latch的spin

Latch behavior. differs on single and multiple CPU servers. On a single CPU server, a process requesting an in-use latch will release the CPU and sleep before trying the latch again. On multiple CPU servers, a process requesting an in-use latch will “spin” on the CPU a specific number of times before releasing the CPU and trying again. The number of spins the process will use is OS specific.

Latch在单CPU跟多CPU上的表现是不同的。