Pool Allocation

Our Lisp is very simple, it is not fast. Its performance is relative to some scripting languages such as Python and Ruby. Most of the performance overhead in our program comes from the fact that doing almost anything requires us to construct and destruct lval. We therefore call malloc very often. This is a slow function as it requires the operating system to do some management for us. When doing calculations there is lots of copying, allocation and deallocation of lval types.

If we wish to reduce this overhead we need to lower the number of calls to malloc. One method of doing this is to call malloc once at the beginning of the program, allocating a large pool of memory. We should then replace all our malloc calls with calls to some function that slices and dices up this memory for use in the program. This means that we are emulating some of the behaviour of the operating system, but in a faster local way. This idea is called memory pool allocation and is a common technique used in game development, and other performance sensitive applications.

This can be tricky to implement correctly, but conceptually does not need to be complex. If you want a quick method for getting large gains in performance, looking into this might interest you.