netdev - Re: Packet mmap: TX RING and zero copy

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Date:	Tue, 2 Sep 2008 23:46:04 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Johann Baudy <johaahn@...il.com>
Cc:	netdev@...r.kernel.org,
	Ulisses Alonso Camaró <uaca@...mni.uv.es>
Subject: Re: Packet mmap: TX RING and zero copy

Hi Johann.

On Tue, Sep 02, 2008 at 08:27:36PM +0200, Johann Baudy (johaahn@...il.com) wrote:
> I've made lot of tests, playing with jumbo frames, raw sockets, ...
> I've never exceeded ~25Mbytes/s. So I've decided to analyze deeply the
> packet socket transmission process.
> 
> The main blocking point was the memcpy_fromiovec() function that is
> located in the packet_sendmsg() of af_packet.c.

Can you saturate the link with usual tcp/udp socket?

> But, I would like to get as much criticism as possible in order to
> start a discussion with experts about a conceivable way to mix
> zero-copy, sk_buff management and packet socket.
> Which is perhaps impossible with current network kernel flow ...

Did you try vmsplice and splice?
It is the preferred way to do a zero-copy.

-- 
	Evgeniy Polyakov
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