This graph serves as a testimony to the efficiency of Oracle's latch acquisition algorithm, because even as the load increases pushing CPU utilization toward 100%, latch acquisition time does not significantly increase. If you look closely, only at 97% utilization does the average acquisition time begin to increase. Even more amazing is that, based on queuing theory, with four cores running at 80% utilization, around 50% of the response time is composed of queue time. Yet based on this test with Oracle's algorithm, queue time doesn't hit 50% of response time till 100% CPU utilization. So Oracle beat queuing theory!

Oracle's hidden instance parameter _spin_count eventually comes up when talking about latches. Because it's common for latching articles to recommend increasing _spin_count, this parameter deserves special attention.

Understanding both the algorithms and observing actual real-system results, as in Figure 3-9, I hope you understand that increasing _spin_count diminishes the likelihood of a latch-requesting process to sleep. In fact, if you want to effectively remove Oracle's sleep capability, keep increasing the _spin_count value until sleep requests are effectively zero.