linux-kernel - Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value

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Date:   Mon, 20 Apr 2020 16:19:42 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Patrick Bellasi <patrick.bellasi@...bug.net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jonathan Corbet <corbet@....net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Quentin Perret <qperret@...gle.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Pavan Kondeti <pkondeti@...eaurora.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default
 boost value

On 04/20/20 10:24, Dietmar Eggemann wrote:
> >> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> >> index ad5b88a53c5a..0272ae8c6147 100644
> >> --- a/kernel/sysctl.c
> >> +++ b/kernel/sysctl.c
> >> @@ -465,6 +465,13 @@ static struct ctl_table kern_table[] = {
> >>  		.mode		= 0644,
> >>  		.proc_handler	= sysctl_sched_uclamp_handler,
> >>  	},
> >> +	{
> >> +		.procname	= "sched_rt_default_util_clamp_min",
> 
> root@...0:~# find / -name "*util_clamp*"
> /proc/sys/kernel/sched_rt_default_util_clamp_min
> /proc/sys/kernel/sched_util_clamp_max
> /proc/sys/kernel/sched_util_clamp_min
> 
> IMHO, keeping the common 'sched_util_clamp_' would be helpful here, e.g.
> 
> /proc/sys/kernel/sched_util_clamp_rt_default_min

All RT related knobs are prefixed with 'sched_rt'. I kept the 'util_clamp_min'
coherent with the current sysctl (sched_util_clamp_min). Quentin suggested
adding 'default' to be more obvious, so I ended up with

	'sched_rt' + '_default' + '_util_clamp_min'.

I think this is the logical and most consistent form. Given that Patrick seems
to be okay with the 'default' now, does this look good to you too?

Thanks

--
Qais Yousef