Section: New Results

Developing infrastructure software using Domain Specific Languages

In terms of DSL design for domains where correctness is critical, our current focus is first on process scheduling for multicore architecture, and second on selfishness in distributed systems. Ten years ago, we developed Bossa, targeting process scheduling on unicore processors, and primarily focusing on the correctness of a scheduling policy with respect to the requirements of the target kernel. At that time, the main use cases were soft real-time applications, such as video playback. Bossa was and still continues to be used in teaching, because the associated verifications allow a student to develop a kernel-level process scheduling policy without the risk of a kernel crash. Today, however, there is again a need for the development of new scheduling policies, now targeting multicore architectures. As identified by Lozi et al.  [61], large-scale server applications, having specific resource access properties, can exhibit pathological properties when run with the Linux kernel's various load balancing heuristics. We are working on a new domain-specific language, Ipanema, to enable verification of critical scheduling properties such as liveness and work-conservation; for the latter, we are exploring the use of the Leon theorem prover from EPFL [17]. A first version of the language has been designed and we expect to release a prototype of Ipanema working next year. The work around Ipanema is the subject of a very active collaboration between researchers at four institutions (Inria, University of Nice, University of Grenoble, and EPFL (groups of V. Kuncak and W. Zwaenepoel)). Baptiste Lepers (EPFL) is supported in 2017 as a postdoc as part of the Inria-EPFL joint laboratory.

Selfishness is one of the key problems that confronts developers of cooperative distributed systems (e.g., file-sharing networks, voluntary computing). It has the potential to severely degrade system performance and to lead to instability and failures. Current techniques for understanding the impact of selfish behaviours and designing effective countermeasures remain manual and time-consuming, requiring multi-domain expertise. To overcome these difficulties, we have proposed SEINE, a simulation framework for rapid modelling and evaluation of selfish behaviours in a cooperative system. SEINE relies on a domain-specific language (SEINE-L) for specifying selfishness scenarios, and provides semi-automatic support for their implementation and study in a state-of-the-art simulator. We show in a paper published at DSN 2017 [14] that (1) SEINE-L is expressive enough to specify fifteen selfishness scenarios taken from the literature, (2) SEINE is accurate in predicting the impact of selfishness compared to real experiments, and (3) SEINE substantially reduces the development effort compared to traditional manual approaches.