Project Panama - Beyond the (JVM) Wall

https://middleofnowheregaming.ﬁles.wordpress.com/2015/04/game-of-thrones_20150327091828.jpg
Project Panama
Beyond the (JVM) Wall

www.hazelcast.com@noctarius2k
Disclaimer
This is not a rant - promised!
Just a little bit about JNI ;-)

Disclaimer #2
If you haven’t seen Game of Thrones yet 
keep your eyes closed!

Disclaimer #3
Everything is provisional
Don’t take anything as ﬁnal!

Who’s that dude?
• Chris Engelbert
• Manager of Developer Relations @Hazelcast
• Java-Passionate (10+ years)
• Performance
• Garbage Collection
• JVM / Benchmark Fairytales

I drink and I know things (sometimes)

Project Panama
The True Native Love

Unite Enemies
C/C++Java

JNI! That's a good name for you!

JNI brings interaction between
native code and Java
#include <unistd.h>
int pid = getpid();
simple kernel call

#include <unistd.h>
int pid = getpid();
simple kernel call header import

#include <unistd.h>
int pid = getpid();
simple kernel call header import
request PID

#include <unistd.h>
int pid = getpid();
Isn’t that easy in C?

You know nothing, of JNI!

Starting with the C part :-)

extern C {
JNIEXPORT int JNICALL
Java_ProcessIdentiﬁer_getProcessId(JNIEnv *, jobject);
}

extern C {
}
export it as a JNI method

extern C {
}
Java Classname

extern C {
}
Java Classname Java Methodname

extern C {
}
Java_ProcessIdentiﬁer_getProcessId(JNIEnv *env, jobject thisObject) {
return getpid();
}

extern C {
}
return getpid();
}
kernel call

When you think you just won…

extern C {
}
return getpid();
}
JNIEXPORT jint JNICALL
JNI_OnLoad(JavaVM *vm, void *reserved) {
return JNI_VERSION_1_2;
}

extern C {
}
return getpid();
}
}
JNI version deﬁnition

extern C {
}
return getpid();
}
done, easy right?
}

extern C {
}
return getpid();
}
oh, missing the Java side, still
}
public class ProcessIdentiﬁer {
static {
System.loadLibrary("processidentiﬁer");
}
public native void getProcessId();
}

extern C {
}
return getpid();
}
}
static {
}
}
Java Classname

extern C {
}
return getpid();
}
}
static {
}
}

extern C {
}
return getpid();
}
ok, ok, now we’re done!
}
static {
}
}

Wasn’t that easy?

Wasn’t that easy?
but remember…

Everybody struggles with JNI!

meanwhile behind 
the wall…

Java 9 to the rescue

long pid = ProcessHandle.current().getPid();

long pid = ProcessHandle.current().getPid();
convenient, eh?

but how many can
just update?

So? JNI?

So? JNI? - NO!

A Song From Methods And Handles

MethodHandles
MethodType type = MethodType.methodType(int.class);
MethodHandle mh = MethodHandles.lookup()
.ﬁndVirtual(ProcessIdentiﬁer.class, "getProcessId", type);
int pid = mh.invokeExact();

MethodHandles
type deﬁnition

MethodHandles
returntypetype deﬁnition

MethodHandles
Java Classname

MethodHandles

MethodHandles
Java Classname Java Methodnamecall the new callsite

MethodHandles
So? What’s the deal? Java 7, right?

MethodHandles
virtual call

MethodHandles
.ﬁndNative(null, "getpid", type);
native

MethodHandles
native
native call

MethodHandles
native
native call null = kernel call 
otherwise lib name

Easier than taking
the Iron Throne!

The Mad King

Pointer with sun.misc.Unsafe
Unsafe unsafe = getUnsafeWithMagic();
long ptr = unsafe.allocateMemory(20);
byte val = unsafe.getByte(ptr + 5);

retrieve sun.misc.Unsafe instance

allocate 20 bytes

allocate 20 bytesget byte at ptr+5

So I die, for using Unsafe?

Who needs Unsafe anyways
LayoutType<Byte> layout =
NativeLibrary.createLayout(byte.class);
try (Scope scope = new NativeScope()) {
Pointer<Byte> p = scope.allocate(layout, 20);
Reference<Byte> ref = p.offset(5).deref();
byte val = ref.get();
}

}
byte-array
layout

}
byte-array
layout
create a
scope

}
byte-array
layout
create a
scope
allocate 
20 bytes

}
byte-array
layout
create a
scope
allocate 
20 bytes
get byte 
at ptr+5

A REAL NULL POINTER! THANK YOU JAVA!

About Structs and
other Creatures

Struct in Java? No, Layout!
typedef struct {
int32_t val;
Node next;
} Node;

Same LinkedList Node in Java
@LayoutDesc({"x:jint:4", "y:Node:8"})
public interface Node extends Layout {
// …
}

interface EffectiveAddress {
IntPointer val();
Pointer<Node> next();
}
// …
}

Node.EffectiveAddress EA();
long sizeof();
int val();
// …
}

Node next();
void val(int val);
void next(Node next);
String toString();
}

Scope scope = new NativeScope();
Pointer<Node> ptr = scope.allocate(Node.class);
Node node = ptr.getLayout();
int val = node.val();
Node next = node.next();
Creating layouted Objects

I slayed the Mad King

Value Isn’t A Pit. Value Is A Ladder.

Value Types
value class Point {
int x;
int y;
}

Value Types
Point point = __make Point(1, 2);
int x = point.x;
int y = point.y;

Yet another layout?

class Point {}
Point[] points = …
Arrays of Points

value class Point {}
Point[] points = …
Arrays of Points

I’m feeling so Assembler today

Coding a Vector-Function in Java
MethodType type = MethodType.methodType(
Float.class, Float.class, Float.class);
MethodHandle m256_vadds = CodeSnippets
.make(..., type, …);
m256_vadds.invokeExact(out, in1, in2);
low-level

high-level
interface Vector<E, S extends Shape<Vector?, S>> {
Vector<E, S> add (Vector<E, S> other);
Vector<E, S> mul (Vector<E, S> other);
Vector<E, S> and (Vector<E, S> other);
// ... more operations
}

high-level
void addVector(float[] left, float[] right,
float[] res, int length) {
// …
}

high-level
FloatVector<S256Bit> l =
ﬂoat256FromArray(left, length);
FloatVector<S256Bit> r =
ﬂoat256FromArray(right, length);
// …
}

high-level
// …
FloatVector<S256Bit> lr = l.add(r);
lr.intoArray(res, length);
}

Razersharp tooling

So what do we expect?

Peace with the Dragons

Peace with the Dragons
C / C++

Painless communication…

Painless communication…
…between native and Java code

More fun…

More fun…
… and faster code …

More fun…
…without JNI
… and faster code …

Thank You &
George R.R. Martin

More information:
• http://openjdk.java.net/projects/valhalla/
• http://openjdk.java.net/projects/panama/
• http://cr.openjdk.java.net/~jrose/values/values-0.html
• http://blog.codefx.org/java/dev/the-road-to-valhalla/
• http://openjdk.java.net/jeps/191
• https://www.youtube.com/watch?v=JR1zI5gLhRM
• https://github.com/J9Java/panama-layout-prototype
• https://developer.ibm.com/open/openprojects/project-panama-layout-prototype/
• https://www.youtube.com/watch?v=Tc9vs_HFHVo
• https://www.youtube.com/watch?v=Z2XgO1H6xPM
Thank You!

Thank You!
Any Questions?
@noctarius2k
http://www.sourceprojects.org
http://github.com/noctarius
@hazelcast
http://www.hazelcast.com
http://www.hazelcast.org
http://github.com/hazelcast

German
speaking?
JVM related talk
on Slack
Get your own invite at:
https://slackin-jvm-german.herokuapp.com

Project Panama - Beyond the (JVM) Wall

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