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From: David Hildenbrand <david@redhat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Zi Yan <ziy@nvidia.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	"Liam R . Howlett" <Liam.Howlett@oracle.com>,
	Nico Pache <npache@redhat.com>,
	Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
	Barry Song <baohua@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
	linux-mm@kvack.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] docs: update THP documentation to clarify sysfs "never" setting
Date: Tue, 22 Jul 2025 09:20:19 +0200	[thread overview]
Message-ID: <39a75435-5fea-4816-b484-477d400c3564@redhat.com> (raw)
In-Reply-To: <20250721155530.75944-1-lorenzo.stoakes@oracle.com>

On 21.07.25 17:55, Lorenzo Stoakes wrote:
> Rather confusingly, setting all Transparent Huge Page sysfs settings to
> "never" does not in fact result in THP being globally disabled.
> 
> Rather, it results in khugepaged being disabled, but one can still obtain
> THP pages using madvise(..., MADV_COLLAPSE).
> 
> This is something that has remained poorly documented for some time, and it
> is likely the received wisdom of most users of THP that never does, in
> fact, mean never.
> 
> It is therefore important to highlight, very clearly, that this is not the
> ase.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> ---

Can we also somehow tone down or clarify the "entirely disabled"?

Something as simple as

diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index bd49b46398c92..2267d22277238 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -107,7 +107,7 @@ sysfs
  Global THP controls
  -------------------
  
-Transparent Hugepage Support for anonymous memory can be entirely disabled
+Transparent Hugepage Support for anonymous memory can be mostly disabled
  (mostly for debugging purposes) or only enabled inside MADV_HUGEPAGE
  regions (to avoid the risk of consuming more memory resources) or enabled
  system wide. This can be achieved per-supported-THP-size with one of::


-- 
Cheers,

David / dhildenb



  parent reply	other threads:[~2025-07-22  7:20 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-07-21 15:55 Lorenzo Stoakes
2025-07-21 16:27 ` SeongJae Park
2025-07-22  1:13 ` Zi Yan
2025-07-22  1:30 ` Baolin Wang
2025-07-22  2:23   ` Barry Song
2025-07-22  2:33     ` Baolin Wang
2025-07-22  3:37       ` Barry Song
2025-07-22  5:29         ` Lorenzo Stoakes
2025-07-23 15:41           ` Lorenzo Stoakes
2025-07-22  5:24     ` Lorenzo Stoakes
2025-07-22  5:25   ` Lorenzo Stoakes
2025-07-22  5:34 ` Lorenzo Stoakes
2025-07-22  5:59   ` Baolin Wang
2025-07-22  8:19   ` Barry Song
2025-07-22  7:20 ` David Hildenbrand [this message]
2025-07-22  7:59   ` David Hildenbrand

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