linux-kernel - Re: Performance loss 2.6.22->22.6.23->2.6.24-rc7 on CPU intensive benchmark on 8 Core Xeon

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Date:	Wed, 16 Jan 2008 16:38:33 +0000
From:	"Colin Fowler" <elethiomel@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Subject: Re: Performance loss 2.6.22->22.6.23->2.6.24-rc7 on CPU intensive benchmark on 8 Core Xeon

Hi Ingo,

I have permission for a binary only release (mailed the supervisor
intermediately after your earler mail). I'm sure the abstract code
simulating the workload will be alright too, but I need time to put it
together as I'm a bit swamped at the moment. Will hope to have it in
the next few days.

regards,
       Colin

On Jan 16, 2008 4:19 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Colin Fowler <elethiomel@...il.com> wrote:
>
> > Hi Ingo, I'll need to convince my supervisor first if I can release a
> > binary. Technically anythin glike this needs to go through our
> > University's "innovations department" and requires lengthy paperwork
> > and NDAs :(.
>
> a binary wouldnt work for me anyway. But you could try to write a
> "workload simulator": just pick out the pthread ops and replace the
> worker functions with some dummy stuff that just touches an array that
> has similar size to the tiles (in a tight loop). Make sure it has
> similar context-switch rate and idle percentage as your real workload -
> then send us the .c file. As long as it's a single .c file that runs for
> a few seconds and outputs a precise enough "run time" result, kernel
> developers would pick it up and use it for optimizations. To get the #
> of cpus automatically you can do:
>
>         cpus = system("exit `grep processor /proc/cpuinfo  | wc -l`");
>         cpus = WEXITSTATUS(cpus);
>
> and start as many threads as many CPUs there are in the system.
>
>         Ingo
>
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