Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932190AbaFPPB2 (ORCPT ); Mon, 16 Jun 2014 11:01:28 -0400 Received: from mail-oa0-f42.google.com ([209.85.219.42]:45536 "EHLO mail-oa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754832AbaFPPBY (ORCPT ); Mon, 16 Jun 2014 11:01:24 -0400 MIME-Version: 1.0 In-Reply-To: <87wqckqrxe.fsf@x220.int.ebiederm.org> References: <20140611133919.GZ4581@linux.vnet.ibm.com> <539879B8.4010204@canonical.com> <20140611161857.GC4581@linux.vnet.ibm.com> <53989F7B.6000004@canonical.com> <874mzr41kf.fsf@x220.int.ebiederm.org> <20140611225228.GO4581@linux.vnet.ibm.com> <87ioo7vy5s.fsf@x220.int.ebiederm.org> <20140611234902.GQ4581@linux.vnet.ibm.com> <87bntzt24g.fsf@x220.int.ebiederm.org> <874mzrszlk.fsf@x220.int.ebiederm.org> <87wqckqrxe.fsf@x220.int.ebiederm.org> Date: Mon, 16 Jun 2014 12:01:23 -0300 Message-ID: Subject: Re: Possible netns creation and execution performance/scalability regression since v3.8 due to rcu callbacks being offloaded to multiple cpus From: Rafael Tinoco To: "Eric W. Biederman" Cc: Paul McKenney , Dave Chiluk , linux-kernel@vger.kernel.org, davem@davemloft.net, Christopher Arges , Jay Vosburgh Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ... On Fri, Jun 13, 2014 at 9:02 PM, Eric W. Biederman wrote: > Rafael Tinoco writes: > >> Okay, >> >> Tests with the same script were done. >> I'm comparing : master + patch vs 3.15.0-rc5 (last sync'ed rcu commit) >> and 3.9 last bisect good. >> >> Same tests were made. I'm comparing the following versions: >> >> 1) master + suggested patch >> 2) 3.15.0-rc5 (last rcu commit in my clone) >> 3) 3.9-rc2 (last bisect good) > > I am having a hard time making sense of your numbers. > > If I have read your email correctly my suggested patch caused: > "ip netns add" numbers to improve > 1x "ip netns exec" to improve some > 2x "ip netns exec" to show no improvement > "ip link add" to show no effect (after the 2x ip netns exec) - "netns add" are as good as they were before this regression. - "netns exec" are improved but still 50% of the last good bisect commit. - "link add" didn't show difference. > This is interesting in a lot of ways. > - This seems to confirm that the only rcu usage in ip netns add > was switch_task_namespaces. Which is convinient as that rules > out most of the network stack when looking for performance oddities. > > - "ip netns exec" had an expected performance improvement > - "ip netns exec" is still slow (so something odd is still going on) > - "ip link add" appears immaterial to the performance problem. > > It would be interesting to switch the "ip link add" and "ip netns exec" > in your test case to confirm that there is nothing interesting/slow > going on in "ip link add" - will do that. > > Which leaves me with the question what ip "ip netns exec" remains > that is using rcu and is slowing all of this down. - will check this also. > Eric Tks Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/