Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756319Ab0KKMVx (ORCPT ); Thu, 11 Nov 2010 07:21:53 -0500 Received: from mail-ew0-f46.google.com ([209.85.215.46]:61016 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756133Ab0KKMVw (ORCPT ); Thu, 11 Nov 2010 07:21:52 -0500 Date: Thu, 11 Nov 2010 12:21:43 +0000 From: Jamie Iles To: Peter Zijlstra Cc: Jamie Iles , Ming Lei , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , Russell King , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [Questions] How to run 'perf top' on ARM to profile kernel functions with modules loaded Message-ID: <20101111122143.GF2929@pulham.picochip.com> References: <20101111091733.GA2929@pulham.picochip.com> <1289477176.2084.64.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1289477176.2084.64.camel@laptop> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1867 Lines: 45 On Thu, Nov 11, 2010 at 01:06:16PM +0100, Peter Zijlstra wrote: > On Thu, 2010-11-11 at 09:17 +0000, Jamie Iles wrote: > > On Thu, Nov 11, 2010 at 03:52:07PM +0800, Ming Lei wrote: > > > 2010/11/11 Ming Lei : > > > > Hi, > > > > > > > > 'perf top' can't display any functions when modules are loaded on ARM. > > > > > > Sorry, should be can't display any kernel functions when modules are loaded > > > on ARM. > > I've noticed this myself and I spent a bit of time looking into it last week > > but didn't get too far. I did wonder if it was something to do with the map > > fixups after loading the modules. If you look at the raw events after a perf > > record with 'perf report -D' then the last module has a size that takes it to > > 0xFFFFFFFF which overlaps with the rest of the kernel symbols. > > > > On x86 it looks like the modules are loaded after the kernel image in VM > > unlike ARM. > > Order shouldn't matter, but that overlap is very likely what kills it. > That module size is buggy. I'm guessing that its in util/symbol.c:__map_groups__fixup_end(): for (nd = rb_next(prevnd); nd; nd = rb_next(nd)) { prev = curr; curr = rb_entry(nd, struct map, rb_node); prev->end = curr->start - 1; } /* * We still haven't the actual symbols, so guess the * last map final address. */ curr->end = ~0UL; I've noticed that if I change the symbol_conf.{use_modules,try_vmlinux_path} then I can get perf events for kernel symbols from /proc/kallsyms but nothing for the modules. Jamie -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/