Fri, 17 May 2013 11:57:05 +0200
8014277: Remove ObjectClosure as base class for BoolObjectClosure
Reviewed-by: brutisso, tschatzl
1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/bufferingOopClosure.hpp"
27 #include "gc_implementation/g1/concurrentG1Refine.hpp"
28 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
29 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
30 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
31 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
32 #include "gc_implementation/g1/g1HotCardCache.hpp"
33 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
34 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
35 #include "gc_implementation/g1/g1RemSet.inline.hpp"
36 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
37 #include "memory/iterator.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "utilities/intHisto.hpp"
41 #define CARD_REPEAT_HISTO 0
43 #if CARD_REPEAT_HISTO
44 static size_t ct_freq_sz;
45 static jbyte* ct_freq = NULL;
47 void init_ct_freq_table(size_t heap_sz_bytes) {
48 if (ct_freq == NULL) {
49 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
50 ct_freq = new jbyte[ct_freq_sz];
51 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
52 }
53 }
55 void ct_freq_note_card(size_t index) {
56 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
57 if (ct_freq[index] < 100) { ct_freq[index]++; }
58 }
60 static IntHistogram card_repeat_count(10, 10);
62 void ct_freq_update_histo_and_reset() {
63 for (size_t j = 0; j < ct_freq_sz; j++) {
64 card_repeat_count.add_entry(ct_freq[j]);
65 ct_freq[j] = 0;
66 }
68 }
69 #endif
71 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
72 : _g1(g1), _conc_refine_cards(0),
73 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
74 _cg1r(g1->concurrent_g1_refine()),
75 _cset_rs_update_cl(NULL),
76 _cards_scanned(NULL), _total_cards_scanned(0)
77 {
78 _seq_task = new SubTasksDone(NumSeqTasks);
79 guarantee(n_workers() > 0, "There should be some workers");
80 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC);
81 for (uint i = 0; i < n_workers(); i++) {
82 _cset_rs_update_cl[i] = NULL;
83 }
84 }
86 G1RemSet::~G1RemSet() {
87 delete _seq_task;
88 for (uint i = 0; i < n_workers(); i++) {
89 assert(_cset_rs_update_cl[i] == NULL, "it should be");
90 }
91 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC);
92 }
94 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
95 if (_g1->is_in_g1_reserved(mr.start())) {
96 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
97 if (_start_first == NULL) _start_first = mr.start();
98 }
99 }
101 class ScanRSClosure : public HeapRegionClosure {
102 size_t _cards_done, _cards;
103 G1CollectedHeap* _g1h;
104 OopsInHeapRegionClosure* _oc;
105 G1BlockOffsetSharedArray* _bot_shared;
106 CardTableModRefBS *_ct_bs;
107 int _worker_i;
108 int _block_size;
109 bool _try_claimed;
110 public:
111 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
112 _oc(oc),
113 _cards(0),
114 _cards_done(0),
115 _worker_i(worker_i),
116 _try_claimed(false)
117 {
118 _g1h = G1CollectedHeap::heap();
119 _bot_shared = _g1h->bot_shared();
120 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
121 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
122 }
124 void set_try_claimed() { _try_claimed = true; }
126 void scanCard(size_t index, HeapRegion *r) {
127 // Stack allocate the DirtyCardToOopClosure instance
128 HeapRegionDCTOC cl(_g1h, r, _oc,
129 CardTableModRefBS::Precise,
130 HeapRegionDCTOC::IntoCSFilterKind);
132 // Set the "from" region in the closure.
133 _oc->set_region(r);
134 HeapWord* card_start = _bot_shared->address_for_index(index);
135 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
136 Space *sp = SharedHeap::heap()->space_containing(card_start);
137 MemRegion sm_region = sp->used_region_at_save_marks();
138 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
139 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
140 // We make the card as "claimed" lazily (so races are possible
141 // but they're benign), which reduces the number of duplicate
142 // scans (the rsets of the regions in the cset can intersect).
143 _ct_bs->set_card_claimed(index);
144 _cards_done++;
145 cl.do_MemRegion(mr);
146 }
147 }
149 void printCard(HeapRegion* card_region, size_t card_index,
150 HeapWord* card_start) {
151 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
152 "RS names card %p: "
153 "[" PTR_FORMAT ", " PTR_FORMAT ")",
154 _worker_i,
155 card_region->bottom(), card_region->end(),
156 card_index,
157 card_start, card_start + G1BlockOffsetSharedArray::N_words);
158 }
160 bool doHeapRegion(HeapRegion* r) {
161 assert(r->in_collection_set(), "should only be called on elements of CS.");
162 HeapRegionRemSet* hrrs = r->rem_set();
163 if (hrrs->iter_is_complete()) return false; // All done.
164 if (!_try_claimed && !hrrs->claim_iter()) return false;
165 // If we ever free the collection set concurrently, we should also
166 // clear the card table concurrently therefore we won't need to
167 // add regions of the collection set to the dirty cards region.
168 _g1h->push_dirty_cards_region(r);
169 // If we didn't return above, then
170 // _try_claimed || r->claim_iter()
171 // is true: either we're supposed to work on claimed-but-not-complete
172 // regions, or we successfully claimed the region.
173 HeapRegionRemSetIterator iter(hrrs);
174 size_t card_index;
176 // We claim cards in block so as to recude the contention. The block size is determined by
177 // the G1RSetScanBlockSize parameter.
178 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
179 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
180 if (current_card >= jump_to_card + _block_size) {
181 jump_to_card = hrrs->iter_claimed_next(_block_size);
182 }
183 if (current_card < jump_to_card) continue;
184 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
185 #if 0
186 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
187 card_start, card_start + CardTableModRefBS::card_size_in_words);
188 #endif
190 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
191 assert(card_region != NULL, "Yielding cards not in the heap?");
192 _cards++;
194 if (!card_region->is_on_dirty_cards_region_list()) {
195 _g1h->push_dirty_cards_region(card_region);
196 }
198 // If the card is dirty, then we will scan it during updateRS.
199 if (!card_region->in_collection_set() &&
200 !_ct_bs->is_card_dirty(card_index)) {
201 scanCard(card_index, card_region);
202 }
203 }
204 if (!_try_claimed) {
205 hrrs->set_iter_complete();
206 }
207 return false;
208 }
209 size_t cards_done() { return _cards_done;}
210 size_t cards_looked_up() { return _cards;}
211 };
213 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
214 double rs_time_start = os::elapsedTime();
215 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
217 ScanRSClosure scanRScl(oc, worker_i);
219 _g1->collection_set_iterate_from(startRegion, &scanRScl);
220 scanRScl.set_try_claimed();
221 _g1->collection_set_iterate_from(startRegion, &scanRScl);
223 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
225 assert( _cards_scanned != NULL, "invariant" );
226 _cards_scanned[worker_i] = scanRScl.cards_done();
228 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
229 }
231 // Closure used for updating RSets and recording references that
232 // point into the collection set. Only called during an
233 // evacuation pause.
235 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
236 G1RemSet* _g1rs;
237 DirtyCardQueue* _into_cset_dcq;
238 public:
239 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
240 DirtyCardQueue* into_cset_dcq) :
241 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
242 {}
243 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
244 // The only time we care about recording cards that
245 // contain references that point into the collection set
246 // is during RSet updating within an evacuation pause.
247 // In this case worker_i should be the id of a GC worker thread.
248 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
249 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
251 if (_g1rs->refine_card(card_ptr, worker_i, true)) {
252 // 'card_ptr' contains references that point into the collection
253 // set. We need to record the card in the DCQS
254 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
255 // that's used for that purpose.
256 //
257 // Enqueue the card
258 _into_cset_dcq->enqueue(card_ptr);
259 }
260 return true;
261 }
262 };
264 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
265 double start = os::elapsedTime();
266 // Apply the given closure to all remaining log entries.
267 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
269 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
271 // Now there should be no dirty cards.
272 if (G1RSLogCheckCardTable) {
273 CountNonCleanMemRegionClosure cl(_g1);
274 _ct_bs->mod_card_iterate(&cl);
275 // XXX This isn't true any more: keeping cards of young regions
276 // marked dirty broke it. Need some reasonable fix.
277 guarantee(cl.n() == 0, "Card table should be clean.");
278 }
280 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
281 }
283 void G1RemSet::cleanupHRRS() {
284 HeapRegionRemSet::cleanup();
285 }
287 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
288 int worker_i) {
289 #if CARD_REPEAT_HISTO
290 ct_freq_update_histo_and_reset();
291 #endif
293 // We cache the value of 'oc' closure into the appropriate slot in the
294 // _cset_rs_update_cl for this worker
295 assert(worker_i < (int)n_workers(), "sanity");
296 _cset_rs_update_cl[worker_i] = oc;
298 // A DirtyCardQueue that is used to hold cards containing references
299 // that point into the collection set. This DCQ is associated with a
300 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
301 // circumstances (i.e. the pause successfully completes), these cards
302 // are just discarded (there's no need to update the RSets of regions
303 // that were in the collection set - after the pause these regions
304 // are wholly 'free' of live objects. In the event of an evacuation
305 // failure the cards/buffers in this queue set are:
306 // * passed to the DirtyCardQueueSet that is used to manage deferred
307 // RSet updates, or
308 // * scanned for references that point into the collection set
309 // and the RSet of the corresponding region in the collection set
310 // is updated immediately.
311 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
313 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
315 // The two flags below were introduced temporarily to serialize
316 // the updating and scanning of remembered sets. There are some
317 // race conditions when these two operations are done in parallel
318 // and they are causing failures. When we resolve said race
319 // conditions, we'll revert back to parallel remembered set
320 // updating and scanning. See CRs 6677707 and 6677708.
321 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
322 updateRS(&into_cset_dcq, worker_i);
323 } else {
324 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0);
325 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
326 }
327 if (G1UseParallelRSetScanning || (worker_i == 0)) {
328 scanRS(oc, worker_i);
329 } else {
330 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
331 }
333 // We now clear the cached values of _cset_rs_update_cl for this worker
334 _cset_rs_update_cl[worker_i] = NULL;
335 }
337 void G1RemSet::prepare_for_oops_into_collection_set_do() {
338 cleanupHRRS();
339 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
340 _g1->set_refine_cte_cl_concurrency(false);
341 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
342 dcqs.concatenate_logs();
344 if (G1CollectedHeap::use_parallel_gc_threads()) {
345 // Don't set the number of workers here. It will be set
346 // when the task is run
347 // _seq_task->set_n_termination((int)n_workers());
348 }
349 guarantee( _cards_scanned == NULL, "invariant" );
350 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
351 for (uint i = 0; i < n_workers(); ++i) {
352 _cards_scanned[i] = 0;
353 }
354 _total_cards_scanned = 0;
355 }
358 // This closure, applied to a DirtyCardQueueSet, is used to immediately
359 // update the RSets for the regions in the CSet. For each card it iterates
360 // through the oops which coincide with that card. It scans the reference
361 // fields in each oop; when it finds an oop that points into the collection
362 // set, the RSet for the region containing the referenced object is updated.
363 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
364 G1CollectedHeap* _g1;
365 CardTableModRefBS* _ct_bs;
366 public:
367 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
368 CardTableModRefBS* bs):
369 _g1(g1), _ct_bs(bs)
370 { }
372 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
373 // Construct the region representing the card.
374 HeapWord* start = _ct_bs->addr_for(card_ptr);
375 // And find the region containing it.
376 HeapRegion* r = _g1->heap_region_containing(start);
377 assert(r != NULL, "unexpected null");
379 // Scan oops in the card looking for references into the collection set
380 // Don't use addr_for(card_ptr + 1) which can ask for
381 // a card beyond the heap. This is not safe without a perm
382 // gen.
383 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
384 MemRegion scanRegion(start, end);
386 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
387 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
388 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
390 // We can pass false as the "filter_young" parameter here as:
391 // * we should be in a STW pause,
392 // * the DCQS to which this closure is applied is used to hold
393 // references that point into the collection set from the prior
394 // RSet updating,
395 // * the post-write barrier shouldn't be logging updates to young
396 // regions (but there is a situation where this can happen - see
397 // the comment in G1RemSet::refine_card() below -
398 // that should not be applicable here), and
399 // * during actual RSet updating, the filtering of cards in young
400 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
401 // employed.
402 // As a result, when this closure is applied to "refs into cset"
403 // DCQS, we shouldn't see any cards in young regions.
404 update_rs_cl.set_region(r);
405 HeapWord* stop_point =
406 r->oops_on_card_seq_iterate_careful(scanRegion,
407 &filter_then_update_rs_cset_oop_cl,
408 false /* filter_young */,
409 NULL /* card_ptr */);
411 // Since this is performed in the event of an evacuation failure, we
412 // we shouldn't see a non-null stop point
413 assert(stop_point == NULL, "saw an unallocated region");
414 return true;
415 }
416 };
418 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
419 guarantee( _cards_scanned != NULL, "invariant" );
420 _total_cards_scanned = 0;
421 for (uint i = 0; i < n_workers(); ++i) {
422 _total_cards_scanned += _cards_scanned[i];
423 }
424 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
425 _cards_scanned = NULL;
426 // Cleanup after copy
427 _g1->set_refine_cte_cl_concurrency(true);
428 // Set all cards back to clean.
429 _g1->cleanUpCardTable();
431 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
432 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
434 if (_g1->evacuation_failed()) {
435 // Restore remembered sets for the regions pointing into the collection set.
437 if (G1DeferredRSUpdate) {
438 // If deferred RS updates are enabled then we just need to transfer
439 // the completed buffers from (a) the DirtyCardQueueSet used to hold
440 // cards that contain references that point into the collection set
441 // to (b) the DCQS used to hold the deferred RS updates
442 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
443 } else {
445 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
446 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
448 int n_completed_buffers = 0;
449 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
450 0, 0, true)) {
451 n_completed_buffers++;
452 }
453 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
454 }
455 }
457 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
458 // which contain references that point into the collection.
459 _g1->into_cset_dirty_card_queue_set().clear();
460 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
461 "all buffers should be freed");
462 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
463 }
465 class ScrubRSClosure: public HeapRegionClosure {
466 G1CollectedHeap* _g1h;
467 BitMap* _region_bm;
468 BitMap* _card_bm;
469 CardTableModRefBS* _ctbs;
470 public:
471 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
472 _g1h(G1CollectedHeap::heap()),
473 _region_bm(region_bm), _card_bm(card_bm),
474 _ctbs(NULL)
475 {
476 ModRefBarrierSet* bs = _g1h->mr_bs();
477 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
478 _ctbs = (CardTableModRefBS*)bs;
479 }
481 bool doHeapRegion(HeapRegion* r) {
482 if (!r->continuesHumongous()) {
483 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
484 }
485 return false;
486 }
487 };
489 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
490 ScrubRSClosure scrub_cl(region_bm, card_bm);
491 _g1->heap_region_iterate(&scrub_cl);
492 }
494 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
495 uint worker_num, int claim_val) {
496 ScrubRSClosure scrub_cl(region_bm, card_bm);
497 _g1->heap_region_par_iterate_chunked(&scrub_cl,
498 worker_num,
499 n_workers(),
500 claim_val);
501 }
503 G1TriggerClosure::G1TriggerClosure() :
504 _triggered(false) { }
506 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
507 OopClosure* oop_cl) :
508 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
510 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
511 _c1(c1), _c2(c2) { }
513 G1UpdateRSOrPushRefOopClosure::
514 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
515 G1RemSet* rs,
516 OopsInHeapRegionClosure* push_ref_cl,
517 bool record_refs_into_cset,
518 int worker_i) :
519 _g1(g1h), _g1_rem_set(rs), _from(NULL),
520 _record_refs_into_cset(record_refs_into_cset),
521 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
523 // Returns true if the given card contains references that point
524 // into the collection set, if we're checking for such references;
525 // false otherwise.
527 bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i,
528 bool check_for_refs_into_cset) {
530 // If the card is no longer dirty, nothing to do.
531 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
532 // No need to return that this card contains refs that point
533 // into the collection set.
534 return false;
535 }
537 // Construct the region representing the card.
538 HeapWord* start = _ct_bs->addr_for(card_ptr);
539 // And find the region containing it.
540 HeapRegion* r = _g1->heap_region_containing(start);
541 if (r == NULL) {
542 // Again no need to return that this card contains refs that
543 // point into the collection set.
544 return false; // Not in the G1 heap (might be in perm, for example.)
545 }
547 // Why do we have to check here whether a card is on a young region,
548 // given that we dirty young regions and, as a result, the
549 // post-barrier is supposed to filter them out and never to enqueue
550 // them? When we allocate a new region as the "allocation region" we
551 // actually dirty its cards after we release the lock, since card
552 // dirtying while holding the lock was a performance bottleneck. So,
553 // as a result, it is possible for other threads to actually
554 // allocate objects in the region (after the acquire the lock)
555 // before all the cards on the region are dirtied. This is unlikely,
556 // and it doesn't happen often, but it can happen. So, the extra
557 // check below filters out those cards.
558 if (r->is_young()) {
559 return false;
560 }
562 // While we are processing RSet buffers during the collection, we
563 // actually don't want to scan any cards on the collection set,
564 // since we don't want to update remebered sets with entries that
565 // point into the collection set, given that live objects from the
566 // collection set are about to move and such entries will be stale
567 // very soon. This change also deals with a reliability issue which
568 // involves scanning a card in the collection set and coming across
569 // an array that was being chunked and looking malformed. Note,
570 // however, that if evacuation fails, we have to scan any objects
571 // that were not moved and create any missing entries.
572 if (r->in_collection_set()) {
573 return false;
574 }
576 // The result from the hot card cache insert call is either:
577 // * pointer to the current card
578 // (implying that the current card is not 'hot'),
579 // * null
580 // (meaning we had inserted the card ptr into the "hot" card cache,
581 // which had some headroom),
582 // * a pointer to a "hot" card that was evicted from the "hot" cache.
583 //
585 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
586 if (hot_card_cache->use_cache()) {
587 assert(!check_for_refs_into_cset, "sanity");
588 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
590 card_ptr = hot_card_cache->insert(card_ptr);
591 if (card_ptr == NULL) {
592 // There was no eviction. Nothing to do.
593 return false;
594 }
596 start = _ct_bs->addr_for(card_ptr);
597 r = _g1->heap_region_containing(start);
598 if (r == NULL) {
599 // Not in the G1 heap
600 return false;
601 }
603 // Checking whether the region we got back from the cache
604 // is young here is inappropriate. The region could have been
605 // freed, reallocated and tagged as young while in the cache.
606 // Hence we could see its young type change at any time.
607 }
609 // Don't use addr_for(card_ptr + 1) which can ask for
610 // a card beyond the heap. This is not safe without a perm
611 // gen at the upper end of the heap.
612 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
613 MemRegion dirtyRegion(start, end);
615 #if CARD_REPEAT_HISTO
616 init_ct_freq_table(_g1->max_capacity());
617 ct_freq_note_card(_ct_bs->index_for(start));
618 #endif
620 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
621 if (check_for_refs_into_cset) {
622 // ConcurrentG1RefineThreads have worker numbers larger than what
623 // _cset_rs_update_cl[] is set up to handle. But those threads should
624 // only be active outside of a collection which means that when they
625 // reach here they should have check_for_refs_into_cset == false.
626 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
627 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
628 }
629 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
630 _g1->g1_rem_set(),
631 oops_in_heap_closure,
632 check_for_refs_into_cset,
633 worker_i);
634 update_rs_oop_cl.set_from(r);
636 G1TriggerClosure trigger_cl;
637 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
638 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
639 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
641 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
642 (check_for_refs_into_cset ?
643 (OopClosure*)&mux :
644 (OopClosure*)&update_rs_oop_cl));
646 // The region for the current card may be a young region. The
647 // current card may have been a card that was evicted from the
648 // card cache. When the card was inserted into the cache, we had
649 // determined that its region was non-young. While in the cache,
650 // the region may have been freed during a cleanup pause, reallocated
651 // and tagged as young.
652 //
653 // We wish to filter out cards for such a region but the current
654 // thread, if we're running concurrently, may "see" the young type
655 // change at any time (so an earlier "is_young" check may pass or
656 // fail arbitrarily). We tell the iteration code to perform this
657 // filtering when it has been determined that there has been an actual
658 // allocation in this region and making it safe to check the young type.
659 bool filter_young = true;
661 HeapWord* stop_point =
662 r->oops_on_card_seq_iterate_careful(dirtyRegion,
663 &filter_then_update_rs_oop_cl,
664 filter_young,
665 card_ptr);
667 // If stop_point is non-null, then we encountered an unallocated region
668 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
669 // card and re-enqueue: if we put off the card until a GC pause, then the
670 // unallocated portion will be filled in. Alternatively, we might try
671 // the full complexity of the technique used in "regular" precleaning.
672 if (stop_point != NULL) {
673 // The card might have gotten re-dirtied and re-enqueued while we
674 // worked. (In fact, it's pretty likely.)
675 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
676 *card_ptr = CardTableModRefBS::dirty_card_val();
677 MutexLockerEx x(Shared_DirtyCardQ_lock,
678 Mutex::_no_safepoint_check_flag);
679 DirtyCardQueue* sdcq =
680 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
681 sdcq->enqueue(card_ptr);
682 }
683 } else {
684 _conc_refine_cards++;
685 }
687 // This gets set to true if the card being refined has
688 // references that point into the collection set.
689 bool has_refs_into_cset = trigger_cl.triggered();
691 // We should only be detecting that the card contains references
692 // that point into the collection set if the current thread is
693 // a GC worker thread.
694 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
695 "invalid result at non safepoint");
697 return has_refs_into_cset;
698 }
700 class HRRSStatsIter: public HeapRegionClosure {
701 size_t _occupied;
702 size_t _total_mem_sz;
703 size_t _max_mem_sz;
704 HeapRegion* _max_mem_sz_region;
705 public:
706 HRRSStatsIter() :
707 _occupied(0),
708 _total_mem_sz(0),
709 _max_mem_sz(0),
710 _max_mem_sz_region(NULL)
711 {}
713 bool doHeapRegion(HeapRegion* r) {
714 if (r->continuesHumongous()) return false;
715 size_t mem_sz = r->rem_set()->mem_size();
716 if (mem_sz > _max_mem_sz) {
717 _max_mem_sz = mem_sz;
718 _max_mem_sz_region = r;
719 }
720 _total_mem_sz += mem_sz;
721 size_t occ = r->rem_set()->occupied();
722 _occupied += occ;
723 return false;
724 }
725 size_t total_mem_sz() { return _total_mem_sz; }
726 size_t max_mem_sz() { return _max_mem_sz; }
727 size_t occupied() { return _occupied; }
728 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
729 };
731 class PrintRSThreadVTimeClosure : public ThreadClosure {
732 public:
733 virtual void do_thread(Thread *t) {
734 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
735 gclog_or_tty->print(" %5.2f", crt->vtime_accum());
736 }
737 };
739 void G1RemSet::print_summary_info() {
740 G1CollectedHeap* g1 = G1CollectedHeap::heap();
742 #if CARD_REPEAT_HISTO
743 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
744 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
745 card_repeat_count.print_on(gclog_or_tty);
746 #endif
748 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
749 _conc_refine_cards);
750 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
751 jint tot_processed_buffers =
752 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
753 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers);
754 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.",
755 dcqs.processed_buffers_rs_thread(),
756 100.0*(float)dcqs.processed_buffers_rs_thread()/
757 (float)tot_processed_buffers);
758 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.",
759 dcqs.processed_buffers_mut(),
760 100.0*(float)dcqs.processed_buffers_mut()/
761 (float)tot_processed_buffers);
762 gclog_or_tty->print_cr(" Conc RS threads times(s)");
763 PrintRSThreadVTimeClosure p;
764 gclog_or_tty->print(" ");
765 g1->concurrent_g1_refine()->threads_do(&p);
766 gclog_or_tty->print_cr("");
768 HRRSStatsIter blk;
769 g1->heap_region_iterate(&blk);
770 gclog_or_tty->print_cr(" Total heap region rem set sizes = "SIZE_FORMAT"K."
771 " Max = "SIZE_FORMAT"K.",
772 blk.total_mem_sz()/K, blk.max_mem_sz()/K);
773 gclog_or_tty->print_cr(" Static structures = "SIZE_FORMAT"K,"
774 " free_lists = "SIZE_FORMAT"K.",
775 HeapRegionRemSet::static_mem_size() / K,
776 HeapRegionRemSet::fl_mem_size() / K);
777 gclog_or_tty->print_cr(" "SIZE_FORMAT" occupied cards represented.",
778 blk.occupied());
779 HeapRegion* max_mem_sz_region = blk.max_mem_sz_region();
780 HeapRegionRemSet* rem_set = max_mem_sz_region->rem_set();
781 gclog_or_tty->print_cr(" Max size region = "HR_FORMAT", "
782 "size = "SIZE_FORMAT "K, occupied = "SIZE_FORMAT"K.",
783 HR_FORMAT_PARAMS(max_mem_sz_region),
784 (rem_set->mem_size() + K - 1)/K,
785 (rem_set->occupied() + K - 1)/K);
786 gclog_or_tty->print_cr(" Did %d coarsenings.",
787 HeapRegionRemSet::n_coarsenings());
788 }
790 void G1RemSet::prepare_for_verify() {
791 if (G1HRRSFlushLogBuffersOnVerify &&
792 (VerifyBeforeGC || VerifyAfterGC)
793 && !_g1->full_collection()) {
794 cleanupHRRS();
795 _g1->set_refine_cte_cl_concurrency(false);
796 if (SafepointSynchronize::is_at_safepoint()) {
797 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
798 dcqs.concatenate_logs();
799 }
801 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
802 bool use_hot_card_cache = hot_card_cache->use_cache();
803 hot_card_cache->set_use_cache(false);
805 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
806 updateRS(&into_cset_dcq, 0);
807 _g1->into_cset_dirty_card_queue_set().clear();
809 hot_card_cache->set_use_cache(use_hot_card_cache);
810 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
811 }
812 }