Added documentation for the newly added sysfs mTHP "zswpout" stats.

Clarified that only non-ZSWAP mTHP swapouts will be accounted in the mTHP
"swpout" stats.

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
---
 Documentation/admin-guide/mm/transhuge.rst | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index cfdd16a52e39..a65f905e9ca7 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -530,10 +530,14 @@ anon_fault_fallback_charge
 	instead falls back to using huge pages with lower orders or
 	small pages even though the allocation was successful.
 
-swpout
-	is incremented every time a huge page is swapped out in one
+zswpout
+	is incremented every time a huge page is swapped out to ZSWAP in one
 	piece without splitting.
 
+swpout
+	is incremented every time a huge page is swapped out to a non-ZSWAP
+	swap entity in one piece without splitting.
+
 swpout_fallback
 	is incremented if a huge page has to be split before swapout.
 	Usually because failed to allocate some continuous swap space
-- 
2.27.0

On Mon, Sep 23, 2024 at 6:17 PM Kanchana P Sridhar
<kanchana.p.sridhar@intel.com> wrote:
>
> Added documentation for the newly added sysfs mTHP "zswpout" stats.
>
> Clarified that only non-ZSWAP mTHP swapouts will be accounted in the mTHP
> "swpout" stats.
>
> Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
> ---
>  Documentation/admin-guide/mm/transhuge.rst | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> index cfdd16a52e39..a65f905e9ca7 100644
> --- a/Documentation/admin-guide/mm/transhuge.rst
> +++ b/Documentation/admin-guide/mm/transhuge.rst
> @@ -530,10 +530,14 @@ anon_fault_fallback_charge
>         instead falls back to using huge pages with lower orders or
>         small pages even though the allocation was successful.
>
> -swpout
> -       is incremented every time a huge page is swapped out in one
> +zswpout
> +       is incremented every time a huge page is swapped out to ZSWAP in one
>         piece without splitting.

nit: a bit weird to capitalize ZSWAP no? :)

>
> +swpout
> +       is incremented every time a huge page is swapped out to a non-ZSWAP
> +       swap entity in one piece without splitting.
> +

nit: "non-zswap swap entity" is a bit awkward. Maybe swapped out to a
non-zswap swap device?

> -----Original Message-----
> From: Nhat Pham <nphamcs@gmail.com>
> Sent: Tuesday, September 24, 2024 10:37 AM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> hannes@cmpxchg.org; yosryahmed@google.com;
> chengming.zhou@linux.dev; usamaarif642@gmail.com;
> shakeel.butt@linux.dev; ryan.roberts@arm.com; Huang, Ying
> <ying.huang@intel.com>; 21cnbao@gmail.com; akpm@linux-foundation.org;
> Zou, Nanhai <nanhai.zou@intel.com>; Feghali, Wajdi K
> <wajdi.k.feghali@intel.com>; Gopal, Vinodh <vinodh.gopal@intel.com>
> Subject: Re: [PATCH v7 8/8] mm: Document the newly added mTHP zswpout
> stats, clarify swpout semantics.
> 
> On Mon, Sep 23, 2024 at 6:17 PM Kanchana P Sridhar
> <kanchana.p.sridhar@intel.com> wrote:
> >
> > Added documentation for the newly added sysfs mTHP "zswpout" stats.
> >
> > Clarified that only non-ZSWAP mTHP swapouts will be accounted in the
> mTHP
> > "swpout" stats.
> >
> > Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
> > ---
> >  Documentation/admin-guide/mm/transhuge.rst | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/mm/transhuge.rst
> b/Documentation/admin-guide/mm/transhuge.rst
> > index cfdd16a52e39..a65f905e9ca7 100644
> > --- a/Documentation/admin-guide/mm/transhuge.rst
> > +++ b/Documentation/admin-guide/mm/transhuge.rst
> > @@ -530,10 +530,14 @@ anon_fault_fallback_charge
> >         instead falls back to using huge pages with lower orders or
> >         small pages even though the allocation was successful.
> >
> > -swpout
> > -       is incremented every time a huge page is swapped out in one
> > +zswpout
> > +       is incremented every time a huge page is swapped out to ZSWAP in
> one
> >         piece without splitting.
> 
> nit: a bit weird to capitalize ZSWAP no? :)

No problem :). Will fix in v8.

> 
> >
> > +swpout
> > +       is incremented every time a huge page is swapped out to a non-ZSWAP
> > +       swap entity in one piece without splitting.
> > +
> 
> nit: "non-zswap swap entity" is a bit awkward. Maybe swapped out to a
> non-zswap swap device?

Sure, will make this change in v8. Thanks Nhat!