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    Subject[RFCv5 PATCH 39/46] sched/cpufreq_sched: use static key for cpu frequency selection
    Date
    From: Juri Lelli <juri.lelli@arm.com>

    Introduce a static key to only affect scheduler hot paths when sched
    governor is enabled.

    cc: Ingo Molnar <mingo@redhat.com>
    cc: Peter Zijlstra <peterz@infradead.org>

    Signed-off-by: Juri Lelli <juri.lelli@arm.com>
    ---
    kernel/sched/cpufreq_sched.c | 14 ++++++++++++++
    kernel/sched/fair.c | 1 +
    kernel/sched/sched.h | 6 ++++++
    3 files changed, 21 insertions(+)

    diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c
    index 5020f24..2968f3a 100644
    --- a/kernel/sched/cpufreq_sched.c
    +++ b/kernel/sched/cpufreq_sched.c
    @@ -203,6 +203,18 @@ void cpufreq_sched_set_cap(int cpu, unsigned long capacity)
    return;
    }

    +static inline void set_sched_energy_freq(void)
    +{
    + if (!sched_energy_freq())
    + static_key_slow_inc(&__sched_energy_freq);
    +}
    +
    +static inline void clear_sched_energy_freq(void)
    +{
    + if (sched_energy_freq())
    + static_key_slow_dec(&__sched_energy_freq);
    +}
    +
    static int cpufreq_sched_start(struct cpufreq_policy *policy)
    {
    struct gov_data *gd;
    @@ -243,6 +255,7 @@ static int cpufreq_sched_start(struct cpufreq_policy *policy)

    policy->governor_data = gd;
    gd->policy = policy;
    + set_sched_energy_freq();
    return 0;

    err:
    @@ -254,6 +267,7 @@ static int cpufreq_sched_stop(struct cpufreq_policy *policy)
    {
    struct gov_data *gd = policy->governor_data;

    + clear_sched_energy_freq();
    if (cpufreq_driver_might_sleep()) {
    kthread_stop(gd->task);
    }
    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index f7cb6c9..d395bc9 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -4282,6 +4282,7 @@ static inline void hrtick_update(struct rq *rq)
    #endif

    static bool cpu_overutilized(int cpu);
    +struct static_key __sched_energy_freq __read_mostly = STATIC_KEY_INIT_FALSE;

    /*
    * The enqueue_task method is called before nr_running is
    diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
    index 30aa0c4..b5e27d9 100644
    --- a/kernel/sched/sched.h
    +++ b/kernel/sched/sched.h
    @@ -1476,6 +1476,12 @@ unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
    }
    #endif

    +extern struct static_key __sched_energy_freq;
    +static inline bool sched_energy_freq(void)
    +{
    + return static_key_false(&__sched_energy_freq);
    +}
    +
    #ifdef CONFIG_CPU_FREQ_GOV_SCHED
    void cpufreq_sched_set_cap(int cpu, unsigned long util);
    #else
    --
    1.9.1


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