linux-kernel - Re: [PATCH v3 0/4] mm: add more kernel parameters to control mTHP

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Message-Id: <20241030155059.9e27019842ef7c009b728b27@linux-foundation.org>
Date: Wed, 30 Oct 2024 15:50:59 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Maíra Canal <mcanal@...lia.com>
Cc: Jonathan Corbet <corbet@....net>, Hugh Dickins <hughd@...gle.com>, Barry
 Song <baohua@...nel.org>, David Hildenbrand <david@...hat.com>, Ryan
 Roberts <ryan.roberts@....com>, Baolin Wang
 <baolin.wang@...ux.alibaba.com>, Lance Yang <ioworker0@...il.com>,
 linux-mm@...ck.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, kernel-dev@...lia.com
Subject: Re: [PATCH v3 0/4] mm: add more kernel parameters to control mTHP

On Wed, 30 Oct 2024 09:58:54 -0300 Maíra Canal <mcanal@...lia.com> wrote:

> The second and third patches focus on controlling THP support for shmem
> via the kernel command line. The second patch introduces a parameter to
> control the global default huge page allocation policy for the internal
> shmem mount. 

The changelogs for patches 2 and 3 both say

: By configuring ..., applications that use shmem, such as the DRM GEM objects,
: can take advantage of mTHP before it's been configured through sysfs.

There isn't a lot of info here - please explain this timing issue in
more detail.

Because the question which leaps to mind is: shouldn't the
"applications that use shmem" be changed to "configure mTHP through
sysfs" *before* "using shmem"?  Seems pretty basic.

Also, please consider my question to be a critique of the changelogs. 
If the changelogs were complete, I wouldn't need to ask any questions!