Is it possible to log data with uniform sampling rate?

Hi, I’m using version 1.14 with cube orange+, tring to log the flying data to the SD card.

I followed the instruction listed here:

and modifyed the logger_topics.txt like this:
vehicle_attitude 0 0
vehicle_attitude_setpoint 0 0
vehicle_torque_setpoint 0 0
vehicle_rates_setpoint 0 0
vehicle_thrust_setpoint 0 0
vehicle_angular_velocity 0 0

But the logged data has the sampling rate somewhat like this:

the sampling rate jitters between 18, 20 and 22 Hz.

I personally consider it as a problem of logging module, and the control system should be still working under a fixed sampling rate? Is it correct? If so, how can I get a logged data with uniform sampling rate? Thanks in advance.