RE: [PATCH v6 3/3] mm: swap: Count successful mTHP ZSWAP stores in sysfs mTHP zswpout stats.

["Sridhar, Kanchana P" <kanchana.p.sridhar@intel.com>]

> -----Original Message-----
> From: Yosry Ahmed <yosryahmed@google.com>
> Sent: Friday, September 20, 2024 3:58 PM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> hannes@cmpxchg.org; nphamcs@gmail.com; chengming.zhou@linux.dev;
> usamaarif642@gmail.com; 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 v6 3/3] mm: swap: Count successful mTHP ZSWAP stores
> in sysfs mTHP zswpout stats.
> 
> On Thu, Aug 29, 2024 at 2:27 PM Kanchana P Sridhar
> <kanchana.p.sridhar@intel.com> wrote:
> >
> > Add a new MTHP_STAT_ZSWPOUT entry to the sysfs mTHP stats so that
> > per-order mTHP folio ZSWAP stores can be accounted.
> >
> > If zswap_store() successfully swaps out an mTHP, it will be counted under
> > the per-order sysfs "zswpout" stats:
> >
> > /sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/zswpout
> >
> > Other block dev/fs mTHP swap-out events will be counted under
> > the existing sysfs "swpout" stats:
> >
> > /sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/swpout
> >
> > Based on changes made in commit
> 61e751c01466ffef5dc72cb64349454a691c6bfe
> > ("mm: cleanup count_mthp_stat() definition"), this patch also moves
> > the call to count_mthp_stat() in count_swpout_vm_event() to be outside
> > the "ifdef CONFIG_TRANSPARENT_HUGEPAGE".
> 
> This should be in a separate change, it's irrelevant to
> MTHP_STAT_ZSWPOUT being added.

Sure. I will submit this as a separate change.

Thanks,
Kanchana

> 
> >
> > Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
> > ---
> >  include/linux/huge_mm.h | 1 +
> >  mm/huge_memory.c        | 3 +++
> >  mm/page_io.c            | 3 ++-
> >  3 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 4da102b74a8c..8b690328e78b 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -118,6 +118,7 @@ enum mthp_stat_item {
> >         MTHP_STAT_ANON_FAULT_ALLOC,
> >         MTHP_STAT_ANON_FAULT_FALLBACK,
> >         MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
> > +       MTHP_STAT_ZSWPOUT,
> >         MTHP_STAT_SWPOUT,
> >         MTHP_STAT_SWPOUT_FALLBACK,
> >         MTHP_STAT_SHMEM_ALLOC,
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 15418ffdd377..ad921c4b2ad8 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -587,6 +587,7 @@ static struct kobj_attribute _name##_attr =
> __ATTR_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_FALLBACK);
> >  DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge,
> MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
> > +DEFINE_MTHP_STAT_ATTR(zswpout, MTHP_STAT_ZSWPOUT);
> >  DEFINE_MTHP_STAT_ATTR(swpout, MTHP_STAT_SWPOUT);
> >  DEFINE_MTHP_STAT_ATTR(swpout_fallback,
> MTHP_STAT_SWPOUT_FALLBACK);
> >  #ifdef CONFIG_SHMEM
> > @@ -605,6 +606,7 @@ static struct attribute *anon_stats_attrs[] = {
> >         &anon_fault_fallback_attr.attr,
> >         &anon_fault_fallback_charge_attr.attr,
> >  #ifndef CONFIG_SHMEM
> > +       &zswpout_attr.attr,
> >         &swpout_attr.attr,
> >         &swpout_fallback_attr.attr,
> >  #endif
> > @@ -637,6 +639,7 @@ static struct attribute_group file_stats_attr_grp = {
> >
> >  static struct attribute *any_stats_attrs[] = {
> >  #ifdef CONFIG_SHMEM
> > +       &zswpout_attr.attr,
> >         &swpout_attr.attr,
> >         &swpout_fallback_attr.attr,
> >  #endif
> > diff --git a/mm/page_io.c b/mm/page_io.c
> > index b6f1519d63b0..26106e745d73 100644
> > --- a/mm/page_io.c
> > +++ b/mm/page_io.c
> > @@ -289,6 +289,7 @@ int swap_writepage(struct page *page, struct
> writeback_control *wbc)
> >                 swap_zeromap_folio_clear(folio);
> >         }
> >         if (zswap_store(folio)) {
> > +               count_mthp_stat(folio_order(folio), MTHP_STAT_ZSWPOUT);
> >                 folio_unlock(folio);
> >                 return 0;
> >         }
> > @@ -308,8 +309,8 @@ static inline void count_swpout_vm_event(struct
> folio *folio)
> >                 count_memcg_folio_events(folio, THP_SWPOUT, 1);
> >                 count_vm_event(THP_SWPOUT);
> >         }
> > -       count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT);
> >  #endif
> > +       count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT);
> >         count_vm_events(PSWPOUT, folio_nr_pages(folio));
> >  }
> >
> > --
> > 2.27.0
> >