tor/changes/multi-priority

  o Minor features (relay, thread pool):
    - Allow background work to be queued with different priorities, so
      that a big pile of slow low-priority jobs will not starve out
      higher priority jobs. This lays the groundwork for a fix for bug
      22883.
Add support for multi-priority workqueues Each piece of queued work now has an associated priority value; each priority goes on a separate queue. With probability (N-1)/N, the workers will take work from the highest priority nonempty queue. Otherwise, they'll look for work in a queue of lower priority. This behavior is meant to prevent starvation for lower-priority tasks. 2017-07-12 11:47:01 -04:00			`o Minor features (relay, thread pool):`
			`- Allow background work to be queued with different priorities, so`
			`that a big pile of slow low-priority jobs will not starve out`
			`higher priority jobs. This lays the groundwork for a fix for bug`
			`22883.`