Messages in this thread | | | Subject | Re: [PATCH v3] sched/pelt: fix update_blocked_averages() for dl and rt | From | Dietmar Eggemann <> | Date | Sun, 2 Sep 2018 21:36:48 -0700 |
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On 08/31/2018 08:22 AM, 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().
Shouldn't this be 's/that no/if an' ?
You still update the utilization of the rt or dl task if they are running (accrue + decay) instead of only decay. Similar to the 'cfs_rq->curr != NULL' in __update_load_avg_cfs_rq().
> 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.
I assume this sentence is indirectly saying this.
> > Fixes: 371bf4273269 ("sched/rt: Add rt_rq utilization tracking") > Fixes: 3727e0e16340 ("sched/dl: Add dl_rq utilization tracking") > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > --- > > -V3 > - move rq->curr dereference under the rq->lock > > -V2 > - Add missing fixes tags > - apply fix to other version of update_blocked_averages > > kernel/sched/fair.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 309c93f..53bbcd4 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; > struct rq_flags rf; > bool done = true; > > @@ -7298,8 +7299,10 @@ 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); > + > + curr_class = rq->curr->sched_class; > + 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)) > @@ -7364,13 +7367,16 @@ static inline void update_blocked_averages(int cpu) > { > struct rq *rq = cpu_rq(cpu); > struct cfs_rq *cfs_rq = &rq->cfs; > + const struct sched_class *curr_class; > struct rq_flags rf; > > rq_lock_irqsave(rq, &rf); > update_rq_clock(rq); > update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq); > - update_rt_rq_load_avg(rq_clock_task(rq), rq, 0); > - update_dl_rq_load_avg(rq_clock_task(rq), rq, 0); > + > + curr_class = rq->curr->sched_class; > + 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); > #ifdef CONFIG_NO_HZ_COMMON > rq->last_blocked_load_update_tick = jiffies; >
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