linux-kernel - Re: [PATCH] rcu: Stop shrinker loop

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Date:   Thu, 4 Jun 2020 15:42:55 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Peter Enderborg <peter.enderborg@...y.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: Stop shrinker loop

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@...y.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@...il.com>

--
Vlad Rezki