A method of calculating utilization and bottleneck performance parameters of a processing unit within a graphical processing unit (GPU). The utilization is a measure of a percentage that the processing unit is utilized over a draw call execution time. The bottleneck is the sum of the time period that the processing unit is active, the time period that the processing unit is full and does not accept data from an upstream processing unit, minus the time period that the processing unit is paused because the downstream processing unit is busy and cannot accept data, all over the execution time of the draw call. Performance parameters may be determined by sampling the processing unit and incrementing a counter when a condition is true. The method is repeated for the same draw call, for each processing unit of the GPU, and for a plurality of draw calls comprising a frame.