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

Kris Kennaway kris at
Mon Mar 13 20:57:57 UTC 2006

On Mon, Mar 13, 2006 at 12:46:46PM -0800, Nate Lawson wrote:
> Kris Kennaway wrote:
> >On Mon, Mar 13, 2006 at 09:03:35AM -0800, Nate Lawson wrote:
> >
> >>>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.
> >>Are you sure that's the cause?  (Does setting cx_lowest to C1 fix it?) 
> >
> >Absolutely sure: the system worked at C1 after boot, then I set it to
> >C2, observed that beeping was broken, then set it back to C1 and
> >observed that it worked again.
> Ok, good to know.  This looks like a different failure mode where 
> occasionally the system is waking up from the idle too often, but not 
> enough to affect system performance.

Actually when I retried C2, performance is bad again.  e.g. opening a
mailbox in mutt pauses for about 30 seconds before it starts to read
the mailbox.

top shows CPU activity ping-ponging between:

CPU states:  0.0% user,  0.0% nice, 50.0% system,  0.0% interrupt, 50.0% idle


CPU states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle

> >>Can you send the output of sysctl hw.acpi so we can see how often each 
> >>cx type is being run?
> >
> >hw.acpi.cpu.cx_supported: C1/0 C2/1
> >hw.acpi.cpu.cx_lowest: C1
> >hw.acpi.cpu.cx_usage: 100.00% 0.00%
> I'd like to see it after you've set it to C2 for a few minutes.  I'm 
> looking to see what happens with cx_usage.

It stays at hw.acpi.cpu.cx_usage: 0.00% 100.00% always.

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