Re: [PATCH] smaps: count large pages smaller than PMD size to anonymous_thp

[Lance Yang <ioworker0@gmail.com>]

On Tue, Dec 3, 2024 at 10:17 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 03.12.24 14:49, Wenchao Hao wrote:
> > Currently, /proc/xxx/smaps reports the size of anonymous huge pages for
> > each VMA, but it does not include large pages smaller than PMD size.
> >
> > This patch adds the statistics of anonymous huge pages allocated by
> > mTHP which is smaller than PMD size to AnonHugePages field in smaps.
> >
> > Signed-off-by: Wenchao Hao <haowenchao22@gmail.com>
> > ---
> >   fs/proc/task_mmu.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 38a5a3e9cba2..b655011627d8 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -717,6 +717,12 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
> >               if (!folio_test_swapbacked(folio) && !dirty &&
> >                   !folio_test_dirty(folio))
> >                       mss->lazyfree += size;
> > +
> > +             /*
> > +              * Count large pages smaller than PMD size to anonymous_thp
> > +              */
> > +             if (!compound && PageHead(page) && folio_order(folio))
> > +                     mss->anonymous_thp += folio_size(folio);
> >       }
> >
> >       if (folio_test_ksm(folio))
>
>
> I think we decided to leave this (and /proc/meminfo) be one of the last
> interfaces where this is only concerned with PMD-sized ones:
>
> Documentation/admin-guide/mm/transhuge.rst:
>
> The number of PMD-sized anonymous transparent huge pages currently used by the
> system is available by reading the AnonHugePages field in ``/proc/meminfo``.
> To identify what applications are using PMD-sized anonymous transparent huge
> pages, it is necessary to read ``/proc/PID/smaps`` and count the AnonHugePages
> fields for each mapping. (Note that AnonHugePages only applies to traditional
> PMD-sized THP for historical reasons and should have been called
> AnonHugePmdMapped).

Yeah, I think we need to keep AnonHugePages unchanged within these interfaces
due to historical reasons ;)

Perhaps, there might be another way to count all THP allocated for each process.

Thanks,
Lance


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