Runtime scheduling mechanism in Go language

With the popularity of concurrent programming, more and more programming languages ​​have begun to provide native concurrency support. Among these supports, there is a runtime scheduling mechanism that is widely used - coroutine scheduling. This article will discuss the coroutine scheduling mechanism in Go language.

Go language is a fast, statically typed programming language developed by Google. It has strong concurrency support and can easily create high-performance, reliable programs. Coroutines in the Go language, or Goroutines, are a very lightweight concurrency mechanism that can start thousands of coroutines.

Before discussing the coroutine scheduling mechanism in Go language, let’s first understand the coroutine. In computers, a coroutine is a lightweight thread that can be executed concurrently in the same address space. The coroutine has its own registers and stack. Compared to threads, coroutines switch much faster and take up much less memory. In the Go language, the implementation of coroutines is very lightweight, even more lightweight than the implementation of threads.

Coroutine in Go language is a special function defined by Go syntax. When executing a function, if you add the keyword Go in front of the function, the function can be packaged into a coroutine. Put it in other coroutines to execute at the same time.

In the Go language, each coroutine has a corresponding coroutine state and context. Coroutines are scheduled across multiple operating system threads as needed. When a coroutine encounters some IO operations or long-term calculation operations, the Go runtime will suspend it and then allocate the processor to other coroutines for execution.

The coroutine scheduling mechanism in the Go language is based on the M:N model. M represents the thread of the operating system and N represents the coroutine. In fact, the Go runtime maintains a number of operating system threads (M) that handle the execution of coroutines. Correspondingly, the Go runtime also maintains many coroutines (N), and uses these coroutines to complete tasks that require concurrent execution.

The main task of the Go language scheduler is to assign coroutines to M, and then assign M to one or more available processors. The number of processors is determined by the value of the GOMAXPROCS environment variable. When a processor has a coroutine that needs to be processed, it will be executed. When the coroutine is completed, the processor will continue to remove a coroutine from the queue and execute it. If a coroutine is executed but there are no new tasks available for execution, the coroutine will be put back into the coroutine pool to wait for the next allocation.

In addition, the coroutine scheduler in the Go language also has adaptive features. For example, under low load conditions, the scheduler can assign multiple coroutines to the same operating system thread to save system resources. Under high load conditions, the scheduler can create more operating system threads as needed and assign coroutines to these threads to increase processing speed.

In general, the coroutine scheduling mechanism in the Go language is a very efficient and flexible concurrency mechanism. It can easily create a large number of coroutines and execute them on multiple threads to meet the needs of high-concurrency applications. At the same time, the Go language scheduler can also adaptively adjust resource usage to improve system performance and stability.

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