Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756128Ab3GOLxd (ORCPT ); Mon, 15 Jul 2013 07:53:33 -0400 Received: from mail-oa0-f44.google.com ([209.85.219.44]:60712 "EHLO mail-oa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755987Ab3GOLxb (ORCPT ); Mon, 15 Jul 2013 07:53:31 -0400 MIME-Version: 1.0 In-Reply-To: <51E3932C.5000905@intel.com> References: <1373548341-24119-1-git-send-email-adrian.hunter@intel.com> <1373548341-24119-10-git-send-email-adrian.hunter@intel.com> <20130712095600.GT25631@dyad.programming.kicks-ass.net> <51DFFCE1.1070203@intel.com> <20130712145515.GI17211@twins.programming.kicks-ass.net> <51E3932C.5000905@intel.com> Date: Mon, 15 Jul 2013 13:53:31 +0200 Message-ID: Subject: Re: [PATCH V5 09/12] perf: make events stream always parsable From: Stephane Eranian To: Adrian Hunter Cc: Peter Zijlstra , Arnaldo Carvalho de Melo , LKML , David Ahern , Frederic Weisbecker , Jiri Olsa , Mike Galbraith , Namhyung Kim , Paul Mackerras , Ingo Molnar Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1568 Lines: 35 On Mon, Jul 15, 2013 at 8:14 AM, Adrian Hunter wrote: > On 12/07/13 17:55, Peter Zijlstra wrote: >> On Fri, Jul 12, 2013 at 03:56:01PM +0300, Adrian Hunter wrote: >>>> There's events where this isn't a possible location; take PERF_RECORD_MMAP for >>>> instance; the tail is the complete filename. >>> >>> PERF_RECORD_MMAP falls in the category I have called non-sample events. >>> Those events are appended with an ID sample. perf tools parses the ID >>> sample backwards from header.size. So the ID is at the last position >>> relative to header.size >> >> But why? Why make it different per PERF_RECORD type? > > There have always been two formats: > > 1. PERF_RECORD_SAMPLE as defined by perf_output_sample() > > 2. everything else as defined by __perf_event__output_id_sample() > > The two formats are not the same, and there is no reason for them to be. > > PERF_RECORD_SAMPLE is parsed forwards, so the ID is at the first position. > > ID samples are parsed backwards, so the ID is at the last position (i.e. the > first position parsed). > I am missing something here. Why do we need an event ID for RECORD_MMAP records? I understand those are requested by events, but do we care which one? The information is global to the monitored process and not specific to an event. -- 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/