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

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Date:	Mon, 23 Jun 2008 10:28:13 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Michael Kerrisk <mtk.manpages@...il.com>
Cc:	Laurent Vivier <Laurent.Vivier@...l.net>,
	Samuel Thibault <samuel.thibault@...-lyon.org>, ap@....com.au,
	lkml <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: /proc 2.6.24 changes for guest CPU accounting

Am Sonntag, 22. Juni 2008 schrieb Michael Kerrisk:
> Hi Laurent,
> 
> 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.
[...]
> +.TP
> +\fIguest_time\fP %lu (since Linux 2.6.24)
> +Guest time of the process (time spent running a virtual CPU
> +for a guest operating system), in centiseconds.
> +.TP
> +\fIcguest_time\fP %ld (since Linux 2.6.24)
> +Guest time of the process's children, in centiseconds.
[...]
> +
> +Since Linux 2.6.24, there is a ninth column,
> +.IR guest ,
> +which is the time spent running a virtual CPU for guest
> +operating systems under teh control of the Linux kernel.
> +.\" See Changelog entry for 5e84cfde51cf303d368fcb48f22059f37b3872de

Maybe you should mention that guest time is accounted twice: user and guest. 
So if guest time aware userspace wants to to calcuate user time without 
guests time, it should subtract the guest time from user.

Christian
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