Advanced Guide to Concurrent Programming in Golang: Discussing the preemptive scheduling of Goroutines

Advanced Guide to Concurrent Programming in Golang: Discussing the preemptive scheduling of Goroutines

Introduction:
In Golang, Goroutines is a lightweight concurrency implementation that can create a large number of Concurrent tasks to improve program execution efficiency. The concurrent scheduling of Goroutines is implemented through Golang's runtime system, which adopts a preemptive scheduling mechanism. This article will explore the preemptive scheduling principle of Goroutines and its implementation, and illustrate it through code examples.

1. The basic principles of Goroutines
Goroutines are the basic unit of concurrency in Golang. It can be regarded as a lightweight thread. Goroutines can run on a smaller stack space than traditional operating system threads and can communicate without the need for locks or condition variables. Scheduling between Goroutines is done by Golang's runtime system.

Golang's runtime system adopts the M:N scheduling model, which maps M Goroutines to N operating system threads to achieve parallel execution. The runtime system dynamically schedules between operating system threads and Goroutines to achieve optimal concurrency. When a Goroutine performs a blocking operation (such as waiting for an I/O operation), the runtime system will automatically separate it from the current thread and then reschedule it to another thread to improve resource utilization.

2. The principle of preemptive scheduling
In Golang, the scheduling of Goroutines adopts a preemptive scheduling mechanism. This means that the execution time of a Goroutine will not be limited by other Goroutines, because the runtime system will periodically check whether the executing Goroutine needs to be preempted, and then suspend it to give other Goroutines a chance to execute.

In terms of specific implementation, Golang's runtime system will periodically trigger an event called "preemption point". When a Goroutine executes this event, the runtime system will check whether the current time slice has been used. If it is finished, the current Goroutine will be suspended and control will be given to other Goroutines. This method can effectively avoid the problem that some Goroutines occupy resources for a long time, causing other Goroutines to be unable to execute.

3. Sample code analysis
In order to better understand the preemptive scheduling principle of Goroutines, we can analyze it through the following sample code.

package main

import (
    "fmt"
    "time"
)

func main() {
    go longRunningTask()
    time.Sleep(time.Millisecond)
}

func longRunningTask() {
    for {
        fmt.Println("I am a long running task!")
        time.Sleep(time.Second)
    }
}

In the above code, we created a Goroutine to execute a long-running task (longRunningTask) and added a time slice delay to the main function. Due to the preemptive scheduling mechanism of Goroutines, the task will be preempted by other Goroutines even if we do not explicitly call yield or similar functions.

In this example, the longRunningTask function will print "I am a long running task!" and sleep for one second, then print again, and execute in a loop. When the time slice delay in the main function ends, the main function will exit and the program ends. During this process, the longRunningTask task will be preempted by other Goroutines, thus ensuring the smooth execution of other tasks.

4. Summary
Through the introduction of this article, we understand the preemptive scheduling principle and implementation method of Goroutines in Golang. Goroutines' preemptive scheduling is one of the core mechanisms of Golang's concurrent programming. It can make full use of computing resources and improve program execution efficiency. By rationally using Goroutines and preemptive scheduling, we can give full play to the advantages of Golang concurrent programming and achieve more efficient concurrent programs.

I hope this article will help you understand the preemptive scheduling of Goroutines in Golang. In actual development, proper use of Goroutines, channels and preemptive scheduling mechanisms can improve the performance and concurrent processing capabilities of applications.

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