jvm 1 7

First, introduce one person: Jon Masamitsu. This person's background is unknown, but he does JVM in Sun, so his blog I think everyone who wants to tune the JVM should read it. Many of the ideas and figures in this article are also taken from his blog.Blog link: http://blogs.sun.com/jonthecollector/ In his blog [1], the three most important options for GC optimiza

phase. We can understand that the static final constant puts its result in the constant pool of the class that called it at compile timeParse: Converts a symbolic reference in a class to a direct referenceThe parsing phase is the process by which a virtual machine replaces a symbolic reference within a constant pool with a direct reference, and the parsing action is primarily for a class or interface, a field, a class method, an interface method, a method type, a method handle, and a call Point

=4: Sets the ratio of the size of Eden and survivor in the younger generation. Set to 4, the ratio of two survivor to one Eden area is 2:4, and a survivor area represents 1/6 of the entire young generation. -xx:maxpermsize=16m: Set the persistent generation size to 16m. -xx:maxtenuringthreshold=0: sets the maximum age for garbage. If set to 0, then the young generation object does not go through the survivor area, directly into the old generat

Java job interview, the JVM is the basic skills of the programmer to investigate, usually ask you to understand the JVM? You can answer this question in a few parts, first JVM memory Partitioning | What the JVM garbage collection means | What are the GC algorithms and the characteristics of the younger generation and t

OOM is the biggest headache During Java program development: out of memory. In the development process of many developers, such problems are more or less encountered. It is difficult to locate such problems. You often need to judge the code that may cause problems based on experience. There are two main reasons: the object is not released (in many cases, it is often caused by concealed references, leading to hold and cannot be recycled ). The other is that memory is not enough, and

divided into several areas, that is, the run-time data zone (run-time data areas ); these regions have different functions and lifecycles. They are mainly divided into two categories: one is created with the startup of the JVM process and destroyed with the demise of the JVM process; one is created with the creation of threads and destroyed with the destruction of threads. The memory areas stipulated in Ja

process.Bootstrap ClassLoader, Extension ClassLoader, App ClassLoader The relationship between the following:Bootstrap ClassLoader is Extension classloader parent,extension ClassLoader is the parent of app ClassLoader.But this is not an inheritance relationship, just a semantic definition, basically, every ClassLoader implementation, there is a parent ClassLoader.The parent of the current ClassLoader can be obtained through the ClassLoader GetParent method. Bootstrap ClassLoader is special beca

ObjectiveAfter Java is started as a process running in the operating system, the process has to allocate the following memory:1. Java Heap:Stores the Java memory area, where the heap size is when the JVM starts up as if the operating system request is complete, where-xmx and-xms represent the maximum and initial sizes, respectively. GC management that is fixed and belongs to Java after the heap size allocat

, when heap is insufficient, traverses the heap and upgrades young to the older area. The size of the older area equals-xmx minus-xmn, and the-XMS value cannot be set too large because the second thread is forced to run, which degrades the performance of the JVM. The reasons that can cause frequent GC occurrences are: 1, the program calls the System.GC () or RUNTIME.GC (). 2. Some middleware software calls

, including young, tenured and perm. The full GC is slower than the scavenge GC because it needs to be recycled for the entire pair, so you should minimize the number of times that you want to have the whole GC. In the process of tuning the JVM, a large part of the work is the regulation of FULLGC. a full GC can occur for the following reasons: · The old generation (tenured) is written full · Persistent generation (Perm) is written full · System.GC ()

Summary after reading Java Virtual Machine 1) Sun HotSpot JVM Memory Model 2) Sun HotSpot JVM Memory Allocation Iii) Sun HotSpot JVM memory monitoring 4) Sun HotSpot JVM garbage collection Based on Sun HotSpot JVM Direct: 650) t

There are many formulas for calculating pi pai in history, in which Gregory and Leibniz found the following formula: Pai = 4* (1-1/3+1/5-1/7 ...) The formula is simple and graceful, but in a bad way, it converges too slowly. If we rounded to keep its two decimal digits,

method, the lock is the object instance (this), when the 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.

Document directory 1. thread status and State Conversion 2. spin lock 3. Biased lock 4. Summary Currently, there are two lock mechanisms in Java: synchronized and lock. The lock interface and its implementation class are added by jdk5. the author is Doug Lea, a famous concurrency expert. This article does not compare synchronized and lock ratio, but only introduces the implementation principles of the two. Data Synchronization depends on the l

by Storm, which uses standard input and outputSpoutAndBoltCommunication channel between processes. Messages are transmitted in the channel in JSON or plain text format. Let's look at a non-JVM Language DevelopmentSpoutAndBolt. In this exampleSpoutGenerate a number from 1 to 10,000,BoltFilter prime numbers. Both are implemented using PHP. NOTE :?In this example, we use a very stupid method to verify the pri

-(void) Touchesbegan: (nonnull nssetAlgorithmic entry[Self func2:9];}Calculate factorial factor (m) = m!-(int) factor: (int) m{int factornum=0;if (m==0|m==1)return 1;else{Factornum=m*[self Factor:m-1];NSLog (@ "%d", factornum);return factornum;}}Calculate Func1 (m) = 1! +3! +5! + ... +m!-(int) func1: (int) m{int sum=0;

When you start eclipse, the JVM terminated is not up. Exit Code=-1There is an error, do not know what the reason for the original good eclipse, this morning, a problem, start up also throw JVM terminated. Exit Code=-1, the Internet to check the information, the original many people and I have such a problem, really thank the predecessors. Eclipse does not start u

the internal structure of the JVM. CMDVisual GC, Tools---installation. -xms1g//Heap Initial Size-xmx1g//Heap Maximum Value-xmn1g//Young Generation Size-xx:newsize=1g//Young Generation Initial value-xx:maxnewsize=1g//Young Generation Max-xx:newratio=1//set a multiplier (ratio) of old age and youth, which is 2 by default.-xx:survivorratio=1//set the ratio of the E

area in the younger generation. Set to 4, the ratio of two survivor to an Eden area was 2:4, and a survivor area accounted for 1/6 of the entire young generation. -XX:MAXPERMSIZE=16M: Sets the persistent generation size to 16m. -xx:maxtenuringthreshold=0: Set the maximum age of rubbish. If set to 0, then the younger generation objects do not go through the survivor area, directly into the old generation. More applications for older generations can

Today, the JVM terminated exit code =-1 cannot be started in eclipse. No changes made in the impact are confusing. So Baidu There are basically two possibilities 1. After jdk6.0 is installed, the JVM. dll is jre6/bin/client/JVM. dll, which should be changed to