How Does Go\'s Scheduler Detect the Completion of Non-Blocking I/O Operations?

Scheduler Identification of Non-Blocking I/O in Go

In Go, the scheduler automatically switches between goroutines when one encounters I/O blocking. However, the mechanism behind detecting when a goroutine exits I/O blocking remains unclear.

How the Scheduler Detects Restored Execution

Unlike conventional programming models where threads directly perform I/O operations, Go employs a runtime-managed system. All I/O in Go is handled through syscalls, which the runtime intercepts and executes on behalf of goroutines.

Instead of adhering to the typical call pattern where direct control is ceded to the kernel, the runtime receives notification of syscall intent. This enables critical runtime operations such as non-blocking syscalls, where the kernel is instructed to proceed without blocking until the operation completes.

Consequently, the runtime gains the flexibility to continue concurrent execution. It can track the status of I/O operations, avoiding constant polling or dedicated background threads. When an I/O operation reaches completion, the runtime can reliably identify the associated goroutine and resume its execution.

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