Java Performance Boost
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There are many factors that may lead to slow performance of Java code. This presentation helps identify and overcome them. This presentation by Andrii Antilikatorov (Lead Software Engineer, GlobalLogic) was delivered at Java.io 3.0 conference in Kharkiv on March 23, 2016, and GlobalLogic Mykolaiv Java Conference on June 11, 2016.
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Java Performance Boost
- 2. 2 Java Performance Boost By Andrii Antilikatorov
- 3. 3
- 4. 4 Optimize or not optimize?
- 5. 5 Rule
- 6. 6
- 7. 7
- 8. 8 Avoid usage byte[] to String constructor (Java 6)
- 9. 9 Avoid usage byte[] to String constructor (Java 6) • Update to Java 7 or later • Minimize usage of constructor
- 10. 10 Understanding of “switch on String”
- 11. 11 String Internation String String String String String String String String String String StringString Do not use String.intern() on Java 6 Internation is efficient on Java 7 and above Works great in multithreaded code JVM string pool is NOT thread local String
- 12. 12 String Deduplication Available from Java 8 update 20 Requires G1 collector to be enabled. Optional phase of G1. Unlikely to run on the loaded systems Processes only strings that survived after few garbage collections Doesn’t mean you shouldn’t use internation String String String String String String String String String String StringString String
- 13. 13 String Deduplication Available from Java 8 update 20 Requires G1 collector to be enabled. Optional phase of G1. Unlikely to run on the loaded systems Processes only strings that survived after few garbage collections Doesn’t mean you shouldn’t use internation String String String String String String String String String String StringString String String before Java 7 update 6 • char [] symbols; • Offset • Count • Hash code
- 14. 14 String Deduplication Available from Java 8 update 20 Requires G1 collector to be enabled. Optional phase of G1. Unlikely to run on the loaded systems Processes only strings that survived after few garbage collections Doesn’t mean you shouldn’t use internation String String String String String String String String String String StringString String String before Java 7 update 6 • char [] symbols; • Offset • Count • Hash code This is very very long string which consumes a lot of memory… This is very very long string which consumes a lot of memory…
- 15. 15 String Deduplication Available from Java 8 update 20 Requires G1 collector to be enabled. Optional phase of G1. Unlikely to run on the loaded systems Processes only strings that survived after few garbage collections Doesn’t mean you shouldn’t use internation String String String String String String String String String String StringString String String after Java 7 update 6 • char [] symbols; • Hash code
- 16. 16 String Deduplication Available from Java 8 update 20 Requires G1 collector to be enabled. Optional phase of G1. Unlikely to run on the loaded systems Processes only strings that survived after few garbage collections Doesn’t mean you shouldn’t use internation String String String String String String String String String String StringString String • Serial • Parallel • Concurrent Mark Sweep (CMS) • Garbage-First (G1)
- 17. 17 Avoid heavy logic in static constructors
- 18. 18 Avoid heavy logic in static constructors
- 19. 19 Avoid heavy logic in static constructors
- 20. 20 Problem with inner classes
- 21. 21 Problem with inner classes
- 22. 22 Cost of method calls invokestatic invokevirtual invokeinterface invokespecial
- 23. 23 Cost of method calls invokestatic invokevirtual invokeinterface invokespecial Dependency Injection
- 24. 24 Maps & Sets - Hints Set: Map:
- 25. 25 Maps & Sets - Hints • emptyList/emptyMap/emptySet - for empty collections • singletonList/singletonMap/singleton Set - for collections containing a single element/pair
- 26. 26 Performance of Date/Time entities java.util.Date java.util.GregorianCalendar
- 27. 27 Performance of Date/Time entities 24 bytes 448 bytes java.util.Date java.util.GregorianCalendar
- 28. 28 Performance of Date/Time entities 24 bytes 448 bytes java.util.Date java.util.GregorianCalendar
- 29. 29 Synchronized block or synchronized method?
- 30. 30 Synchronized block or synchronized method? 0: aload_0 1: getfield 2: nop 3: iconst_m1 4: ireturn
- 31. 31 Synchronized block or synchronized method? 0: aload_0 1: dup 2: astore_1 3: monitorenter 4: aload_0 5: getfield 6: nop 7: iconst_m1 8: aload_1 9: monitorexit 10: ireturn 11: astore_2 12: aload_1 13: monitorexit 14: aload_2 15: athrow
- 32. 32 Thread-safe variants of List and Set Manual synchronization of operations with collections Use CopyOnWrite* collections
- 33. 33 Synchronized or volatile variables? Volatile variables are less expensive than synchronized Volatile are thread-safe for atomic operations Volatile acquires lock on variable, therefore not thread- safe for non-atomic operations Synchronized blocks have no performance impact if no synchronization required
- 34. 34 Synchronized or volatile variables? MESI Protocol • Modified • Exclusive • Shared • Invalid
- 35. 35 Summary Architecture first Remember rule 80/20 Don’t try to write ideal code from the beginning Don’t create bicycles Don’t optimize for particular platform