linux-kernel - Re: [PATCH] sched: cgroup SCHED

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Date:   Fri, 25 Jun 2021 10:14:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Don <joshdon@...gle.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Paul Turner <pjt@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Oleg Rombakh <olegrom@...gle.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Steve Sistare <steven.sistare@...cle.com>,
        Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: cgroup SCHED_IDLE support

On Tue, Jun 08, 2021 at 04:11:32PM -0700, Josh Don wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 8ab69d01dab4..a82f5d3b85d3 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -10234,6 +10234,18 @@ static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
>  
>  	return sched_group_set_shares(css_tg(css), scale_load(weight));
>  }
> +
> +static s64 cpu_idle_read_s64(struct cgroup_subsys_state *css,
> +			       struct cftype *cft)
> +{
> +	return css_tg(css)->idle;
> +}
> +
> +static int cpu_idle_write_s64(struct cgroup_subsys_state *css,
> +				struct cftype *cft, s64 idle)
> +{
> +	return sched_group_set_idle(css_tg(css), idle);
> +}
>  #endif
>  
>  static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
> @@ -10306,6 +10318,12 @@ static struct cftype cpu_files[] = {
>  		.read_s64 = cpu_weight_nice_read_s64,
>  		.write_s64 = cpu_weight_nice_write_s64,
>  	},
> +	{
> +		.name = "idle",
> +		.flags = CFTYPE_NOT_ON_ROOT,
> +		.read_s64 = cpu_idle_read_s64,
> +		.write_s64 = cpu_idle_write_s64,
> +	},
>  #endif
>  #ifdef CONFIG_CFS_BANDWIDTH
>  	{

You should probably also make cpu_weight_*write_?64() return -EINVAL when
IDLE. Similar to how SCHED_IDLE doesn't do nice.