How/why would dev.cpu.0.freq_levels change??!?

[David Wolfskill]

On Sun, Jun 29, 2008 at 06:43:36PM -0400, Alexandre Sunny Kovalenko wrote:
> I am coming in late in the thread, so if I have misunderstood your
> problem, I do apologize.

Not at all; thank you for your suggestions!

> ...
> > * As you can see, this can lead to the "interesting" situation that the
> >   current CPU frequency is higher than the maximum "available."
> >From my (somewhat limited) understanding of the ACPI spec, BIOS can
> change _PSS object (one containing available clock frequencies) and
> issue notification to the OS to reevaluate said object. There is no
> requirement that BIOS change current CPU frequency while doing that.

OK; I confess ignorance on that score: I'm posting to -acpi because I
rather suspect that ACPI is (at least) profoundly implicated in what's
going on, if not responsible for it.

> You can try to dump your ASL and see if anything there messes up with
> _PSS and then issues Notify (xxx.CPU0, 0x80) on the same breath. Killing
> that piece of ASL dead should ensure constant CPU frequencies set. ???You
> can post your ASL someplace where I can get to it, I just could not
> promise that I'll understand it much better than you.

I ran

	sudo acpidump -dt -o >laptop.i8200.dsdt >laptop.i8200.asl

and placed the results in www.catwhisker.org:~david/public_html/FreeBSD/,
so <http://www.catwhisker.org/~david/FreeBSD/laptop.i8200.asl> and
<http://www.catwhisker.org/~david/FreeBSD/laptop.i8200.dsdt> should
work.  I just tried it from my laptop (sick as it is), and the MD5
hashes matched.  They are:

g1-60(6.3-S)[6] md5 laptop.i8200.*
MD5 (laptop.i8200.asl) = 7c83c27ad30bbd0957f10a5a3ffc90e5
MD5 (laptop.i8200.dsdt) = c290ab9be7c97eb7ae98523a5f5a4ddc
g1-60(6.3-S)[7] 

> > * The phenomenon is not limited to when I run RELENG_6; in an effort to
> >   avoid the continuous fan whine, I tried running RELENG_7 for a while,
> >   and encountered a recurrence rather quickly.  :-(
> If it is the mechanism, I have described above, I would expect it to
> behave similarly under RELENG_6 and RELENG_7.

Right.  Until I had encountered it as reported above, I hadn't seen an
occurrence of the phenomenon under either RELENG_7 or HEAD.

> > * I tried firing up the Dell diagnostics; they reported OK for each of
> >   the CPU & motherboard fans at high speed, but when the diags tried to
> >   switch to low speed, they reported that the fans only went down (from
> >   10-11K RPM) to about 7K RPM instead of 5K RPM. 
> I just emptied can of compressed air into all of the orifices of my
> ThinkPad X60 with the end result of average running temperature dropping
> about 7C and fan speed reduced appropriately. I am surprised no one
> suggested this yet.

Well, in fairness, the reported temperature is quite low:  I get reports
(from sysctl hw.acpi.thermal.tz0.temperature) of around 85C for extended
periods during a "make buildworld," but the reported temperature when
this sort of thing occurs is around 45C.

On the other hand, this did just start happening recently -- within the
last 4-5 days.

> > I still don't know what the problems are, but it's apparent that
> > something outside FreeBSD's control is misbehaving.  Given that, I
> > suppose it would be unreasonable to expect FreeBSD to compensate
> > in an attempt to enforce rationality.  :-(
> Why not -- I had powerd patch (now obsolete) to compensate for the
> excess of the thermal paste under the CPU heatsink -- the sky is the
> limit.

Hmmm....

> > Which still leaves me wondering what type(s) of evasive actions
> > make sense: I've become rather accustomed to using a laptop with a
> > 1600x1200 screen, and finding another laptop similarly-equipped
> > (but newer) at a reasoonable price that will run FreeBSD well appears
> > to be somewhat of a challenge.  I'm open to suggestions.
> If you are looking for suggestion on the replacement laptop model --
> ThinkPad T42p (aftermarket) should fit the bill nicely, otherwise, see
> above.

Thanks for the suggestion; I will look into it.

> > Maybe I should just see if the local laptop repair place can fix it. :-(
> ... or start with the canned air.

Well, I did just disassemble the whole thing -- it's actually a
somewhat curious mix of a couple of used i8200s plus a handful of
spare parts I've bought.  I managed to remove some dust & a few cat
hairs, but there was no effective change in beavior.

I tried swapping my disk drive for the one that came with it (and
which has Windows XP on it).  At first, the phenomenon (fans full
on; CPU throttled to half-speed) wouldn't recur, but eventually,
it seems to have done.  (At least I could tell that the fans were
full on and that the machine was often marginally responsive to
(e.g.) mouse movements.) I have no idea how to find out about ACPI
stuff (or much of anything else) in a Microsoft environment -- I
did this in preparation for bringing the machine to a repair shop:
I figured they'd want the Microsoft environment (and unless the
problem existed there, it wouldn't be "real"), and I certainly
didn't want to entrust my FreeBSD disk to their tender mercies.  :-{

Thanks again for the suggestions so far.

Peace,
david
-- 
David H. Wolfskill				david at catwhisker.org
I submit that "conspiracy" would be an appropriate collective noun for cats.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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