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SubjectRe: [PATCH RFC 3/3] locktorture: Make the rt_boost factor a tunable
On 2022-11-23 at 01:21:04 +0000, Joel Fernandes (Google) wrote:
> The rt boosting in locktorture has a factor variable large enough that
> boosting only happens once every minute or so. Add a tunable to educe
> 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
>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
> 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 5a388ac96a9b..e4529c2166e9 100644
> --- a/kernel/locking/locktorture.c
> +++ b/kernel/locking/locktorture.c
> @@ -47,6 +47,7 @@ torture_param(int, stat_interval, 60,
> "Number of seconds between stats printk()s");
> torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
> torture_param(int, rt_boost, 0, "Perform an rt-boost from the writer, always 1 for rtmutex_lock");
> +torture_param(int, rt_boost_factor, 50000, "A factor determining how often rt-boost happens");
> torture_param(int, verbose, 1,
> "Enable verbose debugging printk()s");
> torture_param(int, nlocks, 1,
> @@ -132,15 +133,15 @@ 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; /* yes, quite arbitrary */
>
> if (!rt_boost)
> return;
>
> 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) %
> @@ -150,8 +151,9 @@ 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
Maybe I understand incorrectly, the code is
cxt.nrealwriters_stress * factor * 2, should it be 2 rather than 10?
May I know where the 10 comes from?

thanks,
Chenyu

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