linux-kernel - Re: [PATCH] perf tools: Synthesize anon MMAP records on the heap

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Date:	Thu, 16 Jan 2014 10:03:48 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Gaurav Jain <gjain@...com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arun Sharma <asharma@...com>
Subject: Re: [PATCH] perf tools: Synthesize anon MMAP records on the heap

Hi Don,

On Wed, 15 Jan 2014 09:27:27 -0500, Don Zickus wrote:
> On Tue, Jan 14, 2014 at 08:48:23PM +0000, Gaurav Jain wrote:
>> On 1/13/14, 11:54 AM, "Don Zickus" <dzickus@...hat.com> wrote:
>> 
>> >On Sat, Jan 11, 2014 at 08:32:14PM -0800, Gaurav Jain wrote:
>> >> Anon records usually do not have the 'execname' entry. However if they
>> >>are on
>> >> the heap, the execname shows up as '[heap]'. The fix considers any
>> >>executable
>> >> entries in the map that do not have a name or are on the heap as anon
>> >>records
>> >> and sets the name to '//anon'.
>> >> 
>> >> This fixes JIT profiling for records on the heap.
>> >
>> >I guess I don't understand the need for this fix.  It seems breaking out
>> >//anon vs. [heap] would be useful.  Your patch is saying otherwise.  Can
>> >give a description of the problem you are trying to solve?
>> 
>> Thank you for looking at the patch.
>> 
>> We generate a perf map file which includes certain JIT¹ed functions that
>> show up as [heap] entries. As a result, I included the executable heap
>> entries as anon pages so that it would be handled in
>> util/map.c:map__new(). The alternative would be to handle heap entries in
>> map__new() directly, however I wasn¹t sure if this would break something
>> as it seems that heap and stack entries are expected to fail all
>> map__find_* functions. Thus I considered executable heap entries as
>> //anon, but perhaps there is a better way.
>
> Thanks for the improved problem description.   I see it led to a better
> patch. :-)  That is why it is generally a good idea to describe the
> problem you are trying to solve to see if others have a better solution.

Yes, thank you very much for pointing it out and helping to resolve this
issue!

Thanks,
Namhyung
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