Tuning CPU-bound systems

If it has been determined that the system is CPU bound, there are a number of things that can be done:

• If possible, consider rescheduling the existing job load on your system. If many large jobs are being run at once, rescheduling them to run at different times may improve performance. You should also check the system's crontab(C) files to see if any jobs running at peak times can be scheduled to run at other times.

• If possible, tune the applications so that they use require less CPU power. Consider replacing non-critical applications with ones that require a less powerful system.

• If you have evidence that the system is I/O bound serving interrupts from non-intelligent serial cards, replacing these with intelligent serial cards will offload some of the I/O burden from the CPUs. See ``Serial device resources'' for more details.

• Check if the hard disk controllers in the system are capable of using DMA to transfer data to and from memory. If the CPU has to perform programmed I/O on behalf of the controller, this can limit its performance.

• It is possible that because of a lack of free memory the system is swapping, which could result in a considerable portion of the CPU resources being used to transfer processes back and forth between the disk and memory. To determine if this is the case see the section ``Tuning memory resources''.

• Upgrade to a faster CPU or CPUs.

• Upgrade to a multiprocessor system from a single processor system. This will help if there are runnable jobs on the run queue or the applications being run are multithreaded.

• Add one or more CPUs to a multiprocessor system.

• Purchase an additional system and divide your processing requirements between it and your current system.