Re: 2.4.x SMP scalability question.

From: lamont@icopyright.com
Date: Mon Aug 21 2000 - 14:18:23 EST


On Sat, 19 Aug 2000, Ingo Molnar wrote:
> On Fri, 18 Aug 2000, Matthew Wilcox wrote:
> > (From memory, we were acheiving 80%+ scalability on 2 and 4 CPUs and
> > then dropped to 65% on the 8 CPU test -- equivalent to using 5 CPUs at
> > 100%.)
>
> i can show you pure user-space workloads that will not scale past 2 CPUs
> on any x86 SMP system.
 
Can you point me/us to any references on the SMP scalability of various
workloads and/or how to diagnose them?

I suppose if you're runing 1/2 as slow as you think you should be on a 4
CPU box and you disable two of the CPUs and it doesn't get any slower then
you know you've got a scalability problem somewhere. I don't know how I
would got about determining that the userspace workload inherantly didn't
scale though.

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