[jira] [Commented] (MAPREDUCE-5785) Derive task attempt JVM max heap size automatically from mapreduce.*.memory.mb

["Karthik Kambatla (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13924923#comment-13924923 ] 

Karthik Kambatla commented on MAPREDUCE-5785:
---------------------------------------------

Good idea. Thanks for filing and working on this, [~jira.shegalov]. What are your thoughts on having a constant headroom (say, 200 MB) instead of a ratio? Also, it would be nice to pick mapreduce.task.io.sort.mb automatically using a ratio, by default. Would be nice to do that too.

> Derive task attempt JVM max heap size 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
>
>
> Currently users have to set 2 memory-related configs for per Job / per task type.  One fist choses some container size mapreduce.*.memory.mb and then a corresponding Xmx < mapreduce.*.memory.mb to make sure that the JVM with the user code heap, and its native memory do not  exceed this limit. If one forgets to tune Xmx, MR-AM might be allocating big containers whereas the JVM will only use the default -Xmx200m.
> With this JIRA, we propose to set Xmx automatically base on an empirical ratio that can be adjusted. Xmx is not changed automaically if provided by the user.



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