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https://issues.apache.org/jira/browse/HBASE-21879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16774211#comment-16774211
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Zheng Hu commented on HBASE-21879:
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There is also an simple way to fix the refCnt now, no need to replace
hbase.nio.ByteBuff with netty.ByteBuf, just let the hbase.nio.ByteBuff extend
the io.netty.util.AbstractReferenceCounted and implement our own deallocate()
method, the refCnt can work now. seems not too hard, then we can move this
issue forward firstly.
After that, I can start to replace the hbase.nio.ByteBuff with netty.ByteBuf in
an new branch. read the netty code today, seems lots of work if we start the
replacement, the ByteBuff is widely used in our project, and lots of BB
interface are not compatible. How do you guys think ?
> Read HFile's block to ByteBuffer directly instead of to byte for reducing
> young gc purpose
> ------------------------------------------------------------------------------------------
>
> Key: HBASE-21879
> URL: https://issues.apache.org/jira/browse/HBASE-21879
> Project: HBase
> Issue Type: Improvement
> Reporter: Zheng Hu
> Assignee: Zheng Hu
> Priority: Major
> Fix For: 3.0.0, 2.2.0, 2.3.0, 2.1.4
>
> Attachments: QPS-latencies-before-HBASE-21879.png,
> gc-data-before-HBASE-21879.png
>
>
> In HFileBlock#readBlockDataInternal, we have the following:
> {code}
> @VisibleForTesting
> protected HFileBlock readBlockDataInternal(FSDataInputStream is, long offset,
> long onDiskSizeWithHeaderL, boolean pread, boolean verifyChecksum,
> boolean updateMetrics)
> throws IOException {
> // .....
> // TODO: Make this ByteBuffer-based. Will make it easier to go to HDFS with
> BBPool (offheap).
> byte [] onDiskBlock = new byte[onDiskSizeWithHeader + hdrSize];
> int nextBlockOnDiskSize = readAtOffset(is, onDiskBlock, preReadHeaderSize,
> onDiskSizeWithHeader - preReadHeaderSize, true, offset +
> preReadHeaderSize, pread);
> if (headerBuf != null) {
> // ...
> }
> // ...
> }
> {code}
> In the read path, we still read the block from hfile to on-heap byte[], then
> copy the on-heap byte[] to offheap bucket cache asynchronously, and in my
> 100% get performance test, I also observed some frequent young gc, The
> largest memory footprint in the young gen should be the on-heap block byte[].
> In fact, we can read HFile's block to ByteBuffer directly instead of to
> byte[] for reducing young gc purpose. we did not implement this before,
> because no ByteBuffer reading interface in the older HDFS client, but 2.7+
> has supported this now, so we can fix this now. I think.
> Will provide an patch and some perf-comparison for this.
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