linux-kernel - Re: [PATCH 8/9] mm, slub: extend checks guarded by slub

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Message-ID: <20200610220947.GC702969@carbon.DHCP.thefacebook.com>
Date:   Wed, 10 Jun 2020 15:09:47 -0700
From:   Roman Gushchin <guro@...com>
To:     Vlastimil Babka <vbabka@...e.cz>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <kernel-team@...roid.com>,
        <vinmenon@...eaurora.org>, Kees Cook <keescook@...omium.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Vijayanand Jitta <vjitta@...eaurora.org>
Subject: Re: [PATCH 8/9] mm, slub: extend checks guarded by slub_debug static
 key

On Wed, Jun 10, 2020 at 06:31:34PM +0200, Vlastimil Babka wrote:
> There are few more places in SLUB that could benefit from reduced overhead of
> the static key introduced by a previous patch:
> 
> - setup_object_debug() called on each object in newly allocated slab page
> - setup_page_debug() called on newly allocated slab page
> - __free_slab() called on freed slab page
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Roman Gushchin <guro@...com>

Thanks!

> ---
>  mm/slub.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index c8e8b4ae2451..efb08f2e9c66 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1130,7 +1130,7 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node, int objects)
>  static void setup_object_debug(struct kmem_cache *s, struct page *page,
>  								void *object)
>  {
> -	if (!(s->flags & (SLAB_STORE_USER|SLAB_RED_ZONE|__OBJECT_POISON)))
> +	if (!kmem_cache_debug_flags(s, SLAB_STORE_USER|SLAB_RED_ZONE|__OBJECT_POISON))
>  		return;

This part is nice! It might bring some perf improvements.

>  
>  	init_object(s, object, SLUB_RED_INACTIVE);
> @@ -1140,7 +1140,7 @@ static void setup_object_debug(struct kmem_cache *s, struct page *page,
>  static
>  void setup_page_debug(struct kmem_cache *s, struct page *page, void *addr)
>  {
> -	if (!(s->flags & SLAB_POISON))
> +	if (!kmem_cache_debug_flags(s, SLAB_POISON))
>  		return;
>  
>  	metadata_access_enable();
> @@ -1857,7 +1857,7 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
>  	int order = compound_order(page);
>  	int pages = 1 << order;
>  
> -	if (s->flags & SLAB_CONSISTENCY_CHECKS) {
> +	if (kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS)) {
>  		void *p;
>  
>  		slab_pad_check(s, page);
> -- 
> 2.26.2
>