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https://issues.apache.org/jira/browse/MAPREDUCE-6020?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14533948#comment-14533948
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Ameya Sakhalkar commented on MAPREDUCE-6020:
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Looks good to me.
> Too many threads blocking on the global JobTracker lock from getJobCounters,
> optimize getJobCounters to release global JobTracker lock before access the
> per job counter in JobInProgress
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-6020
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6020
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Affects Versions: 0.23.10
> Reporter: zhihai xu
> Assignee: zhihai xu
> Labels: BB2015-05-TBR
> Attachments: MAPREDUCE-6020.branch1.patch
>
>
> Too many threads blocking on the global JobTracker lock from getJobCounters,
> optimize getJobCounters to release global JobTracker lock before access the
> per job counter in JobInProgress. It may be a lot of JobClients to call
> getJobCounters in JobTracker at the same time, Current code will lock the
> JobTracker to block all the threads to get counter from JobInProgress. It is
> better to unlock the JobTracker when get counter from
> JobInProgress(job.getCounters(counters)). So all the theads can run parallel
> when access its own job counter.
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