Performance measurement

[afreg11]

I have a set of GPUCommandBuffer units and want to measure performance of each of them.
My current solution is to use something like this:
const start = performance.now();
GPUQueue.submit([this_GPUCommandBuffer]);
await smallest_GPUBuffer.mapAsync(GPUMapMode.READ);
const end = performance.now();

Obviously for performance it is better to avoid extra buffer mapping, but in that case idk how to measure execution time of any given command buffer.
Is there any better way to measure execution times of my units?