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https://issues.apache.org/jira/browse/MAPREDUCE-3205?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arun C Murthy updated MAPREDUCE-3205:
-------------------------------------

    Status: Open  (was: Patch Available)

Todd, the patch looks good. 

Some comments:
# vmem.to.pmem.limit.ratio should we vmem-pmem-limit-ratio (better 
vmem-pmem-ratio :) ) to be more consistent with our current naming scheme.
# Should we default the ratio to 1.0 to be compatible with current CS in 0.20?
# Do you want to make resource.memory-gb as resource.memory-mb i.e. incorporate 
MAPREDUCE-3266?
# The 80% limit on available RAM needs to be more conservative? I shudder to 
think it probably should be configurable...
# Might be helpful to add both pmem and vmem in error msgs for both exceptional 
conditions for users?
                
> 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
>         Attachments: 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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