);
2635 }
2636 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2637 guarantee(has_overflown() ||
2638 satb_mq_set.completed_buffers_num() == 0,
2639 err_msg("Invariant: has_overflown = %s, num buffers = %d",
2640 BOOL_TO_STR(has_overflown()),
2641 satb_mq_set.completed_buffers_num()));
2643 print_stats();
2644 }
2646 #ifndef PRODUCT
2648 class PrintReachableOopClosure: public OopClosure {
2649 private:
2650 G1CollectedHeap* _g1h;
2651 outputStream* _out;
2652 VerifyOption _vo;
2653 bool _all;
2655 public:
2656 PrintReachableOopClosure(outputStream* out,
2657 VerifyOption vo,
2658 bool all) :
2659 _g1h(G1CollectedHeap::heap()),
2660 _out(out), _vo(vo), _all(all) { }
2662 void do_oop(narrowOop* p) { do_oop_work(p); }
2663 void do_oop( oop* p) { do_oop_work(p); }
2665 template <class T> void do_oop_work(T* p) {
2666 oop obj = oopDesc::load_decode_heap_oop(p);
2667 const char* str = NULL;
2668 const char* str2 = "";
2670 if (obj == NULL) {
2671 str = "";
2672 } else if (!_g1h->is_in_g1_reserved(obj)) {
2673 str = " O";
2674 } else {
2675 HeapRegion* hr = _g1h->heap_region_containing(obj);
2676 guarantee(hr != NULL, "invariant");
2677 bool over_tams = _g1h->allocated_since_marking(obj, hr, _vo);
2678 bool marked = _g1h->is_marked(obj, _vo);
2680 if (over_tams) {
2681 str = " >";
2682 if (marked) {
2683 str2 = " AND MARKED";
2684 }
2685 } else if (marked) {
2686 str = " M";
2687 } else {
2688 str = " NOT";
2689 }
2690 }
2692 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s",
2693 p2i(p), p2i((void*) obj), str, str2);
2694 }
2695 };
2697 class PrintReachableObjectClosure : public ObjectClosure {
2698 private:
2699 G1CollectedHeap* _g1h;
2700 outputStream* _out;
2701 VerifyOption _vo;
2702 bool _all;
2703 HeapRegion* _hr;
2705 public:
2706 PrintReachableObjectClosure(outputStream* out,
2707 VerifyOption vo,
2708 bool all,
2709 HeapRegion* hr) :
2710 _g1h(G1CollectedHeap::heap()),
2711 _out(out), _vo(vo), _all(all), _hr(hr) { }
2713 void do_object(oop o) {
2714 bool over_tams = _g1h->allocated_since_marking(o, _hr, _vo);
2715 bool marked = _g1h->is_marked(o, _vo);
2716 bool print_it = _all || over_tams || marked;
2718 if (print_it) {
2719 _out->print_cr(" "PTR_FORMAT"%s",
2720 p2i((void *)o), (over_tams) ? " >" : (marked) ? " M" : "");
2721 PrintReachableOopClosure oopCl(_out, _vo, _all);
2722 o->oop_iterate_no_header(&oopCl);
2723 }
2724 }
2725 };
2727 class PrintReachableRegionClosure : public HeapRegionClosure {
2728 private:
2729 G1CollectedHeap* _g1h;
2730 outputStream* _out;
2731 VerifyOption _vo;
2732 bool _all;
2734 public:
2735 bool doHeapRegion(HeapRegion* hr) {
2736 HeapWord* b = hr->bottom();
2737 HeapWord* e = hr->end();
2738 HeapWord* t = hr->top();
2739 HeapWord* p = _g1h->top_at_mark_start(hr, _vo);
2740 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" "
2741 "TAMS: " PTR_FORMAT, p2i(b), p2i(e), p2i(t), p2i(p));
2742 _out->cr();
2744 HeapWord* from = b;
2745 HeapWord* to = t;
2747 if (to > from) {
2748 _out->print_cr("Objects in [" PTR_FORMAT ", " PTR_FORMAT "]", p2i(from), p2i(to));
2749 _out->cr();
2750 PrintReachableObjectClosure ocl(_out, _vo, _all, hr);
2751 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl);
2752 _out->cr();
2753 }
2755 return false;
2756 }
2758 PrintReachableRegionClosure(outputStream* out,
2759 VerifyOption vo,
2760 bool all) :
2761 _g1h(G1CollectedHeap::heap()), _out(out), _vo(vo), _all(all) { }
2762 };
2764 void ConcurrentMark::print_reachable(const char* str,
2765 VerifyOption vo,
2766 bool all) {
2767 gclog_or_tty->cr();
2768 gclog_or_tty->print_cr("== Doing heap dump... ");
2770 if (G1PrintReachableBaseFile == NULL) {
2771 gclog_or_tty->print_cr(" #### error: no base file defined");
2772 return;
2773 }
2775 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) >
2776 (JVM_MAXPATHLEN - 1)) {
2777 gclog_or_tty->print_cr(" #### error: file name too long");
2778 return;
2779 }
2781 char file_name[JVM_MAXPATHLEN];
2782 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str);
2783 gclog_or_tty->print_cr(" dumping to file %s", file_name);
2785 fileStream fout(file_name);
2786 if (!fout.is_open()) {
2787 gclog_or_tty->print_cr(" #### error: could not open file");
2788 return;
2789 }
2791 outputStream* out = &fout;
2792 out->print_cr("-- USING %s", _g1h->top_at_mark_start_str(vo));
2793 out->cr();
2795 out->print_cr("--- ITERATING OVER REGIONS");
2796 out->cr();
2797 PrintReachableRegionClosure rcl(out, vo, all);
2798 _g1h->heap_region_iterate(&rcl);
2799 out->cr();
2801 gclog_or_tty->print_cr(" done");
2802 gclog_or_tty->flush();
2803 }
2805 #endif // PRODUCT
2807 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2808 // Note we are overriding the read-only view of the prev map here, via
2809 // the cast.
2810 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2811 }
2813 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2814 _nextMarkBitMap->clearRange(mr);
2815 }
2817 void ConcurrentMark::clearRangeBothBitmaps(MemRegion mr) {
2818 clearRangePrevBitmap(mr);
2819 clearRangeNextBitmap(mr);
2820 }
2822 HeapRegion*
2823 ConcurrentMark::claim_region(uint worker_id) {
2824 // "checkpoint" the finger
2825 HeapWord* finger = _finger;
2827 // _heap_end will not change underneath our feet; it only changes at
2828 // yield points.
2829 while (finger < _heap_end) {
2830 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2832 // Note on how this code handles humongous regions. In the
2833 // normal case the finger will reach the start of a "starts
2834 // humongous" (SH) region. Its end will either be the end of the
2835 // last "continues humongous" (CH) region in the sequence, or the
2836 // standard end of the SH region (if the SH is the only region in
2837 // the sequence). That way claim_region() will skip over the CH
2838 // regions. However, there is a subtle race between a CM thread
2839 // executing this method and a mutator thread doing a humongous
2840 // object allocation. The two are not mutually exclusive as the CM
2841 // thread does not need to hold the Heap_lock when it gets
2842 // here. So there is a chance that claim_region() will come across
2843 // a free region that's in the progress of becoming a SH or a CH
2844 // region. In the former case, it will either
2845 // a) Miss the update to the region's end, in which case it will
2846 // visit every subsequent CH region, will find their bitmaps
2847 // empty, and do nothing, or
2848 // b) Will observe the update of the region's end (in which case
2849 // it will skip the subsequent CH regions).
2850 // If it comes across a region that suddenly becomes CH, the
2851 // scenario will be similar to b). So, the race between
2852 // claim_region() and a humongous object allocation might force us
2853 // to do a bit of unnecessary work (due to some unnecessary bitmap
2854 // iterations) but it should not introduce and correctness issues.
2855 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2856 HeapWord* bottom = curr_region->bottom();
2857 HeapWord* end = curr_region->end();
2858 HeapWord* limit = curr_region->next_top_at_mark_start();
2860 if (verbose_low()) {
2861 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" "
2862 "["PTR_FORMAT", "PTR_FORMAT"), "
2863 "limit = "PTR_FORMAT,
2864 worker_id, p2i(curr_region), p2i(bottom), p2i(end), p2i(limit));
2865 }
2867 // Is the gap between reading the finger and doing the CAS too long?
2868 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2869 if (res == finger) {
2870 // we succeeded
2872 // notice that _finger == end cannot be guaranteed here since,
2873 // someone else might have moved the finger even further
2874 assert(_finger >= end, "the finger should have moved forward");
2876 if (verbose_low()) {
2877 gclog_or_tty->print_cr("[%u] we were successful with region = "
2878 PTR_FORMAT, worker_id, p2i(curr_region));
2879 }
2881 if (limit > bottom) {
2882 if (verbose_low()) {
2883 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, "
2884 "returning it ", worker_id, p2i(curr_region));
2885 }
2886 return curr_region;
2887 } else {
2888 assert(limit == bottom,
2889 "the region limit should be at bottom");
2890 if (verbose_low()) {
2891 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, "
2892 "returning NULL", worker_id, p2i(curr_region));
2893 }
2894 // we return NULL and the caller should try calling
2895 // claim_region() again.
2896 return NULL;
2897 }
2898 } else {
2899 assert(_finger > finger, "the finger should have moved forward");
2900 if (verbose_low()) {
2901 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2902 "global finger = "PTR_FORMAT", "
2903 "our finger = "PTR_FORMAT,
2904 worker_id, p2i(_finger), p2i(finger));
2905 }
2907 // read it again
2908 finger = _finger;
2909 }
2910 }
2912 return NULL;
2913 }
2915 #ifndef PRODUCT
2916 enum VerifyNoCSetOopsPhase {
2917 VerifyNoCSetOopsStack,
2918 VerifyNoCSetOopsQueues,
2919 VerifyNoCSetOopsSATBCompleted,
2920 VerifyNoCSetOopsSATBThread
2921 };
2923 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure {
2924 private:
2925 G1CollectedHeap* _g1h;
2926 VerifyNoCSetOopsPhase _phase;
2927 int _info;
2929 const char* phase_str() {
2930 switch (_phase) {
2931 case VerifyNoCSetOopsStack: return "Stack";
2932 case VerifyNoCSetOopsQueues: return "Queue";
2933 case VerifyNoCSetOopsSATBCompleted: return "Completed SATB Buffers";
2934 case VerifyNoCSetOopsSATBThread: return "Thread SATB Buffers";
2935 default: ShouldNotReachHere();
2936 }
2937 return NULL;
2938 }
2940 void do_object_work(oop obj) {
2941 guarantee(!_g1h->obj_in_cs(obj),
2942 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d",
2943 p2i((void*) obj), phase_str(), _info));
2944 }
2946 public:
2947 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { }
2949 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) {
2950 _phase = phase;
2951 _info = info;
2952 }
2954 virtual void do_oop(oop* p) {
2955 oop obj = oopDesc::load_decode_heap_oop(p);
2956 do_object_work(obj);
2957 }
2959 virtual void do_oop(narrowOop* p) {
2960 // We should not come across narrow oops while scanning marking
2961 // stacks and SATB buffers.
2962 ShouldNotReachHere();
2963 }
2965 virtual void do_object(oop obj) {
2966 do_object_work(obj);
2967 }
2968 };
2970 void ConcurrentMark::verify_no_cset_oops(bool verify_stacks,
2971 bool verify_enqueued_buffers,
2972 bool verify_thread_buffers,
2973 bool verify_fingers) {
2974 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2975 if (!G1CollectedHeap::heap()->mark_in_progress()) {
2976 return;
2977 }
2979 VerifyNoCSetOopsClosure cl;
2981 if (verify_stacks) {
2982 // Verify entries on the global mark stack
2983 cl.set_phase(VerifyNoCSetOopsStack);
2984 _markStack.oops_do(&cl);
2986 // Verify entries on the task queues
2987 for (uint i = 0; i < _max_worker_id; i += 1) {
2988 cl.set_phase(VerifyNoCSetOopsQueues, i);
2989 CMTaskQueue* queue = _task_queues->queue(i);
2990 queue->oops_do(&cl);
2991 }
2992 }
2994 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
2996 // Verify entries on the enqueued SATB buffers
2997 if (verify_enqueued_buffers) {
2998 cl.set_phase(VerifyNoCSetOopsSATBCompleted);
2999 satb_qs.iterate_completed_buffers_read_only(&cl);
3000 }
3002 // Verify entries on the per-thread SATB buffers
3003 if (verify_thread_buffers) {
3004 cl.set_phase(VerifyNoCSetOopsSATBThread);
3005 satb_qs.iterate_thread_buffers_read_only(&cl);
3006 }
3008 if (verify_fingers) {
3009 // Verify the global finger
3010 HeapWord* global_finger = finger();
3011 if (global_finger != NULL && global_finger < _heap_end) {
3012 // The global finger always points to a heap region boundary. We
3013 // use heap_region_containing_raw() to get the containing region
3014 // given that the global finger could be pointing to a free region
3015 // which subsequently becomes continues humongous. If that
3016 // happens, heap_region_containing() will return the bottom of the
3017 // corresponding starts humongous region and the check below will
3018 // not hold any more.
3019 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
3020 guarantee(global_finger == global_hr->bottom(),
3021 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT,
3022 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)));
3023 }
3025 // Verify the task fingers
3026 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
3027 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) {
3028 CMTask* task = _tasks[i];
3029 HeapWord* task_finger = task->finger();
3030 if (task_finger != NULL && task_finger < _heap_end) {
3031 // See above note on the global finger verification.
3032 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
3033 guarantee(task_finger == task_hr->bottom() ||
3034 !task_hr->in_collection_set(),
3035 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT,
3036 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)));
3037 }
3038 }
3039 }
3040 }
3041 #endif // PRODUCT
3043 // Aggregate the counting data that was constructed concurrently
3044 // with marking.
3045 class AggregateCountDataHRClosure: public HeapRegionClosure {
3046 G1CollectedHeap* _g1h;
3047 ConcurrentMark* _cm;
3048 CardTableModRefBS* _ct_bs;
3049 BitMap* _cm_card_bm;
3050 uint _max_worker_id;
3052 public:
3053 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
3054 BitMap* cm_card_bm,
3055 uint max_worker_id) :
3056 _g1h(g1h), _cm(g1h->concurrent_mark()),
3057 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
3058 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
3060 bool doHeapRegion(HeapRegion* hr) {
3061 if (hr->continuesHumongous()) {
3062 // We will ignore these here and process them when their
3063 // associated "starts humongous" region is processed.
3064 // Note that we cannot rely on their associated
3065 // "starts humongous" region to have their bit set to 1
3066 // since, due to the region chunking in the parallel region
3067 // iteration, a "continues humongous" region might be visited
3068 // before its associated "starts humongous".
3069 return false;
3070 }
3072 HeapWord* start = hr->bottom();
3073 HeapWord* limit = hr->next_top_at_mark_start();
3074 HeapWord* end = hr->end();
3076 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
3077 err_msg("Preconditions not met - "
3078 "start: "PTR_FORMAT", limit: "PTR_FORMAT", "
3079 "top: "PTR_FORMAT", end: "PTR_FORMAT,
3080 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end())));
3082 assert(hr->next_marked_bytes() == 0, "Precondition");
3084 if (start == limit) {
3085 // NTAMS of this region has not been set so nothing to do.
3086 return false;
3087 }
3089 // 'start' should be in the heap.
3090 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
3091 // 'end' *may* be just beyone the end of the heap (if hr is the last region)
3092 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
3094 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
3095 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
3096 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
3098 // If ntams is not card aligned then we bump card bitmap index
3099 // for limit so that we get the all the cards spanned by
3100 // the object ending at ntams.
3101 // Note: if this is the last region in the heap then ntams
3102 // could be actually just beyond the end of the the heap;
3103 // limit_idx will then correspond to a (non-existent) card
3104 // that is also outside the heap.
3105 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
3106 limit_idx += 1;
3107 }
3109 assert(limit_idx <= end_idx, "or else use atomics");
3111 // Aggregate the "stripe" in the count data associated with hr.
3112 uint hrs_index = hr->hrs_index();
3113 size_t marked_bytes = 0;
3115 for (uint i = 0; i < _max_worker_id; i += 1) {
3116 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
3117 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
3119 // Fetch the marked_bytes in this region for task i and
3120 // add it to the running total for this region.
3121 marked_bytes += marked_bytes_array[hrs_index];
3123 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
3124 // into the global card bitmap.
3125 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
3127 while (scan_idx < limit_idx) {
3128 assert(task_card_bm->at(scan_idx) == true, "should be");
3129 _cm_card_bm->set_bit(scan_idx);
3130 assert(_cm_card_bm->at(scan_idx) == true, "should be");
3132 // BitMap::get_next_one_offset() can handle the case when
3133 // its left_offset parameter is greater than its right_offset
3134 // parameter. It does, however, have an early exit if
3135 // left_offset == right_offset. So let's limit the value
3136 // passed in for left offset here.
3137 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
3138 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
3139 }
3140 }
3142 // Update the marked bytes for this region.
3143 hr->add_to_marked_bytes(marked_bytes);
3145 // Next heap region
3146 return false;
3147 }
3148 };
3150 class G1AggregateCountDataTask: public AbstractGangTask {
3151 protected:
3152 G1CollectedHeap* _g1h;
3153 ConcurrentMark* _cm;
3154 BitMap* _cm_card_bm;
3155 uint _max_worker_id;
3156 int _active_workers;
3158 public:
3159 G1AggregateCountDataTask(G1CollectedHeap* g1h,
3160 ConcurrentMark* cm,
3161 BitMap* cm_card_bm,
3162 uint max_worker_id,
3163 int n_workers) :
3164 AbstractGangTask("Count Aggregation"),
3165 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
3166 _max_worker_id(max_worker_id),
3167 _active_workers(n_workers) { }
3169 void work(uint worker_id) {
3170 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
3172 if (G1CollectedHeap::use_parallel_gc_threads()) {
3173 _g1h->heap_region_par_iterate_chunked(&cl, worker_id,
3174 _active_workers,
3175 HeapRegion::AggregateCountClaimValue);
3176 } else {
3177 _g1h->heap_region_iterate(&cl);
3178 }
3179 }
3180 };
3183 void ConcurrentMark::aggregate_count_data() {
3184 int n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3185 _g1h->workers()->active_workers() :
3186 1);
3188 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
3189 _max_worker_id, n_workers);
3191 if (G1CollectedHeap::use_parallel_gc_threads()) {
3192 assert(_g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3193 "sanity check");
3194 _g1h->set_par_threads(n_workers);
3195 _g1h->workers()->run_task(&g1_par_agg_task);
3196 _g1h->set_par_threads(0);
3198 assert(_g1h->check_heap_region_claim_values(HeapRegion::AggregateCountClaimValue),
3199 "sanity check");
3200 _g1h->reset_heap_region_claim_values();
3201 } else {
3202 g1_par_agg_task.work(0);
3203 }
3204 }
3206 // Clear the per-worker arrays used to store the per-region counting data
3207 void ConcurrentMark::clear_all_count_data() {
3208 // Clear the global card bitmap - it will be filled during
3209 // liveness count aggregation (during remark) and the
3210 // final counting task.
3211 _card_bm.clear();
3213 // Clear the global region bitmap - it will be filled as part
3214 // of the final counting task.
3215 _region_bm.clear();
3217 uint max_regions = _g1h->max_regions();
3218 assert(_max_worker_id > 0, "uninitialized");
3220 for (uint i = 0; i < _max_worker_id; i += 1) {
3221 BitMap* task_card_bm = count_card_bitmap_for(i);
3222 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
3224 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
3225 assert(marked_bytes_array != NULL, "uninitialized");
3227 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
3228 task_card_bm->clear();
3229 }
3230 }
3232 void ConcurrentMark::print_stats() {
3233 if (verbose_stats()) {
3234 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3235 for (size_t i = 0; i < _active_tasks; ++i) {
3236 _tasks[i]->print_stats();
3237 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3238 }
3239 }
3240 }
3242 // abandon current marking iteration due to a Full GC
3243 void ConcurrentMark::abort() {
3244 // Clear all marks to force marking thread to do nothing
3245 _nextMarkBitMap->clearAll();
3246 // Clear the liveness counting data
3247 clear_all_count_data();
3248 // Empty mark stack
3249 reset_marking_state();
3250 for (uint i = 0; i < _max_worker_id; ++i) {
3251 _tasks[i]->clear_region_fields();
3252 }
3253 _first_overflow_barrier_sync.abort();
3254 _second_overflow_barrier_sync.abort();
3255 _has_aborted = true;
3257 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3258 satb_mq_set.abandon_partial_marking();
3259 // This can be called either during or outside marking, we'll read
3260 // the expected_active value from the SATB queue set.
3261 satb_mq_set.set_active_all_threads(
3262 false, /* new active value */
3263 satb_mq_set.is_active() /* expected_active */);
3265 _g1h->trace_heap_after_concurrent_cycle();
3266 _g1h->register_concurrent_cycle_end();
3267 }
3269 static void print_ms_time_info(const char* prefix, const char* name,
3270 NumberSeq& ns) {
3271 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3272 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3273 if (ns.num() > 0) {
3274 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3275 prefix, ns.sd(), ns.maximum());
3276 }
3277 }
3279 void ConcurrentMark::print_summary_info() {
3280 gclog_or_tty->print_cr(" Concurrent marking:");
3281 print_ms_time_info(" ", "init marks", _init_times);
3282 print_ms_time_info(" ", "remarks", _remark_times);
3283 {
3284 print_ms_time_info(" ", "final marks", _remark_mark_times);
3285 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3287 }
3288 print_ms_time_info(" ", "cleanups", _cleanup_times);
3289 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3290 _total_counting_time,
3291 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3292 (double)_cleanup_times.num()
3293 : 0.0));
3294 if (G1ScrubRemSets) {
3295 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3296 _total_rs_scrub_time,
3297 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3298 (double)_cleanup_times.num()
3299 : 0.0));
3300 }
3301 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3302 (_init_times.sum() + _remark_times.sum() +
3303 _cleanup_times.sum())/1000.0);
3304 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3305 "(%8.2f s marking).",
3306 cmThread()->vtime_accum(),
3307 cmThread()->vtime_mark_accum());
3308 }
3310 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3311 if (use_parallel_marking_threads()) {
3312 _parallel_workers->print_worker_threads_on(st);
3313 }
3314 }
3316 void ConcurrentMark::print_on_error(outputStream* st) const {
3317 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
3318 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
3319 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
3320 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
3321 }
3323 // We take a break if someone is trying to stop the world.
3324 bool ConcurrentMark::do_yield_check(uint worker_id) {
3325 if (should_yield()) {
3326 if (worker_id == 0) {
3327 _g1h->g1_policy()->record_concurrent_pause();
3328 }
3329 cmThread()->yield();
3330 return true;
3331 } else {
3332 return false;
3333 }
3334 }
3336 bool ConcurrentMark::should_yield() {
3337 return cmThread()->should_yield();
3338 }
3340 bool ConcurrentMark::containing_card_is_marked(void* p) {
3341 size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1);
3342 return _card_bm.at(offset >> CardTableModRefBS::card_shift);
3343 }
3345 bool ConcurrentMark::containing_cards_are_marked(void* start,
3346 void* last) {
3347 return containing_card_is_marked(start) &&
3348 containing_card_is_marked(last);
3349 }
3351 #ifndef PRODUCT
3352 // for debugging purposes
3353 void ConcurrentMark::print_finger() {
3354 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3355 p2i(_heap_start), p2i(_heap_end), p2i(_finger));
3356 for (uint i = 0; i < _max_worker_id; ++i) {
3357 gclog_or_tty->print(" %u: " PTR_FORMAT, i, p2i(_tasks[i]->finger()));
3358 }
3359 gclog_or_tty->cr();
3360 }
3361 #endif
3363 void CMTask::scan_object(oop obj) {
3364 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3366 if (_cm->verbose_high()) {
3367 gclog_or_tty->print_cr("[%u] we're scanning object "PTR_FORMAT,
3368 _worker_id, p2i((void*) obj));
3369 }
3371 size_t obj_size = obj->size();
3372 _words_scanned += obj_size;
3374 obj->oop_iterate(_cm_oop_closure);
3375 statsOnly( ++_objs_scanned );
3376 check_limits();
3377 }
3379 // Closure for iteration over bitmaps
3380 class CMBitMapClosure : public BitMapClosure {
3381 private:
3382 // the bitmap that is being iterated over
3383 CMBitMap* _nextMarkBitMap;
3384 ConcurrentMark* _cm;
3385 CMTask* _task;
3387 public:
3388 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3389 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3391 bool do_bit(size_t offset) {
3392 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3393 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3394 assert( addr < _cm->finger(), "invariant");
3396 statsOnly( _task->increase_objs_found_on_bitmap() );
3397 assert(addr >= _task->finger(), "invariant");
3399 // We move that task's local finger along.
3400 _task->move_finger_to(addr);
3402 _task->scan_object(oop(addr));
3403 // we only partially drain the local queue and global stack
3404 _task->drain_local_queue(true);
3405 _task->drain_global_stack(true);
3407 // if the has_aborted flag has been raised, we need to bail out of
3408 // the iteration
3409 return !_task->has_aborted();
3410 }
3411 };
3413 // Closure for iterating over objects, currently only used for
3414 // processing SATB buffers.
3415 class CMObjectClosure : public ObjectClosure {
3416 private:
3417 CMTask* _task;
3419 public:
3420 void do_object(oop obj) {
3421 _task->deal_with_reference(obj);
3422 }
3424 CMObjectClosure(CMTask* task) : _task(task) { }
3425 };
3427 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3428 ConcurrentMark* cm,
3429 CMTask* task)
3430 : _g1h(g1h), _cm(cm), _task(task) {
3431 assert(_ref_processor == NULL, "should be initialized to NULL");
3433 if (G1UseConcMarkReferenceProcessing) {
3434 _ref_processor = g1h->ref_processor_cm();
3435 assert(_ref_processor != NULL, "should not be NULL");
3436 }
3437 }
3439 void CMTask::setup_for_region(HeapRegion* hr) {
3440 // Separated the asserts so that we know which one fires.
3441 assert(hr != NULL,
3442 "claim_region() should have filtered out continues humongous regions");
3443 assert(!hr->continuesHumongous(),
3444 "claim_region() should have filtered out continues humongous regions");
3446 if (_cm->verbose_low()) {
3447 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT,
3448 _worker_id, p2i(hr));
3449 }
3451 _curr_region = hr;
3452 _finger = hr->bottom();
3453 update_region_limit();
3454 }
3456 void CMTask::update_region_limit() {
3457 HeapRegion* hr = _curr_region;
3458 HeapWord* bottom = hr->bottom();
3459 HeapWord* limit = hr->next_top_at_mark_start();
3461 if (limit == bottom) {
3462 if (_cm->verbose_low()) {
3463 gclog_or_tty->print_cr("[%u] found an empty region "
3464 "["PTR_FORMAT", "PTR_FORMAT")",
3465 _worker_id, p2i(bottom), p2i(limit));
3466 }
3467 // The region was collected underneath our feet.
3468 // We set the finger to bottom to ensure that the bitmap
3469 // iteration that will follow this will not do anything.
3470 // (this is not a condition that holds when we set the region up,
3471 // as the region is not supposed to be empty in the first place)
3472 _finger = bottom;
3473 } else if (limit >= _region_limit) {
3474 assert(limit >= _finger, "peace of mind");
3475 } else {
3476 assert(limit < _region_limit, "only way to get here");
3477 // This can happen under some pretty unusual circumstances. An
3478 // evacuation pause empties the region underneath our feet (NTAMS
3479 // at bottom). We then do some allocation in the region (NTAMS
3480 // stays at bottom), followed by the region being used as a GC
3481 // alloc region (NTAMS will move to top() and the objects
3482 // originally below it will be grayed). All objects now marked in
3483 // the region are explicitly grayed, if below the global finger,
3484 // and we do not need in fact to scan anything else. So, we simply
3485 // set _finger to be limit to ensure that the bitmap iteration
3486 // doesn't do anything.
3487 _finger = limit;
3488 }
3490 _region_limit = limit;
3491 }
3493 void CMTask::giveup_current_region() {
3494 assert(_curr_region != NULL, "invariant");
3495 if (_cm->verbose_low()) {
3496 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT,
3497 _worker_id, p2i(_curr_region));
3498 }
3499 clear_region_fields();
3500 }
3502 void CMTask::clear_region_fields() {
3503 // Values for these three fields that indicate that we're not
3504 // holding on to a region.
3505 _curr_region = NULL;
3506 _finger = NULL;
3507 _region_limit = NULL;
3508 }
3510 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3511 if (cm_oop_closure == NULL) {
3512 assert(_cm_oop_closure != NULL, "invariant");
3513 } else {
3514 assert(_cm_oop_closure == NULL, "invariant");
3515 }
3516 _cm_oop_closure = cm_oop_closure;
3517 }
3519 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3520 guarantee(nextMarkBitMap != NULL, "invariant");
3522 if (_cm->verbose_low()) {
3523 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3524 }
3526 _nextMarkBitMap = nextMarkBitMap;
3527 clear_region_fields();
3529 _calls = 0;
3530 _elapsed_time_ms = 0.0;
3531 _termination_time_ms = 0.0;
3532 _termination_start_time_ms = 0.0;
3534 #if _MARKING_STATS_
3535 _local_pushes = 0;
3536 _local_pops = 0;
3537 _local_max_size = 0;
3538 _objs_scanned = 0;
3539 _global_pushes = 0;
3540 _global_pops = 0;
3541 _global_max_size = 0;
3542 _global_transfers_to = 0;
3543 _global_transfers_from = 0;
3544 _regions_claimed = 0;
3545 _objs_found_on_bitmap = 0;
3546 _satb_buffers_processed = 0;
3547 _steal_attempts = 0;
3548 _steals = 0;
3549 _aborted = 0;
3550 _aborted_overflow = 0;
3551 _aborted_cm_aborted = 0;
3552 _aborted_yield = 0;
3553 _aborted_timed_out = 0;
3554 _aborted_satb = 0;
3555 _aborted_termination = 0;
3556 #endif // _MARKING_STATS_
3557 }
3559 bool CMTask::should_exit_termination() {
3560 regular_clock_call();
3561 // This is called when we are in the termination protocol. We should
3562 // quit if, for some reason, this task wants to abort or the global
3563 // stack is not empty (this means that we can get work from it).
3564 return !_cm->mark_stack_empty() || has_aborted();
3565 }
3567 void CMTask::reached_limit() {
3568 assert(_words_scanned >= _words_scanned_limit ||
3569 _refs_reached >= _refs_reached_limit ,
3570 "shouldn't have been called otherwise");
3571 regular_clock_call();
3572 }
3574 void CMTask::regular_clock_call() {
3575 if (has_aborted()) return;
3577 // First, we need to recalculate the words scanned and refs reached
3578 // limits for the next clock call.
3579 recalculate_limits();
3581 // During the regular clock call we do the following
3583 // (1) If an overflow has been flagged, then we abort.
3584 if (_cm->has_overflown()) {
3585 set_has_aborted();
3586 return;
3587 }
3589 // If we are not concurrent (i.e. we're doing remark) we don't need
3590 // to check anything else. The other steps are only needed during
3591 // the concurrent marking phase.
3592 if (!concurrent()) return;
3594 // (2) If marking has been aborted for Full GC, then we also abort.
3595 if (_cm->has_aborted()) {
3596 set_has_aborted();
3597 statsOnly( ++_aborted_cm_aborted );
3598 return;
3599 }
3601 double curr_time_ms = os::elapsedVTime() * 1000.0;
3603 // (3) If marking stats are enabled, then we update the step history.
3604 #if _MARKING_STATS_
3605 if (_words_scanned >= _words_scanned_limit) {
3606 ++_clock_due_to_scanning;
3607 }
3608 if (_refs_reached >= _refs_reached_limit) {
3609 ++_clock_due_to_marking;
3610 }
3612 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3613 _interval_start_time_ms = curr_time_ms;
3614 _all_clock_intervals_ms.add(last_interval_ms);
3616 if (_cm->verbose_medium()) {
3617 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3618 "scanned = %d%s, refs reached = %d%s",
3619 _worker_id, last_interval_ms,
3620 _words_scanned,
3621 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3622 _refs_reached,
3623 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3624 }
3625 #endif // _MARKING_STATS_
3627 // (4) We check whether we should yield. If we have to, then we abort.
3628 if (_cm->should_yield()) {
3629 // We should yield. To do this we abort the task. The caller is
3630 // responsible for yielding.
3631 set_has_aborted();
3632 statsOnly( ++_aborted_yield );
3633 return;
3634 }
3636 // (5) We check whether we've reached our time quota. If we have,
3637 // then we abort.
3638 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3639 if (elapsed_time_ms > _time_target_ms) {
3640 set_has_aborted();
3641 _has_timed_out = true;
3642 statsOnly( ++_aborted_timed_out );
3643 return;
3644 }
3646 // (6) Finally, we check whether there are enough completed STAB
3647 // buffers available for processing. If there are, we abort.
3648 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3649 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3650 if (_cm->verbose_low()) {
3651 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3652 _worker_id);
3653 }
3654 // we do need to process SATB buffers, we'll abort and restart
3655 // the marking task to do so
3656 set_has_aborted();
3657 statsOnly( ++_aborted_satb );
3658 return;
3659 }
3660 }
3662 void CMTask::recalculate_limits() {
3663 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3664 _words_scanned_limit = _real_words_scanned_limit;
3666 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3667 _refs_reached_limit = _real_refs_reached_limit;
3668 }
3670 void CMTask::decrease_limits() {
3671 // This is called when we believe that we're going to do an infrequent
3672 // operation which will increase the per byte scanned cost (i.e. move
3673 // entries to/from the global stack). It basically tries to decrease the
3674 // scanning limit so that the clock is called earlier.
3676 if (_cm->verbose_medium()) {
3677 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3678 }
3680 _words_scanned_limit = _real_words_scanned_limit -
3681 3 * words_scanned_period / 4;
3682 _refs_reached_limit = _real_refs_reached_limit -
3683 3 * refs_reached_period / 4;
3684 }
3686 void CMTask::move_entries_to_global_stack() {
3687 // local array where we'll store the entries that will be popped
3688 // from the local queue
3689 oop buffer[global_stack_transfer_size];
3691 int n = 0;
3692 oop obj;
3693 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3694 buffer[n] = obj;
3695 ++n;
3696 }
3698 if (n > 0) {
3699 // we popped at least one entry from the local queue
3701 statsOnly( ++_global_transfers_to; _local_pops += n );
3703 if (!_cm->mark_stack_push(buffer, n)) {
3704 if (_cm->verbose_low()) {
3705 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3706 _worker_id);
3707 }
3708 set_has_aborted();
3709 } else {
3710 // the transfer was successful
3712 if (_cm->verbose_medium()) {
3713 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3714 _worker_id, n);
3715 }
3716 statsOnly( int tmp_size = _cm->mark_stack_size();
3717 if (tmp_size > _global_max_size) {
3718 _global_max_size = tmp_size;
3719 }
3720 _global_pushes += n );
3721 }
3722 }
3724 // this operation was quite expensive, so decrease the limits
3725 decrease_limits();
3726 }
3728 void CMTask::get_entries_from_global_stack() {
3729 // local array where we'll store the entries that will be popped
3730 // from the global stack.
3731 oop buffer[global_stack_transfer_size];
3732 int n;
3733 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3734 assert(n <= global_stack_transfer_size,
3735 "we should not pop more than the given limit");
3736 if (n > 0) {
3737 // yes, we did actually pop at least one entry
3739 statsOnly( ++_global_transfers_from; _global_pops += n );
3740 if (_cm->verbose_medium()) {
3741 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3742 _worker_id, n);
3743 }
3744 for (int i = 0; i < n; ++i) {
3745 bool success = _task_queue->push(buffer[i]);
3746 // We only call this when the local queue is empty or under a
3747 // given target limit. So, we do not expect this push to fail.
3748 assert(success, "invariant");
3749 }
3751 statsOnly( int tmp_size = _task_queue->size();
3752 if (tmp_size > _local_max_size) {
3753 _local_max_size = tmp_size;
3754 }
3755 _local_pushes += n );
3756 }
3758 // this operation was quite expensive, so decrease the limits
3759 decrease_limits();
3760 }
3762 void CMTask::drain_local_queue(bool partially) {
3763 if (has_aborted()) return;
3765 // Decide what the target size is, depending whether we're going to
3766 // drain it partially (so that other tasks can steal if they run out
3767 // of things to do) or totally (at the very end).
3768 size_t target_size;
3769 if (partially) {
3770 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3771 } else {
3772 target_size = 0;
3773 }
3775 if (_task_queue->size() > target_size) {
3776 if (_cm->verbose_high()) {
3777 gclog_or_tty->print_cr("[%u] draining local queue, target size = " SIZE_FORMAT,
3778 _worker_id, target_size);
3779 }
3781 oop obj;
3782 bool ret = _task_queue->pop_local(obj);
3783 while (ret) {
3784 statsOnly( ++_local_pops );
3786 if (_cm->verbose_high()) {
3787 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id,
3788 p2i((void*) obj));
3789 }
3791 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3792 assert(!_g1h->is_on_master_free_list(
3793 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3795 scan_object(obj);
3797 if (_task_queue->size() <= target_size || has_aborted()) {
3798 ret = false;
3799 } else {
3800 ret = _task_queue->pop_local(obj);
3801 }
3802 }
3804 if (_cm->verbose_high()) {
3805 gclog_or_tty->print_cr("[%u] drained local queue, size = %d",
3806 _worker_id, _task_queue->size());
3807 }
3808 }
3809 }
3811 void CMTask::drain_global_stack(bool partially) {
3812 if (has_aborted()) return;
3814 // We have a policy to drain the local queue before we attempt to
3815 // drain the global stack.
3816 assert(partially || _task_queue->size() == 0, "invariant");
3818 // Decide what the target size is, depending whether we're going to
3819 // drain it partially (so that other tasks can steal if they run out
3820 // of things to do) or totally (at the very end). Notice that,
3821 // because we move entries from the global stack in chunks or
3822 // because another task might be doing the same, we might in fact
3823 // drop below the target. But, this is not a problem.
3824 size_t target_size;
3825 if (partially) {
3826 target_size = _cm->partial_mark_stack_size_target();
3827 } else {
3828 target_size = 0;
3829 }
3831 if (_cm->mark_stack_size() > target_size) {
3832 if (_cm->verbose_low()) {
3833 gclog_or_tty->print_cr("[%u] draining global_stack, target size " SIZE_FORMAT,
3834 _worker_id, target_size);
3835 }
3837 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3838 get_entries_from_global_stack();
3839 drain_local_queue(partially);
3840 }
3842 if (_cm->verbose_low()) {
3843 gclog_or_tty->print_cr("[%u] drained global stack, size = " SIZE_FORMAT,
3844 _worker_id, _cm->mark_stack_size());
3845 }
3846 }
3847 }
3849 // SATB Queue has several assumptions on whether to call the par or
3850 // non-par versions of the methods. this is why some of the code is
3851 // replicated. We should really get rid of the single-threaded version
3852 // of the code to simplify things.
3853 void CMTask::drain_satb_buffers() {
3854 if (has_aborted()) return;
3856 // We set this so that the regular clock knows that we're in the
3857 // middle of draining buffers and doesn't set the abort flag when it
3858 // notices that SATB buffers are available for draining. It'd be
3859 // very counter productive if it did that. :-)
3860 _draining_satb_buffers = true;
3862 CMObjectClosure oc(this);
3863 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3864 if (G1CollectedHeap::use_parallel_gc_threads()) {
3865 satb_mq_set.set_par_closure(_worker_id, &oc);
3866 } else {
3867 satb_mq_set.set_closure(&oc);
3868 }
3870 // This keeps claiming and applying the closure to completed buffers
3871 // until we run out of buffers or we need to abort.
3872 if (G1CollectedHeap::use_parallel_gc_threads()) {
3873 while (!has_aborted() &&
3874 satb_mq_set.par_apply_closure_to_completed_buffer(_worker_id)) {
3875 if (_cm->verbose_medium()) {
3876 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3877 }
3878 statsOnly( ++_satb_buffers_processed );
3879 regular_clock_call();
3880 }
3881 } else {
3882 while (!has_aborted() &&
3883 satb_mq_set.apply_closure_to_completed_buffer()) {
3884 if (_cm->verbose_medium()) {
3885 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3886 }
3887 statsOnly( ++_satb_buffers_processed );
3888 regular_clock_call();
3889 }
3890 }
3892 if (!concurrent() && !has_aborted()) {
3893 // We should only do this during remark.
3894 if (G1CollectedHeap::use_parallel_gc_threads()) {
3895 satb_mq_set.par_iterate_closure_all_threads(_worker_id);
3896 } else {
3897 satb_mq_set.iterate_closure_all_threads();
3898 }
3899 }
3901 _draining_satb_buffers = false;
3903 assert(has_aborted() ||
3904 concurrent() ||
3905 satb_mq_set.completed_buffers_num() == 0, "invariant");
3907 if (G1CollectedHeap::use_parallel_gc_threads()) {
3908 satb_mq_set.set_par_closure(_worker_id, NULL);
3909 } else {
3910 satb_mq_set.set_closure(NULL);
3911 }
3913 // again, this was a potentially expensive operation, decrease the
3914 // limits to get the regular clock call early
3915 decrease_limits();
3916 }
3918 void CMTask::print_stats() {
3919 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3920 _worker_id, _calls);
3921 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3922 _elapsed_time_ms, _termination_time_ms);
3923 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3924 _step_times_ms.num(), _step_times_ms.avg(),
3925 _step_times_ms.sd());
3926 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3927 _step_times_ms.maximum(), _step_times_ms.sum());
3929 #if _MARKING_STATS_
3930 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3931 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3932 _all_clock_intervals_ms.sd());
3933 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3934 _all_clock_intervals_ms.maximum(),
3935 _all_clock_intervals_ms.sum());
3936 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d",
3937 _clock_due_to_scanning, _clock_due_to_marking);
3938 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d",
3939 _objs_scanned, _objs_found_on_bitmap);
3940 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d",
3941 _local_pushes, _local_pops, _local_max_size);
3942 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d",
3943 _global_pushes, _global_pops, _global_max_size);
3944 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d",
3945 _global_transfers_to,_global_transfers_from);
3946 gclog_or_tty->print_cr(" Regions: claimed = %d", _regions_claimed);
3947 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed);
3948 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d",
3949 _steal_attempts, _steals);
3950 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted);
3951 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d",
3952 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3953 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d",
3954 _aborted_timed_out, _aborted_satb, _aborted_termination);
3955 #endif // _MARKING_STATS_
3956 }
3958 /*****************************************************************************
3960 The do_marking_step(time_target_ms, ...) method is the building
3961 block of the parallel marking framework. It can be called in parallel
3962 with other invocations of do_marking_step() on different tasks
3963 (but only one per task, obviously) and concurrently with the
3964 mutator threads, or during remark, hence it eliminates the need
3965 for two versions of the code. When called during remark, it will
3966 pick up from where the task left off during the concurrent marking
3967 phase. Interestingly, tasks are also claimable during evacuation
3968 pauses too, since do_marking_step() ensures that it aborts before
3969 it needs to yield.
3971 The data structures that it uses to do marking work are the
3972 following:
3974 (1) Marking Bitmap. If there are gray objects that appear only
3975 on the bitmap (this happens either when dealing with an overflow
3976 or when the initial marking phase has simply marked the roots
3977 and didn't push them on the stack), then tasks claim heap
3978 regions whose bitmap they then scan to find gray objects. A
3979 global finger indicates where the end of the last claimed region
3980 is. A local finger indicates how far into the region a task has
3981 scanned. The two fingers are used to determine how to gray an
3982 object (i.e. whether simply marking it is OK, as it will be
3983 visited by a task in the future, or whether it needs to be also
3984 pushed on a stack).
3986 (2) Local Queue. The local queue of the task which is accessed
3987 reasonably efficiently by the task. Other tasks can steal from
3988 it when they run out of work. Throughout the marking phase, a
3989 task attempts to keep its local queue short but not totally
3990 empty, so that entries are available for stealing by other
3991 tasks. Only when there is no more work, a task will totally
3992 drain its local queue.
3994 (3) Global Mark Stack. This handles local queue overflow. During
3995 marking only sets of entries are moved between it and the local
3996 queues, as access to it requires a mutex and more fine-grain
3997 interaction with it which might cause contention. If it
3998 overflows, then the marking phase should restart and iterate
3999 over the bitmap to identify gray objects. Throughout the marking
4000 phase, tasks attempt to keep the global mark stack at a small
4001 length but not totally empty, so that entries are available for
4002 popping by other tasks. Only when there is no more work, tasks
4003 will totally drain the global mark stack.
4005 (4) SATB Buffer Queue. This is where completed SATB buffers are
4006 made available. Buffers are regularly removed from this queue
4007 and scanned for roots, so that the queue doesn't get too
4008 long. During remark, all completed buffers are processed, as
4009 well as the filled in parts of any uncompleted buffers.
4011 The do_marking_step() method tries to abort when the time target
4012 has been reached. There are a few other cases when the
4013 do_marking_step() method also aborts:
4015 (1) When the marking phase has been aborted (after a Full GC).
4017 (2) When a global overflow (on the global stack) has been
4018 triggered. Before the task aborts, it will actually sync up with
4019 the other tasks to ensure that all the marking data structures
4020 (local queues, stacks, fingers etc.) are re-initialized so that
4021 when do_marking_step() completes, the marking phase can
4022 immediately restart.
4024 (3) When enough completed SATB buffers are available. The
4025 do_marking_step() method only tries to drain SATB buffers right
4026 at the beginning. So, if enough buffers are available, the
4027 marking step aborts and the SATB buffers are processed at
4028 the beginning of the next invocation.
4030 (4) To yield. when we have to yield then we abort and yield
4031 right at the end of do_marking_step(). This saves us from a lot
4032 of hassle as, by yielding we might allow a Full GC. If this
4033 happens then objects will be compacted underneath our feet, the
4034 heap might shrink, etc. We save checking for this by just
4035 aborting and doing the yield right at the end.
4037 From the above it follows that the do_marking_step() method should
4038 be called in a loop (or, otherwise, regularly) until it completes.
4040 If a marking step completes without its has_aborted() flag being
4041 true, it means it has completed the current marking phase (and
4042 also all other marking tasks have done so and have all synced up).
4044 A method called regular_clock_call() is invoked "regularly" (in
4045 sub ms intervals) throughout marking. It is this clock method that
4046 checks all the abort conditions which were mentioned above and
4047 decides when the task should abort. A work-based scheme is used to
4048 trigger this clock method: when the number of object words the
4049 marking phase has scanned or the number of references the marking
4050 phase has visited reach a given limit. Additional invocations to
4051 the method clock have been planted in a few other strategic places
4052 too. The initial reason for the clock method was to avoid calling
4053 vtime too regularly, as it is quite expensive. So, once it was in
4054 place, it was natural to piggy-back all the other conditions on it
4055 too and not constantly check them throughout the code.
4057 If do_termination is true then do_marking_step will enter its
4058 termination protocol.
4060 The value of is_serial must be true when do_marking_step is being
4061 called serially (i.e. by the VMThread) and do_marking_step should
4062 skip any synchronization in the termination and overflow code.
4063 Examples include the serial remark code and the serial reference
4064 processing closures.
4066 The value of is_serial must be false when do_marking_step is
4067 being called by any of the worker threads in a work gang.
4068 Examples include the concurrent marking code (CMMarkingTask),
4069 the MT remark code, and the MT reference processing closures.
4071 *****************************************************************************/
4073 void CMTask::do_marking_step(double time_target_ms,
4074 bool do_termination,
4075 bool is_serial) {
4076 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
4077 assert(concurrent() == _cm->concurrent(), "they should be the same");
4079 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
4080 assert(_task_queues != NULL, "invariant");
4081 assert(_task_queue != NULL, "invariant");
4082 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
4084 assert(!_claimed,
4085 "only one thread should claim this task at any one time");
4087 // OK, this doesn't safeguard again all possible scenarios, as it is
4088 // possible for two threads to set the _claimed flag at the same
4089 // time. But it is only for debugging purposes anyway and it will
4090 // catch most problems.
4091 _claimed = true;
4093 _start_time_ms = os::elapsedVTime() * 1000.0;
4094 statsOnly( _interval_start_time_ms = _start_time_ms );
4096 // If do_stealing is true then do_marking_step will attempt to
4097 // steal work from the other CMTasks. It only makes sense to
4098 // enable stealing when the termination protocol is enabled
4099 // and do_marking_step() is not being called serially.
4100 bool do_stealing = do_termination && !is_serial;
4102 double diff_prediction_ms =
4103 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
4104 _time_target_ms = time_target_ms - diff_prediction_ms;
4106 // set up the variables that are used in the work-based scheme to
4107 // call the regular clock method
4108 _words_scanned = 0;
4109 _refs_reached = 0;
4110 recalculate_limits();
4112 // clear all flags
4113 clear_has_aborted();
4114 _has_timed_out = false;
4115 _draining_satb_buffers = false;
4117 ++_calls;
4119 if (_cm->verbose_low()) {
4120 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
4121 "target = %1.2lfms >>>>>>>>>>",
4122 _worker_id, _calls, _time_target_ms);
4123 }
4125 // Set up the bitmap and oop closures. Anything that uses them is
4126 // eventually called from this method, so it is OK to allocate these
4127 // statically.
4128 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
4129 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
4130 set_cm_oop_closure(&cm_oop_closure);
4132 if (_cm->has_overflown()) {
4133 // This can happen if the mark stack overflows during a GC pause
4134 // and this task, after a yield point, restarts. We have to abort
4135 // as we need to get into the overflow protocol which happens
4136 // right at the end of this task.
4137 set_has_aborted();
4138 }
4140 // First drain any available SATB buffers. After this, we will not
4141 // look at SATB buffers before the next invocation of this method.
4142 // If enough completed SATB buffers are queued up, the regular clock
4143 // will abort this task so that it restarts.
4144 drain_satb_buffers();
4145 // ...then partially drain the local queue and the global stack
4146 drain_local_queue(true);
4147 drain_global_stack(true);
4149 do {
4150 if (!has_aborted() && _curr_region != NULL) {
4151 // This means that we're already holding on to a region.
4152 assert(_finger != NULL, "if region is not NULL, then the finger "
4153 "should not be NULL either");
4155 // We might have restarted this task after an evacuation pause
4156 // which might have evacuated the region we're holding on to
4157 // underneath our feet. Let's read its limit again to make sure
4158 // that we do not iterate over a region of the heap that
4159 // contains garbage (update_region_limit() will also move
4160 // _finger to the start of the region if it is found empty).
4161 update_region_limit();
4162 // We will start from _finger not from the start of the region,
4163 // as we might be restarting this task after aborting half-way
4164 // through scanning this region. In this case, _finger points to
4165 // the address where we last found a marked object. If this is a
4166 // fresh region, _finger points to start().
4167 MemRegion mr = MemRegion(_finger, _region_limit);
4169 if (_cm->verbose_low()) {
4170 gclog_or_tty->print_cr("[%u] we're scanning part "
4171 "["PTR_FORMAT", "PTR_FORMAT") "
4172 "of region "HR_FORMAT,
4173 _worker_id, p2i(_finger), p2i(_region_limit),
4174 HR_FORMAT_PARAMS(_curr_region));
4175 }
4177 assert(!_curr_region->isHumongous() || mr.start() == _curr_region->bottom(),
4178 "humongous regions should go around loop once only");
4180 // Some special cases:
4181 // If the memory region is empty, we can just give up the region.
4182 // If the current region is humongous then we only need to check
4183 // the bitmap for the bit associated with the start of the object,
4184 // scan the object if it's live, and give up the region.
4185 // Otherwise, let's iterate over the bitmap of the part of the region
4186 // that is left.
4187 // If the iteration is successful, give up the region.
4188 if (mr.is_empty()) {
4189 giveup_current_region();
4190 regular_clock_call();
4191 } else if (_curr_region->isHumongous() && mr.start() == _curr_region->bottom()) {
4192 if (_nextMarkBitMap->isMarked(mr.start())) {
4193 // The object is marked - apply the closure
4194 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
4195 bitmap_closure.do_bit(offset);
4196 }
4197 // Even if this task aborted while scanning the humongous object
4198 // we can (and should) give up the current region.
4199 giveup_current_region();
4200 regular_clock_call();
4201 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
4202 giveup_current_region();
4203 regular_clock_call();
4204 } else {
4205 assert(has_aborted(), "currently the only way to do so");
4206 // The only way to abort the bitmap iteration is to return
4207 // false from the do_bit() method. However, inside the
4208 // do_bit() method we move the _finger to point to the
4209 // object currently being looked at. So, if we bail out, we
4210 // have definitely set _finger to something non-null.
4211 assert(_finger != NULL, "invariant");
4213 // Region iteration was actually aborted. So now _finger
4214 // points to the address of the object we last scanned. If we
4215 // leave it there, when we restart this task, we will rescan
4216 // the object. It is easy to avoid this. We move the finger by
4217 // enough to point to the next possible object header (the
4218 // bitmap knows by how much we need to move it as it knows its
4219 // granularity).
4220 assert(_finger < _region_limit, "invariant");
4221 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
4222 // Check if bitmap iteration was aborted while scanning the last object
4223 if (new_finger >= _region_limit) {
4224 giveup_current_region();
4225 } else {
4226 move_finger_to(new_finger);
4227 }
4228 }
4229 }
4230 // At this point we have either completed iterating over the
4231 // region we were holding on to, or we have aborted.
4233 // We then partially drain the local queue and the global stack.
4234 // (Do we really need this?)
4235 drain_local_queue(true);
4236 drain_global_stack(true);
4238 // Read the note on the claim_region() method on why it might
4239 // return NULL with potentially more regions available for
4240 // claiming and why we have to check out_of_regions() to determine
4241 // whether we're done or not.
4242 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
4243 // We are going to try to claim a new region. We should have
4244 // given up on the previous one.
4245 // Separated the asserts so that we know which one fires.
4246 assert(_curr_region == NULL, "invariant");
4247 assert(_finger == NULL, "invariant");
4248 assert(_region_limit == NULL, "invariant");
4249 if (_cm->verbose_low()) {
4250 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
4251 }
4252 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
4253 if (claimed_region != NULL) {
4254 // Yes, we managed to claim one
4255 statsOnly( ++_regions_claimed );
4257 if (_cm->verbose_low()) {
4258 gclog_or_tty->print_cr("[%u] we successfully claimed "
4259 "region "PTR_FORMAT,
4260 _worker_id, p2i(claimed_region));
4261 }
4263 setup_for_region(claimed_region);
4264 assert(_curr_region == claimed_region, "invariant");
4265 }
4266 // It is important to call the regular clock here. It might take
4267 // a while to claim a region if, for example, we hit a large
4268 // block of empty regions. So we need to call the regular clock
4269 // method once round the loop to make sure it's called
4270 // frequently enough.
4271 regular_clock_call();
4272 }
4274 if (!has_aborted() && _curr_region == NULL) {
4275 assert(_cm->out_of_regions(),
4276 "at this point we should be out of regions");
4277 }
4278 } while ( _curr_region != NULL && !has_aborted());
4280 if (!has_aborted()) {
4281 // We cannot check whether the global stack is empty, since other
4282 // tasks might be pushing objects to it concurrently.
4283 assert(_cm->out_of_regions(),
4284 "at this point we should be out of regions");
4286 if (_cm->verbose_low()) {
4287 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
4288 }
4290 // Try to reduce the number of available SATB buffers so that
4291 // remark has less work to do.
4292 drain_satb_buffers();
4293 }
4295 // Since we've done everything else, we can now totally drain the
4296 // local queue and global stack.
4297 drain_local_queue(false);
4298 drain_global_stack(false);
4300 // Attempt at work stealing from other task's queues.
4301 if (do_stealing && !has_aborted()) {
4302 // We have not aborted. This means that we have finished all that
4303 // we could. Let's try to do some stealing...
4305 // We cannot check whether the global stack is empty, since other
4306 // tasks might be pushing objects to it concurrently.
4307 assert(_cm->out_of_regions() && _task_queue->size() == 0,
4308 "only way to reach here");
4310 if (_cm->verbose_low()) {
4311 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
4312 }
4314 while (!has_aborted()) {
4315 oop obj;
4316 statsOnly( ++_steal_attempts );
4318 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
4319 if (_cm->verbose_medium()) {
4320 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully",
4321 _worker_id, p2i((void*) obj));
4322 }
4324 statsOnly( ++_steals );
4326 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
4327 "any stolen object should be marked");
4328 scan_object(obj);
4330 // And since we're towards the end, let's totally drain the
4331 // local queue and global stack.
4332 drain_local_queue(false);
4333 drain_global_stack(false);
4334 } else {
4335 break;
4336 }
4337 }
4338 }
4340 // If we are about to wrap up and go into termination, check if we
4341 // should raise the overflow flag.
4342 if (do_termination && !has_aborted()) {
4343 if (_cm->force_overflow()->should_force()) {
4344 _cm->set_has_overflown();
4345 regular_clock_call();
4346 }
4347 }
4349 // We still haven't aborted. Now, let's try to get into the
4350 // termination protocol.
4351 if (do_termination && !has_aborted()) {
4352 // We cannot check whether the global stack is empty, since other
4353 // tasks might be concurrently pushing objects on it.
4354 // Separated the asserts so that we know which one fires.
4355 assert(_cm->out_of_regions(), "only way to reach here");
4356 assert(_task_queue->size() == 0, "only way to reach here");
4358 if (_cm->verbose_low()) {
4359 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4360 }
4362 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4364 // The CMTask class also extends the TerminatorTerminator class,
4365 // hence its should_exit_termination() method will also decide
4366 // whether to exit the termination protocol or not.
4367 bool finished = (is_serial ||
4368 _cm->terminator()->offer_termination(this));
4369 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4370 _termination_time_ms +=
4371 termination_end_time_ms - _termination_start_time_ms;
4373 if (finished) {
4374 // We're all done.
4376 if (_worker_id == 0) {
4377 // let's allow task 0 to do this
4378 if (concurrent()) {
4379 assert(_cm->concurrent_marking_in_progress(), "invariant");
4380 // we need to set this to false before the next
4381 // safepoint. This way we ensure that the marking phase
4382 // doesn't observe any more heap expansions.
4383 _cm->clear_concurrent_marking_in_progress();
4384 }
4385 }
4387 // We can now guarantee that the global stack is empty, since
4388 // all other tasks have finished. We separated the guarantees so
4389 // that, if a condition is false, we can immediately find out
4390 // which one.
4391 guarantee(_cm->out_of_regions(), "only way to reach here");
4392 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4393 guarantee(_task_queue->size() == 0, "only way to reach here");
4394 guarantee(!_cm->has_overflown(), "only way to reach here");
4395 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4397 if (_cm->verbose_low()) {
4398 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4399 }
4400 } else {
4401 // Apparently there's more work to do. Let's abort this task. It
4402 // will restart it and we can hopefully find more things to do.
4404 if (_cm->verbose_low()) {
4405 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4406 _worker_id);
4407 }
4409 set_has_aborted();
4410 statsOnly( ++_aborted_termination );
4411 }
4412 }
4414 // Mainly for debugging purposes to make sure that a pointer to the
4415 // closure which was statically allocated in this frame doesn't
4416 // escape it by accident.
4417 set_cm_oop_closure(NULL);
4418 double end_time_ms = os::elapsedVTime() * 1000.0;
4419 double elapsed_time_ms = end_time_ms - _start_time_ms;
4420 // Update the step history.
4421 _step_times_ms.add(elapsed_time_ms);
4423 if (has_aborted()) {
4424 // The task was aborted for some reason.
4426 statsOnly( ++_aborted );
4428 if (_has_timed_out) {
4429 double diff_ms = elapsed_time_ms - _time_target_ms;
4430 // Keep statistics of how well we did with respect to hitting
4431 // our target only if we actually timed out (if we aborted for
4432 // other reasons, then the results might get skewed).
4433 _marking_step_diffs_ms.add(diff_ms);
4434 }
4436 if (_cm->has_overflown()) {
4437 // This is the interesting one. We aborted because a global
4438 // overflow was raised. This means we have to restart the
4439 // marking phase and start iterating over regions. However, in
4440 // order to do this we have to make sure that all tasks stop
4441 // what they are doing and re-initialise in a safe manner. We
4442 // will achieve this with the use of two barrier sync points.
4444 if (_cm->verbose_low()) {
4445 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4446 }
4448 if (!is_serial) {
4449 // We only need to enter the sync barrier if being called
4450 // from a parallel context
4451 _cm->enter_first_sync_barrier(_worker_id);
4453 // When we exit this sync barrier we know that all tasks have
4454 // stopped doing marking work. So, it's now safe to
4455 // re-initialise our data structures. At the end of this method,
4456 // task 0 will clear the global data structures.
4457 }
4459 statsOnly( ++_aborted_overflow );
4461 // We clear the local state of this task...
4462 clear_region_fields();
4464 if (!is_serial) {
4465 // ...and enter the second barrier.
4466 _cm->enter_second_sync_barrier(_worker_id);
4467 }
4468 // At this point, if we're during the concurrent phase of
4469 // marking, everything has been re-initialized and we're
4470 // ready to restart.
4471 }
4473 if (_cm->verbose_low()) {
4474 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4475 "elapsed = %1.2lfms <<<<<<<<<<",
4476 _worker_id, _time_target_ms, elapsed_time_ms);
4477 if (_cm->has_aborted()) {
4478 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4479 _worker_id);
4480 }
4481 }
4482 } else {
4483 if (_cm->verbose_low()) {
4484 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4485 "elapsed = %1.2lfms <<<<<<<<<<",
4486 _worker_id, _time_target_ms, elapsed_time_ms);
4487 }
4488 }
4490 _claimed = false;
4491 }
4493 CMTask::CMTask(uint worker_id,
4494 ConcurrentMark* cm,
4495 size_t* marked_bytes,
4496 BitMap* card_bm,
4497 CMTaskQueue* task_queue,
4498 CMTaskQueueSet* task_queues)
4499 : _g1h(G1CollectedHeap::heap()),
4500 _worker_id(worker_id), _cm(cm),
4501 _claimed(false),
4502 _nextMarkBitMap(NULL), _hash_seed(17),
4503 _task_queue(task_queue),
4504 _task_queues(task_queues),
4505 _cm_oop_closure(NULL),
4506 _marked_bytes_array(marked_bytes),
4507 _card_bm(card_bm) {
4508 guarantee(task_queue != NULL, "invariant");
4509 guarantee(task_queues != NULL, "invariant");
4511 statsOnly( _clock_due_to_scanning = 0;
4512 _clock_due_to_marking = 0 );
4514 _marking_step_diffs_ms.add(0.5);
4515 }
4517 // These are formatting macros that are used below to ensure
4518 // consistent formatting. The *_H_* versions are used to format the
4519 // header for a particular value and they should be kept consistent
4520 // with the corresponding macro. Also note that most of the macros add
4521 // the necessary white space (as a prefix) which makes them a bit
4522 // easier to compose.
4524 // All the output lines are prefixed with this string to be able to
4525 // identify them easily in a large log file.
4526 #define G1PPRL_LINE_PREFIX "###"
4528 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT
4529 #ifdef _LP64
4530 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4531 #else // _LP64
4532 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4533 #endif // _LP64
4535 // For per-region info
4536 #define G1PPRL_TYPE_FORMAT " %-4s"
4537 #define G1PPRL_TYPE_H_FORMAT " %4s"
4538 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9)
4539 #define G1PPRL_BYTE_H_FORMAT " %9s"
4540 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4541 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4543 // For summary info
4544 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT
4545 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT
4546 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB"
4547 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%"
4549 G1PrintRegionLivenessInfoClosure::
4550 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4551 : _out(out),
4552 _total_used_bytes(0), _total_capacity_bytes(0),
4553 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4554 _hum_used_bytes(0), _hum_capacity_bytes(0),
4555 _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
4556 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
4557 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4558 MemRegion g1_committed = g1h->g1_committed();
4559 MemRegion g1_reserved = g1h->g1_reserved();
4560 double now = os::elapsedTime();
4562 // Print the header of the output.
4563 _out->cr();
4564 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4565 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4566 G1PPRL_SUM_ADDR_FORMAT("committed")
4567 G1PPRL_SUM_ADDR_FORMAT("reserved")
4568 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4569 p2i(g1_committed.start()), p2i(g1_committed.end()),
4570 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
4571 HeapRegion::GrainBytes);
4572 _out->print_cr(G1PPRL_LINE_PREFIX);
4573 _out->print_cr(G1PPRL_LINE_PREFIX
4574 G1PPRL_TYPE_H_FORMAT
4575 G1PPRL_ADDR_BASE_H_FORMAT
4576 G1PPRL_BYTE_H_FORMAT
4577 G1PPRL_BYTE_H_FORMAT
4578 G1PPRL_BYTE_H_FORMAT
4579 G1PPRL_DOUBLE_H_FORMAT
4580 G1PPRL_BYTE_H_FORMAT
4581 G1PPRL_BYTE_H_FORMAT,
4582 "type", "address-range",
4583 "used", "prev-live", "next-live", "gc-eff",
4584 "remset", "code-roots");
4585 _out->print_cr(G1PPRL_LINE_PREFIX
4586 G1PPRL_TYPE_H_FORMAT
4587 G1PPRL_ADDR_BASE_H_FORMAT
4588 G1PPRL_BYTE_H_FORMAT
4589 G1PPRL_BYTE_H_FORMAT
4590 G1PPRL_BYTE_H_FORMAT
4591 G1PPRL_DOUBLE_H_FORMAT
4592 G1PPRL_BYTE_H_FORMAT
4593 G1PPRL_BYTE_H_FORMAT,
4594 "", "",
4595 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
4596 "(bytes)", "(bytes)");
4597 }
4599 // It takes as a parameter a reference to one of the _hum_* fields, it
4600 // deduces the corresponding value for a region in a humongous region
4601 // series (either the region size, or what's left if the _hum_* field
4602 // is < the region size), and updates the _hum_* field accordingly.
4603 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4604 size_t bytes = 0;
4605 // The > 0 check is to deal with the prev and next live bytes which
4606 // could be 0.
4607 if (*hum_bytes > 0) {
4608 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4609 *hum_bytes -= bytes;
4610 }
4611 return bytes;
4612 }
4614 // It deduces the values for a region in a humongous region series
4615 // from the _hum_* fields and updates those accordingly. It assumes
4616 // that that _hum_* fields have already been set up from the "starts
4617 // humongous" region and we visit the regions in address order.
4618 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4619 size_t* capacity_bytes,
4620 size_t* prev_live_bytes,
4621 size_t* next_live_bytes) {
4622 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4623 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4624 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4625 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4626 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4627 }
4629 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4630 const char* type = "";
4631 HeapWord* bottom = r->bottom();
4632 HeapWord* end = r->end();
4633 size_t capacity_bytes = r->capacity();
4634 size_t used_bytes = r->used();
4635 size_t prev_live_bytes = r->live_bytes();
4636 size_t next_live_bytes = r->next_live_bytes();
4637 double gc_eff = r->gc_efficiency();
4638 size_t remset_bytes = r->rem_set()->mem_size();
4639 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
4641 if (r->used() == 0) {
4642 type = "FREE";
4643 } else if (r->is_survivor()) {
4644 type = "SURV";
4645 } else if (r->is_young()) {
4646 type = "EDEN";
4647 } else if (r->startsHumongous()) {
4648 type = "HUMS";
4650 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4651 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4652 "they should have been zeroed after the last time we used them");
4653 // Set up the _hum_* fields.
4654 _hum_capacity_bytes = capacity_bytes;
4655 _hum_used_bytes = used_bytes;
4656 _hum_prev_live_bytes = prev_live_bytes;
4657 _hum_next_live_bytes = next_live_bytes;
4658 get_hum_bytes(&used_bytes, &capacity_bytes,
4659 &prev_live_bytes, &next_live_bytes);
4660 end = bottom + HeapRegion::GrainWords;
4661 } else if (r->continuesHumongous()) {
4662 type = "HUMC";
4663 get_hum_bytes(&used_bytes, &capacity_bytes,
4664 &prev_live_bytes, &next_live_bytes);
4665 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4666 } else {
4667 type = "OLD";
4668 }
4670 _total_used_bytes += used_bytes;
4671 _total_capacity_bytes += capacity_bytes;
4672 _total_prev_live_bytes += prev_live_bytes;
4673 _total_next_live_bytes += next_live_bytes;
4674 _total_remset_bytes += remset_bytes;
4675 _total_strong_code_roots_bytes += strong_code_roots_bytes;
4677 // Print a line for this particular region.
4678 _out->print_cr(G1PPRL_LINE_PREFIX
4679 G1PPRL_TYPE_FORMAT
4680 G1PPRL_ADDR_BASE_FORMAT
4681 G1PPRL_BYTE_FORMAT
4682 G1PPRL_BYTE_FORMAT
4683 G1PPRL_BYTE_FORMAT
4684 G1PPRL_DOUBLE_FORMAT
4685 G1PPRL_BYTE_FORMAT
4686 G1PPRL_BYTE_FORMAT,
4687 type, p2i(bottom), p2i(end),
4688 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
4689 remset_bytes, strong_code_roots_bytes);
4691 return false;
4692 }
4694 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4695 // add static memory usages to remembered set sizes
4696 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
4697 // Print the footer of the output.
4698 _out->print_cr(G1PPRL_LINE_PREFIX);
4699 _out->print_cr(G1PPRL_LINE_PREFIX
4700 " SUMMARY"
4701 G1PPRL_SUM_MB_FORMAT("capacity")
4702 G1PPRL_SUM_MB_PERC_FORMAT("used")
4703 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4704 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
4705 G1PPRL_SUM_MB_FORMAT("remset")
4706 G1PPRL_SUM_MB_FORMAT("code-roots"),
4707 bytes_to_mb(_total_capacity_bytes),
4708 bytes_to_mb(_total_used_bytes),
4709 perc(_total_used_bytes, _total_capacity_bytes),
4710 bytes_to_mb(_total_prev_live_bytes),
4711 perc(_total_prev_live_bytes, _total_capacity_bytes),
4712 bytes_to_mb(_total_next_live_bytes),
4713 perc(_total_next_live_bytes, _total_capacity_bytes),
4714 bytes_to_mb(_total_remset_bytes),
4715 bytes_to_mb(_total_strong_code_roots_bytes));
4716 _out->cr();
4717 }