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Date: Mon, 6 Aug 2012 20:49:04 +0000 (UTC)
From: "Ahmed Radwan (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
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Subject: [jira] [Commented] (MAPREDUCE-4469) Resource calculation in child
 tasks is CPU-heavy
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-4469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13429412#comment-13429412 ] 

Ahmed Radwan commented on MAPREDUCE-4469:
-----------------------------------------

Here is a patch that adds this option of disabling the use of  ResourceCalculatorPlugin in the task. I have confirmed that this change doesn't affect TestTTResourceReporting.
                
> Resource calculation in child tasks is CPU-heavy
> ------------------------------------------------
>
>                 Key: MAPREDUCE-4469
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4469
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: performance, task
>    Affects Versions: 1.0.3
>            Reporter: Todd Lipcon
>         Attachments: MAPREDUCE-4469.patch
>
>
> In doing some benchmarking on a hadoop-1 derived codebase, I noticed that each of the child tasks was doing a ton of syscalls. Upon stracing, I noticed that it's spending a lot of time looping through all the files in /proc to calculate resource usage.
> As a test, I added a flag to disable use of the ResourceCalculatorPlugin within the tasks. On a CPU-bound 500G-sort workload, this improved total job runtime by about 10% (map slot-seconds by 14%, reduce slot seconds by 8%)

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