Linux Kernel

RETIS @ Linux Kernel Summit 2010

The Real-Time Systems Laboratory (RETIS Lab) of Scuola Superiore Sant'Anna was present at the Linux Kernel Summit held in Cambridge (MA, USA). This is an event dedicated to kernel developers with a restricted access, where Dario Faggioli, PhD student at the RETIS Lab, has been invited for discussing the possible integration into the kernel of its SCHED_DEADLINE patch. This adds deadline-based scheduling and resource reservations to the Linux kernel by means of a new scheduling class. This work has been done in collaboration with Evidence S.r.l., spin-off company of the RETIS Lab, as part of the research activities carried out in the context of the ACTORS European Project.

Dario had the opportunity to discuss the advantages of having such a scheduling policy inside the Linux kernel for time sensitive, real-time and multimedia applications, directly in front of core kernel developers. Linus Torvalds showed some skepticism about the real usefulness of the patch, however, thanks to the support given to Dario by key people such as Thomas Gleixner and Peter Zijlstra, in the end Linus admitted that, if people responsible for the scheduler are happy with it, he will eventually accept it. If you are interested, read some details of the discussion on the article published by Jonathan Corbet on
Also, the RETIS was present at the Linux Plumbers Conference held in the same place in the subsequent days: Tommaso Cucinotta participated into the main conference with a talk about the key features of reservation based real-time schedulers, where he also highlighted the hierarchical scheduling features of the IRMOS real-time scheduler, developed in the context of the IRMOS European Project. Also, he participated into the real-time micro conference track chaired by Thomas Gleixner, raising a fruitful discussion about a suitable API for the user-space for such types of schedulers in order to make the features easily available to application developers. The discussion involved various people, including Peter Zijlstra from RedHat, maintainer of the CPU scheduler. Finally, Dhaval Giani, research collaborator at the RETIS, had a talk about performance isolation of Virtual Machines by real-time scheduling, and he had the opportunity to discuss technical details of the approach with core KVM developers.

The IRMOS Real-Time Scheduler @ LWN.NET!

An article about the new IRMOS real-time scheduler for Linux appeared on, a website dedicated to the latest features available for the Linux kernel (both mainline and experimental), mainly targeting the community of Linux kernel developers and experienced users willing to try/test the latest features.
The article includes a general description of the scheduler features, a mini-tutorial on how it can be practically used, a comparison with the SCHED_DEADLINE EDF scheduler, etc. Feel free to comment.

Adaptive Quality of Service Architecture (AQuoSA)

AQuoSA is an open-source project for the provisioning of Adaptive Quality of Service functionality into the Linux kernel, developed at the Real Time Systems Laboratory of Scuola Superiore Sant'Anna. The project features a flexible, portable, lightweight and open architecture for supporting soft real-time applications with facilities related to timing guarantees and QoS, on the top of a general-purpose operating system as Linux. More information is available on the official project website.

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