linux-kernel - Re: [PATCH] sched/debug: print column titles of show_state

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Message-ID: <20210812103826.27dfad5f@oasis.local.home>
Date:   Thu, 12 Aug 2021 10:38:26 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Shirish S <shirish.s@....com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>,
        "Mel Gorman" <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/debug: print column titles of show_state_filter()

On Thu, 12 Aug 2021 16:35:34 +0530
Shirish S <shirish.s@....com> wrote:

> This addition in the debug output shall improve readablitly..
> Its not intuitive for users that the pid printed in last column
> is of parent process.
> 
> Without this patch:
> 	localhost ~ # dmesg -w &
> 	localhost ~ # echo w > /proc/sysrq-trigger
> 	[22148.730225] sysrq: Show Blocked State
> 	localhost ~ #
> 
> With this patch:
> 	localhost ~ # dmesg -w &
> 	localhost ~ # echo w > /proc/sysrq-trigger
> 	[   99.979365] sysrq: Show Blocked State
> -->	[   99.983471]   task                        PC stack   pid father  
> 	localhost ~ #
> 

It would had been more informative, if there were content to those lists.

Just a few lines would be good enough. But the above, just looks like
you are adding a useless header. :-/

In fact, I would argue that the title should not be displayed if the
content is empty.

Also, s/father/parent/  or s/father/ppid/

-- Steve



> v2: Dropped #ifdef logic
> v3: Sample output in commit message
> 
> Signed-off-by: Shirish S <shirish.s@....com>
> Suggested-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  kernel/sched/core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 20ffcc044134..1c7ea3ef5a9f 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8174,6 +8174,9 @@ void show_state_filter(unsigned int state_filter)
>  {
>  	struct task_struct *g, *p;
>  
> +	pr_info("  task%*s", BITS_PER_LONG == 32 ? 38 : 46,
> +		"PC stack   pid father\n");
> +
>  	rcu_read_lock();
>  	for_each_process_thread(g, p) {
>  		/*