From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: UDP regression with packets rates < 10k per sec Date: Wed, 09 Sep 2009 00:52:41 +0200 Message-ID: <4AA6E039.4000907@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org To: Christoph Lameter Return-path: Received: from gw1.cosmosbay.com ([212.99.114.194]:41294 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751822AbZIHWwl (ORCPT ); Tue, 8 Sep 2009 18:52:41 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Christoph Lameter a =E9crit : > Looks like we have a regression since 2.6.22 due to latency increases= in > the network stack? The following is the result of measuring latencies= for > UDP multicast traffic at packet rates of 10pps 100pps 1kpps 10kpps an= d > 100k pps. Two system running "mcast -n1 -r" (mcast tool from > http://gentwo.org/ll). >=20 > Measurements in microseconds for one hop using bnx2 on Dell R610 (64 = bit > 2.6.31-rc9) and Dell 1950 (32 bit 2.6.22.19 3.3Ghz). Dell R610 RX use= cs > tuned to 0. 32 bit tuned to 1 (NIC is flaky at 0). >=20 > Kernel 10pps 100pps 1kpps 10kpps 100kpps > --------------------------------------------------------------- > 2.6.22 (32bit) 30 29.5 29 30 41 > 2.6.31-rc9(64 bit) 64 63 46 30 40 >=20 > The only minor improvement is at a rate of 100kpps. All rates > lower than 10k regress significantly. >=20 > Could there be something wrong with the bnx2 interrupt routing? They = all > end up on cpu0 here. There are 8 of them in a system with 16 "process= ors". > How do those need to be configured? There are some sparse comments in > Documentation/networking/multiqueue.txt but the text does not say any= thing > about the irq routing. >=20 >=20 Hi Christoph In order to reproduce this here, could you tell me if you use=20 Producer linux-2.6.22 -> Receiver 2.6.22 Producer linux-2.6.31 -> Receiver 2.6.31 Or a mix of Producer linux-2.6.31 -> Receiver 2.6.22 Producer linux-2.6.22 -> Receiver 2.6.31-rc9 Not clear what is your exact setup Thanks