Configuring the heap size

Once you have installed Maven in your system, the next step is to fine-tune it for optimal performance. By default, the maximum heap allocation is 256 - 512 MB (-Xms256m to -Xmx512m). This default limit does not work while building a large, complex Java project, and it is recommended that you have at least 1024 MB of maximum heap. If you encounter the java.lang.OutOfMemoryError error at any point during a Maven build, it is mostly due to the lack of memory. You can use the MAVEN_OPTS environment variable to set the maximum allowed heap size for Maven at a global level.

The following command will set the heap size in Linux. Make sure that the value set as the maximum heap size does not exceed your system memory of the machine that runs Maven.

$ export MAVEN_OPTS="-Xmx1024m -XX:MaxPermSize=128m"

If you are on Microsoft Windows, use the following command:

$ set MAVEN_OPTS=-Xmx1024m -XX:MaxPermSize=128m

Here -Xmx takes the maximum heap size and -XX:MaxPermSize takes the maximum PermGen size.

Note

Maven runs as a Java process on JVM. As Java proceeds with a build, it keeps on creating Java objects. These objects are stored in the memory allocated to Maven. This area of memory where Java objects are stored is known as heap. Heap is created at the JVM start, and it increases as more and more objects are created up to the defined maximum limit. The -Xms JVM flag is used to instruct JVM the minimum value it should set at the time it creates the heap. The -Xmx JVM flag sets the maximum heap size.

Permanent Generation (PermGen) is an area of memory managed by JVM, which stores the internal representations of Java classes. The maximum size of PermGen can be set by the -XX:MaxPermSize JVM flag.

To learn about the Maven OutOfMemoryError error, check out the information at this link: https://cwiki.apache.org/confluence/display/MAVEN/OutOfMemoryError.