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, true)) {
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 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
268 double start = os::elapsedTime();
269 // Apply the given closure to all remaining log entries.
270 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
271
272 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
273
274 // Now there should be no dirty cards.
275 if (G1RSLogCheckCardTable) {
276 CountNonCleanMemRegionClosure cl(_g1);
277 _ct_bs->mod_card_iterate(&cl);
278 // XXX This isn't true any more: keeping cards of young regions
279 // marked dirty broke it. Need some reasonable fix.
280 guarantee(cl.n() == 0, "Card table should be clean.");
281 }
282
283 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
284 }
285
286 void G1RemSet::cleanupHRRS() {
287 HeapRegionRemSet::cleanup();
288 }
289
290 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
291 int worker_i) {
292 #if CARD_REPEAT_HISTO
293 ct_freq_update_histo_and_reset();
294 #endif
295
296 // We cache the value of 'oc' closure into the appropriate slot in the
297 // _cset_rs_update_cl for this worker
298 assert(worker_i < (int)n_workers(), "sanity");
299 _cset_rs_update_cl[worker_i] = oc;
300
301 // A DirtyCardQueue that is used to hold cards containing references
302 // that point into the collection set. This DCQ is associated with a
303 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
304 // circumstances (i.e. the pause successfully completes), these cards
305 // are just discarded (there's no need to update the RSets of regions
306 // that were in the collection set - after the pause these regions
307 // are wholly 'free' of live objects. In the event of an evacuation
308 // failure the cards/buffers in this queue set are:
309 // * passed to the DirtyCardQueueSet that is used to manage deferred
310 // RSet updates, or
311 // * scanned for references that point into the collection set
312 // and the RSet of the corresponding region in the collection set
313 // is updated immediately.
314 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
315
316 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
317
318 // The two flags below were introduced temporarily to serialize
319 // the updating and scanning of remembered sets. There are some
320 // race conditions when these two operations are done in parallel
321 // and they are causing failures. When we resolve said race
322 // conditions, we'll revert back to parallel remembered set
323 // updating and scanning. See CRs 6677707 and 6677708.
324 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
325 updateRS(&into_cset_dcq, worker_i);
326 } else {
327 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0);
328 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
329 }
330 if (G1UseParallelRSetScanning || (worker_i == 0)) {
331 scanRS(oc, worker_i);
332 } else {
333 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
334 }
335
336 // We now clear the cached values of _cset_rs_update_cl for this worker
337 _cset_rs_update_cl[worker_i] = NULL;
338 }
339
340 void G1RemSet::prepare_for_oops_into_collection_set_do() {
341 cleanupHRRS();
342 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
343 _g1->set_refine_cte_cl_concurrency(false);
344 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
345 dcqs.concatenate_logs();
346
347 if (G1CollectedHeap::use_parallel_gc_threads()) {
348 // Don't set the number of workers here. It will be set
349 // when the task is run
350 // _seq_task->set_n_termination((int)n_workers());
351 }
352 guarantee( _cards_scanned == NULL, "invariant" );
353 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
354 for (uint i = 0; i < n_workers(); ++i) {
355 _cards_scanned[i] = 0;
356 }
357 _total_cards_scanned = 0;
358 }
359
360
361 // This closure, applied to a DirtyCardQueueSet, is used to immediately
362 // update the RSets for the regions in the CSet. For each card it iterates
363 // through the oops which coincide with that card. It scans the reference
364 // fields in each oop; when it finds an oop that points into the collection
365 // set, the RSet for the region containing the referenced object is updated.
366 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
367 G1CollectedHeap* _g1;
368 CardTableModRefBS* _ct_bs;
369 public:
370 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
371 CardTableModRefBS* bs):
372 _g1(g1), _ct_bs(bs)
373 { }
374
375 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
376 // Construct the region representing the card.
377 HeapWord* start = _ct_bs->addr_for(card_ptr);
378 // And find the region containing it.
379 HeapRegion* r = _g1->heap_region_containing(start);
380 assert(r != NULL, "unexpected null");
381
382 // Scan oops in the card looking for references into the collection set
383 // Don't use addr_for(card_ptr + 1) which can ask for
384 // a card beyond the heap. This is not safe without a perm
385 // gen.
386 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
387 MemRegion scanRegion(start, end);
388
389 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
390 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
391 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
392
393 // We can pass false as the "filter_young" parameter here as:
394 // * we should be in a STW pause,
395 // * the DCQS to which this closure is applied is used to hold
396 // references that point into the collection set from the prior
397 // RSet updating,
398 // * the post-write barrier shouldn't be logging updates to young
399 // regions (but there is a situation where this can happen - see
400 // the comment in G1RemSet::refine_card() below -
401 // that should not be applicable here), and
402 // * during actual RSet updating, the filtering of cards in young
403 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
404 // employed.
405 // As a result, when this closure is applied to "refs into cset"
406 // DCQS, we shouldn't see any cards in young regions.
407 update_rs_cl.set_region(r);
408 HeapWord* stop_point =
409 r->oops_on_card_seq_iterate_careful(scanRegion,
410 &filter_then_update_rs_cset_oop_cl,
411 false /* filter_young */,
412 NULL /* card_ptr */);
413
414 // Since this is performed in the event of an evacuation failure, we
415 // we shouldn't see a non-null stop point
416 assert(stop_point == NULL, "saw an unallocated region");
417 return true;
418 }
419 };
420
421 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
422 guarantee( _cards_scanned != NULL, "invariant" );
423 _total_cards_scanned = 0;
424 for (uint i = 0; i < n_workers(); ++i) {
425 _total_cards_scanned += _cards_scanned[i];
426 }
427 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
428 _cards_scanned = NULL;
429 // Cleanup after copy
430 _g1->set_refine_cte_cl_concurrency(true);
431 // Set all cards back to clean.
432 _g1->cleanUpCardTable();
433
434 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
435 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
436
437 if (_g1->evacuation_failed()) {
438 // Restore remembered sets for the regions pointing into the collection set.
439
440 if (G1DeferredRSUpdate) {
441 // If deferred RS updates are enabled then we just need to transfer
442 // the completed buffers from (a) the DirtyCardQueueSet used to hold
443 // cards that contain references that point into the collection set
444 // to (b) the DCQS used to hold the deferred RS updates
445 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
446 } else {
447
448 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
449 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
450
451 int n_completed_buffers = 0;
452 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
453 0, 0, true)) {
454 n_completed_buffers++;
455 }
456 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
457 }
458 }
459
460 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
461 // which contain references that point into the collection.
462 _g1->into_cset_dirty_card_queue_set().clear();
463 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
464 "all buffers should be freed");
465 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
466 }
467
468 class ScrubRSClosure: public HeapRegionClosure {
469 G1CollectedHeap* _g1h;
470 BitMap* _region_bm;
471 BitMap* _card_bm;
472 CardTableModRefBS* _ctbs;
473 public:
474 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
475 _g1h(G1CollectedHeap::heap()),
476 _region_bm(region_bm), _card_bm(card_bm),
477 _ctbs(NULL)
478 {
479 ModRefBarrierSet* bs = _g1h->mr_bs();
480 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
481 _ctbs = (CardTableModRefBS*)bs;
482 }
483
484 bool doHeapRegion(HeapRegion* r) {
485 if (!r->continuesHumongous()) {
486 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
487 }
488 return false;
489 }
490 };
491
492 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
493 ScrubRSClosure scrub_cl(region_bm, card_bm);
494 _g1->heap_region_iterate(&scrub_cl);
495 }
496
497 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
498 uint worker_num, int claim_val) {
499 ScrubRSClosure scrub_cl(region_bm, card_bm);
500 _g1->heap_region_par_iterate_chunked(&scrub_cl,
501 worker_num,
502 n_workers(),
503 claim_val);
504 }
505
506 G1TriggerClosure::G1TriggerClosure() :
507 _triggered(false) { }
508
509 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
510 OopClosure* oop_cl) :
511 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
512
513 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
514 _c1(c1), _c2(c2) { }
515
516 G1UpdateRSOrPushRefOopClosure::
517 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
518 G1RemSet* rs,
519 OopsInHeapRegionClosure* push_ref_cl,
520 bool record_refs_into_cset,
521 int worker_i) :
522 _g1(g1h), _g1_rem_set(rs), _from(NULL),
523 _record_refs_into_cset(record_refs_into_cset),
524 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
525
526 // Returns true if the given card contains references that point
527 // into the collection set, if we're checking for such references;
528 // false otherwise.
529
530 bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i,
531 bool check_for_refs_into_cset) {
532
533 // If the card is no longer dirty, nothing to do.
534 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
535 // No need to return that this card contains refs that point
536 // into the collection set.
537 return false;
538 }
539
540 // Construct the region representing the card.
541 HeapWord* start = _ct_bs->addr_for(card_ptr);
542 // And find the region containing it.
543 HeapRegion* r = _g1->heap_region_containing(start);
544 if (r == NULL) {
545 // Again no need to return that this card contains refs that
546 // point into the collection set.
547 return false; // Not in the G1 heap (might be in perm, for example.)
548 }
549
550 // Why do we have to check here whether a card is on a young region,
551 // given that we dirty young regions and, as a result, the
552 // post-barrier is supposed to filter them out and never to enqueue
553 // them? When we allocate a new region as the "allocation region" we
554 // actually dirty its cards after we release the lock, since card
555 // dirtying while holding the lock was a performance bottleneck. So,
556 // as a result, it is possible for other threads to actually
557 // allocate objects in the region (after the acquire the lock)
558 // before all the cards on the region are dirtied. This is unlikely,
559 // and it doesn't happen often, but it can happen. So, the extra
560 // check below filters out those cards.
561 if (r->is_young()) {
562 return false;
563 }
564
565 // While we are processing RSet buffers during the collection, we
566 // actually don't want to scan any cards on the collection set,
567 // since we don't want to update remebered sets with entries that
568 // point into the collection set, given that live objects from the
569 // collection set are about to move and such entries will be stale
570 // very soon. This change also deals with a reliability issue which
571 // involves scanning a card in the collection set and coming across
572 // an array that was being chunked and looking malformed. Note,
573 // however, that if evacuation fails, we have to scan any objects
574 // that were not moved and create any missing entries.
575 if (r->in_collection_set()) {
576 return false;
577 }
578
579 // The result from the hot card cache insert call is either:
580 // * pointer to the current card
581 // (implying that the current card is not 'hot'),
582 // * null
583 // (meaning we had inserted the card ptr into the "hot" card cache,
584 // which had some headroom),
585 // * a pointer to a "hot" card that was evicted from the "hot" cache.
586 //
587
588 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
589 if (hot_card_cache->use_cache()) {
590 assert(!check_for_refs_into_cset, "sanity");
591 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
592
593 card_ptr = hot_card_cache->insert(card_ptr);
594 if (card_ptr == NULL) {
595 // There was no eviction. Nothing to do.
596 return false;
597 }
598
599 start = _ct_bs->addr_for(card_ptr);
600 r = _g1->heap_region_containing(start);
601 if (r == NULL) {
602 // Not in the G1 heap
603 return false;
604 }
605
606 // Checking whether the region we got back from the cache
607 // is young here is inappropriate. The region could have been
608 // freed, reallocated and tagged as young while in the cache.
609 // Hence we could see its young type change at any time.
610 }
611
612 // Don't use addr_for(card_ptr + 1) which can ask for
613 // a card beyond the heap. This is not safe without a perm
614 // gen at the upper end of the heap.
615 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
616 MemRegion dirtyRegion(start, end);
617
618 #if CARD_REPEAT_HISTO
619 init_ct_freq_table(_g1->max_capacity());
620 ct_freq_note_card(_ct_bs->index_for(start));
621 #endif
622
623 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
624 if (check_for_refs_into_cset) {
625 // ConcurrentG1RefineThreads have worker numbers larger than what
626 // _cset_rs_update_cl[] is set up to handle. But those threads should
627 // only be active outside of a collection which means that when they
628 // reach here they should have check_for_refs_into_cset == false.
629 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
630 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
631 }
632 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
633 _g1->g1_rem_set(),
634 oops_in_heap_closure,
635 check_for_refs_into_cset,
636 worker_i);
637 update_rs_oop_cl.set_from(r);
638
639 G1TriggerClosure trigger_cl;
640 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
641 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
642 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
643
644 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
645 (check_for_refs_into_cset ?
646 (OopClosure*)&mux :
647 (OopClosure*)&update_rs_oop_cl));
648
649 // The region for the current card may be a young region. The
650 // current card may have been a card that was evicted from the
651 // card cache. When the card was inserted into the cache, we had
652 // determined that its region was non-young. While in the cache,
653 // the region may have been freed during a cleanup pause, reallocated
654 // and tagged as young.
655 //
656 // We wish to filter out cards for such a region but the current
657 // thread, if we're running concurrently, may "see" the young type
658 // change at any time (so an earlier "is_young" check may pass or
659 // fail arbitrarily). We tell the iteration code to perform this
660 // filtering when it has been determined that there has been an actual
661 // allocation in this region and making it safe to check the young type.
662 bool filter_young = true;
663
664 HeapWord* stop_point =
665 r->oops_on_card_seq_iterate_careful(dirtyRegion,
666 &filter_then_update_rs_oop_cl,
667 filter_young,
668 card_ptr);
669
670 // If stop_point is non-null, then we encountered an unallocated region
671 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
672 // card and re-enqueue: if we put off the card until a GC pause, then the
673 // unallocated portion will be filled in. Alternatively, we might try
674 // the full complexity of the technique used in "regular" precleaning.
675 if (stop_point != NULL) {
676 // The card might have gotten re-dirtied and re-enqueued while we
677 // worked. (In fact, it's pretty likely.)
678 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
679 *card_ptr = CardTableModRefBS::dirty_card_val();
680 MutexLockerEx x(Shared_DirtyCardQ_lock,
681 Mutex::_no_safepoint_check_flag);
682 DirtyCardQueue* sdcq =
683 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
684 sdcq->enqueue(card_ptr);
685 }
686 } else {
687 _conc_refine_cards++;
688 }
689
690 // This gets set to true if the card being refined has
691 // references that point into the collection set.
692 bool has_refs_into_cset = trigger_cl.triggered();
693
694 // We should only be detecting that the card contains references
695 // that point into the collection set if the current thread is
696 // a GC worker thread.
697 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
698 "invalid result at non safepoint");
699
700 return has_refs_into_cset;
701 }
702
703 void G1RemSet::print_periodic_summary_info(const char* header) {
704 G1RemSetSummary current;
705 current.initialize(this, n_workers());
706
707 _prev_period_summary.subtract_from(¤t);
708 print_summary_info(&_prev_period_summary, header);
709
710 _prev_period_summary.set(¤t);
711 }
712
713 void G1RemSet::print_summary_info() {
714 G1RemSetSummary current;
715 current.initialize(this, n_workers());
716
717 print_summary_info(¤t, " Cumulative RS summary");
718 }
719
720 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
721 assert(summary != NULL, "just checking");
722
723 if (header != NULL) {
724 gclog_or_tty->print_cr("%s", header);
725 }
726
727 #if CARD_REPEAT_HISTO
728 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
729 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
730 card_repeat_count.print_on(gclog_or_tty);
731 #endif
732
733 summary->print_on(gclog_or_tty);
734 }
735
736 void G1RemSet::prepare_for_verify() {
737 if (G1HRRSFlushLogBuffersOnVerify &&
738 (VerifyBeforeGC || VerifyAfterGC)
739 && !_g1->full_collection()) {
740 cleanupHRRS();
741 _g1->set_refine_cte_cl_concurrency(false);
742 if (SafepointSynchronize::is_at_safepoint()) {
743 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
744 dcqs.concatenate_logs();
745 }
746
747 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
748 bool use_hot_card_cache = hot_card_cache->use_cache();
749 hot_card_cache->set_use_cache(false);
750
751 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
752 updateRS(&into_cset_dcq, 0);
753 _g1->into_cset_dirty_card_queue_set().clear();
754
755 hot_card_cache->set_use_cache(use_hot_card_cache);
756 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
757 }
758 }