linux-kernel - Re: [PATCH v4 3/3] khugepaged: Optimize collapse_pte_mapped

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Message-ID: <87D756B5-3D64-4CC9-BDCE-9FC9DC04B8BC@nvidia.com>
Date: Tue, 29 Jul 2025 10:41:16 -0400
From: Zi Yan <ziy@...dia.com>
To: Dev Jain <dev.jain@....com>
Cc: akpm@...ux-foundation.org, david@...hat.com,
 baolin.wang@...ux.alibaba.com, lorenzo.stoakes@...cle.com,
 Liam.Howlett@...cle.com, npache@...hat.com, ryan.roberts@....com,
 baohua@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] khugepaged: Optimize collapse_pte_mapped_thp() by
 PTE batching

On 24 Jul 2025, at 1:23, Dev Jain wrote:

> Use PTE batching to batch process PTEs mapping the same large folio. An
> improvement is expected due to batching mapcount manipulation on the
> folios, and for arm64 which supports contig mappings, the number of
> TLB flushes is also reduced.
>
> Note that we do not need to make a change to the check
> "if (folio_page(folio, i) != page)"; if i'th page of the folio is equal
> to the first page of our batch, then i + 1, .... i + nr_batch_ptes - 1
> pages of the folio will be equal to the corresponding pages of our
> batch mapping consecutive pages.
>
> Acked-by: David Hildenbrand <david@...hat.com>
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Signed-off-by: Dev Jain <dev.jain@....com>
> ---
>  mm/khugepaged.c | 33 +++++++++++++++++++++------------
>  1 file changed, 21 insertions(+), 12 deletions(-)
>
Reviewed-by: Zi Yan <ziy@...dia.com>

Best Regards,
Yan, Zi