Re: RFC: remove the "tile" architecture from glibc

[John Paul Adrian Glaubitz <glaubitz at physik dot fu-berlin dot de>]

Hi Chris!

On 12/01/2017 10:34 PM, Chris Metcalf wrote:
> The tile architecture was introduced to glibc in 2011 and first
> appeared in glibc 2.15.  The chip family of TILEPro and TILE-Gx was
> developed by Tilera, which was eventually acquired by Mellanox.  Now
> at Mellanox we are developing new chips based on the ARM64
> architecture; our last TILE-Gx chip (the Gx72) was released in 2013,
> and our customers using the tile architecture products are now all in
> maintenance mode, as far as we know, and not looking to upgrade their
> software to newer open-source releases.

This feels very odd. It isn't been very long until I heard about TileGX
for the first time when I saw a talk by a Japanese Debian guy who showed
me his efforts to get Debian running on a small router with impressive
performance [1]. The board built gcc natively in just about two hours.

Tile has also been added to Debian Rebootstrap and it's currently possible
to bootstrap for this architecture from source. The Jenkins job shows
that this currently is successful.

> Compounding this state of affairs is the fact that after twelve years
> here I am moving on next week; my last day at Mellanox is December
> 8th.  Since tracking upstream development of the old tile architecture
> is not a high priority for Mellanox, reasonably enough, it seems
> cleanest at this point to propose removal of the architecture from the
> glibc tree, so that the 2.26 release will be the last release to have
> tile support.

But why should it be only up to Mellanox whether support for Tile is
part of glibc or not. I find straight up removal a bit too strong,
especially since QEMU supports Tile as well. I think the first step
should just be to mark the Tile port of glibc as unmaintained but not
remove it altogether. That could be too frustrating for people using
it. I'm pretty sure that there are more than just Mellanox' customers
who are using Linux on Tile.

> If there is any desire to continue to support the tile architecture in
> glibc, I'm happy to hand off to someone else as maintainer.  I'm aware
> of one issue in the current code, which is that upstream gcc vector
> insn support has a bug in it that causes some of the string functions
> to misbehave; I can publish a fix for that before handing off, if desired.

Yes, that would be great. If it's a known bug and there is a known,
working fix, it would be great if it could be merged upstream and
Tile support be kept for a while for the people hacking on Debian
on Tile.

> I will in any case be dropping off the glibc list (other than perhaps
> occasionally reading the archives) at the end of next week.  It's been
> a rewarding experience following glibc's development over the last six
> years and I will certainly miss being part of this community.

And here I am just having joined the list, this being one of the first
things too read :/.

> I'm keeping that libc.so.6 sticker I got from Carlos, though!  :)

Adrian

> [1] https://mikrotik.com/product/CCR1009-7G-1C-1SplusPC
> [2] https://jenkins.debian.net/view/rebootstrap/

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913