linux-kernel - Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v2)

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Date:	Tue, 14 Apr 2009 21:28:40 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	Jeff Chua <jeff.chua.linux@...il.com>,
	Patrick McHardy <kaber@...sh.net>, paulmck@...ux.vnet.ibm.com,
	David Miller <davem@...emloft.net>, paulus@...ba.org,
	mingo@...e.hu, torvalds@...ux-foundation.org, laijs@...fujitsu.com,
	jengelh@...ozas.de, r000n@...0n.net, linux-kernel@...r.kernel.org,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	benh@...nel.crashing.org
Subject: Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v2)

Stephen Hemminger a écrit :
> Subject: iptables: 
> 
> This is an alternative version of ip/ip6/arp tables locking using
> per-cpu locks.  This avoids the overhead of synchronize_net() during
> update but still removes the expensive rwlock in earlier versions.
> 
> The idea for this came from an earlier version done by Eric Duzamet.
> Locking is done per-cpu, the fast path locks on the current cpu
> and updates counters.  The slow case involves acquiring the locks on
> all cpu's.
> 
> The mutex that was added for 2.6.30 in xt_table is unnecessary since
> there already is a mutex for xt[af].mutex that is held.
> 
> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
> 
> ---
>  include/linux/netfilter/x_tables.h |    5 -
>  net/ipv4/netfilter/arp_tables.c    |  112 +++++++++------------------------
>  net/ipv4/netfilter/ip_tables.c     |  123 +++++++++++--------------------------
>  net/ipv6/netfilter/ip6_tables.c    |  119 +++++++++++------------------------
>  net/netfilter/x_tables.c           |   28 --------
>  5 files changed, 110 insertions(+), 277 deletions(-)

Oh well, it seems factorization of this stuff is not what you want, so
I'll stop arguing.

Please check spelling of my name in ChangeLog, and more importantly :
initialize arp_tables_lock that is missing in V1/2

	for_each_possible_cpu(cpu)
		spin_lock_init(&per_cpu(arp_tables_lock, cpu));

Then please add my :

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

Thanks


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