linux-kernel - Re: [PATCH] CFS: Fix missing digit off in wmult table

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Message-ID: <20070716112037.GA6895@elte.hu>
Date:	Mon, 16 Jul 2007 13:20:37 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Roman Zippel <zippel@...ux-m68k.org>
Cc:	James Bruce <bruce@...rew.cmu.edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrea Arcangeli <andrea@...e.de>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [PATCH] CFS: Fix missing digit off in wmult table


* Roman Zippel <zippel@...ux-m68k.org> wrote:

> > yes, the weight multiplier 1.25, but the actual difference in CPU 
> > utilization, when running two CPU intense tasks, is ~10%:
> > 
> >   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> >  8246 mingo     20   0  1576  244  196 R   55  0.0   0:11.96 loop
> >  8247 mingo     21   1  1576  244  196 R   45  0.0   0:10.52 loop
> > 
> > so the first task 'wins' +10% CPU utilization (relative to the 50% 
> > it had before), the second task 'loses' -10% CPU utilization 
> > (relative to the 50% it had before).
> 
> As soon as you add another loop the difference changes again, while 
> it's always correct to say it gets 25% more cpu time [...]

yep, and i'll add the relative effect to the comment too.

	Ingo
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