Adjust number of slots in sync requests channel (paritytech#8492)

client/network/src/block_request_handler.rs

@@ -121,14 +121,9 @@ impl<B: BlockT> BlockRequestHandler<B> {
 		client: Arc<dyn Client<B>>,
 		num_peer_hint: usize,
 	) -> (Self, ProtocolConfig) {
-		// Rate of arrival multiplied with the waiting time in the queue equals the queue length.
-		//
-		// An average Polkadot node serves less than 5 requests per second. The 95th percentile
-		// serving a request is less than 2 second. Thus one would estimate the queue length to be
-		// below 10.
-		//
-		// Choosing 20 as the queue length to give some additional buffer.
-		let (tx, request_receiver) = mpsc::channel(20);
+		// Reserve enough request slots for one request per peer when we are at the maximum
+		// number of peers.
+		let (tx, request_receiver) = mpsc::channel(num_peer_hint);
 
 		let mut protocol_config = generate_protocol_config(protocol_id);
 		protocol_config.inbound_queue = Some(tx);