Re: [PATCH 1/1] hugetlb: pull gigantic page initialisation out of the default path

Mel Gorman
2008-10-08T14:57:34Z

On (08/10/08 10:34), Andy Whitcroft didst pronounce:
> As we can determine exactly when a gigantic page is in use we can optimise
> the common regular page cases by pulling out gigantic page initialisation
> into its own function. As gigantic pages are never released to buddy we
> do not need a destructor. This effectivly reverts the previous change
> to the main buddy allocator. It also adds a paranoid check to ensure we
> never release gigantic pages from hugetlbfs to the main buddy.
>
> Signed-off-by: Andy Whitcroft <apw@shadowen.org>
> Cc: Nick Piggin <nickpiggin@yahoo.com.au>

Acked-by: Mel Gorman <mel@csn.ul.ie>

> ---
> mm/hugetlb.c | 4 +++-
> mm/internal.h | 1 +
> mm/page_alloc.c | 26 +++++++++++++++++++-------
> 3 files changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index bb5cf81..716b151 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -460,6 +460,8 @@ static void update_and_free_page(struct hstate *h, struct page *page)
> {
> int i;
>
> + BUG_ON(h->order >= MAX_ORDER);
> +
> h->nr_huge_pages--;
> h->nr_huge_pages_node[page_to_nid(page)]--;
> for (i = 0; i < pages_per_huge_page(h); i++) {
> @@ -984,7 +986,7 @@ static void __init gather_bootmem_prealloc(void)
> struct hstate *h = m->hstate;
> __ClearPageReserved(page);
> WARN_ON(page_count(page) != 1);
> - prep_compound_page(page, h->order);
> + prep_compound_gigantic_page(page, h->order);
> prep_new_huge_page(h, page, page_to_nid(page));
> }
> }
> diff --git a/mm/internal.h b/mm/internal.h
> index 08b8dea..92729ea 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -17,6 +17,7 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
> unsigned long floor, unsigned long ceiling);
>
> extern void prep_compound_page(struct page *page, unsigned long order);
> +extern void prep_compound_gigantic_page(struct page *page, unsigned long order);
>
> static inline void set_page_count(struct page *page, int v)
> {
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 27b8681..dbeb3f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -268,14 +268,28 @@ void prep_compound_page(struct page *page, unsigned long order)
> {
> int i;
> int nr_pages = 1 << order;
> +
> + set_compound_page_dtor(page, free_compound_page);
> + set_compound_order(page, order);
> + __SetPageHead(page);
> + for (i = 1; i < nr_pages; i++) {
> + struct page *p = page + i;
> +
> + __SetPageTail(p);
> + p->first_page = 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_order(page, order);
> __SetPageHead(page);
> - for (i = 1; i < nr_pages; i++, p++) {
> - if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
> - p = pfn_to_page(page_to_pfn(page) + i);
> + for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
> __SetPageTail(p);
> p->first_page = page;
> }
> @@ -285,7 +299,6 @@ static void destroy_compound_page(struct page *page, unsigned long order)
> {
> int i;
> int nr_pages = 1 << order;
> - struct page *p = page + 1;
>
> if (unlikely(compound_order(page) != order))
> bad_page(page);
> @@ -293,9 +306,8 @@ static void destroy_compound_page(struct page *page, unsigned long order)
> if (unlikely(!PageHead(page)))
> bad_page(page);
> __ClearPageHead(page);
> - for (i = 1; i < nr_pages; i++, p++) {
> - if (unlikely((i & (MAX_ORDER_NR_PAGES - 1)) == 0))
> - p = pfn_to_page(page_to_pfn(page) + i);
> + for (i = 1; i < nr_pages; i++) {
> + struct page *p = page + i;
>
> if (unlikely(!PageTail(p) |
> (p->first_page != page)))
> --
> 1.6.0.1.451.gc8d31
>

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab