Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751212AbdFBPXs (ORCPT ); Fri, 2 Jun 2017 11:23:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58264 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbdFBPXq (ORCPT ); Fri, 2 Jun 2017 11:23:46 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com E337F80F94 Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=acme@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com E337F80F94 Date: Fri, 2 Jun 2017 12:23:41 -0300 From: Arnaldo Carvalho de Melo To: Milian Wolff Cc: Linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Namhyung Kim , Jiri Olsa Subject: Re: [PATCH 1/2] perf report: ensure the perf DSO mapping matches what libdw sees Message-ID: <20170602152341.GB7901@redhat.com> References: <20170602143753.16907-1-milian.wolff@kdab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170602143753.16907-1-milian.wolff@kdab.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.20 (2009-12-10) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 02 Jun 2017 15:23:46 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1905 Lines: 40 Em Fri, Jun 02, 2017 at 04:37:52PM +0200, Milian Wolff escreveu: > In some situations the libdw unwinder stopped working properly. > I.e. with libunwind we see: > > ~~~~~ > heaptrack_gui 2228 135073.400112: 641314 cycles: > e8ed _dl_fixup (/usr/lib/ld-2.25.so) > 15f06 _dl_runtime_resolve_sse_vex (/usr/lib/ld-2.25.so) > ed94c KDynamicJobTracker::KDynamicJobTracker (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0) > 608f3 _GLOBAL__sub_I_kdynamicjobtracker.cpp (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0) > f199 call_init.part.0 (/usr/lib/ld-2.25.so) > f2a5 _dl_init (/usr/lib/ld-2.25.so) > db9 _dl_start_user (/usr/lib/ld-2.25.so) > ~~~~~ > > But with libdw and without this patch this sample is not properly > unwound: > > ~~~~~ > heaptrack_gui 2228 135073.400112: 641314 cycles: > e8ed _dl_fixup (/usr/lib/ld-2.25.so) > 15f06 _dl_runtime_resolve_sse_vex (/usr/lib/ld-2.25.so) > ed94c KDynamicJobTracker::KDynamicJobTracker (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0) > ~~~~~ > > Debug output showed me that libdw found a module for the last frame > address, but it thinks it belongs to /usr/lib/ld-2.25.so. This patch > double-checks what libdw sees and what perf knows. If the mappings > mismatch, we now report the elf known to perf. This fixes the > situation above, and the libdw unwinder produces the same stack as > libunwind. Looks ok, having both implementations matching and the callchains making sense for your workloads is a good way to verify the sanity, thanks. I wonder if we shouldn't somehow script this, i.e. build it with one implementation, generate output from some test workload, build it with the other, second output, diff it, report when not the same. - Arnaldo