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Message-ID: <CAKfTPtCV4d=1nSDcU8J4x=MF7HmuyRxKr-4XiYAxPZYPKd1okA@mail.gmail.com>
Date: Wed, 9 Dec 2015 09:50:27 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Steve Muckle <steve.muckle@...aro.org>,
Luca Abeni <luca.abeni@...tn.it>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
linux-kernel <linux-kernel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
Morten Rasmussen <morten.rasmussen@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Juri Lelli <Juri.Lelli@....com>,
Patrick Bellasi <patrick.bellasi@....com>,
Michael Turquette <mturquette@...libre.com>
Subject: Re: [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in scale_rt_capacity
adding Lucas
On 9 December 2015 at 07:19, Steve Muckle <steve.muckle@...aro.org> wrote:
> From: Vincent Guittot <vincent.guittot@...aro.org>
>
> Instead of monitoring the exec time of deadline tasks to evaluate the
> CPU capacity consumed by deadline scheduler class, we can directly
> calculate it thanks to the sum of utilization of deadline tasks on the
> CPU. We can remove deadline tasks from rt_avg metric and directly use
> the average bandwidth of deadline scheduler in scale_rt_capacity.
>
> Based in part on a similar patch from Luca Abeni <luca.abeni@...tn.it>.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> Signed-off-by: Steve Muckle <smuckle@...aro.org>
> ---
> kernel/sched/deadline.c | 33 +++++++++++++++++++++++++++++++--
> kernel/sched/fair.c | 8 ++++++++
> kernel/sched/sched.h | 2 ++
> 3 files changed, 41 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 8b0a15e..9d9eb50 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -43,6 +43,24 @@ static inline int on_dl_rq(struct sched_dl_entity *dl_se)
> return !RB_EMPTY_NODE(&dl_se->rb_node);
> }
>
> +static void add_average_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
> +{
> + u64 se_bw = dl_se->dl_bw;
> +
> + dl_rq->avg_bw += se_bw;
> +}
> +
> +static void clear_average_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
> +{
> + u64 se_bw = dl_se->dl_bw;
> +
> + dl_rq->avg_bw -= se_bw;
> + if (dl_rq->avg_bw < 0) {
> + WARN_ON(1);
> + dl_rq->avg_bw = 0;
> + }
> +}
> +
> static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
> {
> struct sched_dl_entity *dl_se = &p->dl;
> @@ -494,6 +512,9 @@ static void update_dl_entity(struct sched_dl_entity *dl_se,
> struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
> struct rq *rq = rq_of_dl_rq(dl_rq);
>
> + if (dl_se->dl_new)
> + add_average_bw(dl_se, dl_rq);
> +
> /*
> * The arrival of a new instance needs special treatment, i.e.,
> * the actual scheduling parameters have to be "renewed".
> @@ -741,8 +762,6 @@ static void update_curr_dl(struct rq *rq)
> curr->se.exec_start = rq_clock_task(rq);
> cpuacct_charge(curr, delta_exec);
>
> - sched_rt_avg_update(rq, delta_exec);
> -
> dl_se->runtime -= dl_se->dl_yielded ? 0 : delta_exec;
> if (dl_runtime_exceeded(dl_se)) {
> dl_se->dl_throttled = 1;
> @@ -1241,6 +1260,8 @@ static void task_fork_dl(struct task_struct *p)
> static void task_dead_dl(struct task_struct *p)
> {
> struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
> + struct dl_rq *dl_rq = dl_rq_of_se(&p->dl);
> + struct rq *rq = rq_of_dl_rq(dl_rq);
>
> /*
> * Since we are TASK_DEAD we won't slip out of the domain!
> @@ -1249,6 +1270,8 @@ static void task_dead_dl(struct task_struct *p)
> /* XXX we should retain the bw until 0-lag */
> dl_b->total_bw -= p->dl.dl_bw;
> raw_spin_unlock_irq(&dl_b->lock);
> +
> + clear_average_bw(&p->dl, &rq->dl);
> }
>
> static void set_curr_task_dl(struct rq *rq)
> @@ -1556,7 +1579,9 @@ retry:
> }
>
> deactivate_task(rq, next_task, 0);
> + clear_average_bw(&next_task->dl, &rq->dl);
> set_task_cpu(next_task, later_rq->cpu);
> + add_average_bw(&next_task->dl, &later_rq->dl);
> activate_task(later_rq, next_task, 0);
> ret = 1;
>
> @@ -1644,7 +1669,9 @@ static void pull_dl_task(struct rq *this_rq)
> resched = true;
>
> deactivate_task(src_rq, p, 0);
> + clear_average_bw(&p->dl, &src_rq->dl);
> set_task_cpu(p, this_cpu);
> + add_average_bw(&p->dl, &this_rq->dl);
> activate_task(this_rq, p, 0);
> dmin = p->dl.deadline;
>
> @@ -1750,6 +1777,8 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
> if (!start_dl_timer(p))
> __dl_clear_params(p);
>
> + clear_average_bw(&p->dl, &rq->dl);
> +
> /*
> * Since this might be the only -deadline task on the rq,
> * this is the right place to try to pull some other one
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 4c49f76..ce05f61 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6203,6 +6203,14 @@ static unsigned long scale_rt_capacity(int cpu)
>
> used = div_u64(avg, total);
>
> + /*
> + * deadline bandwidth is defined at system level so we must
> + * weight this bandwidth with the max capacity of the system.
> + * As a reminder, avg_bw is 20bits width and
> + * scale_cpu_capacity is 10 bits width
> + */
> + used += div_u64(rq->dl.avg_bw, arch_scale_cpu_capacity(NULL, cpu));
> +
> if (likely(used < SCHED_CAPACITY_SCALE))
> return SCHED_CAPACITY_SCALE - used;
>
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 08858d1..e44c6be 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -519,6 +519,8 @@ struct dl_rq {
> #else
> struct dl_bw dl_bw;
> #endif
> + /* This is the "average utilization" for this runqueue */
> + s64 avg_bw;
> };
>
> #ifdef CONFIG_SMP
> --
> 2.4.10
>
--
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