Messages in this thread |  | | | Subject | Re: [RFC] maximum latency tracking infrastructure | | From | Daniel Walker <> | | Date | Thu, 24 Aug 2006 15:16:35 -0700 |
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On Thu, 2006-08-24 at 23:57 +0200, Arjan van de Ven wrote: > > I was just thinking that it might be cleaner to register a structure > > instead of tracking identifiers to usecs. You might get a speed up on > > some of the operations, like unregister. > > it makes things a lot more complex for both the user and the > infrastructure though, and I doubt it's going to be a performance gain; > you need to walk all registered items anyway to decide the new minimum > value if you unregister one for example.
Might be time for a priority list (lib/plist.c), but that might be like swatting a gnat with a sledge hammer.
> > Another thing I was thinking about is that this seems somewhat contrary > > to the idea of using dynamic tick (assuming it was in mainline) to > > heuristically pick a power state. Do you have any thoughts on how you > > would combine the two? > > Actually it's designed in part FOR this case! > So how that will work (thought experiment, I don't have the code yet) > > In idle, determine the time the next scheduled event is. > Then given that time go over the C-states and pick the deepest C-state > that > 1) satisfies the requested latency > 2) has a latency that is a small enough fraction of the total time > > (2 is needed to not pick a 1 msec-latency C state for a 1ms idle, that > won't save you power most likely, so you need to have enough time in > "real" idle) > > so when you know your latency requirements, you now can pick a DEEPER > sleepstate than you could before (or at least the right one)... dynticks > needs this more than anything :)
Sounds pretty good. Since dynamic tick tracks timer events one could also add a method to track interrupts in general if they are regular enough to do so. That's just thinking while typing, so it might not be sane.
Daniel
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