ge jvm

Jvm performance monitoring and common tools, common tools for jvm monitoring Common JDK command line tools Jps: jps [options] [hostid].-q only displays the jvmid,-m parameter passed to main class,-l class full name, and-v jvm startup parameter. Jstat: jstat [options] vmid [interval [s] | MS] [count]-gc-gcutil Jinfo: jinfo [option] pid Jmap: jmap [opt

JVM-graphics display bytecode execution engine execution process, jvm-bytecode In my previous blog JVM-String comparison-bytecode analysis, I introduced the reasons for String comparison. By analyzing bytecode, this blog will show the internal bytecode execution process of the method. Not to mention, paste the Java method code we will analyze: public static void

JVM re-sorting and JVM re-sorting Reordering is usually a method used by the compiler or runtime environment to re-sort and execute commands to optimize program performance. There are two types of re-sorting: Re-sorting during compilation and re-sorting during runtime, which correspond to the compiling and runtime environments respectively. In a concurrent program, the programmer pays special attention to d

This section Xiao Wang focuses on the next Java memory, first ask: How 1.JVM memory is allocated 2. Why divide the new generation and the old age, in practice which belong to what belongs to the old 3. Briefly describe how JSTAT-GC How 1.JVM memory is allocated 1.1 Concept Introduction Memory is divided into two parts of the stack Stack: Thread Private Heap: Thread sharing Stack: Program counter: The byte

Comparison between Dalvik Virtual Machine and JVM: Dalvik Virtual Machine JVM The Dalvik virtual machine has many similar features as the Java Virtual Machine, including GC, JIT, and JNI. The main difference is that the file format and instruction set are different, and the features of the two are compared and discussed below.Difference1: File Format Dalvik's virtual machine files use the dex format, while

Let's talk about the JVM class loading mechanism and jvm loading mechanism. I wrote this article a few months ago to deeply understand the Java class loading principle. I briefly talked about my understanding of Java class loading. Recently, I also studied the book "deep understanding of Java virtual machines, I have a more systematic understanding of the JVM cl

Java basic questions (JVM), java basic questions jvm 1. What is a Java Virtual Machine? Why is Java called a platform-independent programming language "? A Java virtual machine is a virtual machine process that can execute Java bytecode. Java source files are compiled into bytecode files executed by Java virtual machines. Java is designed to allow applications to run on any platform without the need for pro

Based on common JVM garbage collection algorithms, jvm garbage collection There are four common garbage collection algorithms in JVM: Mark-clearing algorithm (Mark-Sweep ); Copying ); Mark-Compact ); Generational collection; Next we will introduce them one by one: I. Mark-clearing algorithm (Mark-Sweep) This is the most basic garbage collection algorithm. The alg

JVM-program compilation and code early (during compilation) optimization, jvm-CompilationEarly (Compilation) Optimization I. Javac Compiler 1. Javac source code and debugging The source code of Javac is stored in JDK_SRC_HOME/langtools/src/shares/classes/com/sun/tools/javac. Besides JDK APIs, only the code in JDK_SRC_HOME/langtools/src/shares/classes/com/sun/* is referenced. The debugging environment is sim

Deep understanding of JVM (1)-Java memory region, jvm-java 1. Data Area During Running During Java program execution, the Java Virtual Machine divides the memory it manages into several different data regions. The memory managed by the Java Virtual Machine will include the following runtime data areas: 1. Program counters 1) The Program counter (Program CounterRegister) is a small memory space. Its functio

JVM garbage collection algorithm and jvm garbage collection 1. Mark-cleanup algorithm: the most basic garbage collection algorithm. Just like its name, the algorithm consists of two steps: Marking and cleanup: first, marking the objects to be cleansed, after marking is completed, all marked objects are recycled in a unified manner. The disadvantage of this algorithm is efficiency, low efficiency in the mark

JVM-class loading mechanism and jvm-Loading MechanismVirtual Machine Loading Mechanism The Virtual Machine loads the class data described from the class file to the memory, verifies the data, converts the parsing and initialization, and finally forms the Java type that can be directly used by the virtual machine, this is the class loading mechanism of virtual machines. Class loading time Class is loaded to

Complete parsing of JVM-class file-field table set, jvm-class fieldField table set This class file has been parsed for a long time. this section describes the category magic number, version number, main board number, constant pool entry, constant pool, access flag, class index, parent class index, and interface index set. the field table set should be included below. Then the set of interface indexes is the

JVM tuning summary, jvm Tuning Auxiliary InformationJVM provides a large number of command line parameters and prints information for debugging. There are mainly the following: -XX: + PrintGCOutput Format: [GC 118250 K-> 113543 K (130112 K), 0.0094143 secs][Full GC 121376 K-> 10414 K (130112 K), 0.0650971 secs] -XX: + PrintGCDetailsOutput Format: [GC [DefNew: 8614 K-> 781 K (9088 K), 0.0123035 secs] 1

I. Introduction of TOOLSJconsole: A Java GUI monitoring tool that can display a variety of data in a tabular format. Remote server VMS can be monitored through remote connections. A GUI program written in Java, used to monitor VMS, and to monitor remote VMS, is very easy to use and very powerful. Command line to play Jconsole, select the process is OK.It is important to note that before running the Jconsole, the environment variable display must be set up first;2, the use of the process2.1 Enter

When executing a Java program, the Java Virtual Machine divides the memory it manages into several different data regions. These regions have their own purposes, as well as the creation and destruction time. Some regions exist with the startup of virtual machine processes, some regions are created and destroyed Based on the startup and termination of the user's thread. The memory managed by the Java Virtual Machine will include several runtime data regions, as shown in:650) This. width = 650; "s

Oom?Java.lang.OutOfMemoryError:java head space heap memory overflowJava.lang.OutOfMemoryError:Permgen Space Java Eternal Overflow, that is, methods to overflow, generally because of the emergence of a large number of classes and JSPs, or the use of Cglib reflection mechanism,This can be resolved by changing the size of the method area and modifying it in the form of a similar-xx:permsize=64m-xx:maxpermsize=256m. In addition, too many constants, especially strings, can cause the method area to ov

The JVM's full name is Java Virtual Machine (Java VM), which shields the software and hardware differences associated with each computer platform. in the coming days, I'll learn the JVM in the form of blogging, to make myself more aware of the Java This series of articles is "Deep analysis of Javaweb Technology Insider" and "in-depth understanding of Java Virtual Machine" Summary, welcome everyone to spit together, progress together

A rough understanding of JVM and JVM 1. How Java is cross-platform Java compiles source code into a Class file based on bytecode. bytecode is a file stored in bytes and is combined with cross-platform. It is a set of virtual commands that describe the program to run, this virtual command has nothing to do with any platform. The Java Virtual Machine knows it and the Java Virtual Machine translates it into co

The individual believes that JVM tuning is primarily addressed by the following methods1. Set the appropriate maximum heap memory (maximum and value for Cenozoic and Laosheng generations) and minimum heap memory (the operating system memory size consumed by JVM startup), and set the scale allocation of the heap.2, set up the suitable new generation because of its impact on the system performance and GC reco