How to schedule in golang

Golang is an efficient and reliable programming language that is widely used in concurrent programming and network programming because of its excellent performance and lightweight threading model. In Golang, the scheduler is one of the cores of its concurrency model and plays an important role. This article mainly introduces how Golang's scheduler is implemented and how to schedule it.

1. How to implement Golang’s scheduler?

Golang’s scheduler adopts the M:N thread model (M represents the number of kernel threads, N represents the number of goroutines). The main function of the scheduler is to schedule a large number of goroutines on a small number of OS threads and ensure collaboration and data synchronization between them. The implementation of this model requires two core components: scheduler and goroutine.

1. Scheduler

The scheduler in Golang is a piece of code running in an independent OS thread. It is mainly responsible for the allocation of CPU time and the scheduling of goroutine. The main function of the scheduler is to schedule goroutines to run on OS threads, control the execution order and time slice allocation of goroutines, and manage resources such as memory. The scheduler is the core of the Golang concurrency model, and its implementation involves the following three aspects:

(1) Scheduling strategy: Golang’s scheduling strategy is based on preemptive scheduling. When an IO operation occurs in a running goroutine Or when calling blocking operations such as time.Sleep, the current OS thread will stop running the goroutine and create a new OS thread to run other goroutines.

(2) Task queue: Golang’s scheduler uses a task queue to store all goroutines waiting to be executed. When an idle OS thread appears, the scheduler takes the next task from the task queue and places it Assigned to OS thread for execution.

(3) Thread management: Golang uses the M:N thread model to manage OS threads and goroutines. M represents the fixed number of threads maintained internally by the system, and N represents the total number of goroutines created by the user. The number of M is automatically managed by the system, while N is created by the developer as needed.

2.goroutine

Golang's goroutine is a lightweight thread, which can be considered a more efficient way to implement threads. Goroutines are created and destroyed faster than threads and consume less memory. Goroutine implementation and scheduling are completely controlled by the scheduler, so developers only need to focus on writing goroutines.

In addition, Golang's goroutine has also made many optimizations in terms of optimized scheduling, memory sharing and deadlock detection.

2. How does Golang’s scheduler perform scheduling?

Golang's scheduler is based on preemptive scheduling, which means that when a goroutine is executing, if it blocks, the scheduler will immediately stop the goroutine and switch it to other goroutines waiting to be executed. . When a new OS thread becomes available, the scheduler will reassign the tasks to the new OS thread, thereby enabling fast switching between multiple tasks.

In order to better understand how Golang's scheduler schedules, the following will introduce some of Golang's key mechanisms:

1.Goroutine scheduling

Golang's goroutine is interruptible. The scheduler will insert special checkpoints in the goroutine and check whether there are new goroutines that need to be run at the checkpoint. When the scheduler detects that a goroutine is interrupted, it stops the goroutine and switches to other goroutines waiting to be executed until the goroutine is available again.

2. Task Scheduling

Golang’s scheduler uses task queues to store all goroutines waiting to be executed. When a new OS thread appears, the scheduler will take the next task from the task queue and assign it to the OS thread for execution. The role of the task queue is to ensure that tasks are executed in order without any conflicts.

3. Blocking Scheduling

When a goroutine blocks, it will be suspended by the scheduler and queued to wait for complete execution. The scheduler will set the goroutine's status to "blocked" and put it in the blocking queue. When the goroutine becomes available again, the scheduler reassigns it to a new OS thread for execution.

4. Preemptive scheduling

Golang’s scheduler is based on preemptive scheduling, which means that when a running goroutine occurs an IO operation or calls time.Sleep and other blocking operations, The scheduler will immediately stop the goroutine and switch to other goroutines waiting to be executed. This approach ensures that all tasks can be executed in the shortest possible time and reduces possible context switches.

Summary

This article introduces how Golang's scheduler is implemented and scheduled, including the two core components of the scheduler and goroutine, as well as the important mechanisms of the scheduler, such as task queues , preemptive scheduling, etc. These mechanisms ensure that Golang's concurrency model has excellent performance and reliability and is suitable for various high-concurrency scenarios. As a popular language, Golang's scheduler is closely related to its excellent performance and reliability, and is also a very important issue for developers.

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