Abstract

Tips: This note is even Mo Shu (JVM expert) big guy has praised the recommendation, still don’t hurry to collect a return good chew?

JVMS are still not relevant to actual simple development, and few people want to take the time to learn about JVMS, understand what JVMS are, and how they work. In fact, I personally think this is very necessary to learn carefully, for advanced developers JVM is the foundation of Java, learning JVM is to help you have a deeper understanding of Java and better solve online troubleshooting problems.

Learn the JVM well if you want to interview with a big company like Ali

I’ve picked out a few basic JVM questions that Ali often asks in interviews.

  • How does the JMM execute bytecode? What data is on the stack? What data is in the heap?
  • How are your objects allocated in JVM memory? How does it flow
  • How to set the JVM heap size for a payment system with millions of transactions per day
  • When can an object in JVM memory be garbage collected
  • What garbage collection algorithms are available in the JVM, and the pros and cons of each algorithm
  • How to optimize the garbage recycling parameters of the old generation and the young generation in an e-commerce system with hundreds of millions of requests per day
  • How can Young GCS occur so frequently in a BI system with 100,000 concurrent transactions per second

Most people are aware of the above problems do not know what it is, many books on the Internet are biased to theory, this time I give you to this JVM full excellent notes is the theory and practice of flying, after understanding the resume write proficient completely no problem.

Note download method:“JVM” download here

PART1: JVM basics

  • The JVM goes from compilation to execution
  • From cross-platform to cross-language
  • JVM evolution (non-focus)

PART2: JAVA methods run with the virtual machine stack

  • Runtime data area
  • Effect of stack frame execution on memory area
  • The runtime data area and the overall memory structure of the JVM

PART3: JVM overall knowledge module

  • dimension
  • Run-time constant pool
  • The heap
  • Direct memory (off-heap memory)

PART4: Automatic memory management

Java memory area and memory overflow exception

  • An overview of the
  • Runtime data area
  • HotSpot VIRTUAL machine object Exploration
  • Actual combat: OutOfMemoryError

Garbage collector and memory allocation strategy

  • An overview of the
  • Is the object dead?
  • Garbage collection algorithm
  • HotSpot algorithm details implementation
  • Classic garbage collector
  • Low latency garbage collector
  • Select the appropriate garbage collector
  • Actual combat: memory allocation and recycling strategy

Vm performance monitoring and troubleshooting tools

  • An overview of the
  • Basic troubleshooting tools
  • Visual troubleshooting tool
  • HotSpot VIRTUAL machine plug-in and tools

Tuning case analysis and practice

  • An overview of the
  • Case analysis
  • Actual combat: Eclipse speed tuning

PART5: VM execution subsystem

Class file structure

  • An overview of the
  • The cornerstone of irrelevance
  • Class The structure of the Class file
  • Introduction to bytecode instructions
  • Public design, private implementation
  • Class file structure development

Vm class loading mechanism

  • An overview of the
  • The timing of class loading
  • The process of class loading
  • Class loader
  • Java modular System

Virtual machine bytecode execution engine

  • An overview of the
  • Run time stack frame structure
  • The method call
  • Dynamically typed language support
  • Stack – based bytecode interpretation execution engine

Case and practice of class loading and execution subsystem

  • An overview of the
  • Case analysis
  • Actual combat: their own hands to achieve remote executive function

PART6: Program compilation and code optimization

Front-end compilation and optimization

  • An overview of the
  • Javac compiler
  • The taste of Java syntax sugar
  • Real: Plug-in annotation processor

Back-end compilation and optimization

  • An overview of the
  • Just-in-time compiler
  • Ahead of time compiler
  • Compiler optimization techniques
  • Practice: In-depth understanding of the Graal compiler

PART7: Efficient concurrency

Java memory model and threads

  • An overview of the
  • Hardware efficiency and consistency
  • Java memory model
  • The Java and thread
  • Java and coroutines

Thread safety and lock optimization

  • An overview of the
  • Thread safety
  • Lock the optimization

Summary of JVM core knowledge

Java memory region

  • Runtime data area
  • HotSpot VIRTUAL machine object Exploration
  • Highlights (String class and constant pool; String s1 = new String(“abc”); How many string objects does this sentence create? Eight basic types of wrapper classes and constant pools)

JVM garbage Collection

  • Demystify JVM memory allocation and reclamation
  • The subject is dead?
  • Garbage collection algorithm
  • Garbage collector

JDK monitoring and troubleshooting tools

  • JDK command line tools
  • JDK visual analysis tools

Class file structure

  • Class file structure summary

Class loading process

  • Class loading process

Loading:

Validation:

Preparation:

Resolution:

Initialization:

  • uninstall

Class loader

  • Review the class loading process
  • Class loader summary
  • Parental delegation model
  • Custom class loaders

Example of tuning JVM memory allocation

  • AB pressure measurement

  • Pressure measurement results + results analysis

100 concurrent users / 100,000 requests (total)– first time

100 concurrent users / 100,000 requests (Total)

1000 concurrent users / 100,000 requests (Total)

  • The tuning scheme

  • Summary of memory optimization + recommended strategies

  • More (space limited)

The last

Learning JVM suggests that we learn according to this diagram from top to bottom, only after combining the theory and practice can avoid forgetting knowledge, if you need the complete version of the above document, forward + comment article, pay attention to me, stamping here “JVM” can be.