Re: [patch v5 14/15] sched: power aware load balance

Alex Shi
2013-03-29T13:40:14Z

On 03/29/2013 08:42 PM, Preeti U Murthy wrote:
>> > did you try the simplest benchmark: while true; do :; done
> Yeah I tried out this while true; do :; done benchmark on a vm which ran

Thanks a lot for trying!

What's do you mean 'vm'? Virtual machine?

> on 2 socket, 2 cores each socket and 2 threads each core emulation.
> I ran two instances of this loop with balance policy on, and it was
> found that there was one instance running on each socket, rather than
> both instances getting consolidated on one socket.
>
> But when I apply the change where we do not consider rq->util if it has
> no nr_running on the rq,the two instances of the above benchmark get
> consolidated onto one socket.
>
>

I don't know much of virtual machine, guess the unstable VCPU to CPU pin
cause rq->util keep large? Did you try to pin VCPU to physical CPU?

I still give the rq->util weight even the nr_running is 0, because some
transitory tasks may actived on the cpu, but just missed on balancing point.

I just wondering that forgetting rq->util when nr_running = 0 is the
real root cause if your finding is just on VM and without fixed VCPU to
CPU pin.

--
Thanks
Alex