what is a tickless OS?

operating-system

Solution

A 'tick' in OS terms is an interval after which the OS will wake up to process any pending events.

So, if you have a 100Hz tick, then 100 times a second, the OS will wake up, check to see whether any timers have expired, execute their actions if there are, then go to sleep again. On a tick-less system, rather than waking up 100 times a second to see if anything is ready to process, the OS will look at when the next timer is due to expire and then sleep until that time.

Note that when the CPU is active, it's obviously not going to go into any kind of sleep mode, and the kernel will set up an interrupt for scheduling purposes. It's only tickless (as the comment points out) when there's nothing running on the CPU or (in very modern Linux kernels) when only one process is running.

Linux can run with or without ticks, with a compile-time switch. I don't know about any other systems.

Problem

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