netdev - Re: [RFC PATCH v2 1/5] bpf: add PHYS_DEV prog type for early driver filter

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Message-ID: <20160409172634.GA55330@ast-mbp.thefacebook.com>
Date:	Sat, 9 Apr 2016 10:26:37 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Jamal Hadi Salim <jhs@...atatu.com>
Cc:	Tom Herbert <tom@...bertland.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Brenden Blanco <bblanco@...mgrid.com>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Edward Cree <ecree@...arflare.com>,
	john fastabend <john.fastabend@...il.com>,
	Thomas Graf <tgraf@...g.ch>,
	Johannes Berg <johannes@...solutions.net>,
	eranlinuxmellanox@...il.com, Lorenzo Colitti <lorenzo@...gle.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC PATCH v2 1/5] bpf: add PHYS_DEV prog type for early driver
 filter

On Sat, Apr 09, 2016 at 11:29:18AM -0400, Jamal Hadi Salim wrote:
> On 16-04-09 07:29 AM, Tom Herbert wrote:
> 
> >+1. Forwarding which will be a common application almost always
> >requires modification (decrement TTL), and header data split has
> >always been a weak feature since the device has to have some arbitrary
> >rules about what headers needs to be split out (either implements
> >protocol specific parsing or some fixed length).
> 
> Then this is sensible. I was cruising the threads and
> confused by your earlier emails Tom because you talked
> about XPS etc. It sounded like the idea evolved into putting
> the whole freaking stack on bpf.

yeah, no stack, no queues in bpf.

> If this is _forwarding only_ it maybe useful to look at
> Alexey's old code in particular the DMA bits;
> he built his own lookup algorithm but sounds like bpf is
> a much better fit today.

a link to these old bits?

Just to be clear: this rfc is not the only thing we're considering.
In particular huawei guys did a monster effort to improve performance
in this area as well. We'll try to blend all the code together and
pick what's the best.