From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754800Ab1JASlH (ORCPT ); Sat, 1 Oct 2011 14:41:07 -0400 Received: from 1wt.eu ([62.212.114.60]:33330 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754154Ab1JASlA (ORCPT ); Sat, 1 Oct 2011 14:41:00 -0400 Date: Sat, 1 Oct 2011 20:40:49 +0200 From: Willy Tarreau To: starlight@binnacle.cx Cc: Eric Dumazet , linux-kernel@vger.kernel.org, netdev , Peter Zijlstra Subject: Re: big picture UDP/IP performance question re 2.6.18 -> 2.6.32 Message-ID: <20111001184049.GE18690@1wt.eu> References: <6.2.5.6.2.20111001141002.05af4b20@binnacle.cx> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6.2.5.6.2.20111001141002.05af4b20@binnacle.cx> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 01, 2011 at 02:16:05PM -0400, starlight@binnacle.cx wrote: > At 08:44 AM 10/1/2011 +0200, Eric Dumazet wrote: > >In my experience, I have the exact opposite : > >performance greatly improved in recent > >kernels. Unless you compile your kernel to include > >new features that might reduce performance > >(namespaces, cgroup, ...) > > RH has both of the above turned on in the > 2.6.32-71.29.1.el6.x86_64 kernel tested. > > If these are big negatives to network > performance, could you list what should > specifically turned off to maximize > results? Also a recommendation for > the best recent kernel for another > benchmark would be helpful. > > Probably can't convince anyone to deploy a > kernel without commercial support, but if > an alternate compile fixes performance it > might be possible to convince RH to support > the alternative build. Just a suggestion, instead of measuring CPU usage at a given load, could you check what maximal load you can achieve ? It is very possible that CPU usage report is not accurate. We observed this in a number of situations, especially in high packet rate environments where the usage is a sum of many micro-measurements. Also, I did not notice any indication on the load level you were reaching (packets per second and bandwidth). Have you compared the interrupt rate ? It is possible that they differ between the two kernels, for instance because the NIC auto-adapts instead of being throttled to a given rate. This can have a significant impact on measurements and performance. Regards, Willy