linux-kernel - Re: [PATCH v3] cpufreq: schedutil: rate limits for SCHED

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Date:   Thu, 8 Mar 2018 16:03:05 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Claudio Scordino <claudio@...dence.eu.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] cpufreq: schedutil: rate limits for SCHED_DEADLINE

On 08-03-18, 11:29, Claudio Scordino wrote:
> 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 with up to 10 SCHED_DEADLINE tasks have
> shown reductions of even 10% of deadline misses with a negligible
> increase of energy consumption (measured through Baylibre Cape).
> 
> Signed-off-by: Claudio Scordino <claudio@...dence.eu.com>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Patrick Bellasi <patrick.bellasi@....com>
> CC: Dietmar Eggemann <dietmar.eggemann@....com>
> CC: Morten Rasmussen <morten.rasmussen@....com>
> CC: Juri Lelli <juri.lelli@...hat.com>
> CC: Viresh Kumar <viresh.kumar@...aro.org>
> CC: Vincent Guittot <vincent.guittot@...aro.org>
> CC: Todd Kjos <tkjos@...roid.com>
> CC: Joel Fernandes <joelaf@...gle.com>
> CC: linux-pm@...r.kernel.org
> CC: linux-kernel@...r.kernel.org
> ---
> Changes from v2:
>  - Rate limit ignored also in case of "fast switch"
>  - Specific routine added
> ---
> Changes from v1:
>  - Logic moved from sugov_should_update_freq() to
>    sugov_update_single()/_shared() to not duplicate data structures
>  - Rate limit not ignored in case of "fast switch"
> ---
>  kernel/sched/cpufreq_schedutil.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 7936f54..13f9cce 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -260,6 +260,17 @@ static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
>  static inline bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu) { return false; }
>  #endif /* CONFIG_NO_HZ_COMMON */
>  
> +/*
> + * Make sugov_should_update_freq() ignore the rate limit when DL
> + * has increased the utilization.
> + */
> +static inline
> +void set_dl_rate_limit(struct sugov_cpu *sg_cpu, struct sugov_policy *sg_policy)

Maybe it could be renamed as ignore_dl_rate_limit() ? Lets see what others have
to say. But looks fine otherwise.

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh