Re: [PATCH] sched: cgroup SCHED_IDLE support

From: Peter Zijlstra <peterz@infradead.org>
To: Josh Don <joshdon@google.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Paul Turner <pjt@google.com>,
	David Rientjes <rientjes@google.com>,
	Oleg Rombakh <olegrom@google.com>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Steve Sistare <steven.sistare@oracle.com>,
	Tejun Heo <tj@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched: cgroup SCHED_IDLE support
Date: Fri, 25 Jun 2021 10:14:53 +0200	[thread overview]
Message-ID: <YNWQfZfMNyEsiKTb@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210608231132.32012-1-joshdon@google.com>

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.