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Date: Wed, 25 Nov 2020 16:36:34 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Juri Lelli <juri.lelli@...hat.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Quentin Perret <qperret@...gle.com>,
Lukasz Luba <lukasz.luba@....com>,
Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH V4 1/3] sched/core: Move schedutil_cpu_util() to core.c
On Tue, Nov 24, 2020 at 7:26 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> There is nothing schedutil specific in schedutil_cpu_util(), move it to
> core.c and define it only for CONFIG_SMP.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
For the schedutil part:
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> kernel/sched/core.c | 108 +++++++++++++++++++++++++++++++
> kernel/sched/cpufreq_schedutil.c | 106 ------------------------------
> kernel/sched/sched.h | 12 +---
> 3 files changed, 109 insertions(+), 117 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index d2003a7d5ab5..b81265aec4a0 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5117,6 +5117,114 @@ struct task_struct *idle_task(int cpu)
> return cpu_rq(cpu)->idle;
> }
>
> +#ifdef CONFIG_SMP
> +/*
> + * This function computes an effective utilization for the given CPU, to be
> + * used for frequency selection given the linear relation: f = u * f_max.
> + *
> + * The scheduler tracks the following metrics:
> + *
> + * cpu_util_{cfs,rt,dl,irq}()
> + * cpu_bw_dl()
> + *
> + * Where the cfs,rt and dl util numbers are tracked with the same metric and
> + * synchronized windows and are thus directly comparable.
> + *
> + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> + * which excludes things like IRQ and steal-time. These latter are then accrued
> + * in the irq utilization.
> + *
> + * The DL bandwidth number otoh is not a measured metric but a value computed
> + * based on the task model parameters and gives the minimal utilization
> + * required to meet deadlines.
> + */
> +unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
> + unsigned long max, enum schedutil_type type,
> + struct task_struct *p)
> +{
> + unsigned long dl_util, util, irq;
> + struct rq *rq = cpu_rq(cpu);
> +
> + if (!uclamp_is_used() &&
> + type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
> + return max;
> + }
> +
> + /*
> + * Early check to see if IRQ/steal time saturates the CPU, can be
> + * because of inaccuracies in how we track these -- see
> + * update_irq_load_avg().
> + */
> + irq = cpu_util_irq(rq);
> + if (unlikely(irq >= max))
> + return max;
> +
> + /*
> + * Because the time spend on RT/DL tasks is visible as 'lost' time to
> + * CFS tasks and we use the same metric to track the effective
> + * utilization (PELT windows are synchronized) we can directly add them
> + * to obtain the CPU's actual utilization.
> + *
> + * CFS and RT utilization can be boosted or capped, depending on
> + * utilization clamp constraints requested by currently RUNNABLE
> + * tasks.
> + * When there are no CFS RUNNABLE tasks, clamps are released and
> + * frequency will be gracefully reduced with the utilization decay.
> + */
> + util = util_cfs + cpu_util_rt(rq);
> + if (type == FREQUENCY_UTIL)
> + util = uclamp_rq_util_with(rq, util, p);
> +
> + dl_util = cpu_util_dl(rq);
> +
> + /*
> + * For frequency selection we do not make cpu_util_dl() a permanent part
> + * of this sum because we want to use cpu_bw_dl() later on, but we need
> + * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
> + * that we select f_max when there is no idle time.
> + *
> + * NOTE: numerical errors or stop class might cause us to not quite hit
> + * saturation when we should -- something for later.
> + */
> + if (util + dl_util >= max)
> + return max;
> +
> + /*
> + * OTOH, for energy computation we need the estimated running time, so
> + * include util_dl and ignore dl_bw.
> + */
> + if (type == ENERGY_UTIL)
> + util += dl_util;
> +
> + /*
> + * There is still idle time; further improve the number by using the
> + * irq metric. Because IRQ/steal time is hidden from the task clock we
> + * need to scale the task numbers:
> + *
> + * max - irq
> + * U' = irq + --------- * U
> + * max
> + */
> + util = scale_irq_capacity(util, irq, max);
> + util += irq;
> +
> + /*
> + * Bandwidth required by DEADLINE must always be granted while, for
> + * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
> + * to gracefully reduce the frequency when no tasks show up for longer
> + * periods of time.
> + *
> + * Ideally we would like to set bw_dl as min/guaranteed freq and util +
> + * bw_dl as requested freq. However, cpufreq is not yet ready for such
> + * an interface. So, we only do the latter for now.
> + */
> + if (type == FREQUENCY_UTIL)
> + util += cpu_bw_dl(rq);
> +
> + return min(max, util);
> +}
> +#endif /* CONFIG_SMP */
> +
> /**
> * find_process_by_pid - find a process with a matching PID value.
> * @pid: the pid in question.
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index e254745a82cb..2d44befb322b 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -169,112 +169,6 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
> return cpufreq_driver_resolve_freq(policy, freq);
> }
>
> -/*
> - * This function computes an effective utilization for the given CPU, to be
> - * used for frequency selection given the linear relation: f = u * f_max.
> - *
> - * The scheduler tracks the following metrics:
> - *
> - * cpu_util_{cfs,rt,dl,irq}()
> - * cpu_bw_dl()
> - *
> - * Where the cfs,rt and dl util numbers are tracked with the same metric and
> - * synchronized windows and are thus directly comparable.
> - *
> - * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> - * which excludes things like IRQ and steal-time. These latter are then accrued
> - * in the irq utilization.
> - *
> - * The DL bandwidth number otoh is not a measured metric but a value computed
> - * based on the task model parameters and gives the minimal utilization
> - * required to meet deadlines.
> - */
> -unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
> - unsigned long max, enum schedutil_type type,
> - struct task_struct *p)
> -{
> - unsigned long dl_util, util, irq;
> - struct rq *rq = cpu_rq(cpu);
> -
> - if (!uclamp_is_used() &&
> - type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
> - return max;
> - }
> -
> - /*
> - * Early check to see if IRQ/steal time saturates the CPU, can be
> - * because of inaccuracies in how we track these -- see
> - * update_irq_load_avg().
> - */
> - irq = cpu_util_irq(rq);
> - if (unlikely(irq >= max))
> - return max;
> -
> - /*
> - * Because the time spend on RT/DL tasks is visible as 'lost' time to
> - * CFS tasks and we use the same metric to track the effective
> - * utilization (PELT windows are synchronized) we can directly add them
> - * to obtain the CPU's actual utilization.
> - *
> - * CFS and RT utilization can be boosted or capped, depending on
> - * utilization clamp constraints requested by currently RUNNABLE
> - * tasks.
> - * When there are no CFS RUNNABLE tasks, clamps are released and
> - * frequency will be gracefully reduced with the utilization decay.
> - */
> - util = util_cfs + cpu_util_rt(rq);
> - if (type == FREQUENCY_UTIL)
> - util = uclamp_rq_util_with(rq, util, p);
> -
> - dl_util = cpu_util_dl(rq);
> -
> - /*
> - * For frequency selection we do not make cpu_util_dl() a permanent part
> - * of this sum because we want to use cpu_bw_dl() later on, but we need
> - * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
> - * that we select f_max when there is no idle time.
> - *
> - * NOTE: numerical errors or stop class might cause us to not quite hit
> - * saturation when we should -- something for later.
> - */
> - if (util + dl_util >= max)
> - return max;
> -
> - /*
> - * OTOH, for energy computation we need the estimated running time, so
> - * include util_dl and ignore dl_bw.
> - */
> - if (type == ENERGY_UTIL)
> - util += dl_util;
> -
> - /*
> - * There is still idle time; further improve the number by using the
> - * irq metric. Because IRQ/steal time is hidden from the task clock we
> - * need to scale the task numbers:
> - *
> - * max - irq
> - * U' = irq + --------- * U
> - * max
> - */
> - util = scale_irq_capacity(util, irq, max);
> - util += irq;
> -
> - /*
> - * Bandwidth required by DEADLINE must always be granted while, for
> - * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
> - * to gracefully reduce the frequency when no tasks show up for longer
> - * periods of time.
> - *
> - * Ideally we would like to set bw_dl as min/guaranteed freq and util +
> - * bw_dl as requested freq. However, cpufreq is not yet ready for such
> - * an interface. So, we only do the latter for now.
> - */
> - if (type == FREQUENCY_UTIL)
> - util += cpu_bw_dl(rq);
> -
> - return min(max, util);
> -}
> -
> static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
> {
> struct rq *rq = cpu_rq(sg_cpu->cpu);
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index df80bfcea92e..0db6bcf0881f 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2484,7 +2484,6 @@ static inline unsigned long capacity_orig_of(int cpu)
> {
> return cpu_rq(cpu)->cpu_capacity_orig;
> }
> -#endif
>
> /**
> * enum schedutil_type - CPU utilization type
> @@ -2501,8 +2500,6 @@ enum schedutil_type {
> ENERGY_UTIL,
> };
>
> -#ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL
> -
> unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
> unsigned long max, enum schedutil_type type,
> struct task_struct *p);
> @@ -2533,14 +2530,7 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
> {
> return READ_ONCE(rq->avg_rt.util_avg);
> }
> -#else /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */
> -static inline unsigned long schedutil_cpu_util(int cpu, unsigned long util_cfs,
> - unsigned long max, enum schedutil_type type,
> - struct task_struct *p)
> -{
> - return 0;
> -}
> -#endif /* CONFIG_CPU_FREQ_GOV_SCHEDUTIL */
> +#endif
>
> #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
> static inline unsigned long cpu_util_irq(struct rq *rq)
> --
> 2.25.0.rc1.19.g042ed3e048af
>
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