Brief introduction:JAVA virtual machine is not only a cross-platform software, but also a new network computing platform. The platform includes many related technologies, such as APIs conforming to open interface standards, optimization techniques, etc.
You may have the following questions when learning about the Java Virtual Machine:
What is the principle of the Java Virtual Machine?
What is the principle of JNI and class loaders?
What is the SafePoint mechanism?
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The JVM in Action
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JNI in Java
Master the mutual call between Java and Native, greatly enrich the use of Java scenarios. Understanding the principles makes it easier to learn JVM/ fault location. Click to see more >>
Safepoint mechanism
SafePoint is going to suspend all the application threads in the entire JVM and the main concern here is that when a VM thread makes a request, the Java lab is going to be able to respond to SafePoint’s request in a timely way, and it’s going to be able to stop itself immediately, and if it stops some threads and it stops others, Other threads will waste time waiting, so a timely response is an important metric. Click to see more >>
Principle of class loader
For the class loading part, first the user has a Java file, then the Java file is compiled in Java C to get a.class file, and then the virtual machine loads the.class file into the virtual machine’s metadata. For example, in C ++ it will be Klass *, Method *, ConstantPool *, etc. These are all metadata descriptions in the Java virtual machine. Click to see more >>
DragonWell Feature: Multi-tenancy
The previous blocking API is supported without any need to change the code, you can change the previous code with coroutine directly to the coroutine model, a model transformation, so from Java Thread and Pthread on the operating system 1:1 model to call a large number of WISP into a small number of operating threads, performance greatly improved. Click to see more >>
DragonWell feature: JwarmUp
Before a Java method can be executed, the class in which the method resides needs to be loaded by the JVM. This process includes the validation, parsing, linking of various files, and class initialization. When the class is loaded, the JVM can execute the method. Click to see more >>
DragonWell Features: WISP
Context switching eats up valuable CPU resources. In many cases, people misunderstand the context. There is a big difference between entering and leaving the kernel and scheduling. If we see multiple threads calling back and forth in a scenario like this, which thread will be chosen next if it runs out of resources or is blocked? In fact, the operating system needs to be scheduled, and the real cost is far greater than imagined. Click to see more >>
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