jvm monitor

In this section we summarize the memory allocation policy in the JVM. The directory is as follows: Memory allocation policyObject first in New Generation Eden AssignmentLarge objects go straight into the old ageLong-lived objects will enter the old age.Dynamic Object Age DeterminationSpace allocation guaranteed memory allocation policyThe automatic memory management advocated in the Java technology system can be attributed to two parts: allocating mem

Difference between heap memory and stack memory in JVM, and between jvm heap memory Java divides memory into two types: stack memory and stack memory. TheSome basic types of variables and Object Reference variables are allocated in the function stack memory.. When a variable is defined in a code block, java allocates memory space for the variable in the stack. When the scope of the variable is exceeded, jav

JVM learning-runtime data zone and jvm learning data Zone Unlike C and C ++ programs, the memory management of Java programs is taken over by the java Virtual Machine (JVM), which reduces the burden on Java programmers, however, if an OutOfMemory or StackOverFlow Exception error occurs, it is difficult to locate the error quickly if you do not know the memory man

JVM review notes and jvm Review -- Take it easy Garbage collection: Young generation ------- serial, parnew, parallel scavengeTenured gencration --------- CMS, Serial old (MSC), parallel old.The parallel scavenge collector is a new generation collector that uses apparel algorithms and parallel multi-thread collectors.It looks like parnew. What's special?-- The characteristics of parallel scavenge collecto

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

JVM tuning-calculate the active data size and jvm tuning Active Data Active Data, sometimes called survival data, refers to the size of long-lived objects in the Java heap when the application is in stable running state. In other words, the space occupied by the Java heap after FullGC in the stable running state of the application (memory usage ). 1. Importance of active data computing The calculation of t

As we all know, the JVM used to be interpreted in the past, but later in the history of the revision also added to the implementation of the compilation. So in general the JVM is comprised of interpretation execution and compilation execution. This part does not belong to the scope of the JVM, has been compiled, most of them are lexical analysis and the like, the

JVM class loading mechanism ---- 2. jvm Loading Mechanism The first phase of the class loading mechanism is: 1. Use a fully qualified Class name (package name and Class Name) to obtain the binary byte stream (Class file) that defines this Class ). You can use the jar package, war package, network retrieval, and JSP file generation methods. 2. Convert the static storage structure represented by this byte st

Jvm memory growth troubleshooting examples and jvm troubleshooting examplesTroubleshoot jvm memory Growth Troubleshoot the problem that the jvm memory usage continues to increase. record it and take it as a warning. The O M team found that the jvm memory usage of the applic

Jvm running data distribution and jvm Data Distribution I have a deep understanding of jvm (java se7 of this version) Data Area During java Runtime When executing a java program, the java Virtual Machine divides the memory into several different stages and has different time. Different purposes First Program counter: A small memory space in the

JVM garbage collection algorithm and jvm garbage collection 1. Reference Counting Collector) The reference counting algorithm is a simple but inefficient algorithm. Its main principle is as follows: each object in the heap has a reference counter; when the object is referenced, add 1 to the reference counter; when the referenced object is left empty or out of scope, the reference counter minus 1. This metho

Garbage collection in Jvm and Jvm garbage collection I. Concept of garbage collection Memory collection in Java is the memory collection during Jvm runtime. The areas to be recycled include the method area and Java heap. Because of program counters, Java Virtual Machine stacks and local method stacks are automatically recycled at the end of methods or threads, so

corresponding memory allocations. If there are too many threads, a outofmemory error is caused. Even if you have enough space for the heap to hold the object, your app may crash because it creates a new thread. In this case, you need to consider limiting the maximum stack size in the thread. The thread stack size can be set by parameters when the JVM is started, -Xss and the default value is set to between 320KB and 1024KB, which is related to the pl

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