linux-kernel - [tip:perf/core] perf machine: Fallback to MAP_

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Message-ID: <tip-06b2afc0b9a26e7673856a24ab57bfb307dad394@git.kernel.org>
Date:	Sun, 24 Aug 2014 07:59:13 -0700
From:	tip-bot for Don Zickus <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, linux-kernel@...r.kernel.org, eranian@...gle.com,
	hpa@...or.com, mingo@...nel.org, jolsa@...nel.org,
	jmario@...hat.com, jolsa@...hat.com, tglx@...utronix.de,
	dzickus@...hat.com
Subject: [tip:perf/core] perf machine:
  Fallback to MAP__FUNCTION if daddr maps are NULL

Commit-ID:  06b2afc0b9a26e7673856a24ab57bfb307dad394
Gitweb:     http://git.kernel.org/tip/06b2afc0b9a26e7673856a24ab57bfb307dad394
Author:     Don Zickus <dzickus@...hat.com>
AuthorDate: Wed, 20 Aug 2014 23:25:11 -0400
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Fri, 22 Aug 2014 13:12:13 -0300

perf machine: Fallback to MAP__FUNCTION if daddr maps are NULL

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>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Joe Mario <jmario@...hat.com>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lkml.kernel.org/r/1408591511-57884-1-git-send-email-dzickus@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/machine.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index e00daf0..b2ec38b 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1314,6 +1314,16 @@ static void ip__resolve_data(struct machine *machine, struct thread *thread,
 
 	thread__find_addr_location(thread, machine, m, MAP__VARIABLE, addr,
 				   &al);
+	if (al.map == NULL) {
+		/*
+		 * some shared data regions have execute bit set which puts
+		 * their mapping in the MAP__FUNCTION type array.
+		 * Check there as a fallback option before dropping the sample.
+		 */
+		thread__find_addr_location(thread, machine, m, MAP__FUNCTION, addr,
+					   &al);
+	}
+
 	ams->addr = addr;
 	ams->al_addr = al.addr;
 	ams->sym = al.sym;
--
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