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

[Yosry Ahmed <yosryahmed@google.com>]

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.

>
> 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
>