netdev - Re: Data corruption issue with splice() on 2.6.27.10

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Message-ID: <20090106085442.GA9513@ff.dom.local>
Date:	Tue, 6 Jan 2009 08:54:42 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Willy Tarreau <w@....eu>
Cc:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: Data corruption issue with splice() on 2.6.27.10

On 24-12-2008 16:28, Willy Tarreau wrote:
> Hi Jens,
> 
> I'm facing a data corruption problem with splice() between two
> non-blocking TCP sockets on 2.6.27.10. I could finally write a
> simpler proof of concept, and capture a snapshot of the issue
> with the associated strace result.
...
> I found an analysis [1] for a potential corruption problem between two
> sockets, but I noticed there were no responses and I did not fully
> understand the report anyway.
> 
> What can I do to help debug the problem ? I'm really willing to help
> getting this fixed, and I also have at least one user who definitely
> wants splice() to work because the recv/send model currently limits
> haproxy to 3 Gbps on his machines, while I have no problem reaching
> 10 Gbps with splice().
...
> ----
> [1] http://lkml.org/lkml/2008/2/26/210

Great story! Alas I don't understand this fully either, but it seems
Changli Gao was concerned with sendpage sending this "as pages", so
when NETIF_F_SG flag is available. Did you try this without SG btw?

Thanks,
Jarek P.
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