linux-kernel - Re: [PATCH v2] kernel/sched/core: Print the time when the process entered the D state

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Date:   Fri, 9 Jul 2021 15:06:23 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     zhouchuangao <zhouchuangao@...o.com>
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>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kernel/sched/core: Print the time when the process
 entered the D state

On Fri, Jul 09, 2021 at 04:54:49AM -0700, zhouchuangao wrote:
> Sometimes we need to trigger /proc/sysrq-trigger to view the information
> of the D state process in the system.
> e.g:
> echo w > /proc/sysrq-trigger
> 
> Here we print the scheduling time of the process, which is convenient
> for us to judge the state of the system and for debugging.
> 
> Signed-off-by: zhouchuangao <zhouchuangao@...o.com>
> ---
>  kernel/sched/core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index cf16f8f..ab422ab 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8154,10 +8154,12 @@ void sched_show_task(struct task_struct *p)
>  	if (pid_alive(p))
>  		ppid = task_pid_nr(rcu_dereference(p->real_parent));
>  	rcu_read_unlock();
> -	pr_cont(" stack:%5lu pid:%5d ppid:%6d flags:0x%08lx\n",
> +	pr_cont(" stack:%5lu pid:%5d ppid:%6d flags:0x%08lx",
>  		free, task_pid_nr(p), ppid,
>  		(unsigned long)task_thread_info(p)->flags);
> -
> +#ifdef CONFIG_SCHED_INFO
> +	pr_cont(" sched:%llu\n", p->sched_info.last_arrival);

"sched:" isn't really descriptive here, is it?

> +#endif

Also, you lost the "\n" for SCHED_INFO=n.

Please, take more than 5 minutes to fix the issues and test your patch
before sending it again.

>  	print_worker_info(KERN_INFO, p);
>  	print_stop_info(KERN_INFO, p);
>  	show_stack(p, NULL, KERN_INFO);
> -- 
> 2.7.4
>