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https://issues.apache.org/jira/browse/HBASE-21879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16904456#comment-16904456
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Hudson commented on HBASE-21879:
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Results for branch HBASE-21879
[build #204 on
builds.a.o|https://builds.apache.org/job/HBase%20Nightly/job/HBASE-21879/204/]:
(x) *{color:red}-1 overall{color}*
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(x) {color:red}-1 jdk8 hadoop2 checks{color}
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(/) {color:green}+1 source release artifact{color}
-- See build output for details.
(/) {color:green}+1 client integration test{color}
> 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, 2.3.0
>
> Attachments: HBASE-21879.v1.patch, HBASE-21879.v1.patch,
> 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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