AP_Scheduler: PerfInfo: allow specification of loop rate

libraries/AP_Scheduler/PerfInfo.h

@@ -23,7 +23,13 @@ public:
     uint32_t get_avg_time() const;
     uint32_t get_stddev_time() const;
 
+    void set_loop_rate(uint16_t rate_hz) {
+        // allow a 20% overrun before we consider a loop "slow":
+        overtime_threshold_micros = 1000000/rate_hz * 1.2f;
+    }
+
 private:
+    uint16_t overtime_threshold_micros;
     uint16_t loop_count;
     uint32_t max_time; // in microseconds
     uint32_t min_time; // in microseconds
@@ -33,6 +39,7 @@ private:
     uint32_t log_dropped;
     uint32_t overtime_threshold_us;
     bool ignore_loop;
+
 };
 
 };