4.11.2 Example of Detecting a System Bottleneck

Suppose Client 1 requires 4 seconds to print to the screen. Calls to time(2) determine that the tpcall to service A is the culprit with a 3.7 second delay. Service A is monitored at the top and bottom and takes 0.5 seconds. This implies that a queue may be clogged, which was determined by using the pq command.

On the other hand, suppose service A takes 3.2 seconds. The individual parts of Service A can be bracketed and measured. Perhaps Service A issues a tpcall to Service B, which requires 2.8 seconds. It must then be possible to isolate queue time or message send blocking time. Once the relevant amount of time has been identified, the application can be retuned to handle the traffic.

Using time(2), you can measure the duration of the following:

• The entire client program.
• A client service request only.
• The entire service function.
• The service function making a service request (if any).