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From the webMethods Technical Report “Hardware, JVM, and Operating System Performance Tuning Recommendations” dated November 2005 (Version 1.0)

Microsoft Windows

• JVM selection: For Intel machines, IBM JVMs consistently outperform Sun JVMs. The gap has been narrowing, but is still substantial. The gap is particularly pronounced on Xeon processors, because the IBM JVMs can take advantage of the hyperthreading, which Sun JVMs cannot. Recommendation: On Intel hardware, use the latest IBM JVM available.
• Sun JVM options: On Sun JVMs, the –server and -XX:+AggressiveHeap options usually improves performance, typically by a substantial amount. Recommendation: Always use the –server and -XX:+AggressiveHeap options when using a Sun JVM.

Sun Solaris

• Sun JVM options: The –server and -XX:+AggressiveHeap options usually improves performance, typically by a substantial amount. For Sun 1.5 JVMs on SPARC hardware, the -server option is automatic on “server class” machines (those with two or more processors). Recommendation: Always use the –server and –XX:+AggressiveHeap
  options.

Linux

• There are no recommendations for Linux.

Hewlett-Packard HP-UX

• Set the size of the “young” generation on the heap by including the –Xmn256M parameter in the Java startup options. The -XX:+ForceMmapReserved option reserves space for all large memory regions used by the JVM. This includes the Java Heap, which is memory mapped. Most large server-side applications will use all of this space, so performance may be improved by reserving the space at program initialization.

IBM AIX

• The Native Heap size should be increased if “out of memory” errors are encountered.

IBM OS/400

• There are no recommendations for OS/400.