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

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Message-ID: <54ac2709-54e5-7a33-a6af-0a07e272365c@arm.com>
Date:   Mon, 20 Apr 2020 10:24:33 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Patrick Bellasi <patrick.bellasi@...bug.net>,
        Qais Yousef <qais.yousef@....com>
Cc:     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 14/04/2020 20:21, Patrick Bellasi wrote:
> Hi Qais!
> 
> On 03-Apr 13:30, Qais Yousef wrote:

[...]

>> @@ -924,6 +945,14 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
>>  	return uc_req;
>>  }
>>  
>> +static void uclamp_rt_sync_default_util_min(struct task_struct *p)
>> +{
>> +	struct uclamp_se *uc_se = &p->uclamp_req[UCLAMP_MIN];
> 
> Don't we have to filter for RT tasks only here?

I think so. It's probably because it got moved from rt.c to core.c.

[...]

>> 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

[...]