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(OopsInHeapRegionClosure*, 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(OopsInHeapRegionClosure*, _cset_rs_update_cl);
98 }
99
100 class ScanRSClosure : public HeapRegionClosure {
101 size_t _cards_done, _cards;
102 G1CollectedHeap* _g1h;
103
104 OopsInHeapRegionClosure* _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(OopsInHeapRegionClosure* 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 HeapRegionDCTOC::IntoCSFilterKind);
140
141 // Set the "from" region in the closure.
142 _oc->set_region(r);
143 MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
144 MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
145 MemRegion mr = pre_gc_allocated.intersection(card_region);
146 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
147 // We make the card as "claimed" lazily (so races are possible
148 // but they're benign), which reduces the number of duplicate
149 // scans (the rsets of the regions in the cset can intersect).
150 _ct_bs->set_card_claimed(index);
151 _cards_done++;
152 cl.do_MemRegion(mr);
153 }
154 }
155
156 void printCard(HeapRegion* card_region, size_t card_index,
157 HeapWord* card_start) {
158 gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") "
159 "RS names card " SIZE_FORMAT_HEX ": "
160 "[" PTR_FORMAT ", " PTR_FORMAT ")",
161 _worker_i,
162 card_region->bottom(), card_region->end(),
163 card_index,
164 card_start, card_start + G1BlockOffsetSharedArray::N_words);
165 }
166
167 void scan_strong_code_roots(HeapRegion* r) {
168 double scan_start = os::elapsedTime();
169 r->strong_code_roots_do(_code_root_cl);
170 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
171 }
172
173 bool doHeapRegion(HeapRegion* r) {
174 assert(r->in_collection_set(), "should only be called on elements of CS.");
175 HeapRegionRemSet* hrrs = r->rem_set();
176 if (hrrs->iter_is_complete()) return false; // All done.
177 if (!_try_claimed && !hrrs->claim_iter()) return false;
178 // If we ever free the collection set concurrently, we should also
179 // clear the card table concurrently therefore we won't need to
180 // add regions of the collection set to the dirty cards region.
181 _g1h->push_dirty_cards_region(r);
182 // If we didn't return above, then
183 // _try_claimed || r->claim_iter()
184 // is true: either we're supposed to work on claimed-but-not-complete
185 // regions, or we successfully claimed the region.
186
187 HeapRegionRemSetIterator iter(hrrs);
188 size_t card_index;
189
190 // We claim cards in block so as to reduce the contention. The block size is determined by
191 // the G1RSetScanBlockSize parameter.
192 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
193 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
194 if (current_card >= jump_to_card + _block_size) {
195 jump_to_card = hrrs->iter_claimed_next(_block_size);
196 }
197 if (current_card < jump_to_card) continue;
198 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
199 #if 0
200 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
201 card_start, card_start + CardTableModRefBS::card_size_in_words);
202 #endif
203
204 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
205 _cards++;
206
207 if (!card_region->is_on_dirty_cards_region_list()) {
208 _g1h->push_dirty_cards_region(card_region);
209 }
210
211 // If the card is dirty, then we will scan it during updateRS.
212 if (!card_region->in_collection_set() &&
213 !_ct_bs->is_card_dirty(card_index)) {
214 scanCard(card_index, card_region);
215 }
216 }
217 if (!_try_claimed) {
218 // Scan the strong code root list attached to the current region
219 scan_strong_code_roots(r);
220
221 hrrs->set_iter_complete();
222 }
223 return false;
224 }
225
226 double strong_code_root_scan_time_sec() {
227 return _strong_code_root_scan_time_sec;
228 }
229
230 size_t cards_done() { return _cards_done;}
231 size_t cards_looked_up() { return _cards;}
232 };
233
234 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc,
235 CodeBlobClosure* code_root_cl,
236 uint worker_i) {
237 double rs_time_start = os::elapsedTime();
238 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
239
240 ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
241
242 _g1->collection_set_iterate_from(startRegion, &scanRScl);
243 scanRScl.set_try_claimed();
244 _g1->collection_set_iterate_from(startRegion, &scanRScl);
245
246 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
247 - scanRScl.strong_code_root_scan_time_sec();
248
249 assert(_cards_scanned != NULL, "invariant");
250 _cards_scanned[worker_i] = scanRScl.cards_done();
251
252 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
253 _g1p->phase_times()->record_strong_code_root_scan_time(worker_i,
254 scanRScl.strong_code_root_scan_time_sec() * 1000.0);
255 }
256
257 // Closure used for updating RSets and recording references that
258 // point into the collection set. Only called during an
259 // evacuation pause.
260
261 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
262 G1RemSet* _g1rs;
263 DirtyCardQueue* _into_cset_dcq;
264 public:
265 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
266 DirtyCardQueue* into_cset_dcq) :
267 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
268 {}
269 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
270 // The only time we care about recording cards that
271 // contain references that point into the collection set
272 // is during RSet updating within an evacuation pause.
273 // In this case worker_i should be the id of a GC worker thread.
274 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
275 assert(worker_i < ParallelGCThreads, "should be a GC worker");
276
277 if (_g1rs->refine_card(card_ptr, worker_i, true)) {
278 // 'card_ptr' contains references that point into the collection
279 // set. We need to record the card in the DCQS
280 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
281 // that's used for that purpose.
282 //
283 // Enqueue the card
284 _into_cset_dcq->enqueue(card_ptr);
285 }
286 return true;
287 }
288 };
289
290 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
291 double start = os::elapsedTime();
292 // Apply the given closure to all remaining log entries.
293 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
294
295 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
296
297 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
298 }
299
300 void G1RemSet::cleanupHRRS() {
301 HeapRegionRemSet::cleanup();
302 }
303
304 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
305 CodeBlobClosure* code_root_cl,
306 uint worker_i) {
307 #if CARD_REPEAT_HISTO
308 ct_freq_update_histo_and_reset();
309 #endif
310
311 // We cache the value of 'oc' closure into the appropriate slot in the
312 // _cset_rs_update_cl for this worker
313 assert(worker_i < n_workers(), "sanity");
314 _cset_rs_update_cl[worker_i] = oc;
315
316 // A DirtyCardQueue that is used to hold cards containing references
317 // that point into the collection set. This DCQ is associated with a
318 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
319 // circumstances (i.e. the pause successfully completes), these cards
320 // are just discarded (there's no need to update the RSets of regions
321 // that were in the collection set - after the pause these regions
322 // are wholly 'free' of live objects. In the event of an evacuation
323 // failure the cards/buffers in this queue set are passed to the
324 // DirtyCardQueueSet that is used to manage RSet updates
325 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
326
327 updateRS(&into_cset_dcq, worker_i);
328 scanRS(oc, code_root_cl, worker_i);
329
330 // We now clear the cached values of _cset_rs_update_cl for this worker
331 _cset_rs_update_cl[worker_i] = NULL;
332 }
333
334 void G1RemSet::prepare_for_oops_into_collection_set_do() {
335 cleanupHRRS();
336 _g1->set_refine_cte_cl_concurrency(false);
337 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
338 dcqs.concatenate_logs();
339
340 guarantee( _cards_scanned == NULL, "invariant" );
341 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
342 for (uint i = 0; i < n_workers(); ++i) {
343 _cards_scanned[i] = 0;
344 }
345 _total_cards_scanned = 0;
346 }
347
348 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
349 guarantee( _cards_scanned != NULL, "invariant" );
350 _total_cards_scanned = 0;
351 for (uint i = 0; i < n_workers(); ++i) {
352 _total_cards_scanned += _cards_scanned[i];
353 }
354 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
355 _cards_scanned = NULL;
356 // Cleanup after copy
357 _g1->set_refine_cte_cl_concurrency(true);
358 // Set all cards back to clean.
359 _g1->cleanUpCardTable();
360
361 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
362 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
363
364 if (_g1->evacuation_failed()) {
365 double restore_remembered_set_start = os::elapsedTime();
366
367 // Restore remembered sets for the regions pointing into the collection set.
368 // We just need to transfer the completed buffers from the DirtyCardQueueSet
369 // used to hold cards that contain references that point into the collection set
370 // to the DCQS used to hold the deferred RS updates.
371 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
372 _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
373 }
374
375 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
376 // which contain references that point into the collection.
377 _g1->into_cset_dirty_card_queue_set().clear();
378 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
379 "all buffers should be freed");
380 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
381 }
382
383 class ScrubRSClosure: public HeapRegionClosure {
384 G1CollectedHeap* _g1h;
385 BitMap* _region_bm;
386 BitMap* _card_bm;
387 CardTableModRefBS* _ctbs;
388 public:
389 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
390 _g1h(G1CollectedHeap::heap()),
391 _region_bm(region_bm), _card_bm(card_bm),
392 _ctbs(_g1h->g1_barrier_set()) {}
393
394 bool doHeapRegion(HeapRegion* r) {
395 if (!r->is_continues_humongous()) {
396 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
397 }
398 return false;
399 }
400 };
401
402 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {
403 ScrubRSClosure scrub_cl(region_bm, card_bm);
404 _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
405 }
406
407 G1TriggerClosure::G1TriggerClosure() :
408 _triggered(false) { }
409
410 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
411 OopClosure* oop_cl) :
412 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
413
414 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
415 _c1(c1), _c2(c2) { }
416
417 G1UpdateRSOrPushRefOopClosure::
418 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
419 G1RemSet* rs,
420 OopsInHeapRegionClosure* push_ref_cl,
421 bool record_refs_into_cset,
422 uint worker_i) :
423 _g1(g1h), _g1_rem_set(rs), _from(NULL),
424 _record_refs_into_cset(record_refs_into_cset),
425 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
426
427 // Returns true if the given card contains references that point
428 // into the collection set, if we're checking for such references;
429 // false otherwise.
430
431 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
432 bool check_for_refs_into_cset) {
433 assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
434 err_msg("Card at "PTR_FORMAT" index "SIZE_FORMAT" representing heap at "PTR_FORMAT" (%u) must be in committed heap",
435 p2i(card_ptr),
436 _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
437 _ct_bs->addr_for(card_ptr),
438 _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
439
440 // If the card is no longer dirty, nothing to do.
441 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
442 // No need to return that this card contains refs that point
443 // into the collection set.
444 return false;
445 }
446
447 // Construct the region representing the card.
448 HeapWord* start = _ct_bs->addr_for(card_ptr);
449 // And find the region containing it.
450 HeapRegion* r = _g1->heap_region_containing(start);
451
452 // Why do we have to check here whether a card is on a young region,
453 // given that we dirty young regions and, as a result, the
454 // post-barrier is supposed to filter them out and never to enqueue
455 // them? When we allocate a new region as the "allocation region" we
456 // actually dirty its cards after we release the lock, since card
457 // dirtying while holding the lock was a performance bottleneck. So,
458 // as a result, it is possible for other threads to actually
459 // allocate objects in the region (after the acquire the lock)
460 // before all the cards on the region are dirtied. This is unlikely,
461 // and it doesn't happen often, but it can happen. So, the extra
462 // check below filters out those cards.
463 if (r->is_young()) {
464 return false;
465 }
466
467 // While we are processing RSet buffers during the collection, we
468 // actually don't want to scan any cards on the collection set,
469 // since we don't want to update remembered sets with entries that
470 // point into the collection set, given that live objects from the
471 // collection set are about to move and such entries will be stale
472 // very soon. This change also deals with a reliability issue which
473 // involves scanning a card in the collection set and coming across
474 // an array that was being chunked and looking malformed. Note,
475 // however, that if evacuation fails, we have to scan any objects
476 // that were not moved and create any missing entries.
477 if (r->in_collection_set()) {
478 return false;
479 }
480
481 // The result from the hot card cache insert call is either:
482 // * pointer to the current card
483 // (implying that the current card is not 'hot'),
484 // * null
485 // (meaning we had inserted the card ptr into the "hot" card cache,
486 // which had some headroom),
487 // * a pointer to a "hot" card that was evicted from the "hot" cache.
488 //
489
490 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
491 if (hot_card_cache->use_cache()) {
492 assert(!check_for_refs_into_cset, "sanity");
493 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
494
495 card_ptr = hot_card_cache->insert(card_ptr);
496 if (card_ptr == NULL) {
497 // There was no eviction. Nothing to do.
498 return false;
499 }
500
501 start = _ct_bs->addr_for(card_ptr);
502 r = _g1->heap_region_containing(start);
503
504 // Checking whether the region we got back from the cache
505 // is young here is inappropriate. The region could have been
506 // freed, reallocated and tagged as young while in the cache.
507 // Hence we could see its young type change at any time.
508 }
509
510 // Don't use addr_for(card_ptr + 1) which can ask for
511 // a card beyond the heap. This is not safe without a perm
512 // gen at the upper end of the heap.
513 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
514 MemRegion dirtyRegion(start, end);
515
516 #if CARD_REPEAT_HISTO
517 init_ct_freq_table(_g1->max_capacity());
518 ct_freq_note_card(_ct_bs->index_for(start));
519 #endif
520
521 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
522 if (check_for_refs_into_cset) {
523 // ConcurrentG1RefineThreads have worker numbers larger than what
524 // _cset_rs_update_cl[] is set up to handle. But those threads should
525 // only be active outside of a collection which means that when they
526 // reach here they should have check_for_refs_into_cset == false.
527 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
528 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
529 }
530 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
531 _g1->g1_rem_set(),
532 oops_in_heap_closure,
533 check_for_refs_into_cset,
534 worker_i);
535 update_rs_oop_cl.set_from(r);
536
537 G1TriggerClosure trigger_cl;
538 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
539 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
540 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
541
542 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
543 (check_for_refs_into_cset ?
544 (OopClosure*)&mux :
545 (OopClosure*)&update_rs_oop_cl));
546
547 // The region for the current card may be a young region. The
548 // current card may have been a card that was evicted from the
549 // card cache. When the card was inserted into the cache, we had
550 // determined that its region was non-young. While in the cache,
551 // the region may have been freed during a cleanup pause, reallocated
552 // and tagged as young.
553 //
554 // We wish to filter out cards for such a region but the current
555 // thread, if we're running concurrently, may "see" the young type
556 // change at any time (so an earlier "is_young" check may pass or
557 // fail arbitrarily). We tell the iteration code to perform this
558 // filtering when it has been determined that there has been an actual
559 // allocation in this region and making it safe to check the young type.
560 bool filter_young = true;
561
562 HeapWord* stop_point =
563 r->oops_on_card_seq_iterate_careful(dirtyRegion,
564 &filter_then_update_rs_oop_cl,
565 filter_young,
566 card_ptr);
567
568 // If stop_point is non-null, then we encountered an unallocated region
569 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
570 // card and re-enqueue: if we put off the card until a GC pause, then the
571 // unallocated portion will be filled in. Alternatively, we might try
572 // the full complexity of the technique used in "regular" precleaning.
573 if (stop_point != NULL) {
574 // The card might have gotten re-dirtied and re-enqueued while we
575 // worked. (In fact, it's pretty likely.)
576 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
577 *card_ptr = CardTableModRefBS::dirty_card_val();
578 MutexLockerEx x(Shared_DirtyCardQ_lock,
579 Mutex::_no_safepoint_check_flag);
580 DirtyCardQueue* sdcq =
581 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
582 sdcq->enqueue(card_ptr);
583 }
584 } else {
585 _conc_refine_cards++;
586 }
587
588 // This gets set to true if the card being refined has
589 // references that point into the collection set.
590 bool has_refs_into_cset = trigger_cl.triggered();
591
592 // We should only be detecting that the card contains references
593 // that point into the collection set if the current thread is
594 // a GC worker thread.
595 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
596 "invalid result at non safepoint");
597
598 return has_refs_into_cset;
599 }
600
601 void G1RemSet::print_periodic_summary_info(const char* header) {
602 G1RemSetSummary current;
603 current.initialize(this);
604
605 _prev_period_summary.subtract_from(¤t);
606 print_summary_info(&_prev_period_summary, header);
607
608 _prev_period_summary.set(¤t);
609 }
610
611 void G1RemSet::print_summary_info() {
612 G1RemSetSummary current;
613 current.initialize(this);
614
615 print_summary_info(¤t, " Cumulative RS summary");
616 }
617
618 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
619 assert(summary != NULL, "just checking");
620
621 if (header != NULL) {
622 gclog_or_tty->print_cr("%s", header);
623 }
624
625 #if CARD_REPEAT_HISTO
626 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
627 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
628 card_repeat_count.print_on(gclog_or_tty);
629 #endif
630
631 summary->print_on(gclog_or_tty);
632 }
633
634 void G1RemSet::prepare_for_verify() {
635 if (G1HRRSFlushLogBuffersOnVerify &&
636 (VerifyBeforeGC || VerifyAfterGC)
637 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
638 cleanupHRRS();
639 _g1->set_refine_cte_cl_concurrency(false);
640 if (SafepointSynchronize::is_at_safepoint()) {
641 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
642 dcqs.concatenate_logs();
643 }
644
645 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
646 bool use_hot_card_cache = hot_card_cache->use_cache();
647 hot_card_cache->set_use_cache(false);
648
649 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
650 updateRS(&into_cset_dcq, 0);
651 _g1->into_cset_dirty_card_queue_set().clear();
652
653 hot_card_cache->set_use_cache(use_hot_card_cache);
654 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
655 }
656 }