linux-kernel - Re: [PATCH v2] rcu/kvfree: Prevents cache growing when the backoff_page_cache

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Message-ID: <ZC5MoREk30MIt79u@pc636>
Date:   Thu, 6 Apr 2023 06:37:53 +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 v2] rcu/kvfree: Prevents cache growing when the
 backoff_page_cache_fill is set

On Thu, Apr 06, 2023 at 08:12:38AM +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 add a check
> for krcp structure's->backoff_page_cache_fill in put_cached_bnode(),
> if the krcp structure's->backoff_page_cache_fill is set, prevent page
> cache growing.
> 
> Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> ---
>  kernel/rcu/tree.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 9cc0a7766fd2..f25430ae1936 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2907,6 +2907,8 @@ static inline bool
>  put_cached_bnode(struct kfree_rcu_cpu *krcp,
>  	struct kvfree_rcu_bulk_data *bnode)
>  {
> +	if (atomic_read(&krcp->backoff_page_cache_fill))
> +		return false;
>  	// Check the limit.
>  	if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
>  		return false;
> -- 
> 2.32.0
>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>

--
Uladzislau Rezki