LOL, I’ve solved this problem, and the reason is CPU frequency conversion .
A. RESEON :

When I commented out the “usleep(100 * 1000)” code, The CPU is in high performance state；you can check the ‘CPU MHz’ by running the command : lscpu
When I keep the “usleep(100 * 1000)” code，the CPU will switch between high performance and low performance which slows down the calculation. so the duration of function ‘module.forward’ is getting longer.

B. HOW CAN I FIND THIS QUESTION ?


I do a lot of experiments. I am confuesed about the phenomenon, it is very strange. There’s no reason to suspect that the ‘module.forward’ function has a bug because of running ‘usleep(100*1000)’;


When the experiment is in operation, I check the CPU state and  I found that the CPU MHz is changging.       Suddenly inspiration came， and  I remember this will slow down the calculation， because I’ve had similar problems before


So I run the command : cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
The output is : powersave


Run the command : sudo cpupower -c all frequency-set -g performance


Rerun the test code, it works.