maedhroz commented on code in PR #3606: URL: https://github.com/apache/cassandra/pull/3606#discussion_r1794153535
########## src/java/org/apache/cassandra/io/util/ThreadLocalReadAheadBuffer.java: ########## @@ -0,0 +1,154 @@ +/* + * 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. + */ + +package org.apache.cassandra.io.util; + +import java.nio.ByteBuffer; +import java.util.Map; +import java.util.concurrent.ConcurrentHashMap; + +import io.netty.util.concurrent.FastThreadLocal; +import org.apache.cassandra.io.compress.BufferType; +import org.apache.cassandra.io.compress.CorruptBlockException; +import org.apache.cassandra.io.sstable.CorruptSSTableException; + +public final class ThreadLocalReadAheadBuffer +{ + + private final ChannelProxy channel; + + private final BufferType bufferType; + + private static final Map<String, FastThreadLocal<ByteBuffer>> blockBufferHolders = new ConcurrentHashMap<>(); + + private static final Map<String, FastThreadLocal<Integer>> storedBlockNos = new ConcurrentHashMap<>(); + + private final FastThreadLocal<ByteBuffer> blockBufferHolder; + + private final FastThreadLocal<Integer> storedBlockNo; + + private final int bufferSize; + + public ThreadLocalReadAheadBuffer(ChannelProxy channel, int bufferSize, BufferType bufferType) + { + this.channel = channel; + this.bufferSize = bufferSize; + this.bufferType = bufferType; + blockBufferHolders.putIfAbsent(channel.filePath(), new FastThreadLocal<>() + { + @Override + protected ByteBuffer initialValue() throws Exception + { + return null; + } + }); + storedBlockNos.putIfAbsent(channel.filePath(), new FastThreadLocal<>() { + @Override + protected Integer initialValue() throws Exception + { + return -1; + } + }); + blockBufferHolder = blockBufferHolders.get(channel.filePath()); + storedBlockNo = storedBlockNos.get(channel.filePath()); + } + + public boolean hasBuffer() + { + return blockBufferHolder.get() != null; + } + + public int remaining() + { + return getBlockBuffer().remaining(); + } + + + public ByteBuffer getBlockBuffer() + { + ByteBuffer buffer = blockBufferHolder.get(); + if (buffer == null) + { + buffer = bufferType.allocate(bufferSize); + buffer.clear(); + blockBufferHolder.set(buffer); + } + return buffer; + } + + public void fill(long position) throws CorruptBlockException + { + ByteBuffer blockBuffer = getBlockBuffer(); + long channelSize = channel.size(); + long realPosition = Math.min(channelSize, position); + long blockLength = blockBuffer.limit(); + int blockNo = (int) (realPosition / blockLength); + long blockPosition = blockNo * blockLength; + + if (storedBlockNo.get() != blockNo) Review Comment: nit: Quick comment on this being here/necessary to skip when we've already read 256KiB worth of 16KiB chunks and just need to advance `blockBuffer` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
