[PATCH] perf: Fallback to MAP__FUNCTION if daddr maps are NULL

[PATCH] perf: Fallback to MAP__FUNCTION if daddr maps are NULL

[Don Zickus]

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@redhat.com>
Tested-by: Joe Mario <jmario@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 tools/perf/util/machine.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 0e5fea9..e62bd87 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1241,6 +1241,16 @@ 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;
-- 
1.7.1

Re: [PATCH] perf: Fallback to MAP__FUNCTION if daddr maps are NULL

[Jiri Olsa]

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@redhat.com>
> Tested-by: Joe Mario <jmario@redhat.com>
> Signed-off-by: Don Zickus <dzickus@redhat.com>

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

thanks,
jirka

Re: [PATCH] perf: Fallback to MAP__FUNCTION if daddr maps are NULL

[Arnaldo Carvalho de Melo]

Em Thu, Aug 21, 2014 at 09:04:51AM +0200, Jiri Olsa escreveu:
> 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@redhat.com>
> > Tested-by: Joe Mario <jmario@redhat.com>
> > Signed-off-by: Don Zickus <dzickus@redhat.com>
> 
> Acked-by: Jiri Olsa <jolsa@kernel.org>

Thanks, applied.

- Arnaldo

[tip:perf/core] perf machine: Fallback to MAP__FUNCTION if daddr maps are NULL

[tip-bot for Don Zickus]

Commit-ID:  06b2afc0b9a26e7673856a24ab57bfb307dad394
Gitweb:     http://git.kernel.org/tip/06b2afc0b9a26e7673856a24ab57bfb307dad394
Author:     Don Zickus <dzickus@redhat.com>
AuthorDate: Wed, 20 Aug 2014 23:25:11 -0400
Committer:  Arnaldo Carvalho de Melo <acme@redhat.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@redhat.com>
Tested-by: Joe Mario <jmario@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1408591511-57884-1-git-send-email-dzickus@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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;