Re: [HTCondor-users] sharing CPU

[Todd Tannenbaum <tannenba@xxxxxxxxxxx>]

On 3/2/2015 2:17 AM, Ricardo Oda wrote:
> Sorry, I meant core instead of CPU.
>
> Refrasing:
> Is it possible to assign a single core of the CPU to different slots of
> execution? And maybe limit a percentage of the core to each slot.
>
> So jobs that doesn't require much CPU, like IO intensive, can share the
> CPU core usage with other jobs.

Currently CPUs in HTCondor slots need to be an integer, although in a 
future release we hope to support fractional cores.

Although it is a bit inelegant, you can achieve what you want right now 
by telling HTCondor your machine has more CPU cores than it really does 
via the NUM_CPUS config settings, which defaults to $(DETECTED_CPUS). 
So for instance, you could tell HTCondor a machine has 4 times the cores 
it really does via the following in condor_config :

   NUM_CPUS = 4 * $(DETECTED_CPUS)

Now every htcondor "cpu" provisioned by HTCondor is really only 25% of 
an actual CPU core, so if you made a slot with one CPU that slot in 
reality would only have 25% of one core.  If you want to enforce that 
the job will not use more cores than provisioned, either enable cgroups 
support (see the manual) or set

  ASSIGN_CPU_AFFINITY = True

in condor_config - both ASSIGN_CPU_AFFINITY and cgroups enforcement do 
the right thing when HTCondor is told there are more cores than the 
machine actually has.

Hope the above helps,
Todd