From: Baolin Wang <baolin.wang@linux.alibaba.com>
To: Dev Jain <dev.jain@arm.com>,
akpm@linux-foundation.org, david@kernel.org,
lorenzo.stoakes@oracle.com
Cc: ziy@nvidia.com, Liam.Howlett@oracle.com, npache@redhat.com,
ryan.roberts@arm.com, baohua@kernel.org, lance.yang@linux.dev,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] khugepaged: remove redundant index check for pmd-folios
Date: Tue, 3 Mar 2026 10:16:00 +0800 [thread overview]
Message-ID: <0c742d98-82ee-4085-bf3b-26fac5897bde@linux.alibaba.com> (raw)
In-Reply-To: <20260227143501.1488110-1-dev.jain@arm.com>
On 2/27/26 10:35 PM, Dev Jain wrote:
> Claim: folio_order(folio) == HPAGE_PMD_ORDER => folio->index == start.
>
> Proof: Both loops in hpage_collapse_scan_file and collapse_file, which
> iterate on the xarray, have the invariant that
> start <= folio->index < start + HPAGE_PMD_NR ... (i)
>
> A folio is always naturally aligned in the pagecache, therefore
> folio_order == HPAGE_PMD_ORDER => IS_ALIGNED(folio->index, HPAGE_PMD_NR) == true ... (ii)
>
> thp_vma_allowable_order -> thp_vma_suitable_order requires that the virtual
> offsets in the VMA are aligned to the order,
> => IS_ALIGNED(start, HPAGE_PMD_NR) == true ... (iii)
>
> Combining (i), (ii) and (iii), the claim is proven.
>
> Therefore, remove this check.
> While at it, simplify the comments.
>
> Signed-off-by: Dev Jain <dev.jain@arm.com>
> ---
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
prev parent reply other threads:[~2026-03-03 2:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 14:35 Dev Jain
2026-02-27 20:57 ` David Hildenbrand (Arm)
2026-02-28 4:44 ` Lance Yang
2026-03-03 2:16 ` Baolin Wang [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=0c742d98-82ee-4085-bf3b-26fac5897bde@linux.alibaba.com \
--to=baolin.wang@linux.alibaba.com \
--cc=Liam.Howlett@oracle.com \
--cc=akpm@linux-foundation.org \
--cc=baohua@kernel.org \
--cc=david@kernel.org \
--cc=dev.jain@arm.com \
--cc=lance.yang@linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lorenzo.stoakes@oracle.com \
--cc=npache@redhat.com \
--cc=ryan.roberts@arm.com \
--cc=ziy@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox