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

[Konstantin Khlebnikov]

On 15/10/2019 11.20, Michal Hocko wrote:

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.

Surprisingly I don't see any users at this moment.
So, there is no effect in mainline kernel.

Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
Signed-off-by: Konstantin Khlebnikov <khlebni...@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 <mho...@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