a post-apocalyptic sun.misc.unsafe world

http://www.superbwallpapers.com/fantasy/post-apocalyptic-tower-bridge-london-26546/

A Post-Apocalypticsun.misc.Unsafe

www.hazelcast.com@noctarius2k

DisclaimerThis talk is not going to be negative!

Who’s that dude?• Chris Engelbert • Manager of Developer Relations @Hazelcast

• Java-Passionate (10+ years)

• Performance • Garbage Collection • Benchmark Fairytales

sun.misc.Unsafe?

dangerous

low level

discourageperformance

platform specificpointers

UNSAFE

sun.misc.Scissors

“My precious.”

“My precious.”The Lord of the Rings

Internal Class of the JDK

Internal Class of the JDKand those are not intended for outside use :)

Used inside and outside the JDK / JRE

custom (64-bit)

memory allocation

fastmemory access

(de)serialization

minimizegc overhead

custommemory fences

efficientmemory layout(array element)

volatile semantics

Used inside and outside the JDK / JRE// Unsafe mechanicsprivate static final sun.misc.Unsafe U; private static final long QBASE; private static final long QLOCK; private static final int ABASE; private static final int ASHIFT; static { try { U = sun.misc.Unsafe.getUnsafe(); Class<?> k = WorkQueue.class; Class<?> ak = ForkJoinTask[].class; QBASE = U.objectFieldOffset (k.getDeclaredField("base")); QLOCK = U.objectFieldOffset (k.getDeclaredField("qlock")); ABASE = U.arrayBaseOffset(ak); int scale = U.arrayIndexScale(ak); if ((scale & (scale - 1)) != 0) throw new Error("data type scale not a power of two"); ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); } catch (Exception e) { throw new Error(e); } }}

example: java.util.concurrent.ForkJoinPool

“I’m the kind of the world!”

“I’m the kind of the world!”Titanic

## A fatal error has been detected by the Java Runtime Environment:## SIGSEGV (0xb) at pc=0x00000001067314b5, pid=25244, tid=5891## JRE version: Java(TM) SE Runtime Environment (8.0_05-b13) (build 1.8.0_05-b13)# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.5-b02 mixed mode bsd-amd64 compressed oops)# Problematic frame:# V [libjvm.dylib+0x5314b5] Unsafe_SetNativeAddress+0x36## An error report file with more information is saved as:# /Users/noctarius/git/hazelcast-only.idea/hs_err_pid25244.log## If you would like to submit a bug report, please visit:# http://bugreport.sun.com/bugreport/crash.jsp#

“Supercalifragilisticexpialidocious!”

“Supercalifragilisticexpialidocious!”Mary Poppins

MapDBNettyHazelcast

Cassandra Mockito

EasyMock

ScalaRobolectric

Grails

GsonNeo4j

Apache Ignite

Apache Spark

Apache KafkaApache Storm

Apache Continuum

Zookeeper

Dropwizard

Byte Buddy

Hibernate

Liquibase

Spring Framework

Ehcache

OrientDB

Chronicle

Apache Hadoop

Apache HBase GWTDisruptor

JRubyAkka

Agrona

AeronSimple Binary Encoding

XRebel

Presto

XStream

CapLogic

WildFly

Infinispan

MapDBNettyHazelcast

Cassandra Mockito

EasyMock

ScalaRobolectric

Grails

GsonNeo4j

Apache Ignite

Apache Spark

Apache Continuum

Zookeeper

Dropwizard

Byte Buddy

Hibernate

Liquibase

Spring Framework

Ehcache

OrientDB

Chronicle

Apache Hadoop

JRubyAkka

Agrona

XRebel

Presto

XStream

CapLogic

WildFly

Infinispan

MapDBNetty HazelcastCassandra Mockito

EasyMock

ScalaRobolectric

Grails

GsonNeo4j

Apache Ignite

Apache Spark

Apache Continuum

Zookeeper

Dropwizard

Byte Buddy

Hibernate

Liquibase

Spring Framework

Ehcache

OrientDB

Chronicle

Apache Hadoop

JRubyAkka

Agrona

XRebel

Presto

XStream

CapLogic

WildFly

Infinispan

Hazelcast Use Cases

Hazelcast Use Casescustom (64-bit)

memory allocation

fastmemory access

(de)serialization

minimizegc overhead

custom memory fences

efficient memory layout(array element)

volatile semantics

“There’s no place like home.”

“There’s no place like home.”The Wizard of Oz

Close ;-)Language URL sun.misc.Unsafe

Avian C++ https://github.com/ReadyTalk/avian YesBicaVM JavaScript https://github.com/nurv/BicaVM NoCacao C http://www.cacaojvm.org Yes

Excelsior JVM C / C++ ? http://www.excelsiorjet.com YesDalvik / ART / Android C / C++ https://source.android.com/source/index.html Yes

Graal mainly Java http://openjdk.java.net/projects/graal YesGCJ C / C++ https://gcc.gnu.org/java Yes

HaikuVM C http://haiku-vm.sourceforge.net NoIBM J9 C / C++ ? http://www.ibm.com/developerworks/java/jdk/index.html YesIcedTea C / C++ http://icedtea.classpath.org/wiki/Main_Page Yes

IKVM.NET C# http://www.ikvm.net YesJamiga C https://sourceforge.net/projects/jamiga2 NoJamVM C http://jamvm.sourceforge.net YesJatoVM C http://jatovm.org Yes

JikesRVM C microkernel, Java http://www.jikesrvm.org YesJNode C microkernel, Java http://www.jnode.org YesJVM.go Go https://github.com/zxh0/jvm.go Yes

JX C http://www4.cs.fau.de/Projects/JX/index.html NoKaffe C https://github.com/kaffe/kaffe Yes

NanoVM C http://harbaum.org/till/nanovm/index.shtml NoOpenJDK / Oracle / Zulu C / C++ http://openjdk.java.net Yes

RoboVM C / C++ / ObjC https://robovm.com YesSAPJVM C / C++ ? http://help.sap.com/saphelp_nwce10/helpdata/en/47/

dc90b4ef17452289f9128b8c2bbd77/content.htmYes

Waratek Multitenant JVM C / C++ ? http://www.waratek.com YesZing JVM C / C++ ? https://www.azul.com/products/zing Yes

“To infinity and beyond!”

“To infinity and beyond!”Toy Story

http://mail.openjdk.java.net/pipermail/openjfx-dev/2015-April/017028.html

Let me be blunt -- sun.misc.Unsafe must die in a fire. It is -- wait for it -- Unsafe. It must go. Ignore any kind of theoretical rope and

start the path to righteousness _*/now/*_. It is still years until the end of public updates to JDK 8, so we have /*years */to work this out

properly. But sticking our heads in the collective sands and hoping for trivial work arounds to Unsafe is not going to work. If you're using

Unsafe, this is the year to explain where the API is broken and get it straight....

Please help us kill Unsafe, kill Unsafe dead, kill Unsafe right, and do so as quickly as possible to the ultimate benefit of everyone.

Wed Apr 8 19:15:42 UTC 2015, OpenJFX Mailinglist, Donald Smith, Oracle

Oracle created a new Taskforce

K.U.T.T. - Kill Unsafe To Total death

https://docs.google.com/document/d/1GDm_cAxYInmoHMor-AkStzWvwE9pw6tnz_CebJQxuUE

Hazelcast

jClarityAzul Systems

Higher Frequency Trading

Rafael Winterhalter

Richard Warburton

and many others…

Mutation: it is the key to our evolution.

Mutation: it is the key to our evolution.X-Men

Problem 1: Get Access

Unsafe unsafe = Unsafe.getUnsafe();Easy One (not working outside the JRE / JDK)

private static final Unsafe UNSAFE; static { try { Field theUnsafeField = Unsafe.class.getDeclaredField("theUnsafe"); theUnsafeField.setAccessible(true); UNSAFE = (Unsafe) theUnsafeField.get(Unsafe.class); } catch (Exception e) { // We need you! =( throw new Error(e); }}

The Ugly One

Problem 1: Get Accessprivate static Unsafe findUnsafe() { try { return Unsafe.getUnsafe(); } catch (SecurityException se) { return AccessController.doPrivileged(new PrivilegedAction<Unsafe>() { @Override public Unsafe run() { try { Class<Unsafe> type = Unsafe.class; try { Field field = type.getDeclaredField("theUnsafe"); field.setAccessible(true); return type.cast(field.get(type)); } catch (Exception e) { for (Field field : type.getDeclaredFields()) { if (type.isAssignableFrom(field.getType())) { field.setAccessible(true); return type.cast(field.get(type)); } } } } catch (Exception e) { throw new RuntimeException("Unsafe unavailable", e); } throw new RuntimeException("Unsafe unavailable"); } }); }}

The Hazelcast One(also working in most other JVMs)

The Tricky Oneprivate static final Unsafe UNSAFE; static { try { Constructor<Unsafe> constructor = Unsafe.class.getDeclaredConstructor(); constructor.setAccessible(true); UNSAFE = constructor.newInstance(); } catch (Exception e) { // We need you! =( throw new Error(e); }}

Does Any Of This Feel Right?

Weird!

WAAAAAT!?!?

Solution 1: Get Access

Nothing; not needed anymore!

Problem 2: Atomic Updatesprivate static final Unsafe UNSAFE = findUnsafe();private static long VERSION_OFFSET = findVersionOffset();

// Updated through Unsafe only!private volatile long version = 0;

public long increment() { while(true) { long version = this.version; long newVersion = version + 1; if (UNSAFE.compareAndSwapLong( this, VERSION_OFFSET, version, newVersion)) {

return newVersion; } }}

Going Unsafe

Problem 2: Atomic Updates

We can do better! There’s an API already!

private final AtomicLong version = new AtomicLong(0);

public long increment() { return version.incrementAndGet();}

We can do better! There’s an API already!

But one AtomicLong instance per version

We can still do better! There’s yet another API already!

We can still do better! There’s yet another API already!private static final AtomicLongFieldUpdater<Record> VERSION = AtomicLongFieldUpdater.newUpdater(Record, "version");

// Updated through atomic field updater only! private volatile long version = 0; public long increment() { return VERSION.incrementAndGet(this); }

Solution 2: Atomic Updates

We can still do better! There’s yet another API already!private static final AtomicLongFieldUpdater<Record> VERSION = AtomicLongFieldUpdater.newUpdater(Record, "version");

// Updated through atomic field updater only! private volatile long version = 0; public long increment() { return VERSION.incrementAndGet(this); }

You guessed it, __ uses it ;-)

private static final VarHandle VERSION = findVersionVarHandle();// Updated through VarHandle only!private volatile long version = 0; public long increment() { return (long) VERSION.addAndGet(this, 1);}

JVM can inline those calls

public static VarHandle findVersionVarHandle() { try { return MethodHandles.lookup(). findFieldVarHandle(Record.class, "version", long.class); } catch (Exception e) { throw new Error(e); }}

Statically cache the VarHandle instance

Problem 3: Memory Management

public long memory() { long address = UNSAFE.allocateMemory(8); UNSAFE.putLong(address, Long.MAX_VALUE); return UNSAFE.getLong(address);}

Keyword: Off-Heap

Problem 3: Memory Management

ByteBuffer possible; API is 32bit though

public long memory() { ByteBuffer byteBuffer = ByteBuffer.allocateDirect(8); byteBuffer.putLong(0, Long.MAX_VALUE); return byteBuffer.getLong(0);}

Solution 3: Memory Management

public long memory() { ByteBuffer byteBuffer = ByteBuffer.allocateDirect(8); VarHandle bufferView = MethodHandles.byteBufferViewVarHandle(long[].class, true); bufferView.set(byteBuffer, 0, Long.MAX_VALUE); return bufferView.get(byteBuffer, 0); }

Simplifies off-heap implementations,empowers new ideas

Solution 3.5: Memory Management

Even easier to build a great off-heap

public long memory(long index) { try (Scope scope = new NativeScope()) { Pointer<Long> ptr = scope.allocate( NativeLibrary.createLayout(long.class), numElements); Reference<Long> ref = ptr.offset(index).deref(); ref.set(Long.MAX_VALUE); return ref.get(); }}

Problem 4: Serialization

private static final Unsafe UNSAFE = findUnsafe();private static final long VALUE_OFFSET = findValueOffset();public String deserializeString() throws Exception { char[] chars = magicallyDecodeUTF8FromStream(); String allocated = (String) UNSAFE.allocateInstance(String.class); UNSAFE.putObjectVolatile(allocated, VALUE_OFFSET, chars); return allocated;}

Problem 4: Serialization

private static final Unsafe UNSAFE = findUnsafe();private static final long VALUE_OFFSET = findValueOffset();public String deserializeString() throws Exception { char[] chars = magicallyDecodeUTF8FromStream(); String allocated = (String) UNSAFE.allocateInstance(String.class); UNSAFE.putObjectVolatile(allocated, VALUE_OFFSET, chars); return allocated;}

Will break in Java 9 (compressed Strings)

Solution 4: Serialization

public String deserializeString() throws Exception { char[] chars = magicallyDecodeUTF8FromStream(); ReflectionFactory reflectionFactory = ReflectionFactory.getReflectionFactory(); Constructor<String> constructor = reflectionFactory .newConstructorForSerialization(String.class, char[].class); return constructor.newInstance(chars);}

sun.reflect.ReflectionFactory -> java.lang.reflect.ReflectionFactory (or similar)

Problem 5: Native Interoperabilityextern c { JNIEXPORT int JNICALL Java_ProcessIdentifier_getProcessId(JNIEnv *, jobject);} JNIEXPORT int JNICALLJava_ProcessIdentifier_getProcessId(JNIEnv *env, jobject thisObj) { return getpid();} public class ProcessIdentifier { static { System.loadLibrary("processidentifier"); } public native void getProcessId();}

Fortunately we don’t deal with it, but who loves it anyways ;-)

Solution 5: Native Interoperability (for now)

interface LibC { void getpid();} public int call() { LibC c = LibraryLoader.create(LibC.class).load("c"); return c.getpid();}

JNR, but guess what it uses internally ;-)

Solution 5: Native Interoperability

public void call() { MethodType intType = MethodType.methodType(int.class); MethodHandle handle = MethodHandles .findNative(null, “getpid”, intType); return (int) handle.invokeExact();}

They inline … just fine.

Problem 6: Immutable Types

Defensive Copies, no real optimization yet

Solution 6: Immutable Types

value class Point { final int x; final int y; } // Create a Point instancePoint point = makeValue(1, 2);

Value Types

int[] values = new int[2];int x = values[0]; int y = values[1];

Looks like

Value Types

Value Types int[] values = new int[2];int x = values[0]; int y = values[1];

Looks like

Stack Allocation!

Problem 7: Generics

HazelcastInstance client = HazelcastClient.newHazelcastClient();Map<Long, String> messages = client.getMap("messages");String message = messages.get(1234L);

No generics on primitives

Problem 7: Generics

Auto-(Un)Boxing

Problem 7: Generics

Auto-(Un)Boxing

Solution 7: Generics

class Box<any T> { void set(T element) { ... }; T get() { ... };}

Specialized Generics (yeah it’s kind of a template)

Solution 7: Generics

class Box<any T> { void set(T element) { ... }; T get() { ... };}

Specialized Generics (yeah it’s kind of a template)

Box<int> Box${T=int}.classBox<String> Box${T=java.lang.String}.classBox<RandomClass> Box${T=RandomClass}.class

Solution 7: Genericspublic void generics() { List<int> intList = client.getList("foo"); intList.add(1); int intValue = intList.get(0); Queue<String> stringQueue = client.getQueue("foo"); stringQueue.offer("hello"); String stringValue = stringQueue.poll(); Map<int, String> messages = client.getMap("messages"); messages.put(1234L, "hello"); String message = messages.get(1234L); }

Arrays 2.0

int[] values = new int[Long.MAX_VALUE];

Arrays 2.0

Arrays.chop(T[] a, int newlength);

Arrays 2.0

Box<String>[] ... = new Box<String>[];

Arrays 2.0

Box<int>[] ... = new Box<int>[];

Arrays 2.0

char[] frozen = new char[20L].freeze();

Arrays 2.0

char[] frozen = new char[20L].freeze();

Cleaner APIpackage java.nio;

import sun.misc.Cleaner;

class DirectByteBuffer extends MappedByteBuffer implements DirectBuffer {

private static class Deallocator implements Runnable { private Deallocator(long address, long size, int capacity) {...}

public void run() {...} }

private final Cleaner cleaner; DirectByteBuffer(int cap) { ... cleaner = Cleaner.create(this, new Deallocator(base, size, cap)); } }

Cleaner API

public selfCleaning() { try(AutoCleaning autoCleaning : new AutoCleaning()) { // do your thing here } }

Cleaner APIpublic class AutoCleaning implements AutoCloseable { // A cleaner, preferably one shared within a library private static final Cleaner cleaner = ...;

static class State implements Runnable {

State(...) {/* initialize State needed for cleaning action */} public void run() {/*cleanup action accessing State, executed at most once*/} }

private final State state; private final Cleaner.Cleanable cleanable;

public AutoCleaning() { this.state = new State(...); this.cleanable = cleaner.register(this, state); }

public void close() { cleanable.clean(); }}

Class Dynamic

• Templating functionality

Class Dynamic

• Templating functionality • Aspect-like approach

Class Dynamic

• Templating functionality • Aspect-like approach • Group common functionality

Class Dynamic

• Templating functionality • Aspect-like approach • Group common functionality • Enhanced Proxies

R methodName(ARGS) { synchronized (this) { underlying.methodName(ARGS); }}

Collections::sychronizedMap

Class Dynamic

• Templating functionality • Aspect-like approach • Group common functionality • Enhanced Proxies

Logging / Tracing

R methodName(ARGS) { logger.trace("Before methodname X"); underlying.methodName(ARGS); logger.trace("After methodname X");}

What Else?

No idea!

A lot is changing now.Java / JVM will be different.

… but lots of interesting features, not only for us :)

What Else?

Don’t forget about Jigsaw,test your application with Java 9 EA builds!

https://jdk9.java.net/jigsaw/

“My mama always said, ‘Life was like a box of chocolates. You never know what you’re gonna get.”

Forrest Gump

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

More information:• http://openjdk.java.net/jeps/193 • http://openjdk.java.net/jeps/254 • http://openjdk.java.net/jeps/285 • http://openjdk.java.net/projects/valhalla/ • http://cr.openjdk.java.net/~jrose/arrays/frozen-array-value-rules.html • https://twitter.com/PaulSandoz/status/623891528432394240 • http://openjdk.java.net/projects/panama/ • http://cr.openjdk.java.net/~jrose/values/values-0.html • http://cr.openjdk.java.net/~briangoetz/valhalla/spec-classdyn.html • http://blog.codefx.org/java/dev/the-road-to-valhalla/

Thank You!

Thank You!http://openjdk.java.net/jeps/259 http://openjdk.java.net/jeps/286 http://openjdk.java.net/jeps/276 http://openjdk.java.net/jeps/269 http://openjdk.java.net/jeps/266 http://openjdk.java.net/jeps/191 http://openjdk.java.net/jeps/186 http://openjdk.java.net/jeps/277

a post-apocalyptic sun.misc.unsafe world

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