Technologies are generally described for systems, devices and methods effective to monitor performance of a computing device. A computing device may receive a specified counting rate. The computing device may count at the specified counting rate to generate a sequence of counting numbers. The computing device may identify a first output of a process, such as results from computations performed on data, and may identify a first counting number when the first output is identified. The computing device may identify a second output of the process, such as additional results from the computations, and may identify a second counting number when the second output is identified. The computing device may then determine whether an alert should be generated based on the first and second counting numbers such as when a difference between the first and second counting numbers exceeds a threshold value.