How you change it

In the SunOS 4.x kernel, the only thing you really can change is the nice value associated with a process. The algorithm is hardcoded; it would be necessary to replace the subsystem with new functions in order to change the way the scheduler works.

In Solaris 2, it's obviously possible to manipulate the scheduling dispatch tables. A utility, dispadmin , can be used to dump out the tables and replace them.

The nice value still exists and is used essentially the same way ” to artificially adjust the selection of the dispatch queue by some constant number. Another utility, priocntl , can manipulate the scheduling parameters and the basic class for a particular process or an individual thread within a process.

In general, the scheduling algorithm in the SunOS 4.x kernel is fixed and unchanging, but fairly robust. Panics or traps occurring in this area are normally due to hardware problems. They get escalated and fixed promptly if they are software related . However, there haven't been any major software changes in this area for quite a while.

The Solaris 2 mechanism is simple, but the table setup could have unexpected repercussions if the numbers are just slightly wrong. The errors, though, should show up as performance issues rather than system crashes.