BumpAllocator struct
BumpAllocator - satisfy allocations by bumping an offset into mmap based spans. This allocator satisfies allocation requests from pre-allocated mmap regions. The regions support transparent huge pages and are setup to allow upwards growth instead of accumulating a long list of individual mappings. As long as enough pre-allocated memory is available, allocation requests are served via a single lock-free offset increment. Atm, no memory is released back to the OS ever.