On macOS, we currently use libmalloc. We could roll our own allocator: e.g. tcmalloc, jemalloc, etc. I'm not aware of any significant evaluation of tradeoffs.

libmalloc doesn't work well with cross-thread frees:
https://bugs.chromium.org/p/chromium/issues/detail?id=897064

libmalloc's implementation of nanozone doesn't free memory on 10.13 and older:
https://bugs.chromium.org/p/chromium/issues/detail?id=861939#c15