diff options
Diffstat (limited to 'erts/preloaded/src/erts_literal_area_collector.erl')
| -rw-r--r-- | erts/preloaded/src/erts_literal_area_collector.erl | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/erts/preloaded/src/erts_literal_area_collector.erl b/erts/preloaded/src/erts_literal_area_collector.erl new file mode 100644 index 0000000000..3befad8dfb --- /dev/null +++ b/erts/preloaded/src/erts_literal_area_collector.erl @@ -0,0 +1,113 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 2016. All Rights Reserved. +%% +%% Licensed under the Apache License, Version 2.0 (the "License"); +%% you may not use this file except in compliance with the License. +%% You may obtain a copy of the License at +%% +%% http://www.apache.org/licenses/LICENSE-2.0 +%% +%% Unless required by applicable law or agreed to in writing, software +%% distributed under the License is distributed on an "AS IS" BASIS, +%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +%% See the License for the specific language governing permissions and +%% limitations under the License. +%% +%% %CopyrightEnd% +%% +-module(erts_literal_area_collector). + +-export([start/0]). + +%% Currently we only allow two outstanding literal +%% copying jobs that garbage collect in order to +%% copy the literals. Maybe we could allow more +%% than two outstanding processes, but for now we +%% play it safe... +-define(MAX_GC_OUTSTND, 2). + +%% +%% The erts_literal_area_collector is started at +%% VM boot by the VM. It is a spawned as a system +%% process, i.e, the whole VM will terminate if +%% this process terminates. +%% +start() -> + process_flag(trap_exit, true), + msg_loop(undefined, 0, 0, []). + +%% +%% The VM will send us a 'copy_literals' message +%% when it has a new literal area that needs to +%% be handled is added. We will also be informed +%% about more areas when we call +%% erts_internal:release_literal_area_switch(). +%% +msg_loop(Area, Outstnd, GcOutstnd, NeedGC) -> + receive + + %% A new area to handle has arrived... + copy_literals when Outstnd == 0 -> + switch_area(); + + %% Process (_Pid) has completed the request... + {copy_literals, {Area, _GcAllowed, _Pid}, ok} when Outstnd == 1 -> + switch_area(); %% Last process completed... + {copy_literals, {Area, false, _Pid}, ok} -> + msg_loop(Area, Outstnd-1, GcOutstnd, NeedGC); + {copy_literals, {Area, true, _Pid}, ok} when NeedGC == [] -> + msg_loop(Area, Outstnd-1, GcOutstnd-1, []); + {copy_literals, {Area, true, _Pid}, ok} -> + send_copy_req(hd(NeedGC), Area, true), + msg_loop(Area, Outstnd-1, GcOutstnd, tl(NeedGC)); + + %% Process (Pid) failed to complete the request + %% since it needs to garbage collect in order to + %% complete the request... + {copy_literals, {Area, false, Pid}, need_gc} when GcOutstnd < ?MAX_GC_OUTSTND -> + send_copy_req(Pid, Area, true), + msg_loop(Area, Outstnd, GcOutstnd+1, NeedGC); + {copy_literals, {Area, false, Pid}, need_gc} -> + msg_loop(Area, Outstnd, GcOutstnd, [Pid|NeedGC]); + + %% Not handled message regarding the area that we + %% currently are working with. Crash the VM so + %% we notice this bug... + {copy_literals, {Area, _, _}, _} = Msg when erlang:is_reference(Area) -> + exit({not_handled_message, Msg}); + + %% Unexpected garbage message. Get rid of it... + _Ignore -> + msg_loop(Area, Outstnd, GcOutstnd, NeedGC) + + end. + +switch_area() -> + Res = erts_internal:release_literal_area_switch(), + erlang:garbage_collect(), %% Almost no live data now... + case Res of + false -> + %% No more areas to handle... + msg_loop(undefined, 0, 0, []); + true -> + %% Send requests to all processes to copy + %% all live data they have referring to the + %% literal area that is to be released... + Area = make_ref(), + Outstnd = send_copy_reqs(erlang:processes(), Area, false), + msg_loop(Area, Outstnd, 0, []) + end. + +send_copy_reqs(Ps, Area, GC) -> + send_copy_reqs(Ps, Area, GC, 0). + +send_copy_reqs([], _Area, _GC, N) -> + N; +send_copy_reqs([P|Ps], Area, GC, N) -> + send_copy_req(P, Area, GC), + send_copy_reqs(Ps, Area, GC, N+1). + +send_copy_req(P, Area, GC) -> + erts_internal:request_system_task(P, normal, {copy_literals, {Area, GC, P}, GC}). |