Date: Thu, 13 Aug 2015 08:57:41 +0900
From: Byungchul Park <byungchul.park@lge.com>
To: Yuyang Du <yuyang.du@intel.com>
Cc: mingo@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] sched: sync with the prev cfs when changing cgroup
 within a cpu
Message-ID: <20150812235741.GM3956@byungchulpark-X58A-UD3R>
References: <1439363115-2259-1-git-send-email-byungchul.park@lge.com>
 <20150812010548.GA28764@intel.com>
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On Wed, Aug 12, 2015 at 09:05:48AM +0800, Yuyang Du wrote:
> On Wed, Aug 12, 2015 at 04:05:15PM +0900, byungchul.park@lge.com wrote:
> > 
> > current code seems to be wrong with cfs_rq's avg loads when changing
> > a task's cgroup(=cfs_rq) to another. i tested with "echo pid > cgroup" and
> > found that e.g. cfs_rq->avg.load_avg became larger and larger whenever i
> > changed a cgroup to another again and again.
> > 
> > we have to sync se's average load with both *prev* cfs_rq and next cfs_rq
> > when changing its group.
> > 
> 
> I think you are right in general, it has nothing to do with
> migrate_task_rq_fair() and the load should be carried to new cfs_rq.
> 
> But whether it is queued or not should be doing the same thing, so what about:

hello yuyang,

i worked with code based on torvalds git, but now.. in tip git where sched
code is renewed much, i think you are right. i will fix it.

thank you much. :)
Byungchul

> 
> /* if queued, the previous dequeue_task() should have already done it */
> if (!queued)
> 	__upload_load_avg()
> 
> remove_from_old_cfs_rq();
> 
> /* virtually catch up because of the skew between cfs_rqs */
> task's last_update_time = cfs_rq's last_update_time;
> add_to_new_cfs_rq();
> 
> Thanks,
> Yuyang
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