From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756423Ab3GLGfx (ORCPT ); Fri, 12 Jul 2013 02:35:53 -0400 Received: from mga01.intel.com ([192.55.52.88]:57208 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753017Ab3GLGfw (ORCPT ); Fri, 12 Jul 2013 02:35:52 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.89,651,1367996400"; d="scan'208";a="369044539" Message-ID: <51DFA53A.9020200@intel.com> Date: Fri, 12 Jul 2013 09:42:02 +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:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: David Ahern CC: Stephane Eranian , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Frederic Weisbecker , Jiri Olsa , Mike Galbraith , Namhyung Kim , Paul Mackerras , Peter Zijlstra , Ingo Molnar Subject: Re: [PATCH V5 09/12] perf: make events stream always parsable References: <1373548341-24119-1-git-send-email-adrian.hunter@intel.com> <1373548341-24119-10-git-send-email-adrian.hunter@intel.com> <51DED2AA.6030307@gmail.com> In-Reply-To: <51DED2AA.6030307@gmail.com> 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 11/07/13 18:43, David Ahern wrote: > On 7/11/13 7:12 AM, Adrian Hunter wrote: >> The event stream is not always parsable because the format of a sample >> is dependent on the sample_type of the selected event. When there >> is more than one selected event and the sample_types are not the >> same then parsing becomes problematic. A sample can be matched to its >> selected event using the ID that is allocated when the event is opened. >> Unfortunately, to get the ID from the sample means first parsing it. > > Here's an alternative suggestion -- one that does not involve changing the > kernel API or requiring a common denominator in sample_type options. The kernel API is designed to be extensible. Extending it in a way that is perhaps unexpected but nevertheless backward compatible, is an appropriate solution. > > perf handles event streams through an mmap which can be directly tied to an > evsel (a single event) when the mmap is created. ie., when events are read > we know exactly which evsel they correspond to. (See > perf_evlist__mmap_per_cpu and perf_evlist__mmap_per_thread and add struct > perf_evsel *evsel entry to struct perf_mmap). > > Commands like perf-record can inject a user event into the stream and hence > the data file every time the evsel changes while walking all of the mmap's > reading events -- very similar to the way finished round is done. The event > would only contain a perf_event_header which is 8 bytes so this does not add > a lot to a data file. As an optimization the evsel event could only be > injected if the sample_types differ. > > Live commands would just use the evsel connected to the mmap -- no lookups > needed which would simplify things a bit processing the events. > > In short, the information to associate event streams to an event (evsel) is > currently available -- it's just being discarded in the many layers. > > I'll try to whip up some code that implements this in the next few days. > > David > > >