garbage collection analysis

, in addition to checking procedures, print heap memory and other methods to troubleshoot, but also with some memory analysis tools, such as Mat is very good.2. Persistent overflow, the performance is: Java.lang.OutOfMemoryError:PermGenspace usually because the persistent generation set too small, dynamically loaded a large number of Java classes and caused overflow, the solution is only the parameter-xx:maxpermsize Large (256m can meet most applicati

uses, but any garbage collection algorithm typically does 2 basic things:(1) Finding useless information objects;(2) Reclaim the memory space occupied by the useless object, so that the space can be reused by the program.　1. Reference counting method (Reference counting Collector)1.1 Algorithm Analysis　The reference count is an early policy in the

With the garbage collection mechanism in Microsoft. Net clr, programmers do not need to pay attention to when to release the memory. The memory is released completely by GC, which is transparent to programmers. However, as a. Net programmer, it is necessary to understand how garbage collection works. In this article, w

virtual address space fragmentation. This means that there are some available blocks in the address space called holes. When a virtual memory allocation is requested, the virtual Memory manager must find a single free block that is large enough to satisfy the allocation request. Even if you have 2 GB of free space, 2 GB of allocation requests may not succeed unless all of these spaces must be in a single address block. If you run out of reserved virtual address space or committed physical s

program executes, unless the space is reassigned or reclaimed by another method. This shows that it is impossible to completely eradicate the generation of memory leaks. Don't forget, though, that Java's garbage collector frees programmers from the heavy work of manually reclaiming memory space. Imagine a programmer using C or C + + to write a 100,000-line statement of code, then he will be fully aware of the Java

as we know, the Sun JVM divides the garbage collector into 3 pieces of heap space: Young Gen: The younger generation, which includes 1 Eden Districts and 2 suvivor areas, the newly created objects (most of which are short cycle objects) will enter this area, where virtual opportunities are frequently garbage collected. Old Gen: older generation, when the object in young Gen long enough (after several

reference exists, does not affect its lifetime at all, and cannot obtain an object instance through a virtual reference. The only purpose of setting a virtual reference association for an object is to be able to receive a system notification when the object is reclaimed by the collector . After JDK 1.2, the Phantomreference class is provided to implement the virtual reference. When is it recycled? Finalize Method With the above algorithms, a virtual machine can know what objects in memory need

of references were presented: strong reference, soft reference, weak reference, virtual reference. There are a lot of explanations on the use of these references on the Internet, here is a recommended article, do not do too much description: here.Strong references: Ubiquitous, new and the like. A strong reference is present and will not be recycled.Soft references: Objects that are useful, but are not required. Before a memory overflow occurs, it is recycled and throws an exception if it is not

exitsFour. GC Module common function analysis Garbage Collector Interface The GC module provides an interface for developers to set options for garbage collection. As mentioned above, one flaw in managing memory using reference counting is circular referencing, and one of the main functions of GC modules is to solve t

Player 11 and air 3 (). Memory Allocation Flash Player uses the gcheap to allocate a large amount of blank storage space (Millions of bytes) from the operating system (OS). Then gcheap splits the large amount of storage space into smaller 4 K pages and submits these pages to the memory manager of the garbage collection mechanism (GC) as needed. Figure 1. gcheap allocates memory from the OS, splits the memo

Brief Introduction to Java garbage collection mechanismA Who is doing garbage Collection. A popular saying: in C + +, the system is doing garbage collection, and in Java, Java itself is doing. In C + +, freeing the memory is h

The opening crap .If we want to do the memory optimization work, still need to understand, but this piece of knowledge is purely theoretical, it may seem a bit dull, I try to put this piece of content in accordance with certain logic to go through. First of all, why we should learn the mechanism of garbage collection, I probably summed up a few points:1.方便我们理解什么样的对象，什么时候，会被系统回收掉2.有助于我们后面的内存优化3.了解这一块的知识也能提升自

optimized garbage collection (garbage COLLECTION,GC) is critical to achieving these metrics.This article uses a series of steps to clarify requirements and optimize the GC, and the target audience is a developer who is interested in using system methods to optimize GC for high throughput and low latency for applicatio

Compared to C + +, Java has the technical advantage of dynamically allocating memory and garbage collection mechanisms , so that we don't have to focus on memory management, so why do we need to know about GC and memory allocation? The reason is simple: when you need to troubleshoot various memory overflows, When a memory leak problem occurs, when garbage

The first part of the garbage collection mechanism in the early-C + + development, the life cycle of an object is probably like this: compute the object size--Find the available memory--Initialize the object--use the object--to destroy the object. If in the process above, the developer forgets the "destroy object" step, it is likely to lead to memory leaks! This is a very terrible thing! Fortunately, the de