sync:: atomic:: spin_loop_hint
pub fn spin_loop_hint()
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_hint 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_hint 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
Note: On platforms that do not support receiving spin-loop hints this function does not do anything at all.