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https://issues.apache.org/jira/browse/TEZ-1491?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15009706#comment-15009706
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Hitesh Shah commented on TEZ-1491:
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[~rajesh.balamohan] review please?
> Tez reducer-side merge's counter update is slow
> -----------------------------------------------
>
> Key: TEZ-1491
> URL: https://issues.apache.org/jira/browse/TEZ-1491
> Project: Apache Tez
> Issue Type: Bug
> Affects Versions: 0.6.0, 0.7.0, 0.8.0-alpha
> Reporter: Gopal V
> Assignee: Gopal V
> Labels: Performance
> Attachments: TEZ-1491.1.patch, perf-top-counters.png
>
>
> TezMerger$MergeQueue::next() shows up in profiles due a synchronized block in
> a tight loop.
> Part of the slow operation was due to DataInputBuffer issues identified
> earlier in HADOOP-10694, but along with that approx 11% of my lock prefix
> calls were originating from the following line.
> {code}
> mergeProgress.set(totalBytesProcessed * progPerByte);
> {code}
> in two places within the core loop.
> !perf-top-counters.png!
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