What is meant by fastpath and slowpath function in linux kernel?

["Manjunath Naik" <peter.desouzain@xxxxxxxxx>]

Hi All,

 

What is the major difference between and mutex and semaphore. till this time I though mutext is binary semaphore. While going through the linux code thier is seperate generic mutext subsystem in avaliable in linux kernel.

 

while going through the kernel/mutext.h and kernel/mutex.c their are two specific keyword "fastpath" and "slowpath" functions. What is meant by it.

 

per ex: following comments I coppied from kernel/mutext.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 void fastcall noinline __sched
__mutex_lock_slowpath(atomic_t *lock_count __IP_DECL__);
 

 

 

Thanks

Manjunath