"Adaptive Quality of Service Architecture"
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
Timing guarantees are provided through an in-kernel reservation based process scheduler, whose services are exposed to applications through a well-designed API.
A supervisor performs admission control, so that admitting into the system new applications with timing guarantees does not affect the timing guarantees of already admitted applications. Also, it takes care of guaranteeing appropriate security policies in the assignment of timing guarantees to users and user groups, as configured by the system administrator.
A feedback-based QoS control layer may be optionally used by applications who want to keep their timing guarantees by using a CPU allocation that is continuously adapted according to their actual needs. This leaverages the programmer, within certain limits, to hard-code any particular reservation amount within the application, because the best allocation is found out automatically at run-time. Also, this enhances the possibilities for the system to host additional QoS controlled applications. The available control algorithms are well founded on formal scheduling models and control theoretical results.