Re: [PATCH] rcu: Stop shrinker loop

From: "Paul E. McKenney" <paulmck@kernel.org>
To: Uladzislau Rezki <urezki@gmail.com>
Cc: Peter Enderborg <peter.enderborg@sony.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rcu: Stop shrinker loop
Date: Thu, 4 Jun 2020 09:31:00 -0700	[thread overview]
Message-ID: <20200604163100.GB29598@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200604134255.GA24897@pc636>

On Thu, Jun 04, 2020 at 03:42:55PM +0200, Uladzislau Rezki wrote:
> On Thu, Jun 04, 2020 at 12:23:20PM +0200, Peter Enderborg wrote:
> > The count and scan can be separated in time. It is a fair chance
> > that all work is already done when the scan starts. It
> > then might retry. This is can be avoided with returning SHRINK_STOP.
> > 
> > Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
> > ---
> >  kernel/rcu/tree.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index c716eadc7617..8b36c6b2887d 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -3310,7 +3310,7 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> >  			break;
> >  	}
> >  
> > -	return freed;
> > +	return freed == 0 ? SHRINK_STOP : freed;
> >  }
> >  
> The loop will be stopped anyway sooner or later, but sooner is better :)
> To me that change makes sense.
> 
> Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Queued, thank you both!

							Thanx, Paul