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Showing posts from February, 2009

Class Data Sharing

Class data sharing (CDS) a feature introduced in J2SE 5.0 reduces the startup time for Java
programming language applications.

When the JRE is installed on 32-bit platforms using the Sun provided installer, the installer loads a set of
classes from the system jar file into a private internal representation, and dumps that representation to a file,
called a "shared archive".Class data sharing is not supported in Microsoft Windows 95/98/ME.

During subsequent JVM invocations, the shared archive is memory-mapped in, saving the cost of loading those
classes and allowing much of the JVM's metadata for these classes to be shared among multiple JVM processes.

The primary motivation for including CDS in the 5.0 release is the decrease in startup time it provides.
CDS produces better results for smaller applications because it eliminates a fixed cost: that of loading
certain core classes. The smaller the application relative to the number of core classes it uses, the
larger the saved…