+ {
+ processor_cpu_load_info_t cpu_load_info;
+ timer_t idle_state;
+ uint64_t idle_time_snapshot1, idle_time_snapshot2;
+ uint64_t idle_time_tstamp1, idle_time_tstamp2;
+
+ /*
+ * We capture the accumulated idle time twice over
+ * the course of this function, as well as the timestamps
+ * when each were last updated. Since these are
+ * all done using non-atomic racy mechanisms, the
+ * most we can infer is whether values are stable.
+ * timer_grab() is the only function that can be
+ * used reliably on another processor's per-processor
+ * data.
+ */
+
+ if (*count < PROCESSOR_CPU_LOAD_INFO_COUNT) {
+ return KERN_FAILURE;
+ }
+
+ cpu_load_info = (processor_cpu_load_info_t) info;
+ if (precise_user_kernel_time) {
+ cpu_load_info->cpu_ticks[CPU_STATE_USER] =
+ (uint32_t)(timer_grab(&processor->user_state) / hz_tick_interval);
+ cpu_load_info->cpu_ticks[CPU_STATE_SYSTEM] =
+ (uint32_t)(timer_grab(&processor->system_state) / hz_tick_interval);
+ } else {
+ uint64_t tval = timer_grab(&processor->user_state) +
+ timer_grab(&processor->system_state);
+
+ cpu_load_info->cpu_ticks[CPU_STATE_USER] = (uint32_t)(tval / hz_tick_interval);
+ cpu_load_info->cpu_ticks[CPU_STATE_SYSTEM] = 0;
+ }
+
+ idle_state = &processor->idle_state;
+ idle_time_snapshot1 = timer_grab(idle_state);
+ idle_time_tstamp1 = idle_state->tstamp;
+
+ /*
+ * Idle processors are not continually updating their
+ * per-processor idle timer, so it may be extremely
+ * out of date, resulting in an over-representation
+ * of non-idle time between two measurement
+ * intervals by e.g. top(1). If we are non-idle, or
+ * have evidence that the timer is being updated
+ * concurrently, we consider its value up-to-date.
+ */
+ if (processor->current_state != idle_state) {
+ cpu_load_info->cpu_ticks[CPU_STATE_IDLE] =
+ (uint32_t)(idle_time_snapshot1 / hz_tick_interval);
+ } else if ((idle_time_snapshot1 != (idle_time_snapshot2 = timer_grab(idle_state))) ||
+ (idle_time_tstamp1 != (idle_time_tstamp2 = idle_state->tstamp))) {
+ /* Idle timer is being updated concurrently, second stamp is good enough */
+ cpu_load_info->cpu_ticks[CPU_STATE_IDLE] =
+ (uint32_t)(idle_time_snapshot2 / hz_tick_interval);
+ } else {
+ /*
+ * Idle timer may be very stale. Fortunately we have established
+ * that idle_time_snapshot1 and idle_time_tstamp1 are unchanging
+ */
+ idle_time_snapshot1 += mach_absolute_time() - idle_time_tstamp1;
+
+ cpu_load_info->cpu_ticks[CPU_STATE_IDLE] =
+ (uint32_t)(idle_time_snapshot1 / hz_tick_interval);
+ }
+
+ cpu_load_info->cpu_ticks[CPU_STATE_NICE] = 0;
+
+ *count = PROCESSOR_CPU_LOAD_INFO_COUNT;
+ *host = &realhost;
+
+ return KERN_SUCCESS;
+ }
+