diff mbox series

mm: migrate LRU_REFS_MASK bits in folio_migrate_flags

Message ID 20240925030225.236143-1-zhaoyang.huang@unisoc.com (mailing list archive)
State New
Headers show
Series mm: migrate LRU_REFS_MASK bits in folio_migrate_flags | expand

Commit Message

zhaoyang.huang Sept. 25, 2024, 3:02 a.m. UTC 
From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

Bits of LRU_REFS_MASK are not inherited during migration which lead to
new_folio start from tier0. Fix this by migrate the bits domain.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 include/linux/mm_inline.h | 8 ++++++++
 mm/migrate.c              | 1 +
 2 files changed, 9 insertions(+)

Comments

Andrew Morton Sept. 25, 2024, 9:42 a.m. UTC | #1 
On Wed, 25 Sep 2024 11:02:25 +0800 "zhaoyang.huang" <zhaoyang.huang@unisoc.com> wrote:

> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> 
> Bits of LRU_REFS_MASK are not inherited during migration which lead to
> new_folio start from tier0. Fix this by migrate the bits domain.

I'm having trouble understanding this, sorry.  Please more fully
describe the runtime effects of this flaw.

> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -291,6 +291,12 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
>  	return true;
>  }
>  
> +static inline void folio_migrate_refs(struct folio *new_folio, struct folio *folio)
> +{
> +	unsigned long refs = READ_ONCE(folio->flags) & LRU_REFS_MASK;
> +
> +	set_mask_bits(&new_folio->flags, LRU_REFS_MASK, refs);
> +}
>  #else /* !CONFIG_LRU_GEN */
>  
>  static inline bool lru_gen_enabled(void)
> @@ -313,6 +319,8 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
>  	return false;
>  }
>  
> +static inline void folio_migrate_refs(struct folio *new_folio, struct folio *folio)
> +{}
>  #endif /* CONFIG_LRU_GEN */
>  
>  static __always_inline
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 923ea80ba744..60c97e235ae7 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -618,6 +618,7 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
>  	if (folio_test_idle(folio))
>  		folio_set_idle(newfolio);
>  
> +	folio_migrate_refs(newfolio, folio);
>  	/*
>  	 * Copy NUMA information to the new page, to prevent over-eager
>  	 * future migrations of this same page.
> -- 
> 2.25.1
Zhaoyang Huang Sept. 25, 2024, 11:49 a.m. UTC | #2 
On Wed, Sep 25, 2024 at 5:42 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 25 Sep 2024 11:02:25 +0800 "zhaoyang.huang" <zhaoyang.huang@unisoc.com> wrote:
>
> > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> >
> > Bits of LRU_REFS_MASK are not inherited during migration which lead to
> > new_folio start from tier0. Fix this by migrate the bits domain.
>
> I'm having trouble understanding this, sorry.  Please more fully
> describe the runtime effects of this flaw.
Sorry for bringing confusion. According to my understanding, MGLRU
records how many times that vfs access this page in a range of bits
domain(LRU_REFS_MASK) in folio->flags which are not being migrated to
new_folios so far. This commit would like to do so to have the
new_folio inherit these bits from the old folio. Is it right and
worthy to do?
>
> > --- a/include/linux/mm_inline.h
> > +++ b/include/linux/mm_inline.h
> > @@ -291,6 +291,12 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
> >       return true;
> >  }
> >
> > +static inline void folio_migrate_refs(struct folio *new_folio, struct folio *folio)
> > +{
> > +     unsigned long refs = READ_ONCE(folio->flags) & LRU_REFS_MASK;
> > +
> > +     set_mask_bits(&new_folio->flags, LRU_REFS_MASK, refs);
> > +}
> >  #else /* !CONFIG_LRU_GEN */
> >
> >  static inline bool lru_gen_enabled(void)
> > @@ -313,6 +319,8 @@ static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
> >       return false;
> >  }
> >
> > +static inline void folio_migrate_refs(struct folio *new_folio, struct folio *folio)
> > +{}
> >  #endif /* CONFIG_LRU_GEN */
> >
> >  static __always_inline
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index 923ea80ba744..60c97e235ae7 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -618,6 +618,7 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
> >       if (folio_test_idle(folio))
> >               folio_set_idle(newfolio);
> >
> > +     folio_migrate_refs(newfolio, folio);
> >       /*
> >        * Copy NUMA information to the new page, to prevent over-eager
> >        * future migrations of this same page.
> > --
> > 2.25.1
diff mbox series

Patch

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index f4fe593c1400..ecf07a2a8201 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -291,6 +291,12 @@  static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
 	return true;
 }
 
+static inline void folio_migrate_refs(struct folio *new_folio, struct folio *folio)
+{
+	unsigned long refs = READ_ONCE(folio->flags) & LRU_REFS_MASK;
+
+	set_mask_bits(&new_folio->flags, LRU_REFS_MASK, refs);
+}
 #else /* !CONFIG_LRU_GEN */
 
 static inline bool lru_gen_enabled(void)
@@ -313,6 +319,8 @@  static inline bool lru_gen_del_folio(struct lruvec *lruvec, struct folio *folio,
 	return false;
 }
 
+static inline void folio_migrate_refs(struct folio *new_folio, struct folio *folio)
+{}
 #endif /* CONFIG_LRU_GEN */
 
 static __always_inline
diff --git a/mm/migrate.c b/mm/migrate.c
index 923ea80ba744..60c97e235ae7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -618,6 +618,7 @@  void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
 	if (folio_test_idle(folio))
 		folio_set_idle(newfolio);
 
+	folio_migrate_refs(newfolio, folio);
 	/*
 	 * Copy NUMA information to the new page, to prevent over-eager
 	 * future migrations of this same page.