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Date: Mon, 11 May 2009 21:24:26 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] Transforming stdin and stdout pair into a socket
References: <8e04b5820905101119u39ae84bfp1bae24be6e057086@mail.gmail.com>
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To: Paul Brook <paul@codesourcery.com>
Cc: nbd-general@lists.sourceforge.net, "Ciprian Dorin,
	Craciun" <ciprian.craciun@gmail.com>, linux-newbie@vger.kernel.org, qemu-devel@nongnu.org

Paul Brook wrote:
>>     I've seen socat, and I could use it as you described. My only
>> objection to this solution is that there is an unneeded process in the
>> middle that just pipes data around...
>>
>>    (Instead of socat, I think it would be more efficient to just write
>> a simple application that uses the "new" Linux syscall "splice" that
>> I've just found by mistake yesterday...)
>>     
>
> In that case you need to fix socat to use splice() when available. I have a 
> hard time believing socat adds measurable overhead, especially if you're 
> already tunnelling over ssh.
>   

splice() doesn't really buy you anything when copying from a socket to 
another socket.  The data is going to get copied just like it would if 
you dropped to userspace.  It's useful if you introduce pipe-to-pipe 
copies because they'll be eliminated but if you're going from socket -> 
pipe -> socket it'll be the same as using socat.

Regards,

Anthony Liguori
> Paul
>