2.6. The System Clock
The Solaris kernel relies on hardware timer interrupts for general housekeeping chores that need to be done at regular intervals. For example, the system clock triggers the dispatcher to recalculate process priorities at regular intervals and also initiates callout queue processing.
The kernel (software) sets up the programmable interrupt generator (hardware) to generate a clock interrupt at regular intervals, by default 100 times per second. The clock interrupts at interrupt level 10 (SPARC); nothing else on the system generates interrupts at this level. With each clock interrupt, a handler is entered. It performs the following functions:
Sets available kernel anon space (anon_free) value, for tracking and reporting.