Samenvatting

Like most UNIX-like operating systems, FreeBSD has a kernel subsystem called the TTY layer. This subsystem is responsible for serving as a front-end for devices that provide serial line communication. Because this layer also integrates seamlessly with the UNIX process model, TTY’s are often used to provide interactive user login sessions. Even though the FreeBSD project was only founded in the 1990s, its TTY layer is at least 25 years old and has become unmaintained. This means it misses a lot of modern features that are alreadypresentinothersubsystemsthroughoutthekernel, suchasscalabilityonmultiprocessor (SMP) systems, low latency and hotplugging. During this project a successful attempt has been made to rewrite the TTY layer that is part of the latest FreeBSD development code. The new implementation provides modern features. Because this TTY layer supports fine-grained locking, it is expected that its performance will now scale better on multiprocessor systems. The buffers that contain the data transmit and receive queues have also been changed to perform less copying of data. This means data throughput is also expected to be improved. An important aspect of this assignment was to establish a good relationship with the FreeBSD project. Because the new implementation would be granted to the project, it was very imporant that it also matched the wishes of the FreeBSD project. During the internship a visit has been brought to the yearly BSDCan conference in Ottawa, Canada. During this conference Ed has given a presentation on the status of the new TTY layer, which was well received among the FreeBSD developers. If further development goes according to plan, the new TTY layer will be part of the next major FreeBSD release, version 8.0.