On 2017/7/17 17:21, Peter Zijlstra wrote: > On Fri, Jul 14, 2017 at 09:03:14AM -0700, Andi Kleen wrote: >> fast idle doesn't have an upper bound. >> >> If the prediction exceeds the fast idle threshold any C state can be used. >> >> It's just another state (fast C1), but right now it has an own threshold >> which may be different from standard C1. > > Given it uses the same estimate we end up with: > > > Now, unless you're mister Turnbull, C2 will never get selected when > fast_threshold > C2_threshold. > > Which is wrong. If you want to effectively scale the selection of C1, > why not also change the C2 and further criteria. > That's not our intention, I think. As long as the predicted coming idle period > threshold, we'll enter normal idle path, you can select any supported c-states, tick can also be turned off for power saving. Any deferrable stuff can be invoke as well because we'll sleep long enough.
Thanks, -Aubrey
