Re: [patch v6 03/21] sched: only count runnable avg on cfs_rq's nr_running

[Alex Shi <alex.shi@intel.com>]

On 04/02/2013 10:30 PM, Vincent Guittot wrote:
> On 30 March 2013 15:34, Alex Shi <alex.shi@intel.com> wrote:
>> Old function count the runnable avg on rq's nr_running even there is
>> only rt task in rq. That is incorrect, so correct it to cfs_rq's
>> nr_running.
>>
>> Signed-off-by: Alex Shi <alex.shi@intel.com>
>> ---
>>  kernel/sched/fair.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 2881d42..026e959 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -2829,7 +2829,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>>         }
>>
>>         if (!se) {
>> -               update_rq_runnable_avg(rq, rq->nr_running);
>> +               update_rq_runnable_avg(rq, rq->cfs.nr_running);
> 
> A RT task that preempts your CFS task will be accounted in the
> runnable_avg fields. So whatever you do, RT task will impact your
> runnable_avg statistics. Instead of trying to get only CFS tasks, you
> should take into account all tasks activity in the rq.

Thanks for comments, Vincent!

Yes, I know some rt task time was counted into cfs, but now we have no
good idea to remove them clearly. So I just want to a bit more precise
cfs runnable load here.
On the other side, periodic LB balance on combined the cfs/rt load, but
removed the RT utilisation in cpu_power.

So, PJT, Peter, what's your idea of this point?
> 
> Vincent
>>                 inc_nr_running(rq);
>>         }
>>         hrtick_update(rq);
>> --
>> 1.7.12
>>


-- 
Thanks Alex