linux-kernel - Re: Keyboard Stuttering

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Date:	Thu, 12 Oct 2006 12:12:44 -0400
From:	Lee Revell <rlrevell@...-job.com>
To:	john stultz <johnstul@...ibm.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Frank Sorenson <frank@...rocks.com>,
	linux-kernel@...r.kernel.org, David Gerber <dg-lkml@...ek.com>
Subject: Re: Keyboard Stuttering

On Tue, 2006-10-10 at 11:25 -0700, john stultz wrote:
> On Tue, 2006-10-10 at 13:09 -0400, Dmitry Torokhov wrote:
> > > Same problem here. Intel Core 2 Duo with 2.6.19-rc1 x86_64 SMP. Happens on
> > > 2.6.17 too. I use 'noapic' as a workaround but that disables one of the CPU
> > > core of course.
> > >
> > > I cannot reproduce the problem within the console nor gdm. Only on the X
> > > desktop.
> > >
> > 
> > John,
> > 
> > It looks like the only clocksource available on David's box is
> > "jiffies" although the processor shows that it supporst tsc and PM
> > timer is enabled and I think that this is what causes keyboard
> > stuttering in X. See http://bugzilla.kernel.org/show_bug.cgi?id=7291.
> > I believe clocksources is your turf, could you please take a look at
> > this.
> 
> Sure thing. I followed up in the bug, but I don't think the clocksource
> code is involved. x86_64 hasn't converted to GENERIC_TIME, so jiffies is
> what we use to increment xtime, but the TSC, ACPI PM, or HPET is used
> for gettimeofday, etc. 
> 
> I suspect C3 idling is the culprit, since noapic works around the issue.

Wait, does this mean that Intel's x86-64 implementation has the same
buggy TSC as AMD's?

Lee

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