Re: [patch 01/15] sched: (fixlet) dont update shares twice on on_rq parent

[Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>]

(2011/05/11 17:45), Mike Galbraith wrote:
> On Wed, 2011-05-11 at 01:13 -0700, Paul Turner wrote:
>> On Wed, May 11, 2011 at 12:55 AM, Hidetoshi Seto
>> <seto.hidetoshi@jp.fujitsu.com> wrote:
>>> (2011/05/10 17:32), Mike Galbraith wrote:
>>>> On Tue, 2011-05-10 at 16:14 +0900, Hidetoshi Seto wrote:
>>>>> This small fixlet can stand alone.
>>>>> Peter, how about getting this into git tree first?
>>>>
>>>> tip 2f36825b176f67e5c5228aa33d828bc39718811f contains the below.
>>>>
>>>>                 /* Don't dequeue parent if it has other entities besides us */
>>>> -               if (cfs_rq->load.weight)
>>>> +               if (cfs_rq->load.weight) {
>>>> +                       /*
>>>> +                        * Bias pick_next to pick a task from this cfs_rq, as
>>>> +                        * p is sleeping when it is within its sched_slice.
>>>> +                        */
>>>> +                       if (task_sleep && parent_entity(se))
>>>> +                               set_next_buddy(parent_entity(se));
>>>>                         break;
>>>> +               }
>>>>                 flags |= DEQUEUE_SLEEP;
>>>>         }
>>>
>>> Oh, thanks Mike!
>>> It seems that this change in tip is better one.
>>>
>>> Paul, don't you mind rebasing your patches onto tip/sched/core next time?
>>> (...or is there better branch for rebase?)
>>>
>>
>> I thought I had but apparently I missed this.
>>
>> We still need to set se = parent_entity(se) to avoid the pointless
>> double update below.
>>
>> Will definitely rebase.
> 
> Wish I could, wouldn't have 114 other patches just to get evaluation
> tree up to speed :)
> 
> Index: linux-2.6.32/kernel/sched_fair.c
> ===================================================================
> --- linux-2.6.32.orig/kernel/sched_fair.c
> +++ linux-2.6.32/kernel/sched_fair.c
> @@ -1308,12 +1308,15 @@ static void dequeue_task_fair(struct rq
> 
>                 /* Don't dequeue parent if it has other entities besides us */
>                 if (cfs_rq->load.weight) {
> +                       /* Avoid double update below. */
> +                       se = parent_entity(se);
> +
>                         /*
>                          * Bias pick_next to pick a task from this cfs_rq, as
>                          * p is sleeping when it is within its sched_slice.
>                          */
> -                       if (task_sleep && parent_entity(se))
> -                               set_next_buddy(parent_entity(se));
> +                       if (task_sleep && se)
> +                               set_next_buddy(se);
>                         break;
>                 }
>                 flags |= DEQUEUE_SLEEP;

Nice!

It will be better to put this fixlet out from the cfs-bandwidth series
and post as a single patch.


Thanks,
H.Seto