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SoftwareGroup WebSphere
Confidential - Do Not Distribute
2017.
IBM Hybrid Cloud Technical Sales
??? ?? (JungWoon Lee, juwlee@kr.ibm.com)
? Copyright IBM Corporation 2017
Cloud, IBM Korea
IBM JVM ??

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JVM(Java Virtual Machnine)
? JVM ? Java Bytecode ? ??? ? ?? ????. Java Bytecode ? ???? ????? ?? JVM ? JVM ??? ???
?? Java Bytecode ? ????. ??? ?? ?? API?? ??? ??? ??? ??? ????? ????? ?? Java ?
???? CPU? ?? ??? ??? ???? ???? ??? ?? ????.
? Java Platform (JRE) : Java VM + ?? Java ?????
? Java VM : Load & Execute Java binary(.class format)
? ? ?? ?? Component
– ClassLoader
? Java binary load + Runtime data ?? ??
? Loader, Linker
– Execution Engine
? Bytecode ?? + Native?? ??
? Interpreter, Compiler
– VM Runtime
? VM? ?? ?? data ? ? ???
? Heap (GC), Thread, Lock

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? JVM ? ???? ??? ??? ?? ????? ??? ??, ? ??, ?? ??, PC ????, Native ??
? ???? ??? ???.
??? ??
???(method)
??
-????
?????
-??? ??
?(heap) ??
-??
??(stack) ??
-????
-????
PC ???? Native ???
??
?? ?? Native ??? ?????
???? ??? ??(Runtime data area)
??? ??
Native ???
?????
???
?????

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? ?? ?? ??? ???? JVM ??? ??, ?? ??, ? ??? ??? ?? ??
??? ??
?? ?? ? ??
main() ???
??? ??
args null
main
frame
a
5 6 7 8
b
b[2]
b[1]
b[0]
1 2 3
4 5
96 7 8
s1
s2
“Hi Java”
s2[1]
s2[0]
“Java”
“Hi”
? ?? ?? ??
class MemoryTest3 {
public static void main(String[] args)
{ int a[] = new int[] {1,2,3};
a = new int[] {5,6,7,8};
System.out.println(a[3]);
int b[][] = new int[][] {{1,2,3},{4,5},{6,7,8,9}};
System.out.println(b[2][3]);
String s1 = "Hi Java";
System.out.println(s1);
String s2[] = new String[] {"Hi","Java"};
System.out.println(s2[1]);
} }

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??, IBM JVM ?
Oracle ? JVM ?
??????

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IBM SDK for Java
? IBM SDK for Java ? Oracle Platform Java Standard Edition (Java SE) 8 application programming interfaces
(APIs) ??? ???? ?????.
? Generalized Target-Type Inference JEP 101
? Parallel Array Sorting JEP 103
? Annotations on Java Types JEP 104
? DocTree API JEP 105
? ……
? Enhance the Certificate Revocation-Checking API JEP 124
? Lambda Expressions & Virtual Extension Methods JEP 126
? ……
? PKCS#11 Crypto Provider for 64-bit Windows JEP 131
? Unicode 6.2 JEP 133
? Base64 Encoding & Decoding JEP 135
? Date & Time API JEP 150
? ……
? Concurrency Updates JEP 155
? Prepare for Modularization JEP 162
? Leverage CPU Instructions for AES Cryptography JEP 164
? JDBC 4.2 JEP 170
? ……

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Oracle ? IBM Java ? ?? ???
? IBM ? Oracle Java ? ?? Java Class Libraries ? ?? ?? ?? ???? ????? JVM ???? ??
?? ??? ???????.
? IBM and Oracle use the same reference implementation of Java Class Libraries (e.g. OpenJDK)
? Key differences to be aware of:
- Security: Standards do not impose strong separation of interest
- ORB: OMG CORBA standard rules
- XML: Xerces/Xalan used by both vendors as of Java 5, although different levels may be used.
? IBM uses the J9/TR runtime, Oracle uses Hotspot
? Different JIT/GC/VM tuning and controls
? Tooling is distinct (e.g. IBM’s Health Center)

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IBM JVM
? IBM JVM ? J9 ? IBM ?? ???? ?? ???? ???, ????, ?? ??? ??? ???? ???
????.
? IBM’s strategic virtual machine : J9
? Designed from the ground up by IBM
? Focused on high performance , high reliability and serviceability
? Scales from embedded and handheld devices to large SMPs
? Highly configurable with pluggable interfaces for alternative implementations of GC, JIT
? Composed of several key components
? Reconfigurable, portable virtual machine framework and interpreter called “J9”
? Type accurate garbage collection frameworks (Modron, Tarok, Metronome)
? Highly optimizing just-in-time (JIT) compiler “Testarossa”
? Integrated RAS features to enhance problem determination
? Unique Features - SharedClasses, Dynamic AOT

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Java Adaptive Compilation : trade off effort and benefit
? IBM JVM ? ??? ??? ??? just-in-time (JIT) compiler ? ??? runtime profiling ????
bytecode ? ?? ???? ?????.
? Java's bytecodes are compiled as required, optimized based on runtime profiling
? Dynamic compilation determines the target machine capabilities and app demands
? Multiple phases, enable adaptive response to changing environment
cold
hot
scorching
profiling
interpreter
warm
? Methods start out running bytecode form directly
? After many invocations (or via sampling) code get compiled at ‘
cold’ or ‘warm’ level
? Low overhead sampling thread is used to identify hot methods
? Methods may get recompiled at ‘hot’ or ‘scorching’ levels (for m
ore optimizations)
? Transition to ‘scorching’ goes through a temporary profiling step
Results can be stored for future runs and shared across invocations

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Shared Classes Cache
? IBM JVM ? Shared Classes Cache ? ???? ??? ?? ??? ????? ??? ?? ? ??? ??
?? ????.
? IBM JVMs use sharing to reduce memory and startup costs
? Ability to securely common Java class code across multiple JVM instances
? Reduces footprint due to sharing of read-only components (Java code)
? Reduces startup time by caching “ready to run” previously JITed code (Dynamic AOT)
? Dynamic AOT - reuse JIT code from multiple JVMs
? Reduce memory use by 20%, improve startup time 10-30 %
JVM
JVM
JVM
JVM
JVM
Shared Classes Cache
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
JVM
AOT – Ahead Of Time
(JIT code saved for next JVM)
Verified bytecodes
JVM shared index
“Compile once,
run manywhere”

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??, IBM JVM ?
Oracle JVM ?
Heap ??? ??????

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Oracle JVM ? Heap ??
? Oracle JVM ? Heap ??? ???? ???? ???? ??? ?????. (Java 8.0 ??? Perm ???
???? Metaspace ??)
? Oracle JVM ? ???? Heap ?? (Hotspot)
? Permanent Space : Class? ??Meta ??????? ??
- Method of a class(including the bytecodes)
- Names of the classes
- Constant pool ??
- JVM???? ???? ?? ?? ex: java/lang/Object
? New Generation
- Eden: ??(new) ?? ????
- Survivor1(SS1)
> Minor GC???? Eden, Survivor 2????? ? ??????? ???? ??
> Old Space????? ?? ?????
- Survivor 2(SS2)
> Minor GC???? Eden, Survivor 1????? ? ??????? ???? ??
> Old Space????? ?? ?????
? Old Generation
- Survivor 1, Survivor 2 ???????? ??? ??
- Full GC???? ?? ??? ??

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Oracle JVM ? Heap ??
? Oracle JVM ? Heap ??? ???? ???? ???? ??? ?????. (Java 8.0 ??? Perm ???
???? Metaspace ??)

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IBM JVM ? Heap ??
? IBM JVM ? ???? Oracle ? ??? Heap ? ???? ?? single heap ??? ????? IBM JVM
5.0 ?? ?? ??? ??? Heap ??? ?? ??? ??? ? ?? ??? ?????.
? IBM JVM ? ???? Heap ?? (IBM JVM 1.4.2 ??)
? IBM JVM ? ???? Heap ?? (IBM JVM 5.0 ?? – ?? ??)
? IBM JVM ? ???? Heap ?? (IBM JVM 6.0 ?? – gencon ?? ??)

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IBM JVM ? Heap ??
? IBM JVM ? Java 6.0 ?? gencon ??? GC ?? ??? ??? Oracle JVM Heap ? ?????? ??
??? ??? ?????.
? Oracle JVM Heap ??? ??
IBM JVM:
-Xmn (-Xmns/-Xmnx)
Sun:
-XX:NewSize=nn
-XX:MaxNewSize=nn
-Xmn<size>
Sun JVM Only:
-XX:MaxPermSize=nn
Nursery/Young Generation Tenured/Old Generation Permanent Space
JVM Heap
IBM JVM:
-Xmo (-Xmos/-Xmox)
Sun:
-XX:NewRatio=n
? ? JVM ?? ????
- IBM JVMs – Windows, AIX, Linux(x86 and PPC), i5/OS, z/OS
- Oracle HotSpot based JVMs
> Oracle HotSpot JVM on Solaris
> HP’s JVM for HP-UX

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IBM JVM ? Heap ??
? IBM JVM 5.0 ????? pCluster, kCluster ? ???? ??? ?? ??? ???? ??? native ???
???? ???. (Oracle ? Metaspace ? ???? ????? ???. ?, ??? ????? ????.)
Java Object ??? Native ??
Thread objects Native Thread
AWT objects Widgets/Shells
Socket objects Native Socket
Class objects Class structure, Constant Pool, Method Table,
Method Blocks, Compiled Code
Class Loader Class cache
Constraint Table
? Java Objects ?? underpin(??,??) ? ?? ??
? Class Object ? native heap ??

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IBM JVM ? GC ??
? IBM JVM??? 4?? ??? GC ??? ????? ??? ??? ?? GC ??? ???? ??? ? ?
???. (? GC ??? ??? ??? Heap ? ??? ???)
? GC ?? (-Xgcpolicy ?? ??)
? ? ? ? ??
Optthruput ??
???? ??? GC ????? ??.
GC ? compaction ? ???? mark, sweep, compaction ? ??
?? ?? ?????? thread ? ????.
Java 5.0 ??? ???
Optavgpause ??
?????? ??? ?? GC? mark, sweep ???
??????? GC ?? ??? ???. ?? ????? ????
???? ?? ?? ??? ??? ? ??.
Gencon ??
IBM JVM ? ??? ??? ?? GC? ????.
??? ??? GC ????? ????? ?? ???? ????
?? ????. ??? ??? ??? ??? heap ? new ? old
???? ???. ?? ???? ??? new???? ??? GC
?? ??? ???? ???? ??? old ???? ????.
Java 5.0 ?? ?? ???
???? ?? ??? ?????
?? ???? ?? ???
????. (Java 6.0.1 ?? ???)
Balanced ??
????? 4GB ??? Large Heap ? ??? ??? ??? ??
Large Heap ? ????? ?? ??? region ?? ???? ??
?? ???? GC ? ???(gencon ? ??)
Global GC ? ?? long pause time ??? ?? ? ??? ??
??? pause time ?? ??

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IBM JVM ? GC ??
Time
Thread 1
Thread 2
Thread 3
Thread n
GC
Application
? -Xgcpolicy:optthruput
? ???? ?? GC ?? ???? ? ??? ?? ????? ??
Time
Application
Thread 1
Thread 2
Thread 3
Thread n
GC
Concurrent
Tracing
? -Xgcpolicy:optavgpause
? ??? ???? ??? ???? ?? GC ?? ?? ?? ?? ???? ?? (?? ?? ???)

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IBM JVM ? GC ??
? -Xgcpolicy:gencon
? ??? ? Object ?? ??? ?? Object ? ??? ?????. ??? ?? Object ? ?? ?? ????? ?
??? ???? ?? ?? ??? ??? ??? ??? ???? ?????.
? -Xgcpolicy:balanced
? Large Heap ?? ?? ???? ??? ??? ??? ???? ???? ????? ?? ????? ??
Time
Global GC
Application
Concurrent
Tracing
Thread 1
Thread 2
Thread 3
Thread n

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IBM JVM ? ?? ?? ???? ??
? IBM JVM ? ?? ???? ??? ??? ????? Health Center, GCMV, Memory Analyzer ?? ???
? ???? ????.
?Memory Analyzer
-Heapdump ? IBM System dump? ???? ??
-??? ?? ?? ? ???? ?? ??
-?? Java Heap? ?? ???? ?????? ??
?Health Center
-?? ?? ????? ?? ???? ??
-??? ?????, GC, class loading, locking? ?? ??
??? ??
-??? ?? ??? ?? ??? ?? ??
?Garbage Collection and Memory Visualizer
-Java verbose GC logs? ???? ??
-?? ??? ???? ??? ??? ????? ???
??
-GC? Java Heap ?? ?? ? ?? ?? ?? ???

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End of The Document.

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