why the generation speed seems abnormally slow?

<img width="1228" height="220" alt="Image" src="https://github.com/user-attachments/assets/7b94e1ea-4030-4b66-bfe2-9c3ff5e1575f" />
open-sora plan, Nvidia A100 40G, 1GPU,
the loop is set to be 1, and all other generated setting is set by default.
the generation speed seems much slower than it shoube be, taking roughly 2~3 minutes per video.