A tour of upcoming JVM technologies and beyond
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This document provides an overview of upcoming technologies beyond the Java Virtual Machine (JVM). It begins with introductions and then discusses several topics: - There are many open-source JVMs beyond Oracle's HotSpot such as JamVM, Maxine, and JikesRVM. - Reasons for using the JVM include its large standard library and ease of portability compared to alternative virtual machines. However, startup time can be slow. - Techniques for improving JVM startup time are discussed, such as saving JIT-compiled code and using the Drip tool to pre-initialize JVMs. - Native interoperability is explored through the Java Native Interface (JNI
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A tour of upcoming JVM technologies and beyond
- 1. Beyond JVM A tour of upcoming technologies
- 2. Me • Charles Oliver Nutter • Red Hat (yes, I have one; no, I don’t wear it) • JRuby and JVM languages • JVM hacking and spelunking • @headius
- 3. Goals • Get you excited about the future of JVM • Show you there are very few unsolvables • Convince you to get involved
- 4. What is “JVM”? • The JVM is software that runs JVM bytecode • Java, Scala, Groovy, JRuby, Clojure, … • OpenJDK contains Sun’s JVM “HotSpot” • Oracle’s JDK is based on OpenJDK • Many other JVMs exist for many platforms • Some just replace HotSpot
- 5. OSS JVMs • • • • • • • • • Avian Azul Zulu CACAO Dalvik GCJ HaikuVM HotSpot • • • • • • • IcedTea IKVM.NET • Jamiga JamVM Jaos Jato VM Jelatine JVM JESSICA Jikes RVM (Jikes Research Virtual Machine) JOP • • • • • • • • • Juice Jupiter JwiK Kaffe leDos MateVM Maxine Mika VM miniMV • • • • • Mysaifu • • • • SuperWaba NanoVM RoboVM SableVM Squawk virtual machine TakaTuka TinyVM. VM02
- 6. Why JVM?
- 7. Why Not JVM?
- 10. Startup Time
- 13. Java-Heavy JDK • + Less native code to maintain • + Easier portability • + Easier to swap out native side • – Takes longer to warm up
- 14. Save JITed Code? • Code will change across runs • Often has specific memory addresses • May optimize object layout differently • Which JIT output? • Client, Server, Tiered (1-4)
- 15. JRuby Startup C Ruby JRuby JRuby (best) -e 1 gem --help rake -T 0 2.5 5 7.5 10
- 16. Drip • Start a new JVM after each command • Pre-boot JVM plus optional code • Analyze command line for differences • Age out unused instances • https://github.com/flatland/drip
- 17. $ export JAVACMD=`which drip` ! $ time jruby -e 1 ! real 0m1.655s user 0m4.486s sys 0m0.231s ! system ~/projects/jruby $ time jruby -e 1 ! real 0m0.577s user 0m0.052s sys 0m0.065s
- 18. $ export DRIP_INIT_CLASS=org.jruby.main.DripMain ! $ export DRIP_INIT="" ! $ time jruby -e 1 ! real 0m0.580s user 0m0.052s sys 0m0.063s ! system ~/projects/jruby $ time jruby -e 1 ! real 0m0.155s user 0m0.049s sys 0m0.058s
- 19. $ cat dripmain.rb # Preload some code Rails always needs require File.expand_path('../config/application', __FILE__)
- 20. JRuby Startup C Ruby JRuby (drip init) JRuby (best) JRuby (dripmain) JRuby (drip) -e 1 gem --help rake -T 0 1.25 2.5 3.75 5
- 21. Native Interop
- 22. Native Interop
- 25. User Code Java JNI call C/native JNI impl Target Library
- 26. JNI public class GetPidJNI {! public static native long getpid();! ! public static void main( String[] args ) {! getpid();! }! ! static {! System.load(! System.getProperty("user.dir") +! "/getpidjni.dylib");! }! }
- 27. JNI /* DO NOT EDIT THIS FILE - it is machine generated */! #include <jni.h>! /* Header for class com_headius_jnr_presentation_GetPidJNI */! ! #ifndef _Included_com_headius_jnr_presentation_GetPidJNI! #define _Included_com_headius_jnr_presentation_GetPidJNI! #ifdef __cplusplus! extern "C" {! #endif! /*! * Class: com_headius_jnr_presentation_GetPidJNI! * Method: getpid! * Signature: ()J! */! JNIEXPORT jlong JNICALL Java_com_headius_jnr_1presentation_GetPidJNI_getpid! (JNIEnv *, jclass);! ! #ifdef __cplusplus! }! #endif! #endif
- 28. JNI #include "com_headius_jnr_presentation_GetPidJNI.h"! ! jlong JNICALL Java_com_headius_jnr_1presentation_GetPidJNI_getpid! (JNIEnv *env, jclass c) {! ! return getpid();! }
- 29. JNI $ gcc -I $JAVA_HOME/include -I $JAVA_HOME/include/darwin -L $JAVA_HOME/jre/lib/ -dynamiclib -ljava -o getpidjni.dylib com_headius_jnr_presentation_GetPidJNI. c! ! $ java -Djava.library.path=`pwd` -cp target/jnr_presentation-1.0SNAPSHOT.jar com.headius.jnr_presentation.GetPidJNI
- 30. Nobody enjoys calling native libraries...
- 31. ...but if you have to call native libraries, you might as well enjoy it.
- 32. Java Native Runtime • Java API • for calling Native code • supported by a rich Runtime library • You may be familiar with JNA • Foreign Function Interface (FFI) • https://github.com/jnr • Maven artifacts for everything
- 33. A Java API for binding native libraries and native memory
- 34. Justifications • NIO, NIO.2 • Native IO, symlinks, FS-walking, • Unmanaged memory • Selectable stdio, process IO • Low-level or other sockets (UNIX, ICMP, ...) • New APIs (graphics, crypto, OS, ...)
- 35. User Code Java JNI call C/native JNI impl Target Library
- 36. User Code Java JNI call C/native JNI impl Target Library
- 37. User Code JNR stub Java JNI call C/native JNI impl libffi Target Library
- 38. JNR import jnr.ffi.LibraryLoader;! import jnr.ffi.annotations.IgnoreError;! ! public class GetPidJNRExample {! public interface GetPid {! long getpid();! }! ! public static void main( String[] args ) {! GetPid getpid = LibraryLoader! .create(GetPid.class)! .load("c");! ! getpid.getpid();! }! }
- 40. JNR Platforms • Darwin (OS X): universal (+ppc?) • Linux: i386, x86_64, arm, ppc, ppc64, s390x • Windows: i386, x86_64 • FreeBSD, OpenBSD: i386, x86_64 • SunOS: i386, x86_64, sparc, sparcv9 • AIX: ppc • OpenVMS, AS/400: builds out there somewhere • If your platform isn't here, contribute a build
- 41. jnr-ffi • User-oriented API • Roughly equivalent to what JNA gives you • Functions, structs, callbacks, memory • https://github.com/jnr/jnr-ffi
- 42. jnr-ffi import jnr.ffi.LibraryLoader;! import jnr.ffi.annotations.IgnoreError;! ! public class GetPidJNRExample {! public interface GetPid {! long getpid();! }! ! public static void main( String[] args ) {! GetPid getpid = LibraryLoader! .create(GetPid.class)! .load("c");! ! getpid.getpid();! }! }
- 43. jnr-posix • Pre-bound set of POSIX functions • Mostly driven by what JRuby, Jython use • Goal: 100% of POSIX bound to Java
- 44. public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public public List<? int chmod(String string, int i);! int chown(String string, int i, int i1);! int execv(String string, String[] strings);! int execve(String string, String[] strings, String[] strings1);! int fork();! int seteuid(int i);! int getgid();! String getlogin();! int getpgid();! int getpgid(int i);! int getpgrp();! int getpid();! int getppid();! Passwd getpwent();! Passwd getpwuid(int i);! Passwd getpwnam(String string);! Group getgrgid(int i);! Group getgrnam(String string);! int getuid();! boolean isatty(FileDescriptor fd);! int kill(int i, int i1);! int symlink(String string, String string1);! int link(String string, String string1);! String readlink(String string) throws IOException;! String getenv(String string);! int setenv(String string, String string1, int i);! int unsetenv(String string);! int getpriority(int i, int i1);! int setpriority(int i, int i1, int i2);! int setuid(int i);! FileStat stat(String string);! int stat(String string, FileStat fs);! int umask(int i);! Times times();! int utimes(String string, long[] longs, long[] longs1);! int waitpid(int i, int[] ints, int i1);! int wait(int[] ints);! int errno();! void errno(int i);! int posix_spawnp(String string, List<? extends SpawnFileAction> list, extends CharSequence> list1, List<? extends CharSequence> list2);
- 45. POSIX posix = POSIXFactory.getPOSIX(! new MyPOSIXHandler(this),! isNativeEnabled);
- 46. public interface POSIXHandler {! public void error(Errno errno, String string);! public void unimplementedError(String string);! public void warn(WARNING_ID wrngd, String string, Object[] os);! public boolean isVerbose();! public File getCurrentWorkingDirectory();! public String[] getEnv();! public InputStream getInputStream();! public PrintStream getOutputStream();! public int getPID();! public PrintStream getErrorStream();! }
- 47. jnr-enxio • Extended Native X-platform IO • NIO-compatible JNR-backed IO library • Read, write, select (kqueue, epoll, etc) • Low-level fcntl control • https://github.com/jnr/jnr-enxio
- 48. public class NativeSocketChannel! extends AbstractSelectableChannel! implements ByteChannel, NativeSelectableChannel {! public NativeSocketChannel(int fd);! public NativeSocketChannel(int fd, int ops);! public final int validOps();! public final int getFD();! public int read(ByteBuffer dst) throws IOException;! public int write(ByteBuffer src) throws IOException! public void shutdownInput() throws IOException;! public void shutdownOutput() throws IOException;! }
- 49. jnr-unixsocket • UNIX sockets for NIO • Built atop jnr-enxio • Fully selectable, etc • https://github.com/jnr/jnr-unixsocket
- 50. How Does It Perform?
- 51. JNA getpid JNR getpid getpid calls, 100M times 100000ms 10000ms 1000ms 100ms 10ms 1ms
- 52. @IgnoreError import jnr.ffi.LibraryLoader;! import jnr.ffi.annotations.IgnoreError;! ! public class GetPidJNRExample {! public interface GetPid {! @IgnoreError! long getpid();! }! ! public static void main( String[] args ) {! GetPid getpid = LibraryLoader! .create(GetPid.class)! .load("c");! ! getpid.getpid();! }! }
- 53. JNR getpid JNR getpid @IgnoreError getpid calls, 100M times 2000ms 1500ms 1000ms 500ms 0ms
- 54. But There's More to Do JNR getpid JNI JNR @IgnoreError getpid calls, 100M times 2000ms 1500ms 1000ms 500ms 0ms GCC -O3
- 55. JVM Help is Coming • Standard FFI API in JDK • JIT intelligence • Drop JNI overhead where possible • Bind native call directly at call site • Security policies, segv protection, etc • Time for an FFI JSR
- 57. History • JVM authors mentioned non-Java languages • Language authors have targeted JVM • Hundreds of JVM languages now • But JVM was a mismatch for many of them • Usually required tricks that defeated JVM optimizations • Or required features JDK could not provide
- 59. JVM Opcodes Invocation Field Access invokevirtual! invokeinterface! invokestatic! invokespecial getfield! setfield! getstatic! setstatic Stack Flow Control Boolean and Numeric Array Access *aload! *astore! b,s,c,i,l,d,f,a Local Vars Allocation
- 60. Goals of JSR 292 • A user-definable bytecode • Full freedom to define VM behavior • Fast method pointers + adapters • Optimizable like normal Java code • Avoid future modifications
- 61. A User-definable Bytecode You decide how the JVM implements it + Method Pointers and Adapters Faster than reflection, with user-defined argument, flow, and exception handling
- 62. invokedynamic opcode user-def’d bytecode method pointers MethodHandles invokedynamic
- 63. Method Invocation VM Operations Method Lookup Type Checking Branch Method Cache obj.foo() Target Object JVM Call Site instanceof Object’s Class void foo() void foo() static void bar()
- 64. // Static! System.currentTimeMillis()! Math.log(1.0)! ! // Virtual! "hello".toUpperCase()! System.out.println()! ! // Interface! myList.add("happy happy")! myRunnable.run()! ! // Special! new ArrayList()! super.equals(other)
- 65. // Static! invokestatic java/lang/System.currentTimeMillis:()J! invokestatic java/lang/Math.log:(D)D! ! // Virtual! invokevirtual java/lang/String.toUpperCase:()Ljava/lang/String;! invokevirtual java/io/PrintStream.println:()V! ! // Interface! invokeinterface java/util/List.add:(Ljava/lang/Object;)Z! invokeinterface java/lang/Runnable.add:()V! ! // Special! invokespecial java/util/ArrayList.<init>:()V! invokespecial java/lang/Object.equals:(java/lang/Object)Z
- 66. invokevirtual! 1. Confirm object is of correct type 2. Confirm arguments are of correct type 3. Look up method on Java class invokestatic 4. Cache method 5. Invoke method invokestatic! 1. Confirm arguments are of correct type 2. Look up method on Java class 3. Cache method 4. Invoke method invokevirtual invokeinterface! 1. Confirm object’s type implements interface 2. Confirm arguments are of correct type 3. Look up method on Java class invokeinterface 4. Cache method 5. Invoke method invokespecial! 1. Confirm object is of correct type 2. Confirm arguments are of correct type 3. Confirm target method is visible 4. Look up method on Java class 5. Cache method 6. Invoke method invokespecial invokedynamic! 1. Call your bootstrap code 2. Bootstrap wires up a target function 3. Target function invoked directly until you change it
- 68. How Do You Benefit?
- 69. Indy Languages • New language impls • JavaScript: Dyn.js and Nashorn • Redline Smalltalk • Improved language performance • JRuby, Groovy, Jython • Java features too!
- 70. JRuby/Java 6 JRuby/Java 7 Times Faster than Ruby 1.9.3 5 4.32 3.75 3.66 3.44 2.5 2.658 1.914 1.25 0 1.346 base64 1.565 1.538 richards neural redblack
- 71. red/black tree, pure Ruby versus native ruby-2.0.0 + Ruby 2.48s ruby-2.0.0 + C ext 0.51s jruby + Ruby 0.29s 0 0.75 1.5 Runtime per iteration 2.25 3
- 72. Indy + JNR Ruby getpid Java getpid 100M getpid calls 2700 2025 1350 675 0
- 73. Caveat Emptor • Indy was really slow in first Java 7 release • Got fast in 7u2...and turned out broken • Rewritten for 7u40 • Slow to warm up • Still some issues (memory use, etc) • Java 8 due in March…
- 74. All That C++
- 75. JVM Language JVM Bytecode Out of our control Written in C++ Bytecode Interpreter Bytecode JIT Native Code
- 76. What If… • The JVM’s JIT optimizer were written in Java • You could customize how the JIT works for your language or library • JITed code could directly make native calls
- 77. Graal • A 100% Java-based JIT framework • Grew out of the 100% Java “Maxine” JVM • Backends to assembly or HotSpot IR • Directly control code generation • Build a language without using JVM bytecode • http://openjdk.java.net/projects/graal/
- 78. JVM Language Plain Java APIs Graal Intermediate Representation Graal Optimizer Under your control Your Transformations Your Optimizations Native Code
- 79. However… • Not everyone is a compiler writer • Graal’s IR is low-level and nontrivial • Need to understand JVM internals • Need some understanding of CPU
- 80. The Dream • Design your language • ??? • PROFIT
- 81. Typical JVM Language • Design your language • Maybe write an interpreter • Compile to JVM bytecode • Pray that the JVM optimizes it right • PROFIT
- 82. What We Want • Design your language • Write an interpreter • PROFIT
- 83. Truffle • Language framework built on Graal • Designed to fulfill the dream • Implement interpreter • Truffle feeds that to backend • No compiler expertise needed • https://wiki.openjdk.java.net/display/Graal/Truffle+FAQ+and+Guidelines
- 84. JVM Language Truffle AST All we need Graal Intermediate Representation Graal Optimizer Native Code
- 87. The Final Word • JVM is a powerful platform • Java and other languages are evolving • The JVM is adapting to our needs • New tools breaking JVM’s boundaries
- 88. Thank you! • Charles Oliver Nutter • @headius, headius@headius.com • http://blog.headius.com