Re: [PATCH 2/9] mm: Call the hugetlb destructor directly

[David Hildenbrand <david@redhat.com>]

On 15.08.23 05:26, Matthew Wilcox (Oracle) wrote:
> Indirect calls are expensive, thanks to Spectre.  Convert this one to
> a direct call, and pass a folio instead of the head page to save a few
> more instructions.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>   include/linux/hugetlb.h |  3 ++-
>   include/linux/mm.h      |  6 +-----
>   mm/hugetlb.c            | 26 ++++++++++++--------------
>   mm/page_alloc.c         |  8 +++++---
>   4 files changed, 20 insertions(+), 23 deletions(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 0a393bc02f25..9555859537a3 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -26,6 +26,8 @@ typedef struct { unsigned long pd; } hugepd_t;
>   #define __hugepd(x) ((hugepd_t) { (x) })
>   #endif
>   
> +void free_huge_page(struct folio *folio);
> +
>   #ifdef CONFIG_HUGETLB_PAGE
>   
>   #include <linux/mempolicy.h>
> @@ -165,7 +167,6 @@ int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
>   				bool *migratable_cleared);
>   void folio_putback_active_hugetlb(struct folio *folio);
>   void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int reason);
> -void free_huge_page(struct page *page);
>   void hugetlb_fix_reserve_counts(struct inode *inode);
>   extern struct mutex *hugetlb_fault_mutex_table;
>   u32 hugetlb_fault_mutex_hash(struct address_space *mapping, pgoff_t idx);
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 19493d6a2bb8..7fb529dbff31 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1278,13 +1278,9 @@ typedef void compound_page_dtor(struct page *);
>   enum compound_dtor_id {
>   	NULL_COMPOUND_DTOR,
>   	COMPOUND_PAGE_DTOR,
> -#ifdef CONFIG_HUGETLB_PAGE
>   	HUGETLB_PAGE_DTOR,
> -#endif
> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>   	TRANSHUGE_PAGE_DTOR,
> -#endif
> -	NR_COMPOUND_DTORS,
> +	NR_COMPOUND_DTORS
>   };
>   
>   static inline void folio_set_compound_dtor(struct folio *folio,
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e327a5a7602c..bc340f5dbbd4 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1875,13 +1875,12 @@ struct hstate *size_to_hstate(unsigned long size)
>   	return NULL;
>   }
>   
> -void free_huge_page(struct page *page)
> +void free_huge_page(struct folio *folio)

free_huge_page" but passing a folio, hm. Maybe something like 
"free_hugetlb_folio" would be better.


Apart from that LGTM.

-- 
Cheers,

David / dhildenb