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

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Date:	Wed, 15 Jan 2014 09:27:27 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	Gaurav Jain <gjain@...com>
Cc:	"linux-kernel@...r.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

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.

Cheers,
Don

> 
> >Also style issue below..
> >
> >> 
> >> Signed-off-by: Gaurav Jain <gjain@...com>
> >> Cc: Ingo Molnar <mingo@...nel.org>
> >> Cc: Jiri Olsa <jolsa@...hat.com>
> >> Cc: Paul Mackerras <paulus@...ba.org>
> >> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> >> Cc: Don Zickus <dzickus@...hat.com>
> >> Cc: Arun Sharma <asharma@...com>
> >> ---
> >>  tools/perf/util/event.c | 5 ++---
> >>  1 file changed, 2 insertions(+), 3 deletions(-)
> >> 
> >> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> >> index bb788c1..ae9c55b 100644
> >> --- a/tools/perf/util/event.c
> >> +++ b/tools/perf/util/event.c
> >> @@ -224,10 +224,9 @@ static int
> >>perf_event__synthesize_mmap_events(struct perf_tool *tool,
> >>  				continue;
> >>  
> >>  			event->header.misc |= PERF_RECORD_MISC_MMAP_DATA;
> >> -		}
> >> -
> >> -		if (!strcmp(execname, ""))
> >> +		} if (!strcmp(execname, "") || !strcmp(execname, "[heap]")) {
> >
> >The '} if' part should seperate the 'if' on to its own line (unless you
> >meant an 'else' in there).
> 
> Bah yes, I intended 'else if'. I apologize for that. Does the fact that I
> filtered anon entries to only those marked as executable break the
> existing behavior?
> 
> Thanks,
> 
> Gaurav
> 
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