Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756986Ab1DHOIn (ORCPT ); Fri, 8 Apr 2011 10:08:43 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:40189 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752433Ab1DHOIm convert rfc822-to-8bit (ORCPT ); Fri, 8 Apr 2011 10:08:42 -0400 Subject: Re: [RFC] tracing: Adding cgroup aware tracing functionality From: Peter Zijlstra To: Steven Rostedt Cc: Frederic Weisbecker , David Sharp , Vaibhav Nagarnaik , Paul Menage , Li Zefan , Stephane Eranian , Andrew Morton , Michael Rubin , Ken Chen , linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, Thomas Gleixner , Ingo Molnar , Arnaldo Carvalho de Melo In-Reply-To: <1302248268.21026.18.camel@frodo> References: <20110407013349.GH1867@nowhere> <20110407120608.GB1798@nowhere> <20110407213208.GE1798@nowhere> <20110408002812.GG1798@nowhere> <1302248268.21026.18.camel@frodo> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Fri, 08 Apr 2011 16:07:50 +0200 Message-ID: <1302271670.9086.154.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1393 Lines: 32 On Fri, 2011-04-08 at 03:37 -0400, Steven Rostedt wrote: > I don't think this is about perf and ftrace as competitors, but they are > currently two different infrastructures that are existing in the kernel. > They are currently optimized for different purposes. ftrace is optimized > for system tracing (persistent buffers and such) where as perf is > optimized for user tracing. That's complete nonsense, perf isn't build for tracing at all, its just that tracing is a special case of the larger problem set of sampling/profiling it is build for. Nor is perf in any way shape or form better suited for user than for kernel space, it really doesn't care, if we'd only be interested in user crap we'd never have done NMI sampling for instance. > But the two can do both but the other > feature is not as efficient as the other tool. Well, neither can do user-space-tracing at all, simply because we don't have hooks into userspace, although the uprobes stuff looks to cure some of that. > As you said perf has a lot of overhead due to data that it saves per > event. Someday you should actually read the perf code before you say something. -- 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/