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