netdev - RE: [PATCH net-next 08/12] r8152: support TSO

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D0F6D0334@AcuExch.aculab.com>
Date:	Tue, 4 Mar 2014 15:14:01 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Eric Dumazet' <eric.dumazet@...il.com>
CC:	'hayeswang' <hayeswang@...ltek.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"nic_swsd@...ltek.com" <nic_swsd@...ltek.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: RE: [PATCH net-next 08/12] r8152: support TSO

From: Eric Dumazet 
> On Tue, 2014-03-04 at 14:35 +0000, David Laight wrote:
> 
> > Does that mean you are splitting the 64k 'ethernet packet' from TCP
> > is software? I've looked at the ax88179 where the hardware can do it.
> >
> > Is there really a gain doing segmentation here if you have to do the
> > extra data copy?
> 
> There is no 'extra' copy.
> 
> There is _already_ a copy, so what's the deal of doing this copy in a SG
> enabled way ?

Ok.

But there is one more copy than for a normal ethernet chipset which
can use multiple ring entries to send the MAC+IP+TCP headers from a
different buffer to the TCP userdata.

	David