linux-kernel - Re: [PATCH] mm: set pageblock_order to HPAGE_PMD_ORDER in case with !CONFIG_HUGETLB

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Date: Fri, 5 Apr 2024 16:38:52 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>, akpm@...ux-foundation.org
Cc: mgorman@...hsingularity.net, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: set pageblock_order to HPAGE_PMD_ORDER in case with
 !CONFIG_HUGETLB_PAGE but THP enabled

On 4/5/24 2:24 PM, Baolin Wang wrote:
> As Vlastimil suggested in previous discussion[1], it doesn't make sense to set
> pageblock_order as MAX_PAGE_ORDER when hugetlbfs is not enabled and THP is enabled.
> Instead, it should be set to HPAGE_PMD_ORDER.
> 
> [1] https://lore.kernel.org/all/76457ec5-d789-449b-b8ca-dcb6ceb12445@suse.cz/
> Suggested-by: Vlastimil Babka <vbabka@...e.cz>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!

> ---
>  include/linux/pageblock-flags.h | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
> index 3f2409b968ec..547e82cdc89a 100644
> --- a/include/linux/pageblock-flags.h
> +++ b/include/linux/pageblock-flags.h
> @@ -28,7 +28,7 @@ enum pageblock_bits {
>  	NR_PAGEBLOCK_BITS
>  };
>  
> -#ifdef CONFIG_HUGETLB_PAGE
> +#if defined(CONFIG_HUGETLB_PAGE)
>  
>  #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
>  
> @@ -45,7 +45,11 @@ extern unsigned int pageblock_order;
>  
>  #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
>  
> -#else /* CONFIG_HUGETLB_PAGE */
> +#elif defined(CONFIG_TRANSPARENT_HUGEPAGE)
> +
> +#define pageblock_order		min_t(unsigned int, HPAGE_PMD_ORDER, MAX_PAGE_ORDER)
> +
> +#else /* CONFIG_TRANSPARENT_HUGEPAGE */
>  
>  /* If huge pages are not used, group by MAX_ORDER_NR_PAGES */
>  #define pageblock_order		MAX_PAGE_ORDER