A File Server Optimization Using Scatter/Gather IPC on L4 Based Multi-Server Operating System

Operating systems for PCs and workstations adopt finetuned monolithic configuration. On the other hand, microkernel based multi-server operating systems are expected to play important roles especially for real-time and embedded systems, for several reasons. Operating systems for real-time systems are not yet standardized. Requirements to these OS depends on their wide-ranged applications. Therefore, it must be easy to build tailor-made systems. Ease of maintenance and future extension is are additional important aspects. However, in multi-server operating systems, frequent inter-process communications (IPC) are required. Without careful design, performance suffers from excess IPCs. In this paper, communication optimization strategy used for file server as one of multi-server operating system components running on L4 micro-kernel is proposed. Number of IPCs between application and the file server is only 1 round-trip for read system call, 1.5 for write system call. Preliminary performance evaluation conducted on Intel Pentium PC proved that proposed optimization reduces wall-clock time performance by a factor of 2.