diff --git a/src/emqx_session.erl b/src/emqx_session.erl
index 3f9fd1610..eac258bcf 100644
--- a/src/emqx_session.erl
+++ b/src/emqx_session.erl
@@ -138,12 +138,6 @@
           %% Stats timer
           stats_timer  :: reference() | undefined,
 
-          %% Deliver stats
-          deliver_stats = 0,
-
-          %% Enqueue stats
-          enqueue_stats = 0,
-
           %% GC State
           gc_state,
 
@@ -224,9 +218,7 @@ stats(#state{max_subscriptions = MaxSubscriptions,
              inflight = Inflight,
              mqueue = MQueue,
              max_awaiting_rel = MaxAwaitingRel,
-             awaiting_rel = AwaitingRel,
-             deliver_stats = DeliverMsg,
-             enqueue_stats = EnqueueMsg}) ->
+             awaiting_rel = AwaitingRel}) ->
     lists:append(emqx_misc:proc_stats(),
                  [{max_subscriptions, MaxSubscriptions},
                   {subscriptions_count, maps:size(Subscriptions)},
@@ -237,8 +229,8 @@ stats(#state{max_subscriptions = MaxSubscriptions,
                   {mqueue_dropped, emqx_mqueue:dropped(MQueue)},
                   {max_awaiting_rel, MaxAwaitingRel},
                   {awaiting_rel_len, maps:size(AwaitingRel)},
-                  {deliver_msg, DeliverMsg},
-                  {enqueue_msg, EnqueueMsg}]).
+                  {deliver_msg, emqx_pd:get_counter(deliver_stats)},
+                  {enqueue_msg, emqx_pd:get_counter(enqueue_stats)}]).
 
 %%------------------------------------------------------------------------------
 %% PubSub API
@@ -366,8 +358,6 @@ init([Parent, #{zone            := Zone,
                    max_awaiting_rel  = get_env(Zone, max_awaiting_rel),
                    expiry_interval   = ExpiryInterval,
                    enable_stats      = get_env(Zone, enable_stats, true),
-                   deliver_stats     = 0,
-                   enqueue_stats     = 0,
                    gc_state          = emqx_gc:init(GcPolicy),
                    created_at        = os:timestamp(),
                    will_msg          = WillMsg
@@ -593,7 +583,8 @@ handle_info({dispatch, Topic, Msg = #message{}}, State) ->
             ok = emqx_shared_sub:nack_no_connection(Msg),
             {noreply, State};
         false ->
-            noreply(ensure_stats_timer(handle_dispatch(Topic, Msg, State)))
+            NewState = handle_dispatch(Topic, Msg, State),
+            noreply(ensure_stats_timer(maybe_gc({1, msg_size(Msg)}, NewState)))
     end;
 
 %% Do nothing if the client has been disconnected.
@@ -834,30 +825,31 @@ run_dispatch_steps([{subid, SubId}|Steps], Msg, State) ->
 %% Enqueue message if the client has been disconnected
 dispatch(Msg, State = #state{client_id = ClientId, conn_pid = undefined}) ->
     case emqx_hooks:run('message.dropped', [#{client_id => ClientId}, Msg]) of
-        ok   -> enqueue_msg(Msg, State);
+        ok -> enqueue_msg(Msg, State);
         stop -> State
     end;
 
 %% Deliver qos0 message directly to client
 dispatch(Msg = #message{qos = ?QOS_0} = Msg, State) ->
-    deliver(undefined, Msg, State),
-    inc_stats(deliver, Msg, State);
+    ok = deliver(undefined, Msg, State),
+    State;
 
 dispatch(Msg = #message{qos = QoS} = Msg,
          State = #state{next_pkt_id = PacketId, inflight = Inflight})
-  when QoS =:= ?QOS_1 orelse QoS =:= ?QOS_2 ->
+    when QoS =:= ?QOS_1 orelse QoS =:= ?QOS_2 ->
     case emqx_inflight:is_full(Inflight) of
         true ->
             enqueue_msg(Msg, State);
         false ->
-            deliver(PacketId, Msg, State),
-            await(PacketId, Msg, inc_stats(deliver, Msg, next_pkt_id(State)))
+            ok = deliver(PacketId, Msg, State),
+            await(PacketId, Msg, next_pkt_id(State))
     end.
 
 enqueue_msg(Msg, State = #state{mqueue = Q}) ->
+    emqx_pd:update_counter(enqueue_stats, 1),
     {Dropped, NewQ} = emqx_mqueue:in(Msg, Q),
     Dropped =/= undefined andalso emqx_shared_sub:maybe_nack_dropped(Dropped),
-    inc_stats(enqueue, Msg, State#state{mqueue = NewQ}).
+    State#state{mqueue = NewQ}.
 
 %%------------------------------------------------------------------------------
 %% Deliver
@@ -872,6 +864,7 @@ redeliver({pubrel, PacketId}, #state{conn_pid = ConnPid}) ->
     ConnPid ! {deliver, {pubrel, PacketId}}.
 
 deliver(PacketId, Msg, State) ->
+    emqx_pd:update_counter(deliver_stats, 1),
     %% Ack QoS1/QoS2 messages when message is delivered to connection.
     %% NOTE: NOT to wait for PUBACK because:
     %% The sender is monitoring this session process,
@@ -882,7 +875,7 @@ deliver(PacketId, Msg, State) ->
     do_deliver(PacketId, emqx_shared_sub:maybe_ack(Msg), State).
 
 do_deliver(PacketId, Msg, #state{conn_pid = ConnPid, binding = local}) ->
-    ConnPid ! {deliver, {publish, PacketId, Msg}};
+    ConnPid ! {deliver, {publish, PacketId, Msg}}, ok;
 do_deliver(PacketId, Msg, #state{conn_pid = ConnPid, binding = remote}) ->
     emqx_rpc:cast(node(ConnPid), erlang, send, [ConnPid, {deliver, {publish, PacketId, Msg}}]).
 
@@ -994,21 +987,21 @@ next_pkt_id(State = #state{next_pkt_id = 16#FFFF}) ->
 next_pkt_id(State = #state{next_pkt_id = Id}) ->
     State#state{next_pkt_id = Id + 1}.
 
-%%------------------------------------------------------------------------------
-%% Inc stats
-
-inc_stats(deliver, Msg, State = #state{deliver_stats = I}) ->
-    State1 = maybe_gc({1, msg_size(Msg)}, State),
-    State1#state{deliver_stats = I + 1};
-inc_stats(enqueue, _Msg, State = #state{enqueue_stats = I}) ->
-    State#state{enqueue_stats = I + 1}.
-
 %% Take only the payload size into account, add other fields if necessary
 msg_size(#message{payload = Payload}) -> payload_size(Payload).
 
 %% Payload should be binary(), but not 100% sure. Need dialyzer!
 payload_size(Payload) -> erlang:iolist_size(Payload).
 
+%%------------------------------------------------------------------------------
+%% Maybe GC
+
+maybe_gc(_, State = #state{gc_state = undefined}) ->
+    State;
+maybe_gc({Cnt, Oct}, State = #state{gc_state = GCSt}) ->
+    {_, GCSt1} = emqx_gc:run(Cnt, Oct, GCSt),
+    State#state{gc_state = GCSt1}.
+
 %%------------------------------------------------------------------------------
 %% Helper functions
 
@@ -1024,9 +1017,3 @@ noreply(State) ->
 shutdown(Reason, State) ->
     {stop, Reason, State}.
 
-maybe_gc(_, State = #state{gc_state = undefined}) ->
-    State;
-maybe_gc({Cnt, Oct}, State = #state{gc_state = GCSt}) ->
-    {_, GCSt1} = emqx_gc:run(Cnt, Oct, GCSt),
-    State#state{gc_state = GCSt1}.
-