evsel__open_per_cpu
err = evsel__open_per_cpu(evsel, cpus, -1);
err = evsel__open_per_cpu(evsel, cpus, -1);
if (evsel__open_per_cpu(cgrp_switch, evlist->core.all_cpus, -1) < 0) {
err = evsel__open_per_cpu(evsel, evsel->core.cpus, -1);
int evsel__open_per_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, int cpu_map_idx);