Abstract
Resource Reservation (RR) techniques, such as those realized by the Constant Bandwidth Server (CBS), have proved their eectiveness in providing Quality of Services (QoS) guarantees, especially in systems made up of time and non real-time tasks, mainly due to the temporal isolation property (or Bandwidth Isolation Property, BIP), that is the ensuring the temporal misbehaviour of an application does not aect any other one. However nding any way of handling resource sharing in these systems without breaking the BIP has been an open problem for long time, as long as the idea of solving it using mechanisms similar to the ones that control resource accesses and avoid priority inversions -one above all Priority Inheritance-arose, and a smart and powerful extension of Priority Inheritance, suited for reser-vation based systems, was proposed and named BandWidth Inheritance (BWI). So, now, with the BandWidth Inheritance protocol tasks of a dynamic reservation based system can interact between each other by means of shared resources in a controlled manner.
We already have the AQuoSA framework, a functional, e cient and stable im-plementation of the RR framework (that is the CBS or some other algorithms) on top of the Linux kernel by a very lightweight modi cation of its core structures and the addition of some external kernel loadable modules (non intrusive approach) but it does not include the BWI protocol yet and so it suers from non optimal handling of two or more tasks sharing resources and BIP breakout anytime this happens.
The proposed work try to achieve the main objectives of implement and investi-gate the behaviour of the BandWidth Inheritance protocol in such a system (Linux plus AQuoSA).
We'll then proceed in tho phases: rstly a modi cation of the Linux kernel and of the framework implementation is proposed and realized, in order to provide them the BWI protocol so to get the whole system to support resource sharing. After that a deep analysis of the behaviour and the performances of the modi ed system is accomplished, in order to investigate both the bene ts actually produced and the protocol and implementation overhead and provide as much quantitative data as we can for future research steps in this area.
