linux-kernel - 答复: [PATCH V4] sched/cpufreq: initialize iowait_boost_max and iowait

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Date:   Mon, 4 Mar 2019 07:35:04 +0000
From:   Wang, Vincent (王争) <Vincent.Wang@...soc.com>
To:     Quentin Perret <quentin.perret@....com>,
        Zhang, Chunyan (张春艳) 
        <Chunyan.Zhang@...soc.com>
CC:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chunyan Zhang <zhang.lyra@...il.com>
Subject: 答复: [PATCH V4] sched/cpufreq: initialize iowait_boost_max and iowait_boost with cpu capacity

Did you mean the value of arch_scale_cpu_capacity() is changed in cpu_capacity_store()?
If so, I can restart schedutil governor after new capacity is updated.
________________________________________
发件人: Quentin Perret <quentin.perret@....com>
发送时间: 2019年2月22日 18:59
收件人: Zhang, Chunyan (张春艳)
抄送: Ingo Molnar; Peter Zijlstra; Wang, Vincent (王争); linux-kernel@...r.kernel.org; Chunyan Zhang
主题: Re: [PATCH V4] sched/cpufreq: initialize iowait_boost_max and iowait_boost with cpu capacity

On Friday 22 Feb 2019 at 18:37:46 (+0800), Chunyan Zhang wrote:
> @@ -823,6 +823,8 @@ static int sugov_start(struct cpufreq_policy *policy)
>  {
>       struct sugov_policy *sg_policy = policy->governor_data;
>       unsigned int cpu;
> +     unsigned long max_cap = arch_scale_cpu_capacity(NULL, policy->cpu);
> +     unsigned long min_cap = max_cap * policy->min / policy->cpuinfo.max_freq;
>
>       sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
>       sg_policy->last_freq_update_time        = 0;
> @@ -837,7 +839,9 @@ static int sugov_start(struct cpufreq_policy *policy)
>               memset(sg_cpu, 0, sizeof(*sg_cpu));
>               sg_cpu->cpu                     = cpu;
>               sg_cpu->sg_policy               = sg_policy;
> -             sg_cpu->iowait_boost_max        = policy->cpuinfo.max_freq;
> +             sg_cpu->max                     = max_cap;
> +             sg_cpu->min                     = min_cap;
> +             sg_cpu->iowait_boost_max        = max_cap;

Unfortunately, I don't think you can do that only here. The return value
of arch_scale_cpu_capacity() can change at run time. And it does on arm64,
see drivers/base/arch_topology.c.

>       }
>
>       for_each_cpu(cpu, policy->cpus) {
> --
> 2.17.1
>

Thanks,
Quentin