Thu, 07 Aug 2014 22:28:53 +0200
8054341: Remove some obsolete code in G1CollectedHeap class
Summary: Remove dead code.
Reviewed-by: stefank, brutisso
1 /*
2 * Copyright (c) 2001, 2014, 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/concurrentG1Refine.hpp"
27 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
28 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
30 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
31 #include "gc_implementation/g1/g1HotCardCache.hpp"
32 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
33 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
34 #include "gc_implementation/g1/g1RemSet.inline.hpp"
35 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
37 #include "memory/iterator.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "utilities/intHisto.hpp"
41 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
43 #define CARD_REPEAT_HISTO 0
45 #if CARD_REPEAT_HISTO
46 static size_t ct_freq_sz;
47 static jbyte* ct_freq = NULL;
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 }
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 }
62 static IntHistogram card_repeat_count(10, 10);
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 }
70 }
71 #endif
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 _seq_task = new SubTasksDone(NumSeqTasks);
82 guarantee(n_workers() > 0, "There should be some workers");
83 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC);
84 for (uint i = 0; i < n_workers(); i++) {
85 _cset_rs_update_cl[i] = NULL;
86 }
87 if (G1SummarizeRSetStats) {
88 _prev_period_summary.initialize(this);
89 }
90 }
92 G1RemSet::~G1RemSet() {
93 delete _seq_task;
94 for (uint i = 0; i < n_workers(); i++) {
95 assert(_cset_rs_update_cl[i] == NULL, "it should be");
96 }
97 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC);
98 }
100 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
101 if (_g1->is_in_g1_reserved(mr.start())) {
102 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
103 if (_start_first == NULL) _start_first = mr.start();
104 }
105 }
107 class ScanRSClosure : public HeapRegionClosure {
108 size_t _cards_done, _cards;
109 G1CollectedHeap* _g1h;
111 OopsInHeapRegionClosure* _oc;
112 CodeBlobToOopClosure* _code_root_cl;
114 G1BlockOffsetSharedArray* _bot_shared;
115 G1SATBCardTableModRefBS *_ct_bs;
117 double _strong_code_root_scan_time_sec;
118 uint _worker_i;
119 int _block_size;
120 bool _try_claimed;
122 public:
123 ScanRSClosure(OopsInHeapRegionClosure* oc,
124 CodeBlobToOopClosure* code_root_cl,
125 uint worker_i) :
126 _oc(oc),
127 _code_root_cl(code_root_cl),
128 _strong_code_root_scan_time_sec(0.0),
129 _cards(0),
130 _cards_done(0),
131 _worker_i(worker_i),
132 _try_claimed(false)
133 {
134 _g1h = G1CollectedHeap::heap();
135 _bot_shared = _g1h->bot_shared();
136 _ct_bs = _g1h->g1_barrier_set();
137 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
138 }
140 void set_try_claimed() { _try_claimed = true; }
142 void scanCard(size_t index, HeapRegion *r) {
143 // Stack allocate the DirtyCardToOopClosure instance
144 HeapRegionDCTOC cl(_g1h, r, _oc,
145 CardTableModRefBS::Precise,
146 HeapRegionDCTOC::IntoCSFilterKind);
148 // Set the "from" region in the closure.
149 _oc->set_region(r);
150 HeapWord* card_start = _bot_shared->address_for_index(index);
151 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
152 Space *sp = SharedHeap::heap()->space_containing(card_start);
153 MemRegion sm_region = sp->used_region_at_save_marks();
154 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
155 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
156 // We make the card as "claimed" lazily (so races are possible
157 // but they're benign), which reduces the number of duplicate
158 // scans (the rsets of the regions in the cset can intersect).
159 _ct_bs->set_card_claimed(index);
160 _cards_done++;
161 cl.do_MemRegion(mr);
162 }
163 }
165 void printCard(HeapRegion* card_region, size_t card_index,
166 HeapWord* card_start) {
167 gclog_or_tty->print_cr("T " UINT32_FORMAT " Region [" PTR_FORMAT ", " PTR_FORMAT ") "
168 "RS names card %p: "
169 "[" PTR_FORMAT ", " PTR_FORMAT ")",
170 _worker_i,
171 card_region->bottom(), card_region->end(),
172 card_index,
173 card_start, card_start + G1BlockOffsetSharedArray::N_words);
174 }
176 void scan_strong_code_roots(HeapRegion* r) {
177 double scan_start = os::elapsedTime();
178 r->strong_code_roots_do(_code_root_cl);
179 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
180 }
182 bool doHeapRegion(HeapRegion* r) {
183 assert(r->in_collection_set(), "should only be called on elements of CS.");
184 HeapRegionRemSet* hrrs = r->rem_set();
185 if (hrrs->iter_is_complete()) return false; // All done.
186 if (!_try_claimed && !hrrs->claim_iter()) return false;
187 // If we ever free the collection set concurrently, we should also
188 // clear the card table concurrently therefore we won't need to
189 // add regions of the collection set to the dirty cards region.
190 _g1h->push_dirty_cards_region(r);
191 // If we didn't return above, then
192 // _try_claimed || r->claim_iter()
193 // is true: either we're supposed to work on claimed-but-not-complete
194 // regions, or we successfully claimed the region.
196 HeapRegionRemSetIterator iter(hrrs);
197 size_t card_index;
199 // We claim cards in block so as to recude the contention. The block size is determined by
200 // the G1RSetScanBlockSize parameter.
201 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
202 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
203 if (current_card >= jump_to_card + _block_size) {
204 jump_to_card = hrrs->iter_claimed_next(_block_size);
205 }
206 if (current_card < jump_to_card) continue;
207 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
208 #if 0
209 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
210 card_start, card_start + CardTableModRefBS::card_size_in_words);
211 #endif
213 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
214 assert(card_region != NULL, "Yielding cards not in the heap?");
215 _cards++;
217 if (!card_region->is_on_dirty_cards_region_list()) {
218 _g1h->push_dirty_cards_region(card_region);
219 }
221 // If the card is dirty, then we will scan it during updateRS.
222 if (!card_region->in_collection_set() &&
223 !_ct_bs->is_card_dirty(card_index)) {
224 scanCard(card_index, card_region);
225 }
226 }
227 if (!_try_claimed) {
228 // Scan the strong code root list attached to the current region
229 scan_strong_code_roots(r);
231 hrrs->set_iter_complete();
232 }
233 return false;
234 }
236 double strong_code_root_scan_time_sec() {
237 return _strong_code_root_scan_time_sec;
238 }
240 size_t cards_done() { return _cards_done;}
241 size_t cards_looked_up() { return _cards;}
242 };
244 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc,
245 CodeBlobToOopClosure* code_root_cl,
246 uint worker_i) {
247 double rs_time_start = os::elapsedTime();
248 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
250 ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
252 _g1->collection_set_iterate_from(startRegion, &scanRScl);
253 scanRScl.set_try_claimed();
254 _g1->collection_set_iterate_from(startRegion, &scanRScl);
256 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
257 - scanRScl.strong_code_root_scan_time_sec();
259 assert(_cards_scanned != NULL, "invariant");
260 _cards_scanned[worker_i] = scanRScl.cards_done();
262 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
263 _g1p->phase_times()->record_strong_code_root_scan_time(worker_i,
264 scanRScl.strong_code_root_scan_time_sec() * 1000.0);
265 }
267 // Closure used for updating RSets and recording references that
268 // point into the collection set. Only called during an
269 // evacuation pause.
271 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
272 G1RemSet* _g1rs;
273 DirtyCardQueue* _into_cset_dcq;
274 public:
275 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
276 DirtyCardQueue* into_cset_dcq) :
277 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
278 {}
279 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
280 // The only time we care about recording cards that
281 // contain references that point into the collection set
282 // is during RSet updating within an evacuation pause.
283 // In this case worker_i should be the id of a GC worker thread.
284 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
285 assert(worker_i < (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
287 if (_g1rs->refine_card(card_ptr, worker_i, true)) {
288 // 'card_ptr' contains references that point into the collection
289 // set. We need to record the card in the DCQS
290 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
291 // that's used for that purpose.
292 //
293 // Enqueue the card
294 _into_cset_dcq->enqueue(card_ptr);
295 }
296 return true;
297 }
298 };
300 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
301 double start = os::elapsedTime();
302 // Apply the given closure to all remaining log entries.
303 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
305 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
307 // Now there should be no dirty cards.
308 if (G1RSLogCheckCardTable) {
309 CountNonCleanMemRegionClosure cl(_g1);
310 _ct_bs->mod_card_iterate(&cl);
311 // XXX This isn't true any more: keeping cards of young regions
312 // marked dirty broke it. Need some reasonable fix.
313 guarantee(cl.n() == 0, "Card table should be clean.");
314 }
316 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
317 }
319 void G1RemSet::cleanupHRRS() {
320 HeapRegionRemSet::cleanup();
321 }
323 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
324 CodeBlobToOopClosure* code_root_cl,
325 uint worker_i) {
326 #if CARD_REPEAT_HISTO
327 ct_freq_update_histo_and_reset();
328 #endif
330 // We cache the value of 'oc' closure into the appropriate slot in the
331 // _cset_rs_update_cl for this worker
332 assert(worker_i < n_workers(), "sanity");
333 _cset_rs_update_cl[worker_i] = oc;
335 // A DirtyCardQueue that is used to hold cards containing references
336 // that point into the collection set. This DCQ is associated with a
337 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
338 // circumstances (i.e. the pause successfully completes), these cards
339 // are just discarded (there's no need to update the RSets of regions
340 // that were in the collection set - after the pause these regions
341 // are wholly 'free' of live objects. In the event of an evacuation
342 // failure the cards/buffers in this queue set are:
343 // * passed to the DirtyCardQueueSet that is used to manage deferred
344 // RSet updates, or
345 // * scanned for references that point into the collection set
346 // and the RSet of the corresponding region in the collection set
347 // is updated immediately.
348 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
350 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
352 // The two flags below were introduced temporarily to serialize
353 // the updating and scanning of remembered sets. There are some
354 // race conditions when these two operations are done in parallel
355 // and they are causing failures. When we resolve said race
356 // conditions, we'll revert back to parallel remembered set
357 // updating and scanning. See CRs 6677707 and 6677708.
358 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
359 updateRS(&into_cset_dcq, worker_i);
360 } else {
361 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0);
362 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
363 }
364 if (G1UseParallelRSetScanning || (worker_i == 0)) {
365 scanRS(oc, code_root_cl, worker_i);
366 } else {
367 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
368 }
370 // We now clear the cached values of _cset_rs_update_cl for this worker
371 _cset_rs_update_cl[worker_i] = NULL;
372 }
374 void G1RemSet::prepare_for_oops_into_collection_set_do() {
375 cleanupHRRS();
376 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
377 _g1->set_refine_cte_cl_concurrency(false);
378 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
379 dcqs.concatenate_logs();
381 guarantee( _cards_scanned == NULL, "invariant" );
382 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
383 for (uint i = 0; i < n_workers(); ++i) {
384 _cards_scanned[i] = 0;
385 }
386 _total_cards_scanned = 0;
387 }
390 // This closure, applied to a DirtyCardQueueSet, is used to immediately
391 // update the RSets for the regions in the CSet. For each card it iterates
392 // through the oops which coincide with that card. It scans the reference
393 // fields in each oop; when it finds an oop that points into the collection
394 // set, the RSet for the region containing the referenced object is updated.
395 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
396 G1CollectedHeap* _g1;
397 CardTableModRefBS* _ct_bs;
398 public:
399 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
400 CardTableModRefBS* bs):
401 _g1(g1), _ct_bs(bs)
402 { }
404 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
405 // Construct the region representing the card.
406 HeapWord* start = _ct_bs->addr_for(card_ptr);
407 // And find the region containing it.
408 HeapRegion* r = _g1->heap_region_containing(start);
409 assert(r != NULL, "unexpected null");
411 // Scan oops in the card looking for references into the collection set
412 // Don't use addr_for(card_ptr + 1) which can ask for
413 // a card beyond the heap. This is not safe without a perm
414 // gen.
415 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
416 MemRegion scanRegion(start, end);
418 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
419 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
420 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
422 // We can pass false as the "filter_young" parameter here as:
423 // * we should be in a STW pause,
424 // * the DCQS to which this closure is applied is used to hold
425 // references that point into the collection set from the prior
426 // RSet updating,
427 // * the post-write barrier shouldn't be logging updates to young
428 // regions (but there is a situation where this can happen - see
429 // the comment in G1RemSet::refine_card() below -
430 // that should not be applicable here), and
431 // * during actual RSet updating, the filtering of cards in young
432 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
433 // employed.
434 // As a result, when this closure is applied to "refs into cset"
435 // DCQS, we shouldn't see any cards in young regions.
436 update_rs_cl.set_region(r);
437 HeapWord* stop_point =
438 r->oops_on_card_seq_iterate_careful(scanRegion,
439 &filter_then_update_rs_cset_oop_cl,
440 false /* filter_young */,
441 NULL /* card_ptr */);
443 // Since this is performed in the event of an evacuation failure, we
444 // we shouldn't see a non-null stop point
445 assert(stop_point == NULL, "saw an unallocated region");
446 return true;
447 }
448 };
450 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
451 guarantee( _cards_scanned != NULL, "invariant" );
452 _total_cards_scanned = 0;
453 for (uint i = 0; i < n_workers(); ++i) {
454 _total_cards_scanned += _cards_scanned[i];
455 }
456 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
457 _cards_scanned = NULL;
458 // Cleanup after copy
459 _g1->set_refine_cte_cl_concurrency(true);
460 // Set all cards back to clean.
461 _g1->cleanUpCardTable();
463 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
464 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
466 if (_g1->evacuation_failed()) {
467 double restore_remembered_set_start = os::elapsedTime();
469 // Restore remembered sets for the regions pointing into the collection set.
470 if (G1DeferredRSUpdate) {
471 // If deferred RS updates are enabled then we just need to transfer
472 // the completed buffers from (a) the DirtyCardQueueSet used to hold
473 // cards that contain references that point into the collection set
474 // to (b) the DCQS used to hold the deferred RS updates
475 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
476 } else {
478 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
479 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
481 int n_completed_buffers = 0;
482 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
483 0, 0, true)) {
484 n_completed_buffers++;
485 }
486 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
487 }
489 _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
490 }
492 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
493 // which contain references that point into the collection.
494 _g1->into_cset_dirty_card_queue_set().clear();
495 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
496 "all buffers should be freed");
497 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
498 }
500 class ScrubRSClosure: public HeapRegionClosure {
501 G1CollectedHeap* _g1h;
502 BitMap* _region_bm;
503 BitMap* _card_bm;
504 CardTableModRefBS* _ctbs;
505 public:
506 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
507 _g1h(G1CollectedHeap::heap()),
508 _region_bm(region_bm), _card_bm(card_bm),
509 _ctbs(_g1h->g1_barrier_set()) {}
511 bool doHeapRegion(HeapRegion* r) {
512 if (!r->continuesHumongous()) {
513 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
514 }
515 return false;
516 }
517 };
519 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
520 ScrubRSClosure scrub_cl(region_bm, card_bm);
521 _g1->heap_region_iterate(&scrub_cl);
522 }
524 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
525 uint worker_num, int claim_val) {
526 ScrubRSClosure scrub_cl(region_bm, card_bm);
527 _g1->heap_region_par_iterate_chunked(&scrub_cl,
528 worker_num,
529 n_workers(),
530 claim_val);
531 }
533 G1TriggerClosure::G1TriggerClosure() :
534 _triggered(false) { }
536 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
537 OopClosure* oop_cl) :
538 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
540 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
541 _c1(c1), _c2(c2) { }
543 G1UpdateRSOrPushRefOopClosure::
544 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
545 G1RemSet* rs,
546 OopsInHeapRegionClosure* push_ref_cl,
547 bool record_refs_into_cset,
548 uint worker_i) :
549 _g1(g1h), _g1_rem_set(rs), _from(NULL),
550 _record_refs_into_cset(record_refs_into_cset),
551 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
553 // Returns true if the given card contains references that point
554 // into the collection set, if we're checking for such references;
555 // false otherwise.
557 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
558 bool check_for_refs_into_cset) {
560 // If the card is no longer dirty, nothing to do.
561 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
562 // No need to return that this card contains refs that point
563 // into the collection set.
564 return false;
565 }
567 // Construct the region representing the card.
568 HeapWord* start = _ct_bs->addr_for(card_ptr);
569 // And find the region containing it.
570 HeapRegion* r = _g1->heap_region_containing(start);
571 if (r == NULL) {
572 // Again no need to return that this card contains refs that
573 // point into the collection set.
574 return false; // Not in the G1 heap (might be in perm, for example.)
575 }
577 // Why do we have to check here whether a card is on a young region,
578 // given that we dirty young regions and, as a result, the
579 // post-barrier is supposed to filter them out and never to enqueue
580 // them? When we allocate a new region as the "allocation region" we
581 // actually dirty its cards after we release the lock, since card
582 // dirtying while holding the lock was a performance bottleneck. So,
583 // as a result, it is possible for other threads to actually
584 // allocate objects in the region (after the acquire the lock)
585 // before all the cards on the region are dirtied. This is unlikely,
586 // and it doesn't happen often, but it can happen. So, the extra
587 // check below filters out those cards.
588 if (r->is_young()) {
589 return false;
590 }
592 // While we are processing RSet buffers during the collection, we
593 // actually don't want to scan any cards on the collection set,
594 // since we don't want to update remebered sets with entries that
595 // point into the collection set, given that live objects from the
596 // collection set are about to move and such entries will be stale
597 // very soon. This change also deals with a reliability issue which
598 // involves scanning a card in the collection set and coming across
599 // an array that was being chunked and looking malformed. Note,
600 // however, that if evacuation fails, we have to scan any objects
601 // that were not moved and create any missing entries.
602 if (r->in_collection_set()) {
603 return false;
604 }
606 // The result from the hot card cache insert call is either:
607 // * pointer to the current card
608 // (implying that the current card is not 'hot'),
609 // * null
610 // (meaning we had inserted the card ptr into the "hot" card cache,
611 // which had some headroom),
612 // * a pointer to a "hot" card that was evicted from the "hot" cache.
613 //
615 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
616 if (hot_card_cache->use_cache()) {
617 assert(!check_for_refs_into_cset, "sanity");
618 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
620 card_ptr = hot_card_cache->insert(card_ptr);
621 if (card_ptr == NULL) {
622 // There was no eviction. Nothing to do.
623 return false;
624 }
626 start = _ct_bs->addr_for(card_ptr);
627 r = _g1->heap_region_containing(start);
628 if (r == NULL) {
629 // Not in the G1 heap
630 return false;
631 }
633 // Checking whether the region we got back from the cache
634 // is young here is inappropriate. The region could have been
635 // freed, reallocated and tagged as young while in the cache.
636 // Hence we could see its young type change at any time.
637 }
639 // Don't use addr_for(card_ptr + 1) which can ask for
640 // a card beyond the heap. This is not safe without a perm
641 // gen at the upper end of the heap.
642 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
643 MemRegion dirtyRegion(start, end);
645 #if CARD_REPEAT_HISTO
646 init_ct_freq_table(_g1->max_capacity());
647 ct_freq_note_card(_ct_bs->index_for(start));
648 #endif
650 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
651 if (check_for_refs_into_cset) {
652 // ConcurrentG1RefineThreads have worker numbers larger than what
653 // _cset_rs_update_cl[] is set up to handle. But those threads should
654 // only be active outside of a collection which means that when they
655 // reach here they should have check_for_refs_into_cset == false.
656 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
657 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
658 }
659 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
660 _g1->g1_rem_set(),
661 oops_in_heap_closure,
662 check_for_refs_into_cset,
663 worker_i);
664 update_rs_oop_cl.set_from(r);
666 G1TriggerClosure trigger_cl;
667 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
668 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
669 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
671 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
672 (check_for_refs_into_cset ?
673 (OopClosure*)&mux :
674 (OopClosure*)&update_rs_oop_cl));
676 // The region for the current card may be a young region. The
677 // current card may have been a card that was evicted from the
678 // card cache. When the card was inserted into the cache, we had
679 // determined that its region was non-young. While in the cache,
680 // the region may have been freed during a cleanup pause, reallocated
681 // and tagged as young.
682 //
683 // We wish to filter out cards for such a region but the current
684 // thread, if we're running concurrently, may "see" the young type
685 // change at any time (so an earlier "is_young" check may pass or
686 // fail arbitrarily). We tell the iteration code to perform this
687 // filtering when it has been determined that there has been an actual
688 // allocation in this region and making it safe to check the young type.
689 bool filter_young = true;
691 HeapWord* stop_point =
692 r->oops_on_card_seq_iterate_careful(dirtyRegion,
693 &filter_then_update_rs_oop_cl,
694 filter_young,
695 card_ptr);
697 // If stop_point is non-null, then we encountered an unallocated region
698 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
699 // card and re-enqueue: if we put off the card until a GC pause, then the
700 // unallocated portion will be filled in. Alternatively, we might try
701 // the full complexity of the technique used in "regular" precleaning.
702 if (stop_point != NULL) {
703 // The card might have gotten re-dirtied and re-enqueued while we
704 // worked. (In fact, it's pretty likely.)
705 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
706 *card_ptr = CardTableModRefBS::dirty_card_val();
707 MutexLockerEx x(Shared_DirtyCardQ_lock,
708 Mutex::_no_safepoint_check_flag);
709 DirtyCardQueue* sdcq =
710 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
711 sdcq->enqueue(card_ptr);
712 }
713 } else {
714 _conc_refine_cards++;
715 }
717 // This gets set to true if the card being refined has
718 // references that point into the collection set.
719 bool has_refs_into_cset = trigger_cl.triggered();
721 // We should only be detecting that the card contains references
722 // that point into the collection set if the current thread is
723 // a GC worker thread.
724 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
725 "invalid result at non safepoint");
727 return has_refs_into_cset;
728 }
730 void G1RemSet::print_periodic_summary_info(const char* header) {
731 G1RemSetSummary current;
732 current.initialize(this);
734 _prev_period_summary.subtract_from(¤t);
735 print_summary_info(&_prev_period_summary, header);
737 _prev_period_summary.set(¤t);
738 }
740 void G1RemSet::print_summary_info() {
741 G1RemSetSummary current;
742 current.initialize(this);
744 print_summary_info(¤t, " Cumulative RS summary");
745 }
747 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) {
748 assert(summary != NULL, "just checking");
750 if (header != NULL) {
751 gclog_or_tty->print_cr("%s", header);
752 }
754 #if CARD_REPEAT_HISTO
755 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
756 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
757 card_repeat_count.print_on(gclog_or_tty);
758 #endif
760 summary->print_on(gclog_or_tty);
761 }
763 void G1RemSet::prepare_for_verify() {
764 if (G1HRRSFlushLogBuffersOnVerify &&
765 (VerifyBeforeGC || VerifyAfterGC)
766 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) {
767 cleanupHRRS();
768 _g1->set_refine_cte_cl_concurrency(false);
769 if (SafepointSynchronize::is_at_safepoint()) {
770 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
771 dcqs.concatenate_logs();
772 }
774 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
775 bool use_hot_card_cache = hot_card_cache->use_cache();
776 hot_card_cache->set_use_cache(false);
778 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
779 updateRS(&into_cset_dcq, 0);
780 _g1->into_cset_dirty_card_queue_set().clear();
782 hot_card_cache->set_use_cache(use_hot_card_cache);
783 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
784 }
785 }