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JFokus Java 9 contended locking performance
The document discusses Java Development Kit (JDK) 9 enhancements, focusing on JEP 143, which improves the performance of contended locks compared to JDK 8. It outlines two performance approaches—top-down and bottom-up—along with benchmarking strategies to measure the impact of these improvements. The presentation concludes with observations and metrics demonstrating the enhanced performance in JDK 9.
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JFokus Java 9 contended locking performance
- 2. About Me Java/JVM/GC performanceperson Current Life: Consultant who solves Managed Runtime performance issues Past Life: Worked with Oracle, Sun,AMD… ©2017 CodeKaram1
- 3. Agenda • Setting thestage • A quick glance at JDK 9 JEPs • Building a problem statement • Studying JEP 143 – Improve contended locking ©2017 CodeKaram2
- 4. Agenda • Quick overviewof top-down and bottom-up performance approaches • Choosing the right approach! • Building our arsenal! ©2017 CodeKaram3
- 5. Agenda • Observing thetargeted improvements • Demo comparing JDK 9 with JDK 8 • Summarizing the observations ©2017 CodeKaram4
- 6. Setting The Stage ©2017CodeKaram5
- 7. JEPs in JDK9 ©2017 CodeKaram6 There are 89 total JEPs in JDK 9
- 8. JEPs in JDK9 …and contended locking performanceimprovement (JEP143) is one of them J ©2017 CodeKaram7
- 9. What is JEP143? ©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 ©2017CodeKaram9
- 11. Summary of JEP143 ©2017 CodeKaram10 “Improve the performance of contended Java object monitors”
- 12. ©2017 CodeKaram11 “Improve theperformance of contended Java object monitors” Summary of JEP 143
- 13. Uncontended Locks ©2017 CodeKaram12 Asingle thread ‘t’ is executing a synchronized method
- 14. Contended Locks ©2017 CodeKaram13 Adifferent thread ‘u’ wants to enter the synchronized method that is already locked by thread ‘t’
- 15. Contended Locks ©2017 CodeKaram14 Thisis a heavy weight lock also known as inflated lock Object Monitor maintains “WaitSet” for threads waiting for the contended lock
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- 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
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- 20. What areYouTrying toAchieve? ©2017 CodeKaram19 Improve application?
- 21. Top-Down Approach ©2017 CodeKaram20 OS Hardware ApplicationEcosystem Application JRE JVM
- 22. Top Down Approach- Process •Step 1Monitor •Step 2 Profile •Step 3Analyze •Step 4 Tune + Apply
- 23.
- 24. What areYouTrying toAchieve? ©2017 CodeKaram23 Improve the platform?
- 25. Bottom-Up Approach ©2017 CodeKaram24 OS Hardware ApplicationEcosystem 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 WhatAreWeTryingTo Do? ©2017 CodeKaram27
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- 30. Bottom Up Approach ©2017CodeKaram29 I NEED the power!! … to stress the platform
- 31. Setting Up For Benchmarking ©2017CodeKaram30
- 32. Where to Start? ©2017CodeKaram31 • Know what you are stressing • Get/ write the appropriate workload/ application • Get/write the appropriate tools
- 33. Know What You’re Stressing… ©2017CodeKaram32
- 34. Speed UpTargets ©2017 CodeKaram33 •PlatformEvent::unpark() • Java monitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
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- 36. FromThe JEP … ©2017CodeKaram35 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 ©2017CodeKaram36 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 ©2017CodeKaram37 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? ©2017CodeKaram38 Ensure that you are in fact measuring contended object monitor performance!
- 40. How DoWe DoThat? ©2017CodeKaram39 Bypass biased locking: Use -XX:-UseBiasedLocking Bypass stack based locking: Use -XX:+UseHeavyMonitors
- 41. Get/Write The Appropriate Tools… ©2017 CodeKaram40
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- 43. Profiling with ‘collect’ ©2017CodeKaram42 • -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
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- 45. Speed UpTargets ©2017 CodeKaram44 •PlatformEvent::unpark() • Java monitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
- 46. Demo - Comparing ContendedLocking in JDK 9 to JDK 8 ©2017 CodeKaram45
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- 48. Speed UpTargets ©2017 CodeKaram47 •PlatformEvent::unpark() •Java monitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
- 49. ©2017 CodeKaram48 JDK 9ExclusiveTime JDK8 ExclusiveTime Method Name 0.400 0.941 os::PlatformEvent::unpark() Unpark
- 50. ImprovementTargets ©2017 CodeKaram49 • PlatformEvent::unpark() •Javamonitor enter operations • Java monitor exit operations • Java monitor notify/notifyAll operations
- 51. ©2017 CodeKaram50 JDK 9ExclusiveTime 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 9ExclusiveTime 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 leavethat as a take-home exercise for you all! J Notify/ NotifyAll
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