From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lennert Buytenhek <buytenh@wantstofly.org>
Subject: Re: 1.03Mpps on e1000 (was: Re: [E1000-devel] Transmission limit)
Date: Sun, 5 Dec 2004 19:14:29 +0100
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Cc: Scott Feldman <sfeldma@pobox.com>, jamal <hadi@cyberus.ca>,
        Robert Olsson <Robert.Olsson@data.slu.se>, P@draigBrady.com,
        mellia@prezzemolo.polito.it, e1000-devel@lists.sourceforge.net,
        Jorge Manuel Finochietto <jorge.finochietto@polito.it>,
        Giulio Galante <galante@polito.it>, netdev@oss.sgi.com
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To: Martin Josefsson <gandalf@wlug.westbo.se>
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On Sun, Dec 05, 2004 at 06:38:05PM +0100, Martin Josefsson wrote:

> e1000: MMIO read took 481 clocks
> e1000: MMIO read took 369 clocks
> e1000: MMIO read took 481 clocks
> e1000: MMIO read took 11 clocks
> e1000: MMIO read took 477 clocks
> e1000: MMIO read took 316 clocks

Interesting.  On a 1667MHz CPU, this is around ~0.28us per MMIO read
in the worst case.  On my hardware (dual Xeon 2.4GHz), the best case
I've ever seen was ~0.83us.

This alone can make a hell of a difference, esp. for 60B packets.


--L