Re: [PATCH] msleep() with hrtimers

From: Arjan van de Ven <arjan@infradead.org>
To: Roman Zippel <zippel@linux-m68k.org>
Cc: Jonathan Corbet <corbet@lwn.net>,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	akpm@linux-foundation.org, Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] msleep() with hrtimers
Date: Tue, 07 Aug 2007 21:15:12 -0700	[thread overview]
Message-ID: <1186546512.2862.3.camel@laptopd505.fenrus.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0708071417200.1817@scrub.home>

On Tue, 2007-08-07 at 14:45 +0200, Roman Zippel wrote:
> Hi,
> 
> On Mon, 6 Aug 2007, Arjan van de Ven wrote:
> 
> > So, let me ask a direct question: What do you think is specifically
> > wrong about changing the msleep() implementation as is done here? The
> > behavior is clearly an improvement, so what is your objection on the
> > flipside?
> 
> Again, we have two different timer APIs for a reason

yes because we have different usage patterns for timers. (exact/course
or expiring/not-typically-expiring; I know you have some other opinion
here than other people).

For this case it's relatively simple imo: The existing implementation
has a *typical* behavior which is 100% to 2000% worse than what the user
of the API asks for. And that is totally unneeded to be so crappy; it
can be much more exact easily as shown by this patch.

You keep claiming that hrtimers are so incredibly expensive; but for
msleep()... which is mostly called during driver init ... I really don't
buy that it's really expensive. We're not doing this a gazilion times
per second obviously...

-- 
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