Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752802AbZGCH1i (ORCPT ); Fri, 3 Jul 2009 03:27:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751329AbZGCH1b (ORCPT ); Fri, 3 Jul 2009 03:27:31 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:59981 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751418AbZGCH1a (ORCPT ); Fri, 3 Jul 2009 03:27:30 -0400 Date: Fri, 3 Jul 2009 09:27:17 +0200 From: Ingo Molnar To: Mike Galbraith Cc: Arnaldo Carvalho de Melo , Paul Mackerras , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , LKML , Peter Zijlstra Subject: Re: [patch 0/4] perf_counter tools: support annotation of live kernel modules Message-ID: <20090703072717.GB7943@elte.hu> References: <1246514639.13293.40.camel@marge.simson.net> <20090702064712.GA26690@elte.hu> <1246519076.6384.22.camel@marge.simson.net> <20090702074214.GA19187@elte.hu> <1246521342.8681.5.camel@marge.simson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1246521342.8681.5.camel@marge.simson.net> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1650 Lines: 41 * Mike Galbraith wrote: > On Thu, 2009-07-02 at 09:42 +0200, Ingo Molnar wrote: > > (squirrels suggestions away for later reference) > > > Btw, another thing: we are thinking about making -F 1000 (1 KHz > > auto-freq sampling) the default for perf top and perf record. This > > way we'd always gather enough data (and never too much or too little > > data), regardless of the intensity of the workload. Have you played > > with -F before, what's your general experience about it? It's > > particularly useful for 'rare' and highly fluctuating events like > > cache-misses. > > > > Maybe 1KHz is a bit too low - Oprofile defaults to 100000 cycles > > interval by default which is about 10 KHz on a 1GHz box and 30 > > KHz on a 3GHz box. Perhaps 10 KHz is a better default? > > My default usage is 1000Hz to keep overhead low. Works fine for > me. ah, so you use -F by default? I still think 10 KHz would be better - especially for really short runs like 'perf record -f -g ./git gc'. Since Oprofile samples at 26 KHz by default, we must not go to a too low frequency, otherwise people might get a 'hm, the perf profiles are worse than the Oprofile ones' first impression ... We could perhaps add a freq=1000 switch to .perfconfig - we have Git's util/config.c facility - it's just unused right now ;-) [ Look at the Git sources about how config.c is used. ] Ingo -- 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/