+static long perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu, int group_fd, unsigned long flags)
+{
+ return syscall(__NR_perf_event_open, hw_event, pid, cpu, group_fd, flags);
+}
+
+static int perf_instr_count_open(int cpu_num)
+{
+ struct perf_event_attr pea;
+ int fd;
+
+ memset(&pea, 0, sizeof(struct perf_event_attr));
+ pea.type = PERF_TYPE_HARDWARE;
+ pea.size = sizeof(struct perf_event_attr);
+ pea.config = PERF_COUNT_HW_INSTRUCTIONS;
+
+ /* counter for cpu_num, including user + kernel and all processes */
+ fd = perf_event_open(&pea, -1, cpu_num, -1, 0);
+ if (fd == -1)
+ err(-1, "cpu%d: perf instruction counter\n", cpu_num);
+
+ return fd;
+}
+
+int get_instr_count_fd(int cpu)
+{
+ if (fd_instr_count_percpu[cpu])
+ return fd_instr_count_percpu[cpu];
+
+ fd_instr_count_percpu[cpu] = perf_instr_count_open(cpu);
+
+ return fd_instr_count_percpu[cpu];
+}
+