Project Valhalla Update - JVMLS Feedback

This material was used at JVMLS feedback in Tokyo, Osaka, and Fukuoka (August 9, 23, and 30).

Transcript

1. Project Valhalla Update JVM Language Summit Feedback #JVMLS_jp
2. Agenda
3. Project Valhalla
4. Project Valhalla - Reboot JVM relationship with data in memory
5. Project Valhalla - Reboot JVM relationship with data in memory  Value Types  Generic Specialization
6. Will be discussed in JVMLS 2020...
7. Why are flatter and denser memory layouts required? e.g. Intel Broadwell-EP L1 L2 Main Memory Intel® 64 and IA-32 Architectures Optimization Reference Manual https://software.intel.com/sites/default/files/managed/9e/bc/64-ia-32-architectures-optimization-manual.pdf L3 Cache
8. For example... class Point { int x; int y; } public class App { ... Point[] points = new Point[5]; points[0] = new Point(); ... }
9. As is... header x y header x y header x y header x y header x y header
10. To be... header x y header x y header x y header x y header x y header header x y x y x y x y x y
11. Who cares about project Valhalla?
12. Value Type is available in CLR System.ValueType https://docs.microsoft.com/ja-jp/dotnet/csharp/language-reference/keywords/value-types
13. What the project has done
14. Drilling from JVM side and programming model side L World Early prototypes (M1-M3) Compiler-only Exploring language side • Specialized generics, wildcards • Informed VM requirements • Many of these problems still require considerable work “MVT” prototype VM-only Exploring the “Q-World” model For more detail, check the JVMLS 2018 video! Current prototype VM and compiler support No support yet for specialized generics or migration Still drilling...
15. Q World Q qload
16. Worked, but...
17. L World a*
18. L World benefits
19. L World costs
20. Project status
21. Milestone L2 (LW2) https://wiki.openjdk.java.net/display/valhalla/LW2
22. LW2 prototype binary http://jdk.java.net/valhalla/
23. Inline class value class Point { int x; int y; } inline class Point { int x; int y; }
24. Compiler optimizations
26. Considerations
27. Construction defaultvalue withfield
28. class Point { int x; int y; Point() { this.x = 0; this.y = 0; } Point(int x, int y) { this.x = x; this.y = y; } } Point(int, int); descriptor: (II)V flags: (0x0000) Code: stack=2, locals=3, args_size=3 0: aload_0 1: invokespecial #1 // Method java/lang/Object."<init>":()V 4: aload_0 5: iload_1 6: putfield #7 // Field x:I 9: aload_0 10: iload_2 11: putfield #13 // Field y:I 14: return LineNumberTable: line 10: 0 line 11: 4 line 12: 9 line 13: 14
29. inline class Point { final int x; final int y; Point() { this.x = 0; this.y = 0; } Point(int x, int y) { this.x = x; this.y = y; } } static Point Point(int, int); descriptor: (II)QPoint; flags: (0x0008) ACC_STATIC Code: stack=2, locals=3, args_size=2 0: defaultvalue #1 // class Point 3: astore_2 4: iload_0 5: aload_2 6: swap 7: withfield #3 // Field x:I 10: astore_2 11: iload_1 12: aload_2 13: swap 14: withfield #7 // Field y:I 17: astore_2 18: aload_2 19: areturn LineNumberTable: line 10: 0 line 11: 4 line 12: 11 line 13: 18 }
30. Arrays
31. Default values Foo.default x = T.default x = null
32. Default values
33. Flattening Value types are flattenable, but flattening is not mandatory in every scene.
34. Flattening V? ( http://hg.openjdk.java.net/valhalla/valhalla/file/a32457198d 3e/test/jdk/valhalla/valuetypes/NonFlattenValue.java public inline class NonFlattenValue { Point? nfp; NonFlattenValue() { this.nfp = Point.makePoint(0,0); } NonFlattenValue(Point p) { this.nfp = p; } public Point? point() { return nfp; } public Point pointValue() { return (Point) nfp; } ... }
35. Generics – specialized and erased Foo<V> Foo<V?>
36. New top types (not yet in LW2, under discussion)
37. New top types (not yet in LW2, under discussion) By bringing ref-ness and val-ness into the type system x instance of RefObject RefObject m() { ... } void m(RefObject o) { … } class Foo<T extents RefObject> { ... }
38. Nullity
39. Nullity Options
40. Equality
41. Equality Options
42. Migration https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/lang/doc- files/ValueBased.html https://docs.oracle.com/javase/jp/12/docs/api/java.base/java/lang/doc-files/ValueBased.html
43. Other identity-sensitive operations
44. Next action
45. Tons of things to do!
46. From Brian Goetz...
47. Resources
48. Resources https://youtu.be/1H4vmT-Va4o https://youtu.be/_26KZAegYRM https://youtu.be/49GUljUmGHg https://www.slideshare.net/DavidBuck7/valhalla-update-jjug-ccc-spring-2019