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Completely fair queueing

Completely Fair Queuing

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General referenceInterpretive dossier study · Crown Archives visual atlas
Record originEnglish Wikipedia
Text licenseCC BY-SA 4.0
Source revisionJun 10, 2025
Entity authorityQ2990443 ↗
Source-derived summary

Completely Fair Queuing (CFQ) is an I/O scheduler for the Linux kernel which was written in 2003 by Jens Axboe.

Description

CFQ places synchronous requests submitted by processes into a number of per-process queues and then allocates timeslices for each of the queues to access the disk. The length of the time slice and the number of requests a queue is allowed to submit depends on the I/O priority of the given process. Asynchronous requests for all processes are batched together in fewer queues, one per priority. While CFQ does not do explicit anticipatory I/O scheduling, it achieves the same effect of having good aggregate throughput for the system as a whole, by allowing a process queue to idle at the end of synchronous I/O thereby "anticipating" further close I/O from that process. It can be considered a natural extension of granting I/O time slices to a process.

History

Prior to the integration

In February 2003 Andrea Arcangeli put forward his idea for a Stochastic Fair Queueing I/O scheduler to Jens Axboe who then implemented it. Jens Axboe made improvements to his first implementation, calling the new version the Completely Fair Queueing scheduler, and produced a patch to apply it to the 2.5.60 development series kernel.

Kernel 2.6.6 (10 May 2004)

The CFQ I/O scheduler was first integrated into the mainline kernel as an optional I/O scheduler. It was possible to change the scheduler at boot time with the 'elevator' parameter to kernel.

Editorial summary

Begin with the source’s own compact description: “Completely fair queueing” is completely Fair Queuing. The dossier treats that line as a proposition to test through Completely, fair and queueing, not as a finished interpretation.

Editorial reviewA dependable orientation record for establishing vocabulary, names and a first evidence trail. The current lead gives the account dated anchors—2003, 2004—that can be checked directly. The selected authority fields contribute no independent date. For this dossier, Completely, fair and queueing is the immediate research focus.
Editorial analysis

Why this record matters

The phrase “completely Fair Queuing” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.

Evidence profile

Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Jun 10, 2025. The linked authority identifier is Q2990443. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2003 and 2004.

Critical limits

A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.

How to read it

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Source & attribution

This entry incorporates text from “Completely fair queueing” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.