Java Virtual Machine - Architecture

The architecture of the HotSpot JVM 3 is shown below −

The execution engine comprises of the garbage collector and the JIT compiler. The JVM comes in two flavors − client and server. Both of these share the same runtime code but differ in what JIT is used. We shall learn more on this later. The user can control what flavor to use by specifying the JVM flags -client or -server. The server JVM has been designed for long-running Java applications on servers.

The JVM comes in 32b and 64b versions. The user can specify what version to use by using -d32 or -d64 in the VM arguments. The 32b version could only address up to 4G of memory. With critical applications maintaining large datasets in memory, the 64b version meets that need.