gtps4m0c | System Generation |
TPF tightly coupled (TC) processor support is part of the base product. It provides a single TPF system image when running on processors with more than 1 CPU. By installing a processor with more than 1 CPU and by modifying application programs as described in TPF Application Programming, users can achieve greater performance than that available with single CPU processors. TPF tightly coupled support can also be used in combination with the loosely coupled facility of the High Performance Option licensed feature (described below) to achieve even greater levels of performance.
The number of CPUs (also known as instruction streams or I-streams) that the TPF system uses is essentially transparent to the system operator. Existing operator commands operate on the single TPF image.
No new system generation options are required for a TC system. All TPF systems generated are capable of running on processors with 1 or more CPUs. If desired, an operator message can restrict the system to using only a single CPU, but there is no path length benefit in doing this. Generally, the TPF system should be set to allow use of all available CPUs.
TC support provides a load balancing mechanism called the I-stream or tightly coupled scheduler. The I-stream scheduler, when invoked, chooses the CPU on which a message is processed. This scheduler has 2 tuning parameters that you can use to change the way the scheduler behaves. These values may be left at the default setting or may be modified online by operator command. There is no method for setting these values at system generation time. (See Tightly Coupled Scheduler for more information.)