1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/bufferingOopClosure.hpp"
27 #include "gc_implementation/g1/concurrentG1Refine.hpp"
28 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
29 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
30 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
31 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
32 #include "gc_implementation/g1/g1HotCardCache.hpp"
33 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
34 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
35 #include "gc_implementation/g1/g1RemSet.inline.hpp"
36 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
37 #include "gc_implementation/g1/heapRegionRemSet.hpp"
38 #include "memory/iterator.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "utilities/intHisto.hpp"
41
42 #define CARD_REPEAT_HISTO 0
43
44 #if CARD_REPEAT_HISTO
45 static size_t ct_freq_sz;
46 static jbyte* ct_freq = NULL;
47
48 void init_ct_freq_table(size_t heap_sz_bytes) {
49 if (ct_freq == NULL) {
50 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
51 ct_freq = new jbyte[ct_freq_sz];
52 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
53 }
54 }
55
56 void ct_freq_note_card(size_t index) {
57 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
58 if (ct_freq[index] < 100) { ct_freq[index]++; }
59 }
60
61 static IntHistogram card_repeat_count(10, 10);
62
63 void ct_freq_update_histo_and_reset() {
64 for (size_t j = 0; j < ct_freq_sz; j++) {
65 card_repeat_count.add_entry(ct_freq[j]);
66 ct_freq[j] = 0;
67 }
68
69 }
70 #endif
71
72 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
73 : _g1(g1), _conc_refine_cards(0),
74 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
75 _cg1r(g1->concurrent_g1_refine()),
76 _cset_rs_update_cl(NULL),
77 _cards_scanned(NULL), _total_cards_scanned(0),
78 _prev_period_summary()
79 {
80 _seq_task = new SubTasksDone(NumSeqTasks);
81 guarantee(n_workers() > 0, "There should be some workers");
82 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC);
83 for (uint i = 0; i < n_workers(); i++) {
84 _cset_rs_update_cl[i] = NULL;
85 }
86 _prev_period_summary.initialize(this, n_workers());
87 }
88
89 G1RemSet::~G1RemSet() {
90 delete _seq_task;
91 for (uint i = 0; i < n_workers(); i++) {
92 assert(_cset_rs_update_cl[i] == NULL, "it should be");
93 }
94 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC);
95 }
96
97 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
98 if (_g1->is_in_g1_reserved(mr.start())) {
99 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
100 if (_start_first == NULL) _start_first = mr.start();
101 }
102 }
103
104 class ScanRSClosure : public HeapRegionClosure {
105 size_t _cards_done, _cards;
106 G1CollectedHeap* _g1h;
107 OopsInHeapRegionClosure* _oc;
108 G1BlockOffsetSharedArray* _bot_shared;
109 CardTableModRefBS *_ct_bs;
110 int _worker_i;
111 int _block_size;
112 bool _try_claimed;
113 public:
114 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
115 _oc(oc),
116 _cards(0),
117 _cards_done(0),
118 _worker_i(worker_i),
119 _try_claimed(false)
120 {
121 _g1h = G1CollectedHeap::heap();
122 _bot_shared = _g1h->bot_shared();
123 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
124 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
125 }
126
127 void set_try_claimed() { _try_claimed = true; }
128
129 void scanCard(size_t index, HeapRegion *r) {
130 // Stack allocate the DirtyCardToOopClosure instance
131 HeapRegionDCTOC cl(_g1h, r, _oc,
132 CardTableModRefBS::Precise,
133 HeapRegionDCTOC::IntoCSFilterKind);
134
135 // Set the "from" region in the closure.
136 _oc->set_region(r);
137 HeapWord* card_start = _bot_shared->address_for_index(index);
138 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
139 Space *sp = SharedHeap::heap()->space_containing(card_start);
140 MemRegion sm_region = sp->used_region_at_save_marks();
141 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
142 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
143 // We make the card as "claimed" lazily (so races are possible
144 // but they're benign), which reduces the number of duplicate
145 // scans (the rsets of the regions in the cset can intersect).
146 _ct_bs->set_card_claimed(index);
147 _cards_done++;
148 cl.do_MemRegion(mr);
149 }
150 }
151
152 void printCard(HeapRegion* card_region, size_t card_index,
153 HeapWord* card_start) {
154 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
155 "RS names card %p: "
156 "[" PTR_FORMAT ", " PTR_FORMAT ")",
157 _worker_i,
158 card_region->bottom(), card_region->end(),
159 card_index,
160 card_start, card_start + G1BlockOffsetSharedArray::N_words);
161 }
162
163 bool doHeapRegion(HeapRegion* r) {
164 assert(r->in_collection_set(), "should only be called on elements of CS.");
165 HeapRegionRemSet* hrrs = r->rem_set();
166 if (hrrs->iter_is_complete()) return false; // All done.
167 if (!_try_claimed && !hrrs->claim_iter()) return false;
168 // If we ever free the collection set concurrently, we should also
169 // clear the card table concurrently therefore we won't need to
170 // add regions of the collection set to the dirty cards region.
171 _g1h->push_dirty_cards_region(r);
172 // If we didn't return above, then
173 // _try_claimed || r->claim_iter()
174 // is true: either we're supposed to work on claimed-but-not-complete
175 // regions, or we successfully claimed the region.
176 HeapRegionRemSetIterator iter(hrrs);
177 size_t card_index;
178
179 // We claim cards in block so as to recude the contention. The block size is determined by
180 // the G1RSetScanBlockSize parameter.
181 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
182 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
183 if (current_card >= jump_to_card + _block_size) {
184 jump_to_card = hrrs->iter_claimed_next(_block_size);
185 }
186 if (current_card < jump_to_card) continue;
187 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
188 #if 0
189 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
190 card_start, card_start + CardTableModRefBS::card_size_in_words);
191 #endif
192
193 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
194 assert(card_region != NULL, "Yielding cards not in the heap?");
195 _cards++;
196
197 if (!card_region->is_on_dirty_cards_region_list()) {
198 _g1h->push_dirty_cards_region(card_region);
199 }
200
201 // If the card is dirty, then we will scan it during updateRS.
202 if (!card_region->in_collection_set() &&
203 !_ct_bs->is_card_dirty(card_index)) {
204 scanCard(card_index, card_region);
205 }
206 }
207 if (!_try_claimed) {
208 hrrs->set_iter_complete();
209 }
210 return false;
211 }
212 size_t cards_done() { return _cards_done;}
213 size_t cards_looked_up() { return _cards;}
214 };
215
216 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
217 double rs_time_start = os::elapsedTime();
218 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
219
220 ScanRSClosure scanRScl(oc, worker_i);
221
222 _g1->collection_set_iterate_from(startRegion, &scanRScl);
223 scanRScl.set_try_claimed();
224 _g1->collection_set_iterate_from(startRegion, &scanRScl);
225
226 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
227
228 assert( _cards_scanned != NULL, "invariant" );
229 _cards_scanned[worker_i] = scanRScl.cards_done();
230
231 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
232 }
233
234 // Closure used for updating RSets and recording references that
235 // point into the collection set. Only called during an
236 // evacuation pause.
237
238 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
239 G1RemSet* _g1rs;
240 DirtyCardQueue* _into_cset_dcq;
241 public:
242 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
243 DirtyCardQueue* into_cset_dcq) :
244 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
245 {}
246 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
247 // The only time we care about recording cards that
248 // contain references that point into the collection set
249 // is during RSet updating within an evacuation pause.
250 // In this case worker_i should be the id of a GC worker thread.
251 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
252 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
253
254 if (_g1rs->refine_card(card_ptr, worker_i, (_into_cset_dcq != NULL))) {
255 // 'card_ptr' contains references that point into the collection
256 // set. We need to record the card in the DCQS
257 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
258 // that's used for that purpose.
259 //
260 // Enqueue the card
261 _into_cset_dcq->enqueue(card_ptr);
262 }
263 return true;
264 }
265 };
266
267 class RefineTransferredCardsClosure: public CardTableEntryClosure {
268 G1RemSet* _g1rs;
269 DirtyCardQueue* _into_cset_dcq;
270 public:
271 RefineTransferredCardsClosure(G1CollectedHeap* g1h,
272 DirtyCardQueue* into_cset_dcq) :
273 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
274 {}
275 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
276 // The only time we care about recording cards that
277 // contain references that point into the collection set
278 // is during RSet updating within an evacuation pause.
279 // In this case worker_i should be the id of a GC worker thread.
280 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
281 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
282
283 if (_g1rs->refine_card_without_check(card_ptr, worker_i, (_into_cset_dcq != NULL))) {
284 // 'card_ptr' contains references that point into the collection
285 // set. We need to record the card in the DCQS
286 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
287 // that's used for that purpose.
288 //
289 // Enqueue the card
290 _into_cset_dcq->enqueue(card_ptr);
291 }
292 return true;
293 }
294 };
295
296 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i, bool update_accounting) {
297 double start = os::elapsedTime();
298 // Apply the given closure to all remaining log entries.
299 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, update_accounting ? into_cset_dcq : NULL);
300 RefineTransferredCardsClosure update_cleaned_cards_rs_cl(_g1, update_accounting ? into_cset_dcq : NULL);
301
302 int processed_buffers = _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl,
303 &update_cleaned_cards_rs_cl,
304 into_cset_dcq, false, worker_i);
305
306 // Now there should be no dirty cards.
307 if (G1RSLogCheckCardTable) {
308 CountNonCleanMemRegionClosure cl(_g1);
309 _ct_bs->mod_card_iterate(&cl);
310 // XXX This isn't true any more: keeping cards of young regions
311 // marked dirty broke it. Need some reasonable fix.
312 guarantee(cl.n() == 0, "Card table should be clean.");
313 }
314
315 if (update_accounting) {
316 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, processed_buffers);
317 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
318 }
319 }
320
321 void G1RemSet::cleanupHRRS() {
322 HeapRegionRemSet::cleanup();
323 }
324
325 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
326 int worker_i) {
327 #if CARD_REPEAT_HISTO
328 ct_freq_update_histo_and_reset();
329 #endif
330
331 // We cache the value of 'oc' closure into the appropriate slot in the
332 // _cset_rs_update_cl for this worker
333 assert(worker_i < (int)n_workers(), "sanity");
334 _cset_rs_update_cl[worker_i] = oc;
335
336 // A DirtyCardQueue that is used to hold cards containing references
337 // that point into the collection set. This DCQ is associated with a
338 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
339 // circumstances (i.e. the pause successfully completes), these cards
340 // are just discarded (there's no need to update the RSets of regions
341 // that were in the collection set - after the pause these regions
342 // are wholly 'free' of live objects. In the event of an evacuation
343 // failure the cards/buffers in this queue set are:
344 // * passed to the DirtyCardQueueSet that is used to manage deferred
345 // RSet updates, or
346 // * scanned for references that point into the collection set
347 // and the RSet of the corresponding region in the collection set
348 // is updated immediately.
349 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
350
351 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
352
353 // The two flags below were introduced temporarily to serialize
354 // the updating and scanning of remembered sets. There are some
355 // race conditions when these two operations are done in parallel
356 // and they are causing failures. When we resolve said race
357 // conditions, we'll revert back to parallel remembered set
358 // updating and scanning. See CRs 6677707 and 6677708.
359 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
360 updateRS(&into_cset_dcq, worker_i, /* update_accounting */ true);
361 } else {
362 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0);
363 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
364 }
365 if (G1UseParallelRSetScanning || (worker_i == 0)) {
366 scanRS(oc, worker_i);
367 } else {
368 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
369 }
370
371 // We now clear the cached values of _cset_rs_update_cl for this worker
372 _cset_rs_update_cl[worker_i] = NULL;
373 }
374
375 void G1RemSet::prepare_for_oops_into_collection_set_do() {
376 cleanupHRRS();
377 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
378 _g1->set_refine_cte_cl_concurrency(false);
379 _g1->set_use_transferring_cte_cl(false);
380 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
381 dcqs.concatenate_logs();
382
383 if (G1CollectedHeap::use_parallel_gc_threads()) {
384 // Don't set the number of workers here. It will be set
385 // when the task is run
386 // _seq_task->set_n_termination((int)n_workers());
387 }
388 guarantee( _cards_scanned == NULL, "invariant" );
389 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
390 for (uint i = 0; i < n_workers(); ++i) {
391 _cards_scanned[i] = 0;
392 }
393 _total_cards_scanned = 0;
394 }
395
396
397 // This closure, applied to a DirtyCardQueueSet, is used to immediately
398 // update the RSets for the regions in the CSet. For each card it iterates
399 // through the oops which coincide with that card. It scans the reference
400 // fields in each oop; when it finds an oop that points into the collection
401 // set, the RSet for the region containing the referenced object is updated.
402 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
403 G1CollectedHeap* _g1;
404 CardTableModRefBS* _ct_bs;
405 public:
406 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
407 CardTableModRefBS* bs):
408 _g1(g1), _ct_bs(bs)
409 { }
410
411 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
412 // Construct the region representing the card.
413 HeapWord* start = _ct_bs->addr_for(card_ptr);
414 // And find the region containing it.
415 HeapRegion* r = _g1->heap_region_containing(start);
416 assert(r != NULL, "unexpected null");
417
418 // Scan oops in the card looking for references into the collection set
419 // Don't use addr_for(card_ptr + 1) which can ask for
420 // a card beyond the heap. This is not safe without a perm
421 // gen.
422 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
423 MemRegion scanRegion(start, end);
424
425 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
426 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
427 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
428
429 // We can pass false as the "filter_young" parameter here as:
430 // * we should be in a STW pause,
431 // * the DCQS to which this closure is applied is used to hold
432 // references that point into the collection set from the prior
433 // RSet updating,
434 // * the post-write barrier shouldn't be logging updates to young
435 // regions (but there is a situation where this can happen - see
436 // the comment in G1RemSet::refine_card() below -
437 // that should not be applicable here), and
438 // * during actual RSet updating, the filtering of cards in young
439 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
440 // employed.
441 // As a result, when this closure is applied to "refs into cset"
442 // DCQS, we shouldn't see any cards in young regions.
443 update_rs_cl.set_region(r);
444 HeapWord* stop_point =
445 r->oops_on_card_seq_iterate_careful(scanRegion,
446 &filter_then_update_rs_cset_oop_cl,
447 false /* filter_young */,
448 NULL /* card_ptr */);
449
450 // Since this is performed in the event of an evacuation failure, we
451 // we shouldn't see a non-null stop point
452 assert(stop_point == NULL, "saw an unallocated region");
453 return true;
454 }
455 };
456
457 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
458 guarantee( _cards_scanned != NULL, "invariant" );
459 _total_cards_scanned = 0;
460 for (uint i = 0; i < n_workers(); ++i) {
461 _total_cards_scanned += _cards_scanned[i];
462 }
463 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
464 _cards_scanned = NULL;
465 // Cleanup after copy
466 _g1->set_refine_cte_cl_concurrency(true);
467 _g1->set_use_transferring_cte_cl(true);
468 // Set all cards back to clean.
469 _g1->cleanUpCardTable();
470
471 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
472 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
473
474 if (_g1->evacuation_failed()) {
475 // Restore remembered sets for the regions pointing into the collection set.
476
477 if (G1DeferredRSUpdate) {
478 // If deferred RS updates are enabled then we just need to transfer
479 // the completed buffers from (a) the DirtyCardQueueSet used to hold
480 // cards that contain references that point into the collection set
481 // to (b) the DCQS used to hold the deferred RS updates
482 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
483 } else {
484
485 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
486 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
487
488 int n_completed_buffers = 0;
489 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
490 0, 0, true)) {
491 n_completed_buffers++;
492 }
493 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
494 }
495 }
496
497 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
498 // which contain references that point into the collection.
499 _g1->into_cset_dirty_card_queue_set().clear();
500 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
501 "all buffers should be freed");
502 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
503 }
504
505 class ScrubRSClosure: public HeapRegionClosure {
506 G1CollectedHeap* _g1h;
507 BitMap* _region_bm;
508 BitMap* _card_bm;
509 CardTableModRefBS* _ctbs;
510 public:
511 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
512 _g1h(G1CollectedHeap::heap()),
513 _region_bm(region_bm), _card_bm(card_bm),
514 _ctbs(NULL)
515 {
516 ModRefBarrierSet* bs = _g1h->mr_bs();
517 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
518 _ctbs = (CardTableModRefBS*)bs;
519 }
520
521 bool doHeapRegion(HeapRegion* r) {
522 if (!r->continuesHumongous()) {
523 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
524 }
525 return false;
526 }
527 };
528
529 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
530 ScrubRSClosure scrub_cl(region_bm, card_bm);
531 _g1->heap_region_iterate(&scrub_cl);
532 }
533
534 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
535 uint worker_num, int claim_val) {
536 ScrubRSClosure scrub_cl(region_bm, card_bm);
537 _g1->heap_region_par_iterate_chunked(&scrub_cl,
538 worker_num,
539 n_workers(),
540 claim_val);
541 }
542
543 G1TriggerClosure::G1TriggerClosure() :
544 _triggered(false) { }
545
546 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
547 OopClosure* oop_cl) :
548 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
549
550 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
551 _c1(c1), _c2(c2) { }
552
553 G1UpdateRSOrPushRefOopClosure::
554 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
555 G1RemSet* rs,
556 OopsInHeapRegionClosure* push_ref_cl,
557 bool record_refs_into_cset,
558 int worker_i) :
559 _g1(g1h), _g1_rem_set(rs), _from(NULL),
560 _record_refs_into_cset(record_refs_into_cset),
561 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
562
563 // Returns true if the given card contains references that point
564 // into the collection set, if we're checking for such references;
565 // false otherwise.
566
567 bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i,
568 bool check_for_refs_into_cset) {
569
570 // If the card is no longer dirty, nothing to do.
571 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
572 // No need to return that this card contains refs that point
573 // into the collection set.
574 return false;
575 }
576
577 return refine_card_without_check(card_ptr, worker_i, check_for_refs_into_cset);
578 }
579
580 bool G1RemSet::refine_card_without_check(jbyte* card_ptr, int worker_i,
581 bool check_for_refs_into_cset) {
582 // Construct the region representing the card.
583 HeapWord* start = _ct_bs->addr_for(card_ptr);
584 // And find the region containing it.
585 HeapRegion* r = _g1->heap_region_containing(start);
586 if (r == NULL) {
587 // Again no need to return that this card contains refs that
588 // point into the collection set.
589 return false; // Not in the G1 heap (might be in perm, for example.)
590 }
591
592 // Why do we have to check here whether a card is on a young region,
593 // given that we dirty young regions and, as a result, the
594 // post-barrier is supposed to filter them out and never to enqueue
595 // them? When we allocate a new region as the "allocation region" we
596 // actually dirty its cards after we release the lock, since card
597 // dirtying while holding the lock was a performance bottleneck. So,
598 // as a result, it is possible for other threads to actually
599 // allocate objects in the region (after the acquire the lock)
600 // before all the cards on the region are dirtied. This is unlikely,
601 // and it doesn't happen often, but it can happen. So, the extra
602 // check below filters out those cards.
603 if (r->is_young()) {
604 return false;
605 }
606
607 // While we are processing RSet buffers during the collection, we
608 // actually don't want to scan any cards on the collection set,
609 // since we don't want to update remebered sets with entries that
610 // point into the collection set, given that live objects from the
611 // collection set are about to move and such entries will be stale
612 // very soon. This change also deals with a reliability issue which
613 // involves scanning a card in the collection set and coming across
614 // an array that was being chunked and looking malformed. Note,
615 // however, that if evacuation fails, we have to scan any objects
616 // that were not moved and create any missing entries.
617 if (r->in_collection_set()) {
618 return false;
619 }
620
621 // The result from the hot card cache insert call is either:
622 // * pointer to the current card
623 // (implying that the current card is not 'hot'),
624 // * null
625 // (meaning we had inserted the card ptr into the "hot" card cache,
626 // which had some headroom),
627 // * a pointer to a "hot" card that was evicted from the "hot" cache.
628 //
629
630 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
631 if (hot_card_cache->use_cache()) {
632 assert(!check_for_refs_into_cset, "sanity");
633 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
634
635 card_ptr = hot_card_cache->insert(card_ptr);
636 if (card_ptr == NULL) {
637 // There was no eviction. Nothing to do.
638 return false;
639 }
640
641 start = _ct_bs->addr_for(card_ptr);
642 r = _g1->heap_region_containing(start);
643 if (r == NULL) {
644 // Not in the G1 heap
645 return false;
646 }
647
648 // Checking whether the region we got back from the cache
649 // is young here is inappropriate. The region could have been
650 // freed, reallocated and tagged as young while in the cache.
651 // Hence we could see its young type change at any time.
652 }
653
654 // Don't use addr_for(card_ptr + 1) which can ask for
655 // a card beyond the heap. This is not safe without a perm
656 // gen at the upper end of the heap.
657 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
658 MemRegion dirtyRegion(start, end);
659
660 #if CARD_REPEAT_HISTO
661 init_ct_freq_table(_g1->max_capacity());
662 ct_freq_note_card(_ct_bs->index_for(start));
663 #endif
664
665 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
666 if (check_for_refs_into_cset) {
667 // ConcurrentG1RefineThreads have worker numbers larger than what
668 // _cset_rs_update_cl[] is set up to handle. But those threads should
669 // only be active outside of a collection which means that when they
670 // reach here they should have check_for_refs_into_cset == false.
671 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
672 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
673 }
674 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
675 _g1->g1_rem_set(),
676 oops_in_heap_closure,
677 check_for_refs_into_cset,
678 worker_i);
679 update_rs_oop_cl.set_from(r);
680
681 G1TriggerClosure trigger_cl;
682 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
683 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
684 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
685
686 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
687 (check_for_refs_into_cset ?
688 (OopClosure*)&mux :
689 (OopClosure*)&update_rs_oop_cl));
690
691 // The region for the current card may be a young region. The
692 // current card may have been a card that was evicted from the
693 // card cache. When the card was inserted into the cache, we had
694 // determined that its region was non-young. While in the cache,
695 // the region may have been freed during a cleanup pause, reallocated
696 // and tagged as young.
697 //
698 // We wish to filter out cards for such a region but the current
699 // thread, if we're running concurrently, may "see" the young type
700 // change at any time (so an earlier "is_young" check may pass or
701 // fail arbitrarily). We tell the iteration code to perform this
702 // filtering when it has been determined that there has been an actual
703 // allocation in this region and making it safe to check the young type.
704 bool filter_young = true;
705
706 HeapWord* stop_point =
707 r->oops_on_card_seq_iterate_careful(dirtyRegion,
708 &filter_then_update_rs_oop_cl,
709 filter_young,
710 card_ptr);
711
712 // If stop_point is non-null, then we encountered an unallocated region
713 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
714 // card and re-enqueue: if we put off the card until a GC pause, then the
715 // unallocated portion will be filled in. Alternatively, we might try
716 // the full complexity of the technique used in "regular" precleaning.
717 if (stop_point != NULL) {
718 // The card might have gotten re-dirtied and re-enqueued while we
719 // worked. (In fact, it's pretty likely.)
720 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
721 *card_ptr = CardTableModRefBS::dirty_card_val();
722 MutexLockerEx x(Shared_DirtyCardQ_lock,
723 Mutex::_no_safepoint_check_flag);
724 DirtyCardQueue* sdcq =
725 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
726 sdcq->enqueue(card_ptr);
727 }
728 } else {
729 _conc_refine_cards++;
730 }
731
732 // This gets set to true if the card being refined has
733 // references that point into the collection set.
734 bool has_refs_into_cset = trigger_cl.triggered();
735
736 // We should only be detecting that the card contains references
737 // that point into the collection set if the current thread is
738 // a GC worker thread.
739 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
740 "invalid result at non safepoint");
741
742 return has_refs_into_cset;
743 }
744
745 void G1RemSet::print_periodic_summary_info() {
746 G1RemSetSummary current;
747 current.initialize(this, n_workers());
748
749 _prev_period_summary.subtract_from(¤t);
750 print_summary_info(&_prev_period_summary);
751
752 _prev_period_summary.set(¤t);
753 }
754
755 void G1RemSet::print_summary_info() {
756 G1RemSetSummary current;
757 current.initialize(this, n_workers());
758
759 print_summary_info(¤t, " Cumulative RS summary");
760 }
761
762 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
763 assert(summary != NULL, "just checking");
764
765 if (header != NULL) {
766 gclog_or_tty->print_cr("%s", header);
767 }
768
769 #if CARD_REPEAT_HISTO
770 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
771 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
772 card_repeat_count.print_on(gclog_or_tty);
773 #endif
774
775 summary->print_on(gclog_or_tty);
776 }
777
778
779 void G1RemSet::prepare_for_verify() {
780 if (G1HRRSFlushLogBuffersOnVerify &&
781 (VerifyBeforeGC || VerifyAfterGC)
782 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
783 cleanupHRRS();
784 _g1->set_refine_cte_cl_concurrency(false);
785 if (SafepointSynchronize::is_at_safepoint()) {
786 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
787 dcqs.concatenate_logs();
788 }
789
790 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
791 bool use_hot_card_cache = hot_card_cache->use_cache();
792 hot_card_cache->set_use_cache(false);
793
794 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
795 updateRS(&into_cset_dcq, 0, /* update_accounting */ false);
796 _g1->into_cset_dirty_card_queue_set().clear();
797
798 hot_card_cache->set_use_cache(use_hot_card_cache);
799 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
800 }
801 }