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From "Gera Shegalov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5785) Derive task attempt JVM max heap size and io.sort.mb automatically from mapreduce.*.memory.mb
Date Tue, 18 Nov 2014 05:05:33 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14215723#comment-14215723
] 

Gera Shegalov commented on MAPREDUCE-5785:
------------------------------------------

[~kasha], I agree that for MRv1->MRv2 transition deriving the container size from Xmx is
a better fit. Feel free to take over this JIRA.

A challenge here might be is that there is a (default) value for *.memory.mb. How do you know
it's ok to modify it? Are you going to check {{conf.getPropertySources}} for whether it was
modifed. Or do you want to introduce another boolean switch that disables overrides?

> 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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