linux-kernel - Re: [PATCH] exit,stats: /* obey this comment */

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Message-Id: <20150423144731.2c591c8eb70755b54ac83917@linux-foundation.org>
Date:	Thu, 23 Apr 2015 14:47:31 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH] exit,stats: /* obey this comment */

On Thu, 23 Apr 2015 17:17:59 -0400 Rik van Riel <riel@...hat.com> wrote:

> There is a helpful comment in do_exit() that states we sync the
> mm's RSS info before statistics gathering.
> 
> The function that does the statistics gathering is called right
> above that comment.
> 
> Change the code to obey the comment.
> 
> ...
>
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -711,10 +711,10 @@ void do_exit(long code)
>  			current->comm, task_pid_nr(current),
>  			preempt_count());
>  
> -	acct_update_integrals(tsk);
>  	/* sync mm's RSS info before statistics gathering */
>  	if (tsk->mm)
>  		sync_mm_rss(tsk->mm);
> +	acct_update_integrals(tsk);
>  	group_dead = atomic_dec_and_test(&tsk->signal->live);
>  	if (group_dead) {
>  		hrtimer_cancel(&tsk->signal->real_timer);

I can't actually find anywhere where these counters are used in the
accounting code.

In fact the rss_stat counters don't get used for much at all, really -
non-essential stuff in the oom killer and a bit of procfs eyecandy. 
What have I missed.

The patch makes sense from a defensive POV, but perhaps that
comment is misleading.
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