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https://issues.apache.org/jira/browse/MAPREDUCE-4469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13431639#comment-13431639
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Ahmed Radwan commented on MAPREDUCE-4469:
-----------------------------------------

Here is a draft patch implementing what I described in my previous comment.
                
> 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
>            Assignee: Ahmed Radwan
>         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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