On 15 December 2015 at 13:20, Peter Zijlstra <pet...@infradead.org> wrote: > On Tue, Dec 15, 2015 at 09:50:14AM +0100, Luca Abeni wrote: >> On 12/15/2015 05:59 AM, Vincent Guittot wrote: > >> >The 2nd definition is used to compute the remaining capacity for the >> >CFS scheduler. This one doesn't need to be updated at each wake/sleep >> >of a deadline task but should reflect the capacity used by deadline in >> >a larger time scale. The latter will be used by the CFS scheduler at >> >the periodic load balance pace > >> Ok, so as I wrote above this really looks like an average utilisation. >> My impression (but I do not know the CFS code too much) is that the mainline >> kernel is currently doing the right thing to compute it, so maybe there is no >> need to change the current code in this regard. >> If the current code is not acceptable for some reason, an alternative would >> be to measure the active utilisation for frequency scaling, and then apply a >> low-pass filter to it for CFS. > > So CFS really only needs a 'vague' average idea on how much time it will > not get. Its best effort etc., so being a little wrong isn't a problem. > > The current code suffices, but I think the reason its been changed in > this series is that they want/need separate tracking for fifo/rr and > deadline in the next patch, and taking out deadline like proposed was > the easiest way of achieving that.
yes. you're right. The goal was to minimize the overhead for tracking separately fifo/rr and deadline. > > -- 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/
