On 8 September 2015 at 14:26, Peter Zijlstra <pet...@infradead.org> wrote: > On Tue, Sep 08, 2015 at 09:22:05AM +0200, Vincent Guittot wrote: >> No, but >> sa->util_avg = (sa->util_sum << SCHED_CAPACITY_SHIFT) / LOAD_AVG_MAX; >> will fix the unit issue. > > Tricky that, LOAD_AVG_MAX very much relies on the unit being 1<<10. > > And where load_sum already gets a factor 1024 from the weight > multiplication, util_sum does not get such a factor, and all the scaling > we do on it loose bits.
fair point > > So at the moment we go compute the util_avg value, we need to inflate > util_sum with an extra factor 1024 in order to make it work. > > And seeing that we do the shift up on sa->util_sum without consideration > of overflow, would it not make sense to add that factor before the > scaling and into the addition? Yes this should save 1 left shift and 1 right shift >> > > Now, given all that, units are a complete mess here, and I'd not mind > something like: > > #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != SCHED_CAPACITY_SHIFT > #error "something usefull" > #endif In this case why not simply doing #define SCHED_CAPACITY_SHIFT SCHED_LOAD_SHIFT or the opposite ? > > somewhere near here. > > -- 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/
