Re: [PATCH HOTFIX 6.17] mm/mremap: avoid expensive folio lookup on mremap folio pte batch

[Lorenzo Stoakes]

On Fri, Aug 08, 2025 at 02:14:08PM +0530, Dev Jain wrote:
>
> On 08/08/25 1:26 pm, Ryan Roberts wrote:
> > ACK; Dev, perhaps you can take another look at this and work up a patch to more
> > agressively avoid vm_normal_folio() for mprotect?
>
> Yup I'll investigate this in a few weeks time perhaps - try to use pte_batch_hint(),
> and when we have to unconditionally retrieve the folio, then use that instead.
>
> I'll also look into whether even for arm64, there is any use in retrieving
> the folio at all - the only benefit we get is to batch across contig blocks, but I don't
> think there are any atomic operations (refcount/mapcount manipulation) which will be saved.
> By batching across a single contig block we save on ptep_get calls and TLBIs, which was
> our objective.

Ah nice, if we only ever need to consider a single contig block this makes life
a lot easier I think.