As is widely known, JMeter is a poorly optimized tool. This is due in part to the use of Virtual Threads. By comparison, golang (and the k6 tool that runs on it) uses goroutines, while the Kotlin language has coroutines.

Since JMeter is relatively old for a performance testing tool, several elements should be taken into account when creating and running test scenarios. We have divided them into two sections - scenario optimization (designing scenarios) and the JVM (running tests).

JMeter script optimization

Before running the target test, make changes to the script to reduce RAM consumption on the server.

1. Use the latest version of Jmeter.
2. In testing, it is suggested to use Regexp Variable Extractors to extract data from the server response.
3. Assertions are used sensibly  - not everything must be included, only the most important elements of the response.
4. All listeners should be disabled, e.g. View Results Tree or Summary Report - they are too resource intensive.
5. All Debug Samplers should be disabled.
6. The best optimized language in JMeter is Groovy. If possible, it should be used instead of, for example, Beanshell.
7. If the tests include Transaction Controller, the Generate Parent Sample option should be unchecked.
8. When running the tests through CLI or Redline13, the JVM optimization configuration should be entered.

JVM optimization

The next step is already optimizing the JVM itself, which runs under the JMeter "shell". It is not recommended to run tests from the UI due to the considerable RAM consumption - therefore, it is better to run scenarios from the console.

Someone might ask "What if I want to see the results on the fly?". We answer briefly: invest the time to set up tools locally to observe real time results. InfluxDB + Grafana can serve this purpose.

We run tests in the console along the lines of the following command.

java -XX:+UseConcMarkSweepGC -XX:+DisableExplicitGC -Xms512m -Xmx747520m -d64 -jar C:\jmeter\bin\ApacheJMeter.jar -n -t scenario.jmx results.jtl -e -o results

The parameters inside the command are divided into two sections - JMeter parameters and JVMa parameters.

JVMa parameters

-XX:+UseConcMarkSweepGC -XX:+DisableExplicitGC -Xms512m -Xmx747520m -d64

JMeter parameters.

At this stage it is worth noting that we are not running either the .bat or .sh file. Instead, I use the .jar version - because we are running a java program.

-jar C:\jmeter\bin\ApacheJMeter.jar -n -t scenario.jmx -l results.jtl -e -o results

With the tips above, running JMeter tests will be better optimized, and the team will avoid RAM problems. However, if the advice above fails, you may be left with nothing but distributed testing.