As the incoming work pushes your computing world beyond its limits, this is the throughput graph that you’ll most likely see. Learn to recognize it as a cry for help.
On an idle system, when work shows up, it gets processed right away and exits. ResponseTime = ServiceTime. So early on, as the workload starts to build for the day, the arrival rate of work equals the throughput. This happy circumstance continues until some part of the transaction path can no longer keep up with the arriving work. Now the following things start happening:
- Work has to wait as the computing resource is busy.
- Response Time climbs as it now includes significant Wait time
- The throughput stops matching the arrival rate of new work
At some point the throughput stops going up and can actually go down as algorithms are pushed beyond their design limits and become dysfunctional.
When you see the throughput of the system flatten out like this, somewhere in the transaction path a resource is 100% busy. This is a cry for help. Learn to recognize it.
There is more to learn about this and other subjects in my book:
The Every Computer Performance Book