Improve documentation of memory settings

sonar-application/src/main/assembly/conf/sonar.properties

@@ -75,10 +75,16 @@
 #--------------------------------------------------------------------------------------------------
 # WEB SERVER
 
-# Web server is executed in a dedicated Java process. By default its heap size is 768Mb.
+# Web server is executed in a dedicated Java process. By default heap size is 768Mb.
 # Use the following property to customize JVM options.
-# The HotSpot Server VM is recommended. The property -server should be added if server mode
-# is not enabled by default on your environment: http://docs.oracle.com/javase/7/docs/technotes/guides/vm/server-class.html
+#    Recommendations:
+#
+#    The HotSpot Server VM is recommended. The property -server should be added if server mode
+#    is not enabled by default on your environment: http://docs.oracle.com/javase/7/docs/technotes/guides/vm/server-class.html
+#
+#    Set min and max memory (respectively -Xms and -Xmx) to the same value to prevent heap
+#    from resizing at runtime.
+#
 #sonar.web.javaOpts=-Xmx768m -XX:MaxPermSize=160m -XX:+HeapDumpOnOutOfMemoryError
 
 # Same as previous property, but allows to not repeat all other settings like -Xmx
@@ -177,14 +183,19 @@
 
 
 #--------------------------------------------------------------------------------------------------
-# SEARCH INDEX
-
+# ELASTICSEARCH
 # Elasticsearch is used to facilitate fast and accurate information retrieval.
 # It is executed in a dedicated Java process.
 
-# JVM options
-# The HotSpot Server VM is recommended. The property -server should be added if server mode
-# is not enabled by default on your environment: http://docs.oracle.com/javase/7/docs/technotes/guides/vm/server-class.html
+# JVM options of Elasticsearch process
+#    Recommendations:
+#
+#    Use HotSpot Server VM. The property -server should be added if server mode
+#    is not enabled by default on your environment: http://docs.oracle.com/javase/7/docs/technotes/guides/vm/server-class.html
+#
+#    Set min and max memory (respectively -Xms and -Xmx) to the same value to prevent heap
+#    from resizing at runtime.
+#
 #sonar.search.javaOpts=-Xmx1G -Xms256m -Xss256k -Djava.net.preferIPv4Stack=true \
 #  -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=75 \
 #  -XX:+UseCMSInitiatingOccupancyOnly -XX:+HeapDumpOnOutOfMemoryError
@@ -245,7 +256,6 @@
 #sonar.path.temp=temp
 
 
-
 #--------------------------------------------------------------------------------------------------
 # DEVELOPMENT - only for developers
 # The following properties MUST NOT be used in production environments.