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Date: Tue, 7 Jul 2009 07:18:14 -0700 (PDT)
From: "Vinod K V (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Updated: (MAPREDUCE-722) More slots are getting reserved for
 HiRAM job tasks then required
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     [ https://issues.apache.org/jira/browse/MAPREDUCE-722?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vinod K V updated MAPREDUCE-722:
--------------------------------

    Attachment: MAPREDUCE-722.1.txt

Thought about it a bit more and discussed with Hemanth and Devaraj. This does look like a complicated issue and needs a larger discussion.

For fixing the issue at hand, I am reverting changes w.r.t speculative execution. So, the attached patch fixed cluster drain problem in general for high memory jobs. But if a high memory job enables speculative execution, it might starve. Will track the fix for speculative execution in a follow up JIRA.

> More slots are getting reserved for HiRAM job tasks then required
> -----------------------------------------------------------------
>
>                 Key: MAPREDUCE-722
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-722
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: contrib/capacity-sched
>         Environment: Cluster MR capacity=248/248 Map slot size=1500 mb and  reduce slot size=2048 mb. Total number of nodes=124
> 4 queues each having Capacity=25% User Limit=100%.
>            Reporter: Karam Singh
>            Assignee: Vinod K V
>         Attachments: MAPREDUCE-722.1.txt, MAPREDUCE-722.txt
>
>
> Submitted a normal job with map=124=reduces
> After submitted High RAM with maps=31=reduces map.memory=1800 reduce.memory=2800
> Again 3 job maps=124=reduces
> total of 248 slots were reserved for both maps and reduces for High Job which much higher then required.
> Is observed in Hadoop 0.20.0

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