Re: [RFC PATCH 5/5] mm: shmem: add anonymous share mTHP counters

[Baolin Wang]

On 2024/4/23 09:17, Barry Song wrote:
> On Mon, Apr 22, 2024 at 3:03 PM Baolin Wang
> <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
> > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > ---
> >   include/linux/huge_mm.h | 2 ++
> >   mm/huge_memory.c        | 4 ++++
> >   mm/shmem.c              | 5 ++++-
> >   3 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 26b6fa98d8ac..67b9c1acad31 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -270,6 +270,8 @@ enum mthp_stat_item {
> >          MTHP_STAT_ANON_SWPOUT,
> >          MTHP_STAT_ANON_SWPOUT_FALLBACK,
> >          MTHP_STAT_ANON_SWPIN_REFAULT,
> > +       MTHP_STAT_SHMEM_ANON_ALLOC,
> > +       MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK,
>
> not quite sure about this. for 2MB pmd-mapped THP shmem, we count them
> as FILE_THP.
> here we are counting as SHMEM_ANON. To me, SHMEM_ANON is more correct but
> it doesn't align with pmd-mapped THP. David, Ryan, what do you think?

Thanks for reviewing.

IMO, I think both approaches are acceptable, which also reflects the 
dual nature of anonymous shared pages: on the one hand they are 
anonymous pages, and on the other hand, they are backed by a pseudo 
file. From the user's perspective, I prefer to use the term "anonymous 
shmem", which can be distinguished from the real file-backed THP.

Anyway, let's see what others think.

> >          __MTHP_STAT_COUNT
> >   };
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 9e52c0db7580..dc15240c1ab3 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -557,6 +557,8 @@ DEFINE_MTHP_STAT_ATTR(anon_alloc_fallback, MTHP_STAT_ANON_ALLOC_FALLBACK);
> >   DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
> >   DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK);
> >   DEFINE_MTHP_STAT_ATTR(anon_swpin_refault, MTHP_STAT_ANON_SWPIN_REFAULT);
> > +DEFINE_MTHP_STAT_ATTR(shmem_anon_alloc, MTHP_STAT_SHMEM_ANON_ALLOC);
> > +DEFINE_MTHP_STAT_ATTR(shmem_anon_alloc_fallback, MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK);
> >
> >   static struct attribute *stats_attrs[] = {
> >          &anon_alloc_attr.attr,
> > @@ -564,6 +566,8 @@ static struct attribute *stats_attrs[] = {
> >          &anon_swpout_attr.attr,
> >          &anon_swpout_fallback_attr.attr,
> >          &anon_swpin_refault_attr.attr,
> > +       &shmem_anon_alloc_attr.attr,
> > +       &shmem_anon_alloc_fallback_attr.attr,
> >          NULL,
> >   };
> >
> > diff --git a/mm/shmem.c b/mm/shmem.c
> > index 8b009e7040b2..4a0aa75ab29c 100644
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -1706,11 +1706,14 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
> >                          pages = 1 << order;
> >                          index = round_down(index, pages);
> >                          folio = shmem_alloc_hugefolio(gfp, info, index, order);
> > -                       if (folio)
> > +                       if (folio) {
> > +                               count_mthp_stat(order, MTHP_STAT_SHMEM_ANON_ALLOC);
> >                                  goto allocated;
> > +                       }
> >
> >                          if (pages == HPAGE_PMD_NR)
> >                                  count_vm_event(THP_FILE_FALLBACK);
> > +                       count_mthp_stat(order, MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK);
> >                          order = next_order(&orders, order);
> >                  }
> >          } else {
> > --
> > 2.39.3
>
> Thanks
> Barry