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

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Message-ID: <1abbe4a5-61e6-a918-ff89-3dea0c7a277c@arm.com>
Date:   Tue, 21 Apr 2020 13:16:03 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Qais Yousef <qais.yousef@....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>,
        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 21/04/2020 02:52, Steven Rostedt wrote:
> On Mon, 20 Apr 2020 16:19:42 +0100
> Qais Yousef <qais.yousef@....com> wrote:
> 
>>> 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?
> 
> There's only two files with "sched_rt" and they are tightly coupled
> (they define how much an RT task may use the CPU).
> 
> My question is, is this "sched_rt_default_util_clamp_min" related in
> any way to those other two files that start with "sched_rt", or is it
> more related to the files that start with "sched_util_clamp"?
> 
> If the latter, then I would suggest using
> "sched_util_clamp_min_rt_default", as it looks to be more related to
> the "sched_util_clamp_min" than to anything else.

For me it's the latter.