A tickless kernel is an operating system kernel in which timer interrupts do not occur at regular intervals, but are only delivered as required.
The Linux kernel on s390 from 2.6.6 and on i386 from release 2.6.21 can be configured to turn the timer tick off (tickless or dynamic tick) for idle CPUs using <code>CONFIG_NO_HZ</code>, and from 3.10 with <code>CONFIG_NO_HZ_IDLE</code> extended for non-idle processors with <code>CONFIG_NO_HZ_FULL</code>. The XNU kernel from Mac OS X 10.4 on, and the NT kernel from Windows 8 on, are also tickless. The Solaris 8 kernel introduced the cyclic subsystem which allows arbitrary resolution timers and tickless operation. FreeBSD 9 introduced a "dynamic tick mode" (aka tickless).
As of 2020, there is a plan to add this to MINIX 3 in the medium term.