Linux Device Drivers Development

Dynamic tick/tickless kernel

With the previous HZ options, the kernel is interrupted HZ times per second in order to reschedule tasks, even in an idle state. If HZ is set to 1,000, there will be 1,000 kernel interruptions per second, preventing the CPU from being idle for a long time, thus affecting CPU power consumption.

Now, let's look at a kernel with no fixed or predefined ticks, where the ticks are disabled until some task needs to be performed. We call such a kernel a tickless kernel. In fact, tick activation is scheduled, based on the next action. The right name should be dynamic tick kernel. The kernel is responsible for task scheduling, and maintains a list of runnable tasks (the run queue) in the system. When there is no task to ...