Ngone51 commented on a change in pull request #23677: [SPARK-26755][SCHEDULER]
: Optimize Spark Scheduler to dequeue speculative tasks…
URL: https://github.com/apache/spark/pull/23677#discussion_r303004365
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File path: core/src/main/scala/org/apache/spark/scheduler/TaskSetManager.scala
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@@ -302,15 +272,18 @@ private[spark] class TaskSetManager(
private def dequeueTaskFromList(
execId: String,
host: String,
- list: ArrayBuffer[Int]): Option[Int] = {
+ list: ArrayBuffer[Int],
+ speculative: Boolean = false): Option[Int] = {
var indexOffset = list.size
while (indexOffset > 0) {
indexOffset -= 1
val index = list(indexOffset)
- if (!isTaskBlacklistedOnExecOrNode(index, execId, host)) {
+ if (!isTaskBlacklistedOnExecOrNode(index, execId, host) &&
+ !(speculative && hasAttemptOnHost(index, host))) {
// This should almost always be list.trimEnd(1) to remove tail
list.remove(indexOffset)
- if (copiesRunning(index) == 0 && !successful(index)) {
+ if (((copiesRunning(index) < 2 && speculative) ||
+ (!speculative && copiesRunning(index) == 0)) && !successful(index)) {
Review comment:
How about this ?
```
if (!successful(index)) {
if (copiesRunning(index) == 0) {
return Some(index)
} else if (speculative && copiesRunning(index) == 1) {
return Some(index)
}
}
```
One important reason is that speculation default to be false.
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