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 "incls/_precompiled.incl"
26 #include "incls/_g1RemSet.cpp.incl"
27
28 #define CARD_REPEAT_HISTO 0
29
30 #if CARD_REPEAT_HISTO
31 static size_t ct_freq_sz;
32 static jbyte* ct_freq = NULL;
33
34 void init_ct_freq_table(size_t heap_sz_bytes) {
35 if (ct_freq == NULL) {
36 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
37 ct_freq = new jbyte[ct_freq_sz];
38 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
39 }
40 }
41
42 void ct_freq_note_card(size_t index) {
43 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
44 if (ct_freq[index] < 100) { ct_freq[index]++; }
45 }
46
47 static IntHistogram card_repeat_count(10, 10);
48
49 void ct_freq_update_histo_and_reset() {
50 for (size_t j = 0; j < ct_freq_sz; j++) {
51 card_repeat_count.add_entry(ct_freq[j]);
52 ct_freq[j] = 0;
53 }
54
55 }
56 #endif
57
58
59 class IntoCSOopClosure: public OopsInHeapRegionClosure {
60 OopsInHeapRegionClosure* _blk;
61 G1CollectedHeap* _g1;
62 public:
63 IntoCSOopClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) :
64 _g1(g1), _blk(blk) {}
65 void set_region(HeapRegion* from) {
66 _blk->set_region(from);
67 }
68 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
69 virtual void do_oop( oop* p) { do_oop_work(p); }
70 template <class T> void do_oop_work(T* p) {
71 oop obj = oopDesc::load_decode_heap_oop(p);
72 if (_g1->obj_in_cs(obj)) _blk->do_oop(p);
73 }
74 bool apply_to_weak_ref_discovered_field() { return true; }
75 bool idempotent() { return true; }
76 };
77
78 class IntoCSRegionClosure: public HeapRegionClosure {
79 IntoCSOopClosure _blk;
80 G1CollectedHeap* _g1;
81 public:
82 IntoCSRegionClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) :
83 _g1(g1), _blk(g1, blk) {}
84 bool doHeapRegion(HeapRegion* r) {
85 if (!r->in_collection_set()) {
86 _blk.set_region(r);
87 if (r->isHumongous()) {
88 if (r->startsHumongous()) {
89 oop obj = oop(r->bottom());
90 obj->oop_iterate(&_blk);
91 }
92 } else {
93 r->oop_before_save_marks_iterate(&_blk);
94 }
95 }
96 return false;
97 }
98 };
99
100 class VerifyRSCleanCardOopClosure: public OopClosure {
101 G1CollectedHeap* _g1;
102 public:
103 VerifyRSCleanCardOopClosure(G1CollectedHeap* g1) : _g1(g1) {}
104
105 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
106 virtual void do_oop( oop* p) { do_oop_work(p); }
107 template <class T> void do_oop_work(T* p) {
108 oop obj = oopDesc::load_decode_heap_oop(p);
109 HeapRegion* to = _g1->heap_region_containing(obj);
110 guarantee(to == NULL || !to->in_collection_set(),
111 "Missed a rem set member.");
112 }
113 };
114
115 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
116 : _g1(g1), _conc_refine_cards(0),
117 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
118 _cg1r(g1->concurrent_g1_refine()),
119 _traversal_in_progress(false),
120 _cset_rs_update_cl(NULL),
121 _cards_scanned(NULL), _total_cards_scanned(0)
122 {
123 _seq_task = new SubTasksDone(NumSeqTasks);
124 guarantee(n_workers() > 0, "There should be some workers");
125 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers());
126 for (uint i = 0; i < n_workers(); i++) {
127 _cset_rs_update_cl[i] = NULL;
128 }
129 }
130
131 G1RemSet::~G1RemSet() {
132 delete _seq_task;
133 for (uint i = 0; i < n_workers(); i++) {
134 assert(_cset_rs_update_cl[i] == NULL, "it should be");
135 }
136 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl);
137 }
138
139 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
140 if (_g1->is_in_g1_reserved(mr.start())) {
141 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
142 if (_start_first == NULL) _start_first = mr.start();
143 }
144 }
145
146 class ScanRSClosure : public HeapRegionClosure {
147 size_t _cards_done, _cards;
148 G1CollectedHeap* _g1h;
149 OopsInHeapRegionClosure* _oc;
150 G1BlockOffsetSharedArray* _bot_shared;
151 CardTableModRefBS *_ct_bs;
152 int _worker_i;
153 int _block_size;
154 bool _try_claimed;
155 public:
156 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
157 _oc(oc),
158 _cards(0),
159 _cards_done(0),
160 _worker_i(worker_i),
161 _try_claimed(false)
162 {
163 _g1h = G1CollectedHeap::heap();
164 _bot_shared = _g1h->bot_shared();
165 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
166 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
167 }
168
169 void set_try_claimed() { _try_claimed = true; }
170
171 void scanCard(size_t index, HeapRegion *r) {
172 _cards_done++;
173 DirtyCardToOopClosure* cl =
174 r->new_dcto_closure(_oc,
175 CardTableModRefBS::Precise,
176 HeapRegionDCTOC::IntoCSFilterKind);
177
178 // Set the "from" region in the closure.
179 _oc->set_region(r);
180 HeapWord* card_start = _bot_shared->address_for_index(index);
181 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
182 Space *sp = SharedHeap::heap()->space_containing(card_start);
183 MemRegion sm_region;
184 if (ParallelGCThreads > 0) {
185 // first find the used area
186 sm_region = sp->used_region_at_save_marks();
187 } else {
188 // The closure is not idempotent. We shouldn't look at objects
189 // allocated during the GC.
190 sm_region = sp->used_region_at_save_marks();
191 }
192 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
193 if (!mr.is_empty()) {
194 cl->do_MemRegion(mr);
195 }
196 }
197
198 void printCard(HeapRegion* card_region, size_t card_index,
199 HeapWord* card_start) {
200 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
201 "RS names card %p: "
202 "[" PTR_FORMAT ", " PTR_FORMAT ")",
203 _worker_i,
204 card_region->bottom(), card_region->end(),
205 card_index,
206 card_start, card_start + G1BlockOffsetSharedArray::N_words);
207 }
208
209 bool doHeapRegion(HeapRegion* r) {
210 assert(r->in_collection_set(), "should only be called on elements of CS.");
211 HeapRegionRemSet* hrrs = r->rem_set();
212 if (hrrs->iter_is_complete()) return false; // All done.
213 if (!_try_claimed && !hrrs->claim_iter()) return false;
214 _g1h->push_dirty_cards_region(r);
215 // If we didn't return above, then
216 // _try_claimed || r->claim_iter()
217 // is true: either we're supposed to work on claimed-but-not-complete
218 // regions, or we successfully claimed the region.
219 HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i);
220 hrrs->init_iterator(iter);
221 size_t card_index;
222
223 // We claim cards in block so as to recude the contention. The block size is determined by
224 // the G1RSetScanBlockSize parameter.
225 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
226 for (size_t current_card = 0; iter->has_next(card_index); current_card++) {
227 if (current_card >= jump_to_card + _block_size) {
228 jump_to_card = hrrs->iter_claimed_next(_block_size);
229 }
230 if (current_card < jump_to_card) continue;
231 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
232 #if 0
233 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
234 card_start, card_start + CardTableModRefBS::card_size_in_words);
235 #endif
236
237 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
238 assert(card_region != NULL, "Yielding cards not in the heap?");
239 _cards++;
240
241 if (!card_region->is_on_dirty_cards_region_list()) {
242 _g1h->push_dirty_cards_region(card_region);
243 }
244
245 // If the card is dirty, then we will scan it during updateRS.
246 if (!card_region->in_collection_set() && !_ct_bs->is_card_dirty(card_index)) {
247 // We make the card as "claimed" lazily (so races are possible but they're benign),
248 // which reduces the number of duplicate scans (the rsets of the regions in the cset
249 // can intersect).
250 if (!_ct_bs->is_card_claimed(card_index)) {
251 _ct_bs->set_card_claimed(card_index);
252 scanCard(card_index, card_region);
253 }
254 }
255 }
256 if (!_try_claimed) {
257 hrrs->set_iter_complete();
258 }
259 return false;
260 }
261 // Set all cards back to clean.
262 void cleanup() {_g1h->cleanUpCardTable();}
263 size_t cards_done() { return _cards_done;}
264 size_t cards_looked_up() { return _cards;}
265 };
266
267 // We want the parallel threads to start their scanning at
268 // different collection set regions to avoid contention.
269 // If we have:
270 // n collection set regions
271 // p threads
272 // Then thread t will start at region t * floor (n/p)
273
274 HeapRegion* G1RemSet::calculateStartRegion(int worker_i) {
275 HeapRegion* result = _g1p->collection_set();
276 if (ParallelGCThreads > 0) {
277 size_t cs_size = _g1p->collection_set_size();
278 int n_workers = _g1->workers()->total_workers();
279 size_t cs_spans = cs_size / n_workers;
280 size_t ind = cs_spans * worker_i;
281 for (size_t i = 0; i < ind; i++)
282 result = result->next_in_collection_set();
283 }
284 return result;
285 }
286
287 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
288 double rs_time_start = os::elapsedTime();
289 HeapRegion *startRegion = calculateStartRegion(worker_i);
290
291 ScanRSClosure scanRScl(oc, worker_i);
292 _g1->collection_set_iterate_from(startRegion, &scanRScl);
293 scanRScl.set_try_claimed();
294 _g1->collection_set_iterate_from(startRegion, &scanRScl);
295
296 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
297
298 assert( _cards_scanned != NULL, "invariant" );
299 _cards_scanned[worker_i] = scanRScl.cards_done();
300
301 _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
302 }
303
304 // Closure used for updating RSets and recording references that
305 // point into the collection set. Only called during an
306 // evacuation pause.
307
308 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
309 G1RemSet* _g1rs;
310 DirtyCardQueue* _into_cset_dcq;
311 public:
312 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
313 DirtyCardQueue* into_cset_dcq) :
314 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
315 {}
316 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
317 // The only time we care about recording cards that
318 // contain references that point into the collection set
319 // is during RSet updating within an evacuation pause.
320 // In this case worker_i should be the id of a GC worker thread.
321 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
322 assert(worker_i < (int) DirtyCardQueueSet::num_par_ids(), "should be a GC worker");
323
324 if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) {
325 // 'card_ptr' contains references that point into the collection
326 // set. We need to record the card in the DCQS
327 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
328 // that's used for that purpose.
329 //
330 // Enqueue the card
331 _into_cset_dcq->enqueue(card_ptr);
332 }
333 return true;
334 }
335 };
336
337 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
338 double start = os::elapsedTime();
339 // Apply the given closure to all remaining log entries.
340 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
341 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
342
343 // Now there should be no dirty cards.
344 if (G1RSLogCheckCardTable) {
345 CountNonCleanMemRegionClosure cl(_g1);
346 _ct_bs->mod_card_iterate(&cl);
347 // XXX This isn't true any more: keeping cards of young regions
348 // marked dirty broke it. Need some reasonable fix.
349 guarantee(cl.n() == 0, "Card table should be clean.");
350 }
351
352 _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
353 }
354
355 #ifndef PRODUCT
356 class PrintRSClosure : public HeapRegionClosure {
357 int _count;
358 public:
359 PrintRSClosure() : _count(0) {}
360 bool doHeapRegion(HeapRegion* r) {
361 HeapRegionRemSet* hrrs = r->rem_set();
362 _count += (int) hrrs->occupied();
363 if (hrrs->occupied() == 0) {
364 gclog_or_tty->print("Heap Region [" PTR_FORMAT ", " PTR_FORMAT ") "
365 "has no remset entries\n",
366 r->bottom(), r->end());
367 } else {
368 gclog_or_tty->print("Printing rem set for heap region [" PTR_FORMAT ", " PTR_FORMAT ")\n",
369 r->bottom(), r->end());
370 r->print();
371 hrrs->print();
372 gclog_or_tty->print("\nDone printing rem set\n");
373 }
374 return false;
375 }
376 int occupied() {return _count;}
377 };
378 #endif
379
380 class CountRSSizeClosure: public HeapRegionClosure {
381 size_t _n;
382 size_t _tot;
383 size_t _max;
384 HeapRegion* _max_r;
385 enum {
386 N = 20,
387 MIN = 6
388 };
389 int _histo[N];
390 public:
391 CountRSSizeClosure() : _n(0), _tot(0), _max(0), _max_r(NULL) {
392 for (int i = 0; i < N; i++) _histo[i] = 0;
393 }
394 bool doHeapRegion(HeapRegion* r) {
395 if (!r->continuesHumongous()) {
396 size_t occ = r->rem_set()->occupied();
397 _n++;
398 _tot += occ;
399 if (occ > _max) {
400 _max = occ;
401 _max_r = r;
402 }
403 // Fit it into a histo bin.
404 int s = 1 << MIN;
405 int i = 0;
406 while (occ > (size_t) s && i < (N-1)) {
407 s = s << 1;
408 i++;
409 }
410 _histo[i]++;
411 }
412 return false;
413 }
414 size_t n() { return _n; }
415 size_t tot() { return _tot; }
416 size_t mx() { return _max; }
417 HeapRegion* mxr() { return _max_r; }
418 void print_histo() {
419 int mx = N;
420 while (mx >= 0) {
421 if (_histo[mx-1] > 0) break;
422 mx--;
423 }
424 gclog_or_tty->print_cr("Number of regions with given RS sizes:");
425 gclog_or_tty->print_cr(" <= %8d %8d", 1 << MIN, _histo[0]);
426 for (int i = 1; i < mx-1; i++) {
427 gclog_or_tty->print_cr(" %8d - %8d %8d",
428 (1 << (MIN + i - 1)) + 1,
429 1 << (MIN + i),
430 _histo[i]);
431 }
432 gclog_or_tty->print_cr(" > %8d %8d", (1 << (MIN+mx-2))+1, _histo[mx-1]);
433 }
434 };
435
436 void G1RemSet::cleanupHRRS() {
437 HeapRegionRemSet::cleanup();
438 }
439
440 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
441 int worker_i) {
442 #if CARD_REPEAT_HISTO
443 ct_freq_update_histo_and_reset();
444 #endif
445 if (worker_i == 0) {
446 _cg1r->clear_and_record_card_counts();
447 }
448
449 // Make this into a command-line flag...
450 if (G1RSCountHisto && (ParallelGCThreads == 0 || worker_i == 0)) {
451 CountRSSizeClosure count_cl;
452 _g1->heap_region_iterate(&count_cl);
453 gclog_or_tty->print_cr("Avg of %d RS counts is %f, max is %d, "
454 "max region is " PTR_FORMAT,
455 count_cl.n(), (float)count_cl.tot()/(float)count_cl.n(),
456 count_cl.mx(), count_cl.mxr());
457 count_cl.print_histo();
458 }
459
460 // We cache the value of 'oc' closure into the appropriate slot in the
461 // _cset_rs_update_cl for this worker
462 assert(worker_i < (int)n_workers(), "sanity");
463 _cset_rs_update_cl[worker_i] = oc;
464
465 // A DirtyCardQueue that is used to hold cards containing references
466 // that point into the collection set. This DCQ is associated with a
467 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
468 // circumstances (i.e. the pause successfully completes), these cards
469 // are just discarded (there's no need to update the RSets of regions
470 // that were in the collection set - after the pause these regions
471 // are wholly 'free' of live objects. In the event of an evacuation
472 // failure the cards/buffers in this queue set are:
473 // * passed to the DirtyCardQueueSet that is used to manage deferred
474 // RSet updates, or
475 // * scanned for references that point into the collection set
476 // and the RSet of the corresponding region in the collection set
477 // is updated immediately.
478 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
479
480 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
481
482 // The two flags below were introduced temporarily to serialize
483 // the updating and scanning of remembered sets. There are some
484 // race conditions when these two operations are done in parallel
485 // and they are causing failures. When we resolve said race
486 // conditions, we'll revert back to parallel remembered set
487 // updating and scanning. See CRs 6677707 and 6677708.
488 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
489 updateRS(&into_cset_dcq, worker_i);
490 } else {
491 _g1p->record_update_rs_processed_buffers(worker_i, 0.0);
492 _g1p->record_update_rs_time(worker_i, 0.0);
493 }
494 if (G1UseParallelRSetScanning || (worker_i == 0)) {
495 scanRS(oc, worker_i);
496 } else {
497 _g1p->record_scan_rs_time(worker_i, 0.0);
498 }
499
500 // We now clear the cached values of _cset_rs_update_cl for this worker
501 _cset_rs_update_cl[worker_i] = NULL;
502 }
503
504 void G1RemSet::prepare_for_oops_into_collection_set_do() {
505 #if G1_REM_SET_LOGGING
506 PrintRSClosure cl;
507 _g1->collection_set_iterate(&cl);
508 #endif
509 cleanupHRRS();
510 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
511 _g1->set_refine_cte_cl_concurrency(false);
512 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
513 dcqs.concatenate_logs();
514
515 assert(!_traversal_in_progress, "Invariant between iterations.");
516 set_traversal(true);
517 if (ParallelGCThreads > 0) {
518 _seq_task->set_n_threads((int)n_workers());
519 }
520 guarantee( _cards_scanned == NULL, "invariant" );
521 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers());
522 for (uint i = 0; i < n_workers(); ++i) {
523 _cards_scanned[i] = 0;
524 }
525 _total_cards_scanned = 0;
526 }
527
528
529 class cleanUpIteratorsClosure : public HeapRegionClosure {
530 bool doHeapRegion(HeapRegion *r) {
531 HeapRegionRemSet* hrrs = r->rem_set();
532 hrrs->init_for_par_iteration();
533 return false;
534 }
535 };
536
537 // This closure, applied to a DirtyCardQueueSet, is used to immediately
538 // update the RSets for the regions in the CSet. For each card it iterates
539 // through the oops which coincide with that card. It scans the reference
540 // fields in each oop; when it finds an oop that points into the collection
541 // set, the RSet for the region containing the referenced object is updated.
542 // Note: _par_traversal_in_progress in the G1RemSet must be FALSE; otherwise
543 // the UpdateRSetImmediate closure will cause cards to be enqueued on to
544 // the DCQS that we're iterating over, causing an infinite loop.
545 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
546 G1CollectedHeap* _g1;
547 CardTableModRefBS* _ct_bs;
548 public:
549 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
550 CardTableModRefBS* bs):
551 _g1(g1), _ct_bs(bs)
552 { }
553
554 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
555 // Construct the region representing the card.
556 HeapWord* start = _ct_bs->addr_for(card_ptr);
557 // And find the region containing it.
558 HeapRegion* r = _g1->heap_region_containing(start);
559 assert(r != NULL, "unexpected null");
560
561 // Scan oops in the card looking for references into the collection set
562 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
563 MemRegion scanRegion(start, end);
564
565 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
566 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
567 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
568
569 // We can pass false as the "filter_young" parameter here as:
570 // * we should be in a STW pause,
571 // * the DCQS to which this closure is applied is used to hold
572 // references that point into the collection set from the prior
573 // RSet updating,
574 // * the post-write barrier shouldn't be logging updates to young
575 // regions (but there is a situation where this can happen - see
576 // the comment in G1RemSet::concurrentRefineOneCard below -
577 // that should not be applicable here), and
578 // * during actual RSet updating, the filtering of cards in young
579 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
580 // employed.
581 // As a result, when this closure is applied to "refs into cset"
582 // DCQS, we shouldn't see any cards in young regions.
583 update_rs_cl.set_region(r);
584 HeapWord* stop_point =
585 r->oops_on_card_seq_iterate_careful(scanRegion,
586 &filter_then_update_rs_cset_oop_cl,
587 false /* filter_young */);
588
589 // Since this is performed in the event of an evacuation failure, we
590 // we shouldn't see a non-null stop point
591 assert(stop_point == NULL, "saw an unallocated region");
592 return true;
593 }
594 };
595
596 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
597 guarantee( _cards_scanned != NULL, "invariant" );
598 _total_cards_scanned = 0;
599 for (uint i = 0; i < n_workers(); ++i)
600 _total_cards_scanned += _cards_scanned[i];
601 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
602 _cards_scanned = NULL;
603 // Cleanup after copy
604 #if G1_REM_SET_LOGGING
605 PrintRSClosure cl;
606 _g1->heap_region_iterate(&cl);
607 #endif
608 _g1->set_refine_cte_cl_concurrency(true);
609 cleanUpIteratorsClosure iterClosure;
610 _g1->collection_set_iterate(&iterClosure);
611 // Set all cards back to clean.
612 _g1->cleanUpCardTable();
613
614 set_traversal(false);
615
616 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
617 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
618
619 if (_g1->evacuation_failed()) {
620 // Restore remembered sets for the regions pointing into the collection set.
621
622 if (G1DeferredRSUpdate) {
623 // If deferred RS updates are enabled then we just need to transfer
624 // the completed buffers from (a) the DirtyCardQueueSet used to hold
625 // cards that contain references that point into the collection set
626 // to (b) the DCQS used to hold the deferred RS updates
627 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
628 } else {
629
630 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
631 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
632
633 int n_completed_buffers = 0;
634 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
635 0, 0, true)) {
636 n_completed_buffers++;
637 }
638 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
639 }
640 }
641
642 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
643 // which contain references that point into the collection.
644 _g1->into_cset_dirty_card_queue_set().clear();
645 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
646 "all buffers should be freed");
647 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
648
649 assert(!_traversal_in_progress, "Invariant between iterations.");
650 }
651
652 class UpdateRSObjectClosure: public ObjectClosure {
653 UpdateRSOopClosure* _update_rs_oop_cl;
654 public:
655 UpdateRSObjectClosure(UpdateRSOopClosure* update_rs_oop_cl) :
656 _update_rs_oop_cl(update_rs_oop_cl) {}
657 void do_object(oop obj) {
658 obj->oop_iterate(_update_rs_oop_cl);
659 }
660
661 };
662
663 class ScrubRSClosure: public HeapRegionClosure {
664 G1CollectedHeap* _g1h;
665 BitMap* _region_bm;
666 BitMap* _card_bm;
667 CardTableModRefBS* _ctbs;
668 public:
669 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
670 _g1h(G1CollectedHeap::heap()),
671 _region_bm(region_bm), _card_bm(card_bm),
672 _ctbs(NULL)
673 {
674 ModRefBarrierSet* bs = _g1h->mr_bs();
675 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
676 _ctbs = (CardTableModRefBS*)bs;
677 }
678
679 bool doHeapRegion(HeapRegion* r) {
680 if (!r->continuesHumongous()) {
681 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
682 }
683 return false;
684 }
685 };
686
687 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
688 ScrubRSClosure scrub_cl(region_bm, card_bm);
689 _g1->heap_region_iterate(&scrub_cl);
690 }
691
692 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
693 int worker_num, int claim_val) {
694 ScrubRSClosure scrub_cl(region_bm, card_bm);
695 _g1->heap_region_par_iterate_chunked(&scrub_cl, worker_num, claim_val);
696 }
697
698
699 static IntHistogram out_of_histo(50, 50);
700
701 class TriggerClosure : public OopClosure {
702 bool _trigger;
703 public:
704 TriggerClosure() : _trigger(false) { }
705 bool value() const { return _trigger; }
706 template <class T> void do_oop_nv(T* p) { _trigger = true; }
707 virtual void do_oop(oop* p) { do_oop_nv(p); }
708 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
709 };
710
711 class InvokeIfNotTriggeredClosure: public OopClosure {
712 TriggerClosure* _t;
713 OopClosure* _oc;
714 public:
715 InvokeIfNotTriggeredClosure(TriggerClosure* t, OopClosure* oc):
716 _t(t), _oc(oc) { }
717 template <class T> void do_oop_nv(T* p) {
718 if (!_t->value()) _oc->do_oop(p);
719 }
720 virtual void do_oop(oop* p) { do_oop_nv(p); }
721 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
722 };
723
724 class Mux2Closure : public OopClosure {
725 OopClosure* _c1;
726 OopClosure* _c2;
727 public:
728 Mux2Closure(OopClosure *c1, OopClosure *c2) : _c1(c1), _c2(c2) { }
729 template <class T> void do_oop_nv(T* p) {
730 _c1->do_oop(p); _c2->do_oop(p);
731 }
732 virtual void do_oop(oop* p) { do_oop_nv(p); }
733 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
734 };
735
736 bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
737 bool check_for_refs_into_cset) {
738 // Construct the region representing the card.
739 HeapWord* start = _ct_bs->addr_for(card_ptr);
740 // And find the region containing it.
741 HeapRegion* r = _g1->heap_region_containing(start);
742 assert(r != NULL, "unexpected null");
743
744 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
745 MemRegion dirtyRegion(start, end);
746
747 #if CARD_REPEAT_HISTO
748 init_ct_freq_table(_g1->g1_reserved_obj_bytes());
749 ct_freq_note_card(_ct_bs->index_for(start));
750 #endif
751
752 UpdateRSOopClosure update_rs_oop_cl(this, worker_i);
753 update_rs_oop_cl.set_from(r);
754
755 TriggerClosure trigger_cl;
756 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
757 InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
758 Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
759
760 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
761 (check_for_refs_into_cset ?
762 (OopClosure*)&mux :
763 (OopClosure*)&update_rs_oop_cl));
764
765 // Undirty the card.
766 *card_ptr = CardTableModRefBS::clean_card_val();
767 // We must complete this write before we do any of the reads below.
768 OrderAccess::storeload();
769 // And process it, being careful of unallocated portions of TLAB's.
770
771 // The region for the current card may be a young region. The
772 // current card may have been a card that was evicted from the
773 // card cache. When the card was inserted into the cache, we had
774 // determined that its region was non-young. While in the cache,
775 // the region may have been freed during a cleanup pause, reallocated
776 // and tagged as young.
777 //
778 // We wish to filter out cards for such a region but the current
779 // thread, if we're running conucrrently, may "see" the young type
780 // change at any time (so an earlier "is_young" check may pass or
781 // fail arbitrarily). We tell the iteration code to perform this
782 // filtering when it has been determined that there has been an actual
783 // allocation in this region and making it safe to check the young type.
784 bool filter_young = true;
785
786 HeapWord* stop_point =
787 r->oops_on_card_seq_iterate_careful(dirtyRegion,
788 &filter_then_update_rs_oop_cl,
789 filter_young);
790
791 // If stop_point is non-null, then we encountered an unallocated region
792 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
793 // card and re-enqueue: if we put off the card until a GC pause, then the
794 // unallocated portion will be filled in. Alternatively, we might try
795 // the full complexity of the technique used in "regular" precleaning.
796 if (stop_point != NULL) {
797 // The card might have gotten re-dirtied and re-enqueued while we
798 // worked. (In fact, it's pretty likely.)
799 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
800 *card_ptr = CardTableModRefBS::dirty_card_val();
801 MutexLockerEx x(Shared_DirtyCardQ_lock,
802 Mutex::_no_safepoint_check_flag);
803 DirtyCardQueue* sdcq =
804 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
805 sdcq->enqueue(card_ptr);
806 }
807 } else {
808 out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region());
809 _conc_refine_cards++;
810 }
811
812 return trigger_cl.value();
813 }
814
815 bool G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
816 bool check_for_refs_into_cset) {
817 // If the card is no longer dirty, nothing to do.
818 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
819 // No need to return that this card contains refs that point
820 // into the collection set.
821 return false;
822 }
823
824 // Construct the region representing the card.
825 HeapWord* start = _ct_bs->addr_for(card_ptr);
826 // And find the region containing it.
827 HeapRegion* r = _g1->heap_region_containing(start);
828 if (r == NULL) {
829 guarantee(_g1->is_in_permanent(start), "Or else where?");
830 // Again no need to return that this card contains refs that
831 // point into the collection set.
832 return false; // Not in the G1 heap (might be in perm, for example.)
833 }
834 // Why do we have to check here whether a card is on a young region,
835 // given that we dirty young regions and, as a result, the
836 // post-barrier is supposed to filter them out and never to enqueue
837 // them? When we allocate a new region as the "allocation region" we
838 // actually dirty its cards after we release the lock, since card
839 // dirtying while holding the lock was a performance bottleneck. So,
840 // as a result, it is possible for other threads to actually
841 // allocate objects in the region (after the acquire the lock)
842 // before all the cards on the region are dirtied. This is unlikely,
843 // and it doesn't happen often, but it can happen. So, the extra
844 // check below filters out those cards.
845 if (r->is_young()) {
846 return false;
847 }
848 // While we are processing RSet buffers during the collection, we
849 // actually don't want to scan any cards on the collection set,
850 // since we don't want to update remebered sets with entries that
851 // point into the collection set, given that live objects from the
852 // collection set are about to move and such entries will be stale
853 // very soon. This change also deals with a reliability issue which
854 // involves scanning a card in the collection set and coming across
855 // an array that was being chunked and looking malformed. Note,
856 // however, that if evacuation fails, we have to scan any objects
857 // that were not moved and create any missing entries.
858 if (r->in_collection_set()) {
859 return false;
860 }
861
862 // Should we defer processing the card?
863 //
864 // Previously the result from the insert_cache call would be
865 // either card_ptr (implying that card_ptr was currently "cold"),
866 // null (meaning we had inserted the card ptr into the "hot"
867 // cache, which had some headroom), or a "hot" card ptr
868 // extracted from the "hot" cache.
869 //
870 // Now that the _card_counts cache in the ConcurrentG1Refine
871 // instance is an evicting hash table, the result we get back
872 // could be from evicting the card ptr in an already occupied
873 // bucket (in which case we have replaced the card ptr in the
874 // bucket with card_ptr and "defer" is set to false). To avoid
875 // having a data structure (updates to which would need a lock)
876 // to hold these unprocessed dirty cards, we need to immediately
877 // process card_ptr. The actions needed to be taken on return
878 // from cache_insert are summarized in the following table:
879 //
880 // res defer action
881 // --------------------------------------------------------------
882 // null false card evicted from _card_counts & replaced with
883 // card_ptr; evicted ptr added to hot cache.
884 // No need to process res; immediately process card_ptr
885 //
886 // null true card not evicted from _card_counts; card_ptr added
887 // to hot cache.
888 // Nothing to do.
889 //
890 // non-null false card evicted from _card_counts & replaced with
891 // card_ptr; evicted ptr is currently "cold" or
892 // caused an eviction from the hot cache.
893 // Immediately process res; process card_ptr.
894 //
895 // non-null true card not evicted from _card_counts; card_ptr is
896 // currently cold, or caused an eviction from hot
897 // cache.
898 // Immediately process res; no need to process card_ptr.
899
900
901 jbyte* res = card_ptr;
902 bool defer = false;
903
904 // This gets set to true if the card being refined has references
905 // that point into the collection set.
906 bool oops_into_cset = false;
907
908 if (_cg1r->use_cache()) {
909 jbyte* res = _cg1r->cache_insert(card_ptr, &defer);
910 if (res != NULL && (res != card_ptr || defer)) {
911 start = _ct_bs->addr_for(res);
912 r = _g1->heap_region_containing(start);
913 if (r == NULL) {
914 assert(_g1->is_in_permanent(start), "Or else where?");
915 } else {
916 // Checking whether the region we got back from the cache
917 // is young here is inappropriate. The region could have been
918 // freed, reallocated and tagged as young while in the cache.
919 // Hence we could see its young type change at any time.
920 //
921 // Process card pointer we get back from the hot card cache. This
922 // will check whether the region containing the card is young
923 // _after_ checking that the region has been allocated from.
924 oops_into_cset = concurrentRefineOneCard_impl(res, worker_i,
925 false /* check_for_refs_into_cset */);
926 // The above call to concurrentRefineOneCard_impl is only
927 // performed if the hot card cache is enabled. This cache is
928 // disabled during an evacuation pause - which is the only
929 // time when we need know if the card contains references
930 // that point into the collection set. Also when the hot card
931 // cache is enabled, this code is executed by the concurrent
932 // refine threads - rather than the GC worker threads - and
933 // concurrentRefineOneCard_impl will return false.
934 assert(!oops_into_cset, "should not see true here");
935 }
936 }
937 }
938
939 if (!defer) {
940 oops_into_cset =
941 concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset);
942 // We should only be detecting that the card contains references
943 // that point into the collection set if the current thread is
944 // a GC worker thread.
945 assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(),
946 "invalid result at non safepoint");
947 }
948 return oops_into_cset;
949 }
950
951 class HRRSStatsIter: public HeapRegionClosure {
952 size_t _occupied;
953 size_t _total_mem_sz;
954 size_t _max_mem_sz;
955 HeapRegion* _max_mem_sz_region;
956 public:
957 HRRSStatsIter() :
958 _occupied(0),
959 _total_mem_sz(0),
960 _max_mem_sz(0),
961 _max_mem_sz_region(NULL)
962 {}
963
964 bool doHeapRegion(HeapRegion* r) {
965 if (r->continuesHumongous()) return false;
966 size_t mem_sz = r->rem_set()->mem_size();
967 if (mem_sz > _max_mem_sz) {
968 _max_mem_sz = mem_sz;
969 _max_mem_sz_region = r;
970 }
971 _total_mem_sz += mem_sz;
972 size_t occ = r->rem_set()->occupied();
973 _occupied += occ;
974 return false;
975 }
976 size_t total_mem_sz() { return _total_mem_sz; }
977 size_t max_mem_sz() { return _max_mem_sz; }
978 size_t occupied() { return _occupied; }
979 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
980 };
981
982 class PrintRSThreadVTimeClosure : public ThreadClosure {
983 public:
984 virtual void do_thread(Thread *t) {
985 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
986 gclog_or_tty->print(" %5.2f", crt->vtime_accum());
987 }
988 };
989
990 void G1RemSet::print_summary_info() {
991 G1CollectedHeap* g1 = G1CollectedHeap::heap();
992
993 #if CARD_REPEAT_HISTO
994 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
995 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
996 card_repeat_count.print_on(gclog_or_tty);
997 #endif
998
999 if (FILTEROUTOFREGIONCLOSURE_DOHISTOGRAMCOUNT) {
1000 gclog_or_tty->print_cr("\nG1 rem-set out-of-region histogram: ");
1001 gclog_or_tty->print_cr(" # of CS ptrs --> # of cards with that number.");
1002 out_of_histo.print_on(gclog_or_tty);
1003 }
1004 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
1005 _conc_refine_cards);
1006 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1007 jint tot_processed_buffers =
1008 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
1009 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers);
1010 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.",
1011 dcqs.processed_buffers_rs_thread(),
1012 100.0*(float)dcqs.processed_buffers_rs_thread()/
1013 (float)tot_processed_buffers);
1014 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.",
1015 dcqs.processed_buffers_mut(),
1016 100.0*(float)dcqs.processed_buffers_mut()/
1017 (float)tot_processed_buffers);
1018 gclog_or_tty->print_cr(" Conc RS threads times(s)");
1019 PrintRSThreadVTimeClosure p;
1020 gclog_or_tty->print(" ");
1021 g1->concurrent_g1_refine()->threads_do(&p);
1022 gclog_or_tty->print_cr("");
1023
1024 HRRSStatsIter blk;
1025 g1->heap_region_iterate(&blk);
1026 gclog_or_tty->print_cr(" Total heap region rem set sizes = " SIZE_FORMAT "K."
1027 " Max = " SIZE_FORMAT "K.",
1028 blk.total_mem_sz()/K, blk.max_mem_sz()/K);
1029 gclog_or_tty->print_cr(" Static structures = " SIZE_FORMAT "K,"
1030 " free_lists = " SIZE_FORMAT "K.",
1031 HeapRegionRemSet::static_mem_size()/K,
1032 HeapRegionRemSet::fl_mem_size()/K);
1033 gclog_or_tty->print_cr(" %d occupied cards represented.",
1034 blk.occupied());
1035 gclog_or_tty->print_cr(" Max sz region = [" PTR_FORMAT ", " PTR_FORMAT " )"
1036 ", cap = " SIZE_FORMAT "K, occ = " SIZE_FORMAT "K.",
1037 blk.max_mem_sz_region()->bottom(), blk.max_mem_sz_region()->end(),
1038 (blk.max_mem_sz_region()->rem_set()->mem_size() + K - 1)/K,
1039 (blk.max_mem_sz_region()->rem_set()->occupied() + K - 1)/K);
1040 gclog_or_tty->print_cr(" Did %d coarsenings.", HeapRegionRemSet::n_coarsenings());
1041 }
1042
1043 void G1RemSet::prepare_for_verify() {
1044 if (G1HRRSFlushLogBuffersOnVerify &&
1045 (VerifyBeforeGC || VerifyAfterGC)
1046 && !_g1->full_collection()) {
1047 cleanupHRRS();
1048 _g1->set_refine_cte_cl_concurrency(false);
1049 if (SafepointSynchronize::is_at_safepoint()) {
1050 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1051 dcqs.concatenate_logs();
1052 }
1053 bool cg1r_use_cache = _cg1r->use_cache();
1054 _cg1r->set_use_cache(false);
1055 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
1056 updateRS(&into_cset_dcq, 0);
1057 _g1->into_cset_dirty_card_queue_set().clear();
1058 _cg1r->set_use_cache(cg1r_use_cache);
1059
1060 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
1061 }
1062 }