On Tuesday 18 May 2010, Kevin Hilman wrote: > Arve Hjønnevåg <arve@xxxxxxxxxxx> writes: > > > > > PM: Opportunistic suspend support. > > > > Power management features present in the current mainline kernel are > > insufficient to get maximum possible energy savings on some platforms, > > such as Android, because low power states can only safely be entered > > from idle. Suspend, in its current form, cannot be used, since wakeup > > events that occur right after initiating suspend will not be processed > > until another possibly unrelated event wake up the system again. > > I think the problems with wakeups in the current suspend path need to > be described in more detail. In particular, why check_wakeup_irqs() > is not enough etc. That one is really easy.: because some (the majority of?) architectures don't even implement it. > > On some systems idle combined with runtime PM can enter the same power > > state as suspend, but periodic wakeups increase the average power > > consumption. Suspending the system also reduces the harm caused by > > apps that never go idle. On other systems suspend can enter a much > > lower power state than idle. > > > > To allow Android and similar platforms to save more energy than they > > currently can save using the mainline kernel, we introduce a mechanism > > by which the system is automatically suspended (i.e. put into a > > system-wide sleep state) whenever it's not doing useful work, called > > opportunistic suspend. > > A definition of "useful work" here would provide clarity and would > also help clarify by what criteria other on-going work is determined > to be not useful. Probably "useful" is not the right word here. I guess it's more like "work that can be deferred without visible impact on functionality". Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
