On Fri, 31 Aug 2018 at 16:41, Peter Zijlstra <pet...@infradead.org> wrote:
>
> On Fri, Aug 31, 2018 at 03:58:28PM +0200, Vincent Guittot wrote:
> > update_blocked_averages() is called to periodiccally decay the stalled load
> > of idle CPUs and to sync all loads before running load balance.
> >
> > When cfs rq is idle, it trigs a load balance during pick_next_task_fair()
> > in order to potentially pull tasks and to use this newly idle CPU. This
> > load balance happens whereas prev task from another class has not been put
> > and its utilization updated yet. This may lead to wrongly account running
> > time as idle time for rt or dl classes.
> >
> > Test that no rt or dl task is running when updating their utilization in
> > update_blocked_averages().
> >
> > We still update rt and dl utilization instead of simply skipping them to
> > make sure that all metrics are synced when used during load balance.
> >
>
> Fixes: 371bf4273269 ("sched/rt: Add rt_rq utilization tracking")
> Fixes: 3727e0e16340 ("sched/dl: Add dl_rq utilization tracking")
>
> Right?
Yes
>
> > Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
> > ---
> > kernel/sched/fair.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 309c93f..a1babaf 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -7262,6 +7262,7 @@ static void update_blocked_averages(int cpu)
> > {
> > struct rq *rq = cpu_rq(cpu);
> > struct cfs_rq *cfs_rq, *pos;
> > + const struct sched_class *curr_class = rq->curr->sched_class;
> > struct rq_flags rf;
> > bool done = true;
> >
> > @@ -7298,8 +7299,8 @@ static void update_blocked_averages(int cpu)
> > if (cfs_rq_has_blocked(cfs_rq))
> > done = false;
> > }
> > - update_rt_rq_load_avg(rq_clock_task(rq), rq, 0);
> > - update_dl_rq_load_avg(rq_clock_task(rq), rq, 0);
> > + update_rt_rq_load_avg(rq_clock_task(rq), rq, curr_class ==
> > &rt_sched_class);
> > + update_dl_rq_load_avg(rq_clock_task(rq), rq, curr_class ==
> > &dl_sched_class);
> > update_irq_load_avg(rq, 0);
> > /* Don't need periodic decay once load/util_avg are null */
> > if (others_have_blocked(rq))
>
> Did you forget to update the second implementation of
> update_blocked_averages() ?
Yes. I have sent this version to quickly.
I'm going to send an update
