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https://issues.apache.org/jira/browse/HBASE-21879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16774437#comment-16774437
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Anoop Sam John commented on HBASE-21879:
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bq.Anoop Sam John - Is there anything I had missed out here.
The netty ByteBuf is like NIO ByteBuffer. We can replace NIO with netty's. Ya
all the perf reasons were considered.
One main to note is we need a way to club together N buffers. We have
MultiByteBuff.. So our own extension at least is needed. Need to see how the
ref counting within ByteBuff comes out..
So will be creating a branch now?
> 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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