Post on 12-May-2015
description
transcript
Steve Poole IBM
Fast Talking Java Meets Native Code
THE INFORMATION CONTAINED IN THIS PRESENTATION IS PROVIDED FOR INFORMATIONAL PURPOSES ONLY.
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- CREATING ANY WARRANT OR REPRESENTATION FROM IBM, ITS AFFILIATED COMPANIES OR ITS OR THEIR SUPPLIERS AND/OR LICENSORS
Important Disclaimers
!Works at IBM’s Hursley Laboratory in the UK
Involved in IBM Java VM development since before Java was 1
Currently leading IBM’s OpenJDK technical engagement
Steve Poole
“Compact Off-Heap Structures in the Java Language”
“Packed Objects”
aka
What this talk is about
!This technology is being developed to help address important pressures on Java !This talk focuses on how to improve Java interop to Non Java applications
“Compact Off-Heap Structures in the Java Language”
You’ll learn
1. An overview of this technology 2. Why we need your input and support 3. How to get started with using this technology yourself
Part 1Native interoperability Why it’s so important
C
Interoperability - why is it important?
Java is built on talking native !
Operating Systems Processor Architectures File Systems User interfaces Network Interfaces !
Java keeps the WORA monsters away !
!
WORA - the components
Your Java application
JDK Java code
JVM JIT Class Library Native code
Your
JNI c
ode
native
2013 - Not so Java-centric
Your Java application
JDK Java code
JVM JITClass
Library Your
JNI c
ode
native
Your
Nat
ive
code
2013 - clusters and new processors
High speed memory channels (RDMA etc)
Specialised Processors (GPUs etc)
non Java Runtime
2013 - Can we survive with JNI 1.1?
Your Java application
JDK Java code
JVM JITClass
Library Your
JNI c
ode
native
Your
Nat
ive
code
High speed memory channels (RDMA etc)
Specialised Processors (GPUs etc)
Oth
er r
untim
e
?
??
• 1997 - JNI 1.1
• Designed for independence
• Version independence
• Platform Independence
• VM Independence
• Java at the centre of the world
• Not performance focused
2013 - we can’t survive with JNI 1.1
• What we need is
• To be able to share data between Java and other runtimes with minimal overhead
• To not require a Java centric data view
• and share data off-heap too!
• Can we do that?
• Time for a demo.
Packed Objects to the rescue
• Screensaver style
• Rectangles moved around the screen, bounce off the sides…
A simple demo
A simple demo
!15
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!
! typedef struct { int red,green,blue; float vx,vy; SDL_Rect rec; float x,y; ! } RECT;
RGB colour elements
position adjustment vectors
SDL structure contains location , height and width
float version of location - makes it easier to handle different h/w speeds
A simple demo
!16
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!
Initialise
Per frame
Update rectangle locations
Draw rectangles with SDL
terminate
!17
Demo Frames per second number of JNI calls per frame
Standard - all C code calling the SDL graphics routines
Mixed C and JNI. Java updates the location of each element
Mixed C with PackedObjects - Java updates the location of each element
More than one demo
Demo 1 - all C
!18
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!
Initialise
Per frame
Update rectangle locations
Draw rectangles with SDL
terminate
!19
Demo Frames per second number of JNI calls per frame
Standard - all C code calling the SDL graphics routines 20 0
Mixed C and JNI. Java updates the location of each element
Mixed C with PackedObjects - Java updates the location of each element
Results
Demo 2- Mixed JNI and C
!20
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!
Initialise
Per frame
Update rectangle locations
Draw rectangles with SDL
terminate
!21
Demo Frames per second number of JNI calls per frame
Standard - all C code calling the SDL graphics routines 20 0
Mixed C and JNI. Java updates the location of each element
Mixed C with PackedObjects - Java updates the location of each element
Results
!22
Demo Frames per second number of JNI calls per frame
Standard - all C code calling the SDL graphics routines 20 0
Mixed C and JNI. Java updates the location of each element 11 200000
Mixed C with PackedObjects - Java updates the location of each element
Results
200 000 JNI calls per frame. Copying data, validating data everytime.
AND ensuring there is no chance of optimization by the JIT.
(~4MB per frame)
(~4MB per frame)
Demo 2- Details
!23
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!
Initialise
Per frame
Update rectangle locations
Draw rectangles with SDL
terminate
Demo 2- Details
!24
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!for every rectangle…
C function calls Java method via JNI passes in x,y, vx and vy (by copy) Java method updates the rectangles new position Java native calls native method passing in new x,y, vx and vy values (by copy) C native method returns Java method returns C function returns
Demo 3 - Packed Objects
!25
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!
Initialise
Per frame
Update rectangle locations
Draw rectangles with SDL
terminate
!26
Demo Frames per second number of JNI calls per frame
Standard - all C code calling the SDL graphics routines 20 0
Mixed C and JNI. Java updates the location of each element 11 200000
Mixed C with PackedObjects - Java updates the location of each element
Results(~4MB per frame)
(~4MB per frame)
!27
Demo Frames per second number of JNI calls per frame
Standard - all C code calling the SDL graphics routines 20 0
Mixed C and JNI. Java updates the location of each element 11 200000
Mixed C with PackedObjects - Java updates the location of each element
18 1
Results(~4MB per frame)
(~4MB per frame)
(4 bytes per frame)
Demo 3 - Packed Objects
!28
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides
!
Initialise
Per frame
Update rectangle locations
Draw rectangles with SDL
terminate
Demo 3 - Packed Objects
!29
Draw 100 000 random sized rectangles using SDL !Move them around the screen and get them to change direction if they hit the sides !once per frame..
Java method updates each rectangle’s position directly !
for(Rectangle r: rectangles) { r.x=r.x+r.vx; r.y=r.y+r.vy; … }
Today Java only speaks Java
• Getting data into and out of Java has always required some form of marshaling or serialization process
!• Interaction with native data structures in memory is particularly problematic
• JNI is the slowest but safest – But you need good C / C++ knowledge
• Unsafe and NIO are faster but more challenging to use – They both have their own programming ‘model’
• If the Java side is in control of storage layouts it’s easier
• When mapping existing native structures it’s much, much, much more difficult
!• Ironically the JVM is completely aware of native data formats
Tomorrow, with Packed Objects..
! typedef struct { int red,green,blue; float vx,vy; SDL_Rect rec; float x,y; ! } RECT;
Java will let you reference data stored like this
C structure
Tomorrow, with Packed Objects..
! typedef struct { int red,green,blue; float vx,vy; SDL_Rect rec; float x,y; ! } RECT;
! public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; ! }
as if it looked like this
C structure Java structure
Tomorrow, with Packed Objects..
! typedef struct { int red,green,blue; float vx,vy; SDL_Rect rec; float x,y; ! } RECT;
! public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; ! }
C structure Java structure
without copying
!!!!!!!!!!!‘C’ runtime
!!!!!!!!!!!Java heap
Tomorrow, with Packed Objects..
! typedef struct { int red,green,blue; float vx,vy; SDL_Rect rec; float x,y; ! } RECT;
! public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; ! }
And off heap
Part 2Under the covers
http://www.flickr.com/photos/mwichary/
! public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; ! }
Let’s look at these classes from a JVM point of view..
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!Java heap
!37
int red int green int blue float vx float vy SLDRect ptr float x float y
short x short y int width int height
Java structure
! public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; ! }
public class SDLRect { short x,y int width,height } J
Under the covers
!!!!!!!!!!!Java heap
!38
int red int green int blue float vx float vy SLDRect ptr float x float y
short x short y int width int height
Questions !1 - How does a JVM ‘know’ the class of these objects? !!2 - What are the data format rules for these types? !!3 - When synchonizing on a object - where is the monitor stored?
!!!!!!!!!!!Java heap
!39
int red int green int blue float vx float vy SLDRect ptr float x float y
short x short y int width int height
Answers !1 - How does a JVM ‘know’ the class of these objects?
Additional internal ptr !2 - What are the data format rules for these types?
JVM impl specific (including ordering)
3 - When synchonizing on a object - where is the monitor stored?
Additional internal field
class ptr monitor
class ptr monitor
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
!!!!!!!!!!!Java heap
!40
int red int green int blue float vx float vy SLDRect ptr float x float y
short x short y int width int height
class ptr monitor
class ptr monitor
No space for the extra Java fields - what do we do?
No space for the extra Java fields - what do we do?
How to add the metadata
!!!!!!!!!!!Java heap
!41
public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; }
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
!!!!!!!!!!!Java heap
!42
public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; }
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
Rectangle r=PackedObject.newNativePackedObject(Rectangle.class,0x******);
!!!!!!!!!!!Java heap
!43
public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; }
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
class ptr monitor data ptr
“r”
Constructor was not called!
!!!!!!!!!!!Java heap
!44
public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; }
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
class ptr monitor data ptr
“r”
Rectangle r=PackedObject.newNativePackedObject(Rectangle.class,0x******);
SDLRect s=r.rect; !
!!!!!!!!!!!Java heap
!45
public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; }
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
class ptr monitor data ptr
“r”
Rectangle r=PackedObject.newNativePackedObject(Rectangle.class,0x******);
SDLRect s=r.rect; !
class ptr monitor data ptr
“s”
!!!!!!!!!!!Java heap
!46
public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; }
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
class ptr monitor data ptr
“r”
Rectangle r=PackedObject.newNativePackedObject(Rectangle.class,0x******);
SDLRect s=r.rect; SDLRect t=r.rect;
class ptr monitor data ptr
“s”
!!!!!!!!!!!Java heap
!47
public class Rectangle { ! int red,green,blue; float vx,xy; SDLRect rec; float x,y; }
public class SDLRect { short x,y int width,height }
Under the covers
!!!!!!!!!!!‘C’ runtime
[4] red [4] green [4] blue [4] vx [4] vy [2] rect.x [2] rect.y [4] rect.width [4] rect.height [4] x [4] y
class ptr monitor data ptr
“r”
Rectangle r=PackedObject.newNativePackedObject(Rectangle.class,0x******);
SDLRect s=r.rect; SDLRect t=r.rect;
class ptr monitor data ptr
“s”
class ptr monitor data ptr
“t”
Part 3Truth and Consequences
• Off heap Packed Objects are considered to already exist so constructors are not called.
• Since there is limited opportunity to store the vital metadata it is constructed when needed.
• The assumption is that creating new objects when accessing embedded data is confusing and dangerous.
• How does ‘==‘ work?
• What about synchronization?
• The idea of ‘identityless’ objects is being discussed.
• Something that PackedObjects has in common with ValueTypes
• Could you handle Objects of this style?
Design considerations
• This approach offers Java a way forward in the multi environment world
• Almost zero cost data interop will benefit Java when exploiting new processors and memory systems.
• There are additional use cases that ‘fall out’ from this design.
• Low cost r/w of files
• Instant application startup
• Basic unmanaged memory capabilities
• Under the covers heap usage benefits through better control for ‘locality of reference’
The way forward?
• IBM and Oracle have been discussing these sorts of concepts for some time
• We need your input. How important are these use cases to you? What’s missing, not needed? What do you hate?
• We are trying to keep clear of syntax discussions at this point - it’s too early and just distracting.
Is this the right or only way?
• Google for “IBM Java 8 Beta”
You too can use Packed Objects
The current prototype implementation surfaces a lot of the internals that will eventually just disappear
Hard hats must be worn…
This approach makes it easier for us to quickly revise the
design but means users of the prototype have to work harder.
!
AND !
it avoids syntax wars :-)picture courtesy http://www.flickr.com/people/karen_od/
“Compact Off-Heap Structures in the Java Language”
Wrap up -hopefully you now:
1. Have a basic understanding of this technology 2. Know why we need your input and support 3. Know how to get started with using this technology
Thank You