Beaglebone Black i2c and adc sampling rate

I am working on a project that uses beaglebone black to sample data from MPU6050 and two accelerometers(ADXL335).
I am currently aiming at sampling strictly 200hz on both accelerometers and more free ~50hz on MPU6050.
My problem is that whenever the MPU6050 sampling kicks in, the acc. sampling rate gets delayed by 10~20 ms. (Especially during the fifo_read_bytes part of imu)
I have set the i2c frequency to 400kbs.

Help, I’ve been stuck on this problem for quite a time now.