Re: [PATCH v2] PR_*ET_THP_DISABLE.2const: document addition of PR_THP_DISABLE_EXCEPT_ADVISED

[Usama Arif <usamaarif642@gmail.com>]

On 05/11/2025 16:48, Usama Arif wrote:
> PR_THP_DISABLE_EXCEPT_ADVISED extended PR_SET_THP_DISABLE to only provide
> THPs when advised. IOW, it allows individual processes to opt-out of THP =
> "always" into THP = "madvise", without affecting other workloads on the
> system. The series has been merged in [1]. Before [1], the following 2
> calls were allowed with PR_SET_THP_DISABLE:
> 
> prctl(PR_SET_THP_DISABLE, 0, 0, 0, 0); // to reset THP setting.
> prctl(PR_SET_THP_DISABLE, 1, 0, 0, 0); // to disable THPs completely.
> 
> Now in addition to the 2 calls above, you can do:
> 
> prctl(PR_SET_THP_DISABLE, 1, PR_THP_DISABLE_EXCEPT_ADVISED, 0, 0); // to
> disable THPs except madvise.
> 
> This patch documents the changes introduced due to the addition of
> PR_THP_DISABLE_EXCEPT_ADVISED flag:
> - PR_GET_THP_DISABLE returns a value whose bits indicate how THP-disable
>   is configured for the calling thread (with or without
>   PR_THP_DISABLE_EXCEPT_ADVISED).
> - PR_SET_THP_DISABLE now uses arg3 to specify whether to disable THP
>   completely for the process, or disable except madvise
>   (PR_THP_DISABLE_EXCEPT_ADVISED).
> 
> [1] https://github.com/torvalds/linux/commit/9dc21bbd62edeae6f63e6f25e1edb7167452457b
> 
> Signed-off-by: Usama Arif <usamaarif642@gmail.com>
> ---
> v1 -> v2 (Alejandro Colomar):
> - Fixed double negation on when MADV_HUGEPAGE will succeed
> - Turn return values of PR_GET_THP_DISABLE into a table
> - Turn madvise calls into full italics
> - Use semantic newlines
> ---
>  man/man2/madvise.2                      |  6 ++-
>  man/man2const/PR_GET_THP_DISABLE.2const | 20 +++++++---
>  man/man2const/PR_SET_THP_DISABLE.2const | 52 +++++++++++++++++++++----
>  3 files changed, 64 insertions(+), 14 deletions(-)
> 

Resending this for review as the patch to implement this is in merged [1]

[1] https://github.com/torvalds/linux/commit/9dc21bbd62edeae6f63e6f25e1edb7167452457b