linux-kernel - Re: High cpu temperature with 2.6.32, bisection shows commit 69d258 (fwd)

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Message-Id: <20100112160734.89ee6b11.akpm@linux-foundation.org>
Date:	Tue, 12 Jan 2010 16:07:34 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dimitrios Apostolou <jimis@....net>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Alex Chiang <achiang@...com>, Len Brown <lenb@...nel.org>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: High cpu temperature with 2.6.32, bisection shows commit 69d258
 (fwd)

On Sun, 10 Jan 2010 03:05:38 +0200 (EET)
Dimitrios Apostolou <jimis@....net> wrote:

> On Sat, 9 Jan 2010, Arjan van de Ven wrote:
> 
> > On Sun, 10 Jan 2010 02:32:11 +0200 (EET)
> > Dimitrios Apostolou <jimis@....net> wrote:
> >
> >> On Sat, 9 Jan 2010, Arjan van de Ven wrote:
> >>
> >>> On Sun, 10 Jan 2010 01:55:42 +0200 (EET)
> >>> Dimitrios Apostolou <jimis@....net> wrote:
> >>>
> >>>> L8400B series Notebook PC
> >>>
> >>> can you try this patch?
> >>>
> >>
> >> OK I'm compiling a new kernel right now but that will take a while, I
> >> only have access to old hardware at the moment... What exactly this
> >> patch does?
> >>
> >
> > basically it appears that your machine, when the kernel asks for C2,
> > exits C2 immediately again.
> >
> > The old algorithm somehow caught this and stopped asking for C2 most of
> > the time; the new algorithm doesn't see any activity and asks for C2
> > again.
> >
> > What the patch does is tell the kernel to just not use C2 at all...
> 
> Indeed, in the past powertop always showed my processor idling in C1 
> state, and I wondered why it never entered C2. :-)
> 
> So thanks for the patch, I guess it works, and my bet is that this 
> case applies to L8400* (not only B models), except if it is fixed by some 
> old BIOS upgrade that I must have missed.
> 
> While testing your patch, indeed the temperature was not rising and 
> everything was normal, but the tsc was not marked as unstable so it didn't 
> switch to acpi_pm clocksource, so that was probably the reason.
> 

Arjan, can you please prepare a formal version of the fix?  I guess the
cc:stable will be needed as well.

I assume that the effects which Dimitrios described above were the
intended ones?

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