Run IMU MPU-9250 on ROS

Hello guys,
I am new to Beaglebone blue. I am using onboard IMU using ROS on ubuntu 16.04 from the image provided here https://dscl.lcsr.jhu.edu/home/courses/edumip_ros/
I am also using RTIMUlib for kalman filter from this reference https://github.com/jeskesen/i2c_imu
But it turns out that it uses around 80% of CPU and gives a delay of around 5 seconds . What could be the reason?
Any suggestion to decrease delay are welcomed.