1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/concurrentG1Refine.hpp"
27 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
28 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
30 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
31 #include "gc_implementation/g1/g1HotCardCache.hpp"
32 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
33 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
34 #include "gc_implementation/g1/g1RemSet.inline.hpp"
35 #include "gc_implementation/g1/heapRegionManager.inline.hpp"
36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
37 #include "memory/iterator.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "utilities/globalDefinitions.hpp"
40 #include "utilities/intHisto.hpp"
41
42 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
43
44 #define CARD_REPEAT_HISTO 0
45
46 #if CARD_REPEAT_HISTO
47 static size_t ct_freq_sz;
48 static jbyte* ct_freq = NULL;
49
50 void init_ct_freq_table(size_t heap_sz_bytes) {
51 if (ct_freq == NULL) {
52 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
53 ct_freq = new jbyte[ct_freq_sz];
54 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
55 }
56 }
57
58 void ct_freq_note_card(size_t index) {
59 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
60 if (ct_freq[index] < 100) { ct_freq[index]++; }
61 }
62
63 static IntHistogram card_repeat_count(10, 10);
64
65 void ct_freq_update_histo_and_reset() {
66 for (size_t j = 0; j < ct_freq_sz; j++) {
67 card_repeat_count.add_entry(ct_freq[j]);
68 ct_freq[j] = 0;
69 }
70
71 }
72 #endif
73
74 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
75 : _g1(g1), _conc_refine_cards(0),
76 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
77 _cg1r(g1->concurrent_g1_refine()),
78 _cset_rs_update_cl(NULL),
79 _cards_scanned(NULL), _total_cards_scanned(0),
80 _prev_period_summary()
81 {
82 _seq_task = new SubTasksDone(NumSeqTasks);
83 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, n_workers(), mtGC);
84 for (uint i = 0; i < n_workers(); i++) {
85 _cset_rs_update_cl[i] = NULL;
86 }
87 if (G1SummarizeRSetStats) {
88 _prev_period_summary.initialize(this);
89 }
90 }
91
92 G1RemSet::~G1RemSet() {
93 delete _seq_task;
94 for (uint i = 0; i < n_workers(); i++) {
95 assert(_cset_rs_update_cl[i] == NULL, "it should be");
96 }
97 FREE_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, _cset_rs_update_cl);
98 }
99
100 class ScanRSClosure : public HeapRegionClosure {
101 size_t _cards_done, _cards;
102 G1CollectedHeap* _g1h;
103
104 G1ParPushHeapRSClosure* _oc;
105 CodeBlobClosure* _code_root_cl;
106
107 G1BlockOffsetSharedArray* _bot_shared;
108 G1SATBCardTableModRefBS *_ct_bs;
109
110 double _strong_code_root_scan_time_sec;
111 uint _worker_i;
112 int _block_size;
113 bool _try_claimed;
114
115 public:
116 ScanRSClosure(G1ParPushHeapRSClosure* oc,
117 CodeBlobClosure* code_root_cl,
118 uint worker_i) :
119 _oc(oc),
120 _code_root_cl(code_root_cl),
121 _strong_code_root_scan_time_sec(0.0),
122 _cards(0),
123 _cards_done(0),
124 _worker_i(worker_i),
125 _try_claimed(false)
126 {
127 _g1h = G1CollectedHeap::heap();
128 _bot_shared = _g1h->bot_shared();
129 _ct_bs = _g1h->g1_barrier_set();
130 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
131 }
132
133 void set_try_claimed() { _try_claimed = true; }
134
135 void scanCard(size_t index, HeapRegion *r) {
136 // Stack allocate the DirtyCardToOopClosure instance
137 HeapRegionDCTOC cl(_g1h, r, _oc,
138 CardTableModRefBS::Precise);
139
140 // Set the "from" region in the closure.
141 _oc->set_region(r);
142 MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
143 MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
144 MemRegion mr = pre_gc_allocated.intersection(card_region);
145 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
146 // We make the card as "claimed" lazily (so races are possible
147 // but they're benign), which reduces the number of duplicate
148 // scans (the rsets of the regions in the cset can intersect).
149 _ct_bs->set_card_claimed(index);
150 _cards_done++;
151 cl.do_MemRegion(mr);
152 }
153 }
154
155 void printCard(HeapRegion* card_region, size_t card_index,
156 HeapWord* card_start) {
157 gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") "
158 "RS names card " SIZE_FORMAT_HEX ": "
159 "[" PTR_FORMAT ", " PTR_FORMAT ")",
160 _worker_i,
161 card_region->bottom(), card_region->end(),
162 card_index,
163 card_start, card_start + G1BlockOffsetSharedArray::N_words);
164 }
165
166 void scan_strong_code_roots(HeapRegion* r) {
167 double scan_start = os::elapsedTime();
168 r->strong_code_roots_do(_code_root_cl);
169 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
170 }
171
172 bool doHeapRegion(HeapRegion* r) {
173 assert(r->in_collection_set(), "should only be called on elements of CS.");
174 HeapRegionRemSet* hrrs = r->rem_set();
175 if (hrrs->iter_is_complete()) return false; // All done.
176 if (!_try_claimed && !hrrs->claim_iter()) return false;
177 // If we ever free the collection set concurrently, we should also
178 // clear the card table concurrently therefore we won't need to
179 // add regions of the collection set to the dirty cards region.
180 _g1h->push_dirty_cards_region(r);
181 // If we didn't return above, then
182 // _try_claimed || r->claim_iter()
183 // is true: either we're supposed to work on claimed-but-not-complete
184 // regions, or we successfully claimed the region.
185
186 HeapRegionRemSetIterator iter(hrrs);
187 size_t card_index;
188
189 // We claim cards in block so as to reduce the contention. The block size is determined by
190 // the G1RSetScanBlockSize parameter.
191 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
192 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
193 if (current_card >= jump_to_card + _block_size) {
194 jump_to_card = hrrs->iter_claimed_next(_block_size);
195 }
196 if (current_card < jump_to_card) continue;
197 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
198 #if 0
199 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
200 card_start, card_start + CardTableModRefBS::card_size_in_words);
201 #endif
202
203 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
204 _cards++;
205
206 if (!card_region->is_on_dirty_cards_region_list()) {
207 _g1h->push_dirty_cards_region(card_region);
208 }
209
210 // If the card is dirty, then we will scan it during updateRS.
211 if (!card_region->in_collection_set() &&
212 !_ct_bs->is_card_dirty(card_index)) {
213 scanCard(card_index, card_region);
214 }
215 }
216 if (!_try_claimed) {
217 // Scan the strong code root list attached to the current region
218 scan_strong_code_roots(r);
219
220 hrrs->set_iter_complete();
221 }
222 return false;
223 }
224
225 double strong_code_root_scan_time_sec() {
226 return _strong_code_root_scan_time_sec;
227 }
228
229 size_t cards_done() { return _cards_done;}
230 size_t cards_looked_up() { return _cards;}
231 };
232
233 void G1RemSet::scanRS(G1ParPushHeapRSClosure* oc,
234 CodeBlobClosure* code_root_cl,
235 uint worker_i) {
236 double rs_time_start = os::elapsedTime();
237 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
238
239 ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
240
241 _g1->collection_set_iterate_from(startRegion, &scanRScl);
242 scanRScl.set_try_claimed();
243 _g1->collection_set_iterate_from(startRegion, &scanRScl);
244
245 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
246 - scanRScl.strong_code_root_scan_time_sec();
247
248 assert(_cards_scanned != NULL, "invariant");
249 _cards_scanned[worker_i] = scanRScl.cards_done();
250
251 _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
252 _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, scanRScl.strong_code_root_scan_time_sec());
253 }
254
255 // Closure used for updating RSets and recording references that
256 // point into the collection set. Only called during an
257 // evacuation pause.
258
259 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
260 G1RemSet* _g1rs;
261 DirtyCardQueue* _into_cset_dcq;
262 public:
263 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
264 DirtyCardQueue* into_cset_dcq) :
265 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
266 {}
267 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
268 // The only time we care about recording cards that
269 // contain references that point into the collection set
270 // is during RSet updating within an evacuation pause.
271 // In this case worker_i should be the id of a GC worker thread.
272 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
273 assert(worker_i < ParallelGCThreads, "should be a GC worker");
274
275 if (_g1rs->refine_card(card_ptr, worker_i, true)) {
276 // 'card_ptr' contains references that point into the collection
277 // set. We need to record the card in the DCQS
278 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
279 // that's used for that purpose.
280 //
281 // Enqueue the card
282 _into_cset_dcq->enqueue(card_ptr);
283 }
284 return true;
285 }
286 };
287
288 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
289 G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);
290 // Apply the given closure to all remaining log entries.
291 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
292
293 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
294 }
295
296 void G1RemSet::cleanupHRRS() {
297 HeapRegionRemSet::cleanup();
298 }
299
300 void G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* oc,
301 CodeBlobClosure* code_root_cl,
302 uint worker_i) {
303 #if CARD_REPEAT_HISTO
304 ct_freq_update_histo_and_reset();
305 #endif
306
307 // We cache the value of 'oc' closure into the appropriate slot in the
308 // _cset_rs_update_cl for this worker
309 assert(worker_i < n_workers(), "sanity");
310 _cset_rs_update_cl[worker_i] = oc;
311
312 // A DirtyCardQueue that is used to hold cards containing references
313 // that point into the collection set. This DCQ is associated with a
314 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
315 // circumstances (i.e. the pause successfully completes), these cards
316 // are just discarded (there's no need to update the RSets of regions
317 // that were in the collection set - after the pause these regions
318 // are wholly 'free' of live objects. In the event of an evacuation
319 // failure the cards/buffers in this queue set are passed to the
320 // DirtyCardQueueSet that is used to manage RSet updates
321 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
322
323 updateRS(&into_cset_dcq, worker_i);
324 scanRS(oc, code_root_cl, worker_i);
325
326 // We now clear the cached values of _cset_rs_update_cl for this worker
327 _cset_rs_update_cl[worker_i] = NULL;
328 }
329
330 void G1RemSet::prepare_for_oops_into_collection_set_do() {
331 cleanupHRRS();
332 _g1->set_refine_cte_cl_concurrency(false);
333 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
334 dcqs.concatenate_logs();
335
336 guarantee( _cards_scanned == NULL, "invariant" );
337 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
338 for (uint i = 0; i < n_workers(); ++i) {
339 _cards_scanned[i] = 0;
340 }
341 _total_cards_scanned = 0;
342 }
343
344 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
345 guarantee( _cards_scanned != NULL, "invariant" );
346 _total_cards_scanned = 0;
347 for (uint i = 0; i < n_workers(); ++i) {
348 _total_cards_scanned += _cards_scanned[i];
349 }
350 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
351 _cards_scanned = NULL;
352 // Cleanup after copy
353 _g1->set_refine_cte_cl_concurrency(true);
354 // Set all cards back to clean.
355 _g1->cleanUpCardTable();
356
357 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
358 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
359
360 if (_g1->evacuation_failed()) {
361 double restore_remembered_set_start = os::elapsedTime();
362
363 // Restore remembered sets for the regions pointing into the collection set.
364 // We just need to transfer the completed buffers from the DirtyCardQueueSet
365 // used to hold cards that contain references that point into the collection set
366 // to the DCQS used to hold the deferred RS updates.
367 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
368 _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
369 }
370
371 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
372 // which contain references that point into the collection.
373 _g1->into_cset_dirty_card_queue_set().clear();
374 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
375 "all buffers should be freed");
376 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
377 }
378
379 class ScrubRSClosure: public HeapRegionClosure {
380 G1CollectedHeap* _g1h;
381 BitMap* _region_bm;
382 BitMap* _card_bm;
383 CardTableModRefBS* _ctbs;
384 public:
385 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
386 _g1h(G1CollectedHeap::heap()),
387 _region_bm(region_bm), _card_bm(card_bm),
388 _ctbs(_g1h->g1_barrier_set()) {}
389
390 bool doHeapRegion(HeapRegion* r) {
391 if (!r->is_continues_humongous()) {
392 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
393 }
394 return false;
395 }
396 };
397
398 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {
399 ScrubRSClosure scrub_cl(region_bm, card_bm);
400 _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
401 }
402
403 G1TriggerClosure::G1TriggerClosure() :
404 _triggered(false) { }
405
406 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
407 OopClosure* oop_cl) :
408 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
409
410 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
411 _c1(c1), _c2(c2) { }
412
413 G1UpdateRSOrPushRefOopClosure::
414 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
415 G1RemSet* rs,
416 G1ParPushHeapRSClosure* push_ref_cl,
417 bool record_refs_into_cset,
418 uint worker_i) :
419 _g1(g1h), _g1_rem_set(rs), _from(NULL),
420 _record_refs_into_cset(record_refs_into_cset),
421 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
422
423 // Returns true if the given card contains references that point
424 // into the collection set, if we're checking for such references;
425 // false otherwise.
426
427 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
428 bool check_for_refs_into_cset) {
429 assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
430 err_msg("Card at "PTR_FORMAT" index "SIZE_FORMAT" representing heap at "PTR_FORMAT" (%u) must be in committed heap",
431 p2i(card_ptr),
432 _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
433 _ct_bs->addr_for(card_ptr),
434 _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
435
436 // If the card is no longer dirty, nothing to do.
437 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
438 // No need to return that this card contains refs that point
439 // into the collection set.
440 return false;
441 }
442
443 // Construct the region representing the card.
444 HeapWord* start = _ct_bs->addr_for(card_ptr);
445 // And find the region containing it.
446 HeapRegion* r = _g1->heap_region_containing(start);
447
448 // Why do we have to check here whether a card is on a young region,
449 // given that we dirty young regions and, as a result, the
450 // post-barrier is supposed to filter them out and never to enqueue
451 // them? When we allocate a new region as the "allocation region" we
452 // actually dirty its cards after we release the lock, since card
453 // dirtying while holding the lock was a performance bottleneck. So,
454 // as a result, it is possible for other threads to actually
455 // allocate objects in the region (after the acquire the lock)
456 // before all the cards on the region are dirtied. This is unlikely,
457 // and it doesn't happen often, but it can happen. So, the extra
458 // check below filters out those cards.
459 if (r->is_young()) {
460 return false;
461 }
462
463 // While we are processing RSet buffers during the collection, we
464 // actually don't want to scan any cards on the collection set,
465 // since we don't want to update remembered sets with entries that
466 // point into the collection set, given that live objects from the
467 // collection set are about to move and such entries will be stale
468 // very soon. This change also deals with a reliability issue which
469 // involves scanning a card in the collection set and coming across
470 // an array that was being chunked and looking malformed. Note,
471 // however, that if evacuation fails, we have to scan any objects
472 // that were not moved and create any missing entries.
473 if (r->in_collection_set()) {
474 return false;
475 }
476
477 // The result from the hot card cache insert call is either:
478 // * pointer to the current card
479 // (implying that the current card is not 'hot'),
480 // * null
481 // (meaning we had inserted the card ptr into the "hot" card cache,
482 // which had some headroom),
483 // * a pointer to a "hot" card that was evicted from the "hot" cache.
484 //
485
486 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
487 if (hot_card_cache->use_cache()) {
488 assert(!check_for_refs_into_cset, "sanity");
489 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
490
491 card_ptr = hot_card_cache->insert(card_ptr);
492 if (card_ptr == NULL) {
493 // There was no eviction. Nothing to do.
494 return false;
495 }
496
497 start = _ct_bs->addr_for(card_ptr);
498 r = _g1->heap_region_containing(start);
499
500 // Checking whether the region we got back from the cache
501 // is young here is inappropriate. The region could have been
502 // freed, reallocated and tagged as young while in the cache.
503 // Hence we could see its young type change at any time.
504 }
505
506 // Don't use addr_for(card_ptr + 1) which can ask for
507 // a card beyond the heap. This is not safe without a perm
508 // gen at the upper end of the heap.
509 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
510 MemRegion dirtyRegion(start, end);
511
512 #if CARD_REPEAT_HISTO
513 init_ct_freq_table(_g1->max_capacity());
514 ct_freq_note_card(_ct_bs->index_for(start));
515 #endif
516
517 G1ParPushHeapRSClosure* oops_in_heap_closure = NULL;
518 if (check_for_refs_into_cset) {
519 // ConcurrentG1RefineThreads have worker numbers larger than what
520 // _cset_rs_update_cl[] is set up to handle. But those threads should
521 // only be active outside of a collection which means that when they
522 // reach here they should have check_for_refs_into_cset == false.
523 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
524 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
525 }
526 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
527 _g1->g1_rem_set(),
528 oops_in_heap_closure,
529 check_for_refs_into_cset,
530 worker_i);
531 update_rs_oop_cl.set_from(r);
532
533 G1TriggerClosure trigger_cl;
534 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
535 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
536 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
537
538 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
539 (check_for_refs_into_cset ?
540 (OopClosure*)&mux :
541 (OopClosure*)&update_rs_oop_cl));
542
543 // The region for the current card may be a young region. The
544 // current card may have been a card that was evicted from the
545 // card cache. When the card was inserted into the cache, we had
546 // determined that its region was non-young. While in the cache,
547 // the region may have been freed during a cleanup pause, reallocated
548 // and tagged as young.
549 //
550 // We wish to filter out cards for such a region but the current
551 // thread, if we're running concurrently, may "see" the young type
552 // change at any time (so an earlier "is_young" check may pass or
553 // fail arbitrarily). We tell the iteration code to perform this
554 // filtering when it has been determined that there has been an actual
555 // allocation in this region and making it safe to check the young type.
556 bool filter_young = true;
557
558 HeapWord* stop_point =
559 r->oops_on_card_seq_iterate_careful(dirtyRegion,
560 &filter_then_update_rs_oop_cl,
561 filter_young,
562 card_ptr);
563
564 // If stop_point is non-null, then we encountered an unallocated region
565 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
566 // card and re-enqueue: if we put off the card until a GC pause, then the
567 // unallocated portion will be filled in. Alternatively, we might try
568 // the full complexity of the technique used in "regular" precleaning.
569 if (stop_point != NULL) {
570 // The card might have gotten re-dirtied and re-enqueued while we
571 // worked. (In fact, it's pretty likely.)
572 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
573 *card_ptr = CardTableModRefBS::dirty_card_val();
574 MutexLockerEx x(Shared_DirtyCardQ_lock,
575 Mutex::_no_safepoint_check_flag);
576 DirtyCardQueue* sdcq =
577 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
578 sdcq->enqueue(card_ptr);
579 }
580 } else {
581 _conc_refine_cards++;
582 }
583
584 // This gets set to true if the card being refined has
585 // references that point into the collection set.
586 bool has_refs_into_cset = trigger_cl.triggered();
587
588 // We should only be detecting that the card contains references
589 // that point into the collection set if the current thread is
590 // a GC worker thread.
591 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
592 "invalid result at non safepoint");
593
594 return has_refs_into_cset;
595 }
596
597 void G1RemSet::print_periodic_summary_info(const char* header) {
598 G1RemSetSummary current;
599 current.initialize(this);
600
601 _prev_period_summary.subtract_from(¤t);
602 print_summary_info(&_prev_period_summary, header);
603
604 _prev_period_summary.set(¤t);
605 }
606
607 void G1RemSet::print_summary_info() {
608 G1RemSetSummary current;
609 current.initialize(this);
610
611 print_summary_info(¤t, " Cumulative RS summary");
612 }
613
614 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
615 assert(summary != NULL, "just checking");
616
617 if (header != NULL) {
618 gclog_or_tty->print_cr("%s", header);
619 }
620
621 #if CARD_REPEAT_HISTO
622 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
623 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
624 card_repeat_count.print_on(gclog_or_tty);
625 #endif
626
627 summary->print_on(gclog_or_tty);
628 }
629
630 void G1RemSet::prepare_for_verify() {
631 if (G1HRRSFlushLogBuffersOnVerify &&
632 (VerifyBeforeGC || VerifyAfterGC)
633 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
634 cleanupHRRS();
635 _g1->set_refine_cte_cl_concurrency(false);
636 if (SafepointSynchronize::is_at_safepoint()) {
637 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
638 dcqs.concatenate_logs();
639 }
640
641 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
642 bool use_hot_card_cache = hot_card_cache->use_cache();
643 hot_card_cache->set_use_cache(false);
644
645 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
646 updateRS(&into_cset_dcq, 0);
647 _g1->into_cset_dirty_card_queue_set().clear();
648
649 hot_card_cache->set_use_cache(use_hot_card_cache);
650 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
651 }
652 }
--- EOF ---