Re: Heads up: official removal of older AMD (pre-Zen1) support from libpmc/hwpmc

On Tue, 21 Apr 2026 at 18:24, Adrian Chadd <[email protected]> wrote:
>
> On Tue, 21 Apr 2026 at 08:41, Mitchell Horne <[email protected]> wrote:
> >
> > Hello,
> >
> > As the title suggests, I have proposed a change [1] to officially remove
> > the older AMD processor event definitions and logic from the library and
> > module. This means that processors older than the Zen 1 generation
> > (~2017) will not be supported by these tools.
> >
> > I say "officially" because the functionality has been silently disabled
> > for these older processors since 2020 at least [2].
> >
> > Among the many known issues, bugs, and sharp-edges relating to hwpmc(4)
> > and its tools, I am not aware of this complaint being raised or reported
> > anywhere. (Not to say that users haven't experienced this frustrating
> > silent failure.)
> >
>
> I mostly object, mostly because I'd rather we figure out why we've regressed in
> this area and try to fix it to stop it happening in the future.
>
> I have a variety of AMD hardware sprinkled around at home going back to K7
> era stuff that we still boot/run on (and heck I remember debugging our
> earlier AMD counter programming bugs way back when.)
>
> Please don't take "noone has complained" as "noone is using this so we can
> delete it" - I would take it as "everything is utterly broken in stupid ways and
> we should fix the utterly broken stuff and figure out how to make sure it
> isn't broken over time in the future."

I also object, mostly because I stumbled across the issue that my
organisation has several large clusters with older AMD CPUs with
FreeBSD in use [*]

[*] How, why, who, still under investigation since we found out. It's
in legitimate use, running recent FreeBSD, and couple of department
heads wanted to hang me when we touched it. So yes, old stuff is being
used, and no money to replace it for now.

Lionel