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References: <20240424135148.30422-1-ioworker0@gmail.com> <20240424135148.30422-2-ioworker0@gmail.com>
In-Reply-To: <20240424135148.30422-2-ioworker0@gmail.com>
From: Yang Shi <shy828301@gmail.com>
Date: Wed, 24 Apr 2024 12:44:22 -0700
Message-ID: <CAHbLzkq2cnZNj+0V1c=cbdQukpHCQsLCtEQLEzpH2mdjOZj_cQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] mm: add per-order mTHP split counters
To: Lance Yang <ioworker0@gmail.com>, Zi Yan <ziy@nvidia.com>
Cc: akpm@linux-foundation.org, 21cnbao@gmail.com, ryan.roberts@arm.com, 
	david@redhat.com, baolin.wang@linux.alibaba.com, linux-kernel@vger.kernel.org, 
	linux-mm@kvack.org
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On Wed, Apr 24, 2024 at 6:53=E2=80=AFAM Lance Yang <ioworker0@gmail.com> wr=
ote:
>
> At present, the split counters in THP statistics no longer include
> PTE-mapped mTHP. Therefore, this commit introduces per-order mTHP split
> counters to monitor the frequency of mTHP splits. This will assist
> developers in better analyzing and optimizing system performance.
>
> /sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats
>         split_page
>         split_page_failed
>         deferred_split_page

The deferred_split_page counter may easily go insane with the fix from
https://lore.kernel.org/linux-mm/20240411153232.169560-1-zi.yan@sent.com/

Zi Yan,

Will you submit v2 for this patch soon?


>
> Signed-off-by: Lance Yang <ioworker0@gmail.com>
> ---
>  include/linux/huge_mm.h |  3 +++
>  mm/huge_memory.c        | 14 ++++++++++++--
>  2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 56c7ea73090b..7b9c6590e1f7 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -272,6 +272,9 @@ enum mthp_stat_item {
>         MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
>         MTHP_STAT_ANON_SWPOUT,
>         MTHP_STAT_ANON_SWPOUT_FALLBACK,
> +       MTHP_STAT_SPLIT_PAGE,
> +       MTHP_STAT_SPLIT_PAGE_FAILED,
> +       MTHP_STAT_DEFERRED_SPLIT_PAGE,
>         __MTHP_STAT_COUNT
>  };
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 055df5aac7c3..52db888e47a6 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -557,6 +557,9 @@ DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_=
ANON_FAULT_FALLBACK);
>  DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_F=
ALLBACK_CHARGE);
>  DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
>  DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBA=
CK);
> +DEFINE_MTHP_STAT_ATTR(split_page, MTHP_STAT_SPLIT_PAGE);
> +DEFINE_MTHP_STAT_ATTR(split_page_failed, MTHP_STAT_SPLIT_PAGE_FAILED);
> +DEFINE_MTHP_STAT_ATTR(deferred_split_page, MTHP_STAT_DEFERRED_SPLIT_PAGE=
);
>
>  static struct attribute *stats_attrs[] =3D {
>         &anon_fault_alloc_attr.attr,
> @@ -564,6 +567,9 @@ static struct attribute *stats_attrs[] =3D {
>         &anon_fault_fallback_charge_attr.attr,
>         &anon_swpout_attr.attr,
>         &anon_swpout_fallback_attr.attr,
> +       &split_page_attr.attr,
> +       &split_page_failed_attr.attr,
> +       &deferred_split_page_attr.attr,
>         NULL,
>  };
>
> @@ -3083,7 +3089,7 @@ int split_huge_page_to_list_to_order(struct page *p=
age, struct list_head *list,
>         XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_o=
rder);
>         struct anon_vma *anon_vma =3D NULL;
>         struct address_space *mapping =3D NULL;
> -       bool is_thp =3D folio_test_pmd_mappable(folio);
> +       int order =3D folio_order(folio);
>         int extra_pins, ret;
>         pgoff_t end;
>         bool is_hzp;
> @@ -3262,8 +3268,10 @@ int split_huge_page_to_list_to_order(struct page *=
page, struct list_head *list,
>                 i_mmap_unlock_read(mapping);
>  out:
>         xas_destroy(&xas);
> -       if (is_thp)
> +       if (order >=3D HPAGE_PMD_ORDER)
>                 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAI=
LED);
> +       count_mthp_stat(order, !ret ? MTHP_STAT_SPLIT_PAGE :
> +                                     MTHP_STAT_SPLIT_PAGE_FAILED);
>         return ret;
>  }
>
> @@ -3327,6 +3335,8 @@ void deferred_split_folio(struct folio *folio)
>         if (list_empty(&folio->_deferred_list)) {
>                 if (folio_test_pmd_mappable(folio))
>                         count_vm_event(THP_DEFERRED_SPLIT_PAGE);
> +               count_mthp_stat(folio_order(folio),
> +                               MTHP_STAT_DEFERRED_SPLIT_PAGE);
>                 list_add_tail(&folio->_deferred_list, &ds_queue->split_qu=
eue);
>                 ds_queue->split_queue_len++;
>  #ifdef CONFIG_MEMCG
> --
> 2.33.1
>
>