Re: [RFC PATCH 00/40] mm: reliable 1GB page allocation

[Rik van Riel <riel@surriel.com>]

On Sat, 2026-06-27 at 10:28 +0100, Lorenzo Stoakes wrote:
> 
> So really, you need to start again, from scratch, and without the use
> of an
> LLM for generating code, or at least with it kept on a (very very
> short)
> leash.
> 
> And to be clear, I _want_ this concept of GB superpageblocks to land.
> It's
> a really exciting concept.

That is the one reason I sent out RFC code before it
is ready. I am looking for feedback on the concepts
in this series.

How do people feel about splitting up the free lists,
so each gigabyte (well, PUD sized) chunk of memory
has its own free lists?

How can we balance the desire for higher-order kernel
allocations, against the desire to preserve gigabyte
sized chunks of memory that can be used for user space?

> 
> Pulling compaction kicking and screaming into 2026 stands to
> significantly
> benefit linux users and developers.

That's another big question. How do we balance the
desire to keep compaction overhead low with the desire
to do higher order allocations almost everywhere?

> 
> But the execution has to be _completely_ rethought.

There's no argument there.

I am just hoping to figure out what I should be
doing on a conceptual level, before figuring out
how to do it cleanly.

The mess in the RFC is the result of trying something
that seemed right, watching it fail in some subtle
way, and trying to fix it up.

Once I know what I need to do, coming up with a
cleaner implementation is very doable.

> 
> IOW I say we take off and nuke the entire site from orbit. It's the
> only
> way to be sure :)
> 
BOOM?

> Another issue here is maintainer time - even this _extremely_ light-
> touch
> review has taken me a few hours (of my weekend :). To review it in
> detail
> would take probably DAYS of dedicated work.

I suspect there is a mismatch in expectations here.

I already knew this code has to be totally redone.

I was looking for feedback on the basic concepts
and design in the patch series, but failed to
clearly communicate that.

You provided some detailed feedback on the code,
but as of yet nobody has really provided any
opinions on things like whether it is desirable
at all to have the free lists per gigablock,
or whether we need to come up with some totally
different approach.

How do we better communicate that kind of thing
in the future?

Is that something to spell out more clearly in
the cover letter?

Is that kind of feedback something developers
could even reasonably ask for? (if not, how do
we figure out what maintainers want?)


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