Commit 06b2afc0 authored Aug 20, 2014 by Don Zickus Committed by Arnaldo Carvalho de Melo Aug 22, 2014

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>

parent c09a7e75

tools/perf/util/machine.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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;