From: Peter Zijlstra <peterz@infradead.org>
To: kernel test robot <oliver.sang@intel.com>
Cc: Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
lkp@lists.01.org, lkp@intel.com, ying.huang@intel.com,
feng.tang@intel.com, zhengjun.xing@intel.com,
Paul McKenney <paulmck@kernel.org>
Subject: Re: [entry] 47b8ff194c: will-it-scale.per_process_ops -3.0% regression
Date: Thu, 13 May 2021 10:19:21 +0200 [thread overview]
Message-ID: <YJzhCX/CqrMQDB+y@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210428071653.GC13086@xsang-OptiPlex-9020>
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?
---
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));
}
next prev parent reply other threads:[~2021-05-13 8:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-28 7:16 [entry] 47b8ff194c: will-it-scale.per_process_ops -3.0% regression kernel test robot
2021-05-13 8:19 ` Peter Zijlstra [this message]
2021-05-13 17:46 ` Paul E. McKenney
2021-05-13 23:11 ` Frederic Weisbecker
2021-05-14 10:13 ` Peter Zijlstra
2021-05-19 5:27 ` Oliver Sang
2021-05-23 13:26 ` Frederic Weisbecker
2021-05-26 6:20 ` Oliver Sang
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