M:N threading, in which a single kernel thread is multiplexed to run multiple logical user mode threads, has long been a feature of some Unix systems (Solaris and FreeBSD have had it for years). Even Windows NT has had "Fibers" for several releases, though they suffered from the same problems
as other M:N schemes and were incompatible with many Win32 APIs. Join Windows Kernel Architect Dave Probert for a discussion on the new User Mode Scheduling Feature
which solves these problems while allowing applications fine grained control over their threads.
To give you somewhat of an idea of what this is all about:
Dave and team, working very closely with the Parallel Computing Platform People, have created a very compelling new user mode thread scheduling/management system in Windows 7. In a nutshell, the User Mode Scheduler provides a new model for high-performance applications to control the execution of threads by allowing applications to schedule, throttle and control the overhead due to blocking system calls. In other words, applications can switch user threads completely in user mode without going through the kernel level scheduler. This frees up the kernel thread scheduler from having to block unnecessarily, which is a very good thing as we move into the age of Many-Core.
THe best way to make use of this new feature is ConcRT. "ConcRT is built on top of UMS and is the best way to most effectively utilize this new user mode thread scheduling model in Windows 7."
The videos are obviously quite technical, so the faint-hearted might want to do something else.