Go language series - synergy GMP introduction - with ByteDance interpolation

Concurrency is not equal to parallelism ( Concurrency is not parallelism) —— Rob Pike

Go Language is especially suitable for writing high concurrency programs , Simple , Efficient , Cannot do without Go Language native support coroutines （go routine）.

Different from traditional multithreading development ,Go Language makes development more convenient through a more lightweight collaborative process , At the same time, it avoids many difficulties that traditional multithreading development needs to face .

Go Concurrent programming of language , Understand two things —— Xiecheng and GMP Model

coroutines

stay Go In language , Coroutines are considered lightweight threads . Between the coroutine and the thread Go Scheduler Association of language . The relationship between coroutine and thread is M:N, Many to many .

Go The language scheduler schedules multiple coroutines to a thread , Or schedule a coroutine to multiple threads for execution .

If multiple coroutines are assigned to different threads , These threads are simultaneously used by different CPU Core processing , Then these coroutines are processed in parallel .

If a single core executes multiple threads , Threads occupy different time slices , obtain CPU Right to use , These processes are concurrent .

Introduction to simple collaborative process

This section will start with a simple program , Let's feel the synergy .

There is a program to check whether some websites can be accessed , Construct a links As url list .

package main

import (
	"fmt"
	"net/http"
)

// Sequential execution 
func main() {
    
	links := []string{
    
		"http://www.baidu.com",
		"http://www.jd.com/‎",
		"https://www.taobao.com/",
		"https://www.163.com/",
		"https://www.sohu.com/",
	}
	for _, link := range links {
    
		checkLink(link)
	}
}

func checkLink(link string) {
    
	_, err := http.Get(link)
	if err != nil {
    
		fmt.Println(link, "might be down!")
		return
	}
	fmt.Println(link, "is up!")
}

The execution result is ：

http://www.baidu.com is up!
http://www.jd.com/‎ is up!
https://www.taobao.com/ is up!
https://www.163.com/ is up!
https://www.sohu.com/ is up!

The current program can run normally , But there are serious performance problems . Network request is a time-consuming operation , Check one by one url, The previous request has been executed , It's the next request .

If several of the websites respond slowly , The overall time consumption is very high . This situation occurs in network access , Disk file access , Very common scenes .

Actually url There is no sequential dependency between , There is no stipulation to check first baidu, Re examination jd. If you can check concurrently , Can reduce the time .

GMP Model introduction

To be continued

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