Solaris system resource manager. The system administrator can allocate CPU resources according to predefined shares as opposed to fixed percentages, which allows the system to dynamically apportion all available resources according to the relative proportion ?f shares ?f any current user. The SRM pro rates resource shares to users and groups and then adjusts CPU usage to meet the shares.
Dr. Gunther presents two significant differences between the TS and SRM schedulers. The first is that the SRM guarantees a minimum percentage ?f CPU, rather than a fixed percentage. The other difference is that when the allocations are changed dynamically, the SRM changes are not always immediately reflected the in percentages ?f CPU time the users receive. Dr. Gunther’s first example explains that if a user is awarded 10 ?f 100 shares, that user receives a minimum ?f 10% ?f the CPU resources when the machine is busy. If the machine is only 50% active, the same user will receive double or 20% ?f the CPU resources. This CPU usage is determined by an instantaneous and periodic sampling ?f the usage to adjust the resource usage.
Since the user has to be sampled and adjusted, this causes a time lag between the allocation and the realization ?f resources. In his second example, Gunther shows that if two users equally share the system resources, when one is not logged on, the SRM will adjust and allow the single user to use 100% ?f the resources. When the second user logs on, the resources are split in half. For all ?f the examples in this paper, the processes are assumed to be CPU-bound to present a least upper bound model ?f resource usage.
The goal ?f the SRM is to dynamically adjust each user’s CPU usage to reflect the ratio ?f shares to which the user is entitled. Dr. Gunther uses a modeling tool called PDQ to demonstrate several capacity planning scenarios. The first scenario presents two small share users in one group. The data compares TS and SRM response times as well as comparisons ?f SRM response times between scenarios.