lower_boundary
HashedSlab* slab = hash_table.Lookup(::lower_boundary(object, slab_size));
cache->lower_boundary = __fls0(cache->slab_size);
size_t lower_boundary;
return (addr_t)::lower_boundary(key, parent->slab_size)
>> parent->lower_boundary;
return slab_in_pages(lower_boundary(object, slab_size), slab_size);