jvm monitor

". When synchronized is applied to the method, the lock is the object instance (this ); when used as a static method, the lock is the class instance corresponding to the object. Because the class data exists in the permanent band, the static method lock is equivalent to a global lock of the class; when synchronized acts on an object instance, the lock is the corresponding code block. In the hotspot In JVM implementation, the lock has a special name: O

,//10 Monitor Lock, also known as expansion lock, also known as weight level lock 4 Marked_value 3,//11 gc marker 5 biased_lock_pattern 5//101 bias Lock 6 };Here is the source code comment:Figure 3 hotspot source MARKOOP.HPP lock flag bit noteLook at Figure 3, whether 32/64-bit JVM, are 1bit biased lock +2bit lock flag bit. The above red box is biased to the lock (a d

Originally the title Party wanted to write "in-depth JVM", but not too bold, I think a small blog I think it is not enough to explain the JVM, in this article, I would like to introduce you to the JVM a lot of internal knowledge, the concept will be relatively coarse, because too fine content to write, here is certainly not written; , in addition to some official

action in the static method is locked is the object corresponding class instance, because the class data exists perpetual band, So a static method lock is equivalent to a global lock of that class, and when synchronized acts on an object instance, the corresponding code block is locked. In the Hotspot JVM implementation, the lock has a special name: Object Monitor. 1. Thread Status and state transitionsWhe

,Useparallelgc for parallel collection, XX: number of parallel collection threads of parallelgcthreads, which is valid only when useparallelgc is configured.. Useadaptivesizepolicy allows the JVM to dynamically adapt parameters based on the situation. Of course, if you specify some parameters, the JVM will not adjust those parameters, if this parameter is added, other parameters that are not fully considere

JVM structure BasicsSome time ago, due to the performance problems of the widely-spread String and StringBuffer, I did a few small experiments and came to some conclusions. However, according to the reaction of netizens, the research did not play a proper purpose, moreover, some netizens also put forward their own opinions and pointed out some of the content in the experiment. In response to their reactions, I decompiled the code for comparison, howev

Overview When the system bugs need to locate the problem, knowledge, experience is the key foundation, the data is the basis, the tool is the use of knowledge processing data means. The data mentioned here include: Run log, exception stack, GC log, thread snapshot (threaddump/javacore file), heap dump Snapshot (heapdump/hprof file), etc. Using the appropriate virtual machine monitoring and analysis tools can accelerate our ability to analyze data and locate problems. command-line tools for JDK

great impact on garbage collection. The basic order of execution is as follows: The vast majority of objects that have just been created are stored in the Eden space. After the first GC has been performed in Eden Space, the surviving objects are moved to one of the survivor spaces. Thereafter, after the GC is executed in Eden Space, the surviving objects are stacked in the same survivor space. When one survivor is saturated with space, the surviving object is moved to an

This article is the second in a series of articles for the Java GC expert. In the first "Understanding Java garbage Collection mechanism" we learned the implementation of different GC algorithms, how the GC works, what is the new generation and the old age, you should understand the JDK7 of 5 types of GC, and the impact of these 5 types on the application performance.In this article, I'll explain exactly how the JVM performs garbage collection process

_env" = "yes"] Then echo "MySQL Slave is running!" Else echo "####### $DATA #########" >>/data/mysql/mysql_slave_status.log echo "MySQL Slave is not running!" >>/data/mysql/mysql_slave_status.log echo "MySQL Slave is not running!" | mail-s "warn! $MYSQLIP MySQL Slave is not running. "Admin@yourdomain. com Fi Recommended to run every 10 minutes*/10 * * * * root/bin/sh/root/mysql_slave_status.shPrinciple:1) Monitor the running stat

Reprinted article as follows: http://www.cnblogs.com/jiayi/archive/2010/06/08/1753863.html The jvmjob principle and special point are that the operating system is installed with jvmthrough jdk's java.exe, and the following four steps are used to complete the JVM environment. 1. Create a JVM loading environment and Configuration 2. Load JVM. dll 3. initialize

defaults to dynamically set the size of the maxmetaspacesize as needed at run time. GC　　If the Metaspace occupies a set maximum, then a GC is triggered to collect the dead objects and class loaders. Depending on the features of JDK 8, G1 and CMS will collect the Metaspace area (typically with full GC).In order to reduce the frequency and time of garbage collection and control the throughput, it is necessary to monitor and tune the Metaspace properly.

Original Blog Address: https://zhuanlan.zhihu.com/p/25713880Basic concepts of the JVMThe Chinese name of the JVM is called a Java Virtual machine, which is a virtual computer run by software technology that simulates a computer.The JVM also acts as a translator, and the Java program we write is not directly identifiable by the operating system, and the JVM is res

The JVM execution object is a class file that everyone is very familiar with. It is also called a class file. The compiled code file defined by the JVM specification (although not mandatory, it is an actual file) the format is very detailed, but here we only talk about some macro content. In the future, we will have the opportunity to study the details. The format of the class file required by

System CentOS6.4 Yum installed Tomcat6 and jdk1.6, the installation configuration process is as follows: Http://www.111cn.net/sys/CentOS/72007.htm The deployment of two projects A and B in Tomcat, as well as the time of memory overflow error in the deployment times, the system CPU load is soaring, and a, B, and only multiple a, or just multiple B-project systems are deployed separately for normal operation. View Log error: Outofmemoryerror:permgen space ....Query data learned: Non-heap overfl

[Original Pag] Since the release of JDK 5 The JVM uses JMX technology to provide information on performance and resource consumption of T He applicationsrunning in the JVM. Together with the Jconsole tool we can-information to monitor our applications and locate problems. To keep applications running smoothly it's important to is able to get information about th

Tomcat itself cannot run directly on the computer, it needs to rely on a hardware-based operating system and a Java virtual machine. Tomcat's memory overflow is essentially a JVM memory overflow, so at the beginning of this article, the Java JVM's memory-related knowledge should be described in detail.First, Java JVM memory IntroductionThe JVM manages two types o

Tomcat itself cannot run directly on the computer, it needs to rely on a hardware-based operating system and a Java virtual machine. Tomcat's memory overflow is essentially a JVM memory overflow, so at the beginning of this article, the Java JVM's memory-related knowledge should be described in detail.First, Java JVM memory IntroductionThe JVM manages two types o

Tomcat itself cannot run directly on the computer, it needs to rely on a hardware-based operating system and a Java virtual machine. Tomcat's memory overflow is essentially a JVM memory overflow, so at the beginning of this article, the Java JVM's memory-related knowledge should be described in detail.First, Java JVM memory IntroductionThe JVM manages two types o

The jvmjob principle and special point are that the operating system is installed with jvmthrough jdk's java.exe, and the following four steps are used to complete the JVM environment. 1. Create a JVM loading environment and Configuration 2. Load JVM. dll 3. initialize JVM. dll and mount it to the jnienv (JNI call inte