On Thu, Jun 18, 2020 at 04:29:54PM -0400, Joel Fernandes (Google) wrote:
> This is useful to check for any improvements or degradation related to
> number of GP kthread wakeups during testing.
>
> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
This was a good way to collect the data for your testing, but
we can expect rcutorture to only do so much. ;-)
Thanx, Paul
> ---
> kernel/rcu/Kconfig.debug | 1 +
> kernel/rcu/rcu.h | 2 ++
> kernel/rcu/rcutorture.c | 23 ++++++++++++++++++++++-
> kernel/rcu/tree.c | 7 +++++++
> 4 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
> index 3cf6132a4bb9f..3323e3378af5a 100644
> --- a/kernel/rcu/Kconfig.debug
> +++ b/kernel/rcu/Kconfig.debug
> @@ -50,6 +50,7 @@ config RCU_TORTURE_TEST
> select TASKS_RCU
> select TASKS_RUDE_RCU
> select TASKS_TRACE_RCU
> + select SCHEDSTATS
> default n
> help
> This option provides a kernel module that runs torture tests
> diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> index cf66a3ccd7573..7e867e81d9738 100644
> --- a/kernel/rcu/rcu.h
> +++ b/kernel/rcu/rcu.h
> @@ -511,6 +511,7 @@ srcu_batches_completed(struct srcu_struct *sp) { return 0; }
> static inline void rcu_force_quiescent_state(void) { }
> static inline void show_rcu_gp_kthreads(void) { }
> static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
> +static inline struct task_struct *rcu_get_main_gp_kthread(void) { return 0; }
> static inline void rcu_fwd_progress_check(unsigned long j) { }
> #else /* #ifdef CONFIG_TINY_RCU */
> bool rcu_dynticks_zero_in_eqs(int cpu, int *vp);
> @@ -519,6 +520,7 @@ unsigned long rcu_exp_batches_completed(void);
> unsigned long srcu_batches_completed(struct srcu_struct *sp);
> void show_rcu_gp_kthreads(void);
> int rcu_get_gp_kthreads_prio(void);
> +struct task_struct *rcu_get_main_gp_kthread(void);
> void rcu_fwd_progress_check(unsigned long j);
> void rcu_force_quiescent_state(void);
> extern struct workqueue_struct *rcu_gp_wq;
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index d0d265304d147..959a1f84d6904 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -23,6 +23,7 @@
> #include <linux/rcupdate_wait.h>
> #include <linux/interrupt.h>
> #include <linux/sched/signal.h>
> +#include <linux/sched/stat.h>
> #include <uapi/linux/sched/types.h>
> #include <linux/atomic.h>
> #include <linux/bitops.h>
> @@ -460,9 +461,29 @@ static void rcu_sync_torture_init(void)
> INIT_LIST_HEAD(&rcu_torture_removed);
> }
>
> +unsigned long rcu_gp_nr_wakeups;
> +
> +static void rcu_flavor_init(void)
> +{
> + rcu_sync_torture_init();
> +
> + /* Make sure schedstat is enabled for GP thread wakeup count. */
> + force_schedstat_enabled();
> + rcu_gp_nr_wakeups = rcu_get_main_gp_kthread()->se.statistics.nr_wakeups;
> +}
> +
> +static void rcu_flavor_cleanup(void)
> +{
> + unsigned long now_nr = rcu_get_main_gp_kthread()->se.statistics.nr_wakeups;
> +
> + pr_alert("End-test: Cleanup: Total GP-kthread wakeups: %lu\n",
> + now_nr - rcu_gp_nr_wakeups);
> +}
> +
> static struct rcu_torture_ops rcu_ops = {
> .ttype = RCU_FLAVOR,
> - .init = rcu_sync_torture_init,
> + .init = rcu_flavor_init,
> + .cleanup = rcu_flavor_cleanup,
> .readlock = rcu_torture_read_lock,
> .read_delay = rcu_read_delay,
> .readunlock = rcu_torture_read_unlock,
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index c3bae7a83d792..a3a175feb310a 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -175,6 +175,13 @@ int rcu_get_gp_kthreads_prio(void)
> }
> EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio);
>
> +/* Retrieve RCU's main GP kthread task_struct */
> +struct task_struct *rcu_get_main_gp_kthread(void)
> +{
> + return rcu_state.gp_kthread;
> +}
> +EXPORT_SYMBOL_GPL(rcu_get_main_gp_kthread);
> +
> /*
> * Number of grace periods between delays, normalized by the duration of
> * the delay. The longer the delay, the more the grace periods between
> --
> 2.27.0.111.gc72c7da667-goog
>
