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