From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754659AbaE1JJx (ORCPT ); Wed, 28 May 2014 05:09:53 -0400 Received: from mga09.intel.com ([134.134.136.24]:55112 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752489AbaE1JJv (ORCPT ); Wed, 28 May 2014 05:09:51 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.98,926,1392192000"; d="scan'208";a="518924345" Message-ID: <5385A7A9.80702@intel.com> Date: Wed, 28 May 2014 12:08:57 +0300 From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Ingo Molnar , Dave Jones , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, David Ahern , Jiri Olsa , Paul Mackerras Subject: Re: [PATCH] perf: Differentiate exec() and non-exec() comm events References: <1401266704-22572-1-git-send-email-adrian.hunter@intel.com> <20140528085538.GR11096@twins.programming.kicks-ass.net> In-Reply-To: <20140528085538.GR11096@twins.programming.kicks-ass.net> 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 05/28/2014 11:55 AM, Peter Zijlstra wrote: > On Wed, May 28, 2014 at 11:45:04AM +0300, Adrian Hunter wrote: >> perf tools like 'perf report' can aggregate samples by comm >> strings, which generally works. However, there are other >> potential use-cases. For example, to pair up 'calls' >> with 'returns' accurately (from branch events like Intel BTS) >> it is necessary to identify whether the process has exec'd. >> Although a comm event is generated when an 'exec' happens >> it is also generated whenever the comm string is changed >> on a whim (e.g. by prctl PR_SET_NAME). This patch adds a >> flag to the comm event to differentiate one case from the >> other. >> >> In order to determine whether the kernel supports the new >> flag, a selection bit named 'exec' is added to struct >> perf_event_attr. The bit does nothing but will cause >> perf_event_open() to fail if the bit is set on kernels >> that do not have it defined. >> > >> --- a/include/uapi/linux/perf_event.h >> +++ b/include/uapi/linux/perf_event.h >> @@ -302,8 +302,8 @@ struct perf_event_attr { >> exclude_callchain_kernel : 1, /* exclude kernel callchains */ >> exclude_callchain_user : 1, /* exclude user callchains */ >> mmap2 : 1, /* include mmap with inode data */ >> - >> - __reserved_1 : 40; >> + exec : 1, /* flag comm events that are due to an exec */ >> + __reserved_1 : 39; >> > > Yah.. that's just sad :-( > > the only capabilities mask we have is in the mmap() page, so without > mmap()ing we have no way to test that. > > Would it make sense to call it comm_exec? Yes, that is better. Do you want me to resend the patch?