Xiong LIU created JCS-109:
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Summary: poor performance of BlockDisk.write(Serializable object)
Key: JCS-109
URL: https://issues.apache.org/jira/browse/JCS-109
Project: Commons JCS
Issue Type: Improvement
Affects Versions: jcs-2.0.0
Reporter: Xiong LIU
The performance of BlockDisk.write(Serializable object) is poor, because
current implementation involves much ByteBuffer allocation and byte array
allocation and memory copy.
The following is my implementation, which only needs to allocate
HEADER_SIZE_BYTES. A benchmark can be done to show the performance gain.
protected int[] write(Serializable object) throws IOException {
// serialize the object
byte[] data = elementSerializer.serialize(object);
// figure out how many blocks we need.
int numBlocksNeeded = calculateTheNumberOfBlocksNeeded(data);
// allocate blocks
int[] blocks = allocateBlocks(numBlocksNeeded);
int offset = 0;
final int maxChunkSize = blockSizeBytes - HEADER_SIZE_BYTES;
ByteBuffer headerBuffer = ByteBuffer.allocate(HEADER_SIZE_BYTES);
for (int i = 0; i < numBlocksNeeded; i++) {
headerBuffer.clear();
int length = Math.min(maxChunkSize, data.length - offset);
headerBuffer.putInt(length);
ByteBuffer dataBuffer = ByteBuffer.wrap(data, offset, length);
long position = calculateByteOffsetForBlock(blocks[i]);
// write the header
headerBuffer.flip();
int written = fc.write(headerBuffer, position);
assert written == HEADER_SIZE_BYTES;
//write the data
written = fc.write(dataBuffer, position + HEADER_SIZE_BYTES);
assert written == length;
offset += length;
}
fc.force(false);
return blocks;
}
private int[] allocateBlocks(int numBlocksNeeded) {
assert numBlocksNeeded >= 1;
int[] blocks = new int[numBlocksNeeded];
// get them from the empty list or take the next one
for (int i = 0; i < numBlocksNeeded; i++) {
Integer emptyBlock = emptyBlocks.takeFirst();
if (emptyBlock == null) {
emptyBlock = numberOfBlocks.getAndIncrement();
}
blocks[i] = emptyBlock;
}
return blocks;
}
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