Add performance optimization for Java (#117)

* Add performance optimization for Java

* Update code comment

scripts/datadog_wrapper

@@ -67,10 +67,24 @@ then
   fi
   export DD_JMXFETCH_ENABLED="false"
   export DD_RUNTIME_METRICS_ENABLED="false"
+  export DD_REMOTE_CONFIG_ENABLED="false"
+
   DD_Agent_Jar=/opt/java/lib/dd-java-agent.jar
   if [ -f "$DD_Agent_Jar" ]
   then
-    export JAVA_TOOL_OPTIONS="$JAVA_TOOL_OPTIONS -javaagent:$DD_Agent_Jar -XX:+TieredCompilation -XX:TieredStopAtLevel=1"
+    # Removes the -XX:-TieredCompilation flag from the java command passed 
+    # through from the Lambda runtime. Allows the JVM to use the C1 compiler
+    # and Interpreter, which is much faster on cold start and 
+    # uses less memory.
+    START_COMMAND=${args[0]}
+    REMAINDER_ARGS=("${args[@]:1}")
+    for index in "${!REMAINDER_ARGS[@]}" ; do
+      [[ ${REMAINDER_ARGS[$index]} == "-XX:-TieredCompilation" ]] && unset -v 'REMAINDER_ARGS[$index]' ;
+    done
+    REMAINDER_ARGS="${REMAINDER_ARGS[@]}"
+    # -XX:TieredStopAtLevel=1 tells the compiler to stop at the C1 compiler
+    args=($START_COMMAND -javaagent:$DD_Agent_Jar -XX:TieredStopAtLevel=1 ${REMAINDER_ARGS[@]})
+
   else
     echo "File $DD_Agent_Jar does not exist!"
   fi