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Message-Id: <20080530151250.b44a119a.billfink@mindspring.com>
Date: Fri, 30 May 2008 15:12:50 -0400
From: Bill Fink <billfink@...dspring.com>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: James Cammarata <jimi@...x.net>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: add ability to clear stats via ethtool -
e1000/pcnet32
On Thu, 29 May 2008, Alan Cox wrote:
> > > Many of the kernel's accounting accumulators cannot be reset. We
> > > handle that in userspace tools by using subtraction.
> >
> > I don't think that should preclude the ability to reset these, unless it is
> > shown that it would break something very badly.
>
> For one quite a few of the network cards keep the stats in hardware and
> don't neccessarily have a way to reset them. In other cases there is a
> mix of OS accumulated stats bulk updated by overflow events on the device
> itself.
>
> Its a lot of complexity, and changes all over the places for the sake of
> a trivial userspace change. I would suggest you instead write a quick bit
> of perl or python that fetches the stats and then updates every second
> with the changes.
When diagnosing network problems, the ability to zero counters is
a major aid in diagnosis. Writing scripts is not a general solution
since often several systems are involved and it's not simple to do
this via a script. Saving stats output and running beforeafter on
a number of systems is a royal pain when troubleshooting.
I like the idea someone else had. where the clear stats actually did
a checkpoint of the stats, and then future get stats would return the
diff between the checkpointed and current values (perhaps there could
also be a mechanism to still get the absolute values if desired).
-Bill
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