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

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Message-ID: <de3f5502-ef81-4f44-96a9-995e512301a3@redhat.com>
Date: Mon, 15 Sep 2025 12:52:53 +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 12:48, Lorenzo Stoakes wrote:
> On Mon, Sep 15, 2025 at 12:44:34PM +0200, David Hildenbrand wrote:
>>>>> Mapping that to actual THP sizes (#pages in a thp) on an arch will be easy.
>>>>
>>>> And at different mTHP levels too right?
>>>>
>>>
>>> Another point here, since we have to keep:
>>>
>>> /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none
>>>
>>> Around, and users will try to set values there, presumably we will now add:
>>>
>>> /sys/kernel/mm/transparent_hugepage/khugepaged/eagerness
>>>
>>> How will we map <-> the two tunables?
>>
>> Well, the easy case if someone updates eagerness, then we simply et it to
>> whatever magic value we compute and document.
>>
>> The other direction is more problematic, likely we'll simply warn and do
>> something reasonable (map it to whatever eagerness scale is closest or
>> simply indicate it as "-1" -- user intervened or sth like that)
> 
> I don't love the idea of a -1 situation, as that's going to create some
> confusion.

swapiness also has a "max" parameter, so we could just say "override" /" 
disabled" / whatever?

-- 
Cheers

David / dhildenb