[v3,rcu/dev,2/2] locktorture: Make the rt_boost factor a tunable
Commit Message
The rt boosting in locktorture has a factor variable s currently large enough
that boosting only happens once every minute or so. Add a tunable to reduce the
factor so that boosting happens more often, to test paths and arrive at failure
modes earlier. With this change, I can set the factor to like 50 and have the
boosting happens every 10 seconds or so.
Tested with boot parameters:
locktorture.torture_type=mutex_lock
locktorture.onoff_interval=1
locktorture.nwriters_stress=8
locktorture.stutter=0
locktorture.rt_boost=1
locktorture.rt_boost_factor=50
locktorture.nlocks=3
[ Apply Davidlohr Bueso feedback on quoting rt_boost_factor. ]
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
kernel/locking/locktorture.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
Comments
On Tue, Dec 13, 2022 at 08:48:39PM +0000, Joel Fernandes (Google) wrote:
> The rt boosting in locktorture has a factor variable s currently large enough
> that boosting only happens once every minute or so. Add a tunable to reduce the
> factor so that boosting happens more often, to test paths and arrive at failure
> modes earlier. With this change, I can set the factor to like 50 and have the
> boosting happens every 10 seconds or so.
>
> Tested with boot parameters:
> locktorture.torture_type=mutex_lock
> locktorture.onoff_interval=1
> locktorture.nwriters_stress=8
> locktorture.stutter=0
> locktorture.rt_boost=1
> locktorture.rt_boost_factor=50
> locktorture.nlocks=3
>
> [ Apply Davidlohr Bueso feedback on quoting rt_boost_factor. ]
>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Queued and pushed both, thank you both!
I am not seeing any evidence of boot parameters being quoted in the
kernel/locking directory, and I don't feel like I should be the one to
be the first to push that convention into kernel/locking, so I left that
change off. I don't have an opinion either way on it myself, aside from
being more than a bit wary of the churn that would be required to impose
this convention uniformly.
Thanx, Paul
> ---
> kernel/locking/locktorture.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> index e2271e8fc302..87e861da0ad5 100644
> --- a/kernel/locking/locktorture.c
> +++ b/kernel/locking/locktorture.c
> @@ -48,6 +48,7 @@ torture_param(int, stat_interval, 60,
> torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
> torture_param(int, rt_boost, 2,
> "Do periodic rt-boost. 0=Disable, 1=Only for rt_mutex, 2=For all lock types.");
> +torture_param(int, rt_boost_factor, 50, "A factor determining how often rt-boost happens.");
> torture_param(int, verbose, 1,
> "Enable verbose debugging printk()s");
>
> @@ -131,12 +132,12 @@ static void torture_lock_busted_write_unlock(int tid __maybe_unused)
>
> static void __torture_rt_boost(struct torture_random_state *trsp)
> {
> - const unsigned int factor = 50000; /* yes, quite arbitrary */
> + const unsigned int factor = rt_boost_factor;
>
> if (!rt_task(current)) {
> /*
> - * Boost priority once every ~50k operations. When the
> - * task tries to take the lock, the rtmutex it will account
> + * Boost priority once every 'rt_boost_factor' operations. When
> + * the task tries to take the lock, the rtmutex it will account
> * for the new priority, and do any corresponding pi-dance.
> */
> if (trsp && !(torture_random(trsp) %
> @@ -146,8 +147,9 @@ static void __torture_rt_boost(struct torture_random_state *trsp)
> return;
> } else {
> /*
> - * The task will remain boosted for another ~500k operations,
> - * then restored back to its original prio, and so forth.
> + * The task will remain boosted for another 10 * 'rt_boost_factor'
> + * operations, then restored back to its original prio, and so
> + * forth.
> *
> * When @trsp is nil, we want to force-reset the task for
> * stopping the kthread.
> --
> 2.39.0.314.g84b9a713c41-goog
>
@@ -48,6 +48,7 @@ torture_param(int, stat_interval, 60,
torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
torture_param(int, rt_boost, 2,
"Do periodic rt-boost. 0=Disable, 1=Only for rt_mutex, 2=For all lock types.");
+torture_param(int, rt_boost_factor, 50, "A factor determining how often rt-boost happens.");
torture_param(int, verbose, 1,
"Enable verbose debugging printk()s");
@@ -131,12 +132,12 @@ static void torture_lock_busted_write_unlock(int tid __maybe_unused)
static void __torture_rt_boost(struct torture_random_state *trsp)
{
- const unsigned int factor = 50000; /* yes, quite arbitrary */
+ const unsigned int factor = rt_boost_factor;
if (!rt_task(current)) {
/*
- * Boost priority once every ~50k operations. When the
- * task tries to take the lock, the rtmutex it will account
+ * Boost priority once every 'rt_boost_factor' operations. When
+ * the task tries to take the lock, the rtmutex it will account
* for the new priority, and do any corresponding pi-dance.
*/
if (trsp && !(torture_random(trsp) %
@@ -146,8 +147,9 @@ static void __torture_rt_boost(struct torture_random_state *trsp)
return;
} else {
/*
- * The task will remain boosted for another ~500k operations,
- * then restored back to its original prio, and so forth.
+ * The task will remain boosted for another 10 * 'rt_boost_factor'
+ * operations, then restored back to its original prio, and so
+ * forth.
*
* When @trsp is nil, we want to force-reset the task for
* stopping the kthread.