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From "Todd Lipcon (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-3205) MR2 memory limits should be pmem, not vmem
Date Wed, 19 Oct 2011 01:15:10 GMT
MR2 memory limits should be pmem, not vmem

                 Key: MAPREDUCE-3205
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3205
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
          Components: mrv2, nodemanager
    Affects Versions: 0.23.0
            Reporter: Todd Lipcon

Currently, the memory resources requested for a container limit the amount of virtual memory
used by the container. On my test clusters, at least, Java processes take up nearly twice
as much vmem as pmem - a Java process running with -Xmx500m uses 935m of vmem and only about
560m of pmem.

This will force admins to either under-utilize available physical memory, or oversubscribe
it by configuring the available resources on a TT to be larger than the true amount of physical

Instead, I would propose that the resource limit apply to pmem, and allow the admin to configure
a "vmem overcommit ratio" which sets the vmem limit as a function of pmem limit.

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