Re: CVS commit: src/sys/uvm

[Andrew Doran <ad%netbsd.org@localhost>]

On Wed, Jan 22, 2020 at 10:08:16AM +1100, matthew green wrote:

> Andrew Doran writes:
> > I also recommend disabling ACPI idle, at least until it can be made less
> > aggressive by default.  It causes a significant slowdown.  It can be done
> > with detaching all acpicpu devices using "drvctl -d" on each.
> 
> this disables cpufreq support, doesn't it?  that seems like
> an unfortunate side effect..

I dunno, I assume so.  It seems like a tricky one to solve.

I think we could do with a heuristic that does a "fast idle" used when the
system is busy and a "low power idle" when things have gotten quiet.  And
the heuristic likely needs to be controllable with sysctl to suit
preferences (power consumption, performance).

We probably also want to take a CPU in low power idle out of
kcpuset_running, but that imposes its own penalty on x86 because it then
goes from using broadcast IPIs to sending directed IPIs to every CPU;
needs to be tried.

Also I don't know what to do about HyperThreading; it'd be nice if ACPI had
the smarts to handle it.

My problem with this one is I don't know what I'm missing here...  Maybe
time for a mail.

Andrew