From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: dean gaudet <dean-list-linux-kernel@arctic.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [patch] prefer TSC over PM Timer
Date: Wed, 17 Nov 2004 15:25:01 +0000 [thread overview]
Message-ID: <1100705099.420.32.camel@localhost.localdomain> (raw)
In-Reply-To: <Pine.LNX.4.61.0411151531590.22091@twinlark.arctic.org>
On Maw, 2004-11-16 at 00:23, dean gaudet wrote:
> i've heard other folks have independently run into this problem -- in fact
> i see the most recent fc2 kernels already do this. i'd like this to be
> accepted into the main kernel though.
IMHO it was a mistake to make this change in FC2.
> the x86 PM Timer is an order of magnitude slower than the TSC for
> gettimeofday calls. i'm seeing 8%+ of the time spent doing gettimeofday
> in someworkloads... and apparently kernel.org was seeing 80% of its time
> go to gettimeofday during the fc3-release overload. PM timer is also less
> accurate than TSC.
Nobody guarantees that the TSC is clocked at the same rate per CPU and
several power management schemes break it. I see it break on my Thinkpad
600 and its one reason I have to replace the FC kernel with a 2.6-ac
kernel on that system.
Is gettimeofday supposed to return the right value or be fast ?
next prev parent reply other threads:[~2004-11-17 16:28 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-16 0:23 [patch] prefer TSC over PM Timer dean gaudet
2004-11-16 1:38 ` john stultz
2004-11-16 3:21 ` dean gaudet
2004-11-16 9:50 ` john stultz
2004-11-16 20:29 ` Dominik Brodowski
2004-11-16 21:06 ` john stultz
2004-11-16 8:11 ` Arjan van de Ven
2004-11-16 9:36 ` john stultz
2004-11-17 15:25 ` Alan Cox
2004-11-17 15:25 ` Alan Cox [this message]
2004-11-17 17:23 ` Chris Friesen
-- strict thread matches above, loose matches on Subject: below --
2004-11-16 18:27 Pallipadi, Venkatesh
2004-11-17 1:50 ` dean gaudet
2004-11-17 10:43 ` Mikael Pettersson
2004-11-17 14:19 ` Dmitry Torokhov
2004-11-17 15:31 ` Alan Cox
2004-11-18 2:01 ` Krzysztof Halasa
2004-11-17 15:08 Pallipadi, Venkatesh
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