netdev - Re: [RFC] netfilter: get rid of atomic ops in fast path

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Message-ID: <4D81E4C5.5060009@trash.net>
Date:	Thu, 17 Mar 2011 11:39:01 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Netfilter Development Mailinglist 
	<netfilter-devel@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
	Jesper Dangaard Brouer <hawk@...u.dk>
Subject: Re: [RFC] netfilter: get rid of atomic ops in fast path

Am 16.03.2011 20:00, schrieb Eric Dumazet:
> We currently use a percpu spinlock to 'protect' rule bytes/packets
> counters, after various attempts to use RCU instead.
> 
> Lately we added a seqlock so that get_counters() can run without
> blocking BH or 'writers'. But we really use the seqcount in it.
> 
> Spinlock itself is only locked by the current cpu, so we can remove it
> completely.
> 
> This cleanups api, using correct 'writer' vs 'reader' semantic.
> 
> At replace time, the get_counters() call makes sure all cpus are done
> using the old table.
> 
> We could probably avoid blocking BH (we currently block them in xmit
> path), but thats a different topic ;)
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
> This is a POC patch (based on net-next-2.6), only handling ip_tables.
> ip6/arp/... need similar changes.

Thanks Eric, this looks good to me.
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