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From "Todd Lipcon (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-3205) MR2 memory limits should be pmem, not vmem
Date Thu, 27 Oct 2011 00:27:32 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-3205?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated MAPREDUCE-3205:
-----------------------------------

    Release Note: Resource limits are now expressed and enforced in terms of physical memory,
rather than virtual memory. The virtual memory limit is set as a configurable multiple of
the physical limit. The NodeManager's memory usage is now configured in units of MB rather
than GB.
    Hadoop Flags: Incompatible change,Reviewed  (was: Incompatible change)
    
> 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
>            Assignee: Todd Lipcon
>            Priority: Blocker
>             Fix For: 0.23.0
>
>         Attachments: mr-3205.txt, mr-3205.txt, mr-3205.txt, mr-3205.txt, mr-3205.txt,
mr-3205.txt
>
>
> 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
RAM.
> 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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