Recommended Java Heap Size for Commercial JMeter Project

Question

Depending on the nature of the automated workflow and the number of active threads at any given time the Heap size requirement for JMeter can vary and in the testing I am doing there is some ambiguity with respect to the affect of Heap size on the test results. The initial Heap size and the maximum Heap size of the server hosting JMeter is shown in the attached screenshot.

1. Upon executing the test for a large set of current users (eg:100) the in built JMeter report does not render however the results can be seen in the CSV output. Will increasing the Heap size solve this issue and if so to how much should we increase the Heap size?. Note that this issue does not happen for a small user count such as 10 or 15.
2. What is the recommended industrial standard value for Heap size and other system variables for a server used for commercial performance testing using JMeter.

Answer 1

There is no "recommended industrial standard".

Each test is individual and you need to tune JMeter appropriately.

As of JMeter 5.5 default heap size is 1GB which is sufficient for tests development and debugging but might be not sufficient for the load you're trying to conduct.

According to this article:

"If the occupancy of the Java heap is too high, garbage collection occurs frequently. If the occupancy is low, garbage collection is infrequent but lasts longer... Try to keep the memory occupancy of the Java heap between 40% and 70% of the Java heap size... The highest point of occupancy of the Java heap is preferably not above 70% of the maximum heap size, and the average occupancy is between 40% and 70% occupancy. If the occupancy goes over 70%, resize the Java heap."

So I would recommend checking what's going on with your heap using JVisualVM or equivalent and adjusting it up or down as needed.

If your test runs fine and you're experiencing OOM issues only during dashboard generation you can increase it temporarily by setting the relevant HEAP environment variable value.