Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Thu, 13 May 2021 10:19:21 +0200 | From | Peter Zijlstra <> | Subject | Re: [entry] 47b8ff194c: will-it-scale.per_process_ops -3.0% regression |
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On Wed, Apr 28, 2021 at 03:16:53PM +0800, kernel test robot wrote: > > > Greeting, > > FYI, we noticed a -3.0% regression of will-it-scale.per_process_ops due to commit: > > > commit: 47b8ff194c1fd73d58dc339b597d466fe48c8958 ("entry: Explicitly flush pending rcuog wakeup before last rescheduling point")
So the RCU bits are in rcu_user_enter(), which is called from __context_tracking_enter() aka user_enter(), which is under context_tracking_enabled().
But the new code in entry is not; we now unconditionally call rcu_nocb_flush_deferred_wakeup(). Did that want to be under context_tracking_enabled() as well?
Frederic, Paul?
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diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9455476c5ba2..f4df001410fc 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -114,7 +114,12 @@ static inline void rcu_user_exit(void) { } void rcu_init_nohz(void); int rcu_nocb_cpu_offload(int cpu); int rcu_nocb_cpu_deoffload(int cpu); -void rcu_nocb_flush_deferred_wakeup(void); +void __rcu_nocb_flush_deferred_wakeup(void); +static inline void rcu_nocb_flush_deferred_wakeup(void) +{ + if (context_tracking_enabled()) + __rcu_nocb_flush_deferred_wakeup(); +} #else /* #ifdef CONFIG_RCU_NOCB_CPU */ static inline void rcu_init_nohz(void) { } static inline int rcu_nocb_cpu_offload(int cpu) { return -EINVAL; } diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index ad0156b86937..3cdbbf7fba01 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2378,7 +2378,7 @@ static bool do_nocb_deferred_wakeup(struct rcu_data *rdp) return false; } -void rcu_nocb_flush_deferred_wakeup(void) +void __rcu_nocb_flush_deferred_wakeup(void) { do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data)); }
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