Constrain Burp Memory Usage

JVM Options

Search for the application and right click "Edit Application" (KDE Plasma pictured)

Specify -XX:MaxRamPercentage= in the "Arguments" input (again KDE Plasma)

Now, when Burp is launched, the Java VM options will constrain the process to using a maximum of xx percent of the system's entire available memory.

Alternatively, you can set this option in the GUI