Re: [PATCH 3/3] cpufreq: schedutil: remove redundant code from sugov_next_freq_shared()

From: Rafael J. Wysocki
Date: Wed Mar 08 2017 - 08:03:52 EST


On Wed, Mar 8, 2017 at 12:15 PM, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> On 08-03-17, 11:50, Rafael J. Wysocki wrote:
>> So overall, maybe you can move the flags check to
>> sugov_update_shared(), so that you don't need to pass flags to
>> sugov_next_freq_shared(), and then do what you did to util and max.
>
> Just to confirm, below is what you are suggesting ?

Yes, it is.

> -------------------------8<-------------------------
>
> 1 file changed, 9 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 78468aa051ab..f5ffe241812e 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -217,30 +217,19 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
> sugov_update_commit(sg_policy, time, next_f);
> }
>
> -static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
> - unsigned long util, unsigned long max,
> - unsigned int flags)
> +static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu)
> {
> struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> struct cpufreq_policy *policy = sg_policy->policy;
> - unsigned int max_f = policy->cpuinfo.max_freq;
> u64 last_freq_update_time = sg_policy->last_freq_update_time;
> + unsigned long util = 0, max = 1;
> unsigned int j;
>
> - if (flags & SCHED_CPUFREQ_RT_DL)
> - return max_f;
> -
> - sugov_iowait_boost(sg_cpu, &util, &max);
> -
> for_each_cpu(j, policy->cpus) {
> - struct sugov_cpu *j_sg_cpu;
> + struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j);
> unsigned long j_util, j_max;
> s64 delta_ns;
>
> - if (j == smp_processor_id())
> - continue;
> -
> - j_sg_cpu = &per_cpu(sugov_cpu, j);
> /*
> * If the CPU utilization was last updated before the previous
> * frequency update and the time elapsed between the last update
> @@ -254,7 +243,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
> continue;
> }
> if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
> - return max_f;
> + return policy->cpuinfo.max_freq;
>
> j_util = j_sg_cpu->util;
> j_max = j_sg_cpu->max;
> @@ -289,7 +278,11 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> sg_cpu->last_update = time;
>
> if (sugov_should_update_freq(sg_policy, time)) {
> - next_f = sugov_next_freq_shared(sg_cpu, util, max, flags);
> + if (flags & SCHED_CPUFREQ_RT_DL)
> + next_f = sg_policy->policy->cpuinfo.max_freq;
> + else
> + next_f = sugov_next_freq_shared(sg_cpu);
> +
> sugov_update_commit(sg_policy, time, next_f);
> }
>
>> But that would be a 4.12 change anyway.
>
> Sure.

And IMO the subject/changelog should not talk about "redundant code",
because the code in question is not in fact redundant, but about
refactoring the code to eliminate one conditional from the
for_each_cpu() loop and to make that loop treat all CPUs in the same
way (more symmetrically).

Thanks,
Rafael