What is the memory management mechanism in Go language?

Go language is an efficient programming language widely used for system-level programming. One of its main advantages is its memory management mechanism. The Go language's built-in garbage collection mechanism (Garbage Collection, referred to as GC) eliminates the need for programmers to perform memory allocation and release operations themselves, improving development efficiency and code quality. This article will provide a detailed introduction to the memory management mechanism in the Go language.

1. Go memory allocation

In the Go language, memory allocation uses two heap areas: small object heap and large object heap. When memory needs to be allocated, the system will choose which heap area to use based on the size of the object and allocate a piece of memory in the corresponding heap area.

1. Small object heap

The small object heap is a pre-allocated fixed-size memory area with a size of 64KB. When a request is made to allocate an object smaller than 32KB, the system allocates from the small object heap without causing stalls.

When the allocated object size is between 32KB and 2MB, the Go language will use another memory allocation mechanism, namely mcache (memory cache). mcache is a small memory cache bound to each P (Processor), used to cache smaller objects. When allocating smaller objects, the Go language allocates memory from the corresponding mcache. The use of mcache reduces dependence on locks and provides higher performance.

2. Large Object Heap

The large object heap is the heap area where memory is allocated when the object size is greater than 32KB. Because allocating large objects may result in larger memory fragmentation, it is recommended to avoid allocating too many large objects. If a larger memory block needs to be allocated, it is recommended to use a memory pool or optimization algorithm to avoid "waste".

2. Go garbage collection mechanism

The Go language uses a concurrent and non-generational garbage collector. It uses a mark-and-sweep algorithm, which can automatically recycle memory that is no longer used when the program is running.

1. Mark-clear algorithm

The mark-clear algorithm is a memory recycling mechanism. The basic idea is to first mark the memory, mark which memory can be recycled, and then clear the marked memory. The mark here refers to whether the memory has been referenced. If it has not been referenced, it is marked as recyclable. The process of clearing is to release the memory space marked as recyclable.

The mark-clear algorithm has good scalability and efficiency, but its disadvantage is that it needs to stop the running of the application to perform garbage collection, which may cause a certain delay.

2. Go Garbage Collector

Go Garbage Collector uses Tri-color Marking, which is divided into three states: White , black (Black) and gray (Gray).

Before garbage collection begins, all memory is marked white. When the program is executed, all referenced memory is marked black, and unreferenced memory is marked white. Gray indicates untagged memory that is associated with tagged memory.

During garbage collection, scanning starts from the root object (such as global variables, variables on the stack, etc.). If a black memory is scanned, it will be skipped and not processed; if a white memory is scanned, it will be marked gray, and its associated memory will also be marked gray. After the concurrent scan is completed, all memory that is not marked gray is released.

3. Summary

The garbage collection mechanism allows developers to focus on the design and writing of code logic without having to pay too much attention to memory allocation and recycling issues. At the same time, unlike other languages, the Go language garbage collector uses a concurrent mark-and-sweep algorithm, which can recycle memory without stopping the program. This is also a reflection of the efficiency and development efficiency of the Go language.

Of course, the optimization of memory allocation and release is also an issue we need to consider. Using memory pools and avoiding allocating too many large objects are some optimization measures. In general, understanding and mastering the Go memory management mechanism can not only ensure the quality and performance of the code, but also one of the necessary skills to become an excellent Go language developer.

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