1 /*
2 * Copyright (c) 2001, 2012, 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 // Stack allocate the DirtyCardToOopClosure instance
126 HeapRegionDCTOC cl(_g1h, r, _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 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
213 double rs_time_start = os::elapsedTime();
214 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
215
216 ScanRSClosure scanRScl(oc, worker_i);
217
218 _g1->collection_set_iterate_from(startRegion, &scanRScl);
219 scanRScl.set_try_claimed();
220 _g1->collection_set_iterate_from(startRegion, &scanRScl);
221
222 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
223
224 assert( _cards_scanned != NULL, "invariant" );
225 _cards_scanned[worker_i] = scanRScl.cards_done();
226
227 _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
228 }
229
230 // Closure used for updating RSets and recording references that
231 // point into the collection set. Only called during an
232 // evacuation pause.
233
234 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
235 G1RemSet* _g1rs;
236 DirtyCardQueue* _into_cset_dcq;
237 public:
238 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
239 DirtyCardQueue* into_cset_dcq) :
240 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
241 {}
242 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
243 // The only time we care about recording cards that
244 // contain references that point into the collection set
245 // is during RSet updating within an evacuation pause.
246 // In this case worker_i should be the id of a GC worker thread.
247 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
248 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
249
250 if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) {
251 // 'card_ptr' contains references that point into the collection
252 // set. We need to record the card in the DCQS
253 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
254 // that's used for that purpose.
255 //
256 // Enqueue the card
257 _into_cset_dcq->enqueue(card_ptr);
258 }
259 return true;
260 }
261 };
262
263 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
264 double start = os::elapsedTime();
265 // Apply the given closure to all remaining log entries.
266 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
267
268 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
269
270 // Now there should be no dirty cards.
271 if (G1RSLogCheckCardTable) {
272 CountNonCleanMemRegionClosure cl(_g1);
273 _ct_bs->mod_card_iterate(&cl);
274 // XXX This isn't true any more: keeping cards of young regions
275 // marked dirty broke it. Need some reasonable fix.
276 guarantee(cl.n() == 0, "Card table should be clean.");
277 }
278
279 _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
280 }
281
282 void G1RemSet::cleanupHRRS() {
283 HeapRegionRemSet::cleanup();
284 }
285
286 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
287 int worker_i) {
288 #if CARD_REPEAT_HISTO
289 ct_freq_update_histo_and_reset();
290 #endif
291 if (worker_i == 0) {
292 _cg1r->clear_and_record_card_counts();
293 }
294
295 // We cache the value of 'oc' closure into the appropriate slot in the
296 // _cset_rs_update_cl for this worker
297 assert(worker_i < (int)n_workers(), "sanity");
298 _cset_rs_update_cl[worker_i] = oc;
299
300 // A DirtyCardQueue that is used to hold cards containing references
301 // that point into the collection set. This DCQ is associated with a
302 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
303 // circumstances (i.e. the pause successfully completes), these cards
304 // are just discarded (there's no need to update the RSets of regions
305 // that were in the collection set - after the pause these regions
306 // are wholly 'free' of live objects. In the event of an evacuation
307 // failure the cards/buffers in this queue set are:
308 // * passed to the DirtyCardQueueSet that is used to manage deferred
309 // RSet updates, or
310 // * scanned for references that point into the collection set
311 // and the RSet of the corresponding region in the collection set
312 // is updated immediately.
313 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
314
315 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
316
317 // The two flags below were introduced temporarily to serialize
318 // the updating and scanning of remembered sets. There are some
319 // race conditions when these two operations are done in parallel
320 // and they are causing failures. When we resolve said race
321 // conditions, we'll revert back to parallel remembered set
322 // updating and scanning. See CRs 6677707 and 6677708.
323 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
324 updateRS(&into_cset_dcq, worker_i);
325 } else {
326 _g1p->record_update_rs_processed_buffers(worker_i, 0.0);
327 _g1p->record_update_rs_time(worker_i, 0.0);
328 }
329 if (G1UseParallelRSetScanning || (worker_i == 0)) {
330 scanRS(oc, worker_i);
331 } else {
332 _g1p->record_scan_rs_time(worker_i, 0.0);
333 }
334
335 // We now clear the cached values of _cset_rs_update_cl for this worker
336 _cset_rs_update_cl[worker_i] = NULL;
337 }
338
339 void G1RemSet::prepare_for_oops_into_collection_set_do() {
340 cleanupHRRS();
341 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
342 _g1->set_refine_cte_cl_concurrency(false);
343 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
344 dcqs.concatenate_logs();
345
346 if (G1CollectedHeap::use_parallel_gc_threads()) {
347 // Don't set the number of workers here. It will be set
348 // when the task is run
349 // _seq_task->set_n_termination((int)n_workers());
350 }
351 guarantee( _cards_scanned == NULL, "invariant" );
352 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers());
353 for (uint i = 0; i < n_workers(); ++i) {
354 _cards_scanned[i] = 0;
355 }
356 _total_cards_scanned = 0;
357 }
358
359
360 // This closure, applied to a DirtyCardQueueSet, is used to immediately
361 // update the RSets for the regions in the CSet. For each card it iterates
362 // through the oops which coincide with that card. It scans the reference
363 // fields in each oop; when it finds an oop that points into the collection
364 // set, the RSet for the region containing the referenced object is updated.
365 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
366 G1CollectedHeap* _g1;
367 CardTableModRefBS* _ct_bs;
368 public:
369 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
370 CardTableModRefBS* bs):
371 _g1(g1), _ct_bs(bs)
372 { }
373
374 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
375 // Construct the region representing the card.
376 HeapWord* start = _ct_bs->addr_for(card_ptr);
377 // And find the region containing it.
378 HeapRegion* r = _g1->heap_region_containing(start);
379 assert(r != NULL, "unexpected null");
380
381 // Scan oops in the card looking for references into the collection set
382 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
383 MemRegion scanRegion(start, end);
384
385 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
386 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
387 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
388
389 // We can pass false as the "filter_young" parameter here as:
390 // * we should be in a STW pause,
391 // * the DCQS to which this closure is applied is used to hold
392 // references that point into the collection set from the prior
393 // RSet updating,
394 // * the post-write barrier shouldn't be logging updates to young
395 // regions (but there is a situation where this can happen - see
396 // the comment in G1RemSet::concurrentRefineOneCard below -
397 // that should not be applicable here), and
398 // * during actual RSet updating, the filtering of cards in young
399 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
400 // employed.
401 // As a result, when this closure is applied to "refs into cset"
402 // DCQS, we shouldn't see any cards in young regions.
403 update_rs_cl.set_region(r);
404 HeapWord* stop_point =
405 r->oops_on_card_seq_iterate_careful(scanRegion,
406 &filter_then_update_rs_cset_oop_cl,
407 false /* filter_young */,
408 NULL /* card_ptr */);
409
410 // Since this is performed in the event of an evacuation failure, we
411 // we shouldn't see a non-null stop point
412 assert(stop_point == NULL, "saw an unallocated region");
413 return true;
414 }
415 };
416
417 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
418 guarantee( _cards_scanned != NULL, "invariant" );
419 _total_cards_scanned = 0;
420 for (uint i = 0; i < n_workers(); ++i) {
421 _total_cards_scanned += _cards_scanned[i];
422 }
423 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
424 _cards_scanned = NULL;
425 // Cleanup after copy
426 _g1->set_refine_cte_cl_concurrency(true);
427 // Set all cards back to clean.
428 _g1->cleanUpCardTable();
429
430 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
431 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
432
433 if (_g1->evacuation_failed()) {
434 // Restore remembered sets for the regions pointing into the collection set.
435
436 if (G1DeferredRSUpdate) {
437 // If deferred RS updates are enabled then we just need to transfer
438 // the completed buffers from (a) the DirtyCardQueueSet used to hold
439 // cards that contain references that point into the collection set
440 // to (b) the DCQS used to hold the deferred RS updates
441 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
442 } else {
443
444 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
445 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
446
447 int n_completed_buffers = 0;
448 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
449 0, 0, true)) {
450 n_completed_buffers++;
451 }
452 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
453 }
454 }
455
456 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
457 // which contain references that point into the collection.
458 _g1->into_cset_dirty_card_queue_set().clear();
459 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
460 "all buffers should be freed");
461 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
462 }
463
464 class ScrubRSClosure: public HeapRegionClosure {
465 G1CollectedHeap* _g1h;
466 BitMap* _region_bm;
467 BitMap* _card_bm;
468 CardTableModRefBS* _ctbs;
469 public:
470 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
471 _g1h(G1CollectedHeap::heap()),
472 _region_bm(region_bm), _card_bm(card_bm),
473 _ctbs(NULL)
474 {
475 ModRefBarrierSet* bs = _g1h->mr_bs();
476 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
477 _ctbs = (CardTableModRefBS*)bs;
478 }
479
480 bool doHeapRegion(HeapRegion* r) {
481 if (!r->continuesHumongous()) {
482 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
483 }
484 return false;
485 }
486 };
487
488 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
489 ScrubRSClosure scrub_cl(region_bm, card_bm);
490 _g1->heap_region_iterate(&scrub_cl);
491 }
492
493 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
494 uint worker_num, int claim_val) {
495 ScrubRSClosure scrub_cl(region_bm, card_bm);
496 _g1->heap_region_par_iterate_chunked(&scrub_cl,
497 worker_num,
498 n_workers(),
499 claim_val);
500 }
501
502
503
504 G1TriggerClosure::G1TriggerClosure() :
505 _triggered(false) { }
506
507 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
508 OopClosure* oop_cl) :
509 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
510
511 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
512 _c1(c1), _c2(c2) { }
513
514 G1UpdateRSOrPushRefOopClosure::
515 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
516 G1RemSet* rs,
517 OopsInHeapRegionClosure* push_ref_cl,
518 bool record_refs_into_cset,
519 int worker_i) :
520 _g1(g1h), _g1_rem_set(rs), _from(NULL),
521 _record_refs_into_cset(record_refs_into_cset),
522 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
523
524 bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
525 bool check_for_refs_into_cset) {
526 // Construct the region representing the card.
527 HeapWord* start = _ct_bs->addr_for(card_ptr);
528 // And find the region containing it.
529 HeapRegion* r = _g1->heap_region_containing(start);
530 assert(r != NULL, "unexpected null");
531
532 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
533 MemRegion dirtyRegion(start, end);
534
535 #if CARD_REPEAT_HISTO
536 init_ct_freq_table(_g1->max_capacity());
537 ct_freq_note_card(_ct_bs->index_for(start));
538 #endif
539
540 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
541 if (check_for_refs_into_cset) {
542 // ConcurrentG1RefineThreads have worker numbers larger than what
543 // _cset_rs_update_cl[] is set up to handle. But those threads should
544 // only be active outside of a collection which means that when they
545 // reach here they should have check_for_refs_into_cset == false.
546 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
547 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
548 }
549 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
550 _g1->g1_rem_set(),
551 oops_in_heap_closure,
552 check_for_refs_into_cset,
553 worker_i);
554 update_rs_oop_cl.set_from(r);
555
556 G1TriggerClosure trigger_cl;
557 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
558 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
559 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
560
561 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
562 (check_for_refs_into_cset ?
563 (OopClosure*)&mux :
564 (OopClosure*)&update_rs_oop_cl));
565
566 // The region for the current card may be a young region. The
567 // current card may have been a card that was evicted from the
568 // card cache. When the card was inserted into the cache, we had
569 // determined that its region was non-young. While in the cache,
570 // the region may have been freed during a cleanup pause, reallocated
571 // and tagged as young.
572 //
573 // We wish to filter out cards for such a region but the current
574 // thread, if we're running concurrently, may "see" the young type
575 // change at any time (so an earlier "is_young" check may pass or
576 // fail arbitrarily). We tell the iteration code to perform this
577 // filtering when it has been determined that there has been an actual
578 // allocation in this region and making it safe to check the young type.
579 bool filter_young = true;
580
581 HeapWord* stop_point =
582 r->oops_on_card_seq_iterate_careful(dirtyRegion,
583 &filter_then_update_rs_oop_cl,
584 filter_young,
585 card_ptr);
586
587 // If stop_point is non-null, then we encountered an unallocated region
588 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
589 // card and re-enqueue: if we put off the card until a GC pause, then the
590 // unallocated portion will be filled in. Alternatively, we might try
591 // the full complexity of the technique used in "regular" precleaning.
592 if (stop_point != NULL) {
593 // The card might have gotten re-dirtied and re-enqueued while we
594 // worked. (In fact, it's pretty likely.)
595 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
596 *card_ptr = CardTableModRefBS::dirty_card_val();
597 MutexLockerEx x(Shared_DirtyCardQ_lock,
598 Mutex::_no_safepoint_check_flag);
599 DirtyCardQueue* sdcq =
600 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
601 sdcq->enqueue(card_ptr);
602 }
603 } else {
604 _conc_refine_cards++;
605 }
606
607 return trigger_cl.triggered();
608 }
609
610 bool G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
611 bool check_for_refs_into_cset) {
612 // If the card is no longer dirty, nothing to do.
613 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
614 // No need to return that this card contains refs that point
615 // into the collection set.
616 return false;
617 }
618
619 // Construct the region representing the card.
620 HeapWord* start = _ct_bs->addr_for(card_ptr);
621 // And find the region containing it.
622 HeapRegion* r = _g1->heap_region_containing(start);
623 if (r == NULL) {
624 guarantee(_g1->is_in_permanent(start), "Or else where?");
625 // Again no need to return that this card contains refs that
626 // point into the collection set.
627 return false; // Not in the G1 heap (might be in perm, for example.)
628 }
629 // Why do we have to check here whether a card is on a young region,
630 // given that we dirty young regions and, as a result, the
631 // post-barrier is supposed to filter them out and never to enqueue
632 // them? When we allocate a new region as the "allocation region" we
633 // actually dirty its cards after we release the lock, since card
634 // dirtying while holding the lock was a performance bottleneck. So,
635 // as a result, it is possible for other threads to actually
636 // allocate objects in the region (after the acquire the lock)
637 // before all the cards on the region are dirtied. This is unlikely,
638 // and it doesn't happen often, but it can happen. So, the extra
639 // check below filters out those cards.
640 if (r->is_young()) {
641 return false;
642 }
643 // While we are processing RSet buffers during the collection, we
644 // actually don't want to scan any cards on the collection set,
645 // since we don't want to update remebered sets with entries that
646 // point into the collection set, given that live objects from the
647 // collection set are about to move and such entries will be stale
648 // very soon. This change also deals with a reliability issue which
649 // involves scanning a card in the collection set and coming across
650 // an array that was being chunked and looking malformed. Note,
651 // however, that if evacuation fails, we have to scan any objects
652 // that were not moved and create any missing entries.
653 if (r->in_collection_set()) {
654 return false;
655 }
656
657 // Should we defer processing the card?
658 //
659 // Previously the result from the insert_cache call would be
660 // either card_ptr (implying that card_ptr was currently "cold"),
661 // null (meaning we had inserted the card ptr into the "hot"
662 // cache, which had some headroom), or a "hot" card ptr
663 // extracted from the "hot" cache.
664 //
665 // Now that the _card_counts cache in the ConcurrentG1Refine
666 // instance is an evicting hash table, the result we get back
667 // could be from evicting the card ptr in an already occupied
668 // bucket (in which case we have replaced the card ptr in the
669 // bucket with card_ptr and "defer" is set to false). To avoid
670 // having a data structure (updates to which would need a lock)
671 // to hold these unprocessed dirty cards, we need to immediately
672 // process card_ptr. The actions needed to be taken on return
673 // from cache_insert are summarized in the following table:
674 //
675 // res defer action
676 // --------------------------------------------------------------
677 // null false card evicted from _card_counts & replaced with
678 // card_ptr; evicted ptr added to hot cache.
679 // No need to process res; immediately process card_ptr
680 //
681 // null true card not evicted from _card_counts; card_ptr added
682 // to hot cache.
683 // Nothing to do.
684 //
685 // non-null false card evicted from _card_counts & replaced with
686 // card_ptr; evicted ptr is currently "cold" or
687 // caused an eviction from the hot cache.
688 // Immediately process res; process card_ptr.
689 //
690 // non-null true card not evicted from _card_counts; card_ptr is
691 // currently cold, or caused an eviction from hot
692 // cache.
693 // Immediately process res; no need to process card_ptr.
694
695
696 jbyte* res = card_ptr;
697 bool defer = false;
698
699 // This gets set to true if the card being refined has references
700 // that point into the collection set.
701 bool oops_into_cset = false;
702
703 if (_cg1r->use_cache()) {
704 jbyte* res = _cg1r->cache_insert(card_ptr, &defer);
705 if (res != NULL && (res != card_ptr || defer)) {
706 start = _ct_bs->addr_for(res);
707 r = _g1->heap_region_containing(start);
708 if (r == NULL) {
709 assert(_g1->is_in_permanent(start), "Or else where?");
710 } else {
711 // Checking whether the region we got back from the cache
712 // is young here is inappropriate. The region could have been
713 // freed, reallocated and tagged as young while in the cache.
714 // Hence we could see its young type change at any time.
715 //
716 // Process card pointer we get back from the hot card cache. This
717 // will check whether the region containing the card is young
718 // _after_ checking that the region has been allocated from.
719 oops_into_cset = concurrentRefineOneCard_impl(res, worker_i,
720 false /* check_for_refs_into_cset */);
721 // The above call to concurrentRefineOneCard_impl is only
722 // performed if the hot card cache is enabled. This cache is
723 // disabled during an evacuation pause - which is the only
724 // time when we need know if the card contains references
725 // that point into the collection set. Also when the hot card
726 // cache is enabled, this code is executed by the concurrent
727 // refine threads - rather than the GC worker threads - and
728 // concurrentRefineOneCard_impl will return false.
729 assert(!oops_into_cset, "should not see true here");
730 }
731 }
732 }
733
734 if (!defer) {
735 oops_into_cset =
736 concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset);
737 // We should only be detecting that the card contains references
738 // that point into the collection set if the current thread is
739 // a GC worker thread.
740 assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(),
741 "invalid result at non safepoint");
742 }
743 return oops_into_cset;
744 }
745
746 class HRRSStatsIter: public HeapRegionClosure {
747 size_t _occupied;
748 size_t _total_mem_sz;
749 size_t _max_mem_sz;
750 HeapRegion* _max_mem_sz_region;
751 public:
752 HRRSStatsIter() :
753 _occupied(0),
754 _total_mem_sz(0),
755 _max_mem_sz(0),
756 _max_mem_sz_region(NULL)
757 {}
758
759 bool doHeapRegion(HeapRegion* r) {
760 if (r->continuesHumongous()) return false;
761 size_t mem_sz = r->rem_set()->mem_size();
762 if (mem_sz > _max_mem_sz) {
763 _max_mem_sz = mem_sz;
764 _max_mem_sz_region = r;
765 }
766 _total_mem_sz += mem_sz;
767 size_t occ = r->rem_set()->occupied();
768 _occupied += occ;
769 return false;
770 }
771 size_t total_mem_sz() { return _total_mem_sz; }
772 size_t max_mem_sz() { return _max_mem_sz; }
773 size_t occupied() { return _occupied; }
774 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
775 };
776
777 class PrintRSThreadVTimeClosure : public ThreadClosure {
778 public:
779 virtual void do_thread(Thread *t) {
780 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
781 gclog_or_tty->print(" %5.2f", crt->vtime_accum());
782 }
783 };
784
785 void G1RemSet::print_summary_info() {
786 G1CollectedHeap* g1 = G1CollectedHeap::heap();
787
788 #if CARD_REPEAT_HISTO
789 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
790 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
791 card_repeat_count.print_on(gclog_or_tty);
792 #endif
793
794 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
795 _conc_refine_cards);
796 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
797 jint tot_processed_buffers =
798 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
799 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers);
800 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.",
801 dcqs.processed_buffers_rs_thread(),
802 100.0*(float)dcqs.processed_buffers_rs_thread()/
803 (float)tot_processed_buffers);
804 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.",
805 dcqs.processed_buffers_mut(),
806 100.0*(float)dcqs.processed_buffers_mut()/
807 (float)tot_processed_buffers);
808 gclog_or_tty->print_cr(" Conc RS threads times(s)");
809 PrintRSThreadVTimeClosure p;
810 gclog_or_tty->print(" ");
811 g1->concurrent_g1_refine()->threads_do(&p);
812 gclog_or_tty->print_cr("");
813
814 HRRSStatsIter blk;
815 g1->heap_region_iterate(&blk);
816 gclog_or_tty->print_cr(" Total heap region rem set sizes = "SIZE_FORMAT"K."
817 " Max = "SIZE_FORMAT"K.",
818 blk.total_mem_sz()/K, blk.max_mem_sz()/K);
819 gclog_or_tty->print_cr(" Static structures = "SIZE_FORMAT"K,"
820 " free_lists = "SIZE_FORMAT"K.",
821 HeapRegionRemSet::static_mem_size() / K,
822 HeapRegionRemSet::fl_mem_size() / K);
823 gclog_or_tty->print_cr(" "SIZE_FORMAT" occupied cards represented.",
824 blk.occupied());
825 HeapRegion* max_mem_sz_region = blk.max_mem_sz_region();
826 HeapRegionRemSet* rem_set = max_mem_sz_region->rem_set();
827 gclog_or_tty->print_cr(" Max size region = "HR_FORMAT", "
828 "size = "SIZE_FORMAT "K, occupied = "SIZE_FORMAT"K.",
829 HR_FORMAT_PARAMS(max_mem_sz_region),
830 (rem_set->mem_size() + K - 1)/K,
831 (rem_set->occupied() + K - 1)/K);
832 gclog_or_tty->print_cr(" Did %d coarsenings.",
833 HeapRegionRemSet::n_coarsenings());
834 }
835
836 void G1RemSet::prepare_for_verify() {
837 if (G1HRRSFlushLogBuffersOnVerify &&
838 (VerifyBeforeGC || VerifyAfterGC)
839 && !_g1->full_collection()) {
840 cleanupHRRS();
841 _g1->set_refine_cte_cl_concurrency(false);
842 if (SafepointSynchronize::is_at_safepoint()) {
843 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
844 dcqs.concatenate_logs();
845 }
846 bool cg1r_use_cache = _cg1r->use_cache();
847 _cg1r->set_use_cache(false);
848 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
849 updateRS(&into_cset_dcq, 0);
850 _g1->into_cset_dirty_card_queue_set().clear();
851 _cg1r->set_use_cache(cg1r_use_cache);
852
853 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
854 }
855 }