Re: DISCONTIGMEM is deprecated

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Mon, Apr 29, 2019 at 04:58:09PM +0000, Luck, Tony wrote:
> > ia64 has a such a huge number of memory model choices.  Maybe we
> > need to cut it down to a small set that actually work.
> 
> SGI systems had extremely discontiguous memory (they used some high
> order physical address bits in the tens/hundreds of terabyte range for the
> node number ... so there would be a few GBytes of actual memory then
> a huge gap before the next node had a few more Gbytes).
> 
> I don't know of anyone still booting upstream on an SN2, so if we start doing
> serious hack and slash the chances are high that SN2 will be broken (if it isn't
> already).

When I wrote this, I thought of

!NUMA:  flat mem
NUMA:	sparsemem
SN2:	discontig

based on Meelis report.  But now that you mention it, I bet SN2 has
already died slow death from bitrot.  It is so different in places, and
it doesn't seem like anyone care - if people want room sized SGI
machines the Origin is much more sexy (hello Thomas!) :)

So maybe it it time to mark SN2 broken and see if anyone screams?

Without SN2 the whole machvec mess could basically go away - the
only real difference between the remaining machvecs is which iommu
if any we set up.