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Date: Fri, 31 Oct 2008 04:13:50 +0000
From: Bruce Cran <bruce@cran.org.uk>
To: Ivan Voras <ivoras@freebsd.org>
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Cc: freebsd-net@freebsd.org
Subject: Re: two NIC on 2 core system (scheduling problem)
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On Tue, 28 Oct 2008 12:21:32 +0100
Ivan Voras <ivoras@freebsd.org> wrote:

> Oleksandr Samoylyk wrote:
> > Ivan Voras wrote:
> >> Bartosz Giza wrote:
> >>
> >>> Another question is why em0 taskq is eating so much cpu ? BGE
> >>> interface is actually one that pushes 2 times more packets than
> >>> em0 and it uses about half cpu comparing to em0. Is that not
> >>> strange ? Could someone tell my why is this happening ? BGE is
> >>> faster ? or maybe i can tune some
> >>
> >> I have the same problem - em0 taskq eating incredible amounts of
> >> CPU. If you find a solution, contact me!
> >>
> >>
> >=20
> > It could be not just a problem with em driver.
> > Firstly, it's good to make profiling and find out what exactly eats
> > CPU
>=20
> Can you give any pointers on how to profile the driver and/or the
> network stack?
>=20

=46rom what I remember from a couple of years ago you can use hwpmc in
system mode to profile the kernel if you have a supported CPU - I
certainly remember seeing the output of gprof tell me the UDP checksum
function was taking most of the time in a test I ran. To get started
you need options HWPMC_HOOKS and device hwpmc in your kernel config
(hwpmc can also be a module) - then you run pmcstat to run the test.
There's lots more information at http://wiki.freebsd.org/PmcTools

--=20
Bruce Cran