Comparing kernel-space and user-space communication protocols on Amoeba

Most distributed systems contain protocols for reliable communication, which are implemented either in the microkernel or in user space. In the latter case, the microkernel provides only low-level, unreliable primitives and the higher-level protocols are implemented as a library in user space. This approach is more flexible but potentially less efficient. We study the impact on performance of this choice for RPC and group communication protocols on Amoeba. An important goal in this paper is to look at overall system performance. For this purpose, we use several (communication-intensive) parallel applications written in Orca. We look at two implementations of Orca on Amoeba, one using Amoeba's kernel-space protocols and one using user-space protocols built on top of Amoeba's low-level FLIP protocol. The results show that comparable performance can be obtained with user-space protocols.