I use simple prog to get stat from my map type BPF_MAP_TYPE_HASH.
An got too slow speed to delete elems from it, lookup elem 100-1000x faster.
My code is just

while(bpf_map_get_next_key(fd, &key,&nextkey)==0)
bpf_map_lookup_elem(&nextkey,&value);
bpf_map_delete_elem(fd, &nextkey);

whitout deleting code is very fast.