Re: svn commit: r360233 - in head: contrib/jemalloc . . . : This partially breaks a 2-socket 32-bit powerpc (old PowerMac G4) based on head -r360311

[Brandon Bergren]

On Sun, May 3, 2020, at 9:38 AM, Mark Millard via freebsd-ppc wrote:
>
> Observing and reporting the reverting result is an initial
> part of problem isolation. I made no request for FreeBSD
> to give up on using the updated jemalloc. (Unfortunately,
> I'm not sure what a good next step of problem isolation
> might be for the dual-socket PowerMac G4 context.)

I appreciate this testing btw. The only dual-socket G4 I have (my xserve g4) does not have the second socket populated, so I am currently unable to test two-socket ppc32.

> Other than reverting, no patch is known for the issue at
> this point. More problem isolation is needed first.
> 
> While I do not have access, https://wiki.freebsd.org/powerpc
> lists more modern 32-bit powerpc hardware as supported:
> MPC85XX evaluation boards and AmigaOne A1222 (powerpcspe).
> (The AmigaOne A1222 seems to be dual-ore/single-socket.)

jhibbits has an A1222 that is used as an actual primary desktop, and I will hopefully have one at the end of the year. And I have an RB800 that I use for testing.

powerpcspe is really a different beast than aim32 though. I have been mainly working on aim32 on g4 laptops, although I do have an xserve.

> 
> So folks with access to one of those may want to see
> if they also see the problem(s) with head -r360233 or
> later.

Frankly, I wouldn't be surprised if this continues to be down to the timebase skew somehow. I know that jemalloc tends to be sensitive to time problems.

> 
> Another interesting context to test could be single-socket
> with just one core. (I might be able to do that on another
> old PowerMac, booting the same media after moving the
> media.)

That's my primary aim32 testing platform. I have a stack of g4 laptops that I test on, and a magically working usb stick (ADATA C008 / 8GB model. For some reason it just works, I've never seen another stick actually work)

> 
> If I understand right, the most common 32-bit powerpc
> tier 2 hardware platforms may still be old PowerMac's.
> They are considered supported and "mature", instead of
> just "stable". See https://wiki.freebsd.org/powerpc .
> However, the reality is that there are various problems
> for old PowerMacs (32-bit and 64-bit, at least when
> there is more than one socket present). The wiki page
> does not hint at such. (I'm not sure about
> single socket/multi-core PowerMacs: no access to
> such.)

Yes, neither I nor jhibbits have multiple socket g4 hardware at the moment, and I additionally don't have multiple socket g5 either.

> 
> It is certainly possible for some problem to happen
> that would lead to dropping the supported-status
> for some or all old 32-bit PowerMacs, even as tier 2.
> But that has not happened yet and I'd have no say in
> such a choice.

>From a kernel standpoint, I for one have no intention of dropping 32 bit support in the forseeable future. I've actually been putting more work into 32 bit than 64 bit recently in fact.

-- 
  Brandon Bergren
  bdragon at FreeBSD.org