On Mon 2010-04-19 17:47:02, Arjan van de Ven wrote: > On Mon, 19 Apr 2010 16:29:39 +0100 > Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx> wrote: > > > On Monday 19 Apr 2010 14:46:17 Arjan van de Ven wrote: > > > On Mon, 19 Apr 2010 10:09:55 +0100 > > > > Or in other words, does a pure IO workload benefit from now higher > > > > selected frequency? > > > > > > no. > > > Mixed workloads do. > > > but pure IO workloads also don't suffer since while idle, the > > > voltage goes down anyway. > > > > You mean that higher frequency does not have effect on power use if > > CPU is idle? Is that true for all/most processors? > > this is true for most processors that I'm aware of. > there's exceptions for things like where the idle time is really short, Is not that exactly what will happen for 'cat /dev/<usb1>' case? Plus I suspect that older cpus are slower at changing voltages, and slower at powering down when idle... > > How and where in the code and how to enable that behaviour? From my > > experiments frequency goes down to minimum as soon as load goes away. > > What I was talking about is gradual lowering over a configurable > > period. It is not power efficient, but it could be good for latency > > in some workloads. > > it's not even good for that ;-( > > it's better then to stay high longer... at least on modern machines the > inbetween states are pretty much either useless or actually energy > hurting compared to the higher state. So what about hiding those from ondemand on modern hw? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
