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, mtGC);
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 HeapWord* card_start = _bot_shared->address_for_index(index);
144 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
145 Space *sp = SharedHeap::heap()->space_containing(card_start);
146 MemRegion sm_region = sp->used_region_at_save_marks();
147 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
148 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
149 // We make the card as "claimed" lazily (so races are possible
150 // but they're benign), which reduces the number of duplicate
151 // scans (the rsets of the regions in the cset can intersect).
152 _ct_bs->set_card_claimed(index);
153 _cards_done++;
154 cl.do_MemRegion(mr);
155 }
156 }
157
158 void printCard(HeapRegion* card_region, size_t card_index,
159 HeapWord* card_start) {
160 gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") "
161 "RS names card " SIZE_FORMAT_HEX ": "
162 "[" PTR_FORMAT ", " PTR_FORMAT ")",
163 _worker_i,
164 card_region->bottom(), card_region->end(),
165 card_index,
166 card_start, card_start + G1BlockOffsetSharedArray::N_words);
167 }
168
169 void scan_strong_code_roots(HeapRegion* r) {
170 double scan_start = os::elapsedTime();
171 r->strong_code_roots_do(_code_root_cl);
172 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
173 }
174
175 bool doHeapRegion(HeapRegion* r) {
176 assert(r->in_collection_set(), "should only be called on elements of CS.");
177 HeapRegionRemSet* hrrs = r->rem_set();
178 if (hrrs->iter_is_complete()) return false; // All done.
179 if (!_try_claimed && !hrrs->claim_iter()) return false;
180 // If we ever free the collection set concurrently, we should also
181 // clear the card table concurrently therefore we won't need to
182 // add regions of the collection set to the dirty cards region.
183 _g1h->push_dirty_cards_region(r);
184 // If we didn't return above, then
185 // _try_claimed || r->claim_iter()
186 // is true: either we're supposed to work on claimed-but-not-complete
187 // regions, or we successfully claimed the region.
188
189 HeapRegionRemSetIterator iter(hrrs);
190 size_t card_index;
191
192 // We claim cards in block so as to reduce the contention. The block size is determined by
193 // the G1RSetScanBlockSize parameter.
194 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
195 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
196 if (current_card >= jump_to_card + _block_size) {
197 jump_to_card = hrrs->iter_claimed_next(_block_size);
198 }
199 if (current_card < jump_to_card) continue;
200 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
201 #if 0
202 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
203 card_start, card_start + CardTableModRefBS::card_size_in_words);
204 #endif
205
206 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
207 _cards++;
208
209 if (!card_region->is_on_dirty_cards_region_list()) {
210 _g1h->push_dirty_cards_region(card_region);
211 }
212
213 // If the card is dirty, then we will scan it during updateRS.
214 if (!card_region->in_collection_set() &&
215 !_ct_bs->is_card_dirty(card_index)) {
216 scanCard(card_index, card_region);
217 }
218 }
219 if (!_try_claimed) {
220 // Scan the strong code root list attached to the current region
221 scan_strong_code_roots(r);
222
223 hrrs->set_iter_complete();
224 }
225 return false;
226 }
227
228 double strong_code_root_scan_time_sec() {
229 return _strong_code_root_scan_time_sec;
230 }
231
232 size_t cards_done() { return _cards_done;}
233 size_t cards_looked_up() { return _cards;}
234 };
235
236 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc,
237 CodeBlobClosure* code_root_cl,
238 uint worker_i) {
239 double rs_time_start = os::elapsedTime();
240 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
241
242 ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
243
244 _g1->collection_set_iterate_from(startRegion, &scanRScl);
245 scanRScl.set_try_claimed();
246 _g1->collection_set_iterate_from(startRegion, &scanRScl);
247
248 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
249 - scanRScl.strong_code_root_scan_time_sec();
250
251 assert(_cards_scanned != NULL, "invariant");
252 _cards_scanned[worker_i] = scanRScl.cards_done();
253
254 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
255 _g1p->phase_times()->record_strong_code_root_scan_time(worker_i,
256 scanRScl.strong_code_root_scan_time_sec() * 1000.0);
257 }
258
259 // Closure used for updating RSets and recording references that
260 // point into the collection set. Only called during an
261 // evacuation pause.
262
263 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
264 G1RemSet* _g1rs;
265 DirtyCardQueue* _into_cset_dcq;
266 public:
267 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
268 DirtyCardQueue* into_cset_dcq) :
269 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
270 {}
271 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
272 // The only time we care about recording cards that
273 // contain references that point into the collection set
274 // is during RSet updating within an evacuation pause.
275 // In this case worker_i should be the id of a GC worker thread.
276 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
277 assert(worker_i < ParallelGCThreads, "should be a GC worker");
278
279 if (_g1rs->refine_card(card_ptr, worker_i, true)) {
280 // 'card_ptr' contains references that point into the collection
281 // set. We need to record the card in the DCQS
282 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
283 // that's used for that purpose.
284 //
285 // Enqueue the card
286 _into_cset_dcq->enqueue(card_ptr);
287 }
288 return true;
289 }
290 };
291
292 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
293 double start = os::elapsedTime();
294 // Apply the given closure to all remaining log entries.
295 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
296
297 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
298
299 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
300 }
301
302 void G1RemSet::cleanupHRRS() {
303 HeapRegionRemSet::cleanup();
304 }
305
306 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
307 CodeBlobClosure* code_root_cl,
308 uint worker_i) {
309 #if CARD_REPEAT_HISTO
310 ct_freq_update_histo_and_reset();
311 #endif
312
313 // We cache the value of 'oc' closure into the appropriate slot in the
314 // _cset_rs_update_cl for this worker
315 assert(worker_i < n_workers(), "sanity");
316 _cset_rs_update_cl[worker_i] = oc;
317
318 // A DirtyCardQueue that is used to hold cards containing references
319 // that point into the collection set. This DCQ is associated with a
320 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
321 // circumstances (i.e. the pause successfully completes), these cards
322 // are just discarded (there's no need to update the RSets of regions
323 // that were in the collection set - after the pause these regions
324 // are wholly 'free' of live objects. In the event of an evacuation
325 // failure the cards/buffers in this queue set are passed to the
326 // DirtyCardQueueSet that is used to manage RSet updates
327 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
328
329 updateRS(&into_cset_dcq, worker_i);
330 scanRS(oc, code_root_cl, worker_i);
331
332 // We now clear the cached values of _cset_rs_update_cl for this worker
333 _cset_rs_update_cl[worker_i] = NULL;
334 }
335
336 void G1RemSet::prepare_for_oops_into_collection_set_do() {
337 cleanupHRRS();
338 _g1->set_refine_cte_cl_concurrency(false);
339 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
340 dcqs.concatenate_logs();
341
342 guarantee( _cards_scanned == NULL, "invariant" );
343 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
344 for (uint i = 0; i < n_workers(); ++i) {
345 _cards_scanned[i] = 0;
346 }
347 _total_cards_scanned = 0;
348 }
349
350 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
351 guarantee( _cards_scanned != NULL, "invariant" );
352 _total_cards_scanned = 0;
353 for (uint i = 0; i < n_workers(); ++i) {
354 _total_cards_scanned += _cards_scanned[i];
355 }
356 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
357 _cards_scanned = NULL;
358 // Cleanup after copy
359 _g1->set_refine_cte_cl_concurrency(true);
360 // Set all cards back to clean.
361 _g1->cleanUpCardTable();
362
363 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
364 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
365
366 if (_g1->evacuation_failed()) {
367 double restore_remembered_set_start = os::elapsedTime();
368
369 // Restore remembered sets for the regions pointing into the collection set.
370 // We just need to transfer the completed buffers from the DirtyCardQueueSet
371 // used to hold cards that contain references that point into the collection set
372 // to the DCQS used to hold the deferred RS updates.
373 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
374 _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
375 }
376
377 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
378 // which contain references that point into the collection.
379 _g1->into_cset_dirty_card_queue_set().clear();
380 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
381 "all buffers should be freed");
382 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
383 }
384
385 class ScrubRSClosure: public HeapRegionClosure {
386 G1CollectedHeap* _g1h;
387 BitMap* _region_bm;
388 BitMap* _card_bm;
389 CardTableModRefBS* _ctbs;
390 public:
391 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
392 _g1h(G1CollectedHeap::heap()),
393 _region_bm(region_bm), _card_bm(card_bm),
394 _ctbs(_g1h->g1_barrier_set()) {}
395
396 bool doHeapRegion(HeapRegion* r) {
397 if (!r->is_continues_humongous()) {
398 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
399 }
400 return false;
401 }
402 };
403
404 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {
405 ScrubRSClosure scrub_cl(region_bm, card_bm);
406 _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
407 }
408
409 G1TriggerClosure::G1TriggerClosure() :
410 _triggered(false) { }
411
412 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
413 OopClosure* oop_cl) :
414 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
415
416 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
417 _c1(c1), _c2(c2) { }
418
419 G1UpdateRSOrPushRefOopClosure::
420 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
421 G1RemSet* rs,
422 OopsInHeapRegionClosure* push_ref_cl,
423 bool record_refs_into_cset,
424 uint worker_i) :
425 _g1(g1h), _g1_rem_set(rs), _from(NULL),
426 _record_refs_into_cset(record_refs_into_cset),
427 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
428
429 // Returns true if the given card contains references that point
430 // into the collection set, if we're checking for such references;
431 // false otherwise.
432
433 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
434 bool check_for_refs_into_cset) {
435 assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
436 err_msg("Card at "PTR_FORMAT" index "SIZE_FORMAT" representing heap at "PTR_FORMAT" (%u) must be in committed heap",
437 p2i(card_ptr),
438 _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
439 _ct_bs->addr_for(card_ptr),
440 _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
441
442 // If the card is no longer dirty, nothing to do.
443 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
444 // No need to return that this card contains refs that point
445 // into the collection set.
446 return false;
447 }
448
449 // Construct the region representing the card.
450 HeapWord* start = _ct_bs->addr_for(card_ptr);
451 // And find the region containing it.
452 HeapRegion* r = _g1->heap_region_containing(start);
453
454 // Why do we have to check here whether a card is on a young region,
455 // given that we dirty young regions and, as a result, the
456 // post-barrier is supposed to filter them out and never to enqueue
457 // them? When we allocate a new region as the "allocation region" we
458 // actually dirty its cards after we release the lock, since card
459 // dirtying while holding the lock was a performance bottleneck. So,
460 // as a result, it is possible for other threads to actually
461 // allocate objects in the region (after the acquire the lock)
462 // before all the cards on the region are dirtied. This is unlikely,
463 // and it doesn't happen often, but it can happen. So, the extra
464 // check below filters out those cards.
465 if (r->is_young()) {
466 return false;
467 }
468
469 // While we are processing RSet buffers during the collection, we
470 // actually don't want to scan any cards on the collection set,
471 // since we don't want to update remembered sets with entries that
472 // point into the collection set, given that live objects from the
473 // collection set are about to move and such entries will be stale
474 // very soon. This change also deals with a reliability issue which
475 // involves scanning a card in the collection set and coming across
476 // an array that was being chunked and looking malformed. Note,
477 // however, that if evacuation fails, we have to scan any objects
478 // that were not moved and create any missing entries.
479 if (r->in_collection_set()) {
480 return false;
481 }
482
483 // The result from the hot card cache insert call is either:
484 // * pointer to the current card
485 // (implying that the current card is not 'hot'),
486 // * null
487 // (meaning we had inserted the card ptr into the "hot" card cache,
488 // which had some headroom),
489 // * a pointer to a "hot" card that was evicted from the "hot" cache.
490 //
491
492 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
493 if (hot_card_cache->use_cache()) {
494 assert(!check_for_refs_into_cset, "sanity");
495 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
496
497 card_ptr = hot_card_cache->insert(card_ptr);
498 if (card_ptr == NULL) {
499 // There was no eviction. Nothing to do.
500 return false;
501 }
502
503 start = _ct_bs->addr_for(card_ptr);
504 r = _g1->heap_region_containing(start);
505
506 // Checking whether the region we got back from the cache
507 // is young here is inappropriate. The region could have been
508 // freed, reallocated and tagged as young while in the cache.
509 // Hence we could see its young type change at any time.
510 }
511
512 // Don't use addr_for(card_ptr + 1) which can ask for
513 // a card beyond the heap. This is not safe without a perm
514 // gen at the upper end of the heap.
515 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
516 MemRegion dirtyRegion(start, end);
517
518 #if CARD_REPEAT_HISTO
519 init_ct_freq_table(_g1->max_capacity());
520 ct_freq_note_card(_ct_bs->index_for(start));
521 #endif
522
523 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
524 if (check_for_refs_into_cset) {
525 // ConcurrentG1RefineThreads have worker numbers larger than what
526 // _cset_rs_update_cl[] is set up to handle. But those threads should
527 // only be active outside of a collection which means that when they
528 // reach here they should have check_for_refs_into_cset == false.
529 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
530 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
531 }
532 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
533 _g1->g1_rem_set(),
534 oops_in_heap_closure,
535 check_for_refs_into_cset,
536 worker_i);
537 update_rs_oop_cl.set_from(r);
538
539 G1TriggerClosure trigger_cl;
540 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
541 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
542 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
543
544 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
545 (check_for_refs_into_cset ?
546 (OopClosure*)&mux :
547 (OopClosure*)&update_rs_oop_cl));
548
549 // The region for the current card may be a young region. The
550 // current card may have been a card that was evicted from the
551 // card cache. When the card was inserted into the cache, we had
552 // determined that its region was non-young. While in the cache,
553 // the region may have been freed during a cleanup pause, reallocated
554 // and tagged as young.
555 //
556 // We wish to filter out cards for such a region but the current
557 // thread, if we're running concurrently, may "see" the young type
558 // change at any time (so an earlier "is_young" check may pass or
559 // fail arbitrarily). We tell the iteration code to perform this
560 // filtering when it has been determined that there has been an actual
561 // allocation in this region and making it safe to check the young type.
562 bool filter_young = true;
563
564 HeapWord* stop_point =
565 r->oops_on_card_seq_iterate_careful(dirtyRegion,
566 &filter_then_update_rs_oop_cl,
567 filter_young,
568 card_ptr);
569
570 // If stop_point is non-null, then we encountered an unallocated region
571 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
572 // card and re-enqueue: if we put off the card until a GC pause, then the
573 // unallocated portion will be filled in. Alternatively, we might try
574 // the full complexity of the technique used in "regular" precleaning.
575 if (stop_point != NULL) {
576 // The card might have gotten re-dirtied and re-enqueued while we
577 // worked. (In fact, it's pretty likely.)
578 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
579 *card_ptr = CardTableModRefBS::dirty_card_val();
580 MutexLockerEx x(Shared_DirtyCardQ_lock,
581 Mutex::_no_safepoint_check_flag);
582 DirtyCardQueue* sdcq =
583 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
584 sdcq->enqueue(card_ptr);
585 }
586 } else {
587 _conc_refine_cards++;
588 }
589
590 // This gets set to true if the card being refined has
591 // references that point into the collection set.
592 bool has_refs_into_cset = trigger_cl.triggered();
593
594 // We should only be detecting that the card contains references
595 // that point into the collection set if the current thread is
596 // a GC worker thread.
597 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
598 "invalid result at non safepoint");
599
600 return has_refs_into_cset;
601 }
602
603 void G1RemSet::print_periodic_summary_info(const char* header) {
604 G1RemSetSummary current;
605 current.initialize(this);
606
607 _prev_period_summary.subtract_from(¤t);
608 print_summary_info(&_prev_period_summary, header);
609
610 _prev_period_summary.set(¤t);
611 }
612
613 void G1RemSet::print_summary_info() {
614 G1RemSetSummary current;
615 current.initialize(this);
616
617 print_summary_info(¤t, " Cumulative RS summary");
618 }
619
620 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
621 assert(summary != NULL, "just checking");
622
623 if (header != NULL) {
624 gclog_or_tty->print_cr("%s", header);
625 }
626
627 #if CARD_REPEAT_HISTO
628 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
629 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
630 card_repeat_count.print_on(gclog_or_tty);
631 #endif
632
633 summary->print_on(gclog_or_tty);
634 }
635
636 void G1RemSet::prepare_for_verify() {
637 if (G1HRRSFlushLogBuffersOnVerify &&
638 (VerifyBeforeGC || VerifyAfterGC)
639 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
640 cleanupHRRS();
641 _g1->set_refine_cte_cl_concurrency(false);
642 if (SafepointSynchronize::is_at_safepoint()) {
643 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
644 dcqs.concatenate_logs();
645 }
646
647 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
648 bool use_hot_card_cache = hot_card_cache->use_cache();
649 hot_card_cache->set_use_cache(false);
650
651 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
652 updateRS(&into_cset_dcq, 0);
653 _g1->into_cset_dirty_card_queue_set().clear();
654
655 hot_card_cache->set_use_cache(use_hot_card_cache);
656 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
657 }
658 }