On Mon 26-09-16 19:28:11, Gerald Schaefer wrote:
> For every pfn aligned to minimum_order, dissolve_free_huge_pages() will
> call dissolve_free_huge_page() which takes the hugetlb spinlock, even if
> the page is not huge at all or a hugepage that is in-use.
>
> Improve this by doing the PageHuge() and page_count() checks already in
> dissolve_free_huge_pages() before calling dissolve_free_huge_page(). In
> dissolve_free_huge_page(), when holding the spinlock, those checks need
> to be revalidated.
>
> Signed-off-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/hugetlb.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 91ae1f5..770d83e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1476,14 +1476,20 @@ static int dissolve_free_huge_page(struct page *page)
> int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
> {
> unsigned long pfn;
> + struct page *page;
> int rc = 0;
>
> if (!hugepages_supported())
> return rc;
>
> - for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order)
> - if (rc = dissolve_free_huge_page(pfn_to_page(pfn)))
> - break;
> + for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order) {
> + page = pfn_to_page(pfn);
> + if (PageHuge(page) && !page_count(page)) {
> + rc = dissolve_free_huge_page(page);
> + if (rc)
> + break;
> + }
> + }
>
> return rc;
> }
> --
> 2.8.4
--
Michal Hocko
SUSE Labs
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