linux-kernel - Re: [PATCH v3] mm: add per-order mTHP swpin counters

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Message-ID: <CAGsJ_4yoH2qVpiVmYhYH6WTN4yueQ4yYw+P-CG4Q-dKjc9VVRQ@mail.gmail.com>
Date: Thu, 31 Oct 2024 21:21:24 +1300
From: Barry Song <21cnbao@...il.com>
To: "Huang, Ying" <ying.huang@...el.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Barry Song <v-songbaohua@...o.com>, 
	Baolin Wang <baolin.wang@...ux.alibaba.com>, David Hildenbrand <david@...hat.com>, 
	Chris Li <chrisl@...nel.org>, Yosry Ahmed <yosryahmed@...gle.com>, 
	Kairui Song <kasong@...cent.com>, Ryan Roberts <ryan.roberts@....com>, 
	Kanchana P Sridhar <kanchana.p.sridhar@...el.com>, Usama Arif <usamaarif642@...il.com>
Subject: Re: [PATCH v3] mm: add per-order mTHP swpin counters

On Thu, Oct 31, 2024 at 9:09 PM Huang, Ying <ying.huang@...el.com> wrote:
>
> Barry Song <21cnbao@...il.com> writes:
>
> > From: Barry Song <v-songbaohua@...o.com>
> >
> > This helps profile the sizes of folios being swapped in. Currently,
> > only mTHP swap-out is being counted.
> > The new interface can be found at:
> > /sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats/swpin
> > For example,
> > $ cat /sys/kernel/mm/transparent_hugepage/hugepages-64kB/stats/swpin
> > 12809
> > $ cat /sys/kernel/mm/transparent_hugepage/hugepages-32kB/stats/swpin
> > 4763
> >
> > Signed-off-by: Barry Song <v-songbaohua@...o.com>
> > Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> > Acked-by: David Hildenbrand <david@...hat.com>
> > Cc: Chris Li <chrisl@...nel.org>
> > Cc: Yosry Ahmed <yosryahmed@...gle.com>
> > Cc: "Huang, Ying" <ying.huang@...el.com>
> > Cc: Kairui Song <kasong@...cent.com>
> > Cc: Ryan Roberts <ryan.roberts@....com>
> > Cc: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
> > Cc: Usama Arif <usamaarif642@...il.com>
> > ---
> >  -v3: minor refine changelog per Huang, Ying. thanks!
> >
> >  Documentation/admin-guide/mm/transhuge.rst | 4 ++++
> >  include/linux/huge_mm.h                    | 1 +
> >  mm/huge_memory.c                           | 3 +++
> >  mm/page_io.c                               | 3 +++
> >  4 files changed, 11 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> > index 2a171ed5206e..5caa3fb2feb1 100644
> > --- a/Documentation/admin-guide/mm/transhuge.rst
> > +++ b/Documentation/admin-guide/mm/transhuge.rst
> > @@ -534,6 +534,10 @@ zswpout
> >       is incremented every time a huge page is swapped out to zswap in one
> >       piece without splitting.
> >
> > +swpin
> > +     is incremented every time a huge page is swapped in from a non-zswap
> > +     swap device in one piece.
> > +
> >  swpout
> >       is incremented every time a huge page is swapped out to a non-zswap
> >       swap device in one piece without splitting.
>
> In Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage, I
> found
>
> "
> What:           /sys/kernel/mm/transparent_hugepage/
> Date:           April 2024
> Contact:        Linux memory management mailing list <linux-mm@...ck.org>
> Description:
>                 /sys/kernel/mm/transparent_hugepage/ contains a number of files and
>                 subdirectories,
>
>                         - defrag
>                         - enabled
>                         - hpage_pmd_size
>                         - khugepaged
>                         - shmem_enabled
>                         - use_zero_page
>                         - subdirectories of the form hugepages-<size>kB, where <size>
>                           is the page size of the hugepages supported by the kernel/CPU
>                           combination.
>
>                 See Documentation/admin-guide/mm/transhuge.rst for details.
> "
>
> So, Documentation/admin-guide/mm/transhuge.rst will be used as ABI
> document?

Yes. this follows:

sysfs-kernel-mm-hugepages:              See
Documentation/admin-guide/mm/hugetlbpage.rst for details.
sysfs-kernel-mm-ksm:            See Documentation/mm/ksm.rst for more
information.
sysfs-kernel-mm-transparent-hugepage:           See
Documentation/admin-guide/mm/transhuge.rst for details.


>
> [snip]
>
> --
> Best Regards,
> Huang, Ying

Thanks
barry