To increase the memory allocated and available:
1# /etc/default/jenkins
2JAVA_ARGS='Xms4G -Xmx16G -Djava.awt.headless=true'
See also
- Jenkins performance hints: http://soldering-iron.blogspot.com/2014/01/jenkins-performance-hints.html
- Java commandline options: http://docs.oracle.com/javase/7/docs/technotes/tools/windows/java.html