Compact Block Relay (BIP-152) introduced an efficient way to relay blocks when there’s good mempool sync between nodes, best illustrated by this figure from the BIP:
The figure implies block can be relayed before the receiving node finishes processing it.
I want to know what is the situation in practice in Bitcoin Core?
I imagine this would be safe:
- Receive block in full (critical path)
- Verify PoW and Merkle root first (critical path)
- Relay the block (not on critical path, other thread can do)
- Validate fully and connect block (critical path)
- Start mining new tip (critical path)
So, what is the delay between receive and send?
