[GE users] controlling openmp jobs

Ron Chen ron_chen_123 at yahoo.com
Thu May 5 15:24:29 BST 2005


Shing, what OS is it? Some operating systems allow
binding processes to CPUSets. So an OpenMP job binded
to a processer can only use that CPU, which is eactly
what you want!

SGE supports CPUsets on Solaris, IRIX, and tru64, and
IA64 Linux. With some minor work, we can get CPUSet
support on all Linux 2.6 platforms.

 -Ron

--- Reuti <reuti at staff.uni-marburg.de> wrote:
> Hi Shing,
> 
> you can't control the creation of forks/threads. You
> often also see additional 
> forks in MPICH jobs which will handle the
> communication, but not using up any 
> CPU time (besides the communication). It's of course
> correct, that an OpenMP 
> job should also be submitted to a PE for proper slot
> allocation, although you 
> don't have to setup anyting there for the job.
> 
> Maybe seeing the slots from a different view will
> explain it to the users: 
> getting one slot of a dual CPU machine means "give
> me half of the CPU power of 
> this machine". Whether the user starts a pur serial
> job or creats an additonal 
> fork/thread: he/she will get half of the total CPU
> time (unless there is 
> nothing else running).
> 
> HTH - Reuti
> 
> Quoting shing at cz3.nus.edu.sg:
> 
> > 
> > hi,
> > 
> > I wondering how other people are controlling their
> openmp jobs. Ideally of
> > course, openmp jobs should be submitted in a PE.
> However there's nothing
> > to stop openmp jobs from being submitted to a
> serial queue since SGE won't
> > be able to tell that it is an openmp job, and if
> the job gets scheduled on
> > a 2-cpu machine with 2 slots, it will use both
> cpus, effectively using up
> > 2 slots but SGE only records it as 1 slot. How can
> we get SGE to force
> > openmp jobs to use an appropriate PE? Perhaps the
> OMP_NUM_THREADS env var
> > can be set during submission? ie. if submitted to
> a serial queue,
> > OMP_NUM_THREADS gets set to 1 (without the user
> being able to override)
> > and the job uses 1 slot. Could that be done?  If
> so, how?
> > 
> > thanks,
> > --shing
> > 
> >
>
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