perf diff: Don't add the period for unresolved symbols

Since we don't add histograms buckets for them, this way the sum
of baselines should be 100%.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1262047716-23171-4-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-diff.c

@@ -51,12 +51,12 @@ static int diff__process_sample_event(event_t *event, struct perf_session *sessi
 		return -1;
 	}
 
-	if (al.filtered)
+	if (al.filtered || al.sym == NULL)
 		return 0;
 
 	event__parse_sample(event, session->sample_type, &data);
 
-	if (al.sym && perf_session__add_hist_entry(session, &al, data.period)) {
+	if (perf_session__add_hist_entry(session, &al, data.period)) {
 		pr_warning("problem incrementing symbol count, skipping event\n");
 		return -1;
 	}