[Mauiusers] detecting and scheduling vmem

Roy Dragseth roy.dragseth at cc.uit.no
Tue Feb 24 03:37:41 MST 2009

On Friday 20 February 2009 07:08:42 Gareth.Williams at csiro.au wrote:
> Hi All,
> I have been working with CR to get a patch in maui and moab to improve
> treatment of vmem.  The patch is in maui-3.2.6p21-snap.1234905291 and will
> be in upcoming moab releases.  Many thanks to Brian Christiansen at CR.
> With the patch, maui/moab correctly detects a node's available vmem as
> being the total physical memory plus swap space.  This can then be
> scheduled/allocated by requesting vmem and job's virtual memory allocation
> can be limited on a per process basis and periodically measured (and action
> taken or overuse) on a per job basis.
> I think this makes scheduling on vmem a good option.  It's a more
> predictable quantity than mem/pmem.

This is great, but is it possible to get 

    TotMem = (int)(TotMem * MSched.NodeMemOverCommitFactor);

at line 6384?  This will make the NODEMEMOVERCOMMITFACTOR work both for mem 
and swap as earlier.

We want to use a slight overcommit to allow a user to specify -lpvmem=2gb 
instead of -lpvmem=2000mb on a machine with 2GB RAM per core.  Some of the ram 
isn't available to userspace, so using 2gb will underutilize the cores on a 
node and users aren't really good at guessing the memory consumption anyway.


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