[Mauiusers] Overloading a node in a standing reservation ?

Chris Samuel csamuel at vpac.org
Sat Aug 6 21:06:34 MDT 2005

Hi folks,

We've got an IBM Power5 cluster (quad CPU nodes) on which the Linux
kernel can dynamically enable/disable SMT (symetrical multi threading)
based on CPU load. Now normally we don't advertise this (there's a
performance penalty) and mark all our nodes in PBS as having 4 CPUs.

However, I can think of one situation where it would be useful to
us to be able to change the number of CPUs a node is considered as
having within Moab.

We have a testing / short queue for which we dedicate a single node
and as these are typically not high memory users it would be great
to be able to have the standing reservation to say that the node it
is on has 8 CPUs available on that node rather than 4.

Is such overloading doable ?

I guess one thing that might catch us out is whether we can change the
NODEMAXLOAD in the standing reservation for the node involved ?

It's a reservation that runs from 8am-8pm weekdays and we'd like
it to drop back to the 4 CPU normal behavior outside of those

The reservation config is:

SRCFG[sque] STARTTIME=08:00:00 ENDTIME=20:00:00
SRCFG[sque] HOSTLIST=edda034
SRCFG[sque] MAXTIME=00:15:00+*

 Christopher Samuel - (03)9925 4751 - VPAC Deputy Systems Manager
 Victorian Partnership for Advanced Computing http://www.vpac.org/
 Bldg 91, 110 Victoria Street, Carlton South, VIC 3053, Australia

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