linux-kernel - Re: /proc 2.6.24 changes for guest CPU accounting

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Date:	Mon, 23 Jun 2008 12:51:11 +0200
From:	"Michael Kerrisk" <mtk.manpages@...glemail.com>
To:	"Laurent Vivier" <Laurent.Vivier@...l.net>
Cc:	"Michael Kerrisk" <mtk.manpages@...il.com>,
	"Samuel Thibault" <samuel.thibault@...-lyon.org>, ap@....com.au,
	lkml <linux-kernel@...r.kernel.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Christian Borntraeger" <borntraeger@...ibm.com>
Subject: Re: /proc 2.6.24 changes for guest CPU accounting

On Mon, Jun 23, 2008 at 10:48 AM, Laurent Vivier
<Laurent.Vivier@...l.net> wrote:
> Le dimanche 22 juin 2008 à 09:31 +0200, Michael Kerrisk a écrit :
>> Hi Laurent,
>
> Hi Michael,
>
>> A note and patch from Samuel alerted me to your commits
>> 9ac52315d4cf5f561f36dabaf0720c00d3553162 and
>> 5e84cfde51cf303d368fcb48f22059f37b3872de, which in 2.6.24 changed /proc/stat
>> and /proc/PID/stat.  Would you please CC me on kernel-userspace interface
>> changes, so that they have a chance of getting documented in man-pages.
>>
>> (I see that Andrew P tried to get something added to
>> Documentation/filesystems/proc.txt, but that doesn't seem to have made it in.)
>>
>> Below is a patch against the proc.5 man page by Samuel and I to document these
>> changes.  Do the changes look okay to you?  The first part is the change for
>> /proc/<pid>/stat, and the other is for /proc/stat.
>
> Thank you for that. It seems correct to me (except a typo).
>
> You must also notes that "user time" includes "guest time", if you want
> real "user time" you must subtract "guest time".
> The "guest time" is included in "user time" to not loose it when the
> "reader" is not aware of the "guest time".

Hi Laurent (and Christian)

So, I just want to confirm.  You are saying that guest_time and
cguest_time are respectively also included in the following fields

              utime %lu
                     The number of jiffies that this process has  been
                     scheduled in user mode.

              [...]

              cutime %ld
                     The number of jiffies that this process's waited-
                     for  children  have  been scheduled in user mode.
                     (See also times(2).)

Right?

(In fs/proc/array.c, those are the two lines from

                cputime_to_clock_t(utime),
                cputime_to_clock_t(cutime),
)

Cheers,

Michael
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