Use the Char version of split() instead of the String one for efficiency

mllib/src/main/scala/spark/mllib/util/MLUtils.scala

@@ -38,9 +38,9 @@ object MLUtils {
    */
   def loadLabeledData(sc: SparkContext, dir: String): RDD[(Double, Array[Double])] = {
     sc.textFile(dir).map { line =>
-      val parts = line.split(",")
+      val parts = line.split(',')
       val label = parts(0).toDouble
-      val features = parts(1).trim().split(" ").map(_.toDouble)
+      val features = parts(1).trim().split(' ').map(_.toDouble)
       (label, features)
     }
   }