Modify the file: apache-tomcat/bin/setenv.sh
Add this params to CATALINA_OPTS and then restart JIRA service
-XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:+UseCompressedStrings -XX:+OptimizeStringConcat -XX:+OmitStackTraceInFastThrow -XX:+UseCompressedOops