lkml.org 
[lkml]   [2015]   [Jan]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 5/7] sched/fair: fix idle balance when remaining tasks are all non-CFS tasks
On Mon, Jan 19, 2015 at 01:45:28PM +0100, Peter Zijlstra wrote:
>On Wed, Nov 26, 2014 at 08:44:05AM +0800, Wanpeng Li wrote:
>> The overload indicator is used for knowing when we can totally avoid load
>> balancing to a cpu that is about to go idle. We can avoid load balancing
>> when no cpu has cfs task and both rt and deadline have push/pull mechanism
>> to do their own balancing.
>>
>> However, rq->nr_running on behalf of the total number of each class tasks
>> on the cpu, do idle balance when remaining tasks are all non-CFS tasks does
>> not make any sense.
>>
>> This patch fix it by idle balance when there are still other CFS tasks in
>> the rq's root domain.
>>
>
>Please always try and Cc the people who touched that code last; for the
>idle_balance bits commit 4486edd12b5a ("sched/fair: Implement fast
>idling of CPUs when the system is partially loaded") gives a fair clue
>as to who that would be.
>
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index 31f1e4d..f7dd978 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -1269,7 +1269,8 @@ static inline void add_nr_running(struct rq *rq, unsigned count)
>>
>> rq->nr_running = prev_nr + count;
>>
>> - if (prev_nr < 2 && rq->nr_running >= 2) {
>> + if (prev_nr < 2 && rq->nr_running >= 2 &&
>> + rq->cfs.h_nr_running > 0) {
>> #ifdef CONFIG_SMP
>> if (!rq->rd->overload)
>> rq->rd->overload = true;
>
>Here 3882ec643997 ("nohz: Use IPI implicit full barrier against
>rq->nr_running r/w") might be a clue.
>
>Also, this is wrong, it breaks NOHZ_FULL.

Got it. If the modification in update_sg_lb_stats of my patch is still
corrrect, if so I can send out a new version.

Regards,
Wanpeng Li


\
 
 \ /
  Last update: 2015-01-20 00:41    [W:0.143 / U:2.920 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site