I wrote this because I wanted more explicit control over heaps when building different subsystems in C. Standard options like jemalloc and mimalloc are incredibly fast, but they act as black boxes. You can't easily cap a parser's memory at 256MB or wipe it all out in one go without writing a custom pool allocator.
Spaces takes a different approach. It uses 64KB-aligned slabs, and the metadata lookup is just a pointer mask (ptr & ~0xFFFF).
The trade-off is that every free() incurs an L1 cache miss to read the slab header, and there is a 64KB virtual memory floor per slab. But in exchange, you get zero-external-metadata regions, instant teardown of massive structures like ASTs, and performance that surprisingly keeps up with jemalloc on cross-thread workloads (I included the mimalloc-bench scripts in the repo).
It's Linux x86-64 only right now. I'm curious if systems folks think this chunk API is a pragmatic middle ground for memory management, or if the cache-miss penalty on free() makes the pointer-masking approach a dead end for general use.
