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Re: [Xen-devel] [PATCH] Network Checksum Removal

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Network Checksum Removal
From: Bin Ren <bin.ren@xxxxxxxxx>
Date: Mon, 23 May 2005 22:52:42 +0100
Cc: Andrew Theurer <habanero@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Jon Mason <jdmason@xxxxxxxxxx>
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On 5/23/05, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:
> What happens to CPU usage in dom1 when tx checksumming is disabled?

dom1->dom0: 70.7% id,  0.0% wa,  1.7% hi, 15.0% si
dom1->external: 20.0% id,  0.0% wa,  0.7% hi, 60.0% si
dom1->dom2: 77.7% id,  0.0% wa,  1.0% hi,  9.3% si

> 
> Overall though these are the kind of results I would expect. Linux
> usually does csumming at the same time as it has to do a copy anyway,
> and it ends up being limited by memory/L2-cache bandwidth, not the
> extra computation. But the offload extensions haven't cost much to
> implement and there are probably cases where it helps a little.
> 
> Maybe I'm being pessimistic though: Can you reproduce the rather more
> impressive speedups that you previously saw, Jon?
> 
>   -- Keir
> 
> 
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