On Fri, Jun 21, 2019 at 06:15:16PM +0800, Pingfan Liu wrote:
> Both hugetlb and thp locate on the same migration type of pageblock, since
> they are allocated from a free_list[]. Based on this fact, it is enough to
> check on a single subpage to decide the migration type of the whole huge
> page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86,
> similar on other archs.
>
> Furthermore, when executing isolate_huge_page(), it avoid taking global
> hugetlb_lock many times, and meanless remove/add to the local link list
> cma_page_list.
>
> Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Keith Busch <keith.busch@xxxxxxxxx>
> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> Cc: Linux-kernel@xxxxxxxxxxxxxxx
> ---
> mm/gup.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index ddde097..2eecb16 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1342,16 +1342,19 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
> LIST_HEAD(cma_page_list);
>
> check_again:
> - for (i = 0; i < nr_pages; i++) {
> + for (i = 0; i < nr_pages;) {
> +
> + struct page *head = compound_head(pages[i]);
> + long step = 1;
> +
> + if (PageCompound(head))
> + step = compound_order(head) - (pages[i] - head);
> /*
> * If we get a page from the CMA zone, since we are going to
> * be pinning these entries, we might as well move them out
> * of the CMA zone if possible.
> */
> if (is_migrate_cma_page(pages[i])) {
I like this but I think for consistency I would change this pages[i] to be
head. Even though it is not required.
Ira
> -
> - struct page *head = compound_head(pages[i]);
> -
> if (PageHuge(head)) {
> isolate_huge_page(head, &cma_page_list);
> } else {
> @@ -1369,6 +1372,8 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
> }
> }
> }
> +
> + i += step;
> }
>
> if (!list_empty(&cma_page_list)) {
> --
> 2.7.5
>
