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