linux-kernel - Re: Performance/resume issues on Toshiba NB305

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Date:	Fri, 25 Feb 2011 14:27:48 -0600
From:	Seth Forshee <seth.forshee@...onical.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Performance/resume issues on Toshiba NB305

On Fri, Feb 25, 2011 at 03:17:47PM -0500, Steven Rostedt wrote:
> Would be helpful to Cc the people that may help you.
> 
> 
> On Fri, Feb 25, 2011 at 10:42:39AM -0600, Seth Forshee wrote:
> > I've been looking into a couple of problems with this machine that have
> > me a bit stumped at the moment. The two problems may or may not be
> > related, so I'm including details about both issues below. If anyone has
> > any ideas, I'd love to hear them. Note that these are not recent
> > regressions; they've been around since at least 2.6.32.
> > 
> > The CPU in this machine is an Atom N450.
> > 
> > When booted normally the performance on this machine is very poor, but
> > when booted with any of nohz=off, nolapic, or nohpet it improves
> > significantly. The performance also improves if I use the patch below to
> > force the hpet to remain in periodic mode (with hpet=periodic on the
> > command line).
> > 
> > One other thing I noticed when I had added some logging related to hpet
> > rearming is 3-5 second periods of no log activity occurring fairly
> > frequently, whereas such inactive periods are infrequent when
> > performance is good and are also infrequent on another machine with very
> > similar hardware and no performance issues.
> > 
> > The machine also hangs for 5 minutes during resume, unless booted with
> > both nohz=off and highres=off, or with hpet=periodic using the patch
> > below. I've traced this down to hanging in an SMI handler during the
> > ACPI _WAK method execution. The 5 minutes corresponds to how long it
> > takes for the low 32 bits of the hpet to wrap in this machine, and since
> > the options that eliminate the hang result in the hpet being in periodic
> > mode during _WAK method execution I suspect that the SMI handler is
> > hanging until a timer interrupt happens.
> > 
> > One possible explanation here is that the performance problems are also
> > related to hangs in SMI handlers until there's a timer interrupt,
> > although I don't know how that explains why some of the command line
> > options eliminate the performance issues.
> 
> Sounds like a buggy BIOS to me. Is there upgrades available for this
> box?

It does sound like a buggy BIOS. I've already flashed the latest BIOS
though, so no luck there.
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