linux-kernel - Re: [PATCH] perf tools: Fix JIT profiling on heap

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Message-ID: <20B8A056-FE5B-4062-A043-6E34C45B34B8@fb.com>
Date:	Wed, 22 Jan 2014 23:43:45 +0000
From:	Gaurav Jain <gjain@...com>
To:	Namhyung Kim <namhyung@...nel.org>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...hat.com>, David Ahern <dsahern@...il.com>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] perf tools: Fix JIT profiling on heap

> On Jan 17, 2014, at 2:44 AM, "Namhyung Kim" <namhyung@...nel.org> wrote:
> 
> Hi Gaurav,
> 
>> On Thu, 16 Jan 2014 20:23:27 +0000, Gaurav Jain wrote:
>> On 1/16/14, 9:37 AM, "Arnaldo Carvalho de Melo" <acme@...stprotocols.net>
>> wrote:
>> 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
> only function symbols in function mappings and variables in data
> mapping based on the address it accesses.
> 
> 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?

I don't think we generate symbols for dynamic data at the moment. There may be uses in the future. I don't know about other JIT programs.

If we can include this behaviour it would be great, but I don't have a way to test it. I'd guess if somebody had a valid use case, they would report the issue. Otherwise, the patch as you've written it works great for me.

Gaurav--
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