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https://issues.apache.org/jira/browse/MAPREDUCE-5785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14285196#comment-14285196
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Gera Shegalov commented on MAPREDUCE-5785:
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findbugs warnings are unrelated. +1 for the v9 patch. Thanks for accommodating
my comments, Karthik. I'll commit it tomorrow evening if there are no
objections.
> Derive heap size or mapreduce.*.memory.mb automatically
> -------------------------------------------------------
>
> Key: MAPREDUCE-5785
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5785
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Components: mr-am, task
> Reporter: Gera Shegalov
> Assignee: Karthik Kambatla
> Fix For: 3.0.0
>
> Attachments: MAPREDUCE-5785.v01.patch, MAPREDUCE-5785.v02.patch,
> MAPREDUCE-5785.v03.patch, mr-5785-4.patch, mr-5785-5.patch, mr-5785-6.patch,
> mr-5785-7.patch, mr-5785-8.patch, mr-5785-9.patch
>
>
> Currently users have to set 2 memory-related configs per Job / per task type.
> One first chooses some container size map reduce.\*.memory.mb and then a
> corresponding maximum Java heap size Xmx < map reduce.\*.memory.mb. This
> makes sure that the JVM's C-heap (native memory + Java heap) does not exceed
> this mapreduce.*.memory.mb. If one forgets to tune Xmx, MR-AM might be
> - allocating big containers whereas the JVM will only use the default
> -Xmx200m.
> - allocating small containers that will OOM because Xmx is too high.
> With this JIRA, we propose to set Xmx automatically based on an empirical
> ratio that can be adjusted. Xmx is not changed automatically if provided by
> the user.
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