linux-kernel - Re: [PATCH] procfs: export context switch counts in /proc/*/stat

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Message-Id: <1166622487.3365.1386.camel@laptopd505.fenrus.org>
Date:	Wed, 20 Dec 2006 14:48:06 +0100
From:	Arjan van de Ven <arjan@...radead.org>
To:	David Wragg <david@...gg.org>
Cc:	Albert Cahalan <acahalan@...il.com>, linux-kernel@...r.kernel.org,
	bcrl@...ck.org
Subject: Re: [PATCH] procfs: export context switch counts in /proc/*/stat

On Wed, 2006-12-20 at 13:20 +0000, David Wragg wrote:
> "Albert Cahalan" <acahalan@...il.com> writes:
> > On Mon, Dec 18, 2006 at 11:50:08PM +0000, David Wragg wrote:
> >> This patch (against 2.6.19/2.6.19.1) adds the four context
> >> switch values (voluntary context switches, involuntary
> >> context switches, and the same values accumulated from
> >> terminated child processes) to the end of /proc/*/stat,
> >> similarly to min_flt, maj_flt and the time used values.
> >
> > Hmmm, OK, do people have a use for these values?
> 
> My reason for writing the patch was to track which processes are
> active (i.e. got scheduled to run) by polling these context switch
> values.  The time used values are not a reliable way to detect process
> activity on fast machines.  So for example, when sorting by %CPU, top
> often shows many processes using 0% CPU, despite the fact that these
> processes are running occasionally.  If top sorted by (%CPU, context
> switch count delta), it might give a more useful display of which
> processes are active on the system.


if all you care is the number of context switches, you can use the
following system tap script as well:

http://www.fenrus.org/cstop.stp


-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

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