Download to read offline
![Let’s check out the example...
#include <stdio.h>
int main() {
int *a = new int[10];
printf("size(a) = %lun", sizeof(a) / sizeof(int));
return 0;
}](https://image.slidesharecdn.com/jvm-abriefintroduction-170126225733/75/Jvm-a-brief-introduction-14-2048.jpg)
![Memory management
MyClass *obj = new MyClass();
// ...
delete obj;
MyClass **objs = new (MyClass*)[100];
for (int i = 0; i < 100; ++i) {
objs[i] = new MyClass();
}
delete objs;
In C++ you were responsible for freeing the memory:](https://image.slidesharecdn.com/jvm-abriefintroduction-170126225733/75/Jvm-a-brief-introduction-20-2048.jpg)
![Short example
public class Main {
public static final String[] opts = { "Eggs", "Chickens", "Philosophers" };
public static void main(String[] args) {
for (String option : opts) {
process(option);
}
}
public static void process(String option) {
System.out.printf("%sn", option);
}
}](https://image.slidesharecdn.com/jvm-abriefintroduction-170126225733/75/Jvm-a-brief-introduction-23-2048.jpg)
![Loops unrolling
public class Main {
public static final String[] opts = { "Eggs", "Chickens", "Philosophers" };
public static void main(String[] args) {
process(opts[0]);
process(opts[1]);
process(opts[2]);
}
public static void process(String option) {
System.out.printf("%sn", option);
}
}](https://image.slidesharecdn.com/jvm-abriefintroduction-170126225733/75/Jvm-a-brief-introduction-24-2048.jpg)
![Reducing unneeded data loading
public class Main {
public static void main(String[] args) {
System.out.printf("%sn", "Eggs");
System.out.printf("%sn", "Chickens");
System.out.printf("%sn", "Philosophers");
}
}](https://image.slidesharecdn.com/jvm-abriefintroduction-170126225733/75/Jvm-a-brief-introduction-26-2048.jpg)
![Reducing unneeded data loading
public class Main {
public static void main(String[] args) {
System.out.printf("%sn", "Eggs");
System.out.printf("%sn", "Chickens");
System.out.printf("%sn", "Philosophers");
}
}
And unneeded method calls!](https://image.slidesharecdn.com/jvm-abriefintroduction-170126225733/75/Jvm-a-brief-introduction-28-2048.jpg)
![Reducing unneeded data loading
public class Main {
public static void main(String[] args) {
System.out.printf("%sn", "Eggs");
System.out.printf("%sn", "Chickens");
System.out.printf("%sn", "Philosophers");
}
}
Reduced memory cost here](https://image.slidesharecdn.com/jvm-abriefintroduction-170126225733/75/Jvm-a-brief-introduction-30-2048.jpg)
Uploaded byArtem Shoobovych
Jvm a brief introduction
The JVM is a virtual machine that runs Java bytecode. It provides memory management, code optimization through just-in-time compilation, and allows Java programs to run on different platforms. The JVM optimizes code at runtime by techniques like loop unrolling, reducing unnecessary data loading and method calls. It has two compilation modes - client mode for less optimization and server mode for more aggressive optimization based on runtime profiling.
More Related Content
![[232]TensorRT를 활용한 딥러닝 Inference 최적화](https://cdn.slidesharecdn.com/ss_thumbnails/232dlinferenceoptimizationusingtensorrt1-181012004550-thumbnail.jpg?width=640&height=640&fit=bounds)
![[232] TensorRT를 활용한 딥러닝 Inference 최적화](https://cdn.slidesharecdn.com/ss_thumbnails/232dlinferenceoptimizationusingtensorrt1-181012014455-thumbnail.jpg?width=640&height=640&fit=bounds)
![[D2 Campus] Tech meetup (주제: Android) 모바일 머신러닝 [열일한 내 거북ᄆ...](https://cdn.slidesharecdn.com/ss_thumbnails/naverd2techmeetup-mobilemachinelearning-fromtensorflowlitetomlkit-190125125033-thumbnail.jpg?width=640&height=640&fit=bounds)
Similar to Jvm a brief introduction
Jvm a brief introduction
- 1. JVM: a briefintroduction by Artem Shubovych
- 2. What is JVM? JVM(Java Virtual Machine) - is an environment, designed to run Java programs.
- 3.
- 4.
- 5.
- 6. What is JVM? JVMis a environment to run Java bytecode..?
- 7.
- 8. What the hellis JVM?
- 9.
- 10. What is JVM? JavaAPIs Class loader Runtime JIT compiler GC OS + Hardware Application JVM JRE
- 11.
- 12. How do computersrun programs? Programming language Compiler Processor commands
- 14. Let’s check outthe example... #include <stdio.h> int main() { int *a = new int[10]; printf("size(a) = %lun", sizeof(a) / sizeof(int)); return 0; }
- 15. Well, screw it!It’s 2016 already!
- 16.
- 17. JVM puts itthe level higher Programming language Compiler Virtual Machine commands
- 18. What’s the purposeof having Virtual Machine?
- 19. It can handlemany things for us
- 20. Memory management MyClass *obj= new MyClass(); // ... delete obj; MyClass **objs = new (MyClass*)[100]; for (int i = 0; i < 100; ++i) { objs[i] = new MyClass(); } delete objs; In C++ you were responsible for freeing the memory:
- 21. Memory management Java willfree the memory for you. If it can’t do this - it just kills your process.
- 22. Code optimization JIT canoptimize your code in many different ways.
- 23. Short example public classMain { public static final String[] opts = { "Eggs", "Chickens", "Philosophers" }; public static void main(String[] args) { for (String option : opts) { process(option); } } public static void process(String option) { System.out.printf("%sn", option); } }
- 24. Loops unrolling public classMain { public static final String[] opts = { "Eggs", "Chickens", "Philosophers" }; public static void main(String[] args) { process(opts[0]); process(opts[1]); process(opts[2]); } public static void process(String option) { System.out.printf("%sn", option); } }
- 26. Reducing unneeded dataloading public class Main { public static void main(String[] args) { System.out.printf("%sn", "Eggs"); System.out.printf("%sn", "Chickens"); System.out.printf("%sn", "Philosophers"); } }
- 28. Reducing unneeded dataloading public class Main { public static void main(String[] args) { System.out.printf("%sn", "Eggs"); System.out.printf("%sn", "Chickens"); System.out.printf("%sn", "Philosophers"); } } And unneeded method calls!
- 30. Reducing unneeded dataloading public class Main { public static void main(String[] args) { System.out.printf("%sn", "Eggs"); System.out.printf("%sn", "Chickens"); System.out.printf("%sn", "Philosophers"); } } Reduced memory cost here
- 32. How can wecall those?
- 33. OpenJDK’s JIT (Hotspot)has two modes
- 34. Client mode (C1) ●Less aggressive inlines ● Fewer optimization possibilities
- 35. Server mode (C2) ●Aggressive inlines ● Based on rich runtime profiling
- 36.
- 37. Because they’re fast! ●Inlining is cheap (in means of time) ● Inlining gives great speed-up
- 38. How can wecall those?
- 39. How can wecall those? ● C1 tier: 1000 calls to the same method ● C2 tier: 100_000 calls to the same method
Editor's Notes
- #4 But that’s not quite right...
- #5 There are couple of languages, other than Java, which do run on JVM.
- #6 So how these all languages work is they are compiled into runtime-environment-compatible bytecode. This is how .NET works (compiles F#, C#, VB, VC and many others into Common Intermediate Language, CIL). This is how JVM works (compiles all those showed on a slide into a JRE-compatible bytecode).
- #7 So is JVM an environment, designed to run Java bytecode?
- #8 The answer is NO.
- #10 Drums...
- #11 Guess, where’s the JVM?
- #12 That’s JIT. To get closer to JIT we need to go deeper, to the very beginning of programming...
- #16 Yes, programs are run exactly like that. IF you write them in C or something that low-level. But when we go level up, we notice those “managed languages” out there.