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https://issues.apache.org/jira/browse/MAPREDUCE-1533?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12838207#action_12838207
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Rajesh Balamohan commented on MAPREDUCE-1533:
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For the benchmark I ran with short jobs, there were 692 items in
jobQueuesManager.getRunningJobQueue(qsi.queueName).
This essentially means that, for every heartbeat processing String.format() has
to be invoked 692 times. This might be the reason why it turned to be expensive.
> reduce or remove usage of String.format() usage in
> CapacityTaskScheduler.updateQSIObjects
> -----------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-1533
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1533
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 0.20.1
> Reporter: Rajesh Balamohan
>
> When short jobs are executed in hadoop with OutOfBandHeardBeat=true, JT
> executes heartBeat() method heavily. This internally makes a call to
> CapacityTaskScheduler.updateQSIObjects().
> CapacityTaskScheduler.updateQSIObjects(), internally calls String.format()
> for setting the job scheduling information. Based on the datastructure size
> of "jobQueuesManager" and "queueInfoMap", the number of times String.format()
> gets executed becomes very high. String.format() internally does pattern
> matching which turns to be out very heavy (This was revealed while profiling
> JT. Almost 57% of time was spent in CapacityScheduler.assignTasks(), out of
> which String.format() took 46%.
> Would it be possible to do String.format() only at the time of invoking
> JobInProgress.getSchedulingInfo?. This might reduce the pressure on JT while
> processing heartbeats.
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