Re: [Patch v2] mm/huge_memory: add pmd folio to ds_queue in do_huge_zero_wp_pmd()

[Wei Yang <richard.weiyang@gmail.com>]

On Fri, Oct 03, 2025 at 09:49:28PM +0800, Lance Yang wrote:
>Hey Wei,
>
>On 2025/10/2 09:38, Wei Yang wrote:
>> We add pmd folio into ds_queue on the first page fault in
>> __do_huge_pmd_anonymous_page(), so that we can split it in case of
>> memory pressure. This should be the same for a pmd folio during wp
>> page fault.
>> 
>> Commit 1ced09e0331f ("mm: allocate THP on hugezeropage wp-fault") miss
>> to add it to ds_queue, which means system may not reclaim enough memory
>
>IIRC, it was commit dafff3f4c850 ("mm: split underused THPs") that
>started unconditionally adding all new anon THPs to _deferred_list :)
>

Thanks for taking a look.

While at this time do_huge_zero_wp_pmd() is not introduced, how it fix a
non-exist case? And how could it be backported? I am confused here.

>> in case of memory pressure even the pmd folio is under used.
>> 
>> Move deferred_split_folio() into map_anon_folio_pmd() to make the pmd
>> folio installation consistent.
>> 
>> Fixes: 1ced09e0331f ("mm: allocate THP on hugezeropage wp-fault")
>
>Shouldn't this rather be the following?
>
>Fixes: dafff3f4c850 ("mm: split underused THPs")
>
>Thanks,
>Lance

-- 
Wei Yang
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