1 /*
2 * Copyright (c) 2001, 2010, 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
70 class IntoCSOopClosure: public OopsInHeapRegionClosure {
71 OopsInHeapRegionClosure* _blk;
72 G1CollectedHeap* _g1;
73 public:
74 IntoCSOopClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) :
75 _g1(g1), _blk(blk) {}
76 void set_region(HeapRegion* from) {
77 _blk->set_region(from);
78 }
79 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
80 virtual void do_oop( oop* p) { do_oop_work(p); }
81 template <class T> void do_oop_work(T* p) {
82 oop obj = oopDesc::load_decode_heap_oop(p);
83 if (_g1->obj_in_cs(obj)) _blk->do_oop(p);
84 }
85 bool apply_to_weak_ref_discovered_field() { return true; }
86 bool idempotent() { return true; }
87 };
88
89 class IntoCSRegionClosure: public HeapRegionClosure {
90 IntoCSOopClosure _blk;
91 G1CollectedHeap* _g1;
92 public:
93 IntoCSRegionClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) :
94 _g1(g1), _blk(g1, blk) {}
95 bool doHeapRegion(HeapRegion* r) {
96 if (!r->in_collection_set()) {
97 _blk.set_region(r);
98 if (r->isHumongous()) {
99 if (r->startsHumongous()) {
100 oop obj = oop(r->bottom());
101 obj->oop_iterate(&_blk);
102 }
103 } else {
104 r->oop_before_save_marks_iterate(&_blk);
105 }
106 }
107 return false;
108 }
109 };
110
111 class VerifyRSCleanCardOopClosure: public OopClosure {
112 G1CollectedHeap* _g1;
113 public:
114 VerifyRSCleanCardOopClosure(G1CollectedHeap* g1) : _g1(g1) {}
115
116 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
117 virtual void do_oop( oop* p) { do_oop_work(p); }
118 template <class T> void do_oop_work(T* p) {
119 oop obj = oopDesc::load_decode_heap_oop(p);
120 HeapRegion* to = _g1->heap_region_containing(obj);
121 guarantee(to == NULL || !to->in_collection_set(),
122 "Missed a rem set member.");
123 }
124 };
125
126 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
127 : _g1(g1), _conc_refine_cards(0),
128 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
129 _cg1r(g1->concurrent_g1_refine()),
130 _traversal_in_progress(false),
131 _cset_rs_update_cl(NULL),
132 _cards_scanned(NULL), _total_cards_scanned(0)
133 {
134 _seq_task = new SubTasksDone(NumSeqTasks);
135 guarantee(n_workers() > 0, "There should be some workers");
136 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers());
137 for (uint i = 0; i < n_workers(); i++) {
138 _cset_rs_update_cl[i] = NULL;
139 }
140 }
141
142 G1RemSet::~G1RemSet() {
143 delete _seq_task;
144 for (uint i = 0; i < n_workers(); i++) {
145 assert(_cset_rs_update_cl[i] == NULL, "it should be");
146 }
147 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl);
148 }
149
150 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
151 if (_g1->is_in_g1_reserved(mr.start())) {
152 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
153 if (_start_first == NULL) _start_first = mr.start();
154 }
155 }
156
157 class ScanRSClosure : public HeapRegionClosure {
158 size_t _cards_done, _cards;
159 G1CollectedHeap* _g1h;
160 OopsInHeapRegionClosure* _oc;
161 G1BlockOffsetSharedArray* _bot_shared;
162 CardTableModRefBS *_ct_bs;
163 int _worker_i;
164 int _block_size;
165 bool _try_claimed;
166 public:
167 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
168 _oc(oc),
169 _cards(0),
170 _cards_done(0),
171 _worker_i(worker_i),
172 _try_claimed(false)
173 {
174 _g1h = G1CollectedHeap::heap();
175 _bot_shared = _g1h->bot_shared();
176 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
177 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
178 }
179
180 void set_try_claimed() { _try_claimed = true; }
181
182 void scanCard(size_t index, HeapRegion *r) {
183 _cards_done++;
184 DirtyCardToOopClosure* cl =
185 r->new_dcto_closure(_oc,
186 CardTableModRefBS::Precise,
187 HeapRegionDCTOC::IntoCSFilterKind);
188
189 // Set the "from" region in the closure.
190 _oc->set_region(r);
191 HeapWord* card_start = _bot_shared->address_for_index(index);
192 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
193 Space *sp = SharedHeap::heap()->space_containing(card_start);
194 MemRegion sm_region;
195 if (ParallelGCThreads > 0) {
196 // first find the used area
197 sm_region = sp->used_region_at_save_marks();
198 } else {
199 // The closure is not idempotent. We shouldn't look at objects
200 // allocated during the GC.
201 sm_region = sp->used_region_at_save_marks();
202 }
203 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
204 if (!mr.is_empty()) {
205 cl->do_MemRegion(mr);
206 }
207 }
208
209 void printCard(HeapRegion* card_region, size_t card_index,
210 HeapWord* card_start) {
211 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
212 "RS names card %p: "
213 "[" PTR_FORMAT ", " PTR_FORMAT ")",
214 _worker_i,
215 card_region->bottom(), card_region->end(),
216 card_index,
217 card_start, card_start + G1BlockOffsetSharedArray::N_words);
218 }
219
220 bool doHeapRegion(HeapRegion* r) {
221 assert(r->in_collection_set(), "should only be called on elements of CS.");
222 HeapRegionRemSet* hrrs = r->rem_set();
223 if (hrrs->iter_is_complete()) return false; // All done.
224 if (!_try_claimed && !hrrs->claim_iter()) return false;
225 _g1h->push_dirty_cards_region(r);
226 // If we didn't return above, then
227 // _try_claimed || r->claim_iter()
228 // is true: either we're supposed to work on claimed-but-not-complete
229 // regions, or we successfully claimed the region.
230 HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i);
231 hrrs->init_iterator(iter);
232 size_t card_index;
233
234 // We claim cards in block so as to recude the contention. The block size is determined by
235 // the G1RSetScanBlockSize parameter.
236 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
237 for (size_t current_card = 0; iter->has_next(card_index); current_card++) {
238 if (current_card >= jump_to_card + _block_size) {
239 jump_to_card = hrrs->iter_claimed_next(_block_size);
240 }
241 if (current_card < jump_to_card) continue;
242 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
243 #if 0
244 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
245 card_start, card_start + CardTableModRefBS::card_size_in_words);
246 #endif
247
248 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
249 assert(card_region != NULL, "Yielding cards not in the heap?");
250 _cards++;
251
252 if (!card_region->is_on_dirty_cards_region_list()) {
253 _g1h->push_dirty_cards_region(card_region);
254 }
255
256 // If the card is dirty, then we will scan it during updateRS.
257 if (!card_region->in_collection_set() && !_ct_bs->is_card_dirty(card_index)) {
258 // We make the card as "claimed" lazily (so races are possible but they're benign),
259 // which reduces the number of duplicate scans (the rsets of the regions in the cset
260 // can intersect).
261 if (!_ct_bs->is_card_claimed(card_index)) {
262 _ct_bs->set_card_claimed(card_index);
263 scanCard(card_index, card_region);
264 }
265 }
266 }
267 if (!_try_claimed) {
268 hrrs->set_iter_complete();
269 }
270 return false;
271 }
272 // Set all cards back to clean.
273 void cleanup() {_g1h->cleanUpCardTable();}
274 size_t cards_done() { return _cards_done;}
275 size_t cards_looked_up() { return _cards;}
276 };
277
278 // We want the parallel threads to start their scanning at
279 // different collection set regions to avoid contention.
280 // If we have:
281 // n collection set regions
282 // p threads
283 // Then thread t will start at region t * floor (n/p)
284
285 HeapRegion* G1RemSet::calculateStartRegion(int worker_i) {
286 HeapRegion* result = _g1p->collection_set();
287 if (ParallelGCThreads > 0) {
288 size_t cs_size = _g1p->collection_set_size();
289 int n_workers = _g1->workers()->total_workers();
290 size_t cs_spans = cs_size / n_workers;
291 size_t ind = cs_spans * worker_i;
292 for (size_t i = 0; i < ind; i++)
293 result = result->next_in_collection_set();
294 }
295 return result;
296 }
297
298 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
299 double rs_time_start = os::elapsedTime();
300 HeapRegion *startRegion = calculateStartRegion(worker_i);
301
302 ScanRSClosure scanRScl(oc, worker_i);
303 _g1->collection_set_iterate_from(startRegion, &scanRScl);
304 scanRScl.set_try_claimed();
305 _g1->collection_set_iterate_from(startRegion, &scanRScl);
306
307 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
308
309 assert( _cards_scanned != NULL, "invariant" );
310 _cards_scanned[worker_i] = scanRScl.cards_done();
311
312 _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
313 }
314
315 // Closure used for updating RSets and recording references that
316 // point into the collection set. Only called during an
317 // evacuation pause.
318
319 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
320 G1RemSet* _g1rs;
321 DirtyCardQueue* _into_cset_dcq;
322 public:
323 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
324 DirtyCardQueue* into_cset_dcq) :
325 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
326 {}
327 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
328 // The only time we care about recording cards that
329 // contain references that point into the collection set
330 // is during RSet updating within an evacuation pause.
331 // In this case worker_i should be the id of a GC worker thread.
332 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
333 assert(worker_i < (int) DirtyCardQueueSet::num_par_ids(), "should be a GC worker");
334
335 if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) {
336 // 'card_ptr' contains references that point into the collection
337 // set. We need to record the card in the DCQS
338 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
339 // that's used for that purpose.
340 //
341 // Enqueue the card
342 _into_cset_dcq->enqueue(card_ptr);
343 }
344 return true;
345 }
346 };
347
348 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
349 double start = os::elapsedTime();
350 // Apply the given closure to all remaining log entries.
351 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
352 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
353
354 // Now there should be no dirty cards.
355 if (G1RSLogCheckCardTable) {
356 CountNonCleanMemRegionClosure cl(_g1);
357 _ct_bs->mod_card_iterate(&cl);
358 // XXX This isn't true any more: keeping cards of young regions
359 // marked dirty broke it. Need some reasonable fix.
360 guarantee(cl.n() == 0, "Card table should be clean.");
361 }
362
363 _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
364 }
365
366 #ifndef PRODUCT
367 class PrintRSClosure : public HeapRegionClosure {
368 int _count;
369 public:
370 PrintRSClosure() : _count(0) {}
371 bool doHeapRegion(HeapRegion* r) {
372 HeapRegionRemSet* hrrs = r->rem_set();
373 _count += (int) hrrs->occupied();
374 if (hrrs->occupied() == 0) {
375 gclog_or_tty->print("Heap Region [" PTR_FORMAT ", " PTR_FORMAT ") "
376 "has no remset entries\n",
377 r->bottom(), r->end());
378 } else {
379 gclog_or_tty->print("Printing rem set for heap region [" PTR_FORMAT ", " PTR_FORMAT ")\n",
380 r->bottom(), r->end());
381 r->print();
382 hrrs->print();
383 gclog_or_tty->print("\nDone printing rem set\n");
384 }
385 return false;
386 }
387 int occupied() {return _count;}
388 };
389 #endif
390
391 class CountRSSizeClosure: public HeapRegionClosure {
392 size_t _n;
393 size_t _tot;
394 size_t _max;
395 HeapRegion* _max_r;
396 enum {
397 N = 20,
398 MIN = 6
399 };
400 int _histo[N];
401 public:
402 CountRSSizeClosure() : _n(0), _tot(0), _max(0), _max_r(NULL) {
403 for (int i = 0; i < N; i++) _histo[i] = 0;
404 }
405 bool doHeapRegion(HeapRegion* r) {
406 if (!r->continuesHumongous()) {
407 size_t occ = r->rem_set()->occupied();
408 _n++;
409 _tot += occ;
410 if (occ > _max) {
411 _max = occ;
412 _max_r = r;
413 }
414 // Fit it into a histo bin.
415 int s = 1 << MIN;
416 int i = 0;
417 while (occ > (size_t) s && i < (N-1)) {
418 s = s << 1;
419 i++;
420 }
421 _histo[i]++;
422 }
423 return false;
424 }
425 size_t n() { return _n; }
426 size_t tot() { return _tot; }
427 size_t mx() { return _max; }
428 HeapRegion* mxr() { return _max_r; }
429 void print_histo() {
430 int mx = N;
431 while (mx >= 0) {
432 if (_histo[mx-1] > 0) break;
433 mx--;
434 }
435 gclog_or_tty->print_cr("Number of regions with given RS sizes:");
436 gclog_or_tty->print_cr(" <= %8d %8d", 1 << MIN, _histo[0]);
437 for (int i = 1; i < mx-1; i++) {
438 gclog_or_tty->print_cr(" %8d - %8d %8d",
439 (1 << (MIN + i - 1)) + 1,
440 1 << (MIN + i),
441 _histo[i]);
442 }
443 gclog_or_tty->print_cr(" > %8d %8d", (1 << (MIN+mx-2))+1, _histo[mx-1]);
444 }
445 };
446
447 void G1RemSet::cleanupHRRS() {
448 HeapRegionRemSet::cleanup();
449 }
450
451 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
452 int worker_i) {
453 #if CARD_REPEAT_HISTO
454 ct_freq_update_histo_and_reset();
455 #endif
456 if (worker_i == 0) {
457 _cg1r->clear_and_record_card_counts();
458 }
459
460 // Make this into a command-line flag...
461 if (G1RSCountHisto && (ParallelGCThreads == 0 || worker_i == 0)) {
462 CountRSSizeClosure count_cl;
463 _g1->heap_region_iterate(&count_cl);
464 gclog_or_tty->print_cr("Avg of %d RS counts is %f, max is %d, "
465 "max region is " PTR_FORMAT,
466 count_cl.n(), (float)count_cl.tot()/(float)count_cl.n(),
467 count_cl.mx(), count_cl.mxr());
468 count_cl.print_histo();
469 }
470
471 // We cache the value of 'oc' closure into the appropriate slot in the
472 // _cset_rs_update_cl for this worker
473 assert(worker_i < (int)n_workers(), "sanity");
474 _cset_rs_update_cl[worker_i] = oc;
475
476 // A DirtyCardQueue that is used to hold cards containing references
477 // that point into the collection set. This DCQ is associated with a
478 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
479 // circumstances (i.e. the pause successfully completes), these cards
480 // are just discarded (there's no need to update the RSets of regions
481 // that were in the collection set - after the pause these regions
482 // are wholly 'free' of live objects. In the event of an evacuation
483 // failure the cards/buffers in this queue set are:
484 // * passed to the DirtyCardQueueSet that is used to manage deferred
485 // RSet updates, or
486 // * scanned for references that point into the collection set
487 // and the RSet of the corresponding region in the collection set
488 // is updated immediately.
489 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
490
491 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
492
493 // The two flags below were introduced temporarily to serialize
494 // the updating and scanning of remembered sets. There are some
495 // race conditions when these two operations are done in parallel
496 // and they are causing failures. When we resolve said race
497 // conditions, we'll revert back to parallel remembered set
498 // updating and scanning. See CRs 6677707 and 6677708.
499 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
500 updateRS(&into_cset_dcq, worker_i);
501 } else {
502 _g1p->record_update_rs_processed_buffers(worker_i, 0.0);
503 _g1p->record_update_rs_time(worker_i, 0.0);
504 }
505 if (G1UseParallelRSetScanning || (worker_i == 0)) {
506 scanRS(oc, worker_i);
507 } else {
508 _g1p->record_scan_rs_time(worker_i, 0.0);
509 }
510
511 // We now clear the cached values of _cset_rs_update_cl for this worker
512 _cset_rs_update_cl[worker_i] = NULL;
513 }
514
515 void G1RemSet::prepare_for_oops_into_collection_set_do() {
516 #if G1_REM_SET_LOGGING
517 PrintRSClosure cl;
518 _g1->collection_set_iterate(&cl);
519 #endif
520 cleanupHRRS();
521 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
522 _g1->set_refine_cte_cl_concurrency(false);
523 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
524 dcqs.concatenate_logs();
525
526 assert(!_traversal_in_progress, "Invariant between iterations.");
527 set_traversal(true);
528 if (ParallelGCThreads > 0) {
529 _seq_task->set_n_threads((int)n_workers());
530 }
531 guarantee( _cards_scanned == NULL, "invariant" );
532 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers());
533 for (uint i = 0; i < n_workers(); ++i) {
534 _cards_scanned[i] = 0;
535 }
536 _total_cards_scanned = 0;
537 }
538
539
540 class cleanUpIteratorsClosure : public HeapRegionClosure {
541 bool doHeapRegion(HeapRegion *r) {
542 HeapRegionRemSet* hrrs = r->rem_set();
543 hrrs->init_for_par_iteration();
544 return false;
545 }
546 };
547
548 // This closure, applied to a DirtyCardQueueSet, is used to immediately
549 // update the RSets for the regions in the CSet. For each card it iterates
550 // through the oops which coincide with that card. It scans the reference
551 // fields in each oop; when it finds an oop that points into the collection
552 // set, the RSet for the region containing the referenced object is updated.
553 // Note: _par_traversal_in_progress in the G1RemSet must be FALSE; otherwise
554 // the UpdateRSetImmediate closure will cause cards to be enqueued on to
555 // the DCQS that we're iterating over, causing an infinite loop.
556 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
557 G1CollectedHeap* _g1;
558 CardTableModRefBS* _ct_bs;
559 public:
560 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
561 CardTableModRefBS* bs):
562 _g1(g1), _ct_bs(bs)
563 { }
564
565 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
566 // Construct the region representing the card.
567 HeapWord* start = _ct_bs->addr_for(card_ptr);
568 // And find the region containing it.
569 HeapRegion* r = _g1->heap_region_containing(start);
570 assert(r != NULL, "unexpected null");
571
572 // Scan oops in the card looking for references into the collection set
573 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
574 MemRegion scanRegion(start, end);
575
576 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
577 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
578 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
579
580 // We can pass false as the "filter_young" parameter here as:
581 // * we should be in a STW pause,
582 // * the DCQS to which this closure is applied is used to hold
583 // references that point into the collection set from the prior
584 // RSet updating,
585 // * the post-write barrier shouldn't be logging updates to young
586 // regions (but there is a situation where this can happen - see
587 // the comment in G1RemSet::concurrentRefineOneCard below -
588 // that should not be applicable here), and
589 // * during actual RSet updating, the filtering of cards in young
590 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
591 // employed.
592 // As a result, when this closure is applied to "refs into cset"
593 // DCQS, we shouldn't see any cards in young regions.
594 update_rs_cl.set_region(r);
595 HeapWord* stop_point =
596 r->oops_on_card_seq_iterate_careful(scanRegion,
597 &filter_then_update_rs_cset_oop_cl,
598 false /* filter_young */);
599
600 // Since this is performed in the event of an evacuation failure, we
601 // we shouldn't see a non-null stop point
602 assert(stop_point == NULL, "saw an unallocated region");
603 return true;
604 }
605 };
606
607 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
608 guarantee( _cards_scanned != NULL, "invariant" );
609 _total_cards_scanned = 0;
610 for (uint i = 0; i < n_workers(); ++i)
611 _total_cards_scanned += _cards_scanned[i];
612 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
613 _cards_scanned = NULL;
614 // Cleanup after copy
615 #if G1_REM_SET_LOGGING
616 PrintRSClosure cl;
617 _g1->heap_region_iterate(&cl);
618 #endif
619 _g1->set_refine_cte_cl_concurrency(true);
620 cleanUpIteratorsClosure iterClosure;
621 _g1->collection_set_iterate(&iterClosure);
622 // Set all cards back to clean.
623 _g1->cleanUpCardTable();
624
625 set_traversal(false);
626
627 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
628 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
629
630 if (_g1->evacuation_failed()) {
631 // Restore remembered sets for the regions pointing into the collection set.
632
633 if (G1DeferredRSUpdate) {
634 // If deferred RS updates are enabled then we just need to transfer
635 // the completed buffers from (a) the DirtyCardQueueSet used to hold
636 // cards that contain references that point into the collection set
637 // to (b) the DCQS used to hold the deferred RS updates
638 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
639 } else {
640
641 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
642 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
643
644 int n_completed_buffers = 0;
645 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
646 0, 0, true)) {
647 n_completed_buffers++;
648 }
649 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
650 }
651 }
652
653 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
654 // which contain references that point into the collection.
655 _g1->into_cset_dirty_card_queue_set().clear();
656 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
657 "all buffers should be freed");
658 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
659
660 assert(!_traversal_in_progress, "Invariant between iterations.");
661 }
662
663 class UpdateRSObjectClosure: public ObjectClosure {
664 UpdateRSOopClosure* _update_rs_oop_cl;
665 public:
666 UpdateRSObjectClosure(UpdateRSOopClosure* update_rs_oop_cl) :
667 _update_rs_oop_cl(update_rs_oop_cl) {}
668 void do_object(oop obj) {
669 obj->oop_iterate(_update_rs_oop_cl);
670 }
671
672 };
673
674 class ScrubRSClosure: public HeapRegionClosure {
675 G1CollectedHeap* _g1h;
676 BitMap* _region_bm;
677 BitMap* _card_bm;
678 CardTableModRefBS* _ctbs;
679 public:
680 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
681 _g1h(G1CollectedHeap::heap()),
682 _region_bm(region_bm), _card_bm(card_bm),
683 _ctbs(NULL)
684 {
685 ModRefBarrierSet* bs = _g1h->mr_bs();
686 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
687 _ctbs = (CardTableModRefBS*)bs;
688 }
689
690 bool doHeapRegion(HeapRegion* r) {
691 if (!r->continuesHumongous()) {
692 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
693 }
694 return false;
695 }
696 };
697
698 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
699 ScrubRSClosure scrub_cl(region_bm, card_bm);
700 _g1->heap_region_iterate(&scrub_cl);
701 }
702
703 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
704 int worker_num, int claim_val) {
705 ScrubRSClosure scrub_cl(region_bm, card_bm);
706 _g1->heap_region_par_iterate_chunked(&scrub_cl, worker_num, claim_val);
707 }
708
709
710 static IntHistogram out_of_histo(50, 50);
711
712 class TriggerClosure : public OopClosure {
713 bool _trigger;
714 public:
715 TriggerClosure() : _trigger(false) { }
716 bool value() const { return _trigger; }
717 template <class T> void do_oop_nv(T* p) { _trigger = true; }
718 virtual void do_oop(oop* p) { do_oop_nv(p); }
719 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
720 };
721
722 class InvokeIfNotTriggeredClosure: public OopClosure {
723 TriggerClosure* _t;
724 OopClosure* _oc;
725 public:
726 InvokeIfNotTriggeredClosure(TriggerClosure* t, OopClosure* oc):
727 _t(t), _oc(oc) { }
728 template <class T> void do_oop_nv(T* p) {
729 if (!_t->value()) _oc->do_oop(p);
730 }
731 virtual void do_oop(oop* p) { do_oop_nv(p); }
732 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
733 };
734
735 class Mux2Closure : public OopClosure {
736 OopClosure* _c1;
737 OopClosure* _c2;
738 public:
739 Mux2Closure(OopClosure *c1, OopClosure *c2) : _c1(c1), _c2(c2) { }
740 template <class T> void do_oop_nv(T* p) {
741 _c1->do_oop(p); _c2->do_oop(p);
742 }
743 virtual void do_oop(oop* p) { do_oop_nv(p); }
744 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
745 };
746
747 bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
748 bool check_for_refs_into_cset) {
749 // Construct the region representing the card.
750 HeapWord* start = _ct_bs->addr_for(card_ptr);
751 // And find the region containing it.
752 HeapRegion* r = _g1->heap_region_containing(start);
753 assert(r != NULL, "unexpected null");
754
755 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
756 MemRegion dirtyRegion(start, end);
757
758 #if CARD_REPEAT_HISTO
759 init_ct_freq_table(_g1->g1_reserved_obj_bytes());
760 ct_freq_note_card(_ct_bs->index_for(start));
761 #endif
762
763 UpdateRSOopClosure update_rs_oop_cl(this, worker_i);
764 update_rs_oop_cl.set_from(r);
765
766 TriggerClosure trigger_cl;
767 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
768 InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
769 Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
770
771 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
772 (check_for_refs_into_cset ?
773 (OopClosure*)&mux :
774 (OopClosure*)&update_rs_oop_cl));
775
776 // Undirty the card.
777 *card_ptr = CardTableModRefBS::clean_card_val();
778 // We must complete this write before we do any of the reads below.
779 OrderAccess::storeload();
780 // And process it, being careful of unallocated portions of TLAB's.
781
782 // The region for the current card may be a young region. The
783 // current card may have been a card that was evicted from the
784 // card cache. When the card was inserted into the cache, we had
785 // determined that its region was non-young. While in the cache,
786 // the region may have been freed during a cleanup pause, reallocated
787 // and tagged as young.
788 //
789 // We wish to filter out cards for such a region but the current
790 // thread, if we're running conucrrently, may "see" the young type
791 // change at any time (so an earlier "is_young" check may pass or
792 // fail arbitrarily). We tell the iteration code to perform this
793 // filtering when it has been determined that there has been an actual
794 // allocation in this region and making it safe to check the young type.
795 bool filter_young = true;
796
797 HeapWord* stop_point =
798 r->oops_on_card_seq_iterate_careful(dirtyRegion,
799 &filter_then_update_rs_oop_cl,
800 filter_young);
801
802 // If stop_point is non-null, then we encountered an unallocated region
803 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
804 // card and re-enqueue: if we put off the card until a GC pause, then the
805 // unallocated portion will be filled in. Alternatively, we might try
806 // the full complexity of the technique used in "regular" precleaning.
807 if (stop_point != NULL) {
808 // The card might have gotten re-dirtied and re-enqueued while we
809 // worked. (In fact, it's pretty likely.)
810 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
811 *card_ptr = CardTableModRefBS::dirty_card_val();
812 MutexLockerEx x(Shared_DirtyCardQ_lock,
813 Mutex::_no_safepoint_check_flag);
814 DirtyCardQueue* sdcq =
815 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
816 sdcq->enqueue(card_ptr);
817 }
818 } else {
819 out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region());
820 _conc_refine_cards++;
821 }
822
823 return trigger_cl.value();
824 }
825
826 bool G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
827 bool check_for_refs_into_cset) {
828 // If the card is no longer dirty, nothing to do.
829 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
830 // No need to return that this card contains refs that point
831 // into the collection set.
832 return false;
833 }
834
835 // Construct the region representing the card.
836 HeapWord* start = _ct_bs->addr_for(card_ptr);
837 // And find the region containing it.
838 HeapRegion* r = _g1->heap_region_containing(start);
839 if (r == NULL) {
840 guarantee(_g1->is_in_permanent(start), "Or else where?");
841 // Again no need to return that this card contains refs that
842 // point into the collection set.
843 return false; // Not in the G1 heap (might be in perm, for example.)
844 }
845 // Why do we have to check here whether a card is on a young region,
846 // given that we dirty young regions and, as a result, the
847 // post-barrier is supposed to filter them out and never to enqueue
848 // them? When we allocate a new region as the "allocation region" we
849 // actually dirty its cards after we release the lock, since card
850 // dirtying while holding the lock was a performance bottleneck. So,
851 // as a result, it is possible for other threads to actually
852 // allocate objects in the region (after the acquire the lock)
853 // before all the cards on the region are dirtied. This is unlikely,
854 // and it doesn't happen often, but it can happen. So, the extra
855 // check below filters out those cards.
856 if (r->is_young()) {
857 return false;
858 }
859 // While we are processing RSet buffers during the collection, we
860 // actually don't want to scan any cards on the collection set,
861 // since we don't want to update remebered sets with entries that
862 // point into the collection set, given that live objects from the
863 // collection set are about to move and such entries will be stale
864 // very soon. This change also deals with a reliability issue which
865 // involves scanning a card in the collection set and coming across
866 // an array that was being chunked and looking malformed. Note,
867 // however, that if evacuation fails, we have to scan any objects
868 // that were not moved and create any missing entries.
869 if (r->in_collection_set()) {
870 return false;
871 }
872
873 // Should we defer processing the card?
874 //
875 // Previously the result from the insert_cache call would be
876 // either card_ptr (implying that card_ptr was currently "cold"),
877 // null (meaning we had inserted the card ptr into the "hot"
878 // cache, which had some headroom), or a "hot" card ptr
879 // extracted from the "hot" cache.
880 //
881 // Now that the _card_counts cache in the ConcurrentG1Refine
882 // instance is an evicting hash table, the result we get back
883 // could be from evicting the card ptr in an already occupied
884 // bucket (in which case we have replaced the card ptr in the
885 // bucket with card_ptr and "defer" is set to false). To avoid
886 // having a data structure (updates to which would need a lock)
887 // to hold these unprocessed dirty cards, we need to immediately
888 // process card_ptr. The actions needed to be taken on return
889 // from cache_insert are summarized in the following table:
890 //
891 // res defer action
892 // --------------------------------------------------------------
893 // null false card evicted from _card_counts & replaced with
894 // card_ptr; evicted ptr added to hot cache.
895 // No need to process res; immediately process card_ptr
896 //
897 // null true card not evicted from _card_counts; card_ptr added
898 // to hot cache.
899 // Nothing to do.
900 //
901 // non-null false card evicted from _card_counts & replaced with
902 // card_ptr; evicted ptr is currently "cold" or
903 // caused an eviction from the hot cache.
904 // Immediately process res; process card_ptr.
905 //
906 // non-null true card not evicted from _card_counts; card_ptr is
907 // currently cold, or caused an eviction from hot
908 // cache.
909 // Immediately process res; no need to process card_ptr.
910
911
912 jbyte* res = card_ptr;
913 bool defer = false;
914
915 // This gets set to true if the card being refined has references
916 // that point into the collection set.
917 bool oops_into_cset = false;
918
919 if (_cg1r->use_cache()) {
920 jbyte* res = _cg1r->cache_insert(card_ptr, &defer);
921 if (res != NULL && (res != card_ptr || defer)) {
922 start = _ct_bs->addr_for(res);
923 r = _g1->heap_region_containing(start);
924 if (r == NULL) {
925 assert(_g1->is_in_permanent(start), "Or else where?");
926 } else {
927 // Checking whether the region we got back from the cache
928 // is young here is inappropriate. The region could have been
929 // freed, reallocated and tagged as young while in the cache.
930 // Hence we could see its young type change at any time.
931 //
932 // Process card pointer we get back from the hot card cache. This
933 // will check whether the region containing the card is young
934 // _after_ checking that the region has been allocated from.
935 oops_into_cset = concurrentRefineOneCard_impl(res, worker_i,
936 false /* check_for_refs_into_cset */);
937 // The above call to concurrentRefineOneCard_impl is only
938 // performed if the hot card cache is enabled. This cache is
939 // disabled during an evacuation pause - which is the only
940 // time when we need know if the card contains references
941 // that point into the collection set. Also when the hot card
942 // cache is enabled, this code is executed by the concurrent
943 // refine threads - rather than the GC worker threads - and
944 // concurrentRefineOneCard_impl will return false.
945 assert(!oops_into_cset, "should not see true here");
946 }
947 }
948 }
949
950 if (!defer) {
951 oops_into_cset =
952 concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset);
953 // We should only be detecting that the card contains references
954 // that point into the collection set if the current thread is
955 // a GC worker thread.
956 assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(),
957 "invalid result at non safepoint");
958 }
959 return oops_into_cset;
960 }
961
962 class HRRSStatsIter: public HeapRegionClosure {
963 size_t _occupied;
964 size_t _total_mem_sz;
965 size_t _max_mem_sz;
966 HeapRegion* _max_mem_sz_region;
967 public:
968 HRRSStatsIter() :
969 _occupied(0),
970 _total_mem_sz(0),
971 _max_mem_sz(0),
972 _max_mem_sz_region(NULL)
973 {}
974
975 bool doHeapRegion(HeapRegion* r) {
976 if (r->continuesHumongous()) return false;
977 size_t mem_sz = r->rem_set()->mem_size();
978 if (mem_sz > _max_mem_sz) {
979 _max_mem_sz = mem_sz;
980 _max_mem_sz_region = r;
981 }
982 _total_mem_sz += mem_sz;
983 size_t occ = r->rem_set()->occupied();
984 _occupied += occ;
985 return false;
986 }
987 size_t total_mem_sz() { return _total_mem_sz; }
988 size_t max_mem_sz() { return _max_mem_sz; }
989 size_t occupied() { return _occupied; }
990 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
991 };
992
993 class PrintRSThreadVTimeClosure : public ThreadClosure {
994 public:
995 virtual void do_thread(Thread *t) {
996 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
997 gclog_or_tty->print(" %5.2f", crt->vtime_accum());
998 }
999 };
1000
1001 void G1RemSet::print_summary_info() {
1002 G1CollectedHeap* g1 = G1CollectedHeap::heap();
1003
1004 #if CARD_REPEAT_HISTO
1005 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
1006 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
1007 card_repeat_count.print_on(gclog_or_tty);
1008 #endif
1009
1010 if (FILTEROUTOFREGIONCLOSURE_DOHISTOGRAMCOUNT) {
1011 gclog_or_tty->print_cr("\nG1 rem-set out-of-region histogram: ");
1012 gclog_or_tty->print_cr(" # of CS ptrs --> # of cards with that number.");
1013 out_of_histo.print_on(gclog_or_tty);
1014 }
1015 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
1016 _conc_refine_cards);
1017 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1018 jint tot_processed_buffers =
1019 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
1020 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers);
1021 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.",
1022 dcqs.processed_buffers_rs_thread(),
1023 100.0*(float)dcqs.processed_buffers_rs_thread()/
1024 (float)tot_processed_buffers);
1025 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.",
1026 dcqs.processed_buffers_mut(),
1027 100.0*(float)dcqs.processed_buffers_mut()/
1028 (float)tot_processed_buffers);
1029 gclog_or_tty->print_cr(" Conc RS threads times(s)");
1030 PrintRSThreadVTimeClosure p;
1031 gclog_or_tty->print(" ");
1032 g1->concurrent_g1_refine()->threads_do(&p);
1033 gclog_or_tty->print_cr("");
1034
1035 HRRSStatsIter blk;
1036 g1->heap_region_iterate(&blk);
1037 gclog_or_tty->print_cr(" Total heap region rem set sizes = " SIZE_FORMAT "K."
1038 " Max = " SIZE_FORMAT "K.",
1039 blk.total_mem_sz()/K, blk.max_mem_sz()/K);
1040 gclog_or_tty->print_cr(" Static structures = " SIZE_FORMAT "K,"
1041 " free_lists = " SIZE_FORMAT "K.",
1042 HeapRegionRemSet::static_mem_size()/K,
1043 HeapRegionRemSet::fl_mem_size()/K);
1044 gclog_or_tty->print_cr(" %d occupied cards represented.",
1045 blk.occupied());
1046 gclog_or_tty->print_cr(" Max sz region = [" PTR_FORMAT ", " PTR_FORMAT " )"
1047 ", cap = " SIZE_FORMAT "K, occ = " SIZE_FORMAT "K.",
1048 blk.max_mem_sz_region()->bottom(), blk.max_mem_sz_region()->end(),
1049 (blk.max_mem_sz_region()->rem_set()->mem_size() + K - 1)/K,
1050 (blk.max_mem_sz_region()->rem_set()->occupied() + K - 1)/K);
1051 gclog_or_tty->print_cr(" Did %d coarsenings.", HeapRegionRemSet::n_coarsenings());
1052 }
1053
1054 void G1RemSet::prepare_for_verify() {
1055 if (G1HRRSFlushLogBuffersOnVerify &&
1056 (VerifyBeforeGC || VerifyAfterGC)
1057 && !_g1->full_collection()) {
1058 cleanupHRRS();
1059 _g1->set_refine_cte_cl_concurrency(false);
1060 if (SafepointSynchronize::is_at_safepoint()) {
1061 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1062 dcqs.concatenate_logs();
1063 }
1064 bool cg1r_use_cache = _cg1r->use_cache();
1065 _cg1r->set_use_cache(false);
1066 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
1067 updateRS(&into_cset_dcq, 0);
1068 _g1->into_cset_dirty_card_queue_set().clear();
1069 _cg1r->set_use_cache(cg1r_use_cache);
1070
1071 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
1072 }
1073 }