How does the setting "Number of Users per Process" work?
The setting Settings | System Settings | Workbench | Control | Number of Users per Process, specifies the number of virtual users to be run per system process.
If you specify 10 virtual users per process, the first 10 virtual users in your load test will all run inside the same perfrun process. Virtual users 11-20 will run in a second process, virtual users 21-30 will run in the next process, etc. Hence, if you have 100 Virtual users running in total, 10 perfrun processes will be launched. You can confirm this by opening Task Manager | Process while the test is running and seeing how many perfrun processes have been opened.
Note: When using Automatic Calculation the processes are assigned differently, the first 10 users get a process each, thereafter new users share existing processes until the max users per process is reached. . Using the above example, 10 perfrun processes will be opened and users 1-10 will each run inside a perfrun process, users 11, 21, 31, etc will run in the same process as users 1, users 12, 22, 32, etc will run in the same process as user 2, users 13, 23, 34, etc will run in the same process as user 3, etc
BACKGROUND: Specifying multiple virtual users per process (threaded mode) will reduce the memory needs per virtual users significantly. If you are running a large number of virtual users, set this value to 10 for Web and CORBA application load tests, or to 50 for database load tests. Disabling automatic calculation and setting vu per process to 1 means that there is never a threading problem as each user gets its own copy of perfrun. If you want to run a stress test with a low number of virtual users on an agent and want to produce a high volume of load with each of the users, set this value to 1 (process mode).