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author | Adam Budde <budde@amazon.com> | 2016-02-02 19:35:33 -0800 |
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committer | Andrew Or <andrew@databricks.com> | 2016-02-02 19:35:33 -0800 |
commit | ff71261b651a7b289ea2312abd6075da8b838ed9 (patch) | |
tree | 8807de2ed8a8dc00b345d852bff46e880b02aef2 | |
parent | 21112e8a14c042ccef4312079672108a1082a95e (diff) | |
download | spark-ff71261b651a7b289ea2312abd6075da8b838ed9.tar.gz spark-ff71261b651a7b289ea2312abd6075da8b838ed9.tar.bz2 spark-ff71261b651a7b289ea2312abd6075da8b838ed9.zip |
[SPARK-13122] Fix race condition in MemoryStore.unrollSafely()
https://issues.apache.org/jira/browse/SPARK-13122
A race condition can occur in MemoryStore's unrollSafely() method if two threads that
return the same value for currentTaskAttemptId() execute this method concurrently. This
change makes the operation of reading the initial amount of unroll memory used, performing
the unroll, and updating the associated memory maps atomic in order to avoid this race
condition.
Initial proposed fix wraps all of unrollSafely() in a memoryManager.synchronized { } block. A cleaner approach might be introduce a mechanism that synchronizes based on task attempt ID. An alternative option might be to track unroll/pending unroll memory based on block ID rather than task attempt ID.
Author: Adam Budde <budde@amazon.com>
Closes #11012 from budde/master.
-rw-r--r-- | core/src/main/scala/org/apache/spark/storage/MemoryStore.scala | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala b/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala index 76aaa782b9..024b660ce6 100644 --- a/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala +++ b/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala @@ -255,8 +255,8 @@ private[spark] class MemoryStore(blockManager: BlockManager, memoryManager: Memo var memoryThreshold = initialMemoryThreshold // Memory to request as a multiple of current vector size val memoryGrowthFactor = 1.5 - // Previous unroll memory held by this task, for releasing later (only at the very end) - val previousMemoryReserved = currentUnrollMemoryForThisTask + // Keep track of pending unroll memory reserved by this method. + var pendingMemoryReserved = 0L // Underlying vector for unrolling the block var vector = new SizeTrackingVector[Any] @@ -266,6 +266,8 @@ private[spark] class MemoryStore(blockManager: BlockManager, memoryManager: Memo if (!keepUnrolling) { logWarning(s"Failed to reserve initial memory threshold of " + s"${Utils.bytesToString(initialMemoryThreshold)} for computing block $blockId in memory.") + } else { + pendingMemoryReserved += initialMemoryThreshold } // Unroll this block safely, checking whether we have exceeded our threshold periodically @@ -278,6 +280,9 @@ private[spark] class MemoryStore(blockManager: BlockManager, memoryManager: Memo if (currentSize >= memoryThreshold) { val amountToRequest = (currentSize * memoryGrowthFactor - memoryThreshold).toLong keepUnrolling = reserveUnrollMemoryForThisTask(blockId, amountToRequest) + if (keepUnrolling) { + pendingMemoryReserved += amountToRequest + } // New threshold is currentSize * memoryGrowthFactor memoryThreshold += amountToRequest } @@ -304,10 +309,9 @@ private[spark] class MemoryStore(blockManager: BlockManager, memoryManager: Memo // release the unroll memory yet. Instead, we transfer it to pending unroll memory // so `tryToPut` can further transfer it to normal storage memory later. // TODO: we can probably express this without pending unroll memory (SPARK-10907) - val amountToTransferToPending = currentUnrollMemoryForThisTask - previousMemoryReserved - unrollMemoryMap(taskAttemptId) -= amountToTransferToPending + unrollMemoryMap(taskAttemptId) -= pendingMemoryReserved pendingUnrollMemoryMap(taskAttemptId) = - pendingUnrollMemoryMap.getOrElse(taskAttemptId, 0L) + amountToTransferToPending + pendingUnrollMemoryMap.getOrElse(taskAttemptId, 0L) + pendingMemoryReserved } } else { // Otherwise, if we return an iterator, we can only release the unroll memory when |