linux-kernel - Re: [PATCH, RESEND] getrusage: fill ru

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Message-ID: <20081216152054.GA17012@redhat.com>
Date:	Tue, 16 Dec 2008 16:20:54 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Jiri Pirko <jpirko@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michael Kerrisk <mtk.manpages@...glemail.com>,
	linux-api@...r.kernel.org, Hugh Dickins <hugh@...itas.com>,
	jlim@....com, kosaki.motohiro@...fujitsu.com
Subject: Re: [PATCH, RESEND] getrusage: fill ru_maxrss value

On 12/16, Jiri Pirko wrote:
>
> This patch makes ->ru_maxrss value in struct rusage filled accordingly to
> rss hiwater mark. This struct is filled as a parameter to
> getrusage syscall. ->ru_maxrss value is set to pages which might be correct
> as "time" application converts it to KBs.
>
> To make this happen we extend struct signal_struct by two fields. The
> first one is ->maxrss which we use to store rss hiwater of the task. The
> second one is ->cmaxrss which we use to store highest rss hiwater of all
> task childs. These values are used in k_getrusage() to actually fill
> ->ru_maxrss. k_getrusage() uses current rss hiwater value directly
> if mm struct exists.
>
> We clear the ->maxrss as a part of flush_old_exec() to be consistent
> because bprm_mm_init() does not copy ->hiwater_rss.

Imho the patch is fine, but

> @@ -1598,6 +1601,15 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
>  out:
>  	cputime_to_timeval(utime, &r->ru_utime);
>  	cputime_to_timeval(stime, &r->ru_stime);
> +
> +	task_lock(p);
> +	if (p->mm) {
> +		unsigned long maxrss = get_mm_hiwater_rss(p->mm);
> +
> +		if (r->ru_maxrss < maxrss)
> +			r->ru_maxrss = maxrss;
> +	}
> +	task_unlock(p);

I think the code above should check "if (who != RUSAGE_CHILDREN) ?

Oleg.

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