From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754251AbbGHN2P (ORCPT ); Wed, 8 Jul 2015 09:28:15 -0400 Received: from mail.kernel.org ([198.145.29.136]:50375 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758207AbbGHN2N (ORCPT ); Wed, 8 Jul 2015 09:28:13 -0400 Date: Wed, 8 Jul 2015 10:28:05 -0300 From: Arnaldo Carvalho de Melo To: Peter Zijlstra Cc: Adrian Hunter , Andi Kleen , Ingo Molnar , linux-kernel@vger.kernel.org, Jiri Olsa , Stephane Eranian , mathieu.poirier@linaro.org, Pawel Moll Subject: Re: [PATCH V3 1/4] perf: Add PERF_RECORD_SWITCH to indicate context switches Message-ID: <20150708132805.GC3243@kernel.org> References: <1436258202-6540-1-git-send-email-adrian.hunter@intel.com> <1436258202-6540-2-git-send-email-adrian.hunter@intel.com> <20150707132552.GA3326@kernel.org> <20150707134437.GC3326@kernel.org> <20150707153614.GT3644@twins.programming.kicks-ass.net> <20150707161359.GL3326@kernel.org> <20150707225240.GW3644@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150707225240.GW3644@twins.programming.kicks-ass.net> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Wed, Jul 08, 2015 at 12:52:40AM +0200, Peter Zijlstra escreveu: > On Tue, Jul 07, 2015 at 01:13:59PM -0300, Arnaldo Carvalho de Melo wrote: > > Em Tue, Jul 07, 2015 at 05:36:14PM +0200, Peter Zijlstra escreveu: > > > > To help userspace in places where all it has is the union perf_event, we > > > > can reuse one bit in misc to state that, i.e. > > > > #define PERF_RECORD_MISC_SWITCH_NEXT_PREV_PID 14 > > > > For instance. > > > The other option would be a separate RECORD type, which might be > > > simpler. > > Humm, do we really need it? > > I think this is just us wanting to, since we are going to add a new > > record, to make it more useful for other, not right now needed, > > situations, i.e. if the user is priviledged, there are two other options > > to get his info, right? > I was just thinking that 2 records, each with a fixed layout would be > easier to parse than 1 record with variable layout. > The record space is immense, so from that point it really doesn't > matter. We could do a land grab at some point there, if/when we find some reason for that... :-) > Do whatever is easiest, less mistakes get made etc. :-) > No real preference either way, as long we we've thought about it. Right, I just don't want to have two u32 carrying -1 for no reason. - Arnaldo