tool_pmu__read_stat
err = tool_pmu__read_stat(evsel, idx, thread, start_time);
err = tool_pmu__read_stat(evsel, cpu_map_idx, thread, &val);
err = tool_pmu__read_stat(evsel, cpu_map_idx, thread, &val);
err = tool_pmu__read_stat(evsel, cpu_map_idx, thread, &cur_time);