From a86bb2d592486144414fbbebca85ab36ffca2446 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Mon, 1 Apr 2013 18:44:47 +0200
Subject: Don't lookup the node unless required in gen:call/{3,4}

Move some operations that aren't required for the happy path.
The operations were small, so they shouldn't show a big difference
in benchmarks except for systems with many active gen processes.
---
 lib/stdlib/src/gen.erl | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

(limited to 'lib/stdlib/src')

diff --git a/lib/stdlib/src/gen.erl b/lib/stdlib/src/gen.erl
index 42555aedd7..d9db17170b 100644
--- a/lib/stdlib/src/gen.erl
+++ b/lib/stdlib/src/gen.erl
@@ -17,6 +17,7 @@
 %% %CopyrightEnd%
 %%
 -module(gen).
+-compile({inline,[get_node/1]}).
 
 %%%-----------------------------------------------------------------
 %%% This module implements the really generic stuff of the generic
@@ -194,16 +195,6 @@ call({_Name, Node}=Process, Label, Request, Timeout)
     end.
 
 do_call(Process, Label, Request, Timeout) ->
-    %% We trust the arguments to be correct, i.e
-    %% Process is either a local or remote pid,
-    %% or a {Name, Node} tuple (of atoms) and in this 
-    %% case this node (node()) _is_ distributed and Node =/= node().
-    Node = case Process of
- 	       {_S, N} when is_atom(N) ->
- 		   N;
- 	       _ when is_pid(Process) ->
- 		   node(Process)
-	   end,
     try erlang:monitor(process, Process) of
 	Mref ->
 	    %% If the monitor/2 call failed to set up a connection to a
@@ -222,6 +213,7 @@ do_call(Process, Label, Request, Timeout) ->
 		    erlang:demonitor(Mref, [flush]),
 		    {ok, Reply};
 		{'DOWN', Mref, _, _, noconnection} ->
+		    Node = get_node(Process),
 		    exit({nodedown, Node});
 		{'DOWN', Mref, _, _, Reason} ->
 		    exit(Reason)
@@ -241,6 +233,7 @@ do_call(Process, Label, Request, Timeout) ->
 	    %% Do the best possible with monitor_node/2.
 	    %% This code may hang indefinitely if the Process 
 	    %% does not exist. It is only used for featureweak remote nodes.
+	    Node = get_node(Process),
 	    monitor_node(Node, true),
 	    receive
 		{nodedown, Node} -> 
@@ -253,6 +246,18 @@ do_call(Process, Label, Request, Timeout) ->
 	    end
     end.
 
+get_node(Process) ->
+    %% We trust the arguments to be correct, i.e
+    %% Process is either a local or remote pid,
+    %% or a {Name, Node} tuple (of atoms) and in this
+    %% case this node (node()) _is_ distributed and Node =/= node().
+    case Process of
+	{_S, N} when is_atom(N) ->
+	    N;
+	_ when is_pid(Process) ->
+	    node(Process)
+    end.
+
 wait_resp(Node, Tag, Timeout) ->
     receive
 	{Tag, Reply} ->
-- 
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