From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754710AbcFPQdw (ORCPT ); Thu, 16 Jun 2016 12:33:52 -0400 Received: from mail.kernel.org ([198.145.29.136]:60938 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754651AbcFPQdu (ORCPT ); Thu, 16 Jun 2016 12:33:50 -0400 Date: Thu, 16 Jun 2016 13:33:43 -0300 From: Arnaldo Carvalho de Melo To: Adrian Hunter Cc: He Kuang , Jiri Olsa , peterz@infradead.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, jolsa@redhat.com, wangnan0@huawei.com, jpoimboe@redhat.com, ak@linux.intel.com, eranian@google.com, namhyung@kernel.org, sukadev@linux.vnet.ibm.com, masami.hiramatsu.pt@hitachi.com, tumanova@linux.vnet.ibm.com, kan.liang@intel.com, penberg@kernel.org, dsahern@gmail.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/7 UPDATE2] perf tools: Find vdso with the consider of cross-platform Message-ID: <20160616163343.GB13337@kernel.org> References: <573AC939.8070107@intel.com> <1463475894-163531-1-git-send-email-hekuang@huawei.com> <20160615133406.GG3978@kernel.org> <5762A2DC.90903@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5762A2DC.90903@intel.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Thu, Jun 16, 2016 at 04:00:12PM +0300, Adrian Hunter escreveu: > On 15/06/16 16:34, Arnaldo Carvalho de Melo wrote: > > Em Tue, May 17, 2016 at 09:04:54AM +0000, He Kuang escreveu: > >> There's a problem in machine__findnew_vdso(), vdso buildid generated > >> by a 32-bit machine stores it with the name 'vdso', but when > >> processing buildid on a 64-bit machine with the same 'perf.data', perf > >> will search for vdso named as 'vdso32' and get failed. > > > > Without looking at the code, just trying to understand your patch by > > reading your description: Why would we look for names if we have > > build-ids? All this type and name comparasions seems wrong if we have a > > build-id, no? > > > > Adrian? > > We match maps to builds ids using the file name - consider > machine__findnew_[v]dso() called in map__new(). So in the context of a perf > data file, we consider the file name to be unique. > > A vdso map does not have a file name - all we know is that it is vdso. We > look at the thread to tell if it is 32-bit, 64-bit or x32. Then we need to > get the build id which has been recorded using short name "[vdso]" or > "[vdso32]" or "[vdsox32]". > > The problem is that on a 32-bit machine, we use the name "[vdso]". If you > take a 32-bit perf data file to a 64-bit machine, it gets hard to figure out > if "[vdso]" is 32-bit or 64-bit. > > This patch solves that problem. > > I acked it in another email. Ok, somehow this got lost, I thought to have applied it already, but re-reading the changeset comment, I got confused, thanks for providing this explanation, that I will stick to the changeset log for this message, to help understanding this when scratching our heads in the future. - Arnaldo