selftests/mm: optionally pass duration to transhuge-stress

Until now, transhuge-stress runs until its explicitly killed, so when
invoked by run_kselftest.sh, it would run until the test timeout, then it
would be killed and the test would be marked as failed.

Add a new, optional command line parameter that allows the user to specify
the duration in seconds that the program should run.  The program exits
after this duration with a success (0) exit code.  If the argument is
omitted the old behacvior remains.

On it's own, this doesn't quite solve our problem because run_kselftest.sh
does not allow passing parameters to the program under test.  But we will
shortly move this to run_vmtests.sh, which does allow parameter passing.

Link: https://lkml.kernel.org/r/20230724082522.1202616-8-ryan.roberts@arm.comSigned-off-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/mm/transhuge-stress.c

@@ -25,13 +25,14 @@ int main(int argc, char **argv)
 {
 	size_t ram, len;
 	void *ptr, *p;
-	struct timespec a, b;
+	struct timespec start, a, b;
 	int i = 0;
 	char *name = NULL;
 	double s;
 	uint8_t *map;
 	size_t map_len;
 	int pagemap_fd;
+	int duration = 0;
 
 	ram = sysconf(_SC_PHYS_PAGES);
 	if (ram > SIZE_MAX / psize() / 4)
@@ -42,9 +43,11 @@ int main(int argc, char **argv)
 
 	while (++i < argc) {
 		if (!strcmp(argv[i], "-h"))
-			errx(1, "usage: %s [size in MiB]", argv[0]);
+			errx(1, "usage: %s [-f <filename>] [-d <duration>] [size in MiB]", argv[0]);
 		else if (!strcmp(argv[i], "-f"))
 			name = argv[++i];
+		else if (!strcmp(argv[i], "-d"))
+			duration = atoi(argv[++i]);
 		else
 			len = atoll(argv[i]) << 20;
 	}
@@ -78,6 +81,8 @@ int main(int argc, char **argv)
 	if (!map)
 		errx(2, "map malloc");
 
+	clock_gettime(CLOCK_MONOTONIC, &start);
+
 	while (1) {
 		int nr_succeed = 0, nr_failed = 0, nr_pages = 0;
 
@@ -118,5 +123,8 @@ int main(int argc, char **argv)
 		      "%4d succeed, %4d failed, %4d different pages",
 		      s, s * 1000 / (len >> HPAGE_SHIFT), len / s / (1 << 20),
 		      nr_succeed, nr_failed, nr_pages);
+
+		if (duration > 0 && b.tv_sec - start.tv_sec >= duration)
+			return 0;
 	}
 }