From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755314Ab3HLBjL (ORCPT ); Sun, 11 Aug 2013 21:39:11 -0400 Received: from mail-ve0-f169.google.com ([209.85.128.169]:40018 "EHLO mail-ve0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755285Ab3HLBjH (ORCPT ); Sun, 11 Aug 2013 21:39:07 -0400 Message-ID: <52083CB4.2030308@opersys.com> Date: Sun, 11 Aug 2013 22:39:00 -0300 From: Karim Yaghmour User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130804 Thunderbird/17.0.8 MIME-Version: 1.0 To: Andi Kleen CC: linux-kernel@vger.kernel.org, Steven Rostedt , mingo@elte.hu Subject: Re: Reading perf counters at ftrace trace boundaries References: <5208263D.2080205@opersys.com> <87haevog75.fsf@tassilo.jf.intel.com> In-Reply-To: <87haevog75.fsf@tassilo.jf.intel.com> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13-08-11 10:23 PM, Andi Kleen wrote: > KVM does it, see arch/x86/kvm/pmu.c. Essentially it would be doing RDPMC. Thx for the pointer, appreciated. > But the overhead will be likely very high, some sampling approach > is likely better. 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. -- Karim Yaghmour CEO - Opersys inc. / www.opersys.com http://twitter.com/karimyaghmour