linux-kernel - Re: [PATCH 4/9] rcu: Register rcu-lazy shrinker only for CONFIG_RCU

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Date:   Thu, 16 Mar 2023 02:28:53 +0000
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Zqiang <qiang1.zhang@...el.com>, rcu@...r.kernel.org
Subject: Re: [PATCH 4/9] rcu: Register rcu-lazy shrinker only for
 CONFIG_RCU_LAZY=y kernels

On Thu, Mar 16, 2023 at 12:19:19AM +0100, Frederic Weisbecker wrote:
> Le Wed, Mar 15, 2023 at 07:43:44PM +0000, Joel Fernandes (Google) a écrit :
> > From: Zqiang <qiang1.zhang@...el.com>
> > 
> > The lazy_rcu_shrink_count() shrinker function is registered even in
> > kernels built with CONFIG_RCU_LAZY=n, in which case this function
> > uselessly consumes cycles learning that no CPU has any lazy callbacks
> > queued.
> > 
> > This commit therefore registers this shrinker function only in the kernels
> > built with CONFIG_RCU_LAZY=y, where it might actually do something useful.
> > 
> > Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> > Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> 
> Reviewed-by: Frederic Weisbecker <frederic@...nel.org>

Thanks!

 - Joel