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    SubjectRe: [PATCH 1/8] mm: introduce PageHuge() for testing huge/gigantic pages

    * Wu Fengguang <fengguang.wu@intel.com> wrote:

    > Introduce PageHuge(), which identifies huge/gigantic pages
    > by their dedicated compound destructor functions.
    >
    > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    > ---
    > include/linux/mm.h | 24 ++++++++++++++++++++++++
    > mm/hugetlb.c | 2 +-
    > mm/page_alloc.c | 11 ++++++++++-
    > 3 files changed, 35 insertions(+), 2 deletions(-)
    >
    > --- linux.orig/mm/page_alloc.c
    > +++ linux/mm/page_alloc.c
    > @@ -299,13 +299,22 @@ void prep_compound_page(struct page *pag
    > }
    >
    > #ifdef CONFIG_HUGETLBFS
    > +/*
    > + * This (duplicated) destructor function distinguishes gigantic pages from
    > + * normal compound pages.
    > + */
    > +void free_gigantic_page(struct page *page)
    > +{
    > + __free_pages_ok(page, compound_order(page));
    > +}
    > +
    > void prep_compound_gigantic_page(struct page *page, unsigned long order)
    > {
    > int i;
    > int nr_pages = 1 << order;
    > struct page *p = page + 1;
    >
    > - set_compound_page_dtor(page, free_compound_page);
    > + set_compound_page_dtor(page, free_gigantic_page);
    > set_compound_order(page, order);
    > __SetPageHead(page);
    > for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
    > --- linux.orig/mm/hugetlb.c
    > +++ linux/mm/hugetlb.c
    > @@ -550,7 +550,7 @@ struct hstate *size_to_hstate(unsigned l
    > return NULL;
    > }
    >
    > -static void free_huge_page(struct page *page)
    > +void free_huge_page(struct page *page)
    > {
    > /*
    > * Can't pass hstate in here because it is called from the
    > --- linux.orig/include/linux/mm.h
    > +++ linux/include/linux/mm.h
    > @@ -355,6 +355,30 @@ static inline void set_compound_order(st
    > page[1].lru.prev = (void *)order;
    > }
    >
    > +#ifdef CONFIG_HUGETLBFS
    > +void free_huge_page(struct page *page);
    > +void free_gigantic_page(struct page *page);
    > +
    > +static inline int PageHuge(struct page *page)
    > +{
    > + compound_page_dtor *dtor;
    > +
    > + if (!PageCompound(page))
    > + return 0;
    > +
    > + page = compound_head(page);
    > + dtor = get_compound_page_dtor(page);
    > +
    > + return dtor == free_huge_page ||
    > + dtor == free_gigantic_page;
    > +}

    Hm, this function is _way_ too large to be inlined.

    Ingo


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