Messages in this thread | | | From | Daniel Latypov <> | Date | Sat, 11 Dec 2021 12:37:22 -0800 | Subject | Re: [PATCH] kunit: tool: Default --jobs to number of CPUs |
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On Sat, Dec 11, 2021 at 12:49 AM David Gow <davidgow@google.com> wrote: > > 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 present in the system: while there are as many > superstitions as to exactly what the ideal jobs:CPU ratio is, this seems > sufficiently sensible to me. > > Signed-off-by: David Gow <davidgow@google.com>
Reminder: the unit tests depend on this hard-coded value. $ ag '\b8\b' tools/testing/kunit/kunit_tool_test.py 422: self.linux_source_mock.build_kernel.assert_called_once_with(False, 8, '.kunit', None) 529: self.linux_source_mock.build_kernel.assert_called_once_with(False, 8, build_dir, None)
> --- > tools/testing/kunit/kunit.py | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/testing/kunit/kunit.py b/tools/testing/kunit/kunit.py > index 68e6f461c758..2cb6c7db5683 100755 > --- a/tools/testing/kunit/kunit.py > +++ b/tools/testing/kunit/kunit.py > @@ -310,7 +310,7 @@ 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=os.cpu_count(), metavar='jobs')
Just looking for edge cases: https://docs.python.org/3/library/os.html#os.cpu_count says > Returns None if undetermined and > This number is not equivalent to the number of CPUs the current process can use. The number of usable CPUs can be obtained with len(os.sched_getaffinity(0))
I assume the None caveat is mainly for other operating systems and doubt it'll impact any users. The second point is a bit more interesting, but still niche. Up to you if you want to use that instead.
Super unscientific comparison (n=1) running all on CPU #0
$ taskset 0x1 ./tools/testing/kunit/kunit.py run --jobs=1 Elapsed time: ... 155.978s building ...
--jobs=2 (some people swear by the 2x ratio) Elapsed time: ... 158.891s building ...
--jobs=8 (Old behavior) ... Elapsed time: ... 171.448s building
--jobs=32 Elapsed time: ... 170.765s building ...
So the overhead of j being "too high" isn't that bad and it doesn't seem to matter much either way.
> > def add_exec_opts(parser) -> None: > parser.add_argument('--timeout', > -- > 2.34.1.173.g76aa8bc2d0-goog >
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