netdev - Re: [PATCH] sendfile() and UDP socket

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Message-Id: <20080924005335.0117c536.billfink@mindspring.com>
Date:	Wed, 24 Sep 2008 00:53:35 -0400
From:	Bill Fink <billfink@...dspring.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Evgeniy Polyakov <johnpol@....mipt.ru>, davem@...emloft.net,
	johaahn@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] sendfile() and UDP socket

On Tue, 23 Sep 2008, Herbert Xu wrote:

> On Tue, Sep 23, 2008 at 10:27:10AM +0400, Evgeniy Polyakov wrote:
> > On Tue, Sep 23, 2008 at 12:54:27PM +0800, Herbert Xu (herbert@...dor.apana.org.au) wrote:
> > > I think this dicussion is moot since the only time you want to use
> > > sendfile is for bulk transfers and these days anybody designing new
> > > applications that does bulk transfers over UDP should be taken out
> > > and shot.
> > 
> > One can protect himself pointing how slow may be memory bus in some
> > hardware setup, which completely does not allow to perform any copy.
> 
> Yes but bulk transfers over UDP is a bad idea regardless of how
> slow your bus is :)
> 
> So what application needs this?

It seems it might be useful for a video server.  The one thing that
seems to be missing from the sendfile() semantics is a message size
to be used for splitting the file into UDP datagrams, but this could
be provided by a separate ioctl(), and could default to the largest
message size that would fit in the MTU.

						-Bill
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