On Thu, Feb 20, 2014 at 12:09:43PM +0100, Thomas Gleixner wrote: > On Thu, 20 Feb 2014, Alexey Perevalov wrote: > > From: Anton Vorontsov <an...@enomsg.org> > > > > This patch implements a userland-side API for generic deferrable timers, > > per linux/timer.h: > > > > * A deferrable timer will work normally when the system is busy, but > > * will not cause a CPU to come out of idle just to service it; instead, > > * the timer will be serviced when the CPU eventually wakes up with a > > * subsequent non-deferrable timer. > > > > These timers are crucial for power saving, i.e. periodic tasks that want > > to work in background when the system is under use, but don't want to > > cause wakeups themselves. > > > > The deferred timers are somewhat orthogonal to high-res external timers, > > since the deferred timer is tied to the system load, not just to some > > external decrementer source. > > Again this changelog makes no sense. What's orthogonal to high-res > timers and why are they external?
Not trying to defend the current series, just felt the need clarify this one. By orthogonal I meant that comparing to high resolution timers' use cases, deferred timers can be super-low resolution, super inaccurate. We don't know exactly when they will fire, all we know is something like "every 0.2 seconds, iff the system/user is doing something, otherwise don't bother." As for external (my bad, shouldn't invent personal terminology): the hrtimers are tied to some clock source (which is "external" to me), but deferred timers are mostly tied to the system's activity. Thanks, Anton -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
