proposal: remove linux/ppc64 (big endian) port

[bradfitz]

We have an ancient Debian jessie ppc64 builder at OSUOSL, but we can't update it because Linux distros seem to have dropped PowerPC ("ppc64" big endian) support and now only support POWER ("ppc64el" aka "ppc64le").

• Debian dropped it: https://www.debian.org/ports/ -- "powerpc" .. "discontinued"
• Ubuntu dropped it: https://help.ubuntu.com/community/SupportedArchitectures -- "PowerPC (legacy)"
• Fedora dropped it: https://fedoraproject.org/wiki/Architectures (PowerPC64 is crossed out)

I see some old posts saying maybe the Debian port is kinda kept alive on a community best effort basis, but I'm not easily finding package repo URLs for it.

If the point of keeping linux/ppc64 was to root out endianness assumptions, doesn't linux/s390x get that for us? The s390x folk are doing an amazing job maintaining that port.

We can keep the old linux/ppc64 builder running for a bit but it'll get increasingly annoying. And it's Internet-facing and we can't even apply security updates, so, uh, that's not great.

/cc @laboger @ceseo @randall77 @ianlancetaylor @rsc @mdempsky @aclements @bcmills @toothrot @dmitshur @FiloSottile

[ianlancetaylor]

I note that when we required Power8 for ppc64 (#19074) we got a lot of pushback, implying that at least at that time people were using the port.

[bradfitz]

What distro are they running? I don't mind continuing to support it if it there's a way to run secure builders for it.

[ianlancetaylor]

In general, I don't know. I just checked a ppc64 system running in the GCC compile farm; it is running CentOS 7.6.

[mkumatag]

/cc @laboger ^^^

[bradfitz]

@ianlancetaylor, thanks. That led me to https://wiki.centos.org/SpecialInterestGroup/AltArch/ppc64 which I guess is an option.

[andreanidouglas]

Centos 7.7 still supports ppc64 big endian (CentOS 7 EOL is 2024 if I'm not mistaken)

https://wiki.centos.org/SpecialInterestGroup/AltArch/ppc64

[bradfitz]

OSUOSL, who supply & run our Go PPC64x builders, says:

IBM has been pushing very hard to deprecate ppc64 and move everyone over to
ppc64le and we're not spending any additional time or effort on supporting
ppc64. The "newest" OS for ppc64 we have which still has support is Ubuntu
16.04 or CentOS 7. Anything beyond that is only ppc64le. Debian dropped ppc64
support in Stretch (9) and Ubuntu dropped it in 18.04. Fedora also no longer has
ppc64 AFAIK.

So I guess we can run Ubuntu Xenial. That's LTS and has support until April 2021. That at least gets us security updates, and keeps us in the Debian family, consistent with most of of our other builders.

[laboger]

If the point of keeping linux/ppc64 was to root out endianness assumptions, doesn't linux/s390x get that for us? The s390x folk are doing an amazing job maintaining that port.

There's also aix/ppc64 which uses ppc64 big endian. Since that was just added, I'm assuming it will be around for a while. So we will have that to root out the endianness problems in ppc64 codegen.

Using an older distro on linux/ppc64 and one as new as possible on linux/ppc64le sounds fine to me. As @ianlancetaylor mentioned, when ppc64 went to power8 minimum we had complaints so there were users out there who wanted to keep using ppc64. I haven't heard much lately though.

[awilfox]

We at Adélie Linux were one of the groups pushing back on the POWER8 requirement. We support ppc64 back to the 970 (and ppc32 back to the 7xx series).

We're up to date, we don't believe IBM is correct in deprecating Linux big endian (we feel both endians have their place in the world), and we have no plans to ever deprecate ppc64 (I run it myself on my Talos workstation).

So, there's that. After our installer is written (which is happening now) a stable 1.0 will be released.

Edit my personal suggestion would be to run Xenial until we have 1.0 out, then we can work out whether Adélie would be a good fit and what you'd need from us.