Remote specialization for efficient embedded operating systems

Prior to their deployment on an embedded system, operating systems are commonly tailored to reduce code size and improve runtime performance. Program specialization is a promising match for this process: it is predictable and modules, and it allows the reuse of previously implemented specializations. A specialization engine for embedded systems must overcome three main obstacles: (i) Reusing existing compilers for embedded systems, (ii) supporting specialization on a resource-limited system and (iii) coping with dynamic applications by supporting specialization on demand. In this article, we describe a runtime specialization infrastructure that addresses these problems. Our solution proposes: (i) Specialization in two phases of which the former generates specialized C templates and the latter uses a dedicated compiler to generate efficient native code. (ii) A virtualization mechanism that facilitates specialization of code at a remote location. (iii) An API and supporting OS extensions that allow applications to produce, manage and dispose of specialized code. We evaluate our work through two case studies: (i) The TCP/IP implementation of Linux and (ii) The TUX embedded web server. We report appreciable improvements in code size and performance. We also quantify the overhead of specialization and argue that a specialization server can scale to support a sizable workload.