title: Keras does not utilize 100% cpu
body: <p>I build sequential model with keras and tensorflow backend.
  As you seen on picture, model uses all cores but none of them 100%.
  I would like to know, how to make keras+tf utilize every core by 100%.</p>
  
  <p>I tried to build tensorflow from scratch and reinstall, but it didn't help.</p>
  
  <p><a href="https://i.stack.imgur.com/01sae.png" rel="noreferrer"><img src="https://i.stack.imgur.com/01sae.png" alt="enter image description here"></a></p>