Re: unusual scheduling performance

From: Ingo Molnar (mingo@elte.hu)
Date: Wed Nov 20 2002 - 09:12:57 EST


On Mon, 18 Nov 2002, William Lee Irwin III wrote:

> On 16x, 2.5.47 kernel compiles take about 26s when the machine is
> otherwise idle.
>
> On 32x, 2.5.47 kernel compiles take about 48s when the machine is
> otherwise idle.

one thing to note is that the kernel's compilation is not something that
parallelizes well to above 8 CPUs. Our make architecture creates many link
points which serialize 'threads of compilation'.

i'd try two things:

 1) try Erich Focht's NUMA enhancements to the load balancer.

 2) remove the -pipe flag from arch/i386/Makefile

the later thing will reduce the number of processes and makes compilation
more localized to a single CPU - which might (or might not) help NUMA
architectures.

        Ingo

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