From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934596AbcLUNZZ (ORCPT ); Wed, 21 Dec 2016 08:25:25 -0500 Received: from merlin.infradead.org ([205.233.59.134]:32774 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934368AbcLUNZV (ORCPT ); Wed, 21 Dec 2016 08:25:21 -0500 Date: Wed, 21 Dec 2016 14:24:52 +0100 From: Peter Zijlstra To: Hari Bathini Cc: ast@fb.com, lkml , acme@kernel.org, alexander.shishkin@linux.intel.com, mingo@redhat.com, daniel@iogearbox.net, rostedt@goodmis.org, Ananth N Mavinakayanahalli , ebiederm@xmission.com, sargun@sargun.me, Aravinda Prasad , brendan.d.gregg@gmail.com Subject: Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info Message-ID: <20161221132452.GT3124@twins.programming.kicks-ass.net> References: <148182699546.5314.279803283347257825.stgit@hbathini.in.ibm.com> <148182702692.5314.556699668213767056.stgit@hbathini.in.ibm.com> <20161215184646.GP3107@twins.programming.kicks-ass.net> <20161216075703.GE3124@twins.programming.kicks-ass.net> <2c0e3bbb-90a1-b5a4-b6d4-19c419ef5411@linux.vnet.ibm.com> <20161216200536.GI3124@twins.programming.kicks-ass.net> <1702a267-0ce6-86da-7755-11a375e450e2@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1702a267-0ce6-86da-7755-11a375e450e2@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 21, 2016 at 06:39:01PM +0530, Hari Bathini wrote: > Hi Peter, > >I don't see how the tool can parse old records (with NAMESPACES_MAX == > >7) if you set its NAMESPACES_MAX to say 10. > > > >Then it will expect the link_info array to be 10 entries and either read > >past the end of the record (if !sample_all) or try and interpret > >sample_id as link_info records. > > > > Right. There will be inconsistency with data the perf tool tries to read > beyond > what the kernel supports. IIUC, you mean, include nr_namespaces field in the > record and warn the user if it doesn't match with the one perf-tool supports > before proceeding..? Yes, if you add a nr_namespaces field its always parsable. If an old tool finds more namespace than it has 'names' for it can always display the raw index number. If a new tool finds the array short, it will not display the missing ones.