linux-kernel - Re: [PATCH] tcp: splice as many packets as possible at once

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Message-ID: <20090114001345.GB512@ioremap.net>
Date:	Wed, 14 Jan 2009 03:13:45 +0300
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	David Miller <davem@...emloft.net>
Cc:	dada1@...mosbay.com, w@....eu, ben@...s.com, jarkao2@...il.com,
	mingo@...e.hu, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, jens.axboe@...cle.com
Subject: Re: [PATCH] tcp: splice as many packets as possible at once

On Tue, Jan 13, 2009 at 04:07:21PM -0800, David Miller (davem@...emloft.net) wrote:
> > Exactly, and to have it we earlier release a socket so that it could be
> > acked and while we copy it or doing anything else, the next one would
> > received.
> 
> I think the socket release in skb_splice_bits() (although necessary)
> just muddies the waters, and whether the extra one done in
> tcp_splice_read() helps at all is open to debate.

Well, yes, probably simple performance test with and without will
clarify the things.

> That skb_clone() done by skb_splice_bits() pisses me off too,
> we really ought to fix that.  And we also have that data corruption
> bug to cure too.

Clone is needed since tcp expects to own the skb and frees it
unconditionally via __kfree_skb().

What is the best solution for the data corruption bug? To copy the data
all the time or implement own allocator to be used in alloc_skb and
friends to allocate the head? I think it can be done transparently for
the drivers. I can volunteer for this :)
The first one is more appropriate for the current bugfix-only stage,
but this will result in the whole release being too slow.

-- 
	Evgeniy Polyakov
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