From 664ed2a6fd2b324bb6b56db3d3eca853cfda8f61 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang-solutions.com>
Date: Fri, 12 Sep 2014 16:38:00 +0200
Subject: erts: Add microstate accounting

Microstate accounting is a way to track which state the
different threads within ERTS are in. The main usage area
is to pin point performance bottlenecks by checking which
states the threads are in and then from there figuring out
why and where to optimize.

Since checking whether microstate accounting is on or off is
relatively expensive if done in a short loop only a few of the
states are enabled by default and more states can be enabled
through configure.

I've done some benchmarking and the overhead with it turned off
is not noticible and with it on it is a fraction of a percent.
If you enable the extra states, depending on the benchmark,
the ovehead when turned off is about 1% and when turned on
somewhere inbetween 5-15%.

OTP-12345
---
 erts/emulator/test/statistics_SUITE.erl | 95 ++++++++++++++++++++++++++++++++-
 1 file changed, 93 insertions(+), 2 deletions(-)

(limited to 'erts/emulator/test/statistics_SUITE.erl')

diff --git a/erts/emulator/test/statistics_SUITE.erl b/erts/emulator/test/statistics_SUITE.erl
index 53c9ba8715..a1b63716a9 100644
--- a/erts/emulator/test/statistics_SUITE.erl
+++ b/erts/emulator/test/statistics_SUITE.erl
@@ -32,7 +32,7 @@
 	 run_queue_one/1,
 	 scheduler_wall_time/1,
 	 reductions/1, reductions_big/1, garbage_collection/1, io/1,
-	 badarg/1, run_queues_lengths_active_tasks/1]).
+	 badarg/1, run_queues_lengths_active_tasks/1, msacc/1]).
 
 %% Internal exports.
 
@@ -55,7 +55,8 @@ all() ->
     [{group, wall_clock}, {group, runtime}, reductions,
      reductions_big, {group, run_queue}, scheduler_wall_time,
      garbage_collection, io, badarg,
-     run_queues_lengths_active_tasks].
+     run_queues_lengths_active_tasks,
+     msacc].
 
 groups() -> 
     [{wall_clock, [],
@@ -466,3 +467,93 @@ run_queues_lengths_active_tasks(Config) ->
 		  TokLoops),
 
     ok.
+
+msacc(doc) ->
+    "Tests that statistics(microstate_statistics) works.";
+msacc(Config) ->
+
+    %% Test if crypto nif is available
+    Niff = try crypto:strong_rand_bytes(1), ok catch _:_ -> nok end,
+    TmpFile = filename:join(proplists:get_value(priv_dir,Config),"file.tmp"),
+
+    false = erlang:system_flag(microstate_accounting, true),
+
+    msacc_test(TmpFile),
+
+    true = erlang:system_flag(microstate_accounting, false),
+
+    %% Make sure that all states were triggered at least once
+    maps:map(fun(nif, 0) ->
+                     case Niff of
+                         ok ->
+                             ct:fail({zero_state,nif});
+                         nok ->
+                             ok
+                     end;
+                (aux, 0) ->
+                     %% aux will be zero if we do not have smp support
+                     %% or no async threads
+                     case erlang:system_info(smp_support) orelse
+                         erlang:system_info(thread_pool_size) > 0 of
+                         false ->
+                             ok;
+                         true ->
+                             ct:log("msacc: ~p",[erlang:statistics(microstate_accounting)]),
+                             ct:fail({zero_state,aux})
+                         end;
+                 (Key, 0) ->
+                     ct:log("msacc: ~p",[erlang:statistics(microstate_accounting)]),
+                     ct:fail({zero_state,Key});
+                (_,_) -> ok
+             end,msacc_sum_states()),
+
+    erlang:system_flag(microstate_accounting, reset),
+
+    msacc_test(TmpFile),
+
+    %% Make sure all counters are zero after stopping and resetting
+    maps:map(fun(_Key, 0) -> ok;
+                (Key,_) ->
+                     ct:log("msacc: ~p",[erlang:statistics(microstate_accounting)]),
+                     ct:fail({non_zero_state,Key})
+             end,msacc_sum_states()).
+
+%% This test tries to make sure to trigger all of the different available states
+msacc_test(TmpFile) ->
+
+    %% We write some data
+    [file:write_file(TmpFile,<<0:(1024*1024*8)>>,[raw]) || _ <- lists:seq(1,100)],
+
+    %% Do some ETS operations
+    Tid = ets:new(table, []),
+    ets:insert(Tid, {1, hello}),
+    ets:delete(Tid),
+
+    %% Collect some garbage
+    [erlang:garbage_collect() || _ <- lists:seq(1,100)],
+
+    %% Send some messages
+    [begin self() ! {hello},receive _ -> ok end end ||  _ <- lists:seq(1,100)],
+
+    %% Setup some timers
+    Refs = [erlang:send_after(10000,self(),ok) ||  _ <- lists:seq(1,100)],
+
+    %% Do some nif work
+    catch [crypto:strong_rand_bytes(128) || _ <- lists:seq(1,100)],
+
+    %% Cancel some timers
+    [erlang:cancel_timer(R) ||  R <- Refs],
+
+    %% Wait for a while
+    timer:sleep(100).
+
+msacc_sum_states() ->
+    Stats = erlang:statistics(microstate_accounting),
+    [#{ counters := C }|_] = Stats,
+    InitialCounters = maps:map(fun(_,_) -> 0 end,C),
+    lists:foldl(fun(#{ counters := Counters }, Cnt) ->
+                        maps:fold(fun(Key, Value, Acc) ->
+                                          NewValue = Value+maps:get(Key,Acc),
+                                          maps:update(Key, NewValue, Acc)
+                                  end, Cnt, Counters)
+               end,InitialCounters,Stats).
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