On Mon, Jan 13, 2014 at 9:20 AM, Philip Guenther <guent...@gmail.com> wrote: > C0 is the only state where the CPU does real work; the higher C-states > only make sense for when the CPU is idle, so your question presumably > is "does the CPU get put into a higher C-state when idle". Well, > 5.4-current uses the MWAIT instruction for the idle loop when > available, which uses the C1 state by default. > > Have people found 5.4-current to use less power/run cooler since the > MWAIT change in early October? > > The MWAIT instruction can put the CPU into a higher C-state if the CPU > supports it, but we don't use or expose that yet. I have no interest > in adding Yet Another Knob, but maybe making the decision based off > the existing hw.setperf sysctl would be reasonable and sufficient, > overloading the range to not just change the speed but also use a > deeper C-state hw.setperf is smaller, ala > C3 <- 0-33 > C2 <- 34-65 > C1 <- 66-100 > > Or maybe that's a bad idea.
Thanks for the explanation, it was very informative. This would most likely solve my problem. But as other people have said it probably should be a separate sysctl if implemented. John
