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https://issues.apache.org/jira/browse/MAPREDUCE-4469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14524602#comment-14524602
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Hadoop QA commented on MAPREDUCE-4469:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:red}-1{color} | patch |   0m  0s | The patch command could not apply 
the patch during dryrun. |
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|| Subsystem || Report/Notes ||
| Patch URL | 
http://issues.apache.org/jira/secure/attachment/12565910/MAPREDUCE-4469_rev5.patch
 |
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / f1a152c |
| Console output | 
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/5506/console |


This message was automatically generated.

> 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, MAPREDUCE-4469_rev2.patch, 
> MAPREDUCE-4469_rev3.patch, MAPREDUCE-4469_rev4.patch, 
> MAPREDUCE-4469_rev5.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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