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-rw-r--r--erts/emulator/test/process_SUITE.erl50
1 files changed, 31 insertions, 19 deletions
diff --git a/erts/emulator/test/process_SUITE.erl b/erts/emulator/test/process_SUITE.erl
index e14185e881..a65c3f0cad 100644
--- a/erts/emulator/test/process_SUITE.erl
+++ b/erts/emulator/test/process_SUITE.erl
@@ -1024,36 +1024,48 @@ bump_big(Prev, Limit) ->
%% Priority 'low' should be mixed with 'normal' using a factor of
%% about 8. (OTP-2644)
low_prio(Config) when is_list(Config) ->
- case erlang:system_info(schedulers_online) of
- 1 ->
- ok = low_prio_test(Config);
- _ ->
- erlang:system_flag(multi_scheduling, block_normal),
- ok = low_prio_test(Config),
- erlang:system_flag(multi_scheduling, unblock_normal),
- {comment,
- "Test not written for SMP runtime system. "
- "Multi scheduling blocked during test."}
- end.
+ erlang:system_flag(multi_scheduling, block_normal),
+ Prop = low_prio_test(Config),
+ erlang:system_flag(multi_scheduling, unblock_normal),
+ Str = lists:flatten(io_lib:format("Low/high proportion is ~.3f",
+ [Prop])),
+ {comment,Str}.
low_prio_test(Config) when is_list(Config) ->
process_flag(trap_exit, true),
- S = spawn_link(?MODULE, prio_server, [0, 0]),
+
+ %% Spawn the server running with high priority. The server must
+ %% not run at normal priority as that would skew the results for
+ %% two reasons:
+ %%
+ %% 1. There would be one more normal-priority processes than
+ %% low-priority processes.
+ %%
+ %% 2. The receive queue would grow faster than the server process
+ %% could process it. That would in turn trigger the reduction
+ %% punishment for the clients.
+ S = spawn_opt(?MODULE, prio_server, [0, 0], [link,{priority,high}]),
+
+ %% Spawn the clients and let them run for a while.
PCs = spawn_prio_clients(S, erlang:system_info(schedulers_online)),
- ct:sleep({seconds,3}),
+ ct:sleep({seconds,2}),
lists:foreach(fun (P) -> exit(P, kill) end, PCs),
+
+ %% Stop the server and retrieve the result.
S ! exit,
- receive {'EXIT', S, {A, B}} -> check_prio(A, B) end,
- ok.
+ receive
+ {'EXIT', S, {A, B}} ->
+ check_prio(A, B)
+ end.
check_prio(A, B) ->
Prop = A/B,
ok = io:format("Low=~p, High=~p, Prop=~p\n", [A, B, Prop]),
- %% It isn't 1/8, it's more like 0.3, but let's check that
- %% the low-prio processes get some little chance to run at all.
- true = (Prop < 1.0),
- true = (Prop > 1/32).
+ %% Prop is expected to be appr. 1/8. Allow a reasonable margin.
+ true = Prop < 1/4,
+ true = Prop > 1/16,
+ Prop.
prio_server(A, B) ->
receive