Re: [PATCH 1/2] mm: add per-order mTHP split counters

[Lance Yang]

Hey Yang,

Thanks for taking time to review!

On Thu, Apr 25, 2024 at 3:44 AM Yang Shi <shy828301@xxxxxxxxx> wrote:
>
> On Wed, Apr 24, 2024 at 6:53 AM Lance Yang <ioworker0@xxxxxxxxx> wrote:
> >
> > 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@xxxxxxxx/
>
> Zi Yan,
>
> Will you submit v2 for this patch soon?

Thanks for bringing this to my attention!
I'll follow Zi Yan's patch, then submit the next version.

Thanks,
Lance

>
>
> >
> > Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
> > ---
> >  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_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(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[] = {
> >         &anon_fault_alloc_attr.attr,
> > @@ -564,6 +567,9 @@ static struct attribute *stats_attrs[] = {
> >         &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 *page, struct list_head *list,
> >         XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
> >         struct anon_vma *anon_vma = NULL;
> >         struct address_space *mapping = NULL;
> > -       bool is_thp = folio_test_pmd_mappable(folio);
> > +       int order = 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 >= HPAGE_PMD_ORDER)
> >                 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
> > +       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_queue);
> >                 ds_queue->split_queue_len++;
> >  #ifdef CONFIG_MEMCG
> > --
> > 2.33.1
> >
> >