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    Subject[PATCH] cpufreq: schedutil: rate limits for SCHED_DEADLINE
    Date
    When the SCHED_DEADLINE scheduling class increases the CPU utilization,
    we should not wait for the rate limit, otherwise we may miss some deadline.

    Tests using rt-app on Exynos5422 have shown reductions of about 10% of deadline
    misses for tasks with low RT periods.

    The patch applies on top of the one recently proposed by Peter to drop the
    SCHED_CPUFREQ_* flags.

    Signed-off-by: Claudio Scordino <claudio@evidence.eu.com>
    CC: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
    CC: Patrick Bellasi <patrick.bellasi@arm.com>
    CC: Dietmar Eggemann <dietmar.eggemann@arm.com>
    CC: Morten Rasmussen <morten.rasmussen@arm.com>
    CC: Juri Lelli <juri.lelli@redhat.com>
    CC: Viresh Kumar <viresh.kumar@linaro.org>
    CC: Vincent Guittot <vincent.guittot@linaro.org>
    CC: Todd Kjos <tkjos@android.com>
    CC: Joel Fernandes <joelaf@google.com>
    CC: linux-pm@vger.kernel.org
    CC: linux-kernel@vger.kernel.org
    ---
    kernel/sched/cpufreq_schedutil.c | 15 ++++++++++++---
    1 file changed, 12 insertions(+), 3 deletions(-)

    diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
    index b0bd77d..d8dcba2 100644
    --- a/kernel/sched/cpufreq_schedutil.c
    +++ b/kernel/sched/cpufreq_schedutil.c
    @@ -74,7 +74,10 @@ static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);

    /************************ Governor internals ***********************/

    -static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
    +static bool sugov_should_update_freq(struct sugov_policy *sg_policy,
    + u64 time,
    + struct sugov_cpu *sg_cpu_old,
    + struct sugov_cpu *sg_cpu_new)
    {
    s64 delta_ns;

    @@ -111,6 +114,10 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
    return true;
    }

    + /* Ignore rate limit when DL increased utilization. */
    + if (sg_cpu_new->util_dl > sg_cpu_old->util_dl)
    + return true;
    +
    delta_ns = time - sg_policy->last_freq_update_time;
    return delta_ns >= sg_policy->freq_update_delay_ns;
    }
    @@ -271,6 +278,7 @@ static void sugov_update_single(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_cpu sg_cpu_old = *sg_cpu;
    struct sugov_policy *sg_policy = sg_cpu->sg_policy;
    unsigned long util, max;
    unsigned int next_f;
    @@ -279,7 +287,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
    sugov_set_iowait_boost(sg_cpu, time, flags);
    sg_cpu->last_update = time;

    - if (!sugov_should_update_freq(sg_policy, time))
    + if (!sugov_should_update_freq(sg_policy, time, &sg_cpu_old, sg_cpu))
    return;

    busy = sugov_cpu_is_busy(sg_cpu);
    @@ -350,6 +358,7 @@ static void sugov_update_shared(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_cpu sg_cpu_old = *sg_cpu;
    struct sugov_policy *sg_policy = sg_cpu->sg_policy;
    unsigned int next_f;

    @@ -359,7 +368,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
    sugov_set_iowait_boost(sg_cpu, time, flags);
    sg_cpu->last_update = time;

    - if (sugov_should_update_freq(sg_policy, time)) {
    + if (sugov_should_update_freq(sg_policy, time, &sg_cpu_old, sg_cpu)) {
    next_f = sugov_next_freq_shared(sg_cpu, time);
    sugov_update_commit(sg_policy, time, next_f);
    }
    --
    2.7.4
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