On Wed, 19 Dec 2018 at 16:30, Valentin Schneider <valentin.schnei...@arm.com> wrote: > > On 19/12/2018 15:20, Vincent Guittot wrote: > [...] > >> Oh yes, I never said it didn't work - I was doing some investigation on > >> the reason as to why we'd need this fix, because it's wasn't explicit from > >> the commit message. > >> > >> The rounding errors are countered by the +1, yes, but I'd rather remove > >> the errors altogether and go for the snippet I suggested in my previous > >> reply. > > > > except that you don't always want to migrate all group load. > > I prefer keeping current algorithm and fix it for now. Trying "new" > > thing can come in a 2nd step > > We already set the imbalance as the whole group load, we just introduce > rounding errors inbetween. As I've already said: > > in update_sg_lb_stats() we do: > > sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / > sgs->group_capacity; > > and in check_asym_packing() we do: > > env->imbalance = DIV_ROUND_CLOSEST( > sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity, > SCHED_CAPACITY_SCALE) > > So we end up with something like: > > group_load * SCHED_CAPACITY_SCALE * group_capacity > imbalance = -------------------------------------------------- > group_capacity * SCHED_CAPACITY_SCALE > > Which we could reduce down to: > > imbalance = group_load
ah yes, i thought the nr_running was involved but it's not the case. This looks better indeed > > and not get any rounding errors.
