java memory profiling tools

=c:dump.txt 340Note that 340 is my native Java process pid,dump out of the file is a lot more than 10 m, and I just opened Tomcat, ran a very simple application, and no access, can imagine, large busy server, dump out of the file how large. What you need to know is that the dump file information is very primitive, it's not for people to watch directly, and the Jmap-histo display is too simple, such as showing just how much

In Java, memory leaks and other memory-related issues are the most prominent in terms of performance and scalability. We have good reason to discuss them in detail.The Java memory model-or, more specifically, the garbage collector-has overcome a lot of

JVM Tuning-tools Jconsole:java monitoring and management console Jconsole is an opportunity to JMX (Java Management Extensions, Java Management extension) of the JVM monitoring and management tools, monitoring mainly reflected in: stack memory, Thread, CPU, class, V

on the heap? With the gradual maturation of escape analysis technology, stack allocation and scalar substitution optimization technology make "all objects are allocatedOn the heap "also became less absolute. The so-called escape is when a pointer to an object is referenced by multiple methods or threads, we call this pointer to escape.In general, Java objects are allocated in heaps, and only pointers to objects are saved on the stack. Suppose a loc

successfully, any action in thread B happens-before the successful return of thread A from the Thread.Join () operation. Summary 1) as-if-serial semantics guarantees that the execution result of a single-threaded program is not changed, and that the happens-before relationship guarantees that the execution results of correctly synchronized multithreaded programs are not changed.2) As-if-serial semantic creation single-threaded program fantasy: Single-threaded programs are executed

Java Theory and Practice: Use Weak references to block memory leaks-Linux general technology-Linux programming and kernel information. The following is a detailed description. Although Java™In theory, a program written in a language does not have a "memory leak", but sometimes objects are not garbage collected after th

1. Introduction:Javamelody can monitor Java or Java EE application servers in a running environment. It is displayed as a graph: Java memory and Java CPU usage, number of user sessions, JDBC connections, and HTTP requests, SQL requests, JSP pages and Business interface metho

Java Theory and Practice: block memory leakage with weak referencesWeak references make it easy to express object lifecycle relationships. Document options

export the memory footprint of the current Java process to facilitate analysis using specialized memory analysis tools such as: MAT. This command is helpful for analyzing whether there is a memory leak. How to use to view another article in this blog: using Eclipse

named, which expungeStaleEntries() Map is called in most operations, which removes all invalid references in the reference queue and deletes the associated mappings. expungeStaleEntries()a possible implementation is shown in Listing 7. The type used to store the key-value mappings is Entry extended WeakReference , so when the expungeStaleEntries() next invalid weak reference is requested, it gets one Entry . It is more efficient to use a reference queue instead of a regular scan of the content,

in real-world applications, it is often necessary to export data into Excel , the exported method is exported in addition to the original, pagination export, pagination sheet export and large data volume export. For version excel2003, the maximum number of rows and columns per sheet is limited , and when large data is exported it will default to multiple sheet excel2007 There is no such problem. These export methods are implemented in Java programs w

One of the best known advantages of Java technology is that, unlike other languages such as C programmers, Java programmers do not have to be responsible for daunting memory allocations and releases. The Java runtime can manage these tasks for you. Each instantiated object automatically allocates

jmm order and visibility cannot be guaranteed.Happens-before ordering (first occurrence sort) How to avoid this situation?The sorting principle has been achieved:A, in program order, each action in a thread occurs before every operation that occurs after the current operation.b, the object Monitor's unlock occurs before the thread that waits to acquire the object lock.c, a variable write operation for the Volitile keyword, which occurs before the read of the variable.D, a Thread.Start () call t

and resulting values③ declares a public static method that returns a value of collection and modifies it with @parameters④ declares a public constructor with parameters for the test class and assigns a value to the variable in which it is declaredIv. use of JUNIT4 in Web projectsintegration testing of Spring and hibernatewhen we use the Open source framework for project development, there is no doubt that the integration between frameworks is a high error rate, and JUnit can be used for the int

Abstraction Although Java virtual machines and garbage collection mechanisms manage most of the memory transactions, there may still be memory leaks in Java software. Indeed, memory leakage is a common problem in large projects. The first step to avoid

See: http://blog.yemou.net/article/query/info/tytfjhfascvhzxcyt1061. Data area of Java Virtual runtime2. Common Memory Area adjustment parameters-XMS: The initial heap size, default is the physical memory of 1/64 (-XMX: Maximum heap size, default (maxheapfreeratio parameter can be adjusted) when free heap memory is gre

JVM Memory Area Program counterA small amount of memory space that is the line number indicator of the byte code executed by the current thread. Java stackAs with program counters, the Java stack (the virtual machine stack) is also thread-private, with the same lifecycle as the thread. Typically holds the

, we need to troubleshoot on the server. Use the Jmap tool that comes with the JDK to see what the specific objects are in the JAVA application, as well as the number of cases and their size. The specific commands are as follows:Jmap-histo:live ' pid of Java ' # for easy observation, or write output to file Jmap-histo:live ' pid of Java ' >/tmp/jmap00After observ

(wagewagetotal=wage*0.1;System.out.println ("=======" +wagetotal);}else if (wageWagetotal= (100000) *0.1+ (wage-100000) *0.075;}else if (wageWagetotal= (100000) *0.1+ (200000) *0.075+ (wage-200000) *0.05;}else if (wageWagetotal= (100000) *0.1+ (200000) *0.075+ (400000) *0.05+ (wage-400000) *0.03;}else if (wageWagetotal= (100000) *0.1+ (200000) *0.075+ (400000) *0.05+ (600000) *0.03+ (wage-600000) *0.015;}else{Wagetotal= (100000) *0.1+ (200000) *0.075+ (400000) *0.05+ (600000) *0.03+ (1000000) *

Memory Leaks and workarounds1. Some phenomena before the system crash:EachThe garbage collection time is getting longer, from the previous 10ms extended to about 50ms, FULLGC time also has the previous 0.5s extended to 4, 5sFULLGC more and more times, the most frequent lapse of less than 1 minutes to do a FULLGCOlder generations of memory are getting bigger and older generations have no