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

Preeti U Murthy
2013-03-30T15:33:29Z

Hi,

On 03/30/2013 07:34 PM, Alex Shi wrote:
> On 03/30/2013 07:25 PM, Preeti U Murthy wrote:
>>>> 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.
>> I find the same situation on a physical machine too. On a 2 socket, 4
>> core machine as well. In fact, using trace_printks in the load balancing
>> part, I could find that the reason that the load was not getting
>> consolidated onto a socket was because the rq->util of a run-queue with
>> no processes on it, had not decayed to 0, which is why it would consider
>> the socket as overloaded and would rule out power aware balancing.All
>> this was on a physical machine.
>
> Consider of this situation, we may stop account the rq->util when
> nr_running is zero. Tasks will be a bit more compact. but anyway, that's
> powersaving policy.
>
True, the tasks will be packed a bit more compactly, but we can expect
the behaviour of your patchset *defaulting to performance policy when
overloaded*, to come to the rescue of such a situation.

Regards
Preeti U Murthy