From: "Zhang, Qiang1" <qiang1.zhang@intel.com>
To: Uladzislau Rezki <urezki@gmail.com>
Cc: "Zhuo, Qiuxu" <qiuxu.zhuo@intel.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
RCU <rcu@vger.kernel.org>,
"quic_neeraju@quicinc.com" <quic_neeraju@quicinc.com>,
Boqun Feng <boqun.feng@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
LKML <linux-kernel@vger.kernel.org>,
"Oleksiy Avramchenko" <oleksiy.avramchenko@sony.com>,
Steven Rostedt <rostedt@goodmis.org>,
Frederic Weisbecker <frederic@kernel.org>
Subject: RE: [PATCH 1/1] Reduce synchronize_rcu() waiting time
Date: Tue, 28 Mar 2023 00:14:07 +0000 [thread overview]
Message-ID: <PH0PR11MB5880E8E099868473028944D6DA889@PH0PR11MB5880.namprd11.prod.outlook.com> (raw)
In-Reply-To: <ZCHWxD7D9N7v115O@pc636>
> > > From: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > > Sent: Tuesday, March 21, 2023 6:28 PM [...]
> > > Subject: [PATCH 1/1] Reduce synchronize_rcu() waiting time
> > >
> > > A call to a synchronize_rcu() can be expensive from time point of view.
> > > Different workloads can be affected by this especially the ones
> > > which use this API in its time critical sections.
> > >
> >
> > This is interesting and meaningful research. ;-)
> >
> > > For example in case of NOCB scenario the wakeme_after_rcu()
> > > callback invocation depends on where in a nocb-list it is located.
> > > Below is an example when it was the last out of ~3600 callbacks:
> >
>
>
>
> Can it be implemented separately as follows? it seems that the code
> is simpler (only personal opinion) 😊.
>
> But I didn't test whether this reduce synchronize_rcu() waiting time
>
> +static void rcu_poll_wait_gp(struct rcu_tasks *rtp) {
> + unsigned long gp_snap;
> +
> + gp_snap = start_poll_synchronize_rcu();
> + while (!poll_state_synchronize_rcu(gp_snap))
> + schedule_timeout_idle(1); }
> +
> +void call_rcu_poll(struct rcu_head *rhp, rcu_callback_t func);
> +DEFINE_RCU_TASKS(rcu_poll, rcu_poll_wait_gp, call_rcu_poll,
> + "RCU Poll");
> +void call_rcu_poll(struct rcu_head *rhp, rcu_callback_t func) {
> + call_rcu_tasks_generic(rhp, func, &rcu_poll); }
> +EXPORT_SYMBOL_GPL(call_rcu_poll);
> +
> +void synchronize_rcu_poll(void)
> +{
> + synchronize_rcu_tasks_generic(&rcu_poll);
> +}
> +EXPORT_SYMBOL_GPL(synchronize_rcu_poll);
> +
> +static int __init rcu_spawn_poll_kthread(void) {
> + cblist_init_generic(&rcu_poll);
> + rcu_poll.gp_sleep = HZ / 10;
> + rcu_spawn_tasks_kthread_generic(&rcu_poll);
> + return 0;
> +}
>
>Uh.. I am working on v2 of original patch where i need to add a Kconfig parameter. You are inventing a new API :)
Looking forward to V2 😊.
Thanks
Zqiang
>
>--
>Uladzislau Rezki
next prev parent reply other threads:[~2023-03-28 0:14 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 10:27 [PATCH 1/1] Reduce synchronize_rcu() waiting time Uladzislau Rezki (Sony)
2023-03-21 14:03 ` Zhuo, Qiuxu
2023-03-21 15:15 ` Uladzislau Rezki
2023-03-22 1:49 ` Zhuo, Qiuxu
2023-03-22 6:50 ` Uladzislau Rezki
2023-03-22 11:21 ` Zhuo, Qiuxu
2023-03-27 11:21 ` Zhang, Qiang1
2023-03-27 17:47 ` Uladzislau Rezki
2023-03-28 0:14 ` Zhang, Qiang1 [this message]
2023-03-27 21:23 ` Joel Fernandes
2023-03-28 0:12 ` Zhang, Qiang1
2023-03-28 1:06 ` Paul E. McKenney
2023-03-28 1:32 ` Zhang, Qiang1
2023-03-28 1:59 ` Paul E. McKenney
2023-03-28 2:29 ` Joel Fernandes
2023-03-28 15:26 ` Paul E. McKenney
2023-03-28 22:14 ` Paul E. McKenney
2023-03-30 15:11 ` Joel Fernandes
2023-03-30 19:01 ` Paul E. McKenney
2023-03-30 15:09 ` Joel Fernandes
2023-03-30 15:43 ` Uladzislau Rezki
2023-03-30 18:58 ` Paul E. McKenney
2023-03-30 19:18 ` Uladzislau Rezki
2023-03-30 21:16 ` Paul E. McKenney
2023-03-31 10:55 ` Uladzislau Rezki
2023-03-31 18:39 ` Paul E. McKenney
2023-03-30 18:57 ` Paul E. McKenney
2023-03-27 21:48 ` Steven Rostedt
2023-03-27 21:50 ` Steven Rostedt
2023-03-28 1:28 ` Zhuo, Qiuxu
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