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/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/heapRegionSeq.inline.hpp"
36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
37 #include "memory/iterator.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "utilities/intHisto.hpp"
40
41 #define CARD_REPEAT_HISTO 0
42
43 #if CARD_REPEAT_HISTO
44 static size_t ct_freq_sz;
45 static jbyte* ct_freq = NULL;
46
47 void init_ct_freq_table(size_t heap_sz_bytes) {
48 if (ct_freq == NULL) {
49 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
50 ct_freq = new jbyte[ct_freq_sz];
51 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
52 }
53 }
54
55 void ct_freq_note_card(size_t index) {
56 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
57 if (ct_freq[index] < 100) { ct_freq[index]++; }
58 }
59
60 static IntHistogram card_repeat_count(10, 10);
61
62 void ct_freq_update_histo_and_reset() {
63 for (size_t j = 0; j < ct_freq_sz; j++) {
64 card_repeat_count.add_entry(ct_freq[j]);
65 ct_freq[j] = 0;
66 }
67
68 }
69 #endif
70
71 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
72 : _g1(g1), _conc_refine_cards(0),
73 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
74 _cg1r(g1->concurrent_g1_refine()),
75 _cset_rs_update_cl(NULL),
76 _cards_scanned(NULL), _total_cards_scanned(0),
77 _prev_period_summary()
78 {
79 _seq_task = new SubTasksDone(NumSeqTasks);
80 guarantee(n_workers() > 0, "There should be some workers");
81 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC);
82 for (uint i = 0; i < n_workers(); i++) {
83 _cset_rs_update_cl[i] = NULL;
84 }
85 if (G1SummarizeRSetStats) {
86 _prev_period_summary.initialize(this);
87 }
88 }
89
90 G1RemSet::~G1RemSet() {
91 delete _seq_task;
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(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC);
96 }
97
98 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
99 if (_g1->is_in_g1_reserved(mr.start())) {
100 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
101 if (_start_first == NULL) _start_first = mr.start();
102 }
103 }
104
105 class ScanRSClosure : public HeapRegionClosure {
106 size_t _cards_done, _cards;
107 G1CollectedHeap* _g1h;
108
109 OopsInHeapRegionClosure* _oc;
110 CodeBlobToOopClosure* _code_root_cl;
111
112 G1BlockOffsetSharedArray* _bot_shared;
113 G1SATBCardTableModRefBS *_ct_bs;
114
115 double _strong_code_root_scan_time_sec;
116 int _worker_i;
117 int _block_size;
118 bool _try_claimed;
119
120 public:
121 ScanRSClosure(OopsInHeapRegionClosure* oc,
122 CodeBlobToOopClosure* code_root_cl,
123 int worker_i) :
124 _oc(oc),
125 _code_root_cl(code_root_cl),
126 _strong_code_root_scan_time_sec(0.0),
127 _cards(0),
128 _cards_done(0),
129 _worker_i(worker_i),
130 _try_claimed(false)
131 {
132 _g1h = G1CollectedHeap::heap();
133 _bot_shared = _g1h->bot_shared();
134 _ct_bs = _g1h->g1_barrier_set();
135 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
136 }
137
138 void set_try_claimed() { _try_claimed = true; }
139
140 void scanCard(size_t index, HeapRegion *r) {
141 // Stack allocate the DirtyCardToOopClosure instance
142 HeapRegionDCTOC cl(_g1h, r, _oc,
143 CardTableModRefBS::Precise,
144 HeapRegionDCTOC::IntoCSFilterKind);
145
146 // Set the "from" region in the closure.
147 _oc->set_region(r);
148 HeapWord* card_start = _bot_shared->address_for_index(index);
149 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
150 Space *sp = SharedHeap::heap()->space_containing(card_start);
151 MemRegion sm_region = sp->used_region_at_save_marks();
152 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
153 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
154 // We make the card as "claimed" lazily (so races are possible
155 // but they're benign), which reduces the number of duplicate
156 // scans (the rsets of the regions in the cset can intersect).
157 _ct_bs->set_card_claimed(index);
158 _cards_done++;
159 cl.do_MemRegion(mr);
160 }
161 }
162
163 void printCard(HeapRegion* card_region, size_t card_index,
164 HeapWord* card_start) {
165 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
166 "RS names card %p: "
167 "[" PTR_FORMAT ", " PTR_FORMAT ")",
168 _worker_i,
169 card_region->bottom(), card_region->end(),
170 card_index,
171 card_start, card_start + G1BlockOffsetSharedArray::N_words);
172 }
173
174 void scan_strong_code_roots(HeapRegion* r) {
175 double scan_start = os::elapsedTime();
176 r->strong_code_roots_do(_code_root_cl);
177 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
178 }
179
180 bool doHeapRegion(HeapRegion* r) {
181 assert(r->in_collection_set(), "should only be called on elements of CS.");
182 HeapRegionRemSet* hrrs = r->rem_set();
183 if (hrrs->iter_is_complete()) return false; // All done.
184 if (!_try_claimed && !hrrs->claim_iter()) return false;
185 // If we ever free the collection set concurrently, we should also
186 // clear the card table concurrently therefore we won't need to
187 // add regions of the collection set to the dirty cards region.
188 _g1h->push_dirty_cards_region(r);
189 // If we didn't return above, then
190 // _try_claimed || r->claim_iter()
191 // is true: either we're supposed to work on claimed-but-not-complete
192 // regions, or we successfully claimed the region.
193
194 HeapRegionRemSetIterator iter(hrrs);
195 size_t card_index;
196
197 // We claim cards in block so as to recude the contention. The block size is determined by
198 // the G1RSetScanBlockSize parameter.
199 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
200 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
201 if (current_card >= jump_to_card + _block_size) {
202 jump_to_card = hrrs->iter_claimed_next(_block_size);
203 }
204 if (current_card < jump_to_card) continue;
205 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
206 #if 0
207 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
208 card_start, card_start + CardTableModRefBS::card_size_in_words);
209 #endif
210
211 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
212 assert(card_region != NULL, "Yielding cards not in the heap?");
213 _cards++;
214
215 if (!card_region->is_on_dirty_cards_region_list()) {
216 _g1h->push_dirty_cards_region(card_region);
217 }
218
219 // If the card is dirty, then we will scan it during updateRS.
220 if (!card_region->in_collection_set() &&
221 !_ct_bs->is_card_dirty(card_index)) {
222 scanCard(card_index, card_region);
223 }
224 }
225 if (!_try_claimed) {
226 // Scan the strong code root list attached to the current region
227 scan_strong_code_roots(r);
228
229 hrrs->set_iter_complete();
230 }
231 return false;
232 }
233
234 double strong_code_root_scan_time_sec() {
235 return _strong_code_root_scan_time_sec;
236 }
237
238 size_t cards_done() { return _cards_done;}
239 size_t cards_looked_up() { return _cards;}
240 };
241
242 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc,
243 CodeBlobToOopClosure* code_root_cl,
244 int worker_i) {
245 double rs_time_start = os::elapsedTime();
246 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
247
248 ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
249
250 _g1->collection_set_iterate_from(startRegion, &scanRScl);
251 scanRScl.set_try_claimed();
252 _g1->collection_set_iterate_from(startRegion, &scanRScl);
253
254 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
255 - scanRScl.strong_code_root_scan_time_sec();
256
257 assert(_cards_scanned != NULL, "invariant");
258 _cards_scanned[worker_i] = scanRScl.cards_done();
259
260 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
261 _g1p->phase_times()->record_strong_code_root_scan_time(worker_i,
262 scanRScl.strong_code_root_scan_time_sec() * 1000.0);
263 }
264
265 // Closure used for updating RSets and recording references that
266 // point into the collection set. Only called during an
267 // evacuation pause.
268
269 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
270 G1RemSet* _g1rs;
271 DirtyCardQueue* _into_cset_dcq;
272 public:
273 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
274 DirtyCardQueue* into_cset_dcq) :
275 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
276 {}
277 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
278 // The only time we care about recording cards that
279 // contain references that point into the collection set
280 // is during RSet updating within an evacuation pause.
281 // In this case worker_i should be the id of a GC worker thread.
282 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
283 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
284
285 if (_g1rs->refine_card(card_ptr, worker_i, true)) {
286 // 'card_ptr' contains references that point into the collection
287 // set. We need to record the card in the DCQS
288 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
289 // that's used for that purpose.
290 //
291 // Enqueue the card
292 _into_cset_dcq->enqueue(card_ptr);
293 }
294 return true;
295 }
296 };
297
298 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
299 double start = os::elapsedTime();
300 // Apply the given closure to all remaining log entries.
301 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
302
303 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
304
305 // Now there should be no dirty cards.
306 if (G1RSLogCheckCardTable) {
307 CountNonCleanMemRegionClosure cl(_g1);
308 _ct_bs->mod_card_iterate(&cl);
309 // XXX This isn't true any more: keeping cards of young regions
310 // marked dirty broke it. Need some reasonable fix.
311 guarantee(cl.n() == 0, "Card table should be clean.");
312 }
313
314 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
315 }
316
317 void G1RemSet::cleanupHRRS() {
318 HeapRegionRemSet::cleanup();
319 }
320
321 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
322 CodeBlobToOopClosure* code_root_cl,
323 int worker_i) {
324 #if CARD_REPEAT_HISTO
325 ct_freq_update_histo_and_reset();
326 #endif
327
328 // We cache the value of 'oc' closure into the appropriate slot in the
329 // _cset_rs_update_cl for this worker
330 assert(worker_i < (int)n_workers(), "sanity");
331 _cset_rs_update_cl[worker_i] = oc;
332
333 // A DirtyCardQueue that is used to hold cards containing references
334 // that point into the collection set. This DCQ is associated with a
335 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
336 // circumstances (i.e. the pause successfully completes), these cards
337 // are just discarded (there's no need to update the RSets of regions
338 // that were in the collection set - after the pause these regions
339 // are wholly 'free' of live objects. In the event of an evacuation
340 // failure the cards/buffers in this queue set are:
341 // * passed to the DirtyCardQueueSet that is used to manage deferred
342 // RSet updates, or
343 // * scanned for references that point into the collection set
344 // and the RSet of the corresponding region in the collection set
345 // is updated immediately.
346 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
347
348 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
349
350 // The two flags below were introduced temporarily to serialize
351 // the updating and scanning of remembered sets. There are some
352 // race conditions when these two operations are done in parallel
353 // and they are causing failures. When we resolve said race
354 // conditions, we'll revert back to parallel remembered set
355 // updating and scanning. See CRs 6677707 and 6677708.
356 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
357 updateRS(&into_cset_dcq, worker_i);
358 } else {
359 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0);
360 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
361 }
362 if (G1UseParallelRSetScanning || (worker_i == 0)) {
363 scanRS(oc, code_root_cl, worker_i);
364 } else {
365 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
366 }
367
368 // We now clear the cached values of _cset_rs_update_cl for this worker
369 _cset_rs_update_cl[worker_i] = NULL;
370 }
371
372 void G1RemSet::prepare_for_oops_into_collection_set_do() {
373 cleanupHRRS();
374 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
375 _g1->set_refine_cte_cl_concurrency(false);
376 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
377 dcqs.concatenate_logs();
378
379 guarantee( _cards_scanned == NULL, "invariant" );
380 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
381 for (uint i = 0; i < n_workers(); ++i) {
382 _cards_scanned[i] = 0;
383 }
384 _total_cards_scanned = 0;
385 }
386
387
388 // This closure, applied to a DirtyCardQueueSet, is used to immediately
389 // update the RSets for the regions in the CSet. For each card it iterates
390 // through the oops which coincide with that card. It scans the reference
391 // fields in each oop; when it finds an oop that points into the collection
392 // set, the RSet for the region containing the referenced object is updated.
393 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
394 G1CollectedHeap* _g1;
395 CardTableModRefBS* _ct_bs;
396 public:
397 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
398 CardTableModRefBS* bs):
399 _g1(g1), _ct_bs(bs)
400 { }
401
402 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
403 // Construct the region representing the card.
404 HeapWord* start = _ct_bs->addr_for(card_ptr);
405 // And find the region containing it.
406 HeapRegion* r = _g1->heap_region_containing(start);
407 assert(r != NULL, "unexpected null");
408
409 // Scan oops in the card looking for references into the collection set
410 // Don't use addr_for(card_ptr + 1) which can ask for
411 // a card beyond the heap. This is not safe without a perm
412 // gen.
413 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
414 MemRegion scanRegion(start, end);
415
416 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
417 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
418 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
419
420 // We can pass false as the "filter_young" parameter here as:
421 // * we should be in a STW pause,
422 // * the DCQS to which this closure is applied is used to hold
423 // references that point into the collection set from the prior
424 // RSet updating,
425 // * the post-write barrier shouldn't be logging updates to young
426 // regions (but there is a situation where this can happen - see
427 // the comment in G1RemSet::refine_card() below -
428 // that should not be applicable here), and
429 // * during actual RSet updating, the filtering of cards in young
430 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
431 // employed.
432 // As a result, when this closure is applied to "refs into cset"
433 // DCQS, we shouldn't see any cards in young regions.
434 update_rs_cl.set_region(r);
435 HeapWord* stop_point =
436 r->oops_on_card_seq_iterate_careful(scanRegion,
437 &filter_then_update_rs_cset_oop_cl,
438 false /* filter_young */,
439 NULL /* card_ptr */);
440
441 // Since this is performed in the event of an evacuation failure, we
442 // we shouldn't see a non-null stop point
443 assert(stop_point == NULL, "saw an unallocated region");
444 return true;
445 }
446 };
447
448 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
449 guarantee( _cards_scanned != NULL, "invariant" );
450 _total_cards_scanned = 0;
451 for (uint i = 0; i < n_workers(); ++i) {
452 _total_cards_scanned += _cards_scanned[i];
453 }
454 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
455 _cards_scanned = NULL;
456 // Cleanup after copy
457 _g1->set_refine_cte_cl_concurrency(true);
458 // Set all cards back to clean.
459 _g1->cleanUpCardTable();
460
461 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
462 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
463
464 if (_g1->evacuation_failed()) {
465 // Restore remembered sets for the regions pointing into the collection set.
466
467 if (G1DeferredRSUpdate) {
468 // If deferred RS updates are enabled then we just need to transfer
469 // the completed buffers from (a) the DirtyCardQueueSet used to hold
470 // cards that contain references that point into the collection set
471 // to (b) the DCQS used to hold the deferred RS updates
472 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
473 } else {
474
475 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
476 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
477
478 int n_completed_buffers = 0;
479 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
480 0, 0, true)) {
481 n_completed_buffers++;
482 }
483 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
484 }
485 }
486
487 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
488 // which contain references that point into the collection.
489 _g1->into_cset_dirty_card_queue_set().clear();
490 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
491 "all buffers should be freed");
492 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
493 }
494
495 class ScrubRSClosure: public HeapRegionClosure {
496 G1CollectedHeap* _g1h;
497 BitMap* _region_bm;
498 BitMap* _card_bm;
499 CardTableModRefBS* _ctbs;
500 public:
501 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
502 _g1h(G1CollectedHeap::heap()),
503 _region_bm(region_bm), _card_bm(card_bm),
504 _ctbs(_g1h->g1_barrier_set()) {}
505
506 bool doHeapRegion(HeapRegion* r) {
507 if (!r->continuesHumongous()) {
508 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
509 }
510 return false;
511 }
512 };
513
514 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
515 ScrubRSClosure scrub_cl(region_bm, card_bm);
516 _g1->heap_region_iterate(&scrub_cl);
517 }
518
519 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
520 uint worker_num, int claim_val) {
521 ScrubRSClosure scrub_cl(region_bm, card_bm);
522 _g1->heap_region_par_iterate_chunked(&scrub_cl,
523 worker_num,
524 n_workers(),
525 claim_val);
526 }
527
528 G1TriggerClosure::G1TriggerClosure() :
529 _triggered(false) { }
530
531 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
532 OopClosure* oop_cl) :
533 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
534
535 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
536 _c1(c1), _c2(c2) { }
537
538 G1UpdateRSOrPushRefOopClosure::
539 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
540 G1RemSet* rs,
541 OopsInHeapRegionClosure* push_ref_cl,
542 bool record_refs_into_cset,
543 int worker_i) :
544 _g1(g1h), _g1_rem_set(rs), _from(NULL),
545 _record_refs_into_cset(record_refs_into_cset),
546 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
547
548 // Returns true if the given card contains references that point
549 // into the collection set, if we're checking for such references;
550 // false otherwise.
551
552 bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i,
553 bool check_for_refs_into_cset) {
554
555 // If the card is no longer dirty, nothing to do.
556 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
557 // No need to return that this card contains refs that point
558 // into the collection set.
559 return false;
560 }
561
562 // Construct the region representing the card.
563 HeapWord* start = _ct_bs->addr_for(card_ptr);
564 // And find the region containing it.
565 HeapRegion* r = _g1->heap_region_containing(start);
566 if (r == NULL) {
567 // Again no need to return that this card contains refs that
568 // point into the collection set.
569 return false; // Not in the G1 heap (might be in perm, for example.)
570 }
571
572 // Why do we have to check here whether a card is on a young region,
573 // given that we dirty young regions and, as a result, the
574 // post-barrier is supposed to filter them out and never to enqueue
575 // them? When we allocate a new region as the "allocation region" we
576 // actually dirty its cards after we release the lock, since card
577 // dirtying while holding the lock was a performance bottleneck. So,
578 // as a result, it is possible for other threads to actually
579 // allocate objects in the region (after the acquire the lock)
580 // before all the cards on the region are dirtied. This is unlikely,
581 // and it doesn't happen often, but it can happen. So, the extra
582 // check below filters out those cards.
583 if (r->is_young()) {
584 return false;
585 }
586
587 // While we are processing RSet buffers during the collection, we
588 // actually don't want to scan any cards on the collection set,
589 // since we don't want to update remebered sets with entries that
590 // point into the collection set, given that live objects from the
591 // collection set are about to move and such entries will be stale
592 // very soon. This change also deals with a reliability issue which
593 // involves scanning a card in the collection set and coming across
594 // an array that was being chunked and looking malformed. Note,
595 // however, that if evacuation fails, we have to scan any objects
596 // that were not moved and create any missing entries.
597 if (r->in_collection_set()) {
598 return false;
599 }
600
601 // The result from the hot card cache insert call is either:
602 // * pointer to the current card
603 // (implying that the current card is not 'hot'),
604 // * null
605 // (meaning we had inserted the card ptr into the "hot" card cache,
606 // which had some headroom),
607 // * a pointer to a "hot" card that was evicted from the "hot" cache.
608 //
609
610 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
611 if (hot_card_cache->use_cache()) {
612 assert(!check_for_refs_into_cset, "sanity");
613 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
614
615 card_ptr = hot_card_cache->insert(card_ptr);
616 if (card_ptr == NULL) {
617 // There was no eviction. Nothing to do.
618 return false;
619 }
620
621 start = _ct_bs->addr_for(card_ptr);
622 r = _g1->heap_region_containing(start);
623 if (r == NULL) {
624 // Not in the G1 heap
625 return false;
626 }
627
628 // Checking whether the region we got back from the cache
629 // is young here is inappropriate. The region could have been
630 // freed, reallocated and tagged as young while in the cache.
631 // Hence we could see its young type change at any time.
632 }
633
634 // Don't use addr_for(card_ptr + 1) which can ask for
635 // a card beyond the heap. This is not safe without a perm
636 // gen at the upper end of the heap.
637 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
638 MemRegion dirtyRegion(start, end);
639
640 #if CARD_REPEAT_HISTO
641 init_ct_freq_table(_g1->max_capacity());
642 ct_freq_note_card(_ct_bs->index_for(start));
643 #endif
644
645 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
646 if (check_for_refs_into_cset) {
647 // ConcurrentG1RefineThreads have worker numbers larger than what
648 // _cset_rs_update_cl[] is set up to handle. But those threads should
649 // only be active outside of a collection which means that when they
650 // reach here they should have check_for_refs_into_cset == false.
651 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
652 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
653 }
654 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
655 _g1->g1_rem_set(),
656 oops_in_heap_closure,
657 check_for_refs_into_cset,
658 worker_i);
659 update_rs_oop_cl.set_from(r);
660
661 G1TriggerClosure trigger_cl;
662 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
663 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
664 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
665
666 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
667 (check_for_refs_into_cset ?
668 (OopClosure*)&mux :
669 (OopClosure*)&update_rs_oop_cl));
670
671 // The region for the current card may be a young region. The
672 // current card may have been a card that was evicted from the
673 // card cache. When the card was inserted into the cache, we had
674 // determined that its region was non-young. While in the cache,
675 // the region may have been freed during a cleanup pause, reallocated
676 // and tagged as young.
677 //
678 // We wish to filter out cards for such a region but the current
679 // thread, if we're running concurrently, may "see" the young type
680 // change at any time (so an earlier "is_young" check may pass or
681 // fail arbitrarily). We tell the iteration code to perform this
682 // filtering when it has been determined that there has been an actual
683 // allocation in this region and making it safe to check the young type.
684 bool filter_young = true;
685
686 HeapWord* stop_point =
687 r->oops_on_card_seq_iterate_careful(dirtyRegion,
688 &filter_then_update_rs_oop_cl,
689 filter_young,
690 card_ptr);
691
692 // If stop_point is non-null, then we encountered an unallocated region
693 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
694 // card and re-enqueue: if we put off the card until a GC pause, then the
695 // unallocated portion will be filled in. Alternatively, we might try
696 // the full complexity of the technique used in "regular" precleaning.
697 if (stop_point != NULL) {
698 // The card might have gotten re-dirtied and re-enqueued while we
699 // worked. (In fact, it's pretty likely.)
700 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
701 *card_ptr = CardTableModRefBS::dirty_card_val();
702 MutexLockerEx x(Shared_DirtyCardQ_lock,
703 Mutex::_no_safepoint_check_flag);
704 DirtyCardQueue* sdcq =
705 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
706 sdcq->enqueue(card_ptr);
707 }
708 } else {
709 _conc_refine_cards++;
710 }
711
712 // This gets set to true if the card being refined has
713 // references that point into the collection set.
714 bool has_refs_into_cset = trigger_cl.triggered();
715
716 // We should only be detecting that the card contains references
717 // that point into the collection set if the current thread is
718 // a GC worker thread.
719 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
720 "invalid result at non safepoint");
721
722 return has_refs_into_cset;
723 }
724
725 void G1RemSet::print_periodic_summary_info(const char* header) {
726 G1RemSetSummary current;
727 current.initialize(this);
728
729 _prev_period_summary.subtract_from(¤t);
730 print_summary_info(&_prev_period_summary, header);
731
732 _prev_period_summary.set(¤t);
733 }
734
735 void G1RemSet::print_summary_info() {
736 G1RemSetSummary current;
737 current.initialize(this);
738
739 print_summary_info(¤t, " Cumulative RS summary");
740 }
741
742 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
743 assert(summary != NULL, "just checking");
744
745 if (header != NULL) {
746 gclog_or_tty->print_cr("%s", header);
747 }
748
749 #if CARD_REPEAT_HISTO
750 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
751 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
752 card_repeat_count.print_on(gclog_or_tty);
753 #endif
754
755 summary->print_on(gclog_or_tty);
756 }
757
758 void G1RemSet::prepare_for_verify() {
759 if (G1HRRSFlushLogBuffersOnVerify &&
760 (VerifyBeforeGC || VerifyAfterGC)
761 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
762 cleanupHRRS();
763 _g1->set_refine_cte_cl_concurrency(false);
764 if (SafepointSynchronize::is_at_safepoint()) {
765 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
766 dcqs.concatenate_logs();
767 }
768
769 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
770 bool use_hot_card_cache = hot_card_cache->use_cache();
771 hot_card_cache->set_use_cache(false);
772
773 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
774 updateRS(&into_cset_dcq, 0);
775 _g1->into_cset_dirty_card_queue_set().clear();
776
777 hot_card_cache->set_use_cache(use_hot_card_cache);
778 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
779 }
780 }