Marco's study notes thirty -- Tomcat

The Java architecture includes four independent but related technologies:
Java programming language
Java API
Java class file format
JVM: Java Virtual Machine

JVM implementation method:
1. One-time interpreter, interpreting bytecode and executing it;
2. Instant Compiler (just-in-time complier)
Depends on the results of more memory cache interpretations
3. Adaptive Compiler
Cache around 20% code, improving the speed by about 80%;

Runtime data zone:

Private thread memory zone:

Program counters

Java Virtual Machine Stack

Thread shared memory zone:

Method Area

Heap: Java automatic memory recovery, GC (Garbage Collector)

Garbage collection algorithm:

1. Mark-clear

2. Copy

1/2

3. Mark-organize

Java configuration parameters:
-XX: + <option>: enables the function specified by this parameter;
-XX:-<option>: Disable the function.
-XX: <option >=< value>: assigns a value to the option specified by option;

-D <name >=< value>: Set a system property

Java-XX: + printflagsfinal: Display All parameters and their default values
Sun JDK monitoring and troubleshooting tools:
JPS, JVM Process status tool: displays the list of all hotspot VM processes in the specified system
Jstat, JVM statistics monitoring tool: Collects and displays running data of all aspects of the hotspot VM.
Jinfo: displays the configuration information of a running hotspot virtual machine.
Jmap: generate a memory dump snapshot of a hot spot Virtual Machine

Visualization tools:
Jconsole: Java Monitoring and Management Console
Jvisualvm: