From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Bligh Subject: Re: Testing interface removal speedup patches from Eric Dumazet. Date: Mon, 09 May 2011 20:12:39 +0100 Message-ID: References: <4DC83471.7030701@candelatech.com> <06627C760FB049F1A9321BC6@Ximines.local> <4DC83A57.40405@candelatech.com> Reply-To: Alex Bligh Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev , Eric Dumazet , Alex Bligh To: Ben Greear Return-path: Received: from mail.avalus.com ([89.16.176.221]:33310 "EHLO mail.avalus.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753900Ab1EITMl (ORCPT ); Mon, 9 May 2011 15:12:41 -0400 In-Reply-To: <4DC83A57.40405@candelatech.com> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: --On 9 May 2011 12:02:47 -0700 Ben Greear wrote: >> So Eric's patches help in the interface create case, even though >> there is no synchronize_net, sychronize_sched() or rcu_barrier() there. >> >> I had assumed the slow create (which varies by number of pairs) was >> down to sysfs scalability only (see difference between 14ms and 110ms >> there). > > I'm not certain the create case is actually faster. Other runs on the > patched kernel showed create to be much closer to the un-patched kernel. > > The ratios to create/delete are more consistent it seems. > >> Out of interest, if you still happen to have the scripts around, how >> fast is veth creation if you just do 100 pairs? > > Created 500 veth in 17.874695 seconds (0.03574939 per interface). > Created 100 veth in 2.779905 seconds (0.02779905 per interface). Hmmm... well you are getting *far* better linearity than me. Creating 500 interfaces is 8 times slower *per interface* than doing 500. What occurs to me is that your box is faster than one of the ones I tested on, and you use CONFIG_HZ=100 but you get poorer results in absolute terms doing 100 (I see 14ms per interface). This with everything listenting to udev disabled? (so udevd dead, whatever executes your ifup/down scripts dead, unshare -n). -- Alex Bligh