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QLinux: A QoS enhanced Linux Kernel for Multimedia Computing

Jun 06, 1999, 09:14 (24 Talkback[s])

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From Prashant Shenoy, as posted to C.O.L.A.:

We are pleased to announce the public release of the QLinux kernel. QLinux, based on the Linux 2.2.x kernel, combines some of the latest innovations in operating systems research. It includes the following features:

  • Hierarchical Start Time Fair Queuing (H-SFQ) CPU scheduler
  • Hierarchical Start Time Fair Queuing (H-SFQ) network packet scheduler
  • Lazy receiver processing (LRP) network subsystem
  • Cello disk scheduling algorithm [not stable yet]

The H-SFQ CPU scheduler enables hierarchical scheduling of applications by fairly allocating cpu bandwidth to individual applications and application classes. The H-SFQ packet scheduler provides rate guarantees and fair allocation of bandwidth to packets from individual flows as well as flow aggregates (classes). Lazy receiver processing enables accurate charging of TCP/UDP protocol processing overhead (including interrupt processing) to the appropriate process. The Cello disk scheduler supports multiple application classes such as interactive best-effort, throughput-intensive best effort and soft real-time and fairly allocates disk bandwidth to these classes.

When enabled, these features replace the standard features/schedulers available in Linux. QLinux provides the flexibility of allowing any combination of these features to be compiled as needed.

The current version for QLinux (based on the 2.2.0 kernel) is available for download from

A port to 2.2.9 kernel will be available in the near future. The QLinux developers can be reached at QLinux announcements are available by subscribing to the qlinux-announce mailing list To subscribe, send a mail to with the body "subscribe qlinux-announce"

QLinux is a joint effort between AT&T Labs-Research, Distributed Multimedia Computing Laboratory (Univ. of Texas) and the Laboratory for Advanced System Software (Univ. of Massachusetts). QLinux has been developed by the following people:

Pawan Goyal (Ensim Corporation, formerly with AT&T Research)
Jasleen Kaur Sahni (Univ. of Texas)
Prashant Shenoy (Univ. of Massachusetts)
Raghav Srinivasan (Univ. of Massachusetts)
Harrick Vin (Univ. of Texas).
T. R. Vishwanath (Univ. of Texas)

We look forward to feedback from users of QLinux.

Pawan Goyal, Prashant Shenoy and Harrick Vin

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Inputs and/or resources for the QLinux project were provided by Gisli Hjalmtysson (AT&T Research) and R. Gopal (AT&T Research)

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QLinux is based on the following research publications:

[1] P. Goyal and X. Guo and H.M. Vin, A Hierarchical CPU Scheduler for Multimedia Operating Systems, Proceedings of 2nd Symposium on Operating System Design and Implementation (OSDI'96), Seattle, WA, pages 107-122, October 1996.

[2] P. Goyal and H. M. Vin and H. Cheng, Start-time Fair Queuing: A Scheduling Algorithm for Integrated Services Packet Switching Networks, In IEEE/ACM Transaction on Networking, October 1997. A preliminary version appeared in the Proceedings of ACM SIGCOMM'96, pages 157-168, August 1996.

[3] P. Druschel and G. Banga, Lazy Receiver Processing (LRP): A Network Subsystem Architecture for Server Systems, Proceedings of the 2nd Symposium on Operating System Design and Implementation (OSDI'96), Seattle, WA, Pages 261-275, October 1996

[4] P Shenoy and H M. Vin, Cello: A Disk Scheduling Framework for Next Generation Operating Systems, Proceedings of ACM SIGMETRICS Conference, Madison, WI, 44-55, June 1998.