Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754198AbZIIUum (ORCPT ); Wed, 9 Sep 2009 16:50:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754098AbZIIUul (ORCPT ); Wed, 9 Sep 2009 16:50:41 -0400 Received: from brick.kernel.dk ([93.163.65.50]:60085 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754067AbZIIUul (ORCPT ); Wed, 9 Sep 2009 16:50:41 -0400 Date: Wed, 9 Sep 2009 22:50:43 +0200 From: Jens Axboe To: Nikos Chantziaras Cc: Ingo Molnar , Mike Galbraith , Peter Zijlstra , Con Kolivas , linux-kernel@vger.kernel.org Subject: Re: BFS vs. mainline scheduler benchmarks and measurements Message-ID: <20090909205043.GI18599@kernel.dk> References: <20090908091304.GQ18599@kernel.dk> <1252423398.7746.97.camel@twins> <20090908203409.GJ18599@kernel.dk> <20090909061308.GA28109@elte.hu> <1252486344.28645.18.camel@marge.simson.net> <20090909091009.GR18599@kernel.dk> <20090909115429.GY18599@kernel.dk> <20090909122006.GA18599@kernel.dk> <20090909180404.GA11027@elte.hu> <4AA80C1E.2080901@arcor.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4AA80C1E.2080901@arcor.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2917 Lines: 99 On Wed, Sep 09 2009, Nikos Chantziaras wrote: > On 09/09/2009 09:04 PM, Ingo Molnar wrote: >> [...] >> * Jens Axboe wrote: >> >>> On Wed, Sep 09 2009, Jens Axboe wrote: >>> [...] >>> BFS210 runs on the laptop (dual core intel core duo). With make -j4 >>> running, I clock the following latt -c8 'sleep 10' latencies: >>> >>> -rc9 >>> >>> Max 17895 usec >>> Avg 8028 usec >>> Stdev 5948 usec >>> Stdev mean 405 usec >>> >>> Max 17896 usec >>> Avg 4951 usec >>> Stdev 6278 usec >>> Stdev mean 427 usec >>> >>> Max 17885 usec >>> Avg 5526 usec >>> Stdev 6819 usec >>> Stdev mean 464 usec >>> >>> -rc9 + mike >>> >>> Max 6061 usec >>> Avg 3797 usec >>> Stdev 1726 usec >>> Stdev mean 117 usec >>> >>> Max 5122 usec >>> Avg 3958 usec >>> Stdev 1697 usec >>> Stdev mean 115 usec >>> >>> Max 6691 usec >>> Avg 2130 usec >>> Stdev 2165 usec >>> Stdev mean 147 usec >> >> At least in my tests these latencies were mainly due to a bug in >> latt.c - i've attached the fixed version. >> >> The other reason was wakeup batching. If you do this: >> >> echo 0> /proc/sys/kernel/sched_wakeup_granularity_ns >> >> ... then you can switch on insta-wakeups on -tip too. >> >> With a dual-core box and a make -j4 background job running, on >> latest -tip i get the following latencies: >> >> $ ./latt -c8 sleep 30 >> Entries: 656 (clients=8) >> >> Averages: >> ------------------------------ >> Max 158 usec >> Avg 12 usec >> Stdev 10 usec > > With your version of latt.c, I get these results with 2.6-tip vs > 2.6.31-rc9-bfs: > > > (mainline) > Averages: > ------------------------------ > Max 50 usec > Avg 12 usec > Stdev 3 usec > > > (BFS) > Averages: > ------------------------------ > Max 474 usec > Avg 11 usec > Stdev 16 usec > > > However, the interactivity problems still remain. Does that mean it's > not a latency issue? It probably just means that latt isn't a good measure of the problem. Which isn't really too much of a surprise. -- Jens Axboe -- 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/