Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 15 Jun 2016 16:15:29 +0200 | Subject | Re: [PATCH v6 1/4] sched/fair: Fix attaching task sched avgs twice when switching to fair or changing task group |
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On 15 June 2016 at 02:18, Yuyang Du <yuyang.du@intel.com> wrote: > On Wed, Jun 15, 2016 at 09:46:53AM +0200, Vincent Guittot wrote: >> I still have concerned with this change of the behavior that attaches >> the task only when it is enqueued. The load avg of the task will not >> be decayed between the time we move it into its new group until its >> enqueue. With this change, a task's load can stay high whereas it has >> slept for the last couple of seconds. > > The task will be updated when it is moved in the detach, so if it stays > high, it is highly expected to be enqueued soon. But if the task is never
you can't do such assumption because if it's not enqueued soon (keep in mind that a 10ms sleep will decay the value by 20% from max), metrics become just wrong. Furthermore, the load metrics of the task becomes different between a task being moved or the same task staying on same cfs_rq.
> enqueued, we don't bother the new gruop cfs_rq. > > So this is not perfect, and nothing is perfect, but a simple solution.
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