linux-kernel - Re: [PATCH 4/5] debugobjects: Use hlist_splice

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Message-ID: <87le0982vo.ffs@tglx>
Date: Tue, 03 Sep 2024 12:09:47 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Zhen Lei <thunder.leizhen@...wei.com>, Andrew Morton
 <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org
Cc: Zhen Lei <thunder.leizhen@...wei.com>
Subject: Re: [PATCH 4/5] debugobjects: Use hlist_splice_init() to reduce
 lock conflicts

On Mon, Sep 02 2024 at 22:05, Zhen Lei wrote:

> The sub list can be prepared in advance outside the lock, so that the
> operation time inside the lock can be reduced and the possibility of
> lock conflict can be reduced.
>
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  lib/debugobjects.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> index fc8224f9f0eda8f..998724e9dee526b 100644
> --- a/lib/debugobjects.c
> +++ b/lib/debugobjects.c
> @@ -167,23 +167,25 @@ static void fill_pool(void)
>  		return;
>  
>  	while (READ_ONCE(obj_pool_free) < debug_objects_pool_min_level) {
> -		struct debug_obj *new[ODEBUG_BATCH_SIZE];
> +		HLIST_HEAD(batch_list);
> +		struct debug_obj *new, *last;

Variable ordering please.

>  		int cnt;
>  
>  		for (cnt = 0; cnt < ODEBUG_BATCH_SIZE; cnt++) {
> -			new[cnt] = kmem_cache_zalloc(obj_cache, gfp);
> -			if (!new[cnt])
> +			new = kmem_cache_zalloc(obj_cache, gfp);
> +			if (!new)
>  				break;
> +			hlist_add_head(&new->node, &batch_list);
> +			if (cnt == 0)
                        
                        if (!cnt)

but it would be more self explaining if you have:

		struct debug_obj *new, *last = NULL;

and then
                if (!last)

> +				last = new;
>  		}

Thanks,

        tglx