netdev - Re: [PATCH v2] tcp: splice as many packets as possible at once

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Message-ID: <20090127074048.GA4197@ff.dom.local>
Date:	Tue, 27 Jan 2009 07:40:48 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	zbr@...emap.net, herbert@...dor.apana.org.au, w@....eu,
	dada1@...mosbay.com, ben@...s.com, mingo@...e.hu,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	jens.axboe@...cle.com
Subject: Re: [PATCH v2] tcp: splice as many packets as possible at once

On Mon, Jan 26, 2009 at 10:10:56PM -0800, David Miller wrote:
> From: Evgeniy Polyakov <zbr@...emap.net>
> Date: Tue, 27 Jan 2009 00:21:30 +0300
> 
> > Hi Jarek.
> > 
> > On Mon, Jan 26, 2009 at 08:20:36AM +0000, Jarek Poplawski (jarkao2@...il.com) wrote:
> > > > 1. Network (tree) allocator
> > > > http://www.ioremap.net/projects/nta
> > > 
> > > I looked at this a bit, but alas I didn't find much for this Herbert's
> > > idea of payload in fragments/pages. Maybe some kind of API RFC is
> > > needed before this resurrection?
> > 
> > Basic idea is to steal some (probably a lot) pages from the slab
> > allocator and put network buffers there without strict need for
> > power-of-two alignment and possible wraps when we add skb_shared_info at
> > the end, so that old e1000 driver required order-4 allocations for the
> > jumbo frames. We can do that in alloc_skb() and friends and put returned
> > buffers into skb's fraglist and updated reference counters for those
> > pages; and with additional copy of the network headers into skb->head.

I think the main problem is to respect put_page() more, and maybe you
mean to add this to your allocator too, but using slab pages for this
looks a bit complex to me, but I can miss something.

> We are going back and forth saying the same thing, I think :-)
> (BTW, I think NTA is cool and we might do something like that
> eventually)
> 
> The basic thing we have to do is make the drivers receive into
> pages, and then slide the network headers (only) into the linear
> SKB data area.

As a matter of fact, I wonder if these headers should be always
separated. Their "chunk" could be refcounted as well, I guess.

Jarek P.
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