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 <[email protected]>
---
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/[email protected]/
Changes since v1:
https://lore.kernel.org/linux-kselftest/[email protected]/
- 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(+)
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);
--
2.38.1.584.g0f3c55d4c2-goog
On Sat, Nov 19, 2022 at 12:13 AM David Gow <[email protected]> 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 <[email protected]>
Reviewed-by: Daniel Latypov <[email protected]>
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 <[email protected]> wrote:
>
> On Sat, Nov 19, 2022 at 12:13 AM David Gow <[email protected]> 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 <[email protected]>
>
> Reviewed-by: Daniel Latypov <[email protected]>
>
> 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