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Message-ID: <CAKfTPtDiRWa5Gu1Xa6k=Yp+6AhNz3d-9xXhJY-JjzU0+anOHig@mail.gmail.com>
Date: Tue, 31 May 2022 09:59:01 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Vincent Donnefort <vdonnefort@...gle.com>
Cc: peterz@...radead.org, mingo@...hat.com,
linux-kernel@...r.kernel.org, dietmar.eggemann@....com,
morten.rasmussen@....com, chris.redpath@....com,
qperret@...gle.com, tao.zhou@...ux.dev, kernel-team@...roid.com
Subject: Re: [PATCH v9 3/7] sched, drivers: Remove max param from effective_cpu_util()/sched_cpu_util()
On Mon, 23 May 2022 at 17:52, Vincent Donnefort <vdonnefort@...gle.com> wrote:
>
> From: Dietmar Eggemann <dietmar.eggemann@....com>
>
> effective_cpu_util() already has a `int cpu' parameter which allows to
> retrieve the CPU capacity scale factor (or maximum CPU capacity) inside
> this function via an arch_scale_cpu_capacity(cpu).
>
> A lot of code calling effective_cpu_util() (or the shim
> sched_cpu_util()) needs the maximum CPU capacity, i.e. it will call
> arch_scale_cpu_capacity() already.
> But not having to pass it into effective_cpu_util() will make the EAS
> wake-up code easier, especially when the maximum CPU capacity reduced
> by the thermal pressure is passed through the EAS wake-up functions.
>
> Due to the asymmetric CPU capacity support of arm/arm64 architectures,
> arch_scale_cpu_capacity(int cpu) is a per-CPU variable read access via
> per_cpu(cpu_scale, cpu) on such a system.
> On all other architectures it is a a compile-time constant
> (SCHED_CAPACITY_SCALE).
>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
Acked-by: Vincent Guittot <vincent.guittot@...aro.org>
>
> diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c
> index f5eced0842b3..6a88eb7e9f75 100644
> --- a/drivers/powercap/dtpm_cpu.c
> +++ b/drivers/powercap/dtpm_cpu.c
> @@ -71,34 +71,19 @@ static u64 set_pd_power_limit(struct dtpm *dtpm, u64 power_limit)
>
> static u64 scale_pd_power_uw(struct cpumask *pd_mask, u64 power)
> {
> - unsigned long max = 0, sum_util = 0;
> + unsigned long max, sum_util = 0;
> int cpu;
>
> - for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
> -
> - /*
> - * The capacity is the same for all CPUs belonging to
> - * the same perf domain, so a single call to
> - * arch_scale_cpu_capacity() is enough. However, we
> - * need the CPU parameter to be initialized by the
> - * loop, so the call ends up in this block.
> - *
> - * We can initialize 'max' with a cpumask_first() call
> - * before the loop but the bits computation is not
> - * worth given the arch_scale_cpu_capacity() just
> - * returns a value where the resulting assembly code
> - * will be optimized by the compiler.
> - */
> - max = arch_scale_cpu_capacity(cpu);
> - sum_util += sched_cpu_util(cpu, max);
> - }
> -
> /*
> - * In the improbable case where all the CPUs of the perf
> - * domain are offline, 'max' will be zero and will lead to an
> - * illegal operation with a zero division.
> + * The capacity is the same for all CPUs belonging to
> + * the same perf domain.
> */
> - return max ? (power * ((sum_util << 10) / max)) >> 10 : 0;
> + max = arch_scale_cpu_capacity(cpumask_first(pd_mask));
> +
> + for_each_cpu_and(cpu, pd_mask, cpu_online_mask)
> + sum_util += sched_cpu_util(cpu);
> +
> + return (power * ((sum_util << 10) / max)) >> 10;
> }
>
> static u64 get_pd_power_uw(struct dtpm *dtpm)
> diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
> index b8151d95a806..b263b0fde03c 100644
> --- a/drivers/thermal/cpufreq_cooling.c
> +++ b/drivers/thermal/cpufreq_cooling.c
> @@ -137,11 +137,9 @@ static u32 cpu_power_to_freq(struct cpufreq_cooling_device *cpufreq_cdev,
> static u32 get_load(struct cpufreq_cooling_device *cpufreq_cdev, int cpu,
> int cpu_idx)
> {
> - unsigned long max = arch_scale_cpu_capacity(cpu);
> - unsigned long util;
> + unsigned long util = sched_cpu_util(cpu);
>
> - util = sched_cpu_util(cpu, max);
> - return (util * 100) / max;
> + return (util * 100) / arch_scale_cpu_capacity(cpu);
> }
> #else /* !CONFIG_SMP */
> static u32 get_load(struct cpufreq_cooling_device *cpufreq_cdev, int cpu,
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index c46f3a63b758..88b8817b827d 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2257,7 +2257,7 @@ static inline bool owner_on_cpu(struct task_struct *owner)
> }
>
> /* Returns effective CPU energy utilization, as seen by the scheduler */
> -unsigned long sched_cpu_util(int cpu, unsigned long max);
> +unsigned long sched_cpu_util(int cpu);
> #endif /* CONFIG_SMP */
>
> #ifdef CONFIG_RSEQ
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 53596842f0d8..c531976ee960 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7107,12 +7107,14 @@ struct task_struct *idle_task(int cpu)
> * required to meet deadlines.
> */
> unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> - unsigned long max, enum cpu_util_type type,
> + enum cpu_util_type type,
> struct task_struct *p)
> {
> - unsigned long dl_util, util, irq;
> + unsigned long dl_util, util, irq, max;
> struct rq *rq = cpu_rq(cpu);
>
> + max = arch_scale_cpu_capacity(cpu);
> +
> if (!uclamp_is_used() &&
> type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
> return max;
> @@ -7192,10 +7194,9 @@ unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> return min(max, util);
> }
>
> -unsigned long sched_cpu_util(int cpu, unsigned long max)
> +unsigned long sched_cpu_util(int cpu)
> {
> - return effective_cpu_util(cpu, cpu_util_cfs(cpu), max,
> - ENERGY_UTIL, NULL);
> + return effective_cpu_util(cpu, cpu_util_cfs(cpu), ENERGY_UTIL, NULL);
> }
> #endif /* CONFIG_SMP */
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 3dbf351d12d5..1207c78f85c1 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -157,11 +157,10 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
> static void sugov_get_util(struct sugov_cpu *sg_cpu)
> {
> struct rq *rq = cpu_rq(sg_cpu->cpu);
> - unsigned long max = arch_scale_cpu_capacity(sg_cpu->cpu);
>
> - sg_cpu->max = max;
> + sg_cpu->max = arch_scale_cpu_capacity(sg_cpu->cpu);
> sg_cpu->bw_dl = cpu_bw_dl(rq);
> - sg_cpu->util = effective_cpu_util(sg_cpu->cpu, cpu_util_cfs(sg_cpu->cpu), max,
> + sg_cpu->util = effective_cpu_util(sg_cpu->cpu, cpu_util_cfs(sg_cpu->cpu),
> FREQUENCY_UTIL, NULL);
> }
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index df5e6e565b4d..73a9dc522b73 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6703,12 +6703,11 @@ static long
> compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
> {
> struct cpumask *pd_mask = perf_domain_span(pd);
> - unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
> - unsigned long max_util = 0, sum_util = 0;
> - unsigned long _cpu_cap = cpu_cap;
> + unsigned long max_util = 0, sum_util = 0, cpu_cap;
> int cpu;
>
> - _cpu_cap -= arch_scale_thermal_pressure(cpumask_first(pd_mask));
> + cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
> + cpu_cap -= arch_scale_thermal_pressure(cpumask_first(pd_mask));
>
> /*
> * The capacity state of CPUs of the current rd can be driven by CPUs
> @@ -6745,10 +6744,10 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
> * is already enough to scale the EM reported power
> * consumption at the (eventually clamped) cpu_capacity.
> */
> - cpu_util = effective_cpu_util(cpu, util_running, cpu_cap,
> - ENERGY_UTIL, NULL);
> + cpu_util = effective_cpu_util(cpu, util_running, ENERGY_UTIL,
> + NULL);
>
> - sum_util += min(cpu_util, _cpu_cap);
> + sum_util += min(cpu_util, cpu_cap);
>
> /*
> * Performance domain frequency: utilization clamping
> @@ -6757,12 +6756,12 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
> * NOTE: in case RT tasks are running, by default the
> * FREQUENCY_UTIL's utilization can be max OPP.
> */
> - cpu_util = effective_cpu_util(cpu, util_freq, cpu_cap,
> - FREQUENCY_UTIL, tsk);
> - max_util = max(max_util, min(cpu_util, _cpu_cap));
> + cpu_util = effective_cpu_util(cpu, util_freq, FREQUENCY_UTIL,
> + tsk);
> + max_util = max(max_util, min(cpu_util, cpu_cap));
> }
>
> - return em_cpu_energy(pd->em_pd, max_util, sum_util, _cpu_cap);
> + return em_cpu_energy(pd->em_pd, max_util, sum_util, cpu_cap);
> }
>
> /*
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 97bc26e5c8af..07b7c50bd987 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2895,7 +2895,7 @@ enum cpu_util_type {
> };
>
> unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> - unsigned long max, enum cpu_util_type type,
> + enum cpu_util_type type,
> struct task_struct *p);
>
> static inline unsigned long cpu_bw_dl(struct rq *rq)
> --
> 2.36.1.124.g0e6072fb45-goog
>
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