linux-kernel - Re: [PATCH/RFC] msleep() with hrtimers

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Message-ID: <20070716115744.GA14131@elte.hu>
Date:	Mon, 16 Jul 2007 13:57:44 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Roman Zippel <zippel@...ux-m68k.org>
Cc:	Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH/RFC] msleep() with hrtimers


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


> > > One possible problem here is that setting up that timer can be 
> > > considerably more expensive, for a relative timer you have to read 
> > > the current time, which can be quite expensive (e.g. your machine 
> > > now uses the PIT timer, because TSC was deemed unstable).
> >
> > i dont think there's any significant overhead. The OLPC folks are 
> > pretty sensitive to performance, so if there was any genuine 
> > measurable overhead due to this, i'd expect them to report it. And 
> > even if there _was_ overhead, it would be well worth its price, the 
> > legacies of HZ are clearly biting the OLPC project here. The sooner 
> > we get rid of HZ dependencies and HZ artifacts, the better.
>
> How is a sleep function relevant to performace?

i'm not sure how your question relates/connects to what i wrote above, 
could you please re-phrase your question into a bit more verbose form so 
that i can answer it? Thanks,

	Ingo
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