| Message ID | 1449641971-20827-11-git-send-email-smuckle@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On 08/12/15 22:19, Steve Muckle wrote: > From: Vincent Guittot <vincent.guittot@linaro.org> > > RT tasks don't provide any running constraints like deadline ones > except their running priority. The only current usable input to > estimate the capacity needed by RT tasks is the rt_avg metric. We use > it to estimate the CPU capacity needed for the RT scheduler class. > > In order to monitor the evolution for RT task load, we must > peridiocally check it during the tick. > > Then, we use the estimated capacity of the last activity to estimate > the next one which can not be that accurate but is a good starting > point without any impact on the wake up path of RT tasks. > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > Signed-off-by: Steve Muckle <smuckle@linaro.org> > --- > kernel/sched/rt.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 48 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index 8ec86ab..9694204 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1426,6 +1426,41 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag > #endif > } > > +#ifdef CONFIG_SMP s/SMP/CPU_FREQ_GOV_SCHED/ ? > +static void sched_rt_update_capacity_req(struct rq *rq) > +{ > + u64 total, used, age_stamp, avg; > + s64 delta; > + > + if (!sched_freq()) > + return; > + > + sched_avg_update(rq); > + /* > + * Since we're reading these variables without serialization make sure > + * we read them once before doing sanity checks on them. > + */ > + age_stamp = READ_ONCE(rq->age_stamp); > + avg = READ_ONCE(rq->rt_avg); > + delta = rq_clock(rq) - age_stamp; > + > + if (unlikely(delta < 0)) > + delta = 0; > + > + total = sched_avg_period() + delta; > + > + used = div_u64(avg, total); > + if (unlikely(used > SCHED_CAPACITY_SCALE)) > + used = SCHED_CAPACITY_SCALE; > + > + set_rt_cpu_capacity(rq->cpu, 1, (unsigned long)(used)); Minor nitpick: s/1/true/ . Thanks, - Juri > +} > +#else > +static inline void sched_rt_update_capacity_req(struct rq *rq) > +{ } > + > +#endif > + > static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq, > struct rt_rq *rt_rq) > { > @@ -1494,8 +1529,17 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev) > if (prev->sched_class == &rt_sched_class) > update_curr_rt(rq); > > - if (!rt_rq->rt_queued) > + if (!rt_rq->rt_queued) { > + /* > + * The next task to be picked on this rq will have a lower > + * priority than rt tasks so we can spend some time to update > + * the capacity used by rt tasks based on the last activity. > + * This value will be the used as an estimation of the next > + * activity. > + */ > + sched_rt_update_capacity_req(rq); > return NULL; > + } > > put_prev_task(rq, prev); > > @@ -2212,6 +2256,9 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued) > > update_curr_rt(rq); > > + if (rq->rt.rt_nr_running) > + sched_rt_update_capacity_req(rq); > + > watchdog(rq, p); > > /* > -- > 2.4.10 > -- 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/
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 8ec86ab..9694204 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1426,6 +1426,41 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag #endif } +#ifdef CONFIG_SMP +static void sched_rt_update_capacity_req(struct rq *rq) +{ + u64 total, used, age_stamp, avg; + s64 delta; + + if (!sched_freq()) + return; + + sched_avg_update(rq); + /* + * Since we're reading these variables without serialization make sure + * we read them once before doing sanity checks on them. + */ + age_stamp = READ_ONCE(rq->age_stamp); + avg = READ_ONCE(rq->rt_avg); + delta = rq_clock(rq) - age_stamp; + + if (unlikely(delta < 0)) + delta = 0; + + total = sched_avg_period() + delta; + + used = div_u64(avg, total); + if (unlikely(used > SCHED_CAPACITY_SCALE)) + used = SCHED_CAPACITY_SCALE; + + set_rt_cpu_capacity(rq->cpu, 1, (unsigned long)(used)); +} +#else +static inline void sched_rt_update_capacity_req(struct rq *rq) +{ } + +#endif + static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq, struct rt_rq *rt_rq) { @@ -1494,8 +1529,17 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev) if (prev->sched_class == &rt_sched_class) update_curr_rt(rq); - if (!rt_rq->rt_queued) + if (!rt_rq->rt_queued) { + /* + * The next task to be picked on this rq will have a lower + * priority than rt tasks so we can spend some time to update + * the capacity used by rt tasks based on the last activity. + * This value will be the used as an estimation of the next + * activity. + */ + sched_rt_update_capacity_req(rq); return NULL; + } put_prev_task(rq, prev); @@ -2212,6 +2256,9 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued) update_curr_rt(rq); + if (rq->rt.rt_nr_running) + sched_rt_update_capacity_req(rq); + watchdog(rq, p); /*