From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753528Ab0EJFWk (ORCPT ); Mon, 10 May 2010 01:22:40 -0400 Received: from ozlabs.org ([203.10.76.45]:46660 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751126Ab0EJFWj (ORCPT ); Mon, 10 May 2010 01:22:39 -0400 Date: Mon, 10 May 2010 15:20:56 +1000 From: Paul Mackerras To: Tejun Heo Cc: Peter Zijlstra , mingo@elte.hu, efault@gmx.de, avi@redhat.com, acme@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCHSET] sched,perf: unify tracers in sched and move perf on top of TP Message-ID: <20100510052056.GB20793@drongo> References: <1272976724-14312-1-git-send-email-tj@kernel.org> <1272994165.1642.203.camel@laptop> <4BE0FB68.7080403@kernel.org> <1273050400.1642.229.camel@laptop> <4BE13B33.3030709@kernel.org> <1273053073.1642.235.camel@laptop> <4BE1406C.2000400@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BE1406C.2000400@kernel.org> 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 On Wed, May 05, 2010 at 11:54:52AM +0200, Tejun Heo wrote: > On 05/05/2010 11:51 AM, Peter Zijlstra wrote: > >> I was wondering the other way around - ie. the possibility to make > >> perf optional and maybe even as a module which depends on TPs, which > >> would be nicer than the current situation and make the code less > >> cluttered too. > > > > I really really hate making perf rely on tracepoints. > > Hmmm.... may I ask why? Unifying hooking mechanism seems like a good > idea to me and it's not like it's gonna add any runtime overhead > although it does complicate init/exit but well that's something you > have to pay if you wanna do things dynamically and sans the ifdef > stuff it's like a couple hundred lines of isolated code. Don't forget where perf_events started out - as a way to count and record hardware events. So perf_events is very useful even in a kernel that has no tracing infrastructure configured in at all. Paul.