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

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Date:	Sat, 25 Aug 2007 17:10:39 +0200
From:	Guillaume Chazarain <guichaz@...oo.fr>
To:	balbir@...ux.vnet.ibm.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jay Lan <jlan@...r.sgi.com>, Jonathan Lim <jlim@....com>
Subject: Re: [PATCH] Add all thread stats for TASKSTATS_CMD_ATTR_TGID

Le Mon, 20 Aug 2007 22:31:08 +0530,
Balbir Singh <balbir@...ux.vnet.ibm.com> a écrit :

> > --- a/kernel/taskstats.c	Sat Aug 18 17:15:17 2007 -0700
> > +++ b/kernel/taskstats.c	Sun Aug 19 17:20:15 2007 +0200
> > @@ -246,6 +246,8 @@ static int fill_tgid(pid_t tgid, struct 
> > 
> >  		stats->nvcsw += tsk->nvcsw;
> >  		stats->nivcsw += tsk->nivcsw;
> > +		bacct_add_tsk(stats, tsk);
> > +		xacct_add_tsk(stats, tsk);
> 
> I'm afraid this is still not good enough. bacct_add_tsk() will assign
> values and do nothing in the loop (HINT: no summation).

Hi Balbir, thank you for your review. I agree with everything you said
and am on my way to do it as time permits, but I have some trouble
understanding this part. You stated that bacct_add_tsk() would overwrite
the stats of each thread in the tgid stats, but the other part of the
patch is the (actually wrong) combination of stats in xxx_add_tsk()
using min/max/sum.

Also, I don't understand why the code to update btime:

        /* calculate task elapsed time in timespec */
        do_posix_clock_monotonic_gettime(&uptime);
        ts = timespec_sub(uptime, tsk->start_time);
	...
        stats->ac_btime = get_seconds() - ts.tv_sec;

does not simply use tsk->start_time or tsk->real_start_time without
comparing it to the current time.

Thanks.

-- 
Guillaume
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