title: QVector spends different times when adding an element
body: <p>I have a very simple code, I noticed that if I add values ​​to <code>QVector</code> constants, then I spend a lot of time than if I add sequential knowledge</p>
  <p><strong>code example:</strong></p>
  <pre><code>QVector&lt;int&gt; intVector;
  
  QTime myTimer;
  myTimer.start();
  for (int i = 0; i &lt; 8500000; ++i) {
      intVector.push_back(i);
  }
  qDebug()&lt;&lt; myTimer.elapsed(); // output: ~297 ms
  </code></pre>
  <p>but if i add a constant value i get this</p>
  <p><strong>code example:</strong></p>
  <pre><code>QVector&lt;int&gt; intVector;
      
  QTime myTimer;
  myTimer.start();
  for (int i = 0; i &lt; 8500000; ++i) {
      intVector.push_back(1); 
  }
  qDebug()&lt;&lt; myTimer.elapsed(); // output: ~344 ms
  </code></pre>
  <p>tested on <code>Qt_5_15_0_MSVC2019_32bit</code>.</p>
  <p>What explains this?</p>