linux-kernel - Re: [PATCH v5 1/9] slub: Reflow ___slab

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Date:   Wed, 22 Nov 2023 09:26:13 +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 1/9] slub: Reflow ___slab_alloc()

On Thu, Nov 2, 2023 at 12:24 PM <chengming.zhou@...ux.dev> wrote:
>
> From: Chengming Zhou <zhouchengming@...edance.com>
>
> The get_partial() interface used in ___slab_alloc() may return a single
> object in the "kmem_cache_debug(s)" case, in which we will just return
> the "freelist" object.
>
> Move this handling up to prepare for later changes.
>
> And the "pfmemalloc_match()" part is not needed for node partial slab,
> since we already check this in the get_partial_node().
>
> 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 | 31 +++++++++++++++----------------
>  1 file changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 63d281dfacdb..0b0fdc8c189f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3216,8 +3216,21 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>         pc.slab = &slab;
>         pc.orig_size = orig_size;
>         freelist = get_partial(s, node, &pc);
> -       if (freelist)
> -               goto check_new_slab;
> +       if (freelist) {
> +               if (kmem_cache_debug(s)) {
> +                       /*
> +                        * For debug caches here we had to go through
> +                        * alloc_single_from_partial() so just store the
> +                        * tracking info and return the object.
> +                        */
> +                       if (s->flags & SLAB_STORE_USER)
> +                               set_track(s, freelist, TRACK_ALLOC, addr);
> +
> +                       return freelist;
> +               }
> +
> +               goto retry_load_slab;
> +       }
>
>         slub_put_cpu_ptr(s->cpu_slab);
>         slab = new_slab(s, gfpflags, node);
> @@ -3253,20 +3266,6 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>
>         inc_slabs_node(s, slab_nid(slab), slab->objects);
>
> -check_new_slab:
> -
> -       if (kmem_cache_debug(s)) {
> -               /*
> -                * For debug caches here we had to go through
> -                * alloc_single_from_partial() so just store the tracking info
> -                * and return the object
> -                */
> -               if (s->flags & SLAB_STORE_USER)
> -                       set_track(s, freelist, TRACK_ALLOC, addr);
> -
> -               return freelist;
> -       }
> -
>         if (unlikely(!pfmemalloc_match(slab, gfpflags))) {
>                 /*
>                  * For !pfmemalloc_match() case we don't load freelist so that

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

> --
> 2.20.1
>