diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 6b9146c..02b2d80 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -166,7 +166,7 @@
 				    PERF_FORMAT_TOTAL_TIME_RUNNING;
 
 	if (system_wide)
-		return perf_evsel__open_per_cpu(evsel, cpus->nr, cpus->map);
+		return perf_evsel__open_per_cpu(evsel, cpus);
 
 	attr->inherit = !no_inherit;
 	if (target_pid == -1 && target_tid == -1) {
@@ -174,7 +174,7 @@
 		attr->enable_on_exec = 1;
 	}
 
-	return perf_evsel__open_per_thread(evsel, threads->nr, threads->map);
+	return perf_evsel__open_per_thread(evsel, threads);
 }
 
 /*
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index e62cc5e..e44be52 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1,6 +1,8 @@
 #include "evsel.h"
 #include "../perf.h"
 #include "util.h"
+#include "cpumap.h"
+#include "thread.h"
 
 #define FD(e, x, y) (*(int *)xyarray__entry(e->fd, x, y))
 
@@ -123,13 +125,13 @@
 	return 0;
 }
 
-int perf_evsel__open_per_cpu(struct perf_evsel *evsel, int ncpus, int *cpu_map)
+int perf_evsel__open_per_cpu(struct perf_evsel *evsel, struct cpu_map *cpus)
 {
 	int cpu;
 
-	for (cpu = 0; cpu < ncpus; cpu++) {
+	for (cpu = 0; cpu < cpus->nr; cpu++) {
 		FD(evsel, cpu, 0) = sys_perf_event_open(&evsel->attr, -1,
-							cpu_map[cpu], -1, 0);
+							cpus->map[cpu], -1, 0);
 		if (FD(evsel, cpu, 0) < 0)
 			goto out_close;
 	}
@@ -144,13 +146,13 @@
 	return -1;
 }
 
-int perf_evsel__open_per_thread(struct perf_evsel *evsel, int nthreads, int *thread_map)
+int perf_evsel__open_per_thread(struct perf_evsel *evsel, struct thread_map *threads)
 {
 	int thread;
 
-	for (thread = 0; thread < nthreads; thread++) {
+	for (thread = 0; thread < threads->nr; thread++) {
 		FD(evsel, 0, thread) = sys_perf_event_open(&evsel->attr,
-							   thread_map[thread], -1, -1, 0);
+							   threads->map[thread], -1, -1, 0);
 		if (FD(evsel, 0, thread) < 0)
 			goto out_close;
 	}
@@ -165,11 +167,11 @@
 	return -1;
 }
 
-int perf_evsel__open(struct perf_evsel *evsel, int ncpus, int nthreads,
-		     int *cpu_map, int *thread_map)
+int perf_evsel__open(struct perf_evsel *evsel, 
+		     struct cpu_map *cpus, struct thread_map *threads)
 {
-	if (nthreads < 0)
-		return perf_evsel__open_per_cpu(evsel, ncpus, cpu_map);
+	if (threads == NULL)
+		return perf_evsel__open_per_cpu(evsel, cpus);
 
-	return perf_evsel__open_per_thread(evsel, nthreads, thread_map);
+	return perf_evsel__open_per_thread(evsel, threads);
 }
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index a62fb55..863d78d 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -34,6 +34,9 @@
 	void			*priv;
 };
 
+struct cpu_map;
+struct thread_map;
+
 struct perf_evsel *perf_evsel__new(u32 type, u64 config, int idx);
 void perf_evsel__delete(struct perf_evsel *evsel);
 
@@ -42,10 +45,10 @@
 void perf_evsel__free_fd(struct perf_evsel *evsel);
 void perf_evsel__close_fd(struct perf_evsel *evsel, int ncpus, int nthreads);
 
-int perf_evsel__open_per_cpu(struct perf_evsel *evsel, int ncpus, int *cpu_map);
-int perf_evsel__open_per_thread(struct perf_evsel *evsel, int nthreads, int *thread_map);
-int perf_evsel__open(struct perf_evsel *evsel, int ncpus, int nthreads,
-		     int *cpu_map, int *thread_map);
+int perf_evsel__open_per_cpu(struct perf_evsel *evsel, struct cpu_map *cpus);
+int perf_evsel__open_per_thread(struct perf_evsel *evsel, struct thread_map *threads);
+int perf_evsel__open(struct perf_evsel *evsel, 
+		     struct cpu_map *cpus, struct thread_map *threads);
 
 #define perf_evsel__match(evsel, t, c)		\
 	(evsel->attr.type == PERF_TYPE_##t &&	\