diff --git a/src/emqttd_sm.erl b/src/emqttd_sm.erl
index b8a68a733..a46d56fa6 100644
--- a/src/emqttd_sm.erl
+++ b/src/emqttd_sm.erl
@@ -156,7 +156,7 @@ handle_call({start_session, false, {ClientId, Username}, ClientPid}, _From, Stat
                     {reply, {ok, SessPid, true}, State};
                 {error, Erorr} ->
                     {reply, {error, Erorr}, State}
-             end
+            end
     end;
 
 %% Transient Session
@@ -183,16 +183,14 @@ handle_cast(Msg, State) ->
 handle_info({'DOWN', MRef, process, DownPid, _Reason}, State) ->
     case dict:find(MRef, State#state.monitors) of
         {ok, ClientId} ->
-            mnesia:transaction(fun() ->
-                case mnesia:wread({mqtt_session, ClientId}) of
-                    [] ->
-                        ok;
-                    [Sess = #mqtt_session{sess_pid = DownPid}] ->
-                        mnesia:delete_object(mqtt_session, Sess, write);
-                    [_Sess] ->
-                        ok
-                    end
-                end),
+            case mnesia:dirty_read({mqtt_session, ClientId}) of
+                [] ->
+                    ok;
+                [Sess = #mqtt_session{sess_pid = DownPid}] ->
+                    mnesia:dirty_delete_object(Sess);
+                [_Sess] ->
+                    ok
+            end,
             {noreply, erase_monitor(MRef, State), hibernate};
         error ->
             lager:error("MRef of session ~p not found", [DownPid]),
@@ -283,15 +281,14 @@ destroy_session(Session = #mqtt_session{client_id = ClientId, sess_pid  = SessPi
     remove_session(Session);
 
 %% Remote node
-destroy_session(Session = #mqtt_session{client_id = ClientId,
-                                        sess_pid  = SessPid}) ->
+destroy_session(Session = #mqtt_session{client_id = ClientId, sess_pid  = SessPid}) ->
     Node = node(SessPid),
     case rpc:call(Node, emqttd_session, destroy, [SessPid, ClientId]) of
         ok ->
             remove_session(Session);
         {badrpc, nodedown} ->
             ?LOG(error, "Node '~s' down", [Node], Session),
-            remove_session(Session); 
+            remove_session(Session);
         {badrpc, Reason} ->
             ?LOG(error, "Failed to destory ~p on remote node ~p for ~s",
                  [SessPid, Node, Reason], Session),
@@ -299,10 +296,7 @@ destroy_session(Session = #mqtt_session{client_id = ClientId,
      end.
 
 remove_session(Session) ->
-    case mnesia:transaction(fun mnesia:delete_object/1, [Session]) of
-        {atomic, ok}     -> ok;
-        {aborted, Error} -> {error, Error}
-    end.
+    mnesia:dirty_delete_object(Session).
 
 monitor_session(ClientId, SessPid, State = #state{monitors = Monitors}) ->
     MRef = erlang:monitor(process, SessPid),
diff --git a/src/emqttd_sm_sup.erl b/src/emqttd_sm_sup.erl
index efabadb96..1c2e7f31a 100644
--- a/src/emqttd_sm_sup.erl
+++ b/src/emqttd_sm_sup.erl
@@ -24,8 +24,6 @@
 
 -include("emqttd.hrl").
 
--define(SM, emqttd_sm).
-
 -define(HELPER, emqttd_sm_helper).
 
 %% API
@@ -44,11 +42,11 @@ init([]) ->
     %% Helper
     StatsFun = emqttd_stats:statsfun('sessions/count', 'sessions/max'),
     Helper = {?HELPER, {?HELPER, start_link, [StatsFun]},
-                permanent, 5000, worker, [?HELPER]},
+              permanent, 5000, worker, [?HELPER]},
 
     %% SM Pool Sup
-    MFA = {?SM, start_link, []},
-    PoolSup = emqttd_pool_sup:spec([?SM, hash, erlang:system_info(schedulers), MFA]),
+    MFA = {emqttd_sm, start_link, []},
+    PoolSup = emqttd_pool_sup:spec([emqttd_sm, hash, erlang:system_info(schedulers), MFA]),
 
     {ok, {{one_for_all, 10, 3600}, [Helper, PoolSup]}}.