Problems with hw.acpi.cpu.cx_lowest=C2 (Re: cvs commit: src/etc/defaults rc.conf)

[Kris Kennaway]

On Sun, Jan 29, 2006 at 01:30:07AM -0500, Kris Kennaway wrote:
> On Sat, Jan 28, 2006 at 10:17:47PM -0800, Nate Lawson wrote:
> > Kris Kennaway wrote:
> > >On Sun, Jan 29, 2006 at 01:06:54AM -0500, Kris Kennaway wrote:
> > >
> > >>On Sun, Jan 29, 2006 at 05:51:58AM +0000, Nate Lawson wrote:
> > >>
> > >>>njl         2006-01-29 05:51:58 UTC
> > >>>
> > >>> FreeBSD src repository
> > >>>
> > >>> Modified files:
> > >>>   etc/defaults         rc.conf 
> > >>> Log:
> > >>> Enable the lowest Cx state by default.  This will save power and we have
> > >>> had enough testing of acpi_cpu to know this is stable now.
> > >>
> > >>On my desktop system (running RELENG_6 though), setting
> > >>hw.acpi.cpu.cx_lowest=C0 causes atrocious performance.  Is it broken
> > >>in 6.x?
> > >
> > >C2, sorry.
> > 
> > Ah, C0 should be disallowed already I thought (try it).
> > 
> > As for C2, I MFCd a patch to acpi_cpu.c in November that should prevent 
> > this (1.57.2.1).  Do you get a printf on console?
> 
> This might be it: turns out I never rebooted to the newer kernel I
> built earlier this month, and I am still running a kernel from Nov 6.
> I'll get back to you.

I finally managed to test this in RELENG_6.  The system performance is
not obviously bad, but sound playback is distorted (e.g. the 'bell' in
KDE is much higher pitched than it should be, and on the console it is
low pitched and lasting about 3 seconds).  Nothing is logged on
console.

There may be other problems that I didn't notice right away, but the
sound problems were enough to make me turn it off again.

Kris



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