stdlib: Make ets_SUITE memory check try again

as memory stats do not guarantee consistency.

A typical ETS test case ends by a lot of deallocating
that may now trigger homecoming carrier migration,
that in turn can cause quite large inconsistencies
in memory stats when same carrier is accounted for twice
or not at all.

And that's my theory why I now sometimes see transient discrepancies
between before and after memory stats.

1 files changed, 21 insertions, 7 deletions

diff --git a/lib/stdlib/test/ets_SUITE.erl b/lib/stdlib/test/ets_SUITE.erl
index 00e02a06cc..a58497523a 100644
--- a/lib/stdlib/test/ets_SUITE.erl
+++ b/lib/stdlib/test/ets_SUITE.erl
@@ -5716,25 +5716,39 @@ etsmem() ->
 	 end},
     {Mem,AllTabs}.
 
-verify_etsmem({MemInfo,AllTabs}) ->
+
+verify_etsmem(MI) ->
     wait_for_test_procs(),
+    verify_etsmem(MI, 1).
+
+verify_etsmem({MemInfo,AllTabs}, Try) ->
     case etsmem() of
 	{MemInfo,_} ->
 	    io:format("Ets mem info: ~p", [MemInfo]),
-	    case MemInfo of
-		{ErlMem,EtsAlloc} when ErlMem == notsup; EtsAlloc == undefined ->
+	    case {MemInfo, Try} of
+		{{ErlMem,EtsAlloc},_} when ErlMem == notsup; EtsAlloc == undefined ->
 		    %% Use 'erl +Mea max' to do more complete memory leak testing.
 		    {comment,"Incomplete or no mem leak testing"};
-		_ ->
-		    ok
+		{_, 1} ->
+                    ok;
+                _ ->
+                    {comment, "Transient memory discrepancy"}
 	    end;
 	{MemInfo2, AllTabs2} ->
 	    io:format("Expected: ~p", [MemInfo]),
 	    io:format("Actual:   ~p", [MemInfo2]),
 	    io:format("Changed tables before: ~p\n",[AllTabs -- AllTabs2]),
 	    io:format("Changed tables after: ~p\n", [AllTabs2 -- AllTabs]),
-	    ets_test_spawn_logger ! {failed_memcheck, get('__ETS_TEST_CASE__')},
-	    {comment, "Failed memory check"}
+            case Try < 2 of
+                true ->
+                    io:format("\nThis discrepancy could be caused by an "
+                              "inconsistent memory \"snapshot\""
+                              "\nTry again...\n", []),
+                    verify_etsmem({MemInfo, AllTabs}, Try+1);
+                false ->
+                    ets_test_spawn_logger ! {failed_memcheck, get('__ETS_TEST_CASE__')},
+                    {comment, "Failed memory check"}
+            end
     end.