[torquedev] processor affinity

Prakash Velayutham Prakash.Velayutham at cchmc.org
Sat Jun 2 14:21:09 MDT 2007


I think linux currently supports cpusets. At least, I can see the option
in the Kernel source.

Prakash

>>> "Toni L. Harbaugh-Blackford [Contr]" <harbaugh at ncifcrf.gov> 06/02/07
3:41 PM >>>


Torque does not assign specific cpus.

On some architectures (Altix, maybe IRIX still) cpusets are implemented,
and these do restrict jobs to a given set of cpus.  You many want to
take
a look at the cpuset code and see if it could be generalized to other
linux-based systems.

On Sat, 2 Jun 2007, Menshutin Anton wrote:

  > Hi list,
  >
  > I found that there is no processor affinity in torque. Jobs assigned
to run
  > on some cpu's selected by scheduler, could also run on other cpus on
this
  > node. This means that if user lunches more processes or threads on a
node
  > than he has requested, his processes will span over other cpus
according to
  > the operating system scheduling policy. Thus he can get more cpu
resources
  > than he should. Its clear that this is undesired behavior.
  > Nevertheless, starting from linux kernel 2.6 there is a system call
  > sched_setaffinity() which enables programmer to tell OS scheduler
not to use
  > some cpus. So this is thing one have to add to torque.
  >
  > This property is inherited by child process. It is obvious that
setting it
  > after fork() and before exec() will be enough. The only thing I
don't know -
  > where can I get info about cpus assigned to me by scheduler.
  > Qstat shows this info in exec_host attribute, and I suppose I can
get this
  > string, parse it, find out localhostname and get CPUs numbers. But
may be
  > there is a better way for getting this info?
  >
  > I'm asking for help from torque-dev mailing list :) Given an advice,
I could
  > try to implement and test it myself or may be anybody could send me
a patch?
  >
  >
  >
  >
  >
  >
  >
  >
  > _______________________________________________
  > torquedev mailing list
  > torquedev at supercluster.org
  > http://www.supercluster.org/mailman/listinfo/torquedev
  >

-------------------------------------------------------------------
Toni Harbaugh-Blackford                       harbaugh at ncifcrf.gov
System Administrator
Advanced Biomedical Computing Center (ABCC)
National Cancer Institute
Contractor - SAIC/Frederick
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