Workload management diagnosis

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Workload management simply means assessing the priority of each of the components of the workload.

When you have exhausted the program performance-improvement and system-tuning possibilities, and performance is still unsatisfactory at times, you have three choices:

  • Let the situation remain as is
  • Upgrade the performance-limiting resource
  • Adopt workload-management techniques

The first approach leads to frustration and decreased productivity for some of your users. If you choose to upgrade a resource, you have to be able to justify the expenditure. Thus the obvious solution is to investigate the possibilities of workload management.

Usually, there are jobs that you can postpone. For example, a report that you need first thing in the morning is equally useful when run at 3 a.m. as at 4 p.m. on the preceding day. The difference is that it uses CPU cycles and other resources that are most likely idle at 3 a.m. You can use the at or crontab command to request a program to run at a specific time or at regular intervals.

Similarly, some programs that have to run during the day can run at reduced priority. They will take longer to complete, but they will be in less competition with really time-critical processes.

Another technique is to move work from one machine to another; for example, if you run a compilation on the machine where the source code resides. This kind of workload balancing requires more planning and monitoring because reducing the load on the network and increasing the CPU load on a server might result in a net loss.

The AIX® Workload Manager (WLM) is part of the operating system kernel. WLM is designed to give the system administrator greater control over how the scheduler and virtual memory manager (VMM) allocate CPU and physical memory resources to processes. Disk usage can also be controlled by WLM. This can prevent different classes of jobs from interfering with each other and to explicitly apply resources based on the requirements of different groups of users. For further information, see Server Consolidation on RS/6000®.