Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752922AbaAUFyj (ORCPT ); Tue, 21 Jan 2014 00:54:39 -0500 Received: from lgeamrelo02.lge.com ([156.147.1.126]:50677 "EHLO LGEAMRELO02.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752303AbaAUFyf (ORCPT ); Tue, 21 Jan 2014 00:54:35 -0500 X-AuditID: 9c93017e-b7b63ae000000e6a-87-52de0b991c0f From: Namhyung Kim To: Arnaldo Carvalho de Melo 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 References: <20140116143749.GA21526@ghostprotocols.net> <87sisn6ojf.fsf@sejong.aot.lge.com> <20140117143404.GB3207@ghostprotocols.net> Date: Tue, 21 Jan 2014 14:54:32 +0900 In-Reply-To: <20140117143404.GB3207@ghostprotocols.net> (Arnaldo Carvalho de Melo's message of "Fri, 17 Jan 2014 11:34:04 -0300") Message-ID: <87iotd7ucn.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arnaldo, On Fri, 17 Jan 2014 11:34:04 -0300, Arnaldo Carvalho de Melo wrote: > 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? Quoting Documentation/jit-interface.txt: Each line has the following format, fields separated with spaces: START SIZE symbolname START and SIZE are hex numbers without 0x. symbolname is the rest of the line, so it could contain special characters. > > 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). Hmm.. didn't know that, interesting.. > > 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. Yes, but there's no way to do it currently. > >> 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. Right. But in this case we cannot determine whether a symbol in the /tmp/perf-... file is a function or variable. > >> 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? Not sure. For a JIT case, I guess the mapping is always executable and we don't support data mapping yet, so it seems okay for now. Thanks, Namhyung -- 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/