linux-kernel - Re: [PATCH] [RFC] rcu/tree: Reduce wake up for synchronize

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Date: Thu, 7 Mar 2024 16:06:06 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Joel Fernandes <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org, frederic@...nel.org, boqun.feng@...il.com,
	urezki@...il.com, neeraj.iitr10@...il.com, rcu@...r.kernel.org,
	rostedt@...dmis.org, Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>
Subject: Re: [PATCH] [RFC] rcu/tree: Reduce wake up for synchronize_rcu()
 common case

On Thu, Mar 07, 2024 at 06:52:14PM -0500, Joel Fernandes wrote:
> On Thu, Mar 7, 2024 at 6:48 PM Joel Fernandes (Google)
> <joel@...lfernandes.org> wrote:
> >
> > In the synchronize_rcu() common case, we will have less than
> > SR_MAX_USERS_WAKE_FROM_GP number of users per GP. Waking up the kworker
> > is pointless just to free the last injected wait head since at that point,
> > all the users have already been awakened.
> >
> > Introduce a new counter to track this and prevent the wakeup in the
> > common case.
> >
> > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> > ---
> 
> Forgot to mention, this is based on the latest RCU -dev branch and
> passes light rcutorture testing on all configs. Heavier rcutorture
> testing (60 minutes) was performed on TREE03.

Very good, thank you!

Uladzislau, could you please pull this into the next series you send?
I can then replace your commits in -rcu with the updated series.

							Thanx, Paul