Analysis of the management principles of Go language garbage collector

Go language garbage collector management principle analysis

Introduction:
Garbage collection is an important function in modern programming languages, which can help programmers automatically manage memory to reduce its burden. In the Go language, the garbage collector is part of its runtime system and is responsible for recycling memory that is no longer used, making the Go language an extremely easy-to-use and efficient language. This article will provide an in-depth analysis of the garbage collector management principles of the Go language and attach specific code examples.

1. Basic principles of garbage collection
The garbage collector of Go language uses the mark-and-sweep (Mark and Sweep) algorithm. This algorithm starts from the root node (that is, global variables and local variables of running functions), marks unused objects, and after completing the marking, further clears these unused objects to release memory.

The specific garbage collection process is as follows:

1. All root nodes are marked as in use.
2. Recursively traverse all objects starting from the root node and mark them as in use.
3. All unmarked objects will be considered garbage and will be recycled.
4. Clear the memory space occupied by garbage objects.

2. Garbage collector management in Go language
The garbage collector of Go language uses a mixture of algorithm one and algorithm two, that is, concurrent marking and concurrent clearing.

1. Concurrent Mark (Concurrent Mark)
   Concurrent Mark means that the main thread and the garbage collection thread perform marking operations at the same time, without stopping the execution of the main thread. This mode of operation makes full use of the performance of multi-core computers and greatly reduces garbage collection pause times.

The specific process of concurrent marking is as follows:

1. The garbage collector starts a dedicated marking thread.
2. The concurrent marking thread starts from the root node and marks all reachable objects as being in use.
3. During the marking process, the concurrent marking thread may encounter the creation of new objects and recycled objects, and needs to update the corresponding status through write barriers.
4. Concurrent sweep (Concurrent Sweep)
   Concurrent sweep means that the main thread and the garbage collection thread perform cleaning operations at the same time, without stopping the execution of the main thread. This mode of operation also makes full use of the performance of multi-core computers and greatly reduces the pause time of garbage collection.

The specific process of concurrent cleaning is as follows:

1. The garbage collector starts a dedicated cleaning thread.
2. Concurrent clearing thread clears all objects marked as garbage and releases the corresponding memory space.
3. During the cleaning process, the concurrent cleaning thread may encounter the creation of new objects and recycled objects, and needs to update the corresponding status through write barriers.

3. Garbage collector operation example code

package main

import (
    "fmt"
    "runtime"
)

func main() {
    var m runtime.MemStats
    runtime.ReadMemStats(&m)
    fmt.Printf("HeapAlloc = %v MiB
", m.HeapAlloc/1024/1024)

    // 申请并分配10MB内存
    data := make([]byte, 10*1024*1024)

    runtime.ReadMemStats(&m)
    fmt.Printf("HeapAlloc = %v MiB
", m.HeapAlloc/1024/1024)

    // 调用垃圾回收器
    runtime.GC()

    runtime.ReadMemStats(&m)
    fmt.Printf("HeapAlloc = %v MiB
", m.HeapAlloc/1024/1024)
}

The above code uses the runtime package of Go language and the MemStats structure to check memory usage. At the beginning of the program, we read the HeapAlloc field through the ReadMemStats function to obtain the current heap allocated memory size, then used the make function to allocate 10MB of memory, and called the ReadMemStats function again to obtain the allocated memory size. Next, we call the runtime.GC() function to explicitly trigger a garbage collection process, and call the ReadMemStats function again to obtain the memory size after garbage collection. Running the above code, you can find that the garbage collector successfully reclaimed the previously allocated 10MB of memory, thereby reducing memory usage.

Conclusion:
This article provides an in-depth analysis of the garbage collector management principles of the Go language, including the basic principles of garbage collection, the specific operations of concurrent marking and concurrent clearing, and the implementation of sample code. Understanding and mastering the garbage collection mechanism of the Go language is very important for writing high-performance programs, so I hope this article will be helpful to readers.

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