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

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Message-ID: <671c20540701301056l6ff1d876xb8df0d9d83ea2c8a@mail.gmail.com>
Date:	Tue, 30 Jan 2007 13:56:48 -0500
From:	"Tom Burns" <tom.i.burns@...il.com>
To:	"Tim Schmielau" <tim@...sik3.uni-rostock.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Bug: 2.6.15 Process accounting fails to account for small time slice loads (still)

Hi Tim.

That would be great if you could find that patch - I can worry about
porting it to the current kernel.  We're having an issue where our
device, while routing large amounts of network traffic, reports 0% CPU
utilisation when it cannot be the case, and I think this is the cause.

Cheers,
Tom Burns

On 1/30/07, Tim Schmielau <tim@...sik3.uni-rostock.de> wrote:
> 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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