linux-kernel - Re: intel_ips produces constant load of 1

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Date:	Tue, 22 Mar 2011 08:49:58 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Andreas Hartmann <andihartmann@...enet.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: intel_ips produces constant load of 1

On Tue, 22 Mar 2011 08:00:39 +0100
Andreas Hartmann <andihartmann@...enet.de> wrote:

> Jesse Barnes wrote:
> > On Sat, 19 Mar 2011 16:38:38 +0100
> > Andreas Hartmann <andihartmann@...19freenet.de> wrote:
> > 
> >> Hello,
> >>
> >> on my MSI CR620 laptop, intel_ips produces a constant load of 1, even if
> >> the machine is idle.
> >>
> >> The ips-monitor hangs in D state:
> >>
> >> ps aux | grep ips
> >> root       593  0.0  0.0      0     0 ?        S    17:20   0:00
> >> [ips-adjust]
> >> root       594  0.0  0.0      0     0 ?        D    17:20   0:00
> >> [ips-monitor]
> >>
> >> If the module isn't loaded, the load of the machine in idle mode is 0 as
> >> expected.
> > 
> > This is a reporting problem, and probably due to the schedule() call
> > and associated task state in the ips-monitor thread.  I thought setting
> > the task state to interruptible would prevent this, but it seems like
> > it's not enough for the deferrable on-stack timers?
> > 
> > At any rate, it's not actually causing increased CPU usage, so you can
> > safely ignore it until we have a fix.
> > 
> 
> I've got one more question (I found
> http://forum.soft32.com/linux/RFC-Intelligent-power-sharing-driver-ftopict510146.html):
> 
> Where is the difference to the functionality the bios provides? I can't
> see (and hear :-)) any difference between with intel_ips and without
> intel_ips.
> The fan always runs at a minimal speed, very quiet.
> The fan is getting loader, if the load is getting high (during
> compile-sessions e.g.). If the compile session is ready, the fan get's
> slower again.
> 
> If I check the "cpu MHz" in /proc/cpuinfo with or without intel_ips, I
> can't see any difference. The value never exceeds the value given in the
> model name. The lowest values are equal, too.
> 
> 
> What is the added value compared to the bios functionality? How can I
> check it?

Loading the IPS driver will allow graphics turbo.  This can improve gfx
performance quite a bit (up to 3x on some synthetic workloads).  If
you're not really using gfx though, the driver won't really do anything
for you.

-- 
Jesse Barnes, Intel Open Source Technology Center
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