JFokus Java 9 contended locking performance
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At JavaOne keynote this year, Mark Reinhold talked about how Java 9 was much bigger than Jigsaw. To put that in numbers - 80+ JEPs bigger! Yes, we see more presentations on Jigsaw since it brings about modularity to the once monolithic JDK. But what about those other JEPs?! One of those "other" JEPs, is JEP 143 - 'Improve Contended Locking'. Monica will apply her performance engineering approach and talk about JEP 143 and Oracle's Studio Analyzer Performance Tool. The crux of the presentation will entail comparing performance of contended locks in JDK 9 to JDK 8.
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JFokus Java 9 contended locking performance
- 2. About Me Java/JVM/GC performance person Current Life: Consultant who solves Managed Runtime performance issues Past Life: Worked with Oracle, Sun,AMD… ©2017 CodeKaram1
- 3. Agenda • Setting the stage • A quick glance at JDK 9 JEPs • Building a problem statement • Studying JEP 143 – Improve contended locking ©2017 CodeKaram2
- 4. Agenda • Quick overview of top-down and bottom-up performance approaches • Choosing the right approach! • Building our arsenal! ©2017 CodeKaram3
- 5. Agenda • Observing the targeted improvements • Demo comparing JDK 9 with JDK 8 • Summarizing the observations ©2017 CodeKaram4
- 6. Setting The Stage ©2017 CodeKaram5
- 7. JEPs in JDK 9 ©2017 CodeKaram6 There are 89 total JEPs in JDK 9
- 8. JEPs in JDK 9 …and contended locking performanceimprovement (JEP143) is one of them J ©2017 CodeKaram7
- 9. What is JEP 143? ©2017 CodeKaram8 JEP 143 brings about improvements to contended locks* *In the past (Java 6) we have alreadyseen improvements to uncontendedlocksusing BiasedLockingtechnique.
- 10. Building A Problem Statement ©2017 CodeKaram9
- 11. Summary of JEP 143 ©2017 CodeKaram10 “Improve the performance of contended Java object monitors”
- 12. ©2017 CodeKaram11 “Improve the performance of contended Java object monitors” Summary of JEP 143
- 13. Uncontended Locks ©2017 CodeKaram12 A single thread ‘t’ is executing a synchronized method
- 14. Contended Locks ©2017 CodeKaram13 A different thread ‘u’ wants to enter the synchronized method that is already locked by thread ‘t’
- 15. Contended Locks ©2017 CodeKaram14 This is a heavy weight lock also known as inflated lock Object Monitor maintains “WaitSet” for threads waiting for the contended lock
- 17. Wait Set ©2017 CodeKaram16 • A set of threads • At creation – empty set of threads • Can be manipulated only by: • Object.wait, Object.notify, Object.notifyAll
- 20. What areYouTrying to Achieve? ©2017 CodeKaram19 Improve application?
- 21. Top-Down Approach ©2017 CodeKaram20 OS Hardware Application Ecosystem Application JRE JVM
- 22. Top Down Approach - Process •Step 1Monitor •Step 2 Profile •Step 3Analyze •Step 4 Tune + Apply
- 24. What areYouTrying to Achieve? ©2017 CodeKaram23 Improve the platform?
- 25. Bottom-Up Approach ©2017 CodeKaram24 OS Hardware Application Ecosystem Application JRE JVM
- 26. Bottom Up Approach - Process •Step 1Monitor •Step 2 Profile •Step 3Analyze •Step 4 Tune + Apply
- 27. Choosing The Right Approach … ©2017 CodeKaram26
- 28. Improve the JVM What AreWeTryingTo Do? ©2017 CodeKaram27
- 30. Bottom Up Approach ©2017 CodeKaram29 I NEED the power!! … to stress the platform
- 31. Setting Up For Benchmarking ©2017 CodeKaram30
- 32. Where to Start? ©2017 CodeKaram31 • Know what you are stressing • Get/ write the appropriate workload/ application • Get/write the appropriate tools
- 33. Know What You’re Stressing… ©2017 CodeKaram32
- 34. Speed UpTargets ©2017 CodeKaram33 • PlatformEvent::unpark() • Java monitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
- 36. FromThe JEP … ©2017 CodeKaram35 LockLoops-JSR166-Doug-Sept2009 (was LockLoops): The benchmark compares multiple locking techniques For our purpose, we just need to test the contended locks.
- 37. Contended Locking Test ©2017 CodeKaram36 private static class BuiltinLockLoop extends LockLoop { final int loop(int n) { int sum = 0; while (n-- > 0) { synchronized (this) { v = LoopHelpers.compute1(v); } sum += LoopHelpers.compute2(v); } return sum; } }
- 38. Contended Locking Test ©2017 CodeKaram37 private static class BuiltinLockLoop extends LockLoop { final int loop(int n) { int sum = 0; while (n-- > 0) { synchronized (this) { v = LoopHelpers.compute1(v); } sum += LoopHelpers.compute2(v); } return sum; } }
- 39. Where to Next? ©2017 CodeKaram38 Ensure that you are in fact measuring contended object monitor performance!
- 40. How DoWe DoThat? ©2017 CodeKaram39 Bypass biased locking: Use -XX:-UseBiasedLocking Bypass stack based locking: Use -XX:+UseHeavyMonitors
- 41. Get/Write The Appropriate Tools … ©2017 CodeKaram40
- 42. Oracle Developer Studio Performance Tool ©2017 CodeKaram41
- 43. Profiling with ‘collect’ ©2017 CodeKaram42 • -j on: default for when target is Java • -p on: default clock-profiling rate of ~100 samples/second • -H on: heap tracing • -t <duration>: time over which to record data • -h <ctr_def>…: specify HW counter profiling
- 45. Speed UpTargets ©2017 CodeKaram44 • PlatformEvent::unpark() • Java monitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
- 46. Demo - Comparing Contended Locking in JDK 9 to JDK 8 ©2017 CodeKaram45
- 48. Speed UpTargets ©2017 CodeKaram47 •PlatformEvent::unpark() • Java monitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
- 49. ©2017 CodeKaram48 JDK 9 ExclusiveTime JDK8 ExclusiveTime Method Name 0.400 0.941 os::PlatformEvent::unpark() Unpark
- 50. ImprovementTargets ©2017 CodeKaram49 • PlatformEvent::unpark() •Java monitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
- 51. ©2017 CodeKaram50 JDK 9 ExclusiveTime JDK8 ExclusiveTime Method Name 97.678 187.001 ObjectMonitor::enter(Thread*) 2.462 3.432 ObjectMonitor::EnterI(Thread*) Monitor Enter
- 52. Speed UpTargets ©2017 CodeKaram51 • PlatformEvent::unpark() • Java monitor enter operations •Java monitor exit operations • Java monitor notify/notifyAll operations
- 53. ©2017 CodeKaram52 JDK 9 ExclusiveTime JDK8 ExclusiveTime Method Name 2.302 2.352 ObjectMonitor::exit(bool,…) 0.000 0.961 ObjectMonitor::ExitEpilog(Thread* ,…) Monitor Exit
- 54. Speed UpTargets ©2017 CodeKaram53 • PlatformEvent::unpark() • Java monitor enter operations • Java monitor exit operations •Java monitor notify/notifyAll operations
- 55. ©2017 CodeKaram54 I’ll leave that as a take-home exercise for you all! J Notify/ NotifyAll