From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752241AbaAQOeN (ORCPT ); Fri, 17 Jan 2014 09:34:13 -0500 Received: from mail-qc0-f170.google.com ([209.85.216.170]:58170 "EHLO mail-qc0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751960AbaAQOeL (ORCPT ); Fri, 17 Jan 2014 09:34:11 -0500 Date: Fri, 17 Jan 2014 11:34:04 -0300 From: Arnaldo Carvalho de Melo To: Namhyung Kim Cc: Gaurav Jain , Peter Zijlstra , Paul Mackerras , Ingo Molnar , Namhyung Kim , LKML , Jiri Olsa , David Ahern , Andi Kleen Subject: Re: [PATCH] perf tools: Fix JIT profiling on heap Message-ID: <20140117143404.GB3207@ghostprotocols.net> References: <20140116143749.GA21526@ghostprotocols.net> <87sisn6ojf.fsf@sejong.aot.lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87sisn6ojf.fsf@sejong.aot.lge.com> X-Url: http://acmel.wordpress.com 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 Em Fri, Jan 17, 2014 at 04:44:04PM +0900, Namhyung Kim escreveu: > On Thu, 16 Jan 2014 20:23:27 +0000, Gaurav Jain wrote: > > On 1/16/14, 9:37 AM, "Arnaldo Carvalho de Melo" > > wrote: > > > >>Em Thu, Jan 16, 2014 at 10:49:31AM +0900, Namhyung Kim escreveu: > >>> Gaurav reported that perf cannot profile JIT program if it executes > >>> the code on heap. This was because current map__new() only handle JIT > >>> on anon mappings - extends it to handle no_dso (heap, stack) case too. > >>> > >>> This patch assumes JIT profiling only provides dynamic function > >>> symbols so check the mapping type to distinguish the case. It'd > >>> provide no symbols for data mapping - if we need to support symbols on > >>> data mappings later it should be changed. > >> > >>But we do support symbols in data mappings, that is why we have > >>MAP__VARIABLE, etc, can you elaborate? > > Does perf support data mappings from perf map files? Could you please > > share an example of how I may be able to use this. > IIUC there's no difference between function and data mapping. So you > can use same perf map file for both - in fact there's no way to use > different map file in a single task. I guess perf will use it to find Do the /tmp/perf mapping has any per entry indication on the type of symbol it is (data, text) like ELF and kallsyms symtabs have? It is possible for a function and a variable to have the same virtual address in some architectures (SPARC, iirc), that is why we have different MAP_ types (FUNCTION, VARIABLE) (which should really be renamed to TEXT, DATA). So a 'struct map' for a data mmap should possibly point to a different 'dso' of the JIT /tmp/perf-... style if those maps don't have per entry indication of text/data. > only function symbols in function mappings and variables in data > mapping based on the address it accesses. Well, the lookup should figure out if the IP refers to TEXT or DATA and use MAP__{FUNCTION, VARIABLE} accordingly when asking for symbol resolution. > What I wasn't sure is whether JIT program also produces some dynamic data. > And I think only perf mem command cares about data mappings, no? Well, I think it would be great to do that kind of data resolution for JITs the same way it is interesting to do for ELF ones :-) I need to stare harder at that patch, but with the above in mind, do we really have to check if the map is MAP__FUNCTION as IIRC this patch does? - Arnaldo