linux-kernel - Re: [PATCH V6 3/6] sched/fair: Fair server interface

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Date: Thu, 11 Apr 2024 16:43:27 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Daniel Bristot de Oliveira <bristot@...nel.org>
Cc: Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-kernel@...r.kernel.org,
	Luca Abeni <luca.abeni@...tannapisa.it>,
	Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
	Thomas Gleixner <tglx@...utronix.de>,
	Joel Fernandes <joel@...lfernandes.org>,
	Vineeth Pillai <vineeth@...byteword.org>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Phil Auld <pauld@...hat.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Youssef Esmat <youssefesmat@...gle.com>
Subject: Re: [PATCH V6 3/6] sched/fair: Fair server interface

On Fri, Apr 05, 2024 at 07:28:02PM +0200, Daniel Bristot de Oliveira wrote:
> Add an interface for fair server setup on debugfs.
> 
> Each CPU has three files under /debug/sched/fair_server/cpu{ID}:
> 
>  - runtime: set runtime in ns
>  - period:  set period in ns
>  - defer:   on/off for the defer mechanism
> 
> This then leaves /proc/sys/kernel/sched_rt_{period,runtime}_us to set
> bounds on admission control.
> 
> The interface also add the server to the dl bandwidth accounting.

I suppose most people will want to use it like:

  for i in /debug/sched/fair_server/cpu*
  do
	  echo $PERIOD > ${i}/period
	  ecoh $RUNTIME > ${i}/runtime
  done

And I think we agreed to keep this loop in userspace, but memory is
vague.

The 'defer' thing is dubious though, I don't suppose anybody would ever
want to actually change that, other than you while poking around at this
code, right?