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https://issues.apache.org/jira/browse/HBASE-26659?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Duo Zhang resolved HBASE-26659.
-------------------------------
Fix Version/s: 2.5.0
3.0.0-alpha-3
Hadoop Flags: Reviewed
Resolution: Fixed
Pushed to branch-2.5+.
Thanks [~xytss123]!
> The ByteBuffer of metadata in RAMQueueEntry in BucketCache could be reused.
> ---------------------------------------------------------------------------
>
> Key: HBASE-26659
> URL: https://issues.apache.org/jira/browse/HBASE-26659
> Project: HBase
> Issue Type: Improvement
> Components: BucketCache, Performance
> Reporter: Yutong Xiao
> Assignee: Yutong Xiao
> Priority: Major
> Fix For: 2.5.0, 3.0.0-alpha-3
>
>
> Currently, the process to write HFileBlocks into IOEngine in BucketCache is:
> {code:java}
> if (data instanceof HFileBlock) {
> // If an instance of HFileBlock, save on some allocations.
> HFileBlock block = (HFileBlock) data;
> ByteBuff sliceBuf = block.getBufferReadOnly();
> ByteBuffer metadata = block.getMetaData();
> ioEngine.write(sliceBuf, offset);
> ioEngine.write(metadata, offset + len - metadata.limit());
> }
> {code}
> The getMetaData() function in HFileBlock is:
> {code:java}
> public ByteBuffer getMetaData() {
> ByteBuffer bb = ByteBuffer.allocate(BLOCK_METADATA_SPACE);
> bb = addMetaData(bb, true);
> bb.flip();
> return bb;
> }
> {code}
> It will allocate new ByteBuffer every time.
> We could reuse a local variable of WriterThread to reduce the new allocation
> of this small piece ByteBuffer.
> Reasons:
> 1. In a WriterThread, blocks in doDrain() function are written into IOEngine
> sequentially, there is no multi-threads problem.
> 2. After IOEngine.write() function, the data in metadata ByteBuffer has been
> transferred into ByteArray (ByteBufferIOEngine) or FileChannel (FileIOEngine)
> safely. The lifecycle of it is within the if statement above. So that it
> could be cleared and reused by the next block's writing process.
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