NonStop Server for Java 7.0 Programmer's Reference

• The article, Turbo-charging Java HotSpot Virtual Machine, v1.4.x to Improve the Performance
and Scalability of Application Servers.
• Java Performance Documentation.
NOTE:
• The following options do not apply either for the NSJ7 or NonStop system:
-XX:-UseBoundThreads
-XX:+UseAltSigs
-XX:+AllowUserSignalHandlers
-XX:+MaxFDLimit
-XX:-UseLWPSynchronization
-XX:PreBlockSpin=nn
-XX:-UseMPSS
-XX:+UseSpinning
javagc
javagc is a executable file that is used by Java process to launch the GC process on J-series
systems. The GC process is a multi-threaded application. It interacts with Java application using
the standard NonStop Kernel IPC mechanism. The GC processes are launched on the same
processor on which the Java process is running. The maximum number for parallel GC processes
is equal to the number of cores in the processor. If CMS GC is enabled, the number of ParNewGC
processes created will be equal to the number of cores. In addition to these processes, there will
be one CMS GC task process. These processes are unnamed processes.
GC processes are bound to separate IPUs for improved performance. The IPU number to which a
GC process is bound is the ordinal number of that GC process. For example, if parallel GC is
enabled on a 4-core CPU, 4 GC processes are launched. The first GC process created binds to
IPU 0, second to IPU 1, third to IPU 2, and fourth to IPU 3.
You must not invoke javagc executable file directly, and if it is invoked directly, the process
displays the error message:
Internal Error: Cannot invoke directly!!!
NOTE: There are two versions of javagc available in NSJ7, one for 32–bit and the other for
64–bit.
GC profiling
NSJ7 supports an HP proprietary option, -Xverbosegc to capture the Java application's GC
activity. The output of this option can be used to view and analyze the detailed statistics in an
offline mode with HPjmeter. The following -Xverbosegc option generates detailed information
about the spaces within the Java heap before and after garbage collection:
-Xverbosegc[:help]|[0|1][:file=[stdout|stderr|<filename>]]
Fore more information on the syntax options of -Xverbosegc, see java in the NonStop Server
for Java 7.0 Tools Reference Pages.
For more information on application profiling, see “Application tuning and profiling” (page 86).
GC log rotation
When GC logging is enabled using the -Xverbosegc or -Xloggc option, by default, the GC
data is written to a single log file of unlimited size. NSJ7 allows you to control the size and number
of the GC log files. The GC log records are written in the specified number of GC log files in a
javagc 59