From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: rps testing questions Date: Tue, 18 Jan 2011 18:34:36 +0000 Message-ID: <1295375676.3537.83.camel@bwh-desktop> References: <1295269713.3700.5.camel@localhost> <4D35DAB0.9030201@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: mi wake , netdev@vger.kernel.org To: Rick Jones Return-path: Received: from exchange.solarflare.com ([216.237.3.220]:18396 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752457Ab1ARSej convert rfc822-to-8bit (ORCPT ); Tue, 18 Jan 2011 13:34:39 -0500 In-Reply-To: <4D35DAB0.9030201@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2011-01-18 at 10:23 -0800, Rick Jones wrote: > Ben Hutchings wrote: > > On Mon, 2011-01-17 at 17:43 +0800, mi wake wrote: [...] > >>I do ab and tbench testing also find there is less tps with enable > >>rps.but,there is more cpu using when with enable rps.when with enab= le > >>rps =EF=BC=8Csoftirqs is blanced on cpus. > >> > >>is there something wrong with my test=EF=BC=9F > >=20 > >=20 > > In addition to what Eric said, check the interrupt moderation setti= ngs > > (ethtool -c/-C options). One-way latency for a single request/resp= onse > > test will be at least the interrupt moderation value. > >=20 > > I haven't tested RPS by itself (Solarflare NICs have plenty of hard= ware > > queues) so I don't know whether it can improve latency. However, R= =46S > > certainly does when there are many flows. >=20 > Is there actually an expectation that either RPS or RFS would improve= *latency*?=20 > Multiple-stream throughput certainly, but with the additional work = done to=20 > spread things around, I wouldn't expect either to improve latency. Yes, it seems to make a big improvement to latency when many flows are active. Tom told me that one of his benchmarks was 200 * netperf TCP_R= R in parallel, and I've seen over 40% reduction in latency for that. Tha= t said, allocating more RX queues might also help (sfc currently defaults to one per processor package rather than one per processor thread, due to concerns about CPU efficiency). Ben. --=20 Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.