linux-kernel - Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise

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Date: Tue, 27 Feb 2024 09:48:34 +0800
From: Lance Yang <ioworker0@...il.com>
To: Barry Song <21cnbao@...il.com>
Cc: akpm@...ux-foundation.org, david@...hat.com, fengwei.yin@...el.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhocko@...e.com, 
	minchan@...nel.org, peterx@...hat.com, ryan.roberts@....com, 
	shy828301@...il.com, songmuchun@...edance.com, wangkefeng.wang@...wei.com, 
	zokeefe@...gle.com, Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise_free

On Tue, Feb 27, 2024 at 9:21 AM Barry Song <21cnbao@...il.com> wrote:
>
> > Thanks for your suggestion. I'll use folio_pte_batch() in v2.
>
> Hi Lance,
> Obviously, we both need this. While making large folio swap-in
> v2, I am exporting folio_pte_batch() as below,

Thanks, Barry.

Could you separate the export of folio_pte_batch() from the large folio
swap-in v2? Prioritizing the push for this specific change would aid in
the development of the v2 based on it.

Best,
Lance

>
> From: Barry Song <v-songbaohua@...o.com>
> Date: Tue, 27 Feb 2024 14:05:43 +1300
> Subject: [PATCH] mm: export folio_pte_batch as a couple of modules need it
>
> MADV_FREE, MADV_PAGEOUT and some other modules might need folio_pte_batch
> to check if a range of PTEs are completely mapped to a large folio with
> contiguous physcial offset.
>
> Cc: Lance Yang <ioworker0@...il.com>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Cc: David Hildenbrand <david@...hat.com>
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
> ---
>  mm/internal.h | 13 +++++++++++++
>  mm/memory.c   |  2 +-
>  2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 36c11ea41f47..7e11aea3eda9 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -83,6 +83,19 @@ static inline void *folio_raw_mapping(struct folio *folio)
>         return (void *)(mapping & ~PAGE_MAPPING_FLAGS);
>  }
>
> +/* Flags for folio_pte_batch(). */
> +typedef int __bitwise fpb_t;
> +
> +/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */
> +#define FPB_IGNORE_DIRTY               ((__force fpb_t)BIT(0))
> +
> +/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */
> +#define FPB_IGNORE_SOFT_DIRTY          ((__force fpb_t)BIT(1))
> +
> +extern int folio_pte_batch(struct folio *folio, unsigned long addr,
> +               pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags,
> +               bool *any_writable);
> +
>  void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
>                                                 int nr_throttled);
>  static inline void acct_reclaim_writeback(struct folio *folio)
> diff --git a/mm/memory.c b/mm/memory.c
> index 6378f6bc22c5..dd9bd67f037a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -989,7 +989,7 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags)
>   * If "any_writable" is set, it will indicate if any other PTE besides the
>   * first (given) PTE is writable.
>   */
> -static inline int folio_pte_batch(struct folio *folio, unsigned long addr,
> +int folio_pte_batch(struct folio *folio, unsigned long addr,
>                 pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags,
>                 bool *any_writable)
>  {
> --
> 2.34.1
>
> > Best,
> > Lance
>
> Thanks
> Barry
>