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Message-Id: <1165526445.27217.59.camel@laptopd505.fenrus.org>
Date: Thu, 07 Dec 2006 22:20:45 +0100
From: Arjan van de Ven <arjan@...radead.org>
To: Ingo Molnar <mingo@...e.hu>
Cc: Fernando Lopez-Lezcano <nando@...ma.Stanford.EDU>,
linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
Mike Galbraith <efault@....de>,
Clark Williams <williams@...hat.com>,
Sergei Shtylyov <sshtylyov@...mvista.com>,
Thomas Gleixner <tglx@...utronix.de>,
Giandomenico De Tullio <ghisha@...il.it>
Subject: Re: v2.6.19-rt6, yum/rpm
On Thu, 2006-12-07 at 21:58 +0100, Ingo Molnar wrote:
> * Fernando Lopez-Lezcano <nando@...ma.Stanford.EDU> wrote:
>
> > Much better performance in terms of xruns with Jackd. Hardly any at
> > all as it should be. I'm starting to test -rt8 right now.
> >
> > Now, I still don't have an smp machine to test so the improvement
> > could be because I'm just running 64 bit up instead of smp. Or it
> > could have been the hardware on that other machine that had some
> > problem (either because it was starting to fail or because the kernel
> > drivers for that hardware were somehow triggering the xruns).
>
> i think it's the UP vs. SMP difference. We are chasing some SMP
> latencies right now that trigger on boxes that have deeper C sleep
> states. idle=poll seems to work around those problems.
well C-states do cause latencies... as advertized in
the /proc/acpi/processor/CPU0/power file.
You can prevent linux from going into c-states that just take too long,
by setting the latency you can tolerate via the
set_acceptable_latency(). You can see the active maximum latency via the
same power file...
(right now audio playback is the main user of this api; of other parts
should use it too lets talk about it)
--
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org
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