Re: [Lse-tech] [patch] sched-domain cleanups, sched-2.6.5-rc2-mm2-A3

From: Erich Focht
Date: Wed Mar 31 2004 - 16:28:38 EST

On Tuesday 30 March 2004 17:01, Martin J. Bligh wrote:
> > I don't think it's worth to wait and hope that somebody shows up with
> > a magic algorithm which balances every kind of job optimally.
> Especially as I don't believe that exists ;-) It's not deterministic.

Right, so let's choose the initial balancing policy on a per process

> > Benchmarks simulating "user work" like SPECsdet, kernel compile, AIM7
> > are not relevant for HPC. In a compute center it actually doesn't
> > matter much whether some shell command returns 10% faster, it just
> > shouldn't disturb my super simulation code for which I bought an
> > expensive NUMA box.
> OK, but the scheduler can't know the difference automatically, I don't
> think ... and whether we should tune the scheduler for "user work" or
> HPC is going to be a hotly contested point ;-) We need to try to find
> something that works for both. And suppose you have a 4 node system,
> with 4 HPC apps running? Surely you want each app to have one node to
> itself?

If the machine is 100% full all the time and all apps demand the same
amount of bandwidth, yes, I want 1 job per node. If the average load is
less than 100% (sometimes only 2-3 jobs are running) then I'd prefer to
spread the processes of a job across the machine. The average bandwidth
per process will be higher. Modern NUMA machines have big bandwidth to
neighboring nodes and not too bad latency penalties for remote accesses.


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