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Re: Early SPECWeb99 results on 2.5.33 with TSO on e1000

To: Nivedita Singhvi <niv@xxxxxxxxxx>
Subject: Re: Early SPECWeb99 results on 2.5.33 with TSO on e1000
From: jamal <hadi@xxxxxxxxxx>
Date: Thu, 5 Sep 2002 21:47:35 -0400 (EDT)
Cc: Troy Wilson <tcw@xxxxxxxxxxxxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>, <netdev@xxxxxxxxxxx>
In-reply-to: <>
Sender: netdev-bounce@xxxxxxxxxxx

On Thu, 5 Sep 2002, Nivedita Singhvi wrote:

> > value in your results is in saving on retransmits; I would think
> > shoving the data down the NIC and avoid the fragmentation shouldnt
> > give you that much significant CPU savings. Do you have any stats
> Why do say that? Wouldnt the fact that youre now reducing the
> number of calls down the stack by a significant number provide
> a significant saving?

I am not sure; if he gets a busy system in a congested network, i can
see the offloading savings i.e i am not sure if the amortization of the
calls away from the CPU is sufficient enough savings if it doesnt
involve a lot of retransmits. I am also wondering how smart this NIC
in doing the retransmits; example i have doubts if this idea is briliant
to begin with; does it handle SACKs for example? What about
the du-jour algorithm, would you have to upgrade the NIC or can it be
taught some new trickes etc etc.
[also i can see why it makes sense to use this feature only with sendfile;
its pretty much useless for interactive apps]

Troy, i am not interested in the nestat -s data rather the TCP stats
this NIC  has exposed. Unless those somehow show up magically in netstat.


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