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 void
112 StupidG1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
113 int worker_i) {
114 IntoCSRegionClosure rc(_g1, oc);
115 _g1->heap_region_iterate(&rc);
116 }
117
118 class VerifyRSCleanCardOopClosure: public OopClosure {
119 G1CollectedHeap* _g1;
120 public:
121 VerifyRSCleanCardOopClosure(G1CollectedHeap* g1) : _g1(g1) {}
122
123 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
124 virtual void do_oop( oop* p) { do_oop_work(p); }
125 template <class T> void do_oop_work(T* p) {
126 oop obj = oopDesc::load_decode_heap_oop(p);
127 HeapRegion* to = _g1->heap_region_containing(obj);
128 guarantee(to == NULL || !to->in_collection_set(),
129 "Missed a rem set member.");
130 }
131 };
132
133 HRInto_G1RemSet::HRInto_G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
134 : G1RemSet(g1), _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
135 _cg1r(g1->concurrent_g1_refine()),
136 _traversal_in_progress(false),
137 _cset_rs_update_cl(NULL),
138 _cards_scanned(NULL), _total_cards_scanned(0)
139 {
140 _seq_task = new SubTasksDone(NumSeqTasks);
141 guarantee(n_workers() > 0, "There should be some workers");
142 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers());
143 for (uint i = 0; i < n_workers(); i++) {
144 _cset_rs_update_cl[i] = NULL;
145 }
146 }
147
148 HRInto_G1RemSet::~HRInto_G1RemSet() {
149 delete _seq_task;
150 for (uint i = 0; i < n_workers(); i++) {
151 assert(_cset_rs_update_cl[i] == NULL, "it should be");
152 }
153 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl);
154 }
155
156 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
157 if (_g1->is_in_g1_reserved(mr.start())) {
158 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
159 if (_start_first == NULL) _start_first = mr.start();
160 }
161 }
162
163 class ScanRSClosure : public HeapRegionClosure {
164 size_t _cards_done, _cards;
165 G1CollectedHeap* _g1h;
166 OopsInHeapRegionClosure* _oc;
167 G1BlockOffsetSharedArray* _bot_shared;
168 CardTableModRefBS *_ct_bs;
169 int _worker_i;
170 int _block_size;
171 bool _try_claimed;
172 public:
173 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
174 _oc(oc),
175 _cards(0),
176 _cards_done(0),
177 _worker_i(worker_i),
178 _try_claimed(false)
179 {
180 _g1h = G1CollectedHeap::heap();
181 _bot_shared = _g1h->bot_shared();
182 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
183 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
184 }
185
186 void set_try_claimed() { _try_claimed = true; }
187
188 void scanCard(size_t index, HeapRegion *r) {
189 _cards_done++;
190 DirtyCardToOopClosure* cl =
191 r->new_dcto_closure(_oc,
192 CardTableModRefBS::Precise,
193 HeapRegionDCTOC::IntoCSFilterKind);
194
195 // Set the "from" region in the closure.
196 _oc->set_region(r);
197 HeapWord* card_start = _bot_shared->address_for_index(index);
198 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
199 Space *sp = SharedHeap::heap()->space_containing(card_start);
200 MemRegion sm_region;
201 if (ParallelGCThreads > 0) {
202 // first find the used area
203 sm_region = sp->used_region_at_save_marks();
204 } else {
205 // The closure is not idempotent. We shouldn't look at objects
206 // allocated during the GC.
207 sm_region = sp->used_region_at_save_marks();
208 }
209 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
210 if (!mr.is_empty()) {
211 cl->do_MemRegion(mr);
212 }
213 }
214
215 void printCard(HeapRegion* card_region, size_t card_index,
216 HeapWord* card_start) {
217 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
218 "RS names card %p: "
219 "[" PTR_FORMAT ", " PTR_FORMAT ")",
220 _worker_i,
221 card_region->bottom(), card_region->end(),
222 card_index,
223 card_start, card_start + G1BlockOffsetSharedArray::N_words);
224 }
225
226 bool doHeapRegion(HeapRegion* r) {
227 assert(r->in_collection_set(), "should only be called on elements of CS.");
228 HeapRegionRemSet* hrrs = r->rem_set();
229 if (hrrs->iter_is_complete()) return false; // All done.
230 if (!_try_claimed && !hrrs->claim_iter()) return false;
231 _g1h->push_dirty_cards_region(r);
232 // If we didn't return above, then
233 // _try_claimed || r->claim_iter()
234 // is true: either we're supposed to work on claimed-but-not-complete
235 // regions, or we successfully claimed the region.
236 HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i);
237 hrrs->init_iterator(iter);
238 size_t card_index;
239
240 // We claim cards in block so as to recude the contention. The block size is determined by
241 // the G1RSetScanBlockSize parameter.
242 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
243 for (size_t current_card = 0; iter->has_next(card_index); current_card++) {
244 if (current_card >= jump_to_card + _block_size) {
245 jump_to_card = hrrs->iter_claimed_next(_block_size);
246 }
247 if (current_card < jump_to_card) continue;
248 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
249 #if 0
250 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
251 card_start, card_start + CardTableModRefBS::card_size_in_words);
252 #endif
253
254 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
255 assert(card_region != NULL, "Yielding cards not in the heap?");
256 _cards++;
257
258 if (!card_region->is_on_dirty_cards_region_list()) {
259 _g1h->push_dirty_cards_region(card_region);
260 }
261
262 // If the card is dirty, then we will scan it during updateRS.
263 if (!card_region->in_collection_set() && !_ct_bs->is_card_dirty(card_index)) {
264 // We make the card as "claimed" lazily (so races are possible but they're benign),
265 // which reduces the number of duplicate scans (the rsets of the regions in the cset
266 // can intersect).
267 if (!_ct_bs->is_card_claimed(card_index)) {
268 _ct_bs->set_card_claimed(card_index);
269 scanCard(card_index, card_region);
270 }
271 }
272 }
273 if (!_try_claimed) {
274 hrrs->set_iter_complete();
275 }
276 return false;
277 }
278 // Set all cards back to clean.
279 void cleanup() {_g1h->cleanUpCardTable();}
280 size_t cards_done() { return _cards_done;}
281 size_t cards_looked_up() { return _cards;}
282 };
283
284 // We want the parallel threads to start their scanning at
285 // different collection set regions to avoid contention.
286 // If we have:
287 // n collection set regions
288 // p threads
289 // Then thread t will start at region t * floor (n/p)
290
291 HeapRegion* HRInto_G1RemSet::calculateStartRegion(int worker_i) {
292 HeapRegion* result = _g1p->collection_set();
293 if (ParallelGCThreads > 0) {
294 size_t cs_size = _g1p->collection_set_size();
295 int n_workers = _g1->workers()->total_workers();
296 size_t cs_spans = cs_size / n_workers;
297 size_t ind = cs_spans * worker_i;
298 for (size_t i = 0; i < ind; i++)
299 result = result->next_in_collection_set();
300 }
301 return result;
302 }
303
304 void HRInto_G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
305 double rs_time_start = os::elapsedTime();
306 HeapRegion *startRegion = calculateStartRegion(worker_i);
307
308 ScanRSClosure scanRScl(oc, worker_i);
309 _g1->collection_set_iterate_from(startRegion, &scanRScl);
310 scanRScl.set_try_claimed();
311 _g1->collection_set_iterate_from(startRegion, &scanRScl);
312
313 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
314
315 assert( _cards_scanned != NULL, "invariant" );
316 _cards_scanned[worker_i] = scanRScl.cards_done();
317
318 _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
319 }
320
321 // Closure used for updating RSets and recording references that
322 // point into the collection set. Only called during an
323 // evacuation pause.
324
325 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
326 G1RemSet* _g1rs;
327 DirtyCardQueue* _into_cset_dcq;
328 public:
329 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
330 DirtyCardQueue* into_cset_dcq) :
331 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
332 {}
333 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
334 // The only time we care about recording cards that
335 // contain references that point into the collection set
336 // is during RSet updating within an evacuation pause.
337 // In this case worker_i should be the id of a GC worker thread.
338 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
339 assert(worker_i < (int) DirtyCardQueueSet::num_par_ids(), "should be a GC worker");
340
341 if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) {
342 // 'card_ptr' contains references that point into the collection
343 // set. We need to record the card in the DCQS
344 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
345 // that's used for that purpose.
346 //
347 // Enqueue the card
348 _into_cset_dcq->enqueue(card_ptr);
349 }
350 return true;
351 }
352 };
353
354 void HRInto_G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
355 double start = os::elapsedTime();
356 // Apply the given closure to all remaining log entries.
357 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
358 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
359
360 // Now there should be no dirty cards.
361 if (G1RSLogCheckCardTable) {
362 CountNonCleanMemRegionClosure cl(_g1);
363 _ct_bs->mod_card_iterate(&cl);
364 // XXX This isn't true any more: keeping cards of young regions
365 // marked dirty broke it. Need some reasonable fix.
366 guarantee(cl.n() == 0, "Card table should be clean.");
367 }
368
369 _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
370 }
371
372 #ifndef PRODUCT
373 class PrintRSClosure : public HeapRegionClosure {
374 int _count;
375 public:
376 PrintRSClosure() : _count(0) {}
377 bool doHeapRegion(HeapRegion* r) {
378 HeapRegionRemSet* hrrs = r->rem_set();
379 _count += (int) hrrs->occupied();
380 if (hrrs->occupied() == 0) {
381 gclog_or_tty->print("Heap Region [" PTR_FORMAT ", " PTR_FORMAT ") "
382 "has no remset entries\n",
383 r->bottom(), r->end());
384 } else {
385 gclog_or_tty->print("Printing rem set for heap region [" PTR_FORMAT ", " PTR_FORMAT ")\n",
386 r->bottom(), r->end());
387 r->print();
388 hrrs->print();
389 gclog_or_tty->print("\nDone printing rem set\n");
390 }
391 return false;
392 }
393 int occupied() {return _count;}
394 };
395 #endif
396
397 class CountRSSizeClosure: public HeapRegionClosure {
398 size_t _n;
399 size_t _tot;
400 size_t _max;
401 HeapRegion* _max_r;
402 enum {
403 N = 20,
404 MIN = 6
405 };
406 int _histo[N];
407 public:
408 CountRSSizeClosure() : _n(0), _tot(0), _max(0), _max_r(NULL) {
409 for (int i = 0; i < N; i++) _histo[i] = 0;
410 }
411 bool doHeapRegion(HeapRegion* r) {
412 if (!r->continuesHumongous()) {
413 size_t occ = r->rem_set()->occupied();
414 _n++;
415 _tot += occ;
416 if (occ > _max) {
417 _max = occ;
418 _max_r = r;
419 }
420 // Fit it into a histo bin.
421 int s = 1 << MIN;
422 int i = 0;
423 while (occ > (size_t) s && i < (N-1)) {
424 s = s << 1;
425 i++;
426 }
427 _histo[i]++;
428 }
429 return false;
430 }
431 size_t n() { return _n; }
432 size_t tot() { return _tot; }
433 size_t mx() { return _max; }
434 HeapRegion* mxr() { return _max_r; }
435 void print_histo() {
436 int mx = N;
437 while (mx >= 0) {
438 if (_histo[mx-1] > 0) break;
439 mx--;
440 }
441 gclog_or_tty->print_cr("Number of regions with given RS sizes:");
442 gclog_or_tty->print_cr(" <= %8d %8d", 1 << MIN, _histo[0]);
443 for (int i = 1; i < mx-1; i++) {
444 gclog_or_tty->print_cr(" %8d - %8d %8d",
445 (1 << (MIN + i - 1)) + 1,
446 1 << (MIN + i),
447 _histo[i]);
448 }
449 gclog_or_tty->print_cr(" > %8d %8d", (1 << (MIN+mx-2))+1, _histo[mx-1]);
450 }
451 };
452
453 void HRInto_G1RemSet::cleanupHRRS() {
454 HeapRegionRemSet::cleanup();
455 }
456
457 void
458 HRInto_G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
459 int worker_i) {
460 #if CARD_REPEAT_HISTO
461 ct_freq_update_histo_and_reset();
462 #endif
463 if (worker_i == 0) {
464 _cg1r->clear_and_record_card_counts();
465 }
466
467 // Make this into a command-line flag...
468 if (G1RSCountHisto && (ParallelGCThreads == 0 || worker_i == 0)) {
469 CountRSSizeClosure count_cl;
470 _g1->heap_region_iterate(&count_cl);
471 gclog_or_tty->print_cr("Avg of %d RS counts is %f, max is %d, "
472 "max region is " PTR_FORMAT,
473 count_cl.n(), (float)count_cl.tot()/(float)count_cl.n(),
474 count_cl.mx(), count_cl.mxr());
475 count_cl.print_histo();
476 }
477
478 // We cache the value of 'oc' closure into the appropriate slot in the
479 // _cset_rs_update_cl for this worker
480 assert(worker_i < (int)n_workers(), "sanity");
481 _cset_rs_update_cl[worker_i] = oc;
482
483 // A DirtyCardQueue that is used to hold cards containing references
484 // that point into the collection set. This DCQ is associated with a
485 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
486 // circumstances (i.e. the pause successfully completes), these cards
487 // are just discarded (there's no need to update the RSets of regions
488 // that were in the collection set - after the pause these regions
489 // are wholly 'free' of live objects. In the event of an evacuation
490 // failure the cards/buffers in this queue set are:
491 // * passed to the DirtyCardQueueSet that is used to manage deferred
492 // RSet updates, or
493 // * scanned for references that point into the collection set
494 // and the RSet of the corresponding region in the collection set
495 // is updated immediately.
496 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
497
498 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
499
500 // The two flags below were introduced temporarily to serialize
501 // the updating and scanning of remembered sets. There are some
502 // race conditions when these two operations are done in parallel
503 // and they are causing failures. When we resolve said race
504 // conditions, we'll revert back to parallel remembered set
505 // updating and scanning. See CRs 6677707 and 6677708.
506 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
507 updateRS(&into_cset_dcq, worker_i);
508 } else {
509 _g1p->record_update_rs_processed_buffers(worker_i, 0.0);
510 _g1p->record_update_rs_time(worker_i, 0.0);
511 }
512 if (G1UseParallelRSetScanning || (worker_i == 0)) {
513 scanRS(oc, worker_i);
514 } else {
515 _g1p->record_scan_rs_time(worker_i, 0.0);
516 }
517
518 // We now clear the cached values of _cset_rs_update_cl for this worker
519 _cset_rs_update_cl[worker_i] = NULL;
520 }
521
522 void HRInto_G1RemSet::
523 prepare_for_oops_into_collection_set_do() {
524 #if G1_REM_SET_LOGGING
525 PrintRSClosure cl;
526 _g1->collection_set_iterate(&cl);
527 #endif
528 cleanupHRRS();
529 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
530 _g1->set_refine_cte_cl_concurrency(false);
531 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
532 dcqs.concatenate_logs();
533
534 assert(!_traversal_in_progress, "Invariant between iterations.");
535 set_traversal(true);
536 if (ParallelGCThreads > 0) {
537 _seq_task->set_par_threads((int)n_workers());
538 }
539 guarantee( _cards_scanned == NULL, "invariant" );
540 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers());
541 for (uint i = 0; i < n_workers(); ++i) {
542 _cards_scanned[i] = 0;
543 }
544 _total_cards_scanned = 0;
545 }
546
547
548 class cleanUpIteratorsClosure : public HeapRegionClosure {
549 bool doHeapRegion(HeapRegion *r) {
550 HeapRegionRemSet* hrrs = r->rem_set();
551 hrrs->init_for_par_iteration();
552 return false;
553 }
554 };
555
556 // This closure, applied to a DirtyCardQueueSet, is used to immediately
557 // update the RSets for the regions in the CSet. For each card it iterates
558 // through the oops which coincide with that card. It scans the reference
559 // fields in each oop; when it finds an oop that points into the collection
560 // set, the RSet for the region containing the referenced object is updated.
561 // Note: _par_traversal_in_progress in the G1RemSet must be FALSE; otherwise
562 // the UpdateRSetImmediate closure will cause cards to be enqueued on to
563 // the DCQS that we're iterating over, causing an infinite loop.
564 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
565 G1CollectedHeap* _g1;
566 CardTableModRefBS* _ct_bs;
567 public:
568 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
569 CardTableModRefBS* bs):
570 _g1(g1), _ct_bs(bs)
571 { }
572
573 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
574 // Construct the region representing the card.
575 HeapWord* start = _ct_bs->addr_for(card_ptr);
576 // And find the region containing it.
577 HeapRegion* r = _g1->heap_region_containing(start);
578 assert(r != NULL, "unexpected null");
579
580 // Scan oops in the card looking for references into the collection set
581 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
582 MemRegion scanRegion(start, end);
583
584 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
585 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
586 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
587
588 // We can pass false as the "filter_young" parameter here as:
589 // * we should be in a STW pause,
590 // * the DCQS to which this closure is applied is used to hold
591 // references that point into the collection set from the prior
592 // RSet updating,
593 // * the post-write barrier shouldn't be logging updates to young
594 // regions (but there is a situation where this can happen - see
595 // the comment in HRInto_G1RemSet::concurrentRefineOneCard below -
596 // that should not be applicable here), and
597 // * during actual RSet updating, the filtering of cards in young
598 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
599 // employed.
600 // As a result, when this closure is applied to "refs into cset"
601 // DCQS, we shouldn't see any cards in young regions.
602 update_rs_cl.set_region(r);
603 HeapWord* stop_point =
604 r->oops_on_card_seq_iterate_careful(scanRegion,
605 &filter_then_update_rs_cset_oop_cl,
606 false /* filter_young */);
607
608 // Since this is performed in the event of an evacuation failure, we
609 // we shouldn't see a non-null stop point
610 assert(stop_point == NULL, "saw an unallocated region");
611 return true;
612 }
613 };
614
615 void HRInto_G1RemSet::cleanup_after_oops_into_collection_set_do() {
616 guarantee( _cards_scanned != NULL, "invariant" );
617 _total_cards_scanned = 0;
618 for (uint i = 0; i < n_workers(); ++i)
619 _total_cards_scanned += _cards_scanned[i];
620 FREE_C_HEAP_ARRAY(size_t, _cards_scanned);
621 _cards_scanned = NULL;
622 // Cleanup after copy
623 #if G1_REM_SET_LOGGING
624 PrintRSClosure cl;
625 _g1->heap_region_iterate(&cl);
626 #endif
627 _g1->set_refine_cte_cl_concurrency(true);
628 cleanUpIteratorsClosure iterClosure;
629 _g1->collection_set_iterate(&iterClosure);
630 // Set all cards back to clean.
631 _g1->cleanUpCardTable();
632
633 set_traversal(false);
634
635 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
636 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
637
638 if (_g1->evacuation_failed()) {
639 // Restore remembered sets for the regions pointing into the collection set.
640
641 if (G1DeferredRSUpdate) {
642 // If deferred RS updates are enabled then we just need to transfer
643 // the completed buffers from (a) the DirtyCardQueueSet used to hold
644 // cards that contain references that point into the collection set
645 // to (b) the DCQS used to hold the deferred RS updates
646 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
647 } else {
648
649 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
650 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
651
652 int n_completed_buffers = 0;
653 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
654 0, 0, true)) {
655 n_completed_buffers++;
656 }
657 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
658 }
659 }
660
661 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
662 // which contain references that point into the collection.
663 _g1->into_cset_dirty_card_queue_set().clear();
664 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
665 "all buffers should be freed");
666 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
667
668 assert(!_traversal_in_progress, "Invariant between iterations.");
669 }
670
671 class UpdateRSObjectClosure: public ObjectClosure {
672 UpdateRSOopClosure* _update_rs_oop_cl;
673 public:
674 UpdateRSObjectClosure(UpdateRSOopClosure* update_rs_oop_cl) :
675 _update_rs_oop_cl(update_rs_oop_cl) {}
676 void do_object(oop obj) {
677 obj->oop_iterate(_update_rs_oop_cl);
678 }
679
680 };
681
682 class ScrubRSClosure: public HeapRegionClosure {
683 G1CollectedHeap* _g1h;
684 BitMap* _region_bm;
685 BitMap* _card_bm;
686 CardTableModRefBS* _ctbs;
687 public:
688 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
689 _g1h(G1CollectedHeap::heap()),
690 _region_bm(region_bm), _card_bm(card_bm),
691 _ctbs(NULL)
692 {
693 ModRefBarrierSet* bs = _g1h->mr_bs();
694 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
695 _ctbs = (CardTableModRefBS*)bs;
696 }
697
698 bool doHeapRegion(HeapRegion* r) {
699 if (!r->continuesHumongous()) {
700 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
701 }
702 return false;
703 }
704 };
705
706 void HRInto_G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
707 ScrubRSClosure scrub_cl(region_bm, card_bm);
708 _g1->heap_region_iterate(&scrub_cl);
709 }
710
711 void HRInto_G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
712 int worker_num, int claim_val) {
713 ScrubRSClosure scrub_cl(region_bm, card_bm);
714 _g1->heap_region_par_iterate_chunked(&scrub_cl, worker_num, claim_val);
715 }
716
717
718 static IntHistogram out_of_histo(50, 50);
719
720 class TriggerClosure : public OopClosure {
721 bool _trigger;
722 public:
723 TriggerClosure() : _trigger(false) { }
724 bool value() const { return _trigger; }
725 template <class T> void do_oop_nv(T* p) { _trigger = true; }
726 virtual void do_oop(oop* p) { do_oop_nv(p); }
727 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
728 };
729
730 class InvokeIfNotTriggeredClosure: public OopClosure {
731 TriggerClosure* _t;
732 OopClosure* _oc;
733 public:
734 InvokeIfNotTriggeredClosure(TriggerClosure* t, OopClosure* oc):
735 _t(t), _oc(oc) { }
736 template <class T> void do_oop_nv(T* p) {
737 if (!_t->value()) _oc->do_oop(p);
738 }
739 virtual void do_oop(oop* p) { do_oop_nv(p); }
740 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
741 };
742
743 class Mux2Closure : public OopClosure {
744 OopClosure* _c1;
745 OopClosure* _c2;
746 public:
747 Mux2Closure(OopClosure *c1, OopClosure *c2) : _c1(c1), _c2(c2) { }
748 template <class T> void do_oop_nv(T* p) {
749 _c1->do_oop(p); _c2->do_oop(p);
750 }
751 virtual void do_oop(oop* p) { do_oop_nv(p); }
752 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
753 };
754
755 bool HRInto_G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
756 bool check_for_refs_into_cset) {
757 // Construct the region representing the card.
758 HeapWord* start = _ct_bs->addr_for(card_ptr);
759 // And find the region containing it.
760 HeapRegion* r = _g1->heap_region_containing(start);
761 assert(r != NULL, "unexpected null");
762
763 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
764 MemRegion dirtyRegion(start, end);
765
766 #if CARD_REPEAT_HISTO
767 init_ct_freq_table(_g1->g1_reserved_obj_bytes());
768 ct_freq_note_card(_ct_bs->index_for(start));
769 #endif
770
771 UpdateRSOopClosure update_rs_oop_cl(this, worker_i);
772 update_rs_oop_cl.set_from(r);
773
774 TriggerClosure trigger_cl;
775 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
776 InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
777 Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
778
779 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
780 (check_for_refs_into_cset ?
781 (OopClosure*)&mux :
782 (OopClosure*)&update_rs_oop_cl));
783
784 // Undirty the card.
785 *card_ptr = CardTableModRefBS::clean_card_val();
786 // We must complete this write before we do any of the reads below.
787 OrderAccess::storeload();
788 // And process it, being careful of unallocated portions of TLAB's.
789
790 // The region for the current card may be a young region. The
791 // current card may have been a card that was evicted from the
792 // card cache. When the card was inserted into the cache, we had
793 // determined that its region was non-young. While in the cache,
794 // the region may have been freed during a cleanup pause, reallocated
795 // and tagged as young.
796 //
797 // We wish to filter out cards for such a region but the current
798 // thread, if we're running conucrrently, may "see" the young type
799 // change at any time (so an earlier "is_young" check may pass or
800 // fail arbitrarily). We tell the iteration code to perform this
801 // filtering when it has been determined that there has been an actual
802 // allocation in this region and making it safe to check the young type.
803 bool filter_young = true;
804
805 HeapWord* stop_point =
806 r->oops_on_card_seq_iterate_careful(dirtyRegion,
807 &filter_then_update_rs_oop_cl,
808 filter_young);
809
810 // If stop_point is non-null, then we encountered an unallocated region
811 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
812 // card and re-enqueue: if we put off the card until a GC pause, then the
813 // unallocated portion will be filled in. Alternatively, we might try
814 // the full complexity of the technique used in "regular" precleaning.
815 if (stop_point != NULL) {
816 // The card might have gotten re-dirtied and re-enqueued while we
817 // worked. (In fact, it's pretty likely.)
818 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
819 *card_ptr = CardTableModRefBS::dirty_card_val();
820 MutexLockerEx x(Shared_DirtyCardQ_lock,
821 Mutex::_no_safepoint_check_flag);
822 DirtyCardQueue* sdcq =
823 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
824 sdcq->enqueue(card_ptr);
825 }
826 } else {
827 out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region());
828 _conc_refine_cards++;
829 }
830
831 return trigger_cl.value();
832 }
833
834 bool HRInto_G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
835 bool check_for_refs_into_cset) {
836 // If the card is no longer dirty, nothing to do.
837 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
838 // No need to return that this card contains refs that point
839 // into the collection set.
840 return false;
841 }
842
843 // Construct the region representing the card.
844 HeapWord* start = _ct_bs->addr_for(card_ptr);
845 // And find the region containing it.
846 HeapRegion* r = _g1->heap_region_containing(start);
847 if (r == NULL) {
848 guarantee(_g1->is_in_permanent(start), "Or else where?");
849 // Again no need to return that this card contains refs that
850 // point into the collection set.
851 return false; // Not in the G1 heap (might be in perm, for example.)
852 }
853 // Why do we have to check here whether a card is on a young region,
854 // given that we dirty young regions and, as a result, the
855 // post-barrier is supposed to filter them out and never to enqueue
856 // them? When we allocate a new region as the "allocation region" we
857 // actually dirty its cards after we release the lock, since card
858 // dirtying while holding the lock was a performance bottleneck. So,
859 // as a result, it is possible for other threads to actually
860 // allocate objects in the region (after the acquire the lock)
861 // before all the cards on the region are dirtied. This is unlikely,
862 // and it doesn't happen often, but it can happen. So, the extra
863 // check below filters out those cards.
864 if (r->is_young()) {
865 return false;
866 }
867 // While we are processing RSet buffers during the collection, we
868 // actually don't want to scan any cards on the collection set,
869 // since we don't want to update remebered sets with entries that
870 // point into the collection set, given that live objects from the
871 // collection set are about to move and such entries will be stale
872 // very soon. This change also deals with a reliability issue which
873 // involves scanning a card in the collection set and coming across
874 // an array that was being chunked and looking malformed. Note,
875 // however, that if evacuation fails, we have to scan any objects
876 // that were not moved and create any missing entries.
877 if (r->in_collection_set()) {
878 return false;
879 }
880
881 // Should we defer processing the card?
882 //
883 // Previously the result from the insert_cache call would be
884 // either card_ptr (implying that card_ptr was currently "cold"),
885 // null (meaning we had inserted the card ptr into the "hot"
886 // cache, which had some headroom), or a "hot" card ptr
887 // extracted from the "hot" cache.
888 //
889 // Now that the _card_counts cache in the ConcurrentG1Refine
890 // instance is an evicting hash table, the result we get back
891 // could be from evicting the card ptr in an already occupied
892 // bucket (in which case we have replaced the card ptr in the
893 // bucket with card_ptr and "defer" is set to false). To avoid
894 // having a data structure (updates to which would need a lock)
895 // to hold these unprocessed dirty cards, we need to immediately
896 // process card_ptr. The actions needed to be taken on return
897 // from cache_insert are summarized in the following table:
898 //
899 // res defer action
900 // --------------------------------------------------------------
901 // null false card evicted from _card_counts & replaced with
902 // card_ptr; evicted ptr added to hot cache.
903 // No need to process res; immediately process card_ptr
904 //
905 // null true card not evicted from _card_counts; card_ptr added
906 // to hot cache.
907 // Nothing to do.
908 //
909 // non-null false card evicted from _card_counts & replaced with
910 // card_ptr; evicted ptr is currently "cold" or
911 // caused an eviction from the hot cache.
912 // Immediately process res; process card_ptr.
913 //
914 // non-null true card not evicted from _card_counts; card_ptr is
915 // currently cold, or caused an eviction from hot
916 // cache.
917 // Immediately process res; no need to process card_ptr.
918
919
920 jbyte* res = card_ptr;
921 bool defer = false;
922
923 // This gets set to true if the card being refined has references
924 // that point into the collection set.
925 bool oops_into_cset = false;
926
927 if (_cg1r->use_cache()) {
928 jbyte* res = _cg1r->cache_insert(card_ptr, &defer);
929 if (res != NULL && (res != card_ptr || defer)) {
930 start = _ct_bs->addr_for(res);
931 r = _g1->heap_region_containing(start);
932 if (r == NULL) {
933 assert(_g1->is_in_permanent(start), "Or else where?");
934 } else {
935 // Checking whether the region we got back from the cache
936 // is young here is inappropriate. The region could have been
937 // freed, reallocated and tagged as young while in the cache.
938 // Hence we could see its young type change at any time.
939 //
940 // Process card pointer we get back from the hot card cache. This
941 // will check whether the region containing the card is young
942 // _after_ checking that the region has been allocated from.
943 oops_into_cset = concurrentRefineOneCard_impl(res, worker_i,
944 false /* check_for_refs_into_cset */);
945 // The above call to concurrentRefineOneCard_impl is only
946 // performed if the hot card cache is enabled. This cache is
947 // disabled during an evacuation pause - which is the only
948 // time when we need know if the card contains references
949 // that point into the collection set. Also when the hot card
950 // cache is enabled, this code is executed by the concurrent
951 // refine threads - rather than the GC worker threads - and
952 // concurrentRefineOneCard_impl will return false.
953 assert(!oops_into_cset, "should not see true here");
954 }
955 }
956 }
957
958 if (!defer) {
959 oops_into_cset =
960 concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset);
961 // We should only be detecting that the card contains references
962 // that point into the collection set if the current thread is
963 // a GC worker thread.
964 assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(),
965 "invalid result at non safepoint");
966 }
967 return oops_into_cset;
968 }
969
970 class HRRSStatsIter: public HeapRegionClosure {
971 size_t _occupied;
972 size_t _total_mem_sz;
973 size_t _max_mem_sz;
974 HeapRegion* _max_mem_sz_region;
975 public:
976 HRRSStatsIter() :
977 _occupied(0),
978 _total_mem_sz(0),
979 _max_mem_sz(0),
980 _max_mem_sz_region(NULL)
981 {}
982
983 bool doHeapRegion(HeapRegion* r) {
984 if (r->continuesHumongous()) return false;
985 size_t mem_sz = r->rem_set()->mem_size();
986 if (mem_sz > _max_mem_sz) {
987 _max_mem_sz = mem_sz;
988 _max_mem_sz_region = r;
989 }
990 _total_mem_sz += mem_sz;
991 size_t occ = r->rem_set()->occupied();
992 _occupied += occ;
993 return false;
994 }
995 size_t total_mem_sz() { return _total_mem_sz; }
996 size_t max_mem_sz() { return _max_mem_sz; }
997 size_t occupied() { return _occupied; }
998 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
999 };
1000
1001 class PrintRSThreadVTimeClosure : public ThreadClosure {
1002 public:
1003 virtual void do_thread(Thread *t) {
1004 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
1005 gclog_or_tty->print(" %5.2f", crt->vtime_accum());
1006 }
1007 };
1008
1009 void HRInto_G1RemSet::print_summary_info() {
1010 G1CollectedHeap* g1 = G1CollectedHeap::heap();
1011
1012 #if CARD_REPEAT_HISTO
1013 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
1014 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
1015 card_repeat_count.print_on(gclog_or_tty);
1016 #endif
1017
1018 if (FILTEROUTOFREGIONCLOSURE_DOHISTOGRAMCOUNT) {
1019 gclog_or_tty->print_cr("\nG1 rem-set out-of-region histogram: ");
1020 gclog_or_tty->print_cr(" # of CS ptrs --> # of cards with that number.");
1021 out_of_histo.print_on(gclog_or_tty);
1022 }
1023 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
1024 _conc_refine_cards);
1025 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1026 jint tot_processed_buffers =
1027 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
1028 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers);
1029 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.",
1030 dcqs.processed_buffers_rs_thread(),
1031 100.0*(float)dcqs.processed_buffers_rs_thread()/
1032 (float)tot_processed_buffers);
1033 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.",
1034 dcqs.processed_buffers_mut(),
1035 100.0*(float)dcqs.processed_buffers_mut()/
1036 (float)tot_processed_buffers);
1037 gclog_or_tty->print_cr(" Conc RS threads times(s)");
1038 PrintRSThreadVTimeClosure p;
1039 gclog_or_tty->print(" ");
1040 g1->concurrent_g1_refine()->threads_do(&p);
1041 gclog_or_tty->print_cr("");
1042
1043 if (G1UseHRIntoRS) {
1044 HRRSStatsIter blk;
1045 g1->heap_region_iterate(&blk);
1046 gclog_or_tty->print_cr(" Total heap region rem set sizes = " SIZE_FORMAT "K."
1047 " Max = " SIZE_FORMAT "K.",
1048 blk.total_mem_sz()/K, blk.max_mem_sz()/K);
1049 gclog_or_tty->print_cr(" Static structures = " SIZE_FORMAT "K,"
1050 " free_lists = " SIZE_FORMAT "K.",
1051 HeapRegionRemSet::static_mem_size()/K,
1052 HeapRegionRemSet::fl_mem_size()/K);
1053 gclog_or_tty->print_cr(" %d occupied cards represented.",
1054 blk.occupied());
1055 gclog_or_tty->print_cr(" Max sz region = [" PTR_FORMAT ", " PTR_FORMAT " )"
1056 ", cap = " SIZE_FORMAT "K, occ = " SIZE_FORMAT "K.",
1057 blk.max_mem_sz_region()->bottom(), blk.max_mem_sz_region()->end(),
1058 (blk.max_mem_sz_region()->rem_set()->mem_size() + K - 1)/K,
1059 (blk.max_mem_sz_region()->rem_set()->occupied() + K - 1)/K);
1060 gclog_or_tty->print_cr(" Did %d coarsenings.",
1061 HeapRegionRemSet::n_coarsenings());
1062
1063 }
1064 }
1065
1066 void HRInto_G1RemSet::prepare_for_verify() {
1067 if (G1HRRSFlushLogBuffersOnVerify &&
1068 (VerifyBeforeGC || VerifyAfterGC)
1069 && !_g1->full_collection()) {
1070 cleanupHRRS();
1071 _g1->set_refine_cte_cl_concurrency(false);
1072 if (SafepointSynchronize::is_at_safepoint()) {
1073 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1074 dcqs.concatenate_logs();
1075 }
1076 bool cg1r_use_cache = _cg1r->use_cache();
1077 _cg1r->set_use_cache(false);
1078 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
1079 updateRS(&into_cset_dcq, 0);
1080 _g1->into_cset_dirty_card_queue_set().clear();
1081 _cg1r->set_use_cache(cg1r_use_cache);
1082
1083 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
1084 }
1085 }