[LSF/MM/BPF TOPIC] Separately allocating memdescs from struct page

[LSF/MM/BPF TOPIC] Separately allocating memdescs from struct page

[Vishal Moola (Oracle)]

As part of the overarching project to shrink struct page, we've been
creating memdescs that currently function as wrappers around it[1].
Until we separately allocate memdescs, we won't be able to shrink the
page.

We're getting close to being able to allocate memdescs separately from
struct page, and I'd like to propose the topic to discuss how we want
to go about it. We already have Matthew's PoC for ptdescs[2]. I've taken
that on, but we're still running into issues for now...

Heres a non-exhaustive list of things I'd like to discuss:
- What memdescs to separate allocate for shrinking the page right now
- What are the implications of separate allocations
- Should we separately allocate one at a time, or all at once
- How the APIs would look
- Are there other generic fields to be cautious about (i.e. memcg)

I imagine Matthew might have a broader State of the Page talk too, so
this would be more in-depth. Possibly focused on ptdesc & slab (as the
two we're actively looking at right now).

[1] https://kernelnewbies.org/MatthewWilcox/Memdescs
[2] https://lore.kernel.org/linux-mm/20251020001652.2116669-1-willy@infradead.org/