When and Why Do Go Goroutines Yield?

Goroutine Yielding Points: Beyond Syscalls

Goroutines, a fundamental component of Go programming, are scheduled in a lightweight manner, allowing for efficient concurrency. While it is well known that goroutines yield control during blocking syscalls, a deeper understanding of their yielding points is essential for optimizing goroutine scheduling.

Asynchronous Preemption: A Game-Changer

Before Go 1.14, goroutines yielded control only during syscalls or function calls, leading to the misconception that loops without function calls would not yield. However, with the introduction of asynchronous preemption in Go 1.14, the landscape has shifted.

Asynchronous preemption allows goroutines to yield control asynchronously at almost any point, including within code blocks without function calls. This effectively eliminates the potential for deadlock or delayed garbage collection in such loops.

Goroutine Yielding Points in Detail

While the specific yielding points may vary across Go releases, general patterns include:

• Syscalls: Goroutines yield when performing blocking system calls.
• Function calls: Function calls involve internal scheduler checks, providing opportunities for goroutine switching.
• Asynchronous preemption: This机制introduces a wildcard, allowing for goroutine switching almost anywhere, including within loops without function calls.

Other Possible Yielding Points

• Garbage collection: Interactions with the garbage collector (e.g., string manipulation) may introduce locks and scheduling switches.
• Synchronization primitives: Using mutexes or channels can introduce cooperative scheduling points, where goroutines voluntarily yield control.

Implications for Synchronization

Understanding goroutine yielding points is crucial for effective synchronization. By avoiding synchronization around code blocks that are unlikely to yield, developers can optimize program performance and reduce unnecessary contention.

The above is the detailed content of When and Why Do Go Goroutines Yield?. For more information, please follow other related articles on the PHP Chinese website!