Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755320Ab3HLBrx (ORCPT ); Sun, 11 Aug 2013 21:47:53 -0400 Received: from one.firstfloor.org ([193.170.194.197]:37302 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755270Ab3HLBru (ORCPT ); Sun, 11 Aug 2013 21:47:50 -0400 Date: Mon, 12 Aug 2013 03:47:48 +0200 From: Andi Kleen To: Karim Yaghmour Cc: Andi Kleen , linux-kernel@vger.kernel.org, Steven Rostedt , mingo@elte.hu Subject: Re: Reading perf counters at ftrace trace boundaries Message-ID: <20130812014748.GP19750@two.firstfloor.org> References: <5208263D.2080205@opersys.com> <87haevog75.fsf@tassilo.jf.intel.com> <52083CB4.2030308@opersys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52083CB4.2030308@opersys.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 566 Lines: 14 > Indeed. It doesn't actually have to be at every single ftrace > begin/exit. But possibly starting with some kind of every nth and then > drilling down as the culprit is incrementally singled-out. That's what normal sampling already does. If you're worried about systematic shadow effects just randomize a bit. -Andi -- 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/