Solaris™ Internals: Core Kernel Components

9.4. Scheduler Activations

We made several references to scheduler activations in the preceding text and highlighted the preemption control feature in the thread priority descriptions. Scheduler activations were added to Solaris 2.6 to address several deficiencies in the two-level threads architecture of Solaris and to provide a facility for short-term preemption control by a process. (This section and any previous references to scheduler activations do not apply to Solaris 2.5.1; they apply only to Solaris 2.6 and Solaris 7).

The two levels in the design refer to user-level threads and the underlying kthread/LWP. We use the term LWP from this point forward when discussing the kernel level, and we use threads to refer to a user thread created ...