1 /*
2 * Copyright (c) 2001, 2015, 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/g1/concurrentG1Refine.hpp"
27 #include "gc/g1/concurrentG1RefineThread.hpp"
28 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectorPolicy.hpp"
31 #include "gc/g1/g1GCPhaseTimes.hpp"
32 #include "gc/g1/g1HotCardCache.hpp"
33 #include "gc/g1/g1OopClosures.inline.hpp"
34 #include "gc/g1/g1RemSet.inline.hpp"
35 #include "gc/g1/heapRegionManager.inline.hpp"
36 #include "gc/g1/heapRegionRemSet.hpp"
37 #include "memory/iterator.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "utilities/globalDefinitions.hpp"
40 #include "utilities/intHisto.hpp"
41 #include "utilities/stack.inline.hpp"
42
43 #define CARD_REPEAT_HISTO 0
44
45 #if CARD_REPEAT_HISTO
46 static size_t ct_freq_sz;
47 static jbyte* ct_freq = NULL;
48
49 void init_ct_freq_table(size_t heap_sz_bytes) {
50 if (ct_freq == NULL) {
51 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
52 ct_freq = new jbyte[ct_freq_sz];
53 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
54 }
55 }
56
57 void ct_freq_note_card(size_t index) {
58 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
59 if (ct_freq[index] < 100) { ct_freq[index]++; }
60 }
61
62 static IntHistogram card_repeat_count(10, 10);
63
64 void ct_freq_update_histo_and_reset() {
65 for (size_t j = 0; j < ct_freq_sz; j++) {
66 card_repeat_count.add_entry(ct_freq[j]);
67 ct_freq[j] = 0;
68 }
69
70 }
71 #endif
72
73 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
74 : _g1(g1), _conc_refine_cards(0),
75 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
76 _cg1r(g1->concurrent_g1_refine()),
77 _cset_rs_update_cl(NULL),
78 _cards_scanned(NULL), _total_cards_scanned(0),
79 _prev_period_summary()
80 {
81 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, 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 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(G1ParPushHeapRSClosure*, _cset_rs_update_cl);
95 }
96
97 class ScanRSClosure : public HeapRegionClosure {
98 size_t _cards_done, _cards;
99 G1CollectedHeap* _g1h;
100
101 G1ParPushHeapRSClosure* _oc;
102 CodeBlobClosure* _code_root_cl;
103
104 G1BlockOffsetSharedArray* _bot_shared;
105 G1SATBCardTableModRefBS *_ct_bs;
106
107 double _strong_code_root_scan_time_sec;
108 uint _worker_i;
109 size_t _block_size;
110 bool _try_claimed;
111
112 public:
113 ScanRSClosure(G1ParPushHeapRSClosure* oc,
114 CodeBlobClosure* code_root_cl,
115 uint worker_i) :
116 _oc(oc),
117 _code_root_cl(code_root_cl),
118 _strong_code_root_scan_time_sec(0.0),
119 _cards(0),
120 _cards_done(0),
121 _worker_i(worker_i),
122 _try_claimed(false)
123 {
124 _g1h = G1CollectedHeap::heap();
125 _bot_shared = _g1h->bot_shared();
126 _ct_bs = _g1h->g1_barrier_set();
127 _block_size = MAX2<size_t>(G1RSetScanBlockSize, 1);
128 }
129
130 void set_try_claimed() { _try_claimed = true; }
131
132 void scanCard(size_t index, HeapRegion *r) {
133 // Stack allocate the DirtyCardToOopClosure instance
134 HeapRegionDCTOC cl(_g1h, r, _oc,
135 CardTableModRefBS::Precise);
136
137 // Set the "from" region in the closure.
138 _oc->set_region(r);
139 MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
140 MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
141 MemRegion mr = pre_gc_allocated.intersection(card_region);
142 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
143 // We make the card as "claimed" lazily (so races are possible
144 // but they're benign), which reduces the number of duplicate
145 // scans (the rsets of the regions in the cset can intersect).
146 _ct_bs->set_card_claimed(index);
147 _cards_done++;
148 cl.do_MemRegion(mr);
149 }
150 }
151
152 void printCard(HeapRegion* card_region, size_t card_index,
153 HeapWord* card_start) {
154 gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") "
155 "RS names card " SIZE_FORMAT_HEX ": "
156 "[" PTR_FORMAT ", " PTR_FORMAT ")",
157 _worker_i,
158 p2i(card_region->bottom()), p2i(card_region->end()),
159 card_index,
160 p2i(card_start), p2i(card_start + G1BlockOffsetSharedArray::N_words));
161 }
162
163 void scan_strong_code_roots(HeapRegion* r) {
164 double scan_start = os::elapsedTime();
165 r->strong_code_roots_do(_code_root_cl);
166 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
167 }
168
169 bool doHeapRegion(HeapRegion* r) {
170 assert(r->in_collection_set(), "should only be called on elements of CS.");
171 HeapRegionRemSet* hrrs = r->rem_set();
172 if (hrrs->iter_is_complete()) return false; // All done.
173 if (!_try_claimed && !hrrs->claim_iter()) return false;
174 // If we ever free the collection set concurrently, we should also
175 // clear the card table concurrently therefore we won't need to
176 // add regions of the collection set to the dirty cards region.
177 _g1h->push_dirty_cards_region(r);
178 // If we didn't return above, then
179 // _try_claimed || r->claim_iter()
180 // is true: either we're supposed to work on claimed-but-not-complete
181 // regions, or we successfully claimed the region.
182
183 HeapRegionRemSetIterator iter(hrrs);
184 size_t card_index;
185
186 // We claim cards in block so as to reduce the contention. The block size is determined by
187 // the G1RSetScanBlockSize parameter.
188 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
189 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
190 if (current_card >= jump_to_card + _block_size) {
191 jump_to_card = hrrs->iter_claimed_next(_block_size);
192 }
193 if (current_card < jump_to_card) continue;
194 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
195 #if 0
196 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
197 card_start, card_start + CardTableModRefBS::card_size_in_words);
198 #endif
199
200 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
201 _cards++;
202
203 if (!card_region->is_on_dirty_cards_region_list()) {
204 _g1h->push_dirty_cards_region(card_region);
205 }
206
207 // If the card is dirty, then we will scan it during updateRS.
208 if (!card_region->in_collection_set() &&
209 !_ct_bs->is_card_dirty(card_index)) {
210 scanCard(card_index, card_region);
211 }
212 }
213 if (!_try_claimed) {
214 // Scan the strong code root list attached to the current region
215 scan_strong_code_roots(r);
216
217 hrrs->set_iter_complete();
218 }
219 return false;
220 }
221
222 double strong_code_root_scan_time_sec() {
223 return _strong_code_root_scan_time_sec;
224 }
225
226 size_t cards_done() { return _cards_done;}
227 size_t cards_looked_up() { return _cards;}
228 };
229
230 bool G1RemSet::clean_card(jbyte* &card_ptr,
231 uint worker_i,
232 MemRegion &dirty_region) {
233 assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
234 err_msg("Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
235 p2i(card_ptr),
236 _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
237 p2i(_ct_bs->addr_for(card_ptr)),
238 _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
239
240 // If the card is no longer dirty, nothing to do.
241 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
242 // No need to return that this card contains refs that point
243 // into the collection set.
244 return false;
245 }
246
247 // Construct the region representing the card.
248 HeapWord* start = _ct_bs->addr_for(card_ptr);
249 // And find the region containing it.
250 HeapRegion* r = _g1->heap_region_containing(start);
251
252 // Why do we have to check here whether a card is on a young region,
253 // given that we dirty young regions and, as a result, the
254 // post-barrier is supposed to filter them out and never to enqueue
255 // them? When we allocate a new region as the "allocation region" we
256 // actually dirty its cards after we release the lock, since card
257 // dirtying while holding the lock was a performance bottleneck. So,
258 // as a result, it is possible for other threads to actually
259 // allocate objects in the region (after the acquire the lock)
260 // before all the cards on the region are dirtied. This is unlikely,
261 // and it doesn't happen often, but it can happen. So, the extra
262 // check below filters out those cards.
263 if (r->is_young()) {
264 return false;
265 }
266
267 // While we are processing RSet buffers during the collection, we
268 // actually don't want to scan any cards on the collection set,
269 // since we don't want to update remembered sets with entries that
270 // point into the collection set, given that live objects from the
271 // collection set are about to move and such entries will be stale
272 // very soon. This change also deals with a reliability issue which
273 // involves scanning a card in the collection set and coming across
274 // an array that was being chunked and looking malformed. Note,
275 // however, that if evacuation fails, we have to scan any objects
276 // that were not moved and create any missing entries.
277 if (r->in_collection_set()) {
278 return false;
279 }
280
281 // The result from the hot card cache insert call is either:
282 // * pointer to the current card
283 // (implying that the current card is not 'hot'),
284 // * null
285 // (meaning we had inserted the card ptr into the "hot" card cache,
286 // which had some headroom),
287 // * a pointer to a "hot" card that was evicted from the "hot" cache.
288 //
289
290 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
291 if (hot_card_cache->use_cache()) {
292 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
293
294 card_ptr = hot_card_cache->insert(card_ptr);
295 if (card_ptr == NULL) {
296 // There was no eviction. Nothing to do.
297 return false;
298 }
299
300 start = _ct_bs->addr_for(card_ptr);
301 r = _g1->heap_region_containing(start);
302
303 // Checking whether the region we got back from the cache
304 // is young here is inappropriate. The region could have been
305 // freed, reallocated and tagged as young while in the cache.
306 // Hence we could see its young type change at any time.
307 }
308
309 // Don't use addr_for(card_ptr + 1) which can ask for
310 // a card beyond the heap. This is not safe without a perm
311 // gen at the upper end of the heap.
312 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
313 dirty_region = MemRegion(start, end);
314
315 #if CARD_REPEAT_HISTO
316 init_ct_freq_table(_g1->max_capacity());
317 ct_freq_note_card(_ct_bs->index_for(start));
318 #endif
319
320 return r->clean_card(dirty_region, /*filter young*/ true, card_ptr);
321 }
322
323 bool G1RemSet::refine_card_buffered(jbyte* card_ptr,
324 uint worker_i,
325 bool check_for_refs_into_cset,
326 MemRegion dirty_region) {
327 // And find the region containing it.
328 HeapRegion* r = _g1->heap_region_containing(dirty_region.start());
329
330 G1ParPushHeapRSClosure* oops_in_heap_closure = NULL;
331 if (check_for_refs_into_cset) {
332 // ConcurrentG1RefineThreads have worker numbers larger than what
333 // _cset_rs_update_cl[] is set up to handle. But those threads should
334 // only be active outside of a collection which means that when they
335 // reach here they should have check_for_refs_into_cset == false.
336 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
337 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
338 }
339
340 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
341 _g1->g1_rem_set(),
342 oops_in_heap_closure,
343 check_for_refs_into_cset,
344 worker_i);
345 update_rs_oop_cl.set_from(r);
346
347 G1TriggerClosure trigger_cl;
348 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
349 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
350 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
351
352 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
353 (check_for_refs_into_cset ?
354 (OopClosure*)&mux :
355 (OopClosure*)&update_rs_oop_cl));
356
357 // The region for the current card may be a young region. The
358 // current card may have been a card that was evicted from the
359 // card cache. When the card was inserted into the cache, we had
360 // determined that its region was non-young. While in the cache,
361 // the region may have been freed during a cleanup pause, reallocated
362 // and tagged as young.
363 //
364 // We wish to filter out cards for such a region but the current
365 // thread, if we're running concurrently, may "see" the young type
366 // change at any time (so an earlier "is_young" check may pass or
367 // fail arbitrarily). We tell the iteration code to perform this
368 // filtering when it has been determined that there has been an actual
369 // allocation in this region and making it safe to check the young type.
370 bool filter_young = true;
371
372 HeapWord* stop_point =
373 r->process_oops_on_card(dirty_region, &filter_then_update_rs_oop_cl, card_ptr);
374
375 // If stop_point is non-null, then we encountered an unallocated region
376 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
377 // card and re-enqueue: if we put off the card until a GC pause, then the
378 // unallocated portion will be filled in. Alternatively, we might try
379 // the full complexity of the technique used in "regular" precleaning.
380 if (stop_point != NULL) {
381 // The card might have gotten re-dirtied and re-enqueued while we
382 // worked. (In fact, it's pretty likely.)
383 card_ptr = G1CollectedHeap::heap()->g1_barrier_set()->byte_for(stop_point);
384
385 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
386 *card_ptr = CardTableModRefBS::dirty_card_val();
387 MutexLockerEx x(Shared_DirtyCardQ_lock,
388 Mutex::_no_safepoint_check_flag);
389 DirtyCardQueue* sdcq =
390 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
391 sdcq->enqueue(card_ptr);
392 }
393 } else {
394 _conc_refine_cards++;
395 }
396
397 // This gets set to true if the card being refined has
398 // references that point into the collection set.
399 bool has_refs_into_cset = trigger_cl.triggered();
400
401 // We should only be detecting that the card contains references
402 // that point into the collection set if the current thread is
403 // a GC worker thread.
404 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
405 "invalid result at non safepoint");
406
407 return has_refs_into_cset;
408 }
409
410 void G1RemSet::scanRS(G1ParPushHeapRSClosure* oc,
411 CodeBlobClosure* code_root_cl,
412 uint worker_i) {
413 double rs_time_start = os::elapsedTime();
414 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
415
416 ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
417
418 _g1->collection_set_iterate_from(startRegion, &scanRScl);
419 scanRScl.set_try_claimed();
420 _g1->collection_set_iterate_from(startRegion, &scanRScl);
421
422 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
423 - scanRScl.strong_code_root_scan_time_sec();
424
425 assert(_cards_scanned != NULL, "invariant");
426 _cards_scanned[worker_i] = scanRScl.cards_done();
427
428 _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
429 _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, scanRScl.strong_code_root_scan_time_sec());
430 }
431
432 // Closure used for updating RSets and recording references that
433 // point into the collection set. Only called during an
434 // evacuation pause.
435
436 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
437 G1RemSet* _g1rs;
438 DirtyCardQueue* _into_cset_dcq;
439 public:
440 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
441 DirtyCardQueue* into_cset_dcq) :
442 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
443 {}
444 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
445 // The only time we care about recording cards that
446 // contain references that point into the collection set
447 // is during RSet updating within an evacuation pause.
448 // In this case worker_i should be the id of a GC worker thread.
449 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
450 assert(worker_i < ParallelGCThreads, "should be a GC worker");
451
452 if (_g1rs->refine_card(card_ptr, worker_i, true)) {
453 // 'card_ptr' contains references that point into the collection
454 // set. We need to record the card in the DCQS
455 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
456 // that's used for that purpose.
457 //
458 // Enqueue the card
459 _into_cset_dcq->enqueue(card_ptr);
460 }
461 return true;
462 }
463 };
464
465 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
466 G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);
467 // Apply the given closure to all remaining log entries.
468 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
469
470 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
471 }
472
473 void G1RemSet::cleanupHRRS() {
474 HeapRegionRemSet::cleanup();
475 }
476
477 void G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* oc,
478 CodeBlobClosure* code_root_cl,
479 uint worker_i) {
480 #if CARD_REPEAT_HISTO
481 ct_freq_update_histo_and_reset();
482 #endif
483
484 // We cache the value of 'oc' closure into the appropriate slot in the
485 // _cset_rs_update_cl for this worker
486 assert(worker_i < n_workers(), "sanity");
487 _cset_rs_update_cl[worker_i] = oc;
488
489 // A DirtyCardQueue that is used to hold cards containing references
490 // that point into the collection set. This DCQ is associated with a
491 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
492 // circumstances (i.e. the pause successfully completes), these cards
493 // are just discarded (there's no need to update the RSets of regions
494 // that were in the collection set - after the pause these regions
495 // are wholly 'free' of live objects. In the event of an evacuation
496 // failure the cards/buffers in this queue set are passed to the
497 // DirtyCardQueueSet that is used to manage RSet updates
498 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
499
500 updateRS(&into_cset_dcq, worker_i);
501 scanRS(oc, code_root_cl, worker_i);
502
503 // We now clear the cached values of _cset_rs_update_cl for this worker
504 _cset_rs_update_cl[worker_i] = NULL;
505 }
506
507 void G1RemSet::prepare_for_oops_into_collection_set_do() {
508 cleanupHRRS();
509 _g1->set_refine_cte_cl_concurrency(false);
510 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
511 dcqs.concatenate_logs();
512
513 guarantee( _cards_scanned == NULL, "invariant" );
514 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
515 for (uint i = 0; i < n_workers(); ++i) {
516 _cards_scanned[i] = 0;
517 }
518 _total_cards_scanned = 0;
519 }
520
521 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
522 guarantee( _cards_scanned != NULL, "invariant" );
523 _total_cards_scanned = 0;
524 for (uint i = 0; i < n_workers(); ++i) {
525 _total_cards_scanned += _cards_scanned[i];
526 }
527 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
528 _cards_scanned = NULL;
529 // Cleanup after copy
530 _g1->set_refine_cte_cl_concurrency(true);
531 // Set all cards back to clean.
532 _g1->cleanUpCardTable();
533
534 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
535 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
536
537 if (_g1->evacuation_failed()) {
538 double restore_remembered_set_start = os::elapsedTime();
539
540 // Restore remembered sets for the regions pointing into the collection set.
541 // We just need to transfer the completed buffers from the DirtyCardQueueSet
542 // used to hold cards that contain references that point into the collection set
543 // to the DCQS used to hold the deferred RS updates.
544 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
545 _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
546 }
547
548 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
549 // which contain references that point into the collection.
550 _g1->into_cset_dirty_card_queue_set().clear();
551 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
552 "all buffers should be freed");
553 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
554 }
555
556 class ScrubRSClosure: public HeapRegionClosure {
557 G1CollectedHeap* _g1h;
558 BitMap* _region_bm;
559 BitMap* _card_bm;
560 CardTableModRefBS* _ctbs;
561 public:
562 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
563 _g1h(G1CollectedHeap::heap()),
564 _region_bm(region_bm), _card_bm(card_bm),
565 _ctbs(_g1h->g1_barrier_set()) {}
566
567 bool doHeapRegion(HeapRegion* r) {
568 if (!r->is_continues_humongous()) {
569 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
570 }
571 return false;
572 }
573 };
574
575 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {
576 ScrubRSClosure scrub_cl(region_bm, card_bm);
577 _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
578 }
579
580 G1TriggerClosure::G1TriggerClosure() :
581 _triggered(false) { }
582
583 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
584 OopClosure* oop_cl) :
585 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
586
587 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
588 _c1(c1), _c2(c2) { }
589
590 G1UpdateRSOrPushRefOopClosure::
591 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
592 G1RemSet* rs,
593 G1ParPushHeapRSClosure* push_ref_cl,
594 bool record_refs_into_cset,
595 uint worker_i) :
596 _g1(g1h), _g1_rem_set(rs), _from(NULL),
597 _record_refs_into_cset(record_refs_into_cset),
598 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
599
600 // Returns true if the given card contains references that point
601 // into the collection set, if we're checking for such references;
602 // false otherwise.
603
604 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
605 bool check_for_refs_into_cset) {
606 assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
607 err_msg("Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
608 p2i(card_ptr),
609 _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
610 p2i(_ct_bs->addr_for(card_ptr)),
611 _g1->addr_to_region(_ct_bs->addr_for(card_ptr))));
612
613 // If the card is no longer dirty, nothing to do.
614 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
615 // No need to return that this card contains refs that point
616 // into the collection set.
617 return false;
618 }
619
620 // Construct the region representing the card.
621 HeapWord* start = _ct_bs->addr_for(card_ptr);
622 // And find the region containing it.
623 HeapRegion* r = _g1->heap_region_containing(start);
624
625 // Why do we have to check here whether a card is on a young region,
626 // given that we dirty young regions and, as a result, the
627 // post-barrier is supposed to filter them out and never to enqueue
628 // them? When we allocate a new region as the "allocation region" we
629 // actually dirty its cards after we release the lock, since card
630 // dirtying while holding the lock was a performance bottleneck. So,
631 // as a result, it is possible for other threads to actually
632 // allocate objects in the region (after the acquire the lock)
633 // before all the cards on the region are dirtied. This is unlikely,
634 // and it doesn't happen often, but it can happen. So, the extra
635 // check below filters out those cards.
636 if (r->is_young()) {
637 return false;
638 }
639
640 // While we are processing RSet buffers during the collection, we
641 // actually don't want to scan any cards on the collection set,
642 // since we don't want to update remembered sets with entries that
643 // point into the collection set, given that live objects from the
644 // collection set are about to move and such entries will be stale
645 // very soon. This change also deals with a reliability issue which
646 // involves scanning a card in the collection set and coming across
647 // an array that was being chunked and looking malformed. Note,
648 // however, that if evacuation fails, we have to scan any objects
649 // that were not moved and create any missing entries.
650 if (r->in_collection_set()) {
651 return false;
652 }
653
654 // The result from the hot card cache insert call is either:
655 // * pointer to the current card
656 // (implying that the current card is not 'hot'),
657 // * null
658 // (meaning we had inserted the card ptr into the "hot" card cache,
659 // which had some headroom),
660 // * a pointer to a "hot" card that was evicted from the "hot" cache.
661 //
662
663 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
664 if (hot_card_cache->use_cache()) {
665 assert(!check_for_refs_into_cset, "sanity");
666 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
667
668 card_ptr = hot_card_cache->insert(card_ptr);
669 if (card_ptr == NULL) {
670 // There was no eviction. Nothing to do.
671 return false;
672 }
673
674 start = _ct_bs->addr_for(card_ptr);
675 r = _g1->heap_region_containing(start);
676
677 // Checking whether the region we got back from the cache
678 // is young here is inappropriate. The region could have been
679 // freed, reallocated and tagged as young while in the cache.
680 // Hence we could see its young type change at any time.
681 }
682
683 // Don't use addr_for(card_ptr + 1) which can ask for
684 // a card beyond the heap. This is not safe without a perm
685 // gen at the upper end of the heap.
686 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
687 MemRegion dirtyRegion(start, end);
688
689 #if CARD_REPEAT_HISTO
690 init_ct_freq_table(_g1->max_capacity());
691 ct_freq_note_card(_ct_bs->index_for(start));
692 #endif
693
694 G1ParPushHeapRSClosure* oops_in_heap_closure = NULL;
695 if (check_for_refs_into_cset) {
696 // ConcurrentG1RefineThreads have worker numbers larger than what
697 // _cset_rs_update_cl[] is set up to handle. But those threads should
698 // only be active outside of a collection which means that when they
699 // reach here they should have check_for_refs_into_cset == false.
700 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
701 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
702 }
703 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
704 _g1->g1_rem_set(),
705 oops_in_heap_closure,
706 check_for_refs_into_cset,
707 worker_i);
708 update_rs_oop_cl.set_from(r);
709
710 G1TriggerClosure trigger_cl;
711 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
712 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
713 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
714
715 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
716 (check_for_refs_into_cset ?
717 (OopClosure*)&mux :
718 (OopClosure*)&update_rs_oop_cl));
719
720 // The region for the current card may be a young region. The
721 // current card may have been a card that was evicted from the
722 // card cache. When the card was inserted into the cache, we had
723 // determined that its region was non-young. While in the cache,
724 // the region may have been freed during a cleanup pause, reallocated
725 // and tagged as young.
726 //
727 // We wish to filter out cards for such a region but the current
728 // thread, if we're running concurrently, may "see" the young type
729 // change at any time (so an earlier "is_young" check may pass or
730 // fail arbitrarily). We tell the iteration code to perform this
731 // filtering when it has been determined that there has been an actual
732 // allocation in this region and making it safe to check the young type.
733 bool filter_young = true;
734
735 HeapWord* stop_point =
736 r->oops_on_card_seq_iterate_careful(dirtyRegion,
737 &filter_then_update_rs_oop_cl,
738 filter_young,
739 card_ptr);
740
741 // If stop_point is non-null, then we encountered an unallocated region
742 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
743 // card and re-enqueue: if we put off the card until a GC pause, then the
744 // unallocated portion will be filled in. Alternatively, we might try
745 // the full complexity of the technique used in "regular" precleaning.
746 if (stop_point != NULL) {
747 // The card might have gotten re-dirtied and re-enqueued while we
748 // worked. (In fact, it's pretty likely.)
749 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
750 *card_ptr = CardTableModRefBS::dirty_card_val();
751 MutexLockerEx x(Shared_DirtyCardQ_lock,
752 Mutex::_no_safepoint_check_flag);
753 DirtyCardQueue* sdcq =
754 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
755 sdcq->enqueue(card_ptr);
756 }
757 } else {
758 _conc_refine_cards++;
759 }
760
761 // This gets set to true if the card being refined has
762 // references that point into the collection set.
763 bool has_refs_into_cset = trigger_cl.triggered();
764
765 // We should only be detecting that the card contains references
766 // that point into the collection set if the current thread is
767 // a GC worker thread.
768 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
769 "invalid result at non safepoint");
770
771 return has_refs_into_cset;
772 }
773
774 void G1RemSet::print_periodic_summary_info(const char* header) {
775 G1RemSetSummary current;
776 current.initialize(this);
777
778 _prev_period_summary.subtract_from(¤t);
779 print_summary_info(&_prev_period_summary, header);
780
781 _prev_period_summary.set(¤t);
782 }
783
784 void G1RemSet::print_summary_info() {
785 G1RemSetSummary current;
786 current.initialize(this);
787
788 print_summary_info(¤t, " Cumulative RS summary");
789 }
790
791 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
792 assert(summary != NULL, "just checking");
793
794 if (header != NULL) {
795 gclog_or_tty->print_cr("%s", header);
796 }
797
798 #if CARD_REPEAT_HISTO
799 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
800 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
801 card_repeat_count.print_on(gclog_or_tty);
802 #endif
803
804 summary->print_on(gclog_or_tty);
805 }
806
807 void G1RemSet::prepare_for_verify() {
808 if (G1HRRSFlushLogBuffersOnVerify &&
809 (VerifyBeforeGC || VerifyAfterGC)
810 && (!_g1->collector_state()->full_collection() || G1VerifyRSetsDuringFullGC)) {
811 cleanupHRRS();
812 _g1->set_refine_cte_cl_concurrency(false);
813 if (SafepointSynchronize::is_at_safepoint()) {
814 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
815 dcqs.concatenate_logs();
816 }
817
818 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
819 bool use_hot_card_cache = hot_card_cache->use_cache();
820 hot_card_cache->set_use_cache(false);
821
822 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
823 updateRS(&into_cset_dcq, 0);
824 _g1->into_cset_dirty_card_queue_set().clear();
825
826 hot_card_cache->set_use_cache(use_hot_card_cache);
827 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
828 }
829 }