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Re: 1.03Mpps on e1000 (was: Re: [E1000-devel] Transmission limit)

To: Martin Josefsson <gandalf@xxxxxxxxxxxxxx>
Subject: Re: 1.03Mpps on e1000 (was: Re: [E1000-devel] Transmission limit)
From: Lennert Buytenhek <buytenh@xxxxxxxxxxxxxx>
Date: Sun, 5 Dec 2004 19:14:29 +0100
Cc: Scott Feldman <sfeldma@xxxxxxxxx>, jamal <hadi@xxxxxxxxxx>, Robert Olsson <Robert.Olsson@xxxxxxxxxxx>, P@xxxxxxxxxxxxxx, mellia@xxxxxxxxxxxxxxxxxxxx, e1000-devel@xxxxxxxxxxxxxxxxxxxxx, Jorge Manuel Finochietto <jorge.finochietto@xxxxxxxxx>, Giulio Galante <galante@xxxxxxxxx>, netdev@xxxxxxxxxxx
In-reply-to: <Pine.LNX.4.58.0412051836020.29474@tux.rsn.bth.se>
References: <20041201213550.GF14470@xi.wantstofly.org> <1101967983.4782.9.camel@localhost.localdomain> <20041205145051.GA647@xi.wantstofly.org> <Pine.LNX.4.58.0412051559350.29474@tux.rsn.bth.se> <20041205151545.GC647@xi.wantstofly.org> <Pine.LNX.4.58.0412051616090.29474@tux.rsn.bth.se> <Pine.LNX.4.58.0412051622380.29474@tux.rsn.bth.se> <20041205170006.GI647@xi.wantstofly.org> <Pine.LNX.4.58.0412051804370.29474@tux.rsn.bth.se> <Pine.LNX.4.58.0412051836020.29474@tux.rsn.bth.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

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