From 2ea5944504695496e2d8d0364ead14e871c71870 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 16 May 2017 09:22:02 +0200
Subject: Update instructions for how to start the lock-counting VM

---
 lib/tools/doc/src/lcnt_chapter.xml | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

(limited to 'lib')

diff --git a/lib/tools/doc/src/lcnt_chapter.xml b/lib/tools/doc/src/lcnt_chapter.xml
index 6cfdb5cf1b..362f212963 100644
--- a/lib/tools/doc/src/lcnt_chapter.xml
+++ b/lib/tools/doc/src/lcnt_chapter.xml
@@ -48,29 +48,19 @@
     </p>
     <section>
 	<title> Enabling lock-counting </title>
-	<p>For investigation of locks in the emulator we use an internal tool called <c>lcnt</c> (short for lock-count). The VM needs to be compiled with this option enabled. To enable this, use:</p>
+	<p>For investigation of locks in the emulator we use an internal tool called <c>lcnt</c> (short for lock-count). The VM needs to be compiled with this option enabled.
+	To compile a lock-counting VM along with a normal VM, use:</p>
 
 	<pre>
 cd $ERL_TOP
-./configure --enable-lock-counter
-	</pre>
-
-	<p>
-	    Another way to enable this alongside a normal VM is to compile it at emulator directory level, much like a debug build. To compile it this way do the following,
-	</p>
-	<pre>
-cd $ERL_TOP/erts/emulator
-make lcnt FLAVOR=smp
-	</pre>
-	<p> and then starting Erlang with,</p>
+./configure --enable-lock-counter</pre>
+	<p>Start the lock-counting VM like this:</p>
 	<pre>
-$ERL_TOP/bin/cerl -lcnt
-	</pre>
-	<p>To verify that you lock-counting enabled check that <c>[lock-counting]</c> appears in the status text when the VM is started.</p>
+$ERL_TOP/bin/erl -emu_type lcnt</pre>
+	<p>To verify that lock counting is enabled check that <c>[lock-counting]</c> appears in the status text when the VM is started.</p>
 	<pre>
-Erlang R13B03 (erts-5.7.4) [source] [64-bit] [smp:8:8] [rq:8] [async-threads:0] [hipe]
- [kernel-poll:false] [lock-counting]
-	</pre>
+Erlang/OTP 20 [erts-9.0] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:10] [hipe]
+ [kernel-poll:false] [lock-counting]</pre>
     </section>
     <section>
 	<title>Getting started</title>
-- 
cgit v1.2.3


From f3e32131000fc081cbaf2a1ca15f265783fbc040 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 16 May 2017 09:08:43 +0200
Subject: lcnt_SUITE: Add a smoke test for running lock-counting

---
 lib/tools/test/lcnt_SUITE.erl | 85 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 83 insertions(+), 2 deletions(-)

(limited to 'lib')

diff --git a/lib/tools/test/lcnt_SUITE.erl b/lib/tools/test/lcnt_SUITE.erl
index d39a5deeab..2e48b11740 100644
--- a/lib/tools/test/lcnt_SUITE.erl
+++ b/lib/tools/test/lcnt_SUITE.erl
@@ -29,7 +29,8 @@
 -export([t_load/1,
          t_conflicts/1,
          t_locations/1,
-         t_swap_keys/1]).
+         t_swap_keys/1,
+         smoke_lcnt/1]).
 
 init_per_testcase(_Case, Config) ->
     Config.
@@ -43,7 +44,8 @@ suite() ->
      {timetrap,{minutes,4}}].
 
 all() ->
-    [t_load, t_conflicts, t_locations, t_swap_keys].
+    [t_load, t_conflicts, t_locations, t_swap_keys,
+     smoke_lcnt].
 
 %%----------------------------------------------------------------------
 %% Tests
@@ -146,3 +148,82 @@ t_swap_keys_file([File|Files]) ->
     ok = lcnt:conflicts(),
     ok = lcnt:stop(),
     t_swap_keys_file(Files).
+
+%% Simple smoke test of actual lock-counting, if running on
+%% a run-time with lock-counting enabled.
+
+smoke_lcnt(Config) ->
+    case erlang:system_info(build_type) of
+        lcnt ->
+            do_smoke_lcnt(Config);
+        _ ->
+            {skip,"Lock counting is not enabled"}
+    end.
+
+do_smoke_lcnt(Config) ->
+    PrivDir = proplists:get_value(priv_dir, Config),
+    SaveFile = filename:join(PrivDir, atom_to_list(?FUNCTION_NAME)),
+    {Time,ok} = timer:tc(fun() -> lcnt:apply(fun() -> big_bang(200) end) end),
+    io:format("~p ms\n", [Time]),
+    ok = lcnt:conflicts(),
+    ok = lcnt:save(SaveFile),
+    ok = lcnt:load(SaveFile),
+    ok = lcnt:conflicts(),
+    lcnt:stop().
+
+
+%%%
+%%% A slightly modified version of Rickard Green's Big Bang benchmark.
+%%%
+
+big_bang(N) when is_integer(N) ->
+    Procs = spawn_procs(N),
+    RMsgs = lists:map(fun (P) -> {done, P} end, Procs),
+    send_procs(Procs, {procs, Procs, self()}),
+    receive_msgs(RMsgs),
+    lists:foreach(fun (P) -> exit(P, normal) end, Procs).
+
+pinger([], [], true) ->
+    receive
+        {procs, Procs, ReportTo} ->
+            pinger(Procs, [], ReportTo)
+    end;
+pinger([], [], false) ->
+    receive {ping, From} -> From ! {pong, self()} end,
+    pinger([],[],false);
+pinger([], [], ReportTo) ->
+    ReportTo ! {done, self()},
+    pinger([],[],false);
+pinger([],[Po|Pos] = Pongers, ReportTo) ->
+    receive
+        {ping, From} ->
+            From ! {pong, self()},
+            pinger([], Pongers, ReportTo);
+        {pong, Po} ->
+            pinger([], Pos, ReportTo)
+    end;
+pinger([Pi|Pis], Pongers, ReportTo) ->
+    receive {ping, From} -> From ! {pong, self()}
+    after 0 -> ok
+    end,
+    Pi ! {ping, self()},
+    pinger(Pis, [Pi|Pongers], ReportTo).
+
+spawn_procs(N) when N =< 0 ->
+    [];
+spawn_procs(N) ->
+    [spawn_link(fun () -> pinger([], [], true) end) | spawn_procs(N-1)].
+
+send_procs([], Msg) ->
+    Msg;
+send_procs([P|Ps], Msg) ->
+    P ! Msg,
+    send_procs(Ps, Msg).
+
+receive_msgs([]) ->
+    ok;
+receive_msgs([M|Ms]) ->
+    receive
+        M ->
+            receive_msgs(Ms)
+    end.
-- 
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