Analysis of GC implementation in Go language

Analysis of GC implementation in Go language

GC (Garbage Collection, garbage collection) is an automatic memory management technology that can automatically Relieves the programmer's burden by identifying and freeing memory that is no longer in use. As a modern programming language, Go language also uses GC to manage memory, but the GC implementation method of Go language is slightly different from other languages. This article will analyze the GC implementation method in Go language and introduce its internals in detail. Working principle, and some specific code examples are given to illustrate its operating mechanism.

In the Go language, GC mainly manages memory in three ways: mark and sweep, stop and copy, and mark and compact. The GC of the Go language is a concurrent or parallel GC. It does not block the execution of the user program when the program is running, but performs garbage collection in the background. This concurrent GC gives the Go language a great advantage in performance and can manage memory more efficiently.

The GC in the Go language is mainly divided into the following stages:

1. Marking stage: In this stage, the GC will start from the root object and traverse the program All objects in , and mark all reachable objects. This process is to find all root objects by traversing the program's stack, global variables, registers, etc., and then recursively find all reachable objects based on these root objects and mark them.
2. Cleaning phase: After the marking phase is completed, the GC will traverse all objects in the heap and clear those objects that have not been marked. The memory occupied by these cleared objects will be released for subsequent memory allocation.

Next, we use a simple example to demonstrate how GC works in Go language:

package main

import "fmt"

func main() {
    var a, b, c *int

    a = new(int)
    *a = 10

    b = new(int)
    *b = 20

    c = a
    fmt.Println(*c)

    a = nil
    b = nil

    // 手动触发GC
    // runtime.GC()

    // 由于c依然引用a指向的内存，故不会被回收
    fmt.Println(*c)
}

In this example, we create three pointers a, b, c, and allocate memory and assign values ​​to a and b respectively. Then we point c to a, and finally make a and b blank. In the last line, since c still refers to the point pointed by a, the memory pointed to by a will not be reclaimed by GC. To trigger GC manually, you can call the runtime.GC() function.

Through the above example, we can see how the GC of the Go language works. It manages memory through marking and clearing to ensure that memory that is no longer used is released in time. At the same time, the GC of Go language is concurrent, which can recycle memory without affecting the running performance of the program, improving the execution efficiency of the program.

In general, the GC implementation in the Go language is an efficient and superior memory management mechanism. It reduces the memory management burden for programmers and improves the execution efficiency of the program. Through in-depth understanding and analysis of the GC implementation in the Go language, it can help developers better understand and optimize their programs.

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