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 <fba4f0cb-6d18-4d7c-8b2e-3300be1c20e3@redhat.com>
In-Reply-To: <fba4f0cb-6d18-4d7c-8b2e-3300be1c20e3@redhat.com>
From: Barry Song <21cnbao@gmail.com>
Date: Tue, 16 Apr 2024 20:16:42 +1200
Message-ID: <CAGsJ_4zzk2VoR1eZ3NpxhfSF08uC_HGwNp7iQEYz6K1XxHB3Sg@mail.gmail.com>
Subject: Re: [PATCH v6 2/4] mm: add per-order mTHP anon_swpout and
 anon_swpout_fallback counters
To: David Hildenbrand <david@redhat.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org, cerasuolodomenico@gmail.com, 
	chrisl@kernel.org, kasong@tencent.com, linux-kernel@vger.kernel.org, 
	peterx@redhat.com, ryan.roberts@arm.com, surenb@google.com, 
	v-songbaohua@oppo.com, willy@infradead.org, yosryahmed@google.com, 
	yuzhao@google.com, corbet@lwn.net
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On Tue, Apr 16, 2024 at 8:14=E2=80=AFPM David Hildenbrand <david@redhat.com=
> wrote:
>
> On 12.04.24 13:48, Barry Song wrote:
> > From: Barry Song <v-songbaohua@oppo.com>
> >
> > This helps to display the fragmentation situation of the swapfile, know=
ing
> > the proportion of how much we haven't split large folios.  So far, we o=
nly
> > support non-split swapout for anon memory, with the possibility of
> > expanding to shmem in the future.  So, we add the "anon" prefix to the
> > counter names.
> >
> > Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> > Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> > Cc: Chris Li <chrisl@kernel.org>
> > Cc: David Hildenbrand <david@redhat.com>
> > Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> > Cc: Kairui Song <kasong@tencent.com>
> > Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> > Cc: Peter Xu <peterx@redhat.com>
> > Cc: Ryan Roberts <ryan.roberts@arm.com>
> > Cc: Suren Baghdasaryan <surenb@google.com>
> > Cc: Yosry Ahmed <yosryahmed@google.com>
> > Cc: Yu Zhao <yuzhao@google.com>
> > ---
> >   include/linux/huge_mm.h | 2 ++
> >   mm/huge_memory.c        | 4 ++++
> >   mm/page_io.c            | 1 +
> >   mm/vmscan.c             | 3 +++
> >   4 files changed, 10 insertions(+)
> >
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index d4fdb2641070..7cd07b83a3d0 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -268,6 +268,8 @@ enum mthp_stat_item {
> >       MTHP_STAT_ANON_FAULT_ALLOC,
> >       MTHP_STAT_ANON_FAULT_FALLBACK,
> >       MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
> > +     MTHP_STAT_ANON_SWPOUT,
> > +     MTHP_STAT_ANON_SWPOUT_FALLBACK,
> >       __MTHP_STAT_COUNT
> >   };
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index dfc38cc83a04..58f2c4745d80 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -555,11 +555,15 @@ static struct kobj_attribute _name##_attr =3D __A=
TTR_RO(_name)
> >   DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC);
> >   DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLB=
ACK);
> >   DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAUL=
T_FALLBACK_CHARGE);
> > +DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
> > +DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALL=
BACK);
> >
> >   static struct attribute *stats_attrs[] =3D {
> >       &anon_fault_alloc_attr.attr,
> >       &anon_fault_fallback_attr.attr,
> >       &anon_fault_fallback_charge_attr.attr,
> > +     &anon_swpout_attr.attr,
> > +     &anon_swpout_fallback_attr.attr,
> >       NULL,
> >   };
> >
> > diff --git a/mm/page_io.c b/mm/page_io.c
> > index a9a7c236aecc..46c603dddf04 100644
> > --- a/mm/page_io.c
> > +++ b/mm/page_io.c
> > @@ -217,6 +217,7 @@ static inline void count_swpout_vm_event(struct fol=
io *folio)
> >               count_memcg_folio_events(folio, THP_SWPOUT, 1);
> >               count_vm_event(THP_SWPOUT);
> >       }
> > +     count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_SWPOUT);
> >   #endif
> >       count_vm_events(PSWPOUT, folio_nr_pages(folio));
> >   }
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index bca2d9981c95..49bd94423961 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1231,6 +1231,8 @@ static unsigned int shrink_folio_list(struct list=
_head *folio_list,
> >                                               goto activate_locked;
> >                               }
> >                               if (!add_to_swap(folio)) {
> > +                                     int __maybe_unused order =3D foli=
o_order(folio);
> > +
> >                                       if (!folio_test_large(folio))
> >                                               goto activate_locked_spli=
t;
> >                                       /* Fallback to swap normal pages =
*/
> > @@ -1242,6 +1244,7 @@ static unsigned int shrink_folio_list(struct list=
_head *folio_list,
> >                                                       THP_SWPOUT_FALLBA=
CK, 1);
> >                                               count_vm_event(THP_SWPOUT=
_FALLBACK);
> >                                       }
> > +                                     count_mthp_stat(order, MTHP_STAT_=
ANON_SWPOUT_FALLBACK);
>
> Why the temporary variable for order?
>
> count_mthp_stat(folio_order(order),
>                  MTHP_STAT_ANON_SWPOUT_FALLBACK);
>
> ... but now I do wonder if we want to pass the folio to count_mthp_stat()=
 ?

because we have called split_folio_to_list() before counting. that is also
why Ryan is using if (nr_pages >=3D HPAGE_PMD_NR) but not pmd_mappable.


>
> Anyhow
>
> Acked-by: David Hildenbrand <david@redhat.com>

thanks!

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