linux-kernel - Re: CFS not suitable for desktop computers

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Message-Id: <1241459983.5462.70.camel@marge.simson.net>
Date:	Mon, 04 May 2009 19:59:43 +0200
From:	Mike Galbraith <efault@....de>
To:	Nico Schümann <spam@...o22.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: CFS not suitable for desktop computers

On Mon, 2009-05-04 at 17:16 +0200, Nico Schümann wrote:
> Thank you Ray Lee and Mike Galbraith for your responses, I ran the 
> script and attached its gathered information.
> 
> Mike Galbraith wrote:
> > How hard is hard?  Can you describe the loads you're having trouble
> > with, and the hardware you're running them on?
> >
> >   
> I could reproduce "hard" load by just compiling the linux kernel, make 
> -j3 while reading mails with Thunderbird, which is not that hard 
> foreground load. Thunderbird starts reacting really slowly while compiling.
> 
> My system has a 1,3 GHz AMD Athlon CPU (32 bits) and 1 GB of RAM. Now 
> you will say: That is not very much. Of course it is not, but with the 
> old scheduler, the system felt way faster, so it seemed to be enough for 
> compiling and reading mails.

Hm.  The load isn't extreme, but it appears to me that between X and
Thunderbird, CPU demand is high enough that you WILL feel the slowdown
when you toss in three competing CPU hogs plus other system activity all
on one core.

> I hope you can find useful information in the attached log, I enabled 
> SCHED_DEBUG and SCHEDSTATS, if you need any more information, just ask 
> me, I will try to answer.

I'll look closer tomorrow (ill).  For now, how much CPU does
X/Thunderbird consume without the kbuild?

(I know this isn't what you want to hear, but SCHED_IDLE is a major case
of happiness for heavy lifting background loads, especially so on UP.)

	-Mike

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