From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Josefsson Subject: Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU Date: Mon, 13 Apr 2009 21:06:10 +0200 (CEST) Message-ID: References: <20090411174801.GG6822@linux.vnet.ibm.com> <18913.53699.544083.320542@cargo.ozlabs.ibm.com> <20090412173108.GO6822@linux.vnet.ibm.com> <20090412.181330.23529546.davem@davemloft.net> <20090413040413.GQ6822@linux.vnet.ibm.com> <20090413095309.631cf395@nehalam> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: paulmck@linux.vnet.ibm.com, David Miller , paulus@samba.org, mingo@elte.hu, torvalds@linux-foundation.org, laijs@cn.fujitsu.com, jeff.chua.linux@gmail.com, dada1@cosmosbay.com, jengelh@medozas.de, kaber@trash.net, r000n@r000n.net, linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, benh@kernel.crashing.org To: Stephen Hemminger Return-path: In-Reply-To: <20090413095309.631cf395@nehalam> Sender: netdev-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org On Mon, 13 Apr 2009, Stephen Hemminger wrote: > 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. Doesn't spin_lock() result in a pipeline flush on x86? iirc there was a benchmark in an RCU paper that tested using per cpu spin_locks and the result was that it didn't scale well at all. /Martin