linux-kernel - Re: [PATCH v2] mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem

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Date: Tue, 2 Jul 2024 14:14:00 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Bang Li <libang.li@...group.com>, ughd@...gle.com,
 akpm@...ux-foundation.org
Cc: david@...hat.com, ryan.roberts@....com, wangkefeng.wang@...wei.com,
 ioworker0@...il.com, ziy@...dia.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: thp: support "THPeligible" semantics for mTHP with
 anonymous shmem



On 2024/7/2 10:34, Bang Li wrote:
> After the commit 7fb1b252afb5 ("mm: shmem: add mTHP support for
> anonymous shmem"), we can configure different policies through
> the multi-size THP sysfs interface for anonymous shmem. But
> currently "THPeligible" indicates only whether the mapping is
> eligible for allocating THP-pages as well as the THP is PMD
> mappable or not for anonymous shmem, we need to support semantics
> for mTHP with anonymous shmem similar to those for mTHP with
> anonymous memory.
> 
> Signed-off-by: Bang Li <libang.li@...group.com>
> ---
> Changes since v1 [1]:
>   - Put anonymous shmem mthp related logic into
>     thp_vma_allowable_orders() (per David)
> 
> [1] https://lore.kernel.org/linux-mm/20240628104926.34209-1-libang.li@antgroup.com/
> ---
>   include/linux/huge_mm.h | 11 +++++++++++
>   mm/huge_memory.c        | 13 +++++++++----
>   mm/shmem.c              |  9 +--------
>   3 files changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 212cca384d7e..f87136f38aa1 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -267,6 +267,10 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma,
>   	return __thp_vma_allowable_orders(vma, vm_flags, tva_flags, orders);
>   }
>   
> +unsigned long shmem_allowable_huge_orders(struct inode *inode,
> +				struct vm_area_struct *vma, pgoff_t index,
> +				bool global_huge);
> +
>   struct thpsize {
>   	struct kobject kobj;
>   	struct list_head node;
> @@ -460,6 +464,13 @@ static inline unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma,
>   	return 0;
>   }
>   
> +static inline unsigned long shmem_allowable_huge_orders(struct inode *inode,
> +				struct vm_area_struct *vma, pgoff_t index,
> +				bool global_huge)
> +{
> +	return 0;
> +}

This function should be placed in the ‘shmem_fs.h’ header file, just 
like shmem_is_huge().