On Sun, May 22, 2016 at 01:42:52PM -0700, Steve Muckle wrote: > > So does it actually matter what the frequency is when you idle? Isn't > > the whole thing clock gated anyway? > > > > Because this seems to generate contradictory requirements, on the one > > hand we want to stay idle as long as possible while on the other hand > > you seem to want to clock down while idle, which requires not being > > idle. > > > > If it matters; should not your idle state muck explicitly set/restore > > frequency? > > AFAIK this is very platform dependent. Some will waste more power than > others when a CPU idles above fmin due to things like resource (bus > bandwidth, shared cache freq etc) voting.
Oh agreed, completely platform dependent. 'Luckily' all this cpuidle is already very platform dependent. > It is also true that there is power spent going to fmin (and then > perhaps restoring the frequency when idle ends) which will be in part a > function of how slow the frequency change operation is on that platform. Agreed. > I think Daniel Lezcano (added) was exploring the idea of having cpuidle > drivers take the expected idle duration and potentially communicate to > cpufreq to reduce the frequency depending on a platform-specific > cost/benefit analysis. Right; that's along the lines I was thinking. If the idle guestimate and the idle QoS both allow (ie. it wins on power and doesn't violate wake-up latency) muck with DVSF on the idle path. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
