[torquedev] processor affinity

Toni L. Harbaugh-Blackford [Contr] harbaugh at ncifcrf.gov
Sat Jun 2 13:41:08 MDT 2007

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

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