Re: [PATCH 08/10] mm/hugetlb: return non-isolated page in the loop instead of break and check

Baoquan He
2020-08-07T13:09:43Z

On 08/07/20 at 05:12pm, Wei Yang wrote:
> Function dequeue_huge_page_node_exact() iterates the free list and
> return the first non-isolated one.
>
> Instead of break and check the loop variant, we could return in the loop
> directly. This could reduce some redundant check.
>
> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
> ---
> mm/hugetlb.c | 26 ++++++++++++--------------
> 1 file changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index b8e844911b5a..9473eb6800e9 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1035,20 +1035,18 @@ static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
> {
> struct page *page;
>
> - list_for_each_entry(page, &h->hugepage_freelists[nid], lru)
> - if (!PageHWPoison(page))
> - break;

I don't see how it can reduce redundant check, just two different
styles.

> - /*
> - * if 'non-isolated free hugepage' not found on the list,
> - * the allocation fails.

But the above code comment seems stale, it checks HWPoision page
directly, but not the old isolated page checking.

> - */
> - if (&h->hugepage_freelists[nid] == &page->lru)
> - return NULL;
> - list_move(&page->lru, &h->hugepage_activelist);
> - set_page_refcounted(page);
> - h->free_huge_pages--;
> - h->free_huge_pages_node[nid]--;
> - return page;
> + list_for_each_entry(page, &h->hugepage_freelists[nid], lru) {
> + if (PageHWPoison(page))
> + continue;
> +
> + list_move(&page->lru, &h->hugepage_activelist);
> + set_page_refcounted(page);
> + h->free_huge_pages--;
> + h->free_huge_pages_node[nid]--;
> + return page;
> + }
> +
> + return NULL;
> }
>
> static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask, int nid,
> --
> 2.20.1 (Apple Git-117)
>
>