netdev - Re: [PATCH net-next] xen-netfront: try linearizing SKB if it occupies too many slots

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Date:	Fri, 16 May 2014 10:00:33 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Zoltan Kiss <zoltan.kiss@...rix.com>
Cc:	Wei Liu <wei.liu2@...rix.com>, netdev@...r.kernel.org,
	xen-devel@...ts.xen.org, David Vrabel <david.vrabel@...rix.com>,
	Konrad Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Stefan Bader <stefan.bader@...onical.com>
Subject: Re: [PATCH net-next] xen-netfront: try linearizing SKB if it
 occupies too many slots

On Fri, 2014-05-16 at 17:51 +0100, Zoltan Kiss wrote:

> But reducing the gso_max_size would have a bad impact on the general 
> network throughput, right?

Not really.

Sending TSO packets with 44 MSS in them instead of 45 might in fact help
a bit. I never could detect any difference.

LRO/GRO receivers aggregate at most 17 or 22 segments anyway.

I said 56000 only as a quick way to test the thing

If you want an explicit formula, it might be :

SKB_WITH_OVERHEAD(65535 - LL_MAX_HEADER) or something like that...



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