The IMU data interval is unstable with high update frequency

[Rubbishwang]

I used Gazebo 9.19.0, ros noetic, mavros, mavlink and px4 in Ubuntu20.04 environment for co-simulation. Run the rosservice call /mavros/set_message_interval 31 100 command to set the IMU update frequency at 100 Hz. I expect the IMU to refresh at a constant 10ms interval, but in practice it always fluctuates between 8-12ms. I tried to modify max_step_size and real_time_update_rate in the world file, but the problem persisted.What can I do to keep the IMU update rate as stable as possible at 10ms?
Part of my world file is as follows:

<physics name='default_physics' default='0' type='ode'>
  <ode>
    <solver>
      <type>quick</type>
      <iters>200</iters>
      <sor>1.3</sor>
      <use_dynamic_moi_rescaling>0</use_dynamic_moi_rescaling>
    </solver>
    <constraints>
      <cfm>0</cfm>
      <erp>0.2</erp>
      <contact_max_correcting_vel>100</contact_max_correcting_vel>
      <contact_surface_layer>0.001</contact_surface_layer>
    </constraints>
  </ode>
  <max_step_size>0.0001</max_step_size>
  <real_time_factor>1</real_time_factor>
  <real_time_update_rate>10000</real_time_update_rate>
</physics>

<plugin name='rotors_gazebo_imu_plugin' filename='libgazebo_imu_plugin.so'>
    <robotNamespace/>
    <linkName>iris::/imu_link</linkName>
    <imuTopic>/imu</imuTopic>
    <gyroscopeNoiseDensity>0.0</gyroscopeNoiseDensity>
    <gyroscopeRandomWalk>0</gyroscopeRandomWalk>
    <gyroscopeBiasCorrelationTime>1000000.0</gyroscopeBiasCorrelationTime>
    <gyroscopeTurnOnBiasSigma>0.0</gyroscopeTurnOnBiasSigma>
    <accelerometerNoiseDensity>0.0</accelerometerNoiseDensity>
    <accelerometerRandomWalk>0.0</accelerometerRandomWalk>
    <accelerometerBiasCorrelationTime>1000000.0</accelerometerBiasCorrelationTime>
    <accelerometerTurnOnBiasSigma>0.0</accelerometerTurnOnBiasSigma>
  </plugin>

I have been puzzled by this question for a long time. I hope for your answer. Thank you!