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From "Rajesh Balamohan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1533) reduce or remove usage of String.format() usage in CapacityTaskScheduler.updateQSIObjects
Date Thu, 25 Feb 2010 06:38:27 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1533?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12838207#action_12838207
] 

Rajesh Balamohan commented on MAPREDUCE-1533:
---------------------------------------------

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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