From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Bligh Subject: Re: Scalability of interface creation and deletion Date: Sun, 08 May 2011 10:35:02 +0100 Message-ID: References: <891B02256A0667292521A4BF@Ximines.local> <1304770926.2821.1157.camel@edumazet-laptop> <0F4A638C2A523577CDBC295E@Ximines.local> <1304785589.3207.5.camel@edumazet-laptop> <178E8895FB84C07251538EF7@Ximines.local> <1304793174.3207.22.camel@edumazet-laptop> <1304793749.3207.26.camel@edumazet-laptop> <1304838742.3207.45.camel@edumazet-laptop> Reply-To: Alex Bligh Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, "Paul E. McKenney" , Alex Bligh To: Eric Dumazet Return-path: Received: from mail.avalus.com ([89.16.176.221]:33839 "EHLO mail.avalus.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752157Ab1EHJfG (ORCPT ); Sun, 8 May 2011 05:35:06 -0400 In-Reply-To: <1304838742.3207.45.camel@edumazet-laptop> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Eric, --On 8 May 2011 09:12:22 +0200 Eric Dumazet wrote: > By the way, if I change HZ from 1000 to 100 I now have ten times slower > result : I repeated that test here. With HZ set to 1000 I got a total time of 4.022 seconds to remove 100 interfaces, of which: Total 3.03808 Usage 199 Average 0.01527 elsewhere Total 0.93992 Usage 200 Average 0.00470 synchronizing as opposed to a total of 27.917 seconds with HZ set to 100, of which Total 18.98515 Usage 199 Average 0.09540 elsewhere Total 8.77581 Usage 200 Average 0.04388 synchronizing Not quite a factor of 10 improvement, but nearly. I have CONFIG_RCU_FAST_NO_HZ=y I suspect this may just mean an rcu reader holds the rcu_read_lock for a jiffies related time. Though I'm having difficulty seeing what that might be on a system where the net is in essence idle. -- Alex Bligh