Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756133Ab2JJNCI (ORCPT ); Wed, 10 Oct 2012 09:02:08 -0400 Received: from mailout-de.gmx.net ([213.165.64.23]:51826 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755907Ab2JJNCE (ORCPT ); Wed, 10 Oct 2012 09:02:04 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1+9xfsKZrC92QLTR66IlrEXhIs/4D5jt9stPP8ufq bmDR6jwiYY041i Message-ID: <1349874121.6992.80.camel@marge.simpson.net> Subject: Re: Netperf UDP_STREAM regression due to not sending IPIs in ttwu_queue() From: Mike Galbraith To: Mel Gorman Cc: Peter Zijlstra , Suresh Siddha , LKML Date: Wed, 10 Oct 2012 15:02:01 +0200 In-Reply-To: <20121010122921.GX29125@suse.de> References: <20121002065143.GK29125@suse.de> <1349164176.7086.43.camel@marge.simpson.net> <20121002084501.GL29125@suse.de> <1349170282.7086.56.camel@marge.simpson.net> <20121002131421.GN29125@suse.de> <1349247011.4465.24.camel@marge.simpson.net> <1349251997.4465.42.camel@marge.simpson.net> <1349271001.4465.66.camel@marge.simpson.net> <20121010122921.GX29125@suse.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1882 Lines: 38 On Wed, 2012-10-10 at 13:29 +0100, Mel Gorman wrote: > On Wed, Oct 03, 2012 at 03:30:01PM +0200, Mike Galbraith wrote: > > nohz=off, pipe-test with one half pinned to CPU0, the other to CPU1. > > > > procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------ > > r b swpd free buff cache si so bi bo in cs us sy id wa st > > TTW_QUEUE > > 1 0 0 3039488 50948 444720 0 0 0 0 539724 1013417 1 15 84 0 0 > > 1 0 0 3039488 50956 444720 0 0 0 1 540853 1015679 1 15 84 0 0 > > 1 0 0 3039364 50956 444720 0 0 0 0 541630 1017239 1 16 83 0 0 > > 2 0 0 3038992 50956 444720 0 0 0 0 335550 1096569 4 20 76 0 0 > > NO_TTWU_QUEUE > > 1 0 0 3038992 50956 444720 0 0 0 0 33100 1318984 1 27 71 0 0 > > 1 0 0 3038868 50956 444720 0 0 0 0 33100 1319126 2 27 71 0 0 > > 1 0 0 3038868 50956 444720 0 0 0 0 33097 1317968 1 27 72 0 0 > > 2 0 0 3038868 50964 444720 0 0 0 1 33104 1318558 2 27 71 0 0 > > > > We can switch faster with NO_TTWU_QUEUE, so we switch more, and that > > hurts netperf UDP_STREAM throughput.. somehow. Fatter is better is not > > the way context switch happy benchmarks usually work. > > > > Do we really switch more though? Yup, pipe-test measures the full round trip, and agrees with vmstat. netperf TCP_RR agrees, tbench agrees... this STREAM thingy is the only high frequency switcher I've seen go all weird like this. (hm, wonder how fast box can blast IPIs.. 1MHz?) -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/