Possible compromise between space and time efficiency: use bytes instead of bits to mark reserved/committed slots. This wastes 7/8 of space but you can now use

Possible compromise between space and time efficiency: use bytes instead of bits to mark reserved/committed slots. This wastes 7/8 of space but you can now use ordinary byte-width loads/stores instead of CAS (these are guaranteed to be atomic on both x86 and ARM). You still have false sharing of course, but it's diluted somewhat and you avoid atomic RMW overhead. The other problem of course is that you now have 8x more memory to scan for free slots, so not sure whether it's a good tradeoff; only benchmarking will tell.