5장. Execution Engine

Java Performance
artdb@ex-em.com | performeister.tistory.com | twitter @novathinker

Execution Engine

Java Performance
2


Execution Engine
1) Execution Engine
2) Interpreter
3) JIT Compiler
4) Execution Engine
IBM JIT Compiler
1) JIT Compiler
2) Mixed Mode Interpreter
3) JIT Compiler Optimization
4) JIT Compiler
Hotspot Compiler
1) Hotspot Compiler
2) Hotspot Compiler Optimization
3) Hotspot Compiler Option

Java Performance
4
Java Performance Fundamental | twitter @novathinker
artdb@ex-em.com | performeister.tistory.com
Execution Engine

• Execution Engine
Bytecode Runtime Module
• Instruction
– Bytecode = Instruction
– Execution Engine Instruction

• Instruction = Opcode + Operand
• Execution Engine opcode fetch
opcode fetch

Java Performance
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Execution Engine

• Instruction
– Bytecode method level
• Method return Exception

– Instruction
• opcode
opcode
• Goto return opcode
• Exception catch
opcode

Java Performance
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Execution Engine

– Bytecode mnemonic
>javap –c classﬁle (bytecode)

Java Source Code

Method

offset
Instruction Mnemonic
Operand

Java Performance
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Execution Engine

• JVM

(Source: Sun Microsystems)
http://java.sun.com/developer/technicalArticles/Networking/HotSpot/

Execution Engine
Java Performance
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– Bytecode Runtime Module

Java Source Classﬁle
.java .class

Javac .java

JVM

Runtime Interpreting Execution Bytecode
Data Area Engine Stream ClassLoader

Java Performance
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Execution Engine

– Bytecode Interpreting

– Interpreting

• Interpreter

• JIT Compile

Java Performance
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Execution Engine

• Interpreter
– Bytecode compile
– Bytecode

– Bytecode
–
– JVM Bytecode interpreter

Java Performance
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Execution Engine

• JIT(Just-in-time) Compiler
– Bytecode native code

– Native code compile
– Native Code
Cache

– Interpreter

– Lazy fashion

Java Performance
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Execution Engine


bytecode
Class a{ Heap Method Table
a.f1(); f1()
a.f3(); ptr f1()
f3()
} f2()
Object A f3() JIT
f1() native
f4() code
f3()
…

Java Performance
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Execution Engine


Source code bytecode Native code

int a; iload_0 ld [$fp-0] , $r0
st $r0, [$sp+0]
int b; iload_1 ld [$fp-4] , $r1
st $r1, [$sp+4]
int c = a + b; iadd ld [$sp+0] , $r0
ld [$sp+0] , $r1
add $r0, $r1, $r2
st $r2, [$sp+0]

Java Performance
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Execution Engine

– Loop bytecode

Java Performance
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Execution Engine

–
• Java
•

Array_ptr Stack

A[0][0]
Object_ptr A[0] Object_ptr
A[0][1]
length A[1] length A[1][0]
Class_ptr
Class_ptr A[1][1]
Object_ptr
Heap Class_ptr
length

Method Area
Class runtime type Class runtime type info
Method block Method block

Java Performance
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Execution Engine

–
•2 5
• Dimension

Java Performance

IBM JIT Compiler

17

Java Performance
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IBM JIT Compiler

• JIT Compiler
– JIT compiler method
(1) Method Method
table JIT compiler
(2) JIT Compiler Method Native Code
Cache
(3) Method
(4) Method table Native Code
Code
– JVM Method Call

Java Performance
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IBM JIT Compiler

• JIT Compiler

Java Application

Java VM(Interpreter)
bytecode

JIT compiler

native code

Java Performance
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IBM JIT Compiler

• JIT Compiler
– JIT Enable
• JVM Startup Applet

– JIT Disable
• JVM Bytecode
interpret
– IBM JVM Mixed Mode Interpreter(MMI)

Java Performance
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IBM JIT Compiler

• Mixed Mode Interpreter(MMI)
– 1.4
– JVM Runtime

– Fast Assembler bytecode interpreter
– JIT
– Method count threshold
compile
– Low-usage method compile
compile

Java Performance
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IBM JIT Compiler

– 1.4.2 JIT, MMI JVM

– JIT shared library(libjitc.so)
– Java5 JIT JVM component
MMI
– Java5 MMI

Java Performance
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IBM JIT Compiler


Java Application

Java VM(Interpreter)
bytecode

JIT compiler MMI

native code threshold

Java Performance
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IBM JIT Compiler

–
• Method call compile
• count
• Count Compilation Threshold
compile
• Compile count 0
• Count
• JIT Recompile Threshold compile
Optimization recompile
• method

Java Performance
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IBM JIT Compiler

– JIT/MMI Mode
MODE JIT MMI Effect

•JVM ,
default ON ON
•Method Interpret JIT Compile
• IBM_MIXED_MODE_THRESHOLD=0
MMI
ON OFF
Disable
• Method JIT Compile
•JVM
•-Xint
• -Djava.compiler=NONE
JIT • JAVA_COMPILER=NONE
OFF OFF
Disable • Interpret JVM
Runtime
•JIT compile MMI

Java Performance
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IBM JIT Compiler

– MMI Threshold
• IBM_MIXED_MODE_THRESHOLD=<x>[,<y>]

• <x> interpret
– method
– Default OS 500 1000
• <y> compile seed
– compile method
– y x Threshold
– default 0

Java Performance
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IBM JIT Compiler

• JIT Compiler Optimization

Java Performance
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IBM JIT Compiler

• Optimization Level
– Optimization
– -Xjit
– JVM Adaptive

noOpt cold Warm hot veryHot scorching

Java Performance
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IBM JIT Compiler

• Optimization Level
– Adaptive compilation
• Methods interpret interpreted

•N ‘warm’ level compile warm
• Sampling thread hot methods
hot
• Methods ‘hot’ ‘scorching’
recompile profiling

• Temporary proﬁling step
‘scorching’ scorching

Java Performance
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IBM JIT Compiler

• Optimization Phase (~1.4.2)
– 1.4.2 4
• Bytecode Optimization
: bytecode
– Flow analysis
– Static method inlining
– Virtual method inlining
– Idiomatic translation
– Field privatization
– Stack and register analysis
– bytecode quad native code
– conventional native compiler

Java Performance
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IBM JIT Compiler

• Optimization Phase(~1.4.2)
• Quad Optimization
– Control flow optimization
– Data flow optimization
– Escape analysis
– Loop analysis
– Data flow analysis
– Quad Optimization
• DAG(Direct Acyclic Graph) Optimization
– Induction analysis
– Loop Versioning
– Loop Striding
– Induction removal
– Dead storage analysis

Java Performance
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IBM JIT Compiler

• Optimization Phase(~1.4.2)
• Native code Generation
– Bytecode Quad Quad DAG Native
Code

Java Performance
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IBM JIT Compiler

• Optimization Phase (Java5~)
– Java5 5 phase

– Bytecode Method tree
Native Code

– Compile code cache

Java Performance
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IBM JIT Compiler

• Inlining
– caller

inlining

– Trivial inlining
– Call graph inlining
– Tail recursion elimination
– Virtual call guard optimization

IBM JIT Compiler
Java Performance
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• Local optimization
–
– Local data flow analysis and optimizations
– Register usage optimization
– Simplification of Java Idioms
• Control flow optimizations
– Method control flow
– Code reordering, splitting and removal
– Loop reduction and inversion
– Loop Striding and loop-invariant code motion
– Loop unrolling and peeling
– Loop versioning and specialization
– Exception-directed optimization - Switch
analysis

IBM JIT Compiler
Java Performance
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• Global Optimization
– method
– Expensive
– Global data ﬂow analysis and optimizations
– Partial redundancy elimination
– Escape analysis
– GC and memory allocation optimizations
– Synchronization optimization
• Native code generation
– Method tree machine code
– Platform

IBM JIT Compiler
Java Performance
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• JIT Compiler
–
• IBM_MIXED_MODE_THRESHOLD
• JITC_COMPILEOPT
– NMMI2JIT : hot Method compile
– NINLINING : Inline code
– NQOPTIMIZE : Quad
– NDOPT : DAG
– NBCOPT : Bytecode
– NALL : Optimization

– Java5

IBM JIT Compiler
Java Performance
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• JIT Compiler
– JVM Parameter
• -Xint : interpret only
• -Xjit[:<parameter>=<value>,…]
– count=<n>
: compile , n=0 method
compile
– limitFile=(<Filename>,<m>,<n>)
: m n compile
– optlevel=[noOpt | cold | warm | hot | veryHot |
scorching]
: Method Optimization level
– Verbose
: JIT Compiler method compile

Java Performance

• Class Sharing

JVM1

Java Performance

• Class Sharing

Cached Classes

JVM1

Java Performance artdb@ex-em.com | performeister.tistory.com | twitter @novathinker

• Class Sharing

Cached Classes

JVM2


• Class Sharing

Cached Classes

JVM2 JVM3 JVM4


• Class Sharing

Cached Classes Cached Classes

JVM2 JVM3 JVM4


• Class Sharing

Shared Cache 1 Shared Cache 2
AOT Code AOT Code

Cached Classes Cached Classes

JVM2 JVM3 JVM4

Java Performance

-Xscminaot AOT Code

-Xscmaxaot
-Xscmaxaot
AOT Code

-Xscmx

Shared Classes

Metadata

Java Performance

Hotspot Compiler

Java Performance
42
Hotspot Compiler

• Hotspot Compiler
– Mixed Mode system
• Interpreter JIT Compiler
• Bytecode interpreted
• Proﬁling Dynamic Compile
• recompile interpreted

Interpreted

Recompile
Proﬁling
Interpreted Again

Dynamic
Compilation

Java Performance
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Hotspot Compiler

– Mixed Mode system
• Hotspot Default
• Hotspot
– Proﬁling Hot Code compile

– Compile

– Hot code Optimization
– Compile

Java Performance
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Hotspot Compiler

– Hotspot VM
– Client Server
– Compiler

Java Hotspot
Server VM
Java Hotspot
Performance Engine

Java Hotspot
Client VM

Java Performance
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Hotspot Compiler

– Server VM
• Advanced Adaptive Compiler
– Client VM
• Compile

Client Server

C1 Compiler C2 Compiler

Runtime Runtime

Hotspot Compiler
Java Performance
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– Client Compiler
• C1 Compiler
• Optimization
• Value Numbering, inlining, class analysis

• Static Compile

• Proﬁling Counting

Value Numbering

Hotspot Compiler
Java Performance
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– Server Compiler
• Opto C2 Compiler
• High optimizing bytecode compiler
• ‘Intermediate’ optimizing compiler
• Interpreter Proﬁling Optimization

• Inlining
– CHA Proﬁling Data Inline Decision
• Loop Optimization
• Loop Unrolling

Hotspot Compiler
Java Performance
artdb@ex-em.com | performeister.tistory.com48

• Hotspot Compiler Optimization
– Server Compiler
• Common Sub-expression Elimination
–

tmp = b * c;
a = b * c + g; a = tmp + g;
d = b * c * d; CSE d = tmp * d;
e = b * c; e = tmp;
• Loop unrolling
– Loop

array[0] = 0;
for (int i; i < 3; i++)
array[i] = i; Loop Unrolling array[1] = 1;
array[2] = 2;

Hotspot Compiler
Java Performance
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– Server Compiler
• On Stack Replacement
– Loop Interpreted code Compiled code

• Main method 1

• Main loop

• 10000 compile

• main interpreting

• 14000 OSR

• loop Compile code

Hotspot Compiler
Java Performance
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– Server Compiler
• array-bounds check elimination
– Array range check
– Array Index ,

• Dead Code Elimination
– code compile

Hotspot Compiler
Java Performance
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– Server Compiler
• Code Hoisting
– (hoist)

Hoisting

• Data Flow Analysis
– Data
• Deoptimization
– Hotspot
– Compile Interpret

Hotspot Compiler
Java Performance
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• Hotspot Compiler Option
• -Xint
: Interpret Mode
• -XX:+AggressiveOpts (+ Java5 update 6)
: Compile Optimization
• -XX:CompileThreshold=<value>
: compile (Client 1500, Server
10000)
• -Xcomp
: code

Hotspot Compiler
Java Performance
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• -Xbatch
: background compilation
Method compile
background process
• -XX:+AlwaysCompileLoopMethods
: Default false Loop method
Compile
• -XX:+BackgroundCompilation
: background JIT Compile
enable compile interpreted code

Hotspot Compiler
Java Performance
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• -XX:CICompilerCount=<value>
: Maximum concurrent compile Thread
• -XX:+Cltime
: JIT Compiler Print
• -XX:+PrintCompilation
: Method Compile

Java Performance
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5장. Execution Engine

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