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

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Date:	Mon, 16 Jul 2007 20:12:53 +0200 (CEST)
From:	Roman Zippel <zippel@...ux-m68k.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Ingo Molnar <mingo@...e.hu>, James Bruce <bruce@...rew.cmu.edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>,
	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

Hi,

On Mon, 16 Jul 2007, Linus Torvalds wrote:

> How about trying a much less aggressive nice-level (and preferably linear, 
> not exponential)?

I think the exponential increase isn't the problem. The old code did 
approximate something like this rather crudely with the result that there 
was a big gap between level 0 and -1.

Something like this:

echo 'for (i=-20;i<=20;i++) print i, " : ", 1024*e(l(2)*(-i/20*3)), "\n";' | bc -l

would produce a range similiar to the old code. Replacing the factor 3 
with 4 would be IMO a more reasonable increase and had the advantage for 
the user that it's easier to understand that every 5 levels the time a 
process gets is doubled.

bye, Roman
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