From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH 0/2] Get rid of ndo_xmit_flush Date: Wed, 27 Aug 2014 10:37:29 +0200 Message-ID: <20140827103729.69551e29@redhat.com> References: <20140825.163458.1117073971092495452.davem@davemloft.net> <20140826082815.18034199@redhat.com> <20140826121347.0ec7f2ac@redhat.com> <20140826145225.6673ab3f@redhat.com> <53FCB944.9060904@intel.com> <20140827094859.65f4f0fc@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Alexander Duyck , David Miller , netdev@vger.kernel.org, therbert@google.com, jhs@mojatatu.com, hannes@stressinduktion.org, edumazet@google.com, jeffrey.t.kirsher@intel.com, rusty@rustcorp.com.au, dborkman@redhat.com, Jeremy Eder To: Jesper Dangaard Brouer Return-path: Received: from mx1.redhat.com ([209.132.183.28]:18896 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751085AbaH0Iho (ORCPT ); Wed, 27 Aug 2014 04:37:44 -0400 In-Reply-To: <20140827094859.65f4f0fc@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 27 Aug 2014 09:48:59 +0200 Jesper Dangaard Brouer wrote: > Reading Jeremy Eder's blog post: > http://www.breakage.org/2012/11/14/processor-max_cstate-intel_idle-max_cstate-and-devcpu_dma_latency/ > > It seems the best method for disabling these C and P states, and > keeping all CPUs in C0/C1 state is doing: > > # tuned-adm profile latency-performance [...] > I'm also going to disable Hyper-threading in BIOS, even-though I'm only > using one CPU in these tests (I worry that some process running on a > sibling could disturb the accuracy). Disabling Hyper-Threading in BIOS helped the accuracy, now the latency variation is below 0.1ns min:-0.031 and max:0.054 over 120 sec. Still using: # tuned-adm profile latency-performance > Setting: > * sudo ethtool -C eth5 rx-usecs 30 > Result: > * instant rx:1 tx:5603644 pps n:120 average: rx:0 tx:5603317 pps > (instant variation TX 0.010 ns (min:-0.132 max:0.114) RX 0.000 ns) > * instant rx:1 tx:5599820 pps n:300 average: rx:1 tx:5602382 pps > (instant variation TX -0.082 ns (min:-0.209 max:0.114) RX 0.000 ns) With no HT: * instant rx:1 tx:5597616 pps n:120 average: rx:1 tx:5596283 pps (instant variation TX 0.043 ns (min:-0.031 max:0.054) RX 0.000 ns) With this setup, I think we are ready to measure the effect of our API changes with sufficient accuracy. -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer