OPTIMIZING THE TICK STACK
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![Copyright 2018 Kirk Pepperdine
OBJECT ALLOCATION
jClarity
top of heap pointer
Foo Bar byte[]
▸ In multi-threaded apps, top...](https://image.slidesharecdn.com/troublewithmemory-181205085531/75/trouble-with-memory-32-2048.jpg?cb=1670351789)
![Copyright 2018 Kirk Pepperdine
TLAB ALLOCATIONS
jClarity
▸ Thread 1 -> Foo foo = new Foo(); byte[] array = new byte[N];
▸b...](https://image.slidesharecdn.com/troublewithmemory-181205085531/75/trouble-with-memory-34-2048.jpg?cb=1670351789)
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Trouble with memory
- 1. Copyright 2018 Kirk Pepperdine MEMORY THE TROUBLE WITH
- 2. Copyright 2018 Kirk Pepperdine jClarity ▸ Kirk Pepperdine ▸ Author of jPDM, a performance diagnostic model ▸ Author of the original Java Performance Tuning workshop ▸ Co-founded jClarity ▸ Building the smart generation of performance diagnostic tooling ▸ Bring predictability into the diagnostic process ▸ Co-founded JCrete ▸ The hottest unconference on the planet ▸ Java Champion(s) OUR MARKETING SLIDE
- 3. Copyright 2018 Kirk Pepperdine jClarity What is your performance trouble spot
- 4. Copyright 2018 Kirk Pepperdine jClarity > 70% of all applications are bottlenecked on memory
- 5. Copyright 2018 Kirk Pepperdine jClarity and no, Garbage Collection is not a fault!!!!
- 6. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity
- 7. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity Spring Boot
- 8. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity Cassandra
- 9. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity Cassandra or any big nosql solution
- 10. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity Apache Spark
- 11. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity Apache Spark or any big data framework
- 12. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity Log4J
- 13. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity Log4J or any Java logging framework
- 14. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity JSON
- 15. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity JSON With almost any Marshalling protocol
- 16. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity ECom caching products
- 17. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity ECom caching products Hibernate
- 18. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity ECom caching products Hibernate and so on
- 19. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity ECom caching products Hibernate and so on and so on
- 20. Copyright 2018 Kirk Pepperdine DO YOU USE jClarity ECom caching products Hibernate and so on and so on and so on
- 21. Copyright 2018 Kirk Pepperdine jClarity then you are very likely in this 70%
- 22. Copyright 2018 Kirk Pepperdine
- 23. Copyright 2018 Kirk Pepperdine PROBLEMS ▸ High memory churn rates ▸many temporary objects ▸ Large live data set size ▸inflated live data set size ▸ loitering ▸ Unstable live data set size ▸memory leak jClarity
- 24. Copyright 2018 Kirk Pepperdine WAR STORIES ▸ Reduced allocation rates from 1.8gb/sec to 0 ▸tps jumped from 400,000 to 25,000,000!!! ▸ Stripped all logging our of a transactional engine ▸Throughput jumped by a factor of 4x ▸ Wrapped 2 logging statements in a web socket framework ▸Memory churn reduced by a factor of 2 jClarity
- 25. Copyright 2018 Kirk Pepperdine ALLOCATION SITE jClarity Foo foo = new Foo(); forms an allocation site 0: new #2 // class java/lang/Object 2: dup 4: invokespecial #1 // Method java/lang/Object."<init>":()V ▸Allocation will (mostly) occur in Java heap ▸ fast path ▸ slow path ▸ small objects maybe optimized to an on-stack allocation
- 26. Copyright 2018 Kirk Pepperdine JAVA HEAP jClarity Eden Survivor (to) Tenured Java Heap ▸ Java Heap is made of; ▸ Eden - nursery ▸ Survivor - intermediate pool designed to delay promotion ▸ Tenured - to hold long lived data ▸ Each space contributes to a different set of problems ▸ All affect GC overhead
- 27. Copyright 2018 Kirk Pepperdine EDEN ALLOCATIONS jClarity top of heap pointer
- 28. Copyright 2018 Kirk Pepperdine OBJECT ALLOCATION jClarity top of heap pointer Foo foo = new Foo(); Bar bar = new Bar(); byte[] array = new byte[N];
- 29. Copyright 2018 Kirk Pepperdine OBJECT ALLOCATION jClarity top of heap pointer Foo foo = new Foo(); Bar bar = new Bar(); byte[] array = new byte[N]; Foo
- 30. Copyright 2018 Kirk Pepperdine OBJECT ALLOCATION jClarity top of heap pointer Foo foo = new Foo(); Bar bar = new Bar(); byte[] array = new byte[N]; Foo Bar
- 31. Copyright 2018 Kirk Pepperdine OBJECT ALLOCATION jClarity top of heap pointer Foo foo = new Foo(); Bar bar = new Bar(); byte[] array = new byte[N]; Foo Bar byte[]
- 32. Copyright 2018 Kirk Pepperdine OBJECT ALLOCATION jClarity top of heap pointer Foo Bar byte[] ▸ In multi-threaded apps, top of heap pointer must be surrounded by barriers ▸single threads allocation ▸hot memory address ▸ solved by stripping (Thread local allocation blocks)
- 33. Copyright 2018 Kirk Pepperdine TLAB ALLOCATION jClarity top of heap pointer ▸ Assume 2 threads ▸each thread will have it’s own (set of) TLAB(s) TLAB TLAB TLAB pointerTLAB pointer
- 34. Copyright 2018 Kirk Pepperdine TLAB ALLOCATIONS jClarity ▸ Thread 1 -> Foo foo = new Foo(); byte[] array = new byte[N]; ▸byte[] doesn’t fit in a TLAB ▸ Thread 2 -> Bar bar = new Bar(); byte[]TLAB TLAB Foo Bar TLAB pointerTLAB pointer top of heap pointer
- 35. Copyright 2018 Kirk Pepperdine TLAB WASTE % jClarity ▸ Allocation failure to prevent buffer overflow ▸ waste up to 1% of a TLAB FooFoo Foo Foo Foo Foo Foo Foo
- 36. Copyright 2018 Kirk Pepperdine TLAB WASTE % jClarity ▸ Allocation failure to prevent buffer overflow ▸ waste up to 1% of a TLAB Foo Foo Foo Foo Foo Foo Foo Foo Foo
- 37. Copyright 2018 Kirk Pepperdine TENURED SPACE jClarity ▸ Allocations in tenured make use of a free list ▸free list allocation is ~10x the cost of bump and run ▸ Data in tenured tends to be long lived ▸amount of data in tenured do affect GC pause times Bar Bar Foo Foo Free List
- 38. Copyright 2018 Kirk Pepperdine PROBLEMS ▸ High memory churn rates ▸many temporary objects jClarity
- 39. Copyright 2018 Kirk Pepperdine PROBLEMS ▸ High memory churn rates ▸many temporary objects jClarity ▸Quickly fill Eden ▸ frequent young gc cycles ▸ speeds up aging ▸ premature promotion ▸more frequent tenured cycles ▸increased copy costs ▸increased heap fragmentation ▸Allocation is quick ▸ quick * large number = slow
- 40. Copyright 2018 Kirk Pepperdine REDUCING ALLOCATIONS jClarity > 1gb/sec < 300mb/sec sizeofgain
- 41. Copyright 2018 Kirk Pepperdine PROBLEMS ▸ High memory churn rates ▸many temporary objects ▸Large live data set size ▸ inflated live data set size ▸loitering jClarity
- 42. Copyright 2018 Kirk Pepperdine PROBLEMS ▸ High memory churn rates ▸many temporary objects ▸Large live data set size ▸ inflated live data set size ▸loitering jClarity ▸inflated scan for root times ▸reduced page locality ▸Inflated compaction times ▸ increase copy costs ▸ likely less space to copy too
- 43. Copyright 2018 Kirk Pepperdine PAUSE VS OCCUPANCY jClarity
- 44. Copyright 2018 Kirk Pepperdine PROBLEMS ▸ High memory churn rates ▸many temporary objects ▸Large live data set size ▸ inflated live data set size ▸loitering ▸Unstable live data set size ▸ memory leak jClarity
- 45. Copyright 2018 Kirk Pepperdine PROBLEMS ▸ High memory churn rates ▸many temporary objects ▸Large live data set size ▸ inflated live data set size ▸loitering ▸Unstable live data set size ▸ memory leak jClarity ▸Eventually you run out of heap space ▸ each app thread throws an OutOfMemoryError and terminates ▸JVM will shutdown with all non- daemon threads terminate
- 46. Copyright 2018 Kirk Pepperdine jClarity Escape Analysis
- 47. Copyright 2018 Kirk Pepperdine Demo time jClarity
- 48. Copyright 2018 Kirk Pepperdine TEXT TITLE TEXT ▸ Body Level One ▸ Body Level Two ▸ Body Level Three ▸ Body Level Four ▸ Body Level Five Ask out my Java Performance Tuning Workshop Send us a Java 11 GC log or tweet about @jclarity and #censum and receive a free Censum License
