Re: [PATCH 4/5] mm: support batched checking of the young flag for MGLRU

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 2/26/26 5:08 PM, David Hildenbrand (Arm) wrote:
> 
>>>
>>>> +            pte_t pteval = ptep_get(pvmw.pte);
>>>
>>> I wonder if there could be a way to avoid this ptep_get() by letting
>>> page_vma_mapped_walk() just provide the last value it used (in
>>> check_pte() I guess). Something for another patch.
>>
>> Well, we’d need to add a new field to ‘struct page_vma_mapped_walk’ to
>> store the last value (e.g., pvmw.pteval),
> 
> Yes.
> 
>> but this makes me wonder if it
>> is worth adding a new field just to avoid a lightweight read (which
>> should have no obvious performance impact).
> 
> You recall that ptep_get() on arm64 is not that lightweight due to
> con-pte? :)
> 
> But yeah, something for another day.

OK.

>>> What is "batched"? Did you mean "nr_ptes" ? Or just the initial value
>>> for "nr" ?
>>
>> There is already an 'nr' variable in this function. "nr_ptes" sounds
>> good to me, and will use it.
> 
> You can just use "nr" here and reuse it for the existing variable?
> 
> Both have the same semantics (nr of ptes / pages), so having a single
> value might cause less confusion.

Sure. Will do.