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Message-ID: <47054B2E.1050906@redhat.com>
Date: Thu, 04 Oct 2007 16:21:02 -0400
From: Chuck Ebbert <cebbert@...hat.com>
To: Christian Borntraeger <borntraeger@...ibm.com>
CC: Luca Tettamanti <kronos.it@...il.com>,
Frans Pop <elendil@...net.nl>, Willy Tarreau <w@....eu>,
LKML <linux-kernel@...r.kernel.org>,
Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
"Alexander E. Patrakov" <patrakov@....usu.ru>,
Ingo Molnar <mingo@...e.hu>
Subject: Re: Decreasing stime running confuses top
On 10/04/2007 04:00 PM, Christian Borntraeger wrote:
> Am Donnerstag, 4. Oktober 2007 schrieb Chuck Ebbert:
>> Is CONFIG_VIRT_CPU_ACCOUNTING set?
>
> This is s390 and powerpc only, so the answer is probably no ;-)
>
The code in fs/proc/array.c is... interesting.
1. task_stime() converts p->se.sum_exec_runtime to a clock_t
2. it calls task_utime() which does the same thing (can it change
between the two reads?), does some calculations that yield a
clock_t, turns the result into a cputime and returns that
3. task_stime() then converts that result back into a clock_t and
uses it!
static cputime_t task_stime(struct task_struct *p)
{
clock_t stime;
stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
cputime_to_clock_t(task_utime(p));
return clock_t_to_cputime(stime);
}
static cputime_t task_utime(struct task_struct *p)
{
clock_t utime = cputime_to_clock_t(p->utime),
total = utime + cputime_to_clock_t(p->stime);
u64 temp;
temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime);
if (total) {
temp *= utime;
do_div(temp, total);
}
utime = (clock_t)temp;
return clock_t_to_cputime(utime);
}
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