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Scheduling (computing)
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====Linux 2.6.23 to Linux 6.5==== Con Kolivas' work, most significantly his implementation of [[fair-share scheduling|fair scheduling]] named [[Rotating Staircase Deadline]] (RSDL), inspired Ingo Molnár to develop the [[Completely Fair Scheduler]] (CFS) as a replacement for the earlier [[O(1) scheduler]], crediting Kolivas in his announcement.<ref>{{cite mailing list | last=Molnár | first=Ingo | author-link=Ingo Molnár | title=[patch] Modular Scheduler Core and Completely Fair Scheduler [CFS] | url=https://lwn.net/Articles/230501/ | mailing-list=linux-kernel | date=2007-04-13}}</ref> CFS is the first implementation of a fair queuing [[process scheduler]] widely used in a general-purpose operating system.<ref name="dwrr">{{cite web|url=http://happyli.org/tongli/papers/dwrr.pdf|title=Efficient and Scalable Multiprocessor Fair Scheduling Using Distributed Weighted Round-Robin|author1=Tong Li|author2=Dan Baumberger|author3=Scott Hahn|website=Happyli.org|access-date=2016-12-09}}</ref> The CFS uses a well-studied, classic scheduling algorithm called [[fair queuing]] originally invented for [[packet network]]s. Fair queuing had been previously applied to CPU scheduling under the name [[stride scheduling]]. The fair queuing CFS scheduler has a scheduling complexity of <math>O(\log N)</math>, where {{mvar|N}} is the number of tasks in the [[run queue|runqueue]]. Choosing a task can be done in constant time, but reinserting a task after it has run requires <math>O(\log N)</math> operations, because the [[run queue]] is implemented as a [[red–black tree]]. The [[Brain Fuck Scheduler]], also created by Con Kolivas, is an alternative to the CFS.
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