Support parallel testing in libgomp, part II [PR66005]

..., and enable if 'flock' is available for serializing execution testing.

Regarding the default of 19 parallel slots, this turned out to be a local
minimum for wall time when testing this on:

    $ uname -srvi
    Linux 4.2.0-42-generic #49~14.04.1-Ubuntu SMP Wed Jun 29 20:22:11 UTC 2016 x86_64
    $ grep '^model name' < /proc/cpuinfo | uniq -c
         32 model name      : Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz

... in two configurations: case (a) standard configuration, no offloading
configured, case (b) offloading for GCN and nvptx configured but no devices
available.  For both cases, default plus '-m32' variant.

    $ \time make check-target-libgomp RUNTESTFLAGS="--target_board=unix\{,-m32\}"

Case (a), baseline:

    6432.23user 332.38system 47:32.28elapsed 237%CPU (0avgtext+0avgdata 505044maxresident)k
    6382.43user 319.21system 47:06.04elapsed 237%CPU (0avgtext+0avgdata 505172maxresident)k

This is what people have been complaining about, rightly so, in
<https://gcc.gnu.org/PR66005> "libgomp make check time is excessive" and
elsewhere.

Case (a), parallelized:

    -j12 GCC_TEST_PARALLEL_SLOTS=10
    3088.49user 267.74system 6:43.82elapsed 831%CPU (0avgtext+0avgdata 505188maxresident)k
    -j15 GCC_TEST_PARALLEL_SLOTS=15
    3308.08user 294.79system 5:56.04elapsed 1011%CPU (0avgtext+0avgdata 505360maxresident)k
    -j17 GCC_TEST_PARALLEL_SLOTS=17
    3539.93user 298.99system 5:27.86elapsed 1170%CPU (0avgtext+0avgdata 505112maxresident)k
    -j18 GCC_TEST_PARALLEL_SLOTS=18
    3697.50user 317.18system 5:14.63elapsed 1275%CPU (0avgtext+0avgdata 505360maxresident)k
    -j19 GCC_TEST_PARALLEL_SLOTS=19
    3765.94user 324.27system 5:13.22elapsed 1305%CPU (0avgtext+0avgdata 505128maxresident)k
    -j20 GCC_TEST_PARALLEL_SLOTS=20
    3684.66user 312.32system 5:15.26elapsed 1267%CPU (0avgtext+0avgdata 505100maxresident)k
    -j23 GCC_TEST_PARALLEL_SLOTS=23
    4040.59user 347.10system 5:29.12elapsed 1333%CPU (0avgtext+0avgdata 505200maxresident)k
    -j26 GCC_TEST_PARALLEL_SLOTS=26
    3973.24user 377.96system 5:24.70elapsed 1340%CPU (0avgtext+0avgdata 505160maxresident)k
    -j32 GCC_TEST_PARALLEL_SLOTS=32
    4004.42user 346.10system 5:16.11elapsed 1376%CPU (0avgtext+0avgdata 505160maxresident)k

Yay!

Case (b), baseline; 2+ h:

    7227.58user 700.54system 2:14:33elapsed 98%CPU (0avgtext+0avgdata 994264maxresident)k

Case (b), parallelized:

    -j12 GCC_TEST_PARALLEL_SLOTS=10
    7377.46user 777.52system 16:06.63elapsed 843%CPU (0avgtext+0avgdata 994344maxresident)k
    -j15 GCC_TEST_PARALLEL_SLOTS=15
    8019.18user 721.42system 12:13.56elapsed 1191%CPU (0avgtext+0avgdata 994228maxresident)k
    -j17 GCC_TEST_PARALLEL_SLOTS=17
    8530.11user 716.95system 10:45.92elapsed 1431%CPU (0avgtext+0avgdata 994176maxresident)k
    -j18 GCC_TEST_PARALLEL_SLOTS=18
    8776.79user 645.89system 10:27.20elapsed 1502%CPU (0avgtext+0avgdata 994248maxresident)k
    -j19 GCC_TEST_PARALLEL_SLOTS=19
    9332.37user 641.76system 10:15.09elapsed 1621%CPU (0avgtext+0avgdata 994260maxresident)k
    -j20 GCC_TEST_PARALLEL_SLOTS=20
    9609.54user 789.88system 10:26.94elapsed 1658%CPU (0avgtext+0avgdata 994284maxresident)k
    -j23 GCC_TEST_PARALLEL_SLOTS=23
    10362.40user 911.14system 10:44.47elapsed 1749%CPU (0avgtext+0avgdata 994208maxresident)k
    -j26 GCC_TEST_PARALLEL_SLOTS=26
    11159.44user 850.99system 11:09.25elapsed 1794%CPU (0avgtext+0avgdata 994256maxresident)k
    -j32 GCC_TEST_PARALLEL_SLOTS=32
    11453.50user 939.52system 11:00.38elapsed 1876%CPU (0avgtext+0avgdata 994240maxresident)k

On my Dell Precision 7530 laptop:

    $ uname -srvi
    Linux 5.15.0-71-generic #78-Ubuntu SMP Tue Apr 18 09:00:29 UTC 2023 x86_64
    $ grep '^model name' < /proc/cpuinfo | uniq -c
         12 model name      : Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
    $ nvidia-smi -L
    GPU 0: Quadro P1000 (UUID: GPU-e043973b-b52a-d02b-c066-a8fdbf64e8ea)

... in two configurations: case (c) standard configuration, no offloading
configured, case (d) offloading for nvptx configured and device available.
For both cases, only default variant, no '-m32'.

    $ \time make check-target-libgomp

Case (c), baseline; roughly half of case (a) (just one variant):

    1180.98user 110.80system 19:36.40elapsed 109%CPU (0avgtext+0avgdata 505148maxresident)k
    1133.22user 111.08system 19:35.75elapsed 105%CPU (0avgtext+0avgdata 505212maxresident)k

Case (c), parallelized:

    -j12 GCC_TEST_PARALLEL_SLOTS=2
    1143.83user 110.76system 10:20.46elapsed 202%CPU (0avgtext+0avgdata 505216maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=6
    1737.08user 143.94system 4:59.48elapsed 628%CPU (0avgtext+0avgdata 505200maxresident)k
    1730.31user 143.02system 4:58.75elapsed 627%CPU (0avgtext+0avgdata 505152maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=8
    2192.63user 169.34system 4:52.96elapsed 806%CPU (0avgtext+0avgdata 505216maxresident)k
    2219.04user 167.67system 4:53.19elapsed 814%CPU (0avgtext+0avgdata 505152maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=10
    2463.93user 184.98system 4:48.39elapsed 918%CPU (0avgtext+0avgdata 505200maxresident)k
    2455.62user 183.68system 4:47.40elapsed 918%CPU (0avgtext+0avgdata 505216maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=12
    2591.04user 192.64system 4:44.98elapsed 976%CPU (0avgtext+0avgdata 505216maxresident)k
    2581.23user 195.21system 4:47.51elapsed 965%CPU (0avgtext+0avgdata 505212maxresident)k
    -j20 GCC_TEST_PARALLEL_SLOTS=20 [oversubscribe]
    2613.18user 199.51system 4:44.06elapsed 990%CPU (0avgtext+0avgdata 505216maxresident)k

Case (d), baseline (compared to case (b): only nvptx offloading compilation,
but also nvptx offloading execution); ~1 h:

    2841.93user 653.68system 1:02:26elapsed 93%CPU (0avgtext+0avgdata 909792maxresident)k
    2842.03user 654.39system 1:02:24elapsed 93%CPU (0avgtext+0avgdata 909880maxresident)k

Case (d), parallelized:

    -j12 GCC_TEST_PARALLEL_SLOTS=2
    2856.39user 606.87system 33:58.64elapsed 169%CPU (0avgtext+0avgdata 909948maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=6
    3444.90user 666.86system 18:37.57elapsed 367%CPU (0avgtext+0avgdata 909856maxresident)k
    3462.13user 667.13system 18:36.87elapsed 369%CPU (0avgtext+0avgdata 909872maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=8
    3929.74user 716.22system 18:02.36elapsed 429%CPU (0avgtext+0avgdata 909832maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=10
    4152.84user 736.16system 17:43.05elapsed 459%CPU (0avgtext+0avgdata 909872maxresident)k
    -j12 GCC_TEST_PARALLEL_SLOTS=12
    4209.60user 749.00system 17:35.20elapsed 469%CPU (0avgtext+0avgdata 909840maxresident)k
    -j20 GCC_TEST_PARALLEL_SLOTS=20 [oversubscribe]
    4255.54user 756.78system 17:29.06elapsed 477%CPU (0avgtext+0avgdata 909868maxresident)k

Worth noting is that with nvptx offloading, there is one execution test case
that times out ('libgomp.fortran/reverse-offload-5.f90').  This effectively
stalls progress for almost 5 min: quickly other executions test cases queue up
on the lock for all parallel slots.  That's working as expected; just noting
this as it accordingly does skew the wall time numbers.

	PR testsuite/66005
	libgomp/
	* configure.ac: Look for 'flock'.
	* testsuite/Makefile.am (gcc_test_parallel_slots): Enable parallel testing.
	* testsuite/config/default.exp: Don't 'load_lib "standard.exp"' here...
	* testsuite/lib/libgomp.exp: ... but here, instead.
	(libgomp_load): Override for parallel testing.
	* testsuite/libgomp-site-extra.exp.in (FLOCK): Set.
	* configure: Regenerate.
	* Makefile.in: Regenerate.
	* testsuite/Makefile.in: Regenerate.

5 files changed, 35 insertions, 4 deletions

diff --git a/libgomp/testsuite/Makefile.am b/libgomp/testsuite/Makefile.am
index eef02f4a..0cc91cc 100644
--- a/libgomp/testsuite/Makefile.am
+++ b/libgomp/testsuite/Makefile.am
@@ -73,7 +73,8 @@ check_p_numbers4:=$(foreach i,$(check_p_numbers0),$(addprefix $(i),$(check_p_num
 check_p_numbers5:=$(addprefix 0,$(check_p_numbers3)) $(check_p_numbers4)
 check_p_numbers6:=$(foreach i,$(check_p_numbers0),$(addprefix $(i),$(check_p_numbers5)))
 check_p_numbers:=$(check_p_numbers0) $(check_p_numbers2) $(check_p_numbers4) $(check_p_numbers6)
-gcc_test_parallel_slots:=1
+# If unable to serialize execution testing, use just one parallel slot.
+gcc_test_parallel_slots:=$(if $(FLOCK),$(if $(GCC_TEST_PARALLEL_SLOTS),$(GCC_TEST_PARALLEL_SLOTS),19),1)
 check_p_subdirs=$(wordlist 1,$(gcc_test_parallel_slots),$(check_p_numbers))
 check_DEJAGNU_libgomp_targets = $(addprefix check-DEJAGNUlibgomp,$(check_p_subdirs))
 $(check_DEJAGNU_libgomp_targets): check-DEJAGNUlibgomp%: libgomp%/site.exp
diff --git a/libgomp/testsuite/Makefile.in b/libgomp/testsuite/Makefile.in
index 69d5fa7..7215c86 100644
--- a/libgomp/testsuite/Makefile.in
+++ b/libgomp/testsuite/Makefile.in
@@ -162,6 +162,7 @@ EXEEXT = @EXEEXT@
 FC = @FC@
 FCFLAGS = @FCFLAGS@
 FGREP = @FGREP@
+FLOCK = @FLOCK@
 GREP = @GREP@
 INSTALL = @INSTALL@
 INSTALL_DATA = @INSTALL_DATA@
@@ -310,7 +311,8 @@ check_p_numbers4 := $(foreach i,$(check_p_numbers0),$(addprefix $(i),$(check_p_n
 check_p_numbers5 := $(addprefix 0,$(check_p_numbers3)) $(check_p_numbers4)
 check_p_numbers6 := $(foreach i,$(check_p_numbers0),$(addprefix $(i),$(check_p_numbers5)))
 check_p_numbers := $(check_p_numbers0) $(check_p_numbers2) $(check_p_numbers4) $(check_p_numbers6)
-gcc_test_parallel_slots := 1
+# If unable to serialize execution testing, use just one parallel slot.
+gcc_test_parallel_slots := $(if $(FLOCK),$(if $(GCC_TEST_PARALLEL_SLOTS),$(GCC_TEST_PARALLEL_SLOTS),19),1)
 check_p_subdirs = $(wordlist 1,$(gcc_test_parallel_slots),$(check_p_numbers))
 check_DEJAGNU_libgomp_targets = $(addprefix check-DEJAGNUlibgomp,$(check_p_subdirs))
 all: all-am
diff --git a/libgomp/testsuite/config/default.exp b/libgomp/testsuite/config/default.exp
index b7afc82..01569e6 100644
--- a/libgomp/testsuite/config/default.exp
+++ b/libgomp/testsuite/config/default.exp
@@ -13,5 +13,3 @@
 # You should have received a copy of the GNU General Public License
 # along with this program; see the file COPYING3.  If not see
 # <http://www.gnu.org/licenses/>.
-
-load_lib "standard.exp"
diff --git a/libgomp/testsuite/lib/libgomp.exp b/libgomp/testsuite/lib/libgomp.exp
index 4f938b3..3ad5503 100644
--- a/libgomp/testsuite/lib/libgomp.exp
+++ b/libgomp/testsuite/lib/libgomp.exp
@@ -9,6 +9,7 @@ proc load_gcc_lib { filename } {
 }
 
 load_lib dg.exp
+load_lib standard.exp
 
 # Required to use gcc-dg.exp - however, the latter should NOT be
 # loaded until ${tool}_target_compile is defined since it uses that
@@ -327,6 +328,34 @@ proc libgomp_option_proc { option } {
     }
 }
 
+if ![info exists ::env(GCC_RUNTEST_PARALLELIZE_DIR)] {
+    # No parallel testing.
+} elseif { $FLOCK == "" } {
+    # Using just one parallel slot.
+} else {
+    # Using several parallel slots.  Override DejaGnu
+    # 'standard.exp:${tool}_load'...
+    rename libgomp_load standard_libgomp_load
+    proc libgomp_load { program args } {
+	# ... in order to serialize execution testing via an exclusive lock.
+	set lock_file ../lock
+	set lock_kind --exclusive
+	set lock_fd [open $lock_file a+]
+	set lock_clock_begin [clock seconds]
+	global FLOCK
+	exec $FLOCK $lock_kind 0 <@ $lock_fd
+	set lock_clock_end [clock seconds]
+	verbose -log "Got ${FLOCK}('$lock_file', '$lock_kind') at [clock format $lock_clock_end] after [expr $lock_clock_end - $lock_clock_begin] s" 2
+
+	set result [standard_libgomp_load $program $args]
+
+	# Unlock (implicit with 'close').
+	close $lock_fd
+
+	return $result
+    }
+}
+
 # Translate offload target to OpenACC device type.  Return the empty string if
 # not supported, and 'host' for offload target 'disable'.
 proc offload_target_to_openacc_device_type { offload_target } {
diff --git a/libgomp/testsuite/libgomp-site-extra.exp.in b/libgomp/testsuite/libgomp-site-extra.exp.in
index 15407ab..c824d85 100644
--- a/libgomp/testsuite/libgomp-site-extra.exp.in
+++ b/libgomp/testsuite/libgomp-site-extra.exp.in
@@ -1,3 +1,4 @@
+set FLOCK {@FLOCK@}
 set GCC_UNDER_TEST {@CC@}
 set GXX_UNDER_TEST {@CXX@}
 set GFORTRAN_UNDER_TEST {@FC@}