On Mon, Sep 15, 2025 at 12:25:54PM +0200, David Hildenbrand wrote:

quoted

quoted

I would just say "The kernel might decide to use a more conservative approach
when collapsing smaller THPs" etc.


Thoughts?

Well I've sort of reviewed oppositely there :) well at least that it needs to be
a hell of a lot clearer (I find that comment really compressed and I just don't
really understand it).

Right. I think these are just details we should hide from the user. And in
particular, not over-document it so we can more easily change semantics
later.

And when we change semantics we can't change comments?

I mean maybe we're talking across purposes here, I'm talking about code
comments, not the documentation.

I agree the documentation should not mention any of this.

quoted

I guess I didn't think about people reading that and relying on it, so maybe we
could alternatively make that succinct.

But I think it'd be better to say something like "mTHP collapse cannot currently
correctly function with half or more of the PTE entries empty, so we cap at just
below this level" in this case.

IMHO we should just say that the value might be reduced for internal
purposes and that this behavior might change in the future would likely be
good enough.

Again, I assume you mean documentation rather than comments?

--
Cheers

David / dhildenb

Cheers, Lorenzo