How to give Jenkins more heap space when it´s started as a service under Windows?

If you used Aptitude (apt-get) to install Jenkins on Ubuntu 12.04, uncomment the JAVA_ARGS line in the top few lines of /etc/default/jenkins:

# arguments to pass to java
#JAVA_ARGS="-Xmx256m"   # <--default value
JAVA_ARGS="-Xmx2048m"
#JAVA_ARGS="-Djava.net.preferIPv4Stack=true" # make jenkins listen on IPv4 address

In your Jenkins installation directory there is a jenkins.xml, where you can set various options. Add the parameter -Xmx with the size you want to the arguments-tag (or increase the size if its already there).

You need to modify the jenkins.xml file. Specifically you need to change

   <arguments>-Xrs -Xmx256m 
    -Dhudson.lifecycle=hudson.lifecycle.WindowsServiceLifecycle 
    -jar "%BASE%\jenkins.war" --httpPort=8080</arguments>

to

    <arguments>-Xrs -Xmx2048m -XX:MaxPermSize=512m 
    -Dhudson.lifecycle=hudson.lifecycle.WindowsServiceLifecycle 
    -jar "%BASE%\jenkins.war" --httpPort=8080</arguments>

You can also verify the Java options that Jenkins is using by installing the Jenkins monitor plugin via Manage Jenkins / Manage Plugins and then navigating to Managing Jenkins / Monitoring of Hudson / Jenkins master to use monitoring to determine how much memory is available to Jenkins.

If you are getting an out of memory error when Jenkins calls Maven, it may be necessary to set MAVEN_OPTS via Manage Jenkins / Configure System e.g. if you are running on a version of Java prior to JDK 1.8 (the values are suggestions):

-Xmx2048m  -XX:MaxPermSize=512m

If you are using JDK 1.8:

-Xmx2048m

I've added to /etc/sysconfig/jenkins (CentOS):

# Options to pass to java when running Jenkins.
#
JENKINS_JAVA_OPTIONS="-Djava.awt.headless=true -Xmx1024m -XX:MaxPermSize=512m"

For ubuntu the same config should be located in /etc/default