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

Nate Lawson nate at
Mon Mar 13 20:49:13 UTC 2006

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.

>> 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.


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