linux-kernel - Re: [PATCH 1/3] mm: fix the format of the kernel parameter ``thp

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Message-ID: <CAGsJ_4xPr3X_EXh73c4gN-cUSxaXZ-XR=_VNE750zNH61nyR-Q@mail.gmail.com>
Date: Mon, 28 Oct 2024 03:52:16 +0800
From: Barry Song <baohua@...nel.org>
To: Maíra Canal <mcanal@...lia.com>
Cc: Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>, 
	Hugh Dickins <hughd@...gle.com>, 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 1/3] mm: fix the format of the kernel parameter ``thp_anon=``

On Mon, Oct 28, 2024 at 1:58 AM Maíra Canal <mcanal@...lia.com> wrote:
>
> If we add ``thp_anon=32,64KB:always`` to the kernel command line, we
> will see the following error:
>
> [    0.000000] huge_memory: thp_anon=32,64K:always: error parsing string, ignoring setting
>
> This happens because the correct format isn't ``thp_anon=<size>,<size>[KMG]:<state>```,
> as [KMG] must follow each number to especify its unit. So, the correct
> format is ``thp_anon=<size>[KMG],<size>[KMG]:<state>```.

what if 32768,64K: always?

>
> Therefore, adjust the documentation to reflect the correct format of the
> parameter ``thp_anon=``.
>
> Fixes: dd4d30d1cdbe ("mm: override mTHP "enabled" defaults at kernel cmdline")
> Signed-off-by: Maíra Canal <mcanal@...lia.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 2 +-
>  Documentation/admin-guide/mm/transhuge.rst      | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 1518343bbe22..1666576acc0e 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6688,7 +6688,7 @@
>                         0: no polling (default)
>
>         thp_anon=       [KNL]
> -                       Format: <size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>
> +                       Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
>                         state is one of "always", "madvise", "never" or "inherit".
>                         Control the default behavior of the system with respect
>                         to anonymous transparent hugepages.
> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> index 203ba7aaf5fc..745055c3dc09 100644
> --- a/Documentation/admin-guide/mm/transhuge.rst
> +++ b/Documentation/admin-guide/mm/transhuge.rst
> @@ -303,7 +303,7 @@ control by passing the parameter ``transparent_hugepage=always`` or
>  kernel command line.
>
>  Alternatively, each supported anonymous THP size can be controlled by
> -passing ``thp_anon=<size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>``,
> +passing ``thp_anon=<size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>``,
>  where ``<size>`` is the THP size (must be a power of 2 of PAGE_SIZE and
>  supported anonymous THP)  and ``<state>`` is one of ``always``, ``madvise``,
>  ``never`` or ``inherit``.
> --
> 2.46.2
>