[jira] [Comment Edited] (MAPREDUCE-5785) Derive task attempt JVM max heap size and io.sort.mb automatically from mapreduce.*.memory.mb

["Allen Wittenauer (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14215319#comment-14215319 ] 

Allen Wittenauer edited comment on MAPREDUCE-5785 at 11/17/14 10:35 PM:
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bq. Technically this may need to be marked as an incompatible change

I agree: this will likely break all kinds of user jobs.  I don't even want to consider what happens in the streaming and pipes use cases.... 


was (Author: aw):
bq. Technically this may need to be marked as an incompatible change

+1  This will likely break all kinds of user jobs.  I don't even want to consider what happens in the streaming and pipes use cases.... 

> Derive task attempt JVM max heap size and io.sort.mb automatically from mapreduce.*.memory.mb
> ---------------------------------------------------------------------------------------------
>
>                 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: Gera Shegalov
>         Attachments: MAPREDUCE-5785.v01.patch, MAPREDUCE-5785.v02.patch, MAPREDUCE-5785.v03.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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