linux-kernel - Re: [PATCH v13 mm-new 02/16] introduce collapse_single_pmd to unify khugepaged and madvise

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Message-ID: <1B958142-28E9-4910-B870-490826089023@nvidia.com>
Date: Tue, 02 Dec 2025 10:36:22 -0500
From: Zi Yan <ziy@...dia.com>
To: Nico Pache <npache@...hat.com>
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Subject: Re: [PATCH v13 mm-new 02/16] introduce collapse_single_pmd to unify
 khugepaged and madvise_collapse

On 1 Dec 2025, at 12:46, Nico Pache wrote:

> The khugepaged daemon and madvise_collapse have two different
> implementations that do almost the same thing.
>
> Create collapse_single_pmd to increase code reuse and create an entry
> point to these two users.
>
> Refactor madvise_collapse and collapse_scan_mm_slot to use the new
> collapse_single_pmd function. This introduces a minor behavioral change
> that is most likely an undiscovered bug. The current implementation of
> khugepaged tests collapse_test_exit_or_disable before calling
> collapse_pte_mapped_thp, but we weren't doing it in the madvise_collapse
> case. By unifying these two callers madvise_collapse now also performs
> this check. We also modify the return value to be SCAN_ANY_PROCESS which
> properly indicates that this process is no longer valid to operate on.
>
> We also guard the khugepaged_pages_collapsed variable to ensure its only
> incremented for khugepaged.
>
> Reviewed-by: Wei Yang <richard.weiyang@...il.com>
> Reviewed-by: Lance Yang <lance.yang@...ux.dev>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Nico Pache <npache@...hat.com>
> ---
>  mm/khugepaged.c | 97 ++++++++++++++++++++++++++-----------------------
>  1 file changed, 52 insertions(+), 45 deletions(-)
>
LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>

Best Regards,
Yan, Zi