On Thu, Aug 19, 2010 at 04:10:10PM -0700, david@xxxxxxx wrote: > On Fri, 13 Aug 2010, Paul E. McKenney wrote: > > >On Thu, Aug 12, 2010 at 08:52:22PM +0300, Felipe Contreras wrote: > >>On Thu, Aug 12, 2010 at 7:19 PM, Paul E. McKenney > >><paulmck@xxxxxxxxxxxxxxxxxx> wrote: > >>>On Thu, Aug 12, 2010 at 03:17:29AM +0300, Felipe Contreras wrote: > >>>>>It seems to me that the same social-engineering approaches work in > >>>>>both cases. > >>>> > >>>>Yes, but if dynamic PM works as advertised, you don't need > >>>>opportunistic suspend. > >>> > >>>For dynamic power management to totally eliminate the need for something > >>>like suspend blockers, you are having to make some brave assumptions. > >>>Yes, dynamic power management is quite useful, but there is a big > >>>difference between something being useful and something doing everything > >>>for everyone. You have not yet convinced me that dynamic power management > >>>will make it to the "doing everything for everyone" stage. > >> > >>As it has been explained before, there's a sweet-spot of idleness: > >>http://article.gmane.org/gmane.linux.kernel/995525 > >>http://article.gmane.org/gmane.linux.ports.arm.omap/37982 > >> > >>Do you agree that there's such a thing, and if so, do you agree that > >>the benefits of opportunistic suspend are much less once that point is > >>reached? > > > >I agree that there will be a sweet spot of idleness (though I would call > >it a "point of diminishing returns"), but only if all the applications > >are power-optimized. The advantage of opportunistic suspend is instead > >its tolerance of power-oblivious applications with minimal degradation > >of battery life. > > sorry for the late response, the last week has been very hectic. > > I just wanted to note that there is already a tool in the kernel to > deal with this, the timer jitter/fuzz control. This can be set by an > application for itself, or it can be set by some other process for > an application (I don't remember the details of all the ways this > can be set) > > This could be used in a way similar to how userspace wakelocks are > set today, if the power management process (that holds the wakelock > and keep sthe screen lit today) thinks the system should be awake, > let the jitter/fuzz be small, if that process thinks the system > should probably be asleep, set the jitter/fuzz to a larger value. If > other things are running anyway, the timers can fire and be serviced > normally, otherwise the kernel is free to delay the timer going off > even for badly written processes. Indeed, Rafael and Alan Stern are working to make pm_qos do what the Android guys need, which could (very roughly) be thought of as extending the jitter/fuzz such that it meets Android's requirements. Thanx, Paul _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
