JVM, or "Java Virtual Machine", is a bit similar to "operating system" with Java programs running on it.
In fact, in our ordinary work, we do not directly touch the JVM, but we often encounter problems related to it:
- There is a problem with a piece of code, and the execution efficiency is low, but the underlying reason cannot be found.
- The CPU of the online system runs wildly, and the GC time soars, resulting in a freeze, which seriously affects the service response time;
- The running Java program suddenly becomes OOM (out of memory);
- When performing performance optimization, facing a bunch of JVM parameters, there is no way to start...
These problems are actually related to the JVM.
I remember once it took a whole week to locate a tricky off-heap memory leak. At that time, there was very little relevant information and it was very painful to investigate, but after this processing, I gained a lot. And in my future work, it involves a lot of tuning work in high concurrency scenarios. Through a lot of online practice, I have accumulated very rich experience. Now it can be said that in the JVM field, there is no problem that can stump me. .
Interview must ask
In addition, in the Java senior engineer job requirements, JVM has almost become a skill point that must be mastered, and the Java high-frequency exam questions involving JVM knowledge are countless in the big factory.
After studying the JVM systematically, when you answer the interviewer's questions, you can answer the questions in depth and breadth, and let the interviewer shine.
Why is JVM difficult to learn?
1. There are too few practical materials to systematize
2. Too many related issues and too complicated concepts
3. Lack of online JVM tuning experience
In order to allow everyone to improve the JVM tuning technology in a targeted manner, I prepared this "JVM Low-Level Design and Tuning Actual Combat"! From JVM memory management, bytecode operation process, garbage collection mechanism, billion-level flow system GC estimation and tuning, JVM tuning actual combat, etc., you can easily conquer interviewers, and you will be more confident about being promoted and hopping!
JVM interview topics
87 high-frequency JVM interview questions for top Internet companies
JVM learning books
1. In-depth understanding of the Java virtual machine (the first to bear the brunt is this in-depth understanding of the Java virtual machine, which can be described as a classic in JVM)
2. Actual Java virtual machine (step by step, each chapter corresponds to a separate knowledge point, and strive to show the full picture of the virtual machine)
3. Java virtual machine concurrent programming
JVM master notes
1. Arrangement of JVM core knowledge points (including thread, JVM memory area, JVM runtime memory, garbage collection and algorithm, JAVA four reference types, GC generational collection algorithm VS partition collection algorithm, GC garbage collector, JAVA IO/ NIO, JVM class loading mechanism)
2. JVM from entry to enchantment
3. JVM memory area division
4. JVM memory sorting and GC recycling
5. JVM and performance optimization knowledge points finishing
6. JVM execution subsystem
JVM and performance optimization mind map
Friends who need the full version of the JVM tuning above can read this article three times, follow the editor, private message [666] or scan below to get
A lot of actual JVM tuning, master them, you can easily locate the problems in the application, and provide optimization ideas, which will make you more effective in actual work.