Out of Time

In this chapter, we looked at the kernel's concept of time and how both wall time and uptime are managed. We contrasted relative time with absolute time and absolute events with periodic events. We then covered time concepts such as the timer interrupt, timer ticks, HZ, and jiffies.

We looked at the implementation of timers and how you can use them in your own kernel code. We finished the chapter with an overview of other methods developers can use to pass time.

Much of the kernel code that you write will require some understanding of time and its passing. With high probabilityespecially if you hack on driversyou will need to deal with kernel timers. Reading this chapter is good for more than just passing the time.