Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753534Ab2BWLya (ORCPT ); Thu, 23 Feb 2012 06:54:30 -0500 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:53692 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752135Ab2BWLy3 (ORCPT ); Thu, 23 Feb 2012 06:54:29 -0500 Date: Thu, 23 Feb 2012 17:02:24 +0530 From: Srivatsa Vaddagiri To: Ingo Molnar Cc: Mike Galbraith , Peter Zijlstra , Suresh Siddha , linux-kernel , Paul Turner Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible Message-ID: <20120223113224.GB8454@linux.vnet.ibm.com> Reply-To: Srivatsa Vaddagiri References: <1321544313.6308.25.camel@marge.simson.net> <1321545376.2495.1.camel@laptop> <1321547917.6308.48.camel@marge.simson.net> <1321551381.15339.21.camel@sbsiddha-desk.sc.intel.com> <1321629267.7080.13.camel@marge.simson.net> <1329748861.2293.345.camel@twins> <1329761661.6276.146.camel@marge.simpson.net> <20120223104959.GA8454@linux.vnet.ibm.com> <20120223112005.GA7645@linux.vnet.ibm.com> <20120223112650.GA23844@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20120223112650.GA23844@elte.hu> User-Agent: Mutt/1.5.21 (2010-09-15) x-cbid: 12022311-9574-0000-0000-0000017F1506 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1010 Lines: 28 * Ingo Molnar [2012-02-23 12:26:50]: > pro perf tip of the day: did you know that it's possible to run: > > perf stat --repeat 10 --null perf bench sched pipe Ah yes ..had forgotten that! What is the recommended # of iterations to run? > and get meaningful, normalized stddev calculations for free: > > 5.486491487 seconds time elapsed ( +- 5.50% ) > > the percentage at the end shows the level of standard deviation. > > You can add "--sync" as well, which will cause perf stat to call > sync() - this gives extra stability of individual iterations and > makes sure all IO cost is accounted to the right run. Ok ..thanks for the 'pro' tip!! Will use it in my subsequent runs! - vatsa -- 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/