1 /*
2 * Copyright (c) 2001, 2011, 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/g1OopClosures.inline.hpp"
33 #include "gc_implementation/g1/g1RemSet.inline.hpp"
34 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
35 #include "memory/iterator.hpp"
36 #include "oops/oop.inline.hpp"
37 #include "utilities/intHisto.hpp"
38
39 #define CARD_REPEAT_HISTO 0
40
41 #if CARD_REPEAT_HISTO
42 static size_t ct_freq_sz;
43 static jbyte* ct_freq = NULL;
44
45 void init_ct_freq_table(size_t heap_sz_bytes) {
46 if (ct_freq == NULL) {
47 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
48 ct_freq = new jbyte[ct_freq_sz];
49 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
50 }
51 }
52
53 void ct_freq_note_card(size_t index) {
54 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
55 if (ct_freq[index] < 100) { ct_freq[index]++; }
56 }
57
58 static IntHistogram card_repeat_count(10, 10);
59
60 void ct_freq_update_histo_and_reset() {
61 for (size_t j = 0; j < ct_freq_sz; j++) {
62 card_repeat_count.add_entry(ct_freq[j]);
63 ct_freq[j] = 0;
64 }
65
66 }
67 #endif
68
69 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
70 : _g1(g1), _conc_refine_cards(0),
71 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
72 _cg1r(g1->concurrent_g1_refine()),
73 _cset_rs_update_cl(NULL),
74 _cards_scanned(NULL), _total_cards_scanned(0)
75 {
76 _seq_task = new SubTasksDone(NumSeqTasks);
77 guarantee(n_workers() > 0, "There should be some workers");
78 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers());
79 for (uint i = 0; i < n_workers(); i++) {
80 _cset_rs_update_cl[i] = NULL;
81 }
82 }
83
84 G1RemSet::~G1RemSet() {
85 delete _seq_task;
86 for (uint i = 0; i < n_workers(); i++) {
87 assert(_cset_rs_update_cl[i] == NULL, "it should be");
88 }
89 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl);
90 }
91
92 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
93 if (_g1->is_in_g1_reserved(mr.start())) {
94 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
95 if (_start_first == NULL) _start_first = mr.start();
96 }
97 }
98
99 class ScanRSClosure : public HeapRegionClosure {
100 size_t _cards_done, _cards;
101 G1CollectedHeap* _g1h;
102 OopsInHeapRegionClosure* _oc;
103 G1BlockOffsetSharedArray* _bot_shared;
104 CardTableModRefBS *_ct_bs;
105 int _worker_i;
106 int _block_size;
107 bool _try_claimed;
108 public:
109 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
110 _oc(oc),
111 _cards(0),
112 _cards_done(0),
113 _worker_i(worker_i),
114 _try_claimed(false)
115 {
116 _g1h = G1CollectedHeap::heap();
117 _bot_shared = _g1h->bot_shared();
118 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
119 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
120 }
121
122 void set_try_claimed() { _try_claimed = true; }
123
124 void scanCard(size_t index, HeapRegion *r) {
125 DirtyCardToOopClosure* cl =
126 r->new_dcto_closure(_oc,
127 CardTableModRefBS::Precise,
128 HeapRegionDCTOC::IntoCSFilterKind);
129
130 // Set the "from" region in the closure.
131 _oc->set_region(r);
132 HeapWord* card_start = _bot_shared->address_for_index(index);
133 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
134 Space *sp = SharedHeap::heap()->space_containing(card_start);
135 MemRegion sm_region = sp->used_region_at_save_marks();
136 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
137 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
138 // We make the card as "claimed" lazily (so races are possible
139 // but they're benign), which reduces the number of duplicate
140 // scans (the rsets of the regions in the cset can intersect).
141 _ct_bs->set_card_claimed(index);
142 _cards_done++;
143 cl->do_MemRegion(mr);
144 }
145 }
146
147 void printCard(HeapRegion* card_region, size_t card_index,
148 HeapWord* card_start) {
149 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
150 "RS names card %p: "
151 "[" PTR_FORMAT ", " PTR_FORMAT ")",
152 _worker_i,
153 card_region->bottom(), card_region->end(),
154 card_index,
155 card_start, card_start + G1BlockOffsetSharedArray::N_words);
156 }
157
158 bool doHeapRegion(HeapRegion* r) {
159 assert(r->in_collection_set(), "should only be called on elements of CS.");
160 HeapRegionRemSet* hrrs = r->rem_set();
161 if (hrrs->iter_is_complete()) return false; // All done.
162 if (!_try_claimed && !hrrs->claim_iter()) return false;
163 // If we ever free the collection set concurrently, we should also
164 // clear the card table concurrently therefore we won't need to
165 // add regions of the collection set to the dirty cards region.
166 _g1h->push_dirty_cards_region(r);
167 // If we didn't return above, then
168 // _try_claimed || r->claim_iter()
169 // is true: either we're supposed to work on claimed-but-not-complete
170 // regions, or we successfully claimed the region.
171 HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i);
172 hrrs->init_iterator(iter);
173 size_t card_index;
174
175 // We claim cards in block so as to recude the contention. The block size is determined by
176 // the G1RSetScanBlockSize parameter.
177 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
178 for (size_t current_card = 0; iter->has_next(card_index); current_card++) {
179 if (current_card >= jump_to_card + _block_size) {
180 jump_to_card = hrrs->iter_claimed_next(_block_size);
181 }
182 if (current_card < jump_to_card) continue;
183 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
184 #if 0
185 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
186 card_start, card_start + CardTableModRefBS::card_size_in_words);
187 #endif
188
189 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
190 assert(card_region != NULL, "Yielding cards not in the heap?");
191 _cards++;
192
193 if (!card_region->is_on_dirty_cards_region_list()) {
194 _g1h->push_dirty_cards_region(card_region);
195 }
196
197 // If the card is dirty, then we will scan it during updateRS.
198 if (!card_region->in_collection_set() &&
199 !_ct_bs->is_card_dirty(card_index)) {
200 scanCard(card_index, card_region);
201 }
202 }
203 if (!_try_claimed) {
204 hrrs->set_iter_complete();
205 }
206 return false;
207 }
208 size_t cards_done() { return _cards_done;}
209 size_t cards_looked_up() { return _cards;}
210 };
211
212 // We want the parallel threads to start their scanning at
213 // different collection set regions to avoid contention.
214 // If we have:
215 // n collection set regions
216 // p threads
217 // Then thread t will start at region t * floor (n/p)
218
219 HeapRegion* G1RemSet::calculateStartRegion(int worker_i) {
220 HeapRegion* result = _g1p->collection_set();
221 if (ParallelGCThreads > 0) {
222 size_t cs_size = _g1p->collection_set_size();
223 int n_workers = _g1->workers()->total_workers();
224 size_t cs_spans = cs_size / n_workers;
225 size_t ind = cs_spans * worker_i;
226 for (size_t i = 0; i < ind; i++)
227 result = result->next_in_collection_set();
228 }
229 return result;
230 }
231
232 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
233 double rs_time_start = os::elapsedTime();
234 HeapRegion *startRegion = calculateStartRegion(worker_i);
235
236 ScanRSClosure scanRScl(oc, worker_i);
237
238 _g1->collection_set_iterate_from(startRegion, &scanRScl);
239 scanRScl.set_try_claimed();
240 _g1->collection_set_iterate_from(startRegion, &scanRScl);
241
242 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
243
244 assert( _cards_scanned != NULL, "invariant" );
245 _cards_scanned[worker_i] = scanRScl.cards_done();
246
247 _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
248 }
249
250 // Closure used for updating RSets and recording references that
251 // point into the collection set. Only called during an
252 // evacuation pause.
253
254 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
255 G1RemSet* _g1rs;
256 DirtyCardQueue* _into_cset_dcq;
257 public:
258 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
259 DirtyCardQueue* into_cset_dcq) :
260 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
261 {}
262 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
263 // The only time we care about recording cards that
264 // contain references that point into the collection set
265 // is during RSet updating within an evacuation pause.
266 // In this case worker_i should be the id of a GC worker thread.
267 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
268 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
269
270 if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) {
271 // 'card_ptr' contains references that point into the collection
272 // set. We need to record the card in the DCQS
273 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
274 // that's used for that purpose.
275 //
276 // Enqueue the card
277 _into_cset_dcq->enqueue(card_ptr);
278 }
279 return true;
280 }
281 };
282
283 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
284 double start = os::elapsedTime();
285 // Apply the given closure to all remaining log entries.
286 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
287
288 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
289
290 // Now there should be no dirty cards.
291 if (G1RSLogCheckCardTable) {
292 CountNonCleanMemRegionClosure cl(_g1);
293 _ct_bs->mod_card_iterate(&cl);
294 // XXX This isn't true any more: keeping cards of young regions
295 // marked dirty broke it. Need some reasonable fix.
296 guarantee(cl.n() == 0, "Card table should be clean.");
297 }
298
299 _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
300 }
301
302 #ifndef PRODUCT
303 class PrintRSClosure : public HeapRegionClosure {
304 int _count;
305 public:
306 PrintRSClosure() : _count(0) {}
307 bool doHeapRegion(HeapRegion* r) {
308 HeapRegionRemSet* hrrs = r->rem_set();
309 _count += (int) hrrs->occupied();
310 if (hrrs->occupied() == 0) {
311 gclog_or_tty->print("Heap Region [" PTR_FORMAT ", " PTR_FORMAT ") "
312 "has no remset entries\n",
313 r->bottom(), r->end());
314 } else {
315 gclog_or_tty->print("Printing rem set for heap region [" PTR_FORMAT ", " PTR_FORMAT ")\n",
316 r->bottom(), r->end());
317 r->print();
318 hrrs->print();
319 gclog_or_tty->print("\nDone printing rem set\n");
320 }
321 return false;
322 }
323 int occupied() {return _count;}
324 };
325 #endif
326
327 class CountRSSizeClosure: public HeapRegionClosure {
328 size_t _n;
329 size_t _tot;
330 size_t _max;
331 HeapRegion* _max_r;
332 enum {
333 N = 20,
334 MIN = 6
335 };
336 int _histo[N];
337 public:
338 CountRSSizeClosure() : _n(0), _tot(0), _max(0), _max_r(NULL) {
339 for (int i = 0; i < N; i++) _histo[i] = 0;
340 }
341 bool doHeapRegion(HeapRegion* r) {
342 if (!r->continuesHumongous()) {
343 size_t occ = r->rem_set()->occupied();
344 _n++;
345 _tot += occ;
346 if (occ > _max) {
347 _max = occ;
348 _max_r = r;
349 }
350 // Fit it into a histo bin.
351 int s = 1 << MIN;
352 int i = 0;
353 while (occ > (size_t) s && i < (N-1)) {
354 s = s << 1;
355 i++;
356 }
357 _histo[i]++;
358 }
359 return false;
360 }
361 size_t n() { return _n; }
362 size_t tot() { return _tot; }
363 size_t mx() { return _max; }
364 HeapRegion* mxr() { return _max_r; }
365 void print_histo() {
366 int mx = N;
367 while (mx >= 0) {
368 if (_histo[mx-1] > 0) break;
369 mx--;
370 }
371 gclog_or_tty->print_cr("Number of regions with given RS sizes:");
372 gclog_or_tty->print_cr(" <= %8d %8d", 1 << MIN, _histo[0]);
373 for (int i = 1; i < mx-1; i++) {
374 gclog_or_tty->print_cr(" %8d - %8d %8d",
375 (1 << (MIN + i - 1)) + 1,
376 1 << (MIN + i),
377 _histo[i]);
378 }
379 gclog_or_tty->print_cr(" > %8d %8d", (1 << (MIN+mx-2))+1, _histo[mx-1]);
380 }
381 };
382
383 void G1RemSet::cleanupHRRS() {
384 HeapRegionRemSet::cleanup();
385 }
386
387 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
388 int worker_i) {
389 #if CARD_REPEAT_HISTO
390 ct_freq_update_histo_and_reset();
391 #endif
392 if (worker_i == 0) {
393 _cg1r->clear_and_record_card_counts();
394 }
395
396 // Make this into a command-line flag...
397 if (G1RSCountHisto && (ParallelGCThreads == 0 || worker_i == 0)) {
398 CountRSSizeClosure count_cl;
399 _g1->heap_region_iterate(&count_cl);
400 gclog_or_tty->print_cr("Avg of %d RS counts is %f, max is %d, "
401 "max region is " PTR_FORMAT,
402 count_cl.n(), (float)count_cl.tot()/(float)count_cl.n(),
403 count_cl.mx(), count_cl.mxr());
404 count_cl.print_histo();
405 }
406
407 // We cache the value of 'oc' closure into the appropriate slot in the
408 // _cset_rs_update_cl for this worker
409 assert(worker_i < (int)n_workers(), "sanity");
410 _cset_rs_update_cl[worker_i] = oc;
411
412 // A DirtyCardQueue that is used to hold cards containing references
413 // that point into the collection set. This DCQ is associated with a
414 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
415 // circumstances (i.e. the pause successfully completes), these cards
416 // are just discarded (there's no need to update the RSets of regions
417 // that were in the collection set - after the pause these regions
418 // are wholly 'free' of live objects. In the event of an evacuation
419 // failure the cards/buffers in this queue set are:
420 // * passed to the DirtyCardQueueSet that is used to manage deferred
421 // RSet updates, or
422 // * scanned for references that point into the collection set
423 // and the RSet of the corresponding region in the collection set
424 // is updated immediately.
425 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
426
427 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
428
429 // The two flags below were introduced temporarily to serialize
430 // the updating and scanning of remembered sets. There are some
431 // race conditions when these two operations are done in parallel
432 // and they are causing failures. When we resolve said race
433 // conditions, we'll revert back to parallel remembered set
434 // updating and scanning. See CRs 6677707 and 6677708.
435 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
436 updateRS(&into_cset_dcq, worker_i);
437 } else {
438 _g1p->record_update_rs_processed_buffers(worker_i, 0.0);
439 _g1p->record_update_rs_time(worker_i, 0.0);
440 }
441 if (G1UseParallelRSetScanning || (worker_i == 0)) {
442 scanRS(oc, worker_i);
443 } else {
444 _g1p->record_scan_rs_time(worker_i, 0.0);
445 }
446
447 // We now clear the cached values of _cset_rs_update_cl for this worker
448 _cset_rs_update_cl[worker_i] = NULL;
449 }
450
451 void G1RemSet::prepare_for_oops_into_collection_set_do() {
452 #if G1_REM_SET_LOGGING
453 PrintRSClosure cl;
454 _g1->collection_set_iterate(&cl);
455 #endif
456 cleanupHRRS();
457 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
458 _g1->set_refine_cte_cl_concurrency(false);
459 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
460 dcqs.concatenate_logs();
461
462 if (ParallelGCThreads > 0) {
463 _seq_task->set_n_threads((int)n_workers());
464 }
465 guarantee( _cards_scanned == NULL, "invariant" );
466 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers());
467 for (uint i = 0; i < n_workers(); ++i) {
468 _cards_scanned[i] = 0;
469 }
470 _total_cards_scanned = 0;
471 }
472
473
474 class cleanUpIteratorsClosure : public HeapRegionClosure {
475 bool doHeapRegion(HeapRegion *r) {
476 HeapRegionRemSet* hrrs = r->rem_set();
477 hrrs->init_for_par_iteration();
478 return false;
479 }
480 };
481
482 // This closure, applied to a DirtyCardQueueSet, is used to immediately
483 // update the RSets for the regions in the CSet. For each card it iterates
484 // through the oops which coincide with that card. It scans the reference
485 // fields in each oop; when it finds an oop that points into the collection
486 // set, the RSet for the region containing the referenced object is updated.
487 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
488 G1CollectedHeap* _g1;
489 CardTableModRefBS* _ct_bs;
490 public:
491 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
492 CardTableModRefBS* bs):
493 _g1(g1), _ct_bs(bs)
494 { }
495
496 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
497 // Construct the region representing the card.
498 HeapWord* start = _ct_bs->addr_for(card_ptr);
499 // And find the region containing it.
500 HeapRegion* r = _g1->heap_region_containing(start);
501 assert(r != NULL, "unexpected null");
502
503 // Scan oops in the card looking for references into the collection set
504 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
505 MemRegion scanRegion(start, end);
506
507 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
508 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl, NULL /* rp */);
509 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
510
511 // We can pass false as the "filter_young" parameter here as:
512 // * we should be in a STW pause,
513 // * the DCQS to which this closure is applied is used to hold
514 // references that point into the collection set from the prior
515 // RSet updating,
516 // * the post-write barrier shouldn't be logging updates to young
517 // regions (but there is a situation where this can happen - see
518 // the comment in G1RemSet::concurrentRefineOneCard below -
519 // that should not be applicable here), and
520 // * during actual RSet updating, the filtering of cards in young
521 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
522 // employed.
523 // As a result, when this closure is applied to "refs into cset"
524 // DCQS, we shouldn't see any cards in young regions.
525 update_rs_cl.set_region(r);
526 HeapWord* stop_point =
527 r->oops_on_card_seq_iterate_careful(scanRegion,
528 &filter_then_update_rs_cset_oop_cl,
529 false /* filter_young */,
530 NULL /* card_ptr */);
531
532 // Since this is performed in the event of an evacuation failure, we
533 // we shouldn't see a non-null stop point
534 assert(stop_point == NULL, "saw an unallocated region");
535 return true;
536 }
537 };
538
539 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
540 guarantee( _cards_scanned != NULL, "invariant" );
541 _total_cards_scanned = 0;
542 for (uint i = 0; i < n_workers(); ++i)
543 _total_cards_scanned += _cards_scanned[i];
544 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
545 _cards_scanned = NULL;
546 // Cleanup after copy
547 #if G1_REM_SET_LOGGING
548 PrintRSClosure cl;
549 _g1->heap_region_iterate(&cl);
550 #endif
551 _g1->set_refine_cte_cl_concurrency(true);
552 cleanUpIteratorsClosure iterClosure;
553 _g1->collection_set_iterate(&iterClosure);
554 // Set all cards back to clean.
555 _g1->cleanUpCardTable();
556
557 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
558 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
559
560 if (_g1->evacuation_failed()) {
561 // Restore remembered sets for the regions pointing into the collection set.
562
563 if (G1DeferredRSUpdate) {
564 // If deferred RS updates are enabled then we just need to transfer
565 // the completed buffers from (a) the DirtyCardQueueSet used to hold
566 // cards that contain references that point into the collection set
567 // to (b) the DCQS used to hold the deferred RS updates
568 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
569 } else {
570
571 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
572 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
573
574 int n_completed_buffers = 0;
575 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
576 0, 0, true)) {
577 n_completed_buffers++;
578 }
579 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
580 }
581 }
582
583 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
584 // which contain references that point into the collection.
585 _g1->into_cset_dirty_card_queue_set().clear();
586 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
587 "all buffers should be freed");
588 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
589 }
590
591 class ScrubRSClosure: public HeapRegionClosure {
592 G1CollectedHeap* _g1h;
593 BitMap* _region_bm;
594 BitMap* _card_bm;
595 CardTableModRefBS* _ctbs;
596 public:
597 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
598 _g1h(G1CollectedHeap::heap()),
599 _region_bm(region_bm), _card_bm(card_bm),
600 _ctbs(NULL)
601 {
602 ModRefBarrierSet* bs = _g1h->mr_bs();
603 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
604 _ctbs = (CardTableModRefBS*)bs;
605 }
606
607 bool doHeapRegion(HeapRegion* r) {
608 if (!r->continuesHumongous()) {
609 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
610 }
611 return false;
612 }
613 };
614
615 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
616 ScrubRSClosure scrub_cl(region_bm, card_bm);
617 _g1->heap_region_iterate(&scrub_cl);
618 }
619
620 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
621 int worker_num, int claim_val) {
622 ScrubRSClosure scrub_cl(region_bm, card_bm);
623 _g1->heap_region_par_iterate_chunked(&scrub_cl, worker_num, claim_val);
624 }
625
626
627 static IntHistogram out_of_histo(50, 50);
628
629 class TriggerClosure : public OopClosure {
630 bool _trigger;
631 public:
632 TriggerClosure() : _trigger(false) { }
633 bool value() const { return _trigger; }
634 template <class T> void do_oop_nv(T* p) { _trigger = true; }
635 virtual void do_oop(oop* p) { do_oop_nv(p); }
636 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
637 };
638
639 class InvokeIfNotTriggeredClosure: public OopClosure {
640 TriggerClosure* _t;
641 OopClosure* _oc;
642 public:
643 InvokeIfNotTriggeredClosure(TriggerClosure* t, OopClosure* oc):
644 _t(t), _oc(oc) { }
645 template <class T> void do_oop_nv(T* p) {
646 if (!_t->value()) _oc->do_oop(p);
647 }
648 virtual void do_oop(oop* p) { do_oop_nv(p); }
649 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
650 };
651
652 class Mux2Closure : public OopClosure {
653 OopClosure* _c1;
654 OopClosure* _c2;
655 public:
656 Mux2Closure(OopClosure *c1, OopClosure *c2) : _c1(c1), _c2(c2) { }
657 template <class T> void do_oop_nv(T* p) {
658 _c1->do_oop(p); _c2->do_oop(p);
659 }
660 virtual void do_oop(oop* p) { do_oop_nv(p); }
661 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
662 };
663
664 bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
665 bool check_for_refs_into_cset) {
666 // Construct the region representing the card.
667 HeapWord* start = _ct_bs->addr_for(card_ptr);
668 // And find the region containing it.
669 HeapRegion* r = _g1->heap_region_containing(start);
670 assert(r != NULL, "unexpected null");
671
672 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
673 MemRegion dirtyRegion(start, end);
674
675 #if CARD_REPEAT_HISTO
676 init_ct_freq_table(_g1->max_capacity());
677 ct_freq_note_card(_ct_bs->index_for(start));
678 #endif
679
680 assert(!check_for_refs_into_cset || _cset_rs_update_cl[worker_i] != NULL, "sanity");
681 UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
682 _g1->g1_rem_set(),
683 _cset_rs_update_cl[worker_i],
684 check_for_refs_into_cset,
685 worker_i);
686 update_rs_oop_cl.set_from(r);
687
688 TriggerClosure trigger_cl;
689 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl, NULL /* rp */);
690 InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
691 Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
692
693 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
694 (check_for_refs_into_cset ?
695 (OopClosure*)&mux :
696 (OopClosure*)&update_rs_oop_cl));
697
698 // The region for the current card may be a young region. The
699 // current card may have been a card that was evicted from the
700 // card cache. When the card was inserted into the cache, we had
701 // determined that its region was non-young. While in the cache,
702 // the region may have been freed during a cleanup pause, reallocated
703 // and tagged as young.
704 //
705 // We wish to filter out cards for such a region but the current
706 // thread, if we're running concurrently, may "see" the young type
707 // change at any time (so an earlier "is_young" check may pass or
708 // fail arbitrarily). We tell the iteration code to perform this
709 // filtering when it has been determined that there has been an actual
710 // allocation in this region and making it safe to check the young type.
711 bool filter_young = true;
712
713 HeapWord* stop_point =
714 r->oops_on_card_seq_iterate_careful(dirtyRegion,
715 &filter_then_update_rs_oop_cl,
716 filter_young,
717 card_ptr);
718
719 // If stop_point is non-null, then we encountered an unallocated region
720 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
721 // card and re-enqueue: if we put off the card until a GC pause, then the
722 // unallocated portion will be filled in. Alternatively, we might try
723 // the full complexity of the technique used in "regular" precleaning.
724 if (stop_point != NULL) {
725 // The card might have gotten re-dirtied and re-enqueued while we
726 // worked. (In fact, it's pretty likely.)
727 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
728 *card_ptr = CardTableModRefBS::dirty_card_val();
729 MutexLockerEx x(Shared_DirtyCardQ_lock,
730 Mutex::_no_safepoint_check_flag);
731 DirtyCardQueue* sdcq =
732 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
733 sdcq->enqueue(card_ptr);
734 }
735 } else {
736 out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region());
737 _conc_refine_cards++;
738 }
739
740 return trigger_cl.value();
741 }
742
743 bool G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
744 bool check_for_refs_into_cset) {
745 // If the card is no longer dirty, nothing to do.
746 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
747 // No need to return that this card contains refs that point
748 // into the collection set.
749 return false;
750 }
751
752 // Construct the region representing the card.
753 HeapWord* start = _ct_bs->addr_for(card_ptr);
754 // And find the region containing it.
755 HeapRegion* r = _g1->heap_region_containing(start);
756 if (r == NULL) {
757 guarantee(_g1->is_in_permanent(start), "Or else where?");
758 // Again no need to return that this card contains refs that
759 // point into the collection set.
760 return false; // Not in the G1 heap (might be in perm, for example.)
761 }
762 // Why do we have to check here whether a card is on a young region,
763 // given that we dirty young regions and, as a result, the
764 // post-barrier is supposed to filter them out and never to enqueue
765 // them? When we allocate a new region as the "allocation region" we
766 // actually dirty its cards after we release the lock, since card
767 // dirtying while holding the lock was a performance bottleneck. So,
768 // as a result, it is possible for other threads to actually
769 // allocate objects in the region (after the acquire the lock)
770 // before all the cards on the region are dirtied. This is unlikely,
771 // and it doesn't happen often, but it can happen. So, the extra
772 // check below filters out those cards.
773 if (r->is_young()) {
774 return false;
775 }
776 // While we are processing RSet buffers during the collection, we
777 // actually don't want to scan any cards on the collection set,
778 // since we don't want to update remebered sets with entries that
779 // point into the collection set, given that live objects from the
780 // collection set are about to move and such entries will be stale
781 // very soon. This change also deals with a reliability issue which
782 // involves scanning a card in the collection set and coming across
783 // an array that was being chunked and looking malformed. Note,
784 // however, that if evacuation fails, we have to scan any objects
785 // that were not moved and create any missing entries.
786 if (r->in_collection_set()) {
787 return false;
788 }
789
790 // Should we defer processing the card?
791 //
792 // Previously the result from the insert_cache call would be
793 // either card_ptr (implying that card_ptr was currently "cold"),
794 // null (meaning we had inserted the card ptr into the "hot"
795 // cache, which had some headroom), or a "hot" card ptr
796 // extracted from the "hot" cache.
797 //
798 // Now that the _card_counts cache in the ConcurrentG1Refine
799 // instance is an evicting hash table, the result we get back
800 // could be from evicting the card ptr in an already occupied
801 // bucket (in which case we have replaced the card ptr in the
802 // bucket with card_ptr and "defer" is set to false). To avoid
803 // having a data structure (updates to which would need a lock)
804 // to hold these unprocessed dirty cards, we need to immediately
805 // process card_ptr. The actions needed to be taken on return
806 // from cache_insert are summarized in the following table:
807 //
808 // res defer action
809 // --------------------------------------------------------------
810 // null false card evicted from _card_counts & replaced with
811 // card_ptr; evicted ptr added to hot cache.
812 // No need to process res; immediately process card_ptr
813 //
814 // null true card not evicted from _card_counts; card_ptr added
815 // to hot cache.
816 // Nothing to do.
817 //
818 // non-null false card evicted from _card_counts & replaced with
819 // card_ptr; evicted ptr is currently "cold" or
820 // caused an eviction from the hot cache.
821 // Immediately process res; process card_ptr.
822 //
823 // non-null true card not evicted from _card_counts; card_ptr is
824 // currently cold, or caused an eviction from hot
825 // cache.
826 // Immediately process res; no need to process card_ptr.
827
828
829 jbyte* res = card_ptr;
830 bool defer = false;
831
832 // This gets set to true if the card being refined has references
833 // that point into the collection set.
834 bool oops_into_cset = false;
835
836 if (_cg1r->use_cache()) {
837 jbyte* res = _cg1r->cache_insert(card_ptr, &defer);
838 if (res != NULL && (res != card_ptr || defer)) {
839 start = _ct_bs->addr_for(res);
840 r = _g1->heap_region_containing(start);
841 if (r == NULL) {
842 assert(_g1->is_in_permanent(start), "Or else where?");
843 } else {
844 // Checking whether the region we got back from the cache
845 // is young here is inappropriate. The region could have been
846 // freed, reallocated and tagged as young while in the cache.
847 // Hence we could see its young type change at any time.
848 //
849 // Process card pointer we get back from the hot card cache. This
850 // will check whether the region containing the card is young
851 // _after_ checking that the region has been allocated from.
852 oops_into_cset = concurrentRefineOneCard_impl(res, worker_i,
853 false /* check_for_refs_into_cset */);
854 // The above call to concurrentRefineOneCard_impl is only
855 // performed if the hot card cache is enabled. This cache is
856 // disabled during an evacuation pause - which is the only
857 // time when we need know if the card contains references
858 // that point into the collection set. Also when the hot card
859 // cache is enabled, this code is executed by the concurrent
860 // refine threads - rather than the GC worker threads - and
861 // concurrentRefineOneCard_impl will return false.
862 assert(!oops_into_cset, "should not see true here");
863 }
864 }
865 }
866
867 if (!defer) {
868 oops_into_cset =
869 concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset);
870 // We should only be detecting that the card contains references
871 // that point into the collection set if the current thread is
872 // a GC worker thread.
873 assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(),
874 "invalid result at non safepoint");
875 }
876 return oops_into_cset;
877 }
878
879 class HRRSStatsIter: public HeapRegionClosure {
880 size_t _occupied;
881 size_t _total_mem_sz;
882 size_t _max_mem_sz;
883 HeapRegion* _max_mem_sz_region;
884 public:
885 HRRSStatsIter() :
886 _occupied(0),
887 _total_mem_sz(0),
888 _max_mem_sz(0),
889 _max_mem_sz_region(NULL)
890 {}
891
892 bool doHeapRegion(HeapRegion* r) {
893 if (r->continuesHumongous()) return false;
894 size_t mem_sz = r->rem_set()->mem_size();
895 if (mem_sz > _max_mem_sz) {
896 _max_mem_sz = mem_sz;
897 _max_mem_sz_region = r;
898 }
899 _total_mem_sz += mem_sz;
900 size_t occ = r->rem_set()->occupied();
901 _occupied += occ;
902 return false;
903 }
904 size_t total_mem_sz() { return _total_mem_sz; }
905 size_t max_mem_sz() { return _max_mem_sz; }
906 size_t occupied() { return _occupied; }
907 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
908 };
909
910 class PrintRSThreadVTimeClosure : public ThreadClosure {
911 public:
912 virtual void do_thread(Thread *t) {
913 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
914 gclog_or_tty->print(" %5.2f", crt->vtime_accum());
915 }
916 };
917
918 void G1RemSet::print_summary_info() {
919 G1CollectedHeap* g1 = G1CollectedHeap::heap();
920
921 #if CARD_REPEAT_HISTO
922 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
923 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
924 card_repeat_count.print_on(gclog_or_tty);
925 #endif
926
927 if (FILTEROUTOFREGIONCLOSURE_DOHISTOGRAMCOUNT) {
928 gclog_or_tty->print_cr("\nG1 rem-set out-of-region histogram: ");
929 gclog_or_tty->print_cr(" # of CS ptrs --> # of cards with that number.");
930 out_of_histo.print_on(gclog_or_tty);
931 }
932 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
933 _conc_refine_cards);
934 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
935 jint tot_processed_buffers =
936 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
937 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers);
938 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.",
939 dcqs.processed_buffers_rs_thread(),
940 100.0*(float)dcqs.processed_buffers_rs_thread()/
941 (float)tot_processed_buffers);
942 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.",
943 dcqs.processed_buffers_mut(),
944 100.0*(float)dcqs.processed_buffers_mut()/
945 (float)tot_processed_buffers);
946 gclog_or_tty->print_cr(" Conc RS threads times(s)");
947 PrintRSThreadVTimeClosure p;
948 gclog_or_tty->print(" ");
949 g1->concurrent_g1_refine()->threads_do(&p);
950 gclog_or_tty->print_cr("");
951
952 HRRSStatsIter blk;
953 g1->heap_region_iterate(&blk);
954 gclog_or_tty->print_cr(" Total heap region rem set sizes = " SIZE_FORMAT "K."
955 " Max = " SIZE_FORMAT "K.",
956 blk.total_mem_sz()/K, blk.max_mem_sz()/K);
957 gclog_or_tty->print_cr(" Static structures = " SIZE_FORMAT "K,"
958 " free_lists = " SIZE_FORMAT "K.",
959 HeapRegionRemSet::static_mem_size()/K,
960 HeapRegionRemSet::fl_mem_size()/K);
961 gclog_or_tty->print_cr(" %d occupied cards represented.",
962 blk.occupied());
963 gclog_or_tty->print_cr(" Max sz region = [" PTR_FORMAT ", " PTR_FORMAT " )"
964 ", cap = " SIZE_FORMAT "K, occ = " SIZE_FORMAT "K.",
965 blk.max_mem_sz_region()->bottom(), blk.max_mem_sz_region()->end(),
966 (blk.max_mem_sz_region()->rem_set()->mem_size() + K - 1)/K,
967 (blk.max_mem_sz_region()->rem_set()->occupied() + K - 1)/K);
968 gclog_or_tty->print_cr(" Did %d coarsenings.", HeapRegionRemSet::n_coarsenings());
969 }
970
971 void G1RemSet::prepare_for_verify() {
972 if (G1HRRSFlushLogBuffersOnVerify &&
973 (VerifyBeforeGC || VerifyAfterGC)
974 && !_g1->full_collection()) {
975 cleanupHRRS();
976 _g1->set_refine_cte_cl_concurrency(false);
977 if (SafepointSynchronize::is_at_safepoint()) {
978 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
979 dcqs.concatenate_logs();
980 }
981 bool cg1r_use_cache = _cg1r->use_cache();
982 _cg1r->set_use_cache(false);
983 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
984 updateRS(&into_cset_dcq, 0);
985 _g1->into_cset_dirty_card_queue_set().clear();
986 _cg1r->set_use_cache(cg1r_use_cache);
987
988 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
989 }
990 }