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[SPARK-15246][Core] Fix code style and improve volatile for SPARK-4452 #13020

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[SPARK-15246][Core] Fix code style and improve volatile for SPARK-4452 #13020

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2 changes: 1 addition & 1 deletion core/src/main/java/org/apache/spark/memory/TaskMemoryManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -413,7 +413,7 @@ public long getMemoryConsumptionForThisTask() {
/**
* Returns Tungsten memory mode
*/
public MemoryMode getTungstenMemoryMode(){
public MemoryMode getTungstenMemoryMode() {
return tungstenMemoryMode;
}
}
3 changes: 1 addition & 2 deletions core/src/main/scala/org/apache/spark/util/collection/Spillable.scala
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Expand Up @@ -41,7 +41,7 @@ private[spark] abstract class Spillable[C](taskMemoryManager: TaskMemoryManager)
protected def forceSpill(): Boolean

// Number of elements read from input since last spill
@volatile protected def elementsRead: Long = _elementsRead
protected def elementsRead: Long = _elementsRead
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@rxin rxin May 10, 2016

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can you comment on why the changes are safe/correct?

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@lianhuiwang lianhuiwang May 10, 2016

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It has only one thread to use this method. So we can remove volatile.

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@srowen srowen May 10, 2016

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It's not meaningful to make a method volatile anyway right? the fact that it's not an error makes me think I could be missing something. No objection

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@lianhuiwang lianhuiwang May 11, 2016 •
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Yes, I think you understand correctly. we can remove volatile of elementsRead method because there is only one thread to use it.


// Called by subclasses every time a record is read
// It's used for checking spilling frequency
Expand Down Expand Up @@ -112,7 +112,6 @@ private[spark] abstract class Spillable[C](taskMemoryManager: TaskMemoryManager)
if (!isSpilled) {
0L
} else {
_elementsRead = 0
val freeMemory = myMemoryThreshold - initialMemoryThreshold
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@lianhuiwang lianhuiwang May 10, 2016 •
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I delete this code in order to _elementsRead is called by one thread. So we do not need to make _elementsRead volatile.

_memoryBytesSpilled += freeMemory
releaseMemory()
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