linux-kernel - Re: [PATCH] Add all thread stats for TASKSTATS_CMD_ATTR

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Date:	Mon, 10 Sep 2007 15:03:06 +0200
From:	Guillaume Chazarain <guichaz@...oo.fr>
To:	Jonathan Lim <jlim@....com>
Cc:	balbir@...ux.vnet.ibm.com,
	akpm@...ux-foundation.org (Andrew Morton),
	linux-kernel@...r.kernel.org (Linux Kernel Mailing List),
	jlan@...ulhu.engr.sgi.com (Jay Lan)
Subject: Re: [PATCH] Add all thread stats for TASKSTATS_CMD_ATTR_TGID

Le Fri, 7 Sep 2007 16:37:57 -0700 (PDT),
Jonathan Lim <jlim@....com> a écrit :

> > Excellent, so can Guillaume change ac_btime to be just
> > tsk->start_time?
> 
> I don't think so.  Current time (xtime) is relative to the epoch;
> uptime and tsk->start_time (jiffies) are both relative to some boot
> time.  So you need to subtract uptime from xtime to get the boot time
> relative to the epoch, then add tsk->start_time.  The result is what
> ac_btime should be set to.
> 
> I think his recent changes are as follows:
> 
> --- a/kernel/tsacct.c   Fri Aug 31 01:42:23 2007 -0700
> +++ b/kernel/tsacct.c   Tue Aug 28 20:35:27 2007 +0200
> ...
> -void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
> +static void fill_wall_times(struct taskstats *stats, struct
> task_struct *task) ...
> -       ts = timespec_sub(uptime, tsk->start_time);
> +       ts = timespec_sub(uptime, task->start_time);
> ...
> -       stats->ac_btime = get_seconds() - ts.tv_sec;
> ...
> +       stats->ac_btime = get_seconds() - ts.tv_sec;
> 
> So really no different from before, which is correct.

Yes, I just tried to make it clearer that the computations were needed
to get a wall time. Otherwise, as CSA seems to start using taskstats,
do my changes make sense for your usage?

Thanks.

-- 
Guillaume
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