What Nsight system pic means?

Hi. I am fresher on Night System tools. I didn’t understand :

  1. Why the cuStreamSynchronize took so much time?
  2. Is it means the cuStreamSynchronize just wait for all threads are finished?
  3. Is the kernel function time mean a warp execution time or a block execution time?

Thank you for using Nsight Systems. Looks like your post came to the Nsight Graphics forum so I am moving your post over to the Nsight Systems Forum where someone will handle your questions.

@skottapalli , can you respond to this?

  1. From CUDA documentation, “cuStreamSynchronize waits until a stream’s tasks are completed.” CUDA Driver API :: CUDA Toolkit Documentation
  2. See answer to1 above
  3. What kernel function time are you referring to here? If you mean the blue-colored event shown in the CUDA API timeline row just before cuStreamSynchronize, then here’s the explanation:
    you are looking at the CUDA API calls made on the OS thread 1320504 i.e. you are seeing how long the API calls took on the CPU side. If you click on the event, you will see the corresponding GPU work highlighted in cyan color. You could watch the talk Blue Waters Webinar: Introduction to NVIDIA Nsight Systems - YouTube where I go over the different parts of the timeline view. The timeline view in Nsight Systems can be overwhelming for first-time users.