File 2021-Improve-interval-timer-handling.patch of Package erlang
From 8a0720fc0c2aa91851452cff90459521f6685b4a Mon Sep 17 00:00:00 2001
From: Maria Scott <maria-12648430@hnc-agency.org>
Date: Mon, 29 Aug 2022 19:46:47 +0200
Subject: [PATCH 1/4] Improve interval timer handling
Interval timers are run in a separate process in order
to reduce congestion on the timer server.
Co-authored-by: Jan Uhlig <juhlig@hnc-agency.org>
---
lib/stdlib/src/timer.erl | 115 +++++++++++++++++++++++----------------
1 file changed, 67 insertions(+), 48 deletions(-)
diff --git a/lib/stdlib/src/timer.erl b/lib/stdlib/src/timer.erl
index 982a4766f9..9e0be80df8 100644
--- a/lib/stdlib/src/timer.erl
+++ b/lib/stdlib/src/timer.erl
@@ -390,7 +390,7 @@ handle_call({apply_once, {Started, Time, MFA}}, _From, Tab) ->
)
of
SRef ->
- ets:insert(Tab, {SRef, SRef}),
+ ets:insert(Tab, {SRef}),
{ok, {once, SRef}}
catch
error:badarg ->
@@ -399,25 +399,17 @@ handle_call({apply_once, {Started, Time, MFA}}, _From, Tab) ->
{reply, Reply, Tab};
%% Start an interval timer.
handle_call({apply_interval, {Started, Time, Pid, MFA}}, _From, Tab) ->
- NextTimeout = Started + Time,
- TRef = monitor(process, Pid),
- Reply = try
- erlang:start_timer(
- NextTimeout,
- self(),
- {apply_interval, NextTimeout, Time, TRef, MFA},
- [{abs, true}]
- )
- of
- SRef ->
- ets:insert(Tab, {TRef, SRef}),
- {ok, {interval, TRef}}
- catch
- error:badarg ->
- demonitor(TRef, [flush]),
- {error, badarg}
- end,
- {reply, Reply, Tab};
+ Tag = make_ref(),
+ TimeServerPid = self(),
+ {TPid, TRef} = spawn_monitor(fun() ->
+ TimeServerRef = monitor(process, TimeServerPid),
+ TargetRef = monitor(process, Pid),
+ NextTimeout = Started + Time,
+ TimerRef = erlang:start_timer(NextTimeout, self(), {apply_interval, NextTimeout, Time, MFA}, [{abs, true}]),
+ _ = interval_loop(TimeServerRef, TargetRef, Tag, TimerRef)
+ end),
+ ets:insert(Tab, {TRef, TPid, Tag}),
+ {reply, {ok, {interval, TRef}}, Tab};
%% Cancel a one-shot timer.
handle_call({cancel, {once, TRef}}, _From, Tab) ->
_ = remove_timer(TRef, Tab),
@@ -425,11 +417,11 @@ handle_call({cancel, {once, TRef}}, _From, Tab) ->
%% Cancel an interval timer.
handle_call({cancel, {interval, TRef}}, _From, Tab) ->
_ = case remove_timer(TRef, Tab) of
- true ->
- demonitor(TRef, [flush]);
- false ->
- ok
- end,
+ true ->
+ demonitor(TRef, [flush]);
+ false ->
+ ok
+ end,
{reply, {ok, cancel}, Tab};
%% Unexpected.
handle_call(_Req, _From, Tab) ->
@@ -441,30 +433,13 @@ handle_call(_Req, _From, Tab) ->
%% One-shot timer timeout.
handle_info({timeout, TRef, {apply_once, MFA}}, Tab) ->
case ets:take(Tab, TRef) of
- [{TRef, _SRef}] ->
+ [{TRef}] ->
do_apply(MFA);
[] ->
ok
end,
{noreply, Tab};
-%% Interval timer timeout.
-handle_info({timeout, _, {apply_interval, CurTimeout, Time, TRef, MFA}}, Tab) ->
- case ets:member(Tab, TRef) of
- true ->
- NextTimeout = CurTimeout + Time,
- SRef = erlang:start_timer(
- NextTimeout,
- self(),
- {apply_interval, NextTimeout, Time, TRef, MFA},
- [{abs, true}]
- ),
- ets:update_element(Tab, TRef, {2, SRef}),
- do_apply(MFA);
- false ->
- ok
- end,
- {noreply, Tab};
-%% A process related to an interval timer died.
+%% An interval timer loop process died.
handle_info({'DOWN', TRef, process, _Pid, _Reason}, Tab) ->
_ = remove_timer(TRef, Tab),
{noreply, Tab};
@@ -480,24 +455,68 @@ handle_cast(_Req, Tab) ->
{noreply, Tab}.
-spec terminate(term(), _Tab) -> 'ok'.
-terminate(_Reason, _Tab) ->
- ok.
+terminate(_Reason, undefined) ->
+ ok;
+terminate(Reason, Tab) ->
+ _ = ets:foldl(fun
+ ({TRef}, Acc) ->
+ _ = cancel_timer(TRef),
+ Acc;
+ ({_TRef, TPid, Tag}, Acc) ->
+ TPid ! {cancel, Tag},
+ Acc
+ end,
+ undefined,
+ Tab),
+ true = ets:delete(Tab),
+ terminate(Reason, undefined).
-spec code_change(term(), State, term()) -> {'ok', State}.
code_change(_OldVsn, Tab, _Extra) ->
%% According to the man for gen server no timer can be set here.
{ok, Tab}.
+%% Interval timer loop.
+interval_loop(TimerServerMon, TargetMon, Tag, TimerRef0) ->
+ receive
+ {cancel, Tag} ->
+ ok = cancel_timer(TimerRef0);
+ {'DOWN', TimerServerMon, process, _, _} ->
+ ok = cancel_timer(TimerRef0);
+ {'DOWN', TargetMon, process, _, _} ->
+ ok = cancel_timer(TimerRef0);
+ {timeout, TimerRef0, {apply_interval, CurTimeout, Time, MFA}} ->
+ do_apply(MFA),
+ NextTimeout = CurTimeout + Time,
+ TimerRef1 = case NextTimeout =< system_time() of
+ true ->
+ self() ! {timeout, TimerRef0, {apply_interval, NextTimeout, Time, MFA}},
+ TimerRef0;
+ false ->
+ erlang:start_timer(NextTimeout, self(), {apply_interval, NextTimeout, Time, MFA}, [{abs, true}])
+ end,
+ interval_loop(TimerServerMon, TargetMon, Tag, TimerRef1)
+ end.
+
%% Remove a timer.
remove_timer(TRef, Tab) ->
case ets:take(Tab, TRef) of
- [{TRef, SRef}] ->
- ok = erlang:cancel_timer(SRef, [{async, true}, {info, false}]),
+ [{TRef}] -> % One-shot timer.
+ ok = cancel_timer(TRef),
+ true;
+ [{TRef, TPid, Tag}] -> % Interval timer.
+ Mon = monitor(process, TPid),
+ TPid ! {cancel, Tag},
+ receive {'DOWN', Mon, process, _, _} -> ok end,
true;
[] -> % TimerReference does not exist, do nothing
false
end.
+%% Cancel a timer.
+cancel_timer(TRef) ->
+ erlang:cancel_timer(TRef, [{async, true}, {info, false}]).
+
%% Help functions
%% If send op. send directly (faster than spawn)
--
2.35.3
