title: pytest-xdist manage the file order
body: <p>I have 10 test files:</p>
  <p>sc0 - run 4 min</p>
  <p>sc1 - run 6 min</p>
  <p>sc2 - run 6 min</p>
  <p>sc3 - run 25 min</p>
  <p>sc4 - run 25 min</p>
  <p>sc5 - run 5 min</p>
  <p>sc6 - run 5 min</p>
  <p>sc7 - run 5 min</p>
  <p>sc8 - run 6 min</p>
  <p>sc9 - run 33 min</p>
  <p>I use the below command in order to run test in parallel ( each file should run sequentially)</p>
  <pre><code>pytest -n 3 --dist loadfile --junit-xml=pytest-junit.xml -o junit_family=xunit2
  </code></pre>
  <p>I see that workers get test to run based on file name order and the total execution time is 1 h</p>
  <p>the distribution are:</p>
  <p>worker0 - sc0 (4m), sc3 (25m) and sc9 (33m) = 1h</p>
  <p>worker1 - sc1 (6m), sc4 (25m) = 31m</p>
  <p>worker2 - sc2 (6m), sc5 (5m), sc6 (5m), sc7 (5m), sc8 (6m) = 27m</p>
  <p>but if I will have ability to control the worker split decision which file to choose, I can save 20m of test execution</p>
  <p>worker0 - sc3 (25m), sc0 (4m), sc2 (6m), sc7 (5m) = 40m</p>
  <p>worker1 - sc4 (25m), sc1 (6m), sc5 (5m), sc8 (6m) = 42m</p>
  <p>worker2 - sc9 (33m), sc6 (5m) = 38m</p>
  <p>How can I control the order of test file distribution for pytest-xdist plugin? ( I don't want to rename files names)</p>