From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: [PATCH] iptables: lock free counters Date: Fri, 20 Feb 2009 10:37:45 +0100 Message-ID: <499E79E9.1000905@trash.net> References: <20090218051906.174295181@vyatta.com> <20090218052747.321329022@vyatta.com> <20090219114719.560999b5@extreme> <499DEF49.3040602@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Stephen Hemminger , David Miller , Rick Jones , netdev@vger.kernel.org, netfilter-devel@vger.kernel.org To: Eric Dumazet Return-path: Received: from stinky.trash.net ([213.144.137.162]:44766 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752886AbZBTJht (ORCPT ); Fri, 20 Feb 2009 04:37:49 -0500 In-Reply-To: <499DEF49.3040602@cosmosbay.com> Sender: netfilter-devel-owner@vger.kernel.org List-ID: Eric Dumazet wrote: > Stephen Hemminger a =E9crit : >> The reader/writer lock in ip_tables is acquired in the critical path= of >> processing packets and is one of the reasons just loading iptables c= an cause >> a 20% performance loss. The rwlock serves two functions: >> >> 1) it prevents changes to table state (xt_replace) while table is in= use. >> This is now handled by doing rcu on the xt_table. When table is >> replaced, the new table(s) are put in and the old one table(s) ar= e freed >> after RCU period. >> >> 2) it provides synchronization when accesing the counter values. >> This is now handled by swapping in new table_info entries for eac= h cpu >> then summing the old values, and putting the result back onto one >> cpu. On a busy system it may cause sampling to occur at differen= t >> times on each cpu, but no packet/byte counts are lost in the proc= ess. >> >> Signed-off-by: Stephen Hemminger >=20 >=20 > Acked-by: Eric Dumazet >=20 > Sucessfully tested on my dual quad core machine too, but iptables onl= y (no ipv6 here) >=20 > BTW, my new "tbench 8" result is 2450 MB/s, (it was 2150 MB/s not so = long ago) >=20 > Thanks Stephen, thats very cool stuff, yet another rwlock out of kern= el :) Applied, thanks everyone. I've also addes Eric's tbench results to the changelog. -- To unsubscribe from this list: send the line "unsubscribe netfilter-dev= el" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html