Date: Wed, 12 Aug 2015 09:05:48 +0800
From: Yuyang Du <yuyang.du@intel.com>
To: byungchul.park@lge.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: <20150812010548.GA28764@intel.com>
References: <1439363115-2259-1-git-send-email-byungchul.park@lge.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1439363115-2259-1-git-send-email-byungchul.park@lge.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1196
Lines: 33

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:

/* 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/