Java Performance Tuning

Performance Checklist

• Specify the required performance.

  • Ensure performance objectives are clear.

  • Specify target response times for as much of the system as possible.

  • Specify all variations in benchmarks, including expected response ranges (e.g., 80% of responses for X must fall within 3 seconds).

  • Include benchmarks for the full range of scaling expected (e.g., low to high numbers of users, data, files, file sizes, objects, etc.).

  • Specify and use a benchmark suite based on real user behavior. This is particularly important for multiuser benchmarks.

  • Agree on all target times with users, customers, managers, etc., before tuning.

• Make your benchmarks long enough: over five seconds is a good target.

  • Use elapsed time (wall-clock time) for the primary time measurements.

  • Ensure the benchmark harness does not interfere with the performance of the application.

  • Run benchmarks before starting tuning, and again after each tuning exercise.

  • Take care that you are not measuring artificial situations, such as full caches containing exactly the data needed for the test.

• Break down distributed application measurements into components, transfer layers, and network transfer times.

• Tune systematically: understand what affects the performance; define targets; tune; monitor and redefine targets when necessary.

  • Approach tuning scientifically: measure performance; identify bottlenecks; hypothesize on causes; test hypothesis; make changes; measure improved performance.

  • Determine which resources are limiting performance: ...