20 Years of Java

20 years of Java

Vladimir Ivanov HotSpot JVM Compile r Twitter: @iwan0www Oracle Corp. OpenJDK: vlivanov

20 years of Java (The Platform)

Vladimir Ivanov HotSpot JVM Compile r Twitter: @iwan0www Oracle Corp. OpenJDK: vlivanov

The preceding is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

Joined Sun Microsystems (SPBDC) to work JDK 1.0 on HotSpot JVM Now 1996 2002 2005 2010 2015 Wrote my first Became part of program in Java. Oracle Corp. after acquisition

§ 6 packages § # of classes – java.applet – java/ 225 – java.awt – sun/ 379 – java.io – java.lang – java.net – java.util

Inner classes JavaBeans HotSpot JVM JDBC JNDI RMI Java Sound Reflection JVMDI JNI JVMPI

First release JDK 1.1 January, 23 December, 8 J2SE 1.3 February, 6 1995 1996 1997 1998 2000 2002 March February, 19 May, 8 JDK 1.0 J2SE 1.2 J2SE 1.4 Swing AWT Regular Expressions JIT compiler Network IPv6 support Java Plug-in I/O Logging Collections XML, XSLT Java Web Start

§ Scripting Language Support (JSR 223) § Java Compiler API (JSR 199) § Support for pluggable annotations (JSR 269) § Numerous performance improvements – C1: new linear register allocator – C1: IR in SSA form

§ Escape analysis in C2 – 6u23 § NUMA GC Enhancements – Java SE 6u2 § Compressed OOPs – 6u23 § Tiered compilation

§ JVM support for dynamic languages (JSR 292) § Small language changes – e.g. strings in switch, try-with-resources § New file I/O library (defined by JSR 203)

§ JSR 335: Language-level support for lambda expressions

§ JSR 223: Project Nashorn, a JavaScript runtime § JSR 308: Annotation on Java Types § JSR 310: Date and Time API

§ JEP 122: Remove the permanent generation

Scalability Performance Project Jigsaw Security

http://openjdk.java.net

34 Copyright © 2015, Oracle and/or its affiliates. All rights reserved Java 8 tools JDK tools.jaxws tools.base JRE corba devtools tools.jre crypto compact3 jaxws compiler rowset compact2 xmldsig desktop rmi javafx naming jaxp jdbc httpserver auth sctp compact1 prefs jx.annotations instrument 54MB 30 16 11 nashorn

rmic xml.ws hotspot.agent

javadoc xml.bind jconsole jcmd jdi smartcardio crypto.ec compiler se aach crypto.pkcs11 xml.ws hpserver compact3 jvmstat hprof.agent jdwp.agent xml.soap corba instrument sql.rowset naming.rmi localedata xml.bind security.acl naming naming sctp compact2 acvaon compiler management zipfs sql security.auth desktop prefs compact1 rmi security.jgss scripting. annotaons.common xml.crypto xml logging scripng security.sasl nashorn

base charsets

tools

tools.jaxws tools.base cosnaming management.iiop corba devtools tools.jre crypto management kerberos jaxws compiler rowset jta xmldsig desktop rmi

script nashorn

tools

tools.jaxws tools.base cosnaming management.iiop corba devtools tools.jre crypto management kerberos jaxws compiler rowset jta xmldsig desktop rmi

script nashorn

tools

tools.jaxws tools.base cosnaming management.iiop corba devtools tools.jre crypto management kerberos jaxws compiler rowset jta xmldsig desktop rmi

script nashorn

crypto

javafx

script nashorn

JVM image

Fat binary

rt.jar

crypto nashorn.jar, jfxrt.jar, sunjce_provider.jar javafx base script nashorn myapp.jar

crypto

§ Improved class loading architecture javafx – fast class lookup base script nashorn

crypto

§ Improved class loading architecture javafx – fast class lookup base script nashorn

crypto

§ Improved class loading architecture javafx – fast class lookup base script nashorn § Aggressive inlining

crypto

§ Improved class loading architecture javafx – fast class lookup base script nashorn § Aggressive inlining § Ahead-Of-Time compilation

crypto

§ Improved class loading architecture javafx – fast class lookup base script nashorn § Aggressive inlining § Ahead-Of-Time compilation § JVM-specific memory images – e.g. Application Class Data Sharing (AppCDS)

crypto

sun.* *.internal.*

sun.misc.Unsafe?!

- How many of you have used the Unsafe API? …

John Rose JVM Architect, Oracle Corporation @ JVM Language Summit 2014

- How many of you have used the Unsafe API? … - A lot of you. Gosh, I'm sorry.

John Rose JVM Architect, Oracle Corporation @ JVM Language Summit 2014

§ Replacement exists in JDK 8 – Encapsulate/remove the method in JDK 9

§ Replacement exists in JDK 9 – Deprecate in JDK9

§ No replacement exists in JDK 9 – (For widely used internal API) Leave accessible

§ sun.misc.Cleaner § sun.misc.{Signal,SignalHandler} § sun.misc.Unsafe § sun.reflect.Reflection::getCallerClass § sun.reflect.ReflectionFactory

Use case Example methods

Concurrency primitives Unsafe.compareAndSwap*

Unsafe.allocateInstance Serialization (ReflectionFactory.newConstructorForSerialization)

Unsafe.allocate/freeMemory Efficient memory management, Unsafe.get*/put* (and JNI) layout, and access

Interoperate across the JVM Unsafe.get*/put* (and JNI) boundary

Use case Replacement

Concurrency primitives JEP 193 Variable Handles

Reboot JEP 187 Serialization Serialization Improvements

Efficient memory management, Project Panama, Project Valhalla, layout, and access Arrays 2.0, Better GC

Interoperate across the JVM Project Panama, boundary JEP 191 Foreign Function Interface

Use case Replacement

Concurrency primitives JEP 193 Variable Handles

Reboot JEP 187 Serialization Serialization Improvements

Efficient memory management, Project Panama, Project Valhalla, layout, and access Arrays 2.0, Better GC

Interoperate across the JVM Project Panama, boundary JEP 191 Foreign Function Interface

1. Safe, performant, enhanced atomics – access to field and array elements

2. Fence operations for fine-grained control of memory ordering – replacements for Unsafe::{full,store,load}Fence and more

3. Reachability fence – java.lang.ref.Reference::reachabilityFence

“The most fundamental change to Java since its inception.”

Charles Oliver Nutter JRuby Lead Developer

§ like method handles for data – Abstracts over location § static fields, instance fields, arrays, off heap – Supports explicit fences and atomic operations

§ Safer than Unsafe, as fast as method handles

§ Not necessarily… – public native Object allocateInstance(Class cls) throws …;

– Array index vs raw offset long[] base = new long[…]; int idx = …; long offset = (((long) idx) << SCALE + OFFSET) long value = Unsafe.getLong(base, offset);

– JDK-8078629: “VM should constant fold Unsafe.get*() loads from final fields”

Thread #1 Thread #2

a = ?, b = ?

Thread #1 Thread #2

[a,b] = [0,0], [0,1], [1,0], [1,1]

Thread #1 Thread #2

[a,b] = [0,0], [0,1], [1,0], [1,1]

Foreign Function Interface Project Panama Data Layout Control Arrays 2.0

http://openjdk.java.net

final class Point { “Use of identity-sensitive operations public final int x; on instances of value-based classes public final int y; may have unpredictable effects and should be avoided.” } ValueBased javadoc

Point[] points = headerh

x y x y x y x y x y x y

Point[] points = headerh

x y x y x y for (Point p : points) { x y sum += p.x + p.y; x y } x y

int[] xPoints = headerh x x x x x x

int[] yPoints = headerh y y y y y y

assert(xPoints.length == yPoints.length);

for (int i = 0; i < xPoints.length; i++) { sum += xPoint[i] + yPoint[i]; }

int[] points = headerh x y x y x y x y x y x y

assert(points.length % 2 == 0);

for (int i = 0; i < points.length; i+=2) { sum += points[i] + points[i+1]; }

John Rose, Brian Goetz, Guy Steele

“State of the Values”

Point[] points = headerh x y x y x y x y x y x y

value class Point { for (Point p : points) { public final int x; sum += points.x + points.y; } public final int y; }

§ Smaller footprint – no object header § Better locality – no dereference § Simpler semantics – no identity, no aliasing § No object allocation

Rectangle r = value class Point { header y y public final int x; h x x public final int y; } Rectangle r = header h class Rectangle { public final Point corner1; x y public final Point corner2; y } x

Rectangle r = value class Point { header y y public final int x; h x x public final int y; } Rectangle r = header h class Rectangle { public Point corner1; x y public volatile Point corner2; y } x

§ Numerics: complex, decimal, rarely-big-num, etc. § Native types: int128_t, vectors, unsigned, safe native pointers § Algebraic data: optional (no box), choice-of, unit (no bits) § Tuples: multiple-value return! (requires specialization machinery also) § Cursors: unboxed iterators, STL-style bounds § Flat data: values naturally represent pointer-poor data structures

Point[] <:? Object[]

Point[] points = headerh x y x y x y x y x y x y

Point[] <: Object[]

ArrayList

§ Object, String, …, MyClass, …, – 8 primitive types (+ reference)

Integer, Long, … § boolean, byte, short, char, int, long, float, double

§ Object, String, …, MyClass, …, – 8 primitive types (+ reference)

Integer, Long, … § boolean, byte, short, char, int, long, float, double

– Value types

§ User-defined (!!!)

Generic Specialization Motivation

ArrayList

class Box { T val;

public Box(T val) { this.val = val; } public T get() { return val; } }

class Box { T val;

public Box(T val) { this.val = val; } public T get() { return val; } }

class Box