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Subject: Re: Info: NAPI performance at "low" loads
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "David S. Miller" <davem@redhat.com>
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Date: 18 Sep 2002 22:15:27 +0100
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On Wed, 2002-09-18 at 21:46, David S. Miller wrote:
>    From: Alan Cox <alan@lxorguk.ukuu.org.uk>
>    Date: 18 Sep 2002 21:43:09 +0100
>    
>    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
>    
> Matrox isn't using inb/outb instructions to IO space, it is being
> accessed by X using MEM space which is done using normal load and
> store instructions on x86 after the card is mmap()'d into user space.

It doesnt matter what XFree86 is doing. Thats just to load the PCI bus
and jam it up to prove the point. It'll change your inb timing