netdev - Re: [PATCH 2/2 net-next] net: move qdisc ingress filtering code where it belongs

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Message-ID: <554FCE24.8020904@iogearbox.net>
Date:	Sun, 10 May 2015 23:31:16 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Pablo Neira Ayuso <pablo@...filter.org>,
	Alexei Starovoitov <ast@...mgrid.com>
CC:	netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com
Subject: Re: [PATCH 2/2 net-next] net: move qdisc ingress filtering code where
 it belongs

On 05/10/2015 09:50 PM, Pablo Neira Ayuso wrote:
...
> The numbers show that the existing approach and your approach results
> in less performance for everyone that don't need to filter from
> ingress. We have to move ingress to where it belongs.

Your cleanup in patch 1 is okay, thanks for spotting it Pablo.

I agree with you on the qdisc_enqueue_root(), it's not needed, which I
removed in my set as well. Please note that my set doesn't introduce a
regression, it improves ingress performance however.

If there's no ingress user than that code path is simply *nop*'ed out.
If there's one ingress present on one device but not on others, it also
doesn't make anything slower to the current state. And you can also always
compile out CONFIG_NET_CLS_ACT (which we actually could make more fine
grained), if you really care.

A next possible step would be to get rid of the ingress netdev queue so
we can also reduce memory overhead. The only thing that is needed is
the classifier list, which is then being invoked, we all have stated
that many times previously.

My other concern is, if we export qdisc_ingress_hook function pointer,
out of tree modules can simply do rcu_assign_pointer(qdisc_ingress_hook,
my_own_handler) to transparently implement their own hook, hm.

Best,
Daniel
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