System information

10 Logical Partitions on System i5
Figure 1-6 Basic flow of data from disk to processor
Next we show an example of two shared capped logical partitions sharing a single processing
unit from the shared processors pool. There are two logical partitions, logical partition A and
logical partition B. Logical partition A has two jobs, A1 and A2. Logical partition B has two
jobs, B1 and B2. Logical partition A is assigned 0.8 processing units. Logical partition B is
assigned 0.2 processing units. Figure 1-7 illustrates the processor time usage every 10
millisecond time slot. This example is only used to show concepts.
Figure 1-7 Two logical partitions sharing one processing unit
Jobs A1 and B1 are loaded into the cache memory. Since only one job can run on the given
processor, job A1 loaded first into the processor, as it is a high priority job. Job A1 runs for 7
milliseconds and is complete. Job B1 is dispatched to the processor and runs for 2
milliseconds. Job B1 must stop after 2 milliseconds because logical partition B has only 0.2
processing units assigned to it. Job B1 must wait for the next processor cycle to be
dispatched again into the processor to complete. In the next processor cycle, job B1 is
resumed and running.
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A1 B1
Logical partition A (0.8 processing units) jobs: A1, A2
Logical partition B (0.2 processing units) jobs: B1, B2
A1 B1 B1 A2 B1B1
A1 B1A1A1 B1B1
Logical partition A (0.8 processing units) jobs: A1, A2
Logical partition B (0.2 processing units) jobs: B1, B2
A1 B1A1A1 B1B1 B1B1B1 A2A2 B1B1B1B1B1