[torqueusers] limiting resource usage with torque

Christopher Samuel samuel at unimelb.edu.au
Mon Jan 23 17:58:02 MST 2012


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On 20/01/12 20:28, Arnau Bria wrote:

> I don't know if I have understood you or not. 

Yeah, I was wondering if we were talking at cross purposes.

> My point is that limiting is not the same as reserving. 

My take is that the scheduler will try and reserve whatever you ask it
for (and defer if it cannot), and the queuing system should enforce your
request as a limit (if it can).

> So, if I want torque to limit resource usage (6gb in this case) I don't
> want torque to tell MAUI to reserve 6 GB for that job. 

If you don't want Maui to reserve 6GB for a job, then don't tell it to.

Tell it to reserve what you think the job will need.  It's then Torque's
issue to enforce that reservation and prevent the job using more than that.

This then triggers the usual worries about mem/pmem setting resource
limitations that are not enforced by the kernel (under Linux).

> With the reservation, only 4 jobs (4*6=24) can run, but, if jobs behave
> correctly and they don't use more than 2 o 3 GB, we can run up to 8
> jobs. So, I'm trying to tell torque: "ei! if the job usese more than
> 6gb, kill it"...

If the job should never use more than 3GB then set a limit of that plus
a margin of error.

> So, my problem comes from the understanding of limiting/reserving
> (which are very diferent concepts).
> 
> -l
>                Defines  the  resources  that are required by the job
> and establishes a limit to the amount of resource that can be consumed

In Torque you tell the system what the upper bound usage that is allowed
for a job and that's what the scheduler has to reserve (to avoid
overcommitting resources).

Hope this helps!
Chris
- -- 
    Christopher Samuel - Senior Systems Administrator
 VLSCI - Victorian Life Sciences Computation Initiative
 Email: samuel at unimelb.edu.au Phone: +61 (0)3 903 55545
         http://www.vlsci.unimelb.edu.au/

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