From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nir Tzachar Subject: Re: Fwd: [RFC v3] net: Introduce recvmmsg socket syscall Date: Tue, 15 Sep 2009 21:20:13 +0300 Message-ID: <9b2db90b0909151120l71498303w26cfd657c9f18092@mail.gmail.com> References: <9b2db90b0908060014r6a1763e8t1b3ee9310e012c25@mail.gmail.com> <9b2db90b0908060015v45d31060me94cf436f4a25e42@mail.gmail.com> <20090914230902.GC22743@ghostprotocols.net> <9b2db90b0909150137j16c46340o89b55af62f7b613e@mail.gmail.com> <20090915141110.GG22743@ghostprotocols.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: Linux Networking Development Mailing List , Ziv Ayalon To: Arnaldo Carvalho de Melo Return-path: Received: from mail-fx0-f217.google.com ([209.85.220.217]:40937 "EHLO mail-fx0-f217.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753702AbZIOSUL (ORCPT ); Tue, 15 Sep 2009 14:20:11 -0400 Received: by fxm17 with SMTP id 17so1772214fxm.37 for ; Tue, 15 Sep 2009 11:20:14 -0700 (PDT) In-Reply-To: <20090915141110.GG22743@ghostprotocols.net> Sender: netdev-owner@vger.kernel.org List-ID: >> Setup: >> linux 2.6.29.2 with the third version of the patch, running on an >> Intel Xeon X3220 2.4GHz quad core, with 4Gbyte of ram, running Ubuntu >> 9.04 > > Which NIC? 10 Gbit/s? 1G. We do not care as much for throughput as we do about latency... >> Results: >> On general, the recvmmsg beats the pants off the regular recvmsg by a >> whole millisecond (which might not sound much, but is _really_ a lot >> for us ;). The exact distribution fluctuates between half a milli and >> 2 millis, but the average is 1 milli. > > Do you have any testcase using publicly available software? Like qpidd, > etc? I'll eventually have to do that, for now I'm just using that > recvmmsg tool I posted, now with a recvmsg mode, then collecting 'perf > record' with and without callgraphs to post here. The client is just > pktgen spitting datagrams as if there is no tomorrow :-) No. This was on a live, production system. > Showing that we get latency improvements is complementary to what I'm > doing, that is for now just showing the performance improvements and > showing what gives this improvement (perf counters runs). We are more latency oriented, and, naturally, concentrate on this aspect of the problem. Producing numbers here is much more easier.... I can easily come up with a test application which just measures the latency of processing packets, by employing a sending loop between two hosts. > If you could come up with a testcase that you could share with us, > perhaps using one of these AMQP implementations, that would be great > too. Well, in our experience, AMQP and other solutions have latency issues. Moreover, the receiving end of our application is a regular multicast stream. I will implement the simple latency test I mentioned earlier, and post some results soon. Nir.