Merge pull request #303 from talex5/nodelay

Set TCP_NODELAY to avoid Nagle's algorithm

CHANGES.md

@@ -64,7 +64,7 @@ API changes:
 
 Performance and bug fixes:
 
-- Add buffering of outgoing messages (@talex5 #287).  
+- Add buffering of outgoing messages (@talex5 #287 #303).  
   Sending each message in its own TCP packet isn't very efficient, and also interacts very badly with Nagle's algorithm.
   See <https://roscidus.com/blog/blog/2024/07/22/performance/> for details.
 

unix/network.ml

@@ -71,6 +71,10 @@ let close x =
   try Eio.Net.close x
   with Eio.Io (Eio.Net.E Connection_reset _, _) -> ()
 
+let try_set_nodelay socket =
+  try Unix.setsockopt socket Unix.TCP_NODELAY true
+  with Unix.Unix_error ((EINVAL | EOPNOTSUPP), _, _) -> ()         (* Probably a Unix-domain socket *)
+
 let connect net ~sw ~secret_key (addr, auth) =
   let eio_addr =
     match addr with
@@ -87,17 +91,22 @@ let connect net ~sw ~secret_key (addr, auth) =
     begin match addr with
       | `Unix _ -> ()
       | `TCP _ ->
-        let socket = Eio_unix.Resource.fd_opt socket |> Option.get in
-        Eio_unix.Fd.use_exn "keep-alive" socket @@ fun socket ->
-        Unix.setsockopt socket Unix.SO_KEEPALIVE true;
-        Keepalive.try_set_idle socket 60
+        Eio_unix.Resource.fd_opt socket
+        |> Option.iter (fun socket ->
+            Eio_unix.Fd.use_exn "keep-alive" socket @@ fun socket ->
+            Unix.setsockopt socket Unix.SO_KEEPALIVE true;
+            try_set_nodelay socket;
+            Keepalive.try_set_idle socket 60
+          )
     end;
     Tls_wrapper.connect_as_client socket secret_key auth
   | exception ex ->
     Fiber.check ();
     error "@[<v2>Network connection for %a failed:@,%a@]" Location.pp addr Fmt.exn ex
 
 let accept_connection ~secret_key flow =
+  Eio_unix.Resource.fd_opt flow
+  |> Option.iter (fun fd -> Eio_unix.Fd.use_exn "TCP_NODELAY" fd try_set_nodelay);
   Tls_wrapper.connect_as_server flow secret_key
 
 let v t = (t :> [`Generic] Eio.Net.ty r)