| Message ID | 20221119081252.3864249-1-davidgow@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3,1/3] kunit: Provide a static key to check if KUnit is actively running tests | expand |
On Sat, Nov 19, 2022 at 12:13 AM David Gow <davidgow@google.com> wrote: > > KUnit does a few expensive things when enabled. This hasn't been a > problem because KUnit was only enabled on test kernels, but with a few > people enabling (but not _using_) KUnit on production systems, we need a > runtime way of handling this. > > Provide a 'kunit_running' static key (defaulting to false), which allows > us to hide any KUnit code behind a static branch. This should reduce the > performance impact (on other code) of having KUnit enabled to a single > NOP when no tests are running. > > Note that, while it looks unintuitive, tests always run entirely within > __kunit_test_suites_init(), so it's safe to decrement the static key at > the end of this function, rather than in __kunit_test_suites_exit(), > which is only there to clean up results in debugfs. > > Signed-off-by: David Gow <davidgow@google.com> Reviewed-by: Daniel Latypov <dlatypov@google.com> I didn't know anything about the static key support in the kernel before this patch. But from what I read and saw of other uses, this looks good to me. One small question/nit about how we declare the key below. <snip> > +/* Static key: true if any KUnit tests are currently running */ > +extern struct static_key_false kunit_running; Is there any documented preference between this and DECLARE_STATIC_KEY_FALSE(kunit_running); ? I see 89 instances of this macro and 45 of `extern struct static_key_false`. So I'd vote for the macro since it seems like the newer approach and more common. Daniel
On Tue, Nov 22, 2022 at 9:31 AM Daniel Latypov <dlatypov@google.com> wrote: > > On Sat, Nov 19, 2022 at 12:13 AM David Gow <davidgow@google.com> wrote: > > > > KUnit does a few expensive things when enabled. This hasn't been a > > problem because KUnit was only enabled on test kernels, but with a few > > people enabling (but not _using_) KUnit on production systems, we need a > > runtime way of handling this. > > > > Provide a 'kunit_running' static key (defaulting to false), which allows > > us to hide any KUnit code behind a static branch. This should reduce the > > performance impact (on other code) of having KUnit enabled to a single > > NOP when no tests are running. > > > > Note that, while it looks unintuitive, tests always run entirely within > > __kunit_test_suites_init(), so it's safe to decrement the static key at > > the end of this function, rather than in __kunit_test_suites_exit(), > > which is only there to clean up results in debugfs. > > > > Signed-off-by: David Gow <davidgow@google.com> > > Reviewed-by: Daniel Latypov <dlatypov@google.com> > > I didn't know anything about the static key support in the kernel > before this patch. > But from what I read and saw of other uses, this looks good to me. > > One small question/nit about how we declare the key below. > > <snip> > > > +/* Static key: true if any KUnit tests are currently running */ > > +extern struct static_key_false kunit_running; > > Is there any documented preference between this and > DECLARE_STATIC_KEY_FALSE(kunit_running); > ? > > I see 89 instances of this macro and 45 of `extern struct static_key_false`. > So I'd vote for the macro since it seems like the newer approach and > more common. > Yeah, there was no particular reason I put 'extern struct static_key_false'. I'll change it to DECLARE_STATIC_KEY_FALSE in v3. Cheers, -- David
diff --git a/include/kunit/test.h b/include/kunit/test.h index d7f60e8aab30..b948c32a7b6b 100644 --- a/include/kunit/test.h +++ b/include/kunit/test.h @@ -16,6 +16,7 @@ #include <linux/container_of.h> #include <linux/err.h> #include <linux/init.h> +#include <linux/jump_label.h> #include <linux/kconfig.h> #include <linux/kref.h> #include <linux/list.h> @@ -27,6 +28,9 @@ #include <asm/rwonce.h> +/* Static key: true if any KUnit tests are currently running */ +extern struct static_key_false kunit_running; + struct kunit; /* Size of log associated with test. */ diff --git a/lib/kunit/test.c b/lib/kunit/test.c index 90640a43cf62..314717b63080 100644 --- a/lib/kunit/test.c +++ b/lib/kunit/test.c @@ -20,6 +20,8 @@ #include "string-stream.h" #include "try-catch-impl.h" +DEFINE_STATIC_KEY_FALSE(kunit_running); + #if IS_BUILTIN(CONFIG_KUNIT) /* * Fail the current test and print an error message to the log. @@ -612,10 +614,14 @@ int __kunit_test_suites_init(struct kunit_suite * const * const suites, int num_ return 0; } + static_branch_inc(&kunit_running); + for (i = 0; i < num_suites; i++) { kunit_init_suite(suites[i]); kunit_run_tests(suites[i]); } + + static_branch_dec(&kunit_running); return 0; } EXPORT_SYMBOL_GPL(__kunit_test_suites_init);
KUnit does a few expensive things when enabled. This hasn't been a problem because KUnit was only enabled on test kernels, but with a few people enabling (but not _using_) KUnit on production systems, we need a runtime way of handling this. Provide a 'kunit_running' static key (defaulting to false), which allows us to hide any KUnit code behind a static branch. This should reduce the performance impact (on other code) of having KUnit enabled to a single NOP when no tests are running. Note that, while it looks unintuitive, tests always run entirely within __kunit_test_suites_init(), so it's safe to decrement the static key at the end of this function, rather than in __kunit_test_suites_exit(), which is only there to clean up results in debugfs. Signed-off-by: David Gow <davidgow@google.com> --- This should be a no-op (other than a possible performance improvement) functionality-wise, and lays the groundwork for a more optimised static stub implementation. The remaining patches in the series add a kunit_get_current_test() function which is a more friendly and performant wrapper around current->kunit_test, and use this in the slub test. They also improve the documentation a bit. If there are no objections, we'll take the whole series via the KUnit tree. No changes since v2: https://lore.kernel.org/all/20221025071907.1251820-1-davidgow@google.com/ Changes since v1: https://lore.kernel.org/linux-kselftest/20221021072854.333010-1-davidgow@google.com/ - No changes in this patch. - Patch 2/3 is reworked, patch 3/3 is new. --- include/kunit/test.h | 4 ++++ lib/kunit/test.c | 6 ++++++ 2 files changed, 10 insertions(+)