Tracking down the source of the memory usage, I could notice the first QScriptEngine creates a thread (enabled by the USE_BACKGROUND_THREAD_TO_SCAVENGE_MEMORY option), this thread allocates 8MB on my system for its stack.

This thread seems to be shared between all script engines, that’s why there is a difference between the first script engine and the others.

Still trying to optimize the memory size for each script engine (seems like the interpreter maps a 2M memory block)

I finally tracked down the other big memory block, it is instanciated by the RegisterFile class, child of the Interpreter class.

By default it allocates 2MB for the virtual machine’s stack.

I’ll try to play around with the capacity to see if it is possible to optimize it.

The last thing you can tweak if you have a small amount of memory on your system is the BLOCK_SIZE allocated by the collector, the default size is 256K if QT is not compiled for symbian nor wince, which can be much more than your scripts need.