Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755861Ab3J1Iss (ORCPT ); Mon, 28 Oct 2013 04:48:48 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:35431 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755835Ab3J1Isq (ORCPT ); Mon, 28 Oct 2013 04:48:46 -0400 X-Sasl-enc: 8R81TBLe+CmUSXVGOvBmTBot5bf4RWybADWKDLbPqsII 1382950124 Message-ID: <526E24EA.2040701@iki.fi> Date: Mon, 28 Oct 2013 10:48:42 +0200 From: Pekka Enberg User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: David Ahern , Srikar Dronamraju CC: Hemant Kumar , LKML , Peter Zijlstra , Oleg Nesterov , "hegdevasant@linux.vnet.ibm.com" , Ingo Molnar , "anton@redhat.com" , "systemtap@sourceware.org" , Namhyung Kim , Masami Hiramatsu , "aravinda@linux.vnet.ibm.com" Subject: Re: [PATCH v4 2/3] Support for perf to probe into SDT markers: References: <20131023044511.1886.82571.stgit@hemant-fedora> <20131023050502.1886.15779.stgit@hemant-fedora> <20131025125921.GA29424@linux.vnet.ibm.com> <526A8C2B.7000401@gmail.com> In-Reply-To: <526A8C2B.7000401@gmail.com> 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: 2131 Lines: 49 Hi David, On 10/25/2013 06:20 PM, David Ahern wrote: > On 10/25/13 8:20 AM, Pekka Enberg wrote: >>> Technically feasible. But then we would have to parse each of the >>> libraries and executables to list them. Right? I am not sure if such a >>> delay is acceptable. >> >> You could do it at 'perf list' time or even build time and cache it. >> And add lazy discovery to 'perf record' and friends. > > Instead searching all the known files or building a cache, how about > just having an option like: perf list . perf-record could still > do the probe magic behind the scenes. We probably should also support that. But I don't see why 'perf list' could not tell me about SDT markers in libraries that are already installed on my system. The problem I have with all the command line magic is that while the tracing mechanisms are awesome, they're nearly impossible to discover even by a power user such as myself and you almost certainly forget the exact syntax over time. It's not as if you're tracing all the time. I wish people remembed how awesome and simple 'perf stat' and 'perf record' with 'perf report' were compared to oprofile when the first versions came out. I think much of the nice perf features are suffering because we're not paying enough attention how to make them accessible to users. The proposed SDT marker feature is a good example of that. I mean, how on earth would I know about the userspace probes unless I read LKML and know that such a feature exists? And why would I want to provide mappings for SDT markers and perf events if I want to trace 'libc:setjmp'? So I really hope this SDT effort and the ktap effort at least make some effort in unifying all the nice functionality that's simple to use and easy to discover. I really, really would at the end of the day, just 'perf trace' like I 'perf stat' or 'perf record'. Pekka -- 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/