linux-kernel - Re: [PATCH] perf: Fallback to MAP_

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Date:	Thu, 21 Aug 2014 09:04:51 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, eranian@...gle.com,
	jmario@...hat.com
Subject: Re: [PATCH] perf: Fallback to MAP__FUNCTION if daddr maps are NULL

On Wed, Aug 20, 2014 at 11:25:11PM -0400, Don Zickus wrote:
> As we run "perf c2c" on more applications, we noticed we're missing significant
> samples from a common customer's application.  Looking at the
> /proc/<pid>/maps file for the app, we see "rwxs" and "rwxp" permissions on many
> of the shared memory & heap regions, and on all the thread stacks.
> 
> Because those regions have the "x" bit set, perf marks them with a MAP_FUNCTION
> type.  Hence ip_resolve_data() never finds load or store events coming from
> them.
> 
> We fixed this by re-calling thread__find_addr_location with MAP__FUNCTION in
> the case where map is NULL as a last ditch effort to map the sample before
> giving up and dropping it.
> 
> Reported-by: Joe Mario <jmario@...hat.com>
> Tested-by: Joe Mario <jmario@...hat.com>
> Signed-off-by: Don Zickus <dzickus@...hat.com>

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka
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