[GitHub] [spark] mridulm commented on a diff in pull request #38711: [SPARK-41192][Core] Remove unscheduled speculative tasks when task finished to obtain better dynamic

[GitBox <gi...@apache.org>]

mridulm commented on code in PR #38711:
URL: https://github.com/apache/spark/pull/38711#discussion_r1034252202


##########
core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala:
##########
@@ -643,10 +643,11 @@ private[spark] class ExecutorAllocationManager(
     // Should be 0 when no stages are active.
     private val stageAttemptToNumRunningTask = new mutable.HashMap[StageAttempt, Int]
     private val stageAttemptToTaskIndices = new mutable.HashMap[StageAttempt, mutable.HashSet[Int]]
-    // Number of speculative tasks pending/running in each stageAttempt
-    private val stageAttemptToNumSpeculativeTasks = new mutable.HashMap[StageAttempt, Int]
-    // The speculative tasks started in each stageAttempt
+    // Number of speculative tasks running in each stageAttempt
     private val stageAttemptToSpeculativeTaskIndices =
+      new mutable.HashMap[StageAttempt, mutable.HashSet[Int]]()

Review Comment:
   Note: Ideally, we simply need an `Int` for this - since we have split `stageAttemptToUnsubmittedSpeculativeTasks`.
   For now, let us keep it as a HashSet though - I have slight concerns around dropped events which might make the map's go inconsistent.



##########
core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala:
##########
@@ -722,9 +723,8 @@ private[spark] class ExecutorAllocationManager(
         // because the attempt may still have running tasks,
         // even after another attempt for the stage is submitted.
         stageAttemptToNumTasks -= stageAttempt
-        stageAttemptToNumSpeculativeTasks -= stageAttempt
+        stageAttemptToUnsubmittedSpeculativeTasks -= stageAttempt

Review Comment:
   Remove from both maps.



##########
core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala:
##########
@@ -896,9 +897,8 @@ private[spark] class ExecutorAllocationManager(
     }
 
     private def getPendingSpeculativeTaskSum(attempt: StageAttempt): Int = {
-      val numTotalTasks = stageAttemptToNumSpeculativeTasks.getOrElse(attempt, 0)
-      val numRunning = stageAttemptToSpeculativeTaskIndices.get(attempt).map(_.size).getOrElse(0)
-      numTotalTasks - numRunning
+      stageAttemptToUnsubmittedSpeculativeTasks
+        .getOrElse(attempt, mutable.HashSet.empty[Int]).size

Review Comment:
   nit:
   ```suggestion
         stageAttemptToUnsubmittedSpeculativeTasks.get(attempt).map(_.size).getOrElse(0)
   ```



##########
core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala:
##########
@@ -383,8 +383,8 @@ private[spark] class DAGScheduler(
   /**
    * Called by the TaskSetManager when it decides a speculative task is needed.
    */
-  def speculativeTaskSubmitted(task: Task[_]): Unit = {
-    eventProcessLoop.post(SpeculativeTaskSubmitted(task))
+  def speculativeTaskSubmitted(task: Task[_], taskIndex: Int = -1): Unit = {
+    eventProcessLoop.post(SpeculativeTaskSubmitted(task, taskIndex))

Review Comment:
   Why not simply use `task.partitionId` instead for `taskIndex` ?



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