From: Rusty Russell <rusty@rustcorp.com.au>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Glauber de Oliveira Costa <gcosta@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
Jeremy Fitzhardinge <jeremy@goop.org>,
--cc@redhat.com, Ingo Molnar <mingo@elte.hu>,
avi@quramnet.com, kvm-devel@lists.sourceforge.net,
John Stultz <johnstul@us.ibm.com>
Subject: Re: [PATCH] raise tsc clocksource rating
Date: Tue, 30 Oct 2007 13:39:23 +1100 [thread overview]
Message-ID: <200710301339.23628.rusty@rustcorp.com.au> (raw)
In-Reply-To: <alpine.LFD.0.9999.0710292315280.3186@localhost.localdomain>
On Tuesday 30 October 2007 09:17:38 Thomas Gleixner wrote:
> On Mon, 29 Oct 2007, Glauber de Oliveira Costa wrote:
>
> CC'ed John and removed glauber@t60.localdomain :)
>
> > From: Glauber de Oliveira Costa <glauber@t60.localdomain>
> >
> > tsc is very good time source (when it does not have drifts, does not
> > change it's frequency, i.e. when it works), so it should have its rating
> > raised to a value greater than, or equal 400.
> >
> > Since it's being a tendency among paravirt clocksources to use values
> > around 400, we should declare tsc as even better: So we use 500.
> >
> > This patch also touches the comments on clocksource.h, which suggests
> > that 499 would be a limit on the rating values.
> >
> > Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
>
> Acked-by: Thomas Gleixner <tglx@linutronix.de>
No. tsc is very good, it's not perfect. If a paravirt clock registers 400 it
really means "pick me over the tsc".
That's *why* they use > 400: it's in the documentation.
Rusty.
WARNING: multiple messages have this Message-ID (diff)
From: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
To: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Cc: Jeremy Fitzhardinge <jeremy-TSDbQ3PG+2Y@public.gmane.org>,
avi-i/T1Zxg06OZWk0Htik3J/w@public.gmane.org,
kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
John Stultz <johnstul-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Glauber de Oliveira Costa
<gcosta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
--cc-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Subject: Re: [PATCH] raise tsc clocksource rating
Date: Tue, 30 Oct 2007 13:39:23 +1100 [thread overview]
Message-ID: <200710301339.23628.rusty@rustcorp.com.au> (raw)
In-Reply-To: <alpine.LFD.0.9999.0710292315280.3186-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
On Tuesday 30 October 2007 09:17:38 Thomas Gleixner wrote:
> On Mon, 29 Oct 2007, Glauber de Oliveira Costa wrote:
>
> CC'ed John and removed glauber-aMxvdZfKFXomYvmMESoHnA@public.gmane.org :)
>
> > From: Glauber de Oliveira Costa <glauber-aMxvdZfKFXomYvmMESoHnA@public.gmane.org>
> >
> > tsc is very good time source (when it does not have drifts, does not
> > change it's frequency, i.e. when it works), so it should have its rating
> > raised to a value greater than, or equal 400.
> >
> > Since it's being a tendency among paravirt clocksources to use values
> > around 400, we should declare tsc as even better: So we use 500.
> >
> > This patch also touches the comments on clocksource.h, which suggests
> > that 499 would be a limit on the rating values.
> >
> > Signed-off-by: Glauber de Oliveira Costa <gcosta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>
> Acked-by: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
No. tsc is very good, it's not perfect. If a paravirt clock registers 400 it
really means "pick me over the tsc".
That's *why* they use > 400: it's in the documentation.
Rusty.
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next prev parent reply other threads:[~2007-10-30 2:39 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-29 23:10 [PATCH] raise tsc clocksource rating Glauber de Oliveira Costa
2007-10-29 23:10 ` Glauber de Oliveira Costa
2007-10-29 22:17 ` Thomas Gleixner
2007-10-29 22:17 ` Thomas Gleixner
2007-10-29 22:36 ` Ingo Molnar
2007-10-30 1:26 ` john stultz
2007-10-30 2:39 ` Rusty Russell [this message]
2007-10-30 2:39 ` Rusty Russell
2007-10-30 7:37 ` Ingo Molnar
2007-10-30 7:37 ` Ingo Molnar
2007-10-30 10:52 ` Rusty Russell
2007-10-30 10:52 ` Rusty Russell
2007-10-30 12:13 ` Glauber de Oliveira Costa
2007-10-30 12:13 ` Glauber de Oliveira Costa
2007-10-29 22:42 ` Zachary Amsden
2007-10-29 22:42 ` Zachary Amsden
2007-10-29 22:45 ` Jeremy Fitzhardinge
2007-10-29 22:45 ` Jeremy Fitzhardinge
2007-10-29 22:48 ` Ingo Molnar
2007-10-29 22:52 ` Jeremy Fitzhardinge
2007-10-29 22:52 ` Jeremy Fitzhardinge
2007-10-29 22:55 ` Ingo Molnar
2007-10-29 23:17 ` Jeremy Fitzhardinge
2007-10-29 23:17 ` Jeremy Fitzhardinge
2007-10-29 23:21 ` Ingo Molnar
2007-10-29 23:21 ` Ingo Molnar
2007-10-29 23:33 ` Jeremy Fitzhardinge
2007-10-29 23:33 ` Jeremy Fitzhardinge
2007-10-30 0:45 ` Ian Pratt
2007-10-30 0:45 ` Ian Pratt
2007-10-30 7:19 ` Ingo Molnar
2007-10-30 7:19 ` Ingo Molnar
2007-10-29 22:55 ` Zachary Amsden
2007-10-29 22:55 ` Zachary Amsden
2007-10-29 23:02 ` Ingo Molnar
2007-10-29 23:13 ` Zachary Amsden
2007-10-29 23:17 ` Ingo Molnar
2007-10-29 23:17 ` Ingo Molnar
2007-10-30 12:02 ` Glauber de Oliveira Costa
2007-10-30 12:02 ` Glauber de Oliveira Costa
2007-10-30 17:58 ` Zachary Amsden
2007-10-30 17:58 ` Zachary Amsden
2007-10-29 23:24 ` Dan Hecht
2007-10-29 23:24 ` Dan Hecht
2007-10-30 4:24 ` [kvm-devel] " Avi Kivity
2007-10-30 4:24 ` Avi Kivity
2007-10-30 7:14 ` Ingo Molnar
2007-10-30 7:14 ` Ingo Molnar
2007-10-30 11:59 ` Glauber de Oliveira Costa
2007-10-30 11:59 ` Glauber de Oliveira Costa
2007-10-30 0:17 ` H. Peter Anvin
2007-10-30 0:17 ` H. Peter Anvin
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