netdev - Re: [RFC] [TCP 0/3] Receive from socket into bio without copying

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Date:	Fri, 29 Jun 2012 17:08:43 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andreas Gruenbacher <agruen@...bit.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC] [TCP 0/3] Receive from socket into bio without copying

On Fri, 2012-06-29 at 16:53 +0200, Andreas Gruenbacher wrote:
> Hello,
> 
> I'm (still) trying to pass data from the network to the block layer without
> copying. The block layer needs blocks to be contiguous in memory, and may have
> some alignment restrictions as well.  A lot of modern network hardware will
> receive large packets into separate buffers, so individual large packets will
> end up in contiguous, aligned buffers.  I would like to make use of that, but
> tcp currently doesn't allow me to control what ends up in which packets.
> 
> This patch series introduces a new flag for indicating to tcp when it should
> start a new segment. Using that on the sender side, I can get data over the
> network with no cpu copying at all.
> 
> [My last posting on this topic from May 8 is archived here:
>  http://www.spinics.net/lists/netdev/msg197788.html ]
> 
> Thanks,
> Andreas
> 
> Andreas Gruenbacher (3):
>   tcp: Add MSG_NEW_PACKET flag to indicate preferable packet boundaries
>   tcp: Zero-copy receive from a socket into a bio
>   fs: Export bio_release_pages()

This looks like yet another zero copy, needing another couple of hundred
of lines.

Why splice infrastructure doesnt fit your needs ?



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