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Subject: Re: [patch 0/4] taskstats: Improve cumulative time accounting
In-Reply-To: Your message of "Mon, 22 Nov 2010 13:47:55 +0100."
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Date: Mon, 22 Nov 2010 13:11:34 -0500
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Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Oleg Nesterov <oleg@redhat.com>, Shailabh Nagar <nagar1234@in.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, John stultz <johnstul@us.ibm.com>, Thomas Gleixner <tglx@linutronix.de>, Balbir Singh <balbir@linux.vnet.ibm.com>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, Roland McGrath <roland@redhat.com>, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org
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On Mon, 22 Nov 2010 13:47:55 +0100, Michael Holzheu said:

> Currently the cumulative time accounting in Linux is not complete.
> Due to POSIX POSIX.1-2001, the CPU time of processes is not accounted
> to the cumulative time of the parents, if the parents ignore SIGCHLD
> or have set SA_NOCLDWAIT. This behaviour has the major drawback that
> it is not possible to calculate all consumed CPU time of a system by
> looking at the current tasks. CPU time can be lost.
> 
> This patch adds a new sysctl "kernel.full_cdata" that allows to switch
> between the POSIX behavior and complete cumulative accounting.

> +unsigned int full_cdata_enabled = 1;

This probably needs to default to "current kernel behavior" but allow
sysadmins to change to the new behavior.

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