From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755278AbaIHW7d (ORCPT ); Mon, 8 Sep 2014 18:59:33 -0400 Received: from ozlabs.org ([103.22.144.67]:42199 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755110AbaIHW7c (ORCPT ); Mon, 8 Sep 2014 18:59:32 -0400 Date: Tue, 9 Sep 2014 08:59:29 +1000 From: Anton Blanchard To: acme@redhat.com, a.p.zijlstra@chello.nl, paulus@samba.org, mingo@redhat.com Cc: linux-kernel@vger.kernel.org Subject: [PATCH] perf: Ignore stripped vmlinux and fallback to kallsyms Message-ID: <20140909085929.4a5a81f0@kryten> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a vmlinux is stripped, perf will use it and ignore kallsyms. We end up with useless profiles where everything maps to a few runtime symbols: 63.39% swapper [kernel.kallsyms] [k] hcall_real_table 4.90% beam.smp [kernel.kallsyms] [k] hcall_real_table 4.44% beam.smp [kernel.kallsyms] [k] __sched_text_start 3.72% beam.smp [kernel.kallsyms] [k] __run_at_kexec Detect this case and fallback to using kallsyms. This fixes the issue: 62.81% swapper [kernel.kallsyms] [k] snooze_loop 4.44% beam.smp [kernel.kallsyms] [k] __schedule 0.91% beam.smp [kernel.kallsyms] [k] _switch 0.73% beam.smp [kernel.kallsyms] [k] put_prev_entity Signed-off-by: Anton Blanchard --- Index: b/tools/perf/util/symbol-elf.c =================================================================== --- a/tools/perf/util/symbol-elf.c +++ b/tools/perf/util/symbol-elf.c @@ -712,6 +712,14 @@ int dso__load_sym(struct dso *dso, struc symbols__delete(&dso->symbols[map->type]); if (!syms_ss->symtab) { + /* + * If the vmlinux is stripped, fail so we will fall back + * to using kallsyms. The vmlinux runtime symbols aren't + * of much use. + */ + if (dso->kernel) + goto out_elf_end; + syms_ss->symtab = syms_ss->dynsym; syms_ss->symshdr = syms_ss->dynshdr; }