Re: ACPI idle performance problem

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

On Tue, Mar 03, 2020 at 10:12:29PM +0000, Andrew Doran wrote:
> So this is burning power/CPU rather than saving it.  On the face of it I
> think we should put acpicpu's idle method under an option and come back to
> making it the default once the kinks are worked out, unless I have missed
> something.

A little more about this: if we consider only the P-states for the time
being (a.k.a. frequency scaling), the flag ACPICPU_DEP_SW_ANY indicates that
per-CPU (or per-CPU-group) states (frequencies) are possible.

So my original idea was that controls could be done with cpuctl(8) via an
ioctl. I had this working at some point, but I seem to have lost the patch. 
Besides allowing fine-grained controls (e.g., setting a frequency to the
minimum when putting a CPU offline), this would allow eventually deprecating
the sysctl nodes.

- Jukka