Solaris Resource Manager and the Solaris nice Facility

The nice facility in the Solaris environment allows a user to reduce the priority of a process so that normal processes will not be slowed by non-urgent ones. With Solaris Resource Manager, the incentive for users to use this facility is a reduced charge rate for CPU time used at a lower priority.

Solaris Resource Manager implements this effect by allowing the central administrator to bias the sharepri decay rate for processes which have applied nice. The pridecay global Solaris Resource Manager parameter in the srmadm(1MSRM) command is used to set the decay rates for the priorities of processes with normal and maximum nice values. The rates for all intervening nice values are interpolated between them and similarly extrapolated to the minimum nice value. For example, the priority (for example, sharepri) for normal processes may be decayed with a half-life of 2 seconds, while the priority of processes with a maximum nice value may be decayed with a half-life of 60 seconds.

The effect is that processes using nice to reduce their priority get a smaller share of CPU than other processes on the same lnode. Under Solaris Resource Manager nice has little influence on execution rates for processes on different lnodes unless the queue of runnable processes exceeds the number of CPUs.

Solaris Resource Manager treats processes with a maximum nice value (for example, those started with a nice -19 command) specially. Such processes will only be granted CPU ticks if no other process requests them and they would otherwise be idle.

For information on nice, see nice(1) and nice(2SRM). For information on the relationship of Solaris Resource Manager to other resource control features, see Differences Between Solaris Resource Manager and Similar Products.

Dynamic Reconfiguration

The dynamic reconfiguration (DR) feature of Sun Enterprise servers enables users to dynamically add and delete system boards, which contain hardware resources such as processors, memory, and I/O devices. Solaris Resource Manager keeps track of the available processor resources for scheduling purposes and appropriately handles the changes, fairly redistibuting currently available processor resources among eligible users and processes.

Because Solaris Resource Manager controls only the virtual memory sizes of processes, not the physical memory used by processes and users, the effect of a DR operation on memory has no impact on Solaris Resource Manager's memory-limit checking.