Github user kayousterhout commented on a diff in the pull request: https://github.com/apache/spark/pull/3779#discussion_r24065873 --- Diff: core/src/main/scala/org/apache/spark/scheduler/TaskSetManager.scala --- @@ -506,13 +506,59 @@ private[spark] class TaskSetManager( * Get the level we can launch tasks according to delay scheduling, based on current wait time. */ private def getAllowedLocalityLevel(curTime: Long): TaskLocality.TaskLocality = { - while (curTime - lastLaunchTime >= localityWaits(currentLocalityIndex) && - currentLocalityIndex < myLocalityLevels.length - 1) - { - // Jump to the next locality level, and remove our waiting time for the current one since - // we don't want to count it again on the next one - lastLaunchTime += localityWaits(currentLocalityIndex) - currentLocalityIndex += 1 + // Remove the scheduled or finished tasks lazily + def hasNotScheduledTasks(taskIndexes: ArrayBuffer[Int]): Boolean = { + var indexOffset = taskIndexes.size + while (indexOffset > 0) { + indexOffset -= 1 + val index = taskIndexes(indexOffset) + if (copiesRunning(index) == 0 && !successful(index)) { + return true + } else { + taskIndexes.remove(indexOffset) + } + } + false + } + // It removes the empty lists after check + def hasMoreTasks(pendingTasks: HashMap[String, ArrayBuffer[Int]]): Boolean = { + val emptyKeys = new ArrayBuffer[String] + val hasTasks = pendingTasks.exists{ + case (id: String, tasks: ArrayBuffer[Int]) => + if (hasNotScheduledTasks(tasks)) { + true + } else { + emptyKeys += id + false + } + } + emptyKeys.foreach(x => pendingTasks.remove(x)) + hasTasks + } + + while (currentLocalityIndex < myLocalityLevels.length - 1) { + val moreTasks = myLocalityLevels(currentLocalityIndex) match { + case TaskLocality.PROCESS_LOCAL => hasMoreTasks(pendingTasksForExecutor) + case TaskLocality.NODE_LOCAL => hasMoreTasks(pendingTasksForHost) + case TaskLocality.NO_PREF => pendingTasksWithNoPrefs.isEmpty + case TaskLocality.RACK_LOCAL => hasMoreTasks(pendingTasksForRack) + } + if (!moreTasks) { + // Move to next locality level if there is no task for current level --- End diff -- Add something like: "This is a performance optimization: if there are no more tasks that can be scheduled at a particular locality level, there is no point in waiting for the locality wait timeout (SPARK-4939)."
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