Do not use interval timer to update the process state.

If the process takes too long to update in the interval time,
the interval will fill it's message box.
System RSS memory reporting can be overloaded by constant
requests if the message box contains many 'update' messages.

Author: Daniil Fedotov

src/vm_memory_monitor.erl

@@ -225,7 +225,7 @@ start_link(MemFraction, AlarmSet, AlarmClear) ->
                           [MemFraction, {AlarmSet, AlarmClear}], []).
 
 init([MemFraction, AlarmFuns]) ->
-    TRef = start_timer(?DEFAULT_MEMORY_CHECK_INTERVAL),
+    TRef = erlang:send_after(?DEFAULT_MEMORY_CHECK_INTERVAL, self(), update),
     State = #state { timeout    = ?DEFAULT_MEMORY_CHECK_INTERVAL,
                      timer      = TRef,
                      alarmed    = false,
@@ -243,8 +243,14 @@ handle_call(get_check_interval, _From, State) ->
     {reply, State#state.timeout, State};
 
 handle_call({set_check_interval, Timeout}, _From, State) ->
-    {ok, cancel} = timer:cancel(State#state.timer),
-    {reply, ok, State#state{timeout = Timeout, timer = start_timer(Timeout)}};
+    State1 = case erlang:cancel_timer(State#state.timer) of
+        false ->
+            State#state{timeout = Timeout};
+        _ ->
+            State#state{timeout = Timeout,
+                        timer = erlang:send_after(Timeout, self(), update)}
+    end,
+    {reply, ok, State1};
 
 handle_call(get_memory_limit, _From, State) ->
     {reply, State#state.memory_limit, State};
@@ -256,7 +262,10 @@ handle_cast(_Request, State) ->
     {noreply, State}.
 
 handle_info(update, State) ->
-    {noreply, internal_update(State)};
+    erlang:cancel_timer(State#state.timer),
+    State1 = internal_update(State),
+    TRef = erlang:send_after(State1#state.timeout, self(), update),
+    {noreply, State1#state{ timer = TRef }};
 
 handle_info(_Info, State) ->
     {noreply, State}.
@@ -381,10 +390,6 @@ emit_update_info(AlarmState, MemUsed, MemLimit) ->
       "vm_memory_high_watermark ~p. Memory used:~p allowed:~p~n",
       [AlarmState, MemUsed, MemLimit]).
 
-start_timer(Timeout) ->
-    {ok, TRef} = timer:send_interval(Timeout, update),
-    TRef.
-
 %% According to http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx
 %% Windows has 2GB and 8TB of address space for 32 and 64 bit accordingly.
 get_vm_limit({win32,_OSname}) ->