11 files changed, 23 insertions, 14 deletions
diff --git a/lib/compiler/test/andor_SUITE.erl b/lib/compiler/test/andor_SUITE.erl
index b5408ecd8f..22aa19522d 100644
--- a/lib/compiler/test/andor_SUITE.erl
+++ b/lib/compiler/test/andor_SUITE.erl
@@ -33,7 +33,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [t_case,t_and_or,t_andalso,t_orelse,inside,overlap,
        combined,in_case,before_and_inside_if]}].
 
diff --git a/lib/compiler/test/beam_utils_SUITE.erl b/lib/compiler/test/beam_utils_SUITE.erl
index 9142ca6485..d2e24cb5ae 100644
--- a/lib/compiler/test/beam_utils_SUITE.erl
+++ b/lib/compiler/test/beam_utils_SUITE.erl
@@ -32,7 +32,7 @@ all() ->
     [{group,p}].
 
 groups() ->
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [apply_fun,
        apply_mf,
        bs_init,
diff --git a/lib/compiler/test/bs_bit_binaries_SUITE.erl b/lib/compiler/test/bs_bit_binaries_SUITE.erl
index 8609a490f5..2433e7621e 100644
--- a/lib/compiler/test/bs_bit_binaries_SUITE.erl
+++ b/lib/compiler/test/bs_bit_binaries_SUITE.erl
@@ -37,7 +37,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [misc,horrid_match,test_bitstr,test_bit_size,
        asymmetric_tests,big_asymmetric_tests,
        binary_to_and_from_list,big_binary_to_and_from_list,
diff --git a/lib/compiler/test/bs_construct_SUITE.erl b/lib/compiler/test/bs_construct_SUITE.erl
index ce39de2a82..9df874c387 100644
--- a/lib/compiler/test/bs_construct_SUITE.erl
+++ b/lib/compiler/test/bs_construct_SUITE.erl
@@ -39,7 +39,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [two,test1,fail,float_bin,in_guard,in_catch,
        nasty_literals,side_effect,opt,otp_7556,float_arith,
        otp_8054]}].
diff --git a/lib/compiler/test/bs_match_SUITE.erl b/lib/compiler/test/bs_match_SUITE.erl
index e1710988d8..f7af56afcc 100644
--- a/lib/compiler/test/bs_match_SUITE.erl
+++ b/lib/compiler/test/bs_match_SUITE.erl
@@ -48,7 +48,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [fun_shadow,int_float,otp_5269,null_fields,wiger,
        bin_tail,save_restore,shadowed_size_var,
        partitioned_bs_match,function_clause,unit,
diff --git a/lib/compiler/test/core_fold_SUITE.erl b/lib/compiler/test/core_fold_SUITE.erl
index 6a7036d728..6e839f4c6e 100644
--- a/lib/compiler/test/core_fold_SUITE.erl
+++ b/lib/compiler/test/core_fold_SUITE.erl
@@ -36,7 +36,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [t_element,setelement,t_length,append,t_apply,bifs,
        eq,nested_call_in_case,guard_try_catch,coverage,
        unused_multiple_values_error,unused_multiple_values,
diff --git a/lib/compiler/test/guard_SUITE.erl b/lib/compiler/test/guard_SUITE.erl
index 882e2c3f8b..8db47ffa40 100644
--- a/lib/compiler/test/guard_SUITE.erl
+++ b/lib/compiler/test/guard_SUITE.erl
@@ -42,7 +42,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [misc,const_cond,basic_not,complex_not,nested_nots,
        semicolon,complex_semicolon,comma,or_guard,
        more_or_guards,complex_or_guards,and_guard,xor_guard,
diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl
index e5aaf49d6f..033988e4c8 100644
--- a/lib/compiler/test/match_SUITE.erl
+++ b/lib/compiler/test/match_SUITE.erl
@@ -33,7 +33,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [pmatch,mixed,aliases,match_in_call,untuplify,
        shortcut_boolean,letify_guard,selectify,
        underscore,match_map,coverage]}].
diff --git a/lib/compiler/test/misc_SUITE.erl b/lib/compiler/test/misc_SUITE.erl
index 5416e8b6c7..d721a86f5a 100644
--- a/lib/compiler/test/misc_SUITE.erl
+++ b/lib/compiler/test/misc_SUITE.erl
@@ -60,7 +60,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,[],%%test_lib:parallel(),
+    [{p,[],
       [tobias,empty_string,md5,silly_coverage,
        confused_literals,integer_encoding,override_bif]}].
 
diff --git a/lib/compiler/test/test_lib.erl b/lib/compiler/test/test_lib.erl
index a8befbecd9..e06e42276a 100644
--- a/lib/compiler/test/test_lib.erl
+++ b/lib/compiler/test/test_lib.erl
@@ -44,6 +44,10 @@ smoke_disasm(File) when is_list(File) ->
     Res = beam_disasm:file(File),
     {beam_file,_Mod} = {element(1, Res),element(2, Res)}.
 
+%% If we are running cover, we don't want to run test cases that
+%% invokes the compiler in parallel, as doing so would probably
+%% be slower than running them sequentially.
+
 parallel() ->
     case ?t:is_cover() orelse erlang:system_info(schedulers) =:= 1 of
 	true -> [];
@@ -90,13 +94,18 @@ get_data_dir(Config) ->
 %%  Will fail the test case if there were any errors.
 
 p_run(Test, List) ->
+    S = erlang:system_info(schedulers),
     N = case ?t:is_cover() of
 	    false ->
-		erlang:system_info(schedulers);
+		S + 1;
 	    true ->
-		%% Cover is running. Using more than one process
-		%% will probably only slow down compilation.
-		1
+		%% Cover is running. Using too many processes
+		%% could slow us down. Measurements on my computer
+		%% showed that using 4 parallel processes was
+		%% slightly faster than using 3. Using more than
+		%% 4 would not buy us much and could actually be
+		%% slower.
+		max(S, 4)
 	end,
     p_run_loop(Test, List, N, [], 0, 0).
 
diff --git a/lib/compiler/test/trycatch_SUITE.erl b/lib/compiler/test/trycatch_SUITE.erl
index 4530d08c77..b490257a6e 100644
--- a/lib/compiler/test/trycatch_SUITE.erl
+++ b/lib/compiler/test/trycatch_SUITE.erl
@@ -35,7 +35,7 @@ all() ->
     [{group,p}].
 
 groups() -> 
-    [{p,test_lib:parallel(),
+    [{p,[parallel],
       [basic,lean_throw,try_of,try_after,catch_oops,
        after_oops,eclectic,rethrow,nested_of,nested_catch,
        nested_after,nested_horrid,last_call_optimization,