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authorSverker Eriksson <[email protected]>2015-11-30 19:22:53 +0100
committerSverker Eriksson <[email protected]>2015-11-30 19:22:53 +0100
commit16801311ad52b6d50b4c462da26b3d34f0736e48 (patch)
treebcd3aca6c1f65cae273d1d119fc2fc3b6322186c /erts/emulator
parent86545dbd6f6f5a3468b919e4daf68dcdb388e80a (diff)
parentcb62c989e59f0ec8556f9f1d4e9a45b8d9ee32f6 (diff)
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Merge branch 'sverk/rare-gc-map-overflow/OTP-13146' into maint
* sverk/rare-gc-map-overflow/OTP-13146: erts: Fix rare case of faulty heap fragment deallocation
Diffstat (limited to 'erts/emulator')
-rw-r--r--erts/emulator/beam/erl_gc.c36
-rw-r--r--erts/emulator/test/map_SUITE.erl96
2 files changed, 124 insertions, 8 deletions
diff --git a/erts/emulator/beam/erl_gc.c b/erts/emulator/beam/erl_gc.c
index d2604f1595..2f21111a2e 100644
--- a/erts/emulator/beam/erl_gc.c
+++ b/erts/emulator/beam/erl_gc.c
@@ -1237,6 +1237,7 @@ major_collection(Process* p, int need, Eterm* objv, int nobj, Uint *recl)
Uint oh_size = (char *) OLD_HTOP(p) - oh;
Uint n;
Uint new_sz;
+ int done;
/*
* Do a fullsweep GC. First figure out the size of the heap
@@ -1440,6 +1441,8 @@ major_collection(Process* p, int need, Eterm* objv, int nobj, Uint *recl)
*recl += size_before - (HEAP_TOP(p) - HEAP_START(p));
+ remove_message_buffers(p);
+
{
ErlMessage *msgp;
@@ -1458,15 +1461,21 @@ major_collection(Process* p, int need, Eterm* objv, int nobj, Uint *recl)
}
}
- adjust_after_fullsweep(p, need, objv, nobj);
-
-#ifdef HARDDEBUG
- disallow_heap_frag_ref_in_heap(p);
-#endif
- remove_message_buffers(p);
+ if (MBUF(p)) {
+ /* This is a very rare case when distributed messages copied above
+ * contained maps so big they did not fit on the heap causing the
+ * factory to create heap frags.
+ * Solution: Trigger a minor gc (without tenuring)
+ */
+ HIGH_WATER(p) = HEAP_START(p);
+ done = 0;
+ } else {
+ adjust_after_fullsweep(p, need, objv, nobj);
+ done = 1;
+ }
ErtsGcQuickSanityCheck(p);
- return 1; /* We are done. */
+ return done;
}
static void
@@ -1955,7 +1964,18 @@ collect_heap_frags(Process* p, Eterm* n_hstart, Eterm* n_htop,
if (p->dictionary != NULL) {
disallow_heap_frag_ref(p, n_htop, p->dictionary->data, p->dictionary->used);
}
- disallow_heap_frag_ref_in_heap(p);
+ /* OTP-18: Actually we do allow references from heap to heap fragments now.
+ This can happen when doing "binary_to_term" with a "fat" map contained
+ in another term. A "fat" map is a hashmap with higher heap demand than
+ first estimated by "binary_to_term" causing the factory to allocate
+ additional heap (fragments) for the hashmap tree nodes.
+ Run map_SUITE:t_gc_rare_map_overflow to provoke this.
+
+ Inverted references like this does not matter however. The copy done
+ below by move_one_area() with move markers in the fragments and the
+ sweeping done later by the GC should make everything ok in the end.
+ */
+ /***disallow_heap_frag_ref_in_heap(p);***/
#endif
/*
diff --git a/erts/emulator/test/map_SUITE.erl b/erts/emulator/test/map_SUITE.erl
index 62a94e5281..6890c42b7a 100644
--- a/erts/emulator/test/map_SUITE.erl
+++ b/erts/emulator/test/map_SUITE.erl
@@ -58,6 +58,7 @@
%% erlang
t_erlang_hash/1,
t_map_encode_decode/1,
+ t_gc_rare_map_overflow/1,
%% non specific BIF related
t_bif_build_and_check/1,
@@ -121,6 +122,7 @@ all() -> [
%% erlang
t_erlang_hash, t_map_encode_decode,
+ t_gc_rare_map_overflow,
t_map_size, t_is_map,
%% non specific BIF related
@@ -2991,6 +2993,100 @@ do_badmap_17(Config) ->
id(I) -> I.
+%% OTP-13146
+%% Provoke major GC with a lot of "fat" maps on external format in msg queue
+%% causing heap fragments to be allocated.
+t_gc_rare_map_overflow(Config) ->
+ Pa = filename:dirname(code:which(?MODULE)),
+ {ok, Node} = test_server:start_node(gc_rare_map_overflow, slave, [{args, "-pa \""++Pa++"\""}]),
+ Echo = spawn_link(Node, fun Loop() -> receive {From,Msg} -> From ! Msg
+ end,
+ Loop()
+ end),
+ FatMap = fatmap(34),
+ false = (flatmap =:= erts_internal:map_type(FatMap)),
+
+ t_gc_rare_map_overflow_do(Echo, FatMap, fun() -> erlang:garbage_collect() end),
+
+ % Repeat test for minor gc:
+ minor_collect(), % need this to make the next gc really be a minor
+ t_gc_rare_map_overflow_do(Echo, FatMap, fun() -> true = minor_collect() end),
+
+ unlink(Echo),
+ test_server:stop_node(Node).
+
+t_gc_rare_map_overflow_do(Echo, FatMap, GcFun) ->
+ Master = self(),
+ true = receive M -> false after 0 -> true end, % assert empty msg queue
+ Echo ! {Master, token},
+ repeat(1000, fun(_) -> Echo ! {Master, FatMap} end, void),
+
+ timer:sleep(100), % Wait for maps to arrive in our msg queue
+ token = receive Tok -> Tok end, % and provoke move from outer to inner msg queue
+
+ %% Do GC that will "overflow" and create heap frags due to all the fat maps
+ GcFun(),
+
+ %% Now check that all maps in msg queueu are intact
+ %% Will crash emulator in OTP-18.1
+ repeat(1000, fun(_) -> FatMap = receive FM -> FM end end, void),
+ ok.
+
+minor_collect() ->
+ minor_collect(minor_gcs()).
+
+minor_collect(Before) ->
+ After = minor_gcs(),
+ case After of
+ _ when After > Before -> true;
+ _ when After =:= Before -> minor_collect(Before);
+ 0 -> false
+ end.
+
+minor_gcs() ->
+ {garbage_collection, Info} = process_info(self(), garbage_collection),
+ {minor_gcs, GCS} = lists:keyfind(minor_gcs, 1, Info),
+ GCS.
+
+%% Generate a map with N (or N+1) keys that has an abnormal heap demand.
+%% Done by finding keys that collide in the first 32-bit hash.
+fatmap(N) ->
+ erts_debug:set_internal_state(available_internal_state, true),
+ Table = ets:new(void, [bag, private]),
+
+ Seed0 = rand:seed_s(exsplus, {4711, 3141592, 2718281}),
+ Seed1 = fatmap_populate(Table, Seed0, (1 bsl 16)),
+ Keys = fatmap_generate(Table, Seed1, N, []),
+ ets:delete(Table),
+ maps:from_list([{K,K} || K <- Keys]).
+
+fatmap_populate(_, Seed, 0) -> Seed;
+fatmap_populate(Table, Seed, N) ->
+ {I, NextSeed} = rand:uniform_s(1 bsl 48, Seed),
+ Hash = internal_hash(I),
+ ets:insert(Table, [{Hash, I}]),
+ fatmap_populate(Table, NextSeed, N-1).
+
+
+fatmap_generate(_, _, N, Acc) when N =< 0 ->
+ Acc;
+fatmap_generate(Table, Seed, N0, Acc0) ->
+ {I, NextSeed} = rand:uniform_s(1 bsl 48, Seed),
+ Hash = internal_hash(I),
+ case ets:member(Table, Hash) of
+ true ->
+ NewKeys = [I | ets:lookup_element(Table, Hash, 2)],
+ Acc1 = lists:usort(Acc0 ++ NewKeys),
+ N1 = N0 - (length(Acc1) - length(Acc0)),
+ fatmap_generate(Table, NextSeed, N1, Acc1);
+ false ->
+ fatmap_generate(Table, NextSeed, N0, Acc0)
+ end.
+
+internal_hash(Term) ->
+ erts_debug:get_internal_state({internal_hash, Term}).
+
+
%% map external_format (fannerl).
fannerl() ->
<<131,116,0,0,0,28,100,0,13,108,101,97,114,110,105,110,103,95,114,