In-depth analysis of Golang language features: multi-threaded programming and task scheduling

In-depth analysis of Golang language features: multi-threaded programming and task scheduling

Introduction:
Golang (also known as Go language) is a statically strongly typed language with its excellent performance and concise syntax. , gradually become popular among developers. One of its design goals is to support multi-threaded programming. Through the features of Goroutine and Channel, developers can easily implement multi-threaded programming. This article will deeply explore the multi-threaded programming features of Golang, focusing on the relationship between task scheduling and coroutines.

Multi-threaded programming and coroutine:
In Golang, the most basic concurrency unit is the coroutine (Goroutine), which can be understood as a lightweight thread. Compared with traditional threads, the creation and destruction overhead of coroutines is extremely small, and context switching can be performed efficiently. Therefore, in Golang, we can create a large number of coroutines to execute tasks concurrently without worrying about performance issues.

The following is a simple sample code that shows how to create and start a coroutine:

package main

import (
    "fmt"
    "time"
)

func main() {
    go hello()
    time.Sleep(1 * time.Second)
    fmt.Println("main goroutine exit")
}

func hello() {
    fmt.Println("Hello, Golang!")
}

In the above example, we created it through the go keyword A coroutine, and this coroutine is started through the main function. In the main function, we wait for 1 second through the time.Sleep function to ensure that the coroutine can run normally. Finally, we output a message and wait for the coroutine to end before the main function ends. Running the program, you can get the following output:

Hello, Golang!
main goroutine exit

As you can see, the creation and startup of the coroutine is very simple, just use the go keyword. The code in the coroutine will run asynchronously and will not block the execution of the main thread.

The relationship between task scheduling and coroutines:
Golang’s scheduler (Scheduler) is responsible for coordinating the execution between coroutines. The scheduler assigns the coroutine to the system's thread (Thread) to implement the scheduling and execution of the coroutine on the physical thread. Golang's scheduler is part of the runtime system (Runtime). It is responsible for scheduling the execution of tasks during the execution of coroutines, and implements tasks such as priority management, context switching, and blocking/waking up.

In Golang, the scheduler adopts a thread management strategy called the GMP model. G stands for Global, P stands for Physical thread, and M stands for Machine. The core idea of ​​the GMP model is to bind a coroutine (Goroutine) to a physical thread (Thread), and dynamically allocate coroutine execution tasks on different threads through the scheduler (Scheduler).

Golang's scheduler adopts a preemptive scheduling strategy, that is, when a coroutine execution takes too long or is blocked, the scheduler will actively schedule the execution of other coroutines to improve the concurrency performance of the program. The scheduler will also dynamically adjust the execution order of tasks based on the priority and task type of the coroutine to ensure the overall performance of the program.

The following is a sample code that shows the scheduling relationship between multiple coroutines:

package main

import (
    "fmt"
    "time"
)

func main() {
    for i := 0; i < 5; i++ {
        go worker(i)
    }

    time.Sleep(3 * time.Second)
    fmt.Println("main goroutine exit")
}

func worker(id int) {
    fmt.Printf("Worker %d started
", id)
    time.Sleep(1 * time.Second)
    fmt.Printf("Worker %d finished
", id)
}

In the above example, we created 5 coroutines to execute tasks concurrently. Each coroutine will output its own ID, and sleep simulations will be performed before and after task execution. We wait 3 seconds in the main thread to ensure that all coroutines can be executed. Running this program, you can get the following output:

Worker 0 started
Worker 1 started
Worker 2 started
Worker 3 started
Worker 4 started
Worker 4 finished
Worker 0 finished
Worker 1 finished
Worker 2 finished
Worker 3 finished
main goroutine exit

As you can see, the execution order among multiple coroutines is uncertain, and the order of output may be different each time it is run. This is because the scheduler dynamically schedules coroutine execution on different threads to improve concurrency performance. In addition, the execution order of coroutines is also affected by factors such as the operating system and hardware environment.

Conclusion:
Through an in-depth analysis of Golang's multi-threaded programming and task scheduling features, we can find that Golang provides a simple and efficient concurrent programming model. Through the characteristics of coroutines and channels, we can easily implement the allocation and scheduling of concurrent tasks and give full play to the performance advantages of multi-core processors. In actual projects, we can flexibly use coroutines and channels according to specific tasks and needs to achieve high-quality concurrent programming.

References:

1. https://golang.org/
2. https://tour.golang.org/concurrency/1

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