# [−][src]Function std::hint::spin_loop

    pub fn spin_loop()

🔬 This is a nightly-only experimental API. (`renamed_spin_loop` #55002)

Signals the processor that it is entering a busy-wait spin-loop.

Upon receiving spin-loop signal the processor can optimize its behavior by, for example, saving power or switching hyper-threads.

This function is different than `std::thread::yield_now` which directly yields to the system's scheduler, whereas `spin_loop` only signals the processor that it is entering a busy-wait spin-loop without yielding control to the system's scheduler.

Using a busy-wait spin-loop with `spin_loop` is ideally used in situations where a contended lock is held by another thread executed on a different CPU and where the waiting times are relatively small. Because entering busy-wait spin-loop does not trigger the system's scheduler, no overhead for switching threads occurs. However, if the thread holding the contended lock is running on the same CPU, the spin-loop is likely to occupy an entire CPU slice before switching to the thread that holds the lock. If the contending lock is held by a thread on the same CPU or if the waiting times for acquiring the lock are longer, it is often better to use `std::thread::yield_now`.

Note: On platforms that do not support receiving spin-loop hints this function does not do anything at all.

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