From mboxrd@z Thu Jan 1 00:00:00 1970 From: jamal Subject: Re: rps perfomance WAS(Re: rps: question Date: Thu, 15 Apr 2010 07:55:28 -0400 Message-ID: <1271332528.4567.150.camel@bigi> References: <1271268242.16881.1719.camel@edumazet-laptop> <1271271222.4567.51.camel@bigi> <20100415.014857.168270765.davem@davemloft.net> Reply-To: hadi@cyberus.ca Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, therbert@google.com, netdev@vger.kernel.org, robert@herjulf.net, xiaosuo@gmail.com, andi@firstfloor.org To: David Miller Return-path: Received: from mail-qy0-f189.google.com ([209.85.221.189]:53194 "EHLO mail-qy0-f189.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752142Ab0DOMGd (ORCPT ); Thu, 15 Apr 2010 08:06:33 -0400 Received: by qyk27 with SMTP id 27so1541671qyk.23 for ; Thu, 15 Apr 2010 05:06:32 -0700 (PDT) In-Reply-To: <20100415.014857.168270765.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2010-04-15 at 01:48 -0700, David Miller wrote: > A single-queue NIC is actually not a requirement, > RPS helps also in cases where you have 'N' application threads > and N is less than the number of CPUs your multi-queue NIC is > distributing traffic to. sure.. > Moving the bulk of the input packet processing to the cpus where > the applications actually sit had a non-trivial benefit. This is true regardless of rps though. > RFS takes this aspect to yet another level. rfs looks quiet interesting;-> I think with some twist it could be used with multiqueue nics as well > I think for the case where application locality is important, > RPS/RFS can help regardless of cache details. Generally true, as long as there's not much shared data across the cpus or the cost of a cache miss is reasonably tolerable. The socket layer just happens to be not sharing much with ingress packet path and for a single processor Nehalem, the caching system works so well that the cost of cache misses is not as an important a variable. Everything is on the same die including the MM controller etc. I am speculating (didnt get any answer to the question i asked) that people running rps use such hardware;-> I speculate again that it may be too costly to run rps on something like a tigerton or intel clovertown where you have cores sharing/contending for an FSB. If I can get answers to the question: "What h/ware are people running?" i could be proven wrong. [Note: I am not against RPS - i think it has its place; so i hope my desire to find out when to use rps doesnt show as hostility towards rps.] cheers, jamal