On Mon, 2013-09-02 at 12:24 +0530, Srikar Dronamraju wrote: > If we face a runq lock contention, then domain_cost can go up. > The runq lock contention could be temporary, but we carry the domain > cost forever (i.e till the next reboot). How about averaging the cost + > penalty for unsuccessful balance. > > Something like > domain_cost = sched_clock_cpu(smp_processor_id()) - t0; > if (!pulled_task) > domain_cost *= 2; > > sd->max_newidle_lb_cost += domain_cost; > sd->max_newidle_lb_cost /= 2; > > > Maybe the name could then change to avg_newidle_lb_cost. > > > + > > + curr_cost += domain_cost; > > } > >
We tried keeping track of the avg in the v2 patch. It didn't really help reduce the contention in idle balancing and we needed to also reduce avg_idle by a factor of 10-20+ when comparing it to avg_idle_balance_cost in order to get the good performance boosts. One potential explanation why is that avg idle balance cost can often have a large variation. That would make both computing the avg_idle and comparing avg_idle with avg idle balance cost to not really be consistent. I think using the max allows us to keep the cost at a more constant rate so that we can more meaningfully compare avg_idle with respect to "idle balance cost". It also helps reduce the chance avg_idle overruns the balance cost. Patch 3 reduces the max cost so that the value isn't kept until the next reboot. -- 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/
