2장. Runtime Data Areas

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

Runtime Data Areas

Java Performance
2

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

1) Runtime Data Area
2) PC Register
3) Java Stacks
4) Method Area
5) Java Heap
6) Native Method Stacks
7) Runtime Memory

Java Performance
3
Java Performance Fundamental | twitter @novathinker
artdb@ex-em.com | performeister.tistory.com
Runtime Data Area

•Runtime Data Area

Class libraries Class loader Class ﬁles
subsystem

Java Stacks
Method Area Heap Pc Registers
Native Method Stacks

runtime data areas

native
Execution native method interface method
engine libraries

Java Performance
4
PC register

•PC Register

Thread PC register (Program Counter)

Start Create

Java Method Call { … } Native Pointer
or

Current Instruction
Address
(native pointer or method bytecode

Native Method Call undeﬁned

Java Performance
5
Java Virtual Machine Stacks

•Java Virtual Machine Stack

Java Performance
5

Java Stack

Thread

Java Performance
5

Java Stack

Thread
Java Stack

Thread

Java Performance
5

Java Stack

Thread
Java Stack

Thread
Java Stack

Thread

Java Performance
5

Java Stack
Stack Frame • Java Stack Thread

• Stack Frame Push, Pop

Java Stack
Thread

Java Stack
Java Stack

• Thread 1 Stack
Area
• Stack
Thread

Thread
• Thread
Java Stack

• Implement JVM Vendor

Thread Thread
• Stack Frame

Java Performance
6

• Stack Frame

• Local Variable Section, Operand
Local Variable
Section
Stack Compile Time

Operand Stack

• Frame Data
Frame Data
• Method call Class Data
Stack Frame
Stack

Frame Java Stack

Java Performance
7

• Stack Frame
– Local Variable Section

• Zero base Array
0
1
Local Variable Section • Index data access
2
3 -Method Parameters
4 -Local variable • Method Parameter
5
index
• Local Variable Compiler

Java Performance
8
• Java Virtual Machine Stacks

• Stack Frame

Java Performance
9

• Stack Frame
0 reference hidden this

1 int int a

2 int char b
class JvmInternal {
3 long c
public int testMethod (int a, char b, long
long c, float d, Object e, double f,
String g, byte h, short i, boolean j) { 5 ﬂoat ﬂoat d
return 0; 6 reference Object e
}
7 double f
} double

9 reference String g

10 int byte h

11 int short i

12 int boolean j

Java Performance
10

• Stack Frame
– Operand Stack

• Zero base Array

Operand Stack • Instruction pop
-JVM Work Space
• Push
• Data Type Local Variable

Java Performance
11
public void operandStack();
class JvmInternal2 { Code:
public void operandStack() { 0: iconst_5
int a, b, c; 1: istore_1
a = 5; 2: bipush 6
b = 6; 4: istore_2
c = a + b; 5: iload_1
} 6: iload_2
} 7: iadd
8: istore_3
9: return

istore_1istore_2iload_1 iload_2 iadd istore_3

6
Operand Stack
5 5 11

int c 3 11
Local
Variable int b 2 6 6 6 6 6
Section
int a 1 5 5 5 5 5 5
hidden this ref 0 ref ref ref ref ref ref

Java Performance
12

• Stack Frame
– Frame Data

Frame Data
-Constant pool
Resolution
-Normal Method Return
-Exception Dispatch

Java Performance
12

• Stack Frame
• Constant Pool Entry
– Frame Data
• Constant Pool
Symbolic Reference
Frame Data
-Constant pool
Resolution
-Exception Dispatch

Java Performance
12

• Stack Frame
– Frame Data
• Constant Pool
Symbolic Reference
Frame Data
-Constant pool
Resolution
-Exception Dispatch

• Method stack frame
pc
register instruction
pointer
•
operand stack push

Java Performance
12

• Stack Frame
– Frame Data
• Constant Pool
Symbolic Reference
Frame Data
-Constant pool
Resolution
-Exception Dispatch

• Method stack frame • Exception
pc
Frame Data Exception Table
register instruction
pointer
•
operand stack push

Java Performance
13

• Stack Frame
– Frame Data
public void operandStack();
Code:
0: iconst_5
class JvmInternal2 { 1: istore_1
public void operandStack() { 2: bipush 6
int a, b, c; 4: istore_2
a = 5; 5: iload_1
b = 6; 6: iload_2
try { 7: iadd
c = a + b; 8: istore_3
} 9: goto 16
catch (NullPointerException e) { 12: astore 4
c = 0; 14: iconst_0
} 15: istore_3
} 16: return
} Exception table:
from to target type
5 9 12 Class java/lang/
NullPointerException

Java Performance
14
Native Method Stack

•Native Method Stack

Java Stacks Native
Method
Stack

Java Performance
14
Native Method Stack


Java Stacks Native
Method
Stack
Stack
Java Method 1 Frame

Java Performance
14
Native Method Stack


Java Stacks Native
Method
Stack
Stack
Java Method 1 Frame

Native Method 1 Stack
Frame

Java Performance
14
Native Method Stack


Java Stacks Native
Method
Stack
Stack
Java Method 1 Frame

Frame
Native Function
Call

Java Performance
14
Native Method Stack


Java Stacks Native
Method
Stack
Stack
Java Method 1 Frame

Frame
Native Function
Call

Stack
Frame

Java Performance
14
Native Method Stack


Java Stacks Native
Method
Stack
Stack
Java Method 1 Frame

Frame
Native Function
Call

Stack
Frame

Stack
Java Method 2
Frame

Java Performance
15
Method Area

•Method Area
JVM • Class Loader Load Type

Method Area • JVM
• Thread
Class
Data • Class ﬁle type
Class
Data Method Area
Class • GC
Data • Method Area Vendor
Class
Data  Sun Permanent Area
Generation Heap
Share
Thread Thread  IBM Heap

Thread

Java Performance
16
Method Area

Type Information

Constant Pool
Class metadata
in Field Information
Method Area
Method Information

Class Variables

Reference to ClassLoader

class

Reference to Class class

Java Performance
17
Method Area

• Type Information

Type Information

• Type (Package + Class )
• Type Superclass
(Type interface java.lang.object class superclass

)
• Type class interface
• Type modiﬁer (public, abstract, ﬁnal)
• interface ( )

Java Performance
17
Method Area

• Type Information

Type Information

• Type (Package + Class )
• Type Superclass
(Type interface java.lang.object class superclass

)
• Type class interface
• Type modiﬁer (public, abstract, ﬁnal)
• interface ( )
Type  Java Class, Interface
Java Class File  Java Type Standard Binary
Format

Java Performance
18
Method Area

• Constant Pool

• Constant Pool Type Constant Ordered Set

• Literal Constant, Type, Field, Method Symbolic
Reference
• Constant Pool Entry Array index
• Type Type, Method, Field Symbolic
Reference Dynamic Linking

Java Performance
19
Method Area

• Field Information

Field  Member Variable, Class Variable
Type Field

Field Information

• Field
• Field Type
• Field Modiﬁer
(public, private, protected, static, ﬁnal, volatile, transient)

Java Performance
20
Method Area

• Method Information

Type Method
Method

Method Information

• Method
• Method Return Type (or void)
• Method Parameter Type ( )
• Method Modiﬁer
(public, private, protected, static, ﬁnal,
syncronized, native, abstract)

Java Performance
20
Method Area

• Method Information

Type Method
Method

Method Information
Native or abstract
• Method
• Method bytecode
• Method Return Type (or void)
• Method Stack Frame
• Method Parameter Type ( )
Operand Stack Local
• Method Modiﬁer
variable Section
(public, private, protected, static, ﬁnal,
• Exception Table
syncronized, native, abstract)

Java Performance
21
Method Area

• Class Variable
Class Variable
Class
• Class = Static
• instance Instance

• Instance Class
Instance S
ha
re • Class
Instance

Instance
• Final Class
Constant Pool
Instance

Java Performance
22
Method Area

• Reference to class ‘ClassLoader’

Reference ClassLoader class

• Type Type JVM ClassLoader

• Type Classloader
• User-Deﬁned Classloader reference
• Bootstrap Classloader null
• JVM Dynamic Linking Class
Classloader Load

Java Performance
23
Method Area

• Reference to class ‘Class’

java.lang.class
Reference class

• Type load java.lang.class instance
• getClass, forClass, isInterface Method Reference

Java Performance
24
Method Area

• Method Table

Method Area • Class Method direct
Class reference
• Method
Method Table • Method
• Type interface abstract class

Method class
• Class Method
Field superclass Method
Constant reference
Pool
• Class Loading

Java Performance
25
Method Area

• Method Table

Class A
Class A {
void a1() {…} 1 direct reference of a2()
int a2() {…} 0 direct reference of a1()
}
Class B extends A{
Class B
void a1() {…}
2 direct reference of b1()
char b1() {…}
1 direct reference of a2()
}

Java Performance
26
Method Area

• Method Table
Heap
Class A { Class B extends A{
void a1() {…} void a1() {…}
int a2() {…} char b1() {…} B instance1
} }

Method Area A instance2
Class B
…

2 direct reference of b1()
1 direct reference of a2() bi

Java Performance
27
Java Heap

•Java Heap
JVM • Instance Array
• Thread
Java Heap
• JVM Heap
instruction (new, newarray,
Object
Instance anewarray, multianewarray)
Data
• java code
Class
Pointer byte code
Array Garbage Collection
•

Share
• Java Heap Vendor
Thread Thread
 JVM Vendor Heap
Thread Garbage Collection, Garbage
Collector

Java Performance
28
Java Heap

• Hotspot JVM Heap Layout
– Generational Heap

Java Performance
29
Java Heap

• Hotspot JVM Heap Layout

Allocation

Young Generation
Promotion

Old Generation

Java Performance
30
Java Heap

• IBM JVM Heap Layout
– One-Heap : IBM JVM Default Heap Layout

heapbase heaplimit heaptop

Heap
K Cluster

P Cluster

Wilderness
Heap cache or
LOA

Java Performance
31
Java Heap

– Kcluster : Pinned Class Object
• Default 1280 class entries
• 1 Class Entry 300byte(32it), 560byte(64bit)
– Pcluster : Pinned Object
– Kcluster Pcluster
– Pcluster 2KB Pluster
– Pcluster Heap

 Fragmentation

Java Performance
32
Java Heap

– Cache : Cache Allocation
– Object Thread
• Thread Heap Heap Lock
• Heap Lock Thread
•

– Object Cache Allocation
– 512 Bytes Object
–

Java Performance
33
Java Heap

– Large Object Area
• Large Object
• 64KB Object
• Heap
• -Xloratio LOA
(0.5 ~ 0.95 )
• 1MB Object

Java Performance
34
Java Heap

– Heap
Garbage Object Live Object

Java Performance
35
Java Heap

– Sub pool
• Java 1.4
• 16 Core SMP Allocation

• Free Chunk FreeList

Java Performance
36
Java Heap

– Sub Pool

Pool

1 Small Size Freelist Middle Size Freelist

2
3
4
5
…

Large Size Freelist
n

Java Performance
37
Java Heap

– Java 5 Heap
– Heap Generational Heap
– -Xgcpolicy: gencon

Allocation Space Survivor Space Tenured Space

Nursery Tenured

Java Performance
38
Java Heap

• Hotspot JVM Object Layout

• Object Mark Word,
Class Address
Mark Word

Class Address
Object Data
Header
• Array Size
Header !
Class Address
Mark Word

Array Size

• Header 1 Word
Array Data

1Word = 4bytes(32bit)
8bytes(64bit)

Java Performance
39
Java Heap

– Mark Word : Garbage Collection, Synchronization

Hash Code (0)
Mark Word Thread ID (1) Age Biased Tag

23 bit 6 bit 1 bit 2 bit

Hash Code (0)
Age Biased Tag Biased bit Tag
Thread ID (1)
0 01 Unlocked
(000) Lock Record Address 0 00 Light-weight locked

(010) Monitor Address 0 10 Heavy-weight locked
0 11 Marked for GC
(011) Forwarding Address 1 01 Biased / Biasable

Java Performance
40
Java Heap


Class Address
Method Area Object Class Reference

Array Size
Array Object
Array Data

Java Performance
41
Java Heap

• IBM JVM Object Layout
– Object Array
– header 1 Word

Garbage Collection
(2bits) bit (2bits)
Pinned
Size+Flags Object Size G P

mptr Class pointer or array size
Thread Index Count
Array bit (1bit)
locknﬂags S H T A
Monitor Index
Type(5bits)
Monitor Shape bit
Object Data Hash code state (2bits)
(1bit)

Hash code

Java Performance
42
Java Heap

– Size+Flag
• 28 Bits : Object Size
• 2 Bits : Multipinned Bit,
Garbage Collection - Compaction
Swapped Bit
• Pinned Bit : 1 Bit
• Dosed Bit : 1 Bit

Garbage Collection (2bits)

Object Size G P Pinned bit (2bits)

Java Performance
43
Java Heap

– mptr : Method Pointer
– 1word 8byte
– Object Method Table Pointer
– Array Array

mptr

Java Performance
44
Java Heap

– locknﬂags : lock
– 1 word
– Fat Lock Monitor Index 23 bits
– Thin Lock 15 Bits Thread Index, 8 bits count
– 5 Bits Lock

Thread Index Count
Array bit (1bit)
locknﬂags S H T A
Monitor Index
Type(5bits)
Monitor Shape bit
(1bit) Hash code state (2bits)

Java Performance
45
Java Heap

• IBM JVM Object Layout (Java 5~)
– header 1 Word
Lock word
VTable

Object Data
Lock word

Array Size
VTable

Array Data

Java Performance
46
Java Heap

• IBM JVM Object Layout (Java5 ~)
– Vtable Pointer
– Vtable Object Information Table Pointer

Object Information
• Debug Data
VTable OI • Class name
• Object Type (Array,
Object)
• Reference ﬁeld
• Object Size
Array Element
• Offset Information

Java Performance
47
Java Heap

• IBM JVM Object Layout (Java5 ~)
– Lock Word
– 1 bit : Object on  Fat Lock
– Fat Lock : 20 bits Monitor Index
– Reserved Mode : Thread ID (15 bits), Count(5 bits)
– Reserved Mode Locked 1
– Garbage Collector Hash Code (10 bits)

Recursion Count (5
bits)
Thread ID (15 bits) Count Hash Code
0 1 (10 bits)
Monitor index (20 bits)

Contention Bit (1bit) Reservation Bit (1bit)

Java Performance
48
Java Heap

• Array in Heap
– Array Object Heap
– Array Array Class instance
– Type Array Class data
– Array Instance data
– Array Array Array
– Class Data Naming Convention
• ‘[‘ Type Description String

Java Performance
49
Java Heap

• Array in Heap
– Type Description String

Descriptor Type Array Class Data
B Byte byte[] [B
C Char char[][] [[C
D Double double[] [D
F Float float[][] [[F
I Int int[][][] [[[I
J Long long[] [J
S Short short[][] [[S
Z Boolean boolean[][][] [[[Z
L Object java.lang.String[] [Ljava/lang/String

Java Performance
50
Java Heap

• Array in Heap
Java Heap
Class Data Pointer
Length (=2)
Class Data Pointer ar1[0][0] ( int )
ar1[0][1] ( int )
Length ( =2)
ar1[0] (array reference) Class Data Pointer
ar1[1] (array reference) Length (=2)
ar1[1][0] ( int )
ar1[1][1] ( int )

Method Area
ar1 Array Reference
Class Class
Data Data
int [][] ar1 = new int [2][2] [[I [I

Java Performance
51
Runtime Memory

• Java Variables
– Class Variables
– Member Variables
– Parameter Variables
– Local Variables

D:EXEM>type VariableArrange.java
class VariableArrange {
static int ci = 3; // Class Variable
static String cs = "Static"; // Class Variable
int mi = 4; // Member Variable
String ms = "Member"; // Member Variable

void method(int pi, String ps) { // Parameter Variable
int li = 5; // Local Variable
String ls = "Local"; // Local Variable
}
}

Java Performance
52
Runtime Memory artdb@ex-em.com | performeister.tistory.com

Java Stack Java Heap Method Area
[Ljava/lang/String
VariableArrange Instance
method frame
VariableArrange
Local Variable mi = 4
ms = ref2 class
Field Information
3 ls=ref4 String Instance : ref1
“Static” Class Variable
2 li=5 ci 3
String Instance : ref2
“Member”
1 ps method informations
String Instance : ref3 VariableArrange();
0 pi void method(int, String);
static {};
String Instance : ref4
“Local” Constant Pool

int Integer …

Java Performance
53
Runtime Memory

JvmInternal.java

JvmInternal.class Bytecode

Java Performance
54
Runtime Memory

Source class JvmInternal { } bytecode
JvmInternal frame
Frame Data JvmInternal
Instance
Operand Stack
JvmInternal class

Field Information

Local Variable Class Variable

main method
information

addTwoArgs method
information

Constant Pool
0 args fcv 100

Java Performance
55
Runtime Memory

Source static int cv = 0; bytecode 0: iconst_0
JvmInternal frame
Instance [Ljava/lang/String
Operand Stack
JvmInternal class

Field Information


main method
Length = 2 information

addTwoArgs method
args[1] “20” information

args[0] “10” Constant Pool
0 args fcv 100

ICONST - Push value between -1, ..., 5, other values cause an exception

Java Performance
56
Runtime Memory

Source static int cv = 0; bytecode 1: putstatic
JvmInternal frame
Operand Stack
JvmInternal class

Field Information


main method

addTwoArgs method

0 args fcv 100

PUTSTATIC - Put static ﬁeld in class #4; //Field cv:I

Java Performance
57
Runtime Memory

Source JvmInternal(); bytecode 0: aload_0
JvmInternal frame
Operand Stack
JvmInternal class

args Field Information

Class Variable
Local Variable
main method

addTwoArgs method

0 args fcv 100

ALOAD - Load reference from local variable

Java Performance
58
Runtime Memory

Source public static void main(java.lang.String[]); bytecode 1: invokespecial

JvmInternal frame main frame
Frame Data Frame Data JvmInternal
Operand Stack Operand Stack
JvmInternal class


Local Variable Local Variable Class Variable

3 main method
2 addTwoArgs method
1
0 args 0 args fcv 100

INVOKESTATIC - Invoke instance method; special handling for superclass, private and instance
initialization method invocations #1; //Method java/lang/Object."<init>":()V

Java Performance
59
Runtime Memory

Source a = Integer.parseInt(args[0]); bytecode 0: aload_0
main frame
Operand Stack
JvmInternal class



3 main method
2 addTwoArgs method
1
0 args fcv 100


Java Performance
60
Runtime Memory

Source a = Integer.parseInt(args[0]); bytecode 1: iconst_0
main frame
Operand Stack
JvmInternal class

args[0] Field Information


3 main Method
2 addTwoArgs method
1
0 args fcv 100


Java Performance
61
Runtime Memory

Source a = Integer.parseInt(args[0]); bytecode 2: aaload

main frame
Operand Stack
JvmInternal class
“10”


3 main Method
2 addTwoArgs method
1
0 args fcv 100

AALOAD - Load reference from array

Java Performance
62
Runtime Memory

Source a = Integer.parseInt(args[0]); bytecode 3: invokestatic
main frame
java/lang/Integer
Operand Stack
JvmInternal class

10 Field Information


3 main Method
2 addTwoArgs method
1
0 args fcv 100

INVOKESTATIC - Invoke a class (static) method
#2; //Method java/lang/Integer.parseInt:(Ljava/lang/String;)I

Java Performance
63
Runtime Memory

Source a = Integer.parseInt(args[0]); bytecode 6: istore_1
main frame
java/lang/Integer
Operand Stack
JvmInternal class



3 main Method
2 addTwoArgs method
args[1] 20 information
1 a=10
args[0] 10 Constant Pool
0 args fcv 100

ISTORE - Store int from stack into local variable

Java Performance
64
Runtime Memory

Source b = Integer.parseInt(args[1]); bytecode 7: aload_0
main frame
java/lang/Integer
Operand Stack
JvmInternal class



3 main method
2 addTwoArgs method
1 a=10
0 args fcv 100


Java Performance
65
Runtime Memory

Source b = Integer.parseInt(args[1]); bytecode 8: iconst_1
main frame
java/lang/Integer
Operand Stack
JvmInternal class



3 main Method
2 addTwoArgs method
1 a=10
0 args fcv 100


Java Performance
66
Runtime Memory

Source b = Integer.parseInt(args[1]); bytecode 9: aaload
main frame
java/lang/Integer
Operand Stack
JvmInternal class
“20”


3 main Method
2 addTwoArgs method
1 a=10
0 args fcv 100

AALOAD - Load reference from array

Java Performance
67
Runtime Memory

Source b = Integer.parseInt(args[1]); bytecode 10: invokestatic
main frame
java/lang/Integer
Operand Stack
JvmInternal class



3 main Method
2 addTwoArgs method
1 a=10
0 args fcv 100

INVOKESTATIC - Invoke a class (static) method
#2; //Method java/lang/Integer.parseInt:(Ljava/lang/String;)I

Java Performance
68
Runtime Memory

Source b = Integer.parseInt(args[1]); bytecode 13: istore_2
main frame
java/lang/Integer
Operand Stack
JvmInternal class



3 main Method
2 b=20 addTwoArgs method
1 a=10
0 args fcv 100


Java Performance
69
Runtime Memory

Source c = addTwoArgs(a,b); bytecode 14: iload_1
main frame
java/lang/Integer
Operand Stack
JvmInternal class



3 main Method
1 a=10
0 args fcv 100

ILOAD - Load int from local variable onto stack

Java Performance
70
Runtime Memory

Source c = addTwoArgs(a,b); bytecode 15: iload_2
main frame
java/lang/Integer
Operand Stack
JvmInternal class
20


3 main Method
1 a=10
0 args fcv 100


Java Performance
71
Runtime Memory

Source c = addTwoArgs(a,b); bytecode 16:
main frame addTwoArgs frame
java/lang/Integer
Operand Stack main
ref JvmInternal class
20
10 Operand Stack Field Information


3 main Method
Local Variable
1 a=10 1
0 args 0 fcv 100

initialization method invocations #3; //Method addTwoArgs:(II)I

Java Performance
72
Runtime Memory

Source static int addTwoArgs(int, int); bytecode 16:
java/lang/Integer
Operand Stack main
20
10 Operand Stack Field Information


3 main Method
Local Variable
1 a=10 1 20
0 args 0 10 fcv 100

initialization method invocations #3; //Method addTwoArgs:(II)I

Java Performance
73
Runtime Memory

Source cv = fcv ; bytecode 0: bipush
java/lang/Integer
Operand Stack Frame Data JvmInternal
main
ref

Operand Stack Field Information

100
3 main Method
Local Variable
1 a=10 1 20
0 args 0 10 fcv 100

BIPUSH - Push byte on stack, (-128~127)

Java Performance
74
Runtime Memory

Source cv = fcv ; bytecode 2: putstatic
java/lang/Integer
Operand Stack main
ref


Class Variable
Local Variable cv 100
100
3 main Method
Local Variable
1 a=10 1 20
0 args 0 10 fcv 100

PUTSTATIC - Put static ﬁeld in class #4; //Field cv:I

Java Performance
75
Runtime Memory

Source return ( x + y ); bytecode 5: iload_0
java/lang/Integer
Operand Stack main
ref


10
3 main Method
Local Variable
1 a=10 1 20
0 args 0 10 fcv 100


Java Performance
76
Runtime Memory

Source return ( x + y ); bytecode 6: iload_1
java/lang/Integer
Operand Stack main
ref

20
10
3 main Method
Local Variable
1 a=10 1 20
0 args 0 10 fcv 100


Java Performance
77
Runtime Memory

Source return ( x + y ); bytecode 7: iadd
java/lang/Integer
Operand Stack main
ref


30
3 main Method
Local Variable
1 a=10 1 20
0 args 0 10 fcv 100

IADD - Add ints

Java Performance
78
Runtime Memory

Source return ( x + y ); bytecode 8: ireturn
java/lang/Integer
JvmInternal()
ref 30 main
ref

Operand Stack Operand Stack Field Information
pop
Class Variable
30
3 main Method
Local Variable
1 a=10 1 20
0 args 0 10 fcv 100

IRETURN - Return int from method

Java Performance
79
Runtime Memory

Source c = addTwoArgs(a,b); bytecode 19: istore_3
main frame
java/lang/Integer
Operand Stack
JvmInternal class


Class Variable

3 c=30 main Method
1 a=10
0 args fcv 100


Java Performance
80

2장. Runtime Data Areas

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2장. Runtime Data Areas