linux-kernel - Re: [PATCH v2 7/7] mm: shmem: add mTHP counters for anonymous shmem

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Date: Tue, 14 May 2024 22:49:55 +0800
From: Lance Yang <ioworker0@...il.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, willy@...radead.org, 
	david@...hat.com, wangkefeng.wang@...wei.com, ying.huang@...el.com, 
	21cnbao@...il.com, ryan.roberts@....com, shy828301@...il.com, ziy@...dia.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] mm: shmem: add mTHP counters for anonymous shmem

Hi Baolin,

On Mon, May 13, 2024 at 1:08 PM Baolin Wang
<baolin.wang@...ux.alibaba.com> wrote:
>
> Add mTHP counters for anonymous shmem.
>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  include/linux/huge_mm.h |  3 +++
>  mm/huge_memory.c        |  6 ++++++
>  mm/shmem.c              | 18 +++++++++++++++---
>  3 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index b5339210268d..e162498fef82 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -281,6 +281,9 @@ enum mthp_stat_item {
>         MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
>         MTHP_STAT_ANON_SWPOUT,
>         MTHP_STAT_ANON_SWPOUT_FALLBACK,
> +       MTHP_STAT_FILE_ALLOC,
> +       MTHP_STAT_FILE_FALLBACK,
> +       MTHP_STAT_FILE_FALLBACK_CHARGE,
>         __MTHP_STAT_COUNT
>  };
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index d3080a8843f2..fcda6ae604f6 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -555,6 +555,9 @@ DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
>  DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
>  DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
>  DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK);
> +DEFINE_MTHP_STAT_ATTR(file_alloc, MTHP_STAT_FILE_ALLOC);
> +DEFINE_MTHP_STAT_ATTR(file_fallback, MTHP_STAT_FILE_FALLBACK);
> +DEFINE_MTHP_STAT_ATTR(file_fallback_charge, MTHP_STAT_FILE_FALLBACK_CHARGE);
>
>  static struct attribute *stats_attrs[] = {
>         &anon_fault_alloc_attr.attr,
> @@ -562,6 +565,9 @@ static struct attribute *stats_attrs[] = {
>         &anon_fault_fallback_charge_attr.attr,
>         &anon_swpout_attr.attr,
>         &anon_swpout_fallback_attr.attr,
> +       &file_alloc_attr.attr,
> +       &file_fallback_attr.attr,
> +       &file_fallback_charge_attr.attr,
>         NULL,
>  };
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 8b020ff09c72..fd2cb2e73a21 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1786,6 +1786,9 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
>
>                         if (pages == HPAGE_PMD_NR)
>                                 count_vm_event(THP_FILE_FALLBACK);
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +                       count_mthp_stat(order, MTHP_STAT_FILE_FALLBACK);
> +#endif

Seems like we don't need these conditional compilation directives here.

The THP_FILE_FALLBACK above will result in a compilation error if
CONFIG_TRANSPARENT_HUGEPAGE is not defined. So we don't
worry about that :)

See THP_FILE_FALLBACK in include/linux/vm_event_item.h.

>                         order = next_order(&suitable_orders, order);
>                 }
>         } else {
> @@ -1805,9 +1808,15 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
>                 if (xa_find(&mapping->i_pages, &index,
>                                 index + pages - 1, XA_PRESENT)) {
>                         error = -EEXIST;
> -               } else if (pages == HPAGE_PMD_NR) {
> -                       count_vm_event(THP_FILE_FALLBACK);
> -                       count_vm_event(THP_FILE_FALLBACK_CHARGE);
> +               } else if (pages > 1) {
> +                       if (pages == HPAGE_PMD_NR) {
> +                               count_vm_event(THP_FILE_FALLBACK);
> +                               count_vm_event(THP_FILE_FALLBACK_CHARGE);
> +                       }
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +                       count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK);
> +                       count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK_CHARGE);
> +#endif

As above.

>                 }
>                 goto unlock;
>         }
> @@ -2178,6 +2187,9 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
>                 if (!IS_ERR(folio)) {
>                         if (folio_test_pmd_mappable(folio))
>                                 count_vm_event(THP_FILE_ALLOC);
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +                       count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_ALLOC);
> +#endif

As above.

Perhaps we need to define MTHP_STAT_FILE_ALLOC and friends
using a same way as THP_FILE_ALLOC, set as '{ BUILD_BUG(); 0; }'
If CONFIG_TRANSPARENT_HUGEPAGE is not defined.

Likely:

#ifndef CONFIG_TRANSPARENT_HUGEPAGE
#define MTHP_STAT_FILE_ALLOC ({ BUILD_BUG(); 0; })
..
#endif

Thanks,
Lance


>                         goto alloced;
>                 }
>                 if (PTR_ERR(folio) == -EEXIST)
> --
> 2.39.3
>