Messages in this thread | | | From | Vincent Guittot <> | Date | Sat, 16 Nov 2019 09:47:41 +0100 | Subject | Re: [PATCH v4] sched/freq: move call to cpufreq_update_util |
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On Fri, 15 Nov 2019 at 22:52, Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Nov 14, 2019 at 06:07:31PM +0100, Vincent Guittot wrote: > > update_cfs_rq_load_avg() calls cfs_rq_util_change() everytime pelt decays, > > which might be inefficient when cpufreq driver has rate limitation. > > > > When a task is attached on a CPU, we have call path: > > > > update_load_avg() > > update_cfs_rq_load_avg() > > cfs_rq_util_change -- > trig frequency update > > attach_entity_load_avg() > > cfs_rq_util_change -- > trig frequency update > > > > The 1st frequency update will not take into account the utilization of the > > newly attached task and the 2nd one might be discard because of rate > > limitation of the cpufreq driver. > > > > update_cfs_rq_load_avg() is only called by update_blocked_averages() > > and update_load_avg() so we can move the call to > > cfs_rq_util_change/cpufreq_update_util() into these 2 functions. It's also > > interesting to notice that update_load_avg() already calls directly > > cfs_rq_util_change() for !SMP case. > > > > This changes will also ensure that cpufreq_update_util() is called even > > when there is no more CFS rq in the leaf_cfs_rq_list to update but only > > irq, rt or dl pelt signals. > > > > Reported-by: Doug Smythies <dsmythies@telus.net> > > Fixes: 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path") > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> > > --- > > OK, but shall we write it like so instead?
Yes. Looks good to me
> > --- > kernel/sched/fair.c | 111 +++++++++++++++++++++++++++++----------------------- > 1 file changed, 62 insertions(+), 49 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 545bcb90b4de..7a762266c335 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3508,9 +3508,6 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq) > cfs_rq->load_last_update_time_copy = sa->last_update_time; > #endif > > - if (decayed) > - cfs_rq_util_change(cfs_rq, 0); > - > return decayed; > } > > @@ -3620,8 +3617,12 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s > attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION); > update_tg_load_avg(cfs_rq, 0); > > - } else if (decayed && (flags & UPDATE_TG)) > - update_tg_load_avg(cfs_rq, 0); > + } else if (decayed) { > + cfs_rq_util_change(cfs_rq, 0); > + > + if (flags & UPDATE_TG) > + update_tg_load_avg(cfs_rq, 0); > + } > } > > #ifndef CONFIG_64BIT > @@ -7428,6 +7429,28 @@ static inline bool others_have_blocked(struct rq *rq) { return false; } > static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {} > #endif > > +static bool __update_blocked_others(struct rq *rq, bool *done) > +{ > + const struct sched_class *curr_class; > + u64 now = rq_clock_pelt(rq); > + bool decayed; > + > + /* > + * update_load_avg() can call cpufreq_update_util(). Make sure that RT, > + * DL and IRQ signals have been updated before updating CFS. > + */ > + curr_class = rq->curr->sched_class; > + > + decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) | > + update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) | > + update_irq_load_avg(rq, 0); > + > + if (others_have_blocked(rq)) > + *done = false; > + > + return decayed; > +} > + > #ifdef CONFIG_FAIR_GROUP_SCHED > > static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) > @@ -7447,29 +7470,11 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) > return true; > } > > -static void update_blocked_averages(int cpu) > +static bool __update_blocked_fair(struct rq *rq, bool *done) > { > - 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; > - > - rq_lock_irqsave(rq, &rf); > - update_rq_clock(rq); > - > - /* > - * update_cfs_rq_load_avg() can call cpufreq_update_util(). Make sure > - * that RT, DL and IRQ signals have been updated before updating CFS. > - */ > - curr_class = rq->curr->sched_class; > - update_rt_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &rt_sched_class); > - update_dl_rq_load_avg(rq_clock_pelt(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)) > - done = false; > + bool decayed = false; > + int cpu = cpu_of(rq); > > /* > * Iterates the task_group tree in a bottom up fashion, see > @@ -7478,9 +7483,13 @@ static void update_blocked_averages(int cpu) > for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) { > struct sched_entity *se; > > - if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) > + if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) { > update_tg_load_avg(cfs_rq, 0); > > + if (cfs_rq == &rq->cfs) > + decayed = true; > + } > + > /* Propagate pending load changes to the parent, if any: */ > se = cfs_rq->tg->se[cpu]; > if (se && !skip_blocked_update(se)) > @@ -7495,11 +7504,10 @@ static void update_blocked_averages(int cpu) > > /* Don't need periodic decay once load/util_avg are null */ > if (cfs_rq_has_blocked(cfs_rq)) > - done = false; > + *done = false; > } > > - update_blocked_load_status(rq, !done); > - rq_unlock_irqrestore(rq, &rf); > + return decayed; > } > > /* > @@ -7549,29 +7557,16 @@ static unsigned long task_h_load(struct task_struct *p) > cfs_rq_load_avg(cfs_rq) + 1); > } > #else > -static inline void update_blocked_averages(int cpu) > +static bool __update_blocked_fair(struct rq *rq, bool *done) > { > - 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() can call cpufreq_update_util(). Make sure > - * that RT, DL and IRQ signals have been updated before updating CFS. > - */ > - curr_class = rq->curr->sched_class; > - update_rt_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &rt_sched_class); > - update_dl_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &dl_sched_class); > - update_irq_load_avg(rq, 0); > + bool decayed; > > - update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq); > + decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq); > + if (cfs_rq_has_blocked(cfs_rq)) > + *done = false; > > - update_blocked_load_status(rq, cfs_rq_has_blocked(cfs_rq) || others_have_blocked(rq)); > - rq_unlock_irqrestore(rq, &rf); > + return decayed; > } > > static unsigned long task_h_load(struct task_struct *p) > @@ -7580,6 +7575,24 @@ static unsigned long task_h_load(struct task_struct *p) > } > #endif > > +static void update_blocked_averages(int cpu) > +{ > + bool decayed = false, done = true; > + struct rq *rq = cpu_rq(cpu); > + struct rq_flags rf; > + > + rq_lock_irqsave(rq, &rf); > + update_rq_clock(rq); > + > + decayed |= __update_blocked_others(rq, &done); > + decayed |= __update_blocked_fair(rq, &done); > + > + update_blocked_load_status(rq, !done); > + if (decayed) > + cpufreq_update_util(rq, 0); > + rq_unlock_irqrestore(rq, &rf); > +} > + > /********** Helpers for find_busiest_group ************************/ > > /* >
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