Re: [PATCH v3 1/2] mm: add per-order mTHP split counters

[Lance Yang <ioworker0@gmail.com>]

Hi David and Barry,

Thanks a lot for paying attention!

On Fri, Jul 5, 2024 at 6:14 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 05.07.24 12:12, Barry Song wrote:
> > On Fri, Jul 5, 2024 at 9:08 PM David Hildenbrand <david@redhat.com> wrote:
> >>
> >>> @@ -3253,8 +3259,9 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
> >>>                i_mmap_unlock_read(mapping);
> >>>    out:
> >>>        xas_destroy(&xas);
> >>> -     if (is_thp)
> >>> +     if (order >= HPAGE_PMD_ORDER)
> >>
> >> We likely should be using "== HPAGE_PMD_ORDER" here, to be safe for the
> >> future.
> >
> > I feel this might need to be separate since all other places are using
> > folio_test_pmd_mappable() ?
>
> Likely, but as you are moving away from this ... this counter here does
> and will always only care about HPAGE_PMD_ORDER.

I appreciate the different opinions on whether we should use
">= HPAGE_PMD_ORDER" or "==" for this check.

In this context, let's leave it as is and stay consistent with
folio_test_pmd_mappable() by using ">= HPAGE_PMD_ORDER",
what do you think?

Thanks,
Lance

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