Re: [PATCH V2] sched: Improve load balancing in the presence of idle CPUs

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

> When a CPU is kicked to do nohz idle balancing, it wakes up to do load
> balancing on itself, followed by load balancing on behalf of idle CPUs.
> But it may end up with load after the load balancing attempt on itself.
> This aborts nohz idle balancing. As a result several idle CPUs are left
> without tasks till such a time that an ILB CPU finds it unfavorable to
> pull tasks upon itself. This delays spreading of load across idle CPUs
> and worse, clutters only a few CPUs with tasks.
> 

[..... snipped .... ]

> Fix this, by checking if a CPU was woken up to do nohz idle load
> balancing, before it does load balancing upon itself. This way we allow
> idle CPUs across the system to do load balancing which results in
> quicker spread of load, instead of performing load balancing within the
> local sched domain hierarchy of the ILB CPU alone under circumstances
> such as above.
> 
> Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
> ---


Looks good to me.

Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>