SDK/RTE 1.4.2.09 for Debian Linux on Intel Itanium Processors Release Notes

Raising this value may improve overall application performance when the New space
is large and/or when your application keeps a very low percentage of objects.
-XX:+UseCompilerSafepoints
Enables compiler safe points. In this version, compiler safe points is off by default.
Enabling compiler safepoints guarantees a more deterministic delay to stop all running
java threads before doing a safepoint operation, namely garbage collection and
deoptimization.
-XX:+UseGetTimeOfDay
Instructs the JVM to use the gettimeofday call instead of the mechanism whereby
the number of cpu ticks since the application started is used to calculate the current
time. With this new mechanism, changes to the system date or time using date(1),
adjtime(2), or time synchronization utilities such as ntp are not reflected in the date
and time that Java returns, until the process is restarted. If your application requires
that Java immediately reflects such system time changes, you can use the
-XX:+UseGetTimeOfDay option; however, you may notice a drop in performance.
-XX:+UseOnStackReplacement
Enables on stack replacement. In this version, on stack replacement is off by default.
On stack replacement enables the interpreter to go into compiled code while it is
executing the same instance of the method call. For example, if the VM is executing a
method that has a loop with a large number of iterations, an intra-method hotspot will
occur. To get better performance, the method should run in compiled mode instead of
interpreted mode. If you enable on stack replacement, you must also enable compiler
safe points (see -XX:+UseCompilerSafepoints).
Tuning garbage collection
The following is an excerpt from http://java.sun.com/j2se/1.4.2/1.4.2_whitepaper.html#3:
In the J2SE platform version 1.4.1 two new garbage collectors were introduced to make
a total of four garbage collectors from which to choose. In J2SE platform version 1.4.2
the performance of the new collectors have been improved through algorithm
optimizations and bug fixes, along with documentation updates to educate developers
and administrators on what collectors to choose and when.
For a detailed look at garbage collection and the new collectors, see:
http://java.sun.com/docs/hotspot/gc1.4.2/index.html.
Profiling capability
In the SDK version 1.4, a SIGPROF handler to support future profiling capability is
installed automatically. This may cause incompatibilities with other native code or
profiling tools which use SIGPROF.
Usage documentation 11