Devoxx 2009: The not so Dark Art of Performance Tuning

19/11/2009, Kirk Pepperdine & Dan Hardiker

• loadtest <> stresstest:
  • loadtest: test user experience
  • stresstest: find when the application breaks
• performance anti-patterns & solutions:
  • lack of stress testing → introduce a stress test harness
    • repeatable test
    • control load
  • shot in the dark: fix ugly code
    • ugly code runs just fine
    • measure, don't guess!
• Apache JMeter → root node: “Test Plan”
  • Thread Group
    • set looping / # threads
  • HTTP Request
    • → variables: ${var}
      • defeat cache
      • vary testdata
  • Timer child for think-time→ e.g. Uniform Random Timer
  • aggregate report
  • view results tree → captures data of requests: e.g. don't measure 404 errors
• understand the environment, identify dominating consumer → look at the full system
  • actors: usage patterns
  • application
    • locks
    • external systems
  • jvm/os
    • memory
    • hardware management
    • tools e.g.:
      • vmstat on hpux
      • jps
      • jstack
      • visual vm (thread and heap dumps)
  • hardware
    • cpu
    • memory
    • disk I/O
    • network
• response time budgets:
  • detail the time of the different components → add customizable time measures
    • database
    • application server
    • client
• common problems, demo's:
  • poor response times, low cpu
    • thread pools
    • locks
    • → VisualVM, thread dump + plugin thread dump analyzer, identify lock