package org.apache.solr.store.blockcache;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.nio.ByteBuffer;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import com.googlecode.concurrentlinkedhashmap.ConcurrentLinkedHashMap;
import com.googlecode.concurrentlinkedhashmap.EvictionListener;
/**
* @lucene.experimental
*/
public class BlockCache {
public static final int _128M = 134217728;
public static final int _32K = 32768;
private final ConcurrentMap<BlockCacheKey,BlockCacheLocation> cache;
private final ByteBuffer[] banks;
private final BlockLocks[] locks;
private final AtomicInteger[] lockCounters;
private final int blockSize;
private final int numberOfBlocksPerBank;
private final int maxEntries;
private final Metrics metrics;
public BlockCache(Metrics metrics, boolean directAllocation, long totalMemory) {
this(metrics, directAllocation, totalMemory, _128M);
}
public BlockCache(Metrics metrics, boolean directAllocation,
long totalMemory, int slabSize) {
this(metrics, directAllocation, totalMemory, slabSize, _32K);
}
public BlockCache(Metrics metrics, boolean directAllocation,
long totalMemory, int slabSize, int blockSize) {
this.metrics = metrics;
numberOfBlocksPerBank = slabSize / blockSize;
int numberOfBanks = (int) (totalMemory / slabSize);
banks = new ByteBuffer[numberOfBanks];
locks = new BlockLocks[numberOfBanks];
lockCounters = new AtomicInteger[numberOfBanks];
maxEntries = (numberOfBlocksPerBank * numberOfBanks) - 1;
for (int i = 0; i < numberOfBanks; i++) {
if (directAllocation) {
banks[i] = ByteBuffer.allocateDirect(numberOfBlocksPerBank * blockSize);
} else {
banks[i] = ByteBuffer.allocate(numberOfBlocksPerBank * blockSize);
}
locks[i] = new BlockLocks(numberOfBlocksPerBank);
lockCounters[i] = new AtomicInteger();
}
EvictionListener<BlockCacheKey,BlockCacheLocation> listener = new EvictionListener<BlockCacheKey,BlockCacheLocation>() {
@Override
public void onEviction(BlockCacheKey key, BlockCacheLocation location) {
releaseLocation(location);
}
};
cache = new ConcurrentLinkedHashMap.Builder<BlockCacheKey,BlockCacheLocation>()
.maximumWeightedCapacity(maxEntries).listener(listener).build();
this.blockSize = blockSize;
}
private void releaseLocation(BlockCacheLocation location) {
if (location == null) {
return;
}
int bankId = location.getBankId();
int block = location.getBlock();
location.setRemoved(true);
locks[bankId].clear(block);
lockCounters[bankId].decrementAndGet();
metrics.blockCacheEviction.incrementAndGet();
metrics.blockCacheSize.decrementAndGet();
}
public boolean store(BlockCacheKey blockCacheKey, int blockOffset,
byte[] data, int offset, int length) {
if (length + blockOffset > blockSize) {
throw new RuntimeException("Buffer size exceeded, expecting max ["
+ blockSize + "] got length [" + length + "] with blockOffset ["
+ blockOffset + "]");
}
BlockCacheLocation location = cache.get(blockCacheKey);
boolean newLocation = false;
if (location == null) {
newLocation = true;
location = new BlockCacheLocation();
if (!findEmptyLocation(location)) {
return false;
}
}
if (location.isRemoved()) {
return false;
}
int bankId = location.getBankId();
int bankOffset = location.getBlock() * blockSize;
ByteBuffer bank = getBank(bankId);
bank.position(bankOffset + blockOffset);
bank.put(data, offset, length);
if (newLocation) {
releaseLocation(cache.put(blockCacheKey.clone(), location));
metrics.blockCacheSize.incrementAndGet();
}
return true;
}
public boolean fetch(BlockCacheKey blockCacheKey, byte[] buffer,
int blockOffset, int off, int length) {
BlockCacheLocation location = cache.get(blockCacheKey);
if (location == null) {
return false;
}
if (location.isRemoved()) {
return false;
}
int bankId = location.getBankId();
int offset = location.getBlock() * blockSize;
location.touch();
ByteBuffer bank = getBank(bankId);
bank.position(offset + blockOffset);
bank.get(buffer, off, length);
return true;
}
public boolean fetch(BlockCacheKey blockCacheKey, byte[] buffer) {
checkLength(buffer);
return fetch(blockCacheKey, buffer, 0, 0, blockSize);
}
private boolean findEmptyLocation(BlockCacheLocation location) {
// This is a tight loop that will try and find a location to
// place the block before giving up
for (int j = 0; j < 10; j++) {
OUTER: for (int bankId = 0; bankId < banks.length; bankId++) {
AtomicInteger bitSetCounter = lockCounters[bankId];
BlockLocks bitSet = locks[bankId];
if (bitSetCounter.get() == numberOfBlocksPerBank) {
// if bitset is full
continue OUTER;
}
// this check needs to spin, if a lock was attempted but not obtained
// the rest of the bank should not be skipped
int bit = bitSet.nextClearBit(0);
INNER: while (bit != -1) {
if (bit >= numberOfBlocksPerBank) {
// bit set is full
continue OUTER;
}
if (!bitSet.set(bit)) {
// lock was not obtained
// this restarts at 0 because another block could have been unlocked
// while this was executing
bit = bitSet.nextClearBit(0);
continue INNER;
} else {
// lock obtained
location.setBankId(bankId);
location.setBlock(bit);
bitSetCounter.incrementAndGet();
return true;
}
}
}
}
return false;
}
private void checkLength(byte[] buffer) {
if (buffer.length != blockSize) {
throw new RuntimeException("Buffer wrong size, expecting [" + blockSize
+ "] got [" + buffer.length + "]");
}
}
private ByteBuffer getBank(int bankId) {
return banks[bankId].duplicate();
}
public int getSize() {
return cache.size();
}
}