Calculating the Kernel Latency - 2023.2 English

Vitis Tutorials: AI Engine (XD100)

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2023.2 English

From the Profile information in the Vitis Analyzer, analyze the function time of the kernels as explained in Section 9 in the AIE simulation.

For example, compare the function time of the data_shuffle kernel with the standalone AIE simulation result, and calculate the kernel latency. profile hw emulation

From the trace information, you can calculate the kernel latency as follows:

  1. Click the Trace in the AI Engine simulation run summary, and navigate to the any function to calculate the latency. For example, consider the data_shuffle function.

  2. You can notice the function data_shuffle ran for seven iterations. Zoom into the period of one iteration (between two main() function calls as follows), add a marker, and drag it to the end of the kernel function as follows: kernel latency

    Notice the difference of 263.2 ns as highlighted above. This is the time the kernel took to complete one iteration.

    If you click the AI Engine Simulation Summary, you can notice the AI Engine Frequency as 1250 MHz, i.e., 0.8 ns, i.e., one cycle = 0.8 ns. Now, the data_shuffle function took 263.2 ns for one iteration, i.e., 263.2 / 0.8 ~= 329 cycles.

    Compare this with the latency you got during the aiesimulation where the AI Engine is a standalone module; see Section-9 in AIE Simulation.