On Tue 31-05-16 17:38:32, roy.qing.li@xxxxxxxxx wrote:
> From: Li RongQing <roy.qing.li@xxxxxxxxx>
>
> I see the number of page of hpage_nr_pages(page) is charged if page is
> transparent huge or hugetlbfs pages; but when uncharge a huge page,
hugetlb pages do not get charged to the memcg. They have their own
hugetlbfscg controller.
> (1<<compound_order) page is uncharged, and maybe hpage_nr_pages(page) is
> not same as 1<<compound_order.
This should never happen. So this is not a fix. I guess it would a clean
up though.
> And remove VM_BUG_ON_PAGE(!PageTransHuge(page), page); since
> PageTransHuge(page) always is true, when this VM_BUG_ON_PAGE is called.
I guess we can drop this BUG_ON because nobody should be be seeing the
page at this stage so we cannot race with a THP split up. But I would
really have to look closer. This would be a patch on its own with the
full explanation though, IMHO.
> Signed-off-by: Li RongQing <roy.qing.li@xxxxxxxxx>
> ---
> mm/memcontrol.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 12aaadd..28c0137 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5453,8 +5453,7 @@ static void uncharge_list(struct list_head *page_list)
> }
>
> if (PageTransHuge(page)) {
> - nr_pages <<= compound_order(page);
> - VM_BUG_ON_PAGE(!PageTransHuge(page), page);
> + nr_pages = hpage_nr_pages(page);
> nr_huge += nr_pages;
> }
>
> --
> 2.1.4
--
Michal Hocko
SUSE Labs
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