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Date: Wed, 17 Aug 2022 11:48:28 +0200 From: Vincent Guittot <vincent.guittot@...aro.org> To: Qais Yousef <qais.yousef@....com> Cc: Ingo Molnar <mingo@...nel.org>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, Dietmar Eggemann <dietmar.eggemann@....com>, linux-kernel@...r.kernel.org, Xuewen Yan <xuewen.yan94@...il.com>, Wei Wang <wvw@...gle.com>, Jonathan JMChen <Jonathan.JMChen@...iatek.com>, Hank <han.lin@...iatek.com> Subject: Re: [PATCH 2/7] sched/uclamp: Make task_fits_capacity() use util_fits_cpu() On Wed, 27 Jul 2022 at 18:05, Qais Yousef <qais.yousef@....com> wrote: > > Hi Vincent > > On 07/22/22 10:19, Vincent Guittot wrote: > > Le jeudi 21 juil. 2022 � 15:29:49 (+0100), Qais Yousef a �crit : > > > On 07/12/22 11:48, Qais Yousef wrote: > > > > On 07/11/22 15:09, Vincent Guittot wrote: > > > > > On Wed, 29 Jun 2022 at 21:48, Qais Yousef <qais.yousef@....com> wrote: > > > > > > > > [...] > > > > > > > > @@ -9108,7 +9125,7 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd, > > > > > > > > > > > > /* Check if task fits in the group */ > > > > > > if (sd->flags & SD_ASYM_CPUCAPACITY && > > > > > > - !task_fits_capacity(p, group->sgc->max_capacity)) { > > > > > > + !task_fits_cpu(p, group->sgc->max_capacity_cpu)) { > > > > > > > > > > All the changes and added complexity above for this line. Can't you > > > > > find another way ? > > > > > > > > You're right, I might have got carried away trying to keep the logic the same. > > > > > > > > Can we use group->asym_prefer_cpu or pick a cpu from group->sgc->cpumask > > > > instead? > > > > > > > > I'll dig more into it anyway and try to come up with simpler alternative. > > > > > > Actually we can't. > > > > > > I can keep the current {max,min}_capacity field and just add the new > > > {max,min}_capacity_cpu and use them where needed. Should address your concerns > > > this way? That was actually the first version of the code, but then it seemed > > > redundant to keep both {max,min}_capacity and {max,min}_capacity_cpu. > > > > > > OR > > > > > > I can add a new function to search for max spare capacity cpu in the group. > > > > > > Preference? > > > > > > > Isn't the below enough and much simpler ? > > Thanks for that! > > > > > [PATCH] sched/uclamp: Make task_fits_capacity() use util_fits_cpu() > > > > So that the new uclamp rules in regard to migration margin and capacity > > pressure are taken into account correctly. > > --- > > kernel/sched/fair.c | 25 +++++++++++++++---------- > > kernel/sched/sched.h | 9 +++++++++ > > 2 files changed, 24 insertions(+), 10 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 5eecae32a0f6..3e0c7cc490be 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -4317,10 +4317,12 @@ static inline int util_fits_cpu(unsigned long util, > > return fits; > > } > > > > -static inline int task_fits_capacity(struct task_struct *p, > > - unsigned long capacity) > > +static inline int task_fits_cpu(struct task_struct *p, int cpu) > > { > > - return fits_capacity(uclamp_task_util(p), capacity); > > + unsigned long uclamp_min = uclamp_eff_value(p, UCLAMP_MIN); > > + unsigned long uclamp_max = uclamp_eff_value(p, UCLAMP_MAX); > > + unsigned long util = task_util_est(p); > > + return util_fits_cpu(util, uclamp_min, uclamp_max, cpu); > > } > > > > static inline void update_misfit_status(struct task_struct *p, struct rq *rq) > > @@ -4333,7 +4335,7 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq) > > return; > > } > > > > - if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) { > > + if (task_fits_cpu(p, cpu_of(rq))) { > > rq->misfit_task_load = 0; > > return; > > } > > @@ -8104,7 +8106,7 @@ static int detach_tasks(struct lb_env *env) > > > > case migrate_misfit: > > /* This is not a misfit task */ > > - if (task_fits_capacity(p, capacity_of(env->src_cpu))) > > + if (task_fits_cpu(p, env->src_cpu)) > > goto next; > > > > env->imbalance = 0; > > @@ -9085,6 +9087,10 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd, > > > > memset(sgs, 0, sizeof(*sgs)); > > > > + /* Assume that task can't fit any CPU of the group */ > > + if (sd->flags & SD_ASYM_CPUCAPACITY) > > + sgs->group_misfit_task_load = 0; > > Should this be > > sgs->group_misfit_task_load = 1 > > to indicate it doesn't fit? Yes > > > + > > for_each_cpu(i, sched_group_span(group)) { > > struct rq *rq = cpu_rq(i); > > unsigned int local; > > @@ -9104,12 +9110,11 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd, > > if (!nr_running && idle_cpu_without(i, p)) > > sgs->idle_cpus++; > > > > - } > > + /* Check if task fits in the CPU */ > > + if (sd->flags & SD_ASYM_CPUCAPACITY && > > + task_fits_cpu(p, i)) > > + sgs->group_misfit_task_load = 0; > > So we clear the flag if there's any cpu that fits, I think that should work, > yes and much better too. I got tunneled visioned and didn't take a step back to > look at the big picture. Thanks for the suggestion :-) > > I think we can make it more efficient by checking if > sgs->group_misfit_task_load is set > > /* Check if task fits in the CPU */ > if (sd->flags & SD_ASYM_CPUCAPACITY && > sgs->group_misfit_task_load && > task_fits_cpu(p, i)) > sgs->group_misfit_task_load = 0; > > which will avoid calling task_fits_cpu() repeatedly if we got a hit already. yes, looks better > > > Thanks! > > -- > Qais Yousef > > > > > - /* Check if task fits in the group */ > > - if (sd->flags & SD_ASYM_CPUCAPACITY && > > - !task_fits_capacity(p, group->sgc->max_capacity)) { > > - sgs->group_misfit_task_load = 1; > > } > > > > sgs->group_capacity = group->sgc->capacity; > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > > index 02c970501295..3292ad2db4ac 100644 > > --- a/kernel/sched/sched.h > > +++ b/kernel/sched/sched.h > > @@ -2988,6 +2988,15 @@ static inline bool uclamp_is_used(void) > > return static_branch_likely(&sched_uclamp_used); > > } > > #else /* CONFIG_UCLAMP_TASK */ > > +static inline unsigned long uclamp_eff_value(struct task_struct *p, > > + enum uclamp_id clamp_id) > > +{ > > + if (clamp_id == UCLAMP_MIN) > > + return 0; > > + > > + return SCHED_CAPACITY_SCALE; > > +} > > + > > static inline > > unsigned long uclamp_rq_util_with(struct rq *rq, unsigned long util, > > struct task_struct *p) > > -- > > 2.17.1 > > > > > > > > Thanks! > > > > > > -- > > > Qais Yousef
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