kunit: tool: Default --jobs to number of CPUs

The --jobs parameter for kunit_tool currently defaults to 8 CPUs,
regardless of the number available. For systems with significantly more
(or less), this is not as efficient. Instead, default --jobs to the
number of CPUs available to the process: while there are as many
superstitions as to exactly what the ideal jobs:CPU ratio is, this seems
sufficiently sensible to me.

A new helper function to get the default number of jobs is added:
get_default_jobs() -- this is used in kunit_tool_test instead of a
hardcoded value, or an explicit call to len(os.sched_getaffinity()), so
should be more flexible if this needs to change in the future.

Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

diff --git a/tools/testing/kunit/kunit.py b/tools/testing/kunit/kunit.py
index f1be718..7a706f9 100755 (executable)
--- a/tools/testing/kunit/kunit.py
+++ b/tools/testing/kunit/kunit.py
@@ -282,6 +282,9 @@ def massage_argv(argv: Sequence[str]) -> Sequence[str]:
                return  f'{arg}={pseudo_bool_flag_defaults[arg]}'
        return list(map(massage_arg, argv))
 
+def get_default_jobs() -> int:
+       return len(os.sched_getaffinity(0))
+
 def add_common_opts(parser) -> None:
        parser.add_argument('--build_dir',
                            help='As in the make command, it specifies the build '
@@ -332,7 +335,7 @@ def add_build_opts(parser) -> None:
        parser.add_argument('--jobs',
                            help='As in the make command, "Specifies  the number of '
                            'jobs (commands) to run simultaneously."',
-                           type=int, default=8, metavar='jobs')
+                           type=int, default=get_default_jobs(), metavar='jobs')
 
 def add_exec_opts(parser) -> None:
        parser.add_argument('--timeout',

diff --git a/tools/testing/kunit/kunit_tool_test.py b/tools/testing/kunit/kunit_tool_test.py
index b80e333..352369d 100755 (executable)
--- a/tools/testing/kunit/kunit_tool_test.py
+++ b/tools/testing/kunit/kunit_tool_test.py
@@ -527,7 +527,7 @@ class KUnitMainTest(unittest.TestCase):
        def test_build_passes_args_pass(self):
                kunit.main(['build'], self.linux_source_mock)
                self.assertEqual(self.linux_source_mock.build_reconfig.call_count, 1)
-               self.linux_source_mock.build_kernel.assert_called_once_with(False, 8, '.kunit', None)
+               self.linux_source_mock.build_kernel.assert_called_once_with(False, kunit.get_default_jobs(), '.kunit', None)
                self.assertEqual(self.linux_source_mock.run_kernel.call_count, 0)
 
        def test_exec_passes_args_pass(self):
@@ -633,8 +633,9 @@ class KUnitMainTest(unittest.TestCase):
 
        def test_build_builddir(self):
                build_dir = '.kunit'
+               jobs = kunit.get_default_jobs()
                kunit.main(['build', '--build_dir', build_dir], self.linux_source_mock)
-               self.linux_source_mock.build_kernel.assert_called_once_with(False, 8, build_dir, None)
+               self.linux_source_mock.build_kernel.assert_called_once_with(False, jobs, build_dir, None)
 
        def test_exec_builddir(self):
                build_dir = '.kunit'