linux-kernel - Re: [PATCH] fix granularity of task

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Message-ID: <20091123114640.2b37af88@dhcp-lab-109.englab.brq.redhat.com>
Date:	Mon, 23 Nov 2009 11:46:40 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Spencer Candland <spencer@...ehost.com>,
	Am?rico Wang <xiyou.wangcong@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH] fix granularity of task_u/stime(), v2

On Mon, 23 Nov 2009 15:55:28 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> * Stanislaw Gruszka <sgruszka@...hat.com> [2009-11-23 11:09:26]:
> [snip]
> > +
> > +		utime = task_utime(tsk);
> > +		stime = task_stime(tsk);
> > +		if (tsk->utime > utime || tsk->stime > stime) {
> > +			utime = tsk->utime;
> > +			stime = tsk->stime;
> > +		}
> 
> Won't this condition be problematic, since it can reset stime
> when tsk->utime > utime for example?

We use both {u,s}time adjusted values  or  both not adjusted values.
This seems to be right to me. Adjusting not help anyway, if we have
stime/utime ticks disproportion, e.g. task only gets stime ticks but
not gets utime ticks, but it runs in user and kernel space in
the same amount of time.

If this solution whold be accepted, patch will contain additional
comment.

Stanislaw
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