:Julian, Dan, remember that reducing the overhead of task switching :(thread switching) is of vital importance. In that light, the least :context that has to be save/restored when a KSE blocks, the better. : :-- :Daniel C. Sobral (8-DCS) :dc...@newsguy.com :dc...@freebsd.org

I am getting confused by this whole KSE thing. All the threading I've ever implemented has been done simply by splitting out the context information from the Process into a Task, and then allowing N Tasks to reference the same Process. There was no real distinction made between kernel and user mode tasks or processes.

In such a scheme the switch code need only contain a single conditional: One to check if the governing process for a task has a user-level mmu directory that must be setup. That's it, done.

I don't think separate scheduling queues are required either. I can see absolutely no gain in performance by doing that and it unnecessarily complicates the code. We can trivially use the existing priority scheme to schedule interrupt tasks (threads).