code: protected void killOverflowingTasks() throws IOException {
      long localMinSpaceKill;
      synchronized(this){
        localMinSpaceKill = minSpaceKill;
      }
      if (!enoughFreeSpace(localMinSpaceKill)) {
        acceptNewTasks=false;
        //we give up! do not accept new tasks until
        //all the ones running have finished and they're all cleared up
        synchronized (this) {
          TaskInProgress killMe = findTaskToKill(null);
  
          if (killMe!=null) {
            String msg = "Tasktracker running out of space." +
              " Killing task.";
            LOG.info(killMe.getTask().getTaskID() + ": " + msg);
            killMe.reportDiagnosticInfo(msg);
            purgeTask(killMe, false);
          }
        }
      }
    }
docs: Check if we're dangerously low on disk space
  If so, kill jobs to free up space and make sure
  we don't accept any new tasks
  Try killing the reduce jobs first, since I believe they
  use up most space
  Then pick the one with least progress