Re: [RFC 00/12] mm: PUD (1GB) THP implementation

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

OK so this is somewhat unexpected :)

It would have been nice to discuss it in the THP cabal or at a conference
etc. so we could discuss approaches ahead of time. Communication is important,
especially with major changes like this.

And PUD THP is especially problematic in that it requires pages that the page
allocator can't give us, presumably you're doing something with CMA and... it's
a whole kettle of fish.

It's also complicated by the fact we _already_ support it in the DAX, VFIO cases
but it's kinda a weird sorta special case that we need to keep supporting.

There's questions about how this will interact with khugepaged, MADV_COLLAPSE,
mTHP (and really I want to see Nico's series land before we really consider
this).

So overall, I want to be very cautious and SLOW here. So let's please not drop
the RFC tag until David and I are ok with that?

Also the THP code base is in _dire_ need of rework, and I don't really want to
add major new features without us paying down some technical debt, to be honest.

So let's proceed with caution, and treat this as a very early bit of
experimental code.

Thanks, Lorenzo