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System Administration Guide: Resource Management and Network Services

FSS and Processor Sets Examples

Assume that a server with eight CPUs is running several CPU-bound applications in projects A, B, and C. Project A is allocated one share, project B is allocated two shares, and project C is allocated three shares.

Project A is running only on processor set 1. Project B is running on processor sets 1 and 2. Project C is running on processor sets 1, 2, and 3. Assume that each project has enough processes to utilize all available CPU power. Thus, there is always competition for CPU resources on each processor set.

Diagram shows total system-wide project CPU allocations on a server with eight CPUs that is running several CPU-bound applications in three projects.

The total system-wide project CPU allocations on such a system are as follows:

Project A 

4% = (1/6 X 2/8)pset1

Project B 

28% = (2/6 X 2/8)pset1+ (2/5 * 4/8)pset2

Project C 

67% = (3/6 X 2/8)pset1+ (3/5 X 4/8)pset2+ (3/3 X 2/8)pset3

These percentages do not match the corresponding amounts of CPU shares that are given to projects. However, within each processor set, the per-project CPU allocation ratios are proportional to their respective shares.

On the same system without processor sets, the distribution of CPU resources would be different:

Project A 

16.66% = (1/6) 

Project B 

33.33% = (2/6) 

Project C 

50% = (3/6)