free java memory profiler

Java virtual machine (Java VM) referred to as the JVM Java Virtual machine is an imaginary machine that is implemented by software simulations on a real computer. The Java Virtual machine has its own imaginary hardware, such as processor, stack, register, etc., and also has the corresponding instruction system.Java div

environment needs to be consistent with the-XMX, otherwise the value of capacity will bounce back and forth-XMX is the maximum value of the heap area-XSS (or-SS) thread stack size (refers to a thread's native space) 1.5 is the default size after 1M-xx:permsize and-xx:maxpermsize Method area (permanent generation) initial size and maximum value (but not local method area)-xx:newratio old age and Cenozoic ratio-xx:survivorratio Eden and survivor occupancy ratio. For example, 8 indicates that a su

As a Java programmer, because of the automatic memory management of the virtual machine, so there is no need to write to the C and C + + programmers like the disaster area of the delete and the free method, but there is no memory leak in Java, the answer is no, there is a

JVM; This value will be smaller if more and more memory is being used by the current JVM request; /*The maximum number of memory that the *-xmx10m:java process can request to the operating system*-xms1m:java the default requested memory when the process is initialized (as the system runs it will grow larger until it equals-XMX value)*/public class Heapconfig {p

Java the memory becomes garbage when there is no object reference to the memory originally assigned to an object. A system-level thread of the JVM automatically frees the block of memory. Garbage collection means that the object that the program no longer needs is "useless information," and that information is discard

detail the multi-threaded and memory interaction semantics, becomes part of Java specification, improves the original Java semantics error, the ambiguous part, guarantees the Java cross-platform.The definition of the memory model in JSR133 is as follows:Given a program and

Memory Overflow, is the program when requesting memory, there is not enough memory for its use "" ML memory leak, refers to the program after the application of memory, unable to free the requested

This article belongs to author original, the original text is published in Infoq:http://www.infoq.com/cn/articles/java-memory-model-5Lock Release-Get established happens before relationshipLocks are the most important synchronization mechanism in Java concurrent programming. The lock allows the thread that releases the lock to send a message to the thread that ac

One, Java memory allocation1. How many storage areas does Java have? Register Device--within the CPU, developers cannot control the allocation of registers through code and have compilers to manage them.Heap--in Windows, the stack is the data structure to the bottom address extension, is a contiguous area of memory, th

synchronized, then the programmer can follow the sequential consistency model to infer the execution results of the program, and the underlying memory operation implementation , can be optimized according to Relaxed Memory model.The Java memory model contains two areas of content A multithreaded program that

program operation is:Name: Zhang San, age: 30Name: Zhang San, age: 30The output from the program can be found to be Test03. However, there have been some changes in memory allocations, as follows:Note the point: Java itself provides a garbage collection mechanism (garbage COLLECTION,GC), will not periodically cast unused memory space, as long as the obj

One, memory overflow type1. Java.lang.OutOfMemoryError:PermGen SpaceThe JVM manages two types of memory, heap, and non-heap. The heap is intended for developers, and is created at the start of the JVM, and the non-heap is left to the JVM for its own use to store the information for the class. Unlike heaps, the GC does not free up space during the run time. If the

time for big data and we need more memory. In Java, there are two ways to get more memory: 1. Allocate a lot of small chunks of memory, and then logically use them as a continuous large memory.2. Use Sun.misc.Unsafe.allcateMemory (long) for