Change code comments per review comments.

Author: staple

mllib/src/main/scala/org/apache/spark/mllib/clustering/KMeans.scala

@@ -120,7 +120,6 @@ class KMeans private (
   def run(data: RDD[Vector]): KMeansModel = {
 
     if (data.getStorageLevel == StorageLevel.NONE) {
-      // Warn when running an iterative algorithm on uncached data. SPARK-1484
       logWarning("The input data is not directly cached, which may hurt performance if its"
         + " parent RDDs are also uncached.")
     }
@@ -134,6 +133,7 @@ class KMeans private (
     val model = runBreeze(breezeData)
     norms.unpersist()
 
+    // Warn at the end of the run as well, for increased visibility.
     if (data.getStorageLevel == StorageLevel.NONE) {
       logWarning("The input data was not directly cached, which may hurt performance if its"
         + " parent RDDs are also uncached.")

mllib/src/main/scala/org/apache/spark/mllib/linalg/distributed/RowMatrix.scala

@@ -233,7 +233,6 @@ class RowMatrix(
         (sigmaSquaresFull, uFull)
       case SVDMode.DistARPACK =>
         if (rows.getStorageLevel == StorageLevel.NONE) {
-          // Warn when running an iterative algorithm on uncached data. SPARK-1484
           logWarning("The input data is not directly cached, which may hurt performance if its"
             + " parent RDDs are also uncached.")
         }
@@ -262,6 +261,7 @@ class RowMatrix(
       logWarning(s"Requested $k singular values but only found $sk nonzeros.")
     }
 
+    // Warn at the end of the run as well, for increased visibility.
     if (computeMode == SVDMode.DistARPACK && rows.getStorageLevel == StorageLevel.NONE) {
       logWarning("The input data was not directly cached, which may hurt performance if its"
         + " parent RDDs are also uncached.")

mllib/src/main/scala/org/apache/spark/mllib/regression/GeneralizedLinearAlgorithm.scala

@@ -151,7 +151,6 @@ abstract class GeneralizedLinearAlgorithm[M <: GeneralizedLinearModel]
   def run(input: RDD[LabeledPoint], initialWeights: Vector): M = {
 
     if (input.getStorageLevel == StorageLevel.NONE) {
-      // Warn when running an iterative algorithm on uncached data. SPARK-1484
       logWarning("The input data is not directly cached, which may hurt performance if its"
         + " parent RDDs are also uncached.")
     }
@@ -230,6 +229,7 @@ abstract class GeneralizedLinearAlgorithm[M <: GeneralizedLinearModel]
       weights = scaler.transform(weights)
     }
 
+    // Warn at the end of the run as well, for increased visibility.
     if (input.getStorageLevel == StorageLevel.NONE) {
       logWarning("The input data was not directly cached, which may hurt performance if its"
         + " parent RDDs are also uncached.")