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Message-ID: <CAJZ5v0jR2RozeV301u4g90-BpNqkQMRrN=dgaOkJ7veVZ02=aw@mail.gmail.com>
Date: Tue, 23 Aug 2022 20:04:49 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Lukasz Luba <lukasz.luba@....com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux PM <linux-pm@...r.kernel.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH v2] cpufreq: schedutil: Move max CPU capacity to sugov_policy
On Tue, Aug 16, 2022 at 3:06 PM Lukasz Luba <lukasz.luba@....com> wrote:
>
> There is no need to keep the max CPU capacity in the per_cpu instance.
> Furthermore, there is no need to check and update that variable
> (sg_cpu->max) every time in the frequency change request, which is part
> of hot path. Instead use struct sugov_policy to store that information.
> Initialize the max CPU capacity during the setup and start callback.
> We can do that since all CPUs in the same frequency domain have the same
> max capacity (capacity setup and thermal pressure are based on that).
>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
> Changes v2:
> - collected ACK from Viresh
> - re-based on top of latest mainline where the previously conflicting
> change is now merged
>
> kernel/sched/cpufreq_schedutil.c | 30 +++++++++++++++---------------
> 1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 1207c78f85c1..9161d1136d01 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -25,6 +25,9 @@ struct sugov_policy {
> unsigned int next_freq;
> unsigned int cached_raw_freq;
>
> + /* max CPU capacity, which is equal for all CPUs in freq. domain */
> + unsigned long max;
> +
> /* The next fields are only needed if fast switch cannot be used: */
> struct irq_work irq_work;
> struct kthread_work work;
> @@ -48,7 +51,6 @@ struct sugov_cpu {
>
> unsigned long util;
> unsigned long bw_dl;
> - unsigned long max;
>
> /* The field below is for single-CPU policies only: */
> #ifdef CONFIG_NO_HZ_COMMON
> @@ -158,7 +160,6 @@ static void sugov_get_util(struct sugov_cpu *sg_cpu)
> {
> struct rq *rq = cpu_rq(sg_cpu->cpu);
>
> - 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),
> FREQUENCY_UTIL, NULL);
> @@ -253,6 +254,7 @@ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
> */
> static void sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time)
> {
> + struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> unsigned long boost;
>
> /* No boost currently required */
> @@ -280,7 +282,8 @@ static void sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time)
> * sg_cpu->util is already in capacity scale; convert iowait_boost
> * into the same scale so we can compare.
> */
> - boost = (sg_cpu->iowait_boost * sg_cpu->max) >> SCHED_CAPACITY_SHIFT;
> + boost = sg_cpu->iowait_boost * sg_policy->max;
> + boost >>= SCHED_CAPACITY_SHIFT;
> boost = uclamp_rq_util_with(cpu_rq(sg_cpu->cpu), boost, NULL);
> if (sg_cpu->util < boost)
> sg_cpu->util = boost;
> @@ -337,7 +340,7 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time,
> if (!sugov_update_single_common(sg_cpu, time, flags))
> return;
>
> - next_f = get_next_freq(sg_policy, sg_cpu->util, sg_cpu->max);
> + next_f = get_next_freq(sg_policy, sg_cpu->util, sg_policy->max);
> /*
> * Do not reduce the frequency if the CPU has not been idle
> * recently, as the reduction is likely to be premature then.
> @@ -373,6 +376,7 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time,
> unsigned int flags)
> {
> struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
> + struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> unsigned long prev_util = sg_cpu->util;
>
> /*
> @@ -399,7 +403,8 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time,
> sg_cpu->util = prev_util;
>
> cpufreq_driver_adjust_perf(sg_cpu->cpu, map_util_perf(sg_cpu->bw_dl),
> - map_util_perf(sg_cpu->util), sg_cpu->max);
> + map_util_perf(sg_cpu->util),
> + sg_policy->max);
>
> sg_cpu->sg_policy->last_freq_update_time = time;
> }
> @@ -408,25 +413,19 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
> {
> struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> struct cpufreq_policy *policy = sg_policy->policy;
> - unsigned long util = 0, max = 1;
> + unsigned long util = 0;
> unsigned int j;
>
> for_each_cpu(j, policy->cpus) {
> struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j);
> - unsigned long j_util, j_max;
>
> sugov_get_util(j_sg_cpu);
> sugov_iowait_apply(j_sg_cpu, time);
> - j_util = j_sg_cpu->util;
> - j_max = j_sg_cpu->max;
>
> - if (j_util * max > j_max * util) {
> - util = j_util;
> - max = j_max;
> - }
> + util = max(j_sg_cpu->util, util);
> }
>
> - return get_next_freq(sg_policy, util, max);
> + return get_next_freq(sg_policy, util, sg_policy->max);
> }
>
> static void
> @@ -752,7 +751,7 @@ static int sugov_start(struct cpufreq_policy *policy)
> {
> struct sugov_policy *sg_policy = policy->governor_data;
> void (*uu)(struct update_util_data *data, u64 time, unsigned int flags);
> - unsigned int cpu;
> + unsigned int cpu = cpumask_first(policy->cpus);
>
> sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
> sg_policy->last_freq_update_time = 0;
> @@ -760,6 +759,7 @@ static int sugov_start(struct cpufreq_policy *policy)
> sg_policy->work_in_progress = false;
> sg_policy->limits_changed = false;
> sg_policy->cached_raw_freq = 0;
> + sg_policy->max = arch_scale_cpu_capacity(cpu);
>
> sg_policy->need_freq_update = cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS);
>
> --
Applied as 6.1 material, thanks!
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