146 lines
4.6 KiB
C++
146 lines
4.6 KiB
C++
/*
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* Copyright (c) 2013, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_GC_G1_G1HOTCARDCACHE_HPP
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#define SHARE_GC_G1_G1HOTCARDCACHE_HPP
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#include "gc/g1/g1CardCounts.hpp"
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#include "memory/allocation.hpp"
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#include "runtime/safepoint.hpp"
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#include "runtime/thread.hpp"
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#include "utilities/globalDefinitions.hpp"
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class G1CardTableEntryClosure;
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class G1CollectedHeap;
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class HeapRegion;
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// An evicting cache of cards that have been logged by the G1 post
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// write barrier. Placing a card in the cache delays the refinement
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// of the card until the card is evicted, or the cache is drained
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// during the next evacuation pause.
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//
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// The first thing the G1 post write barrier does is to check whether
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// the card containing the updated pointer is already dirty and, if
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// so, skips the remaining code in the barrier.
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//
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// Delaying the refinement of a card will make the card fail the
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// first is_dirty check in the write barrier, skipping the remainder
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// of the write barrier.
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//
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// This can significantly reduce the overhead of the write barrier
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// code, increasing throughput.
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class G1HotCardCache: public CHeapObj<mtGC> {
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public:
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typedef CardTable::CardValue CardValue;
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private:
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G1CollectedHeap* _g1h;
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bool _use_cache;
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G1CardCounts _card_counts;
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// The card cache table
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CardValue** _hot_cache;
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size_t _hot_cache_size;
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size_t _hot_cache_par_chunk_size;
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// Avoids false sharing when concurrently updating _hot_cache_idx or
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// _hot_cache_par_claimed_idx. These are never updated at the same time
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// thus it's not necessary to separate them as well
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char _pad_before[DEFAULT_CACHE_LINE_SIZE];
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volatile size_t _hot_cache_idx;
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volatile size_t _hot_cache_par_claimed_idx;
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char _pad_after[DEFAULT_CACHE_LINE_SIZE];
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// The number of cached cards a thread claims when flushing the cache
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static const int ClaimChunkSize = 32;
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public:
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static bool default_use_cache() {
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return (G1ConcRSLogCacheSize > 0);
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}
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G1HotCardCache(G1CollectedHeap* g1h);
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~G1HotCardCache();
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void initialize(G1RegionToSpaceMapper* card_counts_storage);
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bool use_cache() { return _use_cache; }
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void set_use_cache(bool b) {
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_use_cache = (b ? default_use_cache() : false);
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}
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// Returns the card to be refined or NULL.
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//
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// Increments the count for given the card. if the card is not 'hot',
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// it is returned for immediate refining. Otherwise the card is
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// added to the hot card cache.
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// If there is enough room in the hot card cache for the card we're
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// adding, NULL is returned and no further action in needed.
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// If we evict a card from the cache to make room for the new card,
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// the evicted card is then returned for refinement.
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CardValue* insert(CardValue* card_ptr);
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// Refine the cards that have delayed as a result of
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// being in the cache.
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void drain(G1CardTableEntryClosure* cl, uint worker_i);
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// Set up for parallel processing of the cards in the hot cache
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void reset_hot_cache_claimed_index() {
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_hot_cache_par_claimed_idx = 0;
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}
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// Resets the hot card cache and discards the entries.
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void reset_hot_cache() {
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assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");
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assert(Thread::current()->is_VM_thread(), "Current thread should be the VMthread");
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if (default_use_cache()) {
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reset_hot_cache_internal();
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}
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}
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// Zeros the values in the card counts table for the given region
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void reset_card_counts(HeapRegion* hr);
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private:
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void reset_hot_cache_internal() {
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assert(_hot_cache != NULL, "Logic");
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_hot_cache_idx = 0;
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for (size_t i = 0; i < _hot_cache_size; i++) {
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_hot_cache[i] = NULL;
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}
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}
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};
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#endif // SHARE_GC_G1_G1HOTCARDCACHE_HPP
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