[gridengine users] cpu usage calculation

Reuti reuti at staff.uni-marburg.de
Fri Aug 31 10:58:26 UTC 2018


Hi John,

> Am 31.08.2018 um 12:27 schrieb Marshall2, John (SSC/SPC) <john.marshall2 at canada.ca>:
> 
> Hi,
> 
> When gridengine calculates cpu usage (based on wallclock) it uses:
> cpu usage = wallclock * nslots
> 
> This does not account for the number of cpus that may be used for
> each slot, which is problematic.

What was the motivation for implementing it this way? I mean: usually one SLOT represents one CORE in GirdEngine. Hence, to get a proper allocation and accounting while not oversubscribe the nodes you have to request the overall amount of cores in case you want to combine processes (like for MPI) and threads (like for Open MP).

In your case, it looks to me that you assume that necessary cores are available, independent from the actual usage of each node?

-- Reuti

PS: I assume with CPUS you refer to CORES.


> I have written up an article at:
> https://expl.info/display/MISC/Slot+Multiplier+for+Calculating+CPU+Usage+in+Gridengine
> 
> which explains the issue and provides a patch (against sge-8.1.9)
> so that:
> cpu usage = wallclock * nslots * ncpus_per_slot
> 
> This makes the usage information much more useful/accurate
> when using the fair share.
> 
> Have others encountered this issue? Feedback is welcome.
> 
> Thanks,
> John
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