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https://issues.apache.org/jira/browse/MAPREDUCE-6118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14157669#comment-14157669
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Tsuyoshi OZAWA commented on MAPREDUCE-6118:
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One another way we can go is to have fraction approach like Tez: if the 
fraction is 0.8, Xmx will be 0.8 * yarn.app.mapreduce.am.resource.mb and 
configure yarn.app.mapreduce.am.command-opts as 
Xmx(0.8*yarn.app.mapreduce.am.resource.mb) in addition to user-defined 
yarn.app.mapreduce.am.command-opts.

> Uber-mode decision does not consider -Xmx
> -----------------------------------------
>
>                 Key: MAPREDUCE-6118
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6118
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Maysam Yabandeh
>            Priority: Minor
>
> Current the decision on using uber-mode is based on the mapper container size 
> and the AM container size. However the actual memory at AM is limited by -Xmx 
> options passed via yarn.app.mapreduce.am.command-opts.
> For example: AM memory: 4G, yarn.app.mapreduce.am.command-opts=-Xmx2048GB, 
> mapper memory: 3GB. Here the uber job could face OOM whereas a non-uber 
> execution would not.
> We faced this problem recently and forced to disable uber-mode to circumvent 
> the problem. One idea, although a bit ugly, is to parse jvm opts, extract 
> Xmx, and take it into account for uber-mode decision.



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