How Can We Achieve Sub-Millisecond Sleep on Windows?

Sleepover: Achieving Sub-Millisecond Sleep on Windows

Expanding on the topic of thread sleep granularity, let's address the specific issue of sleeping for less than a millisecond on the Windows platform.

Problem Statement

While Unix offers a variety of sleep functions (sleep, usleep, nanosleep) that allow for microsecond precision, Windows only provides Sleep() with millisecond granularity. This raises the question: how can we achieve sub-millisecond sleep on Windows?

Busting Misconceptions

It's important to clarify a common misconception regarding sleep function parameters. The time value passed does not guarantee an exact wake-up time. Instead, it specifies the minimum sleep duration. Threads are not awakened directly; rather, the OS scheduler determines when to execute them.

Windows Solution

Unfortunately, there is no direct equivalent to usleep() in the Windows API. However, as the response suggests, there are alternative approaches to achieve sub-millisecond pauses, such as:

• Busy Loop: Continuously check the elapsed time and yield the thread when it exceeds the desired sleep duration. However, this wastes CPU cycles and should be avoided.
• Low-Level Kernel Calls: Use kernel functions like KeDelayExecutionThread() or NtDelayExecution() to achieve higher precision. However, these require elevated privileges and can introduce complexities.
• High-Performance Timers: Utilize high-precision timers, such as multimedia timers or hardware interrupt timers, to measure elapsed time and maintain sub-millisecond accuracy. This approach is more involved but offers better performance.

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