CPUs, SMP and Parallelisation
| CPUs, SMP and Parallelisation | ||||||||||
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Informix Online/DSA/IDS runs on single processor systems or Symmetric Multi-Processing (SMP) systems. SMP systems have multiple processors but share a common bus, disk and memory systems. There is one version of the operating system controlling the entire system The various manufacturers try to ensure that as the number of processors are increased the system performance will scale accordingly. This is not a trivial exercise, keeping track of thousands of processes running and switching between multiple physical processors. The scaleability can be seen as a measure of how many processors can be added before there is no performance increase delivered. With SMP systems the OS is capable of executing multiple jobs at the same time as opposed to just providing the illusion as it does on single processor machines. Without parallelisation of the task though the task would take the same time on a single processor machine as it would on a multiple processor system, the other processors would just remain idle. But if the task can be broken down into sub-tasks that be run in parallel then multiple processors can be used to speed the process. Often the basic algorithms used to produce the desired result do not lend themselves to effective parallelisation and need a fundamental re-design. This is what happened with the introduction the DSA architecture, it was re-write of a substantial part of the Online product. The following operations are now parallelized and can potentially run faster in a multiprocessor system.
Parallelising decision support queries (PDQ) are discussed later. |
