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 <redacted>
---
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