linux-kernel - Re: [PATCH v8 10/15] sched: Introduce a sysctl for Energy Aware Scheduling

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Date:   Tue, 16 Oct 2018 14:36:24 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     peterz@...radead.org, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        gregkh@...uxfoundation.org, mingo@...hat.com,
        dietmar.eggemann@....com, morten.rasmussen@....com,
        chris.redpath@....com, patrick.bellasi@....com,
        valentin.schneider@....com, vincent.guittot@...aro.org,
        thara.gopinath@...aro.org, viresh.kumar@...aro.org,
        tkjos@...gle.com, joel@...lfernandes.org, smuckle@...gle.com,
        adharmap@...eaurora.org, skannan@...eaurora.org,
        pkondeti@...eaurora.org, edubezval@...il.com,
        srinivas.pandruvada@...ux.intel.com, currojerez@...eup.net,
        javi.merino@...nel.org
Subject: Re: [PATCH v8 10/15] sched: Introduce a sysctl for Energy Aware
 Scheduling

Hi,

On Tuesday 16 Oct 2018 at 14:50:58 (+0200), Juri Lelli wrote:
> Hi,
> 
> On 16/10/18 11:15, Quentin Perret wrote:
> 
> [...]
> 
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index cc02050fd0c4..481309a11174 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -466,6 +466,17 @@ static struct ctl_table kern_table[] = {
> >  		.extra1		= &one,
> >  	},
> >  #endif
> > +#if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
> > +	{
> > +		.procname	= "sched_energy_aware",
> > +		.data		= &sysctl_sched_energy_aware,
> > +		.maxlen		= sizeof(unsigned int),
> > +		.mode		= 0644,
> > +		.proc_handler	= sched_energy_aware_handler,
> > +		.extra1		= &zero,
> > +		.extra2		= &one,
> > +	},
> > +#endif
> 
> Doesn't this need to be documented in Documentation/sysctl/kernel.txt?

Right, that'd be a good practice indeed. What do you think about the
patch below ?

> Also, do we want a kernel parameter as well to be able to disable this
> at boot?

Yeah, why not. But I guess we could always add that later if need be ?

Thanks,
Quentin

---
From: Quentin Perret <quentin.perret@....com>
Date: Tue, 16 Oct 2018 14:26:06 +0100
Subject: [PATCH] sched: Document sched_energy_aware sysctl

Add a new entry to Documentation/sysctl/kernel.txt explaining how
the new 'sched_energy_aware' knob should be used.

Signed-off-by: Quentin Perret <quentin.perret@....com>
---
 Documentation/sysctl/kernel.txt | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 37a679501ddc..36bee799ee9e 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -78,6 +78,7 @@ show up in /proc/sys/kernel:
 - reboot-cmd                  [ SPARC only ]
 - rtsig-max
 - rtsig-nr
+- sched_energy_aware
 - seccomp/                    ==> Documentation/userspace-api/seccomp_filter.rst
 - sem
 - sem_next_id		      [ sysv ipc ]
@@ -872,6 +873,17 @@ rtsig-nr shows the number of RT signals currently queued.
 
 ==============================================================
 
+sched_energy_aware:
+
+Enables/disables Energy Aware Scheduling (EAS). EAS starts
+automatically on platforms where it can run (that is,
+platforms with asymmetric CPU topologies and having an Energy
+Model available). If your platform happens to meet the
+requirements for EAS but you do not want to use it, change
+this value to 0.
+
+==============================================================
+
 sched_schedstats:
 
 Enables/disables scheduler statistics. Enabling this feature