linux-kernel - Re: [PATCH mm-new v3 1/1] mm/khugepaged: abort collapse scan on non-swap entries

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Message-ID: <24b12296-aa82-4269-a9ff-def815c3cef3@lucifer.local>
Date: Tue, 14 Oct 2025 16:57:17 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org,
        Liam.Howlett@...cle.com, baohua@...nel.org,
        baolin.wang@...ux.alibaba.com, dev.jain@....com, hughd@...gle.com,
        ioworker0@...il.com, kirill@...temov.name,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, mpenttil@...hat.com,
        npache@...hat.com, ryan.roberts@....com, ziy@...dia.com,
        richard.weiyang@...il.com
Subject: Re: [PATCH mm-new v3 1/1] mm/khugepaged: abort collapse scan on
 non-swap entries

On Tue, Oct 14, 2025 at 05:48:04PM +0200, David Hildenbrand wrote:
> On 14.10.25 17:41, Lorenzo Stoakes wrote:
> > On Tue, Oct 14, 2025 at 05:12:18PM +0200, David Hildenbrand wrote:
> > > Can we please take a step back and make sure we are not starting to do stuff
> > > differently than elswehere in the kernel, please?
> >
> > The code already had the is_swap_pte() check in it, so this is not changing
> > anything, it's just avoiding confusion.
>
> Well, in hpage_collapse_scan_pmd(), in __collapse_huge_page_isolate() no :)
>
> And then it's called SCAN_PTE_NON_PRESENT and it all starts being a mess
> TBH.

Yeah ugh. THP code is generally a mess :(

>
> But as raised offline, I don't have the time+energy for that today, so I
> don't care enough.

Time, energy? What are those? :P

>
> --
> Cheers
>
> David / dhildenb
>

Cheers, Lorenzo