From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753920AbaIEPoK (ORCPT ); Fri, 5 Sep 2014 11:44:10 -0400 Received: from mail.kernel.org ([198.145.19.201]:49721 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751054AbaIEPoI (ORCPT ); Fri, 5 Sep 2014 11:44:08 -0400 Date: Fri, 5 Sep 2014 12:44:02 -0300 From: Arnaldo Carvalho de Melo To: Namhyung Kim Cc: Adrian Hunter , Peter Zijlstra , Ingo Molnar , Paul Mackerras , Namhyung Kim , LKML , Jiri Olsa , David Ahern , Stephane Eranian , Andi Kleen , stable@vger.kernel.org Subject: Re: [PATCH v2] perf tools: Fix build-id matching on vmlinux Message-ID: <20140905154402.GF30520@kernel.org> References: <1409893157-469-1-git-send-email-namhyung@kernel.org> <540964C0.1050702@intel.com> <20140905141123.GE30520@kernel.org> <1409930200.1662.16.camel@leonhard> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1409930200.1662.16.camel@leonhard> 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 Sat, Sep 06, 2014 at 12:16:40AM +0900, Namhyung Kim escreveu: > Hi Adrian and Arnaldo, > > 2014-09-05 (금), 11:11 -0300, Arnaldo Carvalho de Melo: > > Em Fri, Sep 05, 2014 at 10:22:40AM +0300, Adrian Hunter escreveu: > > > On 09/05/2014 07:59 AM, Namhyung Kim wrote: > > > > +++ b/tools/perf/util/machine.c > > > > @@ -1060,10 +1060,14 @@ static int machine__process_kernel_mmap_event(struct machine *machine, > > > > strlen(kmmap_prefix)); > > > > /* > > > > * Should be there already, from the build-id table in > > > > - * the header. > > > > + * the header (but maybe with a different name: "vmlinux"). > > > > */ > > > > - struct dso *kernel = __dsos__findnew(&machine->kernel_dsos, > > > > - kmmap_prefix); > > > > + struct dso *kernel = dsos__find(&machine->kernel_dsos, > > > > + "vmlinux", true); > > > > > Isn't "vmlinux" just the basename of the original file name, so if it had a > > > different name this wouldn't work e.g. if the filename had been > > > /boot/vmlinuz-3.11.0-26-generic then you would need > > > "vmlinuz-3.11.0-26-generic" for this to work? > > > > Yeah, looking for well known pathnames to then check if the build-id > > matches the one we're looking for, be it because we obtained it from > > /sys/kernel/notes (for the running kernel), or from the perf.data file > > build-id table is ok, as we don't know where it is. > > > > Plain sticking "vmlinux" there is not. > > I don't get it. AFAIK when perf record runs, it uses [kernel.kallsyms] > name for kernel map. But it can be changed only if it found a "vmlinux" > file in the vmlinux_path[]. So short name will always be "vmlinux" - > okay, it might be vmlinux-$(uname -r) too; I can add it. > > As you know, the vmlinux file is a ELF image that created during kernel > build process so I guess its name is fixed. It's different from the > vmlinu"z" which resides in /boot directory. > > Am I missing something? [acme@zoo linux]$ perf report --help 2>&1 | grep vmlin -k, --vmlinux= vmlinux pathname [acme@zoo linux]$ Yes, it is using [kernel.kallsyms].ref_reloc_sym for the synthesized KERNEL mmap event, but it stores the full path in the build-id table. It seems we need a way to state that an entry in the build-id table is for the kernel, without looking at its file name. That or to put the build-id into the synthesized kernel mmap event. Which is better, because: That leads to another problem that needs to get solved eventually: We need to have the build-id into PERF_RECORD_MMAP, because we're now using just the mmap filename as the key, not the contents, and for long running sessions, DSOs can get updated, etc. - Arnaldo