linux-kernel - Re: [PATCH v11 00/15] khugepaged: mTHP support

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Message-ID: <78d75263-e0ab-4dcd-ae97-5c5c9bb10193@redhat.com>
Date: Mon, 15 Sep 2025 12:25:54 +0200
From: David Hildenbrand <david@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
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Subject: Re: [PATCH v11 00/15] khugepaged: mTHP support

>>
>> 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.

> 
> 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.

-- 
Cheers

David / dhildenb