Tuning Windows 2008 / 7 for running 5000+ virtual users with Neoload

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After some tweaks we were able to run 5000 users on a single load generator with the Neoload 64-bit agent (v3.2.4) for windows on both Windows 2008 R2 64-bit and Windows 7 64-bit.

From past experience we have observed that 1 simple http/html user in Neoload uses 2-3 MB of memory. To meet our target of 5000 VUs per load generator we build out the load generators to have 12 GB of Ram. 2 GB was allocated for the OS and the other 10 GB was allocated for the Neoload JVM. Next you have to configure Neoload to use the 10 GB of memory.

This setting can be modified by editing the lg.launcher.vm.parameters key in C:\Program Files\NeoLoad 3.x\conf\ agent.properties file.

[LoadGenerator]
lg.home=.
lg.launcher=jre/bin/java
lg.launcher.vm.parameters=-server -Xmx10240m -Xss192k
lg.start.delay=20000

We have also found that having 2 GB of memory per core seems to be a good balance for Neoload to squeeze the most virtual users out of a single load generator. The hardware we used had 6 cores.

With these changes alone we were able to host 3500 virtual users. When we tried to push higher we noticed errors occurring and response times increasing. We confirmed that the system under test was not generating any errors or having performance issues so we moved our attention back to the load generation platform.

In the past we have had to tune tcp settings to increase available ports by editing the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\MaxUserPort key in the registry. Windows 2008 / 7 does not have this key but you can increase max available ports.

Open a command prompt as administrator.

At the prompt paste the following commands:

netsh int ipv4 set dynamicport tcp start=10000 num=50000
netsh int ipv4 set dynamicport udp start=10000 num=50000
netsh int ipv6 set dynamicport tcp start=10000 num=50000
netsh int ipv6 set dynamicport udp start=10000 num=50000

Restart your system to enable these changes.

Source: http://www.symantec.com/business/support/index?page=content&id=HOWTO56225#v55194030

After that we were able to reach the 5000 user mark.

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