netdev - Re: [PATCH 0/4] Netfilter ingress support (v3)

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Message-ID: <20150504222131.GA4348@salvia>
Date:	Tue, 5 May 2015 00:21:31 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Florian Westphal <fw@...len.de>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	netfilter-devel@...r.kernel.org, davem@...emloft.net,
	netdev@...r.kernel.org, kaber@...sh.net
Subject: Re: [PATCH 0/4] Netfilter ingress support (v3)

On Mon, May 04, 2015 at 01:05:08PM -0700, Alexei Starovoitov wrote:
> [...] TC critical path becomes slower with extra dereference and
> indirect jump.

You complained on the performance impact of the initial generic hook
infrastructure that allows qdisc ingress and nft to co-exist, fair
enough.

I came back with an even more simple hook infrastructure, to address
performance concerns, and you indicate that an *extra dereference and
indirect jump* makes this slowier and that both cannot co-exist with
this.

Well, any kind of hook generalization will need at least those minimal
changes. And that allows us to move code that belongs to sch_ingress.
That got embedded into net/core/dev.c because at the time this code
was made when there was no RCU around.

This sounds as an excuse to me.
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