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Date: Mon, 20 Apr 2020 16:13:41 +0100
From: Qais Yousef <qais.yousef@....com>
To: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Jonathan Corbet <corbet@....net>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Luis Chamberlain <mcgrof@...nel.org>,
Kees Cook <keescook@...omium.org>,
Iurii Zaikin <yzaikin@...gle.com>,
Quentin Perret <qperret@...gle.com>,
Valentin Schneider <valentin.schneider@....com>,
Patrick Bellasi <patrick.bellasi@...bug.net>,
Pavan Kondeti <pkondeti@...eaurora.org>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default
boost value
On 04/20/20 10:29, Dietmar Eggemann wrote:
> On 03.04.20 14:30, Qais Yousef wrote:
>
> [...]
>
> > @@ -924,6 +945,14 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
> > return uc_req;
> > }
> >
> > +static void uclamp_rt_sync_default_util_min(struct task_struct *p)
> > +{
> > + struct uclamp_se *uc_se = &p->uclamp_req[UCLAMP_MIN];
> > +
> > + if (!uc_se->user_defined)
> > + uclamp_se_set(uc_se, sysctl_sched_rt_default_uclamp_util_min, false);
> > +}
> > +
> > unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
> > {
> > struct uclamp_se uc_eff;
> > @@ -1030,6 +1059,12 @@ static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
> > if (unlikely(!p->sched_class->uclamp_enabled))
> > return;
> >
> > + /*
> > + * When sysctl_sched_rt_default_uclamp_util_min value is changed by the
> > + * user, we apply any new value on the next wakeup, which is here.
> > + */
> > + uclamp_rt_sync_default_util_min(p);
> > +
>
> Does this have to be an extra function? Can we not reuse
> uclamp_tg_restrict() by slightly rename it to uclamp_restrict()?
Hmm the thing is that we're not restricting here. In contrary we're boosting,
so the name would be misleading.
>
> This function will then deal with enforcing restrictions, whether system
> and taskgroup hierarchy related or default value (latter only for rt-min
> right now since the others are fixed) related.
>
> uclamp_eff_get() -> uclamp_restrict() is called from:
>
> 'enqueue_task(), uclamp_update_active() -> uclamp_rq_inc() -> uclamp_rq_inc_id()' and
>
> 'task_fits_capacity() -> clamp_task_util(), rt_task_fits_capacity() -> uclamp_eff_value()' and
>
> 'schedutil_cpu_util(), find_energy_efficient_cpu() -> uclamp_rq_util_with() -> uclamp_eff_value()'
>
> so there would be more check-points than the one in 'enqueue_task() -> uclamp_rq_inc()' now.
I think you're revolving around the same idea that Patrick was suggesting.
I think it is possible to do something in uclamp_eff_get() too.
Thanks
--
Qais Yousef
>
> Only lightly tested:
>
> ---8<---
>
> From: Dietmar Eggemann <dietmar.eggemann@....com>
> Date: Sun, 19 Apr 2020 01:20:17 +0200
> Subject: [PATCH] sched/core: uclamp: Move uclamp_rt_sync_default_util_min()
> into uclamp_tg_restrict()
>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
> ---
> kernel/sched/core.c | 34 +++++++++++++++-------------------
> 1 file changed, 15 insertions(+), 19 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 8f4e0d5c7daf..6802113d6d4b 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -899,12 +899,22 @@ unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
> }
>
> static inline struct uclamp_se
> -uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
> +uclamp_restrict(struct task_struct *p, enum uclamp_id clamp_id)
> {
> - struct uclamp_se uc_req = p->uclamp_req[clamp_id];
> -#ifdef CONFIG_UCLAMP_TASK_GROUP
> - struct uclamp_se uc_max;
> + struct uclamp_se uc_req, __maybe_unused uc_max;
> +
> + if (unlikely(rt_task(p)) && clamp_id == UCLAMP_MIN &&
> + !uc_req.user_defined) {
> + struct uclamp_se *uc_se = &p->uclamp_req[UCLAMP_MIN];
> + int rt_min = sysctl_sched_rt_default_uclamp_util_min;
> +
> + if (uc_se->value != rt_min)
> + uclamp_se_set(uc_se, rt_min, false);
> + }
>
> + uc_req = p->uclamp_req[clamp_id];
> +
> +#ifdef CONFIG_UCLAMP_TASK_GROUP
> /*
> * Tasks in autogroups or root task group will be
> * restricted by system defaults.
> @@ -933,7 +943,7 @@ uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
> static inline struct uclamp_se
> uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
> {
> - struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
> + struct uclamp_se uc_req = uclamp_restrict(p, clamp_id);
> struct uclamp_se uc_max = uclamp_default[clamp_id];
>
> /* System default restrictions always apply */
> @@ -943,14 +953,6 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
> return uc_req;
> }
>
> -static void uclamp_rt_sync_default_util_min(struct task_struct *p)
> -{
> - struct uclamp_se *uc_se = &p->uclamp_req[UCLAMP_MIN];
> -
> - if (!uc_se->user_defined)
> - uclamp_se_set(uc_se, sysctl_sched_rt_default_uclamp_util_min, false);
> -}
> -
> unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
> {
> struct uclamp_se uc_eff;
> @@ -1057,12 +1059,6 @@ static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
> if (unlikely(!p->sched_class->uclamp_enabled))
> return;
>
> - /*
> - * When sysctl_sched_rt_default_uclamp_util_min value is changed by the
> - * user, we apply any new value on the next wakeup, which is here.
> - */
> - uclamp_rt_sync_default_util_min(p);
> -
> for_each_clamp_id(clamp_id)
> uclamp_rq_inc_id(rq, p, clamp_id);
>
> --
> 2.17.1
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