From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758111Ab3GZI5o (ORCPT ); Fri, 26 Jul 2013 04:57:44 -0400 Received: from merlin.infradead.org ([205.233.59.134]:58028 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753365Ab3GZI5l (ORCPT ); Fri, 26 Jul 2013 04:57:41 -0400 Date: Fri, 26 Jul 2013 10:57:30 +0200 From: Peter Zijlstra To: Vince Weaver Cc: Adrian Hunter , mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:perf/core] perf: Update perf_event_type documentation Message-ID: <20130726085730.GD27075@twins.programming.kicks-ass.net> References: <20130716150907.GL23818@dyad.programming.kicks-ass.net> <51F0C41C.8080005@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 25, 2013 at 11:20:24PM -0400, Vince Weaver wrote: > > On Thu, 25 Jul 2013, Adrian Hunter wrote: > > > >> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > > >> index 0b1df41..00d8274 100644 > > >> --- a/include/uapi/linux/perf_event.h > > >> +++ b/include/uapi/linux/perf_event.h > > >> @@ -478,6 +478,16 @@ enum perf_event_type { > > >> * file will be supported by older perf tools, with these new optional > > >> * fields being ignored. > > >> * > > >> + * struct sample_id { > > >> + * { u32 pid, tid; } && PERF_SAMPLE_TID > > >> + * { u64 time; } && PERF_SAMPLE_TIME > > >> + * { u64 id; } && PERF_SAMPLE_ID > > >> + * { u64 stream_id;} && PERF_SAMPLE_STREAM_ID > > >> + * { u32 cpu, res; } && PERF_SAMPLE_CPU > > >> + * } && perf_event_attr::sample_id_all > > >> + */ > > >> + > > a thing that personally bothers me are these imaginary struct definitions > added as part of the documentation that aren't actually available in the > public perf_event.h > > I can see why it's done, but it can be confusing picking out in later > definitions which struct fields are real and which ones are conceptual. Would it help if we changed the syntax to not look as much as real C would? > > >> @@ -498,6 +508,7 @@ enum perf_event_type { > > >> * struct perf_event_header header; > > >> * u64 id; > > >> * u64 lost; > > >> + * struct sample_id sample_id; > > >> * }; > > This is what confused me; this documentation shows the sample_id > as always being there, but in reality that struct is only there > if perf_event_attr::sample_id_all is set. > > It might be clearer > if you stuck the perf_event_attr::sample_id_all qualifier each > place you add the sample_id field. Ah, I actually considered that but then got lazy and used the 0 sized struct idea :/