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Re: Info: NAPI performance at "low" loads

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: Info: NAPI performance at "low" loads
From: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Date: 18 Sep 2002 21:43:09 +0100
Cc: ebiederm@xxxxxxxxxxxx, hadi@xxxxxxxxxx, akpm@xxxxxxxxx, manfred@xxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <20020918.132334.102949210.davem@redhat.com>
References: <Pine.GSO.4.30.0209172053360.3686-100000@shell.cyberus.ca> <20020917.180014.07882539.davem@redhat.com> <m1hegnky2h.fsf@frodo.biederman.org> <20020918.132334.102949210.davem@redhat.com>
Sender: netdev-bounce@xxxxxxxxxxx
On Wed, 2002-09-18 at 21:23, David S. Miller wrote:
> The x86 processor has a well defined timing for executing inb
> etc. instructions, the timing is fixed and is independant of the
> speed of the PCI bus the device is on.

Earth calling Dave Miller

The inb timing depends on the PCI bus. If you want proof set a Matrox
G400 into no pci retry mode, run a large X load at it and time some inbs
you should be able to get to about 100 milliseconds for an inb to
execute


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