linux-kernel - Re: [PATCH v3 6/6] mm: khugepaged: set to next mm direct when mm has MMF_DISABLE_THP

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Message-ID: <bfb6f8ca-fa17-4ce8-a2b5-09155c50cb22@linux.dev>
Date: Sun, 4 Jan 2026 20:20:29 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: Vernon Yang <vernon2gm@...il.com>
Cc: lorenzo.stoakes@...cle.com, ziy@...dia.com, dev.jain@....com,
 baohua@...nel.org, richard.weiyang@...il.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, david@...nel.org,
 Vernon Yang <yanglincheng@...inos.cn>, akpm@...ux-foundation.org
Subject: Re: [PATCH v3 6/6] mm: khugepaged: set to next mm direct when mm has
 MMF_DISABLE_THP_COMPLETELY



On 2026/1/4 13:41, Vernon Yang wrote:
> When an mm with the MMF_DISABLE_THP_COMPLETELY flag is detected during
> scanning, directly set khugepaged_scan.mm_slot to the next mm_slot,
> reduce redundant operation.
> 
> Signed-off-by: Vernon Yang <yanglincheng@...inos.cn>
> ---
>   mm/khugepaged.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 1ca034a5f653..d4ed0f397335 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2541,7 +2541,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
>   	 * Release the current mm_slot if this mm is about to die, or
>   	 * if we scanned all vmas of this mm.
>   	 */
> -	if (hpage_collapse_test_exit(mm) || !vma) {
> +	if (hpage_collapse_test_exit_or_disable(mm) || !vma) {
>   		/*
>   		 * Make sure that if mm_users is reaching zero while
>   		 * khugepaged runs here, khugepaged_exit will find


Let's convert hpage_collapse_test_exit() in collect_mm_slot() as well,
otherwise the mm_slot would not be freed and will be scanned again ...

static void collect_mm_slot(struct mm_slot *slot)
{
	struct mm_struct *mm = slot->mm;

	lockdep_assert_held(&khugepaged_mm_lock);

	if (hpage_collapse_test_exit(mm)) { <-

		hash_del(&slot->hash);
		list_del(&slot->mm_node);

		mm_slot_free(mm_slot_cache, slot);
		mmdrop(mm);
	}
}