Split in_channel and out_channel in binary_rpc. (#992)

This improves performance, sadly not optimized by OCaml.

src/base/Utils.ml

@@ -30,3 +30,10 @@ let int_fold ~init ~(f : 'a -> int -> 'a) n =
       recurser acc' (i + 1)
   in
   recurser init 0
+
+(* Execute f() and print time taken. *)
+let ftimer name ~f =
+  let t = Core.Unix.gettimeofday () in
+  let res = f () in
+  Printf.printf "%s,%f\n" name (Core.Unix.gettimeofday () -. t);
+  res

src/base/Utils.mli

@@ -22,3 +22,5 @@ open Core_kernel
 val list_add_unique : equal:('a -> 'a -> bool) -> 'a List.t -> 'a -> 'a List.t
 
 val int_fold : init:'a -> f:('a -> int -> 'a) -> int -> 'a
+
+val ftimer : string -> f:(unit -> 'a) -> 'a

src/eval/StateIPCClient.ml

@@ -58,9 +58,8 @@ let binary_rpc ~socket_addr (call : Rpc.call) : Rpc.response M.t =
     Unix.socket ~domain:Unix.PF_UNIX ~kind:Unix.SOCK_STREAM ~protocol:0 ()
   in
   Unix.connect socket ~addr:(Unix.ADDR_UNIX socket_addr);
-  let ic, oc =
-    (Unix.in_channel_of_descr socket, Unix.out_channel_of_descr socket)
-  in
+  let ic = Unix.in_channel_of_descr socket in
+  let oc = Unix.out_channel_of_descr socket in
   let msg_buf = Jsonrpc.string_of_call ~version:Jsonrpc.V2 call in
   DebugMessage.plog (Printf.sprintf "Sending: %s\n" msg_buf);
   (* Send data to the socket. *)