linux-kernel - Re: Bug: 2.6.15 Process accounting fails to account for small time slice loads (still)

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Message-ID: <Pine.LNX.4.63.0701301840470.14441@gockel.physik3.uni-rostock.de>
Date:	Tue, 30 Jan 2007 18:48:33 +0100 (CET)
From:	Tim Schmielau <tim@...sik3.uni-rostock.de>
To:	Tom Burns <tom.i.burns@...il.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: Bug: 2.6.15 Process accounting fails to account for small time
 slice loads (still)

On Tue, 30 Jan 2007, Tom Burns wrote:

> The bug described back in 2004 in the following message still seems to exist:
> 
> http://linux.derkeiler.com/Mailing-Lists/Kernel/2004-05/4313.html
> 
> Essentially, it appears that if a process sleeps before it uses up a
> complete jiffy then no charge is made to its process accounting table.

That's not a bug, it's a feature. ;-)

More seriously, it's a design decision. The benefit of exactly correct 
micro bookkeeping does not seem to warrant the extra cost in terms of cpu 
cycles spent in the accounting code.

IIRC there was a patch for that some years ago, if you are interested I 
will try to find it. No idea how much work it would be to port it to 
current kernels, though.

Tim
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