linux-kernel - Re: [PATCH] slub: Set __GFP_COMP in kmem

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Date: Mon, 15 Apr 2024 16:52:01 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Haifeng Xu <haifeng.xu@...pee.com>, cl@...ux.com, willy@...radead.org
Cc: penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
 akpm@...ux-foundation.org, roman.gushchin@...ux.dev, 42.hyeyoo@...il.com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] slub: Set __GFP_COMP in kmem_cache by default

On 4/13/24 5:56 PM, Haifeng Xu wrote:
> Now the __GFP_COMP is set only if the higher-order is not 0. However,
> __GFP_COMP flag can be set unconditionally because compound page can
> not be created in the order-0 case. And this can also simplify the code
> a bit (no need to check the order is 0 or not).
> 
> Signed-off-by: Haifeng Xu <haifeng.xu@...pee.com>
> Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>

Thanks, added to slab/for-next

> ---
>  mm/slub.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index e7bf1a1a31a8..49a3ebefab86 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4461,9 +4461,7 @@ static int calculate_sizes(struct kmem_cache *s)
>  	if ((int)order < 0)
>  		return 0;
>  
> -	s->allocflags = 0;
> -	if (order)
> -		s->allocflags |= __GFP_COMP;
> +	s->allocflags = __GFP_COMP;
>  
>  	if (s->flags & SLAB_CACHE_DMA)
>  		s->allocflags |= GFP_DMA;