Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932880Ab0KPWHO (ORCPT ); Tue, 16 Nov 2010 17:07:14 -0500 Received: from mga14.intel.com ([143.182.124.37]:31502 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932758Ab0KPWHN (ORCPT ); Tue, 16 Nov 2010 17:07:13 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.59,207,1288594800"; d="scan'208";a="349619482" Message-ID: <4CE30086.2070806@linux.intel.com> Date: Tue, 16 Nov 2010 14:07:02 -0800 From: Darren Hart User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.12) Gecko/20101027 Lightning/1.0b2 Thunderbird/3.1.6 MIME-Version: 1.0 To: Ingo Molnar CC: Thomas Gleixner , LKML , Linus Torvalds , Andrew Morton , Peter Zijlstra , Steven Rostedt , Arjan van de Ven , Arnaldo Carvalho de Melo , Frederic Weisbecker , Masami Hiramatsu , Tom Zanussi , Mathieu Desnoyers , Li Zefan , Jason Baron , "David S. Miller" , Christoph Hellwig , Pekka Enberg , Lai Jiangshan , Eric Dumazet Subject: Re: [ANNOUNCE] New utility: 'trace' References: <4CE2F747.4060406@linux.intel.com> <20101116215940.GA13912@elte.hu> In-Reply-To: <20101116215940.GA13912@elte.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2487 Lines: 65 On 11/16/2010 01:59 PM, Ingo Molnar wrote: > > * Darren Hart wrote: > >> On 11/16/2010 01:04 PM, Thomas Gleixner wrote: >>> We are pleased to announce a new tracing tool called 'trace'. >>> >> >> Hi Thomas, Ingo - Congrats and Thanks! > > You are welcome :) > >>> At this point we'd like to ask for feedback from other users of tracing tools, >>> which workflow components would you like to see in addition to what the 'trace' >>> tool is offering? >>> >>> Comments, bug reports, suggestions welcome, >> >> The first thing that comes to mind is trace_marker: >> >> echo "Test point A"> /sys/kernel/debug/tracing/trace_marker >> >> I've found this sort of markup to be useful using ftrace (with C equivalents >> embedded in the test case). Is this supported? > > Yes, LatencyTop uses something similar IIRC, via a prctl() hack: it uses > prctl(PR_SET_NAME) to inject up to 16 characters into the comm - and then every perf > event gets that comm. You can utilize that straight away if you need a marker > solution right now. OK, definitely much more limited than trace_marker. > > A cleaner, more generic approach would be a more free-form ASCII event facility for > this: a generic 'user-space triggered event' with injection capabilities. > > To inject it, we could put that into a prctl() as well, for easy, single-syscall > access from C. We already have two perf prctls: PR_TASK_PERF_EVENTS_DISABLE, > PR_TASK_PERF_EVENTS_ENABLE - and this would be a third one: PR_TASK_PERF_USER_EVENT. > > This would, like the existing perf_event_task_enable()/disable() methods, loop > through current events and inject a string into matching user events. > > Ideally i'd like to see basically user-space access to trace_printk(), and proper Right, this would be ideal. > integration into /debug/tracing/events/ enumeration and availability - not a > ftrace-specific and admin-only hack like /sys/kernel/debug/tracing/trace_marker is > today. > > Would you be interested in helping out with (and testing) such a more generic > approach? I would. I need some time to familiarize myself with perf first (I've been a relatively happy ftrace/trace-cmd user for the last couple years). -- Darren Hart Yocto Linux Kernel -- 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/