A tickless kernel is an

operating system kernel The kernel is a computer program at the core of a computer's operating system and generally has complete control over everything in the system. It is the portion of the operating system code that is always resident in memory and facilitates in ...

in which timer

interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted ...

s do not occur at regular intervals, but are only delivered as required. The

Linux kernel The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU ...

s390 The IBM System/390 is a discontinued mainframe product family implementing the ESA/390, the fifth generation of the System/360 instruction set architecture. The first computers to use the ESA/390 were the Enterprise System/9000 (ES/9000 ...

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 CONFIG_NO_HZ, and from 3.10 with CONFIG_NO_HZ_IDLE extended for non-idle processors with CONFIG_NO_HZ_FULL. The

XNU XNU is the computer operating system (OS) kernel developed at Apple Inc. since December 1996 for use in the Mac OS X (now macOS) operating system and released as free and open-source software as part of the Darwin OS, which in addition to macOS ...

kernel in Mac OS X 10.4 on, and the NT kernel in

Windows 8 Windows 8 is a major release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on August 1, 2012; it was subsequently made available for download via MSDN and TechNet on August 15, 2012, and later to ...

on, are also tickless. The Solaris 8 kernel introduced the cyclic subsystem which allows arbitrary resolution timers and tickless operation..

FreeBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...

9 introduced a "dynamic tick mode" (aka tickless). As of 2020, there is a plan to add this to

MINIX 3 Minix 3 is a small, Unix-like operating system. It is published under a BSD-3-Clause license and is a successor project to the earlier versions, Minix 1 and 2. The project's main goal is for the system to be fault-tolerant by detecting and rep ...

in the medium term.

References

Operating system kernels {{operating-system-stub