cloud-fan commented on a change in pull request #25470: [SPARK-28751][Core] 
Imporve java serializer deserialization performance
URL: https://github.com/apache/spark/pull/25470#discussion_r314566092
 
 

 ##########
 File path: core/src/main/scala/org/apache/spark/serializer/JavaSerializer.scala
 ##########
 @@ -58,19 +59,32 @@ private[spark] class JavaSerializationStream(
   def close() { objOut.close() }
 }
 
-private[spark] class JavaDeserializationStream(in: InputStream, loader: 
ClassLoader)
-  extends DeserializationStream {
+private[spark] class JavaDeserializationStream(
+    in: InputStream,
+    loader: ClassLoader,
+    useCache: Boolean,
+    serializerInstance: JavaSerializerInstance) extends DeserializationStream {
 
   private val objIn = new ObjectInputStream(in) {
-    override def resolveClass(desc: ObjectStreamClass): Class[_] =
+    override def resolveClass(desc: ObjectStreamClass): Class[_] = {
+      if (useCache) {
+        serializerInstance.resolvedClassesCache.computeIfAbsent(
+          (desc.getName, loader), pair => normalResolve(pair._1))
+      } else {
+        normalResolve(desc.getName)
+      }
+    }
+
+    private def normalResolve(name: String): Class[_] = {
       try {
         // scalastyle:off classforname
-        Class.forName(desc.getName, false, loader)
+        Class.forName(name, false, loader)
 
 Review comment:
   @rednaxelafx does JVM classloader have cache?

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