You've learned about many of the new features of the latest version of the Windows kernel in the Mark Russinovich Inside Windows 7 conversation here on Channel 9. One of Mark’s favorite kernel innovations is the new way the kernel manages the scheduling of threads and the underlying synchronization primitives. Prior to Windows 7 (and Windows Server 2008 R2) the Windows kernel dispatcher employed a single lock, the dispatcher lock, which worked well for a relatively small numbers of processors (like 64). However, now that we find ourselves in the midst of the ManyCore era, well, 64 processors aren’t that many... A new strategy was required to scale Windows to large numbers of processors since a single lock is limited in capability, by design: The masterful David Cutler, one of the world's greatest software engineers, wrote the NT scheduler in a time when the notion of affordable 256-processor machines was more science fiction than probable. 

As we learned in the Mark Russinovich video, Windows 7 can now scale to 256 processors thanks to the great engineering of Arun Kishan, a kernel architect you've met on C9 back in the Vista days. In order to promote further scalability of the NT kernel, Arun completely eliminated the dispatcher lock and replaced it with a much finer grained set of synchronization primitives. Gone are the days of contention for a single spinlock. How did Arun pull this off, exactly, you ask? Who is this genius? Well, tune in. Lots of answers await…

Arun's work directly benefits the overall performance of Windows running on multiple processor hardware and means, simply, Windows can really scale. Thank you, Arun!

Spinlocks are synchronization primitives that cause a processor to busy-wait until the state of the lock’s memory location changes.

 
As the name implies, the dispatcher lock is the fundamental lock associated with the kernel dispatcher, or the scheduler.