Recommended Java Settings

The following Java HotSpot VM Options are recommended for running Fedora 4:

-Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms512m -Xmx1024m -XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:+DisableExplicitGC

-Djava.awt.headless=true

Headless mode is a system configuration in which the display device, keyboard, or mouse is lacking. Sounds unexpected, but actually you can perform different operations in this mode, even with graphic data.

-server

The JDK includes two flavors of the VM -- a client-side offering, and a VM tuned for server applications. These two solutions share the Java HotSpot runtime environment code base, but use different compilers that are suited to the distinctly unique performance characteristics of clients and servers. These differences include the compilation inlining policy and heap defaults. Although the Server and the Client VMs are similar, the Server VM has been specially tuned to maximize peak operating speed. It is intended for executing long-running server applications, which need the fastest possible operating speed more than a fast start-up time or smaller runtime memory footprint. 

-Dfile.encoding=UTF-8  

Tell the JVM to use UTF-8 as an encoding for text files to be more platform independent

-Xms512m

Set the initial Java Heap memory size to 512 Megabytes

-Xmx1024m

Set the maximal Java Heap memory size to 1024 Megabytes

-XX:PermSize=64m

Set the initial HotSpot PermGen Memory size to 64 Megabytes

-XX:MaxPermSize=256m

Set the maximum PermGen size to 256 Megabytes. This is especially recommended when redeploying Fedora 4 often, since otherwise OutOfMemory in the PermGen space errors will occur.

-XX:+DisableExplicitGC

 Disable calls to System.gc(), JVM still performs garbage collection when necessary.