Notes on Thread Models in Mach

During the Mach In Kernel Servers work we explored two alternate thread models that could be used to support traps to in kernel servers In the migrating threads model we used the client s thread temporarily moves into the server s task for the duration of the call In the thread switching model an actual server thread is dispatched to handle client traps Based on our experience we nd that the migrating threads model is quite complex and di cult to implement in the context of the current design of Mach and the Unix single server The thread switching model would t more naturally and would probably be much simpler and more robust than migrating threads making it a valuable approach to explore in the near future However we believe migrating threads inherently to be faster than thread switching and ultimately to be the best long term direction This research was sponsored by the Hewlett Packard Research Grants Program