On Tue, Jul 22, 2025 at 06:29:15AM +0100, Lorenzo Stoakes wrote:

Re: man page - I _do_ intend to update the man page as I find it far too
vague on this topic currently, so that patch will be coming soon.

Actually:

              MADV_COLLAPSE is independent of any sysfs (see sysfs(5))
              setting under /sys/kernel/mm/transparent_hugepage, both in
              terms of determining THP eligibility, and allocation
              semantics.  See Linux kernel source file
              Documentation/admin-guide/mm/transhuge.rst for more
              information.  MADV_COLLAPSE also ignores huge= tmpfs mount
              when operating on tmpfs files.  Allocation for the new
              hugepage may enter direct reclaim and/or compaction,
              regardless of VMA flags (though VM_NOHUGEPAGE is still
              respected).

I think this is clear enough to require no update.

THe confusion arose from the doc page seemingly contradicting this. By
referring to the doc page which now makes things clear, we're all good! :)

Cheers, Lorenzo