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Re: [E1000-devel] Transmission limit

To: Robert Olsson <Robert.Olsson@xxxxxxxxxxx>
Subject: Re: [E1000-devel] Transmission limit
From: "David S. Miller" <davem@xxxxxxxxxxxxx>
Date: Mon, 29 Nov 2004 12:16:04 -0800
Cc: hadi@xxxxxxxxxx, P@xxxxxxxxxxxxxx, mellia@xxxxxxxxxxxxxxxxxxxx, Robert.Olsson@xxxxxxxxxxx, e1000-devel@xxxxxxxxxxxxxxxxxxxxx, jorge.finochietto@xxxxxxxxx, galante@xxxxxxxxx, netdev@xxxxxxxxxxx
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On Mon, 29 Nov 2004 14:09:08 +0100
Robert Olsson <Robert.Olsson@xxxxxxxxxxx> wrote:

>  Did I dream or did someone tell me that S2IO 
>  could have several TX ring that could via MSI be routed to proper cpu?

One of Sun's gigabit chips can do this too, except it isn't
via MSI, the driver has to read the descriptor to figure out
which cpu gets the software interrupt to process the packet.

SGI had hardware which allowed you to do this kind of stuff too.

Obviously the MSI version works much better.

It is important, the cpu selection process.  First of all, it must
be calculated such that flows always go through the same cpu.
Otherwise TCP sockets bounce between the cpus for a streaming
transfer.

And even this doesn't avoid all such problems, TCP LISTEN state
sockets will still thrash between the cpus with such a "pick
a cpu based upon" flow scheme.

Anyways, just some thoughts.

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