[RFC] Add GNU_PROPERTY_1_NEEDED_THP_ON_[READ_ONLY_SEGMENTS|MALLOC]

[H.J. Lu]

On Fri, Apr 17, 2026 at 9:31 PM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 17/04/26 07:27, H.J. Lu wrote:
> > On Fri, Apr 17, 2026 at 5:29 PM Florian Weimer <fweimer@redhat.com> wrote:
> >>
> >> * H. J. Lu via Gnu-gabi:
> >>
> >>> 1. GNU_PROPERTY_1_NEEDED_THP_ON_READ_ONLY_SEGMENTS
> >>
> >>> 2. GNU_PROPERTY_1_NEEDED_THP_ON_MALLOC
> >>
> >> Why NEEDED?  Isn't this purely optional, and the program has to work
> >> whether glibc enables THP or not?
> >>
> >
> > What do you prefer to call it?  Optional, desired, recommended, required?
> >
>
>
> Maybe Optional or without any prepend, the property is an opt-in feature
> that can not always be satisfied by the runtime (due missing kernel or
> architecture support).

Linux gABI has

GNU_PROPERTY_1_NEEDED The pr_data field contains a 4-byte integer
to indicate the properties needed by object file.

We can update it to

GNU_PROPERTY_1_NEEDED The pr_data field contains a 4-byte integer
to indicate the properties needed by object file for correctness or performance.

> I am still not sure about the need of this, I discussed something similar
> privately with Wilco and he raised some concerns about it (CCing him,
> he might have more to add).

These bits provide a way to opt-in a feature which hurts performance in
some cases when enabled by default.

-- 
H.J.