title: Parallel.For becomes single threaded near the end
body: <p>There is a problem I'm currently experiencing with Parallel.For.
  I'm trying to run a batch of ~1000 of pretty long running tasks( each running for like 120 seconds), and my problem seems to be, that on the last 10-20 iterations, the processing becomes single-threaded.</p>
  
  <p>Pseudocode:</p>
  
  <pre class="lang-cs prettyprint-override"><code>Parallel.For(0, 1000,
             (i, loopState)=&gt; 
             {
              //Do lots of work
              Thread.Sleep(120_000);
             });
  </code></pre>
  
  <p>Do you guys know why this is happening, and how can this issue be fixed?</p>