[GitHub] 10110346 commented on a change in pull request #23679: [SPARK-23516][CORE] It is unnecessary to transfer unroll memory to storage memory

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10110346 commented on a change in pull request #23679: [SPARK-23516][CORE] It is unnecessary to transfer unroll memory to storage memory
URL: https://github.com/apache/spark/pull/23679#discussion_r251697130
 
 

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 File path: core/src/main/scala/org/apache/spark/storage/memory/MemoryStore.scala
 ##########
 @@ -247,18 +247,18 @@ private[spark] class MemoryStore(
         val amountToRequest = size - unrollMemoryUsedByThisBlock
         keepUnrolling = reserveUnrollMemoryForThisTask(blockId, amountToRequest, memoryMode)
         if (keepUnrolling) {
-          unrollMemoryUsedByThisBlock += amountToRequest
+          unrollMemoryUsedByThisBlock = size
         }
+      } else if (size < unrollMemoryUsedByThisBlock) {
+        releaseUnrollMemoryForThisTask(memoryMode, unrollMemoryUsedByThisBlock - size)
+        unrollMemoryUsedByThisBlock = size
       }
 
       if (keepUnrolling) {
         val entry = entryBuilder.build()
-        // Synchronize so that transfer is atomic
-        memoryManager.synchronized {
-          releaseUnrollMemoryForThisTask(memoryMode, unrollMemoryUsedByThisBlock)
-          val success = memoryManager.acquireStorageMemory(blockId, entry.size, memoryMode)
-          assert(success, "transferring unroll memory to storage memory failed")
-        }
+        // In fact, unroll memory is also storage memory, it is unnecessary to
+        // release unroll memory really, and then to get storage memory again.
+        releaseUnrollMemoryForThisTask(memoryMode, unrollMemoryUsedByThisBlock, false)
 
 Review comment:
   Yeah,thanks

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