linux-kernel - Re: CFS review

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Date:	Wed, 1 Aug 2007 15:33:17 +0200 (CEST)
From:	Roman Zippel <zippel@...ux-m68k.org>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Mike Galbraith <efault@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: CFS review

Hi,

On Wed, 1 Aug 2007, Andi Kleen wrote:

> > especially if one already knows that
> > scheduler clock has only limited resolution (because it's based on
> > jiffies), it becomes possible to use mostly 32bit values.
> 
> jiffies based sched_clock should be soon very rare. It's probably
> not worth optimizing for it.

I'm not so sure about that. sched_clock() has to be fast, so many archs 
may want to continue to use jiffies. As soon as one does that one can also 
save a lot of computational overhead by using 32bit instead of 64bit.
The question is then how easy that is possible.

bye, Roman
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