linux-kernel - Re: [PATCH 1/4] mm/slub: fix bulk alloc and free stats

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Date:   Tue, 5 Dec 2023 16:11:03 +0800
From:   Chengming Zhou <chengming.zhou@...ux.dev>
To:     Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com
Subject: Re: [PATCH 1/4] mm/slub: fix bulk alloc and free stats

On 2023/12/5 03:34, Vlastimil Babka wrote:
> The SLUB sysfs stats enabled CONFIG_SLUB_STATS have two deficiencies
> identified wrt bulk alloc/free operations:
> 
> - Bulk allocations from cpu freelist are not counted. Add the
>   ALLOC_FASTPATH counter there.
> 
> - Bulk fastpath freeing will count a list of multiple objects with a
>   single FREE_FASTPATH inc. Add a stat_add() variant to count them all.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Looks good to me!

Reviewed-by: Chengming Zhou <zhouchengming@...edance.com>

> ---
>  mm/slub.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 3f8b95757106..d7b0ca6012e0 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -396,6 +396,14 @@ static inline void stat(const struct kmem_cache *s, enum stat_item si)
>  #endif
>  }
>  
> +static inline
> +void stat_add(const struct kmem_cache *s, enum stat_item si, int v)
> +{
> +#ifdef CONFIG_SLUB_STATS
> +	raw_cpu_add(s->cpu_slab->stat[si], v);
> +#endif
> +}
> +
>  /*
>   * The slab lists for all objects.
>   */
> @@ -4268,7 +4276,7 @@ static __always_inline void do_slab_free(struct kmem_cache *s,
>  
>  		local_unlock(&s->cpu_slab->lock);
>  	}
> -	stat(s, FREE_FASTPATH);
> +	stat_add(s, FREE_FASTPATH, cnt);
>  }
>  #else /* CONFIG_SLUB_TINY */
>  static void do_slab_free(struct kmem_cache *s,
> @@ -4545,6 +4553,7 @@ static inline int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
>  		c->freelist = get_freepointer(s, object);
>  		p[i] = object;
>  		maybe_wipe_obj_freeptr(s, p[i]);
> +		stat(s, ALLOC_FASTPATH);
>  	}
>  	c->tid = next_tid(c->tid);
>  	local_unlock_irqrestore(&s->cpu_slab->lock, irqflags);
>