IBM User Guide for Java V7 on Windows > Troubleshooting and support > Problem determination > Windows problem determination

Debugging performance problems

Locating the causes of poor performance is often difficult. Although many factors can affect performance, the overall effect is generally perceived as poor response time or slow execution of your program.

Correcting one performance problem might cause more problems in another area. By finding and correcting a bottleneck in one place you might only shift the cause of poor performance to other areas. To improve performance, experiment with tuning different parameters, monitoring the effect, and retuning until you are satisfied that your system is performing acceptably

• Finding the bottleneck
  The aspects of the system that you are most interested in measuring are CPU usage and memory usage. It is possible that even after extensive tuning efforts the CPU is not powerful enough to handle the workload, in which case a CPU upgrade is required. Similarly, if the program is running in an environment in which it does not have enough memory after tuning, you must increase memory size.
• Windows systems resource usage
  The Windows Task Manager display gives a good general view of system resource usage. You can use this tool to determine which processes are using excessive CPU time and memory. This tool also provides a summary view of network I/O activity.
• JVM heap sizing
  The Java™ heap size is one of the most important tuning parameters of your JVM. A poorly chosen size can result in significant performance problems as the Garbage Collector has to work harder to stay ahead of utilization.
• JIT compilation and performance
  The JIT is another area that can affect the performance of your program. When deciding whether or not to use JIT compilation, you must make a balance between faster execution and increased processor usage during compilation.
• Application profiling
  You can learn a lot about your Java application by using the hprof profiling agent. Statistics about CPU and memory usage are presented along with many other options.
• Testing JVM optimizations
  Performance problems might be associated with new optimizations that have been introduced for this release.

Parent: Windows problem determination

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