How to set up golang scheduling

Golang is a modern programming language popular for its powerful concurrency performance. In Golang, the scheduler is a key part of implementing concurrent processing. The scheduler determines how Goroutines (coroutines) in the program allocate execution time on the CPU to achieve concurrent operations.

The default settings of the scheduler can meet the needs in most cases, but in some special cases, you may need to manually adjust the scheduler settings to obtain better performance.

This article will introduce the default settings and manual adjustment methods of the Golang scheduler.

1. The default setting of the Golang scheduler

The default setting of the Golang scheduler is an M:N scheduler based on preemptive scheduling (M represents the operating system thread, N Represents a user-level thread). This means that Golang's scheduler allocates Goroutines to multiple operating system threads to achieve concurrent computation. When a Goroutine is blocked, the scheduler will transfer it to another thread to continue execution.

In Golang, we can control the maximum number of CPU cores used by the scheduler through the GOMAXPROCS environment variable. By default, the value of GOMAXPROCS is equal to the number of CPU cores of the local computer.

2. Manual settings of Golang scheduler

If we need to control the behavior of the Golang scheduler, or need to optimize the scheduler in a specific scenario, then we can Set some parameters manually.

2.1. GOMAXPROCS

By default, the Golang scheduler creates an operating system thread for each available CPU core to maximize program performance. However, in some cases, this setup may lead to a waste of resources, so we can use GOMAXPROCS to limit the number of CPU cores used by the scheduler.

For example, if our program needs to share computer resources with other applications, then we can set GOMAXPROCS to a smaller value to avoid excessive use of CPU resources.

2.2. runtime.GOMAXPROCS()

In addition to controlling the number of cores of the scheduler through the environment variable GOMAXPROCS, we can also use the Golang standard library The runtime package sets the number of cores of the scheduler in the code by calling the runtime.GOMAXPROCS() function.

For example, the following code sets GOMAXPROCS to 2:

import (
    "fmt"
    "runtime"
)

func main() {
    runtime.GOMAXPROCS(2)
    // Do something here
}

2.3. runtime.LockOSThread() and runtime.UnlockOSThread( )

In Golang, each Goroutine will be assigned to a system thread for execution. However, in some concurrent computing scenarios, we may need to bind certain Goroutines to specific threads to avoid the overhead of context switching.

In this case, we can use the runtime.LockOSThread() function to bind the current Goroutine to the current system thread for execution, thereby ensuring that it will not be switched by any thread. After executing the task, we can use runtime.UnlockOSThread() to release the thread.

For example, the following code shows how to bind Goroutine to a specific thread for execution:

func doSomething() {
    runtime.LockOSThread()
    defer runtime.UnlockOSThread()

    // Do the work here
}

2.4. runtime.Gosched()

In Golang, the runtime.Gosched() function can be used to give up the current Goroutine and let the scheduler reallocate threads. This function is very useful to avoid blocking certain long-running tasks, as it gives other Goroutines a chance to run.

For example, the following code shows how to use runtime.Gosched() to yield the current Goroutine:

func doSomething() {
    // Do some work here

    runtime.Gosched()

    // Do more work here
}

Summary

In Golang, scheduling The controller is a key part of achieving concurrency. Generally speaking, the scheduler's default settings meet the needs of most situations. However, in some special cases, we may need to manually adjust the scheduler's behavior to obtain better performance. This article introduces the default settings and manual adjustment methods of the Golang scheduler, hoping to be helpful to Golang developers.

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