Re: [PATCH] mm/memcontrol: update lruvec counters in mem_cgroup_move_account

Michal Hocko
2019-10-15T08:20:51Z

On Tue 15-10-19 11:09:59, Konstantin Khlebnikov wrote:
> Mapped, dirty and writeback pages are also counted in per-lruvec stats.
> These counters needs update when page is moved between cgroups.

Please describe the user visible effect.

> Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>

We want Cc: stable I suspect because broken stats might be really
misleading.

The patch looks ok to me otherwise
Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/memcontrol.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index bdac56009a38..363106578876 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5420,6 +5420,8 @@ static int mem_cgroup_move_account(struct page *page,
> struct mem_cgroup *from,
> struct mem_cgroup *to)
> {
> + struct lruvec *from_vec, *to_vec;
> + struct pglist_data *pgdat;
> unsigned long flags;
> unsigned int nr_pages = compound ? hpage_nr_pages(page) : 1;
> int ret;
> @@ -5443,11 +5445,15 @@ static int mem_cgroup_move_account(struct page *page,
>
> anon = PageAnon(page);
>
> + pgdat = page_pgdat(page);
> + from_vec = mem_cgroup_lruvec(pgdat, from);
> + to_vec = mem_cgroup_lruvec(pgdat, to);
> +
> spin_lock_irqsave(&from->move_lock, flags);
>
> if (!anon && page_mapped(page)) {
> - __mod_memcg_state(from, NR_FILE_MAPPED, -nr_pages);
> - __mod_memcg_state(to, NR_FILE_MAPPED, nr_pages);
> + __mod_lruvec_state(from_vec, NR_FILE_MAPPED, -nr_pages);
> + __mod_lruvec_state(to_vec, NR_FILE_MAPPED, nr_pages);
> }
>
> /*
> @@ -5459,14 +5465,14 @@ static int mem_cgroup_move_account(struct page *page,
> struct address_space *mapping = page_mapping(page);
>
> if (mapping_cap_account_dirty(mapping)) {
> - __mod_memcg_state(from, NR_FILE_DIRTY, -nr_pages);
> - __mod_memcg_state(to, NR_FILE_DIRTY, nr_pages);
> + __mod_lruvec_state(from_vec, NR_FILE_DIRTY, -nr_pages);
> + __mod_lruvec_state(to_vec, NR_FILE_DIRTY, nr_pages);
> }
> }
>
> if (PageWriteback(page)) {
> - __mod_memcg_state(from, NR_WRITEBACK, -nr_pages);
> - __mod_memcg_state(to, NR_WRITEBACK, nr_pages);
> + __mod_lruvec_state(from_vec, NR_WRITEBACK, -nr_pages);
> + __mod_lruvec_state(to_vec, NR_WRITEBACK, nr_pages);
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE

--
Michal Hocko
SUSE Labs