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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Tickless kernel</span></span>
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<p>A <b>tickless kernel</b> is an <a href="Kernel_(operating_system)" title="Kernel (operating system)">operating system kernel</a> in which timer <a href="Interrupt" title="Interrupt">interrupts</a> do not occur at regular intervals, but are only delivered as required.<sup id="cite_ref-ars-technica-win8_1-0" class="reference"><a href="#cite_note-ars-technica-win8-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>
</p><p>The <a href="Linux_kernel" title="Linux kernel">Linux kernel</a> on <a href="ESA/390" class="mw-redirect" title="ESA/390">s390</a> from 2.6.6<sup id="cite_ref-lwn-Torvalds_2-0" class="reference"><a href="#cite_note-lwn-Torvalds-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> and on i386 from release 2.6.21<sup id="cite_ref-lwn-corbet_3-0" class="reference"><a href="#cite_note-lwn-corbet-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> can be configured to turn the timer tick off (<i>tickless</i> or <i>dynamic tick</i>) 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>.<sup id="cite_ref-full-tickless_4-0" class="reference"><a href="#cite_note-full-tickless-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The <a href="XNU" title="XNU">XNU</a> kernel from <a href="Mac_OS_X_10.4" class="mw-redirect" title="Mac OS X 10.4">Mac OS X 10.4</a> on, and the <a href="NT_kernel" class="mw-redirect" title="NT kernel">NT kernel</a> from <a href="Windows_8" title="Windows 8">Windows 8</a> on, are also tickless.<sup id="cite_ref-ars-technica-win8_1-1" class="reference"><a href="#cite_note-ars-technica-win8-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The <a href="Solaris_(operating_system)" class="mw-redirect" title="Solaris (operating system)">Solaris</a> 8 kernel introduced the cyclic subsystem which allows arbitrary resolution timers and tickless operation.<sup id="cite_ref-solaris-tickless_5-0" class="reference"><a href="#cite_note-solaris-tickless-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> <a href="FreeBSD" title="FreeBSD">FreeBSD</a> 9 introduced a "dynamic tick mode" (aka tickless).<sup id="cite_ref-freebsd-dynamic-tick_6-0" class="reference"><a href="#cite_note-freebsd-dynamic-tick-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>
</p><p>As of 2020, there is a plan to add this to <a href="MINIX_3" class="mw-redirect" title="MINIX 3">MINIX 3</a><sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> in the medium term.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>
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<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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</style><cite id="CITEREFBright2012" class="citation web cs1">Bright, Peter (October 28, 2012). <a rel="nofollow" class="external text" href="https://arstechnica.com/information-technology/2012/10/better-on-the-inside-under-the-hood-of-windows-8/2/">"Better on the inside: under the hood of Windows 8"</a>. Ars Technica. section "Tick tock".</cite></span>
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<li id="cite_note-lwn-corbet-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-lwn-corbet_3-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://lwn.net/Articles/223185/">"Clockevents and dyntick"</a>. Lwn.net. 2007-02-21<span class="reference-accessdate">. Retrieved <span class="nowrap">2015-04-09</span></span>.</cite></span>
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<li id="cite_note-full-tickless-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-full-tickless_4-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://lwn.net/Articles/549580/">"(Nearly) full tickless operation in 3.10"</a>. Lwn.net<span class="reference-accessdate">. Retrieved <span class="nowrap">2015-04-09</span></span>.</cite></span>
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<li id="cite_note-solaris-tickless-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-solaris-tickless_5-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://news.ycombinator.com/item?id=13091162">"Bryan Cantrill (former Solaris kernel engineer) comment"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2017-01-07</span></span>.</cite>.</span>
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<li id="cite_note-freebsd-dynamic-tick-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-freebsd-dynamic-tick_6-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.ivoras.net/freebsd/freebsd9.html">"What's cooking for FreeBSD 9?"</a>.</cite></span>
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<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://wiki.minix3.org/doku.php?id=tickless">"Tickless Kernel"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2020</span>.</cite></span>
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<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://wiki.minix3.org/doku.php?id=roadmap">"The MINIX 3 Road Map"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2020</span>.</cite></span>
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