DOSS

Dynamic Operating-System Specialisation

(Third Party Funds Single)


Project leader: ,
Project members: , , ,
Start date: 1. May 2022
Acronym: DOSS
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
URL: https://sys.cs.fau.de/research/doss

Abstract:

An operating system is located between two fronts: On the one hand ("above") the machine programs of the applications with their sometimes very different functional and non-functional requirements and on the other hand ("below") the computer hardware, whose features and equipment ideally are to be made available "unfiltered" and "noise-free" for the applications. However, a general purpose system cannot be as efficient in any of its functions as a system designed specifically for a specific purpose, and less demanding applications may require that they are not forced to pay for the resources consumed by the unneeded functions. So it is not uncommon for large systems, once put into operation, to be subject to frequent changes --- precisely in order to achieve a better fit to changing application requirements.

The ideal operating system offers exactly what is required for the respective application --- no more and no less, but also depending on the characteristics of the hardware platform. However, such an ideal is only realistic, if at all, for an uni-programming mode of operation. In the case of multi-programming, the various applications would have to have "sufficiently the same" functional and non-functional requirement characteristics in order not to burden any of the applications with the overhead that the unneeded functions entail. An operating system with these characteristics falls into the category of special purpose operating system, it is tailored to the needs of applications of a certain type.

This is in contrast to the general purpose operating system, where the ultimate hope is that an application will not be burdened with excessive overhead from the unneeded functions. At least one can try to minimise the "background noise" in the operating system if necessary --- ideally in this case with a different "discount" depending on the program type. The operating system would then not only have to be dynamically freed from unnecessary ballast and shrink with less demanding applications, but also be able to grow again with more demanding applications with the necessary and additional functions. Specialisation of an operating system depending on the respective application ultimately means functional reduction and enrichment, for which a suitable system software design is desirable, but often can no longer be implemented, especially with legacy systems.

One circumstance for the specialisation of an operating system relates to measures explicitly initiated "from outside". On the one hand, this affects selected system calls and, on the other hand, tasks such as bootstrapping and the loading of machine programs, operating system kernel modules or programs that are to be executed in sandbox-like virtual machines within the operating system kernel. This form of specialisation also enables the dynamic generation of targeted protective measures as a result of particularly vulnerable operating system operations, such as loading external modules of the operating system kernel. The other determinant of the specialisation of an operating system relates to measures initiated implicitly "from within". This concerns possible reactions of an operating system to changes in its own runtime behavior that are only noticeable during operation, in order to then adapt the strategies of resource management to the respective workload and to seamlessly integrate the corresponding software components into the existing system.

The project focus is the dynamic operating system specialisation triggered by extrinsic and intrinsic events. The focus is on concepts and techniques that (a) are independent of a specific programming paradigm or hardware approach and (b) are based on just in time (JIT) compilation of parts of the operating system (kernel) in order to to be loaded on demand or to be replaced anticipatory to the respective conditions on the "operating system fronts". Existing general-purpose systems such as Linux are the subject of investigation.

Publications: