The Mutex_Sleep function has the same objectives as with latches, but Oracle takes advantage of inherent mutex function calls. Figure 3-15 shows Oracle developers have a number of options to sleep an Oracle process. The desired sleep tactic is established when the mutex is created. In essence, it's part of the mutex creation process. Oracle developers can use mutex-specific sleep options, or they can create their own hybrid routine. But regardless, the general mutex options are to either yield the CPU, sleep, or block other processes from acquiring the mutex. By operating system tracing some Oracle server processes with heavy mutex contention, it appears Oracle is currently using the CPU yield option.

As you can see, Oracle has taken what was designed for high-concurrency thread control and incorporated-or perhaps retrofitted is a better word-mutexes into its serialization control scheme. The result is a stellar serialization scheme that is both flexible and fast. I suspect we'll continue to see Oracle kernel code developers take advantage of mutexes.

It is exceptionally rare to have mutex-related contention. I don't state this lightly, but if I found such contention in a system, I would immediately suspect an Oracle bug and contact Oracle support.