linux-kernel - Re: [PATCH] rcu/kvfree: Delay the execution of drain_page

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Message-ID: <ZC2IpnVzW6pjjqbk@pc636>
Date:   Wed, 5 Apr 2023 16:41:42 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Zqiang <qiang1.zhang@...el.com>
Cc:     urezki@...il.com, paulmck@...nel.org, frederic@...nel.org,
        joel@...lfernandes.org, qiang.zhang1211@...il.com,
        rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu/kvfree: Delay the execution of drain_page_cache()

On Wed, Apr 05, 2023 at 10:13:42AM +0800, Zqiang wrote:
> Currently, in kfree_rcu_shrink_scan(), the drain_page_cache() is
> executed before kfree_rcu_monitor() to drain page cache, if the
> bnode structure's->gp_snap has done, the kvfree_rcu_bulk() will
> fill the page cache again in kfree_rcu_monitor(), this commit
> therefore move drain_page_cache() after kfree_rcu_monitor() to
> drain page cache.
> 
> Signed-off-by: Zqiang <qiang1.zhang@...el.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 35be35f8236b..3461fc2640b9 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3424,8 +3424,8 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
>  		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
>  
>  		count = krc_count(krcp);
> -		count += drain_page_cache(krcp);
>  		kfree_rcu_monitor(&krcp->monitor_work.work);
> +		count += drain_page_cache(krcp);
>  
>  		sc->nr_to_scan -= count;
>  		freed += count;
> -- 
> 2.32.0
One question. Maybe we can update the put_cached_bnode() with
checking if backoff_page_cache_fill was set to prevent cache
growing?

Thanks!

--
Uladzislau Rezki