Github user lirui-intel commented on the pull request:
https://github.com/apache/spark/pull/892#issuecomment-45184290
That's true @kayousterhout , but my point is that what if all the tasks
only specify NODE_LOCAL preference (common case when the RDD is created from
some HDFS file)? Then tasks in pendingTasksWithNoPrefs (considered
PROCESS_LOCAL) will get priority to run. I ran into this during the test for
the patch.
Is it possible that we set some time out waiting for new executors to come
up? Before the time out, only tasks without preference (if any) in
pendingTasksWithNoPrefs can run as PROCESS_LOCAL. After this period, we believe
it's unlikely new executors gonna come up, so all tasks in
pendingTasksWithNoPrefs can be treated as PROCESS_LOCAL
(pendingTasksWithNoPrefs can still be re-computed if new executors do come up
later).
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