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The document discusses the performance improvements of the Nashorn JavaScript runtime for the JVM, focusing on its compliance with ECMAScript standards and its use of invokedynamic for efficient execution. It highlights Nashorn's release schedule, benchmarking results against other JavaScript engines, and the optimization techniques employed for enhancing runtime performance. Additionally, it addresses the challenges of bridging dynamic languages with the JVM's bytecode and provides insights into future developments and enhancements in the compiler architecture.

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Towards  na*ve  performance  with   dynamic  languages  on  the  JVM   Marcus  Lagergren,  Oracle  
Towards  na*ve  performance  with   dynamic  languages  on  the  JVM   Marcus  Lagergren,  Oracle   How  far  does  invokedynamic  take  us?  
Towards  na*ve  performance  with   dynamic  languages  on  the  JVM   Marcus  Lagergren,  Oracle   How  far  does  invokedynamic  take  us?   Pre$y  far  actually!  
The  Legal  Slide   "THE FOLLOWING 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 DECISION. THE DEVELOPMENT, RELEASE, AND TIMING OF ANY FEATURES OR FUNCTIONALITY DESCRIBED FOR ORACLE'S PRODUCTS REMAINS AT THE SOLE DISCRETION OF ORACLE."  
Who  am  I?   @lagergren    
Agenda   •  Nashorn  summary   •  The  last  nine  months  of  Nashorn  and   invokedynamic  performance  work   •  How  did  we  do  it?     •  The  future  
Nashorn   •  Part  of  JDK  8   – 100%  ECMA  compliant  JavaScript  run*me  wriPen   in  Java   •  ECMA  5.1  support   – Limited  ECMA  6  support  (8u40)   •  invokedynamic  based   •  Generates  bytecode   – Currently  no  AST  interpreta*on  
Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on  
Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements  
Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements   •  Java  8u40   – Performance  release  
Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements   •  Java  8u40   – Performance  release   •  Java  9    
Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements   •  Java  8u40   – Performance  release   •  Java  9    
Evangelist  Blurb   “Nashorn  is  a  really  fast  100%  JS  compilant   invokedynamic  based  JavaScript  run*me  wriPen   in  Java.  It  runs  on  top  of  the  JVM”  
…  or  maybe?   “Nashorn  is  a  run*me  for  dynamic  languages  on   the  JVM.  Nashorn  takes  away  the  pain  and   performance  loss  of  bridging  the  gap  between   language  and  bytecode.  Types,  objects  and  code   are  automa*cally  adapted  to  be  an  op*mal  fit  in   the  JVM  mould”  
JavaScript  
JavaScript   “Once  you  admit  that  EVERYTHING  IS  TERRIBLE,      the  universe  opens  infinitely  many  doors  for            you...    TO  TERRIBLE.”                      -­‐  Jerry  Kuch  
Where  were  we  last  October?   Octane  Benchmark  r31   0   0.2   0.4   0.6   0.8   1   1.2   rhino   nashorn  jdk8  
Where  are  we  today?   Octane  Benchmark  r31   0   1   2   3   4   5   6   7   rhino   nashorn  jdk8   nashorn  jdk9  
…  against  v8   Octane  Benchmark  r31   0   2   4   6   8   10   12   rhino   nashorn  jdk8   nashorn  jdk9   v8  
v8  bleeding  edge…   Octane  Benchmark  r31   0   2   4   6   8   10   12   14   rhino   nashorn  jdk8   nashorn  jdk9   v8   v8  latest  
Let’s  not  forget  node  
avatar.js   •  Project  Avatar   – HTTP  benchmark   – REST  benchmark   •  Comparable  to  v8  /  na*ve  performance   •  8u40  will  deliver  plenty  of  improvements   •  Use  of  exposed  mechanisms   – BufferArrayData  
avatar.js   •  Project  Avatar   – HTTP  benchmark   – REST  benchmark   •  Comparable  to  v8  /  na*ve  performance   •  8u40  will  deliver  plenty  of  improvements   •  Use  of  exposed  mechanisms   – BufferArrayData  
The  last  year  
“The  Secret  Sauce”  
Op*mis*c  Type  Run*me  Architecture   [hPp://openjdk.java.net/jeps/196]  
Just  compile  to  bytecode!   •  “The  JVM  is  technically  advanced  and  has  man   decades  of  JIT  op*miza*ons”   •  “The  JVM  magically  JITs  arbitrary  bytecode  to   fast  na*ve  code”  
Just  compile  to  bytecode!   •  “The  JVM  is  technically  advanced  and  has  man   decades  of  JIT  op*miza*ons”   •  “The  JVM  magically  JITs  arbitrary  bytecode  to   fast  na*ve  code”   •  Nope  :-­‐(  
function gcd(x, y) { var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } gcd(x, y); GCD  
GCD  –  Naïve  &  JS  Compliant   public static gcd(Object;Object;Object;)Object; aload 1 astore 4 aload 2 astore 5 goto L2 aload 4 aload 5 invokedynamic GT:ZOO_Z(Object;Object;)Z; ifeq L4 aload 4 invokestatic JSType.toNumber(Object;)D aload 5 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 4 goto L2 aload 5 invokestatic JSType.toNumber(Object;)D aload 4 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 5 aload 4 aload 5 invokedynamic NE:ZOO_Z(Object;Object;)Z ifne L3 aload 4 areturn
GCD  –  vs  Ideal   public static gcd(Object;Object;Object;)Object; aload 1 astore 4 aload 2 astore 5 goto L2 aload 4 aload 5 invokedynamic GT:ZOO_Z(Object;Object;)Z; ifeq L4 aload 4 invokestatic JSType.toNumber(Object;)D aload 5 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 4 goto L2 aload 5 invokestatic JSType.toNumber(Object;)D aload 4 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 5 aload 4 aload 5 invokedynamic NE:ZOO_Z(Object;Object;)Z ifne L3 aload 4 areturn public static gcd(Object;II)I iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 isub istore 3 goto L14 iload 4 iload 3 isub istore 4 goto L9 iload 3 ireturn
Op*mis*c  Types   •  Factor  150x  difference  in  execu*on  speed   between  the  two   •  “Generate  Java-­‐like  bytecode”  
Op*mis*c  Types   •  Generate  as  op*mis*c  a  func*on  as  possible   •  Surround  op*mis*c  opera*ons  with  excep*on   handlers   •  When  a  type  is  too  narrow   – Store  frame  state  (no  bytecode  stack)   – Take  a  con*nua*on  and  finish  method   – Tell  linker  to  regenerate  more  conserva*vely  
Op*mis*c  Types   long   double   Object  (pessimis*c)  int    
Implementa*on   function f() { return x * y; // x,y in scope }
public static f(ScriptFunction;Object;)D aload 0 invokevirtual ScriptFunction.getScope()LScriptObject; astore 2 // store scope in slot 2 aload 2 // load scope invokedynamic get:x(Object;)Object; aload 2 // load scope invokedynamic get:y(Object;)Object; swap invokestatic JSType.toNumber(Object;)D dup2_x1 pop2 invokestatic JSType.toNumber(Object;)D dmul dreturn  
public static f(ScriptFunction;Object;)I aload 0 invokevirtual ScriptFunction.getScope()ScriptObject; astore 2 // store scope in slot 2 aload 2 invokedynamic get:x(Object;)I istore 3 iload 3 aload 2 invokedynamic get:y(Object;)I invokedynamic imul(II)I ireturn  
public static f(ScriptFunction;Object;)I aload 0 invokevirtual ScriptFunction.getScope()ScriptObject; astore 2 // store scope in slot 2 aload 2 invokedynamic get:x(Object;)I // program point 1 istore 3 iload 3 aload 2 invokedynamic get:y(Object;)I // program point 2 invokedynamic imul(II)I // program point 3 ireturn  
public static f(ScriptFunction;Object;)I aload 0 invokevirtual ScriptFunction.getScope()ScriptObject; astore 2 aload 2 invokedynamic get:x(Object;)I // program point 1 istore 3 iload 3 aload 2 invokedynamic get:y(Object;)I // program point 2 invokedynamic imul(II)I // program point 3 ireturn // catch (UnwarrantedOptimismException e) iconst_4 anewarray Object // 4 local variables in frame iload 3 // load variable 3 (tmp = x) invokedynamic populateArray([Object;I)[Object; goto rwe iconst_3 anewarray Object // 3 local variables in frame rwe: aload 0 // load function aload 1 // load ‘this’ aload 2 // load scope invokedynamic populateArray([Object;Object;Object;Object;)[Object; iconst_0 invokestatic getString$array(I)[String; invokestatic RewriteException.create(UnwarrantedOptimismException;[Object; [String;)RewriteException; athrow  
GCD  –  Ideal   public static gcd(Object;II)I iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 isub istore 3 goto L14 iload 4 iload 3 isub istore 4 goto L9 iload 3 ireturn
GCD  –  vs  Nashorn   public static gcd(Object;II)I iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 isub istore 3 goto L14 iload 4 iload 3 isub istore 4 goto L9 iload 3 ireturn public static gcd(Object;II)I try { iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 invokedynamic isub(II)I //indy because sub may overflow istore 3 goto L14 iload 4 iload 3 invokedynamic isub(II)I //indy because sub may overflow istore 4 goto L9 iload 3 ireturn } catch (UnwarrantedOptimismException e) { //save state and throw RewriteException to linker }
Sta*c  Compiler  Enhancements   •  Liveness   function liveness() { var x = 0; for (var i = 0;i < 10; i++) { x += i; } x += "test"; return x; } What  about  local  variables?  The  slot   type  is  hard  coded  in  the  local   variable  table!  
Sta*c  Compiler  Enhancements   •  Liveness   function liveness() { var x = 0; for (var i = 0;i < 10; i++) { x += i; } x += "test"; return x; }  public static liveness(LObject;)LObject; iconst_0 invokestatic Integer.valueOf (I)Integer; astore 2 dconst_0 dstore 3 goto L2 aload 2 invokestatic JSType.toNumber (LObject;)D dload 3 dadd invokestatic Double.valueOf (D)Double; astore 2 dload 3 dconst_1 dadd dstore 3 dload 3 ldc 10.0 dcmpg iflt L3 aload 2 ldc "test" invokedynamic ADD:OOO_I(LObject;LObject;)Object astore 2 aload 2 areturn local x Ljava/lang/Object; L0 L6 2 local i D L0 L6 3
Sta*c  Compiler  Enhancements   •  Liveness   function liveness() { var x = 0; for (var i = 0;i < 10; i++) { x += i; } x += "test"; return x; }   public static liveness(Object;)Object; iconst_0 istore 1 iconst_0 istore 3 iload 3 bipush 10 if_icmpge L10 iload 1 iload 3 invokedynamic iadd(II)I istore 1 iload 3 dup iconst_1 invokedynamic iadd(II)I istore 3 pop goto L9 iload 1 invokestatic Integer.valueOf(I)Integer; ldc "test" invokestatic ADD(Object;Object;)Object; astore 2 aload 2 areturn // exception handler goes here... local x L6 L13 1 I local x L13 L2 2 Object; local i L8 L2 3 I
Field  Representa*on  
Field  Representa*on   •  jdk.nashorn.internal.runtime.ScriptObject –  Contains  a  PropertyMap •  Shape   –  Contains  a  number  of  fields   •  Scope  variables   –  Contains  a  growing  array   •  Spills  –  also  scope  variables   –  and  lots  of  other  things,  e.g.  ArrayData    
Field  Representa*on   public abstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; long spillPrimitives; // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; long p1, p2, p3, p4; }                
Property  Maps   PropertyMap AccessorProperty: red (flags = 0) slot = 0 AccessorProperty: green (flags = 0) slot = 1 AccessorProperty: blue (flags = 0) slot = 3 SpillProperty: timeStamp (flags = NON_MODIFIABLE), index = 0 •  Immutable   •  Copy  on  write  when  any  aspect   changes   •  Used  for  reference  guards  for  almost   all  invokedynamic  sites  
Field  Representa*on   var scopeVar; function f() { scopeVar &= 17; }            
Field  Representa*on   var scopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as  Object,  is  a   java.lang.Integer 2.  Coerce  to  int  (unbox  from  java.lang.Integer)   3.  Execute  logical  and  (iand)   4.  Coerce  result  to  object  (box  to  java.lang.Integer)   5.  putfield  result  
Field  Representa*on   var scopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as   java.lang.Integer 2.  Coerce  to  int  (unbox  from  java.lang.Integer)   3.  Execute  logical  and     4.  Coerce  result  to  object  (box  to  java.lang.Integer)   5.  putfield  result  
Field  Representa*on   public abstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; long spillPrimitives; // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; p4; }                
Field  Representa*on   public abstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; protected long[] spillPrimitives; s // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; private long j0, j1, j2, j3;, p2, p3, p4; }
Field  Representa*on   “EWW!  Fat  pointers”   public abstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; protected long[] spillPrimitives; s // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; private long j0, j1, j2, j3;, p2, p3, p4; }
Field  Representa*on   obj.j = (long)x; //int obj.j = x; //long obj.j = Double.doubleToLongBits(x); //double obj.o = x; //object return (int)obj.j; //int return obj.j; //long return Double.longBitsToDouble(obj.j); //double return obj.o; //object SePers   GePers  
Property  Maps  and  Types   •  Immutable   •  Copy  on  write  when  any  aspect  changes   •  Used  for  reference  guards  for  almost  all   invokedynamic  sites   PropertyMap AccessorProperty: red (flags = 0) slot = 0, type = int AccessorProperty: green (flags = 0) slot = 1, type = int AccessorProperty: blue (flags = 0) slot = 3, type = int SpillProperty: timeStamp (flags = NON_MODIFIABLE), index = 0, type = object
Property  Maps  and  Types   PropertyMap AccessorProperty: red (flags = 0) type=int AccessorProperty: green (flags = 0) type=int AccessorProperty: blue (flags = 0) type=object SpillProperty: timeStamp (flags = NON_MODIFIABLE),type=object •  Immutable   •  Copy  on  write  when  any  aspect  changes   •  INCLUDING  FIELD  TYPE   •  Used  for  reference  guards  for  almost  all   invokedynamic  sites   •  INCLUDING  FIELD  GETTERS  AND  SETTERS   PropertyMap AccessorProperty: red (flags = 0) slot = 0, type = int AccessorProperty: green (flags = 0) slot = 1, type = int AccessorProperty: blue (flags = 0) slot = 3, type = int SpillProperty: timeStamp (flags = NON_MODIFIABLE), index = 0, type = object
Field  Representa*on   var scopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as   java.lang.Integer 2.  Coerce  to  int  (unbox  from  java.lang.Integer)   3.  Execute  logical  and  (iand)   4.  Coerce  result  to  object  (box  to  java.lang.Integer)   5.  putfield  result  
Field  Representa*on   var scopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as                  long 1.  Coerce  to  int  (l2i)   2.  Execute  logical  and  (iand)   3.  Coerce  to  long  (i2l)   4.  putfield  result  
Field  Representa*on   •  BePer  representa*on?   – Unsafe?   – Needs  some  JVM  magic,  anyway   – Test  implementa*on:   sun.misc.TaggedArray – Object  shape  change  on  GC?   – Let’s  form  an  expert  group!        
Closing  the  circle:      Op*mis*c  Buil*ns    
Op*mis*c  buil*ns       /** * ECMA 15.4.4.7 Array.prototype.push (args...) * * @param self self reference * @param args arguments to push * @return array length after pushes */ @Function(attributes = Attribute.NOT_ENUMERABLE, arity = 1) public static Object push(final Object self, final Object... args) { try { final ScriptObject sobj = (ScriptObject)self; if (bulkable(sobj) && sobj.getArray().length() + args.length <= JSType.MAX_UINT) { final ArrayData newData = sobj.getArray().push(true, args); sobj.setArray(newData); return newData.length(); } long len = JSType.toUint32(sobj.getLength()); for (final Object element : args) { sobj.set(len++, element, true); } sobj.set("length", len, true); return len; } catch (final ClassCastException | NullPointerException e) { throw typeError(Context.getGlobal(), e, "not.an.object", ScriptRuntime.safeToString(self)); } }    
Relinking  Callsites   •  Can  now  be  done  with  Excep*ons  as  well  as  guards  or  SwitchPoints   •  For  example:  con*nuous  arrays   –  Previously  done  with  mul*ple  guards   •  array[x] & 17 •  Array  gePer  links  to:   try { //combinator – not real code return ((ContinuousArrayData)scriptObject. getArrayData()). getElementGetter(int.class). get(index); //turns AIOOBE to CCE } catch (ClassCastException e) { //relink } "  
Op*mis*c  buil*ns       /** * ECMA 15.4.4.7 Array.prototype.push (args...) * * @param self self reference * @param args arguments to push * @return array length after pushes */ @Function(attributes = Attribute.NOT_ENUMERABLE, arity = 1) public static Object push(final Object self, final Object... args) { try { final ScriptObject sobj = (ScriptObject)self; if (bulkable(sobj) && sobj.getArray().length() + args.length <= JSType.MAX_UINT) { final ArrayData newData = sobj.getArray().push(true, args); sobj.setArray(newData); return newData.length(); } long len = JSType.toUint32(sobj.getLength()); for (final Object element : args) { sobj.set(len++, element, true); } sobj.set("length", len, true); return len; } catch (final ClassCastException | NullPointerException e) { throw typeError(Context.getGlobal(), e, "not.an.object", ScriptRuntime.safeToString(self)); } }    
Op*mis*c  buil*ns       // pre: linker checks that callsite argument matches @SpecializedFunction(guard=SpecializedFunction.Guard.CLASSCAST_EXCEPTION_CONTINUOUS_ARRAY) public static long push(final Object self, final int arg) { try { return ((ContinuousArrayData)self).getArray()).push(arg); } catch (final NullPointerException e) { //fallthru } throw new ClassCastException();  }
Op*mis*c  buil*ns •  Lots  of  candidates   –  Array •  push, pop, shift, unshift, length –  String •  charAt, charCodeAt, length –  Number, Math –  Function.apply to    Function.call –  … •  We  can  use  the  same  recompila*on  framework   for  na*ve  methods  as  for  JavaScript  methods  
An*paPern  that  JS  programmers  love   var Class = { create: function() { return function() { //vararg this.initialize.apply(this, arguments); } } }; Color = Class.create(); Color.prototype = { red: 0, green: 0, blue: 0, initialize: function(r, g, b) { this.red = r; this.green = g; this.blue = b; }, toString: function() { return this.red + “ “ + this.green + “ “ + this.blue; } } print(new Color(0xff, 0xee, 0xcc));
Other  op*miza*ons  
Par*al  Evalua*on   for (var i = 0; i < x.length; i++) { //x is loop invariant ) •  x  can  use  MethodHandle.constant  as  an  indy   gePer.   •  We  can  use  a  SwitchPoint  to  invalidate  it,   given  that  x  is  modified  in  the  scope   •  Either  forbid  this  callsite  from  being  constant   again,  or  allow  n  retries   •  Or  try  with  a  receiver  guard  
U*lize  java.nio.ByteBuffer •  Anyone  using  WebGL/ECMA  6  TypedArrays   can  get  near-­‐na*ve  performance   •  java.nio.ByteBuffer   •  5-­‐10x  microbenchmark  improvements   •  Exported  BufferArray  to  avatar.js  
JVM  /  JDK  op*miza*ons   •  BePer  type  checking   •  Math  intrinsics   •  Inlining  modifica*on   •  Experiments  with  par*al  escape  analysis  /  boxing   removal   •  Uncommon  trap  placement   •  java.lang.invoke –  Had  to  significantly  beef  up   MethodHandles.catchException and  many  more •   …  
There’s  SO  MUCH  MORE  I  WANT  TO   TELL  YOU  
The  cost  of  all  this:  warmup  
Warmup   •  The  need  to  recompile  methods  has  increased   warmup  *me   •  Tricks   – RewriteException  contains  scope   •  More  types  are  known  when  recompiling   – Heuris*cs   – Lazy  compila*on  
function gcd(x, y) { var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } gcd(x, y); Compiles  gcd  
function gcd(x, y) { var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } gcd(x, y); Compiles  gcd  
function gcd(x, y) { var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } Does  not  compile  gcd  
Lazy  Compila*on   •  Methods  are  only  compiled  on  demand   •  At  link  *me   – if  no  matching  signature  exists,  compile  one,  as   specific  as  possible   – If  matching  signature  does  exist,  try  to  compile  an   even  more  specific  one   •  Code  quality  is  the  same  as  eager  compila*on   – Scope  depths  are  maintained  
Warmup   •  Tricks  (for  run  2)   – Persistent  code  cache  (--persistent-code- cache)   – Op*mis*c  type  informa*on  also  cached  to  disk   – TODO:  parsed  script  for  par*al  recompila*on   •  Reduces  the  second  run  to  a  very  fast  startup   – …  not  the  first  run,  however  
The  Future  
   
Profiling  and  Java  Flight  Recorder   •  A  JFR  “Nashorn”  buPon   •  JFR  event  produc*on  is  simple,  low  overhead,   and  doesn’t  require  closing  the  source  base   •  Unique  possibility  to  create  a  JavaScript   profiler  that  no  one  else  can  do  
Profiling  and  Java  Flight  Recorder   •  A  Nashorn  JavaScript  method  is  bytecode   •  It  has  local  variable  tables,  names,  line   numbers   •  Fits  100%  into  the  JFR  framework  already   •  (IDE  plugin  for  source  level  mapping)   •  I  already  use  JFR  every  day  with  this  
JFR  events  –  the  sky’s  the  limit   •  Megamorphic  callsite   •  Subop*mal  object  shape   •  Callsite  hits,  misses,  values   •  Scope  access   •  Fast  scope  access   •  with  entry/exit,  eval,  an*paPerns   •  Split  methods   •  Excep*ons   •  Relink  with  relink  reason   •  Assump*on  made   •  Assump*on  invalidated     •  Code  pipeline  reuse     •  Timing     •  Specialized  method  invoca*on     •  Type  widening   •  Method  invalida*on   •  Boxing  /  unboxing     •  Non-­‐trivial  callsites   •  Use  of  arguments     •  Use  of  callee   •  Code  spliung   •  Class  crea*on   •  Versions  of  compiled  func*ons     •  Code  cache  store/reuse     •  Array  meta  informa*on     •  Compila*on  *me     •  Slow  source  lines     •  Byte  code  size   •  IR  size  histograms     •  Index  access  on  non-­‐arrays   •  Non-­‐index  access  on  arrays   •  …  
The  Future   •  Avatar   •  the  JVM     •  the  JDK     •  Nashorn     •  the  Hardware  (?)  
0   1   2   3   4   5   6   7   rhino   nashorn  jdk8   nashorn  jdk9  
The  Future   Let  Nashorn  be  the  intelligent  dynamic  language   execu*on  framework  for  the  JVM,  regardless  of   frontend.  
Q  &  A?   Give  us  your  benchmarks,  your  experiments,  your  hacks,     your  patch  sets,  we’d  love  your  help!  
Extra  Slides  awer  this  point  
Relinking  Callsites   •  An  indy  callsite  is  a  subclass  of   GuardedInvocation •  Invalida*on  mechanisms:   – Op*onal  guard   – Op*onal  SwitchPoint
Relinking  Callsites   •  An  indy  callsite  is  a  subclass  of   GuardedInvocation •  Invalida*on  mechanisms:   – Op*onal  guard   – Op*onal  SwitchPoints  (0  …  n)   – Op*onal  Excep*on   •  Typically  ClassCastException
/** * Constructor for a rewrite exception thrown from an optimistic function. * * @param e the {@link UnwarrantedOptimismException} that triggered this exception. * @param byteCodeSlots contents of local variable slots at the time of rewrite at the program point * @param byteCodeSymbolNames the names of the variables in the {@code byteCodeSlots} parameter. * * The array might have less elements, and some elements might be unnamed (the name can be null). The * information is provided in an effort to assist evaluation of expressions for their types by the * compiler doing the deoptimizing recompilation, * and can thus be incomplete - the more complete it is, the more expressions can be evaluated by the * compiler, and the more unnecessary deoptimizing compilations can be avoided. * * @return a new rewrite exception */ public static RewriteException create(final UnwarrantedOptimismException e, final Object[] byteCodeSlots, final String[] byteCodeSymbolNames); Linker  generates  “restOf”  method,  which  is  idenLcal  but  takes  only   RewriteExcepLon  as  argument,  rewrites  the  frame  state  and  jumps  to   the  corresponding  execuLon  point  unLl  “restOf”  method  has   executed.  Old  method  is  invalidated.  Next  call  will  generate  a  wider   version.  
apply  to  call return function() { //vararg this.initialize.apply(this, arguments); } public static L:3(ScriptFunction;Object;[Object;)Object; aload 2 // args array aload 0 // callee iconst_0 // actual number of declared params invokestatic Global.allocateArguments([Object;Object;I)[Object; astore 3 aload 1 invokedynamic get:initialize(Object;)Object; dup invokedynamic get:apply(Object;)Object; swap aload 1 aload 3 invokedynamic dyn:call(Object;Object;Object;Object;)Object; pop getstatic ScriptRuntime.UNDEFINED areturn  
return function() { //vararg this.initialize.apply(this, arguments); } public static L:3(ScriptFunction;Object;III)Object; aload 1 invokedynamic get:initialize(Object;)Object; dup invokedynamic get:apply(Object;)Object; //really loads “call” swap aload 1 iload 2 iload 3 iload 4 invokedynamic dyn:call(Object;Object;Object;III)Object; pop getstatic ScriptRuntime.UNDEFINED; areturn apply  to  call
return function() { //vararg this.initialize.apply(this, arguments); } public static L:3(ScriptFunction;Object;III)Object; aload 1 invokedynamic get:initialize(Object;)Object; dup invokedynamic get:apply(Object;)Object; //really loads “call” swap aload 1 iload 2 iload 3 iload 4 invokedynamic dyn:call(Object;Object;Object;III)Object; pop getstatic ScriptRuntime.UNDEFINED; areturn apply  to  call local :callee L0 L1 0 ScriptFunction; local :this L0 L1 1 Object; local :xarg0 L0 L1 2 I local :xarg1 L0 L1 3 I local :xarg2 L0 L1 4 I
Function.prototype.call = function() { throw “This is a JavaScript! No performance for you!”; } SwitchPoint  based  dynamic  invalida*on  –  same  mechanism  as  everewhere  else   apply  to  call

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Lagergren jvmls-2014-final

  • 1.
    Towards  na*ve  performance  with   dynamic  languages  on  the  JVM   Marcus  Lagergren,  Oracle  
  • 2.
    Towards  na*ve  performance  with   dynamic  languages  on  the  JVM   Marcus  Lagergren,  Oracle   How  far  does  invokedynamic  take  us?  
  • 3.
    Towards  na*ve  performance  with   dynamic  languages  on  the  JVM   Marcus  Lagergren,  Oracle   How  far  does  invokedynamic  take  us?   Pre$y  far  actually!  
  • 4.
    The  Legal  Slide   "THE FOLLOWING 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 DECISION. THE DEVELOPMENT, RELEASE, AND TIMING OF ANY FEATURES OR FUNCTIONALITY DESCRIBED FOR ORACLE'S PRODUCTS REMAINS AT THE SOLE DISCRETION OF ORACLE."  
  • 5.
    Who  am  I?   @lagergren    
  • 6.
    Agenda   •  Nashorn  summary   •  The  last  nine  months  of  Nashorn  and   invokedynamic  performance  work   •  How  did  we  do  it?     •  The  future  
  • 7.
    Nashorn   •  Part  of  JDK  8   – 100%  ECMA  compliant  JavaScript  run*me  wriPen   in  Java   •  ECMA  5.1  support   – Limited  ECMA  6  support  (8u40)   •  invokedynamic  based   •  Generates  bytecode   – Currently  no  AST  interpreta*on  
  • 8.
    Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on  
  • 9.
    Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements  
  • 10.
    Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements   •  Java  8u40   – Performance  release  
  • 11.
    Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements   •  Java  8u40   – Performance  release   •  Java  9    
  • 12.
    Nashorn  –  release  schedule   •  Java  8     – First  version  for  public  consump*on   •  Java  8u20   – Security  fixes  and  several  JIT  /  JDK  improvements   •  Java  8u40   – Performance  release   •  Java  9    
  • 13.
    Evangelist  Blurb   “Nashorn  is  a  really  fast  100%  JS  compilant   invokedynamic  based  JavaScript  run*me  wriPen   in  Java.  It  runs  on  top  of  the  JVM”  
  • 14.
    …  or  maybe?   “Nashorn  is  a  run*me  for  dynamic  languages  on   the  JVM.  Nashorn  takes  away  the  pain  and   performance  loss  of  bridging  the  gap  between   language  and  bytecode.  Types,  objects  and  code   are  automa*cally  adapted  to  be  an  op*mal  fit  in   the  JVM  mould”  
  • 15.
  • 16.
    JavaScript   “Once  you  admit  that  EVERYTHING  IS  TERRIBLE,      the  universe  opens  infinitely  many  doors  for            you...    TO  TERRIBLE.”                      -­‐  Jerry  Kuch  
  • 17.
    Where  were  we  last  October?   Octane  Benchmark  r31   0   0.2   0.4   0.6   0.8   1   1.2   rhino   nashorn  jdk8  
  • 18.
    Where  are  we  today?   Octane  Benchmark  r31   0   1   2   3   4   5   6   7   rhino   nashorn  jdk8   nashorn  jdk9  
  • 19.
    …  against  v8   Octane  Benchmark  r31   0   2   4   6   8   10   12   rhino   nashorn  jdk8   nashorn  jdk9   v8  
  • 20.
    v8  bleeding  edge…   Octane  Benchmark  r31   0   2   4   6   8   10   12   14   rhino   nashorn  jdk8   nashorn  jdk9   v8   v8  latest  
  • 21.
  • 22.
    avatar.js   •  Project  Avatar   – HTTP  benchmark   – REST  benchmark   •  Comparable  to  v8  /  na*ve  performance   •  8u40  will  deliver  plenty  of  improvements   •  Use  of  exposed  mechanisms   – BufferArrayData  
  • 23.
    avatar.js   •  Project  Avatar   – HTTP  benchmark   – REST  benchmark   •  Comparable  to  v8  /  na*ve  performance   •  8u40  will  deliver  plenty  of  improvements   •  Use  of  exposed  mechanisms   – BufferArrayData  
  • 24.
  • 25.
  • 26.
    Op*mis*c  Type  Run*me  Architecture   [hPp://openjdk.java.net/jeps/196]  
  • 27.
    Just  compile  to  bytecode!   •  “The  JVM  is  technically  advanced  and  has  man   decades  of  JIT  op*miza*ons”   •  “The  JVM  magically  JITs  arbitrary  bytecode  to   fast  na*ve  code”  
  • 28.
    Just  compile  to  bytecode!   •  “The  JVM  is  technically  advanced  and  has  man   decades  of  JIT  op*miza*ons”   •  “The  JVM  magically  JITs  arbitrary  bytecode  to   fast  na*ve  code”   •  Nope  :-­‐(  
  • 30.
    function gcd(x, y){ var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } gcd(x, y); GCD  
  • 31.
    GCD  –  Naïve  &  JS  Compliant   public static gcd(Object;Object;Object;)Object; aload 1 astore 4 aload 2 astore 5 goto L2 aload 4 aload 5 invokedynamic GT:ZOO_Z(Object;Object;)Z; ifeq L4 aload 4 invokestatic JSType.toNumber(Object;)D aload 5 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 4 goto L2 aload 5 invokestatic JSType.toNumber(Object;)D aload 4 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 5 aload 4 aload 5 invokedynamic NE:ZOO_Z(Object;Object;)Z ifne L3 aload 4 areturn
  • 32.
    GCD  –  vs  Ideal   public static gcd(Object;Object;Object;)Object; aload 1 astore 4 aload 2 astore 5 goto L2 aload 4 aload 5 invokedynamic GT:ZOO_Z(Object;Object;)Z; ifeq L4 aload 4 invokestatic JSType.toNumber(Object;)D aload 5 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 4 goto L2 aload 5 invokestatic JSType.toNumber(Object;)D aload 4 invokestatic JSType.toNumber(Object;)D dsub invokestatic java/lang/Double.valueOf(D)Ljava/lang/Double; astore 5 aload 4 aload 5 invokedynamic NE:ZOO_Z(Object;Object;)Z ifne L3 aload 4 areturn public static gcd(Object;II)I iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 isub istore 3 goto L14 iload 4 iload 3 isub istore 4 goto L9 iload 3 ireturn
  • 33.
    Op*mis*c  Types   • Factor  150x  difference  in  execu*on  speed   between  the  two   •  “Generate  Java-­‐like  bytecode”  
  • 35.
    Op*mis*c  Types   • Generate  as  op*mis*c  a  func*on  as  possible   •  Surround  op*mis*c  opera*ons  with  excep*on   handlers   •  When  a  type  is  too  narrow   – Store  frame  state  (no  bytecode  stack)   – Take  a  con*nua*on  and  finish  method   – Tell  linker  to  regenerate  more  conserva*vely  
  • 36.
    Op*mis*c  Types   long   double   Object  (pessimis*c)  int    
  • 37.
    Implementa*on   function f(){ return x * y; // x,y in scope }
  • 38.
    public static f(ScriptFunction;Object;)D aload0 invokevirtual ScriptFunction.getScope()LScriptObject; astore 2 // store scope in slot 2 aload 2 // load scope invokedynamic get:x(Object;)Object; aload 2 // load scope invokedynamic get:y(Object;)Object; swap invokestatic JSType.toNumber(Object;)D dup2_x1 pop2 invokestatic JSType.toNumber(Object;)D dmul dreturn  
  • 39.
    public static f(ScriptFunction;Object;)I aload0 invokevirtual ScriptFunction.getScope()ScriptObject; astore 2 // store scope in slot 2 aload 2 invokedynamic get:x(Object;)I istore 3 iload 3 aload 2 invokedynamic get:y(Object;)I invokedynamic imul(II)I ireturn  
  • 40.
    public static f(ScriptFunction;Object;)I aload0 invokevirtual ScriptFunction.getScope()ScriptObject; astore 2 // store scope in slot 2 aload 2 invokedynamic get:x(Object;)I // program point 1 istore 3 iload 3 aload 2 invokedynamic get:y(Object;)I // program point 2 invokedynamic imul(II)I // program point 3 ireturn  
  • 41.
    public static f(ScriptFunction;Object;)I aload0 invokevirtual ScriptFunction.getScope()ScriptObject; astore 2 aload 2 invokedynamic get:x(Object;)I // program point 1 istore 3 iload 3 aload 2 invokedynamic get:y(Object;)I // program point 2 invokedynamic imul(II)I // program point 3 ireturn // catch (UnwarrantedOptimismException e) iconst_4 anewarray Object // 4 local variables in frame iload 3 // load variable 3 (tmp = x) invokedynamic populateArray([Object;I)[Object; goto rwe iconst_3 anewarray Object // 3 local variables in frame rwe: aload 0 // load function aload 1 // load ‘this’ aload 2 // load scope invokedynamic populateArray([Object;Object;Object;Object;)[Object; iconst_0 invokestatic getString$array(I)[String; invokestatic RewriteException.create(UnwarrantedOptimismException;[Object; [String;)RewriteException; athrow  
  • 42.
    GCD  –  Ideal   public static gcd(Object;II)I iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 isub istore 3 goto L14 iload 4 iload 3 isub istore 4 goto L9 iload 3 ireturn
  • 43.
    GCD  –  vs  Nashorn   public static gcd(Object;II)I iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 isub istore 3 goto L14 iload 4 iload 3 isub istore 4 goto L9 iload 3 ireturn public static gcd(Object;II)I try { iload 1 istore 3 iload 2 istore 4 iload 3 iload 4 if_icmpeq L10 iload 3 iload 4 if_icmple L12 iload 3 iload 4 invokedynamic isub(II)I //indy because sub may overflow istore 3 goto L14 iload 4 iload 3 invokedynamic isub(II)I //indy because sub may overflow istore 4 goto L9 iload 3 ireturn } catch (UnwarrantedOptimismException e) { //save state and throw RewriteException to linker }
  • 44.
    Sta*c  Compiler  Enhancements   •  Liveness   function liveness() { var x = 0; for (var i = 0;i < 10; i++) { x += i; } x += "test"; return x; } What  about  local  variables?  The  slot   type  is  hard  coded  in  the  local   variable  table!  
  • 45.
    Sta*c  Compiler  Enhancements   •  Liveness   function liveness() { var x = 0; for (var i = 0;i < 10; i++) { x += i; } x += "test"; return x; }  public static liveness(LObject;)LObject; iconst_0 invokestatic Integer.valueOf (I)Integer; astore 2 dconst_0 dstore 3 goto L2 aload 2 invokestatic JSType.toNumber (LObject;)D dload 3 dadd invokestatic Double.valueOf (D)Double; astore 2 dload 3 dconst_1 dadd dstore 3 dload 3 ldc 10.0 dcmpg iflt L3 aload 2 ldc "test" invokedynamic ADD:OOO_I(LObject;LObject;)Object astore 2 aload 2 areturn local x Ljava/lang/Object; L0 L6 2 local i D L0 L6 3
  • 46.
    Sta*c  Compiler  Enhancements   •  Liveness   function liveness() { var x = 0; for (var i = 0;i < 10; i++) { x += i; } x += "test"; return x; }   public static liveness(Object;)Object; iconst_0 istore 1 iconst_0 istore 3 iload 3 bipush 10 if_icmpge L10 iload 1 iload 3 invokedynamic iadd(II)I istore 1 iload 3 dup iconst_1 invokedynamic iadd(II)I istore 3 pop goto L9 iload 1 invokestatic Integer.valueOf(I)Integer; ldc "test" invokestatic ADD(Object;Object;)Object; astore 2 aload 2 areturn // exception handler goes here... local x L6 L13 1 I local x L13 L2 2 Object; local i L8 L2 3 I
  • 47.
  • 48.
    Field  Representa*on   • jdk.nashorn.internal.runtime.ScriptObject –  Contains  a  PropertyMap •  Shape   –  Contains  a  number  of  fields   •  Scope  variables   –  Contains  a  growing  array   •  Spills  –  also  scope  variables   –  and  lots  of  other  things,  e.g.  ArrayData    
  • 49.
    Field  Representa*on   publicabstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; long spillPrimitives; // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; long p1, p2, p3, p4; }                
  • 50.
    Property  Maps   PropertyMap AccessorProperty:red (flags = 0) slot = 0 AccessorProperty: green (flags = 0) slot = 1 AccessorProperty: blue (flags = 0) slot = 3 SpillProperty: timeStamp (flags = NON_MODIFIABLE), index = 0 •  Immutable   •  Copy  on  write  when  any  aspect   changes   •  Used  for  reference  guards  for  almost   all  invokedynamic  sites  
  • 51.
    Field  Representa*on   varscopeVar; function f() { scopeVar &= 17; }            
  • 52.
    Field  Representa*on   varscopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as  Object,  is  a   java.lang.Integer 2.  Coerce  to  int  (unbox  from  java.lang.Integer)   3.  Execute  logical  and  (iand)   4.  Coerce  result  to  object  (box  to  java.lang.Integer)   5.  putfield  result  
  • 53.
    Field  Representa*on   varscopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as   java.lang.Integer 2.  Coerce  to  int  (unbox  from  java.lang.Integer)   3.  Execute  logical  and     4.  Coerce  result  to  object  (box  to  java.lang.Integer)   5.  putfield  result  
  • 54.
    Field  Representa*on   publicabstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; long spillPrimitives; // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; p4; }                
  • 55.
    Field  Representa*on   publicabstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; protected long[] spillPrimitives; s // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; private long j0, j1, j2, j3;, p2, p3, p4; }
  • 56.
    Field  Representa*on   “EWW!  Fat  pointers”   public abstract class ScriptObject implements PropertyAccess { protected Object[] spillObjects; protected long[] spillPrimitives; s // most guards are a ref comparison on map private PropertyMap map; } public JO$4 extends ScriptObject { private Object o0, o1, o2, o3; private long j0, j1, j2, j3;, p2, p3, p4; }
  • 57.
    Field  Representa*on   obj.j= (long)x; //int obj.j = x; //long obj.j = Double.doubleToLongBits(x); //double obj.o = x; //object return (int)obj.j; //int return obj.j; //long return Double.longBitsToDouble(obj.j); //double return obj.o; //object SePers   GePers  
  • 58.
    Property  Maps  and  Types   •  Immutable   •  Copy  on  write  when  any  aspect  changes   •  Used  for  reference  guards  for  almost  all   invokedynamic  sites   PropertyMap AccessorProperty: red (flags = 0) slot = 0, type = int AccessorProperty: green (flags = 0) slot = 1, type = int AccessorProperty: blue (flags = 0) slot = 3, type = int SpillProperty: timeStamp (flags = NON_MODIFIABLE), index = 0, type = object
  • 59.
    Property  Maps  and  Types   PropertyMap AccessorProperty: red (flags = 0) type=int AccessorProperty: green (flags = 0) type=int AccessorProperty: blue (flags = 0) type=object SpillProperty: timeStamp (flags = NON_MODIFIABLE),type=object •  Immutable   •  Copy  on  write  when  any  aspect  changes   •  INCLUDING  FIELD  TYPE   •  Used  for  reference  guards  for  almost  all   invokedynamic  sites   •  INCLUDING  FIELD  GETTERS  AND  SETTERS   PropertyMap AccessorProperty: red (flags = 0) slot = 0, type = int AccessorProperty: green (flags = 0) slot = 1, type = int AccessorProperty: blue (flags = 0) slot = 3, type = int SpillProperty: timeStamp (flags = NON_MODIFIABLE), index = 0, type = object
  • 60.
    Field  Representa*on   varscopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as   java.lang.Integer 2.  Coerce  to  int  (unbox  from  java.lang.Integer)   3.  Execute  logical  and  (iand)   4.  Coerce  result  to  object  (box  to  java.lang.Integer)   5.  putfield  result  
  • 61.
    Field  Representa*on   varscopeVar; function f() { scopeVar &= 17; }             1.  Load  scope  var  (getfield),  stored  as                  long 1.  Coerce  to  int  (l2i)   2.  Execute  logical  and  (iand)   3.  Coerce  to  long  (i2l)   4.  putfield  result  
  • 62.
    Field  Representa*on   • BePer  representa*on?   – Unsafe?   – Needs  some  JVM  magic,  anyway   – Test  implementa*on:   sun.misc.TaggedArray – Object  shape  change  on  GC?   – Let’s  form  an  expert  group!        
  • 63.
    Closing  the  circle:      Op*mis*c  Buil*ns    
  • 64.
    Op*mis*c  buil*ns       /** * ECMA 15.4.4.7 Array.prototype.push (args...) * * @param self self reference * @param args arguments to push * @return array length after pushes */ @Function(attributes = Attribute.NOT_ENUMERABLE, arity = 1) public static Object push(final Object self, final Object... args) { try { final ScriptObject sobj = (ScriptObject)self; if (bulkable(sobj) && sobj.getArray().length() + args.length <= JSType.MAX_UINT) { final ArrayData newData = sobj.getArray().push(true, args); sobj.setArray(newData); return newData.length(); } long len = JSType.toUint32(sobj.getLength()); for (final Object element : args) { sobj.set(len++, element, true); } sobj.set("length", len, true); return len; } catch (final ClassCastException | NullPointerException e) { throw typeError(Context.getGlobal(), e, "not.an.object", ScriptRuntime.safeToString(self)); } }    
  • 65.
    Relinking  Callsites   • Can  now  be  done  with  Excep*ons  as  well  as  guards  or  SwitchPoints   •  For  example:  con*nuous  arrays   –  Previously  done  with  mul*ple  guards   •  array[x] & 17 •  Array  gePer  links  to:   try { //combinator – not real code return ((ContinuousArrayData)scriptObject. getArrayData()). getElementGetter(int.class). get(index); //turns AIOOBE to CCE } catch (ClassCastException e) { //relink } "  
  • 66.
    Op*mis*c  buil*ns       /** * ECMA 15.4.4.7 Array.prototype.push (args...) * * @param self self reference * @param args arguments to push * @return array length after pushes */ @Function(attributes = Attribute.NOT_ENUMERABLE, arity = 1) public static Object push(final Object self, final Object... args) { try { final ScriptObject sobj = (ScriptObject)self; if (bulkable(sobj) && sobj.getArray().length() + args.length <= JSType.MAX_UINT) { final ArrayData newData = sobj.getArray().push(true, args); sobj.setArray(newData); return newData.length(); } long len = JSType.toUint32(sobj.getLength()); for (final Object element : args) { sobj.set(len++, element, true); } sobj.set("length", len, true); return len; } catch (final ClassCastException | NullPointerException e) { throw typeError(Context.getGlobal(), e, "not.an.object", ScriptRuntime.safeToString(self)); } }    
  • 67.
    Op*mis*c  buil*ns       // pre: linker checks that callsite argument matches @SpecializedFunction(guard=SpecializedFunction.Guard.CLASSCAST_EXCEPTION_CONTINUOUS_ARRAY) public static long push(final Object self, final int arg) { try { return ((ContinuousArrayData)self).getArray()).push(arg); } catch (final NullPointerException e) { //fallthru } throw new ClassCastException();  }
  • 68.
    Op*mis*c  buil*ns •  Lots  of  candidates   –  Array •  push, pop, shift, unshift, length –  String •  charAt, charCodeAt, length –  Number, Math –  Function.apply to    Function.call –  … •  We  can  use  the  same  recompila*on  framework   for  na*ve  methods  as  for  JavaScript  methods  
  • 69.
    An*paPern  that  JS  programmers  love   var Class = { create: function() { return function() { //vararg this.initialize.apply(this, arguments); } } }; Color = Class.create(); Color.prototype = { red: 0, green: 0, blue: 0, initialize: function(r, g, b) { this.red = r; this.green = g; this.blue = b; }, toString: function() { return this.red + “ “ + this.green + “ “ + this.blue; } } print(new Color(0xff, 0xee, 0xcc));
  • 70.
  • 71.
    Par*al  Evalua*on   for(var i = 0; i < x.length; i++) { //x is loop invariant ) •  x  can  use  MethodHandle.constant  as  an  indy   gePer.   •  We  can  use  a  SwitchPoint  to  invalidate  it,   given  that  x  is  modified  in  the  scope   •  Either  forbid  this  callsite  from  being  constant   again,  or  allow  n  retries   •  Or  try  with  a  receiver  guard  
  • 72.
    U*lize  java.nio.ByteBuffer •  Anyone  using  WebGL/ECMA  6  TypedArrays   can  get  near-­‐na*ve  performance   •  java.nio.ByteBuffer   •  5-­‐10x  microbenchmark  improvements   •  Exported  BufferArray  to  avatar.js  
  • 73.
    JVM  /  JDK  op*miza*ons   •  BePer  type  checking   •  Math  intrinsics   •  Inlining  modifica*on   •  Experiments  with  par*al  escape  analysis  /  boxing   removal   •  Uncommon  trap  placement   •  java.lang.invoke –  Had  to  significantly  beef  up   MethodHandles.catchException and  many  more •   …  
  • 74.
    There’s  SO  MUCH  MORE  I  WANT  TO   TELL  YOU  
  • 75.
    The  cost  of  all  this:  warmup  
  • 76.
    Warmup   •  The  need  to  recompile  methods  has  increased   warmup  *me   •  Tricks   – RewriteException  contains  scope   •  More  types  are  known  when  recompiling   – Heuris*cs   – Lazy  compila*on  
  • 77.
    function gcd(x, y){ var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } gcd(x, y); Compiles  gcd  
  • 78.
    function gcd(x, y){ var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } gcd(x, y); Compiles  gcd  
  • 79.
    function gcd(x, y){ var a = x; var b = y; while (a != b) { if (a > b) { a = a - b; } else { b = b - a; } } return a; } Does  not  compile  gcd  
  • 80.
    Lazy  Compila*on   • Methods  are  only  compiled  on  demand   •  At  link  *me   – if  no  matching  signature  exists,  compile  one,  as   specific  as  possible   – If  matching  signature  does  exist,  try  to  compile  an   even  more  specific  one   •  Code  quality  is  the  same  as  eager  compila*on   – Scope  depths  are  maintained  
  • 81.
    Warmup   •  Tricks  (for  run  2)   – Persistent  code  cache  (--persistent-code- cache)   – Op*mis*c  type  informa*on  also  cached  to  disk   – TODO:  parsed  script  for  par*al  recompila*on   •  Reduces  the  second  run  to  a  very  fast  startup   – …  not  the  first  run,  however  
  • 82.
  • 83.
  • 84.
    Profiling  and  Java  Flight  Recorder   •  A  JFR  “Nashorn”  buPon   •  JFR  event  produc*on  is  simple,  low  overhead,   and  doesn’t  require  closing  the  source  base   •  Unique  possibility  to  create  a  JavaScript   profiler  that  no  one  else  can  do  
  • 85.
    Profiling  and  Java  Flight  Recorder   •  A  Nashorn  JavaScript  method  is  bytecode   •  It  has  local  variable  tables,  names,  line   numbers   •  Fits  100%  into  the  JFR  framework  already   •  (IDE  plugin  for  source  level  mapping)   •  I  already  use  JFR  every  day  with  this  
  • 86.
    JFR  events  –  the  sky’s  the  limit   •  Megamorphic  callsite   •  Subop*mal  object  shape   •  Callsite  hits,  misses,  values   •  Scope  access   •  Fast  scope  access   •  with  entry/exit,  eval,  an*paPerns   •  Split  methods   •  Excep*ons   •  Relink  with  relink  reason   •  Assump*on  made   •  Assump*on  invalidated     •  Code  pipeline  reuse     •  Timing     •  Specialized  method  invoca*on     •  Type  widening   •  Method  invalida*on   •  Boxing  /  unboxing     •  Non-­‐trivial  callsites   •  Use  of  arguments     •  Use  of  callee   •  Code  spliung   •  Class  crea*on   •  Versions  of  compiled  func*ons     •  Code  cache  store/reuse     •  Array  meta  informa*on     •  Compila*on  *me     •  Slow  source  lines     •  Byte  code  size   •  IR  size  histograms     •  Index  access  on  non-­‐arrays   •  Non-­‐index  access  on  arrays   •  …  
  • 87.
    The  Future   • Avatar   •  the  JVM     •  the  JDK     •  Nashorn     •  the  Hardware  (?)  
  • 88.
    0   1   2   3   4   5   6   7   rhino   nashorn  jdk8   nashorn  jdk9  
  • 89.
    The  Future   Let  Nashorn  be  the  intelligent  dynamic  language   execu*on  framework  for  the  JVM,  regardless  of   frontend.  
  • 90.
    Q  &  A?   Give  us  your  benchmarks,  your  experiments,  your  hacks,     your  patch  sets,  we’d  love  your  help!  
  • 91.
    Extra  Slides  awer  this  point  
  • 92.
    Relinking  Callsites   • An  indy  callsite  is  a  subclass  of   GuardedInvocation •  Invalida*on  mechanisms:   – Op*onal  guard   – Op*onal  SwitchPoint
  • 93.
    Relinking  Callsites   • An  indy  callsite  is  a  subclass  of   GuardedInvocation •  Invalida*on  mechanisms:   – Op*onal  guard   – Op*onal  SwitchPoints  (0  …  n)   – Op*onal  Excep*on   •  Typically  ClassCastException
  • 94.
    /** * Constructor fora rewrite exception thrown from an optimistic function. * * @param e the {@link UnwarrantedOptimismException} that triggered this exception. * @param byteCodeSlots contents of local variable slots at the time of rewrite at the program point * @param byteCodeSymbolNames the names of the variables in the {@code byteCodeSlots} parameter. * * The array might have less elements, and some elements might be unnamed (the name can be null). The * information is provided in an effort to assist evaluation of expressions for their types by the * compiler doing the deoptimizing recompilation, * and can thus be incomplete - the more complete it is, the more expressions can be evaluated by the * compiler, and the more unnecessary deoptimizing compilations can be avoided. * * @return a new rewrite exception */ public static RewriteException create(final UnwarrantedOptimismException e, final Object[] byteCodeSlots, final String[] byteCodeSymbolNames); Linker  generates  “restOf”  method,  which  is  idenLcal  but  takes  only   RewriteExcepLon  as  argument,  rewrites  the  frame  state  and  jumps  to   the  corresponding  execuLon  point  unLl  “restOf”  method  has   executed.  Old  method  is  invalidated.  Next  call  will  generate  a  wider   version.  
  • 95.
    apply  to  call returnfunction() { //vararg this.initialize.apply(this, arguments); } public static L:3(ScriptFunction;Object;[Object;)Object; aload 2 // args array aload 0 // callee iconst_0 // actual number of declared params invokestatic Global.allocateArguments([Object;Object;I)[Object; astore 3 aload 1 invokedynamic get:initialize(Object;)Object; dup invokedynamic get:apply(Object;)Object; swap aload 1 aload 3 invokedynamic dyn:call(Object;Object;Object;Object;)Object; pop getstatic ScriptRuntime.UNDEFINED areturn  
  • 96.
    return function() {//vararg this.initialize.apply(this, arguments); } public static L:3(ScriptFunction;Object;III)Object; aload 1 invokedynamic get:initialize(Object;)Object; dup invokedynamic get:apply(Object;)Object; //really loads “call” swap aload 1 iload 2 iload 3 iload 4 invokedynamic dyn:call(Object;Object;Object;III)Object; pop getstatic ScriptRuntime.UNDEFINED; areturn apply  to  call
  • 97.
    return function() {//vararg this.initialize.apply(this, arguments); } public static L:3(ScriptFunction;Object;III)Object; aload 1 invokedynamic get:initialize(Object;)Object; dup invokedynamic get:apply(Object;)Object; //really loads “call” swap aload 1 iload 2 iload 3 iload 4 invokedynamic dyn:call(Object;Object;Object;III)Object; pop getstatic ScriptRuntime.UNDEFINED; areturn apply  to  call local :callee L0 L1 0 ScriptFunction; local :this L0 L1 1 Object; local :xarg0 L0 L1 2 I local :xarg1 L0 L1 3 I local :xarg2 L0 L1 4 I
  • 98.
    Function.prototype.call = function(){ throw “This is a JavaScript! No performance for you!”; } SwitchPoint  based  dynamic  invalida*on  –  same  mechanism  as  everewhere  else   apply  to  call