Tickless kernel
{{Short description|Type of operating system kernel}}
A tickless kernel is an operating system kernel in which timer interrupts do not occur at regular intervals, but are only delivered as required.{{cite web|url=https://arstechnica.com/information-technology/2012/10/better-on-the-inside-under-the-hood-of-windows-8/2/|title=Better on the inside: under the hood of Windows 8|at=section "Tick tock"|first1= Peter|last1=Bright|publisher=Ars Technica|date=October 28, 2012}}
The Linux kernel on s390 from 2.6.6{{cite web|url=https://lwn.net/Articles/82378/ |title=Linux 2.6.6-rc3 |publisher=Lwn.net |date= |accessdate=2015-04-09}} and on i386 from release 2.6.21{{cite web|author= |url=https://lwn.net/Articles/223185/ |title=Clockevents and dyntick |publisher=Lwn.net |date=2007-02-21 |accessdate=2015-04-09}} 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.{{cite web|url=https://lwn.net/Articles/549580/ |title=(Nearly) full tickless operation in 3.10 |publisher=Lwn.net |date= |accessdate=2015-04-09}} 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.{{cite web|url=https://news.ycombinator.com/item?id=13091162 |title=Bryan Cantrill (former Solaris kernel engineer) comment |accessdate=2017-01-07}}. FreeBSD 9 introduced a "dynamic tick mode" (aka tickless).{{cite web|url=http://www.ivoras.net/freebsd/freebsd9.html|title=What's cooking for FreeBSD 9?}}
As of 2020, there is a plan to add this to MINIX 3{{cite web |title=Tickless Kernel |url=https://wiki.minix3.org/doku.php?id=tickless |accessdate=25 February 2020}} in the medium term.{{cite web |title=The MINIX 3 Road Map |url=https://wiki.minix3.org/doku.php?id=roadmap |accessdate=25 February 2020}}