> I can imagine one use-case for this: a task that is scheduled from and executed by a work-stealing thread-pool can allocate memory in one thread but by design there's no guarantee that the memory will be necessarily freed from that exact thread. Would that be a good use-case for snmalloc?
Yes. A work stealing runtime is a perfect use case for this. Also, cases where you might have a dedicated IO ingress thread that allocates work items, these get picked up by worker threads, and then sent to a dedicated IO egress thread. The ingress thread does a lot of allocation, the egress thread does a lot of deallocation, and the workers do a bit of both. The deallocations typically flow the opposite direction to the work flow, and this works extremely well with snmalloc.
> This sounds much like a bump allocator use-case but which can do this exact thing by calling a single munmap(addr, len) and unmap multiple allocations all at once.
Where suitable bump allocated arena management will be fast, but some times the lifetime are more complex. Certain algorithms for memory management can often release a lot of memory in a batch that is not necessarily allocated in batch, i.e. Lock-free epoch based memory reclamation, or Linux RCU, both batch deciding memory is no longer required. There are also application level things like periodic flushes of a cache/log that can cause batching of deallocations, but are not well suited to bump allocators.