Yeah per thread virtual memory is called a process. Within a process the memory manager has to maintain a single virtual address space. You could do it with a red black tree and a global lock. Or you could use potentially cleverer algorithms. Skip lists are friendly to scalable concurrency. You could also do a radix tree of page tables, similar to what x86-64 processors do internally, then have each item be its own atomic long, and use some kind of optimistic transactional locking strategy when allocating mappings that span multiple pages. Personally, I think the rbtree is easiest, since it's better to leave memory scalability to malloc(). The way I like to make malloc() scale is having an arena for each CPU and then indexing them using sched_getcpu().