Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 27 Feb 2020 14:12:09 +0100 | Subject | Re: [PATCH] sched/fair: fix runnable_avg for throttled cfs |
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On Thu, 27 Feb 2020 at 14:10, Tao Zhou <zhout@vivaldi.net> wrote: > > Hi Dietmar, > > On Thu, Feb 27, 2020 at 11:20:05AM +0000, Dietmar Eggemann wrote: > > On 26.02.20 21:01, Vincent Guittot wrote: > > > On Wed, 26 Feb 2020 at 20:04, <bsegall@google.com> wrote: > > >> > > >> Vincent Guittot <vincent.guittot@linaro.org> writes: > > >> > > >>> When a cfs_rq is throttled, its group entity is dequeued and its running > > >>> tasks are removed. We must update runnable_avg with current h_nr_running > > >>> and update group_se->runnable_weight with new h_nr_running at each level > > > > ^^^ > > > > Shouldn't his be 'curren' rather 'new' h_nr_running for > > group_se->runnable_weight? IMHO, you want to cache the current value > > before you add/subtract task_delta. > > /me think Vincent is right. h_nr_running is updated in the previous > level or out. The next level will use current h_nr_running to update > runnable_avg and use the new group cfs_rq's h_nr_running which was > updated in the previous level or out to update se runnable_weight.
Yes that's what I want to say
> > update_h_nr_running (E.G. in enqueue_task_fair) > > throttle_cfs_rq() > for() { > update_load_avg() > se_runnable() --> current h_nr_running > update_se_runnable() --> use group cfs_rq h_nr_running > updated in the prev level or out > update_h_nr_running > } > > Thanks, > Tao > > > >>> of the hierarchy. > > >> > > >> You'll also need to do this for task enqueue/dequeue inside of a > > >> throttled hierarchy, I'm pretty sure. > > > > > > AFAICT, this is already done with patch "sched/pelt: Add a new > > > runnable average signal" when task is enqueued/dequeued inside a > > > throttled hierarchy > > > > > >> > > >>> > > >>> Fixes: 9f68395333ad ("sched/pelt: Add a new runnable average signal") > > >>> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > > >>> --- > > >>> This patch applies on top of tip/sched/core > > >>> > > >>> kernel/sched/fair.c | 10 ++++++++++ > > >>> 1 file changed, 10 insertions(+) > > >>> > > >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > >>> index fcc968669aea..6d46974e9be7 100644 > > >>> --- a/kernel/sched/fair.c > > >>> +++ b/kernel/sched/fair.c > > >>> @@ -4703,6 +4703,11 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq) > > >>> > > >>> if (dequeue) > > >>> dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); > > >>> + else { > > >>> + update_load_avg(qcfs_rq, se, 0); > > >>> + se_update_runnable(se); > > >>> + } > > >>> + > > >>> qcfs_rq->h_nr_running -= task_delta; > > >>> qcfs_rq->idle_h_nr_running -= idle_task_delta; > > >>> > > >>> @@ -4772,6 +4777,11 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) > > >>> cfs_rq = cfs_rq_of(se); > > >>> if (enqueue) > > >>> enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); > > >>> + else { > > >>> + update_load_avg(cfs_rq, se, 0); > > >> > > >> > > >>> + se_update_runnable(se); > > >>> + } > > >>> + > > >>> cfs_rq->h_nr_running += task_delta; > > >>> cfs_rq->idle_h_nr_running += idle_task_delta;
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