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

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Message-ID: <e450009a-56c9-4820-bd0c-da1d782d3962@redhat.com>
Date: Mon, 15 Sep 2025 13:14:32 +0200
From: David Hildenbrand <david@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Kiryl Shutsemau <kas@...nel.org>, Nico Pache <npache@...hat.com>,
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Subject: Re: [PATCH v11 00/15] khugepaged: mTHP support

On 15.09.25 13:02, Lorenzo Stoakes wrote:
> On Mon, Sep 15, 2025 at 12:52:03PM +0200, David Hildenbrand wrote:
>> On 15.09.25 12:43, Lorenzo Stoakes wrote:
>>> On Mon, Sep 15, 2025 at 12:22:07PM +0200, David Hildenbrand wrote:
>>>>
>>>> 0 -> ~100% used (~0% none)
>>>> 1 -> ~50% used (~50% none)
>>>> 2 -> ~25% used (~75% none)
>>>> 3 -> ~12.5% used (~87.5% none)
>>>> 4 -> ~11.25% used (~88,75% none)
>>>> ...
>>>> 10 -> ~0% used (~100% none)
>>>
>>> Oh and shouldn't this be inverted?
>>>
>>> 0 eagerness = we eat up all none PTE entries? Isn't that pretty eager? :P
>>> 10 eagerness = we aren't eager to eat up none PTE entries at all?
>>>
>>> Or am I being dumb here?
>>
>> Good question.
>>
>> For swappiness it's: 0 -> no swap (conservative)
>>
>> So intuitively I assumed: 0 -> no pte_none (conservative)
>>
>> You're the native speaker, so you tell me :)
> 
> To me this is about 'eagerness to consume empty PTE entries' so 10 is more
> eager, 0 is not eager at all, i.e. inversion of what you suggest :)

Just so we are on the same page: it is about "eagerness to collapse", right?

Wouldn't a 0 mean "I am not eager, I will not waste any memory, I am 
very careful and bail out on any pte_none" vs. 10 meaning "I am very 
eager, I will collapse no matter what I find in the page table, waste as 
much memory as I want"?

-- 
Cheers

David / dhildenb