linux-kernel - Re: [PATCH v2 1/1] x86,sched: On AMD EPYC set freq_max = max

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Message-ID: <20210203060414.hexqlimjol3tdtvq@vireshk-i7>
Date:   Wed, 3 Feb 2021 11:34:14 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Giovanni Gherdovich <ggherdovich@...e.cz>
Cc:     Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Jon Grimm <Jon.Grimm@....com>,
        Nathan Fontenot <Nathan.Fontenot@....com>,
        Yazen Ghannam <Yazen.Ghannam@....com>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Suthikulpanit Suravee <Suravee.Suthikulpanit@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pu Wen <puwen@...on.cn>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Michael Larabel <Michael@...ronix.com>, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 1/1] x86,sched: On AMD EPYC set freq_max = max_boost
 in schedutil invariant formula

I am sorry but I wasn't able to get the full picture (not your fault,
it is me), but ...

On 22-01-21, 21:40, Giovanni Gherdovich wrote:
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index d0a3525ce27f..b96677f6b57e 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2721,6 +2721,9 @@ int cpufreq_boost_enabled(void)
>  }
>  EXPORT_SYMBOL_GPL(cpufreq_boost_enabled);
>  
> +DEFINE_STATIC_KEY_FALSE(cpufreq_amd_max_boost);
> +EXPORT_SYMBOL_GPL(cpufreq_amd_max_boost);
> +
>  /*********************************************************************
>   *               REGISTER / UNREGISTER CPUFREQ DRIVER                *
>   *********************************************************************/
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 9c8b7437b6cd..341cac76d254 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -40,9 +40,14 @@ enum cpufreq_table_sorting {
>  	CPUFREQ_TABLE_SORTED_DESCENDING
>  };
>  
> +DECLARE_STATIC_KEY_FALSE(cpufreq_amd_max_boost);
> +
> +#define cpufreq_driver_has_max_boost() static_branch_unlikely(&cpufreq_amd_max_boost)
> +

I am not happy with AMD specific code/changes in common parts..

>  struct cpufreq_cpuinfo {
>  	unsigned int		max_freq;
>  	unsigned int		min_freq;
> +	unsigned int		max_boost;
>  
>  	/* in 10^(-9) s = nanoseconds */
>  	unsigned int		transition_latency;
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 6931f0cdeb80..541f3db3f576 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -159,8 +159,12 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
>  				  unsigned long util, unsigned long max)
>  {
>  	struct cpufreq_policy *policy = sg_policy->policy;
> -	unsigned int freq = arch_scale_freq_invariant() ?
> -				policy->cpuinfo.max_freq : policy->cur;
> +	unsigned int freq, max_freq;
> +
> +	max_freq = cpufreq_driver_has_max_boost() ?
> +			policy->cpuinfo.max_boost : policy->cpuinfo.max_freq;

Also, can't we update max_freq itself from the cpufreq driver? What
troubles will it cost ?

> +
> +	freq = arch_scale_freq_invariant() ? max_freq : policy->cur;
>  
>  	freq = map_util_freq(util, freq, max);
>  
> -- 
> 2.26.2

-- 
viresh