title: Unity Profiler : Update.Preloading cpu spike
body: <p>I'm using Unity 2019 and I'm trying to understand why I have CPU spike when I load a scene, empty or not.</p>
  
  <p>This is what I have in the profilter when I load a scene with SceneManager.LoadScene(xxx) :</p>
  
  <p><a href="https://i.stack.imgur.com/hAlnq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hAlnq.png" alt="Spike when I load a scene"></a></p>
  
  <p>And the hierarchy : </p>
  
  <p><a href="https://i.stack.imgur.com/SITRH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SITRH.png" alt="enter image description here"></a></p>
  
  <p>The scene I load is empty (all gameobjects, canvas, scripts etc.. are disabled). I only have a camera.</p>
  
  <p>On each scene I load I have <code>UpdatePreloading</code> and <code>Application.WaitForAsyncOperationToComplete</code> in the hierarchy, and I dont know why.</p>
  
  <p>I disabled all my coroutines, I dont load the scene with LoadSceneAsync, so I dont know what are these "async operations to complete".</p>
  
  <p>I tried to use the profiler with the editor on Windows or from my Android device but it's the same result.</p>
  
  <p>Do you have any ideas ?</p>
  
  <p>What <code>Loading.UpdatePreloading()</code> means ?</p>
  
  <p>What <code>Application.WaitForAsyncOperationToComplete</code> means ?</p>
  
  <p>On each scene load I have these spikes.</p>
  
  <p>Thanks !</p>