HADOOP-8913. Merging change 1396904 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1396907 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/src/main/conf/hadoop-metrics2.properties

@@ -2,7 +2,7 @@
 # See javadoc of package-info.java for org.apache.hadoop.metrics2 for details
 
 *.sink.file.class=org.apache.hadoop.metrics2.sink.FileSink
-# default sampling period
+# default sampling period, in seconds
 *.period=10
 
 # The namenode-metrics.out will contain metrics from all context

hadoop-hdfs-project/hadoop-hdfs/src/main/conf/hadoop-metrics2.properties

@@ -19,7 +19,7 @@
 # See javadoc of package-info.java for org.apache.hadoop.metrics2 for details
 
 *.sink.file.class=org.apache.hadoop.metrics2.sink.FileSink
-# default sampling period
+# default sampling period, in seconds
 *.period=10
 
 # The namenode-metrics.out will contain metrics from all context