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

From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Patrick Bellasi <patrick.bellasi@matbug.net>,
	Qais Yousef <qais.yousef@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Iurii Zaikin <yzaikin@google.com>,
	Quentin Perret <qperret@google.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Pavan Kondeti <pkondeti@codeaurora.org>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value
Date: Mon, 20 Apr 2020 10:24:33 +0200	[thread overview]
Message-ID: <54ac2709-54e5-7a33-a6af-0a07e272365c@arm.com> (raw)
In-Reply-To: <20200414182152.GB20442@darkstar>

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@h960:~# 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

[...]