Hi,
You are running on GPU right?
You can check in the doc here 6 that the bottleneck tool won’t perform synchronization with the GPU.
Here you see that the only expensive functions are the transfer between CPU/GPU. This is expected as these are the only place where we synchronize with the GPU and actually wait for the GPU to do the work.
I think you want to use the autograd profiler with cuda setting turned on to get a better idea of which function is actually taking a long time on the GPU.