There is a bothersome issue with freelists fronting general-purpose allocators (https://en.wikipedia.org/wiki/Free_list): they can grow indefinitely. Because they keep memory allocated in their parent, they cause fragmentation to it.
You can look at jemalloc which has a GC algorithm for this problem.
https://m.facebook.com/notes/facebook-engineering/scalable-memory-allocation-using-jemalloc/480222803919
