JVM Performance

Description

OVERVIEW OF JVM PERFORMANCE

                      For improved performance, JVM setting requires careful tunings. Tune your JVM setting to avoid experiencing memory allocation error. The symptoms for these error can vary from intermittent performance problems to the periodic failure and restart of the JVM. Consider the default JVM settings set by Futuregen  as a starting point. The information in the JVM performance tuning topic is specific to the any JDK release.JVM tuning is a systematic and complex task. At present, the automatic adjustment under JVMs is very excellent and basic initial parameters can ensure that common applications runs stably.

Tuning Just-In-Time Compiler:

Java virtual machines (JVM) use Just-In-Time (JIT) compiler to compile Java byte code into native instructions during server run time. A JIT compiler is a platform-specific compiler that generates machine instructions for each method as needed. These compilers can affect startup or runtime performance.

Advantages of the 64-bit JVM:

IBM recommends 64bit JVMs. The 64-bit JVM provides a number of advantages over the 32-bit JVM:The 64-bit JVM gives you the ability to keep more cached data in the JVM heap. This capacity leads to less reliance on the DynaCache disk offload feature and, as a consequence, less I/O traffic to disk.
The ability to increase the maximum heap size beyond 1.8 GB is beneficial when the store is experiencing heap contention issues due to large number of non-cacheable application objects.

Java Performance Optimizations Best Practices:

Most Java performance problems can be attributed to one of the following four shared resources:

CPU
Memory
I/O operations
Threads

Use different monitoring tool to investigate a flight recording with special attention to the following metrics:

CPU utilization
system context switching
physical memory utilization
heap consumption over time
network bandwidth used
disk I/O latency
database locks
SQL latency
garbage collection frequency
garbage collection pause time
thread contentions
thread pauses
thread locks
Java Performance Optimization Targets:

Once you know which shared resource causes the JVM performance problem, examine stack traces to identify the active Java classes and methods when 
the performance problem occurs. Eighty percent of the time, Java performance optimization is achieved when you:

Use faster database queries;
Identify and fix memory leaks;
Optimize garbage collection routines;
Resolve thread locks and concurrency issues;
Fix inefficient code in the application; and
Use the correct collection class for list processing.