linux-kernel - Re: [PATCH v2 5/5] mm: add per-order mTHP swpin

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Message-ID: <CAGsJ_4yoz=UH+=Z+ZmRy_9=vu_JWuOXnNO0gFtkBZ-rKJppMPA@mail.gmail.com>
Date: Wed, 17 Apr 2024 09:16:01 +0800
From: Barry Song <21cnbao@...il.com>
To: "Huang, Ying" <ying.huang@...el.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	baolin.wang@...ux.alibaba.com, chrisl@...nel.org, david@...hat.com, 
	hanchuanhua@...o.com, hannes@...xchg.org, hughd@...gle.com, 
	kasong@...cent.com, ryan.roberts@....com, surenb@...gle.com, 
	v-songbaohua@...o.com, willy@...radead.org, xiang@...nel.org, 
	yosryahmed@...gle.com, yuzhao@...gle.com, ziy@...dia.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] mm: add per-order mTHP swpin_refault counter

On Wed, Apr 17, 2024 at 8:47 AM Huang, Ying <ying.huang@...el.com> wrote:
>
> Barry Song <21cnbao@...il.com> writes:
>
> > From: Barry Song <v-songbaohua@...o.com>
> >
> > Currently, we are handling the scenario where we've hit a
> > large folio in the swapcache, and the reclaiming process
> > for this large folio is still ongoing.
> >
> > Signed-off-by: Barry Song <v-songbaohua@...o.com>
> > ---
> >  include/linux/huge_mm.h | 1 +
> >  mm/huge_memory.c        | 2 ++
> >  mm/memory.c             | 1 +
> >  3 files changed, 4 insertions(+)
> >
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index c8256af83e33..b67294d5814f 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -269,6 +269,7 @@ enum mthp_stat_item {
> >       MTHP_STAT_ANON_ALLOC_FALLBACK,
> >       MTHP_STAT_ANON_SWPOUT,
> >       MTHP_STAT_ANON_SWPOUT_FALLBACK,
> > +     MTHP_STAT_ANON_SWPIN_REFAULT,
>
> This is different from the refault concept used in other place in mm
> subystem.  Please check the following code
>
>         if (shadow)
>                 workingset_refault(folio, shadow);
>
> in __read_swap_cache_async().

right. it is slightly different as refault can also cover the case folios
have been entirely released and a new page fault happens soon
after it.
Do you have a better name for this?
MTHP_STAT_ANON_SWPIN_UNDER_RECLAIM
or
MTHP_STAT_ANON_SWPIN_RECLAIMING ?

>
> >       __MTHP_STAT_COUNT
> >  };
>
> --
> Best Regards,
> Huang, Ying
>
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index d8d2ed80b0bf..fb95345b0bde 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -556,12 +556,14 @@ DEFINE_MTHP_STAT_ATTR(anon_alloc, MTHP_STAT_ANON_ALLOC);
> >  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);
> >
> >  static struct attribute *stats_attrs[] = {
> >       &anon_alloc_attr.attr,
> >       &anon_alloc_fallback_attr.attr,
> >       &anon_swpout_attr.attr,
> >       &anon_swpout_fallback_attr.attr,
> > +     &anon_swpin_refault_attr.attr,
> >       NULL,
> >  };
> >
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 9818dc1893c8..acc023795a4d 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -4167,6 +4167,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> >               nr_pages = nr;
> >               entry = folio->swap;
> >               page = &folio->page;
> > +             count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_SWPIN_REFAULT);
> >       }
> >
> >  check_pte: