linux-kernel - Re: 2.6.20.3-rt8 - DMA suffers excessive delay periodically

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Date:	Thu, 29 Mar 2007 15:31:35 -0400
From:	"Lee Revell" <rlrevell@...-job.com>
To:	"Kevin Perros" <kevin.perros@...e.fr>
Cc:	John <linux.kernel@...e.fr>, linux-kernel@...r.kernel.org
Subject: Re: 2.6.20.3-rt8 - DMA suffers excessive delay periodically

On 3/29/07, Kevin Perros <kevin.perros@...e.fr> wrote:
> > No it is an "indutrial" motherboard.
> > Although I don't know what makes it "industrial".
> >
> > Regards.
> >
> > Is this related to SMM?
> >
> > As far as I can tell, the BIOS is Phoenix AwardBIOS v6.00PG.
> >
> > Would someone know how to disable SMM in this BIOS?
>
> Usually you cannot disable SMM via the BIOS. You have to write chipset
> specific Kernel code for that.

The problem could also be something other than SMM, like DMA
starvation by a video or disk controller.  Try disabling all hard
drive controllers and booting from a CD or USB stick.

Also, try tweaking the expire_centisecs and writeback_centisecs values
in /proc/sys/vm and see if it changes the period of the glitches.

Lee
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