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Message-ID: <20221207221515.GI4001@paulmck-ThinkPad-P17-Gen-1>
Date: Wed, 7 Dec 2022 14:15:15 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org, Ben Segall <bsegall@...gle.com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Davidlohr Bueso <dave@...olabs.net>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Ingo Molnar <mingo@...hat.com>,
Josh Triplett <josh@...htriplett.org>,
Juri Lelli <juri.lelli@...hat.com>,
Mel Gorman <mgorman@...e.de>,
Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Valentin Schneider <vschneid@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
kernel-team@...roid.com, John Stultz <jstultz@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
Qais Yousef <qais.yousef@....com>,
Will Deacon <will@...nel.org>,
Waiman Long <longman@...hat.com>,
Boqun Feng <boqun.feng@...il.com>,
Connor O'Brien <connoro@...gle.com>
Subject: Re: [PATCH RFC 3/3] locktorture: Make the rt_boost factor a tunable
On Wed, Nov 23, 2022 at 01:21:04AM +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@...lfernandes.org>
This looks good, and is what I should have done to start with. But
it depends on the first commit, so I will hold off for the moment.
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 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
> + * 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.
> --
> 2.38.1.584.g0f3c55d4c2-goog
>
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