From: Daniel Walker <dwalker@mvista.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: john stultz <johnstul@us.ibm.com>, Andi Kleen <ak@suse.de>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Con Kolivas <kernel@kolivas.org>,
Rusty Russell <rusty@rustcorp.com.au>,
Zachary Amsden <zach@vmware.com>,
James Morris <jmorris@namei.org>,
Chris Wright <chrisw@sous-sol.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
cpufreq@lists.linux.org.uk,
Virtualization Mailing List <virtualization@lists.osdl.org>
Subject: Re: Stolen and degraded time and schedulers
Date: Tue, 13 Mar 2007 14:27:04 -0700 [thread overview]
Message-ID: <1173821224.1416.24.camel@dwalker1> (raw)
In-Reply-To: <45F70A71.9090205@goop.org>
On Tue, 2007-03-13 at 13:32 -0700, Jeremy Fitzhardinge wrote:
> Most of the existing clocksource infrastructure would only operate on
> CLOCK_TIMEBASE_REALTIME clocksources, so I'm not sure how much overlap
> there would be here. In the case of dealing with cpufreq, there's a
> certain appeal to manipulating the shift/mult parameters to reflect the
> fractional speed of a cpu as it changes.
The frequency tracking you mention is done to some extent inside the
timekeeping adjustment functions, but I'm not sure it's totally accurate
for non-timekeeping, and it also tracks things like interrupt latency.
Tracking frequency changes where it's important to get it right
shouldn't be done I think ..
If you want accurate time accounting, don't use the TSC .
> sched_clock would definitely be the interface which exposes all this
> stuff to the rest of the kernel. After all, its basically a very simple
> interface, though the backend implementation details may not be.
The sched_clock interface is basically a stripped down clocksource..
I've implemented sched_clock as a clocksource in the past ..
> We currently have a sched_clock interface in paravirt_ops to deal with
> the hypervisor aspect. It only occurred to me this morning that cpufreq
> presents exactly the same problem to the rest of the kernel, and so
> there's room for a more general solution.
Are there other architecture which have this per-cpu clock frequency
changing issue? I worked with several other architectures beyond just
x86 and haven't seen this issue ..
Daniel
next prev parent reply other threads:[~2007-03-13 21:27 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-13 16:31 Stolen and degraded time and schedulers Jeremy Fitzhardinge
2007-03-13 20:12 ` john stultz
2007-03-13 20:32 ` Jeremy Fitzhardinge
2007-03-13 21:27 ` Daniel Walker [this message]
2007-03-13 21:59 ` Jeremy Fitzhardinge
2007-03-14 0:43 ` Dan Hecht
2007-03-14 4:37 ` Jeremy Fitzhardinge
2007-03-14 13:58 ` Lennart Sorensen
2007-03-14 15:08 ` Jeremy Fitzhardinge
2007-03-14 15:12 ` Lennart Sorensen
2007-03-14 19:02 ` Dan Hecht
2007-03-14 19:34 ` Jeremy Fitzhardinge
2007-03-14 19:45 ` Rik van Riel
2007-03-14 19:47 ` Jeremy Fitzhardinge
2007-03-14 20:02 ` Rik van Riel
2007-03-14 20:26 ` Dan Hecht
2007-03-14 20:31 ` Jeremy Fitzhardinge
2007-03-14 20:46 ` Dan Hecht
2007-03-14 21:18 ` Jeremy Fitzhardinge
2007-03-15 19:09 ` Dan Hecht
2007-03-15 19:18 ` Jeremy Fitzhardinge
2007-03-15 19:48 ` Rik van Riel
2007-03-15 19:53 ` Jeremy Fitzhardinge
2007-03-15 20:07 ` Dan Hecht
2007-03-15 20:14 ` Rik van Riel
2007-03-15 20:35 ` Dan Hecht
2007-03-16 8:59 ` Martin Schwidefsky
2007-03-14 20:38 ` Ingo Molnar
2007-03-14 20:59 ` Jeremy Fitzhardinge
2007-03-16 8:38 ` Ingo Molnar
2007-03-16 16:53 ` Jeremy Fitzhardinge
2007-03-15 5:23 ` Paul Mackerras
2007-03-15 19:33 ` Jeremy Fitzhardinge
2007-03-14 2:00 ` Daniel Walker
2007-03-14 6:52 ` Jeremy Fitzhardinge
2007-03-14 8:20 ` Zan Lynx
2007-03-14 16:11 ` Daniel Walker
2007-03-14 16:37 ` Jeremy Fitzhardinge
2007-03-14 16:59 ` Daniel Walker
2007-03-14 17:08 ` Jeremy Fitzhardinge
2007-03-14 18:06 ` Daniel Walker
2007-03-14 18:41 ` Jeremy Fitzhardinge
2007-03-14 19:00 ` Daniel Walker
2007-03-14 19:44 ` Jeremy Fitzhardinge
2007-03-14 20:33 ` Daniel Walker
2007-03-14 21:16 ` Jeremy Fitzhardinge
2007-03-14 21:34 ` Daniel Walker
2007-03-14 21:42 ` Jeremy Fitzhardinge
2007-03-14 21:36 ` Con Kolivas
2007-03-14 21:38 ` Jeremy Fitzhardinge
2007-03-14 21:40 ` Con Kolivas
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