How Can I Calculate the Number of Load Generators Required for TruClient Scripts

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Question ID: 105130

How Can I Calculate the Number of Load Generators Required for TruClient Scripts?

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Asked on October 3, 2013 6:57 pm
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This describes how to calculate the number of load generators required to run multiple TruClient Vusers in the Controller.

Note: This task is part of a higher-level task. For details, see How to Develop Ajax TruClient Scripts.
TruClient technology provides you with the ability to quickly and easily record complex business processes. However, because TruClient records at the user level and requires a browser for replay;, the more complex an application's client logic is, the more CPU and memory is required to run a Vuser.

Note: The TruClient footprint can be significantly larger than the footprints of other Vuser protocols. This larger footprint will require more CPU and memory capacity than would be required to run a similar business process recorded in another protocol.
Use the following method to determine the required number of load generators:

1. Record a script using Ajax TruClient.

2. Replay a single Vuser in Controller and check the average CPU and the peak memory consumption of the mdrv.exe process by adding a counter for % Processor Time and Private Bytes. For details on working with Windows Resource Monitors, see Add Windows Resources Measurements Dialog Box.
3. Based on your load generator hardware and the CPU and memory consumption of a single Vuser, calculate the number of Vusers per machine.
For example:
Let us assume that each of our load generators has 8 core processors and 8GB of memory.
Let us also assume that a single Vuser consumes 80MB of peak memory and 10% CPU on average for the specific business process.
From a CPU perspective, if we limit the CPU consumption up to 70% utilization, we can have 7 Vusers per core processor (70% /10%). If our load generator has a total of 8 cores processors, 8 * 7 Vusers per processor equals 56 Vusers per load generator.
From a memory perspective, the load generator machine has 8GB memory of which 7GB is available for the Vusers so approximately 87 Vusers per load generator machine (7GB / 80MB).
Therefore, to meet both the CPU and memory capacity limits, we use the lower number of Vusers and we calculate that for this business process, we can run approximately 56 Vusers per load generator.

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Answered on October 3, 2013 6:58 pm