Github user CodingCat commented on a diff in the pull request:

    https://github.com/apache/spark/pull/214#discussion_r10918466
  
    --- Diff: 
core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala ---
    @@ -198,6 +201,13 @@ private[spark] class TaskSchedulerImpl(
        */
       def resourceOffers(offers: Seq[WorkerOffer]): Seq[Seq[TaskDescription]] 
= synchronized {
         SparkEnv.set(sc.env)
    +    // Make thread pool local for shutdown before the function returns
    +    // This is for driver can exit normally which not call sc.stop or 
sys.exit
    +    val serializeWorkerPool = new ThreadPoolExecutor(
    --- End diff --
    
    Hi, I didn't check your previous discussion in JIRA, but according to Kay, 
the ideal case is to make the process of serializing tasks asynchronous; in 
your current approach, it's actually synchronous (L278 - L281); 
    
    
    you can check how TaskResultGetter works: the taskRunner finishes the task 
and sends a message to the driver, CoarseSchedulerBackend (CSB)...CSB receives 
that and then taskScheduler -> taskManager -> dagScheduler (simply function 
call, no message) to mark the task as finished. The Async process is achieved 
by the message
    
    I think @kayousterhout 's idea is that you develop new messages in your 
patch, when the serialization is finished, it notifies the CSB to launch the 
task....


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