Ryan Sciampacone IBM Managed Runtime Architect 29 th July Packed Objects IBM Corporation

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1 Ryan Sciampacone IBM Managed Runtime Architect 29 th July 2013 Packed Objects 2013 IBM Corporation

2 Important Disclaimers THE INFORMATION CONTAINED IN THIS PRESENTATION IS PROVIDED FOR INFORMATIONAL PURPOSES ONLY. WHILST EFFORTS WERE MADE TO VERIFY THE COMPLETENESS AND ACCURACY OF THE INFORMATION CONTAINED IN THIS PRESENTATION, IT IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED. ALL PERFORMANCE DATA INCLUDED IN THIS PRESENTATION HAVE BEEN GATHERED IN A CONTROLLED ENVIRONMENT. YOUR OWN TEST RESULTS MAY VARY BASED ON HARDWARE, SOFTWARE OR INFRASTRUCTURE DIFFERENCES. ALL DATA INCLUDED IN THIS PRESENTATION ARE MEANT TO BE USED ONLY AS A GUIDE. IN ADDITION, THE INFORMATION CONTAINED IN THIS PRESENTATION IS BASED ON IBM S CURRENT PRODUCT PLANS AND STRATEGY, WHICH ARE SUBJECT TO CHANGE BY IBM, WITHOUT NOTICE. IBM AND ITS AFFILIATED COMPANIES SHALL NOT BE RESPONSIBLE FOR ANY DAMAGES ARISING OUT OF THE USE OF, OR OTHERWISE RELATED TO, THIS PRESENTATION OR ANY OTHER DOCUMENTATION. NOTHING CONTAINED IN THIS PRESENTATION IS INTENDED TO, OR SHALL HAVE THE EFFECT OF: - CREATING ANY WARRANT OR REPRESENTATION FROM IBM, ITS AFFILIATED COMPANIES OR ITS OR THEIR SUPPLIERS AND/OR LICENSORS IBM Corporation

3 Problem IBM Corporation

4 Problem? What problem? JNI just isn t a great way to marshal data Locality in Java can matter (e.g., JEP 142) Existing native and data placement stories aren t very good In many cases, legacy systems exist the interop is just terrible So we want something that integrates well with the Java language and helps us IBM Corporation

5 Native Access Java Native anobject int[] d int int int int int Object header Object field / data Fighting the Java/Native interface IBM Corporation

6 Everything is an Object Array (object) Hash table Entry key Object header (object) Object field / data value IBM Corporation

7 Everything is an Object Array (object) Hash table Entry key Object header (object) Object field / data value IBM Corporation

8 Everything is an Object Array (object) Hash table Entry key Object header (object) Object field / data value IBM Corporation

9 Everything is an Object Array (object) Hash table Entry key Object header (object) Object field / data value IBM Corporation

10 Object Internals Object header Hot fields. Object field / data Field ordering has performance implications JVM can potentially reorder your fields for you IBM Corporation

11 Establishing Goals On heap / off heap seamless referencing of data Ability to do away with headers Ability to bring related objects close together This actually sounds a lot like C structure types struct Address { char[4] addr; short port; } struct Header { struct Address src; struct Address dst; } struct Header addr port addr port Address src Address dst Packed Objects! IBM Corporation

12 Basics IBM Corporation

13 Packed Objects: Under the covers Object header Object field / data apoint IBM Corporation

14 Packed Objects: Under the covers Object header Object field / data apoint apackedpoint IBM Corporation

15 Packed Objects: Under the covers Object header Object field / data apoint apackedpoint IBM Corporation

16 Packed Objects: In Practice Object header apoint Object field / data aline Point s Point e apoint IBM Corporation

17 Packed Objects: In Practice apoint apackedline Object header Object field / data aline Point s Point e apoint IBM Corporation

18 Packed Objects: In Practice apoint apackedline Object header Object field / data aline Point s Point e apoint apackedpoint s apackedpoint e IBM Corporation

19 Packed Objects: In Practice apoint apackedline Object header Object field / data aline Point s Point e apoint apackedpoint s apackedpoint final class PackedPoint extends PackedObject { ; ; final class PackedLine extends PackedObject { PackedPoint s; PackedPoint e; } IBM Corporation

20 Packed Objects: In Practice apoint apackedline Object header Object field / data aline Point s Point e apoint IBM Corporation

21 Packed Objects: In Practice apoint apackedline Object header Object field / data aline Point s Point e apoint apackedline.e IBM Corporation

22 Packed Objects: In Practice apoint apackedline Object header Object field / data aline Point s Point e apoint apackedpoint apackedline.e IBM Corporation

23 Packed Objects: In Practice with Arrays anarrayofpackedpoints Object header Object field / data. apackedpoint IBM Corporation

24 Packed Objects: In Practice with Native Access Java Native Object header Struct field / data struct Point { ; ; } IBM Corporation

25 Packed Objects: In Practice with Native Access Java Native Object header Struct field / data final class PackedPoint extends PackedObject { ; ; } struct Point { ; ; } IBM Corporation

26 Packed Objects: In Practice with Native Access Java Native Object header Struct field / data apackedpoint final class PackedPoint extends PackedObject { ; ; } struct Point { ; ; } IBM Corporation

27 Advantages IBM Corporation

28 Lets Build Something in C! struct Address { char[4] addr; short port; } struct Header { struct Address src; struct Address dst; } struct Header addr port addr port Address src Address dst Nested substructures Compact Alignment IBM Corporation

29 Let s Build the Same Something in Java! Address byte[] class Address { byte[] addr; short port; } class Header { Address src; Address dst; } Header Address src Address dst addr port Address addr port addr byte[] addr Headers Locality Alignment IBM Corporation

30 What does the Java code look like under the covers? Bytecodes: aload1 getfield Header.dest LAddress; getfield Address.addr [B iconst0 baload bipush 192 ificmpeq... JIT (32 bit): mov EBX, dword ptr -4[ECX] mov EBX, dword ptr 8[EBX] mov EBX, dword ptr 4[EBX] movsx EDI, byte ptr 8[EBX] cmp EDI, 192 // load temp1 // load dest // load addr // array[0] From a code point of view, this isn t terrible IBM Corporation

31 What if we did this with Packed final class Address extends PackedObject { PackedByte[[4]] addr; short port; final class PacketHeader extends PackedObject { Address src; Address dest; } apackedheader addr port addr port Address src Address dst The Java code is pretty clean and a pretty good result! IBM Corporation

32 Ok, what about the code under the covers? Bytecodes: aload1 getfield PackedHeader.dest LAddress; getfield Address.addr [B iconst0 baload bipush 192 ificmpeq... JIT (32 bit): mov EBX, dword ptr -4[ECX] // load temp1 mov EAX, dword ptr 4[EBX] // load mov EDX, dword ptr 8[EBX] // load lea EBX, dword ptr [EAX + EDX] movsx EDI, byte ptr 0[EBX] // array[0] cmp EDI, 192 Bytecodes don t change JIT code is pretty good too! IBM Corporation

33 What about native access? Java Native anobject addr port addr port How do we implement this normally? IBM Corporation

34 JNI implementation Usual stash pointers in long types tricks JNI costs tend to be high IBM Corporation

35 JNI implementation Usual stash pointers in long types tricks JNI costs tend to be high IBM Corporation

36 Unsafe implementation You shouldn t be here Keeping your indices straight is never fun IBM Corporation

37 DirectByteBuffer implementation No extra JNI to write (this is good) Still playing the indices game IBM Corporation

38 PackedObject answer apackedheader Ø addr port addr port Looks like natural Java code Foregoes JNI Same type capable of on-heap representation IBM Corporation

39 Challenges IBM Corporation

40 Identity Crisis Java Native apackedline Ø anotherpackedline Ø What does apackedline == anotherpackedline mean? The data is what really matters 2013 IBM Corporation

41 Synchronization Java Native apackedline Ø anotherpackedline Ø 2013 IBM Corporation

42 Synchronization Java Native apackedline Ø anotherpackedline apackedline.e.x = 10 anotherpackedline.e.x = 13 Ø Thread T1: synchronized (apackedline) { apackedline.e.x = 10; } Thread T2: synchronized (anotherpackedline) { anotherpackedline.e.x = 13; } 2013 IBM Corporation

43 Finalization apackedpoint apackedline IBM Corporation

44 Finalization apackedpoint apackedline IBM Corporation

45 Finalization apackedpoint apackedline Finalization? IBM Corporation

46 Finalization apackedpoint apackedline Finalization? Finalization? IBM Corporation

47 Finalization Java Native apackedline Ø anotherpackedline Finalization? Ø 2013 IBM Corporation

48 Nested Data Structures apackedline.s = apackedpoint; apackedline PackedPoint s PackedPoint e apackedpoint IBM Corporation

49 Nested Data Structures apackedline.s := apackedpoint; apackedline PackedPoint s PackedPoint e apackedpoint Base types do share the same assignment operator Helps convey apackedline == anotherpackedline as meaningless IBM Corporation

50 Field final class PackedPoint extends PackedObject { ; ; } PackedPoint(, ) { } No no-argument final class PackedLine extends PackedObject { PackedPoint s; PackedPoint e; } PackedLine(int sx, int sy, int ex, int ey) { } Implicitly instantiates PackedPoint objects for s & e fields 2013 IBM Corporation

51 Field final class PackedPoint extends PackedObject { ; ; void init(, ) { this.x = x; this.y = y; } } PackedPoint(, ) { final class PackedLine extends PackedObject { PackedPoint s; PackedPoint e; } PackedLine(int sx, int sy, int ex, int ey) { s.init(sx, sy); e.init(ex, ey); } 2013 IBM Corporation

52 Advanced IBM Corporation

53 Modeling Native Data Pointers struct BinaryTreeNode { struct BinaryTreeNode* left; struct BinaryTreeNode* right; // data } Java abinarytreenode Ø Native *left *right <data> *left *right <data> *left *right <data> IBM Corporation

54 Modeling Native Data Pointers? abinarytreenode.right struct BinaryTreeNode { struct BinaryTreeNode* left; struct BinaryTreeNode* right; // data } Java abinarytreenode Ø Native *left *right <data> *left *right <data> *left *right <data> IBM Corporation

55 Modeling Native Data Pointers? abinarytreenode.right struct BinaryTreeNode { struct BinaryTreeNode* left; struct BinaryTreeNode* right; // data } Java abinarytreenode Ø Native *left *right <data> 32b or 64b? *left *right <data> *left *right <data> IBM Corporation

56 Modeling Native Data class BinaryTreeNode extends PackedObject BinaryTreeNode BinaryTreeNode right; // data } Annotation to mark a field as a native pointer (rather than a Java one) Enhance getfield / putfield to recognize Restrict for security reasons Unmanaged pointers (no GC involvement) IBM Corporation

57 Modeling Native Data Pointers Java Native abinarytreenode Ø *left *right <data> *left *right <data> abinarytreenode.right IBM Corporation

58 Modeling Native Data Pointers Java Native abinarytreenode Ø Ø *left *right <data> *left *right <data> abinarytreenode.right IBM Corporation

59 final class Address extends PackedObject { PackedByte[[4]] addr; short port; final class PacketHeader extends PackedObject { Address src; Address dest; } apackedheader addr port addr port IBM Corporation

60 final class Address extends PackedObject { PackedByte[[4]] addr; short port; final class PacketHeader extends PackedObject { Address src; Address dest; } apackedheader addr port addr port apackedheader addr port addr addr port Which is the correct default behavior? How do you get the alternate if that s what you want? IBM Corporation

61 Alignment class A { int i; short s; short padding; // align long l; } class A { int i; short long l; } IBM Corporation

62 Alignment class A { int i; short s; short padding; // align long l; } class A { int i; short long l; } Padding isn t quite right in the context of nested final class Address extends PackedObject { PackedByte[[4]] addr; short port; final class PacketHeader extends PackedObject Address Address dest; } IBM Corporation

63 final class SimpleValue extends PackedObject { int value; } Java Native asimplevalue Ø DE 37 C4 FE Provide a field IBM Corporation

64 Possibilities IBM Corporation

65 Let s look at transferring data Heap A C B IBM Corporation

66 Let s look at transferring data Heap A Remote Transfer C B IBM Corporation

67 Let s look at transferring data Heap A Remote Transfer C B IBM Corporation

68 Let s look at transferring data Heap A Remote Transfer C B IBM Corporation

69 PackedObjects could help Heap A Remote Transfer C B IBM Corporation

70 PackedObjects could help Heap Packed A A Remote Transfer C B B C IBM Corporation

71 PackedObjects could help Heap Packed Packed A A A Remote Transfer C B B B C C IBM Corporation

72 Making the data transfer easier Heap Remote Transfer IBM Corporation

73 Making the data transfer easier Heap Remote Transfer Specialized Heap Area IBM Corporation

74 Making the data transfer easier Heap C Remote Transfer A A B B C Specialized Heap Area IBM Corporation

75 Making the data transfer easier Heap C Remote Transfer A A B B C Specialized Heap Area IBM Corporation

76 Making the data transfer seamless Heap Remote Transfer Specialized Heap Area IBM Corporation

77 Making the data transfer seamless Heap A B C Remote Transfer A B A C B Specialized Heap Area C IBM Corporation

78 Making the data transfer seamless Heap A B Packed C Remote Transfer Packed A B A C B Specialized Heap Area C IBM Corporation

79 Questions? IBM Corporation

80 References Get Products and Technologies: IBM Java Runtimes and SDKs: IBM Monitoring and Diagnostic Tools for Java: Learn: IBM Java InfoCenter: Discuss: IBM Java Runtimes and SDKs Forum: IBM Corporation

81 Copyright and Trademarks IBM Corporation All Rights Reserved. IBM, the IBM logo, and ibm.com are trademarks or registered trademarks of International Business Machines Corp., and registered in many jurisdictions worldwide. Other product and service names might be trademarks of IBM or other companies. A current list of IBM trademarks is available on the Web see the IBM Copyright and trademark information page at URL: IBM Corporation

From Java Code to Java Heap Understanding the Memory Usage of Your Application

Chris Bailey IBM Java Service Architect 3 rd October 2012 From Java Code to Java Heap Understanding the Memory Usage of Your Application 2012 IBM Corporation Important Disclaimers THE INFORMATION CONTAINED