netdev - Re: [PATCH] flow-dissector: Fix alignment issue in __skb_flow_get

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Date:	Fri, 10 Oct 2014 08:33:39 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	"'alexander.h.duyck@...hat.com'" <alexander.h.duyck@...hat.com>,
	David Miller <davem@...emloft.net>,
	"alexander.duyck@...il.com" <alexander.duyck@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] flow-dissector: Fix alignment issue in
 __skb_flow_get_ports

On Fri, 2014-10-10 at 14:57 +0000, David Laight wrote:

> I think there is code to copy the IP and TCP headers to aligned memory
> before they are parsed.

There is no such thing. You are here on netdev list, please read the
code before doing such claims.

> ...
> > 
> > The problem is the igb / ixgbe / fm10k hardware doesn't have a means of
> > inserting padding from its side...
> 
> Shoot the hardware engineers.
> 
> You aren't going to get the performance you expect from a 10Ge card
> unless the rx buffers are 'correctly' aligned.

That is simply not true on current x86 cpus. They simply dont care at
all.

You cannot blame Intel for other arches.



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