Some doubts on MUTEX

Hi All, I am trying to understand how to use mutex API's properly,so while going through the documentation, there is section mentioning fast path and slow path for mutexes. For your reference I am pasting this here.(kernel/mutex.c) /* * We split the mutex lock/unlock logic into separate fastpath and * slowpath functions, to reduce the register pressure on the fastpath. * We also put the fastpath first in the kernel image, to make sure the * branch is predicted by the CPU as default-untaken. */ static __used noinline void __sched __mutex_lock_slowpath(atomic_t *lock_count); Can someone help me to understand what is the difference between fastpath lock and slowpath lock? Thanks in advance Subin Gangadharan