Thu, 19 Jul 2012 15:15:54 -0700
7114678: G1: various small fixes, code cleanup, and refactoring
Summary: Various cleanups as a prelude to introducing iterators for HeapRegions.
Reviewed-by: johnc, brutisso
1 /*
2 * Copyright (c) 2001, 2012, 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
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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).
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/bufferingOopClosure.hpp"
27 #include "gc_implementation/g1/concurrentG1Refine.hpp"
28 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
29 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
30 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
31 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
32 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
33 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
34 #include "gc_implementation/g1/g1RemSet.inline.hpp"
35 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
36 #include "memory/iterator.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "utilities/intHisto.hpp"
40 #define CARD_REPEAT_HISTO 0
42 #if CARD_REPEAT_HISTO
43 static size_t ct_freq_sz;
44 static jbyte* ct_freq = NULL;
46 void init_ct_freq_table(size_t heap_sz_bytes) {
47 if (ct_freq == NULL) {
48 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;
49 ct_freq = new jbyte[ct_freq_sz];
50 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;
51 }
52 }
54 void ct_freq_note_card(size_t index) {
55 assert(0 <= index && index < ct_freq_sz, "Bounds error.");
56 if (ct_freq[index] < 100) { ct_freq[index]++; }
57 }
59 static IntHistogram card_repeat_count(10, 10);
61 void ct_freq_update_histo_and_reset() {
62 for (size_t j = 0; j < ct_freq_sz; j++) {
63 card_repeat_count.add_entry(ct_freq[j]);
64 ct_freq[j] = 0;
65 }
67 }
68 #endif
70 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
71 : _g1(g1), _conc_refine_cards(0),
72 _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
73 _cg1r(g1->concurrent_g1_refine()),
74 _cset_rs_update_cl(NULL),
75 _cards_scanned(NULL), _total_cards_scanned(0)
76 {
77 _seq_task = new SubTasksDone(NumSeqTasks);
78 guarantee(n_workers() > 0, "There should be some workers");
79 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC);
80 for (uint i = 0; i < n_workers(); i++) {
81 _cset_rs_update_cl[i] = NULL;
82 }
83 }
85 G1RemSet::~G1RemSet() {
86 delete _seq_task;
87 for (uint i = 0; i < n_workers(); i++) {
88 assert(_cset_rs_update_cl[i] == NULL, "it should be");
89 }
90 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC);
91 }
93 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
94 if (_g1->is_in_g1_reserved(mr.start())) {
95 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));
96 if (_start_first == NULL) _start_first = mr.start();
97 }
98 }
100 class ScanRSClosure : public HeapRegionClosure {
101 size_t _cards_done, _cards;
102 G1CollectedHeap* _g1h;
103 OopsInHeapRegionClosure* _oc;
104 G1BlockOffsetSharedArray* _bot_shared;
105 CardTableModRefBS *_ct_bs;
106 int _worker_i;
107 int _block_size;
108 bool _try_claimed;
109 public:
110 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
111 _oc(oc),
112 _cards(0),
113 _cards_done(0),
114 _worker_i(worker_i),
115 _try_claimed(false)
116 {
117 _g1h = G1CollectedHeap::heap();
118 _bot_shared = _g1h->bot_shared();
119 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());
120 _block_size = MAX2<int>(G1RSetScanBlockSize, 1);
121 }
123 void set_try_claimed() { _try_claimed = true; }
125 void scanCard(size_t index, HeapRegion *r) {
126 // Stack allocate the DirtyCardToOopClosure instance
127 HeapRegionDCTOC cl(_g1h, r, _oc,
128 CardTableModRefBS::Precise,
129 HeapRegionDCTOC::IntoCSFilterKind);
131 // Set the "from" region in the closure.
132 _oc->set_region(r);
133 HeapWord* card_start = _bot_shared->address_for_index(index);
134 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;
135 Space *sp = SharedHeap::heap()->space_containing(card_start);
136 MemRegion sm_region = sp->used_region_at_save_marks();
137 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));
138 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
139 // We make the card as "claimed" lazily (so races are possible
140 // but they're benign), which reduces the number of duplicate
141 // scans (the rsets of the regions in the cset can intersect).
142 _ct_bs->set_card_claimed(index);
143 _cards_done++;
144 cl.do_MemRegion(mr);
145 }
146 }
148 void printCard(HeapRegion* card_region, size_t card_index,
149 HeapWord* card_start) {
150 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "
151 "RS names card %p: "
152 "[" PTR_FORMAT ", " PTR_FORMAT ")",
153 _worker_i,
154 card_region->bottom(), card_region->end(),
155 card_index,
156 card_start, card_start + G1BlockOffsetSharedArray::N_words);
157 }
159 bool doHeapRegion(HeapRegion* r) {
160 assert(r->in_collection_set(), "should only be called on elements of CS.");
161 HeapRegionRemSet* hrrs = r->rem_set();
162 if (hrrs->iter_is_complete()) return false; // All done.
163 if (!_try_claimed && !hrrs->claim_iter()) return false;
164 // If we ever free the collection set concurrently, we should also
165 // clear the card table concurrently therefore we won't need to
166 // add regions of the collection set to the dirty cards region.
167 _g1h->push_dirty_cards_region(r);
168 // If we didn't return above, then
169 // _try_claimed || r->claim_iter()
170 // is true: either we're supposed to work on claimed-but-not-complete
171 // regions, or we successfully claimed the region.
172 HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i);
173 hrrs->init_iterator(iter);
174 size_t card_index;
176 // We claim cards in block so as to recude the contention. The block size is determined by
177 // the G1RSetScanBlockSize parameter.
178 size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
179 for (size_t current_card = 0; iter->has_next(card_index); current_card++) {
180 if (current_card >= jump_to_card + _block_size) {
181 jump_to_card = hrrs->iter_claimed_next(_block_size);
182 }
183 if (current_card < jump_to_card) continue;
184 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
185 #if 0
186 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",
187 card_start, card_start + CardTableModRefBS::card_size_in_words);
188 #endif
190 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
191 assert(card_region != NULL, "Yielding cards not in the heap?");
192 _cards++;
194 if (!card_region->is_on_dirty_cards_region_list()) {
195 _g1h->push_dirty_cards_region(card_region);
196 }
198 // If the card is dirty, then we will scan it during updateRS.
199 if (!card_region->in_collection_set() &&
200 !_ct_bs->is_card_dirty(card_index)) {
201 scanCard(card_index, card_region);
202 }
203 }
204 if (!_try_claimed) {
205 hrrs->set_iter_complete();
206 }
207 return false;
208 }
209 size_t cards_done() { return _cards_done;}
210 size_t cards_looked_up() { return _cards;}
211 };
213 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
214 double rs_time_start = os::elapsedTime();
215 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
217 ScanRSClosure scanRScl(oc, worker_i);
219 _g1->collection_set_iterate_from(startRegion, &scanRScl);
220 scanRScl.set_try_claimed();
221 _g1->collection_set_iterate_from(startRegion, &scanRScl);
223 double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
225 assert( _cards_scanned != NULL, "invariant" );
226 _cards_scanned[worker_i] = scanRScl.cards_done();
228 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
229 }
231 // Closure used for updating RSets and recording references that
232 // point into the collection set. Only called during an
233 // evacuation pause.
235 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
236 G1RemSet* _g1rs;
237 DirtyCardQueue* _into_cset_dcq;
238 public:
239 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
240 DirtyCardQueue* into_cset_dcq) :
241 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
242 {}
243 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
244 // The only time we care about recording cards that
245 // contain references that point into the collection set
246 // is during RSet updating within an evacuation pause.
247 // In this case worker_i should be the id of a GC worker thread.
248 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
249 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
251 if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) {
252 // 'card_ptr' contains references that point into the collection
253 // set. We need to record the card in the DCQS
254 // (G1CollectedHeap::into_cset_dirty_card_queue_set())
255 // that's used for that purpose.
256 //
257 // Enqueue the card
258 _into_cset_dcq->enqueue(card_ptr);
259 }
260 return true;
261 }
262 };
264 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) {
265 double start = os::elapsedTime();
266 // Apply the given closure to all remaining log entries.
267 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
269 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);
271 // Now there should be no dirty cards.
272 if (G1RSLogCheckCardTable) {
273 CountNonCleanMemRegionClosure cl(_g1);
274 _ct_bs->mod_card_iterate(&cl);
275 // XXX This isn't true any more: keeping cards of young regions
276 // marked dirty broke it. Need some reasonable fix.
277 guarantee(cl.n() == 0, "Card table should be clean.");
278 }
280 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);
281 }
283 void G1RemSet::cleanupHRRS() {
284 HeapRegionRemSet::cleanup();
285 }
287 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
288 int worker_i) {
289 #if CARD_REPEAT_HISTO
290 ct_freq_update_histo_and_reset();
291 #endif
292 if (worker_i == 0) {
293 _cg1r->clear_and_record_card_counts();
294 }
296 // We cache the value of 'oc' closure into the appropriate slot in the
297 // _cset_rs_update_cl for this worker
298 assert(worker_i < (int)n_workers(), "sanity");
299 _cset_rs_update_cl[worker_i] = oc;
301 // A DirtyCardQueue that is used to hold cards containing references
302 // that point into the collection set. This DCQ is associated with a
303 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
304 // circumstances (i.e. the pause successfully completes), these cards
305 // are just discarded (there's no need to update the RSets of regions
306 // that were in the collection set - after the pause these regions
307 // are wholly 'free' of live objects. In the event of an evacuation
308 // failure the cards/buffers in this queue set are:
309 // * passed to the DirtyCardQueueSet that is used to manage deferred
310 // RSet updates, or
311 // * scanned for references that point into the collection set
312 // and the RSet of the corresponding region in the collection set
313 // is updated immediately.
314 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
316 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
318 // The two flags below were introduced temporarily to serialize
319 // the updating and scanning of remembered sets. There are some
320 // race conditions when these two operations are done in parallel
321 // and they are causing failures. When we resolve said race
322 // conditions, we'll revert back to parallel remembered set
323 // updating and scanning. See CRs 6677707 and 6677708.
324 if (G1UseParallelRSetUpdating || (worker_i == 0)) {
325 updateRS(&into_cset_dcq, worker_i);
326 } else {
327 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0.0);
328 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
329 }
330 if (G1UseParallelRSetScanning || (worker_i == 0)) {
331 scanRS(oc, worker_i);
332 } else {
333 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
334 }
336 // We now clear the cached values of _cset_rs_update_cl for this worker
337 _cset_rs_update_cl[worker_i] = NULL;
338 }
340 void G1RemSet::prepare_for_oops_into_collection_set_do() {
341 cleanupHRRS();
342 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
343 _g1->set_refine_cte_cl_concurrency(false);
344 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
345 dcqs.concatenate_logs();
347 if (G1CollectedHeap::use_parallel_gc_threads()) {
348 // Don't set the number of workers here. It will be set
349 // when the task is run
350 // _seq_task->set_n_termination((int)n_workers());
351 }
352 guarantee( _cards_scanned == NULL, "invariant" );
353 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC);
354 for (uint i = 0; i < n_workers(); ++i) {
355 _cards_scanned[i] = 0;
356 }
357 _total_cards_scanned = 0;
358 }
361 // This closure, applied to a DirtyCardQueueSet, is used to immediately
362 // update the RSets for the regions in the CSet. For each card it iterates
363 // through the oops which coincide with that card. It scans the reference
364 // fields in each oop; when it finds an oop that points into the collection
365 // set, the RSet for the region containing the referenced object is updated.
366 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
367 G1CollectedHeap* _g1;
368 CardTableModRefBS* _ct_bs;
369 public:
370 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
371 CardTableModRefBS* bs):
372 _g1(g1), _ct_bs(bs)
373 { }
375 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
376 // Construct the region representing the card.
377 HeapWord* start = _ct_bs->addr_for(card_ptr);
378 // And find the region containing it.
379 HeapRegion* r = _g1->heap_region_containing(start);
380 assert(r != NULL, "unexpected null");
382 // Scan oops in the card looking for references into the collection set
383 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
384 MemRegion scanRegion(start, end);
386 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
387 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
388 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
390 // We can pass false as the "filter_young" parameter here as:
391 // * we should be in a STW pause,
392 // * the DCQS to which this closure is applied is used to hold
393 // references that point into the collection set from the prior
394 // RSet updating,
395 // * the post-write barrier shouldn't be logging updates to young
396 // regions (but there is a situation where this can happen - see
397 // the comment in G1RemSet::concurrentRefineOneCard below -
398 // that should not be applicable here), and
399 // * during actual RSet updating, the filtering of cards in young
400 // regions in HeapRegion::oops_on_card_seq_iterate_careful is
401 // employed.
402 // As a result, when this closure is applied to "refs into cset"
403 // DCQS, we shouldn't see any cards in young regions.
404 update_rs_cl.set_region(r);
405 HeapWord* stop_point =
406 r->oops_on_card_seq_iterate_careful(scanRegion,
407 &filter_then_update_rs_cset_oop_cl,
408 false /* filter_young */,
409 NULL /* card_ptr */);
411 // Since this is performed in the event of an evacuation failure, we
412 // we shouldn't see a non-null stop point
413 assert(stop_point == NULL, "saw an unallocated region");
414 return true;
415 }
416 };
418 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
419 guarantee( _cards_scanned != NULL, "invariant" );
420 _total_cards_scanned = 0;
421 for (uint i = 0; i < n_workers(); ++i) {
422 _total_cards_scanned += _cards_scanned[i];
423 }
424 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC);
425 _cards_scanned = NULL;
426 // Cleanup after copy
427 _g1->set_refine_cte_cl_concurrency(true);
428 // Set all cards back to clean.
429 _g1->cleanUpCardTable();
431 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set();
432 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
434 if (_g1->evacuation_failed()) {
435 // Restore remembered sets for the regions pointing into the collection set.
437 if (G1DeferredRSUpdate) {
438 // If deferred RS updates are enabled then we just need to transfer
439 // the completed buffers from (a) the DirtyCardQueueSet used to hold
440 // cards that contain references that point into the collection set
441 // to (b) the DCQS used to hold the deferred RS updates
442 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
443 } else {
445 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
446 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
448 int n_completed_buffers = 0;
449 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
450 0, 0, true)) {
451 n_completed_buffers++;
452 }
453 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
454 }
455 }
457 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
458 // which contain references that point into the collection.
459 _g1->into_cset_dirty_card_queue_set().clear();
460 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
461 "all buffers should be freed");
462 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
463 }
465 class ScrubRSClosure: public HeapRegionClosure {
466 G1CollectedHeap* _g1h;
467 BitMap* _region_bm;
468 BitMap* _card_bm;
469 CardTableModRefBS* _ctbs;
470 public:
471 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
472 _g1h(G1CollectedHeap::heap()),
473 _region_bm(region_bm), _card_bm(card_bm),
474 _ctbs(NULL)
475 {
476 ModRefBarrierSet* bs = _g1h->mr_bs();
477 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
478 _ctbs = (CardTableModRefBS*)bs;
479 }
481 bool doHeapRegion(HeapRegion* r) {
482 if (!r->continuesHumongous()) {
483 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
484 }
485 return false;
486 }
487 };
489 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) {
490 ScrubRSClosure scrub_cl(region_bm, card_bm);
491 _g1->heap_region_iterate(&scrub_cl);
492 }
494 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm,
495 uint worker_num, int claim_val) {
496 ScrubRSClosure scrub_cl(region_bm, card_bm);
497 _g1->heap_region_par_iterate_chunked(&scrub_cl,
498 worker_num,
499 n_workers(),
500 claim_val);
501 }
505 G1TriggerClosure::G1TriggerClosure() :
506 _triggered(false) { }
508 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
509 OopClosure* oop_cl) :
510 _trigger_cl(t_cl), _oop_cl(oop_cl) { }
512 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
513 _c1(c1), _c2(c2) { }
515 G1UpdateRSOrPushRefOopClosure::
516 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
517 G1RemSet* rs,
518 OopsInHeapRegionClosure* push_ref_cl,
519 bool record_refs_into_cset,
520 int worker_i) :
521 _g1(g1h), _g1_rem_set(rs), _from(NULL),
522 _record_refs_into_cset(record_refs_into_cset),
523 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
525 bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
526 bool check_for_refs_into_cset) {
527 // Construct the region representing the card.
528 HeapWord* start = _ct_bs->addr_for(card_ptr);
529 // And find the region containing it.
530 HeapRegion* r = _g1->heap_region_containing(start);
531 assert(r != NULL, "unexpected null");
533 HeapWord* end = _ct_bs->addr_for(card_ptr + 1);
534 MemRegion dirtyRegion(start, end);
536 #if CARD_REPEAT_HISTO
537 init_ct_freq_table(_g1->max_capacity());
538 ct_freq_note_card(_ct_bs->index_for(start));
539 #endif
541 OopsInHeapRegionClosure* oops_in_heap_closure = NULL;
542 if (check_for_refs_into_cset) {
543 // ConcurrentG1RefineThreads have worker numbers larger than what
544 // _cset_rs_update_cl[] is set up to handle. But those threads should
545 // only be active outside of a collection which means that when they
546 // reach here they should have check_for_refs_into_cset == false.
547 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
548 oops_in_heap_closure = _cset_rs_update_cl[worker_i];
549 }
550 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
551 _g1->g1_rem_set(),
552 oops_in_heap_closure,
553 check_for_refs_into_cset,
554 worker_i);
555 update_rs_oop_cl.set_from(r);
557 G1TriggerClosure trigger_cl;
558 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
559 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
560 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
562 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
563 (check_for_refs_into_cset ?
564 (OopClosure*)&mux :
565 (OopClosure*)&update_rs_oop_cl));
567 // The region for the current card may be a young region. The
568 // current card may have been a card that was evicted from the
569 // card cache. When the card was inserted into the cache, we had
570 // determined that its region was non-young. While in the cache,
571 // the region may have been freed during a cleanup pause, reallocated
572 // and tagged as young.
573 //
574 // We wish to filter out cards for such a region but the current
575 // thread, if we're running concurrently, may "see" the young type
576 // change at any time (so an earlier "is_young" check may pass or
577 // fail arbitrarily). We tell the iteration code to perform this
578 // filtering when it has been determined that there has been an actual
579 // allocation in this region and making it safe to check the young type.
580 bool filter_young = true;
582 HeapWord* stop_point =
583 r->oops_on_card_seq_iterate_careful(dirtyRegion,
584 &filter_then_update_rs_oop_cl,
585 filter_young,
586 card_ptr);
588 // If stop_point is non-null, then we encountered an unallocated region
589 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the
590 // card and re-enqueue: if we put off the card until a GC pause, then the
591 // unallocated portion will be filled in. Alternatively, we might try
592 // the full complexity of the technique used in "regular" precleaning.
593 if (stop_point != NULL) {
594 // The card might have gotten re-dirtied and re-enqueued while we
595 // worked. (In fact, it's pretty likely.)
596 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
597 *card_ptr = CardTableModRefBS::dirty_card_val();
598 MutexLockerEx x(Shared_DirtyCardQ_lock,
599 Mutex::_no_safepoint_check_flag);
600 DirtyCardQueue* sdcq =
601 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
602 sdcq->enqueue(card_ptr);
603 }
604 } else {
605 _conc_refine_cards++;
606 }
608 return trigger_cl.triggered();
609 }
611 bool G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
612 bool check_for_refs_into_cset) {
613 // If the card is no longer dirty, nothing to do.
614 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
615 // No need to return that this card contains refs that point
616 // into the collection set.
617 return false;
618 }
620 // Construct the region representing the card.
621 HeapWord* start = _ct_bs->addr_for(card_ptr);
622 // And find the region containing it.
623 HeapRegion* r = _g1->heap_region_containing(start);
624 if (r == NULL) {
625 guarantee(_g1->is_in_permanent(start), "Or else where?");
626 // Again no need to return that this card contains refs that
627 // point into the collection set.
628 return false; // Not in the G1 heap (might be in perm, for example.)
629 }
630 // Why do we have to check here whether a card is on a young region,
631 // given that we dirty young regions and, as a result, the
632 // post-barrier is supposed to filter them out and never to enqueue
633 // them? When we allocate a new region as the "allocation region" we
634 // actually dirty its cards after we release the lock, since card
635 // dirtying while holding the lock was a performance bottleneck. So,
636 // as a result, it is possible for other threads to actually
637 // allocate objects in the region (after the acquire the lock)
638 // before all the cards on the region are dirtied. This is unlikely,
639 // and it doesn't happen often, but it can happen. So, the extra
640 // check below filters out those cards.
641 if (r->is_young()) {
642 return false;
643 }
644 // While we are processing RSet buffers during the collection, we
645 // actually don't want to scan any cards on the collection set,
646 // since we don't want to update remebered sets with entries that
647 // point into the collection set, given that live objects from the
648 // collection set are about to move and such entries will be stale
649 // very soon. This change also deals with a reliability issue which
650 // involves scanning a card in the collection set and coming across
651 // an array that was being chunked and looking malformed. Note,
652 // however, that if evacuation fails, we have to scan any objects
653 // that were not moved and create any missing entries.
654 if (r->in_collection_set()) {
655 return false;
656 }
658 // Should we defer processing the card?
659 //
660 // Previously the result from the insert_cache call would be
661 // either card_ptr (implying that card_ptr was currently "cold"),
662 // null (meaning we had inserted the card ptr into the "hot"
663 // cache, which had some headroom), or a "hot" card ptr
664 // extracted from the "hot" cache.
665 //
666 // Now that the _card_counts cache in the ConcurrentG1Refine
667 // instance is an evicting hash table, the result we get back
668 // could be from evicting the card ptr in an already occupied
669 // bucket (in which case we have replaced the card ptr in the
670 // bucket with card_ptr and "defer" is set to false). To avoid
671 // having a data structure (updates to which would need a lock)
672 // to hold these unprocessed dirty cards, we need to immediately
673 // process card_ptr. The actions needed to be taken on return
674 // from cache_insert are summarized in the following table:
675 //
676 // res defer action
677 // --------------------------------------------------------------
678 // null false card evicted from _card_counts & replaced with
679 // card_ptr; evicted ptr added to hot cache.
680 // No need to process res; immediately process card_ptr
681 //
682 // null true card not evicted from _card_counts; card_ptr added
683 // to hot cache.
684 // Nothing to do.
685 //
686 // non-null false card evicted from _card_counts & replaced with
687 // card_ptr; evicted ptr is currently "cold" or
688 // caused an eviction from the hot cache.
689 // Immediately process res; process card_ptr.
690 //
691 // non-null true card not evicted from _card_counts; card_ptr is
692 // currently cold, or caused an eviction from hot
693 // cache.
694 // Immediately process res; no need to process card_ptr.
697 jbyte* res = card_ptr;
698 bool defer = false;
700 // This gets set to true if the card being refined has references
701 // that point into the collection set.
702 bool oops_into_cset = false;
704 if (_cg1r->use_cache()) {
705 jbyte* res = _cg1r->cache_insert(card_ptr, &defer);
706 if (res != NULL && (res != card_ptr || defer)) {
707 start = _ct_bs->addr_for(res);
708 r = _g1->heap_region_containing(start);
709 if (r == NULL) {
710 assert(_g1->is_in_permanent(start), "Or else where?");
711 } else {
712 // Checking whether the region we got back from the cache
713 // is young here is inappropriate. The region could have been
714 // freed, reallocated and tagged as young while in the cache.
715 // Hence we could see its young type change at any time.
716 //
717 // Process card pointer we get back from the hot card cache. This
718 // will check whether the region containing the card is young
719 // _after_ checking that the region has been allocated from.
720 oops_into_cset = concurrentRefineOneCard_impl(res, worker_i,
721 false /* check_for_refs_into_cset */);
722 // The above call to concurrentRefineOneCard_impl is only
723 // performed if the hot card cache is enabled. This cache is
724 // disabled during an evacuation pause - which is the only
725 // time when we need know if the card contains references
726 // that point into the collection set. Also when the hot card
727 // cache is enabled, this code is executed by the concurrent
728 // refine threads - rather than the GC worker threads - and
729 // concurrentRefineOneCard_impl will return false.
730 assert(!oops_into_cset, "should not see true here");
731 }
732 }
733 }
735 if (!defer) {
736 oops_into_cset =
737 concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset);
738 // We should only be detecting that the card contains references
739 // that point into the collection set if the current thread is
740 // a GC worker thread.
741 assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(),
742 "invalid result at non safepoint");
743 }
744 return oops_into_cset;
745 }
747 class HRRSStatsIter: public HeapRegionClosure {
748 size_t _occupied;
749 size_t _total_mem_sz;
750 size_t _max_mem_sz;
751 HeapRegion* _max_mem_sz_region;
752 public:
753 HRRSStatsIter() :
754 _occupied(0),
755 _total_mem_sz(0),
756 _max_mem_sz(0),
757 _max_mem_sz_region(NULL)
758 {}
760 bool doHeapRegion(HeapRegion* r) {
761 if (r->continuesHumongous()) return false;
762 size_t mem_sz = r->rem_set()->mem_size();
763 if (mem_sz > _max_mem_sz) {
764 _max_mem_sz = mem_sz;
765 _max_mem_sz_region = r;
766 }
767 _total_mem_sz += mem_sz;
768 size_t occ = r->rem_set()->occupied();
769 _occupied += occ;
770 return false;
771 }
772 size_t total_mem_sz() { return _total_mem_sz; }
773 size_t max_mem_sz() { return _max_mem_sz; }
774 size_t occupied() { return _occupied; }
775 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
776 };
778 class PrintRSThreadVTimeClosure : public ThreadClosure {
779 public:
780 virtual void do_thread(Thread *t) {
781 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t;
782 gclog_or_tty->print(" %5.2f", crt->vtime_accum());
783 }
784 };
786 void G1RemSet::print_summary_info() {
787 G1CollectedHeap* g1 = G1CollectedHeap::heap();
789 #if CARD_REPEAT_HISTO
790 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: ");
791 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number.");
792 card_repeat_count.print_on(gclog_or_tty);
793 #endif
795 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards",
796 _conc_refine_cards);
797 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
798 jint tot_processed_buffers =
799 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread();
800 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers);
801 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.",
802 dcqs.processed_buffers_rs_thread(),
803 100.0*(float)dcqs.processed_buffers_rs_thread()/
804 (float)tot_processed_buffers);
805 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.",
806 dcqs.processed_buffers_mut(),
807 100.0*(float)dcqs.processed_buffers_mut()/
808 (float)tot_processed_buffers);
809 gclog_or_tty->print_cr(" Conc RS threads times(s)");
810 PrintRSThreadVTimeClosure p;
811 gclog_or_tty->print(" ");
812 g1->concurrent_g1_refine()->threads_do(&p);
813 gclog_or_tty->print_cr("");
815 HRRSStatsIter blk;
816 g1->heap_region_iterate(&blk);
817 gclog_or_tty->print_cr(" Total heap region rem set sizes = "SIZE_FORMAT"K."
818 " Max = "SIZE_FORMAT"K.",
819 blk.total_mem_sz()/K, blk.max_mem_sz()/K);
820 gclog_or_tty->print_cr(" Static structures = "SIZE_FORMAT"K,"
821 " free_lists = "SIZE_FORMAT"K.",
822 HeapRegionRemSet::static_mem_size() / K,
823 HeapRegionRemSet::fl_mem_size() / K);
824 gclog_or_tty->print_cr(" "SIZE_FORMAT" occupied cards represented.",
825 blk.occupied());
826 HeapRegion* max_mem_sz_region = blk.max_mem_sz_region();
827 HeapRegionRemSet* rem_set = max_mem_sz_region->rem_set();
828 gclog_or_tty->print_cr(" Max size region = "HR_FORMAT", "
829 "size = "SIZE_FORMAT "K, occupied = "SIZE_FORMAT"K.",
830 HR_FORMAT_PARAMS(max_mem_sz_region),
831 (rem_set->mem_size() + K - 1)/K,
832 (rem_set->occupied() + K - 1)/K);
833 gclog_or_tty->print_cr(" Did %d coarsenings.",
834 HeapRegionRemSet::n_coarsenings());
835 }
837 void G1RemSet::prepare_for_verify() {
838 if (G1HRRSFlushLogBuffersOnVerify &&
839 (VerifyBeforeGC || VerifyAfterGC)
840 && !_g1->full_collection()) {
841 cleanupHRRS();
842 _g1->set_refine_cte_cl_concurrency(false);
843 if (SafepointSynchronize::is_at_safepoint()) {
844 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
845 dcqs.concatenate_logs();
846 }
847 bool cg1r_use_cache = _cg1r->use_cache();
848 _cg1r->set_use_cache(false);
849 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
850 updateRS(&into_cset_dcq, 0);
851 _g1->into_cset_dirty_card_queue_set().clear();
852 _cg1r->set_use_cache(cg1r_use_cache);
854 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
855 }
856 }