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

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Date: Mon, 1 Jul 2024 08:57:32 +0200
From: David Hildenbrand <david@...hat.com>
To: Bang Li <libang.li@...group.com>, hughd@...gle.com,
 akpm@...ux-foundation.org
Cc: ryan.roberts@....com, wangkefeng.wang@...wei.com,
 baolin.wang@...ux.alibaba.com, ziy@...dia.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH] support "THPeligible" semantics for mTHP with anonymous
 shmem

On 28.06.24 12:49, 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>
> ---
>   fs/proc/task_mmu.c      | 10 +++++++---
>   include/linux/huge_mm.h | 11 +++++++++++
>   mm/shmem.c              |  9 +--------
>   3 files changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 93fb2c61b154..09b5db356886 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -870,6 +870,7 @@ static int show_smap(struct seq_file *m, void *v)
>   {
>   	struct vm_area_struct *vma = v;
>   	struct mem_size_stats mss = {};
> +	bool thp_eligible;
>   
>   	smap_gather_stats(vma, &mss, 0);
>   
> @@ -882,9 +883,12 @@ static int show_smap(struct seq_file *m, void *v)
>   
>   	__show_smap(m, &mss, false);
>   
> -	seq_printf(m, "THPeligible:    %8u\n",
> -		   !!thp_vma_allowable_orders(vma, vma->vm_flags,
> -			   TVA_SMAPS | TVA_ENFORCE_SYSFS, THP_ORDERS_ALL));
> +	thp_eligible = !!thp_vma_allowable_orders(vma, vma->vm_flags,
> +						TVA_SMAPS | TVA_ENFORCE_SYSFS, THP_ORDERS_ALL);
> +	if (vma_is_anon_shmem(vma))
> +		thp_eligible = !!shmem_allowable_huge_orders(file_inode(vma->vm_file),
> +							vma, vma->vm_pgoff, thp_eligible);

I would have thought the correct fix is to return the correct result 
from thp_vma_allowable_orders().

-- 
Cheers,

David / dhildenb