Mon, 20 Jan 2014 11:47:07 +0100
8027476: Improve performance of Stringtable unlink
8027455: Improve symbol table scan times during gc pauses
Summary: Parallelize string table and symbol table scan during remark and full GC. Some additional statistics output if the experimental flag G1TraceStringSymbolTableScrubbing is set.
Reviewed-by: mgerdin, coleenp, brutisso
1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "gc_implementation/g1/concurrentMark.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 = "PTR_FORMAT, _heap_start, _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 (" UINT32_FORMAT ") "
571 "than ParallelGCThreads (" UINT32_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, 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, 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(_finger == _heap_end,
823 err_msg("only way to get here: _finger: "PTR_FORMAT", _heap_end: "PTR_FORMAT,
824 _finger, _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 }
981 _first_overflow_barrier_sync.enter();
982 if (concurrent()) {
983 ConcurrentGCThread::stsJoin();
984 }
985 // at this point everyone should have synced up and not be doing any
986 // more work
988 if (verbose_low()) {
989 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id);
990 }
992 // If we're executing the concurrent phase of marking, reset the marking
993 // state; otherwise the marking state is reset after reference processing,
994 // during the remark pause.
995 // If we reset here as a result of an overflow during the remark we will
996 // see assertion failures from any subsequent set_concurrency_and_phase()
997 // calls.
998 if (concurrent()) {
999 // let the task associated with with worker 0 do this
1000 if (worker_id == 0) {
1001 // task 0 is responsible for clearing the global data structures
1002 // We should be here because of an overflow. During STW we should
1003 // not clear the overflow flag since we rely on it being true when
1004 // we exit this method to abort the pause and restart concurent
1005 // marking.
1006 reset_marking_state(true /* clear_overflow */);
1007 force_overflow()->update();
1009 if (G1Log::fine()) {
1010 gclog_or_tty->date_stamp(PrintGCDateStamps);
1011 gclog_or_tty->stamp(PrintGCTimeStamps);
1012 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
1013 }
1014 }
1015 }
1017 // after this, each task should reset its own data structures then
1018 // then go into the second barrier
1019 }
1021 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
1022 if (verbose_low()) {
1023 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id);
1024 }
1026 if (concurrent()) {
1027 ConcurrentGCThread::stsLeave();
1028 }
1029 _second_overflow_barrier_sync.enter();
1030 if (concurrent()) {
1031 ConcurrentGCThread::stsJoin();
1032 }
1033 // at this point everything should be re-initialized and ready to go
1035 if (verbose_low()) {
1036 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id);
1037 }
1038 }
1040 #ifndef PRODUCT
1041 void ForceOverflowSettings::init() {
1042 _num_remaining = G1ConcMarkForceOverflow;
1043 _force = false;
1044 update();
1045 }
1047 void ForceOverflowSettings::update() {
1048 if (_num_remaining > 0) {
1049 _num_remaining -= 1;
1050 _force = true;
1051 } else {
1052 _force = false;
1053 }
1054 }
1056 bool ForceOverflowSettings::should_force() {
1057 if (_force) {
1058 _force = false;
1059 return true;
1060 } else {
1061 return false;
1062 }
1063 }
1064 #endif // !PRODUCT
1066 class CMConcurrentMarkingTask: public AbstractGangTask {
1067 private:
1068 ConcurrentMark* _cm;
1069 ConcurrentMarkThread* _cmt;
1071 public:
1072 void work(uint worker_id) {
1073 assert(Thread::current()->is_ConcurrentGC_thread(),
1074 "this should only be done by a conc GC thread");
1075 ResourceMark rm;
1077 double start_vtime = os::elapsedVTime();
1079 ConcurrentGCThread::stsJoin();
1081 assert(worker_id < _cm->active_tasks(), "invariant");
1082 CMTask* the_task = _cm->task(worker_id);
1083 the_task->record_start_time();
1084 if (!_cm->has_aborted()) {
1085 do {
1086 double start_vtime_sec = os::elapsedVTime();
1087 double start_time_sec = os::elapsedTime();
1088 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1090 the_task->do_marking_step(mark_step_duration_ms,
1091 true /* do_termination */,
1092 false /* is_serial*/);
1094 double end_time_sec = os::elapsedTime();
1095 double end_vtime_sec = os::elapsedVTime();
1096 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1097 double elapsed_time_sec = end_time_sec - start_time_sec;
1098 _cm->clear_has_overflown();
1100 bool ret = _cm->do_yield_check(worker_id);
1102 jlong sleep_time_ms;
1103 if (!_cm->has_aborted() && the_task->has_aborted()) {
1104 sleep_time_ms =
1105 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1106 ConcurrentGCThread::stsLeave();
1107 os::sleep(Thread::current(), sleep_time_ms, false);
1108 ConcurrentGCThread::stsJoin();
1109 }
1110 double end_time2_sec = os::elapsedTime();
1111 double elapsed_time2_sec = end_time2_sec - start_time_sec;
1113 #if 0
1114 gclog_or_tty->print_cr("CM: elapsed %1.4lf ms, sleep %1.4lf ms, "
1115 "overhead %1.4lf",
1116 elapsed_vtime_sec * 1000.0, (double) sleep_time_ms,
1117 the_task->conc_overhead(os::elapsedTime()) * 8.0);
1118 gclog_or_tty->print_cr("elapsed time %1.4lf ms, time 2: %1.4lf ms",
1119 elapsed_time_sec * 1000.0, elapsed_time2_sec * 1000.0);
1120 #endif
1121 } while (!_cm->has_aborted() && the_task->has_aborted());
1122 }
1123 the_task->record_end_time();
1124 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1126 ConcurrentGCThread::stsLeave();
1128 double end_vtime = os::elapsedVTime();
1129 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
1130 }
1132 CMConcurrentMarkingTask(ConcurrentMark* cm,
1133 ConcurrentMarkThread* cmt) :
1134 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1136 ~CMConcurrentMarkingTask() { }
1137 };
1139 // Calculates the number of active workers for a concurrent
1140 // phase.
1141 uint ConcurrentMark::calc_parallel_marking_threads() {
1142 if (G1CollectedHeap::use_parallel_gc_threads()) {
1143 uint n_conc_workers = 0;
1144 if (!UseDynamicNumberOfGCThreads ||
1145 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
1146 !ForceDynamicNumberOfGCThreads)) {
1147 n_conc_workers = max_parallel_marking_threads();
1148 } else {
1149 n_conc_workers =
1150 AdaptiveSizePolicy::calc_default_active_workers(
1151 max_parallel_marking_threads(),
1152 1, /* Minimum workers */
1153 parallel_marking_threads(),
1154 Threads::number_of_non_daemon_threads());
1155 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
1156 // that scaling has already gone into "_max_parallel_marking_threads".
1157 }
1158 assert(n_conc_workers > 0, "Always need at least 1");
1159 return n_conc_workers;
1160 }
1161 // If we are not running with any parallel GC threads we will not
1162 // have spawned any marking threads either. Hence the number of
1163 // concurrent workers should be 0.
1164 return 0;
1165 }
1167 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
1168 // Currently, only survivors can be root regions.
1169 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
1170 G1RootRegionScanClosure cl(_g1h, this, worker_id);
1172 const uintx interval = PrefetchScanIntervalInBytes;
1173 HeapWord* curr = hr->bottom();
1174 const HeapWord* end = hr->top();
1175 while (curr < end) {
1176 Prefetch::read(curr, interval);
1177 oop obj = oop(curr);
1178 int size = obj->oop_iterate(&cl);
1179 assert(size == obj->size(), "sanity");
1180 curr += size;
1181 }
1182 }
1184 class CMRootRegionScanTask : public AbstractGangTask {
1185 private:
1186 ConcurrentMark* _cm;
1188 public:
1189 CMRootRegionScanTask(ConcurrentMark* cm) :
1190 AbstractGangTask("Root Region Scan"), _cm(cm) { }
1192 void work(uint worker_id) {
1193 assert(Thread::current()->is_ConcurrentGC_thread(),
1194 "this should only be done by a conc GC thread");
1196 CMRootRegions* root_regions = _cm->root_regions();
1197 HeapRegion* hr = root_regions->claim_next();
1198 while (hr != NULL) {
1199 _cm->scanRootRegion(hr, worker_id);
1200 hr = root_regions->claim_next();
1201 }
1202 }
1203 };
1205 void ConcurrentMark::scanRootRegions() {
1206 // scan_in_progress() will have been set to true only if there was
1207 // at least one root region to scan. So, if it's false, we
1208 // should not attempt to do any further work.
1209 if (root_regions()->scan_in_progress()) {
1210 _parallel_marking_threads = calc_parallel_marking_threads();
1211 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1212 "Maximum number of marking threads exceeded");
1213 uint active_workers = MAX2(1U, parallel_marking_threads());
1215 CMRootRegionScanTask task(this);
1216 if (use_parallel_marking_threads()) {
1217 _parallel_workers->set_active_workers((int) active_workers);
1218 _parallel_workers->run_task(&task);
1219 } else {
1220 task.work(0);
1221 }
1223 // It's possible that has_aborted() is true here without actually
1224 // aborting the survivor scan earlier. This is OK as it's
1225 // mainly used for sanity checking.
1226 root_regions()->scan_finished();
1227 }
1228 }
1230 void ConcurrentMark::markFromRoots() {
1231 // we might be tempted to assert that:
1232 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1233 // "inconsistent argument?");
1234 // However that wouldn't be right, because it's possible that
1235 // a safepoint is indeed in progress as a younger generation
1236 // stop-the-world GC happens even as we mark in this generation.
1238 _restart_for_overflow = false;
1239 force_overflow_conc()->init();
1241 // _g1h has _n_par_threads
1242 _parallel_marking_threads = calc_parallel_marking_threads();
1243 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1244 "Maximum number of marking threads exceeded");
1246 uint active_workers = MAX2(1U, parallel_marking_threads());
1248 // Parallel task terminator is set in "set_concurrency_and_phase()"
1249 set_concurrency_and_phase(active_workers, true /* concurrent */);
1251 CMConcurrentMarkingTask markingTask(this, cmThread());
1252 if (use_parallel_marking_threads()) {
1253 _parallel_workers->set_active_workers((int)active_workers);
1254 // Don't set _n_par_threads because it affects MT in proceess_strong_roots()
1255 // and the decisions on that MT processing is made elsewhere.
1256 assert(_parallel_workers->active_workers() > 0, "Should have been set");
1257 _parallel_workers->run_task(&markingTask);
1258 } else {
1259 markingTask.work(0);
1260 }
1261 print_stats();
1262 }
1264 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1265 // world is stopped at this checkpoint
1266 assert(SafepointSynchronize::is_at_safepoint(),
1267 "world should be stopped");
1269 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1271 // If a full collection has happened, we shouldn't do this.
1272 if (has_aborted()) {
1273 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1274 return;
1275 }
1277 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1279 if (VerifyDuringGC) {
1280 HandleMark hm; // handle scope
1281 Universe::heap()->prepare_for_verify();
1282 Universe::verify(VerifyOption_G1UsePrevMarking,
1283 " VerifyDuringGC:(before)");
1284 }
1286 G1CollectorPolicy* g1p = g1h->g1_policy();
1287 g1p->record_concurrent_mark_remark_start();
1289 double start = os::elapsedTime();
1291 checkpointRootsFinalWork();
1293 double mark_work_end = os::elapsedTime();
1295 weakRefsWork(clear_all_soft_refs);
1297 if (has_overflown()) {
1298 // Oops. We overflowed. Restart concurrent marking.
1299 _restart_for_overflow = true;
1300 if (G1TraceMarkStackOverflow) {
1301 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1302 }
1304 // Verify the heap w.r.t. the previous marking bitmap.
1305 if (VerifyDuringGC) {
1306 HandleMark hm; // handle scope
1307 Universe::heap()->prepare_for_verify();
1308 Universe::verify(VerifyOption_G1UsePrevMarking,
1309 " VerifyDuringGC:(overflow)");
1310 }
1312 // Clear the marking state because we will be restarting
1313 // marking due to overflowing the global mark stack.
1314 reset_marking_state();
1315 } else {
1316 // Aggregate the per-task counting data that we have accumulated
1317 // while marking.
1318 aggregate_count_data();
1320 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1321 // We're done with marking.
1322 // This is the end of the marking cycle, we're expected all
1323 // threads to have SATB queues with active set to true.
1324 satb_mq_set.set_active_all_threads(false, /* new active value */
1325 true /* expected_active */);
1327 if (VerifyDuringGC) {
1328 HandleMark hm; // handle scope
1329 Universe::heap()->prepare_for_verify();
1330 Universe::verify(VerifyOption_G1UseNextMarking,
1331 " VerifyDuringGC:(after)");
1332 }
1333 assert(!restart_for_overflow(), "sanity");
1334 // Completely reset the marking state since marking completed
1335 set_non_marking_state();
1336 }
1338 // Expand the marking stack, if we have to and if we can.
1339 if (_markStack.should_expand()) {
1340 _markStack.expand();
1341 }
1343 // Statistics
1344 double now = os::elapsedTime();
1345 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1346 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1347 _remark_times.add((now - start) * 1000.0);
1349 g1p->record_concurrent_mark_remark_end();
1351 G1CMIsAliveClosure is_alive(g1h);
1352 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
1353 }
1355 // Base class of the closures that finalize and verify the
1356 // liveness counting data.
1357 class CMCountDataClosureBase: public HeapRegionClosure {
1358 protected:
1359 G1CollectedHeap* _g1h;
1360 ConcurrentMark* _cm;
1361 CardTableModRefBS* _ct_bs;
1363 BitMap* _region_bm;
1364 BitMap* _card_bm;
1366 // Takes a region that's not empty (i.e., it has at least one
1367 // live object in it and sets its corresponding bit on the region
1368 // bitmap to 1. If the region is "starts humongous" it will also set
1369 // to 1 the bits on the region bitmap that correspond to its
1370 // associated "continues humongous" regions.
1371 void set_bit_for_region(HeapRegion* hr) {
1372 assert(!hr->continuesHumongous(), "should have filtered those out");
1374 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1375 if (!hr->startsHumongous()) {
1376 // Normal (non-humongous) case: just set the bit.
1377 _region_bm->par_at_put(index, true);
1378 } else {
1379 // Starts humongous case: calculate how many regions are part of
1380 // this humongous region and then set the bit range.
1381 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1382 _region_bm->par_at_put_range(index, end_index, true);
1383 }
1384 }
1386 public:
1387 CMCountDataClosureBase(G1CollectedHeap* g1h,
1388 BitMap* region_bm, BitMap* card_bm):
1389 _g1h(g1h), _cm(g1h->concurrent_mark()),
1390 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
1391 _region_bm(region_bm), _card_bm(card_bm) { }
1392 };
1394 // Closure that calculates the # live objects per region. Used
1395 // for verification purposes during the cleanup pause.
1396 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1397 CMBitMapRO* _bm;
1398 size_t _region_marked_bytes;
1400 public:
1401 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1402 BitMap* region_bm, BitMap* card_bm) :
1403 CMCountDataClosureBase(g1h, region_bm, card_bm),
1404 _bm(bm), _region_marked_bytes(0) { }
1406 bool doHeapRegion(HeapRegion* hr) {
1408 if (hr->continuesHumongous()) {
1409 // We will ignore these here and process them when their
1410 // associated "starts humongous" region is processed (see
1411 // set_bit_for_heap_region()). Note that we cannot rely on their
1412 // associated "starts humongous" region to have their bit set to
1413 // 1 since, due to the region chunking in the parallel region
1414 // iteration, a "continues humongous" region might be visited
1415 // before its associated "starts humongous".
1416 return false;
1417 }
1419 HeapWord* ntams = hr->next_top_at_mark_start();
1420 HeapWord* start = hr->bottom();
1422 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1423 err_msg("Preconditions not met - "
1424 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT,
1425 start, ntams, hr->end()));
1427 // Find the first marked object at or after "start".
1428 start = _bm->getNextMarkedWordAddress(start, ntams);
1430 size_t marked_bytes = 0;
1432 while (start < ntams) {
1433 oop obj = oop(start);
1434 int obj_sz = obj->size();
1435 HeapWord* obj_end = start + obj_sz;
1437 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1438 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1440 // Note: if we're looking at the last region in heap - obj_end
1441 // could be actually just beyond the end of the heap; end_idx
1442 // will then correspond to a (non-existent) card that is also
1443 // just beyond the heap.
1444 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1445 // end of object is not card aligned - increment to cover
1446 // all the cards spanned by the object
1447 end_idx += 1;
1448 }
1450 // Set the bits in the card BM for the cards spanned by this object.
1451 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1453 // Add the size of this object to the number of marked bytes.
1454 marked_bytes += (size_t)obj_sz * HeapWordSize;
1456 // Find the next marked object after this one.
1457 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1458 }
1460 // Mark the allocated-since-marking portion...
1461 HeapWord* top = hr->top();
1462 if (ntams < top) {
1463 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1464 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1466 // Note: if we're looking at the last region in heap - top
1467 // could be actually just beyond the end of the heap; end_idx
1468 // will then correspond to a (non-existent) card that is also
1469 // just beyond the heap.
1470 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1471 // end of object is not card aligned - increment to cover
1472 // all the cards spanned by the object
1473 end_idx += 1;
1474 }
1475 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1477 // This definitely means the region has live objects.
1478 set_bit_for_region(hr);
1479 }
1481 // Update the live region bitmap.
1482 if (marked_bytes > 0) {
1483 set_bit_for_region(hr);
1484 }
1486 // Set the marked bytes for the current region so that
1487 // it can be queried by a calling verificiation routine
1488 _region_marked_bytes = marked_bytes;
1490 return false;
1491 }
1493 size_t region_marked_bytes() const { return _region_marked_bytes; }
1494 };
1496 // Heap region closure used for verifying the counting data
1497 // that was accumulated concurrently and aggregated during
1498 // the remark pause. This closure is applied to the heap
1499 // regions during the STW cleanup pause.
1501 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1502 G1CollectedHeap* _g1h;
1503 ConcurrentMark* _cm;
1504 CalcLiveObjectsClosure _calc_cl;
1505 BitMap* _region_bm; // Region BM to be verified
1506 BitMap* _card_bm; // Card BM to be verified
1507 bool _verbose; // verbose output?
1509 BitMap* _exp_region_bm; // Expected Region BM values
1510 BitMap* _exp_card_bm; // Expected card BM values
1512 int _failures;
1514 public:
1515 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1516 BitMap* region_bm,
1517 BitMap* card_bm,
1518 BitMap* exp_region_bm,
1519 BitMap* exp_card_bm,
1520 bool verbose) :
1521 _g1h(g1h), _cm(g1h->concurrent_mark()),
1522 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1523 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1524 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1525 _failures(0) { }
1527 int failures() const { return _failures; }
1529 bool doHeapRegion(HeapRegion* hr) {
1530 if (hr->continuesHumongous()) {
1531 // We will ignore these here and process them when their
1532 // associated "starts humongous" region is processed (see
1533 // set_bit_for_heap_region()). Note that we cannot rely on their
1534 // associated "starts humongous" region to have their bit set to
1535 // 1 since, due to the region chunking in the parallel region
1536 // iteration, a "continues humongous" region might be visited
1537 // before its associated "starts humongous".
1538 return false;
1539 }
1541 int failures = 0;
1543 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1544 // this region and set the corresponding bits in the expected region
1545 // and card bitmaps.
1546 bool res = _calc_cl.doHeapRegion(hr);
1547 assert(res == false, "should be continuing");
1549 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1550 Mutex::_no_safepoint_check_flag);
1552 // Verify the marked bytes for this region.
1553 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1554 size_t act_marked_bytes = hr->next_marked_bytes();
1556 // We're not OK if expected marked bytes > actual marked bytes. It means
1557 // we have missed accounting some objects during the actual marking.
1558 if (exp_marked_bytes > act_marked_bytes) {
1559 if (_verbose) {
1560 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1561 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1562 hr->hrs_index(), exp_marked_bytes, act_marked_bytes);
1563 }
1564 failures += 1;
1565 }
1567 // Verify the bit, for this region, in the actual and expected
1568 // (which was just calculated) region bit maps.
1569 // We're not OK if the bit in the calculated expected region
1570 // bitmap is set and the bit in the actual region bitmap is not.
1571 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1573 bool expected = _exp_region_bm->at(index);
1574 bool actual = _region_bm->at(index);
1575 if (expected && !actual) {
1576 if (_verbose) {
1577 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1578 "expected: %s, actual: %s",
1579 hr->hrs_index(),
1580 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1581 }
1582 failures += 1;
1583 }
1585 // Verify that the card bit maps for the cards spanned by the current
1586 // region match. We have an error if we have a set bit in the expected
1587 // bit map and the corresponding bit in the actual bitmap is not set.
1589 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1590 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1592 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1593 expected = _exp_card_bm->at(i);
1594 actual = _card_bm->at(i);
1596 if (expected && !actual) {
1597 if (_verbose) {
1598 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1599 "expected: %s, actual: %s",
1600 hr->hrs_index(), i,
1601 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1602 }
1603 failures += 1;
1604 }
1605 }
1607 if (failures > 0 && _verbose) {
1608 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1609 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1610 HR_FORMAT_PARAMS(hr), hr->next_top_at_mark_start(),
1611 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1612 }
1614 _failures += failures;
1616 // We could stop iteration over the heap when we
1617 // find the first violating region by returning true.
1618 return false;
1619 }
1620 };
1622 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1623 protected:
1624 G1CollectedHeap* _g1h;
1625 ConcurrentMark* _cm;
1626 BitMap* _actual_region_bm;
1627 BitMap* _actual_card_bm;
1629 uint _n_workers;
1631 BitMap* _expected_region_bm;
1632 BitMap* _expected_card_bm;
1634 int _failures;
1635 bool _verbose;
1637 public:
1638 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1639 BitMap* region_bm, BitMap* card_bm,
1640 BitMap* expected_region_bm, BitMap* expected_card_bm)
1641 : AbstractGangTask("G1 verify final counting"),
1642 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1643 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1644 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1645 _failures(0), _verbose(false),
1646 _n_workers(0) {
1647 assert(VerifyDuringGC, "don't call this otherwise");
1649 // Use the value already set as the number of active threads
1650 // in the call to run_task().
1651 if (G1CollectedHeap::use_parallel_gc_threads()) {
1652 assert( _g1h->workers()->active_workers() > 0,
1653 "Should have been previously set");
1654 _n_workers = _g1h->workers()->active_workers();
1655 } else {
1656 _n_workers = 1;
1657 }
1659 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1660 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1662 _verbose = _cm->verbose_medium();
1663 }
1665 void work(uint worker_id) {
1666 assert(worker_id < _n_workers, "invariant");
1668 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1669 _actual_region_bm, _actual_card_bm,
1670 _expected_region_bm,
1671 _expected_card_bm,
1672 _verbose);
1674 if (G1CollectedHeap::use_parallel_gc_threads()) {
1675 _g1h->heap_region_par_iterate_chunked(&verify_cl,
1676 worker_id,
1677 _n_workers,
1678 HeapRegion::VerifyCountClaimValue);
1679 } else {
1680 _g1h->heap_region_iterate(&verify_cl);
1681 }
1683 Atomic::add(verify_cl.failures(), &_failures);
1684 }
1686 int failures() const { return _failures; }
1687 };
1689 // Closure that finalizes the liveness counting data.
1690 // Used during the cleanup pause.
1691 // Sets the bits corresponding to the interval [NTAMS, top]
1692 // (which contains the implicitly live objects) in the
1693 // card liveness bitmap. Also sets the bit for each region,
1694 // containing live data, in the region liveness bitmap.
1696 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1697 public:
1698 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1699 BitMap* region_bm,
1700 BitMap* card_bm) :
1701 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1703 bool doHeapRegion(HeapRegion* hr) {
1705 if (hr->continuesHumongous()) {
1706 // We will ignore these here and process them when their
1707 // associated "starts humongous" region is processed (see
1708 // set_bit_for_heap_region()). Note that we cannot rely on their
1709 // associated "starts humongous" region to have their bit set to
1710 // 1 since, due to the region chunking in the parallel region
1711 // iteration, a "continues humongous" region might be visited
1712 // before its associated "starts humongous".
1713 return false;
1714 }
1716 HeapWord* ntams = hr->next_top_at_mark_start();
1717 HeapWord* top = hr->top();
1719 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1721 // Mark the allocated-since-marking portion...
1722 if (ntams < top) {
1723 // This definitely means the region has live objects.
1724 set_bit_for_region(hr);
1726 // Now set the bits in the card bitmap for [ntams, top)
1727 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1728 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1730 // Note: if we're looking at the last region in heap - top
1731 // could be actually just beyond the end of the heap; end_idx
1732 // will then correspond to a (non-existent) card that is also
1733 // just beyond the heap.
1734 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1735 // end of object is not card aligned - increment to cover
1736 // all the cards spanned by the object
1737 end_idx += 1;
1738 }
1740 assert(end_idx <= _card_bm->size(),
1741 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1742 end_idx, _card_bm->size()));
1743 assert(start_idx < _card_bm->size(),
1744 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1745 start_idx, _card_bm->size()));
1747 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1748 }
1750 // Set the bit for the region if it contains live data
1751 if (hr->next_marked_bytes() > 0) {
1752 set_bit_for_region(hr);
1753 }
1755 return false;
1756 }
1757 };
1759 class G1ParFinalCountTask: public AbstractGangTask {
1760 protected:
1761 G1CollectedHeap* _g1h;
1762 ConcurrentMark* _cm;
1763 BitMap* _actual_region_bm;
1764 BitMap* _actual_card_bm;
1766 uint _n_workers;
1768 public:
1769 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1770 : AbstractGangTask("G1 final counting"),
1771 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1772 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1773 _n_workers(0) {
1774 // Use the value already set as the number of active threads
1775 // in the call to run_task().
1776 if (G1CollectedHeap::use_parallel_gc_threads()) {
1777 assert( _g1h->workers()->active_workers() > 0,
1778 "Should have been previously set");
1779 _n_workers = _g1h->workers()->active_workers();
1780 } else {
1781 _n_workers = 1;
1782 }
1783 }
1785 void work(uint worker_id) {
1786 assert(worker_id < _n_workers, "invariant");
1788 FinalCountDataUpdateClosure final_update_cl(_g1h,
1789 _actual_region_bm,
1790 _actual_card_bm);
1792 if (G1CollectedHeap::use_parallel_gc_threads()) {
1793 _g1h->heap_region_par_iterate_chunked(&final_update_cl,
1794 worker_id,
1795 _n_workers,
1796 HeapRegion::FinalCountClaimValue);
1797 } else {
1798 _g1h->heap_region_iterate(&final_update_cl);
1799 }
1800 }
1801 };
1803 class G1ParNoteEndTask;
1805 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1806 G1CollectedHeap* _g1;
1807 int _worker_num;
1808 size_t _max_live_bytes;
1809 uint _regions_claimed;
1810 size_t _freed_bytes;
1811 FreeRegionList* _local_cleanup_list;
1812 OldRegionSet* _old_proxy_set;
1813 HumongousRegionSet* _humongous_proxy_set;
1814 HRRSCleanupTask* _hrrs_cleanup_task;
1815 double _claimed_region_time;
1816 double _max_region_time;
1818 public:
1819 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1820 int worker_num,
1821 FreeRegionList* local_cleanup_list,
1822 OldRegionSet* old_proxy_set,
1823 HumongousRegionSet* humongous_proxy_set,
1824 HRRSCleanupTask* hrrs_cleanup_task) :
1825 _g1(g1), _worker_num(worker_num),
1826 _max_live_bytes(0), _regions_claimed(0),
1827 _freed_bytes(0),
1828 _claimed_region_time(0.0), _max_region_time(0.0),
1829 _local_cleanup_list(local_cleanup_list),
1830 _old_proxy_set(old_proxy_set),
1831 _humongous_proxy_set(humongous_proxy_set),
1832 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1834 size_t freed_bytes() { return _freed_bytes; }
1836 bool doHeapRegion(HeapRegion *hr) {
1837 if (hr->continuesHumongous()) {
1838 return false;
1839 }
1840 // We use a claim value of zero here because all regions
1841 // were claimed with value 1 in the FinalCount task.
1842 _g1->reset_gc_time_stamps(hr);
1843 double start = os::elapsedTime();
1844 _regions_claimed++;
1845 hr->note_end_of_marking();
1846 _max_live_bytes += hr->max_live_bytes();
1847 _g1->free_region_if_empty(hr,
1848 &_freed_bytes,
1849 _local_cleanup_list,
1850 _old_proxy_set,
1851 _humongous_proxy_set,
1852 _hrrs_cleanup_task,
1853 true /* par */);
1854 double region_time = (os::elapsedTime() - start);
1855 _claimed_region_time += region_time;
1856 if (region_time > _max_region_time) {
1857 _max_region_time = region_time;
1858 }
1859 return false;
1860 }
1862 size_t max_live_bytes() { return _max_live_bytes; }
1863 uint regions_claimed() { return _regions_claimed; }
1864 double claimed_region_time_sec() { return _claimed_region_time; }
1865 double max_region_time_sec() { return _max_region_time; }
1866 };
1868 class G1ParNoteEndTask: public AbstractGangTask {
1869 friend class G1NoteEndOfConcMarkClosure;
1871 protected:
1872 G1CollectedHeap* _g1h;
1873 size_t _max_live_bytes;
1874 size_t _freed_bytes;
1875 FreeRegionList* _cleanup_list;
1877 public:
1878 G1ParNoteEndTask(G1CollectedHeap* g1h,
1879 FreeRegionList* cleanup_list) :
1880 AbstractGangTask("G1 note end"), _g1h(g1h),
1881 _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list) { }
1883 void work(uint worker_id) {
1884 double start = os::elapsedTime();
1885 FreeRegionList local_cleanup_list("Local Cleanup List");
1886 OldRegionSet old_proxy_set("Local Cleanup Old Proxy Set");
1887 HumongousRegionSet humongous_proxy_set("Local Cleanup Humongous Proxy Set");
1888 HRRSCleanupTask hrrs_cleanup_task;
1889 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, worker_id, &local_cleanup_list,
1890 &old_proxy_set,
1891 &humongous_proxy_set,
1892 &hrrs_cleanup_task);
1893 if (G1CollectedHeap::use_parallel_gc_threads()) {
1894 _g1h->heap_region_par_iterate_chunked(&g1_note_end, worker_id,
1895 _g1h->workers()->active_workers(),
1896 HeapRegion::NoteEndClaimValue);
1897 } else {
1898 _g1h->heap_region_iterate(&g1_note_end);
1899 }
1900 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1902 // Now update the lists
1903 _g1h->update_sets_after_freeing_regions(g1_note_end.freed_bytes(),
1904 NULL /* free_list */,
1905 &old_proxy_set,
1906 &humongous_proxy_set,
1907 true /* par */);
1908 {
1909 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1910 _max_live_bytes += g1_note_end.max_live_bytes();
1911 _freed_bytes += g1_note_end.freed_bytes();
1913 // If we iterate over the global cleanup list at the end of
1914 // cleanup to do this printing we will not guarantee to only
1915 // generate output for the newly-reclaimed regions (the list
1916 // might not be empty at the beginning of cleanup; we might
1917 // still be working on its previous contents). So we do the
1918 // printing here, before we append the new regions to the global
1919 // cleanup list.
1921 G1HRPrinter* hr_printer = _g1h->hr_printer();
1922 if (hr_printer->is_active()) {
1923 HeapRegionLinkedListIterator iter(&local_cleanup_list);
1924 while (iter.more_available()) {
1925 HeapRegion* hr = iter.get_next();
1926 hr_printer->cleanup(hr);
1927 }
1928 }
1930 _cleanup_list->add_as_tail(&local_cleanup_list);
1931 assert(local_cleanup_list.is_empty(), "post-condition");
1933 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1934 }
1935 }
1936 size_t max_live_bytes() { return _max_live_bytes; }
1937 size_t freed_bytes() { return _freed_bytes; }
1938 };
1940 class G1ParScrubRemSetTask: public AbstractGangTask {
1941 protected:
1942 G1RemSet* _g1rs;
1943 BitMap* _region_bm;
1944 BitMap* _card_bm;
1945 public:
1946 G1ParScrubRemSetTask(G1CollectedHeap* g1h,
1947 BitMap* region_bm, BitMap* card_bm) :
1948 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()),
1949 _region_bm(region_bm), _card_bm(card_bm) { }
1951 void work(uint worker_id) {
1952 if (G1CollectedHeap::use_parallel_gc_threads()) {
1953 _g1rs->scrub_par(_region_bm, _card_bm, worker_id,
1954 HeapRegion::ScrubRemSetClaimValue);
1955 } else {
1956 _g1rs->scrub(_region_bm, _card_bm);
1957 }
1958 }
1960 };
1962 void ConcurrentMark::cleanup() {
1963 // world is stopped at this checkpoint
1964 assert(SafepointSynchronize::is_at_safepoint(),
1965 "world should be stopped");
1966 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1968 // If a full collection has happened, we shouldn't do this.
1969 if (has_aborted()) {
1970 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1971 return;
1972 }
1974 HRSPhaseSetter x(HRSPhaseCleanup);
1975 g1h->verify_region_sets_optional();
1977 if (VerifyDuringGC) {
1978 HandleMark hm; // handle scope
1979 Universe::heap()->prepare_for_verify();
1980 Universe::verify(VerifyOption_G1UsePrevMarking,
1981 " VerifyDuringGC:(before)");
1982 }
1984 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
1985 g1p->record_concurrent_mark_cleanup_start();
1987 double start = os::elapsedTime();
1989 HeapRegionRemSet::reset_for_cleanup_tasks();
1991 uint n_workers;
1993 // Do counting once more with the world stopped for good measure.
1994 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1996 if (G1CollectedHeap::use_parallel_gc_threads()) {
1997 assert(g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
1998 "sanity check");
2000 g1h->set_par_threads();
2001 n_workers = g1h->n_par_threads();
2002 assert(g1h->n_par_threads() == n_workers,
2003 "Should not have been reset");
2004 g1h->workers()->run_task(&g1_par_count_task);
2005 // Done with the parallel phase so reset to 0.
2006 g1h->set_par_threads(0);
2008 assert(g1h->check_heap_region_claim_values(HeapRegion::FinalCountClaimValue),
2009 "sanity check");
2010 } else {
2011 n_workers = 1;
2012 g1_par_count_task.work(0);
2013 }
2015 if (VerifyDuringGC) {
2016 // Verify that the counting data accumulated during marking matches
2017 // that calculated by walking the marking bitmap.
2019 // Bitmaps to hold expected values
2020 BitMap expected_region_bm(_region_bm.size(), false);
2021 BitMap expected_card_bm(_card_bm.size(), false);
2023 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
2024 &_region_bm,
2025 &_card_bm,
2026 &expected_region_bm,
2027 &expected_card_bm);
2029 if (G1CollectedHeap::use_parallel_gc_threads()) {
2030 g1h->set_par_threads((int)n_workers);
2031 g1h->workers()->run_task(&g1_par_verify_task);
2032 // Done with the parallel phase so reset to 0.
2033 g1h->set_par_threads(0);
2035 assert(g1h->check_heap_region_claim_values(HeapRegion::VerifyCountClaimValue),
2036 "sanity check");
2037 } else {
2038 g1_par_verify_task.work(0);
2039 }
2041 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
2042 }
2044 size_t start_used_bytes = g1h->used();
2045 g1h->set_marking_complete();
2047 double count_end = os::elapsedTime();
2048 double this_final_counting_time = (count_end - start);
2049 _total_counting_time += this_final_counting_time;
2051 if (G1PrintRegionLivenessInfo) {
2052 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
2053 _g1h->heap_region_iterate(&cl);
2054 }
2056 // Install newly created mark bitMap as "prev".
2057 swapMarkBitMaps();
2059 g1h->reset_gc_time_stamp();
2061 // Note end of marking in all heap regions.
2062 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list);
2063 if (G1CollectedHeap::use_parallel_gc_threads()) {
2064 g1h->set_par_threads((int)n_workers);
2065 g1h->workers()->run_task(&g1_par_note_end_task);
2066 g1h->set_par_threads(0);
2068 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue),
2069 "sanity check");
2070 } else {
2071 g1_par_note_end_task.work(0);
2072 }
2073 g1h->check_gc_time_stamps();
2075 if (!cleanup_list_is_empty()) {
2076 // The cleanup list is not empty, so we'll have to process it
2077 // concurrently. Notify anyone else that might be wanting free
2078 // regions that there will be more free regions coming soon.
2079 g1h->set_free_regions_coming();
2080 }
2082 // call below, since it affects the metric by which we sort the heap
2083 // regions.
2084 if (G1ScrubRemSets) {
2085 double rs_scrub_start = os::elapsedTime();
2086 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm);
2087 if (G1CollectedHeap::use_parallel_gc_threads()) {
2088 g1h->set_par_threads((int)n_workers);
2089 g1h->workers()->run_task(&g1_par_scrub_rs_task);
2090 g1h->set_par_threads(0);
2092 assert(g1h->check_heap_region_claim_values(
2093 HeapRegion::ScrubRemSetClaimValue),
2094 "sanity check");
2095 } else {
2096 g1_par_scrub_rs_task.work(0);
2097 }
2099 double rs_scrub_end = os::elapsedTime();
2100 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
2101 _total_rs_scrub_time += this_rs_scrub_time;
2102 }
2104 // this will also free any regions totally full of garbage objects,
2105 // and sort the regions.
2106 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers);
2108 // Statistics.
2109 double end = os::elapsedTime();
2110 _cleanup_times.add((end - start) * 1000.0);
2112 if (G1Log::fine()) {
2113 g1h->print_size_transition(gclog_or_tty,
2114 start_used_bytes,
2115 g1h->used(),
2116 g1h->capacity());
2117 }
2119 // Clean up will have freed any regions completely full of garbage.
2120 // Update the soft reference policy with the new heap occupancy.
2121 Universe::update_heap_info_at_gc();
2123 // We need to make this be a "collection" so any collection pause that
2124 // races with it goes around and waits for completeCleanup to finish.
2125 g1h->increment_total_collections();
2127 // We reclaimed old regions so we should calculate the sizes to make
2128 // sure we update the old gen/space data.
2129 g1h->g1mm()->update_sizes();
2131 if (VerifyDuringGC) {
2132 HandleMark hm; // handle scope
2133 Universe::heap()->prepare_for_verify();
2134 Universe::verify(VerifyOption_G1UsePrevMarking,
2135 " VerifyDuringGC:(after)");
2136 }
2138 g1h->verify_region_sets_optional();
2139 g1h->trace_heap_after_concurrent_cycle();
2140 }
2142 void ConcurrentMark::completeCleanup() {
2143 if (has_aborted()) return;
2145 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2147 _cleanup_list.verify_optional();
2148 FreeRegionList tmp_free_list("Tmp Free List");
2150 if (G1ConcRegionFreeingVerbose) {
2151 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2152 "cleanup list has %u entries",
2153 _cleanup_list.length());
2154 }
2156 // Noone else should be accessing the _cleanup_list at this point,
2157 // so it's not necessary to take any locks
2158 while (!_cleanup_list.is_empty()) {
2159 HeapRegion* hr = _cleanup_list.remove_head();
2160 assert(hr != NULL, "the list was not empty");
2161 hr->par_clear();
2162 tmp_free_list.add_as_tail(hr);
2164 // Instead of adding one region at a time to the secondary_free_list,
2165 // we accumulate them in the local list and move them a few at a
2166 // time. This also cuts down on the number of notify_all() calls
2167 // we do during this process. We'll also append the local list when
2168 // _cleanup_list is empty (which means we just removed the last
2169 // region from the _cleanup_list).
2170 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2171 _cleanup_list.is_empty()) {
2172 if (G1ConcRegionFreeingVerbose) {
2173 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2174 "appending %u entries to the secondary_free_list, "
2175 "cleanup list still has %u entries",
2176 tmp_free_list.length(),
2177 _cleanup_list.length());
2178 }
2180 {
2181 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2182 g1h->secondary_free_list_add_as_tail(&tmp_free_list);
2183 SecondaryFreeList_lock->notify_all();
2184 }
2186 if (G1StressConcRegionFreeing) {
2187 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2188 os::sleep(Thread::current(), (jlong) 1, false);
2189 }
2190 }
2191 }
2192 }
2193 assert(tmp_free_list.is_empty(), "post-condition");
2194 }
2196 // Supporting Object and Oop closures for reference discovery
2197 // and processing in during marking
2199 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2200 HeapWord* addr = (HeapWord*)obj;
2201 return addr != NULL &&
2202 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2203 }
2205 // 'Keep Alive' oop closure used by both serial parallel reference processing.
2206 // Uses the CMTask associated with a worker thread (for serial reference
2207 // processing the CMTask for worker 0 is used) to preserve (mark) and
2208 // trace referent objects.
2209 //
2210 // Using the CMTask and embedded local queues avoids having the worker
2211 // threads operating on the global mark stack. This reduces the risk
2212 // of overflowing the stack - which we would rather avoid at this late
2213 // state. Also using the tasks' local queues removes the potential
2214 // of the workers interfering with each other that could occur if
2215 // operating on the global stack.
2217 class G1CMKeepAliveAndDrainClosure: public OopClosure {
2218 ConcurrentMark* _cm;
2219 CMTask* _task;
2220 int _ref_counter_limit;
2221 int _ref_counter;
2222 bool _is_serial;
2223 public:
2224 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2225 _cm(cm), _task(task), _is_serial(is_serial),
2226 _ref_counter_limit(G1RefProcDrainInterval) {
2227 assert(_ref_counter_limit > 0, "sanity");
2228 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2229 _ref_counter = _ref_counter_limit;
2230 }
2232 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2233 virtual void do_oop( oop* p) { do_oop_work(p); }
2235 template <class T> void do_oop_work(T* p) {
2236 if (!_cm->has_overflown()) {
2237 oop obj = oopDesc::load_decode_heap_oop(p);
2238 if (_cm->verbose_high()) {
2239 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2240 "*"PTR_FORMAT" = "PTR_FORMAT,
2241 _task->worker_id(), p, (void*) obj);
2242 }
2244 _task->deal_with_reference(obj);
2245 _ref_counter--;
2247 if (_ref_counter == 0) {
2248 // We have dealt with _ref_counter_limit references, pushing them
2249 // and objects reachable from them on to the local stack (and
2250 // possibly the global stack). Call CMTask::do_marking_step() to
2251 // process these entries.
2252 //
2253 // We call CMTask::do_marking_step() in a loop, which we'll exit if
2254 // there's nothing more to do (i.e. we're done with the entries that
2255 // were pushed as a result of the CMTask::deal_with_reference() calls
2256 // above) or we overflow.
2257 //
2258 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2259 // flag while there may still be some work to do. (See the comment at
2260 // the beginning of CMTask::do_marking_step() for those conditions -
2261 // one of which is reaching the specified time target.) It is only
2262 // when CMTask::do_marking_step() returns without setting the
2263 // has_aborted() flag that the marking step has completed.
2264 do {
2265 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2266 _task->do_marking_step(mark_step_duration_ms,
2267 false /* do_termination */,
2268 _is_serial);
2269 } while (_task->has_aborted() && !_cm->has_overflown());
2270 _ref_counter = _ref_counter_limit;
2271 }
2272 } else {
2273 if (_cm->verbose_high()) {
2274 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2275 }
2276 }
2277 }
2278 };
2280 // 'Drain' oop closure used by both serial and parallel reference processing.
2281 // Uses the CMTask associated with a given worker thread (for serial
2282 // reference processing the CMtask for worker 0 is used). Calls the
2283 // do_marking_step routine, with an unbelievably large timeout value,
2284 // to drain the marking data structures of the remaining entries
2285 // added by the 'keep alive' oop closure above.
2287 class G1CMDrainMarkingStackClosure: public VoidClosure {
2288 ConcurrentMark* _cm;
2289 CMTask* _task;
2290 bool _is_serial;
2291 public:
2292 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2293 _cm(cm), _task(task), _is_serial(is_serial) {
2294 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2295 }
2297 void do_void() {
2298 do {
2299 if (_cm->verbose_high()) {
2300 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s",
2301 _task->worker_id(), BOOL_TO_STR(_is_serial));
2302 }
2304 // We call CMTask::do_marking_step() to completely drain the local
2305 // and global marking stacks of entries pushed by the 'keep alive'
2306 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
2307 //
2308 // CMTask::do_marking_step() is called in a loop, which we'll exit
2309 // if there's nothing more to do (i.e. we'completely drained the
2310 // entries that were pushed as a a result of applying the 'keep alive'
2311 // closure to the entries on the discovered ref lists) or we overflow
2312 // the global marking stack.
2313 //
2314 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2315 // flag while there may still be some work to do. (See the comment at
2316 // the beginning of CMTask::do_marking_step() for those conditions -
2317 // one of which is reaching the specified time target.) It is only
2318 // when CMTask::do_marking_step() returns without setting the
2319 // has_aborted() flag that the marking step has completed.
2321 _task->do_marking_step(1000000000.0 /* something very large */,
2322 true /* do_termination */,
2323 _is_serial);
2324 } while (_task->has_aborted() && !_cm->has_overflown());
2325 }
2326 };
2328 // Implementation of AbstractRefProcTaskExecutor for parallel
2329 // reference processing at the end of G1 concurrent marking
2331 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2332 private:
2333 G1CollectedHeap* _g1h;
2334 ConcurrentMark* _cm;
2335 WorkGang* _workers;
2336 int _active_workers;
2338 public:
2339 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2340 ConcurrentMark* cm,
2341 WorkGang* workers,
2342 int n_workers) :
2343 _g1h(g1h), _cm(cm),
2344 _workers(workers), _active_workers(n_workers) { }
2346 // Executes the given task using concurrent marking worker threads.
2347 virtual void execute(ProcessTask& task);
2348 virtual void execute(EnqueueTask& task);
2349 };
2351 class G1CMRefProcTaskProxy: public AbstractGangTask {
2352 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2353 ProcessTask& _proc_task;
2354 G1CollectedHeap* _g1h;
2355 ConcurrentMark* _cm;
2357 public:
2358 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2359 G1CollectedHeap* g1h,
2360 ConcurrentMark* cm) :
2361 AbstractGangTask("Process reference objects in parallel"),
2362 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
2363 ReferenceProcessor* rp = _g1h->ref_processor_cm();
2364 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
2365 }
2367 virtual void work(uint worker_id) {
2368 CMTask* task = _cm->task(worker_id);
2369 G1CMIsAliveClosure g1_is_alive(_g1h);
2370 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
2371 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
2373 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2374 }
2375 };
2377 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2378 assert(_workers != NULL, "Need parallel worker threads.");
2379 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2381 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2383 // We need to reset the concurrency level before each
2384 // proxy task execution, so that the termination protocol
2385 // and overflow handling in CMTask::do_marking_step() knows
2386 // how many workers to wait for.
2387 _cm->set_concurrency(_active_workers);
2388 _g1h->set_par_threads(_active_workers);
2389 _workers->run_task(&proc_task_proxy);
2390 _g1h->set_par_threads(0);
2391 }
2393 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2394 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2395 EnqueueTask& _enq_task;
2397 public:
2398 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2399 AbstractGangTask("Enqueue reference objects in parallel"),
2400 _enq_task(enq_task) { }
2402 virtual void work(uint worker_id) {
2403 _enq_task.work(worker_id);
2404 }
2405 };
2407 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2408 assert(_workers != NULL, "Need parallel worker threads.");
2409 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2411 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2413 // Not strictly necessary but...
2414 //
2415 // We need to reset the concurrency level before each
2416 // proxy task execution, so that the termination protocol
2417 // and overflow handling in CMTask::do_marking_step() knows
2418 // how many workers to wait for.
2419 _cm->set_concurrency(_active_workers);
2420 _g1h->set_par_threads(_active_workers);
2421 _workers->run_task(&enq_task_proxy);
2422 _g1h->set_par_threads(0);
2423 }
2425 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2426 if (has_overflown()) {
2427 // Skip processing the discovered references if we have
2428 // overflown the global marking stack. Reference objects
2429 // only get discovered once so it is OK to not
2430 // de-populate the discovered reference lists. We could have,
2431 // but the only benefit would be that, when marking restarts,
2432 // less reference objects are discovered.
2433 return;
2434 }
2436 ResourceMark rm;
2437 HandleMark hm;
2439 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2441 // Is alive closure.
2442 G1CMIsAliveClosure g1_is_alive(g1h);
2444 // Inner scope to exclude the cleaning of the string and symbol
2445 // tables from the displayed time.
2446 {
2447 if (G1Log::finer()) {
2448 gclog_or_tty->put(' ');
2449 }
2450 GCTraceTime t("GC ref-proc", G1Log::finer(), false, g1h->gc_timer_cm());
2452 ReferenceProcessor* rp = g1h->ref_processor_cm();
2454 // See the comment in G1CollectedHeap::ref_processing_init()
2455 // about how reference processing currently works in G1.
2457 // Set the soft reference policy
2458 rp->setup_policy(clear_all_soft_refs);
2459 assert(_markStack.isEmpty(), "mark stack should be empty");
2461 // Instances of the 'Keep Alive' and 'Complete GC' closures used
2462 // in serial reference processing. Note these closures are also
2463 // used for serially processing (by the the current thread) the
2464 // JNI references during parallel reference processing.
2465 //
2466 // These closures do not need to synchronize with the worker
2467 // threads involved in parallel reference processing as these
2468 // instances are executed serially by the current thread (e.g.
2469 // reference processing is not multi-threaded and is thus
2470 // performed by the current thread instead of a gang worker).
2471 //
2472 // The gang tasks involved in parallel reference procssing create
2473 // their own instances of these closures, which do their own
2474 // synchronization among themselves.
2475 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
2476 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
2478 // We need at least one active thread. If reference processing
2479 // is not multi-threaded we use the current (VMThread) thread,
2480 // otherwise we use the work gang from the G1CollectedHeap and
2481 // we utilize all the worker threads we can.
2482 bool processing_is_mt = rp->processing_is_mt() && g1h->workers() != NULL;
2483 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
2484 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2486 // Parallel processing task executor.
2487 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2488 g1h->workers(), active_workers);
2489 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
2491 // Set the concurrency level. The phase was already set prior to
2492 // executing the remark task.
2493 set_concurrency(active_workers);
2495 // Set the degree of MT processing here. If the discovery was done MT,
2496 // the number of threads involved during discovery could differ from
2497 // the number of active workers. This is OK as long as the discovered
2498 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2499 rp->set_active_mt_degree(active_workers);
2501 // Process the weak references.
2502 const ReferenceProcessorStats& stats =
2503 rp->process_discovered_references(&g1_is_alive,
2504 &g1_keep_alive,
2505 &g1_drain_mark_stack,
2506 executor,
2507 g1h->gc_timer_cm());
2508 g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
2510 // The do_oop work routines of the keep_alive and drain_marking_stack
2511 // oop closures will set the has_overflown flag if we overflow the
2512 // global marking stack.
2514 assert(_markStack.overflow() || _markStack.isEmpty(),
2515 "mark stack should be empty (unless it overflowed)");
2517 if (_markStack.overflow()) {
2518 // This should have been done already when we tried to push an
2519 // entry on to the global mark stack. But let's do it again.
2520 set_has_overflown();
2521 }
2523 assert(rp->num_q() == active_workers, "why not");
2525 rp->enqueue_discovered_references(executor);
2527 rp->verify_no_references_recorded();
2528 assert(!rp->discovery_enabled(), "Post condition");
2529 }
2531 g1h->unlink_string_and_symbol_table(&g1_is_alive);
2532 }
2534 void ConcurrentMark::swapMarkBitMaps() {
2535 CMBitMapRO* temp = _prevMarkBitMap;
2536 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2537 _nextMarkBitMap = (CMBitMap*) temp;
2538 }
2540 class CMRemarkTask: public AbstractGangTask {
2541 private:
2542 ConcurrentMark* _cm;
2543 bool _is_serial;
2544 public:
2545 void work(uint worker_id) {
2546 // Since all available tasks are actually started, we should
2547 // only proceed if we're supposed to be actived.
2548 if (worker_id < _cm->active_tasks()) {
2549 CMTask* task = _cm->task(worker_id);
2550 task->record_start_time();
2551 do {
2552 task->do_marking_step(1000000000.0 /* something very large */,
2553 true /* do_termination */,
2554 _is_serial);
2555 } while (task->has_aborted() && !_cm->has_overflown());
2556 // If we overflow, then we do not want to restart. We instead
2557 // want to abort remark and do concurrent marking again.
2558 task->record_end_time();
2559 }
2560 }
2562 CMRemarkTask(ConcurrentMark* cm, int active_workers, bool is_serial) :
2563 AbstractGangTask("Par Remark"), _cm(cm), _is_serial(is_serial) {
2564 _cm->terminator()->reset_for_reuse(active_workers);
2565 }
2566 };
2568 void ConcurrentMark::checkpointRootsFinalWork() {
2569 ResourceMark rm;
2570 HandleMark hm;
2571 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2573 g1h->ensure_parsability(false);
2575 if (G1CollectedHeap::use_parallel_gc_threads()) {
2576 G1CollectedHeap::StrongRootsScope srs(g1h);
2577 // this is remark, so we'll use up all active threads
2578 uint active_workers = g1h->workers()->active_workers();
2579 if (active_workers == 0) {
2580 assert(active_workers > 0, "Should have been set earlier");
2581 active_workers = (uint) ParallelGCThreads;
2582 g1h->workers()->set_active_workers(active_workers);
2583 }
2584 set_concurrency_and_phase(active_workers, false /* concurrent */);
2585 // Leave _parallel_marking_threads at it's
2586 // value originally calculated in the ConcurrentMark
2587 // constructor and pass values of the active workers
2588 // through the gang in the task.
2590 CMRemarkTask remarkTask(this, active_workers, false /* is_serial */);
2591 // We will start all available threads, even if we decide that the
2592 // active_workers will be fewer. The extra ones will just bail out
2593 // immediately.
2594 g1h->set_par_threads(active_workers);
2595 g1h->workers()->run_task(&remarkTask);
2596 g1h->set_par_threads(0);
2597 } else {
2598 G1CollectedHeap::StrongRootsScope srs(g1h);
2599 uint active_workers = 1;
2600 set_concurrency_and_phase(active_workers, false /* concurrent */);
2602 // Note - if there's no work gang then the VMThread will be
2603 // the thread to execute the remark - serially. We have
2604 // to pass true for the is_serial parameter so that
2605 // CMTask::do_marking_step() doesn't enter the sync
2606 // barriers in the event of an overflow. Doing so will
2607 // cause an assert that the current thread is not a
2608 // concurrent GC thread.
2609 CMRemarkTask remarkTask(this, active_workers, true /* is_serial*/);
2610 remarkTask.work(0);
2611 }
2612 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2613 guarantee(has_overflown() ||
2614 satb_mq_set.completed_buffers_num() == 0,
2615 err_msg("Invariant: has_overflown = %s, num buffers = %d",
2616 BOOL_TO_STR(has_overflown()),
2617 satb_mq_set.completed_buffers_num()));
2619 print_stats();
2620 }
2622 #ifndef PRODUCT
2624 class PrintReachableOopClosure: public OopClosure {
2625 private:
2626 G1CollectedHeap* _g1h;
2627 outputStream* _out;
2628 VerifyOption _vo;
2629 bool _all;
2631 public:
2632 PrintReachableOopClosure(outputStream* out,
2633 VerifyOption vo,
2634 bool all) :
2635 _g1h(G1CollectedHeap::heap()),
2636 _out(out), _vo(vo), _all(all) { }
2638 void do_oop(narrowOop* p) { do_oop_work(p); }
2639 void do_oop( oop* p) { do_oop_work(p); }
2641 template <class T> void do_oop_work(T* p) {
2642 oop obj = oopDesc::load_decode_heap_oop(p);
2643 const char* str = NULL;
2644 const char* str2 = "";
2646 if (obj == NULL) {
2647 str = "";
2648 } else if (!_g1h->is_in_g1_reserved(obj)) {
2649 str = " O";
2650 } else {
2651 HeapRegion* hr = _g1h->heap_region_containing(obj);
2652 guarantee(hr != NULL, "invariant");
2653 bool over_tams = _g1h->allocated_since_marking(obj, hr, _vo);
2654 bool marked = _g1h->is_marked(obj, _vo);
2656 if (over_tams) {
2657 str = " >";
2658 if (marked) {
2659 str2 = " AND MARKED";
2660 }
2661 } else if (marked) {
2662 str = " M";
2663 } else {
2664 str = " NOT";
2665 }
2666 }
2668 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s",
2669 p, (void*) obj, str, str2);
2670 }
2671 };
2673 class PrintReachableObjectClosure : public ObjectClosure {
2674 private:
2675 G1CollectedHeap* _g1h;
2676 outputStream* _out;
2677 VerifyOption _vo;
2678 bool _all;
2679 HeapRegion* _hr;
2681 public:
2682 PrintReachableObjectClosure(outputStream* out,
2683 VerifyOption vo,
2684 bool all,
2685 HeapRegion* hr) :
2686 _g1h(G1CollectedHeap::heap()),
2687 _out(out), _vo(vo), _all(all), _hr(hr) { }
2689 void do_object(oop o) {
2690 bool over_tams = _g1h->allocated_since_marking(o, _hr, _vo);
2691 bool marked = _g1h->is_marked(o, _vo);
2692 bool print_it = _all || over_tams || marked;
2694 if (print_it) {
2695 _out->print_cr(" "PTR_FORMAT"%s",
2696 (void *)o, (over_tams) ? " >" : (marked) ? " M" : "");
2697 PrintReachableOopClosure oopCl(_out, _vo, _all);
2698 o->oop_iterate_no_header(&oopCl);
2699 }
2700 }
2701 };
2703 class PrintReachableRegionClosure : public HeapRegionClosure {
2704 private:
2705 G1CollectedHeap* _g1h;
2706 outputStream* _out;
2707 VerifyOption _vo;
2708 bool _all;
2710 public:
2711 bool doHeapRegion(HeapRegion* hr) {
2712 HeapWord* b = hr->bottom();
2713 HeapWord* e = hr->end();
2714 HeapWord* t = hr->top();
2715 HeapWord* p = _g1h->top_at_mark_start(hr, _vo);
2716 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" "
2717 "TAMS: "PTR_FORMAT, b, e, t, p);
2718 _out->cr();
2720 HeapWord* from = b;
2721 HeapWord* to = t;
2723 if (to > from) {
2724 _out->print_cr("Objects in ["PTR_FORMAT", "PTR_FORMAT"]", from, to);
2725 _out->cr();
2726 PrintReachableObjectClosure ocl(_out, _vo, _all, hr);
2727 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl);
2728 _out->cr();
2729 }
2731 return false;
2732 }
2734 PrintReachableRegionClosure(outputStream* out,
2735 VerifyOption vo,
2736 bool all) :
2737 _g1h(G1CollectedHeap::heap()), _out(out), _vo(vo), _all(all) { }
2738 };
2740 void ConcurrentMark::print_reachable(const char* str,
2741 VerifyOption vo,
2742 bool all) {
2743 gclog_or_tty->cr();
2744 gclog_or_tty->print_cr("== Doing heap dump... ");
2746 if (G1PrintReachableBaseFile == NULL) {
2747 gclog_or_tty->print_cr(" #### error: no base file defined");
2748 return;
2749 }
2751 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) >
2752 (JVM_MAXPATHLEN - 1)) {
2753 gclog_or_tty->print_cr(" #### error: file name too long");
2754 return;
2755 }
2757 char file_name[JVM_MAXPATHLEN];
2758 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str);
2759 gclog_or_tty->print_cr(" dumping to file %s", file_name);
2761 fileStream fout(file_name);
2762 if (!fout.is_open()) {
2763 gclog_or_tty->print_cr(" #### error: could not open file");
2764 return;
2765 }
2767 outputStream* out = &fout;
2768 out->print_cr("-- USING %s", _g1h->top_at_mark_start_str(vo));
2769 out->cr();
2771 out->print_cr("--- ITERATING OVER REGIONS");
2772 out->cr();
2773 PrintReachableRegionClosure rcl(out, vo, all);
2774 _g1h->heap_region_iterate(&rcl);
2775 out->cr();
2777 gclog_or_tty->print_cr(" done");
2778 gclog_or_tty->flush();
2779 }
2781 #endif // PRODUCT
2783 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2784 // Note we are overriding the read-only view of the prev map here, via
2785 // the cast.
2786 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2787 }
2789 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2790 _nextMarkBitMap->clearRange(mr);
2791 }
2793 void ConcurrentMark::clearRangeBothBitmaps(MemRegion mr) {
2794 clearRangePrevBitmap(mr);
2795 clearRangeNextBitmap(mr);
2796 }
2798 HeapRegion*
2799 ConcurrentMark::claim_region(uint worker_id) {
2800 // "checkpoint" the finger
2801 HeapWord* finger = _finger;
2803 // _heap_end will not change underneath our feet; it only changes at
2804 // yield points.
2805 while (finger < _heap_end) {
2806 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2808 // Note on how this code handles humongous regions. In the
2809 // normal case the finger will reach the start of a "starts
2810 // humongous" (SH) region. Its end will either be the end of the
2811 // last "continues humongous" (CH) region in the sequence, or the
2812 // standard end of the SH region (if the SH is the only region in
2813 // the sequence). That way claim_region() will skip over the CH
2814 // regions. However, there is a subtle race between a CM thread
2815 // executing this method and a mutator thread doing a humongous
2816 // object allocation. The two are not mutually exclusive as the CM
2817 // thread does not need to hold the Heap_lock when it gets
2818 // here. So there is a chance that claim_region() will come across
2819 // a free region that's in the progress of becoming a SH or a CH
2820 // region. In the former case, it will either
2821 // a) Miss the update to the region's end, in which case it will
2822 // visit every subsequent CH region, will find their bitmaps
2823 // empty, and do nothing, or
2824 // b) Will observe the update of the region's end (in which case
2825 // it will skip the subsequent CH regions).
2826 // If it comes across a region that suddenly becomes CH, the
2827 // scenario will be similar to b). So, the race between
2828 // claim_region() and a humongous object allocation might force us
2829 // to do a bit of unnecessary work (due to some unnecessary bitmap
2830 // iterations) but it should not introduce and correctness issues.
2831 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2832 HeapWord* bottom = curr_region->bottom();
2833 HeapWord* end = curr_region->end();
2834 HeapWord* limit = curr_region->next_top_at_mark_start();
2836 if (verbose_low()) {
2837 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" "
2838 "["PTR_FORMAT", "PTR_FORMAT"), "
2839 "limit = "PTR_FORMAT,
2840 worker_id, curr_region, bottom, end, limit);
2841 }
2843 // Is the gap between reading the finger and doing the CAS too long?
2844 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2845 if (res == finger) {
2846 // we succeeded
2848 // notice that _finger == end cannot be guaranteed here since,
2849 // someone else might have moved the finger even further
2850 assert(_finger >= end, "the finger should have moved forward");
2852 if (verbose_low()) {
2853 gclog_or_tty->print_cr("[%u] we were successful with region = "
2854 PTR_FORMAT, worker_id, curr_region);
2855 }
2857 if (limit > bottom) {
2858 if (verbose_low()) {
2859 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, "
2860 "returning it ", worker_id, curr_region);
2861 }
2862 return curr_region;
2863 } else {
2864 assert(limit == bottom,
2865 "the region limit should be at bottom");
2866 if (verbose_low()) {
2867 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, "
2868 "returning NULL", worker_id, curr_region);
2869 }
2870 // we return NULL and the caller should try calling
2871 // claim_region() again.
2872 return NULL;
2873 }
2874 } else {
2875 assert(_finger > finger, "the finger should have moved forward");
2876 if (verbose_low()) {
2877 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2878 "global finger = "PTR_FORMAT", "
2879 "our finger = "PTR_FORMAT,
2880 worker_id, _finger, finger);
2881 }
2883 // read it again
2884 finger = _finger;
2885 }
2886 }
2888 return NULL;
2889 }
2891 #ifndef PRODUCT
2892 enum VerifyNoCSetOopsPhase {
2893 VerifyNoCSetOopsStack,
2894 VerifyNoCSetOopsQueues,
2895 VerifyNoCSetOopsSATBCompleted,
2896 VerifyNoCSetOopsSATBThread
2897 };
2899 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure {
2900 private:
2901 G1CollectedHeap* _g1h;
2902 VerifyNoCSetOopsPhase _phase;
2903 int _info;
2905 const char* phase_str() {
2906 switch (_phase) {
2907 case VerifyNoCSetOopsStack: return "Stack";
2908 case VerifyNoCSetOopsQueues: return "Queue";
2909 case VerifyNoCSetOopsSATBCompleted: return "Completed SATB Buffers";
2910 case VerifyNoCSetOopsSATBThread: return "Thread SATB Buffers";
2911 default: ShouldNotReachHere();
2912 }
2913 return NULL;
2914 }
2916 void do_object_work(oop obj) {
2917 guarantee(!_g1h->obj_in_cs(obj),
2918 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d",
2919 (void*) obj, phase_str(), _info));
2920 }
2922 public:
2923 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { }
2925 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) {
2926 _phase = phase;
2927 _info = info;
2928 }
2930 virtual void do_oop(oop* p) {
2931 oop obj = oopDesc::load_decode_heap_oop(p);
2932 do_object_work(obj);
2933 }
2935 virtual void do_oop(narrowOop* p) {
2936 // We should not come across narrow oops while scanning marking
2937 // stacks and SATB buffers.
2938 ShouldNotReachHere();
2939 }
2941 virtual void do_object(oop obj) {
2942 do_object_work(obj);
2943 }
2944 };
2946 void ConcurrentMark::verify_no_cset_oops(bool verify_stacks,
2947 bool verify_enqueued_buffers,
2948 bool verify_thread_buffers,
2949 bool verify_fingers) {
2950 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2951 if (!G1CollectedHeap::heap()->mark_in_progress()) {
2952 return;
2953 }
2955 VerifyNoCSetOopsClosure cl;
2957 if (verify_stacks) {
2958 // Verify entries on the global mark stack
2959 cl.set_phase(VerifyNoCSetOopsStack);
2960 _markStack.oops_do(&cl);
2962 // Verify entries on the task queues
2963 for (uint i = 0; i < _max_worker_id; i += 1) {
2964 cl.set_phase(VerifyNoCSetOopsQueues, i);
2965 CMTaskQueue* queue = _task_queues->queue(i);
2966 queue->oops_do(&cl);
2967 }
2968 }
2970 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
2972 // Verify entries on the enqueued SATB buffers
2973 if (verify_enqueued_buffers) {
2974 cl.set_phase(VerifyNoCSetOopsSATBCompleted);
2975 satb_qs.iterate_completed_buffers_read_only(&cl);
2976 }
2978 // Verify entries on the per-thread SATB buffers
2979 if (verify_thread_buffers) {
2980 cl.set_phase(VerifyNoCSetOopsSATBThread);
2981 satb_qs.iterate_thread_buffers_read_only(&cl);
2982 }
2984 if (verify_fingers) {
2985 // Verify the global finger
2986 HeapWord* global_finger = finger();
2987 if (global_finger != NULL && global_finger < _heap_end) {
2988 // The global finger always points to a heap region boundary. We
2989 // use heap_region_containing_raw() to get the containing region
2990 // given that the global finger could be pointing to a free region
2991 // which subsequently becomes continues humongous. If that
2992 // happens, heap_region_containing() will return the bottom of the
2993 // corresponding starts humongous region and the check below will
2994 // not hold any more.
2995 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2996 guarantee(global_finger == global_hr->bottom(),
2997 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT,
2998 global_finger, HR_FORMAT_PARAMS(global_hr)));
2999 }
3001 // Verify the task fingers
3002 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
3003 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) {
3004 CMTask* task = _tasks[i];
3005 HeapWord* task_finger = task->finger();
3006 if (task_finger != NULL && task_finger < _heap_end) {
3007 // See above note on the global finger verification.
3008 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
3009 guarantee(task_finger == task_hr->bottom() ||
3010 !task_hr->in_collection_set(),
3011 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT,
3012 task_finger, HR_FORMAT_PARAMS(task_hr)));
3013 }
3014 }
3015 }
3016 }
3017 #endif // PRODUCT
3019 // Aggregate the counting data that was constructed concurrently
3020 // with marking.
3021 class AggregateCountDataHRClosure: public HeapRegionClosure {
3022 G1CollectedHeap* _g1h;
3023 ConcurrentMark* _cm;
3024 CardTableModRefBS* _ct_bs;
3025 BitMap* _cm_card_bm;
3026 uint _max_worker_id;
3028 public:
3029 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
3030 BitMap* cm_card_bm,
3031 uint max_worker_id) :
3032 _g1h(g1h), _cm(g1h->concurrent_mark()),
3033 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
3034 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
3036 bool doHeapRegion(HeapRegion* hr) {
3037 if (hr->continuesHumongous()) {
3038 // We will ignore these here and process them when their
3039 // associated "starts humongous" region is processed.
3040 // Note that we cannot rely on their associated
3041 // "starts humongous" region to have their bit set to 1
3042 // since, due to the region chunking in the parallel region
3043 // iteration, a "continues humongous" region might be visited
3044 // before its associated "starts humongous".
3045 return false;
3046 }
3048 HeapWord* start = hr->bottom();
3049 HeapWord* limit = hr->next_top_at_mark_start();
3050 HeapWord* end = hr->end();
3052 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
3053 err_msg("Preconditions not met - "
3054 "start: "PTR_FORMAT", limit: "PTR_FORMAT", "
3055 "top: "PTR_FORMAT", end: "PTR_FORMAT,
3056 start, limit, hr->top(), hr->end()));
3058 assert(hr->next_marked_bytes() == 0, "Precondition");
3060 if (start == limit) {
3061 // NTAMS of this region has not been set so nothing to do.
3062 return false;
3063 }
3065 // 'start' should be in the heap.
3066 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
3067 // 'end' *may* be just beyone the end of the heap (if hr is the last region)
3068 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
3070 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
3071 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
3072 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
3074 // If ntams is not card aligned then we bump card bitmap index
3075 // for limit so that we get the all the cards spanned by
3076 // the object ending at ntams.
3077 // Note: if this is the last region in the heap then ntams
3078 // could be actually just beyond the end of the the heap;
3079 // limit_idx will then correspond to a (non-existent) card
3080 // that is also outside the heap.
3081 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
3082 limit_idx += 1;
3083 }
3085 assert(limit_idx <= end_idx, "or else use atomics");
3087 // Aggregate the "stripe" in the count data associated with hr.
3088 uint hrs_index = hr->hrs_index();
3089 size_t marked_bytes = 0;
3091 for (uint i = 0; i < _max_worker_id; i += 1) {
3092 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
3093 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
3095 // Fetch the marked_bytes in this region for task i and
3096 // add it to the running total for this region.
3097 marked_bytes += marked_bytes_array[hrs_index];
3099 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
3100 // into the global card bitmap.
3101 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
3103 while (scan_idx < limit_idx) {
3104 assert(task_card_bm->at(scan_idx) == true, "should be");
3105 _cm_card_bm->set_bit(scan_idx);
3106 assert(_cm_card_bm->at(scan_idx) == true, "should be");
3108 // BitMap::get_next_one_offset() can handle the case when
3109 // its left_offset parameter is greater than its right_offset
3110 // parameter. It does, however, have an early exit if
3111 // left_offset == right_offset. So let's limit the value
3112 // passed in for left offset here.
3113 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
3114 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
3115 }
3116 }
3118 // Update the marked bytes for this region.
3119 hr->add_to_marked_bytes(marked_bytes);
3121 // Next heap region
3122 return false;
3123 }
3124 };
3126 class G1AggregateCountDataTask: public AbstractGangTask {
3127 protected:
3128 G1CollectedHeap* _g1h;
3129 ConcurrentMark* _cm;
3130 BitMap* _cm_card_bm;
3131 uint _max_worker_id;
3132 int _active_workers;
3134 public:
3135 G1AggregateCountDataTask(G1CollectedHeap* g1h,
3136 ConcurrentMark* cm,
3137 BitMap* cm_card_bm,
3138 uint max_worker_id,
3139 int n_workers) :
3140 AbstractGangTask("Count Aggregation"),
3141 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
3142 _max_worker_id(max_worker_id),
3143 _active_workers(n_workers) { }
3145 void work(uint worker_id) {
3146 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
3148 if (G1CollectedHeap::use_parallel_gc_threads()) {
3149 _g1h->heap_region_par_iterate_chunked(&cl, worker_id,
3150 _active_workers,
3151 HeapRegion::AggregateCountClaimValue);
3152 } else {
3153 _g1h->heap_region_iterate(&cl);
3154 }
3155 }
3156 };
3159 void ConcurrentMark::aggregate_count_data() {
3160 int n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3161 _g1h->workers()->active_workers() :
3162 1);
3164 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
3165 _max_worker_id, n_workers);
3167 if (G1CollectedHeap::use_parallel_gc_threads()) {
3168 assert(_g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3169 "sanity check");
3170 _g1h->set_par_threads(n_workers);
3171 _g1h->workers()->run_task(&g1_par_agg_task);
3172 _g1h->set_par_threads(0);
3174 assert(_g1h->check_heap_region_claim_values(HeapRegion::AggregateCountClaimValue),
3175 "sanity check");
3176 _g1h->reset_heap_region_claim_values();
3177 } else {
3178 g1_par_agg_task.work(0);
3179 }
3180 }
3182 // Clear the per-worker arrays used to store the per-region counting data
3183 void ConcurrentMark::clear_all_count_data() {
3184 // Clear the global card bitmap - it will be filled during
3185 // liveness count aggregation (during remark) and the
3186 // final counting task.
3187 _card_bm.clear();
3189 // Clear the global region bitmap - it will be filled as part
3190 // of the final counting task.
3191 _region_bm.clear();
3193 uint max_regions = _g1h->max_regions();
3194 assert(_max_worker_id > 0, "uninitialized");
3196 for (uint i = 0; i < _max_worker_id; i += 1) {
3197 BitMap* task_card_bm = count_card_bitmap_for(i);
3198 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
3200 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
3201 assert(marked_bytes_array != NULL, "uninitialized");
3203 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
3204 task_card_bm->clear();
3205 }
3206 }
3208 void ConcurrentMark::print_stats() {
3209 if (verbose_stats()) {
3210 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3211 for (size_t i = 0; i < _active_tasks; ++i) {
3212 _tasks[i]->print_stats();
3213 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3214 }
3215 }
3216 }
3218 // abandon current marking iteration due to a Full GC
3219 void ConcurrentMark::abort() {
3220 // Clear all marks to force marking thread to do nothing
3221 _nextMarkBitMap->clearAll();
3222 // Clear the liveness counting data
3223 clear_all_count_data();
3224 // Empty mark stack
3225 reset_marking_state();
3226 for (uint i = 0; i < _max_worker_id; ++i) {
3227 _tasks[i]->clear_region_fields();
3228 }
3229 _has_aborted = true;
3231 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3232 satb_mq_set.abandon_partial_marking();
3233 // This can be called either during or outside marking, we'll read
3234 // the expected_active value from the SATB queue set.
3235 satb_mq_set.set_active_all_threads(
3236 false, /* new active value */
3237 satb_mq_set.is_active() /* expected_active */);
3239 _g1h->trace_heap_after_concurrent_cycle();
3240 _g1h->register_concurrent_cycle_end();
3241 }
3243 static void print_ms_time_info(const char* prefix, const char* name,
3244 NumberSeq& ns) {
3245 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3246 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3247 if (ns.num() > 0) {
3248 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3249 prefix, ns.sd(), ns.maximum());
3250 }
3251 }
3253 void ConcurrentMark::print_summary_info() {
3254 gclog_or_tty->print_cr(" Concurrent marking:");
3255 print_ms_time_info(" ", "init marks", _init_times);
3256 print_ms_time_info(" ", "remarks", _remark_times);
3257 {
3258 print_ms_time_info(" ", "final marks", _remark_mark_times);
3259 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3261 }
3262 print_ms_time_info(" ", "cleanups", _cleanup_times);
3263 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3264 _total_counting_time,
3265 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3266 (double)_cleanup_times.num()
3267 : 0.0));
3268 if (G1ScrubRemSets) {
3269 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3270 _total_rs_scrub_time,
3271 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3272 (double)_cleanup_times.num()
3273 : 0.0));
3274 }
3275 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3276 (_init_times.sum() + _remark_times.sum() +
3277 _cleanup_times.sum())/1000.0);
3278 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3279 "(%8.2f s marking).",
3280 cmThread()->vtime_accum(),
3281 cmThread()->vtime_mark_accum());
3282 }
3284 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3285 if (use_parallel_marking_threads()) {
3286 _parallel_workers->print_worker_threads_on(st);
3287 }
3288 }
3290 void ConcurrentMark::print_on_error(outputStream* st) const {
3291 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
3292 _prevMarkBitMap, _nextMarkBitMap);
3293 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
3294 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
3295 }
3297 // We take a break if someone is trying to stop the world.
3298 bool ConcurrentMark::do_yield_check(uint worker_id) {
3299 if (should_yield()) {
3300 if (worker_id == 0) {
3301 _g1h->g1_policy()->record_concurrent_pause();
3302 }
3303 cmThread()->yield();
3304 return true;
3305 } else {
3306 return false;
3307 }
3308 }
3310 bool ConcurrentMark::should_yield() {
3311 return cmThread()->should_yield();
3312 }
3314 bool ConcurrentMark::containing_card_is_marked(void* p) {
3315 size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1);
3316 return _card_bm.at(offset >> CardTableModRefBS::card_shift);
3317 }
3319 bool ConcurrentMark::containing_cards_are_marked(void* start,
3320 void* last) {
3321 return containing_card_is_marked(start) &&
3322 containing_card_is_marked(last);
3323 }
3325 #ifndef PRODUCT
3326 // for debugging purposes
3327 void ConcurrentMark::print_finger() {
3328 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3329 _heap_start, _heap_end, _finger);
3330 for (uint i = 0; i < _max_worker_id; ++i) {
3331 gclog_or_tty->print(" %u: "PTR_FORMAT, i, _tasks[i]->finger());
3332 }
3333 gclog_or_tty->print_cr("");
3334 }
3335 #endif
3337 void CMTask::scan_object(oop obj) {
3338 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3340 if (_cm->verbose_high()) {
3341 gclog_or_tty->print_cr("[%u] we're scanning object "PTR_FORMAT,
3342 _worker_id, (void*) obj);
3343 }
3345 size_t obj_size = obj->size();
3346 _words_scanned += obj_size;
3348 obj->oop_iterate(_cm_oop_closure);
3349 statsOnly( ++_objs_scanned );
3350 check_limits();
3351 }
3353 // Closure for iteration over bitmaps
3354 class CMBitMapClosure : public BitMapClosure {
3355 private:
3356 // the bitmap that is being iterated over
3357 CMBitMap* _nextMarkBitMap;
3358 ConcurrentMark* _cm;
3359 CMTask* _task;
3361 public:
3362 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3363 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3365 bool do_bit(size_t offset) {
3366 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3367 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3368 assert( addr < _cm->finger(), "invariant");
3370 statsOnly( _task->increase_objs_found_on_bitmap() );
3371 assert(addr >= _task->finger(), "invariant");
3373 // We move that task's local finger along.
3374 _task->move_finger_to(addr);
3376 _task->scan_object(oop(addr));
3377 // we only partially drain the local queue and global stack
3378 _task->drain_local_queue(true);
3379 _task->drain_global_stack(true);
3381 // if the has_aborted flag has been raised, we need to bail out of
3382 // the iteration
3383 return !_task->has_aborted();
3384 }
3385 };
3387 // Closure for iterating over objects, currently only used for
3388 // processing SATB buffers.
3389 class CMObjectClosure : public ObjectClosure {
3390 private:
3391 CMTask* _task;
3393 public:
3394 void do_object(oop obj) {
3395 _task->deal_with_reference(obj);
3396 }
3398 CMObjectClosure(CMTask* task) : _task(task) { }
3399 };
3401 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3402 ConcurrentMark* cm,
3403 CMTask* task)
3404 : _g1h(g1h), _cm(cm), _task(task) {
3405 assert(_ref_processor == NULL, "should be initialized to NULL");
3407 if (G1UseConcMarkReferenceProcessing) {
3408 _ref_processor = g1h->ref_processor_cm();
3409 assert(_ref_processor != NULL, "should not be NULL");
3410 }
3411 }
3413 void CMTask::setup_for_region(HeapRegion* hr) {
3414 // Separated the asserts so that we know which one fires.
3415 assert(hr != NULL,
3416 "claim_region() should have filtered out continues humongous regions");
3417 assert(!hr->continuesHumongous(),
3418 "claim_region() should have filtered out continues humongous regions");
3420 if (_cm->verbose_low()) {
3421 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT,
3422 _worker_id, hr);
3423 }
3425 _curr_region = hr;
3426 _finger = hr->bottom();
3427 update_region_limit();
3428 }
3430 void CMTask::update_region_limit() {
3431 HeapRegion* hr = _curr_region;
3432 HeapWord* bottom = hr->bottom();
3433 HeapWord* limit = hr->next_top_at_mark_start();
3435 if (limit == bottom) {
3436 if (_cm->verbose_low()) {
3437 gclog_or_tty->print_cr("[%u] found an empty region "
3438 "["PTR_FORMAT", "PTR_FORMAT")",
3439 _worker_id, bottom, limit);
3440 }
3441 // The region was collected underneath our feet.
3442 // We set the finger to bottom to ensure that the bitmap
3443 // iteration that will follow this will not do anything.
3444 // (this is not a condition that holds when we set the region up,
3445 // as the region is not supposed to be empty in the first place)
3446 _finger = bottom;
3447 } else if (limit >= _region_limit) {
3448 assert(limit >= _finger, "peace of mind");
3449 } else {
3450 assert(limit < _region_limit, "only way to get here");
3451 // This can happen under some pretty unusual circumstances. An
3452 // evacuation pause empties the region underneath our feet (NTAMS
3453 // at bottom). We then do some allocation in the region (NTAMS
3454 // stays at bottom), followed by the region being used as a GC
3455 // alloc region (NTAMS will move to top() and the objects
3456 // originally below it will be grayed). All objects now marked in
3457 // the region are explicitly grayed, if below the global finger,
3458 // and we do not need in fact to scan anything else. So, we simply
3459 // set _finger to be limit to ensure that the bitmap iteration
3460 // doesn't do anything.
3461 _finger = limit;
3462 }
3464 _region_limit = limit;
3465 }
3467 void CMTask::giveup_current_region() {
3468 assert(_curr_region != NULL, "invariant");
3469 if (_cm->verbose_low()) {
3470 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT,
3471 _worker_id, _curr_region);
3472 }
3473 clear_region_fields();
3474 }
3476 void CMTask::clear_region_fields() {
3477 // Values for these three fields that indicate that we're not
3478 // holding on to a region.
3479 _curr_region = NULL;
3480 _finger = NULL;
3481 _region_limit = NULL;
3482 }
3484 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3485 if (cm_oop_closure == NULL) {
3486 assert(_cm_oop_closure != NULL, "invariant");
3487 } else {
3488 assert(_cm_oop_closure == NULL, "invariant");
3489 }
3490 _cm_oop_closure = cm_oop_closure;
3491 }
3493 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3494 guarantee(nextMarkBitMap != NULL, "invariant");
3496 if (_cm->verbose_low()) {
3497 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3498 }
3500 _nextMarkBitMap = nextMarkBitMap;
3501 clear_region_fields();
3503 _calls = 0;
3504 _elapsed_time_ms = 0.0;
3505 _termination_time_ms = 0.0;
3506 _termination_start_time_ms = 0.0;
3508 #if _MARKING_STATS_
3509 _local_pushes = 0;
3510 _local_pops = 0;
3511 _local_max_size = 0;
3512 _objs_scanned = 0;
3513 _global_pushes = 0;
3514 _global_pops = 0;
3515 _global_max_size = 0;
3516 _global_transfers_to = 0;
3517 _global_transfers_from = 0;
3518 _regions_claimed = 0;
3519 _objs_found_on_bitmap = 0;
3520 _satb_buffers_processed = 0;
3521 _steal_attempts = 0;
3522 _steals = 0;
3523 _aborted = 0;
3524 _aborted_overflow = 0;
3525 _aborted_cm_aborted = 0;
3526 _aborted_yield = 0;
3527 _aborted_timed_out = 0;
3528 _aborted_satb = 0;
3529 _aborted_termination = 0;
3530 #endif // _MARKING_STATS_
3531 }
3533 bool CMTask::should_exit_termination() {
3534 regular_clock_call();
3535 // This is called when we are in the termination protocol. We should
3536 // quit if, for some reason, this task wants to abort or the global
3537 // stack is not empty (this means that we can get work from it).
3538 return !_cm->mark_stack_empty() || has_aborted();
3539 }
3541 void CMTask::reached_limit() {
3542 assert(_words_scanned >= _words_scanned_limit ||
3543 _refs_reached >= _refs_reached_limit ,
3544 "shouldn't have been called otherwise");
3545 regular_clock_call();
3546 }
3548 void CMTask::regular_clock_call() {
3549 if (has_aborted()) return;
3551 // First, we need to recalculate the words scanned and refs reached
3552 // limits for the next clock call.
3553 recalculate_limits();
3555 // During the regular clock call we do the following
3557 // (1) If an overflow has been flagged, then we abort.
3558 if (_cm->has_overflown()) {
3559 set_has_aborted();
3560 return;
3561 }
3563 // If we are not concurrent (i.e. we're doing remark) we don't need
3564 // to check anything else. The other steps are only needed during
3565 // the concurrent marking phase.
3566 if (!concurrent()) return;
3568 // (2) If marking has been aborted for Full GC, then we also abort.
3569 if (_cm->has_aborted()) {
3570 set_has_aborted();
3571 statsOnly( ++_aborted_cm_aborted );
3572 return;
3573 }
3575 double curr_time_ms = os::elapsedVTime() * 1000.0;
3577 // (3) If marking stats are enabled, then we update the step history.
3578 #if _MARKING_STATS_
3579 if (_words_scanned >= _words_scanned_limit) {
3580 ++_clock_due_to_scanning;
3581 }
3582 if (_refs_reached >= _refs_reached_limit) {
3583 ++_clock_due_to_marking;
3584 }
3586 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3587 _interval_start_time_ms = curr_time_ms;
3588 _all_clock_intervals_ms.add(last_interval_ms);
3590 if (_cm->verbose_medium()) {
3591 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3592 "scanned = %d%s, refs reached = %d%s",
3593 _worker_id, last_interval_ms,
3594 _words_scanned,
3595 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3596 _refs_reached,
3597 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3598 }
3599 #endif // _MARKING_STATS_
3601 // (4) We check whether we should yield. If we have to, then we abort.
3602 if (_cm->should_yield()) {
3603 // We should yield. To do this we abort the task. The caller is
3604 // responsible for yielding.
3605 set_has_aborted();
3606 statsOnly( ++_aborted_yield );
3607 return;
3608 }
3610 // (5) We check whether we've reached our time quota. If we have,
3611 // then we abort.
3612 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3613 if (elapsed_time_ms > _time_target_ms) {
3614 set_has_aborted();
3615 _has_timed_out = true;
3616 statsOnly( ++_aborted_timed_out );
3617 return;
3618 }
3620 // (6) Finally, we check whether there are enough completed STAB
3621 // buffers available for processing. If there are, we abort.
3622 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3623 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3624 if (_cm->verbose_low()) {
3625 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3626 _worker_id);
3627 }
3628 // we do need to process SATB buffers, we'll abort and restart
3629 // the marking task to do so
3630 set_has_aborted();
3631 statsOnly( ++_aborted_satb );
3632 return;
3633 }
3634 }
3636 void CMTask::recalculate_limits() {
3637 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3638 _words_scanned_limit = _real_words_scanned_limit;
3640 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3641 _refs_reached_limit = _real_refs_reached_limit;
3642 }
3644 void CMTask::decrease_limits() {
3645 // This is called when we believe that we're going to do an infrequent
3646 // operation which will increase the per byte scanned cost (i.e. move
3647 // entries to/from the global stack). It basically tries to decrease the
3648 // scanning limit so that the clock is called earlier.
3650 if (_cm->verbose_medium()) {
3651 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3652 }
3654 _words_scanned_limit = _real_words_scanned_limit -
3655 3 * words_scanned_period / 4;
3656 _refs_reached_limit = _real_refs_reached_limit -
3657 3 * refs_reached_period / 4;
3658 }
3660 void CMTask::move_entries_to_global_stack() {
3661 // local array where we'll store the entries that will be popped
3662 // from the local queue
3663 oop buffer[global_stack_transfer_size];
3665 int n = 0;
3666 oop obj;
3667 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3668 buffer[n] = obj;
3669 ++n;
3670 }
3672 if (n > 0) {
3673 // we popped at least one entry from the local queue
3675 statsOnly( ++_global_transfers_to; _local_pops += n );
3677 if (!_cm->mark_stack_push(buffer, n)) {
3678 if (_cm->verbose_low()) {
3679 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3680 _worker_id);
3681 }
3682 set_has_aborted();
3683 } else {
3684 // the transfer was successful
3686 if (_cm->verbose_medium()) {
3687 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3688 _worker_id, n);
3689 }
3690 statsOnly( int tmp_size = _cm->mark_stack_size();
3691 if (tmp_size > _global_max_size) {
3692 _global_max_size = tmp_size;
3693 }
3694 _global_pushes += n );
3695 }
3696 }
3698 // this operation was quite expensive, so decrease the limits
3699 decrease_limits();
3700 }
3702 void CMTask::get_entries_from_global_stack() {
3703 // local array where we'll store the entries that will be popped
3704 // from the global stack.
3705 oop buffer[global_stack_transfer_size];
3706 int n;
3707 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3708 assert(n <= global_stack_transfer_size,
3709 "we should not pop more than the given limit");
3710 if (n > 0) {
3711 // yes, we did actually pop at least one entry
3713 statsOnly( ++_global_transfers_from; _global_pops += n );
3714 if (_cm->verbose_medium()) {
3715 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3716 _worker_id, n);
3717 }
3718 for (int i = 0; i < n; ++i) {
3719 bool success = _task_queue->push(buffer[i]);
3720 // We only call this when the local queue is empty or under a
3721 // given target limit. So, we do not expect this push to fail.
3722 assert(success, "invariant");
3723 }
3725 statsOnly( int tmp_size = _task_queue->size();
3726 if (tmp_size > _local_max_size) {
3727 _local_max_size = tmp_size;
3728 }
3729 _local_pushes += n );
3730 }
3732 // this operation was quite expensive, so decrease the limits
3733 decrease_limits();
3734 }
3736 void CMTask::drain_local_queue(bool partially) {
3737 if (has_aborted()) return;
3739 // Decide what the target size is, depending whether we're going to
3740 // drain it partially (so that other tasks can steal if they run out
3741 // of things to do) or totally (at the very end).
3742 size_t target_size;
3743 if (partially) {
3744 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3745 } else {
3746 target_size = 0;
3747 }
3749 if (_task_queue->size() > target_size) {
3750 if (_cm->verbose_high()) {
3751 gclog_or_tty->print_cr("[%u] draining local queue, target size = %d",
3752 _worker_id, target_size);
3753 }
3755 oop obj;
3756 bool ret = _task_queue->pop_local(obj);
3757 while (ret) {
3758 statsOnly( ++_local_pops );
3760 if (_cm->verbose_high()) {
3761 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id,
3762 (void*) obj);
3763 }
3765 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3766 assert(!_g1h->is_on_master_free_list(
3767 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3769 scan_object(obj);
3771 if (_task_queue->size() <= target_size || has_aborted()) {
3772 ret = false;
3773 } else {
3774 ret = _task_queue->pop_local(obj);
3775 }
3776 }
3778 if (_cm->verbose_high()) {
3779 gclog_or_tty->print_cr("[%u] drained local queue, size = %d",
3780 _worker_id, _task_queue->size());
3781 }
3782 }
3783 }
3785 void CMTask::drain_global_stack(bool partially) {
3786 if (has_aborted()) return;
3788 // We have a policy to drain the local queue before we attempt to
3789 // drain the global stack.
3790 assert(partially || _task_queue->size() == 0, "invariant");
3792 // Decide what the target size is, depending whether we're going to
3793 // drain it partially (so that other tasks can steal if they run out
3794 // of things to do) or totally (at the very end). Notice that,
3795 // because we move entries from the global stack in chunks or
3796 // because another task might be doing the same, we might in fact
3797 // drop below the target. But, this is not a problem.
3798 size_t target_size;
3799 if (partially) {
3800 target_size = _cm->partial_mark_stack_size_target();
3801 } else {
3802 target_size = 0;
3803 }
3805 if (_cm->mark_stack_size() > target_size) {
3806 if (_cm->verbose_low()) {
3807 gclog_or_tty->print_cr("[%u] draining global_stack, target size %d",
3808 _worker_id, target_size);
3809 }
3811 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3812 get_entries_from_global_stack();
3813 drain_local_queue(partially);
3814 }
3816 if (_cm->verbose_low()) {
3817 gclog_or_tty->print_cr("[%u] drained global stack, size = %d",
3818 _worker_id, _cm->mark_stack_size());
3819 }
3820 }
3821 }
3823 // SATB Queue has several assumptions on whether to call the par or
3824 // non-par versions of the methods. this is why some of the code is
3825 // replicated. We should really get rid of the single-threaded version
3826 // of the code to simplify things.
3827 void CMTask::drain_satb_buffers() {
3828 if (has_aborted()) return;
3830 // We set this so that the regular clock knows that we're in the
3831 // middle of draining buffers and doesn't set the abort flag when it
3832 // notices that SATB buffers are available for draining. It'd be
3833 // very counter productive if it did that. :-)
3834 _draining_satb_buffers = true;
3836 CMObjectClosure oc(this);
3837 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3838 if (G1CollectedHeap::use_parallel_gc_threads()) {
3839 satb_mq_set.set_par_closure(_worker_id, &oc);
3840 } else {
3841 satb_mq_set.set_closure(&oc);
3842 }
3844 // This keeps claiming and applying the closure to completed buffers
3845 // until we run out of buffers or we need to abort.
3846 if (G1CollectedHeap::use_parallel_gc_threads()) {
3847 while (!has_aborted() &&
3848 satb_mq_set.par_apply_closure_to_completed_buffer(_worker_id)) {
3849 if (_cm->verbose_medium()) {
3850 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3851 }
3852 statsOnly( ++_satb_buffers_processed );
3853 regular_clock_call();
3854 }
3855 } else {
3856 while (!has_aborted() &&
3857 satb_mq_set.apply_closure_to_completed_buffer()) {
3858 if (_cm->verbose_medium()) {
3859 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3860 }
3861 statsOnly( ++_satb_buffers_processed );
3862 regular_clock_call();
3863 }
3864 }
3866 if (!concurrent() && !has_aborted()) {
3867 // We should only do this during remark.
3868 if (G1CollectedHeap::use_parallel_gc_threads()) {
3869 satb_mq_set.par_iterate_closure_all_threads(_worker_id);
3870 } else {
3871 satb_mq_set.iterate_closure_all_threads();
3872 }
3873 }
3875 _draining_satb_buffers = false;
3877 assert(has_aborted() ||
3878 concurrent() ||
3879 satb_mq_set.completed_buffers_num() == 0, "invariant");
3881 if (G1CollectedHeap::use_parallel_gc_threads()) {
3882 satb_mq_set.set_par_closure(_worker_id, NULL);
3883 } else {
3884 satb_mq_set.set_closure(NULL);
3885 }
3887 // again, this was a potentially expensive operation, decrease the
3888 // limits to get the regular clock call early
3889 decrease_limits();
3890 }
3892 void CMTask::print_stats() {
3893 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3894 _worker_id, _calls);
3895 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3896 _elapsed_time_ms, _termination_time_ms);
3897 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3898 _step_times_ms.num(), _step_times_ms.avg(),
3899 _step_times_ms.sd());
3900 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3901 _step_times_ms.maximum(), _step_times_ms.sum());
3903 #if _MARKING_STATS_
3904 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3905 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3906 _all_clock_intervals_ms.sd());
3907 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3908 _all_clock_intervals_ms.maximum(),
3909 _all_clock_intervals_ms.sum());
3910 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d",
3911 _clock_due_to_scanning, _clock_due_to_marking);
3912 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d",
3913 _objs_scanned, _objs_found_on_bitmap);
3914 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d",
3915 _local_pushes, _local_pops, _local_max_size);
3916 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d",
3917 _global_pushes, _global_pops, _global_max_size);
3918 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d",
3919 _global_transfers_to,_global_transfers_from);
3920 gclog_or_tty->print_cr(" Regions: claimed = %d", _regions_claimed);
3921 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed);
3922 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d",
3923 _steal_attempts, _steals);
3924 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted);
3925 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d",
3926 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3927 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d",
3928 _aborted_timed_out, _aborted_satb, _aborted_termination);
3929 #endif // _MARKING_STATS_
3930 }
3932 /*****************************************************************************
3934 The do_marking_step(time_target_ms, ...) method is the building
3935 block of the parallel marking framework. It can be called in parallel
3936 with other invocations of do_marking_step() on different tasks
3937 (but only one per task, obviously) and concurrently with the
3938 mutator threads, or during remark, hence it eliminates the need
3939 for two versions of the code. When called during remark, it will
3940 pick up from where the task left off during the concurrent marking
3941 phase. Interestingly, tasks are also claimable during evacuation
3942 pauses too, since do_marking_step() ensures that it aborts before
3943 it needs to yield.
3945 The data structures that it uses to do marking work are the
3946 following:
3948 (1) Marking Bitmap. If there are gray objects that appear only
3949 on the bitmap (this happens either when dealing with an overflow
3950 or when the initial marking phase has simply marked the roots
3951 and didn't push them on the stack), then tasks claim heap
3952 regions whose bitmap they then scan to find gray objects. A
3953 global finger indicates where the end of the last claimed region
3954 is. A local finger indicates how far into the region a task has
3955 scanned. The two fingers are used to determine how to gray an
3956 object (i.e. whether simply marking it is OK, as it will be
3957 visited by a task in the future, or whether it needs to be also
3958 pushed on a stack).
3960 (2) Local Queue. The local queue of the task which is accessed
3961 reasonably efficiently by the task. Other tasks can steal from
3962 it when they run out of work. Throughout the marking phase, a
3963 task attempts to keep its local queue short but not totally
3964 empty, so that entries are available for stealing by other
3965 tasks. Only when there is no more work, a task will totally
3966 drain its local queue.
3968 (3) Global Mark Stack. This handles local queue overflow. During
3969 marking only sets of entries are moved between it and the local
3970 queues, as access to it requires a mutex and more fine-grain
3971 interaction with it which might cause contention. If it
3972 overflows, then the marking phase should restart and iterate
3973 over the bitmap to identify gray objects. Throughout the marking
3974 phase, tasks attempt to keep the global mark stack at a small
3975 length but not totally empty, so that entries are available for
3976 popping by other tasks. Only when there is no more work, tasks
3977 will totally drain the global mark stack.
3979 (4) SATB Buffer Queue. This is where completed SATB buffers are
3980 made available. Buffers are regularly removed from this queue
3981 and scanned for roots, so that the queue doesn't get too
3982 long. During remark, all completed buffers are processed, as
3983 well as the filled in parts of any uncompleted buffers.
3985 The do_marking_step() method tries to abort when the time target
3986 has been reached. There are a few other cases when the
3987 do_marking_step() method also aborts:
3989 (1) When the marking phase has been aborted (after a Full GC).
3991 (2) When a global overflow (on the global stack) has been
3992 triggered. Before the task aborts, it will actually sync up with
3993 the other tasks to ensure that all the marking data structures
3994 (local queues, stacks, fingers etc.) are re-initialized so that
3995 when do_marking_step() completes, the marking phase can
3996 immediately restart.
3998 (3) When enough completed SATB buffers are available. The
3999 do_marking_step() method only tries to drain SATB buffers right
4000 at the beginning. So, if enough buffers are available, the
4001 marking step aborts and the SATB buffers are processed at
4002 the beginning of the next invocation.
4004 (4) To yield. when we have to yield then we abort and yield
4005 right at the end of do_marking_step(). This saves us from a lot
4006 of hassle as, by yielding we might allow a Full GC. If this
4007 happens then objects will be compacted underneath our feet, the
4008 heap might shrink, etc. We save checking for this by just
4009 aborting and doing the yield right at the end.
4011 From the above it follows that the do_marking_step() method should
4012 be called in a loop (or, otherwise, regularly) until it completes.
4014 If a marking step completes without its has_aborted() flag being
4015 true, it means it has completed the current marking phase (and
4016 also all other marking tasks have done so and have all synced up).
4018 A method called regular_clock_call() is invoked "regularly" (in
4019 sub ms intervals) throughout marking. It is this clock method that
4020 checks all the abort conditions which were mentioned above and
4021 decides when the task should abort. A work-based scheme is used to
4022 trigger this clock method: when the number of object words the
4023 marking phase has scanned or the number of references the marking
4024 phase has visited reach a given limit. Additional invocations to
4025 the method clock have been planted in a few other strategic places
4026 too. The initial reason for the clock method was to avoid calling
4027 vtime too regularly, as it is quite expensive. So, once it was in
4028 place, it was natural to piggy-back all the other conditions on it
4029 too and not constantly check them throughout the code.
4031 If do_termination is true then do_marking_step will enter its
4032 termination protocol.
4034 The value of is_serial must be true when do_marking_step is being
4035 called serially (i.e. by the VMThread) and do_marking_step should
4036 skip any synchronization in the termination and overflow code.
4037 Examples include the serial remark code and the serial reference
4038 processing closures.
4040 The value of is_serial must be false when do_marking_step is
4041 being called by any of the worker threads in a work gang.
4042 Examples include the concurrent marking code (CMMarkingTask),
4043 the MT remark code, and the MT reference processing closures.
4045 *****************************************************************************/
4047 void CMTask::do_marking_step(double time_target_ms,
4048 bool do_termination,
4049 bool is_serial) {
4050 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
4051 assert(concurrent() == _cm->concurrent(), "they should be the same");
4053 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
4054 assert(_task_queues != NULL, "invariant");
4055 assert(_task_queue != NULL, "invariant");
4056 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
4058 assert(!_claimed,
4059 "only one thread should claim this task at any one time");
4061 // OK, this doesn't safeguard again all possible scenarios, as it is
4062 // possible for two threads to set the _claimed flag at the same
4063 // time. But it is only for debugging purposes anyway and it will
4064 // catch most problems.
4065 _claimed = true;
4067 _start_time_ms = os::elapsedVTime() * 1000.0;
4068 statsOnly( _interval_start_time_ms = _start_time_ms );
4070 // If do_stealing is true then do_marking_step will attempt to
4071 // steal work from the other CMTasks. It only makes sense to
4072 // enable stealing when the termination protocol is enabled
4073 // and do_marking_step() is not being called serially.
4074 bool do_stealing = do_termination && !is_serial;
4076 double diff_prediction_ms =
4077 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
4078 _time_target_ms = time_target_ms - diff_prediction_ms;
4080 // set up the variables that are used in the work-based scheme to
4081 // call the regular clock method
4082 _words_scanned = 0;
4083 _refs_reached = 0;
4084 recalculate_limits();
4086 // clear all flags
4087 clear_has_aborted();
4088 _has_timed_out = false;
4089 _draining_satb_buffers = false;
4091 ++_calls;
4093 if (_cm->verbose_low()) {
4094 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
4095 "target = %1.2lfms >>>>>>>>>>",
4096 _worker_id, _calls, _time_target_ms);
4097 }
4099 // Set up the bitmap and oop closures. Anything that uses them is
4100 // eventually called from this method, so it is OK to allocate these
4101 // statically.
4102 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
4103 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
4104 set_cm_oop_closure(&cm_oop_closure);
4106 if (_cm->has_overflown()) {
4107 // This can happen if the mark stack overflows during a GC pause
4108 // and this task, after a yield point, restarts. We have to abort
4109 // as we need to get into the overflow protocol which happens
4110 // right at the end of this task.
4111 set_has_aborted();
4112 }
4114 // First drain any available SATB buffers. After this, we will not
4115 // look at SATB buffers before the next invocation of this method.
4116 // If enough completed SATB buffers are queued up, the regular clock
4117 // will abort this task so that it restarts.
4118 drain_satb_buffers();
4119 // ...then partially drain the local queue and the global stack
4120 drain_local_queue(true);
4121 drain_global_stack(true);
4123 do {
4124 if (!has_aborted() && _curr_region != NULL) {
4125 // This means that we're already holding on to a region.
4126 assert(_finger != NULL, "if region is not NULL, then the finger "
4127 "should not be NULL either");
4129 // We might have restarted this task after an evacuation pause
4130 // which might have evacuated the region we're holding on to
4131 // underneath our feet. Let's read its limit again to make sure
4132 // that we do not iterate over a region of the heap that
4133 // contains garbage (update_region_limit() will also move
4134 // _finger to the start of the region if it is found empty).
4135 update_region_limit();
4136 // We will start from _finger not from the start of the region,
4137 // as we might be restarting this task after aborting half-way
4138 // through scanning this region. In this case, _finger points to
4139 // the address where we last found a marked object. If this is a
4140 // fresh region, _finger points to start().
4141 MemRegion mr = MemRegion(_finger, _region_limit);
4143 if (_cm->verbose_low()) {
4144 gclog_or_tty->print_cr("[%u] we're scanning part "
4145 "["PTR_FORMAT", "PTR_FORMAT") "
4146 "of region "HR_FORMAT,
4147 _worker_id, _finger, _region_limit,
4148 HR_FORMAT_PARAMS(_curr_region));
4149 }
4151 assert(!_curr_region->isHumongous() || mr.start() == _curr_region->bottom(),
4152 "humongous regions should go around loop once only");
4154 // Some special cases:
4155 // If the memory region is empty, we can just give up the region.
4156 // If the current region is humongous then we only need to check
4157 // the bitmap for the bit associated with the start of the object,
4158 // scan the object if it's live, and give up the region.
4159 // Otherwise, let's iterate over the bitmap of the part of the region
4160 // that is left.
4161 // If the iteration is successful, give up the region.
4162 if (mr.is_empty()) {
4163 giveup_current_region();
4164 regular_clock_call();
4165 } else if (_curr_region->isHumongous() && mr.start() == _curr_region->bottom()) {
4166 if (_nextMarkBitMap->isMarked(mr.start())) {
4167 // The object is marked - apply the closure
4168 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
4169 bitmap_closure.do_bit(offset);
4170 }
4171 // Even if this task aborted while scanning the humongous object
4172 // we can (and should) give up the current region.
4173 giveup_current_region();
4174 regular_clock_call();
4175 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
4176 giveup_current_region();
4177 regular_clock_call();
4178 } else {
4179 assert(has_aborted(), "currently the only way to do so");
4180 // The only way to abort the bitmap iteration is to return
4181 // false from the do_bit() method. However, inside the
4182 // do_bit() method we move the _finger to point to the
4183 // object currently being looked at. So, if we bail out, we
4184 // have definitely set _finger to something non-null.
4185 assert(_finger != NULL, "invariant");
4187 // Region iteration was actually aborted. So now _finger
4188 // points to the address of the object we last scanned. If we
4189 // leave it there, when we restart this task, we will rescan
4190 // the object. It is easy to avoid this. We move the finger by
4191 // enough to point to the next possible object header (the
4192 // bitmap knows by how much we need to move it as it knows its
4193 // granularity).
4194 assert(_finger < _region_limit, "invariant");
4195 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
4196 // Check if bitmap iteration was aborted while scanning the last object
4197 if (new_finger >= _region_limit) {
4198 giveup_current_region();
4199 } else {
4200 move_finger_to(new_finger);
4201 }
4202 }
4203 }
4204 // At this point we have either completed iterating over the
4205 // region we were holding on to, or we have aborted.
4207 // We then partially drain the local queue and the global stack.
4208 // (Do we really need this?)
4209 drain_local_queue(true);
4210 drain_global_stack(true);
4212 // Read the note on the claim_region() method on why it might
4213 // return NULL with potentially more regions available for
4214 // claiming and why we have to check out_of_regions() to determine
4215 // whether we're done or not.
4216 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
4217 // We are going to try to claim a new region. We should have
4218 // given up on the previous one.
4219 // Separated the asserts so that we know which one fires.
4220 assert(_curr_region == NULL, "invariant");
4221 assert(_finger == NULL, "invariant");
4222 assert(_region_limit == NULL, "invariant");
4223 if (_cm->verbose_low()) {
4224 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
4225 }
4226 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
4227 if (claimed_region != NULL) {
4228 // Yes, we managed to claim one
4229 statsOnly( ++_regions_claimed );
4231 if (_cm->verbose_low()) {
4232 gclog_or_tty->print_cr("[%u] we successfully claimed "
4233 "region "PTR_FORMAT,
4234 _worker_id, claimed_region);
4235 }
4237 setup_for_region(claimed_region);
4238 assert(_curr_region == claimed_region, "invariant");
4239 }
4240 // It is important to call the regular clock here. It might take
4241 // a while to claim a region if, for example, we hit a large
4242 // block of empty regions. So we need to call the regular clock
4243 // method once round the loop to make sure it's called
4244 // frequently enough.
4245 regular_clock_call();
4246 }
4248 if (!has_aborted() && _curr_region == NULL) {
4249 assert(_cm->out_of_regions(),
4250 "at this point we should be out of regions");
4251 }
4252 } while ( _curr_region != NULL && !has_aborted());
4254 if (!has_aborted()) {
4255 // We cannot check whether the global stack is empty, since other
4256 // tasks might be pushing objects to it concurrently.
4257 assert(_cm->out_of_regions(),
4258 "at this point we should be out of regions");
4260 if (_cm->verbose_low()) {
4261 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
4262 }
4264 // Try to reduce the number of available SATB buffers so that
4265 // remark has less work to do.
4266 drain_satb_buffers();
4267 }
4269 // Since we've done everything else, we can now totally drain the
4270 // local queue and global stack.
4271 drain_local_queue(false);
4272 drain_global_stack(false);
4274 // Attempt at work stealing from other task's queues.
4275 if (do_stealing && !has_aborted()) {
4276 // We have not aborted. This means that we have finished all that
4277 // we could. Let's try to do some stealing...
4279 // We cannot check whether the global stack is empty, since other
4280 // tasks might be pushing objects to it concurrently.
4281 assert(_cm->out_of_regions() && _task_queue->size() == 0,
4282 "only way to reach here");
4284 if (_cm->verbose_low()) {
4285 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
4286 }
4288 while (!has_aborted()) {
4289 oop obj;
4290 statsOnly( ++_steal_attempts );
4292 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
4293 if (_cm->verbose_medium()) {
4294 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully",
4295 _worker_id, (void*) obj);
4296 }
4298 statsOnly( ++_steals );
4300 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
4301 "any stolen object should be marked");
4302 scan_object(obj);
4304 // And since we're towards the end, let's totally drain the
4305 // local queue and global stack.
4306 drain_local_queue(false);
4307 drain_global_stack(false);
4308 } else {
4309 break;
4310 }
4311 }
4312 }
4314 // If we are about to wrap up and go into termination, check if we
4315 // should raise the overflow flag.
4316 if (do_termination && !has_aborted()) {
4317 if (_cm->force_overflow()->should_force()) {
4318 _cm->set_has_overflown();
4319 regular_clock_call();
4320 }
4321 }
4323 // We still haven't aborted. Now, let's try to get into the
4324 // termination protocol.
4325 if (do_termination && !has_aborted()) {
4326 // We cannot check whether the global stack is empty, since other
4327 // tasks might be concurrently pushing objects on it.
4328 // Separated the asserts so that we know which one fires.
4329 assert(_cm->out_of_regions(), "only way to reach here");
4330 assert(_task_queue->size() == 0, "only way to reach here");
4332 if (_cm->verbose_low()) {
4333 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4334 }
4336 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4338 // The CMTask class also extends the TerminatorTerminator class,
4339 // hence its should_exit_termination() method will also decide
4340 // whether to exit the termination protocol or not.
4341 bool finished = (is_serial ||
4342 _cm->terminator()->offer_termination(this));
4343 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4344 _termination_time_ms +=
4345 termination_end_time_ms - _termination_start_time_ms;
4347 if (finished) {
4348 // We're all done.
4350 if (_worker_id == 0) {
4351 // let's allow task 0 to do this
4352 if (concurrent()) {
4353 assert(_cm->concurrent_marking_in_progress(), "invariant");
4354 // we need to set this to false before the next
4355 // safepoint. This way we ensure that the marking phase
4356 // doesn't observe any more heap expansions.
4357 _cm->clear_concurrent_marking_in_progress();
4358 }
4359 }
4361 // We can now guarantee that the global stack is empty, since
4362 // all other tasks have finished. We separated the guarantees so
4363 // that, if a condition is false, we can immediately find out
4364 // which one.
4365 guarantee(_cm->out_of_regions(), "only way to reach here");
4366 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4367 guarantee(_task_queue->size() == 0, "only way to reach here");
4368 guarantee(!_cm->has_overflown(), "only way to reach here");
4369 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4371 if (_cm->verbose_low()) {
4372 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4373 }
4374 } else {
4375 // Apparently there's more work to do. Let's abort this task. It
4376 // will restart it and we can hopefully find more things to do.
4378 if (_cm->verbose_low()) {
4379 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4380 _worker_id);
4381 }
4383 set_has_aborted();
4384 statsOnly( ++_aborted_termination );
4385 }
4386 }
4388 // Mainly for debugging purposes to make sure that a pointer to the
4389 // closure which was statically allocated in this frame doesn't
4390 // escape it by accident.
4391 set_cm_oop_closure(NULL);
4392 double end_time_ms = os::elapsedVTime() * 1000.0;
4393 double elapsed_time_ms = end_time_ms - _start_time_ms;
4394 // Update the step history.
4395 _step_times_ms.add(elapsed_time_ms);
4397 if (has_aborted()) {
4398 // The task was aborted for some reason.
4400 statsOnly( ++_aborted );
4402 if (_has_timed_out) {
4403 double diff_ms = elapsed_time_ms - _time_target_ms;
4404 // Keep statistics of how well we did with respect to hitting
4405 // our target only if we actually timed out (if we aborted for
4406 // other reasons, then the results might get skewed).
4407 _marking_step_diffs_ms.add(diff_ms);
4408 }
4410 if (_cm->has_overflown()) {
4411 // This is the interesting one. We aborted because a global
4412 // overflow was raised. This means we have to restart the
4413 // marking phase and start iterating over regions. However, in
4414 // order to do this we have to make sure that all tasks stop
4415 // what they are doing and re-initialise in a safe manner. We
4416 // will achieve this with the use of two barrier sync points.
4418 if (_cm->verbose_low()) {
4419 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4420 }
4422 if (!is_serial) {
4423 // We only need to enter the sync barrier if being called
4424 // from a parallel context
4425 _cm->enter_first_sync_barrier(_worker_id);
4427 // When we exit this sync barrier we know that all tasks have
4428 // stopped doing marking work. So, it's now safe to
4429 // re-initialise our data structures. At the end of this method,
4430 // task 0 will clear the global data structures.
4431 }
4433 statsOnly( ++_aborted_overflow );
4435 // We clear the local state of this task...
4436 clear_region_fields();
4438 if (!is_serial) {
4439 // ...and enter the second barrier.
4440 _cm->enter_second_sync_barrier(_worker_id);
4441 }
4442 // At this point, if we're during the concurrent phase of
4443 // marking, everything has been re-initialized and we're
4444 // ready to restart.
4445 }
4447 if (_cm->verbose_low()) {
4448 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4449 "elapsed = %1.2lfms <<<<<<<<<<",
4450 _worker_id, _time_target_ms, elapsed_time_ms);
4451 if (_cm->has_aborted()) {
4452 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4453 _worker_id);
4454 }
4455 }
4456 } else {
4457 if (_cm->verbose_low()) {
4458 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4459 "elapsed = %1.2lfms <<<<<<<<<<",
4460 _worker_id, _time_target_ms, elapsed_time_ms);
4461 }
4462 }
4464 _claimed = false;
4465 }
4467 CMTask::CMTask(uint worker_id,
4468 ConcurrentMark* cm,
4469 size_t* marked_bytes,
4470 BitMap* card_bm,
4471 CMTaskQueue* task_queue,
4472 CMTaskQueueSet* task_queues)
4473 : _g1h(G1CollectedHeap::heap()),
4474 _worker_id(worker_id), _cm(cm),
4475 _claimed(false),
4476 _nextMarkBitMap(NULL), _hash_seed(17),
4477 _task_queue(task_queue),
4478 _task_queues(task_queues),
4479 _cm_oop_closure(NULL),
4480 _marked_bytes_array(marked_bytes),
4481 _card_bm(card_bm) {
4482 guarantee(task_queue != NULL, "invariant");
4483 guarantee(task_queues != NULL, "invariant");
4485 statsOnly( _clock_due_to_scanning = 0;
4486 _clock_due_to_marking = 0 );
4488 _marking_step_diffs_ms.add(0.5);
4489 }
4491 // These are formatting macros that are used below to ensure
4492 // consistent formatting. The *_H_* versions are used to format the
4493 // header for a particular value and they should be kept consistent
4494 // with the corresponding macro. Also note that most of the macros add
4495 // the necessary white space (as a prefix) which makes them a bit
4496 // easier to compose.
4498 // All the output lines are prefixed with this string to be able to
4499 // identify them easily in a large log file.
4500 #define G1PPRL_LINE_PREFIX "###"
4502 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT
4503 #ifdef _LP64
4504 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4505 #else // _LP64
4506 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4507 #endif // _LP64
4509 // For per-region info
4510 #define G1PPRL_TYPE_FORMAT " %-4s"
4511 #define G1PPRL_TYPE_H_FORMAT " %4s"
4512 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9)
4513 #define G1PPRL_BYTE_H_FORMAT " %9s"
4514 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4515 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4517 // For summary info
4518 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT
4519 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT
4520 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB"
4521 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%"
4523 G1PrintRegionLivenessInfoClosure::
4524 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4525 : _out(out),
4526 _total_used_bytes(0), _total_capacity_bytes(0),
4527 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4528 _hum_used_bytes(0), _hum_capacity_bytes(0),
4529 _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
4530 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
4531 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4532 MemRegion g1_committed = g1h->g1_committed();
4533 MemRegion g1_reserved = g1h->g1_reserved();
4534 double now = os::elapsedTime();
4536 // Print the header of the output.
4537 _out->cr();
4538 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4539 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4540 G1PPRL_SUM_ADDR_FORMAT("committed")
4541 G1PPRL_SUM_ADDR_FORMAT("reserved")
4542 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4543 g1_committed.start(), g1_committed.end(),
4544 g1_reserved.start(), g1_reserved.end(),
4545 HeapRegion::GrainBytes);
4546 _out->print_cr(G1PPRL_LINE_PREFIX);
4547 _out->print_cr(G1PPRL_LINE_PREFIX
4548 G1PPRL_TYPE_H_FORMAT
4549 G1PPRL_ADDR_BASE_H_FORMAT
4550 G1PPRL_BYTE_H_FORMAT
4551 G1PPRL_BYTE_H_FORMAT
4552 G1PPRL_BYTE_H_FORMAT
4553 G1PPRL_DOUBLE_H_FORMAT
4554 G1PPRL_BYTE_H_FORMAT
4555 G1PPRL_BYTE_H_FORMAT,
4556 "type", "address-range",
4557 "used", "prev-live", "next-live", "gc-eff",
4558 "remset", "code-roots");
4559 _out->print_cr(G1PPRL_LINE_PREFIX
4560 G1PPRL_TYPE_H_FORMAT
4561 G1PPRL_ADDR_BASE_H_FORMAT
4562 G1PPRL_BYTE_H_FORMAT
4563 G1PPRL_BYTE_H_FORMAT
4564 G1PPRL_BYTE_H_FORMAT
4565 G1PPRL_DOUBLE_H_FORMAT
4566 G1PPRL_BYTE_H_FORMAT
4567 G1PPRL_BYTE_H_FORMAT,
4568 "", "",
4569 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
4570 "(bytes)", "(bytes)");
4571 }
4573 // It takes as a parameter a reference to one of the _hum_* fields, it
4574 // deduces the corresponding value for a region in a humongous region
4575 // series (either the region size, or what's left if the _hum_* field
4576 // is < the region size), and updates the _hum_* field accordingly.
4577 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4578 size_t bytes = 0;
4579 // The > 0 check is to deal with the prev and next live bytes which
4580 // could be 0.
4581 if (*hum_bytes > 0) {
4582 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4583 *hum_bytes -= bytes;
4584 }
4585 return bytes;
4586 }
4588 // It deduces the values for a region in a humongous region series
4589 // from the _hum_* fields and updates those accordingly. It assumes
4590 // that that _hum_* fields have already been set up from the "starts
4591 // humongous" region and we visit the regions in address order.
4592 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4593 size_t* capacity_bytes,
4594 size_t* prev_live_bytes,
4595 size_t* next_live_bytes) {
4596 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4597 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4598 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4599 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4600 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4601 }
4603 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4604 const char* type = "";
4605 HeapWord* bottom = r->bottom();
4606 HeapWord* end = r->end();
4607 size_t capacity_bytes = r->capacity();
4608 size_t used_bytes = r->used();
4609 size_t prev_live_bytes = r->live_bytes();
4610 size_t next_live_bytes = r->next_live_bytes();
4611 double gc_eff = r->gc_efficiency();
4612 size_t remset_bytes = r->rem_set()->mem_size();
4613 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
4615 if (r->used() == 0) {
4616 type = "FREE";
4617 } else if (r->is_survivor()) {
4618 type = "SURV";
4619 } else if (r->is_young()) {
4620 type = "EDEN";
4621 } else if (r->startsHumongous()) {
4622 type = "HUMS";
4624 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4625 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4626 "they should have been zeroed after the last time we used them");
4627 // Set up the _hum_* fields.
4628 _hum_capacity_bytes = capacity_bytes;
4629 _hum_used_bytes = used_bytes;
4630 _hum_prev_live_bytes = prev_live_bytes;
4631 _hum_next_live_bytes = next_live_bytes;
4632 get_hum_bytes(&used_bytes, &capacity_bytes,
4633 &prev_live_bytes, &next_live_bytes);
4634 end = bottom + HeapRegion::GrainWords;
4635 } else if (r->continuesHumongous()) {
4636 type = "HUMC";
4637 get_hum_bytes(&used_bytes, &capacity_bytes,
4638 &prev_live_bytes, &next_live_bytes);
4639 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4640 } else {
4641 type = "OLD";
4642 }
4644 _total_used_bytes += used_bytes;
4645 _total_capacity_bytes += capacity_bytes;
4646 _total_prev_live_bytes += prev_live_bytes;
4647 _total_next_live_bytes += next_live_bytes;
4648 _total_remset_bytes += remset_bytes;
4649 _total_strong_code_roots_bytes += strong_code_roots_bytes;
4651 // Print a line for this particular region.
4652 _out->print_cr(G1PPRL_LINE_PREFIX
4653 G1PPRL_TYPE_FORMAT
4654 G1PPRL_ADDR_BASE_FORMAT
4655 G1PPRL_BYTE_FORMAT
4656 G1PPRL_BYTE_FORMAT
4657 G1PPRL_BYTE_FORMAT
4658 G1PPRL_DOUBLE_FORMAT
4659 G1PPRL_BYTE_FORMAT
4660 G1PPRL_BYTE_FORMAT,
4661 type, bottom, end,
4662 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
4663 remset_bytes, strong_code_roots_bytes);
4665 return false;
4666 }
4668 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4669 // add static memory usages to remembered set sizes
4670 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
4671 // Print the footer of the output.
4672 _out->print_cr(G1PPRL_LINE_PREFIX);
4673 _out->print_cr(G1PPRL_LINE_PREFIX
4674 " SUMMARY"
4675 G1PPRL_SUM_MB_FORMAT("capacity")
4676 G1PPRL_SUM_MB_PERC_FORMAT("used")
4677 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4678 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
4679 G1PPRL_SUM_MB_FORMAT("remset")
4680 G1PPRL_SUM_MB_FORMAT("code-roots"),
4681 bytes_to_mb(_total_capacity_bytes),
4682 bytes_to_mb(_total_used_bytes),
4683 perc(_total_used_bytes, _total_capacity_bytes),
4684 bytes_to_mb(_total_prev_live_bytes),
4685 perc(_total_prev_live_bytes, _total_capacity_bytes),
4686 bytes_to_mb(_total_next_live_bytes),
4687 perc(_total_next_live_bytes, _total_capacity_bytes),
4688 bytes_to_mb(_total_remset_bytes),
4689 bytes_to_mb(_total_strong_code_roots_bytes));
4690 _out->cr();
4691 }