linux-kernel - Re: [PATCH v5 4/9] slub: Prepare __slab_free() for unfrozen partial slab out of node partial list

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Date:   Sun, 3 Dec 2023 15:01:23 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     chengming.zhou@...ux.dev
Cc:     vbabka@...e.cz, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, roman.gushchin@...ux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [PATCH v5 4/9] slub: Prepare __slab_free() for unfrozen partial
 slab out of node partial list

On Thu, Nov 2, 2023 at 12:24 PM <chengming.zhou@...ux.dev> wrote:
>
> From: Chengming Zhou <zhouchengming@...edance.com>
>
> Now the partially empty slub will be frozen when taken out of node partial
> list, so the __slab_free() will know from "was_frozen" that the partially
> empty slab is not on node partial list and is a cpu or cpu partial slab
> of some cpu.
>
> But we will change this, make partial slabs leave the node partial list
> with unfrozen state, so we need to change __slab_free() to use the new
> slab_test_node_partial() we just introduced.
>
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
> Tested-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
> ---
>  mm/slub.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index eed8ae0dbaf9..1880b483350e 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3631,6 +3631,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
>         unsigned long counters;
>         struct kmem_cache_node *n = NULL;
>         unsigned long flags;
> +       bool on_node_partial;
>
>         stat(s, FREE_SLOWPATH);
>
> @@ -3678,6 +3679,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
>                                  */
>                                 spin_lock_irqsave(&n->list_lock, flags);
>
> +                               on_node_partial = slab_test_node_partial(slab);
>                         }
>                 }
>
> @@ -3706,6 +3708,15 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
>                 return;
>         }
>
> +       /*
> +        * This slab was partially empty but not on the per-node partial list,
> +        * in which case we shouldn't manipulate its list, just return.
> +        */
> +       if (prior && !on_node_partial) {
> +               spin_unlock_irqrestore(&n->list_lock, flags);
> +               return;
> +       }
> +
>         if (unlikely(!new.inuse && n->nr_partial >= s->min_partial))
>                 goto slab_empty;
>

Looks good to me,
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@...il.com>

> --
> 2.20.1
>