linux-kernel - Re: [PATCH] sched/psi: create /proc/pressure and /proc/pressure/{io|memory|cpu} only when psi enabled

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Message-ID: <20200108135526.GH2844@hirez.programming.kicks-ass.net>
Date:   Wed, 8 Jan 2020 14:55:26 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Wang Long <w@...qinren.net>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        linux-kernel@...r.kernel.org, hannes@...xchg.org
Subject: Re: [PATCH] sched/psi: create /proc/pressure and
 /proc/pressure/{io|memory|cpu} only when psi enabled

On Wed, Dec 18, 2019 at 08:38:18PM +0800, Wang Long wrote:
> when CONFIG_PSI_DEFAULT_DISABLED set to N or the command line set psi=0,
> I think we should not create /proc/pressure and
> /proc/pressure/{io|memory|cpu}.
> 
> In the future, user maybe determine whether the psi feature is enabled by
> checking the existence of the /proc/pressure dir or
> /proc/pressure/{io|memory|cpu} files.

Works for me; Johannes?

> Signed-off-by: Wang Long <w@...qinren.net>
> ---
>  kernel/sched/psi.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 517e371..f12ade2 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -1279,10 +1279,12 @@ static int psi_fop_release(struct inode *inode, struct file *file)
>  
>  static int __init psi_proc_init(void)
>  {
> -	proc_mkdir("pressure", NULL);
> -	proc_create("pressure/io", 0, NULL, &psi_io_fops);
> -	proc_create("pressure/memory", 0, NULL, &psi_memory_fops);
> -	proc_create("pressure/cpu", 0, NULL, &psi_cpu_fops);
> +	if (psi_enable) {
> +		proc_mkdir("pressure", NULL);
> +		proc_create("pressure/io", 0, NULL, &psi_io_fops);
> +		proc_create("pressure/memory", 0, NULL, &psi_memory_fops);
> +		proc_create("pressure/cpu", 0, NULL, &psi_cpu_fops);
> +	}
>  	return 0;
>  }
>  module_init(psi_proc_init);
> -- 
> 1.8.3.1
> 
> 
>