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authorKjell Winblad <[email protected]>2019-02-22 16:49:37 +0100
committerKjell Winblad <[email protected]>2019-04-10 15:42:42 +0200
commitc5e9766712436bea2b91bccd062f66a3ad1841bb (patch)
tree25ce2b16b9f847088997b0d4e77af46dbb6d2d66 /lib/stdlib/test
parent326c3cb70c1b37c794b781a42c50725766098810 (diff)
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Decentralized counters for ETS ordered_set with write_concurrency
Previously, all ETS tables used centralized counter variables to keep track of the number of items stored and the amount of memory consumed. These counters can cause scalability problems (especially on big NUMA systems). This commit adds an implementation of a decentralized counter and modifies the implementation of ETS so that ETS tables of type ordered_set with write_concurrency enabled use the decentralized counter. [Experiments][1] indicate that this change substantially improves the scalability of ETS ordered_set tables with write_concurrency enabled in scenarios with frequent `ets:insert/2` and `ets:delete/2` calls. The new counter is implemented in the module erts_flxctr (`erts_flxctr.h` and `erts_flxctr.c`). The module has the suffix flxctr as it contains the implementation of a flexible counter (i.e., counter instances can be configured to be either centralized or decentralized). Counters that are configured to be centralized are implemented with a single counter variable which is modified with atomic operations. Decentralized counters are spread over several cache lines (how many can be configured with the parameter `+dcg`). The scheduler threads are mapped to cache lines so that there is no single point of contention when decentralized counters are updated. The thread progress functionality of the Erlang VM is utilized to implement support for linearizable snapshots of decentralized counters. The snapshot functionality is used by the `ets:info/1` and `ets:info/2` functions. [1]: http://winsh.me/ets_catree_benchmark/flxctr_res.html
Diffstat (limited to 'lib/stdlib/test')
-rw-r--r--lib/stdlib/test/ets_SUITE.erl140
1 files changed, 138 insertions, 2 deletions
diff --git a/lib/stdlib/test/ets_SUITE.erl b/lib/stdlib/test/ets_SUITE.erl
index 87ca9bd32c..cd32f25abd 100644
--- a/lib/stdlib/test/ets_SUITE.erl
+++ b/lib/stdlib/test/ets_SUITE.erl
@@ -42,6 +42,8 @@
select_bound_chunk/1,
t_delete_all_objects/1, t_insert_list/1, t_test_ms/1,
t_select_delete/1,t_select_replace/1,t_select_replace_next_bug/1,t_ets_dets/1]).
+-export([test_table_size_concurrency/1,test_table_memory_concurrency/1,
+ test_delete_table_while_size_snapshot/1, test_delete_table_while_size_snapshot_helper/0]).
-export([ordered/1, ordered_match/1, interface_equality/1,
fixtable_next/1, fixtable_insert/1, rename/1, rename_unnamed/1, evil_rename/1,
@@ -156,7 +158,11 @@ all() ->
whereis_table,
delete_unfix_race,
test_throughput_benchmark,
- {group, benchmark}].
+ {group, benchmark},
+ test_table_size_concurrency,
+ test_table_memory_concurrency,
+ test_delete_table_while_size_snapshot].
+
groups() ->
[{new, [],
@@ -828,7 +834,11 @@ adjust_xmem([_T1,_T2,_T3,_T4], {A0,B0,C0,D0} = _Mem0, EstCnt) ->
{TabSz, EstSz} = erts_debug:get_internal_state('DbTable_words'),
HTabSz = TabSz + EstCnt*EstSz,
- {A0+TabSz, B0+HTabSz, C0+HTabSz, D0+HTabSz}.
+ OrdSetExtra = case erlang:system_info(wordsize) of
+ 8 -> 40; % larger stack on 64 bit architectures
+ _ -> 0
+ end,
+ {A0+TabSz+OrdSetExtra, B0+HTabSz, C0+HTabSz, D0+HTabSz}.
%% Misc. whitebox tests
t_whitebox(Config) when is_list(Config) ->
@@ -4102,6 +4112,11 @@ slot_do(Opts) ->
fill_tab(Tab,foo),
Elts = ets:info(Tab,size),
Elts = slot_loop(Tab,0,0),
+ case ets:info(Tab, type) of
+ ordered_set ->
+ '$end_of_table' = ets:slot(Tab,Elts);
+ _ -> ok
+ end,
true = ets:delete(Tab),
verify_etsmem(EtsMem).
@@ -4453,6 +4468,127 @@ info_do(Opts) ->
undefined = ets:info(non_existing_table_xxyy,safe_fixed),
verify_etsmem(EtsMem).
+size_loop(_T, 0, _, _) ->
+ ok;
+size_loop(T, I, PrevSize, WhatToTest) ->
+ Size = ets:info(T, WhatToTest),
+ case Size < PrevSize of
+ true -> ct:fail("Bad ets:info/2");
+ _ -> ok
+ end,
+ size_loop(T, I -1, Size, WhatToTest).
+
+add_loop(_T, 0) ->
+ ok;
+add_loop(T, I) ->
+ ets:insert(T, {I}),
+ add_loop(T, I -1).
+
+
+test_table_counter_concurrency(WhatToTest) ->
+ ItemsToAdd = 1000000,
+ SizeLoopSize = 1000,
+ T = ets:new(k, [public, ordered_set, {write_concurrency, true}]),
+ 0 = ets:info(T, size),
+ P = self(),
+ SpawnedSizeProcs =
+ [spawn(fun() ->
+ size_loop(T, SizeLoopSize, 0, WhatToTest),
+ P ! done
+ end)
+ || _ <- lists:seq(1, 6)],
+ spawn(fun() ->
+ add_loop(T, ItemsToAdd),
+ P ! done_add
+ end),
+ [receive
+ done -> ok;
+ done_add -> ok
+ end
+ || _ <- [ok|SpawnedSizeProcs]],
+ case WhatToTest =:= size of
+ true ->
+ ItemsToAdd = ets:info(T, size);
+ _ ->
+ ok
+ end,
+ ok.
+
+test_table_size_concurrency(Config) when is_list(Config) ->
+ test_table_counter_concurrency(size).
+
+test_table_memory_concurrency(Config) when is_list(Config) ->
+ test_table_counter_concurrency(memory).
+
+%% Tests that calling the ets:delete operation on a table T with
+%% decentralized counters works while ets:info(T, size) operations are
+%% active
+test_delete_table_while_size_snapshot(Config) when is_list(Config) ->
+ %% Run test case in a slave node as other test suites in stdlib
+ %% depend on that pids are ordered in creation order which is no
+ %% longer the case when many processes have been started before
+ Node = start_slave(),
+ ok = rpc:call(Node, ?MODULE, test_delete_table_while_size_snapshot_helper, []),
+ test_server:stop_node(Node),
+ ok.
+
+test_delete_table_while_size_snapshot_helper()->
+ TopParent = self(),
+ repeat_par(
+ fun() ->
+ Table = ets:new(t, [public, ordered_set,
+ {write_concurrency, true}]),
+ Parent = self(),
+ NrOfSizeProcs = 100,
+ Pids = [ spawn(fun()-> size_process(Table, Parent) end)
+ || _ <- lists:seq(1, NrOfSizeProcs)],
+ timer:sleep(1),
+ ets:delete(Table),
+ [receive
+ table_gone -> ok;
+ Problem -> TopParent ! Problem
+ end || _ <- Pids]
+ end,
+ 15000),
+ receive
+ Problem -> throw(Problem)
+ after 0 -> ok
+ end.
+
+size_process(Table, Parent) ->
+ try ets:info(Table, size) of
+ N when is_integer(N) ->
+ size_process(Table, Parent);
+ undefined -> Parent ! table_gone;
+ E -> Parent ! {got_unexpected, E}
+ catch
+ E -> Parent ! {got_unexpected_exception, E}
+ end.
+
+start_slave() ->
+ MicroSecs = erlang:monotonic_time(),
+ Name = "ets_" ++ integer_to_list(MicroSecs),
+ Pa = filename:dirname(code:which(?MODULE)),
+ {ok, Node} = test_server:start_node(list_to_atom(Name), slave, [{args, "-pa " ++ Pa}]),
+ Node.
+
+repeat_par(FunToRepeat, NrOfTimes) ->
+ repeat_par_help(FunToRepeat, NrOfTimes, NrOfTimes).
+
+repeat_par_help(_FunToRepeat, 0, OrgNrOfTimes) ->
+ repeat(fun()-> receive done -> ok end end, OrgNrOfTimes);
+repeat_par_help(FunToRepeat, NrOfTimes, OrgNrOfTimes) ->
+ Parent = self(),
+ case NrOfTimes rem 5 of
+ 0 -> timer:sleep(1);
+ _ -> ok
+ end,
+ spawn(fun()->
+ FunToRepeat(),
+ Parent ! done
+ end),
+ repeat_par_help(FunToRepeat, NrOfTimes-1, OrgNrOfTimes).
+
%% Test various duplicate_bags stuff.
dups(Config) when is_list(Config) ->
repeat_for_opts(fun dups_do/1).