Improvement related to referencing subscribers data structure in kmod being bitmap #1037
Description
Improvement related to #1015.
- Pass the referencing_subscribers bitmap directly to user-space instead of copying individual subscriber IDs via subscriber_ids_buffer. This eliminates the per-subscriber iteration in the kernel and the copy_to_user of the ID array.
- Currently topic_local_id is monotonically incremented and never reused. With the limit raised to 1024, long-running systems may eventually exhaust the ID space. Introduce a free-ID bitmap to track available IDs and recycle them when subscribers/publishers are removed.