Re: 9.4 broken on alpha

Michael Cree <mcree(at)orcon(dot)net(dot)nz> writes:
> On Tue, Aug 25, 2015 at 06:09:17PM -0400, Tom Lane wrote:
>> It'd be easy enough to s/rmb/mb/ in 9.4 ... but not sure it's worth
>> the trouble, since we're desupporting Alpha as of 9.5 anyway.

> That is disappointing to hear. Why is that? It is still in use on
> Alpha. What is the maintenance load for keeping the Alpha arch
> specific code?

The core problem is that Alpha's unusually lax memory coherency model
creates design and testing problems we face with no other architecture.
We're not really excited about carrying that burden for a legacy
architecture that isn't competitive in the modern world. Even if we
were, it's completely impractical to maintain such an unusual port
when there is no representative of the architecture in our buildfarm
(http://buildfarm.postgresql.org/cgi-bin/show_status.pl). It's worth
pointing out that had there been one, we would have noticed the rmb
problem long before 9.4 ever shipped.

I do not know anything about the prevalence of multi-CPU Alpha machines.
If they're thin on the ground compared to single-CPU, maybe we could just
document that we only support the latter, and not worry too much about
the memory coherency issues. But in any case, without a commitment from
somebody to maintain an Alpha buildfarm member, we will absolutely not
consider reviving that port.

regards, tom lane