linux-kernel - Re: [PATCH 1/8] mm: move highest_order() and next

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Message-ID: <9576c979-8a11-48e2-aec4-646acf0d8e26@arm.com>
Date: Tue, 7 May 2024 11:21:43 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>, akpm@...ux-foundation.org,
 hughd@...gle.com
Cc: willy@...radead.org, david@...hat.com, ioworker0@...il.com,
 wangkefeng.wang@...wei.com, ying.huang@...el.com, 21cnbao@...il.com,
 shy828301@...il.com, ziy@...dia.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] mm: move highest_order() and next_order() out of the
 THP config

On 06/05/2024 09:46, Baolin Wang wrote:
> Move highest_order() and next_order() out of the CONFIG_TRANSPARENT_HUGEPAGE
> macro, which can be common functions to be used.

Sorry if I haven't kept up with the discussion, but why is this needed? I
wouldn't expect a need to iterate over orders if THP is compile-time disabled
because we will never try to allocate THP?

> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  include/linux/huge_mm.h | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 017cee864080..e49b56c40a11 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -106,6 +106,17 @@ extern struct kobj_attribute shmem_enabled_attr;
>  #define HPAGE_PUD_MASK	(~(HPAGE_PUD_SIZE - 1))
>  #define HPAGE_PUD_SIZE	((1UL) << HPAGE_PUD_SHIFT)
>  
> +static inline int highest_order(unsigned long orders)
> +{
> +	return fls_long(orders) - 1;
> +}
> +
> +static inline int next_order(unsigned long *orders, int prev)
> +{
> +	*orders &= ~BIT(prev);
> +	return highest_order(*orders);
> +}
> +
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  
>  extern unsigned long transparent_hugepage_flags;
> @@ -138,17 +149,6 @@ static inline bool hugepage_flags_enabled(void)
>  	       huge_anon_orders_madvise;
>  }
>  
> -static inline int highest_order(unsigned long orders)
> -{
> -	return fls_long(orders) - 1;
> -}
> -
> -static inline int next_order(unsigned long *orders, int prev)
> -{
> -	*orders &= ~BIT(prev);
> -	return highest_order(*orders);
> -}
> -
>  /*
>   * Do the below checks:
>   *   - For file vma, check if the linear page offset of vma is