/*
* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation.
*
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* 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.
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#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP
#include "gc_implementation/g1/g1_globals.hpp"
#include "gc_implementation/g1/g1CardCounts.hpp"
#include "memory/allocation.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/thread.hpp"
#include "utilities/globalDefinitions.hpp"
class DirtyCardQueue;
class G1CollectedHeap;
class G1RemSet;
class HeapRegion;
// An evicting cache of cards that have been logged by the G1 post
// write barrier. Placing a card in the cache delays the refinement
// of the card until the card is evicted, or the cache is drained
// during the next evacuation pause.
//
// The first thing the G1 post write barrier does is to check whether
// the card containing the updated pointer is already dirty and, if
// so, skips the remaining code in the barrier.
//
// Delaying the refinement of a card will make the card fail the
// first is_dirty check in the write barrier, skipping the remainder
// of the write barrier.
//
// This can significantly reduce the overhead of the write barrier
// code, increasing throughput.
class G1HotCardCache: public CHeapObj<mtGC> {
G1CollectedHeap* _g1h;
// The card cache table
jbyte** _hot_cache;
int _hot_cache_size;
int _n_hot;
int _hot_cache_idx;
int _hot_cache_par_chunk_size;
volatile int _hot_cache_par_claimed_idx;
bool _use_cache;
G1CardCounts _card_counts;
bool default_use_cache() const {
return (G1ConcRSLogCacheSize > 0);
}
public:
G1HotCardCache(G1CollectedHeap* g1h);
~G1HotCardCache();
void initialize();
bool use_cache() { return _use_cache; }
void set_use_cache(bool b) {
_use_cache = (b ? default_use_cache() : false);
}
// Returns the card to be refined or NULL.
//
// Increments the count for given the card. if the card is not 'hot',
// it is returned for immediate refining. Otherwise the card is
// added to the hot card cache.
// If there is enough room in the hot card cache for the card we're
// adding, NULL is returned and no further action in needed.
// If we evict a card from the cache to make room for the new card,
// the evicted card is then returned for refinement.
jbyte* insert(jbyte* card_ptr);
// Refine the cards that have delayed as a result of
// being in the cache.
void drain(int worker_i, G1RemSet* g1rs, DirtyCardQueue* into_cset_dcq);
// Set up for parallel processing of the cards in the hot cache
void reset_hot_cache_claimed_index() {
_hot_cache_par_claimed_idx = 0;
}
// Resets the hot card cache and discards the entries.
void reset_hot_cache() {
assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");
assert(Thread::current()->is_VM_thread(), "Current thread should be the VMthread");
_hot_cache_idx = 0; _n_hot = 0;
}
bool hot_cache_is_empty() { return _n_hot == 0; }
// Resizes the card counts table to match the given capacity
void resize_card_counts(size_t heap_capacity);
// Zeros the values in the card counts table for entire committed heap
void reset_card_counts();
// Zeros the values in the card counts table for the given region
void reset_card_counts(HeapRegion* hr);
};
#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP