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Date: Mon, 7 Apr 2014 22:46:19 +0000 (UTC)
From: "Sandy Ryza (JIRA)" <jira@apache.org>
To: yarn-issues@hadoop.apache.org
Message-ID: <JIRA.12707045.1396910538751.76331.1396910779110@arcas>
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Subject: [jira] [Commented] (YARN-1909) FairScheduler isStartvedForFairShare
 does not work when fairShare == 1
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    [ https://issues.apache.org/jira/browse/YARN-1909?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13962349#comment-13962349 ] 

Sandy Ryza commented on YARN-1909:
----------------------------------

This looks like an MR1 issue, so moving it to MAPREDUCE.

> FairScheduler isStartvedForFairShare does not work when fairShare == 1
> ----------------------------------------------------------------------
>
>                 Key: YARN-1909
>                 URL: https://issues.apache.org/jira/browse/YARN-1909
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Anubhav Dhoot
>            Assignee: Anubhav Dhoot
>
> If the fair share returned by the scheduler getFairShare() == 1 the pool will never be marked as being starved because of the following calculation:
> {code}
> boolean isStarvedForFairShare(PoolSchedulable sched) { 
>   int desiredFairShare = (int) Math.floor(Math.min( sched.getFairShare() / 2, sched.getDemand())); 
>   return (sched.getRunningTasks() < desiredFairShare); 
> }
> {code}
> getFairShare() returns 1
> Math.min calculation will return 0.5
> Math.Floor() which will cause the desiredFairShare to be set to 0.
> the return value to be 'false' (0 < 0)
> If you have a small job without a minimum set it will not get scheduled if a large job is hogging the slots.


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