Re: [patch 3/6] sched, nohz: sched group, domain aware nohz idle load balancing

Peter Zijlstra
2011-11-24T11:54:02Z

On Fri, 2011-11-18 at 15:03 -0800, Suresh Siddha wrote:
> Make nohz idle load balancing more scalabale by using the nr_busy_cpus in
> the struct sched_group_power.
>
> Idle load balance is kicked on one of the idle cpu's when there is atleast
> one idle cpu and
>
> - a busy rq having more than one task or
>
> - a busy scheduler group having multiple busy cpus that exceed the sched group
> power or
>
> - for the SD_ASYM_PACKING domain, if the lower numbered cpu's in that
> domain are idle compared to the busy ones.
>
> This will help in kicking the idle load balancing request only when
> there is a real imbalance. And once it is mostly balanced, these kicks will
> be minimized.
>
> These changes helped improve the workload that is context switch intensive
> between number of task pairs by 2x on a 8 socket NHM-EX based system.

OK, but the nohz idle balance will still iterate the whole machine
instead of smaller parts, right?