From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: Song Hu <husong@kylinos.cn>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, david@kernel.org,
ziy@nvidia.com, baolin.wang@linux.alibaba.com,
liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com,
dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev,
usama.arif@linux.dev, vbabka@kernel.org, rppt@kernel.org,
surenb@google.com, mhocko@suse.com, corbet@lwn.net,
skhan@linuxfoundation.org, rdunlap@infradead.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] Docs/ABI: document transparent_hugepage/shrink_underused
Date: Wed, 12 Aug 2026 09:58:33 +0100 [thread overview]
Message-ID: <anw0mM2YVPRRM2Ff@lucifer> (raw)
In-Reply-To: <20260812080313.330413-2-husong@kylinos.cn>
Please don't send patch series like this - we really require a cover letter if
patch count > 1, and every patch should reply to the cover letter.
On Wed, Aug 12, 2026 at 04:03:12PM +0800, Song Hu wrote:
> The shrink_underused knob was added in commit 81d3ff3c6f76 ("mm: add
> sysfs entry to disable splitting underused THPs") but is missing from
> Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage, although
> transhuge.rst already documents it. Add the ABI entry.
Hmm what even is this file? :) What is the contract on this file?
>
> Signed-off-by: Song Hu <husong@kylinos.cn>
> ---
> .../ABI/testing/sysfs-kernel-mm-transparent-hugepage | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage b/Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage
> index 7bfbb9cc2c11..bbdfae2c0caa 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage
> @@ -10,9 +10,19 @@ Description:
> - hpage_pmd_size
> - khugepaged
> - shmem_enabled
> + - shrink_underused
I mean I guess fine for consistency.
> - use_zero_page
> - subdirectories of the form hugepages-<size>kB, where <size>
> is the page size of the hugepages supported by the kernel/CPU
> combination.
But we already handwave literally everything else here....
>
> See Documentation/admin-guide/mm/transhuge.rst for details.
> +
> +What: /sys/kernel/mm/transparent_hugepage/shrink_underused
> +Date: Sep 2024
> +Contact: Linux memory management mailing list <linux-mm@kvack.org>
> +Description: Reading and writing this file controls whether khugepaged
> + splits underused transparent huge pages (THPs) under memory
> + pressure. A THP is considered underused when its number of
> + zero-filled pages is above max_ptes_none. Enabled by default;
> + writing 0 disables the splitting and 1 enables it.
Nothing else is documented in this file so why is this getting special
treatment? And why is it backdated to Sep 2024?...
Drop it please.
> --
> 2.43.0
>
--
Cheers, Lorenzo
next prev parent reply other threads:[~2026-08-12 8:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-12 8:03 [PATCH 0/2] Docs: THP documentation fixes Song Hu
2026-08-12 8:03 ` [PATCH 1/2] Docs/ABI: document transparent_hugepage/shrink_underused Song Hu
2026-08-12 8:58 ` Lorenzo Stoakes (ARM) [this message]
2026-08-12 8:03 ` [PATCH 2/2] Docs/mm: fix THP policy counts in transhuge Song Hu
2026-08-12 8:41 ` Baolin Wang
2026-08-12 9:27 ` Lorenzo Stoakes (ARM)
2026-08-12 10:52 ` Baolin Wang
2026-08-12 10:55 ` Lorenzo Stoakes (ARM)
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