/* * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "gc_implementation/g1/bufferingOopClosure.hpp" #include "gc_implementation/g1/concurrentG1Refine.hpp" #include "gc_implementation/g1/concurrentG1RefineThread.hpp" #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp" #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" #include "gc_implementation/g1/g1CollectorPolicy.hpp" #include "gc_implementation/g1/g1OopClosures.inline.hpp" #include "gc_implementation/g1/g1RemSet.inline.hpp" #include "gc_implementation/g1/heapRegionSeq.inline.hpp" #include "memory/iterator.hpp" #include "oops/oop.inline.hpp" #include "utilities/intHisto.hpp" #define CARD_REPEAT_HISTO 0 #if CARD_REPEAT_HISTO static size_t ct_freq_sz; static jbyte* ct_freq = NULL; void init_ct_freq_table(size_t heap_sz_bytes) { if (ct_freq == NULL) { ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size; ct_freq = new jbyte[ct_freq_sz]; for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0; } } void ct_freq_note_card(size_t index) { assert(0 <= index && index < ct_freq_sz, "Bounds error."); if (ct_freq[index] < 100) { ct_freq[index]++; } } static IntHistogram card_repeat_count(10, 10); void ct_freq_update_histo_and_reset() { for (size_t j = 0; j < ct_freq_sz; j++) { card_repeat_count.add_entry(ct_freq[j]); ct_freq[j] = 0; } } #endif class IntoCSOopClosure: public OopsInHeapRegionClosure { OopsInHeapRegionClosure* _blk; G1CollectedHeap* _g1; public: IntoCSOopClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) : _g1(g1), _blk(blk) {} void set_region(HeapRegion* from) { _blk->set_region(from); } virtual void do_oop(narrowOop* p) { do_oop_work(p); } virtual void do_oop( oop* p) { do_oop_work(p); } template void do_oop_work(T* p) { oop obj = oopDesc::load_decode_heap_oop(p); if (_g1->obj_in_cs(obj)) _blk->do_oop(p); } bool apply_to_weak_ref_discovered_field() { return true; } bool idempotent() { return true; } }; class IntoCSRegionClosure: public HeapRegionClosure { IntoCSOopClosure _blk; G1CollectedHeap* _g1; public: IntoCSRegionClosure(G1CollectedHeap* g1, OopsInHeapRegionClosure* blk) : _g1(g1), _blk(g1, blk) {} bool doHeapRegion(HeapRegion* r) { if (!r->in_collection_set()) { _blk.set_region(r); if (r->isHumongous()) { if (r->startsHumongous()) { oop obj = oop(r->bottom()); obj->oop_iterate(&_blk); } } else { r->oop_before_save_marks_iterate(&_blk); } } return false; } }; class VerifyRSCleanCardOopClosure: public OopClosure { G1CollectedHeap* _g1; public: VerifyRSCleanCardOopClosure(G1CollectedHeap* g1) : _g1(g1) {} virtual void do_oop(narrowOop* p) { do_oop_work(p); } virtual void do_oop( oop* p) { do_oop_work(p); } template void do_oop_work(T* p) { oop obj = oopDesc::load_decode_heap_oop(p); HeapRegion* to = _g1->heap_region_containing(obj); guarantee(to == NULL || !to->in_collection_set(), "Missed a rem set member."); } }; G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs) : _g1(g1), _conc_refine_cards(0), _ct_bs(ct_bs), _g1p(_g1->g1_policy()), _cg1r(g1->concurrent_g1_refine()), _traversal_in_progress(false), _cset_rs_update_cl(NULL), _cards_scanned(NULL), _total_cards_scanned(0) { _seq_task = new SubTasksDone(NumSeqTasks); guarantee(n_workers() > 0, "There should be some workers"); _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers()); for (uint i = 0; i < n_workers(); i++) { _cset_rs_update_cl[i] = NULL; } } G1RemSet::~G1RemSet() { delete _seq_task; for (uint i = 0; i < n_workers(); i++) { assert(_cset_rs_update_cl[i] == NULL, "it should be"); } FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl); } void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) { if (_g1->is_in_g1_reserved(mr.start())) { _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size)); if (_start_first == NULL) _start_first = mr.start(); } } class ScanRSClosure : public HeapRegionClosure { size_t _cards_done, _cards; G1CollectedHeap* _g1h; OopsInHeapRegionClosure* _oc; G1BlockOffsetSharedArray* _bot_shared; CardTableModRefBS *_ct_bs; int _worker_i; int _block_size; bool _try_claimed; public: ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) : _oc(oc), _cards(0), _cards_done(0), _worker_i(worker_i), _try_claimed(false) { _g1h = G1CollectedHeap::heap(); _bot_shared = _g1h->bot_shared(); _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set()); _block_size = MAX2(G1RSetScanBlockSize, 1); } void set_try_claimed() { _try_claimed = true; } void scanCard(size_t index, HeapRegion *r) { _cards_done++; DirtyCardToOopClosure* cl = r->new_dcto_closure(_oc, CardTableModRefBS::Precise, HeapRegionDCTOC::IntoCSFilterKind); // Set the "from" region in the closure. _oc->set_region(r); HeapWord* card_start = _bot_shared->address_for_index(index); HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words; Space *sp = SharedHeap::heap()->space_containing(card_start); MemRegion sm_region; if (ParallelGCThreads > 0) { // first find the used area sm_region = sp->used_region_at_save_marks(); } else { // The closure is not idempotent. We shouldn't look at objects // allocated during the GC. sm_region = sp->used_region_at_save_marks(); } MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end)); if (!mr.is_empty()) { cl->do_MemRegion(mr); } } void printCard(HeapRegion* card_region, size_t card_index, HeapWord* card_start) { gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") " "RS names card %p: " "[" PTR_FORMAT ", " PTR_FORMAT ")", _worker_i, card_region->bottom(), card_region->end(), card_index, card_start, card_start + G1BlockOffsetSharedArray::N_words); } bool doHeapRegion(HeapRegion* r) { assert(r->in_collection_set(), "should only be called on elements of CS."); HeapRegionRemSet* hrrs = r->rem_set(); if (hrrs->iter_is_complete()) return false; // All done. if (!_try_claimed && !hrrs->claim_iter()) return false; _g1h->push_dirty_cards_region(r); // If we didn't return above, then // _try_claimed || r->claim_iter() // is true: either we're supposed to work on claimed-but-not-complete // regions, or we successfully claimed the region. HeapRegionRemSetIterator* iter = _g1h->rem_set_iterator(_worker_i); hrrs->init_iterator(iter); size_t card_index; // We claim cards in block so as to recude the contention. The block size is determined by // the G1RSetScanBlockSize parameter. size_t jump_to_card = hrrs->iter_claimed_next(_block_size); for (size_t current_card = 0; iter->has_next(card_index); current_card++) { if (current_card >= jump_to_card + _block_size) { jump_to_card = hrrs->iter_claimed_next(_block_size); } if (current_card < jump_to_card) continue; HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index); #if 0 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n", card_start, card_start + CardTableModRefBS::card_size_in_words); #endif HeapRegion* card_region = _g1h->heap_region_containing(card_start); assert(card_region != NULL, "Yielding cards not in the heap?"); _cards++; if (!card_region->is_on_dirty_cards_region_list()) { _g1h->push_dirty_cards_region(card_region); } // If the card is dirty, then we will scan it during updateRS. if (!card_region->in_collection_set() && !_ct_bs->is_card_dirty(card_index)) { // We make the card as "claimed" lazily (so races are possible but they're benign), // which reduces the number of duplicate scans (the rsets of the regions in the cset // can intersect). if (!_ct_bs->is_card_claimed(card_index)) { _ct_bs->set_card_claimed(card_index); scanCard(card_index, card_region); } } } if (!_try_claimed) { hrrs->set_iter_complete(); } return false; } // Set all cards back to clean. void cleanup() {_g1h->cleanUpCardTable();} size_t cards_done() { return _cards_done;} size_t cards_looked_up() { return _cards;} }; // We want the parallel threads to start their scanning at // different collection set regions to avoid contention. // If we have: // n collection set regions // p threads // Then thread t will start at region t * floor (n/p) HeapRegion* G1RemSet::calculateStartRegion(int worker_i) { HeapRegion* result = _g1p->collection_set(); if (ParallelGCThreads > 0) { size_t cs_size = _g1p->collection_set_size(); int n_workers = _g1->workers()->total_workers(); size_t cs_spans = cs_size / n_workers; size_t ind = cs_spans * worker_i; for (size_t i = 0; i < ind; i++) result = result->next_in_collection_set(); } return result; } void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) { double rs_time_start = os::elapsedTime(); HeapRegion *startRegion = calculateStartRegion(worker_i); ScanRSClosure scanRScl(oc, worker_i); _g1->collection_set_iterate_from(startRegion, &scanRScl); scanRScl.set_try_claimed(); _g1->collection_set_iterate_from(startRegion, &scanRScl); double scan_rs_time_sec = os::elapsedTime() - rs_time_start; assert( _cards_scanned != NULL, "invariant" ); _cards_scanned[worker_i] = scanRScl.cards_done(); _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0); } // Closure used for updating RSets and recording references that // point into the collection set. Only called during an // evacuation pause. class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure { G1RemSet* _g1rs; DirtyCardQueue* _into_cset_dcq; public: RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h, DirtyCardQueue* into_cset_dcq) : _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq) {} bool do_card_ptr(jbyte* card_ptr, int worker_i) { // The only time we care about recording cards that // contain references that point into the collection set // is during RSet updating within an evacuation pause. // In this case worker_i should be the id of a GC worker thread. assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); assert(worker_i < (int) DirtyCardQueueSet::num_par_ids(), "should be a GC worker"); if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) { // 'card_ptr' contains references that point into the collection // set. We need to record the card in the DCQS // (G1CollectedHeap::into_cset_dirty_card_queue_set()) // that's used for that purpose. // // Enqueue the card _into_cset_dcq->enqueue(card_ptr); } return true; } }; void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) { double start = os::elapsedTime(); // Apply the given closure to all remaining log entries. RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq); _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i); // Now there should be no dirty cards. if (G1RSLogCheckCardTable) { CountNonCleanMemRegionClosure cl(_g1); _ct_bs->mod_card_iterate(&cl); // XXX This isn't true any more: keeping cards of young regions // marked dirty broke it. Need some reasonable fix. guarantee(cl.n() == 0, "Card table should be clean."); } _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0); } #ifndef PRODUCT class PrintRSClosure : public HeapRegionClosure { int _count; public: PrintRSClosure() : _count(0) {} bool doHeapRegion(HeapRegion* r) { HeapRegionRemSet* hrrs = r->rem_set(); _count += (int) hrrs->occupied(); if (hrrs->occupied() == 0) { gclog_or_tty->print("Heap Region [" PTR_FORMAT ", " PTR_FORMAT ") " "has no remset entries\n", r->bottom(), r->end()); } else { gclog_or_tty->print("Printing rem set for heap region [" PTR_FORMAT ", " PTR_FORMAT ")\n", r->bottom(), r->end()); r->print(); hrrs->print(); gclog_or_tty->print("\nDone printing rem set\n"); } return false; } int occupied() {return _count;} }; #endif class CountRSSizeClosure: public HeapRegionClosure { size_t _n; size_t _tot; size_t _max; HeapRegion* _max_r; enum { N = 20, MIN = 6 }; int _histo[N]; public: CountRSSizeClosure() : _n(0), _tot(0), _max(0), _max_r(NULL) { for (int i = 0; i < N; i++) _histo[i] = 0; } bool doHeapRegion(HeapRegion* r) { if (!r->continuesHumongous()) { size_t occ = r->rem_set()->occupied(); _n++; _tot += occ; if (occ > _max) { _max = occ; _max_r = r; } // Fit it into a histo bin. int s = 1 << MIN; int i = 0; while (occ > (size_t) s && i < (N-1)) { s = s << 1; i++; } _histo[i]++; } return false; } size_t n() { return _n; } size_t tot() { return _tot; } size_t mx() { return _max; } HeapRegion* mxr() { return _max_r; } void print_histo() { int mx = N; while (mx >= 0) { if (_histo[mx-1] > 0) break; mx--; } gclog_or_tty->print_cr("Number of regions with given RS sizes:"); gclog_or_tty->print_cr(" <= %8d %8d", 1 << MIN, _histo[0]); for (int i = 1; i < mx-1; i++) { gclog_or_tty->print_cr(" %8d - %8d %8d", (1 << (MIN + i - 1)) + 1, 1 << (MIN + i), _histo[i]); } gclog_or_tty->print_cr(" > %8d %8d", (1 << (MIN+mx-2))+1, _histo[mx-1]); } }; void G1RemSet::cleanupHRRS() { HeapRegionRemSet::cleanup(); } void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc, int worker_i) { #if CARD_REPEAT_HISTO ct_freq_update_histo_and_reset(); #endif if (worker_i == 0) { _cg1r->clear_and_record_card_counts(); } // Make this into a command-line flag... if (G1RSCountHisto && (ParallelGCThreads == 0 || worker_i == 0)) { CountRSSizeClosure count_cl; _g1->heap_region_iterate(&count_cl); gclog_or_tty->print_cr("Avg of %d RS counts is %f, max is %d, " "max region is " PTR_FORMAT, count_cl.n(), (float)count_cl.tot()/(float)count_cl.n(), count_cl.mx(), count_cl.mxr()); count_cl.print_histo(); } // We cache the value of 'oc' closure into the appropriate slot in the // _cset_rs_update_cl for this worker assert(worker_i < (int)n_workers(), "sanity"); _cset_rs_update_cl[worker_i] = oc; // A DirtyCardQueue that is used to hold cards containing references // that point into the collection set. This DCQ is associated with a // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal // circumstances (i.e. the pause successfully completes), these cards // are just discarded (there's no need to update the RSets of regions // that were in the collection set - after the pause these regions // are wholly 'free' of live objects. In the event of an evacuation // failure the cards/buffers in this queue set are: // * passed to the DirtyCardQueueSet that is used to manage deferred // RSet updates, or // * scanned for references that point into the collection set // and the RSet of the corresponding region in the collection set // is updated immediately. DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); assert((ParallelGCThreads > 0) || worker_i == 0, "invariant"); // The two flags below were introduced temporarily to serialize // the updating and scanning of remembered sets. There are some // race conditions when these two operations are done in parallel // and they are causing failures. When we resolve said race // conditions, we'll revert back to parallel remembered set // updating and scanning. See CRs 6677707 and 6677708. if (G1UseParallelRSetUpdating || (worker_i == 0)) { updateRS(&into_cset_dcq, worker_i); } else { _g1p->record_update_rs_processed_buffers(worker_i, 0.0); _g1p->record_update_rs_time(worker_i, 0.0); } if (G1UseParallelRSetScanning || (worker_i == 0)) { scanRS(oc, worker_i); } else { _g1p->record_scan_rs_time(worker_i, 0.0); } // We now clear the cached values of _cset_rs_update_cl for this worker _cset_rs_update_cl[worker_i] = NULL; } void G1RemSet::prepare_for_oops_into_collection_set_do() { #if G1_REM_SET_LOGGING PrintRSClosure cl; _g1->collection_set_iterate(&cl); #endif cleanupHRRS(); ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine(); _g1->set_refine_cte_cl_concurrency(false); DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); dcqs.concatenate_logs(); assert(!_traversal_in_progress, "Invariant between iterations."); set_traversal(true); if (ParallelGCThreads > 0) { _seq_task->set_n_threads((int)n_workers()); } guarantee( _cards_scanned == NULL, "invariant" ); _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers()); for (uint i = 0; i < n_workers(); ++i) { _cards_scanned[i] = 0; } _total_cards_scanned = 0; } class cleanUpIteratorsClosure : public HeapRegionClosure { bool doHeapRegion(HeapRegion *r) { HeapRegionRemSet* hrrs = r->rem_set(); hrrs->init_for_par_iteration(); return false; } }; // This closure, applied to a DirtyCardQueueSet, is used to immediately // update the RSets for the regions in the CSet. For each card it iterates // through the oops which coincide with that card. It scans the reference // fields in each oop; when it finds an oop that points into the collection // set, the RSet for the region containing the referenced object is updated. // Note: _par_traversal_in_progress in the G1RemSet must be FALSE; otherwise // the UpdateRSetImmediate closure will cause cards to be enqueued on to // the DCQS that we're iterating over, causing an infinite loop. class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure { G1CollectedHeap* _g1; CardTableModRefBS* _ct_bs; public: UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1, CardTableModRefBS* bs): _g1(g1), _ct_bs(bs) { } bool do_card_ptr(jbyte* card_ptr, int worker_i) { // Construct the region representing the card. HeapWord* start = _ct_bs->addr_for(card_ptr); // And find the region containing it. HeapRegion* r = _g1->heap_region_containing(start); assert(r != NULL, "unexpected null"); // Scan oops in the card looking for references into the collection set HeapWord* end = _ct_bs->addr_for(card_ptr + 1); MemRegion scanRegion(start, end); UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set()); FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl); FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl); // We can pass false as the "filter_young" parameter here as: // * we should be in a STW pause, // * the DCQS to which this closure is applied is used to hold // references that point into the collection set from the prior // RSet updating, // * the post-write barrier shouldn't be logging updates to young // regions (but there is a situation where this can happen - see // the comment in G1RemSet::concurrentRefineOneCard below - // that should not be applicable here), and // * during actual RSet updating, the filtering of cards in young // regions in HeapRegion::oops_on_card_seq_iterate_careful is // employed. // As a result, when this closure is applied to "refs into cset" // DCQS, we shouldn't see any cards in young regions. update_rs_cl.set_region(r); HeapWord* stop_point = r->oops_on_card_seq_iterate_careful(scanRegion, &filter_then_update_rs_cset_oop_cl, false /* filter_young */); // Since this is performed in the event of an evacuation failure, we // we shouldn't see a non-null stop point assert(stop_point == NULL, "saw an unallocated region"); return true; } }; void G1RemSet::cleanup_after_oops_into_collection_set_do() { guarantee( _cards_scanned != NULL, "invariant" ); _total_cards_scanned = 0; for (uint i = 0; i < n_workers(); ++i) _total_cards_scanned += _cards_scanned[i]; FREE_C_HEAP_ARRAY(size_t, _cards_scanned); _cards_scanned = NULL; // Cleanup after copy #if G1_REM_SET_LOGGING PrintRSClosure cl; _g1->heap_region_iterate(&cl); #endif _g1->set_refine_cte_cl_concurrency(true); cleanUpIteratorsClosure iterClosure; _g1->collection_set_iterate(&iterClosure); // Set all cards back to clean. _g1->cleanUpCardTable(); set_traversal(false); DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set(); int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num(); if (_g1->evacuation_failed()) { // Restore remembered sets for the regions pointing into the collection set. if (G1DeferredRSUpdate) { // If deferred RS updates are enabled then we just need to transfer // the completed buffers from (a) the DirtyCardQueueSet used to hold // cards that contain references that point into the collection set // to (b) the DCQS used to hold the deferred RS updates _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs); } else { CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set(); UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs); int n_completed_buffers = 0; while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate, 0, 0, true)) { n_completed_buffers++; } assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers"); } } // Free any completed buffers in the DirtyCardQueueSet used to hold cards // which contain references that point into the collection. _g1->into_cset_dirty_card_queue_set().clear(); assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0, "all buffers should be freed"); _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers(); assert(!_traversal_in_progress, "Invariant between iterations."); } class UpdateRSObjectClosure: public ObjectClosure { UpdateRSOopClosure* _update_rs_oop_cl; public: UpdateRSObjectClosure(UpdateRSOopClosure* update_rs_oop_cl) : _update_rs_oop_cl(update_rs_oop_cl) {} void do_object(oop obj) { obj->oop_iterate(_update_rs_oop_cl); } }; class ScrubRSClosure: public HeapRegionClosure { G1CollectedHeap* _g1h; BitMap* _region_bm; BitMap* _card_bm; CardTableModRefBS* _ctbs; public: ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) : _g1h(G1CollectedHeap::heap()), _region_bm(region_bm), _card_bm(card_bm), _ctbs(NULL) { ModRefBarrierSet* bs = _g1h->mr_bs(); guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition"); _ctbs = (CardTableModRefBS*)bs; } bool doHeapRegion(HeapRegion* r) { if (!r->continuesHumongous()) { r->rem_set()->scrub(_ctbs, _region_bm, _card_bm); } return false; } }; void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) { ScrubRSClosure scrub_cl(region_bm, card_bm); _g1->heap_region_iterate(&scrub_cl); } void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm, int worker_num, int claim_val) { ScrubRSClosure scrub_cl(region_bm, card_bm); _g1->heap_region_par_iterate_chunked(&scrub_cl, worker_num, claim_val); } static IntHistogram out_of_histo(50, 50); class TriggerClosure : public OopClosure { bool _trigger; public: TriggerClosure() : _trigger(false) { } bool value() const { return _trigger; } template void do_oop_nv(T* p) { _trigger = true; } virtual void do_oop(oop* p) { do_oop_nv(p); } virtual void do_oop(narrowOop* p) { do_oop_nv(p); } }; class InvokeIfNotTriggeredClosure: public OopClosure { TriggerClosure* _t; OopClosure* _oc; public: InvokeIfNotTriggeredClosure(TriggerClosure* t, OopClosure* oc): _t(t), _oc(oc) { } template void do_oop_nv(T* p) { if (!_t->value()) _oc->do_oop(p); } virtual void do_oop(oop* p) { do_oop_nv(p); } virtual void do_oop(narrowOop* p) { do_oop_nv(p); } }; class Mux2Closure : public OopClosure { OopClosure* _c1; OopClosure* _c2; public: Mux2Closure(OopClosure *c1, OopClosure *c2) : _c1(c1), _c2(c2) { } template void do_oop_nv(T* p) { _c1->do_oop(p); _c2->do_oop(p); } virtual void do_oop(oop* p) { do_oop_nv(p); } virtual void do_oop(narrowOop* p) { do_oop_nv(p); } }; bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i, bool check_for_refs_into_cset) { // Construct the region representing the card. HeapWord* start = _ct_bs->addr_for(card_ptr); // And find the region containing it. HeapRegion* r = _g1->heap_region_containing(start); assert(r != NULL, "unexpected null"); HeapWord* end = _ct_bs->addr_for(card_ptr + 1); MemRegion dirtyRegion(start, end); #if CARD_REPEAT_HISTO init_ct_freq_table(_g1->g1_reserved_obj_bytes()); ct_freq_note_card(_ct_bs->index_for(start)); #endif UpdateRSOopClosure update_rs_oop_cl(this, worker_i); update_rs_oop_cl.set_from(r); TriggerClosure trigger_cl; FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl); InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl); Mux2Closure mux(&invoke_cl, &update_rs_oop_cl); FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r, (check_for_refs_into_cset ? (OopClosure*)&mux : (OopClosure*)&update_rs_oop_cl)); // Undirty the card. *card_ptr = CardTableModRefBS::clean_card_val(); // We must complete this write before we do any of the reads below. OrderAccess::storeload(); // And process it, being careful of unallocated portions of TLAB's. // The region for the current card may be a young region. The // current card may have been a card that was evicted from the // card cache. When the card was inserted into the cache, we had // determined that its region was non-young. While in the cache, // the region may have been freed during a cleanup pause, reallocated // and tagged as young. // // We wish to filter out cards for such a region but the current // thread, if we're running conucrrently, may "see" the young type // change at any time (so an earlier "is_young" check may pass or // fail arbitrarily). We tell the iteration code to perform this // filtering when it has been determined that there has been an actual // allocation in this region and making it safe to check the young type. bool filter_young = true; HeapWord* stop_point = r->oops_on_card_seq_iterate_careful(dirtyRegion, &filter_then_update_rs_oop_cl, filter_young); // If stop_point is non-null, then we encountered an unallocated region // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the // card and re-enqueue: if we put off the card until a GC pause, then the // unallocated portion will be filled in. Alternatively, we might try // the full complexity of the technique used in "regular" precleaning. if (stop_point != NULL) { // The card might have gotten re-dirtied and re-enqueued while we // worked. (In fact, it's pretty likely.) if (*card_ptr != CardTableModRefBS::dirty_card_val()) { *card_ptr = CardTableModRefBS::dirty_card_val(); MutexLockerEx x(Shared_DirtyCardQ_lock, Mutex::_no_safepoint_check_flag); DirtyCardQueue* sdcq = JavaThread::dirty_card_queue_set().shared_dirty_card_queue(); sdcq->enqueue(card_ptr); } } else { out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region()); _conc_refine_cards++; } return trigger_cl.value(); } bool G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i, bool check_for_refs_into_cset) { // If the card is no longer dirty, nothing to do. if (*card_ptr != CardTableModRefBS::dirty_card_val()) { // No need to return that this card contains refs that point // into the collection set. return false; } // Construct the region representing the card. HeapWord* start = _ct_bs->addr_for(card_ptr); // And find the region containing it. HeapRegion* r = _g1->heap_region_containing(start); if (r == NULL) { guarantee(_g1->is_in_permanent(start), "Or else where?"); // Again no need to return that this card contains refs that // point into the collection set. return false; // Not in the G1 heap (might be in perm, for example.) } // Why do we have to check here whether a card is on a young region, // given that we dirty young regions and, as a result, the // post-barrier is supposed to filter them out and never to enqueue // them? When we allocate a new region as the "allocation region" we // actually dirty its cards after we release the lock, since card // dirtying while holding the lock was a performance bottleneck. So, // as a result, it is possible for other threads to actually // allocate objects in the region (after the acquire the lock) // before all the cards on the region are dirtied. This is unlikely, // and it doesn't happen often, but it can happen. So, the extra // check below filters out those cards. if (r->is_young()) { return false; } // While we are processing RSet buffers during the collection, we // actually don't want to scan any cards on the collection set, // since we don't want to update remebered sets with entries that // point into the collection set, given that live objects from the // collection set are about to move and such entries will be stale // very soon. This change also deals with a reliability issue which // involves scanning a card in the collection set and coming across // an array that was being chunked and looking malformed. Note, // however, that if evacuation fails, we have to scan any objects // that were not moved and create any missing entries. if (r->in_collection_set()) { return false; } // Should we defer processing the card? // // Previously the result from the insert_cache call would be // either card_ptr (implying that card_ptr was currently "cold"), // null (meaning we had inserted the card ptr into the "hot" // cache, which had some headroom), or a "hot" card ptr // extracted from the "hot" cache. // // Now that the _card_counts cache in the ConcurrentG1Refine // instance is an evicting hash table, the result we get back // could be from evicting the card ptr in an already occupied // bucket (in which case we have replaced the card ptr in the // bucket with card_ptr and "defer" is set to false). To avoid // having a data structure (updates to which would need a lock) // to hold these unprocessed dirty cards, we need to immediately // process card_ptr. The actions needed to be taken on return // from cache_insert are summarized in the following table: // // res defer action // -------------------------------------------------------------- // null false card evicted from _card_counts & replaced with // card_ptr; evicted ptr added to hot cache. // No need to process res; immediately process card_ptr // // null true card not evicted from _card_counts; card_ptr added // to hot cache. // Nothing to do. // // non-null false card evicted from _card_counts & replaced with // card_ptr; evicted ptr is currently "cold" or // caused an eviction from the hot cache. // Immediately process res; process card_ptr. // // non-null true card not evicted from _card_counts; card_ptr is // currently cold, or caused an eviction from hot // cache. // Immediately process res; no need to process card_ptr. jbyte* res = card_ptr; bool defer = false; // This gets set to true if the card being refined has references // that point into the collection set. bool oops_into_cset = false; if (_cg1r->use_cache()) { jbyte* res = _cg1r->cache_insert(card_ptr, &defer); if (res != NULL && (res != card_ptr || defer)) { start = _ct_bs->addr_for(res); r = _g1->heap_region_containing(start); if (r == NULL) { assert(_g1->is_in_permanent(start), "Or else where?"); } else { // Checking whether the region we got back from the cache // is young here is inappropriate. The region could have been // freed, reallocated and tagged as young while in the cache. // Hence we could see its young type change at any time. // // Process card pointer we get back from the hot card cache. This // will check whether the region containing the card is young // _after_ checking that the region has been allocated from. oops_into_cset = concurrentRefineOneCard_impl(res, worker_i, false /* check_for_refs_into_cset */); // The above call to concurrentRefineOneCard_impl is only // performed if the hot card cache is enabled. This cache is // disabled during an evacuation pause - which is the only // time when we need know if the card contains references // that point into the collection set. Also when the hot card // cache is enabled, this code is executed by the concurrent // refine threads - rather than the GC worker threads - and // concurrentRefineOneCard_impl will return false. assert(!oops_into_cset, "should not see true here"); } } } if (!defer) { oops_into_cset = concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset); // We should only be detecting that the card contains references // that point into the collection set if the current thread is // a GC worker thread. assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(), "invalid result at non safepoint"); } return oops_into_cset; } class HRRSStatsIter: public HeapRegionClosure { size_t _occupied; size_t _total_mem_sz; size_t _max_mem_sz; HeapRegion* _max_mem_sz_region; public: HRRSStatsIter() : _occupied(0), _total_mem_sz(0), _max_mem_sz(0), _max_mem_sz_region(NULL) {} bool doHeapRegion(HeapRegion* r) { if (r->continuesHumongous()) return false; size_t mem_sz = r->rem_set()->mem_size(); if (mem_sz > _max_mem_sz) { _max_mem_sz = mem_sz; _max_mem_sz_region = r; } _total_mem_sz += mem_sz; size_t occ = r->rem_set()->occupied(); _occupied += occ; return false; } size_t total_mem_sz() { return _total_mem_sz; } size_t max_mem_sz() { return _max_mem_sz; } size_t occupied() { return _occupied; } HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; } }; class PrintRSThreadVTimeClosure : public ThreadClosure { public: virtual void do_thread(Thread *t) { ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t; gclog_or_tty->print(" %5.2f", crt->vtime_accum()); } }; void G1RemSet::print_summary_info() { G1CollectedHeap* g1 = G1CollectedHeap::heap(); #if CARD_REPEAT_HISTO gclog_or_tty->print_cr("\nG1 card_repeat count histogram: "); gclog_or_tty->print_cr(" # of repeats --> # of cards with that number."); card_repeat_count.print_on(gclog_or_tty); #endif if (FILTEROUTOFREGIONCLOSURE_DOHISTOGRAMCOUNT) { gclog_or_tty->print_cr("\nG1 rem-set out-of-region histogram: "); gclog_or_tty->print_cr(" # of CS ptrs --> # of cards with that number."); out_of_histo.print_on(gclog_or_tty); } gclog_or_tty->print_cr("\n Concurrent RS processed %d cards", _conc_refine_cards); DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); jint tot_processed_buffers = dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread(); gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers); gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.", dcqs.processed_buffers_rs_thread(), 100.0*(float)dcqs.processed_buffers_rs_thread()/ (float)tot_processed_buffers); gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.", dcqs.processed_buffers_mut(), 100.0*(float)dcqs.processed_buffers_mut()/ (float)tot_processed_buffers); gclog_or_tty->print_cr(" Conc RS threads times(s)"); PrintRSThreadVTimeClosure p; gclog_or_tty->print(" "); g1->concurrent_g1_refine()->threads_do(&p); gclog_or_tty->print_cr(""); HRRSStatsIter blk; g1->heap_region_iterate(&blk); gclog_or_tty->print_cr(" Total heap region rem set sizes = " SIZE_FORMAT "K." " Max = " SIZE_FORMAT "K.", blk.total_mem_sz()/K, blk.max_mem_sz()/K); gclog_or_tty->print_cr(" Static structures = " SIZE_FORMAT "K," " free_lists = " SIZE_FORMAT "K.", HeapRegionRemSet::static_mem_size()/K, HeapRegionRemSet::fl_mem_size()/K); gclog_or_tty->print_cr(" %d occupied cards represented.", blk.occupied()); gclog_or_tty->print_cr(" Max sz region = [" PTR_FORMAT ", " PTR_FORMAT " )" ", cap = " SIZE_FORMAT "K, occ = " SIZE_FORMAT "K.", blk.max_mem_sz_region()->bottom(), blk.max_mem_sz_region()->end(), (blk.max_mem_sz_region()->rem_set()->mem_size() + K - 1)/K, (blk.max_mem_sz_region()->rem_set()->occupied() + K - 1)/K); gclog_or_tty->print_cr(" Did %d coarsenings.", HeapRegionRemSet::n_coarsenings()); } void G1RemSet::prepare_for_verify() { if (G1HRRSFlushLogBuffersOnVerify && (VerifyBeforeGC || VerifyAfterGC) && !_g1->full_collection()) { cleanupHRRS(); _g1->set_refine_cte_cl_concurrency(false); if (SafepointSynchronize::is_at_safepoint()) { DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); dcqs.concatenate_logs(); } bool cg1r_use_cache = _cg1r->use_cache(); _cg1r->set_use_cache(false); DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); updateRS(&into_cset_dcq, 0); _g1->into_cset_dirty_card_queue_set().clear(); _cg1r->set_use_cache(cg1r_use_cache); assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); } }